git.oblomov.eu Git - git/blob - sha1_name.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "tag.h"
   4 #include "commit.h"
   5 #include "tree.h"
   6 #include "blob.h"
   7 #include "tree-walk.h"
   8 #include "refs.h"
   9 #include "remote.h"
  10 #include "dir.h"
  11 #include "sha1-array.h"
  12 #include "packfile.h"
  13
  14 static int get_oid_oneline(const char *, struct object_id *, struct commit_list *);
  15
  16 typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
  17
  18 struct disambiguate_state {
  19         int len; /* length of prefix in hex chars */
  20         char hex_pfx[GIT_MAX_HEXSZ + 1];
  21         struct object_id bin_pfx;
  22
  23         disambiguate_hint_fn fn;
  24         void *cb_data;
  25         struct object_id candidate;
  26         unsigned candidate_exists:1;
  27         unsigned candidate_checked:1;
  28         unsigned candidate_ok:1;
  29         unsigned disambiguate_fn_used:1;
  30         unsigned ambiguous:1;
  31         unsigned always_call_fn:1;
  32 };
  33
  34 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
  35 {
  36         if (ds->always_call_fn) {
  37                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  38                 return;
  39         }
  40         if (!ds->candidate_exists) {
  41                 /* this is the first candidate */
  42                 oidcpy(&ds->candidate, current);
  43                 ds->candidate_exists = 1;
  44                 return;
  45         } else if (!oidcmp(&ds->candidate, current)) {
  46                 /* the same as what we already have seen */
  47                 return;
  48         }
  49
  50         if (!ds->fn) {
  51                 /* cannot disambiguate between ds->candidate and current */
  52                 ds->ambiguous = 1;
  53                 return;
  54         }
  55
  56         if (!ds->candidate_checked) {
  57                 ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
  58                 ds->disambiguate_fn_used = 1;
  59                 ds->candidate_checked = 1;
  60         }
  61
  62         if (!ds->candidate_ok) {
  63                 /* discard the candidate; we know it does not satisfy fn */
  64                 oidcpy(&ds->candidate, current);
  65                 ds->candidate_checked = 0;
  66                 return;
  67         }
  68
  69         /* if we reach this point, we know ds->candidate satisfies fn */
  70         if (ds->fn(current, ds->cb_data)) {
  71                 /*
  72                  * if both current and candidate satisfy fn, we cannot
  73                  * disambiguate.
  74                  */
  75                 ds->candidate_ok = 0;
  76                 ds->ambiguous = 1;
  77         }
  78
  79         /* otherwise, current can be discarded and candidate is still good */
  80 }
  81
  82 static int append_loose_object(const struct object_id *oid, const char *path,
  83                                void *data)
  84 {
  85         oid_array_append(data, oid);
  86         return 0;
  87 }
  88
  89 static int match_sha(unsigned, const unsigned char *, const unsigned char *);
  90
  91 static void find_short_object_filename(struct disambiguate_state *ds)
  92 {
  93         int subdir_nr = ds->bin_pfx.hash[0];
  94         struct alternate_object_database *alt;
  95         static struct alternate_object_database *fakeent;
  96
  97         if (!fakeent) {
  98                 /*
  99                  * Create a "fake" alternate object database that
 100                  * points to our own object database, to make it
 101                  * easier to get a temporary working space in
 102                  * alt->name/alt->base while iterating over the
 103                  * object databases including our own.
 104                  */
 105                 fakeent = alloc_alt_odb(get_object_directory());
 106         }
 107         fakeent->next = alt_odb_list;
 108
 109         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 110                 int pos;
 111
 112                 if (!alt->loose_objects_subdir_seen[subdir_nr]) {
 113                         struct strbuf *buf = alt_scratch_buf(alt);
 114                         for_each_file_in_obj_subdir(subdir_nr, buf,
 115                                                     append_loose_object,
 116                                                     NULL, NULL,
 117                                                     &alt->loose_objects_cache);
 118                         alt->loose_objects_subdir_seen[subdir_nr] = 1;
 119                 }
 120
 121                 pos = oid_array_lookup(&alt->loose_objects_cache, &ds->bin_pfx);
 122                 if (pos < 0)
 123                         pos = -1 - pos;
 124                 while (!ds->ambiguous && pos < alt->loose_objects_cache.nr) {
 125                         const struct object_id *oid;
 126                         oid = alt->loose_objects_cache.oid + pos;
 127                         if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
 128                                 break;
 129                         update_candidates(ds, oid);
 130                         pos++;
 131                 }
 132         }
 133 }
 134
 135 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 136 {
 137         do {
 138                 if (*a != *b)
 139                         return 0;
 140                 a++;
 141                 b++;
 142                 len -= 2;
 143         } while (len > 1);
 144         if (len)
 145                 if ((*a ^ *b) & 0xf0)
 146                         return 0;
 147         return 1;
 148 }
 149
 150 static void unique_in_pack(struct packed_git *p,
 151                            struct disambiguate_state *ds)
 152 {
 153         uint32_t num, last, i, first = 0;
 154         const struct object_id *current = NULL;
 155
 156         if (open_pack_index(p) || !p->num_objects)
 157                 return;
 158
 159         num = p->num_objects;
 160         last = num;
 161         while (first < last) {
 162                 uint32_t mid = first + (last - first) / 2;
 163                 const unsigned char *current;
 164                 int cmp;
 165
 166                 current = nth_packed_object_sha1(p, mid);
 167                 cmp = hashcmp(ds->bin_pfx.hash, current);
 168                 if (!cmp) {
 169                         first = mid;
 170                         break;
 171                 }
 172                 if (cmp > 0) {
 173                         first = mid+1;
 174                         continue;
 175                 }
 176                 last = mid;
 177         }
 178
 179         /*
 180          * At this point, "first" is the location of the lowest object
 181          * with an object name that could match "bin_pfx".  See if we have
 182          * 0, 1 or more objects that actually match(es).
 183          */
 184         for (i = first; i < num && !ds->ambiguous; i++) {
 185                 struct object_id oid;
 186                 current = nth_packed_object_oid(&oid, p, i);
 187                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
 188                         break;
 189                 update_candidates(ds, current);
 190         }
 191 }
 192
 193 static void find_short_packed_object(struct disambiguate_state *ds)
 194 {
 195         struct packed_git *p;
 196
 197         prepare_packed_git();
 198         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 199                 unique_in_pack(p, ds);
 200 }
 201
 202 #define SHORT_NAME_NOT_FOUND (-1)
 203 #define SHORT_NAME_AMBIGUOUS (-2)
 204
 205 static int finish_object_disambiguation(struct disambiguate_state *ds,
 206                                         struct object_id *oid)
 207 {
 208         if (ds->ambiguous)
 209                 return SHORT_NAME_AMBIGUOUS;
 210
 211         if (!ds->candidate_exists)
 212                 return SHORT_NAME_NOT_FOUND;
 213
 214         if (!ds->candidate_checked)
 215                 /*
 216                  * If this is the only candidate, there is no point
 217                  * calling the disambiguation hint callback.
 218                  *
 219                  * On the other hand, if the current candidate
 220                  * replaced an earlier candidate that did _not_ pass
 221                  * the disambiguation hint callback, then we do have
 222                  * more than one objects that match the short name
 223                  * given, so we should make sure this one matches;
 224                  * otherwise, if we discovered this one and the one
 225                  * that we previously discarded in the reverse order,
 226                  * we would end up showing different results in the
 227                  * same repository!
 228                  */
 229                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 230                                     ds->fn(&ds->candidate, ds->cb_data));
 231
 232         if (!ds->candidate_ok)
 233                 return SHORT_NAME_AMBIGUOUS;
 234
 235         oidcpy(oid, &ds->candidate);
 236         return 0;
 237 }
 238
 239 static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
 240 {
 241         int kind = sha1_object_info(oid->hash, NULL);
 242         return kind == OBJ_COMMIT;
 243 }
 244
 245 static int disambiguate_committish_only(const struct object_id *oid, void *cb_data_unused)
 246 {
 247         struct object *obj;
 248         int kind;
 249
 250         kind = sha1_object_info(oid->hash, NULL);
 251         if (kind == OBJ_COMMIT)
 252                 return 1;
 253         if (kind != OBJ_TAG)
 254                 return 0;
 255
 256         /* We need to do this the hard way... */
 257         obj = deref_tag(parse_object(oid), NULL, 0);
 258         if (obj && obj->type == OBJ_COMMIT)
 259                 return 1;
 260         return 0;
 261 }
 262
 263 static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
 264 {
 265         int kind = sha1_object_info(oid->hash, NULL);
 266         return kind == OBJ_TREE;
 267 }
 268
 269 static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
 270 {
 271         struct object *obj;
 272         int kind;
 273
 274         kind = sha1_object_info(oid->hash, NULL);
 275         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 276                 return 1;
 277         if (kind != OBJ_TAG)
 278                 return 0;
 279
 280         /* We need to do this the hard way... */
 281         obj = deref_tag(parse_object(oid), NULL, 0);
 282         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 283                 return 1;
 284         return 0;
 285 }
 286
 287 static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
 288 {
 289         int kind = sha1_object_info(oid->hash, NULL);
 290         return kind == OBJ_BLOB;
 291 }
 292
 293 static disambiguate_hint_fn default_disambiguate_hint;
 294
 295 int set_disambiguate_hint_config(const char *var, const char *value)
 296 {
 297         static const struct {
 298                 const char *name;
 299                 disambiguate_hint_fn fn;
 300         } hints[] = {
 301                 { "none", NULL },
 302                 { "commit", disambiguate_commit_only },
 303                 { "committish", disambiguate_committish_only },
 304                 { "tree", disambiguate_tree_only },
 305                 { "treeish", disambiguate_treeish_only },
 306                 { "blob", disambiguate_blob_only }
 307         };
 308         int i;
 309
 310         if (!value)
 311                 return config_error_nonbool(var);
 312
 313         for (i = 0; i < ARRAY_SIZE(hints); i++) {
 314                 if (!strcasecmp(value, hints[i].name)) {
 315                         default_disambiguate_hint = hints[i].fn;
 316                         return 0;
 317                 }
 318         }
 319
 320         return error("unknown hint type for '%s': %s", var, value);
 321 }
 322
 323 static int init_object_disambiguation(const char *name, int len,
 324                                       struct disambiguate_state *ds)
 325 {
 326         int i;
 327
 328         if (len < MINIMUM_ABBREV || len > GIT_SHA1_HEXSZ)
 329                 return -1;
 330
 331         memset(ds, 0, sizeof(*ds));
 332
 333         for (i = 0; i < len ;i++) {
 334                 unsigned char c = name[i];
 335                 unsigned char val;
 336                 if (c >= '0' && c <= '9')
 337                         val = c - '0';
 338                 else if (c >= 'a' && c <= 'f')
 339                         val = c - 'a' + 10;
 340                 else if (c >= 'A' && c <='F') {
 341                         val = c - 'A' + 10;
 342                         c -= 'A' - 'a';
 343                 }
 344                 else
 345                         return -1;
 346                 ds->hex_pfx[i] = c;
 347                 if (!(i & 1))
 348                         val <<= 4;
 349                 ds->bin_pfx.hash[i >> 1] |= val;
 350         }
 351
 352         ds->len = len;
 353         ds->hex_pfx[len] = '\0';
 354         prepare_alt_odb();
 355         return 0;
 356 }
 357
 358 static int show_ambiguous_object(const struct object_id *oid, void *data)
 359 {
 360         const struct disambiguate_state *ds = data;
 361         struct strbuf desc = STRBUF_INIT;
 362         int type;
 363
 364
 365         if (ds->fn && !ds->fn(oid, ds->cb_data))
 366                 return 0;
 367
 368         type = sha1_object_info(oid->hash, NULL);
 369         if (type == OBJ_COMMIT) {
 370                 struct commit *commit = lookup_commit(oid);
 371                 if (commit) {
 372                         struct pretty_print_context pp = {0};
 373                         pp.date_mode.type = DATE_SHORT;
 374                         format_commit_message(commit, " %ad - %s", &desc, &pp);
 375                 }
 376         } else if (type == OBJ_TAG) {
 377                 struct tag *tag = lookup_tag(oid);
 378                 if (!parse_tag(tag) && tag->tag)
 379                         strbuf_addf(&desc, " %s", tag->tag);
 380         }
 381
 382         advise("  %s %s%s",
 383                find_unique_abbrev(oid->hash, DEFAULT_ABBREV),
 384                typename(type) ? typename(type) : "unknown type",
 385                desc.buf);
 386
 387         strbuf_release(&desc);
 388         return 0;
 389 }
 390
 391 static int get_short_oid(const char *name, int len, struct object_id *oid,
 392                           unsigned flags)
 393 {
 394         int status;
 395         struct disambiguate_state ds;
 396         int quietly = !!(flags & GET_OID_QUIETLY);
 397
 398         if (init_object_disambiguation(name, len, &ds) < 0)
 399                 return -1;
 400
 401         if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
 402                 die("BUG: multiple get_short_oid disambiguator flags");
 403
 404         if (flags & GET_OID_COMMIT)
 405                 ds.fn = disambiguate_commit_only;
 406         else if (flags & GET_OID_COMMITTISH)
 407                 ds.fn = disambiguate_committish_only;
 408         else if (flags & GET_OID_TREE)
 409                 ds.fn = disambiguate_tree_only;
 410         else if (flags & GET_OID_TREEISH)
 411                 ds.fn = disambiguate_treeish_only;
 412         else if (flags & GET_OID_BLOB)
 413                 ds.fn = disambiguate_blob_only;
 414         else
 415                 ds.fn = default_disambiguate_hint;
 416
 417         find_short_object_filename(&ds);
 418         find_short_packed_object(&ds);
 419         status = finish_object_disambiguation(&ds, oid);
 420
 421         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
 422                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
 423
 424                 /*
 425                  * We may still have ambiguity if we simply saw a series of
 426                  * candidates that did not satisfy our hint function. In
 427                  * that case, we still want to show them, so disable the hint
 428                  * function entirely.
 429                  */
 430                 if (!ds.ambiguous)
 431                         ds.fn = NULL;
 432
 433                 advise(_("The candidates are:"));
 434                 for_each_abbrev(ds.hex_pfx, show_ambiguous_object, &ds);
 435         }
 436
 437         return status;
 438 }
 439
 440 static int collect_ambiguous(const struct object_id *oid, void *data)
 441 {
 442         oid_array_append(data, oid);
 443         return 0;
 444 }
 445
 446 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 447 {
 448         struct oid_array collect = OID_ARRAY_INIT;
 449         struct disambiguate_state ds;
 450         int ret;
 451
 452         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
 453                 return -1;
 454
 455         ds.always_call_fn = 1;
 456         ds.fn = collect_ambiguous;
 457         ds.cb_data = &collect;
 458         find_short_object_filename(&ds);
 459         find_short_packed_object(&ds);
 460
 461         ret = oid_array_for_each_unique(&collect, fn, cb_data);
 462         oid_array_clear(&collect);
 463         return ret;
 464 }
 465
 466 /*
 467  * Return the slot of the most-significant bit set in "val". There are various
 468  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 469  * probably not a big deal here.
 470  */
 471 static unsigned msb(unsigned long val)
 472 {
 473         unsigned r = 0;
 474         while (val >>= 1)
 475                 r++;
 476         return r;
 477 }
 478
 479 struct min_abbrev_data {
 480         unsigned int init_len;
 481         unsigned int cur_len;
 482         char *hex;
 483         const unsigned char *hash;
 484 };
 485
 486 static inline char get_hex_char_from_oid(const struct object_id *oid,
 487                                          unsigned int pos)
 488 {
 489         static const char hex[] = "0123456789abcdef";
 490
 491         if ((pos & 1) == 0)
 492                 return hex[oid->hash[pos >> 1] >> 4];
 493         else
 494                 return hex[oid->hash[pos >> 1] & 0xf];
 495 }
 496
 497 static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
 498 {
 499         struct min_abbrev_data *mad = cb_data;
 500
 501         unsigned int i = mad->init_len;
 502         while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
 503                 i++;
 504
 505         if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
 506                 mad->cur_len = i + 1;
 507
 508         return 0;
 509 }
 510
 511 static void find_abbrev_len_for_pack(struct packed_git *p,
 512                                      struct min_abbrev_data *mad)
 513 {
 514         int match = 0;
 515         uint32_t num, last, first = 0;
 516         struct object_id oid;
 517
 518         if (open_pack_index(p) || !p->num_objects)
 519                 return;
 520
 521         num = p->num_objects;
 522         last = num;
 523         while (first < last) {
 524                 uint32_t mid = first + (last - first) / 2;
 525                 const unsigned char *current;
 526                 int cmp;
 527
 528                 current = nth_packed_object_sha1(p, mid);
 529                 cmp = hashcmp(mad->hash, current);
 530                 if (!cmp) {
 531                         match = 1;
 532                         first = mid;
 533                         break;
 534                 }
 535                 if (cmp > 0) {
 536                         first = mid + 1;
 537                         continue;
 538                 }
 539                 last = mid;
 540         }
 541
 542         /*
 543          * first is now the position in the packfile where we would insert
 544          * mad->hash if it does not exist (or the position of mad->hash if
 545          * it does exist). Hence, we consider a maximum of three objects
 546          * nearby for the abbreviation length.
 547          */
 548         mad->init_len = 0;
 549         if (!match) {
 550                 nth_packed_object_oid(&oid, p, first);
 551                 extend_abbrev_len(&oid, mad);
 552         } else if (first < num - 1) {
 553                 nth_packed_object_oid(&oid, p, first + 1);
 554                 extend_abbrev_len(&oid, mad);
 555         }
 556         if (first > 0) {
 557                 nth_packed_object_oid(&oid, p, first - 1);
 558                 extend_abbrev_len(&oid, mad);
 559         }
 560         mad->init_len = mad->cur_len;
 561 }
 562
 563 static void find_abbrev_len_packed(struct min_abbrev_data *mad)
 564 {
 565         struct packed_git *p;
 566
 567         prepare_packed_git();
 568         for (p = packed_git; p; p = p->next)
 569                 find_abbrev_len_for_pack(p, mad);
 570 }
 571
 572 int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
 573 {
 574         struct disambiguate_state ds;
 575         struct min_abbrev_data mad;
 576         struct object_id oid_ret;
 577         if (len < 0) {
 578                 unsigned long count = approximate_object_count();
 579                 /*
 580                  * Add one because the MSB only tells us the highest bit set,
 581                  * not including the value of all the _other_ bits (so "15"
 582                  * is only one off of 2^4, but the MSB is the 3rd bit.
 583                  */
 584                 len = msb(count) + 1;
 585                 /*
 586                  * We now know we have on the order of 2^len objects, which
 587                  * expects a collision at 2^(len/2). But we also care about hex
 588                  * chars, not bits, and there are 4 bits per hex. So all
 589                  * together we need to divide by 2 and round up.
 590                  */
 591                 len = DIV_ROUND_UP(len, 2);
 592                 /*
 593                  * For very small repos, we stick with our regular fallback.
 594                  */
 595                 if (len < FALLBACK_DEFAULT_ABBREV)
 596                         len = FALLBACK_DEFAULT_ABBREV;
 597         }
 598
 599         sha1_to_hex_r(hex, sha1);
 600         if (len == GIT_SHA1_HEXSZ || !len)
 601                 return GIT_SHA1_HEXSZ;
 602
 603         mad.init_len = len;
 604         mad.cur_len = len;
 605         mad.hex = hex;
 606         mad.hash = sha1;
 607
 608         find_abbrev_len_packed(&mad);
 609
 610         if (init_object_disambiguation(hex, mad.cur_len, &ds) < 0)
 611                 return -1;
 612
 613         ds.fn = extend_abbrev_len;
 614         ds.always_call_fn = 1;
 615         ds.cb_data = (void *)&mad;
 616
 617         find_short_object_filename(&ds);
 618         (void)finish_object_disambiguation(&ds, &oid_ret);
 619
 620         hex[mad.cur_len] = 0;
 621         return mad.cur_len;
 622 }
 623
 624 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 625 {
 626         static int bufno;
 627         static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
 628         char *hex = hexbuffer[bufno];
 629         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
 630         find_unique_abbrev_r(hex, sha1, len);
 631         return hex;
 632 }
 633
 634 static int ambiguous_path(const char *path, int len)
 635 {
 636         int slash = 1;
 637         int cnt;
 638
 639         for (cnt = 0; cnt < len; cnt++) {
 640                 switch (*path++) {
 641                 case '\0':
 642                         break;
 643                 case '/':
 644                         if (slash)
 645                                 break;
 646                         slash = 1;
 647                         continue;
 648                 case '.':
 649                         continue;
 650                 default:
 651                         slash = 0;
 652                         continue;
 653                 }
 654                 break;
 655         }
 656         return slash;
 657 }
 658
 659 static inline int at_mark(const char *string, int len,
 660                           const char **suffix, int nr)
 661 {
 662         int i;
 663
 664         for (i = 0; i < nr; i++) {
 665                 int suffix_len = strlen(suffix[i]);
 666                 if (suffix_len <= len
 667                     && !strncasecmp(string, suffix[i], suffix_len))
 668                         return suffix_len;
 669         }
 670         return 0;
 671 }
 672
 673 static inline int upstream_mark(const char *string, int len)
 674 {
 675         const char *suffix[] = { "@{upstream}", "@{u}" };
 676         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 677 }
 678
 679 static inline int push_mark(const char *string, int len)
 680 {
 681         const char *suffix[] = { "@{push}" };
 682         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 683 }
 684
 685 static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
 686 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 687
 688 static int get_oid_basic(const char *str, int len, struct object_id *oid,
 689                           unsigned int flags)
 690 {
 691         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 692         static const char *object_name_msg = N_(
 693         "Git normally never creates a ref that ends with 40 hex characters\n"
 694         "because it will be ignored when you just specify 40-hex. These refs\n"
 695         "may be created by mistake. For example,\n"
 696         "\n"
 697         "  git checkout -b $br $(git rev-parse ...)\n"
 698         "\n"
 699         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 700         "examine these refs and maybe delete them. Turn this message off by\n"
 701         "running \"git config advice.objectNameWarning false\"");
 702         struct object_id tmp_oid;
 703         char *real_ref = NULL;
 704         int refs_found = 0;
 705         int at, reflog_len, nth_prior = 0;
 706
 707         if (len == GIT_SHA1_HEXSZ && !get_oid_hex(str, oid)) {
 708                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 709                         refs_found = dwim_ref(str, len, &tmp_oid, &real_ref);
 710                         if (refs_found > 0) {
 711                                 warning(warn_msg, len, str);
 712                                 if (advice_object_name_warning)
 713                                         fprintf(stderr, "%s\n", _(object_name_msg));
 714                         }
 715                         free(real_ref);
 716                 }
 717                 return 0;
 718         }
 719
 720         /* basic@{time or number or -number} format to query ref-log */
 721         reflog_len = at = 0;
 722         if (len && str[len-1] == '}') {
 723                 for (at = len-4; at >= 0; at--) {
 724                         if (str[at] == '@' && str[at+1] == '{') {
 725                                 if (str[at+2] == '-') {
 726                                         if (at != 0)
 727                                                 /* @{-N} not at start */
 728                                                 return -1;
 729                                         nth_prior = 1;
 730                                         continue;
 731                                 }
 732                                 if (!upstream_mark(str + at, len - at) &&
 733                                     !push_mark(str + at, len - at)) {
 734                                         reflog_len = (len-1) - (at+2);
 735                                         len = at;
 736                                 }
 737                                 break;
 738                         }
 739                 }
 740         }
 741
 742         /* Accept only unambiguous ref paths. */
 743         if (len && ambiguous_path(str, len))
 744                 return -1;
 745
 746         if (nth_prior) {
 747                 struct strbuf buf = STRBUF_INIT;
 748                 int detached;
 749
 750                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
 751                         detached = (buf.len == GIT_SHA1_HEXSZ && !get_oid_hex(buf.buf, oid));
 752                         strbuf_release(&buf);
 753                         if (detached)
 754                                 return 0;
 755                 }
 756         }
 757
 758         if (!len && reflog_len)
 759                 /* allow "@{...}" to mean the current branch reflog */
 760                 refs_found = dwim_ref("HEAD", 4, oid, &real_ref);
 761         else if (reflog_len)
 762                 refs_found = dwim_log(str, len, oid, &real_ref);
 763         else
 764                 refs_found = dwim_ref(str, len, oid, &real_ref);
 765
 766         if (!refs_found)
 767                 return -1;
 768
 769         if (warn_ambiguous_refs && !(flags & GET_OID_QUIETLY) &&
 770             (refs_found > 1 ||
 771              !get_short_oid(str, len, &tmp_oid, GET_OID_QUIETLY)))
 772                 warning(warn_msg, len, str);
 773
 774         if (reflog_len) {
 775                 int nth, i;
 776                 timestamp_t at_time;
 777                 timestamp_t co_time;
 778                 int co_tz, co_cnt;
 779
 780                 /* Is it asking for N-th entry, or approxidate? */
 781                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 782                         char ch = str[at+2+i];
 783                         if ('0' <= ch && ch <= '9')
 784                                 nth = nth * 10 + ch - '0';
 785                         else
 786                                 nth = -1;
 787                 }
 788                 if (100000000 <= nth) {
 789                         at_time = nth;
 790                         nth = -1;
 791                 } else if (0 <= nth)
 792                         at_time = 0;
 793                 else {
 794                         int errors = 0;
 795                         char *tmp = xstrndup(str + at + 2, reflog_len);
 796                         at_time = approxidate_careful(tmp, &errors);
 797                         free(tmp);
 798                         if (errors) {
 799                                 free(real_ref);
 800                                 return -1;
 801                         }
 802                 }
 803                 if (read_ref_at(real_ref, flags, at_time, nth, oid, NULL,
 804                                 &co_time, &co_tz, &co_cnt)) {
 805                         if (!len) {
 806                                 if (starts_with(real_ref, "refs/heads/")) {
 807                                         str = real_ref + 11;
 808                                         len = strlen(real_ref + 11);
 809                                 } else {
 810                                         /* detached HEAD */
 811                                         str = "HEAD";
 812                                         len = 4;
 813                                 }
 814                         }
 815                         if (at_time) {
 816                                 if (!(flags & GET_OID_QUIETLY)) {
 817                                         warning("Log for '%.*s' only goes "
 818                                                 "back to %s.", len, str,
 819                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
 820                                 }
 821                         } else {
 822                                 if (flags & GET_OID_QUIETLY) {
 823                                         exit(128);
 824                                 }
 825                                 die("Log for '%.*s' only has %d entries.",
 826                                     len, str, co_cnt);
 827                         }
 828                 }
 829         }
 830
 831         free(real_ref);
 832         return 0;
 833 }
 834
 835 static int get_parent(const char *name, int len,
 836                       struct object_id *result, int idx)
 837 {
 838         struct object_id oid;
 839         int ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
 840         struct commit *commit;
 841         struct commit_list *p;
 842
 843         if (ret)
 844                 return ret;
 845         commit = lookup_commit_reference(&oid);
 846         if (parse_commit(commit))
 847                 return -1;
 848         if (!idx) {
 849                 oidcpy(result, &commit->object.oid);
 850                 return 0;
 851         }
 852         p = commit->parents;
 853         while (p) {
 854                 if (!--idx) {
 855                         oidcpy(result, &p->item->object.oid);
 856                         return 0;
 857                 }
 858                 p = p->next;
 859         }
 860         return -1;
 861 }
 862
 863 static int get_nth_ancestor(const char *name, int len,
 864                             struct object_id *result, int generation)
 865 {
 866         struct object_id oid;
 867         struct commit *commit;
 868         int ret;
 869
 870         ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
 871         if (ret)
 872                 return ret;
 873         commit = lookup_commit_reference(&oid);
 874         if (!commit)
 875                 return -1;
 876
 877         while (generation--) {
 878                 if (parse_commit(commit) || !commit->parents)
 879                         return -1;
 880                 commit = commit->parents->item;
 881         }
 882         oidcpy(result, &commit->object.oid);
 883         return 0;
 884 }
 885
 886 struct object *peel_to_type(const char *name, int namelen,
 887                             struct object *o, enum object_type expected_type)
 888 {
 889         if (name && !namelen)
 890                 namelen = strlen(name);
 891         while (1) {
 892                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 893                         return NULL;
 894                 if (expected_type == OBJ_ANY || o->type == expected_type)
 895                         return o;
 896                 if (o->type == OBJ_TAG)
 897                         o = ((struct tag*) o)->tagged;
 898                 else if (o->type == OBJ_COMMIT)
 899                         o = &(((struct commit *) o)->tree->object);
 900                 else {
 901                         if (name)
 902                                 error("%.*s: expected %s type, but the object "
 903                                       "dereferences to %s type",
 904                                       namelen, name, typename(expected_type),
 905                                       typename(o->type));
 906                         return NULL;
 907                 }
 908         }
 909 }
 910
 911 static int peel_onion(const char *name, int len, struct object_id *oid,
 912                       unsigned lookup_flags)
 913 {
 914         struct object_id outer;
 915         const char *sp;
 916         unsigned int expected_type = 0;
 917         struct object *o;
 918
 919         /*
 920          * "ref^{type}" dereferences ref repeatedly until you cannot
 921          * dereference anymore, or you get an object of given type,
 922          * whichever comes first.  "ref^{}" means just dereference
 923          * tags until you get a non-tag.  "ref^0" is a shorthand for
 924          * "ref^{commit}".  "commit^{tree}" could be used to find the
 925          * top-level tree of the given commit.
 926          */
 927         if (len < 4 || name[len-1] != '}')
 928                 return -1;
 929
 930         for (sp = name + len - 1; name <= sp; sp--) {
 931                 int ch = *sp;
 932                 if (ch == '{' && name < sp && sp[-1] == '^')
 933                         break;
 934         }
 935         if (sp <= name)
 936                 return -1;
 937
 938         sp++; /* beginning of type name, or closing brace for empty */
 939         if (starts_with(sp, "commit}"))
 940                 expected_type = OBJ_COMMIT;
 941         else if (starts_with(sp, "tag}"))
 942                 expected_type = OBJ_TAG;
 943         else if (starts_with(sp, "tree}"))
 944                 expected_type = OBJ_TREE;
 945         else if (starts_with(sp, "blob}"))
 946                 expected_type = OBJ_BLOB;
 947         else if (starts_with(sp, "object}"))
 948                 expected_type = OBJ_ANY;
 949         else if (sp[0] == '}')
 950                 expected_type = OBJ_NONE;
 951         else if (sp[0] == '/')
 952                 expected_type = OBJ_COMMIT;
 953         else
 954                 return -1;
 955
 956         lookup_flags &= ~GET_OID_DISAMBIGUATORS;
 957         if (expected_type == OBJ_COMMIT)
 958                 lookup_flags |= GET_OID_COMMITTISH;
 959         else if (expected_type == OBJ_TREE)
 960                 lookup_flags |= GET_OID_TREEISH;
 961
 962         if (get_oid_1(name, sp - name - 2, &outer, lookup_flags))
 963                 return -1;
 964
 965         o = parse_object(&outer);
 966         if (!o)
 967                 return -1;
 968         if (!expected_type) {
 969                 o = deref_tag(o, name, sp - name - 2);
 970                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 971                         return -1;
 972                 oidcpy(oid, &o->oid);
 973                 return 0;
 974         }
 975
 976         /*
 977          * At this point, the syntax look correct, so
 978          * if we do not get the needed object, we should
 979          * barf.
 980          */
 981         o = peel_to_type(name, len, o, expected_type);
 982         if (!o)
 983                 return -1;
 984
 985         oidcpy(oid, &o->oid);
 986         if (sp[0] == '/') {
 987                 /* "$commit^{/foo}" */
 988                 char *prefix;
 989                 int ret;
 990                 struct commit_list *list = NULL;
 991
 992                 /*
 993                  * $commit^{/}. Some regex implementation may reject.
 994                  * We don't need regex anyway. '' pattern always matches.
 995                  */
 996                 if (sp[1] == '}')
 997                         return 0;
 998
 999                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
1000                 commit_list_insert((struct commit *)o, &list);
1001                 ret = get_oid_oneline(prefix, oid, list);
1002                 free(prefix);
1003                 return ret;
1004         }
1005         return 0;
1006 }
1007
1008 static int get_describe_name(const char *name, int len, struct object_id *oid)
1009 {
1010         const char *cp;
1011         unsigned flags = GET_OID_QUIETLY | GET_OID_COMMIT;
1012
1013         for (cp = name + len - 1; name + 2 <= cp; cp--) {
1014                 char ch = *cp;
1015                 if (!isxdigit(ch)) {
1016                         /* We must be looking at g in "SOMETHING-g"
1017                          * for it to be describe output.
1018                          */
1019                         if (ch == 'g' && cp[-1] == '-') {
1020                                 cp++;
1021                                 len -= cp - name;
1022                                 return get_short_oid(cp, len, oid, flags);
1023                         }
1024                 }
1025         }
1026         return -1;
1027 }
1028
1029 static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags)
1030 {
1031         int ret, has_suffix;
1032         const char *cp;
1033
1034         /*
1035          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
1036          */
1037         has_suffix = 0;
1038         for (cp = name + len - 1; name <= cp; cp--) {
1039                 int ch = *cp;
1040                 if ('0' <= ch && ch <= '9')
1041                         continue;
1042                 if (ch == '~' || ch == '^')
1043                         has_suffix = ch;
1044                 break;
1045         }
1046
1047         if (has_suffix) {
1048                 int num = 0;
1049                 int len1 = cp - name;
1050                 cp++;
1051                 while (cp < name + len)
1052                         num = num * 10 + *cp++ - '0';
1053                 if (!num && len1 == len - 1)
1054                         num = 1;
1055                 if (has_suffix == '^')
1056                         return get_parent(name, len1, oid, num);
1057                 /* else if (has_suffix == '~') -- goes without saying */
1058                 return get_nth_ancestor(name, len1, oid, num);
1059         }
1060
1061         ret = peel_onion(name, len, oid, lookup_flags);
1062         if (!ret)
1063                 return 0;
1064
1065         ret = get_oid_basic(name, len, oid, lookup_flags);
1066         if (!ret)
1067                 return 0;
1068
1069         /* It could be describe output that is "SOMETHING-gXXXX" */
1070         ret = get_describe_name(name, len, oid);
1071         if (!ret)
1072                 return 0;
1073
1074         return get_short_oid(name, len, oid, lookup_flags);
1075 }
1076
1077 /*
1078  * This interprets names like ':/Initial revision of "git"' by searching
1079  * through history and returning the first commit whose message starts
1080  * the given regular expression.
1081  *
1082  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
1083  *
1084  * For a literal '!' character at the beginning of a pattern, you have to repeat
1085  * that, like: ':/!!foo'
1086  *
1087  * For future extension, all other sequences beginning with ':/!' are reserved.
1088  */
1089
1090 /* Remember to update object flag allocation in object.h */
1091 #define ONELINE_SEEN (1u<<20)
1092
1093 static int handle_one_ref(const char *path, const struct object_id *oid,
1094                           int flag, void *cb_data)
1095 {
1096         struct commit_list **list = cb_data;
1097         struct object *object = parse_object(oid);
1098         if (!object)
1099                 return 0;
1100         if (object->type == OBJ_TAG) {
1101                 object = deref_tag(object, path, strlen(path));
1102                 if (!object)
1103                         return 0;
1104         }
1105         if (object->type != OBJ_COMMIT)
1106                 return 0;
1107         commit_list_insert((struct commit *)object, list);
1108         return 0;
1109 }
1110
1111 static int get_oid_oneline(const char *prefix, struct object_id *oid,
1112                             struct commit_list *list)
1113 {
1114         struct commit_list *backup = NULL, *l;
1115         int found = 0;
1116         int negative = 0;
1117         regex_t regex;
1118
1119         if (prefix[0] == '!') {
1120                 prefix++;
1121
1122                 if (prefix[0] == '-') {
1123                         prefix++;
1124                         negative = 1;
1125                 } else if (prefix[0] != '!') {
1126                         return -1;
1127                 }
1128         }
1129
1130         if (regcomp(&regex, prefix, REG_EXTENDED))
1131                 return -1;
1132
1133         for (l = list; l; l = l->next) {
1134                 l->item->object.flags |= ONELINE_SEEN;
1135                 commit_list_insert(l->item, &backup);
1136         }
1137         while (list) {
1138                 const char *p, *buf;
1139                 struct commit *commit;
1140                 int matches;
1141
1142                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1143                 if (!parse_object(&commit->object.oid))
1144                         continue;
1145                 buf = get_commit_buffer(commit, NULL);
1146                 p = strstr(buf, "\n\n");
1147                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1148                 unuse_commit_buffer(commit, buf);
1149
1150                 if (matches) {
1151                         oidcpy(oid, &commit->object.oid);
1152                         found = 1;
1153                         break;
1154                 }
1155         }
1156         regfree(&regex);
1157         free_commit_list(list);
1158         for (l = backup; l; l = l->next)
1159                 clear_commit_marks(l->item, ONELINE_SEEN);
1160         free_commit_list(backup);
1161         return found ? 0 : -1;
1162 }
1163
1164 struct grab_nth_branch_switch_cbdata {
1165         int remaining;
1166         struct strbuf buf;
1167 };
1168
1169 static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
1170                                   const char *email, timestamp_t timestamp, int tz,
1171                                   const char *message, void *cb_data)
1172 {
1173         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1174         const char *match = NULL, *target = NULL;
1175         size_t len;
1176
1177         if (skip_prefix(message, "checkout: moving from ", &match))
1178                 target = strstr(match, " to ");
1179
1180         if (!match || !target)
1181                 return 0;
1182         if (--(cb->remaining) == 0) {
1183                 len = target - match;
1184                 strbuf_reset(&cb->buf);
1185                 strbuf_add(&cb->buf, match, len);
1186                 return 1; /* we are done */
1187         }
1188         return 0;
1189 }
1190
1191 /*
1192  * Parse @{-N} syntax, return the number of characters parsed
1193  * if successful; otherwise signal an error with negative value.
1194  */
1195 static int interpret_nth_prior_checkout(const char *name, int namelen,
1196                                         struct strbuf *buf)
1197 {
1198         long nth;
1199         int retval;
1200         struct grab_nth_branch_switch_cbdata cb;
1201         const char *brace;
1202         char *num_end;
1203
1204         if (namelen < 4)
1205                 return -1;
1206         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1207                 return -1;
1208         brace = memchr(name, '}', namelen);
1209         if (!brace)
1210                 return -1;
1211         nth = strtol(name + 3, &num_end, 10);
1212         if (num_end != brace)
1213                 return -1;
1214         if (nth <= 0)
1215                 return -1;
1216         cb.remaining = nth;
1217         strbuf_init(&cb.buf, 20);
1218
1219         retval = 0;
1220         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1221                 strbuf_reset(buf);
1222                 strbuf_addbuf(buf, &cb.buf);
1223                 retval = brace - name + 1;
1224         }
1225
1226         strbuf_release(&cb.buf);
1227         return retval;
1228 }
1229
1230 int get_oid_mb(const char *name, struct object_id *oid)
1231 {
1232         struct commit *one, *two;
1233         struct commit_list *mbs;
1234         struct object_id oid_tmp;
1235         const char *dots;
1236         int st;
1237
1238         dots = strstr(name, "...");
1239         if (!dots)
1240                 return get_oid(name, oid);
1241         if (dots == name)
1242                 st = get_oid("HEAD", &oid_tmp);
1243         else {
1244                 struct strbuf sb;
1245                 strbuf_init(&sb, dots - name);
1246                 strbuf_add(&sb, name, dots - name);
1247                 st = get_oid_committish(sb.buf, &oid_tmp);
1248                 strbuf_release(&sb);
1249         }
1250         if (st)
1251                 return st;
1252         one = lookup_commit_reference_gently(&oid_tmp, 0);
1253         if (!one)
1254                 return -1;
1255
1256         if (get_oid_committish(dots[3] ? (dots + 3) : "HEAD", &oid_tmp))
1257                 return -1;
1258         two = lookup_commit_reference_gently(&oid_tmp, 0);
1259         if (!two)
1260                 return -1;
1261         mbs = get_merge_bases(one, two);
1262         if (!mbs || mbs->next)
1263                 st = -1;
1264         else {
1265                 st = 0;
1266                 oidcpy(oid, &mbs->item->object.oid);
1267         }
1268         free_commit_list(mbs);
1269         return st;
1270 }
1271
1272 /* parse @something syntax, when 'something' is not {.*} */
1273 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1274 {
1275         const char *next;
1276
1277         if (len || name[1] == '{')
1278                 return -1;
1279
1280         /* make sure it's a single @, or @@{.*}, not @foo */
1281         next = memchr(name + len + 1, '@', namelen - len - 1);
1282         if (next && next[1] != '{')
1283                 return -1;
1284         if (!next)
1285                 next = name + namelen;
1286         if (next != name + 1)
1287                 return -1;
1288
1289         strbuf_reset(buf);
1290         strbuf_add(buf, "HEAD", 4);
1291         return 1;
1292 }
1293
1294 static int reinterpret(const char *name, int namelen, int len,
1295                        struct strbuf *buf, unsigned allowed)
1296 {
1297         /* we have extra data, which might need further processing */
1298         struct strbuf tmp = STRBUF_INIT;
1299         int used = buf->len;
1300         int ret;
1301
1302         strbuf_add(buf, name + len, namelen - len);
1303         ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
1304         /* that data was not interpreted, remove our cruft */
1305         if (ret < 0) {
1306                 strbuf_setlen(buf, used);
1307                 return len;
1308         }
1309         strbuf_reset(buf);
1310         strbuf_addbuf(buf, &tmp);
1311         strbuf_release(&tmp);
1312         /* tweak for size of {-N} versus expanded ref name */
1313         return ret - used + len;
1314 }
1315
1316 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1317 {
1318         char *s = shorten_unambiguous_ref(ref, 0);
1319         strbuf_reset(buf);
1320         strbuf_addstr(buf, s);
1321         free(s);
1322 }
1323
1324 static int branch_interpret_allowed(const char *refname, unsigned allowed)
1325 {
1326         if (!allowed)
1327                 return 1;
1328
1329         if ((allowed & INTERPRET_BRANCH_LOCAL) &&
1330             starts_with(refname, "refs/heads/"))
1331                 return 1;
1332         if ((allowed & INTERPRET_BRANCH_REMOTE) &&
1333             starts_with(refname, "refs/remotes/"))
1334                 return 1;
1335
1336         return 0;
1337 }
1338
1339 static int interpret_branch_mark(const char *name, int namelen,
1340                                  int at, struct strbuf *buf,
1341                                  int (*get_mark)(const char *, int),
1342                                  const char *(*get_data)(struct branch *,
1343                                                          struct strbuf *),
1344                                  unsigned allowed)
1345 {
1346         int len;
1347         struct branch *branch;
1348         struct strbuf err = STRBUF_INIT;
1349         const char *value;
1350
1351         len = get_mark(name + at, namelen - at);
1352         if (!len)
1353                 return -1;
1354
1355         if (memchr(name, ':', at))
1356                 return -1;
1357
1358         if (at) {
1359                 char *name_str = xmemdupz(name, at);
1360                 branch = branch_get(name_str);
1361                 free(name_str);
1362         } else
1363                 branch = branch_get(NULL);
1364
1365         value = get_data(branch, &err);
1366         if (!value)
1367                 die("%s", err.buf);
1368
1369         if (!branch_interpret_allowed(value, allowed))
1370                 return -1;
1371
1372         set_shortened_ref(buf, value);
1373         return len + at;
1374 }
1375
1376 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
1377                           unsigned allowed)
1378 {
1379         char *at;
1380         const char *start;
1381         int len;
1382
1383         if (!namelen)
1384                 namelen = strlen(name);
1385
1386         if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
1387                 len = interpret_nth_prior_checkout(name, namelen, buf);
1388                 if (!len) {
1389                         return len; /* syntax Ok, not enough switches */
1390                 } else if (len > 0) {
1391                         if (len == namelen)
1392                                 return len; /* consumed all */
1393                         else
1394                                 return reinterpret(name, namelen, len, buf, allowed);
1395                 }
1396         }
1397
1398         for (start = name;
1399              (at = memchr(start, '@', namelen - (start - name)));
1400              start = at + 1) {
1401
1402                 if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
1403                         len = interpret_empty_at(name, namelen, at - name, buf);
1404                         if (len > 0)
1405                                 return reinterpret(name, namelen, len, buf,
1406                                                    allowed);
1407                 }
1408
1409                 len = interpret_branch_mark(name, namelen, at - name, buf,
1410                                             upstream_mark, branch_get_upstream,
1411                                             allowed);
1412                 if (len > 0)
1413                         return len;
1414
1415                 len = interpret_branch_mark(name, namelen, at - name, buf,
1416                                             push_mark, branch_get_push,
1417                                             allowed);
1418                 if (len > 0)
1419                         return len;
1420         }
1421
1422         return -1;
1423 }
1424
1425 void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
1426 {
1427         int len = strlen(name);
1428         int used = interpret_branch_name(name, len, sb, allowed);
1429
1430         if (used < 0)
1431                 used = 0;
1432         strbuf_add(sb, name + used, len - used);
1433 }
1434
1435 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1436 {
1437         if (startup_info->have_repository)
1438                 strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
1439         else
1440                 strbuf_addstr(sb, name);
1441
1442         /*
1443          * This splice must be done even if we end up rejecting the
1444          * name; builtin/branch.c::copy_or_rename_branch() still wants
1445          * to see what the name expanded to so that "branch -m" can be
1446          * used as a tool to correct earlier mistakes.
1447          */
1448         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1449
1450         if (*name == '-' ||
1451             !strcmp(sb->buf, "refs/heads/HEAD"))
1452                 return -1;
1453
1454         return check_refname_format(sb->buf, 0);
1455 }
1456
1457 /*
1458  * This is like "get_oid_basic()", except it allows "object ID expressions",
1459  * notably "xyz^" for "parent of xyz"
1460  */
1461 int get_oid(const char *name, struct object_id *oid)
1462 {
1463         struct object_context unused;
1464         return get_oid_with_context(name, 0, oid, &unused);
1465 }
1466
1467
1468 /*
1469  * Many callers know that the user meant to name a commit-ish by
1470  * syntactical positions where the object name appears.  Calling this
1471  * function allows the machinery to disambiguate shorter-than-unique
1472  * abbreviated object names between commit-ish and others.
1473  *
1474  * Note that this does NOT error out when the named object is not a
1475  * commit-ish. It is merely to give a hint to the disambiguation
1476  * machinery.
1477  */
1478 int get_oid_committish(const char *name, struct object_id *oid)
1479 {
1480         struct object_context unused;
1481         return get_oid_with_context(name, GET_OID_COMMITTISH,
1482                                     oid, &unused);
1483 }
1484
1485 int get_oid_treeish(const char *name, struct object_id *oid)
1486 {
1487         struct object_context unused;
1488         return get_oid_with_context(name, GET_OID_TREEISH,
1489                                     oid, &unused);
1490 }
1491
1492 int get_oid_commit(const char *name, struct object_id *oid)
1493 {
1494         struct object_context unused;
1495         return get_oid_with_context(name, GET_OID_COMMIT,
1496                                     oid, &unused);
1497 }
1498
1499 int get_oid_tree(const char *name, struct object_id *oid)
1500 {
1501         struct object_context unused;
1502         return get_oid_with_context(name, GET_OID_TREE,
1503                                     oid, &unused);
1504 }
1505
1506 int get_oid_blob(const char *name, struct object_id *oid)
1507 {
1508         struct object_context unused;
1509         return get_oid_with_context(name, GET_OID_BLOB,
1510                                     oid, &unused);
1511 }
1512
1513 /* Must be called only when object_name:filename doesn't exist. */
1514 static void diagnose_invalid_oid_path(const char *prefix,
1515                                       const char *filename,
1516                                       const struct object_id *tree_oid,
1517                                       const char *object_name,
1518                                       int object_name_len)
1519 {
1520         struct object_id oid;
1521         unsigned mode;
1522
1523         if (!prefix)
1524                 prefix = "";
1525
1526         if (file_exists(filename))
1527                 die("Path '%s' exists on disk, but not in '%.*s'.",
1528                     filename, object_name_len, object_name);
1529         if (is_missing_file_error(errno)) {
1530                 char *fullname = xstrfmt("%s%s", prefix, filename);
1531
1532                 if (!get_tree_entry(tree_oid->hash, fullname,
1533                                     oid.hash, &mode)) {
1534                         die("Path '%s' exists, but not '%s'.\n"
1535                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1536                             fullname,
1537                             filename,
1538                             object_name_len, object_name,
1539                             fullname,
1540                             object_name_len, object_name,
1541                             filename);
1542                 }
1543                 die("Path '%s' does not exist in '%.*s'",
1544                     filename, object_name_len, object_name);
1545         }
1546 }
1547
1548 /* Must be called only when :stage:filename doesn't exist. */
1549 static void diagnose_invalid_index_path(int stage,
1550                                         const char *prefix,
1551                                         const char *filename)
1552 {
1553         const struct cache_entry *ce;
1554         int pos;
1555         unsigned namelen = strlen(filename);
1556         struct strbuf fullname = STRBUF_INIT;
1557
1558         if (!prefix)
1559                 prefix = "";
1560
1561         /* Wrong stage number? */
1562         pos = cache_name_pos(filename, namelen);
1563         if (pos < 0)
1564                 pos = -pos - 1;
1565         if (pos < active_nr) {
1566                 ce = active_cache[pos];
1567                 if (ce_namelen(ce) == namelen &&
1568                     !memcmp(ce->name, filename, namelen))
1569                         die("Path '%s' is in the index, but not at stage %d.\n"
1570                             "Did you mean ':%d:%s'?",
1571                             filename, stage,
1572                             ce_stage(ce), filename);
1573         }
1574
1575         /* Confusion between relative and absolute filenames? */
1576         strbuf_addstr(&fullname, prefix);
1577         strbuf_addstr(&fullname, filename);
1578         pos = cache_name_pos(fullname.buf, fullname.len);
1579         if (pos < 0)
1580                 pos = -pos - 1;
1581         if (pos < active_nr) {
1582                 ce = active_cache[pos];
1583                 if (ce_namelen(ce) == fullname.len &&
1584                     !memcmp(ce->name, fullname.buf, fullname.len))
1585                         die("Path '%s' is in the index, but not '%s'.\n"
1586                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1587                             fullname.buf, filename,
1588                             ce_stage(ce), fullname.buf,
1589                             ce_stage(ce), filename);
1590         }
1591
1592         if (file_exists(filename))
1593                 die("Path '%s' exists on disk, but not in the index.", filename);
1594         if (is_missing_file_error(errno))
1595                 die("Path '%s' does not exist (neither on disk nor in the index).",
1596                     filename);
1597
1598         strbuf_release(&fullname);
1599 }
1600
1601
1602 static char *resolve_relative_path(const char *rel)
1603 {
1604         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1605                 return NULL;
1606
1607         if (!is_inside_work_tree())
1608                 die("relative path syntax can't be used outside working tree.");
1609
1610         /* die() inside prefix_path() if resolved path is outside worktree */
1611         return prefix_path(startup_info->prefix,
1612                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1613                            rel);
1614 }
1615
1616 static int get_oid_with_context_1(const char *name,
1617                                   unsigned flags,
1618                                   const char *prefix,
1619                                   struct object_id *oid,
1620                                   struct object_context *oc)
1621 {
1622         int ret, bracket_depth;
1623         int namelen = strlen(name);
1624         const char *cp;
1625         int only_to_die = flags & GET_OID_ONLY_TO_DIE;
1626
1627         if (only_to_die)
1628                 flags |= GET_OID_QUIETLY;
1629
1630         memset(oc, 0, sizeof(*oc));
1631         oc->mode = S_IFINVALID;
1632         strbuf_init(&oc->symlink_path, 0);
1633         ret = get_oid_1(name, namelen, oid, flags);
1634         if (!ret)
1635                 return ret;
1636         /*
1637          * sha1:path --> object name of path in ent sha1
1638          * :path -> object name of absolute path in index
1639          * :./path -> object name of path relative to cwd in index
1640          * :[0-3]:path -> object name of path in index at stage
1641          * :/foo -> recent commit matching foo
1642          */
1643         if (name[0] == ':') {
1644                 int stage = 0;
1645                 const struct cache_entry *ce;
1646                 char *new_path = NULL;
1647                 int pos;
1648                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1649                         struct commit_list *list = NULL;
1650
1651                         for_each_ref(handle_one_ref, &list);
1652                         commit_list_sort_by_date(&list);
1653                         return get_oid_oneline(name + 2, oid, list);
1654                 }
1655                 if (namelen < 3 ||
1656                     name[2] != ':' ||
1657                     name[1] < '0' || '3' < name[1])
1658                         cp = name + 1;
1659                 else {
1660                         stage = name[1] - '0';
1661                         cp = name + 3;
1662                 }
1663                 new_path = resolve_relative_path(cp);
1664                 if (!new_path) {
1665                         namelen = namelen - (cp - name);
1666                 } else {
1667                         cp = new_path;
1668                         namelen = strlen(cp);
1669                 }
1670
1671                 if (flags & GET_OID_RECORD_PATH)
1672                         oc->path = xstrdup(cp);
1673
1674                 if (!active_cache)
1675                         read_cache();
1676                 pos = cache_name_pos(cp, namelen);
1677                 if (pos < 0)
1678                         pos = -pos - 1;
1679                 while (pos < active_nr) {
1680                         ce = active_cache[pos];
1681                         if (ce_namelen(ce) != namelen ||
1682                             memcmp(ce->name, cp, namelen))
1683                                 break;
1684                         if (ce_stage(ce) == stage) {
1685                                 oidcpy(oid, &ce->oid);
1686                                 oc->mode = ce->ce_mode;
1687                                 free(new_path);
1688                                 return 0;
1689                         }
1690                         pos++;
1691                 }
1692                 if (only_to_die && name[1] && name[1] != '/')
1693                         diagnose_invalid_index_path(stage, prefix, cp);
1694                 free(new_path);
1695                 return -1;
1696         }
1697         for (cp = name, bracket_depth = 0; *cp; cp++) {
1698                 if (*cp == '{')
1699                         bracket_depth++;
1700                 else if (bracket_depth && *cp == '}')
1701                         bracket_depth--;
1702                 else if (!bracket_depth && *cp == ':')
1703                         break;
1704         }
1705         if (*cp == ':') {
1706                 struct object_id tree_oid;
1707                 int len = cp - name;
1708                 unsigned sub_flags = flags;
1709
1710                 sub_flags &= ~GET_OID_DISAMBIGUATORS;
1711                 sub_flags |= GET_OID_TREEISH;
1712
1713                 if (!get_oid_1(name, len, &tree_oid, sub_flags)) {
1714                         const char *filename = cp+1;
1715                         char *new_filename = NULL;
1716
1717                         new_filename = resolve_relative_path(filename);
1718                         if (new_filename)
1719                                 filename = new_filename;
1720                         if (flags & GET_OID_FOLLOW_SYMLINKS) {
1721                                 ret = get_tree_entry_follow_symlinks(tree_oid.hash,
1722                                         filename, oid->hash, &oc->symlink_path,
1723                                         &oc->mode);
1724                         } else {
1725                                 ret = get_tree_entry(tree_oid.hash, filename,
1726                                                      oid->hash, &oc->mode);
1727                                 if (ret && only_to_die) {
1728                                         diagnose_invalid_oid_path(prefix,
1729                                                                    filename,
1730                                                                    &tree_oid,
1731                                                                    name, len);
1732                                 }
1733                         }
1734                         hashcpy(oc->tree, tree_oid.hash);
1735                         if (flags & GET_OID_RECORD_PATH)
1736                                 oc->path = xstrdup(filename);
1737
1738                         free(new_filename);
1739                         return ret;
1740                 } else {
1741                         if (only_to_die)
1742                                 die("Invalid object name '%.*s'.", len, name);
1743                 }
1744         }
1745         return ret;
1746 }
1747
1748 /*
1749  * Call this function when you know "name" given by the end user must
1750  * name an object but it doesn't; the function _may_ die with a better
1751  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1752  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1753  * you have a chance to diagnose the error further.
1754  */
1755 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1756 {
1757         struct object_context oc;
1758         struct object_id oid;
1759         get_oid_with_context_1(name, GET_OID_ONLY_TO_DIE, prefix, &oid, &oc);
1760 }
1761
1762 int get_oid_with_context(const char *str, unsigned flags, struct object_id *oid, struct object_context *oc)
1763 {
1764         if (flags & GET_OID_FOLLOW_SYMLINKS && flags & GET_OID_ONLY_TO_DIE)
1765                 die("BUG: incompatible flags for get_sha1_with_context");
1766         return get_oid_with_context_1(str, flags, NULL, oid, oc);
1767 }