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 #include "remote.h"
   9
  10 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
  11
  12 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
  13 {
  14         struct alternate_object_database *alt;
  15         char hex[40];
  16         int found = 0;
  17         static struct alternate_object_database *fakeent;
  18
  19         if (!fakeent) {
  20                 const char *objdir = get_object_directory();
  21                 int objdir_len = strlen(objdir);
  22                 int entlen = objdir_len + 43;
  23                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  24                 memcpy(fakeent->base, objdir, objdir_len);
  25                 fakeent->name = fakeent->base + objdir_len + 1;
  26                 fakeent->name[-1] = '/';
  27         }
  28         fakeent->next = alt_odb_list;
  29
  30         sprintf(hex, "%.2s", name);
  31         for (alt = fakeent; alt && found < 2; alt = alt->next) {
  32                 struct dirent *de;
  33                 DIR *dir;
  34                 sprintf(alt->name, "%.2s/", name);
  35                 dir = opendir(alt->base);
  36                 if (!dir)
  37                         continue;
  38                 while ((de = readdir(dir)) != NULL) {
  39                         if (strlen(de->d_name) != 38)
  40                                 continue;
  41                         if (memcmp(de->d_name, name + 2, len - 2))
  42                                 continue;
  43                         if (!found) {
  44                                 memcpy(hex + 2, de->d_name, 38);
  45                                 found++;
  46                         }
  47                         else if (memcmp(hex + 2, de->d_name, 38)) {
  48                                 found = 2;
  49                                 break;
  50                         }
  51                 }
  52                 closedir(dir);
  53         }
  54         if (found == 1)
  55                 return get_sha1_hex(hex, sha1) == 0;
  56         return found;
  57 }
  58
  59 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
  60 {
  61         do {
  62                 if (*a != *b)
  63                         return 0;
  64                 a++;
  65                 b++;
  66                 len -= 2;
  67         } while (len > 1);
  68         if (len)
  69                 if ((*a ^ *b) & 0xf0)
  70                         return 0;
  71         return 1;
  72 }
  73
  74 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
  75 {
  76         struct packed_git *p;
  77         const unsigned char *found_sha1 = NULL;
  78         int found = 0;
  79
  80         prepare_packed_git();
  81         for (p = packed_git; p && found < 2; p = p->next) {
  82                 uint32_t num, last;
  83                 uint32_t first = 0;
  84                 open_pack_index(p);
  85                 num = p->num_objects;
  86                 last = num;
  87                 while (first < last) {
  88                         uint32_t mid = (first + last) / 2;
  89                         const unsigned char *now;
  90                         int cmp;
  91
  92                         now = nth_packed_object_sha1(p, mid);
  93                         cmp = hashcmp(match, now);
  94                         if (!cmp) {
  95                                 first = mid;
  96                                 break;
  97                         }
  98                         if (cmp > 0) {
  99                                 first = mid+1;
 100                                 continue;
 101                         }
 102                         last = mid;
 103                 }
 104                 if (first < num) {
 105                         const unsigned char *now, *next;
 106                        now = nth_packed_object_sha1(p, first);
 107                         if (match_sha(len, match, now)) {
 108                                 next = nth_packed_object_sha1(p, first+1);
 109                                if (!next|| !match_sha(len, match, next)) {
 110                                         /* unique within this pack */
 111                                         if (!found) {
 112                                                 found_sha1 = now;
 113                                                 found++;
 114                                         }
 115                                         else if (hashcmp(found_sha1, now)) {
 116                                                 found = 2;
 117                                                 break;
 118                                         }
 119                                 }
 120                                 else {
 121                                         /* not even unique within this pack */
 122                                         found = 2;
 123                                         break;
 124                                 }
 125                         }
 126                 }
 127         }
 128         if (found == 1)
 129                 hashcpy(sha1, found_sha1);
 130         return found;
 131 }
 132
 133 #define SHORT_NAME_NOT_FOUND (-1)
 134 #define SHORT_NAME_AMBIGUOUS (-2)
 135
 136 static int find_unique_short_object(int len, char *canonical,
 137                                     unsigned char *res, unsigned char *sha1)
 138 {
 139         int has_unpacked, has_packed;
 140         unsigned char unpacked_sha1[20], packed_sha1[20];
 141
 142         prepare_alt_odb();
 143         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
 144         has_packed = find_short_packed_object(len, res, packed_sha1);
 145         if (!has_unpacked && !has_packed)
 146                 return SHORT_NAME_NOT_FOUND;
 147         if (1 < has_unpacked || 1 < has_packed)
 148                 return SHORT_NAME_AMBIGUOUS;
 149         if (has_unpacked != has_packed) {
 150                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
 151                 return 0;
 152         }
 153         /* Both have unique ones -- do they match? */
 154         if (hashcmp(packed_sha1, unpacked_sha1))
 155                 return SHORT_NAME_AMBIGUOUS;
 156         hashcpy(sha1, packed_sha1);
 157         return 0;
 158 }
 159
 160 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 161                           int quietly)
 162 {
 163         int i, status;
 164         char canonical[40];
 165         unsigned char res[20];
 166
 167         if (len < MINIMUM_ABBREV || len > 40)
 168                 return -1;
 169         hashclr(res);
 170         memset(canonical, 'x', 40);
 171         for (i = 0; i < len ;i++) {
 172                 unsigned char c = name[i];
 173                 unsigned char val;
 174                 if (c >= '0' && c <= '9')
 175                         val = c - '0';
 176                 else if (c >= 'a' && c <= 'f')
 177                         val = c - 'a' + 10;
 178                 else if (c >= 'A' && c <='F') {
 179                         val = c - 'A' + 10;
 180                         c -= 'A' - 'a';
 181                 }
 182                 else
 183                         return -1;
 184                 canonical[i] = c;
 185                 if (!(i & 1))
 186                         val <<= 4;
 187                 res[i >> 1] |= val;
 188         }
 189
 190         status = find_unique_short_object(i, canonical, res, sha1);
 191         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 192                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
 193         return status;
 194 }
 195
 196 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 197 {
 198         int status, exists;
 199         static char hex[41];
 200
 201         exists = has_sha1_file(sha1);
 202         memcpy(hex, sha1_to_hex(sha1), 40);
 203         if (len == 40 || !len)
 204                 return hex;
 205         while (len < 40) {
 206                 unsigned char sha1_ret[20];
 207                 status = get_short_sha1(hex, len, sha1_ret, 1);
 208                 if (exists
 209                     ? !status
 210                     : status == SHORT_NAME_NOT_FOUND) {
 211                         hex[len] = 0;
 212                         return hex;
 213                 }
 214                 len++;
 215         }
 216         return hex;
 217 }
 218
 219 static int ambiguous_path(const char *path, int len)
 220 {
 221         int slash = 1;
 222         int cnt;
 223
 224         for (cnt = 0; cnt < len; cnt++) {
 225                 switch (*path++) {
 226                 case '\0':
 227                         break;
 228                 case '/':
 229                         if (slash)
 230                                 break;
 231                         slash = 1;
 232                         continue;
 233                 case '.':
 234                         continue;
 235                 default:
 236                         slash = 0;
 237                         continue;
 238                 }
 239                 break;
 240         }
 241         return slash;
 242 }
 243
 244 /*
 245  * *string and *len will only be substituted, and *string returned (for
 246  * later free()ing) if the string passed in is a magic short-hand form
 247  * to name a branch.
 248  */
 249 static char *substitute_branch_name(const char **string, int *len)
 250 {
 251         struct strbuf buf = STRBUF_INIT;
 252         int ret = interpret_branch_name(*string, &buf);
 253
 254         if (ret == *len) {
 255                 size_t size;
 256                 *string = strbuf_detach(&buf, &size);
 257                 *len = size;
 258                 return (char *)*string;
 259         }
 260
 261         return NULL;
 262 }
 263
 264 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 265 {
 266         char *last_branch = substitute_branch_name(&str, &len);
 267         const char **p, *r;
 268         int refs_found = 0;
 269
 270         *ref = NULL;
 271         for (p = ref_rev_parse_rules; *p; p++) {
 272                 char fullref[PATH_MAX];
 273                 unsigned char sha1_from_ref[20];
 274                 unsigned char *this_result;
 275                 int flag;
 276
 277                 this_result = refs_found ? sha1_from_ref : sha1;
 278                 mksnpath(fullref, sizeof(fullref), *p, len, str);
 279                 r = resolve_ref(fullref, this_result, 1, &flag);
 280                 if (r) {
 281                         if (!refs_found++)
 282                                 *ref = xstrdup(r);
 283                         if (!warn_ambiguous_refs)
 284                                 break;
 285                 } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD"))
 286                         warning("ignoring dangling symref %s.", fullref);
 287         }
 288         free(last_branch);
 289         return refs_found;
 290 }
 291
 292 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 293 {
 294         char *last_branch = substitute_branch_name(&str, &len);
 295         const char **p;
 296         int logs_found = 0;
 297
 298         *log = NULL;
 299         for (p = ref_rev_parse_rules; *p; p++) {
 300                 struct stat st;
 301                 unsigned char hash[20];
 302                 char path[PATH_MAX];
 303                 const char *ref, *it;
 304
 305                 mksnpath(path, sizeof(path), *p, len, str);
 306                 ref = resolve_ref(path, hash, 1, NULL);
 307                 if (!ref)
 308                         continue;
 309                 if (!stat(git_path("logs/%s", path), &st) &&
 310                     S_ISREG(st.st_mode))
 311                         it = path;
 312                 else if (strcmp(ref, path) &&
 313                          !stat(git_path("logs/%s", ref), &st) &&
 314                          S_ISREG(st.st_mode))
 315                         it = ref;
 316                 else
 317                         continue;
 318                 if (!logs_found++) {
 319                         *log = xstrdup(it);
 320                         hashcpy(sha1, hash);
 321                 }
 322                 if (!warn_ambiguous_refs)
 323                         break;
 324         }
 325         free(last_branch);
 326         return logs_found;
 327 }
 328
 329 static inline int upstream_mark(const char *string, int len)
 330 {
 331         const char *suffix[] = { "@{upstream}", "@{u}" };
 332         int i;
 333
 334         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 335                 int suffix_len = strlen(suffix[i]);
 336                 if (suffix_len <= len
 337                     && !memcmp(string, suffix[i], suffix_len))
 338                         return suffix_len;
 339         }
 340         return 0;
 341 }
 342
 343 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 344
 345 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 346 {
 347         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 348         char *real_ref = NULL;
 349         int refs_found = 0;
 350         int at, reflog_len;
 351
 352         if (len == 40 && !get_sha1_hex(str, sha1))
 353                 return 0;
 354
 355         /* basic@{time or number or -number} format to query ref-log */
 356         reflog_len = at = 0;
 357         if (len && str[len-1] == '}') {
 358                 for (at = len-2; at >= 0; at--) {
 359                         if (str[at] == '@' && str[at+1] == '{') {
 360                                 if (!upstream_mark(str + at, len - at)) {
 361                                         reflog_len = (len-1) - (at+2);
 362                                         len = at;
 363                                 }
 364                                 break;
 365                         }
 366                 }
 367         }
 368
 369         /* Accept only unambiguous ref paths. */
 370         if (len && ambiguous_path(str, len))
 371                 return -1;
 372
 373         if (!len && reflog_len) {
 374                 struct strbuf buf = STRBUF_INIT;
 375                 int ret;
 376                 /* try the @{-N} syntax for n-th checkout */
 377                 ret = interpret_branch_name(str+at, &buf);
 378                 if (ret > 0) {
 379                         /* substitute this branch name and restart */
 380                         return get_sha1_1(buf.buf, buf.len, sha1);
 381                 } else if (ret == 0) {
 382                         return -1;
 383                 }
 384                 /* allow "@{...}" to mean the current branch reflog */
 385                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 386         } else if (reflog_len)
 387                 refs_found = dwim_log(str, len, sha1, &real_ref);
 388         else
 389                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 390
 391         if (!refs_found)
 392                 return -1;
 393
 394         if (warn_ambiguous_refs && refs_found > 1)
 395                 warning(warn_msg, len, str);
 396
 397         if (reflog_len) {
 398                 int nth, i;
 399                 unsigned long at_time;
 400                 unsigned long co_time;
 401                 int co_tz, co_cnt;
 402
 403                 /* a @{-N} placed anywhere except the start is an error */
 404                 if (str[at+2] == '-')
 405                         return -1;
 406
 407                 /* Is it asking for N-th entry, or approxidate? */
 408                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 409                         char ch = str[at+2+i];
 410                         if ('0' <= ch && ch <= '9')
 411                                 nth = nth * 10 + ch - '0';
 412                         else
 413                                 nth = -1;
 414                 }
 415                 if (100000000 <= nth) {
 416                         at_time = nth;
 417                         nth = -1;
 418                 } else if (0 <= nth)
 419                         at_time = 0;
 420                 else {
 421                         int errors = 0;
 422                         char *tmp = xstrndup(str + at + 2, reflog_len);
 423                         at_time = approxidate_careful(tmp, &errors);
 424                         free(tmp);
 425                         if (errors)
 426                                 return -1;
 427                 }
 428                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 429                                 &co_time, &co_tz, &co_cnt)) {
 430                         if (at_time)
 431                                 warning("Log for '%.*s' only goes "
 432                                         "back to %s.", len, str,
 433                                         show_date(co_time, co_tz, DATE_RFC2822));
 434                         else {
 435                                 free(real_ref);
 436                                 die("Log for '%.*s' only has %d entries.",
 437                                     len, str, co_cnt);
 438                         }
 439                 }
 440         }
 441
 442         free(real_ref);
 443         return 0;
 444 }
 445
 446 static int get_parent(const char *name, int len,
 447                       unsigned char *result, int idx)
 448 {
 449         unsigned char sha1[20];
 450         int ret = get_sha1_1(name, len, sha1);
 451         struct commit *commit;
 452         struct commit_list *p;
 453
 454         if (ret)
 455                 return ret;
 456         commit = lookup_commit_reference(sha1);
 457         if (!commit)
 458                 return -1;
 459         if (parse_commit(commit))
 460                 return -1;
 461         if (!idx) {
 462                 hashcpy(result, commit->object.sha1);
 463                 return 0;
 464         }
 465         p = commit->parents;
 466         while (p) {
 467                 if (!--idx) {
 468                         hashcpy(result, p->item->object.sha1);
 469                         return 0;
 470                 }
 471                 p = p->next;
 472         }
 473         return -1;
 474 }
 475
 476 static int get_nth_ancestor(const char *name, int len,
 477                             unsigned char *result, int generation)
 478 {
 479         unsigned char sha1[20];
 480         struct commit *commit;
 481         int ret;
 482
 483         ret = get_sha1_1(name, len, sha1);
 484         if (ret)
 485                 return ret;
 486         commit = lookup_commit_reference(sha1);
 487         if (!commit)
 488                 return -1;
 489
 490         while (generation--) {
 491                 if (parse_commit(commit) || !commit->parents)
 492                         return -1;
 493                 commit = commit->parents->item;
 494         }
 495         hashcpy(result, commit->object.sha1);
 496         return 0;
 497 }
 498
 499 struct object *peel_to_type(const char *name, int namelen,
 500                             struct object *o, enum object_type expected_type)
 501 {
 502         if (name && !namelen)
 503                 namelen = strlen(name);
 504         if (!o) {
 505                 unsigned char sha1[20];
 506                 if (get_sha1_1(name, namelen, sha1))
 507                         return NULL;
 508                 o = parse_object(sha1);
 509         }
 510         while (1) {
 511                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 512                         return NULL;
 513                 if (o->type == expected_type)
 514                         return o;
 515                 if (o->type == OBJ_TAG)
 516                         o = ((struct tag*) o)->tagged;
 517                 else if (o->type == OBJ_COMMIT)
 518                         o = &(((struct commit *) o)->tree->object);
 519                 else {
 520                         if (name)
 521                                 error("%.*s: expected %s type, but the object "
 522                                       "dereferences to %s type",
 523                                       namelen, name, typename(expected_type),
 524                                       typename(o->type));
 525                         return NULL;
 526                 }
 527         }
 528 }
 529
 530 static int peel_onion(const char *name, int len, unsigned char *sha1)
 531 {
 532         unsigned char outer[20];
 533         const char *sp;
 534         unsigned int expected_type = 0;
 535         struct object *o;
 536
 537         /*
 538          * "ref^{type}" dereferences ref repeatedly until you cannot
 539          * dereference anymore, or you get an object of given type,
 540          * whichever comes first.  "ref^{}" means just dereference
 541          * tags until you get a non-tag.  "ref^0" is a shorthand for
 542          * "ref^{commit}".  "commit^{tree}" could be used to find the
 543          * top-level tree of the given commit.
 544          */
 545         if (len < 4 || name[len-1] != '}')
 546                 return -1;
 547
 548         for (sp = name + len - 1; name <= sp; sp--) {
 549                 int ch = *sp;
 550                 if (ch == '{' && name < sp && sp[-1] == '^')
 551                         break;
 552         }
 553         if (sp <= name)
 554                 return -1;
 555
 556         sp++; /* beginning of type name, or closing brace for empty */
 557         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 558                 expected_type = OBJ_COMMIT;
 559         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 560                 expected_type = OBJ_TREE;
 561         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 562                 expected_type = OBJ_BLOB;
 563         else if (sp[0] == '}')
 564                 expected_type = OBJ_NONE;
 565         else if (sp[0] == '/')
 566                 expected_type = OBJ_COMMIT;
 567         else
 568                 return -1;
 569
 570         if (get_sha1_1(name, sp - name - 2, outer))
 571                 return -1;
 572
 573         o = parse_object(outer);
 574         if (!o)
 575                 return -1;
 576         if (!expected_type) {
 577                 o = deref_tag(o, name, sp - name - 2);
 578                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 579                         return -1;
 580                 hashcpy(sha1, o->sha1);
 581                 return 0;
 582         }
 583
 584         /*
 585          * At this point, the syntax look correct, so
 586          * if we do not get the needed object, we should
 587          * barf.
 588          */
 589         o = peel_to_type(name, len, o, expected_type);
 590         if (!o)
 591                 return -1;
 592
 593         hashcpy(sha1, o->sha1);
 594         if (sp[0] == '/') {
 595                 /* "$commit^{/foo}" */
 596                 char *prefix;
 597                 int ret;
 598                 struct commit_list *list = NULL;
 599
 600                 /*
 601                  * $commit^{/}. Some regex implementation may reject.
 602                  * We don't need regex anyway. '' pattern always matches.
 603                  */
 604                 if (sp[1] == '}')
 605                         return 0;
 606
 607                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
 608                 commit_list_insert((struct commit *)o, &list);
 609                 ret = get_sha1_oneline(prefix, sha1, list);
 610                 free(prefix);
 611                 return ret;
 612         }
 613         return 0;
 614 }
 615
 616 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 617 {
 618         const char *cp;
 619
 620         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 621                 char ch = *cp;
 622                 if (hexval(ch) & ~0377) {
 623                         /* We must be looking at g in "SOMETHING-g"
 624                          * for it to be describe output.
 625                          */
 626                         if (ch == 'g' && cp[-1] == '-') {
 627                                 cp++;
 628                                 len -= cp - name;
 629                                 return get_short_sha1(cp, len, sha1, 1);
 630                         }
 631                 }
 632         }
 633         return -1;
 634 }
 635
 636 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 637 {
 638         int ret, has_suffix;
 639         const char *cp;
 640
 641         /*
 642          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 643          */
 644         has_suffix = 0;
 645         for (cp = name + len - 1; name <= cp; cp--) {
 646                 int ch = *cp;
 647                 if ('0' <= ch && ch <= '9')
 648                         continue;
 649                 if (ch == '~' || ch == '^')
 650                         has_suffix = ch;
 651                 break;
 652         }
 653
 654         if (has_suffix) {
 655                 int num = 0;
 656                 int len1 = cp - name;
 657                 cp++;
 658                 while (cp < name + len)
 659                         num = num * 10 + *cp++ - '0';
 660                 if (!num && len1 == len - 1)
 661                         num = 1;
 662                 if (has_suffix == '^')
 663                         return get_parent(name, len1, sha1, num);
 664                 /* else if (has_suffix == '~') -- goes without saying */
 665                 return get_nth_ancestor(name, len1, sha1, num);
 666         }
 667
 668         ret = peel_onion(name, len, sha1);
 669         if (!ret)
 670                 return 0;
 671
 672         ret = get_sha1_basic(name, len, sha1);
 673         if (!ret)
 674                 return 0;
 675
 676         /* It could be describe output that is "SOMETHING-gXXXX" */
 677         ret = get_describe_name(name, len, sha1);
 678         if (!ret)
 679                 return 0;
 680
 681         return get_short_sha1(name, len, sha1, 0);
 682 }
 683
 684 /*
 685  * This interprets names like ':/Initial revision of "git"' by searching
 686  * through history and returning the first commit whose message starts
 687  * the given regular expression.
 688  *
 689  * For future extension, ':/!' is reserved. If you want to match a message
 690  * beginning with a '!', you have to repeat the exclamation mark.
 691  */
 692 #define ONELINE_SEEN (1u<<20)
 693
 694 static int handle_one_ref(const char *path,
 695                 const unsigned char *sha1, int flag, void *cb_data)
 696 {
 697         struct commit_list **list = cb_data;
 698         struct object *object = parse_object(sha1);
 699         if (!object)
 700                 return 0;
 701         if (object->type == OBJ_TAG) {
 702                 object = deref_tag(object, path, strlen(path));
 703                 if (!object)
 704                         return 0;
 705         }
 706         if (object->type != OBJ_COMMIT)
 707                 return 0;
 708         commit_list_insert_by_date((struct commit *)object, list);
 709         return 0;
 710 }
 711
 712 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 713                             struct commit_list *list)
 714 {
 715         struct commit_list *backup = NULL, *l;
 716         int found = 0;
 717         regex_t regex;
 718
 719         if (prefix[0] == '!') {
 720                 if (prefix[1] != '!')
 721                         die ("Invalid search pattern: %s", prefix);
 722                 prefix++;
 723         }
 724
 725         if (regcomp(&regex, prefix, REG_EXTENDED))
 726                 die("Invalid search pattern: %s", prefix);
 727
 728         for (l = list; l; l = l->next) {
 729                 l->item->object.flags |= ONELINE_SEEN;
 730                 commit_list_insert(l->item, &backup);
 731         }
 732         while (list) {
 733                 char *p, *to_free = NULL;
 734                 struct commit *commit;
 735                 enum object_type type;
 736                 unsigned long size;
 737                 int matches;
 738
 739                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 740                 if (!parse_object(commit->object.sha1))
 741                         continue;
 742                 if (commit->buffer)
 743                         p = commit->buffer;
 744                 else {
 745                         p = read_sha1_file(commit->object.sha1, &type, &size);
 746                         if (!p)
 747                                 continue;
 748                         to_free = p;
 749                 }
 750
 751                 p = strstr(p, "\n\n");
 752                 matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
 753                 free(to_free);
 754
 755                 if (matches) {
 756                         hashcpy(sha1, commit->object.sha1);
 757                         found = 1;
 758                         break;
 759                 }
 760         }
 761         regfree(&regex);
 762         free_commit_list(list);
 763         for (l = backup; l; l = l->next)
 764                 clear_commit_marks(l->item, ONELINE_SEEN);
 765         free_commit_list(backup);
 766         return found ? 0 : -1;
 767 }
 768
 769 struct grab_nth_branch_switch_cbdata {
 770         long cnt, alloc;
 771         struct strbuf *buf;
 772 };
 773
 774 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 775                                   const char *email, unsigned long timestamp, int tz,
 776                                   const char *message, void *cb_data)
 777 {
 778         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 779         const char *match = NULL, *target = NULL;
 780         size_t len;
 781         int nth;
 782
 783         if (!prefixcmp(message, "checkout: moving from ")) {
 784                 match = message + strlen("checkout: moving from ");
 785                 target = strstr(match, " to ");
 786         }
 787
 788         if (!match || !target)
 789                 return 0;
 790
 791         len = target - match;
 792         nth = cb->cnt++ % cb->alloc;
 793         strbuf_reset(&cb->buf[nth]);
 794         strbuf_add(&cb->buf[nth], match, len);
 795         return 0;
 796 }
 797
 798 /*
 799  * Parse @{-N} syntax, return the number of characters parsed
 800  * if successful; otherwise signal an error with negative value.
 801  */
 802 static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
 803 {
 804         long nth;
 805         int i, retval;
 806         struct grab_nth_branch_switch_cbdata cb;
 807         const char *brace;
 808         char *num_end;
 809
 810         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 811                 return -1;
 812         brace = strchr(name, '}');
 813         if (!brace)
 814                 return -1;
 815         nth = strtol(name+3, &num_end, 10);
 816         if (num_end != brace)
 817                 return -1;
 818         if (nth <= 0)
 819                 return -1;
 820         cb.alloc = nth;
 821         cb.buf = xmalloc(nth * sizeof(struct strbuf));
 822         for (i = 0; i < nth; i++)
 823                 strbuf_init(&cb.buf[i], 20);
 824         cb.cnt = 0;
 825         retval = 0;
 826         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 827         if (cb.cnt < nth) {
 828                 cb.cnt = 0;
 829                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 830         }
 831         if (cb.cnt < nth)
 832                 goto release_return;
 833         i = cb.cnt % nth;
 834         strbuf_reset(buf);
 835         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 836         retval = brace-name+1;
 837
 838 release_return:
 839         for (i = 0; i < nth; i++)
 840                 strbuf_release(&cb.buf[i]);
 841         free(cb.buf);
 842
 843         return retval;
 844 }
 845
 846 int get_sha1_mb(const char *name, unsigned char *sha1)
 847 {
 848         struct commit *one, *two;
 849         struct commit_list *mbs;
 850         unsigned char sha1_tmp[20];
 851         const char *dots;
 852         int st;
 853
 854         dots = strstr(name, "...");
 855         if (!dots)
 856                 return get_sha1(name, sha1);
 857         if (dots == name)
 858                 st = get_sha1("HEAD", sha1_tmp);
 859         else {
 860                 struct strbuf sb;
 861                 strbuf_init(&sb, dots - name);
 862                 strbuf_add(&sb, name, dots - name);
 863                 st = get_sha1(sb.buf, sha1_tmp);
 864                 strbuf_release(&sb);
 865         }
 866         if (st)
 867                 return st;
 868         one = lookup_commit_reference_gently(sha1_tmp, 0);
 869         if (!one)
 870                 return -1;
 871
 872         if (get_sha1(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
 873                 return -1;
 874         two = lookup_commit_reference_gently(sha1_tmp, 0);
 875         if (!two)
 876                 return -1;
 877         mbs = get_merge_bases(one, two, 1);
 878         if (!mbs || mbs->next)
 879                 st = -1;
 880         else {
 881                 st = 0;
 882                 hashcpy(sha1, mbs->item->object.sha1);
 883         }
 884         free_commit_list(mbs);
 885         return st;
 886 }
 887
 888 /*
 889  * This reads short-hand syntax that not only evaluates to a commit
 890  * object name, but also can act as if the end user spelled the name
 891  * of the branch from the command line.
 892  *
 893  * - "@{-N}" finds the name of the Nth previous branch we were on, and
 894  *   places the name of the branch in the given buf and returns the
 895  *   number of characters parsed if successful.
 896  *
 897  * - "<branch>@{upstream}" finds the name of the other ref that
 898  *   <branch> is configured to merge with (missing <branch> defaults
 899  *   to the current branch), and places the name of the branch in the
 900  *   given buf and returns the number of characters parsed if
 901  *   successful.
 902  *
 903  * If the input is not of the accepted format, it returns a negative
 904  * number to signal an error.
 905  *
 906  * If the input was ok but there are not N branch switches in the
 907  * reflog, it returns 0.
 908  */
 909 int interpret_branch_name(const char *name, struct strbuf *buf)
 910 {
 911         char *cp;
 912         struct branch *upstream;
 913         int namelen = strlen(name);
 914         int len = interpret_nth_prior_checkout(name, buf);
 915         int tmp_len;
 916
 917         if (!len)
 918                 return len; /* syntax Ok, not enough switches */
 919         if (0 < len && len == namelen)
 920                 return len; /* consumed all */
 921         else if (0 < len) {
 922                 /* we have extra data, which might need further processing */
 923                 struct strbuf tmp = STRBUF_INIT;
 924                 int used = buf->len;
 925                 int ret;
 926
 927                 strbuf_add(buf, name + len, namelen - len);
 928                 ret = interpret_branch_name(buf->buf, &tmp);
 929                 /* that data was not interpreted, remove our cruft */
 930                 if (ret < 0) {
 931                         strbuf_setlen(buf, used);
 932                         return len;
 933                 }
 934                 strbuf_reset(buf);
 935                 strbuf_addbuf(buf, &tmp);
 936                 strbuf_release(&tmp);
 937                 /* tweak for size of {-N} versus expanded ref name */
 938                 return ret - used + len;
 939         }
 940
 941         cp = strchr(name, '@');
 942         if (!cp)
 943                 return -1;
 944         tmp_len = upstream_mark(cp, namelen - (cp - name));
 945         if (!tmp_len)
 946                 return -1;
 947         len = cp + tmp_len - name;
 948         cp = xstrndup(name, cp - name);
 949         upstream = branch_get(*cp ? cp : NULL);
 950         if (!upstream
 951             || !upstream->merge
 952             || !upstream->merge[0]->dst)
 953                 return error("No upstream branch found for '%s'", cp);
 954         free(cp);
 955         cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
 956         strbuf_reset(buf);
 957         strbuf_addstr(buf, cp);
 958         free(cp);
 959         return len;
 960 }
 961
 962 int strbuf_branchname(struct strbuf *sb, const char *name)
 963 {
 964         int len = strlen(name);
 965         if (interpret_branch_name(name, sb) == len)
 966                 return 0;
 967         strbuf_add(sb, name, len);
 968         return len;
 969 }
 970
 971 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
 972 {
 973         strbuf_branchname(sb, name);
 974         if (name[0] == '-')
 975                 return CHECK_REF_FORMAT_ERROR;
 976         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
 977         return check_ref_format(sb->buf);
 978 }
 979
 980 /*
 981  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 982  * notably "xyz^" for "parent of xyz"
 983  */
 984 int get_sha1(const char *name, unsigned char *sha1)
 985 {
 986         struct object_context unused;
 987         return get_sha1_with_context(name, sha1, &unused);
 988 }
 989
 990 /* Must be called only when object_name:filename doesn't exist. */
 991 static void diagnose_invalid_sha1_path(const char *prefix,
 992                                        const char *filename,
 993                                        const unsigned char *tree_sha1,
 994                                        const char *object_name)
 995 {
 996         struct stat st;
 997         unsigned char sha1[20];
 998         unsigned mode;
 999
1000         if (!prefix)
1001                 prefix = "";
1002
1003         if (!lstat(filename, &st))
1004                 die("Path '%s' exists on disk, but not in '%s'.",
1005                     filename, object_name);
1006         if (errno == ENOENT || errno == ENOTDIR) {
1007                 char *fullname = xmalloc(strlen(filename)
1008                                              + strlen(prefix) + 1);
1009                 strcpy(fullname, prefix);
1010                 strcat(fullname, filename);
1011
1012                 if (!get_tree_entry(tree_sha1, fullname,
1013                                     sha1, &mode)) {
1014                         die("Path '%s' exists, but not '%s'.\n"
1015                             "Did you mean '%s:%s'?",
1016                             fullname,
1017                             filename,
1018                             object_name,
1019                             fullname);
1020                 }
1021                 die("Path '%s' does not exist in '%s'",
1022                     filename, object_name);
1023         }
1024 }
1025
1026 /* Must be called only when :stage:filename doesn't exist. */
1027 static void diagnose_invalid_index_path(int stage,
1028                                         const char *prefix,
1029                                         const char *filename)
1030 {
1031         struct stat st;
1032         struct cache_entry *ce;
1033         int pos;
1034         unsigned namelen = strlen(filename);
1035         unsigned fullnamelen;
1036         char *fullname;
1037
1038         if (!prefix)
1039                 prefix = "";
1040
1041         /* Wrong stage number? */
1042         pos = cache_name_pos(filename, namelen);
1043         if (pos < 0)
1044                 pos = -pos - 1;
1045         if (pos < active_nr) {
1046                 ce = active_cache[pos];
1047                 if (ce_namelen(ce) == namelen &&
1048                     !memcmp(ce->name, filename, namelen))
1049                         die("Path '%s' is in the index, but not at stage %d.\n"
1050                             "Did you mean ':%d:%s'?",
1051                             filename, stage,
1052                             ce_stage(ce), filename);
1053         }
1054
1055         /* Confusion between relative and absolute filenames? */
1056         fullnamelen = namelen + strlen(prefix);
1057         fullname = xmalloc(fullnamelen + 1);
1058         strcpy(fullname, prefix);
1059         strcat(fullname, filename);
1060         pos = cache_name_pos(fullname, fullnamelen);
1061         if (pos < 0)
1062                 pos = -pos - 1;
1063         if (pos < active_nr) {
1064                 ce = active_cache[pos];
1065                 if (ce_namelen(ce) == fullnamelen &&
1066                     !memcmp(ce->name, fullname, fullnamelen))
1067                         die("Path '%s' is in the index, but not '%s'.\n"
1068                             "Did you mean ':%d:%s'?",
1069                             fullname, filename,
1070                             ce_stage(ce), fullname);
1071         }
1072
1073         if (!lstat(filename, &st))
1074                 die("Path '%s' exists on disk, but not in the index.", filename);
1075         if (errno == ENOENT || errno == ENOTDIR)
1076                 die("Path '%s' does not exist (neither on disk nor in the index).",
1077                     filename);
1078
1079         free(fullname);
1080 }
1081
1082
1083 int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int gently, const char *prefix)
1084 {
1085         struct object_context oc;
1086         int ret;
1087         ret = get_sha1_with_context_1(name, sha1, &oc, gently, prefix);
1088         *mode = oc.mode;
1089         return ret;
1090 }
1091
1092 static char *resolve_relative_path(const char *rel)
1093 {
1094         if (prefixcmp(rel, "./") && prefixcmp(rel, "../"))
1095                 return NULL;
1096
1097         if (!startup_info)
1098                 die("BUG: startup_info struct is not initialized.");
1099
1100         if (!is_inside_work_tree())
1101                 die("relative path syntax can't be used outside working tree.");
1102
1103         /* die() inside prefix_path() if resolved path is outside worktree */
1104         return prefix_path(startup_info->prefix,
1105                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1106                            rel);
1107 }
1108
1109 int get_sha1_with_context_1(const char *name, unsigned char *sha1,
1110                             struct object_context *oc,
1111                             int gently, const char *prefix)
1112 {
1113         int ret, bracket_depth;
1114         int namelen = strlen(name);
1115         const char *cp;
1116
1117         memset(oc, 0, sizeof(*oc));
1118         oc->mode = S_IFINVALID;
1119         ret = get_sha1_1(name, namelen, sha1);
1120         if (!ret)
1121                 return ret;
1122         /* sha1:path --> object name of path in ent sha1
1123          * :path -> object name of absolute path in index
1124          * :./path -> object name of path relative to cwd in index
1125          * :[0-3]:path -> object name of path in index at stage
1126          * :/foo -> recent commit matching foo
1127          */
1128         if (name[0] == ':') {
1129                 int stage = 0;
1130                 struct cache_entry *ce;
1131                 char *new_path = NULL;
1132                 int pos;
1133                 if (namelen > 2 && name[1] == '/') {
1134                         struct commit_list *list = NULL;
1135                         for_each_ref(handle_one_ref, &list);
1136                         return get_sha1_oneline(name + 2, sha1, list);
1137                 }
1138                 if (namelen < 3 ||
1139                     name[2] != ':' ||
1140                     name[1] < '0' || '3' < name[1])
1141                         cp = name + 1;
1142                 else {
1143                         stage = name[1] - '0';
1144                         cp = name + 3;
1145                 }
1146                 new_path = resolve_relative_path(cp);
1147                 if (!new_path) {
1148                         namelen = namelen - (cp - name);
1149                 } else {
1150                         cp = new_path;
1151                         namelen = strlen(cp);
1152                 }
1153
1154                 strncpy(oc->path, cp,
1155                         sizeof(oc->path));
1156                 oc->path[sizeof(oc->path)-1] = '\0';
1157
1158                 if (!active_cache)
1159                         read_cache();
1160                 pos = cache_name_pos(cp, namelen);
1161                 if (pos < 0)
1162                         pos = -pos - 1;
1163                 while (pos < active_nr) {
1164                         ce = active_cache[pos];
1165                         if (ce_namelen(ce) != namelen ||
1166                             memcmp(ce->name, cp, namelen))
1167                                 break;
1168                         if (ce_stage(ce) == stage) {
1169                                 hashcpy(sha1, ce->sha1);
1170                                 oc->mode = ce->ce_mode;
1171                                 free(new_path);
1172                                 return 0;
1173                         }
1174                         pos++;
1175                 }
1176                 if (!gently)
1177                         diagnose_invalid_index_path(stage, prefix, cp);
1178                 free(new_path);
1179                 return -1;
1180         }
1181         for (cp = name, bracket_depth = 0; *cp; cp++) {
1182                 if (*cp == '{')
1183                         bracket_depth++;
1184                 else if (bracket_depth && *cp == '}')
1185                         bracket_depth--;
1186                 else if (!bracket_depth && *cp == ':')
1187                         break;
1188         }
1189         if (*cp == ':') {
1190                 unsigned char tree_sha1[20];
1191                 char *object_name = NULL;
1192                 if (!gently) {
1193                         object_name = xmalloc(cp-name+1);
1194                         strncpy(object_name, name, cp-name);
1195                         object_name[cp-name] = '\0';
1196                 }
1197                 if (!get_sha1_1(name, cp-name, tree_sha1)) {
1198                         const char *filename = cp+1;
1199                         char *new_filename = NULL;
1200
1201                         new_filename = resolve_relative_path(filename);
1202                         if (new_filename)
1203                                 filename = new_filename;
1204                         ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
1205                         if (!gently) {
1206                                 diagnose_invalid_sha1_path(prefix, filename,
1207                                                            tree_sha1, object_name);
1208                                 free(object_name);
1209                         }
1210                         hashcpy(oc->tree, tree_sha1);
1211                         strncpy(oc->path, filename,
1212                                 sizeof(oc->path));
1213                         oc->path[sizeof(oc->path)-1] = '\0';
1214
1215                         free(new_filename);
1216                         return ret;
1217                 } else {
1218                         if (!gently)
1219                                 die("Invalid object name '%s'.", object_name);
1220                 }
1221         }
1222         return ret;
1223 }