Merge branch 'dk/send-email-avoid-net-smtp-ssl-when-able'
[git] / refs / files-backend.c
1 #include "../cache.h"
2 #include "../refs.h"
3 #include "refs-internal.h"
4 #include "ref-cache.h"
5 #include "../iterator.h"
6 #include "../dir-iterator.h"
7 #include "../lockfile.h"
8 #include "../object.h"
9 #include "../dir.h"
10
11 struct ref_lock {
12         char *ref_name;
13         struct lock_file *lk;
14         struct object_id old_oid;
15 };
16
17 /*
18  * Return true if refname, which has the specified oid and flags, can
19  * be resolved to an object in the database. If the referred-to object
20  * does not exist, emit a warning and return false.
21  */
22 static int ref_resolves_to_object(const char *refname,
23                                   const struct object_id *oid,
24                                   unsigned int flags)
25 {
26         if (flags & REF_ISBROKEN)
27                 return 0;
28         if (!has_sha1_file(oid->hash)) {
29                 error("%s does not point to a valid object!", refname);
30                 return 0;
31         }
32         return 1;
33 }
34
35 struct packed_ref_cache {
36         struct ref_cache *cache;
37
38         /*
39          * Count of references to the data structure in this instance,
40          * including the pointer from files_ref_store::packed if any.
41          * The data will not be freed as long as the reference count
42          * is nonzero.
43          */
44         unsigned int referrers;
45
46         /*
47          * Iff the packed-refs file associated with this instance is
48          * currently locked for writing, this points at the associated
49          * lock (which is owned by somebody else).  The referrer count
50          * is also incremented when the file is locked and decremented
51          * when it is unlocked.
52          */
53         struct lock_file *lock;
54
55         /* The metadata from when this packed-refs cache was read */
56         struct stat_validity validity;
57 };
58
59 /*
60  * Future: need to be in "struct repository"
61  * when doing a full libification.
62  */
63 struct files_ref_store {
64         struct ref_store base;
65         unsigned int store_flags;
66
67         char *gitdir;
68         char *gitcommondir;
69         char *packed_refs_path;
70
71         struct ref_cache *loose;
72         struct packed_ref_cache *packed;
73 };
74
75 /* Lock used for the main packed-refs file: */
76 static struct lock_file packlock;
77
78 /*
79  * Increment the reference count of *packed_refs.
80  */
81 static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
82 {
83         packed_refs->referrers++;
84 }
85
86 /*
87  * Decrease the reference count of *packed_refs.  If it goes to zero,
88  * free *packed_refs and return true; otherwise return false.
89  */
90 static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
91 {
92         if (!--packed_refs->referrers) {
93                 free_ref_cache(packed_refs->cache);
94                 stat_validity_clear(&packed_refs->validity);
95                 free(packed_refs);
96                 return 1;
97         } else {
98                 return 0;
99         }
100 }
101
102 static void clear_packed_ref_cache(struct files_ref_store *refs)
103 {
104         if (refs->packed) {
105                 struct packed_ref_cache *packed_refs = refs->packed;
106
107                 if (packed_refs->lock)
108                         die("internal error: packed-ref cache cleared while locked");
109                 refs->packed = NULL;
110                 release_packed_ref_cache(packed_refs);
111         }
112 }
113
114 static void clear_loose_ref_cache(struct files_ref_store *refs)
115 {
116         if (refs->loose) {
117                 free_ref_cache(refs->loose);
118                 refs->loose = NULL;
119         }
120 }
121
122 /*
123  * Create a new submodule ref cache and add it to the internal
124  * set of caches.
125  */
126 static struct ref_store *files_ref_store_create(const char *gitdir,
127                                                 unsigned int flags)
128 {
129         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
130         struct ref_store *ref_store = (struct ref_store *)refs;
131         struct strbuf sb = STRBUF_INIT;
132
133         base_ref_store_init(ref_store, &refs_be_files);
134         refs->store_flags = flags;
135
136         refs->gitdir = xstrdup(gitdir);
137         get_common_dir_noenv(&sb, gitdir);
138         refs->gitcommondir = strbuf_detach(&sb, NULL);
139         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
140         refs->packed_refs_path = strbuf_detach(&sb, NULL);
141
142         return ref_store;
143 }
144
145 /*
146  * Die if refs is not the main ref store. caller is used in any
147  * necessary error messages.
148  */
149 static void files_assert_main_repository(struct files_ref_store *refs,
150                                          const char *caller)
151 {
152         if (refs->store_flags & REF_STORE_MAIN)
153                 return;
154
155         die("BUG: operation %s only allowed for main ref store", caller);
156 }
157
158 /*
159  * Downcast ref_store to files_ref_store. Die if ref_store is not a
160  * files_ref_store. required_flags is compared with ref_store's
161  * store_flags to ensure the ref_store has all required capabilities.
162  * "caller" is used in any necessary error messages.
163  */
164 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
165                                               unsigned int required_flags,
166                                               const char *caller)
167 {
168         struct files_ref_store *refs;
169
170         if (ref_store->be != &refs_be_files)
171                 die("BUG: ref_store is type \"%s\" not \"files\" in %s",
172                     ref_store->be->name, caller);
173
174         refs = (struct files_ref_store *)ref_store;
175
176         if ((refs->store_flags & required_flags) != required_flags)
177                 die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
178                     caller, required_flags, refs->store_flags);
179
180         return refs;
181 }
182
183 /* The length of a peeled reference line in packed-refs, including EOL: */
184 #define PEELED_LINE_LENGTH 42
185
186 /*
187  * The packed-refs header line that we write out.  Perhaps other
188  * traits will be added later.  The trailing space is required.
189  */
190 static const char PACKED_REFS_HEADER[] =
191         "# pack-refs with: peeled fully-peeled \n";
192
193 /*
194  * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
195  * Return a pointer to the refname within the line (null-terminated),
196  * or NULL if there was a problem.
197  */
198 static const char *parse_ref_line(struct strbuf *line, struct object_id *oid)
199 {
200         const char *ref;
201
202         if (parse_oid_hex(line->buf, oid, &ref) < 0)
203                 return NULL;
204         if (!isspace(*ref++))
205                 return NULL;
206
207         if (isspace(*ref))
208                 return NULL;
209
210         if (line->buf[line->len - 1] != '\n')
211                 return NULL;
212         line->buf[--line->len] = 0;
213
214         return ref;
215 }
216
217 /*
218  * Read f, which is a packed-refs file, into dir.
219  *
220  * A comment line of the form "# pack-refs with: " may contain zero or
221  * more traits. We interpret the traits as follows:
222  *
223  *   No traits:
224  *
225  *      Probably no references are peeled. But if the file contains a
226  *      peeled value for a reference, we will use it.
227  *
228  *   peeled:
229  *
230  *      References under "refs/tags/", if they *can* be peeled, *are*
231  *      peeled in this file. References outside of "refs/tags/" are
232  *      probably not peeled even if they could have been, but if we find
233  *      a peeled value for such a reference we will use it.
234  *
235  *   fully-peeled:
236  *
237  *      All references in the file that can be peeled are peeled.
238  *      Inversely (and this is more important), any references in the
239  *      file for which no peeled value is recorded is not peelable. This
240  *      trait should typically be written alongside "peeled" for
241  *      compatibility with older clients, but we do not require it
242  *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
243  */
244 static void read_packed_refs(FILE *f, struct ref_dir *dir)
245 {
246         struct ref_entry *last = NULL;
247         struct strbuf line = STRBUF_INIT;
248         enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
249
250         while (strbuf_getwholeline(&line, f, '\n') != EOF) {
251                 struct object_id oid;
252                 const char *refname;
253                 const char *traits;
254
255                 if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
256                         if (strstr(traits, " fully-peeled "))
257                                 peeled = PEELED_FULLY;
258                         else if (strstr(traits, " peeled "))
259                                 peeled = PEELED_TAGS;
260                         /* perhaps other traits later as well */
261                         continue;
262                 }
263
264                 refname = parse_ref_line(&line, &oid);
265                 if (refname) {
266                         int flag = REF_ISPACKED;
267
268                         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
269                                 if (!refname_is_safe(refname))
270                                         die("packed refname is dangerous: %s", refname);
271                                 oidclr(&oid);
272                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
273                         }
274                         last = create_ref_entry(refname, &oid, flag, 0);
275                         if (peeled == PEELED_FULLY ||
276                             (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
277                                 last->flag |= REF_KNOWS_PEELED;
278                         add_ref_entry(dir, last);
279                         continue;
280                 }
281                 if (last &&
282                     line.buf[0] == '^' &&
283                     line.len == PEELED_LINE_LENGTH &&
284                     line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
285                     !get_oid_hex(line.buf + 1, &oid)) {
286                         oidcpy(&last->u.value.peeled, &oid);
287                         /*
288                          * Regardless of what the file header said,
289                          * we definitely know the value of *this*
290                          * reference:
291                          */
292                         last->flag |= REF_KNOWS_PEELED;
293                 }
294         }
295
296         strbuf_release(&line);
297 }
298
299 static const char *files_packed_refs_path(struct files_ref_store *refs)
300 {
301         return refs->packed_refs_path;
302 }
303
304 static void files_reflog_path(struct files_ref_store *refs,
305                               struct strbuf *sb,
306                               const char *refname)
307 {
308         if (!refname) {
309                 /*
310                  * FIXME: of course this is wrong in multi worktree
311                  * setting. To be fixed real soon.
312                  */
313                 strbuf_addf(sb, "%s/logs", refs->gitcommondir);
314                 return;
315         }
316
317         switch (ref_type(refname)) {
318         case REF_TYPE_PER_WORKTREE:
319         case REF_TYPE_PSEUDOREF:
320                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
321                 break;
322         case REF_TYPE_NORMAL:
323                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
324                 break;
325         default:
326                 die("BUG: unknown ref type %d of ref %s",
327                     ref_type(refname), refname);
328         }
329 }
330
331 static void files_ref_path(struct files_ref_store *refs,
332                            struct strbuf *sb,
333                            const char *refname)
334 {
335         switch (ref_type(refname)) {
336         case REF_TYPE_PER_WORKTREE:
337         case REF_TYPE_PSEUDOREF:
338                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
339                 break;
340         case REF_TYPE_NORMAL:
341                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
342                 break;
343         default:
344                 die("BUG: unknown ref type %d of ref %s",
345                     ref_type(refname), refname);
346         }
347 }
348
349 /*
350  * Get the packed_ref_cache for the specified files_ref_store,
351  * creating it if necessary.
352  */
353 static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
354 {
355         const char *packed_refs_file = files_packed_refs_path(refs);
356
357         if (refs->packed &&
358             !stat_validity_check(&refs->packed->validity, packed_refs_file))
359                 clear_packed_ref_cache(refs);
360
361         if (!refs->packed) {
362                 FILE *f;
363
364                 refs->packed = xcalloc(1, sizeof(*refs->packed));
365                 acquire_packed_ref_cache(refs->packed);
366                 refs->packed->cache = create_ref_cache(&refs->base, NULL);
367                 refs->packed->cache->root->flag &= ~REF_INCOMPLETE;
368                 f = fopen(packed_refs_file, "r");
369                 if (f) {
370                         stat_validity_update(&refs->packed->validity, fileno(f));
371                         read_packed_refs(f, get_ref_dir(refs->packed->cache->root));
372                         fclose(f);
373                 }
374         }
375         return refs->packed;
376 }
377
378 static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
379 {
380         return get_ref_dir(packed_ref_cache->cache->root);
381 }
382
383 static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
384 {
385         return get_packed_ref_dir(get_packed_ref_cache(refs));
386 }
387
388 /*
389  * Add a reference to the in-memory packed reference cache.  This may
390  * only be called while the packed-refs file is locked (see
391  * lock_packed_refs()).  To actually write the packed-refs file, call
392  * commit_packed_refs().
393  */
394 static void add_packed_ref(struct files_ref_store *refs,
395                            const char *refname, const struct object_id *oid)
396 {
397         struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
398
399         if (!packed_ref_cache->lock)
400                 die("internal error: packed refs not locked");
401         add_ref_entry(get_packed_ref_dir(packed_ref_cache),
402                       create_ref_entry(refname, oid, REF_ISPACKED, 1));
403 }
404
405 /*
406  * Read the loose references from the namespace dirname into dir
407  * (without recursing).  dirname must end with '/'.  dir must be the
408  * directory entry corresponding to dirname.
409  */
410 static void loose_fill_ref_dir(struct ref_store *ref_store,
411                                struct ref_dir *dir, const char *dirname)
412 {
413         struct files_ref_store *refs =
414                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
415         DIR *d;
416         struct dirent *de;
417         int dirnamelen = strlen(dirname);
418         struct strbuf refname;
419         struct strbuf path = STRBUF_INIT;
420         size_t path_baselen;
421
422         files_ref_path(refs, &path, dirname);
423         path_baselen = path.len;
424
425         d = opendir(path.buf);
426         if (!d) {
427                 strbuf_release(&path);
428                 return;
429         }
430
431         strbuf_init(&refname, dirnamelen + 257);
432         strbuf_add(&refname, dirname, dirnamelen);
433
434         while ((de = readdir(d)) != NULL) {
435                 struct object_id oid;
436                 struct stat st;
437                 int flag;
438
439                 if (de->d_name[0] == '.')
440                         continue;
441                 if (ends_with(de->d_name, ".lock"))
442                         continue;
443                 strbuf_addstr(&refname, de->d_name);
444                 strbuf_addstr(&path, de->d_name);
445                 if (stat(path.buf, &st) < 0) {
446                         ; /* silently ignore */
447                 } else if (S_ISDIR(st.st_mode)) {
448                         strbuf_addch(&refname, '/');
449                         add_entry_to_dir(dir,
450                                          create_dir_entry(dir->cache, refname.buf,
451                                                           refname.len, 1));
452                 } else {
453                         if (!refs_resolve_ref_unsafe(&refs->base,
454                                                      refname.buf,
455                                                      RESOLVE_REF_READING,
456                                                      oid.hash, &flag)) {
457                                 oidclr(&oid);
458                                 flag |= REF_ISBROKEN;
459                         } else if (is_null_oid(&oid)) {
460                                 /*
461                                  * It is so astronomically unlikely
462                                  * that NULL_SHA1 is the SHA-1 of an
463                                  * actual object that we consider its
464                                  * appearance in a loose reference
465                                  * file to be repo corruption
466                                  * (probably due to a software bug).
467                                  */
468                                 flag |= REF_ISBROKEN;
469                         }
470
471                         if (check_refname_format(refname.buf,
472                                                  REFNAME_ALLOW_ONELEVEL)) {
473                                 if (!refname_is_safe(refname.buf))
474                                         die("loose refname is dangerous: %s", refname.buf);
475                                 oidclr(&oid);
476                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
477                         }
478                         add_entry_to_dir(dir,
479                                          create_ref_entry(refname.buf, &oid, flag, 0));
480                 }
481                 strbuf_setlen(&refname, dirnamelen);
482                 strbuf_setlen(&path, path_baselen);
483         }
484         strbuf_release(&refname);
485         strbuf_release(&path);
486         closedir(d);
487
488         /*
489          * Manually add refs/bisect, which, being per-worktree, might
490          * not appear in the directory listing for refs/ in the main
491          * repo.
492          */
493         if (!strcmp(dirname, "refs/")) {
494                 int pos = search_ref_dir(dir, "refs/bisect/", 12);
495
496                 if (pos < 0) {
497                         struct ref_entry *child_entry = create_dir_entry(
498                                         dir->cache, "refs/bisect/", 12, 1);
499                         add_entry_to_dir(dir, child_entry);
500                 }
501         }
502 }
503
504 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
505 {
506         if (!refs->loose) {
507                 /*
508                  * Mark the top-level directory complete because we
509                  * are about to read the only subdirectory that can
510                  * hold references:
511                  */
512                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
513
514                 /* We're going to fill the top level ourselves: */
515                 refs->loose->root->flag &= ~REF_INCOMPLETE;
516
517                 /*
518                  * Add an incomplete entry for "refs/" (to be filled
519                  * lazily):
520                  */
521                 add_entry_to_dir(get_ref_dir(refs->loose->root),
522                                  create_dir_entry(refs->loose, "refs/", 5, 1));
523         }
524         return refs->loose;
525 }
526
527 /*
528  * Return the ref_entry for the given refname from the packed
529  * references.  If it does not exist, return NULL.
530  */
531 static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
532                                         const char *refname)
533 {
534         return find_ref_entry(get_packed_refs(refs), refname);
535 }
536
537 /*
538  * A loose ref file doesn't exist; check for a packed ref.
539  */
540 static int resolve_packed_ref(struct files_ref_store *refs,
541                               const char *refname,
542                               unsigned char *sha1, unsigned int *flags)
543 {
544         struct ref_entry *entry;
545
546         /*
547          * The loose reference file does not exist; check for a packed
548          * reference.
549          */
550         entry = get_packed_ref(refs, refname);
551         if (entry) {
552                 hashcpy(sha1, entry->u.value.oid.hash);
553                 *flags |= REF_ISPACKED;
554                 return 0;
555         }
556         /* refname is not a packed reference. */
557         return -1;
558 }
559
560 static int files_read_raw_ref(struct ref_store *ref_store,
561                               const char *refname, unsigned char *sha1,
562                               struct strbuf *referent, unsigned int *type)
563 {
564         struct files_ref_store *refs =
565                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
566         struct strbuf sb_contents = STRBUF_INIT;
567         struct strbuf sb_path = STRBUF_INIT;
568         const char *path;
569         const char *buf;
570         struct stat st;
571         int fd;
572         int ret = -1;
573         int save_errno;
574         int remaining_retries = 3;
575
576         *type = 0;
577         strbuf_reset(&sb_path);
578
579         files_ref_path(refs, &sb_path, refname);
580
581         path = sb_path.buf;
582
583 stat_ref:
584         /*
585          * We might have to loop back here to avoid a race
586          * condition: first we lstat() the file, then we try
587          * to read it as a link or as a file.  But if somebody
588          * changes the type of the file (file <-> directory
589          * <-> symlink) between the lstat() and reading, then
590          * we don't want to report that as an error but rather
591          * try again starting with the lstat().
592          *
593          * We'll keep a count of the retries, though, just to avoid
594          * any confusing situation sending us into an infinite loop.
595          */
596
597         if (remaining_retries-- <= 0)
598                 goto out;
599
600         if (lstat(path, &st) < 0) {
601                 if (errno != ENOENT)
602                         goto out;
603                 if (resolve_packed_ref(refs, refname, sha1, type)) {
604                         errno = ENOENT;
605                         goto out;
606                 }
607                 ret = 0;
608                 goto out;
609         }
610
611         /* Follow "normalized" - ie "refs/.." symlinks by hand */
612         if (S_ISLNK(st.st_mode)) {
613                 strbuf_reset(&sb_contents);
614                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
615                         if (errno == ENOENT || errno == EINVAL)
616                                 /* inconsistent with lstat; retry */
617                                 goto stat_ref;
618                         else
619                                 goto out;
620                 }
621                 if (starts_with(sb_contents.buf, "refs/") &&
622                     !check_refname_format(sb_contents.buf, 0)) {
623                         strbuf_swap(&sb_contents, referent);
624                         *type |= REF_ISSYMREF;
625                         ret = 0;
626                         goto out;
627                 }
628                 /*
629                  * It doesn't look like a refname; fall through to just
630                  * treating it like a non-symlink, and reading whatever it
631                  * points to.
632                  */
633         }
634
635         /* Is it a directory? */
636         if (S_ISDIR(st.st_mode)) {
637                 /*
638                  * Even though there is a directory where the loose
639                  * ref is supposed to be, there could still be a
640                  * packed ref:
641                  */
642                 if (resolve_packed_ref(refs, refname, sha1, type)) {
643                         errno = EISDIR;
644                         goto out;
645                 }
646                 ret = 0;
647                 goto out;
648         }
649
650         /*
651          * Anything else, just open it and try to use it as
652          * a ref
653          */
654         fd = open(path, O_RDONLY);
655         if (fd < 0) {
656                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
657                         /* inconsistent with lstat; retry */
658                         goto stat_ref;
659                 else
660                         goto out;
661         }
662         strbuf_reset(&sb_contents);
663         if (strbuf_read(&sb_contents, fd, 256) < 0) {
664                 int save_errno = errno;
665                 close(fd);
666                 errno = save_errno;
667                 goto out;
668         }
669         close(fd);
670         strbuf_rtrim(&sb_contents);
671         buf = sb_contents.buf;
672         if (starts_with(buf, "ref:")) {
673                 buf += 4;
674                 while (isspace(*buf))
675                         buf++;
676
677                 strbuf_reset(referent);
678                 strbuf_addstr(referent, buf);
679                 *type |= REF_ISSYMREF;
680                 ret = 0;
681                 goto out;
682         }
683
684         /*
685          * Please note that FETCH_HEAD has additional
686          * data after the sha.
687          */
688         if (get_sha1_hex(buf, sha1) ||
689             (buf[40] != '\0' && !isspace(buf[40]))) {
690                 *type |= REF_ISBROKEN;
691                 errno = EINVAL;
692                 goto out;
693         }
694
695         ret = 0;
696
697 out:
698         save_errno = errno;
699         strbuf_release(&sb_path);
700         strbuf_release(&sb_contents);
701         errno = save_errno;
702         return ret;
703 }
704
705 static void unlock_ref(struct ref_lock *lock)
706 {
707         /* Do not free lock->lk -- atexit() still looks at them */
708         if (lock->lk)
709                 rollback_lock_file(lock->lk);
710         free(lock->ref_name);
711         free(lock);
712 }
713
714 /*
715  * Lock refname, without following symrefs, and set *lock_p to point
716  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
717  * and type similarly to read_raw_ref().
718  *
719  * The caller must verify that refname is a "safe" reference name (in
720  * the sense of refname_is_safe()) before calling this function.
721  *
722  * If the reference doesn't already exist, verify that refname doesn't
723  * have a D/F conflict with any existing references. extras and skip
724  * are passed to refs_verify_refname_available() for this check.
725  *
726  * If mustexist is not set and the reference is not found or is
727  * broken, lock the reference anyway but clear sha1.
728  *
729  * Return 0 on success. On failure, write an error message to err and
730  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
731  *
732  * Implementation note: This function is basically
733  *
734  *     lock reference
735  *     read_raw_ref()
736  *
737  * but it includes a lot more code to
738  * - Deal with possible races with other processes
739  * - Avoid calling refs_verify_refname_available() when it can be
740  *   avoided, namely if we were successfully able to read the ref
741  * - Generate informative error messages in the case of failure
742  */
743 static int lock_raw_ref(struct files_ref_store *refs,
744                         const char *refname, int mustexist,
745                         const struct string_list *extras,
746                         const struct string_list *skip,
747                         struct ref_lock **lock_p,
748                         struct strbuf *referent,
749                         unsigned int *type,
750                         struct strbuf *err)
751 {
752         struct ref_lock *lock;
753         struct strbuf ref_file = STRBUF_INIT;
754         int attempts_remaining = 3;
755         int ret = TRANSACTION_GENERIC_ERROR;
756
757         assert(err);
758         files_assert_main_repository(refs, "lock_raw_ref");
759
760         *type = 0;
761
762         /* First lock the file so it can't change out from under us. */
763
764         *lock_p = lock = xcalloc(1, sizeof(*lock));
765
766         lock->ref_name = xstrdup(refname);
767         files_ref_path(refs, &ref_file, refname);
768
769 retry:
770         switch (safe_create_leading_directories(ref_file.buf)) {
771         case SCLD_OK:
772                 break; /* success */
773         case SCLD_EXISTS:
774                 /*
775                  * Suppose refname is "refs/foo/bar". We just failed
776                  * to create the containing directory, "refs/foo",
777                  * because there was a non-directory in the way. This
778                  * indicates a D/F conflict, probably because of
779                  * another reference such as "refs/foo". There is no
780                  * reason to expect this error to be transitory.
781                  */
782                 if (refs_verify_refname_available(&refs->base, refname,
783                                                   extras, skip, err)) {
784                         if (mustexist) {
785                                 /*
786                                  * To the user the relevant error is
787                                  * that the "mustexist" reference is
788                                  * missing:
789                                  */
790                                 strbuf_reset(err);
791                                 strbuf_addf(err, "unable to resolve reference '%s'",
792                                             refname);
793                         } else {
794                                 /*
795                                  * The error message set by
796                                  * refs_verify_refname_available() is
797                                  * OK.
798                                  */
799                                 ret = TRANSACTION_NAME_CONFLICT;
800                         }
801                 } else {
802                         /*
803                          * The file that is in the way isn't a loose
804                          * reference. Report it as a low-level
805                          * failure.
806                          */
807                         strbuf_addf(err, "unable to create lock file %s.lock; "
808                                     "non-directory in the way",
809                                     ref_file.buf);
810                 }
811                 goto error_return;
812         case SCLD_VANISHED:
813                 /* Maybe another process was tidying up. Try again. */
814                 if (--attempts_remaining > 0)
815                         goto retry;
816                 /* fall through */
817         default:
818                 strbuf_addf(err, "unable to create directory for %s",
819                             ref_file.buf);
820                 goto error_return;
821         }
822
823         if (!lock->lk)
824                 lock->lk = xcalloc(1, sizeof(struct lock_file));
825
826         if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
827                 if (errno == ENOENT && --attempts_remaining > 0) {
828                         /*
829                          * Maybe somebody just deleted one of the
830                          * directories leading to ref_file.  Try
831                          * again:
832                          */
833                         goto retry;
834                 } else {
835                         unable_to_lock_message(ref_file.buf, errno, err);
836                         goto error_return;
837                 }
838         }
839
840         /*
841          * Now we hold the lock and can read the reference without
842          * fear that its value will change.
843          */
844
845         if (files_read_raw_ref(&refs->base, refname,
846                                lock->old_oid.hash, referent, type)) {
847                 if (errno == ENOENT) {
848                         if (mustexist) {
849                                 /* Garden variety missing reference. */
850                                 strbuf_addf(err, "unable to resolve reference '%s'",
851                                             refname);
852                                 goto error_return;
853                         } else {
854                                 /*
855                                  * Reference is missing, but that's OK. We
856                                  * know that there is not a conflict with
857                                  * another loose reference because
858                                  * (supposing that we are trying to lock
859                                  * reference "refs/foo/bar"):
860                                  *
861                                  * - We were successfully able to create
862                                  *   the lockfile refs/foo/bar.lock, so we
863                                  *   know there cannot be a loose reference
864                                  *   named "refs/foo".
865                                  *
866                                  * - We got ENOENT and not EISDIR, so we
867                                  *   know that there cannot be a loose
868                                  *   reference named "refs/foo/bar/baz".
869                                  */
870                         }
871                 } else if (errno == EISDIR) {
872                         /*
873                          * There is a directory in the way. It might have
874                          * contained references that have been deleted. If
875                          * we don't require that the reference already
876                          * exists, try to remove the directory so that it
877                          * doesn't cause trouble when we want to rename the
878                          * lockfile into place later.
879                          */
880                         if (mustexist) {
881                                 /* Garden variety missing reference. */
882                                 strbuf_addf(err, "unable to resolve reference '%s'",
883                                             refname);
884                                 goto error_return;
885                         } else if (remove_dir_recursively(&ref_file,
886                                                           REMOVE_DIR_EMPTY_ONLY)) {
887                                 if (refs_verify_refname_available(
888                                                     &refs->base, refname,
889                                                     extras, skip, err)) {
890                                         /*
891                                          * The error message set by
892                                          * verify_refname_available() is OK.
893                                          */
894                                         ret = TRANSACTION_NAME_CONFLICT;
895                                         goto error_return;
896                                 } else {
897                                         /*
898                                          * We can't delete the directory,
899                                          * but we also don't know of any
900                                          * references that it should
901                                          * contain.
902                                          */
903                                         strbuf_addf(err, "there is a non-empty directory '%s' "
904                                                     "blocking reference '%s'",
905                                                     ref_file.buf, refname);
906                                         goto error_return;
907                                 }
908                         }
909                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
910                         strbuf_addf(err, "unable to resolve reference '%s': "
911                                     "reference broken", refname);
912                         goto error_return;
913                 } else {
914                         strbuf_addf(err, "unable to resolve reference '%s': %s",
915                                     refname, strerror(errno));
916                         goto error_return;
917                 }
918
919                 /*
920                  * If the ref did not exist and we are creating it,
921                  * make sure there is no existing ref that conflicts
922                  * with refname:
923                  */
924                 if (refs_verify_refname_available(
925                                     &refs->base, refname,
926                                     extras, skip, err))
927                         goto error_return;
928         }
929
930         ret = 0;
931         goto out;
932
933 error_return:
934         unlock_ref(lock);
935         *lock_p = NULL;
936
937 out:
938         strbuf_release(&ref_file);
939         return ret;
940 }
941
942 static int files_peel_ref(struct ref_store *ref_store,
943                           const char *refname, unsigned char *sha1)
944 {
945         struct files_ref_store *refs =
946                 files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
947                                "peel_ref");
948         int flag;
949         unsigned char base[20];
950
951         if (current_ref_iter && current_ref_iter->refname == refname) {
952                 struct object_id peeled;
953
954                 if (ref_iterator_peel(current_ref_iter, &peeled))
955                         return -1;
956                 hashcpy(sha1, peeled.hash);
957                 return 0;
958         }
959
960         if (refs_read_ref_full(ref_store, refname,
961                                RESOLVE_REF_READING, base, &flag))
962                 return -1;
963
964         /*
965          * If the reference is packed, read its ref_entry from the
966          * cache in the hope that we already know its peeled value.
967          * We only try this optimization on packed references because
968          * (a) forcing the filling of the loose reference cache could
969          * be expensive and (b) loose references anyway usually do not
970          * have REF_KNOWS_PEELED.
971          */
972         if (flag & REF_ISPACKED) {
973                 struct ref_entry *r = get_packed_ref(refs, refname);
974                 if (r) {
975                         if (peel_entry(r, 0))
976                                 return -1;
977                         hashcpy(sha1, r->u.value.peeled.hash);
978                         return 0;
979                 }
980         }
981
982         return peel_object(base, sha1);
983 }
984
985 struct files_ref_iterator {
986         struct ref_iterator base;
987
988         struct packed_ref_cache *packed_ref_cache;
989         struct ref_iterator *iter0;
990         unsigned int flags;
991 };
992
993 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
994 {
995         struct files_ref_iterator *iter =
996                 (struct files_ref_iterator *)ref_iterator;
997         int ok;
998
999         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
1000                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
1001                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
1002                         continue;
1003
1004                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
1005                     !ref_resolves_to_object(iter->iter0->refname,
1006                                             iter->iter0->oid,
1007                                             iter->iter0->flags))
1008                         continue;
1009
1010                 iter->base.refname = iter->iter0->refname;
1011                 iter->base.oid = iter->iter0->oid;
1012                 iter->base.flags = iter->iter0->flags;
1013                 return ITER_OK;
1014         }
1015
1016         iter->iter0 = NULL;
1017         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
1018                 ok = ITER_ERROR;
1019
1020         return ok;
1021 }
1022
1023 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
1024                                    struct object_id *peeled)
1025 {
1026         struct files_ref_iterator *iter =
1027                 (struct files_ref_iterator *)ref_iterator;
1028
1029         return ref_iterator_peel(iter->iter0, peeled);
1030 }
1031
1032 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
1033 {
1034         struct files_ref_iterator *iter =
1035                 (struct files_ref_iterator *)ref_iterator;
1036         int ok = ITER_DONE;
1037
1038         if (iter->iter0)
1039                 ok = ref_iterator_abort(iter->iter0);
1040
1041         release_packed_ref_cache(iter->packed_ref_cache);
1042         base_ref_iterator_free(ref_iterator);
1043         return ok;
1044 }
1045
1046 static struct ref_iterator_vtable files_ref_iterator_vtable = {
1047         files_ref_iterator_advance,
1048         files_ref_iterator_peel,
1049         files_ref_iterator_abort
1050 };
1051
1052 static struct ref_iterator *files_ref_iterator_begin(
1053                 struct ref_store *ref_store,
1054                 const char *prefix, unsigned int flags)
1055 {
1056         struct files_ref_store *refs;
1057         struct ref_iterator *loose_iter, *packed_iter;
1058         struct files_ref_iterator *iter;
1059         struct ref_iterator *ref_iterator;
1060
1061         if (ref_paranoia < 0)
1062                 ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1063         if (ref_paranoia)
1064                 flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1065
1066         refs = files_downcast(ref_store,
1067                               REF_STORE_READ | (ref_paranoia ? 0 : REF_STORE_ODB),
1068                               "ref_iterator_begin");
1069
1070         iter = xcalloc(1, sizeof(*iter));
1071         ref_iterator = &iter->base;
1072         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
1073
1074         /*
1075          * We must make sure that all loose refs are read before
1076          * accessing the packed-refs file; this avoids a race
1077          * condition if loose refs are migrated to the packed-refs
1078          * file by a simultaneous process, but our in-memory view is
1079          * from before the migration. We ensure this as follows:
1080          * First, we call start the loose refs iteration with its
1081          * `prime_ref` argument set to true. This causes the loose
1082          * references in the subtree to be pre-read into the cache.
1083          * (If they've already been read, that's OK; we only need to
1084          * guarantee that they're read before the packed refs, not
1085          * *how much* before.) After that, we call
1086          * get_packed_ref_cache(), which internally checks whether the
1087          * packed-ref cache is up to date with what is on disk, and
1088          * re-reads it if not.
1089          */
1090
1091         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
1092                                               prefix, 1);
1093
1094         iter->packed_ref_cache = get_packed_ref_cache(refs);
1095         acquire_packed_ref_cache(iter->packed_ref_cache);
1096         packed_iter = cache_ref_iterator_begin(iter->packed_ref_cache->cache,
1097                                                prefix, 0);
1098
1099         iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
1100         iter->flags = flags;
1101
1102         return ref_iterator;
1103 }
1104
1105 /*
1106  * Verify that the reference locked by lock has the value old_sha1.
1107  * Fail if the reference doesn't exist and mustexist is set. Return 0
1108  * on success. On error, write an error message to err, set errno, and
1109  * return a negative value.
1110  */
1111 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
1112                        const unsigned char *old_sha1, int mustexist,
1113                        struct strbuf *err)
1114 {
1115         assert(err);
1116
1117         if (refs_read_ref_full(ref_store, lock->ref_name,
1118                                mustexist ? RESOLVE_REF_READING : 0,
1119                                lock->old_oid.hash, NULL)) {
1120                 if (old_sha1) {
1121                         int save_errno = errno;
1122                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
1123                         errno = save_errno;
1124                         return -1;
1125                 } else {
1126                         oidclr(&lock->old_oid);
1127                         return 0;
1128                 }
1129         }
1130         if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
1131                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
1132                             lock->ref_name,
1133                             oid_to_hex(&lock->old_oid),
1134                             sha1_to_hex(old_sha1));
1135                 errno = EBUSY;
1136                 return -1;
1137         }
1138         return 0;
1139 }
1140
1141 static int remove_empty_directories(struct strbuf *path)
1142 {
1143         /*
1144          * we want to create a file but there is a directory there;
1145          * if that is an empty directory (or a directory that contains
1146          * only empty directories), remove them.
1147          */
1148         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
1149 }
1150
1151 static int create_reflock(const char *path, void *cb)
1152 {
1153         struct lock_file *lk = cb;
1154
1155         return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
1156 }
1157
1158 /*
1159  * Locks a ref returning the lock on success and NULL on failure.
1160  * On failure errno is set to something meaningful.
1161  */
1162 static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
1163                                             const char *refname,
1164                                             const unsigned char *old_sha1,
1165                                             const struct string_list *extras,
1166                                             const struct string_list *skip,
1167                                             unsigned int flags, int *type,
1168                                             struct strbuf *err)
1169 {
1170         struct strbuf ref_file = STRBUF_INIT;
1171         struct ref_lock *lock;
1172         int last_errno = 0;
1173         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
1174         int resolve_flags = RESOLVE_REF_NO_RECURSE;
1175         int resolved;
1176
1177         files_assert_main_repository(refs, "lock_ref_sha1_basic");
1178         assert(err);
1179
1180         lock = xcalloc(1, sizeof(struct ref_lock));
1181
1182         if (mustexist)
1183                 resolve_flags |= RESOLVE_REF_READING;
1184         if (flags & REF_DELETING)
1185                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
1186
1187         files_ref_path(refs, &ref_file, refname);
1188         resolved = !!refs_resolve_ref_unsafe(&refs->base,
1189                                              refname, resolve_flags,
1190                                              lock->old_oid.hash, type);
1191         if (!resolved && errno == EISDIR) {
1192                 /*
1193                  * we are trying to lock foo but we used to
1194                  * have foo/bar which now does not exist;
1195                  * it is normal for the empty directory 'foo'
1196                  * to remain.
1197                  */
1198                 if (remove_empty_directories(&ref_file)) {
1199                         last_errno = errno;
1200                         if (!refs_verify_refname_available(
1201                                             &refs->base,
1202                                             refname, extras, skip, err))
1203                                 strbuf_addf(err, "there are still refs under '%s'",
1204                                             refname);
1205                         goto error_return;
1206                 }
1207                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
1208                                                      refname, resolve_flags,
1209                                                      lock->old_oid.hash, type);
1210         }
1211         if (!resolved) {
1212                 last_errno = errno;
1213                 if (last_errno != ENOTDIR ||
1214                     !refs_verify_refname_available(&refs->base, refname,
1215                                                    extras, skip, err))
1216                         strbuf_addf(err, "unable to resolve reference '%s': %s",
1217                                     refname, strerror(last_errno));
1218
1219                 goto error_return;
1220         }
1221
1222         /*
1223          * If the ref did not exist and we are creating it, make sure
1224          * there is no existing packed ref whose name begins with our
1225          * refname, nor a packed ref whose name is a proper prefix of
1226          * our refname.
1227          */
1228         if (is_null_oid(&lock->old_oid) &&
1229             refs_verify_refname_available(&refs->base, refname,
1230                                           extras, skip, err)) {
1231                 last_errno = ENOTDIR;
1232                 goto error_return;
1233         }
1234
1235         lock->lk = xcalloc(1, sizeof(struct lock_file));
1236
1237         lock->ref_name = xstrdup(refname);
1238
1239         if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
1240                 last_errno = errno;
1241                 unable_to_lock_message(ref_file.buf, errno, err);
1242                 goto error_return;
1243         }
1244
1245         if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
1246                 last_errno = errno;
1247                 goto error_return;
1248         }
1249         goto out;
1250
1251  error_return:
1252         unlock_ref(lock);
1253         lock = NULL;
1254
1255  out:
1256         strbuf_release(&ref_file);
1257         errno = last_errno;
1258         return lock;
1259 }
1260
1261 /*
1262  * Write an entry to the packed-refs file for the specified refname.
1263  * If peeled is non-NULL, write it as the entry's peeled value.
1264  */
1265 static void write_packed_entry(FILE *fh, const char *refname,
1266                                const unsigned char *sha1,
1267                                const unsigned char *peeled)
1268 {
1269         fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
1270         if (peeled)
1271                 fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
1272 }
1273
1274 /*
1275  * Lock the packed-refs file for writing. Flags is passed to
1276  * hold_lock_file_for_update(). Return 0 on success. On errors, set
1277  * errno appropriately and return a nonzero value.
1278  */
1279 static int lock_packed_refs(struct files_ref_store *refs, int flags)
1280 {
1281         static int timeout_configured = 0;
1282         static int timeout_value = 1000;
1283         struct packed_ref_cache *packed_ref_cache;
1284
1285         files_assert_main_repository(refs, "lock_packed_refs");
1286
1287         if (!timeout_configured) {
1288                 git_config_get_int("core.packedrefstimeout", &timeout_value);
1289                 timeout_configured = 1;
1290         }
1291
1292         if (hold_lock_file_for_update_timeout(
1293                             &packlock, files_packed_refs_path(refs),
1294                             flags, timeout_value) < 0)
1295                 return -1;
1296         /*
1297          * Get the current packed-refs while holding the lock.  If the
1298          * packed-refs file has been modified since we last read it,
1299          * this will automatically invalidate the cache and re-read
1300          * the packed-refs file.
1301          */
1302         packed_ref_cache = get_packed_ref_cache(refs);
1303         packed_ref_cache->lock = &packlock;
1304         /* Increment the reference count to prevent it from being freed: */
1305         acquire_packed_ref_cache(packed_ref_cache);
1306         return 0;
1307 }
1308
1309 /*
1310  * Write the current version of the packed refs cache from memory to
1311  * disk. The packed-refs file must already be locked for writing (see
1312  * lock_packed_refs()). Return zero on success. On errors, set errno
1313  * and return a nonzero value
1314  */
1315 static int commit_packed_refs(struct files_ref_store *refs)
1316 {
1317         struct packed_ref_cache *packed_ref_cache =
1318                 get_packed_ref_cache(refs);
1319         int ok, error = 0;
1320         int save_errno = 0;
1321         FILE *out;
1322         struct ref_iterator *iter;
1323
1324         files_assert_main_repository(refs, "commit_packed_refs");
1325
1326         if (!packed_ref_cache->lock)
1327                 die("internal error: packed-refs not locked");
1328
1329         out = fdopen_lock_file(packed_ref_cache->lock, "w");
1330         if (!out)
1331                 die_errno("unable to fdopen packed-refs descriptor");
1332
1333         fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
1334
1335         iter = cache_ref_iterator_begin(packed_ref_cache->cache, NULL, 0);
1336         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1337                 struct object_id peeled;
1338                 int peel_error = ref_iterator_peel(iter, &peeled);
1339
1340                 write_packed_entry(out, iter->refname, iter->oid->hash,
1341                                    peel_error ? NULL : peeled.hash);
1342         }
1343
1344         if (ok != ITER_DONE)
1345                 die("error while iterating over references");
1346
1347         if (commit_lock_file(packed_ref_cache->lock)) {
1348                 save_errno = errno;
1349                 error = -1;
1350         }
1351         packed_ref_cache->lock = NULL;
1352         release_packed_ref_cache(packed_ref_cache);
1353         errno = save_errno;
1354         return error;
1355 }
1356
1357 /*
1358  * Rollback the lockfile for the packed-refs file, and discard the
1359  * in-memory packed reference cache.  (The packed-refs file will be
1360  * read anew if it is needed again after this function is called.)
1361  */
1362 static void rollback_packed_refs(struct files_ref_store *refs)
1363 {
1364         struct packed_ref_cache *packed_ref_cache =
1365                 get_packed_ref_cache(refs);
1366
1367         files_assert_main_repository(refs, "rollback_packed_refs");
1368
1369         if (!packed_ref_cache->lock)
1370                 die("internal error: packed-refs not locked");
1371         rollback_lock_file(packed_ref_cache->lock);
1372         packed_ref_cache->lock = NULL;
1373         release_packed_ref_cache(packed_ref_cache);
1374         clear_packed_ref_cache(refs);
1375 }
1376
1377 struct ref_to_prune {
1378         struct ref_to_prune *next;
1379         unsigned char sha1[20];
1380         char name[FLEX_ARRAY];
1381 };
1382
1383 enum {
1384         REMOVE_EMPTY_PARENTS_REF = 0x01,
1385         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
1386 };
1387
1388 /*
1389  * Remove empty parent directories associated with the specified
1390  * reference and/or its reflog, but spare [logs/]refs/ and immediate
1391  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
1392  * REMOVE_EMPTY_PARENTS_REFLOG.
1393  */
1394 static void try_remove_empty_parents(struct files_ref_store *refs,
1395                                      const char *refname,
1396                                      unsigned int flags)
1397 {
1398         struct strbuf buf = STRBUF_INIT;
1399         struct strbuf sb = STRBUF_INIT;
1400         char *p, *q;
1401         int i;
1402
1403         strbuf_addstr(&buf, refname);
1404         p = buf.buf;
1405         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1406                 while (*p && *p != '/')
1407                         p++;
1408                 /* tolerate duplicate slashes; see check_refname_format() */
1409                 while (*p == '/')
1410                         p++;
1411         }
1412         q = buf.buf + buf.len;
1413         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1414                 while (q > p && *q != '/')
1415                         q--;
1416                 while (q > p && *(q-1) == '/')
1417                         q--;
1418                 if (q == p)
1419                         break;
1420                 strbuf_setlen(&buf, q - buf.buf);
1421
1422                 strbuf_reset(&sb);
1423                 files_ref_path(refs, &sb, buf.buf);
1424                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1425                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1426
1427                 strbuf_reset(&sb);
1428                 files_reflog_path(refs, &sb, buf.buf);
1429                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1430                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1431         }
1432         strbuf_release(&buf);
1433         strbuf_release(&sb);
1434 }
1435
1436 /* make sure nobody touched the ref, and unlink */
1437 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1438 {
1439         struct ref_transaction *transaction;
1440         struct strbuf err = STRBUF_INIT;
1441
1442         if (check_refname_format(r->name, 0))
1443                 return;
1444
1445         transaction = ref_store_transaction_begin(&refs->base, &err);
1446         if (!transaction ||
1447             ref_transaction_delete(transaction, r->name, r->sha1,
1448                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
1449             ref_transaction_commit(transaction, &err)) {
1450                 ref_transaction_free(transaction);
1451                 error("%s", err.buf);
1452                 strbuf_release(&err);
1453                 return;
1454         }
1455         ref_transaction_free(transaction);
1456         strbuf_release(&err);
1457 }
1458
1459 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
1460 {
1461         while (r) {
1462                 prune_ref(refs, r);
1463                 r = r->next;
1464         }
1465 }
1466
1467 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1468 {
1469         struct files_ref_store *refs =
1470                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1471                                "pack_refs");
1472         struct ref_iterator *iter;
1473         struct ref_dir *packed_refs;
1474         int ok;
1475         struct ref_to_prune *refs_to_prune = NULL;
1476
1477         lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
1478         packed_refs = get_packed_refs(refs);
1479
1480         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1481         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1482                 /*
1483                  * If the loose reference can be packed, add an entry
1484                  * in the packed ref cache. If the reference should be
1485                  * pruned, also add it to refs_to_prune.
1486                  */
1487                 struct ref_entry *packed_entry;
1488                 int is_tag_ref = starts_with(iter->refname, "refs/tags/");
1489
1490                 /* Do not pack per-worktree refs: */
1491                 if (ref_type(iter->refname) != REF_TYPE_NORMAL)
1492                         continue;
1493
1494                 /* ALWAYS pack tags */
1495                 if (!(flags & PACK_REFS_ALL) && !is_tag_ref)
1496                         continue;
1497
1498                 /* Do not pack symbolic or broken refs: */
1499                 if (iter->flags & REF_ISSYMREF)
1500                         continue;
1501
1502                 if (!ref_resolves_to_object(iter->refname, iter->oid, iter->flags))
1503                         continue;
1504
1505                 /*
1506                  * Create an entry in the packed-refs cache equivalent
1507                  * to the one from the loose ref cache, except that
1508                  * we don't copy the peeled status, because we want it
1509                  * to be re-peeled.
1510                  */
1511                 packed_entry = find_ref_entry(packed_refs, iter->refname);
1512                 if (packed_entry) {
1513                         /* Overwrite existing packed entry with info from loose entry */
1514                         packed_entry->flag = REF_ISPACKED;
1515                         oidcpy(&packed_entry->u.value.oid, iter->oid);
1516                 } else {
1517                         packed_entry = create_ref_entry(iter->refname, iter->oid,
1518                                                         REF_ISPACKED, 0);
1519                         add_ref_entry(packed_refs, packed_entry);
1520                 }
1521                 oidclr(&packed_entry->u.value.peeled);
1522
1523                 /* Schedule the loose reference for pruning if requested. */
1524                 if ((flags & PACK_REFS_PRUNE)) {
1525                         struct ref_to_prune *n;
1526                         FLEX_ALLOC_STR(n, name, iter->refname);
1527                         hashcpy(n->sha1, iter->oid->hash);
1528                         n->next = refs_to_prune;
1529                         refs_to_prune = n;
1530                 }
1531         }
1532         if (ok != ITER_DONE)
1533                 die("error while iterating over references");
1534
1535         if (commit_packed_refs(refs))
1536                 die_errno("unable to overwrite old ref-pack file");
1537
1538         prune_refs(refs, refs_to_prune);
1539         return 0;
1540 }
1541
1542 /*
1543  * Rewrite the packed-refs file, omitting any refs listed in
1544  * 'refnames'. On error, leave packed-refs unchanged, write an error
1545  * message to 'err', and return a nonzero value.
1546  *
1547  * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
1548  */
1549 static int repack_without_refs(struct files_ref_store *refs,
1550                                struct string_list *refnames, struct strbuf *err)
1551 {
1552         struct ref_dir *packed;
1553         struct string_list_item *refname;
1554         int ret, needs_repacking = 0, removed = 0;
1555
1556         files_assert_main_repository(refs, "repack_without_refs");
1557         assert(err);
1558
1559         /* Look for a packed ref */
1560         for_each_string_list_item(refname, refnames) {
1561                 if (get_packed_ref(refs, refname->string)) {
1562                         needs_repacking = 1;
1563                         break;
1564                 }
1565         }
1566
1567         /* Avoid locking if we have nothing to do */
1568         if (!needs_repacking)
1569                 return 0; /* no refname exists in packed refs */
1570
1571         if (lock_packed_refs(refs, 0)) {
1572                 unable_to_lock_message(files_packed_refs_path(refs), errno, err);
1573                 return -1;
1574         }
1575         packed = get_packed_refs(refs);
1576
1577         /* Remove refnames from the cache */
1578         for_each_string_list_item(refname, refnames)
1579                 if (remove_entry_from_dir(packed, refname->string) != -1)
1580                         removed = 1;
1581         if (!removed) {
1582                 /*
1583                  * All packed entries disappeared while we were
1584                  * acquiring the lock.
1585                  */
1586                 rollback_packed_refs(refs);
1587                 return 0;
1588         }
1589
1590         /* Write what remains */
1591         ret = commit_packed_refs(refs);
1592         if (ret)
1593                 strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
1594                             strerror(errno));
1595         return ret;
1596 }
1597
1598 static int files_delete_refs(struct ref_store *ref_store,
1599                              struct string_list *refnames, unsigned int flags)
1600 {
1601         struct files_ref_store *refs =
1602                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1603         struct strbuf err = STRBUF_INIT;
1604         int i, result = 0;
1605
1606         if (!refnames->nr)
1607                 return 0;
1608
1609         result = repack_without_refs(refs, refnames, &err);
1610         if (result) {
1611                 /*
1612                  * If we failed to rewrite the packed-refs file, then
1613                  * it is unsafe to try to remove loose refs, because
1614                  * doing so might expose an obsolete packed value for
1615                  * a reference that might even point at an object that
1616                  * has been garbage collected.
1617                  */
1618                 if (refnames->nr == 1)
1619                         error(_("could not delete reference %s: %s"),
1620                               refnames->items[0].string, err.buf);
1621                 else
1622                         error(_("could not delete references: %s"), err.buf);
1623
1624                 goto out;
1625         }
1626
1627         for (i = 0; i < refnames->nr; i++) {
1628                 const char *refname = refnames->items[i].string;
1629
1630                 if (refs_delete_ref(&refs->base, NULL, refname, NULL, flags))
1631                         result |= error(_("could not remove reference %s"), refname);
1632         }
1633
1634 out:
1635         strbuf_release(&err);
1636         return result;
1637 }
1638
1639 /*
1640  * People using contrib's git-new-workdir have .git/logs/refs ->
1641  * /some/other/path/.git/logs/refs, and that may live on another device.
1642  *
1643  * IOW, to avoid cross device rename errors, the temporary renamed log must
1644  * live into logs/refs.
1645  */
1646 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1647
1648 struct rename_cb {
1649         const char *tmp_renamed_log;
1650         int true_errno;
1651 };
1652
1653 static int rename_tmp_log_callback(const char *path, void *cb_data)
1654 {
1655         struct rename_cb *cb = cb_data;
1656
1657         if (rename(cb->tmp_renamed_log, path)) {
1658                 /*
1659                  * rename(a, b) when b is an existing directory ought
1660                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1661                  * Sheesh. Record the true errno for error reporting,
1662                  * but report EISDIR to raceproof_create_file() so
1663                  * that it knows to retry.
1664                  */
1665                 cb->true_errno = errno;
1666                 if (errno == ENOTDIR)
1667                         errno = EISDIR;
1668                 return -1;
1669         } else {
1670                 return 0;
1671         }
1672 }
1673
1674 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1675 {
1676         struct strbuf path = STRBUF_INIT;
1677         struct strbuf tmp = STRBUF_INIT;
1678         struct rename_cb cb;
1679         int ret;
1680
1681         files_reflog_path(refs, &path, newrefname);
1682         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1683         cb.tmp_renamed_log = tmp.buf;
1684         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1685         if (ret) {
1686                 if (errno == EISDIR)
1687                         error("directory not empty: %s", path.buf);
1688                 else
1689                         error("unable to move logfile %s to %s: %s",
1690                               tmp.buf, path.buf,
1691                               strerror(cb.true_errno));
1692         }
1693
1694         strbuf_release(&path);
1695         strbuf_release(&tmp);
1696         return ret;
1697 }
1698
1699 static int write_ref_to_lockfile(struct ref_lock *lock,
1700                                  const struct object_id *oid, struct strbuf *err);
1701 static int commit_ref_update(struct files_ref_store *refs,
1702                              struct ref_lock *lock,
1703                              const struct object_id *oid, const char *logmsg,
1704                              struct strbuf *err);
1705
1706 static int files_rename_ref(struct ref_store *ref_store,
1707                             const char *oldrefname, const char *newrefname,
1708                             const char *logmsg)
1709 {
1710         struct files_ref_store *refs =
1711                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1712         struct object_id oid, orig_oid;
1713         int flag = 0, logmoved = 0;
1714         struct ref_lock *lock;
1715         struct stat loginfo;
1716         struct strbuf sb_oldref = STRBUF_INIT;
1717         struct strbuf sb_newref = STRBUF_INIT;
1718         struct strbuf tmp_renamed_log = STRBUF_INIT;
1719         int log, ret;
1720         struct strbuf err = STRBUF_INIT;
1721
1722         files_reflog_path(refs, &sb_oldref, oldrefname);
1723         files_reflog_path(refs, &sb_newref, newrefname);
1724         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1725
1726         log = !lstat(sb_oldref.buf, &loginfo);
1727         if (log && S_ISLNK(loginfo.st_mode)) {
1728                 ret = error("reflog for %s is a symlink", oldrefname);
1729                 goto out;
1730         }
1731
1732         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1733                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1734                                 orig_oid.hash, &flag)) {
1735                 ret = error("refname %s not found", oldrefname);
1736                 goto out;
1737         }
1738
1739         if (flag & REF_ISSYMREF) {
1740                 ret = error("refname %s is a symbolic ref, renaming it is not supported",
1741                             oldrefname);
1742                 goto out;
1743         }
1744         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1745                 ret = 1;
1746                 goto out;
1747         }
1748
1749         if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1750                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1751                             oldrefname, strerror(errno));
1752                 goto out;
1753         }
1754
1755         if (refs_delete_ref(&refs->base, logmsg, oldrefname,
1756                             orig_oid.hash, REF_NODEREF)) {
1757                 error("unable to delete old %s", oldrefname);
1758                 goto rollback;
1759         }
1760
1761         /*
1762          * Since we are doing a shallow lookup, oid is not the
1763          * correct value to pass to delete_ref as old_oid. But that
1764          * doesn't matter, because an old_oid check wouldn't add to
1765          * the safety anyway; we want to delete the reference whatever
1766          * its current value.
1767          */
1768         if (!refs_read_ref_full(&refs->base, newrefname,
1769                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1770                                 oid.hash, NULL) &&
1771             refs_delete_ref(&refs->base, NULL, newrefname,
1772                             NULL, REF_NODEREF)) {
1773                 if (errno == EISDIR) {
1774                         struct strbuf path = STRBUF_INIT;
1775                         int result;
1776
1777                         files_ref_path(refs, &path, newrefname);
1778                         result = remove_empty_directories(&path);
1779                         strbuf_release(&path);
1780
1781                         if (result) {
1782                                 error("Directory not empty: %s", newrefname);
1783                                 goto rollback;
1784                         }
1785                 } else {
1786                         error("unable to delete existing %s", newrefname);
1787                         goto rollback;
1788                 }
1789         }
1790
1791         if (log && rename_tmp_log(refs, newrefname))
1792                 goto rollback;
1793
1794         logmoved = log;
1795
1796         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
1797                                    REF_NODEREF, NULL, &err);
1798         if (!lock) {
1799                 error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1800                 strbuf_release(&err);
1801                 goto rollback;
1802         }
1803         oidcpy(&lock->old_oid, &orig_oid);
1804
1805         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1806             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1807                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1808                 strbuf_release(&err);
1809                 goto rollback;
1810         }
1811
1812         ret = 0;
1813         goto out;
1814
1815  rollback:
1816         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
1817                                    REF_NODEREF, NULL, &err);
1818         if (!lock) {
1819                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1820                 strbuf_release(&err);
1821                 goto rollbacklog;
1822         }
1823
1824         flag = log_all_ref_updates;
1825         log_all_ref_updates = LOG_REFS_NONE;
1826         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1827             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1828                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1829                 strbuf_release(&err);
1830         }
1831         log_all_ref_updates = flag;
1832
1833  rollbacklog:
1834         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1835                 error("unable to restore logfile %s from %s: %s",
1836                         oldrefname, newrefname, strerror(errno));
1837         if (!logmoved && log &&
1838             rename(tmp_renamed_log.buf, sb_oldref.buf))
1839                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1840                         oldrefname, strerror(errno));
1841         ret = 1;
1842  out:
1843         strbuf_release(&sb_newref);
1844         strbuf_release(&sb_oldref);
1845         strbuf_release(&tmp_renamed_log);
1846
1847         return ret;
1848 }
1849
1850 static int close_ref(struct ref_lock *lock)
1851 {
1852         if (close_lock_file(lock->lk))
1853                 return -1;
1854         return 0;
1855 }
1856
1857 static int commit_ref(struct ref_lock *lock)
1858 {
1859         char *path = get_locked_file_path(lock->lk);
1860         struct stat st;
1861
1862         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1863                 /*
1864                  * There is a directory at the path we want to rename
1865                  * the lockfile to. Hopefully it is empty; try to
1866                  * delete it.
1867                  */
1868                 size_t len = strlen(path);
1869                 struct strbuf sb_path = STRBUF_INIT;
1870
1871                 strbuf_attach(&sb_path, path, len, len);
1872
1873                 /*
1874                  * If this fails, commit_lock_file() will also fail
1875                  * and will report the problem.
1876                  */
1877                 remove_empty_directories(&sb_path);
1878                 strbuf_release(&sb_path);
1879         } else {
1880                 free(path);
1881         }
1882
1883         if (commit_lock_file(lock->lk))
1884                 return -1;
1885         return 0;
1886 }
1887
1888 static int open_or_create_logfile(const char *path, void *cb)
1889 {
1890         int *fd = cb;
1891
1892         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1893         return (*fd < 0) ? -1 : 0;
1894 }
1895
1896 /*
1897  * Create a reflog for a ref. If force_create = 0, only create the
1898  * reflog for certain refs (those for which should_autocreate_reflog
1899  * returns non-zero). Otherwise, create it regardless of the reference
1900  * name. If the logfile already existed or was created, return 0 and
1901  * set *logfd to the file descriptor opened for appending to the file.
1902  * If no logfile exists and we decided not to create one, return 0 and
1903  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1904  * return -1.
1905  */
1906 static int log_ref_setup(struct files_ref_store *refs,
1907                          const char *refname, int force_create,
1908                          int *logfd, struct strbuf *err)
1909 {
1910         struct strbuf logfile_sb = STRBUF_INIT;
1911         char *logfile;
1912
1913         files_reflog_path(refs, &logfile_sb, refname);
1914         logfile = strbuf_detach(&logfile_sb, NULL);
1915
1916         if (force_create || should_autocreate_reflog(refname)) {
1917                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1918                         if (errno == ENOENT)
1919                                 strbuf_addf(err, "unable to create directory for '%s': "
1920                                             "%s", logfile, strerror(errno));
1921                         else if (errno == EISDIR)
1922                                 strbuf_addf(err, "there are still logs under '%s'",
1923                                             logfile);
1924                         else
1925                                 strbuf_addf(err, "unable to append to '%s': %s",
1926                                             logfile, strerror(errno));
1927
1928                         goto error;
1929                 }
1930         } else {
1931                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1932                 if (*logfd < 0) {
1933                         if (errno == ENOENT || errno == EISDIR) {
1934                                 /*
1935                                  * The logfile doesn't already exist,
1936                                  * but that is not an error; it only
1937                                  * means that we won't write log
1938                                  * entries to it.
1939                                  */
1940                                 ;
1941                         } else {
1942                                 strbuf_addf(err, "unable to append to '%s': %s",
1943                                             logfile, strerror(errno));
1944                                 goto error;
1945                         }
1946                 }
1947         }
1948
1949         if (*logfd >= 0)
1950                 adjust_shared_perm(logfile);
1951
1952         free(logfile);
1953         return 0;
1954
1955 error:
1956         free(logfile);
1957         return -1;
1958 }
1959
1960 static int files_create_reflog(struct ref_store *ref_store,
1961                                const char *refname, int force_create,
1962                                struct strbuf *err)
1963 {
1964         struct files_ref_store *refs =
1965                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1966         int fd;
1967
1968         if (log_ref_setup(refs, refname, force_create, &fd, err))
1969                 return -1;
1970
1971         if (fd >= 0)
1972                 close(fd);
1973
1974         return 0;
1975 }
1976
1977 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1978                             const struct object_id *new_oid,
1979                             const char *committer, const char *msg)
1980 {
1981         int msglen, written;
1982         unsigned maxlen, len;
1983         char *logrec;
1984
1985         msglen = msg ? strlen(msg) : 0;
1986         maxlen = strlen(committer) + msglen + 100;
1987         logrec = xmalloc(maxlen);
1988         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1989                         oid_to_hex(old_oid),
1990                         oid_to_hex(new_oid),
1991                         committer);
1992         if (msglen)
1993                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1994
1995         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1996         free(logrec);
1997         if (written != len)
1998                 return -1;
1999
2000         return 0;
2001 }
2002
2003 static int files_log_ref_write(struct files_ref_store *refs,
2004                                const char *refname, const struct object_id *old_oid,
2005                                const struct object_id *new_oid, const char *msg,
2006                                int flags, struct strbuf *err)
2007 {
2008         int logfd, result;
2009
2010         if (log_all_ref_updates == LOG_REFS_UNSET)
2011                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
2012
2013         result = log_ref_setup(refs, refname,
2014                                flags & REF_FORCE_CREATE_REFLOG,
2015                                &logfd, err);
2016
2017         if (result)
2018                 return result;
2019
2020         if (logfd < 0)
2021                 return 0;
2022         result = log_ref_write_fd(logfd, old_oid, new_oid,
2023                                   git_committer_info(0), msg);
2024         if (result) {
2025                 struct strbuf sb = STRBUF_INIT;
2026                 int save_errno = errno;
2027
2028                 files_reflog_path(refs, &sb, refname);
2029                 strbuf_addf(err, "unable to append to '%s': %s",
2030                             sb.buf, strerror(save_errno));
2031                 strbuf_release(&sb);
2032                 close(logfd);
2033                 return -1;
2034         }
2035         if (close(logfd)) {
2036                 struct strbuf sb = STRBUF_INIT;
2037                 int save_errno = errno;
2038
2039                 files_reflog_path(refs, &sb, refname);
2040                 strbuf_addf(err, "unable to append to '%s': %s",
2041                             sb.buf, strerror(save_errno));
2042                 strbuf_release(&sb);
2043                 return -1;
2044         }
2045         return 0;
2046 }
2047
2048 /*
2049  * Write sha1 into the open lockfile, then close the lockfile. On
2050  * errors, rollback the lockfile, fill in *err and
2051  * return -1.
2052  */
2053 static int write_ref_to_lockfile(struct ref_lock *lock,
2054                                  const struct object_id *oid, struct strbuf *err)
2055 {
2056         static char term = '\n';
2057         struct object *o;
2058         int fd;
2059
2060         o = parse_object(oid);
2061         if (!o) {
2062                 strbuf_addf(err,
2063                             "trying to write ref '%s' with nonexistent object %s",
2064                             lock->ref_name, oid_to_hex(oid));
2065                 unlock_ref(lock);
2066                 return -1;
2067         }
2068         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
2069                 strbuf_addf(err,
2070                             "trying to write non-commit object %s to branch '%s'",
2071                             oid_to_hex(oid), lock->ref_name);
2072                 unlock_ref(lock);
2073                 return -1;
2074         }
2075         fd = get_lock_file_fd(lock->lk);
2076         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
2077             write_in_full(fd, &term, 1) != 1 ||
2078             close_ref(lock) < 0) {
2079                 strbuf_addf(err,
2080                             "couldn't write '%s'", get_lock_file_path(lock->lk));
2081                 unlock_ref(lock);
2082                 return -1;
2083         }
2084         return 0;
2085 }
2086
2087 /*
2088  * Commit a change to a loose reference that has already been written
2089  * to the loose reference lockfile. Also update the reflogs if
2090  * necessary, using the specified lockmsg (which can be NULL).
2091  */
2092 static int commit_ref_update(struct files_ref_store *refs,
2093                              struct ref_lock *lock,
2094                              const struct object_id *oid, const char *logmsg,
2095                              struct strbuf *err)
2096 {
2097         files_assert_main_repository(refs, "commit_ref_update");
2098
2099         clear_loose_ref_cache(refs);
2100         if (files_log_ref_write(refs, lock->ref_name,
2101                                 &lock->old_oid, oid,
2102                                 logmsg, 0, err)) {
2103                 char *old_msg = strbuf_detach(err, NULL);
2104                 strbuf_addf(err, "cannot update the ref '%s': %s",
2105                             lock->ref_name, old_msg);
2106                 free(old_msg);
2107                 unlock_ref(lock);
2108                 return -1;
2109         }
2110
2111         if (strcmp(lock->ref_name, "HEAD") != 0) {
2112                 /*
2113                  * Special hack: If a branch is updated directly and HEAD
2114                  * points to it (may happen on the remote side of a push
2115                  * for example) then logically the HEAD reflog should be
2116                  * updated too.
2117                  * A generic solution implies reverse symref information,
2118                  * but finding all symrefs pointing to the given branch
2119                  * would be rather costly for this rare event (the direct
2120                  * update of a branch) to be worth it.  So let's cheat and
2121                  * check with HEAD only which should cover 99% of all usage
2122                  * scenarios (even 100% of the default ones).
2123                  */
2124                 struct object_id head_oid;
2125                 int head_flag;
2126                 const char *head_ref;
2127
2128                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
2129                                                    RESOLVE_REF_READING,
2130                                                    head_oid.hash, &head_flag);
2131                 if (head_ref && (head_flag & REF_ISSYMREF) &&
2132                     !strcmp(head_ref, lock->ref_name)) {
2133                         struct strbuf log_err = STRBUF_INIT;
2134                         if (files_log_ref_write(refs, "HEAD",
2135                                                 &lock->old_oid, oid,
2136                                                 logmsg, 0, &log_err)) {
2137                                 error("%s", log_err.buf);
2138                                 strbuf_release(&log_err);
2139                         }
2140                 }
2141         }
2142
2143         if (commit_ref(lock)) {
2144                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2145                 unlock_ref(lock);
2146                 return -1;
2147         }
2148
2149         unlock_ref(lock);
2150         return 0;
2151 }
2152
2153 static int create_ref_symlink(struct ref_lock *lock, const char *target)
2154 {
2155         int ret = -1;
2156 #ifndef NO_SYMLINK_HEAD
2157         char *ref_path = get_locked_file_path(lock->lk);
2158         unlink(ref_path);
2159         ret = symlink(target, ref_path);
2160         free(ref_path);
2161
2162         if (ret)
2163                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
2164 #endif
2165         return ret;
2166 }
2167
2168 static void update_symref_reflog(struct files_ref_store *refs,
2169                                  struct ref_lock *lock, const char *refname,
2170                                  const char *target, const char *logmsg)
2171 {
2172         struct strbuf err = STRBUF_INIT;
2173         struct object_id new_oid;
2174         if (logmsg &&
2175             !refs_read_ref_full(&refs->base, target,
2176                                 RESOLVE_REF_READING, new_oid.hash, NULL) &&
2177             files_log_ref_write(refs, refname, &lock->old_oid,
2178                                 &new_oid, logmsg, 0, &err)) {
2179                 error("%s", err.buf);
2180                 strbuf_release(&err);
2181         }
2182 }
2183
2184 static int create_symref_locked(struct files_ref_store *refs,
2185                                 struct ref_lock *lock, const char *refname,
2186                                 const char *target, const char *logmsg)
2187 {
2188         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
2189                 update_symref_reflog(refs, lock, refname, target, logmsg);
2190                 return 0;
2191         }
2192
2193         if (!fdopen_lock_file(lock->lk, "w"))
2194                 return error("unable to fdopen %s: %s",
2195                              lock->lk->tempfile.filename.buf, strerror(errno));
2196
2197         update_symref_reflog(refs, lock, refname, target, logmsg);
2198
2199         /* no error check; commit_ref will check ferror */
2200         fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
2201         if (commit_ref(lock) < 0)
2202                 return error("unable to write symref for %s: %s", refname,
2203                              strerror(errno));
2204         return 0;
2205 }
2206
2207 static int files_create_symref(struct ref_store *ref_store,
2208                                const char *refname, const char *target,
2209                                const char *logmsg)
2210 {
2211         struct files_ref_store *refs =
2212                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
2213         struct strbuf err = STRBUF_INIT;
2214         struct ref_lock *lock;
2215         int ret;
2216
2217         lock = lock_ref_sha1_basic(refs, refname, NULL,
2218                                    NULL, NULL, REF_NODEREF, NULL,
2219                                    &err);
2220         if (!lock) {
2221                 error("%s", err.buf);
2222                 strbuf_release(&err);
2223                 return -1;
2224         }
2225
2226         ret = create_symref_locked(refs, lock, refname, target, logmsg);
2227         unlock_ref(lock);
2228         return ret;
2229 }
2230
2231 static int files_reflog_exists(struct ref_store *ref_store,
2232                                const char *refname)
2233 {
2234         struct files_ref_store *refs =
2235                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
2236         struct strbuf sb = STRBUF_INIT;
2237         struct stat st;
2238         int ret;
2239
2240         files_reflog_path(refs, &sb, refname);
2241         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
2242         strbuf_release(&sb);
2243         return ret;
2244 }
2245
2246 static int files_delete_reflog(struct ref_store *ref_store,
2247                                const char *refname)
2248 {
2249         struct files_ref_store *refs =
2250                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
2251         struct strbuf sb = STRBUF_INIT;
2252         int ret;
2253
2254         files_reflog_path(refs, &sb, refname);
2255         ret = remove_path(sb.buf);
2256         strbuf_release(&sb);
2257         return ret;
2258 }
2259
2260 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
2261 {
2262         struct object_id ooid, noid;
2263         char *email_end, *message;
2264         timestamp_t timestamp;
2265         int tz;
2266         const char *p = sb->buf;
2267
2268         /* old SP new SP name <email> SP time TAB msg LF */
2269         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
2270             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
2271             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
2272             !(email_end = strchr(p, '>')) ||
2273             email_end[1] != ' ' ||
2274             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
2275             !message || message[0] != ' ' ||
2276             (message[1] != '+' && message[1] != '-') ||
2277             !isdigit(message[2]) || !isdigit(message[3]) ||
2278             !isdigit(message[4]) || !isdigit(message[5]))
2279                 return 0; /* corrupt? */
2280         email_end[1] = '\0';
2281         tz = strtol(message + 1, NULL, 10);
2282         if (message[6] != '\t')
2283                 message += 6;
2284         else
2285                 message += 7;
2286         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
2287 }
2288
2289 static char *find_beginning_of_line(char *bob, char *scan)
2290 {
2291         while (bob < scan && *(--scan) != '\n')
2292                 ; /* keep scanning backwards */
2293         /*
2294          * Return either beginning of the buffer, or LF at the end of
2295          * the previous line.
2296          */
2297         return scan;
2298 }
2299
2300 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
2301                                              const char *refname,
2302                                              each_reflog_ent_fn fn,
2303                                              void *cb_data)
2304 {
2305         struct files_ref_store *refs =
2306                 files_downcast(ref_store, REF_STORE_READ,
2307                                "for_each_reflog_ent_reverse");
2308         struct strbuf sb = STRBUF_INIT;
2309         FILE *logfp;
2310         long pos;
2311         int ret = 0, at_tail = 1;
2312
2313         files_reflog_path(refs, &sb, refname);
2314         logfp = fopen(sb.buf, "r");
2315         strbuf_release(&sb);
2316         if (!logfp)
2317                 return -1;
2318
2319         /* Jump to the end */
2320         if (fseek(logfp, 0, SEEK_END) < 0)
2321                 ret = error("cannot seek back reflog for %s: %s",
2322                             refname, strerror(errno));
2323         pos = ftell(logfp);
2324         while (!ret && 0 < pos) {
2325                 int cnt;
2326                 size_t nread;
2327                 char buf[BUFSIZ];
2328                 char *endp, *scanp;
2329
2330                 /* Fill next block from the end */
2331                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
2332                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
2333                         ret = error("cannot seek back reflog for %s: %s",
2334                                     refname, strerror(errno));
2335                         break;
2336                 }
2337                 nread = fread(buf, cnt, 1, logfp);
2338                 if (nread != 1) {
2339                         ret = error("cannot read %d bytes from reflog for %s: %s",
2340                                     cnt, refname, strerror(errno));
2341                         break;
2342                 }
2343                 pos -= cnt;
2344
2345                 scanp = endp = buf + cnt;
2346                 if (at_tail && scanp[-1] == '\n')
2347                         /* Looking at the final LF at the end of the file */
2348                         scanp--;
2349                 at_tail = 0;
2350
2351                 while (buf < scanp) {
2352                         /*
2353                          * terminating LF of the previous line, or the beginning
2354                          * of the buffer.
2355                          */
2356                         char *bp;
2357
2358                         bp = find_beginning_of_line(buf, scanp);
2359
2360                         if (*bp == '\n') {
2361                                 /*
2362                                  * The newline is the end of the previous line,
2363                                  * so we know we have complete line starting
2364                                  * at (bp + 1). Prefix it onto any prior data
2365                                  * we collected for the line and process it.
2366                                  */
2367                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
2368                                 scanp = bp;
2369                                 endp = bp + 1;
2370                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2371                                 strbuf_reset(&sb);
2372                                 if (ret)
2373                                         break;
2374                         } else if (!pos) {
2375                                 /*
2376                                  * We are at the start of the buffer, and the
2377                                  * start of the file; there is no previous
2378                                  * line, and we have everything for this one.
2379                                  * Process it, and we can end the loop.
2380                                  */
2381                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
2382                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2383                                 strbuf_reset(&sb);
2384                                 break;
2385                         }
2386
2387                         if (bp == buf) {
2388                                 /*
2389                                  * We are at the start of the buffer, and there
2390                                  * is more file to read backwards. Which means
2391                                  * we are in the middle of a line. Note that we
2392                                  * may get here even if *bp was a newline; that
2393                                  * just means we are at the exact end of the
2394                                  * previous line, rather than some spot in the
2395                                  * middle.
2396                                  *
2397                                  * Save away what we have to be combined with
2398                                  * the data from the next read.
2399                                  */
2400                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
2401                                 break;
2402                         }
2403                 }
2404
2405         }
2406         if (!ret && sb.len)
2407                 die("BUG: reverse reflog parser had leftover data");
2408
2409         fclose(logfp);
2410         strbuf_release(&sb);
2411         return ret;
2412 }
2413
2414 static int files_for_each_reflog_ent(struct ref_store *ref_store,
2415                                      const char *refname,
2416                                      each_reflog_ent_fn fn, void *cb_data)
2417 {
2418         struct files_ref_store *refs =
2419                 files_downcast(ref_store, REF_STORE_READ,
2420                                "for_each_reflog_ent");
2421         FILE *logfp;
2422         struct strbuf sb = STRBUF_INIT;
2423         int ret = 0;
2424
2425         files_reflog_path(refs, &sb, refname);
2426         logfp = fopen(sb.buf, "r");
2427         strbuf_release(&sb);
2428         if (!logfp)
2429                 return -1;
2430
2431         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2432                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2433         fclose(logfp);
2434         strbuf_release(&sb);
2435         return ret;
2436 }
2437
2438 struct files_reflog_iterator {
2439         struct ref_iterator base;
2440
2441         struct ref_store *ref_store;
2442         struct dir_iterator *dir_iterator;
2443         struct object_id oid;
2444 };
2445
2446 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2447 {
2448         struct files_reflog_iterator *iter =
2449                 (struct files_reflog_iterator *)ref_iterator;
2450         struct dir_iterator *diter = iter->dir_iterator;
2451         int ok;
2452
2453         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2454                 int flags;
2455
2456                 if (!S_ISREG(diter->st.st_mode))
2457                         continue;
2458                 if (diter->basename[0] == '.')
2459                         continue;
2460                 if (ends_with(diter->basename, ".lock"))
2461                         continue;
2462
2463                 if (refs_read_ref_full(iter->ref_store,
2464                                        diter->relative_path, 0,
2465                                        iter->oid.hash, &flags)) {
2466                         error("bad ref for %s", diter->path.buf);
2467                         continue;
2468                 }
2469
2470                 iter->base.refname = diter->relative_path;
2471                 iter->base.oid = &iter->oid;
2472                 iter->base.flags = flags;
2473                 return ITER_OK;
2474         }
2475
2476         iter->dir_iterator = NULL;
2477         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2478                 ok = ITER_ERROR;
2479         return ok;
2480 }
2481
2482 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2483                                    struct object_id *peeled)
2484 {
2485         die("BUG: ref_iterator_peel() called for reflog_iterator");
2486 }
2487
2488 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2489 {
2490         struct files_reflog_iterator *iter =
2491                 (struct files_reflog_iterator *)ref_iterator;
2492         int ok = ITER_DONE;
2493
2494         if (iter->dir_iterator)
2495                 ok = dir_iterator_abort(iter->dir_iterator);
2496
2497         base_ref_iterator_free(ref_iterator);
2498         return ok;
2499 }
2500
2501 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2502         files_reflog_iterator_advance,
2503         files_reflog_iterator_peel,
2504         files_reflog_iterator_abort
2505 };
2506
2507 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2508 {
2509         struct files_ref_store *refs =
2510                 files_downcast(ref_store, REF_STORE_READ,
2511                                "reflog_iterator_begin");
2512         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2513         struct ref_iterator *ref_iterator = &iter->base;
2514         struct strbuf sb = STRBUF_INIT;
2515
2516         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
2517         files_reflog_path(refs, &sb, NULL);
2518         iter->dir_iterator = dir_iterator_begin(sb.buf);
2519         iter->ref_store = ref_store;
2520         strbuf_release(&sb);
2521         return ref_iterator;
2522 }
2523
2524 static int ref_update_reject_duplicates(struct string_list *refnames,
2525                                         struct strbuf *err)
2526 {
2527         int i, n = refnames->nr;
2528
2529         assert(err);
2530
2531         for (i = 1; i < n; i++)
2532                 if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
2533                         strbuf_addf(err,
2534                                     "multiple updates for ref '%s' not allowed.",
2535                                     refnames->items[i].string);
2536                         return 1;
2537                 }
2538         return 0;
2539 }
2540
2541 /*
2542  * If update is a direct update of head_ref (the reference pointed to
2543  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2544  */
2545 static int split_head_update(struct ref_update *update,
2546                              struct ref_transaction *transaction,
2547                              const char *head_ref,
2548                              struct string_list *affected_refnames,
2549                              struct strbuf *err)
2550 {
2551         struct string_list_item *item;
2552         struct ref_update *new_update;
2553
2554         if ((update->flags & REF_LOG_ONLY) ||
2555             (update->flags & REF_ISPRUNING) ||
2556             (update->flags & REF_UPDATE_VIA_HEAD))
2557                 return 0;
2558
2559         if (strcmp(update->refname, head_ref))
2560                 return 0;
2561
2562         /*
2563          * First make sure that HEAD is not already in the
2564          * transaction. This insertion is O(N) in the transaction
2565          * size, but it happens at most once per transaction.
2566          */
2567         item = string_list_insert(affected_refnames, "HEAD");
2568         if (item->util) {
2569                 /* An entry already existed */
2570                 strbuf_addf(err,
2571                             "multiple updates for 'HEAD' (including one "
2572                             "via its referent '%s') are not allowed",
2573                             update->refname);
2574                 return TRANSACTION_NAME_CONFLICT;
2575         }
2576
2577         new_update = ref_transaction_add_update(
2578                         transaction, "HEAD",
2579                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2580                         update->new_oid.hash, update->old_oid.hash,
2581                         update->msg);
2582
2583         item->util = new_update;
2584
2585         return 0;
2586 }
2587
2588 /*
2589  * update is for a symref that points at referent and doesn't have
2590  * REF_NODEREF set. Split it into two updates:
2591  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2592  * - A new, separate update for the referent reference
2593  * Note that the new update will itself be subject to splitting when
2594  * the iteration gets to it.
2595  */
2596 static int split_symref_update(struct files_ref_store *refs,
2597                                struct ref_update *update,
2598                                const char *referent,
2599                                struct ref_transaction *transaction,
2600                                struct string_list *affected_refnames,
2601                                struct strbuf *err)
2602 {
2603         struct string_list_item *item;
2604         struct ref_update *new_update;
2605         unsigned int new_flags;
2606
2607         /*
2608          * First make sure that referent is not already in the
2609          * transaction. This insertion is O(N) in the transaction
2610          * size, but it happens at most once per symref in a
2611          * transaction.
2612          */
2613         item = string_list_insert(affected_refnames, referent);
2614         if (item->util) {
2615                 /* An entry already existed */
2616                 strbuf_addf(err,
2617                             "multiple updates for '%s' (including one "
2618                             "via symref '%s') are not allowed",
2619                             referent, update->refname);
2620                 return TRANSACTION_NAME_CONFLICT;
2621         }
2622
2623         new_flags = update->flags;
2624         if (!strcmp(update->refname, "HEAD")) {
2625                 /*
2626                  * Record that the new update came via HEAD, so that
2627                  * when we process it, split_head_update() doesn't try
2628                  * to add another reflog update for HEAD. Note that
2629                  * this bit will be propagated if the new_update
2630                  * itself needs to be split.
2631                  */
2632                 new_flags |= REF_UPDATE_VIA_HEAD;
2633         }
2634
2635         new_update = ref_transaction_add_update(
2636                         transaction, referent, new_flags,
2637                         update->new_oid.hash, update->old_oid.hash,
2638                         update->msg);
2639
2640         new_update->parent_update = update;
2641
2642         /*
2643          * Change the symbolic ref update to log only. Also, it
2644          * doesn't need to check its old SHA-1 value, as that will be
2645          * done when new_update is processed.
2646          */
2647         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2648         update->flags &= ~REF_HAVE_OLD;
2649
2650         item->util = new_update;
2651
2652         return 0;
2653 }
2654
2655 /*
2656  * Return the refname under which update was originally requested.
2657  */
2658 static const char *original_update_refname(struct ref_update *update)
2659 {
2660         while (update->parent_update)
2661                 update = update->parent_update;
2662
2663         return update->refname;
2664 }
2665
2666 /*
2667  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2668  * are consistent with oid, which is the reference's current value. If
2669  * everything is OK, return 0; otherwise, write an error message to
2670  * err and return -1.
2671  */
2672 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2673                          struct strbuf *err)
2674 {
2675         if (!(update->flags & REF_HAVE_OLD) ||
2676                    !oidcmp(oid, &update->old_oid))
2677                 return 0;
2678
2679         if (is_null_oid(&update->old_oid))
2680                 strbuf_addf(err, "cannot lock ref '%s': "
2681                             "reference already exists",
2682                             original_update_refname(update));
2683         else if (is_null_oid(oid))
2684                 strbuf_addf(err, "cannot lock ref '%s': "
2685                             "reference is missing but expected %s",
2686                             original_update_refname(update),
2687                             oid_to_hex(&update->old_oid));
2688         else
2689                 strbuf_addf(err, "cannot lock ref '%s': "
2690                             "is at %s but expected %s",
2691                             original_update_refname(update),
2692                             oid_to_hex(oid),
2693                             oid_to_hex(&update->old_oid));
2694
2695         return -1;
2696 }
2697
2698 /*
2699  * Prepare for carrying out update:
2700  * - Lock the reference referred to by update.
2701  * - Read the reference under lock.
2702  * - Check that its old SHA-1 value (if specified) is correct, and in
2703  *   any case record it in update->lock->old_oid for later use when
2704  *   writing the reflog.
2705  * - If it is a symref update without REF_NODEREF, split it up into a
2706  *   REF_LOG_ONLY update of the symref and add a separate update for
2707  *   the referent to transaction.
2708  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2709  *   update of HEAD.
2710  */
2711 static int lock_ref_for_update(struct files_ref_store *refs,
2712                                struct ref_update *update,
2713                                struct ref_transaction *transaction,
2714                                const char *head_ref,
2715                                struct string_list *affected_refnames,
2716                                struct strbuf *err)
2717 {
2718         struct strbuf referent = STRBUF_INIT;
2719         int mustexist = (update->flags & REF_HAVE_OLD) &&
2720                 !is_null_oid(&update->old_oid);
2721         int ret;
2722         struct ref_lock *lock;
2723
2724         files_assert_main_repository(refs, "lock_ref_for_update");
2725
2726         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2727                 update->flags |= REF_DELETING;
2728
2729         if (head_ref) {
2730                 ret = split_head_update(update, transaction, head_ref,
2731                                         affected_refnames, err);
2732                 if (ret)
2733                         return ret;
2734         }
2735
2736         ret = lock_raw_ref(refs, update->refname, mustexist,
2737                            affected_refnames, NULL,
2738                            &lock, &referent,
2739                            &update->type, err);
2740         if (ret) {
2741                 char *reason;
2742
2743                 reason = strbuf_detach(err, NULL);
2744                 strbuf_addf(err, "cannot lock ref '%s': %s",
2745                             original_update_refname(update), reason);
2746                 free(reason);
2747                 return ret;
2748         }
2749
2750         update->backend_data = lock;
2751
2752         if (update->type & REF_ISSYMREF) {
2753                 if (update->flags & REF_NODEREF) {
2754                         /*
2755                          * We won't be reading the referent as part of
2756                          * the transaction, so we have to read it here
2757                          * to record and possibly check old_sha1:
2758                          */
2759                         if (refs_read_ref_full(&refs->base,
2760                                                referent.buf, 0,
2761                                                lock->old_oid.hash, NULL)) {
2762                                 if (update->flags & REF_HAVE_OLD) {
2763                                         strbuf_addf(err, "cannot lock ref '%s': "
2764                                                     "error reading reference",
2765                                                     original_update_refname(update));
2766                                         return -1;
2767                                 }
2768                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2769                                 return TRANSACTION_GENERIC_ERROR;
2770                         }
2771                 } else {
2772                         /*
2773                          * Create a new update for the reference this
2774                          * symref is pointing at. Also, we will record
2775                          * and verify old_sha1 for this update as part
2776                          * of processing the split-off update, so we
2777                          * don't have to do it here.
2778                          */
2779                         ret = split_symref_update(refs, update,
2780                                                   referent.buf, transaction,
2781                                                   affected_refnames, err);
2782                         if (ret)
2783                                 return ret;
2784                 }
2785         } else {
2786                 struct ref_update *parent_update;
2787
2788                 if (check_old_oid(update, &lock->old_oid, err))
2789                         return TRANSACTION_GENERIC_ERROR;
2790
2791                 /*
2792                  * If this update is happening indirectly because of a
2793                  * symref update, record the old SHA-1 in the parent
2794                  * update:
2795                  */
2796                 for (parent_update = update->parent_update;
2797                      parent_update;
2798                      parent_update = parent_update->parent_update) {
2799                         struct ref_lock *parent_lock = parent_update->backend_data;
2800                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2801                 }
2802         }
2803
2804         if ((update->flags & REF_HAVE_NEW) &&
2805             !(update->flags & REF_DELETING) &&
2806             !(update->flags & REF_LOG_ONLY)) {
2807                 if (!(update->type & REF_ISSYMREF) &&
2808                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2809                         /*
2810                          * The reference already has the desired
2811                          * value, so we don't need to write it.
2812                          */
2813                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2814                                                  err)) {
2815                         char *write_err = strbuf_detach(err, NULL);
2816
2817                         /*
2818                          * The lock was freed upon failure of
2819                          * write_ref_to_lockfile():
2820                          */
2821                         update->backend_data = NULL;
2822                         strbuf_addf(err,
2823                                     "cannot update ref '%s': %s",
2824                                     update->refname, write_err);
2825                         free(write_err);
2826                         return TRANSACTION_GENERIC_ERROR;
2827                 } else {
2828                         update->flags |= REF_NEEDS_COMMIT;
2829                 }
2830         }
2831         if (!(update->flags & REF_NEEDS_COMMIT)) {
2832                 /*
2833                  * We didn't call write_ref_to_lockfile(), so
2834                  * the lockfile is still open. Close it to
2835                  * free up the file descriptor:
2836                  */
2837                 if (close_ref(lock)) {
2838                         strbuf_addf(err, "couldn't close '%s.lock'",
2839                                     update->refname);
2840                         return TRANSACTION_GENERIC_ERROR;
2841                 }
2842         }
2843         return 0;
2844 }
2845
2846 static int files_transaction_commit(struct ref_store *ref_store,
2847                                     struct ref_transaction *transaction,
2848                                     struct strbuf *err)
2849 {
2850         struct files_ref_store *refs =
2851                 files_downcast(ref_store, REF_STORE_WRITE,
2852                                "ref_transaction_commit");
2853         int ret = 0, i;
2854         struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
2855         struct string_list_item *ref_to_delete;
2856         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2857         char *head_ref = NULL;
2858         int head_type;
2859         struct object_id head_oid;
2860         struct strbuf sb = STRBUF_INIT;
2861
2862         assert(err);
2863
2864         if (transaction->state != REF_TRANSACTION_OPEN)
2865                 die("BUG: commit called for transaction that is not open");
2866
2867         if (!transaction->nr) {
2868                 transaction->state = REF_TRANSACTION_CLOSED;
2869                 return 0;
2870         }
2871
2872         /*
2873          * Fail if a refname appears more than once in the
2874          * transaction. (If we end up splitting up any updates using
2875          * split_symref_update() or split_head_update(), those
2876          * functions will check that the new updates don't have the
2877          * same refname as any existing ones.)
2878          */
2879         for (i = 0; i < transaction->nr; i++) {
2880                 struct ref_update *update = transaction->updates[i];
2881                 struct string_list_item *item =
2882                         string_list_append(&affected_refnames, update->refname);
2883
2884                 /*
2885                  * We store a pointer to update in item->util, but at
2886                  * the moment we never use the value of this field
2887                  * except to check whether it is non-NULL.
2888                  */
2889                 item->util = update;
2890         }
2891         string_list_sort(&affected_refnames);
2892         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2893                 ret = TRANSACTION_GENERIC_ERROR;
2894                 goto cleanup;
2895         }
2896
2897         /*
2898          * Special hack: If a branch is updated directly and HEAD
2899          * points to it (may happen on the remote side of a push
2900          * for example) then logically the HEAD reflog should be
2901          * updated too.
2902          *
2903          * A generic solution would require reverse symref lookups,
2904          * but finding all symrefs pointing to a given branch would be
2905          * rather costly for this rare event (the direct update of a
2906          * branch) to be worth it. So let's cheat and check with HEAD
2907          * only, which should cover 99% of all usage scenarios (even
2908          * 100% of the default ones).
2909          *
2910          * So if HEAD is a symbolic reference, then record the name of
2911          * the reference that it points to. If we see an update of
2912          * head_ref within the transaction, then split_head_update()
2913          * arranges for the reflog of HEAD to be updated, too.
2914          */
2915         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2916                                        RESOLVE_REF_NO_RECURSE,
2917                                        head_oid.hash, &head_type);
2918
2919         if (head_ref && !(head_type & REF_ISSYMREF)) {
2920                 free(head_ref);
2921                 head_ref = NULL;
2922         }
2923
2924         /*
2925          * Acquire all locks, verify old values if provided, check
2926          * that new values are valid, and write new values to the
2927          * lockfiles, ready to be activated. Only keep one lockfile
2928          * open at a time to avoid running out of file descriptors.
2929          */
2930         for (i = 0; i < transaction->nr; i++) {
2931                 struct ref_update *update = transaction->updates[i];
2932
2933                 ret = lock_ref_for_update(refs, update, transaction,
2934                                           head_ref, &affected_refnames, err);
2935                 if (ret)
2936                         goto cleanup;
2937         }
2938
2939         /* Perform updates first so live commits remain referenced */
2940         for (i = 0; i < transaction->nr; i++) {
2941                 struct ref_update *update = transaction->updates[i];
2942                 struct ref_lock *lock = update->backend_data;
2943
2944                 if (update->flags & REF_NEEDS_COMMIT ||
2945                     update->flags & REF_LOG_ONLY) {
2946                         if (files_log_ref_write(refs,
2947                                                 lock->ref_name,
2948                                                 &lock->old_oid,
2949                                                 &update->new_oid,
2950                                                 update->msg, update->flags,
2951                                                 err)) {
2952                                 char *old_msg = strbuf_detach(err, NULL);
2953
2954                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2955                                             lock->ref_name, old_msg);
2956                                 free(old_msg);
2957                                 unlock_ref(lock);
2958                                 update->backend_data = NULL;
2959                                 ret = TRANSACTION_GENERIC_ERROR;
2960                                 goto cleanup;
2961                         }
2962                 }
2963                 if (update->flags & REF_NEEDS_COMMIT) {
2964                         clear_loose_ref_cache(refs);
2965                         if (commit_ref(lock)) {
2966                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2967                                 unlock_ref(lock);
2968                                 update->backend_data = NULL;
2969                                 ret = TRANSACTION_GENERIC_ERROR;
2970                                 goto cleanup;
2971                         }
2972                 }
2973         }
2974         /* Perform deletes now that updates are safely completed */
2975         for (i = 0; i < transaction->nr; i++) {
2976                 struct ref_update *update = transaction->updates[i];
2977                 struct ref_lock *lock = update->backend_data;
2978
2979                 if (update->flags & REF_DELETING &&
2980                     !(update->flags & REF_LOG_ONLY)) {
2981                         if (!(update->type & REF_ISPACKED) ||
2982                             update->type & REF_ISSYMREF) {
2983                                 /* It is a loose reference. */
2984                                 strbuf_reset(&sb);
2985                                 files_ref_path(refs, &sb, lock->ref_name);
2986                                 if (unlink_or_msg(sb.buf, err)) {
2987                                         ret = TRANSACTION_GENERIC_ERROR;
2988                                         goto cleanup;
2989                                 }
2990                                 update->flags |= REF_DELETED_LOOSE;
2991                         }
2992
2993                         if (!(update->flags & REF_ISPRUNING))
2994                                 string_list_append(&refs_to_delete,
2995                                                    lock->ref_name);
2996                 }
2997         }
2998
2999         if (repack_without_refs(refs, &refs_to_delete, err)) {
3000                 ret = TRANSACTION_GENERIC_ERROR;
3001                 goto cleanup;
3002         }
3003
3004         /* Delete the reflogs of any references that were deleted: */
3005         for_each_string_list_item(ref_to_delete, &refs_to_delete) {
3006                 strbuf_reset(&sb);
3007                 files_reflog_path(refs, &sb, ref_to_delete->string);
3008                 if (!unlink_or_warn(sb.buf))
3009                         try_remove_empty_parents(refs, ref_to_delete->string,
3010                                                  REMOVE_EMPTY_PARENTS_REFLOG);
3011         }
3012
3013         clear_loose_ref_cache(refs);
3014
3015 cleanup:
3016         strbuf_release(&sb);
3017         transaction->state = REF_TRANSACTION_CLOSED;
3018
3019         for (i = 0; i < transaction->nr; i++) {
3020                 struct ref_update *update = transaction->updates[i];
3021                 struct ref_lock *lock = update->backend_data;
3022
3023                 if (lock)
3024                         unlock_ref(lock);
3025
3026                 if (update->flags & REF_DELETED_LOOSE) {
3027                         /*
3028                          * The loose reference was deleted. Delete any
3029                          * empty parent directories. (Note that this
3030                          * can only work because we have already
3031                          * removed the lockfile.)
3032                          */
3033                         try_remove_empty_parents(refs, update->refname,
3034                                                  REMOVE_EMPTY_PARENTS_REF);
3035                 }
3036         }
3037
3038         string_list_clear(&refs_to_delete, 0);
3039         free(head_ref);
3040         string_list_clear(&affected_refnames, 0);
3041
3042         return ret;
3043 }
3044
3045 static int ref_present(const char *refname,
3046                        const struct object_id *oid, int flags, void *cb_data)
3047 {
3048         struct string_list *affected_refnames = cb_data;
3049
3050         return string_list_has_string(affected_refnames, refname);
3051 }
3052
3053 static int files_initial_transaction_commit(struct ref_store *ref_store,
3054                                             struct ref_transaction *transaction,
3055                                             struct strbuf *err)
3056 {
3057         struct files_ref_store *refs =
3058                 files_downcast(ref_store, REF_STORE_WRITE,
3059                                "initial_ref_transaction_commit");
3060         int ret = 0, i;
3061         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3062
3063         assert(err);
3064
3065         if (transaction->state != REF_TRANSACTION_OPEN)
3066                 die("BUG: commit called for transaction that is not open");
3067
3068         /* Fail if a refname appears more than once in the transaction: */
3069         for (i = 0; i < transaction->nr; i++)
3070                 string_list_append(&affected_refnames,
3071                                    transaction->updates[i]->refname);
3072         string_list_sort(&affected_refnames);
3073         if (ref_update_reject_duplicates(&affected_refnames, err)) {
3074                 ret = TRANSACTION_GENERIC_ERROR;
3075                 goto cleanup;
3076         }
3077
3078         /*
3079          * It's really undefined to call this function in an active
3080          * repository or when there are existing references: we are
3081          * only locking and changing packed-refs, so (1) any
3082          * simultaneous processes might try to change a reference at
3083          * the same time we do, and (2) any existing loose versions of
3084          * the references that we are setting would have precedence
3085          * over our values. But some remote helpers create the remote
3086          * "HEAD" and "master" branches before calling this function,
3087          * so here we really only check that none of the references
3088          * that we are creating already exists.
3089          */
3090         if (refs_for_each_rawref(&refs->base, ref_present,
3091                                  &affected_refnames))
3092                 die("BUG: initial ref transaction called with existing refs");
3093
3094         for (i = 0; i < transaction->nr; i++) {
3095                 struct ref_update *update = transaction->updates[i];
3096
3097                 if ((update->flags & REF_HAVE_OLD) &&
3098                     !is_null_oid(&update->old_oid))
3099                         die("BUG: initial ref transaction with old_sha1 set");
3100                 if (refs_verify_refname_available(&refs->base, update->refname,
3101                                                   &affected_refnames, NULL,
3102                                                   err)) {
3103                         ret = TRANSACTION_NAME_CONFLICT;
3104                         goto cleanup;
3105                 }
3106         }
3107
3108         if (lock_packed_refs(refs, 0)) {
3109                 strbuf_addf(err, "unable to lock packed-refs file: %s",
3110                             strerror(errno));
3111                 ret = TRANSACTION_GENERIC_ERROR;
3112                 goto cleanup;
3113         }
3114
3115         for (i = 0; i < transaction->nr; i++) {
3116                 struct ref_update *update = transaction->updates[i];
3117
3118                 if ((update->flags & REF_HAVE_NEW) &&
3119                     !is_null_oid(&update->new_oid))
3120                         add_packed_ref(refs, update->refname,
3121                                        &update->new_oid);
3122         }
3123
3124         if (commit_packed_refs(refs)) {
3125                 strbuf_addf(err, "unable to commit packed-refs file: %s",
3126                             strerror(errno));
3127                 ret = TRANSACTION_GENERIC_ERROR;
3128                 goto cleanup;
3129         }
3130
3131 cleanup:
3132         transaction->state = REF_TRANSACTION_CLOSED;
3133         string_list_clear(&affected_refnames, 0);
3134         return ret;
3135 }
3136
3137 struct expire_reflog_cb {
3138         unsigned int flags;
3139         reflog_expiry_should_prune_fn *should_prune_fn;
3140         void *policy_cb;
3141         FILE *newlog;
3142         struct object_id last_kept_oid;
3143 };
3144
3145 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
3146                              const char *email, timestamp_t timestamp, int tz,
3147                              const char *message, void *cb_data)
3148 {
3149         struct expire_reflog_cb *cb = cb_data;
3150         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
3151
3152         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
3153                 ooid = &cb->last_kept_oid;
3154
3155         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
3156                                    message, policy_cb)) {
3157                 if (!cb->newlog)
3158                         printf("would prune %s", message);
3159                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3160                         printf("prune %s", message);
3161         } else {
3162                 if (cb->newlog) {
3163                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
3164                                 oid_to_hex(ooid), oid_to_hex(noid),
3165                                 email, timestamp, tz, message);
3166                         oidcpy(&cb->last_kept_oid, noid);
3167                 }
3168                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3169                         printf("keep %s", message);
3170         }
3171         return 0;
3172 }
3173
3174 static int files_reflog_expire(struct ref_store *ref_store,
3175                                const char *refname, const unsigned char *sha1,
3176                                unsigned int flags,
3177                                reflog_expiry_prepare_fn prepare_fn,
3178                                reflog_expiry_should_prune_fn should_prune_fn,
3179                                reflog_expiry_cleanup_fn cleanup_fn,
3180                                void *policy_cb_data)
3181 {
3182         struct files_ref_store *refs =
3183                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
3184         static struct lock_file reflog_lock;
3185         struct expire_reflog_cb cb;
3186         struct ref_lock *lock;
3187         struct strbuf log_file_sb = STRBUF_INIT;
3188         char *log_file;
3189         int status = 0;
3190         int type;
3191         struct strbuf err = STRBUF_INIT;
3192         struct object_id oid;
3193
3194         memset(&cb, 0, sizeof(cb));
3195         cb.flags = flags;
3196         cb.policy_cb = policy_cb_data;
3197         cb.should_prune_fn = should_prune_fn;
3198
3199         /*
3200          * The reflog file is locked by holding the lock on the
3201          * reference itself, plus we might need to update the
3202          * reference if --updateref was specified:
3203          */
3204         lock = lock_ref_sha1_basic(refs, refname, sha1,
3205                                    NULL, NULL, REF_NODEREF,
3206                                    &type, &err);
3207         if (!lock) {
3208                 error("cannot lock ref '%s': %s", refname, err.buf);
3209                 strbuf_release(&err);
3210                 return -1;
3211         }
3212         if (!refs_reflog_exists(ref_store, refname)) {
3213                 unlock_ref(lock);
3214                 return 0;
3215         }
3216
3217         files_reflog_path(refs, &log_file_sb, refname);
3218         log_file = strbuf_detach(&log_file_sb, NULL);
3219         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3220                 /*
3221                  * Even though holding $GIT_DIR/logs/$reflog.lock has
3222                  * no locking implications, we use the lock_file
3223                  * machinery here anyway because it does a lot of the
3224                  * work we need, including cleaning up if the program
3225                  * exits unexpectedly.
3226                  */
3227                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3228                         struct strbuf err = STRBUF_INIT;
3229                         unable_to_lock_message(log_file, errno, &err);
3230                         error("%s", err.buf);
3231                         strbuf_release(&err);
3232                         goto failure;
3233                 }
3234                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3235                 if (!cb.newlog) {
3236                         error("cannot fdopen %s (%s)",
3237                               get_lock_file_path(&reflog_lock), strerror(errno));
3238                         goto failure;
3239                 }
3240         }
3241
3242         hashcpy(oid.hash, sha1);
3243
3244         (*prepare_fn)(refname, &oid, cb.policy_cb);
3245         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3246         (*cleanup_fn)(cb.policy_cb);
3247
3248         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3249                 /*
3250                  * It doesn't make sense to adjust a reference pointed
3251                  * to by a symbolic ref based on expiring entries in
3252                  * the symbolic reference's reflog. Nor can we update
3253                  * a reference if there are no remaining reflog
3254                  * entries.
3255                  */
3256                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3257                         !(type & REF_ISSYMREF) &&
3258                         !is_null_oid(&cb.last_kept_oid);
3259
3260                 if (close_lock_file(&reflog_lock)) {
3261                         status |= error("couldn't write %s: %s", log_file,
3262                                         strerror(errno));
3263                 } else if (update &&
3264                            (write_in_full(get_lock_file_fd(lock->lk),
3265                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
3266                             write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
3267                             close_ref(lock) < 0)) {
3268                         status |= error("couldn't write %s",
3269                                         get_lock_file_path(lock->lk));
3270                         rollback_lock_file(&reflog_lock);
3271                 } else if (commit_lock_file(&reflog_lock)) {
3272                         status |= error("unable to write reflog '%s' (%s)",
3273                                         log_file, strerror(errno));
3274                 } else if (update && commit_ref(lock)) {
3275                         status |= error("couldn't set %s", lock->ref_name);
3276                 }
3277         }
3278         free(log_file);
3279         unlock_ref(lock);
3280         return status;
3281
3282  failure:
3283         rollback_lock_file(&reflog_lock);
3284         free(log_file);
3285         unlock_ref(lock);
3286         return -1;
3287 }
3288
3289 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3290 {
3291         struct files_ref_store *refs =
3292                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3293         struct strbuf sb = STRBUF_INIT;
3294
3295         /*
3296          * Create .git/refs/{heads,tags}
3297          */
3298         files_ref_path(refs, &sb, "refs/heads");
3299         safe_create_dir(sb.buf, 1);
3300
3301         strbuf_reset(&sb);
3302         files_ref_path(refs, &sb, "refs/tags");
3303         safe_create_dir(sb.buf, 1);
3304
3305         strbuf_release(&sb);
3306         return 0;
3307 }
3308
3309 struct ref_storage_be refs_be_files = {
3310         NULL,
3311         "files",
3312         files_ref_store_create,
3313         files_init_db,
3314         files_transaction_commit,
3315         files_initial_transaction_commit,
3316
3317         files_pack_refs,
3318         files_peel_ref,
3319         files_create_symref,
3320         files_delete_refs,
3321         files_rename_ref,
3322
3323         files_ref_iterator_begin,
3324         files_read_raw_ref,
3325
3326         files_reflog_iterator_begin,
3327         files_for_each_reflog_ent,
3328         files_for_each_reflog_ent_reverse,
3329         files_reflog_exists,
3330         files_create_reflog,
3331         files_delete_reflog,
3332         files_reflog_expire
3333 };