Merge branch 'hv/submodule-alt-odb' into maint
[git] / refs.c
1 #include "cache.h"
2 #include "refs.h"
3 #include "object.h"
4 #include "tag.h"
5 #include "dir.h"
6
7 /* ISSYMREF=0x01, ISPACKED=0x02 and ISBROKEN=0x04 are public interfaces */
8 #define REF_KNOWS_PEELED 0x10
9
10 struct ref_entry {
11         unsigned char flag; /* ISSYMREF? ISPACKED? */
12         unsigned char sha1[20];
13         unsigned char peeled[20];
14         /* The full name of the reference (e.g., "refs/heads/master"): */
15         char name[FLEX_ARRAY];
16 };
17
18 struct ref_array {
19         int nr, alloc;
20
21         /*
22          * Entries with index 0 <= i < sorted are sorted by name.  New
23          * entries are appended to the list unsorted, and are sorted
24          * only when required; thus we avoid the need to sort the list
25          * after the addition of every reference.
26          */
27         int sorted;
28
29         struct ref_entry **refs;
30 };
31
32 /*
33  * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
34  * Return a pointer to the refname within the line (null-terminated),
35  * or NULL if there was a problem.
36  */
37 static const char *parse_ref_line(char *line, unsigned char *sha1)
38 {
39         /*
40          * 42: the answer to everything.
41          *
42          * In this case, it happens to be the answer to
43          *  40 (length of sha1 hex representation)
44          *  +1 (space in between hex and name)
45          *  +1 (newline at the end of the line)
46          */
47         int len = strlen(line) - 42;
48
49         if (len <= 0)
50                 return NULL;
51         if (get_sha1_hex(line, sha1) < 0)
52                 return NULL;
53         if (!isspace(line[40]))
54                 return NULL;
55         line += 41;
56         if (isspace(*line))
57                 return NULL;
58         if (line[len] != '\n')
59                 return NULL;
60         line[len] = 0;
61
62         return line;
63 }
64
65 static struct ref_entry *create_ref_entry(const char *refname,
66                                           const unsigned char *sha1, int flag,
67                                           int check_name)
68 {
69         int len;
70         struct ref_entry *ref;
71
72         if (check_name &&
73             check_refname_format(refname, REFNAME_ALLOW_ONELEVEL|REFNAME_DOT_COMPONENT))
74                 die("Reference has invalid format: '%s'", refname);
75         len = strlen(refname) + 1;
76         ref = xmalloc(sizeof(struct ref_entry) + len);
77         hashcpy(ref->sha1, sha1);
78         hashclr(ref->peeled);
79         memcpy(ref->name, refname, len);
80         ref->flag = flag;
81         return ref;
82 }
83
84 /* Add a ref_entry to the end of the ref_array (unsorted). */
85 static void add_ref(struct ref_array *refs, struct ref_entry *ref)
86 {
87         ALLOC_GROW(refs->refs, refs->nr + 1, refs->alloc);
88         refs->refs[refs->nr++] = ref;
89 }
90
91 static int ref_entry_cmp(const void *a, const void *b)
92 {
93         struct ref_entry *one = *(struct ref_entry **)a;
94         struct ref_entry *two = *(struct ref_entry **)b;
95         return strcmp(one->name, two->name);
96 }
97
98 /*
99  * Emit a warning and return true iff ref1 and ref2 have the same name
100  * and the same sha1.  Die if they have the same name but different
101  * sha1s.
102  */
103 static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2)
104 {
105         if (!strcmp(ref1->name, ref2->name)) {
106                 /* Duplicate name; make sure that the SHA1s match: */
107                 if (hashcmp(ref1->sha1, ref2->sha1))
108                         die("Duplicated ref, and SHA1s don't match: %s",
109                             ref1->name);
110                 warning("Duplicated ref: %s", ref1->name);
111                 return 1;
112         } else {
113                 return 0;
114         }
115 }
116
117 /*
118  * Sort the entries in array (if they are not already sorted).
119  */
120 static void sort_ref_array(struct ref_array *array)
121 {
122         int i, j;
123
124         /*
125          * This check also prevents passing a zero-length array to qsort(),
126          * which is a problem on some platforms.
127          */
128         if (array->sorted == array->nr)
129                 return;
130
131         qsort(array->refs, array->nr, sizeof(*array->refs), ref_entry_cmp);
132
133         /* Remove any duplicates from the ref_array */
134         i = 0;
135         for (j = 1; j < array->nr; j++) {
136                 if (is_dup_ref(array->refs[i], array->refs[j])) {
137                         free(array->refs[j]);
138                         continue;
139                 }
140                 array->refs[++i] = array->refs[j];
141         }
142         array->sorted = array->nr = i + 1;
143 }
144
145 static struct ref_entry *search_ref_array(struct ref_array *array, const char *refname)
146 {
147         struct ref_entry *e, **r;
148         int len;
149
150         if (refname == NULL)
151                 return NULL;
152
153         if (!array->nr)
154                 return NULL;
155         sort_ref_array(array);
156         len = strlen(refname) + 1;
157         e = xmalloc(sizeof(struct ref_entry) + len);
158         memcpy(e->name, refname, len);
159
160         r = bsearch(&e, array->refs, array->nr, sizeof(*array->refs), ref_entry_cmp);
161
162         free(e);
163
164         if (r == NULL)
165                 return NULL;
166
167         return *r;
168 }
169
170 /*
171  * Future: need to be in "struct repository"
172  * when doing a full libification.
173  */
174 static struct ref_cache {
175         struct ref_cache *next;
176         char did_loose;
177         char did_packed;
178         struct ref_array loose;
179         struct ref_array packed;
180         /* The submodule name, or "" for the main repo. */
181         char name[FLEX_ARRAY];
182 } *ref_cache;
183
184 static struct ref_entry *current_ref;
185
186 static void clear_ref_array(struct ref_array *array)
187 {
188         int i;
189         for (i = 0; i < array->nr; i++)
190                 free(array->refs[i]);
191         free(array->refs);
192         array->sorted = array->nr = array->alloc = 0;
193         array->refs = NULL;
194 }
195
196 static void clear_packed_ref_cache(struct ref_cache *refs)
197 {
198         if (refs->did_packed)
199                 clear_ref_array(&refs->packed);
200         refs->did_packed = 0;
201 }
202
203 static void clear_loose_ref_cache(struct ref_cache *refs)
204 {
205         if (refs->did_loose)
206                 clear_ref_array(&refs->loose);
207         refs->did_loose = 0;
208 }
209
210 static struct ref_cache *create_ref_cache(const char *submodule)
211 {
212         int len;
213         struct ref_cache *refs;
214         if (!submodule)
215                 submodule = "";
216         len = strlen(submodule) + 1;
217         refs = xcalloc(1, sizeof(struct ref_cache) + len);
218         memcpy(refs->name, submodule, len);
219         return refs;
220 }
221
222 /*
223  * Return a pointer to a ref_cache for the specified submodule. For
224  * the main repository, use submodule==NULL. The returned structure
225  * will be allocated and initialized but not necessarily populated; it
226  * should not be freed.
227  */
228 static struct ref_cache *get_ref_cache(const char *submodule)
229 {
230         struct ref_cache *refs = ref_cache;
231         if (!submodule)
232                 submodule = "";
233         while (refs) {
234                 if (!strcmp(submodule, refs->name))
235                         return refs;
236                 refs = refs->next;
237         }
238
239         refs = create_ref_cache(submodule);
240         refs->next = ref_cache;
241         ref_cache = refs;
242         return refs;
243 }
244
245 void invalidate_ref_cache(const char *submodule)
246 {
247         struct ref_cache *refs = get_ref_cache(submodule);
248         clear_packed_ref_cache(refs);
249         clear_loose_ref_cache(refs);
250 }
251
252 static void read_packed_refs(FILE *f, struct ref_array *array)
253 {
254         struct ref_entry *last = NULL;
255         char refline[PATH_MAX];
256         int flag = REF_ISPACKED;
257
258         while (fgets(refline, sizeof(refline), f)) {
259                 unsigned char sha1[20];
260                 const char *refname;
261                 static const char header[] = "# pack-refs with:";
262
263                 if (!strncmp(refline, header, sizeof(header)-1)) {
264                         const char *traits = refline + sizeof(header) - 1;
265                         if (strstr(traits, " peeled "))
266                                 flag |= REF_KNOWS_PEELED;
267                         /* perhaps other traits later as well */
268                         continue;
269                 }
270
271                 refname = parse_ref_line(refline, sha1);
272                 if (refname) {
273                         last = create_ref_entry(refname, sha1, flag, 1);
274                         add_ref(array, last);
275                         continue;
276                 }
277                 if (last &&
278                     refline[0] == '^' &&
279                     strlen(refline) == 42 &&
280                     refline[41] == '\n' &&
281                     !get_sha1_hex(refline + 1, sha1))
282                         hashcpy(last->peeled, sha1);
283         }
284 }
285
286 static struct ref_array *get_packed_refs(struct ref_cache *refs)
287 {
288         if (!refs->did_packed) {
289                 const char *packed_refs_file;
290                 FILE *f;
291
292                 if (*refs->name)
293                         packed_refs_file = git_path_submodule(refs->name, "packed-refs");
294                 else
295                         packed_refs_file = git_path("packed-refs");
296                 f = fopen(packed_refs_file, "r");
297                 if (f) {
298                         read_packed_refs(f, &refs->packed);
299                         fclose(f);
300                 }
301                 refs->did_packed = 1;
302         }
303         return &refs->packed;
304 }
305
306 void add_packed_ref(const char *refname, const unsigned char *sha1)
307 {
308         add_ref(get_packed_refs(get_ref_cache(NULL)),
309                         create_ref_entry(refname, sha1, REF_ISPACKED, 1));
310 }
311
312 static void get_ref_dir(struct ref_cache *refs, const char *base,
313                         struct ref_array *array)
314 {
315         DIR *dir;
316         const char *path;
317
318         if (*refs->name)
319                 path = git_path_submodule(refs->name, "%s", base);
320         else
321                 path = git_path("%s", base);
322
323
324         dir = opendir(path);
325
326         if (dir) {
327                 struct dirent *de;
328                 int baselen = strlen(base);
329                 char *refname = xmalloc(baselen + 257);
330
331                 memcpy(refname, base, baselen);
332                 if (baselen && base[baselen-1] != '/')
333                         refname[baselen++] = '/';
334
335                 while ((de = readdir(dir)) != NULL) {
336                         unsigned char sha1[20];
337                         struct stat st;
338                         int flag;
339                         int namelen;
340                         const char *refdir;
341
342                         if (de->d_name[0] == '.')
343                                 continue;
344                         namelen = strlen(de->d_name);
345                         if (namelen > 255)
346                                 continue;
347                         if (has_extension(de->d_name, ".lock"))
348                                 continue;
349                         memcpy(refname + baselen, de->d_name, namelen+1);
350                         refdir = *refs->name
351                                 ? git_path_submodule(refs->name, "%s", refname)
352                                 : git_path("%s", refname);
353                         if (stat(refdir, &st) < 0)
354                                 continue;
355                         if (S_ISDIR(st.st_mode)) {
356                                 get_ref_dir(refs, refname, array);
357                                 continue;
358                         }
359                         if (*refs->name) {
360                                 hashclr(sha1);
361                                 flag = 0;
362                                 if (resolve_gitlink_ref(refs->name, refname, sha1) < 0) {
363                                         hashclr(sha1);
364                                         flag |= REF_ISBROKEN;
365                                 }
366                         } else if (read_ref_full(refname, sha1, 1, &flag)) {
367                                 hashclr(sha1);
368                                 flag |= REF_ISBROKEN;
369                         }
370                         add_ref(array, create_ref_entry(refname, sha1, flag, 1));
371                 }
372                 free(refname);
373                 closedir(dir);
374         }
375 }
376
377 struct warn_if_dangling_data {
378         FILE *fp;
379         const char *refname;
380         const char *msg_fmt;
381 };
382
383 static int warn_if_dangling_symref(const char *refname, const unsigned char *sha1,
384                                    int flags, void *cb_data)
385 {
386         struct warn_if_dangling_data *d = cb_data;
387         const char *resolves_to;
388         unsigned char junk[20];
389
390         if (!(flags & REF_ISSYMREF))
391                 return 0;
392
393         resolves_to = resolve_ref_unsafe(refname, junk, 0, NULL);
394         if (!resolves_to || strcmp(resolves_to, d->refname))
395                 return 0;
396
397         fprintf(d->fp, d->msg_fmt, refname);
398         return 0;
399 }
400
401 void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
402 {
403         struct warn_if_dangling_data data;
404
405         data.fp = fp;
406         data.refname = refname;
407         data.msg_fmt = msg_fmt;
408         for_each_rawref(warn_if_dangling_symref, &data);
409 }
410
411 static struct ref_array *get_loose_refs(struct ref_cache *refs)
412 {
413         if (!refs->did_loose) {
414                 get_ref_dir(refs, "refs", &refs->loose);
415                 refs->did_loose = 1;
416         }
417         return &refs->loose;
418 }
419
420 /* We allow "recursive" symbolic refs. Only within reason, though */
421 #define MAXDEPTH 5
422 #define MAXREFLEN (1024)
423
424 /*
425  * Called by resolve_gitlink_ref_recursive() after it failed to read
426  * from the loose refs in ref_cache refs. Find <refname> in the
427  * packed-refs file for the submodule.
428  */
429 static int resolve_gitlink_packed_ref(struct ref_cache *refs,
430                                       const char *refname, unsigned char *sha1)
431 {
432         struct ref_entry *ref;
433         struct ref_array *array = get_packed_refs(refs);
434
435         ref = search_ref_array(array, refname);
436         if (ref == NULL)
437                 return -1;
438
439         memcpy(sha1, ref->sha1, 20);
440         return 0;
441 }
442
443 static int resolve_gitlink_ref_recursive(struct ref_cache *refs,
444                                          const char *refname, unsigned char *sha1,
445                                          int recursion)
446 {
447         int fd, len;
448         char buffer[128], *p;
449         char *path;
450
451         if (recursion > MAXDEPTH || strlen(refname) > MAXREFLEN)
452                 return -1;
453         path = *refs->name
454                 ? git_path_submodule(refs->name, "%s", refname)
455                 : git_path("%s", refname);
456         fd = open(path, O_RDONLY);
457         if (fd < 0)
458                 return resolve_gitlink_packed_ref(refs, refname, sha1);
459
460         len = read(fd, buffer, sizeof(buffer)-1);
461         close(fd);
462         if (len < 0)
463                 return -1;
464         while (len && isspace(buffer[len-1]))
465                 len--;
466         buffer[len] = 0;
467
468         /* Was it a detached head or an old-fashioned symlink? */
469         if (!get_sha1_hex(buffer, sha1))
470                 return 0;
471
472         /* Symref? */
473         if (strncmp(buffer, "ref:", 4))
474                 return -1;
475         p = buffer + 4;
476         while (isspace(*p))
477                 p++;
478
479         return resolve_gitlink_ref_recursive(refs, p, sha1, recursion+1);
480 }
481
482 int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1)
483 {
484         int len = strlen(path), retval;
485         char *submodule;
486         struct ref_cache *refs;
487
488         while (len && path[len-1] == '/')
489                 len--;
490         if (!len)
491                 return -1;
492         submodule = xstrndup(path, len);
493         refs = get_ref_cache(submodule);
494         free(submodule);
495
496         retval = resolve_gitlink_ref_recursive(refs, refname, sha1, 0);
497         return retval;
498 }
499
500 /*
501  * Try to read ref from the packed references.  On success, set sha1
502  * and return 0; otherwise, return -1.
503  */
504 static int get_packed_ref(const char *refname, unsigned char *sha1)
505 {
506         struct ref_array *packed = get_packed_refs(get_ref_cache(NULL));
507         struct ref_entry *entry = search_ref_array(packed, refname);
508         if (entry) {
509                 hashcpy(sha1, entry->sha1);
510                 return 0;
511         }
512         return -1;
513 }
514
515 const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
516 {
517         int depth = MAXDEPTH;
518         ssize_t len;
519         char buffer[256];
520         static char refname_buffer[256];
521
522         if (flag)
523                 *flag = 0;
524
525         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
526                 return NULL;
527
528         for (;;) {
529                 char path[PATH_MAX];
530                 struct stat st;
531                 char *buf;
532                 int fd;
533
534                 if (--depth < 0)
535                         return NULL;
536
537                 git_snpath(path, sizeof(path), "%s", refname);
538
539                 if (lstat(path, &st) < 0) {
540                         if (errno != ENOENT)
541                                 return NULL;
542                         /*
543                          * The loose reference file does not exist;
544                          * check for a packed reference.
545                          */
546                         if (!get_packed_ref(refname, sha1)) {
547                                 if (flag)
548                                         *flag |= REF_ISPACKED;
549                                 return refname;
550                         }
551                         /* The reference is not a packed reference, either. */
552                         if (reading) {
553                                 return NULL;
554                         } else {
555                                 hashclr(sha1);
556                                 return refname;
557                         }
558                 }
559
560                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
561                 if (S_ISLNK(st.st_mode)) {
562                         len = readlink(path, buffer, sizeof(buffer)-1);
563                         if (len < 0)
564                                 return NULL;
565                         buffer[len] = 0;
566                         if (!prefixcmp(buffer, "refs/") &&
567                                         !check_refname_format(buffer, 0)) {
568                                 strcpy(refname_buffer, buffer);
569                                 refname = refname_buffer;
570                                 if (flag)
571                                         *flag |= REF_ISSYMREF;
572                                 continue;
573                         }
574                 }
575
576                 /* Is it a directory? */
577                 if (S_ISDIR(st.st_mode)) {
578                         errno = EISDIR;
579                         return NULL;
580                 }
581
582                 /*
583                  * Anything else, just open it and try to use it as
584                  * a ref
585                  */
586                 fd = open(path, O_RDONLY);
587                 if (fd < 0)
588                         return NULL;
589                 len = read_in_full(fd, buffer, sizeof(buffer)-1);
590                 close(fd);
591                 if (len < 0)
592                         return NULL;
593                 while (len && isspace(buffer[len-1]))
594                         len--;
595                 buffer[len] = '\0';
596
597                 /*
598                  * Is it a symbolic ref?
599                  */
600                 if (prefixcmp(buffer, "ref:"))
601                         break;
602                 if (flag)
603                         *flag |= REF_ISSYMREF;
604                 buf = buffer + 4;
605                 while (isspace(*buf))
606                         buf++;
607                 if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
608                         if (flag)
609                                 *flag |= REF_ISBROKEN;
610                         return NULL;
611                 }
612                 refname = strcpy(refname_buffer, buf);
613         }
614         /* Please note that FETCH_HEAD has a second line containing other data. */
615         if (get_sha1_hex(buffer, sha1) || (buffer[40] != '\0' && !isspace(buffer[40]))) {
616                 if (flag)
617                         *flag |= REF_ISBROKEN;
618                 return NULL;
619         }
620         return refname;
621 }
622
623 char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag)
624 {
625         const char *ret = resolve_ref_unsafe(ref, sha1, reading, flag);
626         return ret ? xstrdup(ret) : NULL;
627 }
628
629 /* The argument to filter_refs */
630 struct ref_filter {
631         const char *pattern;
632         each_ref_fn *fn;
633         void *cb_data;
634 };
635
636 int read_ref_full(const char *refname, unsigned char *sha1, int reading, int *flags)
637 {
638         if (resolve_ref_unsafe(refname, sha1, reading, flags))
639                 return 0;
640         return -1;
641 }
642
643 int read_ref(const char *refname, unsigned char *sha1)
644 {
645         return read_ref_full(refname, sha1, 1, NULL);
646 }
647
648 #define DO_FOR_EACH_INCLUDE_BROKEN 01
649 static int do_one_ref(const char *base, each_ref_fn fn, int trim,
650                       int flags, void *cb_data, struct ref_entry *entry)
651 {
652         if (prefixcmp(entry->name, base))
653                 return 0;
654
655         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN)) {
656                 if (entry->flag & REF_ISBROKEN)
657                         return 0; /* ignore broken refs e.g. dangling symref */
658                 if (!has_sha1_file(entry->sha1)) {
659                         error("%s does not point to a valid object!", entry->name);
660                         return 0;
661                 }
662         }
663         current_ref = entry;
664         return fn(entry->name + trim, entry->sha1, entry->flag, cb_data);
665 }
666
667 static int filter_refs(const char *refname, const unsigned char *sha1, int flags,
668                        void *data)
669 {
670         struct ref_filter *filter = (struct ref_filter *)data;
671         if (fnmatch(filter->pattern, refname, 0))
672                 return 0;
673         return filter->fn(refname, sha1, flags, filter->cb_data);
674 }
675
676 int peel_ref(const char *refname, unsigned char *sha1)
677 {
678         int flag;
679         unsigned char base[20];
680         struct object *o;
681
682         if (current_ref && (current_ref->name == refname
683                 || !strcmp(current_ref->name, refname))) {
684                 if (current_ref->flag & REF_KNOWS_PEELED) {
685                         hashcpy(sha1, current_ref->peeled);
686                         return 0;
687                 }
688                 hashcpy(base, current_ref->sha1);
689                 goto fallback;
690         }
691
692         if (read_ref_full(refname, base, 1, &flag))
693                 return -1;
694
695         if ((flag & REF_ISPACKED)) {
696                 struct ref_array *array = get_packed_refs(get_ref_cache(NULL));
697                 struct ref_entry *r = search_ref_array(array, refname);
698
699                 if (r != NULL && r->flag & REF_KNOWS_PEELED) {
700                         hashcpy(sha1, r->peeled);
701                         return 0;
702                 }
703         }
704
705 fallback:
706         o = parse_object(base);
707         if (o && o->type == OBJ_TAG) {
708                 o = deref_tag(o, refname, 0);
709                 if (o) {
710                         hashcpy(sha1, o->sha1);
711                         return 0;
712                 }
713         }
714         return -1;
715 }
716
717 static int do_for_each_ref(const char *submodule, const char *base, each_ref_fn fn,
718                            int trim, int flags, void *cb_data)
719 {
720         int retval = 0, p = 0, l = 0;
721         struct ref_cache *refs = get_ref_cache(submodule);
722         struct ref_array *packed = get_packed_refs(refs);
723         struct ref_array *loose = get_loose_refs(refs);
724
725         sort_ref_array(packed);
726         sort_ref_array(loose);
727         while (p < packed->nr && l < loose->nr) {
728                 struct ref_entry *entry;
729                 int cmp = strcmp(packed->refs[p]->name, loose->refs[l]->name);
730                 if (!cmp) {
731                         p++;
732                         continue;
733                 }
734                 if (cmp > 0) {
735                         entry = loose->refs[l++];
736                 } else {
737                         entry = packed->refs[p++];
738                 }
739                 retval = do_one_ref(base, fn, trim, flags, cb_data, entry);
740                 if (retval)
741                         goto end_each;
742         }
743
744         if (l < loose->nr) {
745                 p = l;
746                 packed = loose;
747         }
748
749         for (; p < packed->nr; p++) {
750                 retval = do_one_ref(base, fn, trim, flags, cb_data, packed->refs[p]);
751                 if (retval)
752                         goto end_each;
753         }
754
755 end_each:
756         current_ref = NULL;
757         return retval;
758 }
759
760
761 static int do_head_ref(const char *submodule, each_ref_fn fn, void *cb_data)
762 {
763         unsigned char sha1[20];
764         int flag;
765
766         if (submodule) {
767                 if (resolve_gitlink_ref(submodule, "HEAD", sha1) == 0)
768                         return fn("HEAD", sha1, 0, cb_data);
769
770                 return 0;
771         }
772
773         if (!read_ref_full("HEAD", sha1, 1, &flag))
774                 return fn("HEAD", sha1, flag, cb_data);
775
776         return 0;
777 }
778
779 int head_ref(each_ref_fn fn, void *cb_data)
780 {
781         return do_head_ref(NULL, fn, cb_data);
782 }
783
784 int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
785 {
786         return do_head_ref(submodule, fn, cb_data);
787 }
788
789 int for_each_ref(each_ref_fn fn, void *cb_data)
790 {
791         return do_for_each_ref(NULL, "", fn, 0, 0, cb_data);
792 }
793
794 int for_each_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
795 {
796         return do_for_each_ref(submodule, "", fn, 0, 0, cb_data);
797 }
798
799 int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
800 {
801         return do_for_each_ref(NULL, prefix, fn, strlen(prefix), 0, cb_data);
802 }
803
804 int for_each_ref_in_submodule(const char *submodule, const char *prefix,
805                 each_ref_fn fn, void *cb_data)
806 {
807         return do_for_each_ref(submodule, prefix, fn, strlen(prefix), 0, cb_data);
808 }
809
810 int for_each_tag_ref(each_ref_fn fn, void *cb_data)
811 {
812         return for_each_ref_in("refs/tags/", fn, cb_data);
813 }
814
815 int for_each_tag_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
816 {
817         return for_each_ref_in_submodule(submodule, "refs/tags/", fn, cb_data);
818 }
819
820 int for_each_branch_ref(each_ref_fn fn, void *cb_data)
821 {
822         return for_each_ref_in("refs/heads/", fn, cb_data);
823 }
824
825 int for_each_branch_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
826 {
827         return for_each_ref_in_submodule(submodule, "refs/heads/", fn, cb_data);
828 }
829
830 int for_each_remote_ref(each_ref_fn fn, void *cb_data)
831 {
832         return for_each_ref_in("refs/remotes/", fn, cb_data);
833 }
834
835 int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
836 {
837         return for_each_ref_in_submodule(submodule, "refs/remotes/", fn, cb_data);
838 }
839
840 int for_each_replace_ref(each_ref_fn fn, void *cb_data)
841 {
842         return do_for_each_ref(NULL, "refs/replace/", fn, 13, 0, cb_data);
843 }
844
845 int head_ref_namespaced(each_ref_fn fn, void *cb_data)
846 {
847         struct strbuf buf = STRBUF_INIT;
848         int ret = 0;
849         unsigned char sha1[20];
850         int flag;
851
852         strbuf_addf(&buf, "%sHEAD", get_git_namespace());
853         if (!read_ref_full(buf.buf, sha1, 1, &flag))
854                 ret = fn(buf.buf, sha1, flag, cb_data);
855         strbuf_release(&buf);
856
857         return ret;
858 }
859
860 int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
861 {
862         struct strbuf buf = STRBUF_INIT;
863         int ret;
864         strbuf_addf(&buf, "%srefs/", get_git_namespace());
865         ret = do_for_each_ref(NULL, buf.buf, fn, 0, 0, cb_data);
866         strbuf_release(&buf);
867         return ret;
868 }
869
870 int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
871         const char *prefix, void *cb_data)
872 {
873         struct strbuf real_pattern = STRBUF_INIT;
874         struct ref_filter filter;
875         int ret;
876
877         if (!prefix && prefixcmp(pattern, "refs/"))
878                 strbuf_addstr(&real_pattern, "refs/");
879         else if (prefix)
880                 strbuf_addstr(&real_pattern, prefix);
881         strbuf_addstr(&real_pattern, pattern);
882
883         if (!has_glob_specials(pattern)) {
884                 /* Append implied '/' '*' if not present. */
885                 if (real_pattern.buf[real_pattern.len - 1] != '/')
886                         strbuf_addch(&real_pattern, '/');
887                 /* No need to check for '*', there is none. */
888                 strbuf_addch(&real_pattern, '*');
889         }
890
891         filter.pattern = real_pattern.buf;
892         filter.fn = fn;
893         filter.cb_data = cb_data;
894         ret = for_each_ref(filter_refs, &filter);
895
896         strbuf_release(&real_pattern);
897         return ret;
898 }
899
900 int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
901 {
902         return for_each_glob_ref_in(fn, pattern, NULL, cb_data);
903 }
904
905 int for_each_rawref(each_ref_fn fn, void *cb_data)
906 {
907         return do_for_each_ref(NULL, "", fn, 0,
908                                DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
909 }
910
911 /*
912  * Make sure "ref" is something reasonable to have under ".git/refs/";
913  * We do not like it if:
914  *
915  * - any path component of it begins with ".", or
916  * - it has double dots "..", or
917  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
918  * - it ends with a "/".
919  * - it ends with ".lock"
920  * - it contains a "\" (backslash)
921  */
922
923 /* Return true iff ch is not allowed in reference names. */
924 static inline int bad_ref_char(int ch)
925 {
926         if (((unsigned) ch) <= ' ' || ch == 0x7f ||
927             ch == '~' || ch == '^' || ch == ':' || ch == '\\')
928                 return 1;
929         /* 2.13 Pattern Matching Notation */
930         if (ch == '*' || ch == '?' || ch == '[') /* Unsupported */
931                 return 1;
932         return 0;
933 }
934
935 /*
936  * Try to read one refname component from the front of refname.  Return
937  * the length of the component found, or -1 if the component is not
938  * legal.
939  */
940 static int check_refname_component(const char *refname, int flags)
941 {
942         const char *cp;
943         char last = '\0';
944
945         for (cp = refname; ; cp++) {
946                 char ch = *cp;
947                 if (ch == '\0' || ch == '/')
948                         break;
949                 if (bad_ref_char(ch))
950                         return -1; /* Illegal character in refname. */
951                 if (last == '.' && ch == '.')
952                         return -1; /* Refname contains "..". */
953                 if (last == '@' && ch == '{')
954                         return -1; /* Refname contains "@{". */
955                 last = ch;
956         }
957         if (cp == refname)
958                 return -1; /* Component has zero length. */
959         if (refname[0] == '.') {
960                 if (!(flags & REFNAME_DOT_COMPONENT))
961                         return -1; /* Component starts with '.'. */
962                 /*
963                  * Even if leading dots are allowed, don't allow "."
964                  * as a component (".." is prevented by a rule above).
965                  */
966                 if (refname[1] == '\0')
967                         return -1; /* Component equals ".". */
968         }
969         if (cp - refname >= 5 && !memcmp(cp - 5, ".lock", 5))
970                 return -1; /* Refname ends with ".lock". */
971         return cp - refname;
972 }
973
974 int check_refname_format(const char *refname, int flags)
975 {
976         int component_len, component_count = 0;
977
978         while (1) {
979                 /* We are at the start of a path component. */
980                 component_len = check_refname_component(refname, flags);
981                 if (component_len < 0) {
982                         if ((flags & REFNAME_REFSPEC_PATTERN) &&
983                                         refname[0] == '*' &&
984                                         (refname[1] == '\0' || refname[1] == '/')) {
985                                 /* Accept one wildcard as a full refname component. */
986                                 flags &= ~REFNAME_REFSPEC_PATTERN;
987                                 component_len = 1;
988                         } else {
989                                 return -1;
990                         }
991                 }
992                 component_count++;
993                 if (refname[component_len] == '\0')
994                         break;
995                 /* Skip to next component. */
996                 refname += component_len + 1;
997         }
998
999         if (refname[component_len - 1] == '.')
1000                 return -1; /* Refname ends with '.'. */
1001         if (!(flags & REFNAME_ALLOW_ONELEVEL) && component_count < 2)
1002                 return -1; /* Refname has only one component. */
1003         return 0;
1004 }
1005
1006 const char *prettify_refname(const char *name)
1007 {
1008         return name + (
1009                 !prefixcmp(name, "refs/heads/") ? 11 :
1010                 !prefixcmp(name, "refs/tags/") ? 10 :
1011                 !prefixcmp(name, "refs/remotes/") ? 13 :
1012                 0);
1013 }
1014
1015 const char *ref_rev_parse_rules[] = {
1016         "%.*s",
1017         "refs/%.*s",
1018         "refs/tags/%.*s",
1019         "refs/heads/%.*s",
1020         "refs/remotes/%.*s",
1021         "refs/remotes/%.*s/HEAD",
1022         NULL
1023 };
1024
1025 int refname_match(const char *abbrev_name, const char *full_name, const char **rules)
1026 {
1027         const char **p;
1028         const int abbrev_name_len = strlen(abbrev_name);
1029
1030         for (p = rules; *p; p++) {
1031                 if (!strcmp(full_name, mkpath(*p, abbrev_name_len, abbrev_name))) {
1032                         return 1;
1033                 }
1034         }
1035
1036         return 0;
1037 }
1038
1039 static struct ref_lock *verify_lock(struct ref_lock *lock,
1040         const unsigned char *old_sha1, int mustexist)
1041 {
1042         if (read_ref_full(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
1043                 error("Can't verify ref %s", lock->ref_name);
1044                 unlock_ref(lock);
1045                 return NULL;
1046         }
1047         if (hashcmp(lock->old_sha1, old_sha1)) {
1048                 error("Ref %s is at %s but expected %s", lock->ref_name,
1049                         sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
1050                 unlock_ref(lock);
1051                 return NULL;
1052         }
1053         return lock;
1054 }
1055
1056 static int remove_empty_directories(const char *file)
1057 {
1058         /* we want to create a file but there is a directory there;
1059          * if that is an empty directory (or a directory that contains
1060          * only empty directories), remove them.
1061          */
1062         struct strbuf path;
1063         int result;
1064
1065         strbuf_init(&path, 20);
1066         strbuf_addstr(&path, file);
1067
1068         result = remove_dir_recursively(&path, REMOVE_DIR_EMPTY_ONLY);
1069
1070         strbuf_release(&path);
1071
1072         return result;
1073 }
1074
1075 /*
1076  * Return true iff a reference named refname could be created without
1077  * conflicting with the name of an existing reference.  If oldrefname
1078  * is non-NULL, ignore potential conflicts with oldrefname (e.g.,
1079  * because oldrefname is scheduled for deletion in the same
1080  * operation).
1081  */
1082 static int is_refname_available(const char *refname, const char *oldrefname,
1083                                 struct ref_array *array)
1084 {
1085         int i, namlen = strlen(refname); /* e.g. 'foo/bar' */
1086         for (i = 0; i < array->nr; i++ ) {
1087                 struct ref_entry *entry = array->refs[i];
1088                 /* entry->name could be 'foo' or 'foo/bar/baz' */
1089                 if (!oldrefname || strcmp(oldrefname, entry->name)) {
1090                         int len = strlen(entry->name);
1091                         int cmplen = (namlen < len) ? namlen : len;
1092                         const char *lead = (namlen < len) ? entry->name : refname;
1093                         if (!strncmp(refname, entry->name, cmplen) &&
1094                             lead[cmplen] == '/') {
1095                                 error("'%s' exists; cannot create '%s'",
1096                                       entry->name, refname);
1097                                 return 0;
1098                         }
1099                 }
1100         }
1101         return 1;
1102 }
1103
1104 /*
1105  * *string and *len will only be substituted, and *string returned (for
1106  * later free()ing) if the string passed in is a magic short-hand form
1107  * to name a branch.
1108  */
1109 static char *substitute_branch_name(const char **string, int *len)
1110 {
1111         struct strbuf buf = STRBUF_INIT;
1112         int ret = interpret_branch_name(*string, &buf);
1113
1114         if (ret == *len) {
1115                 size_t size;
1116                 *string = strbuf_detach(&buf, &size);
1117                 *len = size;
1118                 return (char *)*string;
1119         }
1120
1121         return NULL;
1122 }
1123
1124 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
1125 {
1126         char *last_branch = substitute_branch_name(&str, &len);
1127         const char **p, *r;
1128         int refs_found = 0;
1129
1130         *ref = NULL;
1131         for (p = ref_rev_parse_rules; *p; p++) {
1132                 char fullref[PATH_MAX];
1133                 unsigned char sha1_from_ref[20];
1134                 unsigned char *this_result;
1135                 int flag;
1136
1137                 this_result = refs_found ? sha1_from_ref : sha1;
1138                 mksnpath(fullref, sizeof(fullref), *p, len, str);
1139                 r = resolve_ref_unsafe(fullref, this_result, 1, &flag);
1140                 if (r) {
1141                         if (!refs_found++)
1142                                 *ref = xstrdup(r);
1143                         if (!warn_ambiguous_refs)
1144                                 break;
1145                 } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD")) {
1146                         warning("ignoring dangling symref %s.", fullref);
1147                 } else if ((flag & REF_ISBROKEN) && strchr(fullref, '/')) {
1148                         warning("ignoring broken ref %s.", fullref);
1149                 }
1150         }
1151         free(last_branch);
1152         return refs_found;
1153 }
1154
1155 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
1156 {
1157         char *last_branch = substitute_branch_name(&str, &len);
1158         const char **p;
1159         int logs_found = 0;
1160
1161         *log = NULL;
1162         for (p = ref_rev_parse_rules; *p; p++) {
1163                 struct stat st;
1164                 unsigned char hash[20];
1165                 char path[PATH_MAX];
1166                 const char *ref, *it;
1167
1168                 mksnpath(path, sizeof(path), *p, len, str);
1169                 ref = resolve_ref_unsafe(path, hash, 1, NULL);
1170                 if (!ref)
1171                         continue;
1172                 if (!stat(git_path("logs/%s", path), &st) &&
1173                     S_ISREG(st.st_mode))
1174                         it = path;
1175                 else if (strcmp(ref, path) &&
1176                          !stat(git_path("logs/%s", ref), &st) &&
1177                          S_ISREG(st.st_mode))
1178                         it = ref;
1179                 else
1180                         continue;
1181                 if (!logs_found++) {
1182                         *log = xstrdup(it);
1183                         hashcpy(sha1, hash);
1184                 }
1185                 if (!warn_ambiguous_refs)
1186                         break;
1187         }
1188         free(last_branch);
1189         return logs_found;
1190 }
1191
1192 static struct ref_lock *lock_ref_sha1_basic(const char *refname,
1193                                             const unsigned char *old_sha1,
1194                                             int flags, int *type_p)
1195 {
1196         char *ref_file;
1197         const char *orig_refname = refname;
1198         struct ref_lock *lock;
1199         int last_errno = 0;
1200         int type, lflags;
1201         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
1202         int missing = 0;
1203
1204         lock = xcalloc(1, sizeof(struct ref_lock));
1205         lock->lock_fd = -1;
1206
1207         refname = resolve_ref_unsafe(refname, lock->old_sha1, mustexist, &type);
1208         if (!refname && errno == EISDIR) {
1209                 /* we are trying to lock foo but we used to
1210                  * have foo/bar which now does not exist;
1211                  * it is normal for the empty directory 'foo'
1212                  * to remain.
1213                  */
1214                 ref_file = git_path("%s", orig_refname);
1215                 if (remove_empty_directories(ref_file)) {
1216                         last_errno = errno;
1217                         error("there are still refs under '%s'", orig_refname);
1218                         goto error_return;
1219                 }
1220                 refname = resolve_ref_unsafe(orig_refname, lock->old_sha1, mustexist, &type);
1221         }
1222         if (type_p)
1223             *type_p = type;
1224         if (!refname) {
1225                 last_errno = errno;
1226                 error("unable to resolve reference %s: %s",
1227                         orig_refname, strerror(errno));
1228                 goto error_return;
1229         }
1230         missing = is_null_sha1(lock->old_sha1);
1231         /* When the ref did not exist and we are creating it,
1232          * make sure there is no existing ref that is packed
1233          * whose name begins with our refname, nor a ref whose
1234          * name is a proper prefix of our refname.
1235          */
1236         if (missing &&
1237              !is_refname_available(refname, NULL, get_packed_refs(get_ref_cache(NULL)))) {
1238                 last_errno = ENOTDIR;
1239                 goto error_return;
1240         }
1241
1242         lock->lk = xcalloc(1, sizeof(struct lock_file));
1243
1244         lflags = LOCK_DIE_ON_ERROR;
1245         if (flags & REF_NODEREF) {
1246                 refname = orig_refname;
1247                 lflags |= LOCK_NODEREF;
1248         }
1249         lock->ref_name = xstrdup(refname);
1250         lock->orig_ref_name = xstrdup(orig_refname);
1251         ref_file = git_path("%s", refname);
1252         if (missing)
1253                 lock->force_write = 1;
1254         if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
1255                 lock->force_write = 1;
1256
1257         if (safe_create_leading_directories(ref_file)) {
1258                 last_errno = errno;
1259                 error("unable to create directory for %s", ref_file);
1260                 goto error_return;
1261         }
1262
1263         lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, lflags);
1264         return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
1265
1266  error_return:
1267         unlock_ref(lock);
1268         errno = last_errno;
1269         return NULL;
1270 }
1271
1272 struct ref_lock *lock_ref_sha1(const char *refname, const unsigned char *old_sha1)
1273 {
1274         char refpath[PATH_MAX];
1275         if (check_refname_format(refname, 0))
1276                 return NULL;
1277         strcpy(refpath, mkpath("refs/%s", refname));
1278         return lock_ref_sha1_basic(refpath, old_sha1, 0, NULL);
1279 }
1280
1281 struct ref_lock *lock_any_ref_for_update(const char *refname,
1282                                          const unsigned char *old_sha1, int flags)
1283 {
1284         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
1285                 return NULL;
1286         return lock_ref_sha1_basic(refname, old_sha1, flags, NULL);
1287 }
1288
1289 static struct lock_file packlock;
1290
1291 static int repack_without_ref(const char *refname)
1292 {
1293         struct ref_array *packed;
1294         int fd, i;
1295
1296         packed = get_packed_refs(get_ref_cache(NULL));
1297         if (search_ref_array(packed, refname) == NULL)
1298                 return 0;
1299         fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
1300         if (fd < 0) {
1301                 unable_to_lock_error(git_path("packed-refs"), errno);
1302                 return error("cannot delete '%s' from packed refs", refname);
1303         }
1304
1305         for (i = 0; i < packed->nr; i++) {
1306                 char line[PATH_MAX + 100];
1307                 int len;
1308                 struct ref_entry *ref = packed->refs[i];
1309
1310                 if (!strcmp(refname, ref->name))
1311                         continue;
1312                 len = snprintf(line, sizeof(line), "%s %s\n",
1313                                sha1_to_hex(ref->sha1), ref->name);
1314                 /* this should not happen but just being defensive */
1315                 if (len > sizeof(line))
1316                         die("too long a refname '%s'", ref->name);
1317                 write_or_die(fd, line, len);
1318         }
1319         return commit_lock_file(&packlock);
1320 }
1321
1322 int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
1323 {
1324         struct ref_lock *lock;
1325         int err, i = 0, ret = 0, flag = 0;
1326
1327         lock = lock_ref_sha1_basic(refname, sha1, 0, &flag);
1328         if (!lock)
1329                 return 1;
1330         if (!(flag & REF_ISPACKED) || flag & REF_ISSYMREF) {
1331                 /* loose */
1332                 const char *path;
1333
1334                 if (!(delopt & REF_NODEREF)) {
1335                         i = strlen(lock->lk->filename) - 5; /* .lock */
1336                         lock->lk->filename[i] = 0;
1337                         path = lock->lk->filename;
1338                 } else {
1339                         path = git_path("%s", refname);
1340                 }
1341                 err = unlink_or_warn(path);
1342                 if (err && errno != ENOENT)
1343                         ret = 1;
1344
1345                 if (!(delopt & REF_NODEREF))
1346                         lock->lk->filename[i] = '.';
1347         }
1348         /* removing the loose one could have resurrected an earlier
1349          * packed one.  Also, if it was not loose we need to repack
1350          * without it.
1351          */
1352         ret |= repack_without_ref(refname);
1353
1354         unlink_or_warn(git_path("logs/%s", lock->ref_name));
1355         invalidate_ref_cache(NULL);
1356         unlock_ref(lock);
1357         return ret;
1358 }
1359
1360 /*
1361  * People using contrib's git-new-workdir have .git/logs/refs ->
1362  * /some/other/path/.git/logs/refs, and that may live on another device.
1363  *
1364  * IOW, to avoid cross device rename errors, the temporary renamed log must
1365  * live into logs/refs.
1366  */
1367 #define TMP_RENAMED_LOG  "logs/refs/.tmp-renamed-log"
1368
1369 int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
1370 {
1371         unsigned char sha1[20], orig_sha1[20];
1372         int flag = 0, logmoved = 0;
1373         struct ref_lock *lock;
1374         struct stat loginfo;
1375         int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
1376         const char *symref = NULL;
1377         struct ref_cache *refs = get_ref_cache(NULL);
1378
1379         if (log && S_ISLNK(loginfo.st_mode))
1380                 return error("reflog for %s is a symlink", oldrefname);
1381
1382         symref = resolve_ref_unsafe(oldrefname, orig_sha1, 1, &flag);
1383         if (flag & REF_ISSYMREF)
1384                 return error("refname %s is a symbolic ref, renaming it is not supported",
1385                         oldrefname);
1386         if (!symref)
1387                 return error("refname %s not found", oldrefname);
1388
1389         if (!is_refname_available(newrefname, oldrefname, get_packed_refs(refs)))
1390                 return 1;
1391
1392         if (!is_refname_available(newrefname, oldrefname, get_loose_refs(refs)))
1393                 return 1;
1394
1395         if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
1396                 return error("unable to move logfile logs/%s to "TMP_RENAMED_LOG": %s",
1397                         oldrefname, strerror(errno));
1398
1399         if (delete_ref(oldrefname, orig_sha1, REF_NODEREF)) {
1400                 error("unable to delete old %s", oldrefname);
1401                 goto rollback;
1402         }
1403
1404         if (!read_ref_full(newrefname, sha1, 1, &flag) &&
1405             delete_ref(newrefname, sha1, REF_NODEREF)) {
1406                 if (errno==EISDIR) {
1407                         if (remove_empty_directories(git_path("%s", newrefname))) {
1408                                 error("Directory not empty: %s", newrefname);
1409                                 goto rollback;
1410                         }
1411                 } else {
1412                         error("unable to delete existing %s", newrefname);
1413                         goto rollback;
1414                 }
1415         }
1416
1417         if (log && safe_create_leading_directories(git_path("logs/%s", newrefname))) {
1418                 error("unable to create directory for %s", newrefname);
1419                 goto rollback;
1420         }
1421
1422  retry:
1423         if (log && rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", newrefname))) {
1424                 if (errno==EISDIR || errno==ENOTDIR) {
1425                         /*
1426                          * rename(a, b) when b is an existing
1427                          * directory ought to result in ISDIR, but
1428                          * Solaris 5.8 gives ENOTDIR.  Sheesh.
1429                          */
1430                         if (remove_empty_directories(git_path("logs/%s", newrefname))) {
1431                                 error("Directory not empty: logs/%s", newrefname);
1432                                 goto rollback;
1433                         }
1434                         goto retry;
1435                 } else {
1436                         error("unable to move logfile "TMP_RENAMED_LOG" to logs/%s: %s",
1437                                 newrefname, strerror(errno));
1438                         goto rollback;
1439                 }
1440         }
1441         logmoved = log;
1442
1443         lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL);
1444         if (!lock) {
1445                 error("unable to lock %s for update", newrefname);
1446                 goto rollback;
1447         }
1448         lock->force_write = 1;
1449         hashcpy(lock->old_sha1, orig_sha1);
1450         if (write_ref_sha1(lock, orig_sha1, logmsg)) {
1451                 error("unable to write current sha1 into %s", newrefname);
1452                 goto rollback;
1453         }
1454
1455         return 0;
1456
1457  rollback:
1458         lock = lock_ref_sha1_basic(oldrefname, NULL, 0, NULL);
1459         if (!lock) {
1460                 error("unable to lock %s for rollback", oldrefname);
1461                 goto rollbacklog;
1462         }
1463
1464         lock->force_write = 1;
1465         flag = log_all_ref_updates;
1466         log_all_ref_updates = 0;
1467         if (write_ref_sha1(lock, orig_sha1, NULL))
1468                 error("unable to write current sha1 into %s", oldrefname);
1469         log_all_ref_updates = flag;
1470
1471  rollbacklog:
1472         if (logmoved && rename(git_path("logs/%s", newrefname), git_path("logs/%s", oldrefname)))
1473                 error("unable to restore logfile %s from %s: %s",
1474                         oldrefname, newrefname, strerror(errno));
1475         if (!logmoved && log &&
1476             rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", oldrefname)))
1477                 error("unable to restore logfile %s from "TMP_RENAMED_LOG": %s",
1478                         oldrefname, strerror(errno));
1479
1480         return 1;
1481 }
1482
1483 int close_ref(struct ref_lock *lock)
1484 {
1485         if (close_lock_file(lock->lk))
1486                 return -1;
1487         lock->lock_fd = -1;
1488         return 0;
1489 }
1490
1491 int commit_ref(struct ref_lock *lock)
1492 {
1493         if (commit_lock_file(lock->lk))
1494                 return -1;
1495         lock->lock_fd = -1;
1496         return 0;
1497 }
1498
1499 void unlock_ref(struct ref_lock *lock)
1500 {
1501         /* Do not free lock->lk -- atexit() still looks at them */
1502         if (lock->lk)
1503                 rollback_lock_file(lock->lk);
1504         free(lock->ref_name);
1505         free(lock->orig_ref_name);
1506         free(lock);
1507 }
1508
1509 /*
1510  * copy the reflog message msg to buf, which has been allocated sufficiently
1511  * large, while cleaning up the whitespaces.  Especially, convert LF to space,
1512  * because reflog file is one line per entry.
1513  */
1514 static int copy_msg(char *buf, const char *msg)
1515 {
1516         char *cp = buf;
1517         char c;
1518         int wasspace = 1;
1519
1520         *cp++ = '\t';
1521         while ((c = *msg++)) {
1522                 if (wasspace && isspace(c))
1523                         continue;
1524                 wasspace = isspace(c);
1525                 if (wasspace)
1526                         c = ' ';
1527                 *cp++ = c;
1528         }
1529         while (buf < cp && isspace(cp[-1]))
1530                 cp--;
1531         *cp++ = '\n';
1532         return cp - buf;
1533 }
1534
1535 int log_ref_setup(const char *refname, char *logfile, int bufsize)
1536 {
1537         int logfd, oflags = O_APPEND | O_WRONLY;
1538
1539         git_snpath(logfile, bufsize, "logs/%s", refname);
1540         if (log_all_ref_updates &&
1541             (!prefixcmp(refname, "refs/heads/") ||
1542              !prefixcmp(refname, "refs/remotes/") ||
1543              !prefixcmp(refname, "refs/notes/") ||
1544              !strcmp(refname, "HEAD"))) {
1545                 if (safe_create_leading_directories(logfile) < 0)
1546                         return error("unable to create directory for %s",
1547                                      logfile);
1548                 oflags |= O_CREAT;
1549         }
1550
1551         logfd = open(logfile, oflags, 0666);
1552         if (logfd < 0) {
1553                 if (!(oflags & O_CREAT) && errno == ENOENT)
1554                         return 0;
1555
1556                 if ((oflags & O_CREAT) && errno == EISDIR) {
1557                         if (remove_empty_directories(logfile)) {
1558                                 return error("There are still logs under '%s'",
1559                                              logfile);
1560                         }
1561                         logfd = open(logfile, oflags, 0666);
1562                 }
1563
1564                 if (logfd < 0)
1565                         return error("Unable to append to %s: %s",
1566                                      logfile, strerror(errno));
1567         }
1568
1569         adjust_shared_perm(logfile);
1570         close(logfd);
1571         return 0;
1572 }
1573
1574 static int log_ref_write(const char *refname, const unsigned char *old_sha1,
1575                          const unsigned char *new_sha1, const char *msg)
1576 {
1577         int logfd, result, written, oflags = O_APPEND | O_WRONLY;
1578         unsigned maxlen, len;
1579         int msglen;
1580         char log_file[PATH_MAX];
1581         char *logrec;
1582         const char *committer;
1583
1584         if (log_all_ref_updates < 0)
1585                 log_all_ref_updates = !is_bare_repository();
1586
1587         result = log_ref_setup(refname, log_file, sizeof(log_file));
1588         if (result)
1589                 return result;
1590
1591         logfd = open(log_file, oflags);
1592         if (logfd < 0)
1593                 return 0;
1594         msglen = msg ? strlen(msg) : 0;
1595         committer = git_committer_info(0);
1596         maxlen = strlen(committer) + msglen + 100;
1597         logrec = xmalloc(maxlen);
1598         len = sprintf(logrec, "%s %s %s\n",
1599                       sha1_to_hex(old_sha1),
1600                       sha1_to_hex(new_sha1),
1601                       committer);
1602         if (msglen)
1603                 len += copy_msg(logrec + len - 1, msg) - 1;
1604         written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
1605         free(logrec);
1606         if (close(logfd) != 0 || written != len)
1607                 return error("Unable to append to %s", log_file);
1608         return 0;
1609 }
1610
1611 static int is_branch(const char *refname)
1612 {
1613         return !strcmp(refname, "HEAD") || !prefixcmp(refname, "refs/heads/");
1614 }
1615
1616 int write_ref_sha1(struct ref_lock *lock,
1617         const unsigned char *sha1, const char *logmsg)
1618 {
1619         static char term = '\n';
1620         struct object *o;
1621
1622         if (!lock)
1623                 return -1;
1624         if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
1625                 unlock_ref(lock);
1626                 return 0;
1627         }
1628         o = parse_object(sha1);
1629         if (!o) {
1630                 error("Trying to write ref %s with nonexistent object %s",
1631                         lock->ref_name, sha1_to_hex(sha1));
1632                 unlock_ref(lock);
1633                 return -1;
1634         }
1635         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1636                 error("Trying to write non-commit object %s to branch %s",
1637                         sha1_to_hex(sha1), lock->ref_name);
1638                 unlock_ref(lock);
1639                 return -1;
1640         }
1641         if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
1642             write_in_full(lock->lock_fd, &term, 1) != 1
1643                 || close_ref(lock) < 0) {
1644                 error("Couldn't write %s", lock->lk->filename);
1645                 unlock_ref(lock);
1646                 return -1;
1647         }
1648         clear_loose_ref_cache(get_ref_cache(NULL));
1649         if (log_ref_write(lock->ref_name, lock->old_sha1, sha1, logmsg) < 0 ||
1650             (strcmp(lock->ref_name, lock->orig_ref_name) &&
1651              log_ref_write(lock->orig_ref_name, lock->old_sha1, sha1, logmsg) < 0)) {
1652                 unlock_ref(lock);
1653                 return -1;
1654         }
1655         if (strcmp(lock->orig_ref_name, "HEAD") != 0) {
1656                 /*
1657                  * Special hack: If a branch is updated directly and HEAD
1658                  * points to it (may happen on the remote side of a push
1659                  * for example) then logically the HEAD reflog should be
1660                  * updated too.
1661                  * A generic solution implies reverse symref information,
1662                  * but finding all symrefs pointing to the given branch
1663                  * would be rather costly for this rare event (the direct
1664                  * update of a branch) to be worth it.  So let's cheat and
1665                  * check with HEAD only which should cover 99% of all usage
1666                  * scenarios (even 100% of the default ones).
1667                  */
1668                 unsigned char head_sha1[20];
1669                 int head_flag;
1670                 const char *head_ref;
1671                 head_ref = resolve_ref_unsafe("HEAD", head_sha1, 1, &head_flag);
1672                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1673                     !strcmp(head_ref, lock->ref_name))
1674                         log_ref_write("HEAD", lock->old_sha1, sha1, logmsg);
1675         }
1676         if (commit_ref(lock)) {
1677                 error("Couldn't set %s", lock->ref_name);
1678                 unlock_ref(lock);
1679                 return -1;
1680         }
1681         unlock_ref(lock);
1682         return 0;
1683 }
1684
1685 int create_symref(const char *ref_target, const char *refs_heads_master,
1686                   const char *logmsg)
1687 {
1688         const char *lockpath;
1689         char ref[1000];
1690         int fd, len, written;
1691         char *git_HEAD = git_pathdup("%s", ref_target);
1692         unsigned char old_sha1[20], new_sha1[20];
1693
1694         if (logmsg && read_ref(ref_target, old_sha1))
1695                 hashclr(old_sha1);
1696
1697         if (safe_create_leading_directories(git_HEAD) < 0)
1698                 return error("unable to create directory for %s", git_HEAD);
1699
1700 #ifndef NO_SYMLINK_HEAD
1701         if (prefer_symlink_refs) {
1702                 unlink(git_HEAD);
1703                 if (!symlink(refs_heads_master, git_HEAD))
1704                         goto done;
1705                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1706         }
1707 #endif
1708
1709         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
1710         if (sizeof(ref) <= len) {
1711                 error("refname too long: %s", refs_heads_master);
1712                 goto error_free_return;
1713         }
1714         lockpath = mkpath("%s.lock", git_HEAD);
1715         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
1716         if (fd < 0) {
1717                 error("Unable to open %s for writing", lockpath);
1718                 goto error_free_return;
1719         }
1720         written = write_in_full(fd, ref, len);
1721         if (close(fd) != 0 || written != len) {
1722                 error("Unable to write to %s", lockpath);
1723                 goto error_unlink_return;
1724         }
1725         if (rename(lockpath, git_HEAD) < 0) {
1726                 error("Unable to create %s", git_HEAD);
1727                 goto error_unlink_return;
1728         }
1729         if (adjust_shared_perm(git_HEAD)) {
1730                 error("Unable to fix permissions on %s", lockpath);
1731         error_unlink_return:
1732                 unlink_or_warn(lockpath);
1733         error_free_return:
1734                 free(git_HEAD);
1735                 return -1;
1736         }
1737
1738 #ifndef NO_SYMLINK_HEAD
1739         done:
1740 #endif
1741         if (logmsg && !read_ref(refs_heads_master, new_sha1))
1742                 log_ref_write(ref_target, old_sha1, new_sha1, logmsg);
1743
1744         free(git_HEAD);
1745         return 0;
1746 }
1747
1748 static char *ref_msg(const char *line, const char *endp)
1749 {
1750         const char *ep;
1751         line += 82;
1752         ep = memchr(line, '\n', endp - line);
1753         if (!ep)
1754                 ep = endp;
1755         return xmemdupz(line, ep - line);
1756 }
1757
1758 int read_ref_at(const char *refname, unsigned long at_time, int cnt,
1759                 unsigned char *sha1, char **msg,
1760                 unsigned long *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
1761 {
1762         const char *logfile, *logdata, *logend, *rec, *lastgt, *lastrec;
1763         char *tz_c;
1764         int logfd, tz, reccnt = 0;
1765         struct stat st;
1766         unsigned long date;
1767         unsigned char logged_sha1[20];
1768         void *log_mapped;
1769         size_t mapsz;
1770
1771         logfile = git_path("logs/%s", refname);
1772         logfd = open(logfile, O_RDONLY, 0);
1773         if (logfd < 0)
1774                 die_errno("Unable to read log '%s'", logfile);
1775         fstat(logfd, &st);
1776         if (!st.st_size)
1777                 die("Log %s is empty.", logfile);
1778         mapsz = xsize_t(st.st_size);
1779         log_mapped = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, logfd, 0);
1780         logdata = log_mapped;
1781         close(logfd);
1782
1783         lastrec = NULL;
1784         rec = logend = logdata + st.st_size;
1785         while (logdata < rec) {
1786                 reccnt++;
1787                 if (logdata < rec && *(rec-1) == '\n')
1788                         rec--;
1789                 lastgt = NULL;
1790                 while (logdata < rec && *(rec-1) != '\n') {
1791                         rec--;
1792                         if (*rec == '>')
1793                                 lastgt = rec;
1794                 }
1795                 if (!lastgt)
1796                         die("Log %s is corrupt.", logfile);
1797                 date = strtoul(lastgt + 1, &tz_c, 10);
1798                 if (date <= at_time || cnt == 0) {
1799                         tz = strtoul(tz_c, NULL, 10);
1800                         if (msg)
1801                                 *msg = ref_msg(rec, logend);
1802                         if (cutoff_time)
1803                                 *cutoff_time = date;
1804                         if (cutoff_tz)
1805                                 *cutoff_tz = tz;
1806                         if (cutoff_cnt)
1807                                 *cutoff_cnt = reccnt - 1;
1808                         if (lastrec) {
1809                                 if (get_sha1_hex(lastrec, logged_sha1))
1810                                         die("Log %s is corrupt.", logfile);
1811                                 if (get_sha1_hex(rec + 41, sha1))
1812                                         die("Log %s is corrupt.", logfile);
1813                                 if (hashcmp(logged_sha1, sha1)) {
1814                                         warning("Log %s has gap after %s.",
1815                                                 logfile, show_date(date, tz, DATE_RFC2822));
1816                                 }
1817                         }
1818                         else if (date == at_time) {
1819                                 if (get_sha1_hex(rec + 41, sha1))
1820                                         die("Log %s is corrupt.", logfile);
1821                         }
1822                         else {
1823                                 if (get_sha1_hex(rec + 41, logged_sha1))
1824                                         die("Log %s is corrupt.", logfile);
1825                                 if (hashcmp(logged_sha1, sha1)) {
1826                                         warning("Log %s unexpectedly ended on %s.",
1827                                                 logfile, show_date(date, tz, DATE_RFC2822));
1828                                 }
1829                         }
1830                         munmap(log_mapped, mapsz);
1831                         return 0;
1832                 }
1833                 lastrec = rec;
1834                 if (cnt > 0)
1835                         cnt--;
1836         }
1837
1838         rec = logdata;
1839         while (rec < logend && *rec != '>' && *rec != '\n')
1840                 rec++;
1841         if (rec == logend || *rec == '\n')
1842                 die("Log %s is corrupt.", logfile);
1843         date = strtoul(rec + 1, &tz_c, 10);
1844         tz = strtoul(tz_c, NULL, 10);
1845         if (get_sha1_hex(logdata, sha1))
1846                 die("Log %s is corrupt.", logfile);
1847         if (is_null_sha1(sha1)) {
1848                 if (get_sha1_hex(logdata + 41, sha1))
1849                         die("Log %s is corrupt.", logfile);
1850         }
1851         if (msg)
1852                 *msg = ref_msg(logdata, logend);
1853         munmap(log_mapped, mapsz);
1854
1855         if (cutoff_time)
1856                 *cutoff_time = date;
1857         if (cutoff_tz)
1858                 *cutoff_tz = tz;
1859         if (cutoff_cnt)
1860                 *cutoff_cnt = reccnt;
1861         return 1;
1862 }
1863
1864 int for_each_recent_reflog_ent(const char *refname, each_reflog_ent_fn fn, long ofs, void *cb_data)
1865 {
1866         const char *logfile;
1867         FILE *logfp;
1868         struct strbuf sb = STRBUF_INIT;
1869         int ret = 0;
1870
1871         logfile = git_path("logs/%s", refname);
1872         logfp = fopen(logfile, "r");
1873         if (!logfp)
1874                 return -1;
1875
1876         if (ofs) {
1877                 struct stat statbuf;
1878                 if (fstat(fileno(logfp), &statbuf) ||
1879                     statbuf.st_size < ofs ||
1880                     fseek(logfp, -ofs, SEEK_END) ||
1881                     strbuf_getwholeline(&sb, logfp, '\n')) {
1882                         fclose(logfp);
1883                         strbuf_release(&sb);
1884                         return -1;
1885                 }
1886         }
1887
1888         while (!strbuf_getwholeline(&sb, logfp, '\n')) {
1889                 unsigned char osha1[20], nsha1[20];
1890                 char *email_end, *message;
1891                 unsigned long timestamp;
1892                 int tz;
1893
1894                 /* old SP new SP name <email> SP time TAB msg LF */
1895                 if (sb.len < 83 || sb.buf[sb.len - 1] != '\n' ||
1896                     get_sha1_hex(sb.buf, osha1) || sb.buf[40] != ' ' ||
1897                     get_sha1_hex(sb.buf + 41, nsha1) || sb.buf[81] != ' ' ||
1898                     !(email_end = strchr(sb.buf + 82, '>')) ||
1899                     email_end[1] != ' ' ||
1900                     !(timestamp = strtoul(email_end + 2, &message, 10)) ||
1901                     !message || message[0] != ' ' ||
1902                     (message[1] != '+' && message[1] != '-') ||
1903                     !isdigit(message[2]) || !isdigit(message[3]) ||
1904                     !isdigit(message[4]) || !isdigit(message[5]))
1905                         continue; /* corrupt? */
1906                 email_end[1] = '\0';
1907                 tz = strtol(message + 1, NULL, 10);
1908                 if (message[6] != '\t')
1909                         message += 6;
1910                 else
1911                         message += 7;
1912                 ret = fn(osha1, nsha1, sb.buf + 82, timestamp, tz, message,
1913                          cb_data);
1914                 if (ret)
1915                         break;
1916         }
1917         fclose(logfp);
1918         strbuf_release(&sb);
1919         return ret;
1920 }
1921
1922 int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn, void *cb_data)
1923 {
1924         return for_each_recent_reflog_ent(refname, fn, 0, cb_data);
1925 }
1926
1927 static int do_for_each_reflog(const char *base, each_ref_fn fn, void *cb_data)
1928 {
1929         DIR *dir = opendir(git_path("logs/%s", base));
1930         int retval = 0;
1931
1932         if (dir) {
1933                 struct dirent *de;
1934                 int baselen = strlen(base);
1935                 char *log = xmalloc(baselen + 257);
1936
1937                 memcpy(log, base, baselen);
1938                 if (baselen && base[baselen-1] != '/')
1939                         log[baselen++] = '/';
1940
1941                 while ((de = readdir(dir)) != NULL) {
1942                         struct stat st;
1943                         int namelen;
1944
1945                         if (de->d_name[0] == '.')
1946                                 continue;
1947                         namelen = strlen(de->d_name);
1948                         if (namelen > 255)
1949                                 continue;
1950                         if (has_extension(de->d_name, ".lock"))
1951                                 continue;
1952                         memcpy(log + baselen, de->d_name, namelen+1);
1953                         if (stat(git_path("logs/%s", log), &st) < 0)
1954                                 continue;
1955                         if (S_ISDIR(st.st_mode)) {
1956                                 retval = do_for_each_reflog(log, fn, cb_data);
1957                         } else {
1958                                 unsigned char sha1[20];
1959                                 if (read_ref_full(log, sha1, 0, NULL))
1960                                         retval = error("bad ref for %s", log);
1961                                 else
1962                                         retval = fn(log, sha1, 0, cb_data);
1963                         }
1964                         if (retval)
1965                                 break;
1966                 }
1967                 free(log);
1968                 closedir(dir);
1969         }
1970         else if (*base)
1971                 return errno;
1972         return retval;
1973 }
1974
1975 int for_each_reflog(each_ref_fn fn, void *cb_data)
1976 {
1977         return do_for_each_reflog("", fn, cb_data);
1978 }
1979
1980 int update_ref(const char *action, const char *refname,
1981                 const unsigned char *sha1, const unsigned char *oldval,
1982                 int flags, enum action_on_err onerr)
1983 {
1984         static struct ref_lock *lock;
1985         lock = lock_any_ref_for_update(refname, oldval, flags);
1986         if (!lock) {
1987                 const char *str = "Cannot lock the ref '%s'.";
1988                 switch (onerr) {
1989                 case MSG_ON_ERR: error(str, refname); break;
1990                 case DIE_ON_ERR: die(str, refname); break;
1991                 case QUIET_ON_ERR: break;
1992                 }
1993                 return 1;
1994         }
1995         if (write_ref_sha1(lock, sha1, action) < 0) {
1996                 const char *str = "Cannot update the ref '%s'.";
1997                 switch (onerr) {
1998                 case MSG_ON_ERR: error(str, refname); break;
1999                 case DIE_ON_ERR: die(str, refname); break;
2000                 case QUIET_ON_ERR: break;
2001                 }
2002                 return 1;
2003         }
2004         return 0;
2005 }
2006
2007 int ref_exists(const char *refname)
2008 {
2009         unsigned char sha1[20];
2010         return !!resolve_ref_unsafe(refname, sha1, 1, NULL);
2011 }
2012
2013 struct ref *find_ref_by_name(const struct ref *list, const char *name)
2014 {
2015         for ( ; list; list = list->next)
2016                 if (!strcmp(list->name, name))
2017                         return (struct ref *)list;
2018         return NULL;
2019 }
2020
2021 /*
2022  * generate a format suitable for scanf from a ref_rev_parse_rules
2023  * rule, that is replace the "%.*s" spec with a "%s" spec
2024  */
2025 static void gen_scanf_fmt(char *scanf_fmt, const char *rule)
2026 {
2027         char *spec;
2028
2029         spec = strstr(rule, "%.*s");
2030         if (!spec || strstr(spec + 4, "%.*s"))
2031                 die("invalid rule in ref_rev_parse_rules: %s", rule);
2032
2033         /* copy all until spec */
2034         strncpy(scanf_fmt, rule, spec - rule);
2035         scanf_fmt[spec - rule] = '\0';
2036         /* copy new spec */
2037         strcat(scanf_fmt, "%s");
2038         /* copy remaining rule */
2039         strcat(scanf_fmt, spec + 4);
2040
2041         return;
2042 }
2043
2044 char *shorten_unambiguous_ref(const char *refname, int strict)
2045 {
2046         int i;
2047         static char **scanf_fmts;
2048         static int nr_rules;
2049         char *short_name;
2050
2051         /* pre generate scanf formats from ref_rev_parse_rules[] */
2052         if (!nr_rules) {
2053                 size_t total_len = 0;
2054
2055                 /* the rule list is NULL terminated, count them first */
2056                 for (; ref_rev_parse_rules[nr_rules]; nr_rules++)
2057                         /* no +1 because strlen("%s") < strlen("%.*s") */
2058                         total_len += strlen(ref_rev_parse_rules[nr_rules]);
2059
2060                 scanf_fmts = xmalloc(nr_rules * sizeof(char *) + total_len);
2061
2062                 total_len = 0;
2063                 for (i = 0; i < nr_rules; i++) {
2064                         scanf_fmts[i] = (char *)&scanf_fmts[nr_rules]
2065                                         + total_len;
2066                         gen_scanf_fmt(scanf_fmts[i], ref_rev_parse_rules[i]);
2067                         total_len += strlen(ref_rev_parse_rules[i]);
2068                 }
2069         }
2070
2071         /* bail out if there are no rules */
2072         if (!nr_rules)
2073                 return xstrdup(refname);
2074
2075         /* buffer for scanf result, at most refname must fit */
2076         short_name = xstrdup(refname);
2077
2078         /* skip first rule, it will always match */
2079         for (i = nr_rules - 1; i > 0 ; --i) {
2080                 int j;
2081                 int rules_to_fail = i;
2082                 int short_name_len;
2083
2084                 if (1 != sscanf(refname, scanf_fmts[i], short_name))
2085                         continue;
2086
2087                 short_name_len = strlen(short_name);
2088
2089                 /*
2090                  * in strict mode, all (except the matched one) rules
2091                  * must fail to resolve to a valid non-ambiguous ref
2092                  */
2093                 if (strict)
2094                         rules_to_fail = nr_rules;
2095
2096                 /*
2097                  * check if the short name resolves to a valid ref,
2098                  * but use only rules prior to the matched one
2099                  */
2100                 for (j = 0; j < rules_to_fail; j++) {
2101                         const char *rule = ref_rev_parse_rules[j];
2102                         char refname[PATH_MAX];
2103
2104                         /* skip matched rule */
2105                         if (i == j)
2106                                 continue;
2107
2108                         /*
2109                          * the short name is ambiguous, if it resolves
2110                          * (with this previous rule) to a valid ref
2111                          * read_ref() returns 0 on success
2112                          */
2113                         mksnpath(refname, sizeof(refname),
2114                                  rule, short_name_len, short_name);
2115                         if (ref_exists(refname))
2116                                 break;
2117                 }
2118
2119                 /*
2120                  * short name is non-ambiguous if all previous rules
2121                  * haven't resolved to a valid ref
2122                  */
2123                 if (j == rules_to_fail)
2124                         return short_name;
2125         }
2126
2127         free(short_name);
2128         return xstrdup(refname);
2129 }