sha1_name.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tree-walk.h"
   7 #include "refs.h"
   8
   9 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
  10 {
  11         struct alternate_object_database *alt;
  12         char hex[40];
  13         int found = 0;
  14         static struct alternate_object_database *fakeent;
  15
  16         if (!fakeent) {
  17                 const char *objdir = get_object_directory();
  18                 int objdir_len = strlen(objdir);
  19                 int entlen = objdir_len + 43;
  20                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  21                 memcpy(fakeent->base, objdir, objdir_len);
  22                 fakeent->name = fakeent->base + objdir_len + 1;
  23                 fakeent->name[-1] = '/';
  24         }
  25         fakeent->next = alt_odb_list;
  26
  27         sprintf(hex, "%.2s", name);
  28         for (alt = fakeent; alt && found < 2; alt = alt->next) {
  29                 struct dirent *de;
  30                 DIR *dir;
  31                 sprintf(alt->name, "%.2s/", name);
  32                 dir = opendir(alt->base);
  33                 if (!dir)
  34                         continue;
  35                 while ((de = readdir(dir)) != NULL) {
  36                         if (strlen(de->d_name) != 38)
  37                                 continue;
  38                         if (memcmp(de->d_name, name + 2, len - 2))
  39                                 continue;
  40                         if (!found) {
  41                                 memcpy(hex + 2, de->d_name, 38);
  42                                 found++;
  43                         }
  44                         else if (memcmp(hex + 2, de->d_name, 38)) {
  45                                 found = 2;
  46                                 break;
  47                         }
  48                 }
  49                 closedir(dir);
  50         }
  51         if (found == 1)
  52                 return get_sha1_hex(hex, sha1) == 0;
  53         return found;
  54 }
  55
  56 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
  57 {
  58         do {
  59                 if (*a != *b)
  60                         return 0;
  61                 a++;
  62                 b++;
  63                 len -= 2;
  64         } while (len > 1);
  65         if (len)
  66                 if ((*a ^ *b) & 0xf0)
  67                         return 0;
  68         return 1;
  69 }
  70
  71 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
  72 {
  73         struct packed_git *p;
  74         const unsigned char *found_sha1 = NULL;
  75         int found = 0;
  76
  77         prepare_packed_git();
  78         for (p = packed_git; p && found < 2; p = p->next) {
  79                 uint32_t num, last;
  80                 uint32_t first = 0;
  81                 open_pack_index(p);
  82                 num = p->num_objects;
  83                 last = num;
  84                 while (first < last) {
  85                         uint32_t mid = (first + last) / 2;
  86                         const unsigned char *now;
  87                         int cmp;
  88
  89                         now = nth_packed_object_sha1(p, mid);
  90                         cmp = hashcmp(match, now);
  91                         if (!cmp) {
  92                                 first = mid;
  93                                 break;
  94                         }
  95                         if (cmp > 0) {
  96                                 first = mid+1;
  97                                 continue;
  98                         }
  99                         last = mid;
 100                 }
 101                 if (first < num) {
 102                         const unsigned char *now, *next;
 103                        now = nth_packed_object_sha1(p, first);
 104                         if (match_sha(len, match, now)) {
 105                                 next = nth_packed_object_sha1(p, first+1);
 106                                if (!next|| !match_sha(len, match, next)) {
 107                                         /* unique within this pack */
 108                                         if (!found) {
 109                                                 found_sha1 = now;
 110                                                 found++;
 111                                         }
 112                                         else if (hashcmp(found_sha1, now)) {
 113                                                 found = 2;
 114                                                 break;
 115                                         }
 116                                 }
 117                                 else {
 118                                         /* not even unique within this pack */
 119                                         found = 2;
 120                                         break;
 121                                 }
 122                         }
 123                 }
 124         }
 125         if (found == 1)
 126                 hashcpy(sha1, found_sha1);
 127         return found;
 128 }
 129
 130 #define SHORT_NAME_NOT_FOUND (-1)
 131 #define SHORT_NAME_AMBIGUOUS (-2)
 132
 133 static int find_unique_short_object(int len, char *canonical,
 134                                     unsigned char *res, unsigned char *sha1)
 135 {
 136         int has_unpacked, has_packed;
 137         unsigned char unpacked_sha1[20], packed_sha1[20];
 138
 139         prepare_alt_odb();
 140         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
 141         has_packed = find_short_packed_object(len, res, packed_sha1);
 142         if (!has_unpacked && !has_packed)
 143                 return SHORT_NAME_NOT_FOUND;
 144         if (1 < has_unpacked || 1 < has_packed)
 145                 return SHORT_NAME_AMBIGUOUS;
 146         if (has_unpacked != has_packed) {
 147                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
 148                 return 0;
 149         }
 150         /* Both have unique ones -- do they match? */
 151         if (hashcmp(packed_sha1, unpacked_sha1))
 152                 return SHORT_NAME_AMBIGUOUS;
 153         hashcpy(sha1, packed_sha1);
 154         return 0;
 155 }
 156
 157 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 158                           int quietly)
 159 {
 160         int i, status;
 161         char canonical[40];
 162         unsigned char res[20];
 163
 164         if (len < MINIMUM_ABBREV || len > 40)
 165                 return -1;
 166         hashclr(res);
 167         memset(canonical, 'x', 40);
 168         for (i = 0; i < len ;i++) {
 169                 unsigned char c = name[i];
 170                 unsigned char val;
 171                 if (c >= '0' && c <= '9')
 172                         val = c - '0';
 173                 else if (c >= 'a' && c <= 'f')
 174                         val = c - 'a' + 10;
 175                 else if (c >= 'A' && c <='F') {
 176                         val = c - 'A' + 10;
 177                         c -= 'A' - 'a';
 178                 }
 179                 else
 180                         return -1;
 181                 canonical[i] = c;
 182                 if (!(i & 1))
 183                         val <<= 4;
 184                 res[i >> 1] |= val;
 185         }
 186
 187         status = find_unique_short_object(i, canonical, res, sha1);
 188         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 189                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
 190         return status;
 191 }
 192
 193 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 194 {
 195         int status, exists;
 196         static char hex[41];
 197
 198         exists = has_sha1_file(sha1);
 199         memcpy(hex, sha1_to_hex(sha1), 40);
 200         if (len == 40 || !len)
 201                 return hex;
 202         while (len < 40) {
 203                 unsigned char sha1_ret[20];
 204                 status = get_short_sha1(hex, len, sha1_ret, 1);
 205                 if (exists
 206                     ? !status
 207                     : status == SHORT_NAME_NOT_FOUND) {
 208                         hex[len] = 0;
 209                         return hex;
 210                 }
 211                 len++;
 212         }
 213         return hex;
 214 }
 215
 216 static int ambiguous_path(const char *path, int len)
 217 {
 218         int slash = 1;
 219         int cnt;
 220
 221         for (cnt = 0; cnt < len; cnt++) {
 222                 switch (*path++) {
 223                 case '\0':
 224                         break;
 225                 case '/':
 226                         if (slash)
 227                                 break;
 228                         slash = 1;
 229                         continue;
 230                 case '.':
 231                         continue;
 232                 default:
 233                         slash = 0;
 234                         continue;
 235                 }
 236                 break;
 237         }
 238         return slash;
 239 }
 240
 241 /*
 242  * *string and *len will only be substituted, and *string returned (for
 243  * later free()ing) if the string passed in is of the form @{-<n>}.
 244  */
 245 static char *substitute_branch_name(const char **string, int *len)
 246 {
 247         struct strbuf buf = STRBUF_INIT;
 248         int ret = interpret_branch_name(*string, &buf);
 249
 250         if (ret == *len) {
 251                 size_t size;
 252                 *string = strbuf_detach(&buf, &size);
 253                 *len = size;
 254                 return (char *)*string;
 255         }
 256
 257         return NULL;
 258 }
 259
 260 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 261 {
 262         char *last_branch = substitute_branch_name(&str, &len);
 263         const char **p, *r;
 264         int refs_found = 0;
 265
 266         *ref = NULL;
 267         for (p = ref_rev_parse_rules; *p; p++) {
 268                 char fullref[PATH_MAX];
 269                 unsigned char sha1_from_ref[20];
 270                 unsigned char *this_result;
 271                 int flag;
 272
 273                 this_result = refs_found ? sha1_from_ref : sha1;
 274                 mksnpath(fullref, sizeof(fullref), *p, len, str);
 275                 r = resolve_ref(fullref, this_result, 1, &flag);
 276                 if (r) {
 277                         if (!refs_found++)
 278                                 *ref = xstrdup(r);
 279                         if (!warn_ambiguous_refs)
 280                                 break;
 281                 } else if ((flag & REF_ISSYMREF) &&
 282                            (len != 4 || strcmp(str, "HEAD")))
 283                         warning("ignoring dangling symref %s.", fullref);
 284         }
 285         free(last_branch);
 286         return refs_found;
 287 }
 288
 289 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 290 {
 291         char *last_branch = substitute_branch_name(&str, &len);
 292         const char **p;
 293         int logs_found = 0;
 294
 295         *log = NULL;
 296         for (p = ref_rev_parse_rules; *p; p++) {
 297                 struct stat st;
 298                 unsigned char hash[20];
 299                 char path[PATH_MAX];
 300                 const char *ref, *it;
 301
 302                 mksnpath(path, sizeof(path), *p, len, str);
 303                 ref = resolve_ref(path, hash, 1, NULL);
 304                 if (!ref)
 305                         continue;
 306                 if (!stat(git_path("logs/%s", path), &st) &&
 307                     S_ISREG(st.st_mode))
 308                         it = path;
 309                 else if (strcmp(ref, path) &&
 310                          !stat(git_path("logs/%s", ref), &st) &&
 311                          S_ISREG(st.st_mode))
 312                         it = ref;
 313                 else
 314                         continue;
 315                 if (!logs_found++) {
 316                         *log = xstrdup(it);
 317                         hashcpy(sha1, hash);
 318                 }
 319                 if (!warn_ambiguous_refs)
 320                         break;
 321         }
 322         free(last_branch);
 323         return logs_found;
 324 }
 325
 326 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 327
 328 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 329 {
 330         static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
 331         char *real_ref = NULL;
 332         int refs_found = 0;
 333         int at, reflog_len;
 334
 335         if (len == 40 && !get_sha1_hex(str, sha1))
 336                 return 0;
 337
 338         /* basic@{time or number or -number} format to query ref-log */
 339         reflog_len = at = 0;
 340         if (len && str[len-1] == '}') {
 341                 for (at = len-2; at >= 0; at--) {
 342                         if (str[at] == '@' && str[at+1] == '{') {
 343                                 reflog_len = (len-1) - (at+2);
 344                                 len = at;
 345                                 break;
 346                         }
 347                 }
 348         }
 349
 350         /* Accept only unambiguous ref paths. */
 351         if (len && ambiguous_path(str, len))
 352                 return -1;
 353
 354         if (!len && reflog_len) {
 355                 struct strbuf buf = STRBUF_INIT;
 356                 int ret;
 357                 /* try the @{-N} syntax for n-th checkout */
 358                 ret = interpret_branch_name(str+at, &buf);
 359                 if (ret > 0) {
 360                         /* substitute this branch name and restart */
 361                         return get_sha1_1(buf.buf, buf.len, sha1);
 362                 } else if (ret == 0) {
 363                         return -1;
 364                 }
 365                 /* allow "@{...}" to mean the current branch reflog */
 366                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 367         } else if (reflog_len)
 368                 refs_found = dwim_log(str, len, sha1, &real_ref);
 369         else
 370                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 371
 372         if (!refs_found)
 373                 return -1;
 374
 375         if (warn_ambiguous_refs && refs_found > 1)
 376                 fprintf(stderr, warning, len, str);
 377
 378         if (reflog_len) {
 379                 int nth, i;
 380                 unsigned long at_time;
 381                 unsigned long co_time;
 382                 int co_tz, co_cnt;
 383
 384                 /* Is it asking for N-th entry, or approxidate? */
 385                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 386                         char ch = str[at+2+i];
 387                         if ('0' <= ch && ch <= '9')
 388                                 nth = nth * 10 + ch - '0';
 389                         else
 390                                 nth = -1;
 391                 }
 392                 if (100000000 <= nth) {
 393                         at_time = nth;
 394                         nth = -1;
 395                 } else if (0 <= nth)
 396                         at_time = 0;
 397                 else {
 398                         int errors = 0;
 399                         char *tmp = xstrndup(str + at + 2, reflog_len);
 400                         at_time = approxidate_careful(tmp, &errors);
 401                         free(tmp);
 402                         if (errors)
 403                                 return -1;
 404                 }
 405                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 406                                 &co_time, &co_tz, &co_cnt)) {
 407                         if (at_time)
 408                                 fprintf(stderr,
 409                                         "warning: Log for '%.*s' only goes "
 410                                         "back to %s.\n", len, str,
 411                                         show_date(co_time, co_tz, DATE_RFC2822));
 412                         else
 413                                 fprintf(stderr,
 414                                         "warning: Log for '%.*s' only has "
 415                                         "%d entries.\n", len, str, co_cnt);
 416                 }
 417         }
 418
 419         free(real_ref);
 420         return 0;
 421 }
 422
 423 static int get_parent(const char *name, int len,
 424                       unsigned char *result, int idx)
 425 {
 426         unsigned char sha1[20];
 427         int ret = get_sha1_1(name, len, sha1);
 428         struct commit *commit;
 429         struct commit_list *p;
 430
 431         if (ret)
 432                 return ret;
 433         commit = lookup_commit_reference(sha1);
 434         if (!commit)
 435                 return -1;
 436         if (parse_commit(commit))
 437                 return -1;
 438         if (!idx) {
 439                 hashcpy(result, commit->object.sha1);
 440                 return 0;
 441         }
 442         p = commit->parents;
 443         while (p) {
 444                 if (!--idx) {
 445                         hashcpy(result, p->item->object.sha1);
 446                         return 0;
 447                 }
 448                 p = p->next;
 449         }
 450         return -1;
 451 }
 452
 453 static int get_nth_ancestor(const char *name, int len,
 454                             unsigned char *result, int generation)
 455 {
 456         unsigned char sha1[20];
 457         struct commit *commit;
 458         int ret;
 459
 460         ret = get_sha1_1(name, len, sha1);
 461         if (ret)
 462                 return ret;
 463         commit = lookup_commit_reference(sha1);
 464         if (!commit)
 465                 return -1;
 466
 467         while (generation--) {
 468                 if (parse_commit(commit) || !commit->parents)
 469                         return -1;
 470                 commit = commit->parents->item;
 471         }
 472         hashcpy(result, commit->object.sha1);
 473         return 0;
 474 }
 475
 476 struct object *peel_to_type(const char *name, int namelen,
 477                             struct object *o, enum object_type expected_type)
 478 {
 479         if (name && !namelen)
 480                 namelen = strlen(name);
 481         if (!o) {
 482                 unsigned char sha1[20];
 483                 if (get_sha1_1(name, namelen, sha1))
 484                         return NULL;
 485                 o = parse_object(sha1);
 486         }
 487         while (1) {
 488                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 489                         return NULL;
 490                 if (o->type == expected_type)
 491                         return o;
 492                 if (o->type == OBJ_TAG)
 493                         o = ((struct tag*) o)->tagged;
 494                 else if (o->type == OBJ_COMMIT)
 495                         o = &(((struct commit *) o)->tree->object);
 496                 else {
 497                         if (name)
 498                                 error("%.*s: expected %s type, but the object "
 499                                       "dereferences to %s type",
 500                                       namelen, name, typename(expected_type),
 501                                       typename(o->type));
 502                         return NULL;
 503                 }
 504         }
 505 }
 506
 507 static int peel_onion(const char *name, int len, unsigned char *sha1)
 508 {
 509         unsigned char outer[20];
 510         const char *sp;
 511         unsigned int expected_type = 0;
 512         struct object *o;
 513
 514         /*
 515          * "ref^{type}" dereferences ref repeatedly until you cannot
 516          * dereference anymore, or you get an object of given type,
 517          * whichever comes first.  "ref^{}" means just dereference
 518          * tags until you get a non-tag.  "ref^0" is a shorthand for
 519          * "ref^{commit}".  "commit^{tree}" could be used to find the
 520          * top-level tree of the given commit.
 521          */
 522         if (len < 4 || name[len-1] != '}')
 523                 return -1;
 524
 525         for (sp = name + len - 1; name <= sp; sp--) {
 526                 int ch = *sp;
 527                 if (ch == '{' && name < sp && sp[-1] == '^')
 528                         break;
 529         }
 530         if (sp <= name)
 531                 return -1;
 532
 533         sp++; /* beginning of type name, or closing brace for empty */
 534         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 535                 expected_type = OBJ_COMMIT;
 536         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 537                 expected_type = OBJ_TREE;
 538         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 539                 expected_type = OBJ_BLOB;
 540         else if (sp[0] == '}')
 541                 expected_type = OBJ_NONE;
 542         else
 543                 return -1;
 544
 545         if (get_sha1_1(name, sp - name - 2, outer))
 546                 return -1;
 547
 548         o = parse_object(outer);
 549         if (!o)
 550                 return -1;
 551         if (!expected_type) {
 552                 o = deref_tag(o, name, sp - name - 2);
 553                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 554                         return -1;
 555                 hashcpy(sha1, o->sha1);
 556         }
 557         else {
 558                 /*
 559                  * At this point, the syntax look correct, so
 560                  * if we do not get the needed object, we should
 561                  * barf.
 562                  */
 563                 o = peel_to_type(name, len, o, expected_type);
 564                 if (o) {
 565                         hashcpy(sha1, o->sha1);
 566                         return 0;
 567                 }
 568                 return -1;
 569         }
 570         return 0;
 571 }
 572
 573 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 574 {
 575         const char *cp;
 576
 577         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 578                 char ch = *cp;
 579                 if (hexval(ch) & ~0377) {
 580                         /* We must be looking at g in "SOMETHING-g"
 581                          * for it to be describe output.
 582                          */
 583                         if (ch == 'g' && cp[-1] == '-') {
 584                                 cp++;
 585                                 len -= cp - name;
 586                                 return get_short_sha1(cp, len, sha1, 1);
 587                         }
 588                 }
 589         }
 590         return -1;
 591 }
 592
 593 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 594 {
 595         int ret, has_suffix;
 596         const char *cp;
 597
 598         /*
 599          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 600          */
 601         has_suffix = 0;
 602         for (cp = name + len - 1; name <= cp; cp--) {
 603                 int ch = *cp;
 604                 if ('0' <= ch && ch <= '9')
 605                         continue;
 606                 if (ch == '~' || ch == '^')
 607                         has_suffix = ch;
 608                 break;
 609         }
 610
 611         if (has_suffix) {
 612                 int num = 0;
 613                 int len1 = cp - name;
 614                 cp++;
 615                 while (cp < name + len)
 616                         num = num * 10 + *cp++ - '0';
 617                 if (!num && len1 == len - 1)
 618                         num = 1;
 619                 if (has_suffix == '^')
 620                         return get_parent(name, len1, sha1, num);
 621                 /* else if (has_suffix == '~') -- goes without saying */
 622                 return get_nth_ancestor(name, len1, sha1, num);
 623         }
 624
 625         ret = peel_onion(name, len, sha1);
 626         if (!ret)
 627                 return 0;
 628
 629         ret = get_sha1_basic(name, len, sha1);
 630         if (!ret)
 631                 return 0;
 632
 633         /* It could be describe output that is "SOMETHING-gXXXX" */
 634         ret = get_describe_name(name, len, sha1);
 635         if (!ret)
 636                 return 0;
 637
 638         return get_short_sha1(name, len, sha1, 0);
 639 }
 640
 641 static int handle_one_ref(const char *path,
 642                 const unsigned char *sha1, int flag, void *cb_data)
 643 {
 644         struct commit_list **list = cb_data;
 645         struct object *object = parse_object(sha1);
 646         if (!object)
 647                 return 0;
 648         if (object->type == OBJ_TAG) {
 649                 object = deref_tag(object, path, strlen(path));
 650                 if (!object)
 651                         return 0;
 652         }
 653         if (object->type != OBJ_COMMIT)
 654                 return 0;
 655         insert_by_date((struct commit *)object, list);
 656         return 0;
 657 }
 658
 659 /*
 660  * This interprets names like ':/Initial revision of "git"' by searching
 661  * through history and returning the first commit whose message starts
 662  * with the given string.
 663  *
 664  * For future extension, ':/!' is reserved. If you want to match a message
 665  * beginning with a '!', you have to repeat the exclamation mark.
 666  */
 667
 668 #define ONELINE_SEEN (1u<<20)
 669 static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 670 {
 671         struct commit_list *list = NULL, *backup = NULL, *l;
 672         int retval = -1;
 673         char *temp_commit_buffer = NULL;
 674
 675         if (prefix[0] == '!') {
 676                 if (prefix[1] != '!')
 677                         die ("Invalid search pattern: %s", prefix);
 678                 prefix++;
 679         }
 680         for_each_ref(handle_one_ref, &list);
 681         for (l = list; l; l = l->next)
 682                 commit_list_insert(l->item, &backup);
 683         while (list) {
 684                 char *p;
 685                 struct commit *commit;
 686                 enum object_type type;
 687                 unsigned long size;
 688
 689                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 690                 if (!parse_object(commit->object.sha1))
 691                         continue;
 692                 free(temp_commit_buffer);
 693                 if (commit->buffer)
 694                         p = commit->buffer;
 695                 else {
 696                         p = read_sha1_file(commit->object.sha1, &type, &size);
 697                         if (!p)
 698                                 continue;
 699                         temp_commit_buffer = p;
 700                 }
 701                 if (!(p = strstr(p, "\n\n")))
 702                         continue;
 703                 if (!prefixcmp(p + 2, prefix)) {
 704                         hashcpy(sha1, commit->object.sha1);
 705                         retval = 0;
 706                         break;
 707                 }
 708         }
 709         free(temp_commit_buffer);
 710         free_commit_list(list);
 711         for (l = backup; l; l = l->next)
 712                 clear_commit_marks(l->item, ONELINE_SEEN);
 713         return retval;
 714 }
 715
 716 struct grab_nth_branch_switch_cbdata {
 717         long cnt, alloc;
 718         struct strbuf *buf;
 719 };
 720
 721 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 722                                   const char *email, unsigned long timestamp, int tz,
 723                                   const char *message, void *cb_data)
 724 {
 725         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 726         const char *match = NULL, *target = NULL;
 727         size_t len;
 728         int nth;
 729
 730         if (!prefixcmp(message, "checkout: moving from ")) {
 731                 match = message + strlen("checkout: moving from ");
 732                 target = strstr(match, " to ");
 733         }
 734
 735         if (!match || !target)
 736                 return 0;
 737
 738         len = target - match;
 739         nth = cb->cnt++ % cb->alloc;
 740         strbuf_reset(&cb->buf[nth]);
 741         strbuf_add(&cb->buf[nth], match, len);
 742         return 0;
 743 }
 744
 745 /*
 746  * This reads "@{-N}" syntax, finds the name of the Nth previous
 747  * branch we were on, and places the name of the branch in the given
 748  * buf and returns the number of characters parsed if successful.
 749  *
 750  * If the input is not of the accepted format, it returns a negative
 751  * number to signal an error.
 752  *
 753  * If the input was ok but there are not N branch switches in the
 754  * reflog, it returns 0.
 755  */
 756 int interpret_branch_name(const char *name, struct strbuf *buf)
 757 {
 758         long nth;
 759         int i, retval;
 760         struct grab_nth_branch_switch_cbdata cb;
 761         const char *brace;
 762         char *num_end;
 763
 764         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 765                 return -1;
 766         brace = strchr(name, '}');
 767         if (!brace)
 768                 return -1;
 769         nth = strtol(name+3, &num_end, 10);
 770         if (num_end != brace)
 771                 return -1;
 772         if (nth <= 0)
 773                 return -1;
 774         cb.alloc = nth;
 775         cb.buf = xmalloc(nth * sizeof(struct strbuf));
 776         for (i = 0; i < nth; i++)
 777                 strbuf_init(&cb.buf[i], 20);
 778         cb.cnt = 0;
 779         retval = 0;
 780         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 781         if (cb.cnt < nth) {
 782                 cb.cnt = 0;
 783                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 784         }
 785         if (cb.cnt < nth)
 786                 goto release_return;
 787         i = cb.cnt % nth;
 788         strbuf_reset(buf);
 789         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 790         retval = brace-name+1;
 791
 792 release_return:
 793         for (i = 0; i < nth; i++)
 794                 strbuf_release(&cb.buf[i]);
 795         free(cb.buf);
 796
 797         return retval;
 798 }
 799
 800 /*
 801  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 802  * notably "xyz^" for "parent of xyz"
 803  */
 804 int get_sha1(const char *name, unsigned char *sha1)
 805 {
 806         unsigned unused;
 807         return get_sha1_with_mode(name, sha1, &unused);
 808 }
 809
 810 int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 811 {
 812         int ret, bracket_depth;
 813         int namelen = strlen(name);
 814         const char *cp;
 815
 816         *mode = S_IFINVALID;
 817         ret = get_sha1_1(name, namelen, sha1);
 818         if (!ret)
 819                 return ret;
 820         /* sha1:path --> object name of path in ent sha1
 821          * :path -> object name of path in index
 822          * :[0-3]:path -> object name of path in index at stage
 823          */
 824         if (name[0] == ':') {
 825                 int stage = 0;
 826                 struct cache_entry *ce;
 827                 int pos;
 828                 if (namelen > 2 && name[1] == '/')
 829                         return get_sha1_oneline(name + 2, sha1);
 830                 if (namelen < 3 ||
 831                     name[2] != ':' ||
 832                     name[1] < '0' || '3' < name[1])
 833                         cp = name + 1;
 834                 else {
 835                         stage = name[1] - '0';
 836                         cp = name + 3;
 837                 }
 838                 namelen = namelen - (cp - name);
 839                 if (!active_cache)
 840                         read_cache();
 841                 pos = cache_name_pos(cp, namelen);
 842                 if (pos < 0)
 843                         pos = -pos - 1;
 844                 while (pos < active_nr) {
 845                         ce = active_cache[pos];
 846                         if (ce_namelen(ce) != namelen ||
 847                             memcmp(ce->name, cp, namelen))
 848                                 break;
 849                         if (ce_stage(ce) == stage) {
 850                                 hashcpy(sha1, ce->sha1);
 851                                 *mode = ce->ce_mode;
 852                                 return 0;
 853                         }
 854                         pos++;
 855                 }
 856                 return -1;
 857         }
 858         for (cp = name, bracket_depth = 0; *cp; cp++) {
 859                 if (*cp == '{')
 860                         bracket_depth++;
 861                 else if (bracket_depth && *cp == '}')
 862                         bracket_depth--;
 863                 else if (!bracket_depth && *cp == ':')
 864                         break;
 865         }
 866         if (*cp == ':') {
 867                 unsigned char tree_sha1[20];
 868                 if (!get_sha1_1(name, cp-name, tree_sha1))
 869                         return get_tree_entry(tree_sha1, cp+1, sha1,
 870                                               mode);
 871         }
 872         return ret;
 873 }