git.oblomov.eu Git - git/blob - refs.c

   1 /*
   2  * The backend-independent part of the reference module.
   3  */
   4
   5 #include "cache.h"
   6 #include "lockfile.h"
   7 #include "refs.h"
   8 #include "refs/refs-internal.h"
   9 #include "object.h"
  10 #include "tag.h"
  11
  12 /*
  13  * List of all available backends
  14  */
  15 static struct ref_storage_be *refs_backends = &refs_be_files;
  16
  17 static struct ref_storage_be *find_ref_storage_backend(const char *name)
  18 {
  19         struct ref_storage_be *be;
  20         for (be = refs_backends; be; be = be->next)
  21                 if (!strcmp(be->name, name))
  22                         return be;
  23         return NULL;
  24 }
  25
  26 int ref_storage_backend_exists(const char *name)
  27 {
  28         return find_ref_storage_backend(name) != NULL;
  29 }
  30
  31 /*
  32  * How to handle various characters in refnames:
  33  * 0: An acceptable character for refs
  34  * 1: End-of-component
  35  * 2: ., look for a preceding . to reject .. in refs
  36  * 3: {, look for a preceding @ to reject @{ in refs
  37  * 4: A bad character: ASCII control characters, and
  38  *    ":", "?", "[", "\", "^", "~", SP, or TAB
  39  * 5: *, reject unless REFNAME_REFSPEC_PATTERN is set
  40  */
  41 static unsigned char refname_disposition[256] = {
  42         1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
  43         4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
  44         4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 2, 1,
  45         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 4,
  46         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  47         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 0, 4, 0,
  48         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  49         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 4, 4
  50 };
  51
  52 /*
  53  * Try to read one refname component from the front of refname.
  54  * Return the length of the component found, or -1 if the component is
  55  * not legal.  It is legal if it is something reasonable to have under
  56  * ".git/refs/"; We do not like it if:
  57  *
  58  * - any path component of it begins with ".", or
  59  * - it has double dots "..", or
  60  * - it has ASCII control characters, or
  61  * - it has ":", "?", "[", "\", "^", "~", SP, or TAB anywhere, or
  62  * - it has "*" anywhere unless REFNAME_REFSPEC_PATTERN is set, or
  63  * - it ends with a "/", or
  64  * - it ends with ".lock", or
  65  * - it contains a "@{" portion
  66  */
  67 static int check_refname_component(const char *refname, int *flags)
  68 {
  69         const char *cp;
  70         char last = '\0';
  71
  72         for (cp = refname; ; cp++) {
  73                 int ch = *cp & 255;
  74                 unsigned char disp = refname_disposition[ch];
  75                 switch (disp) {
  76                 case 1:
  77                         goto out;
  78                 case 2:
  79                         if (last == '.')
  80                                 return -1; /* Refname contains "..". */
  81                         break;
  82                 case 3:
  83                         if (last == '@')
  84                                 return -1; /* Refname contains "@{". */
  85                         break;
  86                 case 4:
  87                         return -1;
  88                 case 5:
  89                         if (!(*flags & REFNAME_REFSPEC_PATTERN))
  90                                 return -1; /* refspec can't be a pattern */
  91
  92                         /*
  93                          * Unset the pattern flag so that we only accept
  94                          * a single asterisk for one side of refspec.
  95                          */
  96                         *flags &= ~ REFNAME_REFSPEC_PATTERN;
  97                         break;
  98                 }
  99                 last = ch;
 100         }
 101 out:
 102         if (cp == refname)
 103                 return 0; /* Component has zero length. */
 104         if (refname[0] == '.')
 105                 return -1; /* Component starts with '.'. */
 106         if (cp - refname >= LOCK_SUFFIX_LEN &&
 107             !memcmp(cp - LOCK_SUFFIX_LEN, LOCK_SUFFIX, LOCK_SUFFIX_LEN))
 108                 return -1; /* Refname ends with ".lock". */
 109         return cp - refname;
 110 }
 111
 112 int check_refname_format(const char *refname, int flags)
 113 {
 114         int component_len, component_count = 0;
 115
 116         if (!strcmp(refname, "@"))
 117                 /* Refname is a single character '@'. */
 118                 return -1;
 119
 120         while (1) {
 121                 /* We are at the start of a path component. */
 122                 component_len = check_refname_component(refname, &flags);
 123                 if (component_len <= 0)
 124                         return -1;
 125
 126                 component_count++;
 127                 if (refname[component_len] == '\0')
 128                         break;
 129                 /* Skip to next component. */
 130                 refname += component_len + 1;
 131         }
 132
 133         if (refname[component_len - 1] == '.')
 134                 return -1; /* Refname ends with '.'. */
 135         if (!(flags & REFNAME_ALLOW_ONELEVEL) && component_count < 2)
 136                 return -1; /* Refname has only one component. */
 137         return 0;
 138 }
 139
 140 int refname_is_safe(const char *refname)
 141 {
 142         const char *rest;
 143
 144         if (skip_prefix(refname, "refs/", &rest)) {
 145                 char *buf;
 146                 int result;
 147                 size_t restlen = strlen(rest);
 148
 149                 /* rest must not be empty, or start or end with "/" */
 150                 if (!restlen || *rest == '/' || rest[restlen - 1] == '/')
 151                         return 0;
 152
 153                 /*
 154                  * Does the refname try to escape refs/?
 155                  * For example: refs/foo/../bar is safe but refs/foo/../../bar
 156                  * is not.
 157                  */
 158                 buf = xmallocz(restlen);
 159                 result = !normalize_path_copy(buf, rest) && !strcmp(buf, rest);
 160                 free(buf);
 161                 return result;
 162         }
 163
 164         do {
 165                 if (!isupper(*refname) && *refname != '_')
 166                         return 0;
 167                 refname++;
 168         } while (*refname);
 169         return 1;
 170 }
 171
 172 char *resolve_refdup(const char *refname, int resolve_flags,
 173                      unsigned char *sha1, int *flags)
 174 {
 175         return xstrdup_or_null(resolve_ref_unsafe(refname, resolve_flags,
 176                                                   sha1, flags));
 177 }
 178
 179 /* The argument to filter_refs */
 180 struct ref_filter {
 181         const char *pattern;
 182         each_ref_fn *fn;
 183         void *cb_data;
 184 };
 185
 186 int read_ref_full(const char *refname, int resolve_flags, unsigned char *sha1, int *flags)
 187 {
 188         if (resolve_ref_unsafe(refname, resolve_flags, sha1, flags))
 189                 return 0;
 190         return -1;
 191 }
 192
 193 int read_ref(const char *refname, unsigned char *sha1)
 194 {
 195         return read_ref_full(refname, RESOLVE_REF_READING, sha1, NULL);
 196 }
 197
 198 int ref_exists(const char *refname)
 199 {
 200         unsigned char sha1[20];
 201         return !!resolve_ref_unsafe(refname, RESOLVE_REF_READING, sha1, NULL);
 202 }
 203
 204 static int filter_refs(const char *refname, const struct object_id *oid,
 205                            int flags, void *data)
 206 {
 207         struct ref_filter *filter = (struct ref_filter *)data;
 208
 209         if (wildmatch(filter->pattern, refname, 0, NULL))
 210                 return 0;
 211         return filter->fn(refname, oid, flags, filter->cb_data);
 212 }
 213
 214 enum peel_status peel_object(const unsigned char *name, unsigned char *sha1)
 215 {
 216         struct object *o = lookup_unknown_object(name);
 217
 218         if (o->type == OBJ_NONE) {
 219                 int type = sha1_object_info(name, NULL);
 220                 if (type < 0 || !object_as_type(o, type, 0))
 221                         return PEEL_INVALID;
 222         }
 223
 224         if (o->type != OBJ_TAG)
 225                 return PEEL_NON_TAG;
 226
 227         o = deref_tag_noverify(o);
 228         if (!o)
 229                 return PEEL_INVALID;
 230
 231         hashcpy(sha1, o->oid.hash);
 232         return PEEL_PEELED;
 233 }
 234
 235 struct warn_if_dangling_data {
 236         FILE *fp;
 237         const char *refname;
 238         const struct string_list *refnames;
 239         const char *msg_fmt;
 240 };
 241
 242 static int warn_if_dangling_symref(const char *refname, const struct object_id *oid,
 243                                    int flags, void *cb_data)
 244 {
 245         struct warn_if_dangling_data *d = cb_data;
 246         const char *resolves_to;
 247         struct object_id junk;
 248
 249         if (!(flags & REF_ISSYMREF))
 250                 return 0;
 251
 252         resolves_to = resolve_ref_unsafe(refname, 0, junk.hash, NULL);
 253         if (!resolves_to
 254             || (d->refname
 255                 ? strcmp(resolves_to, d->refname)
 256                 : !string_list_has_string(d->refnames, resolves_to))) {
 257                 return 0;
 258         }
 259
 260         fprintf(d->fp, d->msg_fmt, refname);
 261         fputc('\n', d->fp);
 262         return 0;
 263 }
 264
 265 void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
 266 {
 267         struct warn_if_dangling_data data;
 268
 269         data.fp = fp;
 270         data.refname = refname;
 271         data.refnames = NULL;
 272         data.msg_fmt = msg_fmt;
 273         for_each_rawref(warn_if_dangling_symref, &data);
 274 }
 275
 276 void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_list *refnames)
 277 {
 278         struct warn_if_dangling_data data;
 279
 280         data.fp = fp;
 281         data.refname = NULL;
 282         data.refnames = refnames;
 283         data.msg_fmt = msg_fmt;
 284         for_each_rawref(warn_if_dangling_symref, &data);
 285 }
 286
 287 int for_each_tag_ref(each_ref_fn fn, void *cb_data)
 288 {
 289         return for_each_ref_in("refs/tags/", fn, cb_data);
 290 }
 291
 292 int for_each_tag_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 293 {
 294         return for_each_ref_in_submodule(submodule, "refs/tags/", fn, cb_data);
 295 }
 296
 297 int for_each_branch_ref(each_ref_fn fn, void *cb_data)
 298 {
 299         return for_each_ref_in("refs/heads/", fn, cb_data);
 300 }
 301
 302 int for_each_branch_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 303 {
 304         return for_each_ref_in_submodule(submodule, "refs/heads/", fn, cb_data);
 305 }
 306
 307 int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 308 {
 309         return for_each_ref_in("refs/remotes/", fn, cb_data);
 310 }
 311
 312 int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 313 {
 314         return for_each_ref_in_submodule(submodule, "refs/remotes/", fn, cb_data);
 315 }
 316
 317 int head_ref_namespaced(each_ref_fn fn, void *cb_data)
 318 {
 319         struct strbuf buf = STRBUF_INIT;
 320         int ret = 0;
 321         struct object_id oid;
 322         int flag;
 323
 324         strbuf_addf(&buf, "%sHEAD", get_git_namespace());
 325         if (!read_ref_full(buf.buf, RESOLVE_REF_READING, oid.hash, &flag))
 326                 ret = fn(buf.buf, &oid, flag, cb_data);
 327         strbuf_release(&buf);
 328
 329         return ret;
 330 }
 331
 332 int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
 333         const char *prefix, void *cb_data)
 334 {
 335         struct strbuf real_pattern = STRBUF_INIT;
 336         struct ref_filter filter;
 337         int ret;
 338
 339         if (!prefix && !starts_with(pattern, "refs/"))
 340                 strbuf_addstr(&real_pattern, "refs/");
 341         else if (prefix)
 342                 strbuf_addstr(&real_pattern, prefix);
 343         strbuf_addstr(&real_pattern, pattern);
 344
 345         if (!has_glob_specials(pattern)) {
 346                 /* Append implied '/' '*' if not present. */
 347                 strbuf_complete(&real_pattern, '/');
 348                 /* No need to check for '*', there is none. */
 349                 strbuf_addch(&real_pattern, '*');
 350         }
 351
 352         filter.pattern = real_pattern.buf;
 353         filter.fn = fn;
 354         filter.cb_data = cb_data;
 355         ret = for_each_ref(filter_refs, &filter);
 356
 357         strbuf_release(&real_pattern);
 358         return ret;
 359 }
 360
 361 int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
 362 {
 363         return for_each_glob_ref_in(fn, pattern, NULL, cb_data);
 364 }
 365
 366 const char *prettify_refname(const char *name)
 367 {
 368         return name + (
 369                 starts_with(name, "refs/heads/") ? 11 :
 370                 starts_with(name, "refs/tags/") ? 10 :
 371                 starts_with(name, "refs/remotes/") ? 13 :
 372                 0);
 373 }
 374
 375 static const char *ref_rev_parse_rules[] = {
 376         "%.*s",
 377         "refs/%.*s",
 378         "refs/tags/%.*s",
 379         "refs/heads/%.*s",
 380         "refs/remotes/%.*s",
 381         "refs/remotes/%.*s/HEAD",
 382         NULL
 383 };
 384
 385 int refname_match(const char *abbrev_name, const char *full_name)
 386 {
 387         const char **p;
 388         const int abbrev_name_len = strlen(abbrev_name);
 389
 390         for (p = ref_rev_parse_rules; *p; p++) {
 391                 if (!strcmp(full_name, mkpath(*p, abbrev_name_len, abbrev_name))) {
 392                         return 1;
 393                 }
 394         }
 395
 396         return 0;
 397 }
 398
 399 /*
 400  * *string and *len will only be substituted, and *string returned (for
 401  * later free()ing) if the string passed in is a magic short-hand form
 402  * to name a branch.
 403  */
 404 static char *substitute_branch_name(const char **string, int *len)
 405 {
 406         struct strbuf buf = STRBUF_INIT;
 407         int ret = interpret_branch_name(*string, *len, &buf);
 408
 409         if (ret == *len) {
 410                 size_t size;
 411                 *string = strbuf_detach(&buf, &size);
 412                 *len = size;
 413                 return (char *)*string;
 414         }
 415
 416         return NULL;
 417 }
 418
 419 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 420 {
 421         char *last_branch = substitute_branch_name(&str, &len);
 422         int   refs_found  = expand_ref(str, len, sha1, ref);
 423         free(last_branch);
 424         return refs_found;
 425 }
 426
 427 int expand_ref(const char *str, int len, unsigned char *sha1, char **ref)
 428 {
 429         const char **p, *r;
 430         int refs_found = 0;
 431
 432         *ref = NULL;
 433         for (p = ref_rev_parse_rules; *p; p++) {
 434                 char fullref[PATH_MAX];
 435                 unsigned char sha1_from_ref[20];
 436                 unsigned char *this_result;
 437                 int flag;
 438
 439                 this_result = refs_found ? sha1_from_ref : sha1;
 440                 mksnpath(fullref, sizeof(fullref), *p, len, str);
 441                 r = resolve_ref_unsafe(fullref, RESOLVE_REF_READING,
 442                                        this_result, &flag);
 443                 if (r) {
 444                         if (!refs_found++)
 445                                 *ref = xstrdup(r);
 446                         if (!warn_ambiguous_refs)
 447                                 break;
 448                 } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD")) {
 449                         warning("ignoring dangling symref %s.", fullref);
 450                 } else if ((flag & REF_ISBROKEN) && strchr(fullref, '/')) {
 451                         warning("ignoring broken ref %s.", fullref);
 452                 }
 453         }
 454         return refs_found;
 455 }
 456
 457 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 458 {
 459         char *last_branch = substitute_branch_name(&str, &len);
 460         const char **p;
 461         int logs_found = 0;
 462
 463         *log = NULL;
 464         for (p = ref_rev_parse_rules; *p; p++) {
 465                 unsigned char hash[20];
 466                 char path[PATH_MAX];
 467                 const char *ref, *it;
 468
 469                 mksnpath(path, sizeof(path), *p, len, str);
 470                 ref = resolve_ref_unsafe(path, RESOLVE_REF_READING,
 471                                          hash, NULL);
 472                 if (!ref)
 473                         continue;
 474                 if (reflog_exists(path))
 475                         it = path;
 476                 else if (strcmp(ref, path) && reflog_exists(ref))
 477                         it = ref;
 478                 else
 479                         continue;
 480                 if (!logs_found++) {
 481                         *log = xstrdup(it);
 482                         hashcpy(sha1, hash);
 483                 }
 484                 if (!warn_ambiguous_refs)
 485                         break;
 486         }
 487         free(last_branch);
 488         return logs_found;
 489 }
 490
 491 static int is_per_worktree_ref(const char *refname)
 492 {
 493         return !strcmp(refname, "HEAD") ||
 494                 starts_with(refname, "refs/bisect/");
 495 }
 496
 497 static int is_pseudoref_syntax(const char *refname)
 498 {
 499         const char *c;
 500
 501         for (c = refname; *c; c++) {
 502                 if (!isupper(*c) && *c != '-' && *c != '_')
 503                         return 0;
 504         }
 505
 506         return 1;
 507 }
 508
 509 enum ref_type ref_type(const char *refname)
 510 {
 511         if (is_per_worktree_ref(refname))
 512                 return REF_TYPE_PER_WORKTREE;
 513         if (is_pseudoref_syntax(refname))
 514                 return REF_TYPE_PSEUDOREF;
 515        return REF_TYPE_NORMAL;
 516 }
 517
 518 static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
 519                            const unsigned char *old_sha1, struct strbuf *err)
 520 {
 521         const char *filename;
 522         int fd;
 523         static struct lock_file lock;
 524         struct strbuf buf = STRBUF_INIT;
 525         int ret = -1;
 526
 527         strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
 528
 529         filename = git_path("%s", pseudoref);
 530         fd = hold_lock_file_for_update(&lock, filename, LOCK_DIE_ON_ERROR);
 531         if (fd < 0) {
 532                 strbuf_addf(err, "could not open '%s' for writing: %s",
 533                             filename, strerror(errno));
 534                 return -1;
 535         }
 536
 537         if (old_sha1) {
 538                 unsigned char actual_old_sha1[20];
 539
 540                 if (read_ref(pseudoref, actual_old_sha1))
 541                         die("could not read ref '%s'", pseudoref);
 542                 if (hashcmp(actual_old_sha1, old_sha1)) {
 543                         strbuf_addf(err, "unexpected sha1 when writing '%s'", pseudoref);
 544                         rollback_lock_file(&lock);
 545                         goto done;
 546                 }
 547         }
 548
 549         if (write_in_full(fd, buf.buf, buf.len) != buf.len) {
 550                 strbuf_addf(err, "could not write to '%s'", filename);
 551                 rollback_lock_file(&lock);
 552                 goto done;
 553         }
 554
 555         commit_lock_file(&lock);
 556         ret = 0;
 557 done:
 558         strbuf_release(&buf);
 559         return ret;
 560 }
 561
 562 static int delete_pseudoref(const char *pseudoref, const unsigned char *old_sha1)
 563 {
 564         static struct lock_file lock;
 565         const char *filename;
 566
 567         filename = git_path("%s", pseudoref);
 568
 569         if (old_sha1 && !is_null_sha1(old_sha1)) {
 570                 int fd;
 571                 unsigned char actual_old_sha1[20];
 572
 573                 fd = hold_lock_file_for_update(&lock, filename,
 574                                                LOCK_DIE_ON_ERROR);
 575                 if (fd < 0)
 576                         die_errno(_("Could not open '%s' for writing"), filename);
 577                 if (read_ref(pseudoref, actual_old_sha1))
 578                         die("could not read ref '%s'", pseudoref);
 579                 if (hashcmp(actual_old_sha1, old_sha1)) {
 580                         warning("Unexpected sha1 when deleting %s", pseudoref);
 581                         rollback_lock_file(&lock);
 582                         return -1;
 583                 }
 584
 585                 unlink(filename);
 586                 rollback_lock_file(&lock);
 587         } else {
 588                 unlink(filename);
 589         }
 590
 591         return 0;
 592 }
 593
 594 int delete_ref(const char *refname, const unsigned char *old_sha1,
 595                unsigned int flags)
 596 {
 597         struct ref_transaction *transaction;
 598         struct strbuf err = STRBUF_INIT;
 599
 600         if (ref_type(refname) == REF_TYPE_PSEUDOREF)
 601                 return delete_pseudoref(refname, old_sha1);
 602
 603         transaction = ref_transaction_begin(&err);
 604         if (!transaction ||
 605             ref_transaction_delete(transaction, refname, old_sha1,
 606                                    flags, NULL, &err) ||
 607             ref_transaction_commit(transaction, &err)) {
 608                 error("%s", err.buf);
 609                 ref_transaction_free(transaction);
 610                 strbuf_release(&err);
 611                 return 1;
 612         }
 613         ref_transaction_free(transaction);
 614         strbuf_release(&err);
 615         return 0;
 616 }
 617
 618 int copy_reflog_msg(char *buf, const char *msg)
 619 {
 620         char *cp = buf;
 621         char c;
 622         int wasspace = 1;
 623
 624         *cp++ = '\t';
 625         while ((c = *msg++)) {
 626                 if (wasspace && isspace(c))
 627                         continue;
 628                 wasspace = isspace(c);
 629                 if (wasspace)
 630                         c = ' ';
 631                 *cp++ = c;
 632         }
 633         while (buf < cp && isspace(cp[-1]))
 634                 cp--;
 635         *cp++ = '\n';
 636         return cp - buf;
 637 }
 638
 639 int should_autocreate_reflog(const char *refname)
 640 {
 641         switch (log_all_ref_updates) {
 642         case LOG_REFS_ALWAYS:
 643                 return 1;
 644         case LOG_REFS_NORMAL:
 645                 return starts_with(refname, "refs/heads/") ||
 646                         starts_with(refname, "refs/remotes/") ||
 647                         starts_with(refname, "refs/notes/") ||
 648                         !strcmp(refname, "HEAD");
 649         default:
 650                 return 0;
 651         }
 652 }
 653
 654 int is_branch(const char *refname)
 655 {
 656         return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
 657 }
 658
 659 struct read_ref_at_cb {
 660         const char *refname;
 661         unsigned long at_time;
 662         int cnt;
 663         int reccnt;
 664         unsigned char *sha1;
 665         int found_it;
 666
 667         unsigned char osha1[20];
 668         unsigned char nsha1[20];
 669         int tz;
 670         unsigned long date;
 671         char **msg;
 672         unsigned long *cutoff_time;
 673         int *cutoff_tz;
 674         int *cutoff_cnt;
 675 };
 676
 677 static int read_ref_at_ent(unsigned char *osha1, unsigned char *nsha1,
 678                 const char *email, unsigned long timestamp, int tz,
 679                 const char *message, void *cb_data)
 680 {
 681         struct read_ref_at_cb *cb = cb_data;
 682
 683         cb->reccnt++;
 684         cb->tz = tz;
 685         cb->date = timestamp;
 686
 687         if (timestamp <= cb->at_time || cb->cnt == 0) {
 688                 if (cb->msg)
 689                         *cb->msg = xstrdup(message);
 690                 if (cb->cutoff_time)
 691                         *cb->cutoff_time = timestamp;
 692                 if (cb->cutoff_tz)
 693                         *cb->cutoff_tz = tz;
 694                 if (cb->cutoff_cnt)
 695                         *cb->cutoff_cnt = cb->reccnt - 1;
 696                 /*
 697                  * we have not yet updated cb->[n|o]sha1 so they still
 698                  * hold the values for the previous record.
 699                  */
 700                 if (!is_null_sha1(cb->osha1)) {
 701                         hashcpy(cb->sha1, nsha1);
 702                         if (hashcmp(cb->osha1, nsha1))
 703                                 warning("Log for ref %s has gap after %s.",
 704                                         cb->refname, show_date(cb->date, cb->tz, DATE_MODE(RFC2822)));
 705                 }
 706                 else if (cb->date == cb->at_time)
 707                         hashcpy(cb->sha1, nsha1);
 708                 else if (hashcmp(nsha1, cb->sha1))
 709                         warning("Log for ref %s unexpectedly ended on %s.",
 710                                 cb->refname, show_date(cb->date, cb->tz,
 711                                                        DATE_MODE(RFC2822)));
 712                 hashcpy(cb->osha1, osha1);
 713                 hashcpy(cb->nsha1, nsha1);
 714                 cb->found_it = 1;
 715                 return 1;
 716         }
 717         hashcpy(cb->osha1, osha1);
 718         hashcpy(cb->nsha1, nsha1);
 719         if (cb->cnt > 0)
 720                 cb->cnt--;
 721         return 0;
 722 }
 723
 724 static int read_ref_at_ent_oldest(unsigned char *osha1, unsigned char *nsha1,
 725                                   const char *email, unsigned long timestamp,
 726                                   int tz, const char *message, void *cb_data)
 727 {
 728         struct read_ref_at_cb *cb = cb_data;
 729
 730         if (cb->msg)
 731                 *cb->msg = xstrdup(message);
 732         if (cb->cutoff_time)
 733                 *cb->cutoff_time = timestamp;
 734         if (cb->cutoff_tz)
 735                 *cb->cutoff_tz = tz;
 736         if (cb->cutoff_cnt)
 737                 *cb->cutoff_cnt = cb->reccnt;
 738         hashcpy(cb->sha1, osha1);
 739         if (is_null_sha1(cb->sha1))
 740                 hashcpy(cb->sha1, nsha1);
 741         /* We just want the first entry */
 742         return 1;
 743 }
 744
 745 int read_ref_at(const char *refname, unsigned int flags, unsigned long at_time, int cnt,
 746                 unsigned char *sha1, char **msg,
 747                 unsigned long *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
 748 {
 749         struct read_ref_at_cb cb;
 750
 751         memset(&cb, 0, sizeof(cb));
 752         cb.refname = refname;
 753         cb.at_time = at_time;
 754         cb.cnt = cnt;
 755         cb.msg = msg;
 756         cb.cutoff_time = cutoff_time;
 757         cb.cutoff_tz = cutoff_tz;
 758         cb.cutoff_cnt = cutoff_cnt;
 759         cb.sha1 = sha1;
 760
 761         for_each_reflog_ent_reverse(refname, read_ref_at_ent, &cb);
 762
 763         if (!cb.reccnt) {
 764                 if (flags & GET_SHA1_QUIETLY)
 765                         exit(128);
 766                 else
 767                         die("Log for %s is empty.", refname);
 768         }
 769         if (cb.found_it)
 770                 return 0;
 771
 772         for_each_reflog_ent(refname, read_ref_at_ent_oldest, &cb);
 773
 774         return 1;
 775 }
 776
 777 struct ref_transaction *ref_transaction_begin(struct strbuf *err)
 778 {
 779         assert(err);
 780
 781         return xcalloc(1, sizeof(struct ref_transaction));
 782 }
 783
 784 void ref_transaction_free(struct ref_transaction *transaction)
 785 {
 786         int i;
 787
 788         if (!transaction)
 789                 return;
 790
 791         for (i = 0; i < transaction->nr; i++) {
 792                 free(transaction->updates[i]->msg);
 793                 free(transaction->updates[i]);
 794         }
 795         free(transaction->updates);
 796         free(transaction);
 797 }
 798
 799 struct ref_update *ref_transaction_add_update(
 800                 struct ref_transaction *transaction,
 801                 const char *refname, unsigned int flags,
 802                 const unsigned char *new_sha1,
 803                 const unsigned char *old_sha1,
 804                 const char *msg)
 805 {
 806         struct ref_update *update;
 807
 808         if (transaction->state != REF_TRANSACTION_OPEN)
 809                 die("BUG: update called for transaction that is not open");
 810
 811         if ((flags & REF_ISPRUNING) && !(flags & REF_NODEREF))
 812                 die("BUG: REF_ISPRUNING set without REF_NODEREF");
 813
 814         FLEX_ALLOC_STR(update, refname, refname);
 815         ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
 816         transaction->updates[transaction->nr++] = update;
 817
 818         update->flags = flags;
 819
 820         if (flags & REF_HAVE_NEW)
 821                 hashcpy(update->new_sha1, new_sha1);
 822         if (flags & REF_HAVE_OLD)
 823                 hashcpy(update->old_sha1, old_sha1);
 824         update->msg = xstrdup_or_null(msg);
 825         return update;
 826 }
 827
 828 int ref_transaction_update(struct ref_transaction *transaction,
 829                            const char *refname,
 830                            const unsigned char *new_sha1,
 831                            const unsigned char *old_sha1,
 832                            unsigned int flags, const char *msg,
 833                            struct strbuf *err)
 834 {
 835         assert(err);
 836
 837         if ((new_sha1 && !is_null_sha1(new_sha1)) ?
 838             check_refname_format(refname, REFNAME_ALLOW_ONELEVEL) :
 839             !refname_is_safe(refname)) {
 840                 strbuf_addf(err, "refusing to update ref with bad name '%s'",
 841                             refname);
 842                 return -1;
 843         }
 844
 845         flags |= (new_sha1 ? REF_HAVE_NEW : 0) | (old_sha1 ? REF_HAVE_OLD : 0);
 846
 847         ref_transaction_add_update(transaction, refname, flags,
 848                                    new_sha1, old_sha1, msg);
 849         return 0;
 850 }
 851
 852 int ref_transaction_create(struct ref_transaction *transaction,
 853                            const char *refname,
 854                            const unsigned char *new_sha1,
 855                            unsigned int flags, const char *msg,
 856                            struct strbuf *err)
 857 {
 858         if (!new_sha1 || is_null_sha1(new_sha1))
 859                 die("BUG: create called without valid new_sha1");
 860         return ref_transaction_update(transaction, refname, new_sha1,
 861                                       null_sha1, flags, msg, err);
 862 }
 863
 864 int ref_transaction_delete(struct ref_transaction *transaction,
 865                            const char *refname,
 866                            const unsigned char *old_sha1,
 867                            unsigned int flags, const char *msg,
 868                            struct strbuf *err)
 869 {
 870         if (old_sha1 && is_null_sha1(old_sha1))
 871                 die("BUG: delete called with old_sha1 set to zeros");
 872         return ref_transaction_update(transaction, refname,
 873                                       null_sha1, old_sha1,
 874                                       flags, msg, err);
 875 }
 876
 877 int ref_transaction_verify(struct ref_transaction *transaction,
 878                            const char *refname,
 879                            const unsigned char *old_sha1,
 880                            unsigned int flags,
 881                            struct strbuf *err)
 882 {
 883         if (!old_sha1)
 884                 die("BUG: verify called with old_sha1 set to NULL");
 885         return ref_transaction_update(transaction, refname,
 886                                       NULL, old_sha1,
 887                                       flags, NULL, err);
 888 }
 889
 890 int update_ref_oid(const char *msg, const char *refname,
 891                const struct object_id *new_oid, const struct object_id *old_oid,
 892                unsigned int flags, enum action_on_err onerr)
 893 {
 894         return update_ref(msg, refname, new_oid ? new_oid->hash : NULL,
 895                 old_oid ? old_oid->hash : NULL, flags, onerr);
 896 }
 897
 898 int update_ref(const char *msg, const char *refname,
 899                const unsigned char *new_sha1, const unsigned char *old_sha1,
 900                unsigned int flags, enum action_on_err onerr)
 901 {
 902         struct ref_transaction *t = NULL;
 903         struct strbuf err = STRBUF_INIT;
 904         int ret = 0;
 905
 906         if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
 907                 ret = write_pseudoref(refname, new_sha1, old_sha1, &err);
 908         } else {
 909                 t = ref_transaction_begin(&err);
 910                 if (!t ||
 911                     ref_transaction_update(t, refname, new_sha1, old_sha1,
 912                                            flags, msg, &err) ||
 913                     ref_transaction_commit(t, &err)) {
 914                         ret = 1;
 915                         ref_transaction_free(t);
 916                 }
 917         }
 918         if (ret) {
 919                 const char *str = "update_ref failed for ref '%s': %s";
 920
 921                 switch (onerr) {
 922                 case UPDATE_REFS_MSG_ON_ERR:
 923                         error(str, refname, err.buf);
 924                         break;
 925                 case UPDATE_REFS_DIE_ON_ERR:
 926                         die(str, refname, err.buf);
 927                         break;
 928                 case UPDATE_REFS_QUIET_ON_ERR:
 929                         break;
 930                 }
 931                 strbuf_release(&err);
 932                 return 1;
 933         }
 934         strbuf_release(&err);
 935         if (t)
 936                 ref_transaction_free(t);
 937         return 0;
 938 }
 939
 940 char *shorten_unambiguous_ref(const char *refname, int strict)
 941 {
 942         int i;
 943         static char **scanf_fmts;
 944         static int nr_rules;
 945         char *short_name;
 946
 947         if (!nr_rules) {
 948                 /*
 949                  * Pre-generate scanf formats from ref_rev_parse_rules[].
 950                  * Generate a format suitable for scanf from a
 951                  * ref_rev_parse_rules rule by interpolating "%s" at the
 952                  * location of the "%.*s".
 953                  */
 954                 size_t total_len = 0;
 955                 size_t offset = 0;
 956
 957                 /* the rule list is NULL terminated, count them first */
 958                 for (nr_rules = 0; ref_rev_parse_rules[nr_rules]; nr_rules++)
 959                         /* -2 for strlen("%.*s") - strlen("%s"); +1 for NUL */
 960                         total_len += strlen(ref_rev_parse_rules[nr_rules]) - 2 + 1;
 961
 962                 scanf_fmts = xmalloc(st_add(st_mult(sizeof(char *), nr_rules), total_len));
 963
 964                 offset = 0;
 965                 for (i = 0; i < nr_rules; i++) {
 966                         assert(offset < total_len);
 967                         scanf_fmts[i] = (char *)&scanf_fmts[nr_rules] + offset;
 968                         offset += snprintf(scanf_fmts[i], total_len - offset,
 969                                            ref_rev_parse_rules[i], 2, "%s") + 1;
 970                 }
 971         }
 972
 973         /* bail out if there are no rules */
 974         if (!nr_rules)
 975                 return xstrdup(refname);
 976
 977         /* buffer for scanf result, at most refname must fit */
 978         short_name = xstrdup(refname);
 979
 980         /* skip first rule, it will always match */
 981         for (i = nr_rules - 1; i > 0 ; --i) {
 982                 int j;
 983                 int rules_to_fail = i;
 984                 int short_name_len;
 985
 986                 if (1 != sscanf(refname, scanf_fmts[i], short_name))
 987                         continue;
 988
 989                 short_name_len = strlen(short_name);
 990
 991                 /*
 992                  * in strict mode, all (except the matched one) rules
 993                  * must fail to resolve to a valid non-ambiguous ref
 994                  */
 995                 if (strict)
 996                         rules_to_fail = nr_rules;
 997
 998                 /*
 999                  * check if the short name resolves to a valid ref,
1000                  * but use only rules prior to the matched one
1001                  */
1002                 for (j = 0; j < rules_to_fail; j++) {
1003                         const char *rule = ref_rev_parse_rules[j];
1004                         char refname[PATH_MAX];
1005
1006                         /* skip matched rule */
1007                         if (i == j)
1008                                 continue;
1009
1010                         /*
1011                          * the short name is ambiguous, if it resolves
1012                          * (with this previous rule) to a valid ref
1013                          * read_ref() returns 0 on success
1014                          */
1015                         mksnpath(refname, sizeof(refname),
1016                                  rule, short_name_len, short_name);
1017                         if (ref_exists(refname))
1018                                 break;
1019                 }
1020
1021                 /*
1022                  * short name is non-ambiguous if all previous rules
1023                  * haven't resolved to a valid ref
1024                  */
1025                 if (j == rules_to_fail)
1026                         return short_name;
1027         }
1028
1029         free(short_name);
1030         return xstrdup(refname);
1031 }
1032
1033 static struct string_list *hide_refs;
1034
1035 int parse_hide_refs_config(const char *var, const char *value, const char *section)
1036 {
1037         if (!strcmp("transfer.hiderefs", var) ||
1038             /* NEEDSWORK: use parse_config_key() once both are merged */
1039             (starts_with(var, section) && var[strlen(section)] == '.' &&
1040              !strcmp(var + strlen(section), ".hiderefs"))) {
1041                 char *ref;
1042                 int len;
1043
1044                 if (!value)
1045                         return config_error_nonbool(var);
1046                 ref = xstrdup(value);
1047                 len = strlen(ref);
1048                 while (len && ref[len - 1] == '/')
1049                         ref[--len] = '\0';
1050                 if (!hide_refs) {
1051                         hide_refs = xcalloc(1, sizeof(*hide_refs));
1052                         hide_refs->strdup_strings = 1;
1053                 }
1054                 string_list_append(hide_refs, ref);
1055         }
1056         return 0;
1057 }
1058
1059 int ref_is_hidden(const char *refname, const char *refname_full)
1060 {
1061         int i;
1062
1063         if (!hide_refs)
1064                 return 0;
1065         for (i = hide_refs->nr - 1; i >= 0; i--) {
1066                 const char *match = hide_refs->items[i].string;
1067                 const char *subject;
1068                 int neg = 0;
1069                 int len;
1070
1071                 if (*match == '!') {
1072                         neg = 1;
1073                         match++;
1074                 }
1075
1076                 if (*match == '^') {
1077                         subject = refname_full;
1078                         match++;
1079                 } else {
1080                         subject = refname;
1081                 }
1082
1083                 /* refname can be NULL when namespaces are used. */
1084                 if (!subject || !starts_with(subject, match))
1085                         continue;
1086                 len = strlen(match);
1087                 if (!subject[len] || subject[len] == '/')
1088                         return !neg;
1089         }
1090         return 0;
1091 }
1092
1093 const char *find_descendant_ref(const char *dirname,
1094                                 const struct string_list *extras,
1095                                 const struct string_list *skip)
1096 {
1097         int pos;
1098
1099         if (!extras)
1100                 return NULL;
1101
1102         /*
1103          * Look at the place where dirname would be inserted into
1104          * extras. If there is an entry at that position that starts
1105          * with dirname (remember, dirname includes the trailing
1106          * slash) and is not in skip, then we have a conflict.
1107          */
1108         for (pos = string_list_find_insert_index(extras, dirname, 0);
1109              pos < extras->nr; pos++) {
1110                 const char *extra_refname = extras->items[pos].string;
1111
1112                 if (!starts_with(extra_refname, dirname))
1113                         break;
1114
1115                 if (!skip || !string_list_has_string(skip, extra_refname))
1116                         return extra_refname;
1117         }
1118         return NULL;
1119 }
1120
1121 int rename_ref_available(const char *old_refname, const char *new_refname)
1122 {
1123         struct string_list skip = STRING_LIST_INIT_NODUP;
1124         struct strbuf err = STRBUF_INIT;
1125         int ok;
1126
1127         string_list_insert(&skip, old_refname);
1128         ok = !verify_refname_available(new_refname, NULL, &skip, &err);
1129         if (!ok)
1130                 error("%s", err.buf);
1131
1132         string_list_clear(&skip, 0);
1133         strbuf_release(&err);
1134         return ok;
1135 }
1136
1137 int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
1138 {
1139         struct object_id oid;
1140         int flag;
1141
1142         if (submodule) {
1143                 if (resolve_gitlink_ref(submodule, "HEAD", oid.hash) == 0)
1144                         return fn("HEAD", &oid, 0, cb_data);
1145
1146                 return 0;
1147         }
1148
1149         if (!read_ref_full("HEAD", RESOLVE_REF_READING, oid.hash, &flag))
1150                 return fn("HEAD", &oid, flag, cb_data);
1151
1152         return 0;
1153 }
1154
1155 int head_ref(each_ref_fn fn, void *cb_data)
1156 {
1157         return head_ref_submodule(NULL, fn, cb_data);
1158 }
1159
1160 /*
1161  * Call fn for each reference in the specified submodule for which the
1162  * refname begins with prefix. If trim is non-zero, then trim that
1163  * many characters off the beginning of each refname before passing
1164  * the refname to fn. flags can be DO_FOR_EACH_INCLUDE_BROKEN to
1165  * include broken references in the iteration. If fn ever returns a
1166  * non-zero value, stop the iteration and return that value;
1167  * otherwise, return 0.
1168  */
1169 static int do_for_each_ref(const char *submodule, const char *prefix,
1170                            each_ref_fn fn, int trim, int flags, void *cb_data)
1171 {
1172         struct ref_store *refs = get_ref_store(submodule);
1173         struct ref_iterator *iter;
1174
1175         if (!refs)
1176                 return 0;
1177
1178         iter = refs->be->iterator_begin(refs, prefix, flags);
1179         iter = prefix_ref_iterator_begin(iter, prefix, trim);
1180
1181         return do_for_each_ref_iterator(iter, fn, cb_data);
1182 }
1183
1184 int for_each_ref(each_ref_fn fn, void *cb_data)
1185 {
1186         return do_for_each_ref(NULL, "", fn, 0, 0, cb_data);
1187 }
1188
1189 int for_each_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
1190 {
1191         return do_for_each_ref(submodule, "", fn, 0, 0, cb_data);
1192 }
1193
1194 int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
1195 {
1196         return do_for_each_ref(NULL, prefix, fn, strlen(prefix), 0, cb_data);
1197 }
1198
1199 int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data, unsigned int broken)
1200 {
1201         unsigned int flag = 0;
1202
1203         if (broken)
1204                 flag = DO_FOR_EACH_INCLUDE_BROKEN;
1205         return do_for_each_ref(NULL, prefix, fn, 0, flag, cb_data);
1206 }
1207
1208 int for_each_ref_in_submodule(const char *submodule, const char *prefix,
1209                 each_ref_fn fn, void *cb_data)
1210 {
1211         return do_for_each_ref(submodule, prefix, fn, strlen(prefix), 0, cb_data);
1212 }
1213
1214 int for_each_replace_ref(each_ref_fn fn, void *cb_data)
1215 {
1216         return do_for_each_ref(NULL, git_replace_ref_base, fn,
1217                                strlen(git_replace_ref_base), 0, cb_data);
1218 }
1219
1220 int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
1221 {
1222         struct strbuf buf = STRBUF_INIT;
1223         int ret;
1224         strbuf_addf(&buf, "%srefs/", get_git_namespace());
1225         ret = do_for_each_ref(NULL, buf.buf, fn, 0, 0, cb_data);
1226         strbuf_release(&buf);
1227         return ret;
1228 }
1229
1230 int for_each_rawref(each_ref_fn fn, void *cb_data)
1231 {
1232         return do_for_each_ref(NULL, "", fn, 0,
1233                                DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
1234 }
1235
1236 /* This function needs to return a meaningful errno on failure */
1237 static const char *resolve_ref_recursively(struct ref_store *refs,
1238                                            const char *refname,
1239                                            int resolve_flags,
1240                                            unsigned char *sha1, int *flags)
1241 {
1242         static struct strbuf sb_refname = STRBUF_INIT;
1243         int unused_flags;
1244         int symref_count;
1245
1246         if (!flags)
1247                 flags = &unused_flags;
1248
1249         *flags = 0;
1250
1251         if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1252                 if (!(resolve_flags & RESOLVE_REF_ALLOW_BAD_NAME) ||
1253                     !refname_is_safe(refname)) {
1254                         errno = EINVAL;
1255                         return NULL;
1256                 }
1257
1258                 /*
1259                  * dwim_ref() uses REF_ISBROKEN to distinguish between
1260                  * missing refs and refs that were present but invalid,
1261                  * to complain about the latter to stderr.
1262                  *
1263                  * We don't know whether the ref exists, so don't set
1264                  * REF_ISBROKEN yet.
1265                  */
1266                 *flags |= REF_BAD_NAME;
1267         }
1268
1269         for (symref_count = 0; symref_count < SYMREF_MAXDEPTH; symref_count++) {
1270                 unsigned int read_flags = 0;
1271
1272                 if (refs->be->read_raw_ref(refs, refname,
1273                                            sha1, &sb_refname, &read_flags)) {
1274                         *flags |= read_flags;
1275                         if (errno != ENOENT || (resolve_flags & RESOLVE_REF_READING))
1276                                 return NULL;
1277                         hashclr(sha1);
1278                         if (*flags & REF_BAD_NAME)
1279                                 *flags |= REF_ISBROKEN;
1280                         return refname;
1281                 }
1282
1283                 *flags |= read_flags;
1284
1285                 if (!(read_flags & REF_ISSYMREF)) {
1286                         if (*flags & REF_BAD_NAME) {
1287                                 hashclr(sha1);
1288                                 *flags |= REF_ISBROKEN;
1289                         }
1290                         return refname;
1291                 }
1292
1293                 refname = sb_refname.buf;
1294                 if (resolve_flags & RESOLVE_REF_NO_RECURSE) {
1295                         hashclr(sha1);
1296                         return refname;
1297                 }
1298                 if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1299                         if (!(resolve_flags & RESOLVE_REF_ALLOW_BAD_NAME) ||
1300                             !refname_is_safe(refname)) {
1301                                 errno = EINVAL;
1302                                 return NULL;
1303                         }
1304
1305                         *flags |= REF_ISBROKEN | REF_BAD_NAME;
1306                 }
1307         }
1308
1309         errno = ELOOP;
1310         return NULL;
1311 }
1312
1313 /* backend functions */
1314 int refs_init_db(struct strbuf *err)
1315 {
1316         struct ref_store *refs = get_ref_store(NULL);
1317
1318         return refs->be->init_db(refs, err);
1319 }
1320
1321 const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
1322                                unsigned char *sha1, int *flags)
1323 {
1324         return resolve_ref_recursively(get_ref_store(NULL), refname,
1325                                        resolve_flags, sha1, flags);
1326 }
1327
1328 int resolve_gitlink_ref(const char *submodule, const char *refname,
1329                         unsigned char *sha1)
1330 {
1331         size_t len = strlen(submodule);
1332         struct ref_store *refs;
1333         int flags;
1334
1335         while (len && submodule[len - 1] == '/')
1336                 len--;
1337
1338         if (!len)
1339                 return -1;
1340
1341         if (submodule[len]) {
1342                 /* We need to strip off one or more trailing slashes */
1343                 char *stripped = xmemdupz(submodule, len);
1344
1345                 refs = get_ref_store(stripped);
1346                 free(stripped);
1347         } else {
1348                 refs = get_ref_store(submodule);
1349         }
1350
1351         if (!refs)
1352                 return -1;
1353
1354         if (!resolve_ref_recursively(refs, refname, 0, sha1, &flags) ||
1355             is_null_sha1(sha1))
1356                 return -1;
1357         return 0;
1358 }
1359
1360 /* A pointer to the ref_store for the main repository: */
1361 static struct ref_store *main_ref_store;
1362
1363 /* A linked list of ref_stores for submodules: */
1364 static struct ref_store *submodule_ref_stores;
1365
1366 void base_ref_store_init(struct ref_store *refs,
1367                          const struct ref_storage_be *be,
1368                          const char *submodule)
1369 {
1370         refs->be = be;
1371         if (!submodule) {
1372                 if (main_ref_store)
1373                         die("BUG: main_ref_store initialized twice");
1374
1375                 refs->submodule = "";
1376                 refs->next = NULL;
1377                 main_ref_store = refs;
1378         } else {
1379                 if (lookup_ref_store(submodule))
1380                         die("BUG: ref_store for submodule '%s' initialized twice",
1381                             submodule);
1382
1383                 refs->submodule = xstrdup(submodule);
1384                 refs->next = submodule_ref_stores;
1385                 submodule_ref_stores = refs;
1386         }
1387 }
1388
1389 struct ref_store *ref_store_init(const char *submodule)
1390 {
1391         const char *be_name = "files";
1392         struct ref_storage_be *be = find_ref_storage_backend(be_name);
1393
1394         if (!be)
1395                 die("BUG: reference backend %s is unknown", be_name);
1396
1397         if (!submodule || !*submodule)
1398                 return be->init(NULL);
1399         else
1400                 return be->init(submodule);
1401 }
1402
1403 struct ref_store *lookup_ref_store(const char *submodule)
1404 {
1405         struct ref_store *refs;
1406
1407         if (!submodule || !*submodule)
1408                 return main_ref_store;
1409
1410         for (refs = submodule_ref_stores; refs; refs = refs->next) {
1411                 if (!strcmp(submodule, refs->submodule))
1412                         return refs;
1413         }
1414
1415         return NULL;
1416 }
1417
1418 struct ref_store *get_ref_store(const char *submodule)
1419 {
1420         struct ref_store *refs;
1421
1422         if (!submodule || !*submodule) {
1423                 refs = lookup_ref_store(NULL);
1424
1425                 if (!refs)
1426                         refs = ref_store_init(NULL);
1427         } else {
1428                 refs = lookup_ref_store(submodule);
1429
1430                 if (!refs) {
1431                         struct strbuf submodule_sb = STRBUF_INIT;
1432
1433                         strbuf_addstr(&submodule_sb, submodule);
1434                         if (is_nonbare_repository_dir(&submodule_sb))
1435                                 refs = ref_store_init(submodule);
1436                         strbuf_release(&submodule_sb);
1437                 }
1438         }
1439
1440         return refs;
1441 }
1442
1443 void assert_main_repository(struct ref_store *refs, const char *caller)
1444 {
1445         if (*refs->submodule)
1446                 die("BUG: %s called for a submodule", caller);
1447 }
1448
1449 /* backend functions */
1450 int pack_refs(unsigned int flags)
1451 {
1452         struct ref_store *refs = get_ref_store(NULL);
1453
1454         return refs->be->pack_refs(refs, flags);
1455 }
1456
1457 int peel_ref(const char *refname, unsigned char *sha1)
1458 {
1459         struct ref_store *refs = get_ref_store(NULL);
1460
1461         return refs->be->peel_ref(refs, refname, sha1);
1462 }
1463
1464 int create_symref(const char *ref_target, const char *refs_heads_master,
1465                   const char *logmsg)
1466 {
1467         struct ref_store *refs = get_ref_store(NULL);
1468
1469         return refs->be->create_symref(refs, ref_target, refs_heads_master,
1470                                        logmsg);
1471 }
1472
1473 int ref_transaction_commit(struct ref_transaction *transaction,
1474                            struct strbuf *err)
1475 {
1476         struct ref_store *refs = get_ref_store(NULL);
1477
1478         return refs->be->transaction_commit(refs, transaction, err);
1479 }
1480
1481 int verify_refname_available(const char *refname,
1482                              const struct string_list *extra,
1483                              const struct string_list *skip,
1484                              struct strbuf *err)
1485 {
1486         struct ref_store *refs = get_ref_store(NULL);
1487
1488         return refs->be->verify_refname_available(refs, refname, extra, skip, err);
1489 }
1490
1491 int for_each_reflog(each_ref_fn fn, void *cb_data)
1492 {
1493         struct ref_store *refs = get_ref_store(NULL);
1494         struct ref_iterator *iter;
1495
1496         iter = refs->be->reflog_iterator_begin(refs);
1497
1498         return do_for_each_ref_iterator(iter, fn, cb_data);
1499 }
1500
1501 int for_each_reflog_ent_reverse(const char *refname, each_reflog_ent_fn fn,
1502                                 void *cb_data)
1503 {
1504         struct ref_store *refs = get_ref_store(NULL);
1505
1506         return refs->be->for_each_reflog_ent_reverse(refs, refname,
1507                                                      fn, cb_data);
1508 }
1509
1510 int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn,
1511                         void *cb_data)
1512 {
1513         struct ref_store *refs = get_ref_store(NULL);
1514
1515         return refs->be->for_each_reflog_ent(refs, refname, fn, cb_data);
1516 }
1517
1518 int reflog_exists(const char *refname)
1519 {
1520         struct ref_store *refs = get_ref_store(NULL);
1521
1522         return refs->be->reflog_exists(refs, refname);
1523 }
1524
1525 int safe_create_reflog(const char *refname, int force_create,
1526                        struct strbuf *err)
1527 {
1528         struct ref_store *refs = get_ref_store(NULL);
1529
1530         return refs->be->create_reflog(refs, refname, force_create, err);
1531 }
1532
1533 int delete_reflog(const char *refname)
1534 {
1535         struct ref_store *refs = get_ref_store(NULL);
1536
1537         return refs->be->delete_reflog(refs, refname);
1538 }
1539
1540 int reflog_expire(const char *refname, const unsigned char *sha1,
1541                   unsigned int flags,
1542                   reflog_expiry_prepare_fn prepare_fn,
1543                   reflog_expiry_should_prune_fn should_prune_fn,
1544                   reflog_expiry_cleanup_fn cleanup_fn,
1545                   void *policy_cb_data)
1546 {
1547         struct ref_store *refs = get_ref_store(NULL);
1548
1549         return refs->be->reflog_expire(refs, refname, sha1, flags,
1550                                        prepare_fn, should_prune_fn,
1551                                        cleanup_fn, policy_cb_data);
1552 }
1553
1554 int initial_ref_transaction_commit(struct ref_transaction *transaction,
1555                                    struct strbuf *err)
1556 {
1557         struct ref_store *refs = get_ref_store(NULL);
1558
1559         return refs->be->initial_transaction_commit(refs, transaction, err);
1560 }
1561
1562 int delete_refs(struct string_list *refnames, unsigned int flags)
1563 {
1564         struct ref_store *refs = get_ref_store(NULL);
1565
1566         return refs->be->delete_refs(refs, refnames, flags);
1567 }
1568
1569 int rename_ref(const char *oldref, const char *newref, const char *logmsg)
1570 {
1571         struct ref_store *refs = get_ref_store(NULL);
1572
1573         return refs->be->rename_ref(refs, oldref, newref, logmsg);
1574 }