refs.c

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