Merge branch 'jk/quarantine-received-objects'
[git] / refs / files-backend.c
1 #include "../cache.h"
2 #include "../refs.h"
3 #include "refs-internal.h"
4 #include "../iterator.h"
5 #include "../dir-iterator.h"
6 #include "../lockfile.h"
7 #include "../object.h"
8 #include "../dir.h"
9
10 struct ref_lock {
11         char *ref_name;
12         struct lock_file *lk;
13         struct object_id old_oid;
14 };
15
16 struct ref_entry;
17
18 /*
19  * Information used (along with the information in ref_entry) to
20  * describe a single cached reference.  This data structure only
21  * occurs embedded in a union in struct ref_entry, and only when
22  * (ref_entry->flag & REF_DIR) is zero.
23  */
24 struct ref_value {
25         /*
26          * The name of the object to which this reference resolves
27          * (which may be a tag object).  If REF_ISBROKEN, this is
28          * null.  If REF_ISSYMREF, then this is the name of the object
29          * referred to by the last reference in the symlink chain.
30          */
31         struct object_id oid;
32
33         /*
34          * If REF_KNOWS_PEELED, then this field holds the peeled value
35          * of this reference, or null if the reference is known not to
36          * be peelable.  See the documentation for peel_ref() for an
37          * exact definition of "peelable".
38          */
39         struct object_id peeled;
40 };
41
42 struct files_ref_store;
43
44 /*
45  * Information used (along with the information in ref_entry) to
46  * describe a level in the hierarchy of references.  This data
47  * structure only occurs embedded in a union in struct ref_entry, and
48  * only when (ref_entry.flag & REF_DIR) is set.  In that case,
49  * (ref_entry.flag & REF_INCOMPLETE) determines whether the references
50  * in the directory have already been read:
51  *
52  *     (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose
53  *         or packed references, already read.
54  *
55  *     (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose
56  *         references that hasn't been read yet (nor has any of its
57  *         subdirectories).
58  *
59  * Entries within a directory are stored within a growable array of
60  * pointers to ref_entries (entries, nr, alloc).  Entries 0 <= i <
61  * sorted are sorted by their component name in strcmp() order and the
62  * remaining entries are unsorted.
63  *
64  * Loose references are read lazily, one directory at a time.  When a
65  * directory of loose references is read, then all of the references
66  * in that directory are stored, and REF_INCOMPLETE stubs are created
67  * for any subdirectories, but the subdirectories themselves are not
68  * read.  The reading is triggered by get_ref_dir().
69  */
70 struct ref_dir {
71         int nr, alloc;
72
73         /*
74          * Entries with index 0 <= i < sorted are sorted by name.  New
75          * entries are appended to the list unsorted, and are sorted
76          * only when required; thus we avoid the need to sort the list
77          * after the addition of every reference.
78          */
79         int sorted;
80
81         /* A pointer to the files_ref_store that contains this ref_dir. */
82         struct files_ref_store *ref_store;
83
84         struct ref_entry **entries;
85 };
86
87 /*
88  * Bit values for ref_entry::flag.  REF_ISSYMREF=0x01,
89  * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are
90  * public values; see refs.h.
91  */
92
93 /*
94  * The field ref_entry->u.value.peeled of this value entry contains
95  * the correct peeled value for the reference, which might be
96  * null_sha1 if the reference is not a tag or if it is broken.
97  */
98 #define REF_KNOWS_PEELED 0x10
99
100 /* ref_entry represents a directory of references */
101 #define REF_DIR 0x20
102
103 /*
104  * Entry has not yet been read from disk (used only for REF_DIR
105  * entries representing loose references)
106  */
107 #define REF_INCOMPLETE 0x40
108
109 /*
110  * A ref_entry represents either a reference or a "subdirectory" of
111  * references.
112  *
113  * Each directory in the reference namespace is represented by a
114  * ref_entry with (flags & REF_DIR) set and containing a subdir member
115  * that holds the entries in that directory that have been read so
116  * far.  If (flags & REF_INCOMPLETE) is set, then the directory and
117  * its subdirectories haven't been read yet.  REF_INCOMPLETE is only
118  * used for loose reference directories.
119  *
120  * References are represented by a ref_entry with (flags & REF_DIR)
121  * unset and a value member that describes the reference's value.  The
122  * flag member is at the ref_entry level, but it is also needed to
123  * interpret the contents of the value field (in other words, a
124  * ref_value object is not very much use without the enclosing
125  * ref_entry).
126  *
127  * Reference names cannot end with slash and directories' names are
128  * always stored with a trailing slash (except for the top-level
129  * directory, which is always denoted by "").  This has two nice
130  * consequences: (1) when the entries in each subdir are sorted
131  * lexicographically by name (as they usually are), the references in
132  * a whole tree can be generated in lexicographic order by traversing
133  * the tree in left-to-right, depth-first order; (2) the names of
134  * references and subdirectories cannot conflict, and therefore the
135  * presence of an empty subdirectory does not block the creation of a
136  * similarly-named reference.  (The fact that reference names with the
137  * same leading components can conflict *with each other* is a
138  * separate issue that is regulated by verify_refname_available().)
139  *
140  * Please note that the name field contains the fully-qualified
141  * reference (or subdirectory) name.  Space could be saved by only
142  * storing the relative names.  But that would require the full names
143  * to be generated on the fly when iterating in do_for_each_ref(), and
144  * would break callback functions, who have always been able to assume
145  * that the name strings that they are passed will not be freed during
146  * the iteration.
147  */
148 struct ref_entry {
149         unsigned char flag; /* ISSYMREF? ISPACKED? */
150         union {
151                 struct ref_value value; /* if not (flags&REF_DIR) */
152                 struct ref_dir subdir; /* if (flags&REF_DIR) */
153         } u;
154         /*
155          * The full name of the reference (e.g., "refs/heads/master")
156          * or the full name of the directory with a trailing slash
157          * (e.g., "refs/heads/"):
158          */
159         char name[FLEX_ARRAY];
160 };
161
162 static void read_loose_refs(const char *dirname, struct ref_dir *dir);
163 static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
164 static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
165                                           const char *dirname, size_t len,
166                                           int incomplete);
167 static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
168 static int files_log_ref_write(struct files_ref_store *refs,
169                                const char *refname, const unsigned char *old_sha1,
170                                const unsigned char *new_sha1, const char *msg,
171                                int flags, struct strbuf *err);
172
173 static struct ref_dir *get_ref_dir(struct ref_entry *entry)
174 {
175         struct ref_dir *dir;
176         assert(entry->flag & REF_DIR);
177         dir = &entry->u.subdir;
178         if (entry->flag & REF_INCOMPLETE) {
179                 read_loose_refs(entry->name, dir);
180
181                 /*
182                  * Manually add refs/bisect, which, being
183                  * per-worktree, might not appear in the directory
184                  * listing for refs/ in the main repo.
185                  */
186                 if (!strcmp(entry->name, "refs/")) {
187                         int pos = search_ref_dir(dir, "refs/bisect/", 12);
188                         if (pos < 0) {
189                                 struct ref_entry *child_entry;
190                                 child_entry = create_dir_entry(dir->ref_store,
191                                                                "refs/bisect/",
192                                                                12, 1);
193                                 add_entry_to_dir(dir, child_entry);
194                                 read_loose_refs("refs/bisect",
195                                                 &child_entry->u.subdir);
196                         }
197                 }
198                 entry->flag &= ~REF_INCOMPLETE;
199         }
200         return dir;
201 }
202
203 static struct ref_entry *create_ref_entry(const char *refname,
204                                           const unsigned char *sha1, int flag,
205                                           int check_name)
206 {
207         struct ref_entry *ref;
208
209         if (check_name &&
210             check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
211                 die("Reference has invalid format: '%s'", refname);
212         FLEX_ALLOC_STR(ref, name, refname);
213         hashcpy(ref->u.value.oid.hash, sha1);
214         oidclr(&ref->u.value.peeled);
215         ref->flag = flag;
216         return ref;
217 }
218
219 static void clear_ref_dir(struct ref_dir *dir);
220
221 static void free_ref_entry(struct ref_entry *entry)
222 {
223         if (entry->flag & REF_DIR) {
224                 /*
225                  * Do not use get_ref_dir() here, as that might
226                  * trigger the reading of loose refs.
227                  */
228                 clear_ref_dir(&entry->u.subdir);
229         }
230         free(entry);
231 }
232
233 /*
234  * Add a ref_entry to the end of dir (unsorted).  Entry is always
235  * stored directly in dir; no recursion into subdirectories is
236  * done.
237  */
238 static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry)
239 {
240         ALLOC_GROW(dir->entries, dir->nr + 1, dir->alloc);
241         dir->entries[dir->nr++] = entry;
242         /* optimize for the case that entries are added in order */
243         if (dir->nr == 1 ||
244             (dir->nr == dir->sorted + 1 &&
245              strcmp(dir->entries[dir->nr - 2]->name,
246                     dir->entries[dir->nr - 1]->name) < 0))
247                 dir->sorted = dir->nr;
248 }
249
250 /*
251  * Clear and free all entries in dir, recursively.
252  */
253 static void clear_ref_dir(struct ref_dir *dir)
254 {
255         int i;
256         for (i = 0; i < dir->nr; i++)
257                 free_ref_entry(dir->entries[i]);
258         free(dir->entries);
259         dir->sorted = dir->nr = dir->alloc = 0;
260         dir->entries = NULL;
261 }
262
263 /*
264  * Create a struct ref_entry object for the specified dirname.
265  * dirname is the name of the directory with a trailing slash (e.g.,
266  * "refs/heads/") or "" for the top-level directory.
267  */
268 static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
269                                           const char *dirname, size_t len,
270                                           int incomplete)
271 {
272         struct ref_entry *direntry;
273         FLEX_ALLOC_MEM(direntry, name, dirname, len);
274         direntry->u.subdir.ref_store = ref_store;
275         direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
276         return direntry;
277 }
278
279 static int ref_entry_cmp(const void *a, const void *b)
280 {
281         struct ref_entry *one = *(struct ref_entry **)a;
282         struct ref_entry *two = *(struct ref_entry **)b;
283         return strcmp(one->name, two->name);
284 }
285
286 static void sort_ref_dir(struct ref_dir *dir);
287
288 struct string_slice {
289         size_t len;
290         const char *str;
291 };
292
293 static int ref_entry_cmp_sslice(const void *key_, const void *ent_)
294 {
295         const struct string_slice *key = key_;
296         const struct ref_entry *ent = *(const struct ref_entry * const *)ent_;
297         int cmp = strncmp(key->str, ent->name, key->len);
298         if (cmp)
299                 return cmp;
300         return '\0' - (unsigned char)ent->name[key->len];
301 }
302
303 /*
304  * Return the index of the entry with the given refname from the
305  * ref_dir (non-recursively), sorting dir if necessary.  Return -1 if
306  * no such entry is found.  dir must already be complete.
307  */
308 static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len)
309 {
310         struct ref_entry **r;
311         struct string_slice key;
312
313         if (refname == NULL || !dir->nr)
314                 return -1;
315
316         sort_ref_dir(dir);
317         key.len = len;
318         key.str = refname;
319         r = bsearch(&key, dir->entries, dir->nr, sizeof(*dir->entries),
320                     ref_entry_cmp_sslice);
321
322         if (r == NULL)
323                 return -1;
324
325         return r - dir->entries;
326 }
327
328 /*
329  * Search for a directory entry directly within dir (without
330  * recursing).  Sort dir if necessary.  subdirname must be a directory
331  * name (i.e., end in '/').  If mkdir is set, then create the
332  * directory if it is missing; otherwise, return NULL if the desired
333  * directory cannot be found.  dir must already be complete.
334  */
335 static struct ref_dir *search_for_subdir(struct ref_dir *dir,
336                                          const char *subdirname, size_t len,
337                                          int mkdir)
338 {
339         int entry_index = search_ref_dir(dir, subdirname, len);
340         struct ref_entry *entry;
341         if (entry_index == -1) {
342                 if (!mkdir)
343                         return NULL;
344                 /*
345                  * Since dir is complete, the absence of a subdir
346                  * means that the subdir really doesn't exist;
347                  * therefore, create an empty record for it but mark
348                  * the record complete.
349                  */
350                 entry = create_dir_entry(dir->ref_store, subdirname, len, 0);
351                 add_entry_to_dir(dir, entry);
352         } else {
353                 entry = dir->entries[entry_index];
354         }
355         return get_ref_dir(entry);
356 }
357
358 /*
359  * If refname is a reference name, find the ref_dir within the dir
360  * tree that should hold refname.  If refname is a directory name
361  * (i.e., ends in '/'), then return that ref_dir itself.  dir must
362  * represent the top-level directory and must already be complete.
363  * Sort ref_dirs and recurse into subdirectories as necessary.  If
364  * mkdir is set, then create any missing directories; otherwise,
365  * return NULL if the desired directory cannot be found.
366  */
367 static struct ref_dir *find_containing_dir(struct ref_dir *dir,
368                                            const char *refname, int mkdir)
369 {
370         const char *slash;
371         for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
372                 size_t dirnamelen = slash - refname + 1;
373                 struct ref_dir *subdir;
374                 subdir = search_for_subdir(dir, refname, dirnamelen, mkdir);
375                 if (!subdir) {
376                         dir = NULL;
377                         break;
378                 }
379                 dir = subdir;
380         }
381
382         return dir;
383 }
384
385 /*
386  * Find the value entry with the given name in dir, sorting ref_dirs
387  * and recursing into subdirectories as necessary.  If the name is not
388  * found or it corresponds to a directory entry, return NULL.
389  */
390 static struct ref_entry *find_ref(struct ref_dir *dir, const char *refname)
391 {
392         int entry_index;
393         struct ref_entry *entry;
394         dir = find_containing_dir(dir, refname, 0);
395         if (!dir)
396                 return NULL;
397         entry_index = search_ref_dir(dir, refname, strlen(refname));
398         if (entry_index == -1)
399                 return NULL;
400         entry = dir->entries[entry_index];
401         return (entry->flag & REF_DIR) ? NULL : entry;
402 }
403
404 /*
405  * Remove the entry with the given name from dir, recursing into
406  * subdirectories as necessary.  If refname is the name of a directory
407  * (i.e., ends with '/'), then remove the directory and its contents.
408  * If the removal was successful, return the number of entries
409  * remaining in the directory entry that contained the deleted entry.
410  * If the name was not found, return -1.  Please note that this
411  * function only deletes the entry from the cache; it does not delete
412  * it from the filesystem or ensure that other cache entries (which
413  * might be symbolic references to the removed entry) are updated.
414  * Nor does it remove any containing dir entries that might be made
415  * empty by the removal.  dir must represent the top-level directory
416  * and must already be complete.
417  */
418 static int remove_entry(struct ref_dir *dir, const char *refname)
419 {
420         int refname_len = strlen(refname);
421         int entry_index;
422         struct ref_entry *entry;
423         int is_dir = refname[refname_len - 1] == '/';
424         if (is_dir) {
425                 /*
426                  * refname represents a reference directory.  Remove
427                  * the trailing slash; otherwise we will get the
428                  * directory *representing* refname rather than the
429                  * one *containing* it.
430                  */
431                 char *dirname = xmemdupz(refname, refname_len - 1);
432                 dir = find_containing_dir(dir, dirname, 0);
433                 free(dirname);
434         } else {
435                 dir = find_containing_dir(dir, refname, 0);
436         }
437         if (!dir)
438                 return -1;
439         entry_index = search_ref_dir(dir, refname, refname_len);
440         if (entry_index == -1)
441                 return -1;
442         entry = dir->entries[entry_index];
443
444         memmove(&dir->entries[entry_index],
445                 &dir->entries[entry_index + 1],
446                 (dir->nr - entry_index - 1) * sizeof(*dir->entries)
447                 );
448         dir->nr--;
449         if (dir->sorted > entry_index)
450                 dir->sorted--;
451         free_ref_entry(entry);
452         return dir->nr;
453 }
454
455 /*
456  * Add a ref_entry to the ref_dir (unsorted), recursing into
457  * subdirectories as necessary.  dir must represent the top-level
458  * directory.  Return 0 on success.
459  */
460 static int add_ref(struct ref_dir *dir, struct ref_entry *ref)
461 {
462         dir = find_containing_dir(dir, ref->name, 1);
463         if (!dir)
464                 return -1;
465         add_entry_to_dir(dir, ref);
466         return 0;
467 }
468
469 /*
470  * Emit a warning and return true iff ref1 and ref2 have the same name
471  * and the same sha1.  Die if they have the same name but different
472  * sha1s.
473  */
474 static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2)
475 {
476         if (strcmp(ref1->name, ref2->name))
477                 return 0;
478
479         /* Duplicate name; make sure that they don't conflict: */
480
481         if ((ref1->flag & REF_DIR) || (ref2->flag & REF_DIR))
482                 /* This is impossible by construction */
483                 die("Reference directory conflict: %s", ref1->name);
484
485         if (oidcmp(&ref1->u.value.oid, &ref2->u.value.oid))
486                 die("Duplicated ref, and SHA1s don't match: %s", ref1->name);
487
488         warning("Duplicated ref: %s", ref1->name);
489         return 1;
490 }
491
492 /*
493  * Sort the entries in dir non-recursively (if they are not already
494  * sorted) and remove any duplicate entries.
495  */
496 static void sort_ref_dir(struct ref_dir *dir)
497 {
498         int i, j;
499         struct ref_entry *last = NULL;
500
501         /*
502          * This check also prevents passing a zero-length array to qsort(),
503          * which is a problem on some platforms.
504          */
505         if (dir->sorted == dir->nr)
506                 return;
507
508         QSORT(dir->entries, dir->nr, ref_entry_cmp);
509
510         /* Remove any duplicates: */
511         for (i = 0, j = 0; j < dir->nr; j++) {
512                 struct ref_entry *entry = dir->entries[j];
513                 if (last && is_dup_ref(last, entry))
514                         free_ref_entry(entry);
515                 else
516                         last = dir->entries[i++] = entry;
517         }
518         dir->sorted = dir->nr = i;
519 }
520
521 /*
522  * Return true if refname, which has the specified oid and flags, can
523  * be resolved to an object in the database. If the referred-to object
524  * does not exist, emit a warning and return false.
525  */
526 static int ref_resolves_to_object(const char *refname,
527                                   const struct object_id *oid,
528                                   unsigned int flags)
529 {
530         if (flags & REF_ISBROKEN)
531                 return 0;
532         if (!has_sha1_file(oid->hash)) {
533                 error("%s does not point to a valid object!", refname);
534                 return 0;
535         }
536         return 1;
537 }
538
539 /*
540  * Return true if the reference described by entry can be resolved to
541  * an object in the database; otherwise, emit a warning and return
542  * false.
543  */
544 static int entry_resolves_to_object(struct ref_entry *entry)
545 {
546         return ref_resolves_to_object(entry->name,
547                                       &entry->u.value.oid, entry->flag);
548 }
549
550 typedef int each_ref_entry_fn(struct ref_entry *entry, void *cb_data);
551
552 /*
553  * Call fn for each reference in dir that has index in the range
554  * offset <= index < dir->nr.  Recurse into subdirectories that are in
555  * that index range, sorting them before iterating.  This function
556  * does not sort dir itself; it should be sorted beforehand.  fn is
557  * called for all references, including broken ones.
558  */
559 static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
560                                     each_ref_entry_fn fn, void *cb_data)
561 {
562         int i;
563         assert(dir->sorted == dir->nr);
564         for (i = offset; i < dir->nr; i++) {
565                 struct ref_entry *entry = dir->entries[i];
566                 int retval;
567                 if (entry->flag & REF_DIR) {
568                         struct ref_dir *subdir = get_ref_dir(entry);
569                         sort_ref_dir(subdir);
570                         retval = do_for_each_entry_in_dir(subdir, 0, fn, cb_data);
571                 } else {
572                         retval = fn(entry, cb_data);
573                 }
574                 if (retval)
575                         return retval;
576         }
577         return 0;
578 }
579
580 /*
581  * Load all of the refs from the dir into our in-memory cache. The hard work
582  * of loading loose refs is done by get_ref_dir(), so we just need to recurse
583  * through all of the sub-directories. We do not even need to care about
584  * sorting, as traversal order does not matter to us.
585  */
586 static void prime_ref_dir(struct ref_dir *dir)
587 {
588         int i;
589         for (i = 0; i < dir->nr; i++) {
590                 struct ref_entry *entry = dir->entries[i];
591                 if (entry->flag & REF_DIR)
592                         prime_ref_dir(get_ref_dir(entry));
593         }
594 }
595
596 /*
597  * A level in the reference hierarchy that is currently being iterated
598  * through.
599  */
600 struct cache_ref_iterator_level {
601         /*
602          * The ref_dir being iterated over at this level. The ref_dir
603          * is sorted before being stored here.
604          */
605         struct ref_dir *dir;
606
607         /*
608          * The index of the current entry within dir (which might
609          * itself be a directory). If index == -1, then the iteration
610          * hasn't yet begun. If index == dir->nr, then the iteration
611          * through this level is over.
612          */
613         int index;
614 };
615
616 /*
617  * Represent an iteration through a ref_dir in the memory cache. The
618  * iteration recurses through subdirectories.
619  */
620 struct cache_ref_iterator {
621         struct ref_iterator base;
622
623         /*
624          * The number of levels currently on the stack. This is always
625          * at least 1, because when it becomes zero the iteration is
626          * ended and this struct is freed.
627          */
628         size_t levels_nr;
629
630         /* The number of levels that have been allocated on the stack */
631         size_t levels_alloc;
632
633         /*
634          * A stack of levels. levels[0] is the uppermost level that is
635          * being iterated over in this iteration. (This is not
636          * necessary the top level in the references hierarchy. If we
637          * are iterating through a subtree, then levels[0] will hold
638          * the ref_dir for that subtree, and subsequent levels will go
639          * on from there.)
640          */
641         struct cache_ref_iterator_level *levels;
642 };
643
644 static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator)
645 {
646         struct cache_ref_iterator *iter =
647                 (struct cache_ref_iterator *)ref_iterator;
648
649         while (1) {
650                 struct cache_ref_iterator_level *level =
651                         &iter->levels[iter->levels_nr - 1];
652                 struct ref_dir *dir = level->dir;
653                 struct ref_entry *entry;
654
655                 if (level->index == -1)
656                         sort_ref_dir(dir);
657
658                 if (++level->index == level->dir->nr) {
659                         /* This level is exhausted; pop up a level */
660                         if (--iter->levels_nr == 0)
661                                 return ref_iterator_abort(ref_iterator);
662
663                         continue;
664                 }
665
666                 entry = dir->entries[level->index];
667
668                 if (entry->flag & REF_DIR) {
669                         /* push down a level */
670                         ALLOC_GROW(iter->levels, iter->levels_nr + 1,
671                                    iter->levels_alloc);
672
673                         level = &iter->levels[iter->levels_nr++];
674                         level->dir = get_ref_dir(entry);
675                         level->index = -1;
676                 } else {
677                         iter->base.refname = entry->name;
678                         iter->base.oid = &entry->u.value.oid;
679                         iter->base.flags = entry->flag;
680                         return ITER_OK;
681                 }
682         }
683 }
684
685 static enum peel_status peel_entry(struct ref_entry *entry, int repeel);
686
687 static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator,
688                                    struct object_id *peeled)
689 {
690         struct cache_ref_iterator *iter =
691                 (struct cache_ref_iterator *)ref_iterator;
692         struct cache_ref_iterator_level *level;
693         struct ref_entry *entry;
694
695         level = &iter->levels[iter->levels_nr - 1];
696
697         if (level->index == -1)
698                 die("BUG: peel called before advance for cache iterator");
699
700         entry = level->dir->entries[level->index];
701
702         if (peel_entry(entry, 0))
703                 return -1;
704         oidcpy(peeled, &entry->u.value.peeled);
705         return 0;
706 }
707
708 static int cache_ref_iterator_abort(struct ref_iterator *ref_iterator)
709 {
710         struct cache_ref_iterator *iter =
711                 (struct cache_ref_iterator *)ref_iterator;
712
713         free(iter->levels);
714         base_ref_iterator_free(ref_iterator);
715         return ITER_DONE;
716 }
717
718 static struct ref_iterator_vtable cache_ref_iterator_vtable = {
719         cache_ref_iterator_advance,
720         cache_ref_iterator_peel,
721         cache_ref_iterator_abort
722 };
723
724 static struct ref_iterator *cache_ref_iterator_begin(struct ref_dir *dir)
725 {
726         struct cache_ref_iterator *iter;
727         struct ref_iterator *ref_iterator;
728         struct cache_ref_iterator_level *level;
729
730         iter = xcalloc(1, sizeof(*iter));
731         ref_iterator = &iter->base;
732         base_ref_iterator_init(ref_iterator, &cache_ref_iterator_vtable);
733         ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
734
735         iter->levels_nr = 1;
736         level = &iter->levels[0];
737         level->index = -1;
738         level->dir = dir;
739
740         return ref_iterator;
741 }
742
743 struct nonmatching_ref_data {
744         const struct string_list *skip;
745         const char *conflicting_refname;
746 };
747
748 static int nonmatching_ref_fn(struct ref_entry *entry, void *vdata)
749 {
750         struct nonmatching_ref_data *data = vdata;
751
752         if (data->skip && string_list_has_string(data->skip, entry->name))
753                 return 0;
754
755         data->conflicting_refname = entry->name;
756         return 1;
757 }
758
759 /*
760  * Return 0 if a reference named refname could be created without
761  * conflicting with the name of an existing reference in dir.
762  * See verify_refname_available for more information.
763  */
764 static int verify_refname_available_dir(const char *refname,
765                                         const struct string_list *extras,
766                                         const struct string_list *skip,
767                                         struct ref_dir *dir,
768                                         struct strbuf *err)
769 {
770         const char *slash;
771         const char *extra_refname;
772         int pos;
773         struct strbuf dirname = STRBUF_INIT;
774         int ret = -1;
775
776         /*
777          * For the sake of comments in this function, suppose that
778          * refname is "refs/foo/bar".
779          */
780
781         assert(err);
782
783         strbuf_grow(&dirname, strlen(refname) + 1);
784         for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
785                 /* Expand dirname to the new prefix, not including the trailing slash: */
786                 strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
787
788                 /*
789                  * We are still at a leading dir of the refname (e.g.,
790                  * "refs/foo"; if there is a reference with that name,
791                  * it is a conflict, *unless* it is in skip.
792                  */
793                 if (dir) {
794                         pos = search_ref_dir(dir, dirname.buf, dirname.len);
795                         if (pos >= 0 &&
796                             (!skip || !string_list_has_string(skip, dirname.buf))) {
797                                 /*
798                                  * We found a reference whose name is
799                                  * a proper prefix of refname; e.g.,
800                                  * "refs/foo", and is not in skip.
801                                  */
802                                 strbuf_addf(err, "'%s' exists; cannot create '%s'",
803                                             dirname.buf, refname);
804                                 goto cleanup;
805                         }
806                 }
807
808                 if (extras && string_list_has_string(extras, dirname.buf) &&
809                     (!skip || !string_list_has_string(skip, dirname.buf))) {
810                         strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
811                                     refname, dirname.buf);
812                         goto cleanup;
813                 }
814
815                 /*
816                  * Otherwise, we can try to continue our search with
817                  * the next component. So try to look up the
818                  * directory, e.g., "refs/foo/". If we come up empty,
819                  * we know there is nothing under this whole prefix,
820                  * but even in that case we still have to continue the
821                  * search for conflicts with extras.
822                  */
823                 strbuf_addch(&dirname, '/');
824                 if (dir) {
825                         pos = search_ref_dir(dir, dirname.buf, dirname.len);
826                         if (pos < 0) {
827                                 /*
828                                  * There was no directory "refs/foo/",
829                                  * so there is nothing under this
830                                  * whole prefix. So there is no need
831                                  * to continue looking for conflicting
832                                  * references. But we need to continue
833                                  * looking for conflicting extras.
834                                  */
835                                 dir = NULL;
836                         } else {
837                                 dir = get_ref_dir(dir->entries[pos]);
838                         }
839                 }
840         }
841
842         /*
843          * We are at the leaf of our refname (e.g., "refs/foo/bar").
844          * There is no point in searching for a reference with that
845          * name, because a refname isn't considered to conflict with
846          * itself. But we still need to check for references whose
847          * names are in the "refs/foo/bar/" namespace, because they
848          * *do* conflict.
849          */
850         strbuf_addstr(&dirname, refname + dirname.len);
851         strbuf_addch(&dirname, '/');
852
853         if (dir) {
854                 pos = search_ref_dir(dir, dirname.buf, dirname.len);
855
856                 if (pos >= 0) {
857                         /*
858                          * We found a directory named "$refname/"
859                          * (e.g., "refs/foo/bar/"). It is a problem
860                          * iff it contains any ref that is not in
861                          * "skip".
862                          */
863                         struct nonmatching_ref_data data;
864
865                         data.skip = skip;
866                         data.conflicting_refname = NULL;
867                         dir = get_ref_dir(dir->entries[pos]);
868                         sort_ref_dir(dir);
869                         if (do_for_each_entry_in_dir(dir, 0, nonmatching_ref_fn, &data)) {
870                                 strbuf_addf(err, "'%s' exists; cannot create '%s'",
871                                             data.conflicting_refname, refname);
872                                 goto cleanup;
873                         }
874                 }
875         }
876
877         extra_refname = find_descendant_ref(dirname.buf, extras, skip);
878         if (extra_refname)
879                 strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
880                             refname, extra_refname);
881         else
882                 ret = 0;
883
884 cleanup:
885         strbuf_release(&dirname);
886         return ret;
887 }
888
889 struct packed_ref_cache {
890         struct ref_entry *root;
891
892         /*
893          * Count of references to the data structure in this instance,
894          * including the pointer from files_ref_store::packed if any.
895          * The data will not be freed as long as the reference count
896          * is nonzero.
897          */
898         unsigned int referrers;
899
900         /*
901          * Iff the packed-refs file associated with this instance is
902          * currently locked for writing, this points at the associated
903          * lock (which is owned by somebody else).  The referrer count
904          * is also incremented when the file is locked and decremented
905          * when it is unlocked.
906          */
907         struct lock_file *lock;
908
909         /* The metadata from when this packed-refs cache was read */
910         struct stat_validity validity;
911 };
912
913 /*
914  * Future: need to be in "struct repository"
915  * when doing a full libification.
916  */
917 struct files_ref_store {
918         struct ref_store base;
919         unsigned int store_flags;
920
921         char *gitdir;
922         char *gitcommondir;
923         char *packed_refs_path;
924
925         struct ref_entry *loose;
926         struct packed_ref_cache *packed;
927 };
928
929 /* Lock used for the main packed-refs file: */
930 static struct lock_file packlock;
931
932 /*
933  * Increment the reference count of *packed_refs.
934  */
935 static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
936 {
937         packed_refs->referrers++;
938 }
939
940 /*
941  * Decrease the reference count of *packed_refs.  If it goes to zero,
942  * free *packed_refs and return true; otherwise return false.
943  */
944 static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
945 {
946         if (!--packed_refs->referrers) {
947                 free_ref_entry(packed_refs->root);
948                 stat_validity_clear(&packed_refs->validity);
949                 free(packed_refs);
950                 return 1;
951         } else {
952                 return 0;
953         }
954 }
955
956 static void clear_packed_ref_cache(struct files_ref_store *refs)
957 {
958         if (refs->packed) {
959                 struct packed_ref_cache *packed_refs = refs->packed;
960
961                 if (packed_refs->lock)
962                         die("internal error: packed-ref cache cleared while locked");
963                 refs->packed = NULL;
964                 release_packed_ref_cache(packed_refs);
965         }
966 }
967
968 static void clear_loose_ref_cache(struct files_ref_store *refs)
969 {
970         if (refs->loose) {
971                 free_ref_entry(refs->loose);
972                 refs->loose = NULL;
973         }
974 }
975
976 /*
977  * Create a new submodule ref cache and add it to the internal
978  * set of caches.
979  */
980 static struct ref_store *files_ref_store_create(const char *gitdir,
981                                                 unsigned int flags)
982 {
983         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
984         struct ref_store *ref_store = (struct ref_store *)refs;
985         struct strbuf sb = STRBUF_INIT;
986
987         base_ref_store_init(ref_store, &refs_be_files);
988         refs->store_flags = flags;
989
990         refs->gitdir = xstrdup(gitdir);
991         get_common_dir_noenv(&sb, gitdir);
992         refs->gitcommondir = strbuf_detach(&sb, NULL);
993         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
994         refs->packed_refs_path = strbuf_detach(&sb, NULL);
995
996         return ref_store;
997 }
998
999 /*
1000  * Die if refs is not the main ref store. caller is used in any
1001  * necessary error messages.
1002  */
1003 static void files_assert_main_repository(struct files_ref_store *refs,
1004                                          const char *caller)
1005 {
1006         if (refs->store_flags & REF_STORE_MAIN)
1007                 return;
1008
1009         die("BUG: operation %s only allowed for main ref store", caller);
1010 }
1011
1012 /*
1013  * Downcast ref_store to files_ref_store. Die if ref_store is not a
1014  * files_ref_store. required_flags is compared with ref_store's
1015  * store_flags to ensure the ref_store has all required capabilities.
1016  * "caller" is used in any necessary error messages.
1017  */
1018 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
1019                                               unsigned int required_flags,
1020                                               const char *caller)
1021 {
1022         struct files_ref_store *refs;
1023
1024         if (ref_store->be != &refs_be_files)
1025                 die("BUG: ref_store is type \"%s\" not \"files\" in %s",
1026                     ref_store->be->name, caller);
1027
1028         refs = (struct files_ref_store *)ref_store;
1029
1030         if ((refs->store_flags & required_flags) != required_flags)
1031                 die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
1032                     caller, required_flags, refs->store_flags);
1033
1034         return refs;
1035 }
1036
1037 /* The length of a peeled reference line in packed-refs, including EOL: */
1038 #define PEELED_LINE_LENGTH 42
1039
1040 /*
1041  * The packed-refs header line that we write out.  Perhaps other
1042  * traits will be added later.  The trailing space is required.
1043  */
1044 static const char PACKED_REFS_HEADER[] =
1045         "# pack-refs with: peeled fully-peeled \n";
1046
1047 /*
1048  * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
1049  * Return a pointer to the refname within the line (null-terminated),
1050  * or NULL if there was a problem.
1051  */
1052 static const char *parse_ref_line(struct strbuf *line, unsigned char *sha1)
1053 {
1054         const char *ref;
1055
1056         /*
1057          * 42: the answer to everything.
1058          *
1059          * In this case, it happens to be the answer to
1060          *  40 (length of sha1 hex representation)
1061          *  +1 (space in between hex and name)
1062          *  +1 (newline at the end of the line)
1063          */
1064         if (line->len <= 42)
1065                 return NULL;
1066
1067         if (get_sha1_hex(line->buf, sha1) < 0)
1068                 return NULL;
1069         if (!isspace(line->buf[40]))
1070                 return NULL;
1071
1072         ref = line->buf + 41;
1073         if (isspace(*ref))
1074                 return NULL;
1075
1076         if (line->buf[line->len - 1] != '\n')
1077                 return NULL;
1078         line->buf[--line->len] = 0;
1079
1080         return ref;
1081 }
1082
1083 /*
1084  * Read f, which is a packed-refs file, into dir.
1085  *
1086  * A comment line of the form "# pack-refs with: " may contain zero or
1087  * more traits. We interpret the traits as follows:
1088  *
1089  *   No traits:
1090  *
1091  *      Probably no references are peeled. But if the file contains a
1092  *      peeled value for a reference, we will use it.
1093  *
1094  *   peeled:
1095  *
1096  *      References under "refs/tags/", if they *can* be peeled, *are*
1097  *      peeled in this file. References outside of "refs/tags/" are
1098  *      probably not peeled even if they could have been, but if we find
1099  *      a peeled value for such a reference we will use it.
1100  *
1101  *   fully-peeled:
1102  *
1103  *      All references in the file that can be peeled are peeled.
1104  *      Inversely (and this is more important), any references in the
1105  *      file for which no peeled value is recorded is not peelable. This
1106  *      trait should typically be written alongside "peeled" for
1107  *      compatibility with older clients, but we do not require it
1108  *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
1109  */
1110 static void read_packed_refs(FILE *f, struct ref_dir *dir)
1111 {
1112         struct ref_entry *last = NULL;
1113         struct strbuf line = STRBUF_INIT;
1114         enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
1115
1116         while (strbuf_getwholeline(&line, f, '\n') != EOF) {
1117                 unsigned char sha1[20];
1118                 const char *refname;
1119                 const char *traits;
1120
1121                 if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
1122                         if (strstr(traits, " fully-peeled "))
1123                                 peeled = PEELED_FULLY;
1124                         else if (strstr(traits, " peeled "))
1125                                 peeled = PEELED_TAGS;
1126                         /* perhaps other traits later as well */
1127                         continue;
1128                 }
1129
1130                 refname = parse_ref_line(&line, sha1);
1131                 if (refname) {
1132                         int flag = REF_ISPACKED;
1133
1134                         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1135                                 if (!refname_is_safe(refname))
1136                                         die("packed refname is dangerous: %s", refname);
1137                                 hashclr(sha1);
1138                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
1139                         }
1140                         last = create_ref_entry(refname, sha1, flag, 0);
1141                         if (peeled == PEELED_FULLY ||
1142                             (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
1143                                 last->flag |= REF_KNOWS_PEELED;
1144                         add_ref(dir, last);
1145                         continue;
1146                 }
1147                 if (last &&
1148                     line.buf[0] == '^' &&
1149                     line.len == PEELED_LINE_LENGTH &&
1150                     line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
1151                     !get_sha1_hex(line.buf + 1, sha1)) {
1152                         hashcpy(last->u.value.peeled.hash, sha1);
1153                         /*
1154                          * Regardless of what the file header said,
1155                          * we definitely know the value of *this*
1156                          * reference:
1157                          */
1158                         last->flag |= REF_KNOWS_PEELED;
1159                 }
1160         }
1161
1162         strbuf_release(&line);
1163 }
1164
1165 static const char *files_packed_refs_path(struct files_ref_store *refs)
1166 {
1167         return refs->packed_refs_path;
1168 }
1169
1170 static void files_reflog_path(struct files_ref_store *refs,
1171                               struct strbuf *sb,
1172                               const char *refname)
1173 {
1174         if (!refname) {
1175                 /*
1176                  * FIXME: of course this is wrong in multi worktree
1177                  * setting. To be fixed real soon.
1178                  */
1179                 strbuf_addf(sb, "%s/logs", refs->gitcommondir);
1180                 return;
1181         }
1182
1183         switch (ref_type(refname)) {
1184         case REF_TYPE_PER_WORKTREE:
1185         case REF_TYPE_PSEUDOREF:
1186                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
1187                 break;
1188         case REF_TYPE_NORMAL:
1189                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
1190                 break;
1191         default:
1192                 die("BUG: unknown ref type %d of ref %s",
1193                     ref_type(refname), refname);
1194         }
1195 }
1196
1197 static void files_ref_path(struct files_ref_store *refs,
1198                            struct strbuf *sb,
1199                            const char *refname)
1200 {
1201         switch (ref_type(refname)) {
1202         case REF_TYPE_PER_WORKTREE:
1203         case REF_TYPE_PSEUDOREF:
1204                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
1205                 break;
1206         case REF_TYPE_NORMAL:
1207                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
1208                 break;
1209         default:
1210                 die("BUG: unknown ref type %d of ref %s",
1211                     ref_type(refname), refname);
1212         }
1213 }
1214
1215 /*
1216  * Get the packed_ref_cache for the specified files_ref_store,
1217  * creating it if necessary.
1218  */
1219 static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
1220 {
1221         const char *packed_refs_file = files_packed_refs_path(refs);
1222
1223         if (refs->packed &&
1224             !stat_validity_check(&refs->packed->validity, packed_refs_file))
1225                 clear_packed_ref_cache(refs);
1226
1227         if (!refs->packed) {
1228                 FILE *f;
1229
1230                 refs->packed = xcalloc(1, sizeof(*refs->packed));
1231                 acquire_packed_ref_cache(refs->packed);
1232                 refs->packed->root = create_dir_entry(refs, "", 0, 0);
1233                 f = fopen(packed_refs_file, "r");
1234                 if (f) {
1235                         stat_validity_update(&refs->packed->validity, fileno(f));
1236                         read_packed_refs(f, get_ref_dir(refs->packed->root));
1237                         fclose(f);
1238                 }
1239         }
1240         return refs->packed;
1241 }
1242
1243 static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
1244 {
1245         return get_ref_dir(packed_ref_cache->root);
1246 }
1247
1248 static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
1249 {
1250         return get_packed_ref_dir(get_packed_ref_cache(refs));
1251 }
1252
1253 /*
1254  * Add a reference to the in-memory packed reference cache.  This may
1255  * only be called while the packed-refs file is locked (see
1256  * lock_packed_refs()).  To actually write the packed-refs file, call
1257  * commit_packed_refs().
1258  */
1259 static void add_packed_ref(struct files_ref_store *refs,
1260                            const char *refname, const unsigned char *sha1)
1261 {
1262         struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
1263
1264         if (!packed_ref_cache->lock)
1265                 die("internal error: packed refs not locked");
1266         add_ref(get_packed_ref_dir(packed_ref_cache),
1267                 create_ref_entry(refname, sha1, REF_ISPACKED, 1));
1268 }
1269
1270 /*
1271  * Read the loose references from the namespace dirname into dir
1272  * (without recursing).  dirname must end with '/'.  dir must be the
1273  * directory entry corresponding to dirname.
1274  */
1275 static void read_loose_refs(const char *dirname, struct ref_dir *dir)
1276 {
1277         struct files_ref_store *refs = dir->ref_store;
1278         DIR *d;
1279         struct dirent *de;
1280         int dirnamelen = strlen(dirname);
1281         struct strbuf refname;
1282         struct strbuf path = STRBUF_INIT;
1283         size_t path_baselen;
1284
1285         files_ref_path(refs, &path, dirname);
1286         path_baselen = path.len;
1287
1288         d = opendir(path.buf);
1289         if (!d) {
1290                 strbuf_release(&path);
1291                 return;
1292         }
1293
1294         strbuf_init(&refname, dirnamelen + 257);
1295         strbuf_add(&refname, dirname, dirnamelen);
1296
1297         while ((de = readdir(d)) != NULL) {
1298                 unsigned char sha1[20];
1299                 struct stat st;
1300                 int flag;
1301
1302                 if (de->d_name[0] == '.')
1303                         continue;
1304                 if (ends_with(de->d_name, ".lock"))
1305                         continue;
1306                 strbuf_addstr(&refname, de->d_name);
1307                 strbuf_addstr(&path, de->d_name);
1308                 if (stat(path.buf, &st) < 0) {
1309                         ; /* silently ignore */
1310                 } else if (S_ISDIR(st.st_mode)) {
1311                         strbuf_addch(&refname, '/');
1312                         add_entry_to_dir(dir,
1313                                          create_dir_entry(refs, refname.buf,
1314                                                           refname.len, 1));
1315                 } else {
1316                         if (!refs_resolve_ref_unsafe(&refs->base,
1317                                                      refname.buf,
1318                                                      RESOLVE_REF_READING,
1319                                                      sha1, &flag)) {
1320                                 hashclr(sha1);
1321                                 flag |= REF_ISBROKEN;
1322                         } else if (is_null_sha1(sha1)) {
1323                                 /*
1324                                  * It is so astronomically unlikely
1325                                  * that NULL_SHA1 is the SHA-1 of an
1326                                  * actual object that we consider its
1327                                  * appearance in a loose reference
1328                                  * file to be repo corruption
1329                                  * (probably due to a software bug).
1330                                  */
1331                                 flag |= REF_ISBROKEN;
1332                         }
1333
1334                         if (check_refname_format(refname.buf,
1335                                                  REFNAME_ALLOW_ONELEVEL)) {
1336                                 if (!refname_is_safe(refname.buf))
1337                                         die("loose refname is dangerous: %s", refname.buf);
1338                                 hashclr(sha1);
1339                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
1340                         }
1341                         add_entry_to_dir(dir,
1342                                          create_ref_entry(refname.buf, sha1, flag, 0));
1343                 }
1344                 strbuf_setlen(&refname, dirnamelen);
1345                 strbuf_setlen(&path, path_baselen);
1346         }
1347         strbuf_release(&refname);
1348         strbuf_release(&path);
1349         closedir(d);
1350 }
1351
1352 static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
1353 {
1354         if (!refs->loose) {
1355                 /*
1356                  * Mark the top-level directory complete because we
1357                  * are about to read the only subdirectory that can
1358                  * hold references:
1359                  */
1360                 refs->loose = create_dir_entry(refs, "", 0, 0);
1361                 /*
1362                  * Create an incomplete entry for "refs/":
1363                  */
1364                 add_entry_to_dir(get_ref_dir(refs->loose),
1365                                  create_dir_entry(refs, "refs/", 5, 1));
1366         }
1367         return get_ref_dir(refs->loose);
1368 }
1369
1370 /*
1371  * Return the ref_entry for the given refname from the packed
1372  * references.  If it does not exist, return NULL.
1373  */
1374 static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
1375                                         const char *refname)
1376 {
1377         return find_ref(get_packed_refs(refs), refname);
1378 }
1379
1380 /*
1381  * A loose ref file doesn't exist; check for a packed ref.
1382  */
1383 static int resolve_packed_ref(struct files_ref_store *refs,
1384                               const char *refname,
1385                               unsigned char *sha1, unsigned int *flags)
1386 {
1387         struct ref_entry *entry;
1388
1389         /*
1390          * The loose reference file does not exist; check for a packed
1391          * reference.
1392          */
1393         entry = get_packed_ref(refs, refname);
1394         if (entry) {
1395                 hashcpy(sha1, entry->u.value.oid.hash);
1396                 *flags |= REF_ISPACKED;
1397                 return 0;
1398         }
1399         /* refname is not a packed reference. */
1400         return -1;
1401 }
1402
1403 static int files_read_raw_ref(struct ref_store *ref_store,
1404                               const char *refname, unsigned char *sha1,
1405                               struct strbuf *referent, unsigned int *type)
1406 {
1407         struct files_ref_store *refs =
1408                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
1409         struct strbuf sb_contents = STRBUF_INIT;
1410         struct strbuf sb_path = STRBUF_INIT;
1411         const char *path;
1412         const char *buf;
1413         struct stat st;
1414         int fd;
1415         int ret = -1;
1416         int save_errno;
1417         int remaining_retries = 3;
1418
1419         *type = 0;
1420         strbuf_reset(&sb_path);
1421
1422         files_ref_path(refs, &sb_path, refname);
1423
1424         path = sb_path.buf;
1425
1426 stat_ref:
1427         /*
1428          * We might have to loop back here to avoid a race
1429          * condition: first we lstat() the file, then we try
1430          * to read it as a link or as a file.  But if somebody
1431          * changes the type of the file (file <-> directory
1432          * <-> symlink) between the lstat() and reading, then
1433          * we don't want to report that as an error but rather
1434          * try again starting with the lstat().
1435          *
1436          * We'll keep a count of the retries, though, just to avoid
1437          * any confusing situation sending us into an infinite loop.
1438          */
1439
1440         if (remaining_retries-- <= 0)
1441                 goto out;
1442
1443         if (lstat(path, &st) < 0) {
1444                 if (errno != ENOENT)
1445                         goto out;
1446                 if (resolve_packed_ref(refs, refname, sha1, type)) {
1447                         errno = ENOENT;
1448                         goto out;
1449                 }
1450                 ret = 0;
1451                 goto out;
1452         }
1453
1454         /* Follow "normalized" - ie "refs/.." symlinks by hand */
1455         if (S_ISLNK(st.st_mode)) {
1456                 strbuf_reset(&sb_contents);
1457                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
1458                         if (errno == ENOENT || errno == EINVAL)
1459                                 /* inconsistent with lstat; retry */
1460                                 goto stat_ref;
1461                         else
1462                                 goto out;
1463                 }
1464                 if (starts_with(sb_contents.buf, "refs/") &&
1465                     !check_refname_format(sb_contents.buf, 0)) {
1466                         strbuf_swap(&sb_contents, referent);
1467                         *type |= REF_ISSYMREF;
1468                         ret = 0;
1469                         goto out;
1470                 }
1471                 /*
1472                  * It doesn't look like a refname; fall through to just
1473                  * treating it like a non-symlink, and reading whatever it
1474                  * points to.
1475                  */
1476         }
1477
1478         /* Is it a directory? */
1479         if (S_ISDIR(st.st_mode)) {
1480                 /*
1481                  * Even though there is a directory where the loose
1482                  * ref is supposed to be, there could still be a
1483                  * packed ref:
1484                  */
1485                 if (resolve_packed_ref(refs, refname, sha1, type)) {
1486                         errno = EISDIR;
1487                         goto out;
1488                 }
1489                 ret = 0;
1490                 goto out;
1491         }
1492
1493         /*
1494          * Anything else, just open it and try to use it as
1495          * a ref
1496          */
1497         fd = open(path, O_RDONLY);
1498         if (fd < 0) {
1499                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
1500                         /* inconsistent with lstat; retry */
1501                         goto stat_ref;
1502                 else
1503                         goto out;
1504         }
1505         strbuf_reset(&sb_contents);
1506         if (strbuf_read(&sb_contents, fd, 256) < 0) {
1507                 int save_errno = errno;
1508                 close(fd);
1509                 errno = save_errno;
1510                 goto out;
1511         }
1512         close(fd);
1513         strbuf_rtrim(&sb_contents);
1514         buf = sb_contents.buf;
1515         if (starts_with(buf, "ref:")) {
1516                 buf += 4;
1517                 while (isspace(*buf))
1518                         buf++;
1519
1520                 strbuf_reset(referent);
1521                 strbuf_addstr(referent, buf);
1522                 *type |= REF_ISSYMREF;
1523                 ret = 0;
1524                 goto out;
1525         }
1526
1527         /*
1528          * Please note that FETCH_HEAD has additional
1529          * data after the sha.
1530          */
1531         if (get_sha1_hex(buf, sha1) ||
1532             (buf[40] != '\0' && !isspace(buf[40]))) {
1533                 *type |= REF_ISBROKEN;
1534                 errno = EINVAL;
1535                 goto out;
1536         }
1537
1538         ret = 0;
1539
1540 out:
1541         save_errno = errno;
1542         strbuf_release(&sb_path);
1543         strbuf_release(&sb_contents);
1544         errno = save_errno;
1545         return ret;
1546 }
1547
1548 static void unlock_ref(struct ref_lock *lock)
1549 {
1550         /* Do not free lock->lk -- atexit() still looks at them */
1551         if (lock->lk)
1552                 rollback_lock_file(lock->lk);
1553         free(lock->ref_name);
1554         free(lock);
1555 }
1556
1557 /*
1558  * Lock refname, without following symrefs, and set *lock_p to point
1559  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
1560  * and type similarly to read_raw_ref().
1561  *
1562  * The caller must verify that refname is a "safe" reference name (in
1563  * the sense of refname_is_safe()) before calling this function.
1564  *
1565  * If the reference doesn't already exist, verify that refname doesn't
1566  * have a D/F conflict with any existing references. extras and skip
1567  * are passed to verify_refname_available_dir() for this check.
1568  *
1569  * If mustexist is not set and the reference is not found or is
1570  * broken, lock the reference anyway but clear sha1.
1571  *
1572  * Return 0 on success. On failure, write an error message to err and
1573  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
1574  *
1575  * Implementation note: This function is basically
1576  *
1577  *     lock reference
1578  *     read_raw_ref()
1579  *
1580  * but it includes a lot more code to
1581  * - Deal with possible races with other processes
1582  * - Avoid calling verify_refname_available_dir() when it can be
1583  *   avoided, namely if we were successfully able to read the ref
1584  * - Generate informative error messages in the case of failure
1585  */
1586 static int lock_raw_ref(struct files_ref_store *refs,
1587                         const char *refname, int mustexist,
1588                         const struct string_list *extras,
1589                         const struct string_list *skip,
1590                         struct ref_lock **lock_p,
1591                         struct strbuf *referent,
1592                         unsigned int *type,
1593                         struct strbuf *err)
1594 {
1595         struct ref_lock *lock;
1596         struct strbuf ref_file = STRBUF_INIT;
1597         int attempts_remaining = 3;
1598         int ret = TRANSACTION_GENERIC_ERROR;
1599
1600         assert(err);
1601         files_assert_main_repository(refs, "lock_raw_ref");
1602
1603         *type = 0;
1604
1605         /* First lock the file so it can't change out from under us. */
1606
1607         *lock_p = lock = xcalloc(1, sizeof(*lock));
1608
1609         lock->ref_name = xstrdup(refname);
1610         files_ref_path(refs, &ref_file, refname);
1611
1612 retry:
1613         switch (safe_create_leading_directories(ref_file.buf)) {
1614         case SCLD_OK:
1615                 break; /* success */
1616         case SCLD_EXISTS:
1617                 /*
1618                  * Suppose refname is "refs/foo/bar". We just failed
1619                  * to create the containing directory, "refs/foo",
1620                  * because there was a non-directory in the way. This
1621                  * indicates a D/F conflict, probably because of
1622                  * another reference such as "refs/foo". There is no
1623                  * reason to expect this error to be transitory.
1624                  */
1625                 if (refs_verify_refname_available(&refs->base, refname,
1626                                                   extras, skip, err)) {
1627                         if (mustexist) {
1628                                 /*
1629                                  * To the user the relevant error is
1630                                  * that the "mustexist" reference is
1631                                  * missing:
1632                                  */
1633                                 strbuf_reset(err);
1634                                 strbuf_addf(err, "unable to resolve reference '%s'",
1635                                             refname);
1636                         } else {
1637                                 /*
1638                                  * The error message set by
1639                                  * verify_refname_available_dir() is OK.
1640                                  */
1641                                 ret = TRANSACTION_NAME_CONFLICT;
1642                         }
1643                 } else {
1644                         /*
1645                          * The file that is in the way isn't a loose
1646                          * reference. Report it as a low-level
1647                          * failure.
1648                          */
1649                         strbuf_addf(err, "unable to create lock file %s.lock; "
1650                                     "non-directory in the way",
1651                                     ref_file.buf);
1652                 }
1653                 goto error_return;
1654         case SCLD_VANISHED:
1655                 /* Maybe another process was tidying up. Try again. */
1656                 if (--attempts_remaining > 0)
1657                         goto retry;
1658                 /* fall through */
1659         default:
1660                 strbuf_addf(err, "unable to create directory for %s",
1661                             ref_file.buf);
1662                 goto error_return;
1663         }
1664
1665         if (!lock->lk)
1666                 lock->lk = xcalloc(1, sizeof(struct lock_file));
1667
1668         if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
1669                 if (errno == ENOENT && --attempts_remaining > 0) {
1670                         /*
1671                          * Maybe somebody just deleted one of the
1672                          * directories leading to ref_file.  Try
1673                          * again:
1674                          */
1675                         goto retry;
1676                 } else {
1677                         unable_to_lock_message(ref_file.buf, errno, err);
1678                         goto error_return;
1679                 }
1680         }
1681
1682         /*
1683          * Now we hold the lock and can read the reference without
1684          * fear that its value will change.
1685          */
1686
1687         if (files_read_raw_ref(&refs->base, refname,
1688                                lock->old_oid.hash, referent, type)) {
1689                 if (errno == ENOENT) {
1690                         if (mustexist) {
1691                                 /* Garden variety missing reference. */
1692                                 strbuf_addf(err, "unable to resolve reference '%s'",
1693                                             refname);
1694                                 goto error_return;
1695                         } else {
1696                                 /*
1697                                  * Reference is missing, but that's OK. We
1698                                  * know that there is not a conflict with
1699                                  * another loose reference because
1700                                  * (supposing that we are trying to lock
1701                                  * reference "refs/foo/bar"):
1702                                  *
1703                                  * - We were successfully able to create
1704                                  *   the lockfile refs/foo/bar.lock, so we
1705                                  *   know there cannot be a loose reference
1706                                  *   named "refs/foo".
1707                                  *
1708                                  * - We got ENOENT and not EISDIR, so we
1709                                  *   know that there cannot be a loose
1710                                  *   reference named "refs/foo/bar/baz".
1711                                  */
1712                         }
1713                 } else if (errno == EISDIR) {
1714                         /*
1715                          * There is a directory in the way. It might have
1716                          * contained references that have been deleted. If
1717                          * we don't require that the reference already
1718                          * exists, try to remove the directory so that it
1719                          * doesn't cause trouble when we want to rename the
1720                          * lockfile into place later.
1721                          */
1722                         if (mustexist) {
1723                                 /* Garden variety missing reference. */
1724                                 strbuf_addf(err, "unable to resolve reference '%s'",
1725                                             refname);
1726                                 goto error_return;
1727                         } else if (remove_dir_recursively(&ref_file,
1728                                                           REMOVE_DIR_EMPTY_ONLY)) {
1729                                 if (verify_refname_available_dir(
1730                                                     refname, extras, skip,
1731                                                     get_loose_refs(refs),
1732                                                     err)) {
1733                                         /*
1734                                          * The error message set by
1735                                          * verify_refname_available() is OK.
1736                                          */
1737                                         ret = TRANSACTION_NAME_CONFLICT;
1738                                         goto error_return;
1739                                 } else {
1740                                         /*
1741                                          * We can't delete the directory,
1742                                          * but we also don't know of any
1743                                          * references that it should
1744                                          * contain.
1745                                          */
1746                                         strbuf_addf(err, "there is a non-empty directory '%s' "
1747                                                     "blocking reference '%s'",
1748                                                     ref_file.buf, refname);
1749                                         goto error_return;
1750                                 }
1751                         }
1752                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
1753                         strbuf_addf(err, "unable to resolve reference '%s': "
1754                                     "reference broken", refname);
1755                         goto error_return;
1756                 } else {
1757                         strbuf_addf(err, "unable to resolve reference '%s': %s",
1758                                     refname, strerror(errno));
1759                         goto error_return;
1760                 }
1761
1762                 /*
1763                  * If the ref did not exist and we are creating it,
1764                  * make sure there is no existing packed ref whose
1765                  * name begins with our refname, nor a packed ref
1766                  * whose name is a proper prefix of our refname.
1767                  */
1768                 if (verify_refname_available_dir(
1769                                     refname, extras, skip,
1770                                     get_packed_refs(refs),
1771                                     err)) {
1772                         goto error_return;
1773                 }
1774         }
1775
1776         ret = 0;
1777         goto out;
1778
1779 error_return:
1780         unlock_ref(lock);
1781         *lock_p = NULL;
1782
1783 out:
1784         strbuf_release(&ref_file);
1785         return ret;
1786 }
1787
1788 /*
1789  * Peel the entry (if possible) and return its new peel_status.  If
1790  * repeel is true, re-peel the entry even if there is an old peeled
1791  * value that is already stored in it.
1792  *
1793  * It is OK to call this function with a packed reference entry that
1794  * might be stale and might even refer to an object that has since
1795  * been garbage-collected.  In such a case, if the entry has
1796  * REF_KNOWS_PEELED then leave the status unchanged and return
1797  * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
1798  */
1799 static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
1800 {
1801         enum peel_status status;
1802
1803         if (entry->flag & REF_KNOWS_PEELED) {
1804                 if (repeel) {
1805                         entry->flag &= ~REF_KNOWS_PEELED;
1806                         oidclr(&entry->u.value.peeled);
1807                 } else {
1808                         return is_null_oid(&entry->u.value.peeled) ?
1809                                 PEEL_NON_TAG : PEEL_PEELED;
1810                 }
1811         }
1812         if (entry->flag & REF_ISBROKEN)
1813                 return PEEL_BROKEN;
1814         if (entry->flag & REF_ISSYMREF)
1815                 return PEEL_IS_SYMREF;
1816
1817         status = peel_object(entry->u.value.oid.hash, entry->u.value.peeled.hash);
1818         if (status == PEEL_PEELED || status == PEEL_NON_TAG)
1819                 entry->flag |= REF_KNOWS_PEELED;
1820         return status;
1821 }
1822
1823 static int files_peel_ref(struct ref_store *ref_store,
1824                           const char *refname, unsigned char *sha1)
1825 {
1826         struct files_ref_store *refs =
1827                 files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
1828                                "peel_ref");
1829         int flag;
1830         unsigned char base[20];
1831
1832         if (current_ref_iter && current_ref_iter->refname == refname) {
1833                 struct object_id peeled;
1834
1835                 if (ref_iterator_peel(current_ref_iter, &peeled))
1836                         return -1;
1837                 hashcpy(sha1, peeled.hash);
1838                 return 0;
1839         }
1840
1841         if (refs_read_ref_full(ref_store, refname,
1842                                RESOLVE_REF_READING, base, &flag))
1843                 return -1;
1844
1845         /*
1846          * If the reference is packed, read its ref_entry from the
1847          * cache in the hope that we already know its peeled value.
1848          * We only try this optimization on packed references because
1849          * (a) forcing the filling of the loose reference cache could
1850          * be expensive and (b) loose references anyway usually do not
1851          * have REF_KNOWS_PEELED.
1852          */
1853         if (flag & REF_ISPACKED) {
1854                 struct ref_entry *r = get_packed_ref(refs, refname);
1855                 if (r) {
1856                         if (peel_entry(r, 0))
1857                                 return -1;
1858                         hashcpy(sha1, r->u.value.peeled.hash);
1859                         return 0;
1860                 }
1861         }
1862
1863         return peel_object(base, sha1);
1864 }
1865
1866 struct files_ref_iterator {
1867         struct ref_iterator base;
1868
1869         struct packed_ref_cache *packed_ref_cache;
1870         struct ref_iterator *iter0;
1871         unsigned int flags;
1872 };
1873
1874 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
1875 {
1876         struct files_ref_iterator *iter =
1877                 (struct files_ref_iterator *)ref_iterator;
1878         int ok;
1879
1880         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
1881                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
1882                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
1883                         continue;
1884
1885                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
1886                     !ref_resolves_to_object(iter->iter0->refname,
1887                                             iter->iter0->oid,
1888                                             iter->iter0->flags))
1889                         continue;
1890
1891                 iter->base.refname = iter->iter0->refname;
1892                 iter->base.oid = iter->iter0->oid;
1893                 iter->base.flags = iter->iter0->flags;
1894                 return ITER_OK;
1895         }
1896
1897         iter->iter0 = NULL;
1898         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
1899                 ok = ITER_ERROR;
1900
1901         return ok;
1902 }
1903
1904 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
1905                                    struct object_id *peeled)
1906 {
1907         struct files_ref_iterator *iter =
1908                 (struct files_ref_iterator *)ref_iterator;
1909
1910         return ref_iterator_peel(iter->iter0, peeled);
1911 }
1912
1913 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
1914 {
1915         struct files_ref_iterator *iter =
1916                 (struct files_ref_iterator *)ref_iterator;
1917         int ok = ITER_DONE;
1918
1919         if (iter->iter0)
1920                 ok = ref_iterator_abort(iter->iter0);
1921
1922         release_packed_ref_cache(iter->packed_ref_cache);
1923         base_ref_iterator_free(ref_iterator);
1924         return ok;
1925 }
1926
1927 static struct ref_iterator_vtable files_ref_iterator_vtable = {
1928         files_ref_iterator_advance,
1929         files_ref_iterator_peel,
1930         files_ref_iterator_abort
1931 };
1932
1933 static struct ref_iterator *files_ref_iterator_begin(
1934                 struct ref_store *ref_store,
1935                 const char *prefix, unsigned int flags)
1936 {
1937         struct files_ref_store *refs;
1938         struct ref_dir *loose_dir, *packed_dir;
1939         struct ref_iterator *loose_iter, *packed_iter;
1940         struct files_ref_iterator *iter;
1941         struct ref_iterator *ref_iterator;
1942
1943         if (ref_paranoia < 0)
1944                 ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1945         if (ref_paranoia)
1946                 flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1947
1948         refs = files_downcast(ref_store,
1949                               REF_STORE_READ | (ref_paranoia ? 0 : REF_STORE_ODB),
1950                               "ref_iterator_begin");
1951
1952         iter = xcalloc(1, sizeof(*iter));
1953         ref_iterator = &iter->base;
1954         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
1955
1956         /*
1957          * We must make sure that all loose refs are read before
1958          * accessing the packed-refs file; this avoids a race
1959          * condition if loose refs are migrated to the packed-refs
1960          * file by a simultaneous process, but our in-memory view is
1961          * from before the migration. We ensure this as follows:
1962          * First, we call prime_ref_dir(), which pre-reads the loose
1963          * references for the subtree into the cache. (If they've
1964          * already been read, that's OK; we only need to guarantee
1965          * that they're read before the packed refs, not *how much*
1966          * before.) After that, we call get_packed_ref_cache(), which
1967          * internally checks whether the packed-ref cache is up to
1968          * date with what is on disk, and re-reads it if not.
1969          */
1970
1971         loose_dir = get_loose_refs(refs);
1972
1973         if (prefix && *prefix)
1974                 loose_dir = find_containing_dir(loose_dir, prefix, 0);
1975
1976         if (loose_dir) {
1977                 prime_ref_dir(loose_dir);
1978                 loose_iter = cache_ref_iterator_begin(loose_dir);
1979         } else {
1980                 /* There's nothing to iterate over. */
1981                 loose_iter = empty_ref_iterator_begin();
1982         }
1983
1984         iter->packed_ref_cache = get_packed_ref_cache(refs);
1985         acquire_packed_ref_cache(iter->packed_ref_cache);
1986         packed_dir = get_packed_ref_dir(iter->packed_ref_cache);
1987
1988         if (prefix && *prefix)
1989                 packed_dir = find_containing_dir(packed_dir, prefix, 0);
1990
1991         if (packed_dir) {
1992                 packed_iter = cache_ref_iterator_begin(packed_dir);
1993         } else {
1994                 /* There's nothing to iterate over. */
1995                 packed_iter = empty_ref_iterator_begin();
1996         }
1997
1998         iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
1999         iter->flags = flags;
2000
2001         return ref_iterator;
2002 }
2003
2004 /*
2005  * Verify that the reference locked by lock has the value old_sha1.
2006  * Fail if the reference doesn't exist and mustexist is set. Return 0
2007  * on success. On error, write an error message to err, set errno, and
2008  * return a negative value.
2009  */
2010 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
2011                        const unsigned char *old_sha1, int mustexist,
2012                        struct strbuf *err)
2013 {
2014         assert(err);
2015
2016         if (refs_read_ref_full(ref_store, lock->ref_name,
2017                                mustexist ? RESOLVE_REF_READING : 0,
2018                                lock->old_oid.hash, NULL)) {
2019                 if (old_sha1) {
2020                         int save_errno = errno;
2021                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
2022                         errno = save_errno;
2023                         return -1;
2024                 } else {
2025                         oidclr(&lock->old_oid);
2026                         return 0;
2027                 }
2028         }
2029         if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
2030                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
2031                             lock->ref_name,
2032                             oid_to_hex(&lock->old_oid),
2033                             sha1_to_hex(old_sha1));
2034                 errno = EBUSY;
2035                 return -1;
2036         }
2037         return 0;
2038 }
2039
2040 static int remove_empty_directories(struct strbuf *path)
2041 {
2042         /*
2043          * we want to create a file but there is a directory there;
2044          * if that is an empty directory (or a directory that contains
2045          * only empty directories), remove them.
2046          */
2047         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
2048 }
2049
2050 static int create_reflock(const char *path, void *cb)
2051 {
2052         struct lock_file *lk = cb;
2053
2054         return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
2055 }
2056
2057 /*
2058  * Locks a ref returning the lock on success and NULL on failure.
2059  * On failure errno is set to something meaningful.
2060  */
2061 static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
2062                                             const char *refname,
2063                                             const unsigned char *old_sha1,
2064                                             const struct string_list *extras,
2065                                             const struct string_list *skip,
2066                                             unsigned int flags, int *type,
2067                                             struct strbuf *err)
2068 {
2069         struct strbuf ref_file = STRBUF_INIT;
2070         struct ref_lock *lock;
2071         int last_errno = 0;
2072         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
2073         int resolve_flags = RESOLVE_REF_NO_RECURSE;
2074         int resolved;
2075
2076         files_assert_main_repository(refs, "lock_ref_sha1_basic");
2077         assert(err);
2078
2079         lock = xcalloc(1, sizeof(struct ref_lock));
2080
2081         if (mustexist)
2082                 resolve_flags |= RESOLVE_REF_READING;
2083         if (flags & REF_DELETING)
2084                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
2085
2086         files_ref_path(refs, &ref_file, refname);
2087         resolved = !!refs_resolve_ref_unsafe(&refs->base,
2088                                              refname, resolve_flags,
2089                                              lock->old_oid.hash, type);
2090         if (!resolved && errno == EISDIR) {
2091                 /*
2092                  * we are trying to lock foo but we used to
2093                  * have foo/bar which now does not exist;
2094                  * it is normal for the empty directory 'foo'
2095                  * to remain.
2096                  */
2097                 if (remove_empty_directories(&ref_file)) {
2098                         last_errno = errno;
2099                         if (!verify_refname_available_dir(
2100                                             refname, extras, skip,
2101                                             get_loose_refs(refs), err))
2102                                 strbuf_addf(err, "there are still refs under '%s'",
2103                                             refname);
2104                         goto error_return;
2105                 }
2106                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
2107                                                      refname, resolve_flags,
2108                                                      lock->old_oid.hash, type);
2109         }
2110         if (!resolved) {
2111                 last_errno = errno;
2112                 if (last_errno != ENOTDIR ||
2113                     !verify_refname_available_dir(
2114                                     refname, extras, skip,
2115                                     get_loose_refs(refs), err))
2116                         strbuf_addf(err, "unable to resolve reference '%s': %s",
2117                                     refname, strerror(last_errno));
2118
2119                 goto error_return;
2120         }
2121
2122         /*
2123          * If the ref did not exist and we are creating it, make sure
2124          * there is no existing packed ref whose name begins with our
2125          * refname, nor a packed ref whose name is a proper prefix of
2126          * our refname.
2127          */
2128         if (is_null_oid(&lock->old_oid) &&
2129             verify_refname_available_dir(refname, extras, skip,
2130                                          get_packed_refs(refs),
2131                                          err)) {
2132                 last_errno = ENOTDIR;
2133                 goto error_return;
2134         }
2135
2136         lock->lk = xcalloc(1, sizeof(struct lock_file));
2137
2138         lock->ref_name = xstrdup(refname);
2139
2140         if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
2141                 last_errno = errno;
2142                 unable_to_lock_message(ref_file.buf, errno, err);
2143                 goto error_return;
2144         }
2145
2146         if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
2147                 last_errno = errno;
2148                 goto error_return;
2149         }
2150         goto out;
2151
2152  error_return:
2153         unlock_ref(lock);
2154         lock = NULL;
2155
2156  out:
2157         strbuf_release(&ref_file);
2158         errno = last_errno;
2159         return lock;
2160 }
2161
2162 /*
2163  * Write an entry to the packed-refs file for the specified refname.
2164  * If peeled is non-NULL, write it as the entry's peeled value.
2165  */
2166 static void write_packed_entry(FILE *fh, char *refname, unsigned char *sha1,
2167                                unsigned char *peeled)
2168 {
2169         fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
2170         if (peeled)
2171                 fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
2172 }
2173
2174 /*
2175  * An each_ref_entry_fn that writes the entry to a packed-refs file.
2176  */
2177 static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
2178 {
2179         enum peel_status peel_status = peel_entry(entry, 0);
2180
2181         if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2182                 error("internal error: %s is not a valid packed reference!",
2183                       entry->name);
2184         write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
2185                            peel_status == PEEL_PEELED ?
2186                            entry->u.value.peeled.hash : NULL);
2187         return 0;
2188 }
2189
2190 /*
2191  * Lock the packed-refs file for writing. Flags is passed to
2192  * hold_lock_file_for_update(). Return 0 on success. On errors, set
2193  * errno appropriately and return a nonzero value.
2194  */
2195 static int lock_packed_refs(struct files_ref_store *refs, int flags)
2196 {
2197         static int timeout_configured = 0;
2198         static int timeout_value = 1000;
2199         struct packed_ref_cache *packed_ref_cache;
2200
2201         files_assert_main_repository(refs, "lock_packed_refs");
2202
2203         if (!timeout_configured) {
2204                 git_config_get_int("core.packedrefstimeout", &timeout_value);
2205                 timeout_configured = 1;
2206         }
2207
2208         if (hold_lock_file_for_update_timeout(
2209                             &packlock, files_packed_refs_path(refs),
2210                             flags, timeout_value) < 0)
2211                 return -1;
2212         /*
2213          * Get the current packed-refs while holding the lock.  If the
2214          * packed-refs file has been modified since we last read it,
2215          * this will automatically invalidate the cache and re-read
2216          * the packed-refs file.
2217          */
2218         packed_ref_cache = get_packed_ref_cache(refs);
2219         packed_ref_cache->lock = &packlock;
2220         /* Increment the reference count to prevent it from being freed: */
2221         acquire_packed_ref_cache(packed_ref_cache);
2222         return 0;
2223 }
2224
2225 /*
2226  * Write the current version of the packed refs cache from memory to
2227  * disk. The packed-refs file must already be locked for writing (see
2228  * lock_packed_refs()). Return zero on success. On errors, set errno
2229  * and return a nonzero value
2230  */
2231 static int commit_packed_refs(struct files_ref_store *refs)
2232 {
2233         struct packed_ref_cache *packed_ref_cache =
2234                 get_packed_ref_cache(refs);
2235         int error = 0;
2236         int save_errno = 0;
2237         FILE *out;
2238
2239         files_assert_main_repository(refs, "commit_packed_refs");
2240
2241         if (!packed_ref_cache->lock)
2242                 die("internal error: packed-refs not locked");
2243
2244         out = fdopen_lock_file(packed_ref_cache->lock, "w");
2245         if (!out)
2246                 die_errno("unable to fdopen packed-refs descriptor");
2247
2248         fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
2249         do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
2250                                  0, write_packed_entry_fn, out);
2251
2252         if (commit_lock_file(packed_ref_cache->lock)) {
2253                 save_errno = errno;
2254                 error = -1;
2255         }
2256         packed_ref_cache->lock = NULL;
2257         release_packed_ref_cache(packed_ref_cache);
2258         errno = save_errno;
2259         return error;
2260 }
2261
2262 /*
2263  * Rollback the lockfile for the packed-refs file, and discard the
2264  * in-memory packed reference cache.  (The packed-refs file will be
2265  * read anew if it is needed again after this function is called.)
2266  */
2267 static void rollback_packed_refs(struct files_ref_store *refs)
2268 {
2269         struct packed_ref_cache *packed_ref_cache =
2270                 get_packed_ref_cache(refs);
2271
2272         files_assert_main_repository(refs, "rollback_packed_refs");
2273
2274         if (!packed_ref_cache->lock)
2275                 die("internal error: packed-refs not locked");
2276         rollback_lock_file(packed_ref_cache->lock);
2277         packed_ref_cache->lock = NULL;
2278         release_packed_ref_cache(packed_ref_cache);
2279         clear_packed_ref_cache(refs);
2280 }
2281
2282 struct ref_to_prune {
2283         struct ref_to_prune *next;
2284         unsigned char sha1[20];
2285         char name[FLEX_ARRAY];
2286 };
2287
2288 struct pack_refs_cb_data {
2289         unsigned int flags;
2290         struct ref_dir *packed_refs;
2291         struct ref_to_prune *ref_to_prune;
2292 };
2293
2294 /*
2295  * An each_ref_entry_fn that is run over loose references only.  If
2296  * the loose reference can be packed, add an entry in the packed ref
2297  * cache.  If the reference should be pruned, also add it to
2298  * ref_to_prune in the pack_refs_cb_data.
2299  */
2300 static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
2301 {
2302         struct pack_refs_cb_data *cb = cb_data;
2303         enum peel_status peel_status;
2304         struct ref_entry *packed_entry;
2305         int is_tag_ref = starts_with(entry->name, "refs/tags/");
2306
2307         /* Do not pack per-worktree refs: */
2308         if (ref_type(entry->name) != REF_TYPE_NORMAL)
2309                 return 0;
2310
2311         /* ALWAYS pack tags */
2312         if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
2313                 return 0;
2314
2315         /* Do not pack symbolic or broken refs: */
2316         if ((entry->flag & REF_ISSYMREF) || !entry_resolves_to_object(entry))
2317                 return 0;
2318
2319         /* Add a packed ref cache entry equivalent to the loose entry. */
2320         peel_status = peel_entry(entry, 1);
2321         if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2322                 die("internal error peeling reference %s (%s)",
2323                     entry->name, oid_to_hex(&entry->u.value.oid));
2324         packed_entry = find_ref(cb->packed_refs, entry->name);
2325         if (packed_entry) {
2326                 /* Overwrite existing packed entry with info from loose entry */
2327                 packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
2328                 oidcpy(&packed_entry->u.value.oid, &entry->u.value.oid);
2329         } else {
2330                 packed_entry = create_ref_entry(entry->name, entry->u.value.oid.hash,
2331                                                 REF_ISPACKED | REF_KNOWS_PEELED, 0);
2332                 add_ref(cb->packed_refs, packed_entry);
2333         }
2334         oidcpy(&packed_entry->u.value.peeled, &entry->u.value.peeled);
2335
2336         /* Schedule the loose reference for pruning if requested. */
2337         if ((cb->flags & PACK_REFS_PRUNE)) {
2338                 struct ref_to_prune *n;
2339                 FLEX_ALLOC_STR(n, name, entry->name);
2340                 hashcpy(n->sha1, entry->u.value.oid.hash);
2341                 n->next = cb->ref_to_prune;
2342                 cb->ref_to_prune = n;
2343         }
2344         return 0;
2345 }
2346
2347 enum {
2348         REMOVE_EMPTY_PARENTS_REF = 0x01,
2349         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
2350 };
2351
2352 /*
2353  * Remove empty parent directories associated with the specified
2354  * reference and/or its reflog, but spare [logs/]refs/ and immediate
2355  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
2356  * REMOVE_EMPTY_PARENTS_REFLOG.
2357  */
2358 static void try_remove_empty_parents(struct files_ref_store *refs,
2359                                      const char *refname,
2360                                      unsigned int flags)
2361 {
2362         struct strbuf buf = STRBUF_INIT;
2363         struct strbuf sb = STRBUF_INIT;
2364         char *p, *q;
2365         int i;
2366
2367         strbuf_addstr(&buf, refname);
2368         p = buf.buf;
2369         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
2370                 while (*p && *p != '/')
2371                         p++;
2372                 /* tolerate duplicate slashes; see check_refname_format() */
2373                 while (*p == '/')
2374                         p++;
2375         }
2376         q = buf.buf + buf.len;
2377         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
2378                 while (q > p && *q != '/')
2379                         q--;
2380                 while (q > p && *(q-1) == '/')
2381                         q--;
2382                 if (q == p)
2383                         break;
2384                 strbuf_setlen(&buf, q - buf.buf);
2385
2386                 strbuf_reset(&sb);
2387                 files_ref_path(refs, &sb, buf.buf);
2388                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
2389                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
2390
2391                 strbuf_reset(&sb);
2392                 files_reflog_path(refs, &sb, buf.buf);
2393                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
2394                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
2395         }
2396         strbuf_release(&buf);
2397         strbuf_release(&sb);
2398 }
2399
2400 /* make sure nobody touched the ref, and unlink */
2401 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
2402 {
2403         struct ref_transaction *transaction;
2404         struct strbuf err = STRBUF_INIT;
2405
2406         if (check_refname_format(r->name, 0))
2407                 return;
2408
2409         transaction = ref_store_transaction_begin(&refs->base, &err);
2410         if (!transaction ||
2411             ref_transaction_delete(transaction, r->name, r->sha1,
2412                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
2413             ref_transaction_commit(transaction, &err)) {
2414                 ref_transaction_free(transaction);
2415                 error("%s", err.buf);
2416                 strbuf_release(&err);
2417                 return;
2418         }
2419         ref_transaction_free(transaction);
2420         strbuf_release(&err);
2421 }
2422
2423 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
2424 {
2425         while (r) {
2426                 prune_ref(refs, r);
2427                 r = r->next;
2428         }
2429 }
2430
2431 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
2432 {
2433         struct files_ref_store *refs =
2434                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
2435                                "pack_refs");
2436         struct pack_refs_cb_data cbdata;
2437
2438         memset(&cbdata, 0, sizeof(cbdata));
2439         cbdata.flags = flags;
2440
2441         lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
2442         cbdata.packed_refs = get_packed_refs(refs);
2443
2444         do_for_each_entry_in_dir(get_loose_refs(refs), 0,
2445                                  pack_if_possible_fn, &cbdata);
2446
2447         if (commit_packed_refs(refs))
2448                 die_errno("unable to overwrite old ref-pack file");
2449
2450         prune_refs(refs, cbdata.ref_to_prune);
2451         return 0;
2452 }
2453
2454 /*
2455  * Rewrite the packed-refs file, omitting any refs listed in
2456  * 'refnames'. On error, leave packed-refs unchanged, write an error
2457  * message to 'err', and return a nonzero value.
2458  *
2459  * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
2460  */
2461 static int repack_without_refs(struct files_ref_store *refs,
2462                                struct string_list *refnames, struct strbuf *err)
2463 {
2464         struct ref_dir *packed;
2465         struct string_list_item *refname;
2466         int ret, needs_repacking = 0, removed = 0;
2467
2468         files_assert_main_repository(refs, "repack_without_refs");
2469         assert(err);
2470
2471         /* Look for a packed ref */
2472         for_each_string_list_item(refname, refnames) {
2473                 if (get_packed_ref(refs, refname->string)) {
2474                         needs_repacking = 1;
2475                         break;
2476                 }
2477         }
2478
2479         /* Avoid locking if we have nothing to do */
2480         if (!needs_repacking)
2481                 return 0; /* no refname exists in packed refs */
2482
2483         if (lock_packed_refs(refs, 0)) {
2484                 unable_to_lock_message(files_packed_refs_path(refs), errno, err);
2485                 return -1;
2486         }
2487         packed = get_packed_refs(refs);
2488
2489         /* Remove refnames from the cache */
2490         for_each_string_list_item(refname, refnames)
2491                 if (remove_entry(packed, refname->string) != -1)
2492                         removed = 1;
2493         if (!removed) {
2494                 /*
2495                  * All packed entries disappeared while we were
2496                  * acquiring the lock.
2497                  */
2498                 rollback_packed_refs(refs);
2499                 return 0;
2500         }
2501
2502         /* Write what remains */
2503         ret = commit_packed_refs(refs);
2504         if (ret)
2505                 strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
2506                             strerror(errno));
2507         return ret;
2508 }
2509
2510 static int files_delete_refs(struct ref_store *ref_store,
2511                              struct string_list *refnames, unsigned int flags)
2512 {
2513         struct files_ref_store *refs =
2514                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
2515         struct strbuf err = STRBUF_INIT;
2516         int i, result = 0;
2517
2518         if (!refnames->nr)
2519                 return 0;
2520
2521         result = repack_without_refs(refs, refnames, &err);
2522         if (result) {
2523                 /*
2524                  * If we failed to rewrite the packed-refs file, then
2525                  * it is unsafe to try to remove loose refs, because
2526                  * doing so might expose an obsolete packed value for
2527                  * a reference that might even point at an object that
2528                  * has been garbage collected.
2529                  */
2530                 if (refnames->nr == 1)
2531                         error(_("could not delete reference %s: %s"),
2532                               refnames->items[0].string, err.buf);
2533                 else
2534                         error(_("could not delete references: %s"), err.buf);
2535
2536                 goto out;
2537         }
2538
2539         for (i = 0; i < refnames->nr; i++) {
2540                 const char *refname = refnames->items[i].string;
2541
2542                 if (refs_delete_ref(&refs->base, NULL, refname, NULL, flags))
2543                         result |= error(_("could not remove reference %s"), refname);
2544         }
2545
2546 out:
2547         strbuf_release(&err);
2548         return result;
2549 }
2550
2551 /*
2552  * People using contrib's git-new-workdir have .git/logs/refs ->
2553  * /some/other/path/.git/logs/refs, and that may live on another device.
2554  *
2555  * IOW, to avoid cross device rename errors, the temporary renamed log must
2556  * live into logs/refs.
2557  */
2558 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
2559
2560 struct rename_cb {
2561         const char *tmp_renamed_log;
2562         int true_errno;
2563 };
2564
2565 static int rename_tmp_log_callback(const char *path, void *cb_data)
2566 {
2567         struct rename_cb *cb = cb_data;
2568
2569         if (rename(cb->tmp_renamed_log, path)) {
2570                 /*
2571                  * rename(a, b) when b is an existing directory ought
2572                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
2573                  * Sheesh. Record the true errno for error reporting,
2574                  * but report EISDIR to raceproof_create_file() so
2575                  * that it knows to retry.
2576                  */
2577                 cb->true_errno = errno;
2578                 if (errno == ENOTDIR)
2579                         errno = EISDIR;
2580                 return -1;
2581         } else {
2582                 return 0;
2583         }
2584 }
2585
2586 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
2587 {
2588         struct strbuf path = STRBUF_INIT;
2589         struct strbuf tmp = STRBUF_INIT;
2590         struct rename_cb cb;
2591         int ret;
2592
2593         files_reflog_path(refs, &path, newrefname);
2594         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
2595         cb.tmp_renamed_log = tmp.buf;
2596         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
2597         if (ret) {
2598                 if (errno == EISDIR)
2599                         error("directory not empty: %s", path.buf);
2600                 else
2601                         error("unable to move logfile %s to %s: %s",
2602                               tmp.buf, path.buf,
2603                               strerror(cb.true_errno));
2604         }
2605
2606         strbuf_release(&path);
2607         strbuf_release(&tmp);
2608         return ret;
2609 }
2610
2611 static int files_verify_refname_available(struct ref_store *ref_store,
2612                                           const char *newname,
2613                                           const struct string_list *extras,
2614                                           const struct string_list *skip,
2615                                           struct strbuf *err)
2616 {
2617         struct files_ref_store *refs =
2618                 files_downcast(ref_store, REF_STORE_READ, "verify_refname_available");
2619         struct ref_dir *packed_refs = get_packed_refs(refs);
2620         struct ref_dir *loose_refs = get_loose_refs(refs);
2621
2622         if (verify_refname_available_dir(newname, extras, skip,
2623                                          packed_refs, err) ||
2624             verify_refname_available_dir(newname, extras, skip,
2625                                          loose_refs, err))
2626                 return -1;
2627
2628         return 0;
2629 }
2630
2631 static int write_ref_to_lockfile(struct ref_lock *lock,
2632                                  const unsigned char *sha1, struct strbuf *err);
2633 static int commit_ref_update(struct files_ref_store *refs,
2634                              struct ref_lock *lock,
2635                              const unsigned char *sha1, const char *logmsg,
2636                              struct strbuf *err);
2637
2638 static int files_rename_ref(struct ref_store *ref_store,
2639                             const char *oldrefname, const char *newrefname,
2640                             const char *logmsg)
2641 {
2642         struct files_ref_store *refs =
2643                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
2644         unsigned char sha1[20], orig_sha1[20];
2645         int flag = 0, logmoved = 0;
2646         struct ref_lock *lock;
2647         struct stat loginfo;
2648         struct strbuf sb_oldref = STRBUF_INIT;
2649         struct strbuf sb_newref = STRBUF_INIT;
2650         struct strbuf tmp_renamed_log = STRBUF_INIT;
2651         int log, ret;
2652         struct strbuf err = STRBUF_INIT;
2653
2654         files_reflog_path(refs, &sb_oldref, oldrefname);
2655         files_reflog_path(refs, &sb_newref, newrefname);
2656         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
2657
2658         log = !lstat(sb_oldref.buf, &loginfo);
2659         if (log && S_ISLNK(loginfo.st_mode)) {
2660                 ret = error("reflog for %s is a symlink", oldrefname);
2661                 goto out;
2662         }
2663
2664         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
2665                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2666                                 orig_sha1, &flag)) {
2667                 ret = error("refname %s not found", oldrefname);
2668                 goto out;
2669         }
2670
2671         if (flag & REF_ISSYMREF) {
2672                 ret = error("refname %s is a symbolic ref, renaming it is not supported",
2673                             oldrefname);
2674                 goto out;
2675         }
2676         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
2677                 ret = 1;
2678                 goto out;
2679         }
2680
2681         if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
2682                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
2683                             oldrefname, strerror(errno));
2684                 goto out;
2685         }
2686
2687         if (refs_delete_ref(&refs->base, logmsg, oldrefname,
2688                             orig_sha1, REF_NODEREF)) {
2689                 error("unable to delete old %s", oldrefname);
2690                 goto rollback;
2691         }
2692
2693         /*
2694          * Since we are doing a shallow lookup, sha1 is not the
2695          * correct value to pass to delete_ref as old_sha1. But that
2696          * doesn't matter, because an old_sha1 check wouldn't add to
2697          * the safety anyway; we want to delete the reference whatever
2698          * its current value.
2699          */
2700         if (!refs_read_ref_full(&refs->base, newrefname,
2701                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2702                                 sha1, NULL) &&
2703             refs_delete_ref(&refs->base, NULL, newrefname,
2704                             NULL, REF_NODEREF)) {
2705                 if (errno == EISDIR) {
2706                         struct strbuf path = STRBUF_INIT;
2707                         int result;
2708
2709                         files_ref_path(refs, &path, newrefname);
2710                         result = remove_empty_directories(&path);
2711                         strbuf_release(&path);
2712
2713                         if (result) {
2714                                 error("Directory not empty: %s", newrefname);
2715                                 goto rollback;
2716                         }
2717                 } else {
2718                         error("unable to delete existing %s", newrefname);
2719                         goto rollback;
2720                 }
2721         }
2722
2723         if (log && rename_tmp_log(refs, newrefname))
2724                 goto rollback;
2725
2726         logmoved = log;
2727
2728         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
2729                                    REF_NODEREF, NULL, &err);
2730         if (!lock) {
2731                 error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
2732                 strbuf_release(&err);
2733                 goto rollback;
2734         }
2735         hashcpy(lock->old_oid.hash, orig_sha1);
2736
2737         if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2738             commit_ref_update(refs, lock, orig_sha1, logmsg, &err)) {
2739                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
2740                 strbuf_release(&err);
2741                 goto rollback;
2742         }
2743
2744         ret = 0;
2745         goto out;
2746
2747  rollback:
2748         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
2749                                    REF_NODEREF, NULL, &err);
2750         if (!lock) {
2751                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
2752                 strbuf_release(&err);
2753                 goto rollbacklog;
2754         }
2755
2756         flag = log_all_ref_updates;
2757         log_all_ref_updates = LOG_REFS_NONE;
2758         if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2759             commit_ref_update(refs, lock, orig_sha1, NULL, &err)) {
2760                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
2761                 strbuf_release(&err);
2762         }
2763         log_all_ref_updates = flag;
2764
2765  rollbacklog:
2766         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
2767                 error("unable to restore logfile %s from %s: %s",
2768                         oldrefname, newrefname, strerror(errno));
2769         if (!logmoved && log &&
2770             rename(tmp_renamed_log.buf, sb_oldref.buf))
2771                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
2772                         oldrefname, strerror(errno));
2773         ret = 1;
2774  out:
2775         strbuf_release(&sb_newref);
2776         strbuf_release(&sb_oldref);
2777         strbuf_release(&tmp_renamed_log);
2778
2779         return ret;
2780 }
2781
2782 static int close_ref(struct ref_lock *lock)
2783 {
2784         if (close_lock_file(lock->lk))
2785                 return -1;
2786         return 0;
2787 }
2788
2789 static int commit_ref(struct ref_lock *lock)
2790 {
2791         char *path = get_locked_file_path(lock->lk);
2792         struct stat st;
2793
2794         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
2795                 /*
2796                  * There is a directory at the path we want to rename
2797                  * the lockfile to. Hopefully it is empty; try to
2798                  * delete it.
2799                  */
2800                 size_t len = strlen(path);
2801                 struct strbuf sb_path = STRBUF_INIT;
2802
2803                 strbuf_attach(&sb_path, path, len, len);
2804
2805                 /*
2806                  * If this fails, commit_lock_file() will also fail
2807                  * and will report the problem.
2808                  */
2809                 remove_empty_directories(&sb_path);
2810                 strbuf_release(&sb_path);
2811         } else {
2812                 free(path);
2813         }
2814
2815         if (commit_lock_file(lock->lk))
2816                 return -1;
2817         return 0;
2818 }
2819
2820 static int open_or_create_logfile(const char *path, void *cb)
2821 {
2822         int *fd = cb;
2823
2824         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
2825         return (*fd < 0) ? -1 : 0;
2826 }
2827
2828 /*
2829  * Create a reflog for a ref. If force_create = 0, only create the
2830  * reflog for certain refs (those for which should_autocreate_reflog
2831  * returns non-zero). Otherwise, create it regardless of the reference
2832  * name. If the logfile already existed or was created, return 0 and
2833  * set *logfd to the file descriptor opened for appending to the file.
2834  * If no logfile exists and we decided not to create one, return 0 and
2835  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
2836  * return -1.
2837  */
2838 static int log_ref_setup(struct files_ref_store *refs,
2839                          const char *refname, int force_create,
2840                          int *logfd, struct strbuf *err)
2841 {
2842         struct strbuf logfile_sb = STRBUF_INIT;
2843         char *logfile;
2844
2845         files_reflog_path(refs, &logfile_sb, refname);
2846         logfile = strbuf_detach(&logfile_sb, NULL);
2847
2848         if (force_create || should_autocreate_reflog(refname)) {
2849                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
2850                         if (errno == ENOENT)
2851                                 strbuf_addf(err, "unable to create directory for '%s': "
2852                                             "%s", logfile, strerror(errno));
2853                         else if (errno == EISDIR)
2854                                 strbuf_addf(err, "there are still logs under '%s'",
2855                                             logfile);
2856                         else
2857                                 strbuf_addf(err, "unable to append to '%s': %s",
2858                                             logfile, strerror(errno));
2859
2860                         goto error;
2861                 }
2862         } else {
2863                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
2864                 if (*logfd < 0) {
2865                         if (errno == ENOENT || errno == EISDIR) {
2866                                 /*
2867                                  * The logfile doesn't already exist,
2868                                  * but that is not an error; it only
2869                                  * means that we won't write log
2870                                  * entries to it.
2871                                  */
2872                                 ;
2873                         } else {
2874                                 strbuf_addf(err, "unable to append to '%s': %s",
2875                                             logfile, strerror(errno));
2876                                 goto error;
2877                         }
2878                 }
2879         }
2880
2881         if (*logfd >= 0)
2882                 adjust_shared_perm(logfile);
2883
2884         free(logfile);
2885         return 0;
2886
2887 error:
2888         free(logfile);
2889         return -1;
2890 }
2891
2892 static int files_create_reflog(struct ref_store *ref_store,
2893                                const char *refname, int force_create,
2894                                struct strbuf *err)
2895 {
2896         struct files_ref_store *refs =
2897                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
2898         int fd;
2899
2900         if (log_ref_setup(refs, refname, force_create, &fd, err))
2901                 return -1;
2902
2903         if (fd >= 0)
2904                 close(fd);
2905
2906         return 0;
2907 }
2908
2909 static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
2910                             const unsigned char *new_sha1,
2911                             const char *committer, const char *msg)
2912 {
2913         int msglen, written;
2914         unsigned maxlen, len;
2915         char *logrec;
2916
2917         msglen = msg ? strlen(msg) : 0;
2918         maxlen = strlen(committer) + msglen + 100;
2919         logrec = xmalloc(maxlen);
2920         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
2921                         sha1_to_hex(old_sha1),
2922                         sha1_to_hex(new_sha1),
2923                         committer);
2924         if (msglen)
2925                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
2926
2927         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
2928         free(logrec);
2929         if (written != len)
2930                 return -1;
2931
2932         return 0;
2933 }
2934
2935 static int files_log_ref_write(struct files_ref_store *refs,
2936                                const char *refname, const unsigned char *old_sha1,
2937                                const unsigned char *new_sha1, const char *msg,
2938                                int flags, struct strbuf *err)
2939 {
2940         int logfd, result;
2941
2942         if (log_all_ref_updates == LOG_REFS_UNSET)
2943                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
2944
2945         result = log_ref_setup(refs, refname,
2946                                flags & REF_FORCE_CREATE_REFLOG,
2947                                &logfd, err);
2948
2949         if (result)
2950                 return result;
2951
2952         if (logfd < 0)
2953                 return 0;
2954         result = log_ref_write_fd(logfd, old_sha1, new_sha1,
2955                                   git_committer_info(0), msg);
2956         if (result) {
2957                 struct strbuf sb = STRBUF_INIT;
2958                 int save_errno = errno;
2959
2960                 files_reflog_path(refs, &sb, refname);
2961                 strbuf_addf(err, "unable to append to '%s': %s",
2962                             sb.buf, strerror(save_errno));
2963                 strbuf_release(&sb);
2964                 close(logfd);
2965                 return -1;
2966         }
2967         if (close(logfd)) {
2968                 struct strbuf sb = STRBUF_INIT;
2969                 int save_errno = errno;
2970
2971                 files_reflog_path(refs, &sb, refname);
2972                 strbuf_addf(err, "unable to append to '%s': %s",
2973                             sb.buf, strerror(save_errno));
2974                 strbuf_release(&sb);
2975                 return -1;
2976         }
2977         return 0;
2978 }
2979
2980 /*
2981  * Write sha1 into the open lockfile, then close the lockfile. On
2982  * errors, rollback the lockfile, fill in *err and
2983  * return -1.
2984  */
2985 static int write_ref_to_lockfile(struct ref_lock *lock,
2986                                  const unsigned char *sha1, struct strbuf *err)
2987 {
2988         static char term = '\n';
2989         struct object *o;
2990         int fd;
2991
2992         o = parse_object(sha1);
2993         if (!o) {
2994                 strbuf_addf(err,
2995                             "trying to write ref '%s' with nonexistent object %s",
2996                             lock->ref_name, sha1_to_hex(sha1));
2997                 unlock_ref(lock);
2998                 return -1;
2999         }
3000         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
3001                 strbuf_addf(err,
3002                             "trying to write non-commit object %s to branch '%s'",
3003                             sha1_to_hex(sha1), lock->ref_name);
3004                 unlock_ref(lock);
3005                 return -1;
3006         }
3007         fd = get_lock_file_fd(lock->lk);
3008         if (write_in_full(fd, sha1_to_hex(sha1), 40) != 40 ||
3009             write_in_full(fd, &term, 1) != 1 ||
3010             close_ref(lock) < 0) {
3011                 strbuf_addf(err,
3012                             "couldn't write '%s'", get_lock_file_path(lock->lk));
3013                 unlock_ref(lock);
3014                 return -1;
3015         }
3016         return 0;
3017 }
3018
3019 /*
3020  * Commit a change to a loose reference that has already been written
3021  * to the loose reference lockfile. Also update the reflogs if
3022  * necessary, using the specified lockmsg (which can be NULL).
3023  */
3024 static int commit_ref_update(struct files_ref_store *refs,
3025                              struct ref_lock *lock,
3026                              const unsigned char *sha1, const char *logmsg,
3027                              struct strbuf *err)
3028 {
3029         files_assert_main_repository(refs, "commit_ref_update");
3030
3031         clear_loose_ref_cache(refs);
3032         if (files_log_ref_write(refs, lock->ref_name,
3033                                 lock->old_oid.hash, sha1,
3034                                 logmsg, 0, err)) {
3035                 char *old_msg = strbuf_detach(err, NULL);
3036                 strbuf_addf(err, "cannot update the ref '%s': %s",
3037                             lock->ref_name, old_msg);
3038                 free(old_msg);
3039                 unlock_ref(lock);
3040                 return -1;
3041         }
3042
3043         if (strcmp(lock->ref_name, "HEAD") != 0) {
3044                 /*
3045                  * Special hack: If a branch is updated directly and HEAD
3046                  * points to it (may happen on the remote side of a push
3047                  * for example) then logically the HEAD reflog should be
3048                  * updated too.
3049                  * A generic solution implies reverse symref information,
3050                  * but finding all symrefs pointing to the given branch
3051                  * would be rather costly for this rare event (the direct
3052                  * update of a branch) to be worth it.  So let's cheat and
3053                  * check with HEAD only which should cover 99% of all usage
3054                  * scenarios (even 100% of the default ones).
3055                  */
3056                 unsigned char head_sha1[20];
3057                 int head_flag;
3058                 const char *head_ref;
3059
3060                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
3061                                                    RESOLVE_REF_READING,
3062                                                    head_sha1, &head_flag);
3063                 if (head_ref && (head_flag & REF_ISSYMREF) &&
3064                     !strcmp(head_ref, lock->ref_name)) {
3065                         struct strbuf log_err = STRBUF_INIT;
3066                         if (files_log_ref_write(refs, "HEAD",
3067                                                 lock->old_oid.hash, sha1,
3068                                                 logmsg, 0, &log_err)) {
3069                                 error("%s", log_err.buf);
3070                                 strbuf_release(&log_err);
3071                         }
3072                 }
3073         }
3074
3075         if (commit_ref(lock)) {
3076                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3077                 unlock_ref(lock);
3078                 return -1;
3079         }
3080
3081         unlock_ref(lock);
3082         return 0;
3083 }
3084
3085 static int create_ref_symlink(struct ref_lock *lock, const char *target)
3086 {
3087         int ret = -1;
3088 #ifndef NO_SYMLINK_HEAD
3089         char *ref_path = get_locked_file_path(lock->lk);
3090         unlink(ref_path);
3091         ret = symlink(target, ref_path);
3092         free(ref_path);
3093
3094         if (ret)
3095                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
3096 #endif
3097         return ret;
3098 }
3099
3100 static void update_symref_reflog(struct files_ref_store *refs,
3101                                  struct ref_lock *lock, const char *refname,
3102                                  const char *target, const char *logmsg)
3103 {
3104         struct strbuf err = STRBUF_INIT;
3105         unsigned char new_sha1[20];
3106         if (logmsg &&
3107             !refs_read_ref_full(&refs->base, target,
3108                                 RESOLVE_REF_READING, new_sha1, NULL) &&
3109             files_log_ref_write(refs, refname, lock->old_oid.hash,
3110                                 new_sha1, logmsg, 0, &err)) {
3111                 error("%s", err.buf);
3112                 strbuf_release(&err);
3113         }
3114 }
3115
3116 static int create_symref_locked(struct files_ref_store *refs,
3117                                 struct ref_lock *lock, const char *refname,
3118                                 const char *target, const char *logmsg)
3119 {
3120         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
3121                 update_symref_reflog(refs, lock, refname, target, logmsg);
3122                 return 0;
3123         }
3124
3125         if (!fdopen_lock_file(lock->lk, "w"))
3126                 return error("unable to fdopen %s: %s",
3127                              lock->lk->tempfile.filename.buf, strerror(errno));
3128
3129         update_symref_reflog(refs, lock, refname, target, logmsg);
3130
3131         /* no error check; commit_ref will check ferror */
3132         fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
3133         if (commit_ref(lock) < 0)
3134                 return error("unable to write symref for %s: %s", refname,
3135                              strerror(errno));
3136         return 0;
3137 }
3138
3139 static int files_create_symref(struct ref_store *ref_store,
3140                                const char *refname, const char *target,
3141                                const char *logmsg)
3142 {
3143         struct files_ref_store *refs =
3144                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
3145         struct strbuf err = STRBUF_INIT;
3146         struct ref_lock *lock;
3147         int ret;
3148
3149         lock = lock_ref_sha1_basic(refs, refname, NULL,
3150                                    NULL, NULL, REF_NODEREF, NULL,
3151                                    &err);
3152         if (!lock) {
3153                 error("%s", err.buf);
3154                 strbuf_release(&err);
3155                 return -1;
3156         }
3157
3158         ret = create_symref_locked(refs, lock, refname, target, logmsg);
3159         unlock_ref(lock);
3160         return ret;
3161 }
3162
3163 int set_worktree_head_symref(const char *gitdir, const char *target, const char *logmsg)
3164 {
3165         /*
3166          * FIXME: this obviously will not work well for future refs
3167          * backends. This function needs to die.
3168          */
3169         struct files_ref_store *refs =
3170                 files_downcast(get_main_ref_store(),
3171                                REF_STORE_WRITE,
3172                                "set_head_symref");
3173
3174         static struct lock_file head_lock;
3175         struct ref_lock *lock;
3176         struct strbuf head_path = STRBUF_INIT;
3177         const char *head_rel;
3178         int ret;
3179
3180         strbuf_addf(&head_path, "%s/HEAD", absolute_path(gitdir));
3181         if (hold_lock_file_for_update(&head_lock, head_path.buf,
3182                                       LOCK_NO_DEREF) < 0) {
3183                 struct strbuf err = STRBUF_INIT;
3184                 unable_to_lock_message(head_path.buf, errno, &err);
3185                 error("%s", err.buf);
3186                 strbuf_release(&err);
3187                 strbuf_release(&head_path);
3188                 return -1;
3189         }
3190
3191         /* head_rel will be "HEAD" for the main tree, "worktrees/wt/HEAD" for
3192            linked trees */
3193         head_rel = remove_leading_path(head_path.buf,
3194                                        absolute_path(get_git_common_dir()));
3195         /* to make use of create_symref_locked(), initialize ref_lock */
3196         lock = xcalloc(1, sizeof(struct ref_lock));
3197         lock->lk = &head_lock;
3198         lock->ref_name = xstrdup(head_rel);
3199
3200         ret = create_symref_locked(refs, lock, head_rel, target, logmsg);
3201
3202         unlock_ref(lock); /* will free lock */
3203         strbuf_release(&head_path);
3204         return ret;
3205 }
3206
3207 static int files_reflog_exists(struct ref_store *ref_store,
3208                                const char *refname)
3209 {
3210         struct files_ref_store *refs =
3211                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
3212         struct strbuf sb = STRBUF_INIT;
3213         struct stat st;
3214         int ret;
3215
3216         files_reflog_path(refs, &sb, refname);
3217         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
3218         strbuf_release(&sb);
3219         return ret;
3220 }
3221
3222 static int files_delete_reflog(struct ref_store *ref_store,
3223                                const char *refname)
3224 {
3225         struct files_ref_store *refs =
3226                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
3227         struct strbuf sb = STRBUF_INIT;
3228         int ret;
3229
3230         files_reflog_path(refs, &sb, refname);
3231         ret = remove_path(sb.buf);
3232         strbuf_release(&sb);
3233         return ret;
3234 }
3235
3236 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
3237 {
3238         struct object_id ooid, noid;
3239         char *email_end, *message;
3240         unsigned long timestamp;
3241         int tz;
3242         const char *p = sb->buf;
3243
3244         /* old SP new SP name <email> SP time TAB msg LF */
3245         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
3246             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
3247             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
3248             !(email_end = strchr(p, '>')) ||
3249             email_end[1] != ' ' ||
3250             !(timestamp = strtoul(email_end + 2, &message, 10)) ||
3251             !message || message[0] != ' ' ||
3252             (message[1] != '+' && message[1] != '-') ||
3253             !isdigit(message[2]) || !isdigit(message[3]) ||
3254             !isdigit(message[4]) || !isdigit(message[5]))
3255                 return 0; /* corrupt? */
3256         email_end[1] = '\0';
3257         tz = strtol(message + 1, NULL, 10);
3258         if (message[6] != '\t')
3259                 message += 6;
3260         else
3261                 message += 7;
3262         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
3263 }
3264
3265 static char *find_beginning_of_line(char *bob, char *scan)
3266 {
3267         while (bob < scan && *(--scan) != '\n')
3268                 ; /* keep scanning backwards */
3269         /*
3270          * Return either beginning of the buffer, or LF at the end of
3271          * the previous line.
3272          */
3273         return scan;
3274 }
3275
3276 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
3277                                              const char *refname,
3278                                              each_reflog_ent_fn fn,
3279                                              void *cb_data)
3280 {
3281         struct files_ref_store *refs =
3282                 files_downcast(ref_store, REF_STORE_READ,
3283                                "for_each_reflog_ent_reverse");
3284         struct strbuf sb = STRBUF_INIT;
3285         FILE *logfp;
3286         long pos;
3287         int ret = 0, at_tail = 1;
3288
3289         files_reflog_path(refs, &sb, refname);
3290         logfp = fopen(sb.buf, "r");
3291         strbuf_release(&sb);
3292         if (!logfp)
3293                 return -1;
3294
3295         /* Jump to the end */
3296         if (fseek(logfp, 0, SEEK_END) < 0)
3297                 return error("cannot seek back reflog for %s: %s",
3298                              refname, strerror(errno));
3299         pos = ftell(logfp);
3300         while (!ret && 0 < pos) {
3301                 int cnt;
3302                 size_t nread;
3303                 char buf[BUFSIZ];
3304                 char *endp, *scanp;
3305
3306                 /* Fill next block from the end */
3307                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
3308                 if (fseek(logfp, pos - cnt, SEEK_SET))
3309                         return error("cannot seek back reflog for %s: %s",
3310                                      refname, strerror(errno));
3311                 nread = fread(buf, cnt, 1, logfp);
3312                 if (nread != 1)
3313                         return error("cannot read %d bytes from reflog for %s: %s",
3314                                      cnt, refname, strerror(errno));
3315                 pos -= cnt;
3316
3317                 scanp = endp = buf + cnt;
3318                 if (at_tail && scanp[-1] == '\n')
3319                         /* Looking at the final LF at the end of the file */
3320                         scanp--;
3321                 at_tail = 0;
3322
3323                 while (buf < scanp) {
3324                         /*
3325                          * terminating LF of the previous line, or the beginning
3326                          * of the buffer.
3327                          */
3328                         char *bp;
3329
3330                         bp = find_beginning_of_line(buf, scanp);
3331
3332                         if (*bp == '\n') {
3333                                 /*
3334                                  * The newline is the end of the previous line,
3335                                  * so we know we have complete line starting
3336                                  * at (bp + 1). Prefix it onto any prior data
3337                                  * we collected for the line and process it.
3338                                  */
3339                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
3340                                 scanp = bp;
3341                                 endp = bp + 1;
3342                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
3343                                 strbuf_reset(&sb);
3344                                 if (ret)
3345                                         break;
3346                         } else if (!pos) {
3347                                 /*
3348                                  * We are at the start of the buffer, and the
3349                                  * start of the file; there is no previous
3350                                  * line, and we have everything for this one.
3351                                  * Process it, and we can end the loop.
3352                                  */
3353                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
3354                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
3355                                 strbuf_reset(&sb);
3356                                 break;
3357                         }
3358
3359                         if (bp == buf) {
3360                                 /*
3361                                  * We are at the start of the buffer, and there
3362                                  * is more file to read backwards. Which means
3363                                  * we are in the middle of a line. Note that we
3364                                  * may get here even if *bp was a newline; that
3365                                  * just means we are at the exact end of the
3366                                  * previous line, rather than some spot in the
3367                                  * middle.
3368                                  *
3369                                  * Save away what we have to be combined with
3370                                  * the data from the next read.
3371                                  */
3372                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
3373                                 break;
3374                         }
3375                 }
3376
3377         }
3378         if (!ret && sb.len)
3379                 die("BUG: reverse reflog parser had leftover data");
3380
3381         fclose(logfp);
3382         strbuf_release(&sb);
3383         return ret;
3384 }
3385
3386 static int files_for_each_reflog_ent(struct ref_store *ref_store,
3387                                      const char *refname,
3388                                      each_reflog_ent_fn fn, void *cb_data)
3389 {
3390         struct files_ref_store *refs =
3391                 files_downcast(ref_store, REF_STORE_READ,
3392                                "for_each_reflog_ent");
3393         FILE *logfp;
3394         struct strbuf sb = STRBUF_INIT;
3395         int ret = 0;
3396
3397         files_reflog_path(refs, &sb, refname);
3398         logfp = fopen(sb.buf, "r");
3399         strbuf_release(&sb);
3400         if (!logfp)
3401                 return -1;
3402
3403         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
3404                 ret = show_one_reflog_ent(&sb, fn, cb_data);
3405         fclose(logfp);
3406         strbuf_release(&sb);
3407         return ret;
3408 }
3409
3410 struct files_reflog_iterator {
3411         struct ref_iterator base;
3412
3413         struct ref_store *ref_store;
3414         struct dir_iterator *dir_iterator;
3415         struct object_id oid;
3416 };
3417
3418 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
3419 {
3420         struct files_reflog_iterator *iter =
3421                 (struct files_reflog_iterator *)ref_iterator;
3422         struct dir_iterator *diter = iter->dir_iterator;
3423         int ok;
3424
3425         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
3426                 int flags;
3427
3428                 if (!S_ISREG(diter->st.st_mode))
3429                         continue;
3430                 if (diter->basename[0] == '.')
3431                         continue;
3432                 if (ends_with(diter->basename, ".lock"))
3433                         continue;
3434
3435                 if (refs_read_ref_full(iter->ref_store,
3436                                        diter->relative_path, 0,
3437                                        iter->oid.hash, &flags)) {
3438                         error("bad ref for %s", diter->path.buf);
3439                         continue;
3440                 }
3441
3442                 iter->base.refname = diter->relative_path;
3443                 iter->base.oid = &iter->oid;
3444                 iter->base.flags = flags;
3445                 return ITER_OK;
3446         }
3447
3448         iter->dir_iterator = NULL;
3449         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
3450                 ok = ITER_ERROR;
3451         return ok;
3452 }
3453
3454 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
3455                                    struct object_id *peeled)
3456 {
3457         die("BUG: ref_iterator_peel() called for reflog_iterator");
3458 }
3459
3460 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
3461 {
3462         struct files_reflog_iterator *iter =
3463                 (struct files_reflog_iterator *)ref_iterator;
3464         int ok = ITER_DONE;
3465
3466         if (iter->dir_iterator)
3467                 ok = dir_iterator_abort(iter->dir_iterator);
3468
3469         base_ref_iterator_free(ref_iterator);
3470         return ok;
3471 }
3472
3473 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
3474         files_reflog_iterator_advance,
3475         files_reflog_iterator_peel,
3476         files_reflog_iterator_abort
3477 };
3478
3479 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
3480 {
3481         struct files_ref_store *refs =
3482                 files_downcast(ref_store, REF_STORE_READ,
3483                                "reflog_iterator_begin");
3484         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
3485         struct ref_iterator *ref_iterator = &iter->base;
3486         struct strbuf sb = STRBUF_INIT;
3487
3488         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
3489         files_reflog_path(refs, &sb, NULL);
3490         iter->dir_iterator = dir_iterator_begin(sb.buf);
3491         iter->ref_store = ref_store;
3492         strbuf_release(&sb);
3493         return ref_iterator;
3494 }
3495
3496 static int ref_update_reject_duplicates(struct string_list *refnames,
3497                                         struct strbuf *err)
3498 {
3499         int i, n = refnames->nr;
3500
3501         assert(err);
3502
3503         for (i = 1; i < n; i++)
3504                 if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
3505                         strbuf_addf(err,
3506                                     "multiple updates for ref '%s' not allowed.",
3507                                     refnames->items[i].string);
3508                         return 1;
3509                 }
3510         return 0;
3511 }
3512
3513 /*
3514  * If update is a direct update of head_ref (the reference pointed to
3515  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
3516  */
3517 static int split_head_update(struct ref_update *update,
3518                              struct ref_transaction *transaction,
3519                              const char *head_ref,
3520                              struct string_list *affected_refnames,
3521                              struct strbuf *err)
3522 {
3523         struct string_list_item *item;
3524         struct ref_update *new_update;
3525
3526         if ((update->flags & REF_LOG_ONLY) ||
3527             (update->flags & REF_ISPRUNING) ||
3528             (update->flags & REF_UPDATE_VIA_HEAD))
3529                 return 0;
3530
3531         if (strcmp(update->refname, head_ref))
3532                 return 0;
3533
3534         /*
3535          * First make sure that HEAD is not already in the
3536          * transaction. This insertion is O(N) in the transaction
3537          * size, but it happens at most once per transaction.
3538          */
3539         item = string_list_insert(affected_refnames, "HEAD");
3540         if (item->util) {
3541                 /* An entry already existed */
3542                 strbuf_addf(err,
3543                             "multiple updates for 'HEAD' (including one "
3544                             "via its referent '%s') are not allowed",
3545                             update->refname);
3546                 return TRANSACTION_NAME_CONFLICT;
3547         }
3548
3549         new_update = ref_transaction_add_update(
3550                         transaction, "HEAD",
3551                         update->flags | REF_LOG_ONLY | REF_NODEREF,
3552                         update->new_sha1, update->old_sha1,
3553                         update->msg);
3554
3555         item->util = new_update;
3556
3557         return 0;
3558 }
3559
3560 /*
3561  * update is for a symref that points at referent and doesn't have
3562  * REF_NODEREF set. Split it into two updates:
3563  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
3564  * - A new, separate update for the referent reference
3565  * Note that the new update will itself be subject to splitting when
3566  * the iteration gets to it.
3567  */
3568 static int split_symref_update(struct files_ref_store *refs,
3569                                struct ref_update *update,
3570                                const char *referent,
3571                                struct ref_transaction *transaction,
3572                                struct string_list *affected_refnames,
3573                                struct strbuf *err)
3574 {
3575         struct string_list_item *item;
3576         struct ref_update *new_update;
3577         unsigned int new_flags;
3578
3579         /*
3580          * First make sure that referent is not already in the
3581          * transaction. This insertion is O(N) in the transaction
3582          * size, but it happens at most once per symref in a
3583          * transaction.
3584          */
3585         item = string_list_insert(affected_refnames, referent);
3586         if (item->util) {
3587                 /* An entry already existed */
3588                 strbuf_addf(err,
3589                             "multiple updates for '%s' (including one "
3590                             "via symref '%s') are not allowed",
3591                             referent, update->refname);
3592                 return TRANSACTION_NAME_CONFLICT;
3593         }
3594
3595         new_flags = update->flags;
3596         if (!strcmp(update->refname, "HEAD")) {
3597                 /*
3598                  * Record that the new update came via HEAD, so that
3599                  * when we process it, split_head_update() doesn't try
3600                  * to add another reflog update for HEAD. Note that
3601                  * this bit will be propagated if the new_update
3602                  * itself needs to be split.
3603                  */
3604                 new_flags |= REF_UPDATE_VIA_HEAD;
3605         }
3606
3607         new_update = ref_transaction_add_update(
3608                         transaction, referent, new_flags,
3609                         update->new_sha1, update->old_sha1,
3610                         update->msg);
3611
3612         new_update->parent_update = update;
3613
3614         /*
3615          * Change the symbolic ref update to log only. Also, it
3616          * doesn't need to check its old SHA-1 value, as that will be
3617          * done when new_update is processed.
3618          */
3619         update->flags |= REF_LOG_ONLY | REF_NODEREF;
3620         update->flags &= ~REF_HAVE_OLD;
3621
3622         item->util = new_update;
3623
3624         return 0;
3625 }
3626
3627 /*
3628  * Return the refname under which update was originally requested.
3629  */
3630 static const char *original_update_refname(struct ref_update *update)
3631 {
3632         while (update->parent_update)
3633                 update = update->parent_update;
3634
3635         return update->refname;
3636 }
3637
3638 /*
3639  * Check whether the REF_HAVE_OLD and old_oid values stored in update
3640  * are consistent with oid, which is the reference's current value. If
3641  * everything is OK, return 0; otherwise, write an error message to
3642  * err and return -1.
3643  */
3644 static int check_old_oid(struct ref_update *update, struct object_id *oid,
3645                          struct strbuf *err)
3646 {
3647         if (!(update->flags & REF_HAVE_OLD) ||
3648                    !hashcmp(oid->hash, update->old_sha1))
3649                 return 0;
3650
3651         if (is_null_sha1(update->old_sha1))
3652                 strbuf_addf(err, "cannot lock ref '%s': "
3653                             "reference already exists",
3654                             original_update_refname(update));
3655         else if (is_null_oid(oid))
3656                 strbuf_addf(err, "cannot lock ref '%s': "
3657                             "reference is missing but expected %s",
3658                             original_update_refname(update),
3659                             sha1_to_hex(update->old_sha1));
3660         else
3661                 strbuf_addf(err, "cannot lock ref '%s': "
3662                             "is at %s but expected %s",
3663                             original_update_refname(update),
3664                             oid_to_hex(oid),
3665                             sha1_to_hex(update->old_sha1));
3666
3667         return -1;
3668 }
3669
3670 /*
3671  * Prepare for carrying out update:
3672  * - Lock the reference referred to by update.
3673  * - Read the reference under lock.
3674  * - Check that its old SHA-1 value (if specified) is correct, and in
3675  *   any case record it in update->lock->old_oid for later use when
3676  *   writing the reflog.
3677  * - If it is a symref update without REF_NODEREF, split it up into a
3678  *   REF_LOG_ONLY update of the symref and add a separate update for
3679  *   the referent to transaction.
3680  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
3681  *   update of HEAD.
3682  */
3683 static int lock_ref_for_update(struct files_ref_store *refs,
3684                                struct ref_update *update,
3685                                struct ref_transaction *transaction,
3686                                const char *head_ref,
3687                                struct string_list *affected_refnames,
3688                                struct strbuf *err)
3689 {
3690         struct strbuf referent = STRBUF_INIT;
3691         int mustexist = (update->flags & REF_HAVE_OLD) &&
3692                 !is_null_sha1(update->old_sha1);
3693         int ret;
3694         struct ref_lock *lock;
3695
3696         files_assert_main_repository(refs, "lock_ref_for_update");
3697
3698         if ((update->flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
3699                 update->flags |= REF_DELETING;
3700
3701         if (head_ref) {
3702                 ret = split_head_update(update, transaction, head_ref,
3703                                         affected_refnames, err);
3704                 if (ret)
3705                         return ret;
3706         }
3707
3708         ret = lock_raw_ref(refs, update->refname, mustexist,
3709                            affected_refnames, NULL,
3710                            &lock, &referent,
3711                            &update->type, err);
3712         if (ret) {
3713                 char *reason;
3714
3715                 reason = strbuf_detach(err, NULL);
3716                 strbuf_addf(err, "cannot lock ref '%s': %s",
3717                             original_update_refname(update), reason);
3718                 free(reason);
3719                 return ret;
3720         }
3721
3722         update->backend_data = lock;
3723
3724         if (update->type & REF_ISSYMREF) {
3725                 if (update->flags & REF_NODEREF) {
3726                         /*
3727                          * We won't be reading the referent as part of
3728                          * the transaction, so we have to read it here
3729                          * to record and possibly check old_sha1:
3730                          */
3731                         if (refs_read_ref_full(&refs->base,
3732                                                referent.buf, 0,
3733                                                lock->old_oid.hash, NULL)) {
3734                                 if (update->flags & REF_HAVE_OLD) {
3735                                         strbuf_addf(err, "cannot lock ref '%s': "
3736                                                     "error reading reference",
3737                                                     original_update_refname(update));
3738                                         return -1;
3739                                 }
3740                         } else if (check_old_oid(update, &lock->old_oid, err)) {
3741                                 return TRANSACTION_GENERIC_ERROR;
3742                         }
3743                 } else {
3744                         /*
3745                          * Create a new update for the reference this
3746                          * symref is pointing at. Also, we will record
3747                          * and verify old_sha1 for this update as part
3748                          * of processing the split-off update, so we
3749                          * don't have to do it here.
3750                          */
3751                         ret = split_symref_update(refs, update,
3752                                                   referent.buf, transaction,
3753                                                   affected_refnames, err);
3754                         if (ret)
3755                                 return ret;
3756                 }
3757         } else {
3758                 struct ref_update *parent_update;
3759
3760                 if (check_old_oid(update, &lock->old_oid, err))
3761                         return TRANSACTION_GENERIC_ERROR;
3762
3763                 /*
3764                  * If this update is happening indirectly because of a
3765                  * symref update, record the old SHA-1 in the parent
3766                  * update:
3767                  */
3768                 for (parent_update = update->parent_update;
3769                      parent_update;
3770                      parent_update = parent_update->parent_update) {
3771                         struct ref_lock *parent_lock = parent_update->backend_data;
3772                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
3773                 }
3774         }
3775
3776         if ((update->flags & REF_HAVE_NEW) &&
3777             !(update->flags & REF_DELETING) &&
3778             !(update->flags & REF_LOG_ONLY)) {
3779                 if (!(update->type & REF_ISSYMREF) &&
3780                     !hashcmp(lock->old_oid.hash, update->new_sha1)) {
3781                         /*
3782                          * The reference already has the desired
3783                          * value, so we don't need to write it.
3784                          */
3785                 } else if (write_ref_to_lockfile(lock, update->new_sha1,
3786                                                  err)) {
3787                         char *write_err = strbuf_detach(err, NULL);
3788
3789                         /*
3790                          * The lock was freed upon failure of
3791                          * write_ref_to_lockfile():
3792                          */
3793                         update->backend_data = NULL;
3794                         strbuf_addf(err,
3795                                     "cannot update ref '%s': %s",
3796                                     update->refname, write_err);
3797                         free(write_err);
3798                         return TRANSACTION_GENERIC_ERROR;
3799                 } else {
3800                         update->flags |= REF_NEEDS_COMMIT;
3801                 }
3802         }
3803         if (!(update->flags & REF_NEEDS_COMMIT)) {
3804                 /*
3805                  * We didn't call write_ref_to_lockfile(), so
3806                  * the lockfile is still open. Close it to
3807                  * free up the file descriptor:
3808                  */
3809                 if (close_ref(lock)) {
3810                         strbuf_addf(err, "couldn't close '%s.lock'",
3811                                     update->refname);
3812                         return TRANSACTION_GENERIC_ERROR;
3813                 }
3814         }
3815         return 0;
3816 }
3817
3818 static int files_transaction_commit(struct ref_store *ref_store,
3819                                     struct ref_transaction *transaction,
3820                                     struct strbuf *err)
3821 {
3822         struct files_ref_store *refs =
3823                 files_downcast(ref_store, REF_STORE_WRITE,
3824                                "ref_transaction_commit");
3825         int ret = 0, i;
3826         struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
3827         struct string_list_item *ref_to_delete;
3828         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3829         char *head_ref = NULL;
3830         int head_type;
3831         struct object_id head_oid;
3832         struct strbuf sb = STRBUF_INIT;
3833
3834         assert(err);
3835
3836         if (transaction->state != REF_TRANSACTION_OPEN)
3837                 die("BUG: commit called for transaction that is not open");
3838
3839         if (!transaction->nr) {
3840                 transaction->state = REF_TRANSACTION_CLOSED;
3841                 return 0;
3842         }
3843
3844         /*
3845          * Fail if a refname appears more than once in the
3846          * transaction. (If we end up splitting up any updates using
3847          * split_symref_update() or split_head_update(), those
3848          * functions will check that the new updates don't have the
3849          * same refname as any existing ones.)
3850          */
3851         for (i = 0; i < transaction->nr; i++) {
3852                 struct ref_update *update = transaction->updates[i];
3853                 struct string_list_item *item =
3854                         string_list_append(&affected_refnames, update->refname);
3855
3856                 /*
3857                  * We store a pointer to update in item->util, but at
3858                  * the moment we never use the value of this field
3859                  * except to check whether it is non-NULL.
3860                  */
3861                 item->util = update;
3862         }
3863         string_list_sort(&affected_refnames);
3864         if (ref_update_reject_duplicates(&affected_refnames, err)) {
3865                 ret = TRANSACTION_GENERIC_ERROR;
3866                 goto cleanup;
3867         }
3868
3869         /*
3870          * Special hack: If a branch is updated directly and HEAD
3871          * points to it (may happen on the remote side of a push
3872          * for example) then logically the HEAD reflog should be
3873          * updated too.
3874          *
3875          * A generic solution would require reverse symref lookups,
3876          * but finding all symrefs pointing to a given branch would be
3877          * rather costly for this rare event (the direct update of a
3878          * branch) to be worth it. So let's cheat and check with HEAD
3879          * only, which should cover 99% of all usage scenarios (even
3880          * 100% of the default ones).
3881          *
3882          * So if HEAD is a symbolic reference, then record the name of
3883          * the reference that it points to. If we see an update of
3884          * head_ref within the transaction, then split_head_update()
3885          * arranges for the reflog of HEAD to be updated, too.
3886          */
3887         head_ref = refs_resolve_refdup(ref_store, "HEAD",
3888                                        RESOLVE_REF_NO_RECURSE,
3889                                        head_oid.hash, &head_type);
3890
3891         if (head_ref && !(head_type & REF_ISSYMREF)) {
3892                 free(head_ref);
3893                 head_ref = NULL;
3894         }
3895
3896         /*
3897          * Acquire all locks, verify old values if provided, check
3898          * that new values are valid, and write new values to the
3899          * lockfiles, ready to be activated. Only keep one lockfile
3900          * open at a time to avoid running out of file descriptors.
3901          */
3902         for (i = 0; i < transaction->nr; i++) {
3903                 struct ref_update *update = transaction->updates[i];
3904
3905                 ret = lock_ref_for_update(refs, update, transaction,
3906                                           head_ref, &affected_refnames, err);
3907                 if (ret)
3908                         goto cleanup;
3909         }
3910
3911         /* Perform updates first so live commits remain referenced */
3912         for (i = 0; i < transaction->nr; i++) {
3913                 struct ref_update *update = transaction->updates[i];
3914                 struct ref_lock *lock = update->backend_data;
3915
3916                 if (update->flags & REF_NEEDS_COMMIT ||
3917                     update->flags & REF_LOG_ONLY) {
3918                         if (files_log_ref_write(refs,
3919                                                 lock->ref_name,
3920                                                 lock->old_oid.hash,
3921                                                 update->new_sha1,
3922                                                 update->msg, update->flags,
3923                                                 err)) {
3924                                 char *old_msg = strbuf_detach(err, NULL);
3925
3926                                 strbuf_addf(err, "cannot update the ref '%s': %s",
3927                                             lock->ref_name, old_msg);
3928                                 free(old_msg);
3929                                 unlock_ref(lock);
3930                                 update->backend_data = NULL;
3931                                 ret = TRANSACTION_GENERIC_ERROR;
3932                                 goto cleanup;
3933                         }
3934                 }
3935                 if (update->flags & REF_NEEDS_COMMIT) {
3936                         clear_loose_ref_cache(refs);
3937                         if (commit_ref(lock)) {
3938                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3939                                 unlock_ref(lock);
3940                                 update->backend_data = NULL;
3941                                 ret = TRANSACTION_GENERIC_ERROR;
3942                                 goto cleanup;
3943                         }
3944                 }
3945         }
3946         /* Perform deletes now that updates are safely completed */
3947         for (i = 0; i < transaction->nr; i++) {
3948                 struct ref_update *update = transaction->updates[i];
3949                 struct ref_lock *lock = update->backend_data;
3950
3951                 if (update->flags & REF_DELETING &&
3952                     !(update->flags & REF_LOG_ONLY)) {
3953                         if (!(update->type & REF_ISPACKED) ||
3954                             update->type & REF_ISSYMREF) {
3955                                 /* It is a loose reference. */
3956                                 strbuf_reset(&sb);
3957                                 files_ref_path(refs, &sb, lock->ref_name);
3958                                 if (unlink_or_msg(sb.buf, err)) {
3959                                         ret = TRANSACTION_GENERIC_ERROR;
3960                                         goto cleanup;
3961                                 }
3962                                 update->flags |= REF_DELETED_LOOSE;
3963                         }
3964
3965                         if (!(update->flags & REF_ISPRUNING))
3966                                 string_list_append(&refs_to_delete,
3967                                                    lock->ref_name);
3968                 }
3969         }
3970
3971         if (repack_without_refs(refs, &refs_to_delete, err)) {
3972                 ret = TRANSACTION_GENERIC_ERROR;
3973                 goto cleanup;
3974         }
3975
3976         /* Delete the reflogs of any references that were deleted: */
3977         for_each_string_list_item(ref_to_delete, &refs_to_delete) {
3978                 strbuf_reset(&sb);
3979                 files_reflog_path(refs, &sb, ref_to_delete->string);
3980                 if (!unlink_or_warn(sb.buf))
3981                         try_remove_empty_parents(refs, ref_to_delete->string,
3982                                                  REMOVE_EMPTY_PARENTS_REFLOG);
3983         }
3984
3985         clear_loose_ref_cache(refs);
3986
3987 cleanup:
3988         strbuf_release(&sb);
3989         transaction->state = REF_TRANSACTION_CLOSED;
3990
3991         for (i = 0; i < transaction->nr; i++) {
3992                 struct ref_update *update = transaction->updates[i];
3993                 struct ref_lock *lock = update->backend_data;
3994
3995                 if (lock)
3996                         unlock_ref(lock);
3997
3998                 if (update->flags & REF_DELETED_LOOSE) {
3999                         /*
4000                          * The loose reference was deleted. Delete any
4001                          * empty parent directories. (Note that this
4002                          * can only work because we have already
4003                          * removed the lockfile.)
4004                          */
4005                         try_remove_empty_parents(refs, update->refname,
4006                                                  REMOVE_EMPTY_PARENTS_REF);
4007                 }
4008         }
4009
4010         string_list_clear(&refs_to_delete, 0);
4011         free(head_ref);
4012         string_list_clear(&affected_refnames, 0);
4013
4014         return ret;
4015 }
4016
4017 static int ref_present(const char *refname,
4018                        const struct object_id *oid, int flags, void *cb_data)
4019 {
4020         struct string_list *affected_refnames = cb_data;
4021
4022         return string_list_has_string(affected_refnames, refname);
4023 }
4024
4025 static int files_initial_transaction_commit(struct ref_store *ref_store,
4026                                             struct ref_transaction *transaction,
4027                                             struct strbuf *err)
4028 {
4029         struct files_ref_store *refs =
4030                 files_downcast(ref_store, REF_STORE_WRITE,
4031                                "initial_ref_transaction_commit");
4032         int ret = 0, i;
4033         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
4034
4035         assert(err);
4036
4037         if (transaction->state != REF_TRANSACTION_OPEN)
4038                 die("BUG: commit called for transaction that is not open");
4039
4040         /* Fail if a refname appears more than once in the transaction: */
4041         for (i = 0; i < transaction->nr; i++)
4042                 string_list_append(&affected_refnames,
4043                                    transaction->updates[i]->refname);
4044         string_list_sort(&affected_refnames);
4045         if (ref_update_reject_duplicates(&affected_refnames, err)) {
4046                 ret = TRANSACTION_GENERIC_ERROR;
4047                 goto cleanup;
4048         }
4049
4050         /*
4051          * It's really undefined to call this function in an active
4052          * repository or when there are existing references: we are
4053          * only locking and changing packed-refs, so (1) any
4054          * simultaneous processes might try to change a reference at
4055          * the same time we do, and (2) any existing loose versions of
4056          * the references that we are setting would have precedence
4057          * over our values. But some remote helpers create the remote
4058          * "HEAD" and "master" branches before calling this function,
4059          * so here we really only check that none of the references
4060          * that we are creating already exists.
4061          */
4062         if (refs_for_each_rawref(&refs->base, ref_present,
4063                                  &affected_refnames))
4064                 die("BUG: initial ref transaction called with existing refs");
4065
4066         for (i = 0; i < transaction->nr; i++) {
4067                 struct ref_update *update = transaction->updates[i];
4068
4069                 if ((update->flags & REF_HAVE_OLD) &&
4070                     !is_null_sha1(update->old_sha1))
4071                         die("BUG: initial ref transaction with old_sha1 set");
4072                 if (refs_verify_refname_available(&refs->base, update->refname,
4073                                                   &affected_refnames, NULL,
4074                                                   err)) {
4075                         ret = TRANSACTION_NAME_CONFLICT;
4076                         goto cleanup;
4077                 }
4078         }
4079
4080         if (lock_packed_refs(refs, 0)) {
4081                 strbuf_addf(err, "unable to lock packed-refs file: %s",
4082                             strerror(errno));
4083                 ret = TRANSACTION_GENERIC_ERROR;
4084                 goto cleanup;
4085         }
4086
4087         for (i = 0; i < transaction->nr; i++) {
4088                 struct ref_update *update = transaction->updates[i];
4089
4090                 if ((update->flags & REF_HAVE_NEW) &&
4091                     !is_null_sha1(update->new_sha1))
4092                         add_packed_ref(refs, update->refname, update->new_sha1);
4093         }
4094
4095         if (commit_packed_refs(refs)) {
4096                 strbuf_addf(err, "unable to commit packed-refs file: %s",
4097                             strerror(errno));
4098                 ret = TRANSACTION_GENERIC_ERROR;
4099                 goto cleanup;
4100         }
4101
4102 cleanup:
4103         transaction->state = REF_TRANSACTION_CLOSED;
4104         string_list_clear(&affected_refnames, 0);
4105         return ret;
4106 }
4107
4108 struct expire_reflog_cb {
4109         unsigned int flags;
4110         reflog_expiry_should_prune_fn *should_prune_fn;
4111         void *policy_cb;
4112         FILE *newlog;
4113         struct object_id last_kept_oid;
4114 };
4115
4116 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
4117                              const char *email, unsigned long timestamp, int tz,
4118                              const char *message, void *cb_data)
4119 {
4120         struct expire_reflog_cb *cb = cb_data;
4121         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
4122
4123         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
4124                 ooid = &cb->last_kept_oid;
4125
4126         if ((*cb->should_prune_fn)(ooid->hash, noid->hash, email, timestamp, tz,
4127                                    message, policy_cb)) {
4128                 if (!cb->newlog)
4129                         printf("would prune %s", message);
4130                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
4131                         printf("prune %s", message);
4132         } else {
4133                 if (cb->newlog) {
4134                         fprintf(cb->newlog, "%s %s %s %lu %+05d\t%s",
4135                                 oid_to_hex(ooid), oid_to_hex(noid),
4136                                 email, timestamp, tz, message);
4137                         oidcpy(&cb->last_kept_oid, noid);
4138                 }
4139                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
4140                         printf("keep %s", message);
4141         }
4142         return 0;
4143 }
4144
4145 static int files_reflog_expire(struct ref_store *ref_store,
4146                                const char *refname, const unsigned char *sha1,
4147                                unsigned int flags,
4148                                reflog_expiry_prepare_fn prepare_fn,
4149                                reflog_expiry_should_prune_fn should_prune_fn,
4150                                reflog_expiry_cleanup_fn cleanup_fn,
4151                                void *policy_cb_data)
4152 {
4153         struct files_ref_store *refs =
4154                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
4155         static struct lock_file reflog_lock;
4156         struct expire_reflog_cb cb;
4157         struct ref_lock *lock;
4158         struct strbuf log_file_sb = STRBUF_INIT;
4159         char *log_file;
4160         int status = 0;
4161         int type;
4162         struct strbuf err = STRBUF_INIT;
4163
4164         memset(&cb, 0, sizeof(cb));
4165         cb.flags = flags;
4166         cb.policy_cb = policy_cb_data;
4167         cb.should_prune_fn = should_prune_fn;
4168
4169         /*
4170          * The reflog file is locked by holding the lock on the
4171          * reference itself, plus we might need to update the
4172          * reference if --updateref was specified:
4173          */
4174         lock = lock_ref_sha1_basic(refs, refname, sha1,
4175                                    NULL, NULL, REF_NODEREF,
4176                                    &type, &err);
4177         if (!lock) {
4178                 error("cannot lock ref '%s': %s", refname, err.buf);
4179                 strbuf_release(&err);
4180                 return -1;
4181         }
4182         if (!refs_reflog_exists(ref_store, refname)) {
4183                 unlock_ref(lock);
4184                 return 0;
4185         }
4186
4187         files_reflog_path(refs, &log_file_sb, refname);
4188         log_file = strbuf_detach(&log_file_sb, NULL);
4189         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4190                 /*
4191                  * Even though holding $GIT_DIR/logs/$reflog.lock has
4192                  * no locking implications, we use the lock_file
4193                  * machinery here anyway because it does a lot of the
4194                  * work we need, including cleaning up if the program
4195                  * exits unexpectedly.
4196                  */
4197                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
4198                         struct strbuf err = STRBUF_INIT;
4199                         unable_to_lock_message(log_file, errno, &err);
4200                         error("%s", err.buf);
4201                         strbuf_release(&err);
4202                         goto failure;
4203                 }
4204                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
4205                 if (!cb.newlog) {
4206                         error("cannot fdopen %s (%s)",
4207                               get_lock_file_path(&reflog_lock), strerror(errno));
4208                         goto failure;
4209                 }
4210         }
4211
4212         (*prepare_fn)(refname, sha1, cb.policy_cb);
4213         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
4214         (*cleanup_fn)(cb.policy_cb);
4215
4216         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4217                 /*
4218                  * It doesn't make sense to adjust a reference pointed
4219                  * to by a symbolic ref based on expiring entries in
4220                  * the symbolic reference's reflog. Nor can we update
4221                  * a reference if there are no remaining reflog
4222                  * entries.
4223                  */
4224                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
4225                         !(type & REF_ISSYMREF) &&
4226                         !is_null_oid(&cb.last_kept_oid);
4227
4228                 if (close_lock_file(&reflog_lock)) {
4229                         status |= error("couldn't write %s: %s", log_file,
4230                                         strerror(errno));
4231                 } else if (update &&
4232                            (write_in_full(get_lock_file_fd(lock->lk),
4233                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
4234                             write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
4235                             close_ref(lock) < 0)) {
4236                         status |= error("couldn't write %s",
4237                                         get_lock_file_path(lock->lk));
4238                         rollback_lock_file(&reflog_lock);
4239                 } else if (commit_lock_file(&reflog_lock)) {
4240                         status |= error("unable to write reflog '%s' (%s)",
4241                                         log_file, strerror(errno));
4242                 } else if (update && commit_ref(lock)) {
4243                         status |= error("couldn't set %s", lock->ref_name);
4244                 }
4245         }
4246         free(log_file);
4247         unlock_ref(lock);
4248         return status;
4249
4250  failure:
4251         rollback_lock_file(&reflog_lock);
4252         free(log_file);
4253         unlock_ref(lock);
4254         return -1;
4255 }
4256
4257 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
4258 {
4259         struct files_ref_store *refs =
4260                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
4261         struct strbuf sb = STRBUF_INIT;
4262
4263         /*
4264          * Create .git/refs/{heads,tags}
4265          */
4266         files_ref_path(refs, &sb, "refs/heads");
4267         safe_create_dir(sb.buf, 1);
4268
4269         strbuf_reset(&sb);
4270         files_ref_path(refs, &sb, "refs/tags");
4271         safe_create_dir(sb.buf, 1);
4272
4273         strbuf_release(&sb);
4274         return 0;
4275 }
4276
4277 struct ref_storage_be refs_be_files = {
4278         NULL,
4279         "files",
4280         files_ref_store_create,
4281         files_init_db,
4282         files_transaction_commit,
4283         files_initial_transaction_commit,
4284
4285         files_pack_refs,
4286         files_peel_ref,
4287         files_create_symref,
4288         files_delete_refs,
4289         files_rename_ref,
4290
4291         files_ref_iterator_begin,
4292         files_read_raw_ref,
4293         files_verify_refname_available,
4294
4295         files_reflog_iterator_begin,
4296         files_for_each_reflog_ent,
4297         files_for_each_reflog_ent_reverse,
4298         files_reflog_exists,
4299         files_create_reflog,
4300         files_delete_reflog,
4301         files_reflog_expire
4302 };