Merge branch 'bp/fsmonitor'
[git] / refs.c
1 /*
2  * The backend-independent part of the reference module.
3  */
4
5 #include "cache.h"
6 #include "config.h"
7 #include "hashmap.h"
8 #include "lockfile.h"
9 #include "iterator.h"
10 #include "refs.h"
11 #include "refs/refs-internal.h"
12 #include "object.h"
13 #include "tag.h"
14 #include "submodule.h"
15 #include "worktree.h"
16
17 /*
18  * List of all available backends
19  */
20 static struct ref_storage_be *refs_backends = &refs_be_files;
21
22 static struct ref_storage_be *find_ref_storage_backend(const char *name)
23 {
24         struct ref_storage_be *be;
25         for (be = refs_backends; be; be = be->next)
26                 if (!strcmp(be->name, name))
27                         return be;
28         return NULL;
29 }
30
31 int ref_storage_backend_exists(const char *name)
32 {
33         return find_ref_storage_backend(name) != NULL;
34 }
35
36 /*
37  * How to handle various characters in refnames:
38  * 0: An acceptable character for refs
39  * 1: End-of-component
40  * 2: ., look for a preceding . to reject .. in refs
41  * 3: {, look for a preceding @ to reject @{ in refs
42  * 4: A bad character: ASCII control characters, and
43  *    ":", "?", "[", "\", "^", "~", SP, or TAB
44  * 5: *, reject unless REFNAME_REFSPEC_PATTERN is set
45  */
46 static unsigned char refname_disposition[256] = {
47         1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
48         4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
49         4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 2, 1,
50         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 4,
51         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
52         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 0, 4, 0,
53         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
54         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 4, 4
55 };
56
57 /*
58  * Try to read one refname component from the front of refname.
59  * Return the length of the component found, or -1 if the component is
60  * not legal.  It is legal if it is something reasonable to have under
61  * ".git/refs/"; We do not like it if:
62  *
63  * - any path component of it begins with ".", or
64  * - it has double dots "..", or
65  * - it has ASCII control characters, or
66  * - it has ":", "?", "[", "\", "^", "~", SP, or TAB anywhere, or
67  * - it has "*" anywhere unless REFNAME_REFSPEC_PATTERN is set, or
68  * - it ends with a "/", or
69  * - it ends with ".lock", or
70  * - it contains a "@{" portion
71  */
72 static int check_refname_component(const char *refname, int *flags)
73 {
74         const char *cp;
75         char last = '\0';
76
77         for (cp = refname; ; cp++) {
78                 int ch = *cp & 255;
79                 unsigned char disp = refname_disposition[ch];
80                 switch (disp) {
81                 case 1:
82                         goto out;
83                 case 2:
84                         if (last == '.')
85                                 return -1; /* Refname contains "..". */
86                         break;
87                 case 3:
88                         if (last == '@')
89                                 return -1; /* Refname contains "@{". */
90                         break;
91                 case 4:
92                         return -1;
93                 case 5:
94                         if (!(*flags & REFNAME_REFSPEC_PATTERN))
95                                 return -1; /* refspec can't be a pattern */
96
97                         /*
98                          * Unset the pattern flag so that we only accept
99                          * a single asterisk for one side of refspec.
100                          */
101                         *flags &= ~ REFNAME_REFSPEC_PATTERN;
102                         break;
103                 }
104                 last = ch;
105         }
106 out:
107         if (cp == refname)
108                 return 0; /* Component has zero length. */
109         if (refname[0] == '.')
110                 return -1; /* Component starts with '.'. */
111         if (cp - refname >= LOCK_SUFFIX_LEN &&
112             !memcmp(cp - LOCK_SUFFIX_LEN, LOCK_SUFFIX, LOCK_SUFFIX_LEN))
113                 return -1; /* Refname ends with ".lock". */
114         return cp - refname;
115 }
116
117 int check_refname_format(const char *refname, int flags)
118 {
119         int component_len, component_count = 0;
120
121         if (!strcmp(refname, "@"))
122                 /* Refname is a single character '@'. */
123                 return -1;
124
125         while (1) {
126                 /* We are at the start of a path component. */
127                 component_len = check_refname_component(refname, &flags);
128                 if (component_len <= 0)
129                         return -1;
130
131                 component_count++;
132                 if (refname[component_len] == '\0')
133                         break;
134                 /* Skip to next component. */
135                 refname += component_len + 1;
136         }
137
138         if (refname[component_len - 1] == '.')
139                 return -1; /* Refname ends with '.'. */
140         if (!(flags & REFNAME_ALLOW_ONELEVEL) && component_count < 2)
141                 return -1; /* Refname has only one component. */
142         return 0;
143 }
144
145 int refname_is_safe(const char *refname)
146 {
147         const char *rest;
148
149         if (skip_prefix(refname, "refs/", &rest)) {
150                 char *buf;
151                 int result;
152                 size_t restlen = strlen(rest);
153
154                 /* rest must not be empty, or start or end with "/" */
155                 if (!restlen || *rest == '/' || rest[restlen - 1] == '/')
156                         return 0;
157
158                 /*
159                  * Does the refname try to escape refs/?
160                  * For example: refs/foo/../bar is safe but refs/foo/../../bar
161                  * is not.
162                  */
163                 buf = xmallocz(restlen);
164                 result = !normalize_path_copy(buf, rest) && !strcmp(buf, rest);
165                 free(buf);
166                 return result;
167         }
168
169         do {
170                 if (!isupper(*refname) && *refname != '_')
171                         return 0;
172                 refname++;
173         } while (*refname);
174         return 1;
175 }
176
177 /*
178  * Return true if refname, which has the specified oid and flags, can
179  * be resolved to an object in the database. If the referred-to object
180  * does not exist, emit a warning and return false.
181  */
182 int ref_resolves_to_object(const char *refname,
183                            const struct object_id *oid,
184                            unsigned int flags)
185 {
186         if (flags & REF_ISBROKEN)
187                 return 0;
188         if (!has_sha1_file(oid->hash)) {
189                 error("%s does not point to a valid object!", refname);
190                 return 0;
191         }
192         return 1;
193 }
194
195 char *refs_resolve_refdup(struct ref_store *refs,
196                           const char *refname, int resolve_flags,
197                           struct object_id *oid, int *flags)
198 {
199         const char *result;
200
201         result = refs_resolve_ref_unsafe(refs, refname, resolve_flags,
202                                          oid, flags);
203         return xstrdup_or_null(result);
204 }
205
206 char *resolve_refdup(const char *refname, int resolve_flags,
207                      struct object_id *oid, int *flags)
208 {
209         return refs_resolve_refdup(get_main_ref_store(),
210                                    refname, resolve_flags,
211                                    oid, flags);
212 }
213
214 /* The argument to filter_refs */
215 struct ref_filter {
216         const char *pattern;
217         each_ref_fn *fn;
218         void *cb_data;
219 };
220
221 int refs_read_ref_full(struct ref_store *refs, const char *refname,
222                        int resolve_flags, struct object_id *oid, int *flags)
223 {
224         if (refs_resolve_ref_unsafe(refs, refname, resolve_flags, oid, flags))
225                 return 0;
226         return -1;
227 }
228
229 int read_ref_full(const char *refname, int resolve_flags, struct object_id *oid, int *flags)
230 {
231         return refs_read_ref_full(get_main_ref_store(), refname,
232                                   resolve_flags, oid, flags);
233 }
234
235 int read_ref(const char *refname, struct object_id *oid)
236 {
237         return read_ref_full(refname, RESOLVE_REF_READING, oid, NULL);
238 }
239
240 int ref_exists(const char *refname)
241 {
242         return !!resolve_ref_unsafe(refname, RESOLVE_REF_READING, NULL, NULL);
243 }
244
245 static int filter_refs(const char *refname, const struct object_id *oid,
246                            int flags, void *data)
247 {
248         struct ref_filter *filter = (struct ref_filter *)data;
249
250         if (wildmatch(filter->pattern, refname, 0))
251                 return 0;
252         return filter->fn(refname, oid, flags, filter->cb_data);
253 }
254
255 enum peel_status peel_object(const struct object_id *name, struct object_id *oid)
256 {
257         struct object *o = lookup_unknown_object(name->hash);
258
259         if (o->type == OBJ_NONE) {
260                 int type = sha1_object_info(name->hash, NULL);
261                 if (type < 0 || !object_as_type(o, type, 0))
262                         return PEEL_INVALID;
263         }
264
265         if (o->type != OBJ_TAG)
266                 return PEEL_NON_TAG;
267
268         o = deref_tag_noverify(o);
269         if (!o)
270                 return PEEL_INVALID;
271
272         oidcpy(oid, &o->oid);
273         return PEEL_PEELED;
274 }
275
276 struct warn_if_dangling_data {
277         FILE *fp;
278         const char *refname;
279         const struct string_list *refnames;
280         const char *msg_fmt;
281 };
282
283 static int warn_if_dangling_symref(const char *refname, const struct object_id *oid,
284                                    int flags, void *cb_data)
285 {
286         struct warn_if_dangling_data *d = cb_data;
287         const char *resolves_to;
288
289         if (!(flags & REF_ISSYMREF))
290                 return 0;
291
292         resolves_to = resolve_ref_unsafe(refname, 0, NULL, NULL);
293         if (!resolves_to
294             || (d->refname
295                 ? strcmp(resolves_to, d->refname)
296                 : !string_list_has_string(d->refnames, resolves_to))) {
297                 return 0;
298         }
299
300         fprintf(d->fp, d->msg_fmt, refname);
301         fputc('\n', d->fp);
302         return 0;
303 }
304
305 void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
306 {
307         struct warn_if_dangling_data data;
308
309         data.fp = fp;
310         data.refname = refname;
311         data.refnames = NULL;
312         data.msg_fmt = msg_fmt;
313         for_each_rawref(warn_if_dangling_symref, &data);
314 }
315
316 void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_list *refnames)
317 {
318         struct warn_if_dangling_data data;
319
320         data.fp = fp;
321         data.refname = NULL;
322         data.refnames = refnames;
323         data.msg_fmt = msg_fmt;
324         for_each_rawref(warn_if_dangling_symref, &data);
325 }
326
327 int refs_for_each_tag_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
328 {
329         return refs_for_each_ref_in(refs, "refs/tags/", fn, cb_data);
330 }
331
332 int for_each_tag_ref(each_ref_fn fn, void *cb_data)
333 {
334         return refs_for_each_tag_ref(get_main_ref_store(), fn, cb_data);
335 }
336
337 int refs_for_each_branch_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
338 {
339         return refs_for_each_ref_in(refs, "refs/heads/", fn, cb_data);
340 }
341
342 int for_each_branch_ref(each_ref_fn fn, void *cb_data)
343 {
344         return refs_for_each_branch_ref(get_main_ref_store(), fn, cb_data);
345 }
346
347 int refs_for_each_remote_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
348 {
349         return refs_for_each_ref_in(refs, "refs/remotes/", fn, cb_data);
350 }
351
352 int for_each_remote_ref(each_ref_fn fn, void *cb_data)
353 {
354         return refs_for_each_remote_ref(get_main_ref_store(), fn, cb_data);
355 }
356
357 int head_ref_namespaced(each_ref_fn fn, void *cb_data)
358 {
359         struct strbuf buf = STRBUF_INIT;
360         int ret = 0;
361         struct object_id oid;
362         int flag;
363
364         strbuf_addf(&buf, "%sHEAD", get_git_namespace());
365         if (!read_ref_full(buf.buf, RESOLVE_REF_READING, &oid, &flag))
366                 ret = fn(buf.buf, &oid, flag, cb_data);
367         strbuf_release(&buf);
368
369         return ret;
370 }
371
372 int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
373         const char *prefix, void *cb_data)
374 {
375         struct strbuf real_pattern = STRBUF_INIT;
376         struct ref_filter filter;
377         int ret;
378
379         if (!prefix && !starts_with(pattern, "refs/"))
380                 strbuf_addstr(&real_pattern, "refs/");
381         else if (prefix)
382                 strbuf_addstr(&real_pattern, prefix);
383         strbuf_addstr(&real_pattern, pattern);
384
385         if (!has_glob_specials(pattern)) {
386                 /* Append implied '/' '*' if not present. */
387                 strbuf_complete(&real_pattern, '/');
388                 /* No need to check for '*', there is none. */
389                 strbuf_addch(&real_pattern, '*');
390         }
391
392         filter.pattern = real_pattern.buf;
393         filter.fn = fn;
394         filter.cb_data = cb_data;
395         ret = for_each_ref(filter_refs, &filter);
396
397         strbuf_release(&real_pattern);
398         return ret;
399 }
400
401 int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
402 {
403         return for_each_glob_ref_in(fn, pattern, NULL, cb_data);
404 }
405
406 const char *prettify_refname(const char *name)
407 {
408         if (skip_prefix(name, "refs/heads/", &name) ||
409             skip_prefix(name, "refs/tags/", &name) ||
410             skip_prefix(name, "refs/remotes/", &name))
411                 ; /* nothing */
412         return name;
413 }
414
415 static const char *ref_rev_parse_rules[] = {
416         "%.*s",
417         "refs/%.*s",
418         "refs/tags/%.*s",
419         "refs/heads/%.*s",
420         "refs/remotes/%.*s",
421         "refs/remotes/%.*s/HEAD",
422         NULL
423 };
424
425 int refname_match(const char *abbrev_name, const char *full_name)
426 {
427         const char **p;
428         const int abbrev_name_len = strlen(abbrev_name);
429
430         for (p = ref_rev_parse_rules; *p; p++) {
431                 if (!strcmp(full_name, mkpath(*p, abbrev_name_len, abbrev_name))) {
432                         return 1;
433                 }
434         }
435
436         return 0;
437 }
438
439 /*
440  * *string and *len will only be substituted, and *string returned (for
441  * later free()ing) if the string passed in is a magic short-hand form
442  * to name a branch.
443  */
444 static char *substitute_branch_name(const char **string, int *len)
445 {
446         struct strbuf buf = STRBUF_INIT;
447         int ret = interpret_branch_name(*string, *len, &buf, 0);
448
449         if (ret == *len) {
450                 size_t size;
451                 *string = strbuf_detach(&buf, &size);
452                 *len = size;
453                 return (char *)*string;
454         }
455
456         return NULL;
457 }
458
459 int dwim_ref(const char *str, int len, struct object_id *oid, char **ref)
460 {
461         char *last_branch = substitute_branch_name(&str, &len);
462         int   refs_found  = expand_ref(str, len, oid, ref);
463         free(last_branch);
464         return refs_found;
465 }
466
467 int expand_ref(const char *str, int len, struct object_id *oid, char **ref)
468 {
469         const char **p, *r;
470         int refs_found = 0;
471         struct strbuf fullref = STRBUF_INIT;
472
473         *ref = NULL;
474         for (p = ref_rev_parse_rules; *p; p++) {
475                 struct object_id oid_from_ref;
476                 struct object_id *this_result;
477                 int flag;
478
479                 this_result = refs_found ? &oid_from_ref : oid;
480                 strbuf_reset(&fullref);
481                 strbuf_addf(&fullref, *p, len, str);
482                 r = resolve_ref_unsafe(fullref.buf, RESOLVE_REF_READING,
483                                        this_result, &flag);
484                 if (r) {
485                         if (!refs_found++)
486                                 *ref = xstrdup(r);
487                         if (!warn_ambiguous_refs)
488                                 break;
489                 } else if ((flag & REF_ISSYMREF) && strcmp(fullref.buf, "HEAD")) {
490                         warning("ignoring dangling symref %s.", fullref.buf);
491                 } else if ((flag & REF_ISBROKEN) && strchr(fullref.buf, '/')) {
492                         warning("ignoring broken ref %s.", fullref.buf);
493                 }
494         }
495         strbuf_release(&fullref);
496         return refs_found;
497 }
498
499 int dwim_log(const char *str, int len, struct object_id *oid, char **log)
500 {
501         char *last_branch = substitute_branch_name(&str, &len);
502         const char **p;
503         int logs_found = 0;
504         struct strbuf path = STRBUF_INIT;
505
506         *log = NULL;
507         for (p = ref_rev_parse_rules; *p; p++) {
508                 struct object_id hash;
509                 const char *ref, *it;
510
511                 strbuf_reset(&path);
512                 strbuf_addf(&path, *p, len, str);
513                 ref = resolve_ref_unsafe(path.buf, RESOLVE_REF_READING,
514                                          &hash, NULL);
515                 if (!ref)
516                         continue;
517                 if (reflog_exists(path.buf))
518                         it = path.buf;
519                 else if (strcmp(ref, path.buf) && reflog_exists(ref))
520                         it = ref;
521                 else
522                         continue;
523                 if (!logs_found++) {
524                         *log = xstrdup(it);
525                         oidcpy(oid, &hash);
526                 }
527                 if (!warn_ambiguous_refs)
528                         break;
529         }
530         strbuf_release(&path);
531         free(last_branch);
532         return logs_found;
533 }
534
535 static int is_per_worktree_ref(const char *refname)
536 {
537         return !strcmp(refname, "HEAD") ||
538                 starts_with(refname, "refs/bisect/");
539 }
540
541 static int is_pseudoref_syntax(const char *refname)
542 {
543         const char *c;
544
545         for (c = refname; *c; c++) {
546                 if (!isupper(*c) && *c != '-' && *c != '_')
547                         return 0;
548         }
549
550         return 1;
551 }
552
553 enum ref_type ref_type(const char *refname)
554 {
555         if (is_per_worktree_ref(refname))
556                 return REF_TYPE_PER_WORKTREE;
557         if (is_pseudoref_syntax(refname))
558                 return REF_TYPE_PSEUDOREF;
559        return REF_TYPE_NORMAL;
560 }
561
562 long get_files_ref_lock_timeout_ms(void)
563 {
564         static int configured = 0;
565
566         /* The default timeout is 100 ms: */
567         static int timeout_ms = 100;
568
569         if (!configured) {
570                 git_config_get_int("core.filesreflocktimeout", &timeout_ms);
571                 configured = 1;
572         }
573
574         return timeout_ms;
575 }
576
577 static int write_pseudoref(const char *pseudoref, const struct object_id *oid,
578                            const struct object_id *old_oid, struct strbuf *err)
579 {
580         const char *filename;
581         int fd;
582         static struct lock_file lock;
583         struct strbuf buf = STRBUF_INIT;
584         int ret = -1;
585
586         if (!oid)
587                 return 0;
588
589         strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
590
591         filename = git_path("%s", pseudoref);
592         fd = hold_lock_file_for_update_timeout(&lock, filename,
593                                                LOCK_DIE_ON_ERROR,
594                                                get_files_ref_lock_timeout_ms());
595         if (fd < 0) {
596                 strbuf_addf(err, "could not open '%s' for writing: %s",
597                             filename, strerror(errno));
598                 goto done;
599         }
600
601         if (old_oid) {
602                 struct object_id actual_old_oid;
603
604                 if (read_ref(pseudoref, &actual_old_oid))
605                         die("could not read ref '%s'", pseudoref);
606                 if (oidcmp(&actual_old_oid, old_oid)) {
607                         strbuf_addf(err, "unexpected sha1 when writing '%s'", pseudoref);
608                         rollback_lock_file(&lock);
609                         goto done;
610                 }
611         }
612
613         if (write_in_full(fd, buf.buf, buf.len) < 0) {
614                 strbuf_addf(err, "could not write to '%s'", filename);
615                 rollback_lock_file(&lock);
616                 goto done;
617         }
618
619         commit_lock_file(&lock);
620         ret = 0;
621 done:
622         strbuf_release(&buf);
623         return ret;
624 }
625
626 static int delete_pseudoref(const char *pseudoref, const struct object_id *old_oid)
627 {
628         static struct lock_file lock;
629         const char *filename;
630
631         filename = git_path("%s", pseudoref);
632
633         if (old_oid && !is_null_oid(old_oid)) {
634                 int fd;
635                 struct object_id actual_old_oid;
636
637                 fd = hold_lock_file_for_update_timeout(
638                                 &lock, filename, LOCK_DIE_ON_ERROR,
639                                 get_files_ref_lock_timeout_ms());
640                 if (fd < 0)
641                         die_errno(_("Could not open '%s' for writing"), filename);
642                 if (read_ref(pseudoref, &actual_old_oid))
643                         die("could not read ref '%s'", pseudoref);
644                 if (oidcmp(&actual_old_oid, old_oid)) {
645                         warning("Unexpected sha1 when deleting %s", pseudoref);
646                         rollback_lock_file(&lock);
647                         return -1;
648                 }
649
650                 unlink(filename);
651                 rollback_lock_file(&lock);
652         } else {
653                 unlink(filename);
654         }
655
656         return 0;
657 }
658
659 int refs_delete_ref(struct ref_store *refs, const char *msg,
660                     const char *refname,
661                     const struct object_id *old_oid,
662                     unsigned int flags)
663 {
664         struct ref_transaction *transaction;
665         struct strbuf err = STRBUF_INIT;
666
667         if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
668                 assert(refs == get_main_ref_store());
669                 return delete_pseudoref(refname, old_oid);
670         }
671
672         transaction = ref_store_transaction_begin(refs, &err);
673         if (!transaction ||
674             ref_transaction_delete(transaction, refname, old_oid,
675                                    flags, msg, &err) ||
676             ref_transaction_commit(transaction, &err)) {
677                 error("%s", err.buf);
678                 ref_transaction_free(transaction);
679                 strbuf_release(&err);
680                 return 1;
681         }
682         ref_transaction_free(transaction);
683         strbuf_release(&err);
684         return 0;
685 }
686
687 int delete_ref(const char *msg, const char *refname,
688                const struct object_id *old_oid, unsigned int flags)
689 {
690         return refs_delete_ref(get_main_ref_store(), msg, refname,
691                                old_oid, flags);
692 }
693
694 int copy_reflog_msg(char *buf, const char *msg)
695 {
696         char *cp = buf;
697         char c;
698         int wasspace = 1;
699
700         *cp++ = '\t';
701         while ((c = *msg++)) {
702                 if (wasspace && isspace(c))
703                         continue;
704                 wasspace = isspace(c);
705                 if (wasspace)
706                         c = ' ';
707                 *cp++ = c;
708         }
709         while (buf < cp && isspace(cp[-1]))
710                 cp--;
711         *cp++ = '\n';
712         return cp - buf;
713 }
714
715 int should_autocreate_reflog(const char *refname)
716 {
717         switch (log_all_ref_updates) {
718         case LOG_REFS_ALWAYS:
719                 return 1;
720         case LOG_REFS_NORMAL:
721                 return starts_with(refname, "refs/heads/") ||
722                         starts_with(refname, "refs/remotes/") ||
723                         starts_with(refname, "refs/notes/") ||
724                         !strcmp(refname, "HEAD");
725         default:
726                 return 0;
727         }
728 }
729
730 int is_branch(const char *refname)
731 {
732         return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
733 }
734
735 struct read_ref_at_cb {
736         const char *refname;
737         timestamp_t at_time;
738         int cnt;
739         int reccnt;
740         struct object_id *oid;
741         int found_it;
742
743         struct object_id ooid;
744         struct object_id noid;
745         int tz;
746         timestamp_t date;
747         char **msg;
748         timestamp_t *cutoff_time;
749         int *cutoff_tz;
750         int *cutoff_cnt;
751 };
752
753 static int read_ref_at_ent(struct object_id *ooid, struct object_id *noid,
754                 const char *email, timestamp_t timestamp, int tz,
755                 const char *message, void *cb_data)
756 {
757         struct read_ref_at_cb *cb = cb_data;
758
759         cb->reccnt++;
760         cb->tz = tz;
761         cb->date = timestamp;
762
763         if (timestamp <= cb->at_time || cb->cnt == 0) {
764                 if (cb->msg)
765                         *cb->msg = xstrdup(message);
766                 if (cb->cutoff_time)
767                         *cb->cutoff_time = timestamp;
768                 if (cb->cutoff_tz)
769                         *cb->cutoff_tz = tz;
770                 if (cb->cutoff_cnt)
771                         *cb->cutoff_cnt = cb->reccnt - 1;
772                 /*
773                  * we have not yet updated cb->[n|o]oid so they still
774                  * hold the values for the previous record.
775                  */
776                 if (!is_null_oid(&cb->ooid)) {
777                         oidcpy(cb->oid, noid);
778                         if (oidcmp(&cb->ooid, noid))
779                                 warning("Log for ref %s has gap after %s.",
780                                         cb->refname, show_date(cb->date, cb->tz, DATE_MODE(RFC2822)));
781                 }
782                 else if (cb->date == cb->at_time)
783                         oidcpy(cb->oid, noid);
784                 else if (oidcmp(noid, cb->oid))
785                         warning("Log for ref %s unexpectedly ended on %s.",
786                                 cb->refname, show_date(cb->date, cb->tz,
787                                                        DATE_MODE(RFC2822)));
788                 oidcpy(&cb->ooid, ooid);
789                 oidcpy(&cb->noid, noid);
790                 cb->found_it = 1;
791                 return 1;
792         }
793         oidcpy(&cb->ooid, ooid);
794         oidcpy(&cb->noid, noid);
795         if (cb->cnt > 0)
796                 cb->cnt--;
797         return 0;
798 }
799
800 static int read_ref_at_ent_oldest(struct object_id *ooid, struct object_id *noid,
801                                   const char *email, timestamp_t timestamp,
802                                   int tz, const char *message, void *cb_data)
803 {
804         struct read_ref_at_cb *cb = cb_data;
805
806         if (cb->msg)
807                 *cb->msg = xstrdup(message);
808         if (cb->cutoff_time)
809                 *cb->cutoff_time = timestamp;
810         if (cb->cutoff_tz)
811                 *cb->cutoff_tz = tz;
812         if (cb->cutoff_cnt)
813                 *cb->cutoff_cnt = cb->reccnt;
814         oidcpy(cb->oid, ooid);
815         if (is_null_oid(cb->oid))
816                 oidcpy(cb->oid, noid);
817         /* We just want the first entry */
818         return 1;
819 }
820
821 int read_ref_at(const char *refname, unsigned int flags, timestamp_t at_time, int cnt,
822                 struct object_id *oid, char **msg,
823                 timestamp_t *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
824 {
825         struct read_ref_at_cb cb;
826
827         memset(&cb, 0, sizeof(cb));
828         cb.refname = refname;
829         cb.at_time = at_time;
830         cb.cnt = cnt;
831         cb.msg = msg;
832         cb.cutoff_time = cutoff_time;
833         cb.cutoff_tz = cutoff_tz;
834         cb.cutoff_cnt = cutoff_cnt;
835         cb.oid = oid;
836
837         for_each_reflog_ent_reverse(refname, read_ref_at_ent, &cb);
838
839         if (!cb.reccnt) {
840                 if (flags & GET_OID_QUIETLY)
841                         exit(128);
842                 else
843                         die("Log for %s is empty.", refname);
844         }
845         if (cb.found_it)
846                 return 0;
847
848         for_each_reflog_ent(refname, read_ref_at_ent_oldest, &cb);
849
850         return 1;
851 }
852
853 struct ref_transaction *ref_store_transaction_begin(struct ref_store *refs,
854                                                     struct strbuf *err)
855 {
856         struct ref_transaction *tr;
857         assert(err);
858
859         tr = xcalloc(1, sizeof(struct ref_transaction));
860         tr->ref_store = refs;
861         return tr;
862 }
863
864 struct ref_transaction *ref_transaction_begin(struct strbuf *err)
865 {
866         return ref_store_transaction_begin(get_main_ref_store(), err);
867 }
868
869 void ref_transaction_free(struct ref_transaction *transaction)
870 {
871         size_t i;
872
873         if (!transaction)
874                 return;
875
876         switch (transaction->state) {
877         case REF_TRANSACTION_OPEN:
878         case REF_TRANSACTION_CLOSED:
879                 /* OK */
880                 break;
881         case REF_TRANSACTION_PREPARED:
882                 die("BUG: free called on a prepared reference transaction");
883                 break;
884         default:
885                 die("BUG: unexpected reference transaction state");
886                 break;
887         }
888
889         for (i = 0; i < transaction->nr; i++) {
890                 free(transaction->updates[i]->msg);
891                 free(transaction->updates[i]);
892         }
893         free(transaction->updates);
894         free(transaction);
895 }
896
897 struct ref_update *ref_transaction_add_update(
898                 struct ref_transaction *transaction,
899                 const char *refname, unsigned int flags,
900                 const struct object_id *new_oid,
901                 const struct object_id *old_oid,
902                 const char *msg)
903 {
904         struct ref_update *update;
905
906         if (transaction->state != REF_TRANSACTION_OPEN)
907                 die("BUG: update called for transaction that is not open");
908
909         FLEX_ALLOC_STR(update, refname, refname);
910         ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
911         transaction->updates[transaction->nr++] = update;
912
913         update->flags = flags;
914
915         if (flags & REF_HAVE_NEW)
916                 oidcpy(&update->new_oid, new_oid);
917         if (flags & REF_HAVE_OLD)
918                 oidcpy(&update->old_oid, old_oid);
919         update->msg = xstrdup_or_null(msg);
920         return update;
921 }
922
923 int ref_transaction_update(struct ref_transaction *transaction,
924                            const char *refname,
925                            const struct object_id *new_oid,
926                            const struct object_id *old_oid,
927                            unsigned int flags, const char *msg,
928                            struct strbuf *err)
929 {
930         assert(err);
931
932         if ((new_oid && !is_null_oid(new_oid)) ?
933             check_refname_format(refname, REFNAME_ALLOW_ONELEVEL) :
934             !refname_is_safe(refname)) {
935                 strbuf_addf(err, "refusing to update ref with bad name '%s'",
936                             refname);
937                 return -1;
938         }
939
940         if (flags & ~REF_TRANSACTION_UPDATE_ALLOWED_FLAGS)
941                 BUG("illegal flags 0x%x passed to ref_transaction_update()", flags);
942
943         flags |= (new_oid ? REF_HAVE_NEW : 0) | (old_oid ? REF_HAVE_OLD : 0);
944
945         ref_transaction_add_update(transaction, refname, flags,
946                                    new_oid, old_oid, msg);
947         return 0;
948 }
949
950 int ref_transaction_create(struct ref_transaction *transaction,
951                            const char *refname,
952                            const struct object_id *new_oid,
953                            unsigned int flags, const char *msg,
954                            struct strbuf *err)
955 {
956         if (!new_oid || is_null_oid(new_oid))
957                 die("BUG: create called without valid new_oid");
958         return ref_transaction_update(transaction, refname, new_oid,
959                                       &null_oid, flags, msg, err);
960 }
961
962 int ref_transaction_delete(struct ref_transaction *transaction,
963                            const char *refname,
964                            const struct object_id *old_oid,
965                            unsigned int flags, const char *msg,
966                            struct strbuf *err)
967 {
968         if (old_oid && is_null_oid(old_oid))
969                 die("BUG: delete called with old_oid set to zeros");
970         return ref_transaction_update(transaction, refname,
971                                       &null_oid, old_oid,
972                                       flags, msg, err);
973 }
974
975 int ref_transaction_verify(struct ref_transaction *transaction,
976                            const char *refname,
977                            const struct object_id *old_oid,
978                            unsigned int flags,
979                            struct strbuf *err)
980 {
981         if (!old_oid)
982                 die("BUG: verify called with old_oid set to NULL");
983         return ref_transaction_update(transaction, refname,
984                                       NULL, old_oid,
985                                       flags, NULL, err);
986 }
987
988 int refs_update_ref(struct ref_store *refs, const char *msg,
989                     const char *refname, const struct object_id *new_oid,
990                     const struct object_id *old_oid, unsigned int flags,
991                     enum action_on_err onerr)
992 {
993         struct ref_transaction *t = NULL;
994         struct strbuf err = STRBUF_INIT;
995         int ret = 0;
996
997         if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
998                 assert(refs == get_main_ref_store());
999                 ret = write_pseudoref(refname, new_oid, old_oid, &err);
1000         } else {
1001                 t = ref_store_transaction_begin(refs, &err);
1002                 if (!t ||
1003                     ref_transaction_update(t, refname, new_oid, old_oid,
1004                                            flags, msg, &err) ||
1005                     ref_transaction_commit(t, &err)) {
1006                         ret = 1;
1007                         ref_transaction_free(t);
1008                 }
1009         }
1010         if (ret) {
1011                 const char *str = "update_ref failed for ref '%s': %s";
1012
1013                 switch (onerr) {
1014                 case UPDATE_REFS_MSG_ON_ERR:
1015                         error(str, refname, err.buf);
1016                         break;
1017                 case UPDATE_REFS_DIE_ON_ERR:
1018                         die(str, refname, err.buf);
1019                         break;
1020                 case UPDATE_REFS_QUIET_ON_ERR:
1021                         break;
1022                 }
1023                 strbuf_release(&err);
1024                 return 1;
1025         }
1026         strbuf_release(&err);
1027         if (t)
1028                 ref_transaction_free(t);
1029         return 0;
1030 }
1031
1032 int update_ref(const char *msg, const char *refname,
1033                const struct object_id *new_oid,
1034                const struct object_id *old_oid,
1035                unsigned int flags, enum action_on_err onerr)
1036 {
1037         return refs_update_ref(get_main_ref_store(), msg, refname, new_oid,
1038                                old_oid, flags, onerr);
1039 }
1040
1041 char *shorten_unambiguous_ref(const char *refname, int strict)
1042 {
1043         int i;
1044         static char **scanf_fmts;
1045         static int nr_rules;
1046         char *short_name;
1047         struct strbuf resolved_buf = STRBUF_INIT;
1048
1049         if (!nr_rules) {
1050                 /*
1051                  * Pre-generate scanf formats from ref_rev_parse_rules[].
1052                  * Generate a format suitable for scanf from a
1053                  * ref_rev_parse_rules rule by interpolating "%s" at the
1054                  * location of the "%.*s".
1055                  */
1056                 size_t total_len = 0;
1057                 size_t offset = 0;
1058
1059                 /* the rule list is NULL terminated, count them first */
1060                 for (nr_rules = 0; ref_rev_parse_rules[nr_rules]; nr_rules++)
1061                         /* -2 for strlen("%.*s") - strlen("%s"); +1 for NUL */
1062                         total_len += strlen(ref_rev_parse_rules[nr_rules]) - 2 + 1;
1063
1064                 scanf_fmts = xmalloc(st_add(st_mult(sizeof(char *), nr_rules), total_len));
1065
1066                 offset = 0;
1067                 for (i = 0; i < nr_rules; i++) {
1068                         assert(offset < total_len);
1069                         scanf_fmts[i] = (char *)&scanf_fmts[nr_rules] + offset;
1070                         offset += snprintf(scanf_fmts[i], total_len - offset,
1071                                            ref_rev_parse_rules[i], 2, "%s") + 1;
1072                 }
1073         }
1074
1075         /* bail out if there are no rules */
1076         if (!nr_rules)
1077                 return xstrdup(refname);
1078
1079         /* buffer for scanf result, at most refname must fit */
1080         short_name = xstrdup(refname);
1081
1082         /* skip first rule, it will always match */
1083         for (i = nr_rules - 1; i > 0 ; --i) {
1084                 int j;
1085                 int rules_to_fail = i;
1086                 int short_name_len;
1087
1088                 if (1 != sscanf(refname, scanf_fmts[i], short_name))
1089                         continue;
1090
1091                 short_name_len = strlen(short_name);
1092
1093                 /*
1094                  * in strict mode, all (except the matched one) rules
1095                  * must fail to resolve to a valid non-ambiguous ref
1096                  */
1097                 if (strict)
1098                         rules_to_fail = nr_rules;
1099
1100                 /*
1101                  * check if the short name resolves to a valid ref,
1102                  * but use only rules prior to the matched one
1103                  */
1104                 for (j = 0; j < rules_to_fail; j++) {
1105                         const char *rule = ref_rev_parse_rules[j];
1106
1107                         /* skip matched rule */
1108                         if (i == j)
1109                                 continue;
1110
1111                         /*
1112                          * the short name is ambiguous, if it resolves
1113                          * (with this previous rule) to a valid ref
1114                          * read_ref() returns 0 on success
1115                          */
1116                         strbuf_reset(&resolved_buf);
1117                         strbuf_addf(&resolved_buf, rule,
1118                                     short_name_len, short_name);
1119                         if (ref_exists(resolved_buf.buf))
1120                                 break;
1121                 }
1122
1123                 /*
1124                  * short name is non-ambiguous if all previous rules
1125                  * haven't resolved to a valid ref
1126                  */
1127                 if (j == rules_to_fail) {
1128                         strbuf_release(&resolved_buf);
1129                         return short_name;
1130                 }
1131         }
1132
1133         strbuf_release(&resolved_buf);
1134         free(short_name);
1135         return xstrdup(refname);
1136 }
1137
1138 static struct string_list *hide_refs;
1139
1140 int parse_hide_refs_config(const char *var, const char *value, const char *section)
1141 {
1142         const char *key;
1143         if (!strcmp("transfer.hiderefs", var) ||
1144             (!parse_config_key(var, section, NULL, NULL, &key) &&
1145              !strcmp(key, "hiderefs"))) {
1146                 char *ref;
1147                 int len;
1148
1149                 if (!value)
1150                         return config_error_nonbool(var);
1151                 ref = xstrdup(value);
1152                 len = strlen(ref);
1153                 while (len && ref[len - 1] == '/')
1154                         ref[--len] = '\0';
1155                 if (!hide_refs) {
1156                         hide_refs = xcalloc(1, sizeof(*hide_refs));
1157                         hide_refs->strdup_strings = 1;
1158                 }
1159                 string_list_append(hide_refs, ref);
1160         }
1161         return 0;
1162 }
1163
1164 int ref_is_hidden(const char *refname, const char *refname_full)
1165 {
1166         int i;
1167
1168         if (!hide_refs)
1169                 return 0;
1170         for (i = hide_refs->nr - 1; i >= 0; i--) {
1171                 const char *match = hide_refs->items[i].string;
1172                 const char *subject;
1173                 int neg = 0;
1174                 const char *p;
1175
1176                 if (*match == '!') {
1177                         neg = 1;
1178                         match++;
1179                 }
1180
1181                 if (*match == '^') {
1182                         subject = refname_full;
1183                         match++;
1184                 } else {
1185                         subject = refname;
1186                 }
1187
1188                 /* refname can be NULL when namespaces are used. */
1189                 if (subject &&
1190                     skip_prefix(subject, match, &p) &&
1191                     (!*p || *p == '/'))
1192                         return !neg;
1193         }
1194         return 0;
1195 }
1196
1197 const char *find_descendant_ref(const char *dirname,
1198                                 const struct string_list *extras,
1199                                 const struct string_list *skip)
1200 {
1201         int pos;
1202
1203         if (!extras)
1204                 return NULL;
1205
1206         /*
1207          * Look at the place where dirname would be inserted into
1208          * extras. If there is an entry at that position that starts
1209          * with dirname (remember, dirname includes the trailing
1210          * slash) and is not in skip, then we have a conflict.
1211          */
1212         for (pos = string_list_find_insert_index(extras, dirname, 0);
1213              pos < extras->nr; pos++) {
1214                 const char *extra_refname = extras->items[pos].string;
1215
1216                 if (!starts_with(extra_refname, dirname))
1217                         break;
1218
1219                 if (!skip || !string_list_has_string(skip, extra_refname))
1220                         return extra_refname;
1221         }
1222         return NULL;
1223 }
1224
1225 int refs_rename_ref_available(struct ref_store *refs,
1226                               const char *old_refname,
1227                               const char *new_refname)
1228 {
1229         struct string_list skip = STRING_LIST_INIT_NODUP;
1230         struct strbuf err = STRBUF_INIT;
1231         int ok;
1232
1233         string_list_insert(&skip, old_refname);
1234         ok = !refs_verify_refname_available(refs, new_refname,
1235                                             NULL, &skip, &err);
1236         if (!ok)
1237                 error("%s", err.buf);
1238
1239         string_list_clear(&skip, 0);
1240         strbuf_release(&err);
1241         return ok;
1242 }
1243
1244 int refs_head_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
1245 {
1246         struct object_id oid;
1247         int flag;
1248
1249         if (!refs_read_ref_full(refs, "HEAD", RESOLVE_REF_READING,
1250                                 &oid, &flag))
1251                 return fn("HEAD", &oid, flag, cb_data);
1252
1253         return 0;
1254 }
1255
1256 int head_ref(each_ref_fn fn, void *cb_data)
1257 {
1258         return refs_head_ref(get_main_ref_store(), fn, cb_data);
1259 }
1260
1261 struct ref_iterator *refs_ref_iterator_begin(
1262                 struct ref_store *refs,
1263                 const char *prefix, int trim, int flags)
1264 {
1265         struct ref_iterator *iter;
1266
1267         if (ref_paranoia < 0)
1268                 ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1269         if (ref_paranoia)
1270                 flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1271
1272         iter = refs->be->iterator_begin(refs, prefix, flags);
1273
1274         /*
1275          * `iterator_begin()` already takes care of prefix, but we
1276          * might need to do some trimming:
1277          */
1278         if (trim)
1279                 iter = prefix_ref_iterator_begin(iter, "", trim);
1280
1281         /* Sanity check for subclasses: */
1282         if (!iter->ordered)
1283                 BUG("reference iterator is not ordered");
1284
1285         return iter;
1286 }
1287
1288 /*
1289  * Call fn for each reference in the specified submodule for which the
1290  * refname begins with prefix. If trim is non-zero, then trim that
1291  * many characters off the beginning of each refname before passing
1292  * the refname to fn. flags can be DO_FOR_EACH_INCLUDE_BROKEN to
1293  * include broken references in the iteration. If fn ever returns a
1294  * non-zero value, stop the iteration and return that value;
1295  * otherwise, return 0.
1296  */
1297 static int do_for_each_ref(struct ref_store *refs, const char *prefix,
1298                            each_ref_fn fn, int trim, int flags, void *cb_data)
1299 {
1300         struct ref_iterator *iter;
1301
1302         if (!refs)
1303                 return 0;
1304
1305         iter = refs_ref_iterator_begin(refs, prefix, trim, flags);
1306
1307         return do_for_each_ref_iterator(iter, fn, cb_data);
1308 }
1309
1310 int refs_for_each_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
1311 {
1312         return do_for_each_ref(refs, "", fn, 0, 0, cb_data);
1313 }
1314
1315 int for_each_ref(each_ref_fn fn, void *cb_data)
1316 {
1317         return refs_for_each_ref(get_main_ref_store(), fn, cb_data);
1318 }
1319
1320 int refs_for_each_ref_in(struct ref_store *refs, const char *prefix,
1321                          each_ref_fn fn, void *cb_data)
1322 {
1323         return do_for_each_ref(refs, prefix, fn, strlen(prefix), 0, cb_data);
1324 }
1325
1326 int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
1327 {
1328         return refs_for_each_ref_in(get_main_ref_store(), prefix, fn, cb_data);
1329 }
1330
1331 int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data, unsigned int broken)
1332 {
1333         unsigned int flag = 0;
1334
1335         if (broken)
1336                 flag = DO_FOR_EACH_INCLUDE_BROKEN;
1337         return do_for_each_ref(get_main_ref_store(),
1338                                prefix, fn, 0, flag, cb_data);
1339 }
1340
1341 int refs_for_each_fullref_in(struct ref_store *refs, const char *prefix,
1342                              each_ref_fn fn, void *cb_data,
1343                              unsigned int broken)
1344 {
1345         unsigned int flag = 0;
1346
1347         if (broken)
1348                 flag = DO_FOR_EACH_INCLUDE_BROKEN;
1349         return do_for_each_ref(refs, prefix, fn, 0, flag, cb_data);
1350 }
1351
1352 int for_each_replace_ref(each_ref_fn fn, void *cb_data)
1353 {
1354         return do_for_each_ref(get_main_ref_store(),
1355                                git_replace_ref_base, fn,
1356                                strlen(git_replace_ref_base),
1357                                DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
1358 }
1359
1360 int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
1361 {
1362         struct strbuf buf = STRBUF_INIT;
1363         int ret;
1364         strbuf_addf(&buf, "%srefs/", get_git_namespace());
1365         ret = do_for_each_ref(get_main_ref_store(),
1366                               buf.buf, fn, 0, 0, cb_data);
1367         strbuf_release(&buf);
1368         return ret;
1369 }
1370
1371 int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
1372 {
1373         return do_for_each_ref(refs, "", fn, 0,
1374                                DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
1375 }
1376
1377 int for_each_rawref(each_ref_fn fn, void *cb_data)
1378 {
1379         return refs_for_each_rawref(get_main_ref_store(), fn, cb_data);
1380 }
1381
1382 int refs_read_raw_ref(struct ref_store *ref_store,
1383                       const char *refname, struct object_id *oid,
1384                       struct strbuf *referent, unsigned int *type)
1385 {
1386         return ref_store->be->read_raw_ref(ref_store, refname, oid, referent, type);
1387 }
1388
1389 /* This function needs to return a meaningful errno on failure */
1390 const char *refs_resolve_ref_unsafe(struct ref_store *refs,
1391                                     const char *refname,
1392                                     int resolve_flags,
1393                                     struct object_id *oid, int *flags)
1394 {
1395         static struct strbuf sb_refname = STRBUF_INIT;
1396         struct object_id unused_oid;
1397         int unused_flags;
1398         int symref_count;
1399
1400         if (!oid)
1401                 oid = &unused_oid;
1402         if (!flags)
1403                 flags = &unused_flags;
1404
1405         *flags = 0;
1406
1407         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1408                 if (!(resolve_flags & RESOLVE_REF_ALLOW_BAD_NAME) ||
1409                     !refname_is_safe(refname)) {
1410                         errno = EINVAL;
1411                         return NULL;
1412                 }
1413
1414                 /*
1415                  * dwim_ref() uses REF_ISBROKEN to distinguish between
1416                  * missing refs and refs that were present but invalid,
1417                  * to complain about the latter to stderr.
1418                  *
1419                  * We don't know whether the ref exists, so don't set
1420                  * REF_ISBROKEN yet.
1421                  */
1422                 *flags |= REF_BAD_NAME;
1423         }
1424
1425         for (symref_count = 0; symref_count < SYMREF_MAXDEPTH; symref_count++) {
1426                 unsigned int read_flags = 0;
1427
1428                 if (refs_read_raw_ref(refs, refname,
1429                                       oid, &sb_refname, &read_flags)) {
1430                         *flags |= read_flags;
1431
1432                         /* In reading mode, refs must eventually resolve */
1433                         if (resolve_flags & RESOLVE_REF_READING)
1434                                 return NULL;
1435
1436                         /*
1437                          * Otherwise a missing ref is OK. But the files backend
1438                          * may show errors besides ENOENT if there are
1439                          * similarly-named refs.
1440                          */
1441                         if (errno != ENOENT &&
1442                             errno != EISDIR &&
1443                             errno != ENOTDIR)
1444                                 return NULL;
1445
1446                         oidclr(oid);
1447                         if (*flags & REF_BAD_NAME)
1448                                 *flags |= REF_ISBROKEN;
1449                         return refname;
1450                 }
1451
1452                 *flags |= read_flags;
1453
1454                 if (!(read_flags & REF_ISSYMREF)) {
1455                         if (*flags & REF_BAD_NAME) {
1456                                 oidclr(oid);
1457                                 *flags |= REF_ISBROKEN;
1458                         }
1459                         return refname;
1460                 }
1461
1462                 refname = sb_refname.buf;
1463                 if (resolve_flags & RESOLVE_REF_NO_RECURSE) {
1464                         oidclr(oid);
1465                         return refname;
1466                 }
1467                 if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1468                         if (!(resolve_flags & RESOLVE_REF_ALLOW_BAD_NAME) ||
1469                             !refname_is_safe(refname)) {
1470                                 errno = EINVAL;
1471                                 return NULL;
1472                         }
1473
1474                         *flags |= REF_ISBROKEN | REF_BAD_NAME;
1475                 }
1476         }
1477
1478         errno = ELOOP;
1479         return NULL;
1480 }
1481
1482 /* backend functions */
1483 int refs_init_db(struct strbuf *err)
1484 {
1485         struct ref_store *refs = get_main_ref_store();
1486
1487         return refs->be->init_db(refs, err);
1488 }
1489
1490 const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
1491                                struct object_id *oid, int *flags)
1492 {
1493         return refs_resolve_ref_unsafe(get_main_ref_store(), refname,
1494                                        resolve_flags, oid, flags);
1495 }
1496
1497 int resolve_gitlink_ref(const char *submodule, const char *refname,
1498                         struct object_id *oid)
1499 {
1500         struct ref_store *refs;
1501         int flags;
1502
1503         refs = get_submodule_ref_store(submodule);
1504
1505         if (!refs)
1506                 return -1;
1507
1508         if (!refs_resolve_ref_unsafe(refs, refname, 0, oid, &flags) ||
1509             is_null_oid(oid))
1510                 return -1;
1511         return 0;
1512 }
1513
1514 struct ref_store_hash_entry
1515 {
1516         struct hashmap_entry ent; /* must be the first member! */
1517
1518         struct ref_store *refs;
1519
1520         /* NUL-terminated identifier of the ref store: */
1521         char name[FLEX_ARRAY];
1522 };
1523
1524 static int ref_store_hash_cmp(const void *unused_cmp_data,
1525                               const void *entry, const void *entry_or_key,
1526                               const void *keydata)
1527 {
1528         const struct ref_store_hash_entry *e1 = entry, *e2 = entry_or_key;
1529         const char *name = keydata ? keydata : e2->name;
1530
1531         return strcmp(e1->name, name);
1532 }
1533
1534 static struct ref_store_hash_entry *alloc_ref_store_hash_entry(
1535                 const char *name, struct ref_store *refs)
1536 {
1537         struct ref_store_hash_entry *entry;
1538
1539         FLEX_ALLOC_STR(entry, name, name);
1540         hashmap_entry_init(entry, strhash(name));
1541         entry->refs = refs;
1542         return entry;
1543 }
1544
1545 /* A pointer to the ref_store for the main repository: */
1546 static struct ref_store *main_ref_store;
1547
1548 /* A hashmap of ref_stores, stored by submodule name: */
1549 static struct hashmap submodule_ref_stores;
1550
1551 /* A hashmap of ref_stores, stored by worktree id: */
1552 static struct hashmap worktree_ref_stores;
1553
1554 /*
1555  * Look up a ref store by name. If that ref_store hasn't been
1556  * registered yet, return NULL.
1557  */
1558 static struct ref_store *lookup_ref_store_map(struct hashmap *map,
1559                                               const char *name)
1560 {
1561         struct ref_store_hash_entry *entry;
1562
1563         if (!map->tablesize)
1564                 /* It's initialized on demand in register_ref_store(). */
1565                 return NULL;
1566
1567         entry = hashmap_get_from_hash(map, strhash(name), name);
1568         return entry ? entry->refs : NULL;
1569 }
1570
1571 /*
1572  * Create, record, and return a ref_store instance for the specified
1573  * gitdir.
1574  */
1575 static struct ref_store *ref_store_init(const char *gitdir,
1576                                         unsigned int flags)
1577 {
1578         const char *be_name = "files";
1579         struct ref_storage_be *be = find_ref_storage_backend(be_name);
1580         struct ref_store *refs;
1581
1582         if (!be)
1583                 die("BUG: reference backend %s is unknown", be_name);
1584
1585         refs = be->init(gitdir, flags);
1586         return refs;
1587 }
1588
1589 struct ref_store *get_main_ref_store(void)
1590 {
1591         if (main_ref_store)
1592                 return main_ref_store;
1593
1594         main_ref_store = ref_store_init(get_git_dir(), REF_STORE_ALL_CAPS);
1595         return main_ref_store;
1596 }
1597
1598 /*
1599  * Associate a ref store with a name. It is a fatal error to call this
1600  * function twice for the same name.
1601  */
1602 static void register_ref_store_map(struct hashmap *map,
1603                                    const char *type,
1604                                    struct ref_store *refs,
1605                                    const char *name)
1606 {
1607         if (!map->tablesize)
1608                 hashmap_init(map, ref_store_hash_cmp, NULL, 0);
1609
1610         if (hashmap_put(map, alloc_ref_store_hash_entry(name, refs)))
1611                 die("BUG: %s ref_store '%s' initialized twice", type, name);
1612 }
1613
1614 struct ref_store *get_submodule_ref_store(const char *submodule)
1615 {
1616         struct strbuf submodule_sb = STRBUF_INIT;
1617         struct ref_store *refs;
1618         char *to_free = NULL;
1619         size_t len;
1620
1621         if (!submodule)
1622                 return NULL;
1623
1624         len = strlen(submodule);
1625         while (len && is_dir_sep(submodule[len - 1]))
1626                 len--;
1627         if (!len)
1628                 return NULL;
1629
1630         if (submodule[len])
1631                 /* We need to strip off one or more trailing slashes */
1632                 submodule = to_free = xmemdupz(submodule, len);
1633
1634         refs = lookup_ref_store_map(&submodule_ref_stores, submodule);
1635         if (refs)
1636                 goto done;
1637
1638         strbuf_addstr(&submodule_sb, submodule);
1639         if (!is_nonbare_repository_dir(&submodule_sb))
1640                 goto done;
1641
1642         if (submodule_to_gitdir(&submodule_sb, submodule))
1643                 goto done;
1644
1645         /* assume that add_submodule_odb() has been called */
1646         refs = ref_store_init(submodule_sb.buf,
1647                               REF_STORE_READ | REF_STORE_ODB);
1648         register_ref_store_map(&submodule_ref_stores, "submodule",
1649                                refs, submodule);
1650
1651 done:
1652         strbuf_release(&submodule_sb);
1653         free(to_free);
1654
1655         return refs;
1656 }
1657
1658 struct ref_store *get_worktree_ref_store(const struct worktree *wt)
1659 {
1660         struct ref_store *refs;
1661         const char *id;
1662
1663         if (wt->is_current)
1664                 return get_main_ref_store();
1665
1666         id = wt->id ? wt->id : "/";
1667         refs = lookup_ref_store_map(&worktree_ref_stores, id);
1668         if (refs)
1669                 return refs;
1670
1671         if (wt->id)
1672                 refs = ref_store_init(git_common_path("worktrees/%s", wt->id),
1673                                       REF_STORE_ALL_CAPS);
1674         else
1675                 refs = ref_store_init(get_git_common_dir(),
1676                                       REF_STORE_ALL_CAPS);
1677
1678         if (refs)
1679                 register_ref_store_map(&worktree_ref_stores, "worktree",
1680                                        refs, id);
1681         return refs;
1682 }
1683
1684 void base_ref_store_init(struct ref_store *refs,
1685                          const struct ref_storage_be *be)
1686 {
1687         refs->be = be;
1688 }
1689
1690 /* backend functions */
1691 int refs_pack_refs(struct ref_store *refs, unsigned int flags)
1692 {
1693         return refs->be->pack_refs(refs, flags);
1694 }
1695
1696 int refs_peel_ref(struct ref_store *refs, const char *refname,
1697                   struct object_id *oid)
1698 {
1699         int flag;
1700         struct object_id base;
1701
1702         if (current_ref_iter && current_ref_iter->refname == refname) {
1703                 struct object_id peeled;
1704
1705                 if (ref_iterator_peel(current_ref_iter, &peeled))
1706                         return -1;
1707                 oidcpy(oid, &peeled);
1708                 return 0;
1709         }
1710
1711         if (refs_read_ref_full(refs, refname,
1712                                RESOLVE_REF_READING, &base, &flag))
1713                 return -1;
1714
1715         return peel_object(&base, oid);
1716 }
1717
1718 int peel_ref(const char *refname, struct object_id *oid)
1719 {
1720         return refs_peel_ref(get_main_ref_store(), refname, oid);
1721 }
1722
1723 int refs_create_symref(struct ref_store *refs,
1724                        const char *ref_target,
1725                        const char *refs_heads_master,
1726                        const char *logmsg)
1727 {
1728         return refs->be->create_symref(refs, ref_target,
1729                                        refs_heads_master,
1730                                        logmsg);
1731 }
1732
1733 int create_symref(const char *ref_target, const char *refs_heads_master,
1734                   const char *logmsg)
1735 {
1736         return refs_create_symref(get_main_ref_store(), ref_target,
1737                                   refs_heads_master, logmsg);
1738 }
1739
1740 int ref_update_reject_duplicates(struct string_list *refnames,
1741                                  struct strbuf *err)
1742 {
1743         size_t i, n = refnames->nr;
1744
1745         assert(err);
1746
1747         for (i = 1; i < n; i++) {
1748                 int cmp = strcmp(refnames->items[i - 1].string,
1749                                  refnames->items[i].string);
1750
1751                 if (!cmp) {
1752                         strbuf_addf(err,
1753                                     "multiple updates for ref '%s' not allowed.",
1754                                     refnames->items[i].string);
1755                         return 1;
1756                 } else if (cmp > 0) {
1757                         die("BUG: ref_update_reject_duplicates() received unsorted list");
1758                 }
1759         }
1760         return 0;
1761 }
1762
1763 int ref_transaction_prepare(struct ref_transaction *transaction,
1764                             struct strbuf *err)
1765 {
1766         struct ref_store *refs = transaction->ref_store;
1767
1768         switch (transaction->state) {
1769         case REF_TRANSACTION_OPEN:
1770                 /* Good. */
1771                 break;
1772         case REF_TRANSACTION_PREPARED:
1773                 die("BUG: prepare called twice on reference transaction");
1774                 break;
1775         case REF_TRANSACTION_CLOSED:
1776                 die("BUG: prepare called on a closed reference transaction");
1777                 break;
1778         default:
1779                 die("BUG: unexpected reference transaction state");
1780                 break;
1781         }
1782
1783         if (getenv(GIT_QUARANTINE_ENVIRONMENT)) {
1784                 strbuf_addstr(err,
1785                               _("ref updates forbidden inside quarantine environment"));
1786                 return -1;
1787         }
1788
1789         return refs->be->transaction_prepare(refs, transaction, err);
1790 }
1791
1792 int ref_transaction_abort(struct ref_transaction *transaction,
1793                           struct strbuf *err)
1794 {
1795         struct ref_store *refs = transaction->ref_store;
1796         int ret = 0;
1797
1798         switch (transaction->state) {
1799         case REF_TRANSACTION_OPEN:
1800                 /* No need to abort explicitly. */
1801                 break;
1802         case REF_TRANSACTION_PREPARED:
1803                 ret = refs->be->transaction_abort(refs, transaction, err);
1804                 break;
1805         case REF_TRANSACTION_CLOSED:
1806                 die("BUG: abort called on a closed reference transaction");
1807                 break;
1808         default:
1809                 die("BUG: unexpected reference transaction state");
1810                 break;
1811         }
1812
1813         ref_transaction_free(transaction);
1814         return ret;
1815 }
1816
1817 int ref_transaction_commit(struct ref_transaction *transaction,
1818                            struct strbuf *err)
1819 {
1820         struct ref_store *refs = transaction->ref_store;
1821         int ret;
1822
1823         switch (transaction->state) {
1824         case REF_TRANSACTION_OPEN:
1825                 /* Need to prepare first. */
1826                 ret = ref_transaction_prepare(transaction, err);
1827                 if (ret)
1828                         return ret;
1829                 break;
1830         case REF_TRANSACTION_PREPARED:
1831                 /* Fall through to finish. */
1832                 break;
1833         case REF_TRANSACTION_CLOSED:
1834                 die("BUG: commit called on a closed reference transaction");
1835                 break;
1836         default:
1837                 die("BUG: unexpected reference transaction state");
1838                 break;
1839         }
1840
1841         return refs->be->transaction_finish(refs, transaction, err);
1842 }
1843
1844 int refs_verify_refname_available(struct ref_store *refs,
1845                                   const char *refname,
1846                                   const struct string_list *extras,
1847                                   const struct string_list *skip,
1848                                   struct strbuf *err)
1849 {
1850         const char *slash;
1851         const char *extra_refname;
1852         struct strbuf dirname = STRBUF_INIT;
1853         struct strbuf referent = STRBUF_INIT;
1854         struct object_id oid;
1855         unsigned int type;
1856         struct ref_iterator *iter;
1857         int ok;
1858         int ret = -1;
1859
1860         /*
1861          * For the sake of comments in this function, suppose that
1862          * refname is "refs/foo/bar".
1863          */
1864
1865         assert(err);
1866
1867         strbuf_grow(&dirname, strlen(refname) + 1);
1868         for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
1869                 /* Expand dirname to the new prefix, not including the trailing slash: */
1870                 strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
1871
1872                 /*
1873                  * We are still at a leading dir of the refname (e.g.,
1874                  * "refs/foo"; if there is a reference with that name,
1875                  * it is a conflict, *unless* it is in skip.
1876                  */
1877                 if (skip && string_list_has_string(skip, dirname.buf))
1878                         continue;
1879
1880                 if (!refs_read_raw_ref(refs, dirname.buf, &oid, &referent, &type)) {
1881                         strbuf_addf(err, "'%s' exists; cannot create '%s'",
1882                                     dirname.buf, refname);
1883                         goto cleanup;
1884                 }
1885
1886                 if (extras && string_list_has_string(extras, dirname.buf)) {
1887                         strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
1888                                     refname, dirname.buf);
1889                         goto cleanup;
1890                 }
1891         }
1892
1893         /*
1894          * We are at the leaf of our refname (e.g., "refs/foo/bar").
1895          * There is no point in searching for a reference with that
1896          * name, because a refname isn't considered to conflict with
1897          * itself. But we still need to check for references whose
1898          * names are in the "refs/foo/bar/" namespace, because they
1899          * *do* conflict.
1900          */
1901         strbuf_addstr(&dirname, refname + dirname.len);
1902         strbuf_addch(&dirname, '/');
1903
1904         iter = refs_ref_iterator_begin(refs, dirname.buf, 0,
1905                                        DO_FOR_EACH_INCLUDE_BROKEN);
1906         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1907                 if (skip &&
1908                     string_list_has_string(skip, iter->refname))
1909                         continue;
1910
1911                 strbuf_addf(err, "'%s' exists; cannot create '%s'",
1912                             iter->refname, refname);
1913                 ref_iterator_abort(iter);
1914                 goto cleanup;
1915         }
1916
1917         if (ok != ITER_DONE)
1918                 die("BUG: error while iterating over references");
1919
1920         extra_refname = find_descendant_ref(dirname.buf, extras, skip);
1921         if (extra_refname)
1922                 strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
1923                             refname, extra_refname);
1924         else
1925                 ret = 0;
1926
1927 cleanup:
1928         strbuf_release(&referent);
1929         strbuf_release(&dirname);
1930         return ret;
1931 }
1932
1933 int refs_for_each_reflog(struct ref_store *refs, each_ref_fn fn, void *cb_data)
1934 {
1935         struct ref_iterator *iter;
1936
1937         iter = refs->be->reflog_iterator_begin(refs);
1938
1939         return do_for_each_ref_iterator(iter, fn, cb_data);
1940 }
1941
1942 int for_each_reflog(each_ref_fn fn, void *cb_data)
1943 {
1944         return refs_for_each_reflog(get_main_ref_store(), fn, cb_data);
1945 }
1946
1947 int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
1948                                      const char *refname,
1949                                      each_reflog_ent_fn fn,
1950                                      void *cb_data)
1951 {
1952         return refs->be->for_each_reflog_ent_reverse(refs, refname,
1953                                                      fn, cb_data);
1954 }
1955
1956 int for_each_reflog_ent_reverse(const char *refname, each_reflog_ent_fn fn,
1957                                 void *cb_data)
1958 {
1959         return refs_for_each_reflog_ent_reverse(get_main_ref_store(),
1960                                                 refname, fn, cb_data);
1961 }
1962
1963 int refs_for_each_reflog_ent(struct ref_store *refs, const char *refname,
1964                              each_reflog_ent_fn fn, void *cb_data)
1965 {
1966         return refs->be->for_each_reflog_ent(refs, refname, fn, cb_data);
1967 }
1968
1969 int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn,
1970                         void *cb_data)
1971 {
1972         return refs_for_each_reflog_ent(get_main_ref_store(), refname,
1973                                         fn, cb_data);
1974 }
1975
1976 int refs_reflog_exists(struct ref_store *refs, const char *refname)
1977 {
1978         return refs->be->reflog_exists(refs, refname);
1979 }
1980
1981 int reflog_exists(const char *refname)
1982 {
1983         return refs_reflog_exists(get_main_ref_store(), refname);
1984 }
1985
1986 int refs_create_reflog(struct ref_store *refs, const char *refname,
1987                        int force_create, struct strbuf *err)
1988 {
1989         return refs->be->create_reflog(refs, refname, force_create, err);
1990 }
1991
1992 int safe_create_reflog(const char *refname, int force_create,
1993                        struct strbuf *err)
1994 {
1995         return refs_create_reflog(get_main_ref_store(), refname,
1996                                   force_create, err);
1997 }
1998
1999 int refs_delete_reflog(struct ref_store *refs, const char *refname)
2000 {
2001         return refs->be->delete_reflog(refs, refname);
2002 }
2003
2004 int delete_reflog(const char *refname)
2005 {
2006         return refs_delete_reflog(get_main_ref_store(), refname);
2007 }
2008
2009 int refs_reflog_expire(struct ref_store *refs,
2010                        const char *refname, const struct object_id *oid,
2011                        unsigned int flags,
2012                        reflog_expiry_prepare_fn prepare_fn,
2013                        reflog_expiry_should_prune_fn should_prune_fn,
2014                        reflog_expiry_cleanup_fn cleanup_fn,
2015                        void *policy_cb_data)
2016 {
2017         return refs->be->reflog_expire(refs, refname, oid, flags,
2018                                        prepare_fn, should_prune_fn,
2019                                        cleanup_fn, policy_cb_data);
2020 }
2021
2022 int reflog_expire(const char *refname, const struct object_id *oid,
2023                   unsigned int flags,
2024                   reflog_expiry_prepare_fn prepare_fn,
2025                   reflog_expiry_should_prune_fn should_prune_fn,
2026                   reflog_expiry_cleanup_fn cleanup_fn,
2027                   void *policy_cb_data)
2028 {
2029         return refs_reflog_expire(get_main_ref_store(),
2030                                   refname, oid, flags,
2031                                   prepare_fn, should_prune_fn,
2032                                   cleanup_fn, policy_cb_data);
2033 }
2034
2035 int initial_ref_transaction_commit(struct ref_transaction *transaction,
2036                                    struct strbuf *err)
2037 {
2038         struct ref_store *refs = transaction->ref_store;
2039
2040         return refs->be->initial_transaction_commit(refs, transaction, err);
2041 }
2042
2043 int refs_delete_refs(struct ref_store *refs, const char *msg,
2044                      struct string_list *refnames, unsigned int flags)
2045 {
2046         return refs->be->delete_refs(refs, msg, refnames, flags);
2047 }
2048
2049 int delete_refs(const char *msg, struct string_list *refnames,
2050                 unsigned int flags)
2051 {
2052         return refs_delete_refs(get_main_ref_store(), msg, refnames, flags);
2053 }
2054
2055 int refs_rename_ref(struct ref_store *refs, const char *oldref,
2056                     const char *newref, const char *logmsg)
2057 {
2058         return refs->be->rename_ref(refs, oldref, newref, logmsg);
2059 }
2060
2061 int rename_ref(const char *oldref, const char *newref, const char *logmsg)
2062 {
2063         return refs_rename_ref(get_main_ref_store(), oldref, newref, logmsg);
2064 }
2065
2066 int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
2067                     const char *newref, const char *logmsg)
2068 {
2069         return refs->be->copy_ref(refs, oldref, newref, logmsg);
2070 }
2071
2072 int copy_existing_ref(const char *oldref, const char *newref, const char *logmsg)
2073 {
2074         return refs_copy_existing_ref(get_main_ref_store(), oldref, newref, logmsg);
2075 }