git.oblomov.eu Git - git/blob - 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 typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
  13
  14 struct disambiguate_state {
  15         disambiguate_hint_fn fn;
  16         void *cb_data;
  17         unsigned char candidate[20];
  18         unsigned candidate_exists:1;
  19         unsigned candidate_checked:1;
  20         unsigned candidate_ok:1;
  21         unsigned disambiguate_fn_used:1;
  22         unsigned ambiguous:1;
  23         unsigned always_call_fn:1;
  24 };
  25
  26 static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
  27 {
  28         if (ds->always_call_fn) {
  29                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  30                 return;
  31         }
  32         if (!ds->candidate_exists) {
  33                 /* this is the first candidate */
  34                 hashcpy(ds->candidate, current);
  35                 ds->candidate_exists = 1;
  36                 return;
  37         } else if (!hashcmp(ds->candidate, current)) {
  38                 /* the same as what we already have seen */
  39                 return;
  40         }
  41
  42         if (!ds->fn) {
  43                 /* cannot disambiguate between ds->candidate and current */
  44                 ds->ambiguous = 1;
  45                 return;
  46         }
  47
  48         if (!ds->candidate_checked) {
  49                 ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
  50                 ds->disambiguate_fn_used = 1;
  51                 ds->candidate_checked = 1;
  52         }
  53
  54         if (!ds->candidate_ok) {
  55                 /* discard the candidate; we know it does not satisfy fn */
  56                 hashcpy(ds->candidate, current);
  57                 ds->candidate_checked = 0;
  58                 return;
  59         }
  60
  61         /* if we reach this point, we know ds->candidate satisfies fn */
  62         if (ds->fn(current, ds->cb_data)) {
  63                 /*
  64                  * if both current and candidate satisfy fn, we cannot
  65                  * disambiguate.
  66                  */
  67                 ds->candidate_ok = 0;
  68                 ds->ambiguous = 1;
  69         }
  70
  71         /* otherwise, current can be discarded and candidate is still good */
  72 }
  73
  74 static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
  75 {
  76         struct alternate_object_database *alt;
  77         char hex[40];
  78         static struct alternate_object_database *fakeent;
  79
  80         if (!fakeent) {
  81                 /*
  82                  * Create a "fake" alternate object database that
  83                  * points to our own object database, to make it
  84                  * easier to get a temporary working space in
  85                  * alt->name/alt->base while iterating over the
  86                  * object databases including our own.
  87                  */
  88                 const char *objdir = get_object_directory();
  89                 int objdir_len = strlen(objdir);
  90                 int entlen = objdir_len + 43;
  91                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  92                 memcpy(fakeent->base, objdir, objdir_len);
  93                 fakeent->name = fakeent->base + objdir_len + 1;
  94                 fakeent->name[-1] = '/';
  95         }
  96         fakeent->next = alt_odb_list;
  97
  98         sprintf(hex, "%.2s", hex_pfx);
  99         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 100                 struct dirent *de;
 101                 DIR *dir;
 102                 sprintf(alt->name, "%.2s/", hex_pfx);
 103                 dir = opendir(alt->base);
 104                 if (!dir)
 105                         continue;
 106
 107                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
 108                         unsigned char sha1[20];
 109
 110                         if (strlen(de->d_name) != 38)
 111                                 continue;
 112                         if (memcmp(de->d_name, hex_pfx + 2, len - 2))
 113                                 continue;
 114                         memcpy(hex + 2, de->d_name, 38);
 115                         if (!get_sha1_hex(hex, sha1))
 116                                 update_candidates(ds, sha1);
 117                 }
 118                 closedir(dir);
 119         }
 120 }
 121
 122 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 123 {
 124         do {
 125                 if (*a != *b)
 126                         return 0;
 127                 a++;
 128                 b++;
 129                 len -= 2;
 130         } while (len > 1);
 131         if (len)
 132                 if ((*a ^ *b) & 0xf0)
 133                         return 0;
 134         return 1;
 135 }
 136
 137 static void unique_in_pack(int len,
 138                           const unsigned char *bin_pfx,
 139                            struct packed_git *p,
 140                            struct disambiguate_state *ds)
 141 {
 142         uint32_t num, last, i, first = 0;
 143         const unsigned char *current = NULL;
 144
 145         open_pack_index(p);
 146         num = p->num_objects;
 147         last = num;
 148         while (first < last) {
 149                 uint32_t mid = (first + last) / 2;
 150                 const unsigned char *current;
 151                 int cmp;
 152
 153                 current = nth_packed_object_sha1(p, mid);
 154                 cmp = hashcmp(bin_pfx, current);
 155                 if (!cmp) {
 156                         first = mid;
 157                         break;
 158                 }
 159                 if (cmp > 0) {
 160                         first = mid+1;
 161                         continue;
 162                 }
 163                 last = mid;
 164         }
 165
 166         /*
 167          * At this point, "first" is the location of the lowest object
 168          * with an object name that could match "bin_pfx".  See if we have
 169          * 0, 1 or more objects that actually match(es).
 170          */
 171         for (i = first; i < num && !ds->ambiguous; i++) {
 172                 current = nth_packed_object_sha1(p, i);
 173                 if (!match_sha(len, bin_pfx, current))
 174                         break;
 175                 update_candidates(ds, current);
 176         }
 177 }
 178
 179 static void find_short_packed_object(int len, const unsigned char *bin_pfx,
 180                                      struct disambiguate_state *ds)
 181 {
 182         struct packed_git *p;
 183
 184         prepare_packed_git();
 185         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 186                 unique_in_pack(len, bin_pfx, p, ds);
 187 }
 188
 189 #define SHORT_NAME_NOT_FOUND (-1)
 190 #define SHORT_NAME_AMBIGUOUS (-2)
 191
 192 static int finish_object_disambiguation(struct disambiguate_state *ds,
 193                                         unsigned char *sha1)
 194 {
 195         if (ds->ambiguous)
 196                 return SHORT_NAME_AMBIGUOUS;
 197
 198         if (!ds->candidate_exists)
 199                 return SHORT_NAME_NOT_FOUND;
 200
 201         if (!ds->candidate_checked)
 202                 /*
 203                  * If this is the only candidate, there is no point
 204                  * calling the disambiguation hint callback.
 205                  *
 206                  * On the other hand, if the current candidate
 207                  * replaced an earlier candidate that did _not_ pass
 208                  * the disambiguation hint callback, then we do have
 209                  * more than one objects that match the short name
 210                  * given, so we should make sure this one matches;
 211                  * otherwise, if we discovered this one and the one
 212                  * that we previously discarded in the reverse order,
 213                  * we would end up showing different results in the
 214                  * same repository!
 215                  */
 216                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 217                                     ds->fn(ds->candidate, ds->cb_data));
 218
 219         if (!ds->candidate_ok)
 220                 return SHORT_NAME_AMBIGUOUS;
 221
 222         hashcpy(sha1, ds->candidate);
 223         return 0;
 224 }
 225
 226 static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
 227 {
 228         int kind = sha1_object_info(sha1, NULL);
 229         return kind == OBJ_COMMIT;
 230 }
 231
 232 static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
 233 {
 234         struct object *obj;
 235         int kind;
 236
 237         kind = sha1_object_info(sha1, NULL);
 238         if (kind == OBJ_COMMIT)
 239                 return 1;
 240         if (kind != OBJ_TAG)
 241                 return 0;
 242
 243         /* We need to do this the hard way... */
 244         obj = deref_tag(parse_object(sha1), NULL, 0);
 245         if (obj && obj->type == OBJ_COMMIT)
 246                 return 1;
 247         return 0;
 248 }
 249
 250 static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
 251 {
 252         int kind = sha1_object_info(sha1, NULL);
 253         return kind == OBJ_TREE;
 254 }
 255
 256 static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
 257 {
 258         struct object *obj;
 259         int kind;
 260
 261         kind = sha1_object_info(sha1, NULL);
 262         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 263                 return 1;
 264         if (kind != OBJ_TAG)
 265                 return 0;
 266
 267         /* We need to do this the hard way... */
 268         obj = deref_tag(lookup_object(sha1), NULL, 0);
 269         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 270                 return 1;
 271         return 0;
 272 }
 273
 274 static int disambiguate_blob_only(const unsigned char *sha1, void *cb_data_unused)
 275 {
 276         int kind = sha1_object_info(sha1, NULL);
 277         return kind == OBJ_BLOB;
 278 }
 279
 280 static int prepare_prefixes(const char *name, int len,
 281                             unsigned char *bin_pfx,
 282                             char *hex_pfx)
 283 {
 284         int i;
 285
 286         hashclr(bin_pfx);
 287         memset(hex_pfx, 'x', 40);
 288         for (i = 0; i < len ;i++) {
 289                 unsigned char c = name[i];
 290                 unsigned char val;
 291                 if (c >= '0' && c <= '9')
 292                         val = c - '0';
 293                 else if (c >= 'a' && c <= 'f')
 294                         val = c - 'a' + 10;
 295                 else if (c >= 'A' && c <='F') {
 296                         val = c - 'A' + 10;
 297                         c -= 'A' - 'a';
 298                 }
 299                 else
 300                         return -1;
 301                 hex_pfx[i] = c;
 302                 if (!(i & 1))
 303                         val <<= 4;
 304                 bin_pfx[i >> 1] |= val;
 305         }
 306         return 0;
 307 }
 308
 309 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 310                           unsigned flags)
 311 {
 312         int status;
 313         char hex_pfx[40];
 314         unsigned char bin_pfx[20];
 315         struct disambiguate_state ds;
 316         int quietly = !!(flags & GET_SHA1_QUIETLY);
 317
 318         if (len < MINIMUM_ABBREV || len > 40)
 319                 return -1;
 320         if (prepare_prefixes(name, len, bin_pfx, hex_pfx) < 0)
 321                 return -1;
 322
 323         prepare_alt_odb();
 324
 325         memset(&ds, 0, sizeof(ds));
 326         if (flags & GET_SHA1_COMMIT)
 327                 ds.fn = disambiguate_commit_only;
 328         else if (flags & GET_SHA1_COMMITTISH)
 329                 ds.fn = disambiguate_committish_only;
 330         else if (flags & GET_SHA1_TREE)
 331                 ds.fn = disambiguate_tree_only;
 332         else if (flags & GET_SHA1_TREEISH)
 333                 ds.fn = disambiguate_treeish_only;
 334         else if (flags & GET_SHA1_BLOB)
 335                 ds.fn = disambiguate_blob_only;
 336
 337         find_short_object_filename(len, hex_pfx, &ds);
 338         find_short_packed_object(len, bin_pfx, &ds);
 339         status = finish_object_disambiguation(&ds, sha1);
 340
 341         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 342                 return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
 343         return status;
 344 }
 345
 346 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 347 {
 348         char hex_pfx[40];
 349         unsigned char bin_pfx[20];
 350         struct disambiguate_state ds;
 351         int len = strlen(prefix);
 352
 353         if (len < MINIMUM_ABBREV || len > 40)
 354                 return -1;
 355         if (prepare_prefixes(prefix, len, bin_pfx, hex_pfx) < 0)
 356                 return -1;
 357
 358         prepare_alt_odb();
 359
 360         memset(&ds, 0, sizeof(ds));
 361         ds.always_call_fn = 1;
 362         ds.cb_data = cb_data;
 363         ds.fn = fn;
 364
 365         find_short_object_filename(len, hex_pfx, &ds);
 366         find_short_packed_object(len, bin_pfx, &ds);
 367         return ds.ambiguous;
 368 }
 369
 370 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 371 {
 372         int status, exists;
 373         static char hex[41];
 374
 375         exists = has_sha1_file(sha1);
 376         memcpy(hex, sha1_to_hex(sha1), 40);
 377         if (len == 40 || !len)
 378                 return hex;
 379         while (len < 40) {
 380                 unsigned char sha1_ret[20];
 381                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
 382                 if (exists
 383                     ? !status
 384                     : status == SHORT_NAME_NOT_FOUND) {
 385                         hex[len] = 0;
 386                         return hex;
 387                 }
 388                 len++;
 389         }
 390         return hex;
 391 }
 392
 393 static int ambiguous_path(const char *path, int len)
 394 {
 395         int slash = 1;
 396         int cnt;
 397
 398         for (cnt = 0; cnt < len; cnt++) {
 399                 switch (*path++) {
 400                 case '\0':
 401                         break;
 402                 case '/':
 403                         if (slash)
 404                                 break;
 405                         slash = 1;
 406                         continue;
 407                 case '.':
 408                         continue;
 409                 default:
 410                         slash = 0;
 411                         continue;
 412                 }
 413                 break;
 414         }
 415         return slash;
 416 }
 417
 418 static inline int upstream_mark(const char *string, int len)
 419 {
 420         const char *suffix[] = { "@{upstream}", "@{u}" };
 421         int i;
 422
 423         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 424                 int suffix_len = strlen(suffix[i]);
 425                 if (suffix_len <= len
 426                     && !memcmp(string, suffix[i], suffix_len))
 427                         return suffix_len;
 428         }
 429         return 0;
 430 }
 431
 432 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 433
 434 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 435 {
 436         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 437         static const char *object_name_msg = N_(
 438         "Git normally never creates a ref that ends with 40 hex characters\n"
 439         "because it will be ignored when you just specify 40-hex. These refs\n"
 440         "may be created by mistake. For example,\n"
 441         "\n"
 442         "  git checkout -b $br $(git rev-parse ...)\n"
 443         "\n"
 444         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 445         "examine these refs and maybe delete them. Turn this message off by\n"
 446         "running \"git config advice.objectNameWarning false\"");
 447         unsigned char tmp_sha1[20];
 448         char *real_ref = NULL;
 449         int refs_found = 0;
 450         int at, reflog_len, nth_prior = 0;
 451
 452         if (len == 40 && !get_sha1_hex(str, sha1)) {
 453                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 454                         refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
 455                         if (refs_found > 0) {
 456                                 warning(warn_msg, len, str);
 457                                 if (advice_object_name_warning)
 458                                         fprintf(stderr, "%s\n", _(object_name_msg));
 459                         }
 460                         free(real_ref);
 461                 }
 462                 return 0;
 463         }
 464
 465         /* basic@{time or number or -number} format to query ref-log */
 466         reflog_len = at = 0;
 467         if (len && str[len-1] == '}') {
 468                 for (at = len-4; at >= 0; at--) {
 469                         if (str[at] == '@' && str[at+1] == '{') {
 470                                 if (str[at+2] == '-') {
 471                                         if (at != 0)
 472                                                 /* @{-N} not at start */
 473                                                 return -1;
 474                                         nth_prior = 1;
 475                                         continue;
 476                                 }
 477                                 if (!upstream_mark(str + at, len - at)) {
 478                                         reflog_len = (len-1) - (at+2);
 479                                         len = at;
 480                                 }
 481                                 break;
 482                         }
 483                 }
 484         }
 485
 486         /* Accept only unambiguous ref paths. */
 487         if (len && ambiguous_path(str, len))
 488                 return -1;
 489
 490         if (nth_prior) {
 491                 struct strbuf buf = STRBUF_INIT;
 492                 int detached;
 493
 494                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
 495                         detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
 496                         strbuf_release(&buf);
 497                         if (detached)
 498                                 return 0;
 499                 }
 500         }
 501
 502         if (!len && reflog_len)
 503                 /* allow "@{...}" to mean the current branch reflog */
 504                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 505         else if (reflog_len)
 506                 refs_found = dwim_log(str, len, sha1, &real_ref);
 507         else
 508                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 509
 510         if (!refs_found)
 511                 return -1;
 512
 513         if (warn_ambiguous_refs &&
 514             (refs_found > 1 ||
 515              !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
 516                 warning(warn_msg, len, str);
 517
 518         if (reflog_len) {
 519                 int nth, i;
 520                 unsigned long at_time;
 521                 unsigned long co_time;
 522                 int co_tz, co_cnt;
 523
 524                 /* Is it asking for N-th entry, or approxidate? */
 525                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 526                         char ch = str[at+2+i];
 527                         if ('0' <= ch && ch <= '9')
 528                                 nth = nth * 10 + ch - '0';
 529                         else
 530                                 nth = -1;
 531                 }
 532                 if (100000000 <= nth) {
 533                         at_time = nth;
 534                         nth = -1;
 535                 } else if (0 <= nth)
 536                         at_time = 0;
 537                 else {
 538                         int errors = 0;
 539                         char *tmp = xstrndup(str + at + 2, reflog_len);
 540                         at_time = approxidate_careful(tmp, &errors);
 541                         free(tmp);
 542                         if (errors)
 543                                 return -1;
 544                 }
 545                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 546                                 &co_time, &co_tz, &co_cnt)) {
 547                         if (!len) {
 548                                 if (starts_with(real_ref, "refs/heads/")) {
 549                                         str = real_ref + 11;
 550                                         len = strlen(real_ref + 11);
 551                                 } else {
 552                                         /* detached HEAD */
 553                                         str = "HEAD";
 554                                         len = 4;
 555                                 }
 556                         }
 557                         if (at_time)
 558                                 warning("Log for '%.*s' only goes "
 559                                         "back to %s.", len, str,
 560                                         show_date(co_time, co_tz, DATE_RFC2822));
 561                         else {
 562                                 die("Log for '%.*s' only has %d entries.",
 563                                     len, str, co_cnt);
 564                         }
 565                 }
 566         }
 567
 568         free(real_ref);
 569         return 0;
 570 }
 571
 572 static int get_parent(unsigned char *sha1, int idx)
 573 {
 574         struct commit *commit;
 575         struct commit_list *p;
 576
 577         commit = lookup_commit_reference(sha1);
 578         if (parse_commit(commit))
 579                 return -1;
 580         if (!idx) {
 581                 hashcpy(sha1, commit->object.sha1);
 582                 return 0;
 583         }
 584         p = commit->parents;
 585         while (p) {
 586                 if (!--idx) {
 587                         hashcpy(sha1, p->item->object.sha1);
 588                         return 0;
 589                 }
 590                 p = p->next;
 591         }
 592         return -1;
 593 }
 594
 595 static int get_nth_ancestor(unsigned char *sha1, int generation)
 596 {
 597         struct commit *commit;
 598
 599         commit = lookup_commit_reference(sha1);
 600         if (!commit)
 601                 return -1;
 602
 603         while (generation--) {
 604                 if (parse_commit(commit) || !commit->parents)
 605                         return -1;
 606                 commit = commit->parents->item;
 607         }
 608         hashcpy(sha1, commit->object.sha1);
 609         return 0;
 610 }
 611
 612 struct object *peel_to_type(const char *name, int namelen,
 613                             struct object *o, enum object_type expected_type)
 614 {
 615         if (name && !namelen)
 616                 namelen = strlen(name);
 617         while (1) {
 618                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 619                         return NULL;
 620                 if (expected_type == OBJ_ANY || o->type == expected_type)
 621                         return o;
 622                 if (o->type == OBJ_TAG)
 623                         o = ((struct tag*) o)->tagged;
 624                 else if (o->type == OBJ_COMMIT)
 625                         o = &(((struct commit *) o)->tree->object);
 626                 else {
 627                         if (name)
 628                                 error("%.*s: expected %s type, but the object "
 629                                       "dereferences to %s type",
 630                                       namelen, name, typename(expected_type),
 631                                       typename(o->type));
 632                         return NULL;
 633                 }
 634         }
 635 }
 636
 637 static int peel_onion(const char *name, const char *str, int len, unsigned char *sha1)
 638 {
 639         const char *sp, *end = NULL;
 640         unsigned int expected_type = 0;
 641         struct object *o;
 642
 643         /*
 644          * "ref^{type}" dereferences ref repeatedly until you cannot
 645          * dereference anymore, or you get an object of given type,
 646          * whichever comes first.  "ref^{}" means just dereference
 647          * tags until you get a non-tag.  "ref^0" is a shorthand for
 648          * "ref^{commit}".  "commit^{tree}" could be used to find the
 649          * top-level tree of the given commit.
 650          */
 651
 652         if (len < 3)
 653                 return 0;
 654
 655         sp = str;
 656         if (sp[0] != '^' || sp[1] != '{')
 657                 return 0;
 658
 659         for (end = sp; *end; end++)
 660                 if (*end == '}')
 661                         break;
 662         if (!end)
 663                 return 0;
 664
 665         end++;
 666         len = end - str;
 667
 668         sp += 2;
 669         if (!starts_with(sp, "commit}"))
 670                 expected_type = OBJ_COMMIT;
 671         else if (starts_with(sp, "tag}"))
 672                 expected_type = OBJ_TAG;
 673         else if (starts_with(sp, "tree}"))
 674                 expected_type = OBJ_TREE;
 675         else if (starts_with(sp, "blob}"))
 676                 expected_type = OBJ_BLOB;
 677         else if (starts_with(sp, "object}"))
 678                 expected_type = OBJ_ANY;
 679         else if (sp[0] == '}')
 680                 expected_type = OBJ_NONE;
 681         else if (sp[0] == '/')
 682                 expected_type = OBJ_COMMIT;
 683         else
 684                 return -1;
 685
 686         o = parse_object(sha1);
 687         if (!o)
 688                 return -1;
 689         if (!expected_type) {
 690                 o = deref_tag(o, name, end - name);
 691                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 692                         return -1;
 693                 hashcpy(sha1, o->sha1);
 694                 return len;
 695         }
 696
 697         /*
 698          * At this point, the syntax looks correct, so
 699          * if we do not get the needed object, we should
 700          * barf.
 701          */
 702         o = peel_to_type(name, end - name, o, expected_type);
 703         if (!o)
 704                 return -1;
 705
 706         hashcpy(sha1, o->sha1);
 707
 708         if (sp[0] == '/') {
 709                 /* "$commit^{/foo}" */
 710                 char *prefix;
 711                 int ret;
 712                 struct commit_list *list = NULL;
 713
 714                 /*
 715                  * $commit^{/}. Some regex implementation may reject.
 716                  * We don't need regex anyway. '' pattern always matches.
 717                  */
 718                 if (sp[1] == '}')
 719                         return len;
 720
 721                 prefix = xstrndup(sp + 1, end - sp - 2);
 722                 commit_list_insert((struct commit *)o, &list);
 723                 ret = get_sha1_oneline(prefix, sha1, list);
 724                 free(prefix);
 725                 if (ret)
 726                         return -1;
 727         }
 728         return len;
 729 }
 730
 731 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 732 {
 733         const char *cp;
 734         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 735
 736         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 737                 char ch = *cp;
 738                 if (hexval(ch) & ~0377) {
 739                         /* We must be looking at g in "SOMETHING-g"
 740                          * for it to be describe output.
 741                          */
 742                         if (ch == 'g' && cp[-1] == '-') {
 743                                 cp++;
 744                                 len -= cp - name;
 745                                 return get_short_sha1(cp, len, sha1, flags);
 746                         }
 747                 }
 748         }
 749         return -1;
 750 }
 751
 752 /*
 753  * This interprets names like ':/Initial revision of "git"' by searching
 754  * through history and returning the first commit whose message starts
 755  * the given regular expression.
 756  *
 757  * For future extension, ':/!' is reserved. If you want to match a message
 758  * beginning with a '!', you have to repeat the exclamation mark.
 759  */
 760 #define ONELINE_SEEN (1u<<20)
 761
 762 static int handle_one_ref(const char *path,
 763                 const unsigned char *sha1, int flag, void *cb_data)
 764 {
 765         struct commit_list **list = cb_data;
 766         struct object *object = parse_object(sha1);
 767         if (!object)
 768                 return 0;
 769         if (object->type == OBJ_TAG) {
 770                 object = deref_tag(object, path, strlen(path));
 771                 if (!object)
 772                         return 0;
 773         }
 774         if (object->type != OBJ_COMMIT)
 775                 return 0;
 776         commit_list_insert_by_date((struct commit *)object, list);
 777         return 0;
 778 }
 779
 780 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 781                             struct commit_list *list)
 782 {
 783         struct commit_list *backup = NULL, *l;
 784         int found = 0;
 785         regex_t regex;
 786
 787         if (prefix[0] == '!') {
 788                 if (prefix[1] != '!')
 789                         die ("Invalid search pattern: %s", prefix);
 790                 prefix++;
 791         }
 792
 793         if (regcomp(&regex, prefix, REG_EXTENDED))
 794                 die("Invalid search pattern: %s", prefix);
 795
 796         for (l = list; l; l = l->next) {
 797                 l->item->object.flags |= ONELINE_SEEN;
 798                 commit_list_insert(l->item, &backup);
 799         }
 800         while (list) {
 801                 char *p, *to_free = NULL;
 802                 struct commit *commit;
 803                 enum object_type type;
 804                 unsigned long size;
 805                 int matches;
 806
 807                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 808                 if (!parse_object(commit->object.sha1))
 809                         continue;
 810                 if (commit->buffer)
 811                         p = commit->buffer;
 812                 else {
 813                         p = read_sha1_file(commit->object.sha1, &type, &size);
 814                         if (!p)
 815                                 continue;
 816                         to_free = p;
 817                 }
 818
 819                 p = strstr(p, "\n\n");
 820                 matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
 821                 free(to_free);
 822
 823                 if (matches) {
 824                         hashcpy(sha1, commit->object.sha1);
 825                         found = 1;
 826                         break;
 827                 }
 828         }
 829         regfree(&regex);
 830         free_commit_list(list);
 831         for (l = backup; l; l = l->next)
 832                 clear_commit_marks(l->item, ONELINE_SEEN);
 833         free_commit_list(backup);
 834         return found ? 0 : -1;
 835 }
 836
 837 struct grab_nth_branch_switch_cbdata {
 838         int remaining;
 839         struct strbuf buf;
 840 };
 841
 842 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 843                                   const char *email, unsigned long timestamp, int tz,
 844                                   const char *message, void *cb_data)
 845 {
 846         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 847         const char *match = NULL, *target = NULL;
 848         size_t len;
 849
 850         if (starts_with(message, "checkout: moving from ")) {
 851                 match = message + strlen("checkout: moving from ");
 852                 target = strstr(match, " to ");
 853         }
 854
 855         if (!match || !target)
 856                 return 0;
 857         if (--(cb->remaining) == 0) {
 858                 len = target - match;
 859                 strbuf_reset(&cb->buf);
 860                 strbuf_add(&cb->buf, match, len);
 861                 return 1; /* we are done */
 862         }
 863         return 0;
 864 }
 865
 866 /*
 867  * Parse @{-N} syntax, return the number of characters parsed
 868  * if successful; otherwise signal an error with negative value.
 869  */
 870 static int interpret_nth_prior_checkout(const char *name, int namelen,
 871                                         struct strbuf *buf)
 872 {
 873         long nth;
 874         int retval;
 875         struct grab_nth_branch_switch_cbdata cb;
 876         const char *brace;
 877         char *num_end;
 878
 879         if (namelen < 4)
 880                 return -1;
 881         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 882                 return -1;
 883         brace = memchr(name, '}', namelen);
 884         if (!brace)
 885                 return -1;
 886         nth = strtol(name + 3, &num_end, 10);
 887         if (num_end != brace)
 888                 return -1;
 889         if (nth <= 0)
 890                 return -1;
 891         cb.remaining = nth;
 892         strbuf_init(&cb.buf, 20);
 893
 894         retval = 0;
 895         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
 896                 strbuf_reset(buf);
 897                 strbuf_add(buf, cb.buf.buf, cb.buf.len);
 898                 retval = brace - name + 1;
 899         }
 900
 901         strbuf_release(&cb.buf);
 902         return retval;
 903 }
 904
 905 int get_sha1_mb(const char *name, unsigned char *sha1)
 906 {
 907         struct commit *one, *two;
 908         struct commit_list *mbs;
 909         unsigned char sha1_tmp[20];
 910         const char *dots;
 911         int st;
 912
 913         dots = strstr(name, "...");
 914         if (!dots)
 915                 return get_sha1(name, sha1);
 916         if (dots == name)
 917                 st = get_sha1("HEAD", sha1_tmp);
 918         else {
 919                 struct strbuf sb;
 920                 strbuf_init(&sb, dots - name);
 921                 strbuf_add(&sb, name, dots - name);
 922                 st = get_sha1_committish(sb.buf, sha1_tmp);
 923                 strbuf_release(&sb);
 924         }
 925         if (st)
 926                 return st;
 927         one = lookup_commit_reference_gently(sha1_tmp, 0);
 928         if (!one)
 929                 return -1;
 930
 931         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
 932                 return -1;
 933         two = lookup_commit_reference_gently(sha1_tmp, 0);
 934         if (!two)
 935                 return -1;
 936         mbs = get_merge_bases(one, two, 1);
 937         if (!mbs || mbs->next)
 938                 st = -1;
 939         else {
 940                 st = 0;
 941                 hashcpy(sha1, mbs->item->object.sha1);
 942         }
 943         free_commit_list(mbs);
 944         return st;
 945 }
 946
 947 /* parse @something syntax, when 'something' is not {.*} */
 948 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
 949 {
 950         const char *next;
 951
 952         if (len || name[1] == '{')
 953                 return -1;
 954
 955         /* make sure it's a single @, or @@{.*}, not @foo */
 956         next = memchr(name + len + 1, '@', namelen - len - 1);
 957         if (next && next[1] != '{')
 958                 return -1;
 959         if (!next)
 960                 next = name + namelen;
 961         if (next != name + 1)
 962                 return -1;
 963
 964         strbuf_reset(buf);
 965         strbuf_add(buf, "HEAD", 4);
 966         return 1;
 967 }
 968
 969 static int reinterpret(const char *name, int namelen, int len, struct strbuf *buf)
 970 {
 971         /* we have extra data, which might need further processing */
 972         struct strbuf tmp = STRBUF_INIT;
 973         int used = buf->len;
 974         int ret;
 975
 976         strbuf_add(buf, name + len, namelen - len);
 977         ret = interpret_branch_name(buf->buf, buf->len, &tmp);
 978         /* that data was not interpreted, remove our cruft */
 979         if (ret < 0) {
 980                 strbuf_setlen(buf, used);
 981                 return len;
 982         }
 983         strbuf_reset(buf);
 984         strbuf_addbuf(buf, &tmp);
 985         strbuf_release(&tmp);
 986         /* tweak for size of {-N} versus expanded ref name */
 987         return ret - used + len;
 988 }
 989
 990 static void set_shortened_ref(struct strbuf *buf, const char *ref)
 991 {
 992         char *s = shorten_unambiguous_ref(ref, 0);
 993         strbuf_reset(buf);
 994         strbuf_addstr(buf, s);
 995         free(s);
 996 }
 997
 998 static const char *get_upstream_branch(const char *branch_buf, int len)
 999 {
1000         char *branch = xstrndup(branch_buf, len);
1001         struct branch *upstream = branch_get(*branch ? branch : NULL);
1002
1003         /*
1004          * Upstream can be NULL only if branch refers to HEAD and HEAD
1005          * points to something different than a branch.
1006          */
1007         if (!upstream)
1008                 die(_("HEAD does not point to a branch"));
1009         if (!upstream->merge || !upstream->merge[0]->dst) {
1010                 if (!ref_exists(upstream->refname))
1011                         die(_("No such branch: '%s'"), branch);
1012                 if (!upstream->merge) {
1013                         die(_("No upstream configured for branch '%s'"),
1014                                 upstream->name);
1015                 }
1016                 die(
1017                         _("Upstream branch '%s' not stored as a remote-tracking branch"),
1018                         upstream->merge[0]->src);
1019         }
1020         free(branch);
1021
1022         return upstream->merge[0]->dst;
1023 }
1024
1025 static int interpret_upstream_mark(const char *name, int namelen,
1026                                    int at, struct strbuf *buf)
1027 {
1028         int len;
1029
1030         len = upstream_mark(name + at, namelen - at);
1031         if (!len)
1032                 return -1;
1033
1034         if (memchr(name, ':', at))
1035                 return -1;
1036
1037         set_shortened_ref(buf, get_upstream_branch(name, at));
1038         return len + at;
1039 }
1040
1041 /*
1042  * This reads short-hand syntax that not only evaluates to a commit
1043  * object name, but also can act as if the end user spelled the name
1044  * of the branch from the command line.
1045  *
1046  * - "@{-N}" finds the name of the Nth previous branch we were on, and
1047  *   places the name of the branch in the given buf and returns the
1048  *   number of characters parsed if successful.
1049  *
1050  * - "<branch>@{upstream}" finds the name of the other ref that
1051  *   <branch> is configured to merge with (missing <branch> defaults
1052  *   to the current branch), and places the name of the branch in the
1053  *   given buf and returns the number of characters parsed if
1054  *   successful.
1055  *
1056  * If the input is not of the accepted format, it returns a negative
1057  * number to signal an error.
1058  *
1059  * If the input was ok but there are not N branch switches in the
1060  * reflog, it returns 0.
1061  */
1062 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
1063 {
1064         char *at;
1065         const char *start;
1066         int len = interpret_nth_prior_checkout(name, namelen, buf);
1067
1068         if (!namelen)
1069                 namelen = strlen(name);
1070
1071         if (!len) {
1072                 return len; /* syntax Ok, not enough switches */
1073         } else if (len > 0) {
1074                 if (len == namelen)
1075                         return len; /* consumed all */
1076                 else
1077                         return reinterpret(name, namelen, len, buf);
1078         }
1079
1080         for (start = name;
1081              (at = memchr(start, '@', namelen - (start - name)));
1082              start = at + 1) {
1083
1084                 len = interpret_empty_at(name, namelen, at - name, buf);
1085                 if (len > 0)
1086                         return reinterpret(name, namelen, len, buf);
1087
1088                 len = interpret_upstream_mark(name, namelen, at - name, buf);
1089                 if (len > 0)
1090                         return len;
1091         }
1092
1093         return -1;
1094 }
1095
1096 int strbuf_branchname(struct strbuf *sb, const char *name)
1097 {
1098         int len = strlen(name);
1099         int used = interpret_branch_name(name, len, sb);
1100
1101         if (used == len)
1102                 return 0;
1103         if (used < 0)
1104                 used = 0;
1105         strbuf_add(sb, name + used, len - used);
1106         return len;
1107 }
1108
1109 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1110 {
1111         strbuf_branchname(sb, name);
1112         if (name[0] == '-')
1113                 return -1;
1114         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1115         return check_refname_format(sb->buf, 0);
1116 }
1117
1118 /*
1119  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1120  * notably "xyz^" for "parent of xyz"
1121  */
1122 int get_sha1(const char *name, unsigned char *sha1)
1123 {
1124         struct object_context unused;
1125         return get_sha1_with_context(name, 0, sha1, &unused);
1126 }
1127
1128 /*
1129  * Many callers know that the user meant to name a commit-ish by
1130  * syntactical positions where the object name appears.  Calling this
1131  * function allows the machinery to disambiguate shorter-than-unique
1132  * abbreviated object names between commit-ish and others.
1133  *
1134  * Note that this does NOT error out when the named object is not a
1135  * commit-ish. It is merely to give a hint to the disambiguation
1136  * machinery.
1137  */
1138 int get_sha1_committish(const char *name, unsigned char *sha1)
1139 {
1140         struct object_context unused;
1141         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1142                                      sha1, &unused);
1143 }
1144
1145 int get_sha1_treeish(const char *name, unsigned char *sha1)
1146 {
1147         struct object_context unused;
1148         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1149                                      sha1, &unused);
1150 }
1151
1152 int get_sha1_commit(const char *name, unsigned char *sha1)
1153 {
1154         struct object_context unused;
1155         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1156                                      sha1, &unused);
1157 }
1158
1159 int get_sha1_tree(const char *name, unsigned char *sha1)
1160 {
1161         struct object_context unused;
1162         return get_sha1_with_context(name, GET_SHA1_TREE,
1163                                      sha1, &unused);
1164 }
1165
1166 int get_sha1_blob(const char *name, unsigned char *sha1)
1167 {
1168         struct object_context unused;
1169         return get_sha1_with_context(name, GET_SHA1_BLOB,
1170                                      sha1, &unused);
1171 }
1172
1173 /* Must be called only when object_name:filename doesn't exist. */
1174 static void diagnose_invalid_sha1_path(const char *prefix,
1175                                        const char *filename,
1176                                        const unsigned char *tree_sha1,
1177                                        const char *object_name,
1178                                        int object_name_len)
1179 {
1180         struct stat st;
1181         unsigned char sha1[20];
1182         unsigned mode;
1183
1184         if (!prefix)
1185                 prefix = "";
1186
1187         if (!lstat(filename, &st))
1188                 die("Path '%s' exists on disk, but not in '%.*s'.",
1189                     filename, object_name_len, object_name);
1190         if (errno == ENOENT || errno == ENOTDIR) {
1191                 char *fullname = xmalloc(strlen(filename)
1192                                              + strlen(prefix) + 1);
1193                 strcpy(fullname, prefix);
1194                 strcat(fullname, filename);
1195
1196                 if (!get_tree_entry(tree_sha1, fullname,
1197                                     sha1, &mode)) {
1198                         die("Path '%s' exists, but not '%s'.\n"
1199                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1200                             fullname,
1201                             filename,
1202                             object_name_len, object_name,
1203                             fullname,
1204                             object_name_len, object_name,
1205                             filename);
1206                 }
1207                 die("Path '%s' does not exist in '%.*s'",
1208                     filename, object_name_len, object_name);
1209         }
1210 }
1211
1212 /* Must be called only when :stage:filename doesn't exist. */
1213 static void diagnose_invalid_index_path(int stage,
1214                                         const char *prefix,
1215                                         const char *filename)
1216 {
1217         struct stat st;
1218         const struct cache_entry *ce;
1219         int pos;
1220         unsigned namelen = strlen(filename);
1221         unsigned fullnamelen;
1222         char *fullname;
1223
1224         if (!prefix)
1225                 prefix = "";
1226
1227         /* Wrong stage number? */
1228         pos = cache_name_pos(filename, namelen);
1229         if (pos < 0)
1230                 pos = -pos - 1;
1231         if (pos < active_nr) {
1232                 ce = active_cache[pos];
1233                 if (ce_namelen(ce) == namelen &&
1234                     !memcmp(ce->name, filename, namelen))
1235                         die("Path '%s' is in the index, but not at stage %d.\n"
1236                             "Did you mean ':%d:%s'?",
1237                             filename, stage,
1238                             ce_stage(ce), filename);
1239         }
1240
1241         /* Confusion between relative and absolute filenames? */
1242         fullnamelen = namelen + strlen(prefix);
1243         fullname = xmalloc(fullnamelen + 1);
1244         strcpy(fullname, prefix);
1245         strcat(fullname, filename);
1246         pos = cache_name_pos(fullname, fullnamelen);
1247         if (pos < 0)
1248                 pos = -pos - 1;
1249         if (pos < active_nr) {
1250                 ce = active_cache[pos];
1251                 if (ce_namelen(ce) == fullnamelen &&
1252                     !memcmp(ce->name, fullname, fullnamelen))
1253                         die("Path '%s' is in the index, but not '%s'.\n"
1254                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1255                             fullname, filename,
1256                             ce_stage(ce), fullname,
1257                             ce_stage(ce), filename);
1258         }
1259
1260         if (!lstat(filename, &st))
1261                 die("Path '%s' exists on disk, but not in the index.", filename);
1262         if (errno == ENOENT || errno == ENOTDIR)
1263                 die("Path '%s' does not exist (neither on disk nor in the index).",
1264                     filename);
1265
1266         free(fullname);
1267 }
1268
1269
1270 static char *resolve_relative_path(const char *rel)
1271 {
1272         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1273                 return NULL;
1274
1275         if (!startup_info)
1276                 die("BUG: startup_info struct is not initialized.");
1277
1278         if (!is_inside_work_tree())
1279                 die("relative path syntax can't be used outside working tree.");
1280
1281         /* die() inside prefix_path() if resolved path is outside worktree */
1282         return prefix_path(startup_info->prefix,
1283                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1284                            rel);
1285 }
1286
1287 static int resolve_ancestry(const char *str, int len, unsigned char *sha1)
1288 {
1289         int has_suffix;
1290         const char *cp, *end;
1291         int num = 0, ret;
1292
1293         /*
1294          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
1295          */
1296         has_suffix = 0;
1297         for (cp = str; *cp; cp++) {
1298                 int ch = *cp;
1299                 if ('0' <= ch && ch <= '9')
1300                         continue;
1301                 if (ch == '~' || ch == '^') {
1302                         if (has_suffix)
1303                                 break;
1304                         has_suffix = ch;
1305                         continue;
1306                 }
1307                 break;
1308         }
1309
1310         if (!has_suffix)
1311                 return 0;
1312
1313         end = cp;
1314         cp = str + 1;
1315         if (cp == end)
1316                 num = 1;
1317         else
1318                 while (cp < end)
1319                         num = num * 10 + *cp++ - '0';
1320         len = end - str;
1321         if (has_suffix == '^')
1322                 ret = get_parent(sha1, num);
1323         else
1324                 ret = get_nth_ancestor(sha1, num);
1325         if (ret)
1326                 return ret;
1327         return len;
1328 }
1329
1330 static int resolve_tree(struct object_context *oc, const char *str, int len,
1331                 unsigned char *sha1, unsigned char *tree_sha1)
1332 {
1333         int ret;
1334         const char *filename = str + 1;
1335         char *new_filename = NULL;
1336
1337         new_filename = resolve_relative_path(filename);
1338         if (new_filename)
1339                 filename = new_filename;
1340         hashcpy(tree_sha1, sha1);
1341         ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
1342         hashcpy(oc->tree, tree_sha1);
1343         strncpy(oc->path, filename, sizeof(oc->path));
1344         oc->path[sizeof(oc->path) - 1] = '\0';
1345
1346         free(new_filename);
1347         return ret;
1348 }
1349
1350 static int resolve(const char *name, int len, unsigned char *sha1,
1351                 struct object_context *oc, const char *prefix, unsigned flags)
1352 {
1353         const char *cp;
1354         int ret;
1355         int tmp_len;
1356         int bracket_depth;
1357         unsigned char tree_sha1[20];
1358         unsigned lookup_flags = flags;
1359
1360         for (cp = name, bracket_depth = 0; *cp; cp++) {
1361                 if (*cp == '{')
1362                         bracket_depth++;
1363                 else if (bracket_depth && *cp == '}')
1364                         bracket_depth--;
1365                 else if (!bracket_depth) {
1366                         if (*cp == '^') {
1367                                 if (cp[1] == '{') {
1368                                         const char *sp = cp + 2;
1369                                         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
1370                                                 lookup_flags = GET_SHA1_COMMITTISH;
1371                                         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
1372                                                 lookup_flags = GET_SHA1_TREEISH;
1373                                         else if (sp[0] == '/')
1374                                                 lookup_flags = GET_SHA1_COMMITTISH;
1375                                         else
1376                                                 lookup_flags = 0;
1377                                 } else {
1378                                         lookup_flags = GET_SHA1_COMMITTISH;
1379                                 }
1380                                 break;
1381                         }
1382                         if (*cp == '~') {
1383                                 lookup_flags = GET_SHA1_COMMITTISH;
1384                                 break;
1385                         }
1386                         if (*cp == ':') {
1387                                 lookup_flags = GET_SHA1_TREEISH;
1388                                 break;
1389                         }
1390                 }
1391         }
1392
1393         tmp_len = cp - name;
1394         ret = get_sha1_basic(name, tmp_len, sha1);
1395         if (!ret)
1396                 goto next;
1397         ret = get_short_sha1(name, tmp_len, sha1, lookup_flags);
1398         if (!ret)
1399                 goto next;
1400         ret = get_describe_name(name, tmp_len, sha1);
1401         if (!ret)
1402                 goto next;
1403
1404         return -1;
1405
1406 next:
1407         if (!*cp)
1408                 return 0;
1409         while (*cp == '^' || *cp == '~') {
1410                 ret = peel_onion(name, cp, len - (cp - name), sha1);
1411                 if (ret < 0)
1412                         return ret;
1413                 cp += ret;
1414                 ret = resolve_ancestry(cp, len - (cp - name), sha1);
1415                 if (ret < 0)
1416                         return ret;
1417                 cp += ret;
1418         }
1419         if (!*cp)
1420                 return 0;
1421         if (*cp != ':')
1422                 /* malformed */
1423                 return -1;
1424         ret = resolve_tree(oc, cp, len - (cp - name), sha1, tree_sha1);
1425         if (ret < 0) {
1426                 if (flags & GET_SHA1_ONLY_TO_DIE) {
1427                         diagnose_invalid_sha1_path(prefix, oc->path,
1428                                                    tree_sha1,
1429                                                    name, cp - name);
1430                 }
1431                 return ret;
1432         }
1433         return 0;
1434 }
1435
1436 static int get_sha1_with_context_1(const char *name,
1437                                    unsigned flags,
1438                                    const char *prefix,
1439                                    unsigned char *sha1,
1440                                    struct object_context *oc)
1441 {
1442         int namelen = strlen(name);
1443         const char *cp;
1444         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1445
1446         memset(oc, 0, sizeof(*oc));
1447         oc->mode = S_IFINVALID;
1448
1449         /*
1450          * sha1:path --> object name of path in ent sha1
1451          * :path -> object name of absolute path in index
1452          * :./path -> object name of path relative to cwd in index
1453          * :[0-3]:path -> object name of path in index at stage
1454          * :/foo -> recent commit matching foo
1455          */
1456         if (name[0] == ':') {
1457                 int stage = 0;
1458                 const struct cache_entry *ce;
1459                 char *new_path = NULL;
1460                 int pos;
1461                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1462                         struct commit_list *list = NULL;
1463                         for_each_ref(handle_one_ref, &list);
1464                         return get_sha1_oneline(name + 2, sha1, list);
1465                 }
1466                 if (namelen < 3 ||
1467                     name[2] != ':' ||
1468                     name[1] < '0' || '3' < name[1])
1469                         cp = name + 1;
1470                 else {
1471                         stage = name[1] - '0';
1472                         cp = name + 3;
1473                 }
1474                 new_path = resolve_relative_path(cp);
1475                 if (!new_path) {
1476                         namelen = namelen - (cp - name);
1477                 } else {
1478                         cp = new_path;
1479                         namelen = strlen(cp);
1480                 }
1481
1482                 strncpy(oc->path, cp,
1483                         sizeof(oc->path));
1484                 oc->path[sizeof(oc->path)-1] = '\0';
1485
1486                 if (!active_cache)
1487                         read_cache();
1488                 pos = cache_name_pos(cp, namelen);
1489                 if (pos < 0)
1490                         pos = -pos - 1;
1491                 while (pos < active_nr) {
1492                         ce = active_cache[pos];
1493                         if (ce_namelen(ce) != namelen ||
1494                             memcmp(ce->name, cp, namelen))
1495                                 break;
1496                         if (ce_stage(ce) == stage) {
1497                                 hashcpy(sha1, ce->sha1);
1498                                 oc->mode = ce->ce_mode;
1499                                 free(new_path);
1500                                 return 0;
1501                         }
1502                         pos++;
1503                 }
1504                 if (only_to_die && name[1] && name[1] != '/')
1505                         diagnose_invalid_index_path(stage, prefix, cp);
1506                 free(new_path);
1507                 return -1;
1508         }
1509
1510         return resolve(name, namelen, sha1, oc, prefix, flags);
1511 }
1512
1513 /*
1514  * Call this function when you know "name" given by the end user must
1515  * name an object but it doesn't; the function _may_ die with a better
1516  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1517  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1518  * you have a chance to diagnose the error further.
1519  */
1520 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1521 {
1522         struct object_context oc;
1523         unsigned char sha1[20];
1524         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1525 }
1526
1527 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
1528 {
1529         return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
1530 }