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 #include "object-store.h"
  14 #include "repository.h"
  15
  16 static int get_oid_oneline(const char *, struct object_id *, struct commit_list *);
  17
  18 typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
  19
  20 struct disambiguate_state {
  21         int len; /* length of prefix in hex chars */
  22         char hex_pfx[GIT_MAX_HEXSZ + 1];
  23         struct object_id bin_pfx;
  24
  25         disambiguate_hint_fn fn;
  26         void *cb_data;
  27         struct object_id candidate;
  28         unsigned candidate_exists:1;
  29         unsigned candidate_checked:1;
  30         unsigned candidate_ok:1;
  31         unsigned disambiguate_fn_used:1;
  32         unsigned ambiguous:1;
  33         unsigned always_call_fn:1;
  34 };
  35
  36 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
  37 {
  38         if (ds->always_call_fn) {
  39                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  40                 return;
  41         }
  42         if (!ds->candidate_exists) {
  43                 /* this is the first candidate */
  44                 oidcpy(&ds->candidate, current);
  45                 ds->candidate_exists = 1;
  46                 return;
  47         } else if (!oidcmp(&ds->candidate, current)) {
  48                 /* the same as what we already have seen */
  49                 return;
  50         }
  51
  52         if (!ds->fn) {
  53                 /* cannot disambiguate between ds->candidate and current */
  54                 ds->ambiguous = 1;
  55                 return;
  56         }
  57
  58         if (!ds->candidate_checked) {
  59                 ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
  60                 ds->disambiguate_fn_used = 1;
  61                 ds->candidate_checked = 1;
  62         }
  63
  64         if (!ds->candidate_ok) {
  65                 /* discard the candidate; we know it does not satisfy fn */
  66                 oidcpy(&ds->candidate, current);
  67                 ds->candidate_checked = 0;
  68                 return;
  69         }
  70
  71         /* if we reach this point, we know ds->candidate satisfies fn */
  72         if (ds->fn(current, ds->cb_data)) {
  73                 /*
  74                  * if both current and candidate satisfy fn, we cannot
  75                  * disambiguate.
  76                  */
  77                 ds->candidate_ok = 0;
  78                 ds->ambiguous = 1;
  79         }
  80
  81         /* otherwise, current can be discarded and candidate is still good */
  82 }
  83
  84 static int append_loose_object(const struct object_id *oid, const char *path,
  85                                void *data)
  86 {
  87         oid_array_append(data, oid);
  88         return 0;
  89 }
  90
  91 static int match_sha(unsigned, const unsigned char *, const unsigned char *);
  92
  93 static void find_short_object_filename(struct disambiguate_state *ds)
  94 {
  95         int subdir_nr = ds->bin_pfx.hash[0];
  96         struct alternate_object_database *alt;
  97         static struct alternate_object_database *fakeent;
  98
  99         if (!fakeent) {
 100                 /*
 101                  * Create a "fake" alternate object database that
 102                  * points to our own object database, to make it
 103                  * easier to get a temporary working space in
 104                  * alt->name/alt->base while iterating over the
 105                  * object databases including our own.
 106                  */
 107                 fakeent = alloc_alt_odb(get_object_directory());
 108         }
 109         fakeent->next = the_repository->objects->alt_odb_list;
 110
 111         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 112                 int pos;
 113
 114                 if (!alt->loose_objects_subdir_seen[subdir_nr]) {
 115                         struct strbuf *buf = alt_scratch_buf(alt);
 116                         for_each_file_in_obj_subdir(subdir_nr, buf,
 117                                                     append_loose_object,
 118                                                     NULL, NULL,
 119                                                     &alt->loose_objects_cache);
 120                         alt->loose_objects_subdir_seen[subdir_nr] = 1;
 121                 }
 122
 123                 pos = oid_array_lookup(&alt->loose_objects_cache, &ds->bin_pfx);
 124                 if (pos < 0)
 125                         pos = -1 - pos;
 126                 while (!ds->ambiguous && pos < alt->loose_objects_cache.nr) {
 127                         const struct object_id *oid;
 128                         oid = alt->loose_objects_cache.oid + pos;
 129                         if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
 130                                 break;
 131                         update_candidates(ds, oid);
 132                         pos++;
 133                 }
 134         }
 135 }
 136
 137 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 138 {
 139         do {
 140                 if (*a != *b)
 141                         return 0;
 142                 a++;
 143                 b++;
 144                 len -= 2;
 145         } while (len > 1);
 146         if (len)
 147                 if ((*a ^ *b) & 0xf0)
 148                         return 0;
 149         return 1;
 150 }
 151
 152 static void unique_in_pack(struct packed_git *p,
 153                            struct disambiguate_state *ds)
 154 {
 155         uint32_t num, i, first = 0;
 156         const struct object_id *current = NULL;
 157
 158         if (open_pack_index(p) || !p->num_objects)
 159                 return;
 160
 161         num = p->num_objects;
 162         bsearch_pack(&ds->bin_pfx, p, &first);
 163
 164         /*
 165          * At this point, "first" is the location of the lowest object
 166          * with an object name that could match "bin_pfx".  See if we have
 167          * 0, 1 or more objects that actually match(es).
 168          */
 169         for (i = first; i < num && !ds->ambiguous; i++) {
 170                 struct object_id oid;
 171                 current = nth_packed_object_oid(&oid, p, i);
 172                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
 173                         break;
 174                 update_candidates(ds, current);
 175         }
 176 }
 177
 178 static void find_short_packed_object(struct disambiguate_state *ds)
 179 {
 180         struct packed_git *p;
 181
 182         for (p = get_packed_git(the_repository); p && !ds->ambiguous;
 183              p = p->next)
 184                 unique_in_pack(p, ds);
 185 }
 186
 187 #define SHORT_NAME_NOT_FOUND (-1)
 188 #define SHORT_NAME_AMBIGUOUS (-2)
 189
 190 static int finish_object_disambiguation(struct disambiguate_state *ds,
 191                                         struct object_id *oid)
 192 {
 193         if (ds->ambiguous)
 194                 return SHORT_NAME_AMBIGUOUS;
 195
 196         if (!ds->candidate_exists)
 197                 return SHORT_NAME_NOT_FOUND;
 198
 199         if (!ds->candidate_checked)
 200                 /*
 201                  * If this is the only candidate, there is no point
 202                  * calling the disambiguation hint callback.
 203                  *
 204                  * On the other hand, if the current candidate
 205                  * replaced an earlier candidate that did _not_ pass
 206                  * the disambiguation hint callback, then we do have
 207                  * more than one objects that match the short name
 208                  * given, so we should make sure this one matches;
 209                  * otherwise, if we discovered this one and the one
 210                  * that we previously discarded in the reverse order,
 211                  * we would end up showing different results in the
 212                  * same repository!
 213                  */
 214                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 215                                     ds->fn(&ds->candidate, ds->cb_data));
 216
 217         if (!ds->candidate_ok)
 218                 return SHORT_NAME_AMBIGUOUS;
 219
 220         oidcpy(oid, &ds->candidate);
 221         return 0;
 222 }
 223
 224 static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
 225 {
 226         int kind = oid_object_info(the_repository, oid, NULL);
 227         return kind == OBJ_COMMIT;
 228 }
 229
 230 static int disambiguate_committish_only(const struct object_id *oid, void *cb_data_unused)
 231 {
 232         struct object *obj;
 233         int kind;
 234
 235         kind = oid_object_info(the_repository, oid, NULL);
 236         if (kind == OBJ_COMMIT)
 237                 return 1;
 238         if (kind != OBJ_TAG)
 239                 return 0;
 240
 241         /* We need to do this the hard way... */
 242         obj = deref_tag(parse_object(oid), NULL, 0);
 243         if (obj && obj->type == OBJ_COMMIT)
 244                 return 1;
 245         return 0;
 246 }
 247
 248 static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
 249 {
 250         int kind = oid_object_info(the_repository, oid, NULL);
 251         return kind == OBJ_TREE;
 252 }
 253
 254 static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
 255 {
 256         struct object *obj;
 257         int kind;
 258
 259         kind = oid_object_info(the_repository, oid, NULL);
 260         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 261                 return 1;
 262         if (kind != OBJ_TAG)
 263                 return 0;
 264
 265         /* We need to do this the hard way... */
 266         obj = deref_tag(parse_object(oid), NULL, 0);
 267         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 268                 return 1;
 269         return 0;
 270 }
 271
 272 static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
 273 {
 274         int kind = oid_object_info(the_repository, oid, NULL);
 275         return kind == OBJ_BLOB;
 276 }
 277
 278 static disambiguate_hint_fn default_disambiguate_hint;
 279
 280 int set_disambiguate_hint_config(const char *var, const char *value)
 281 {
 282         static const struct {
 283                 const char *name;
 284                 disambiguate_hint_fn fn;
 285         } hints[] = {
 286                 { "none", NULL },
 287                 { "commit", disambiguate_commit_only },
 288                 { "committish", disambiguate_committish_only },
 289                 { "tree", disambiguate_tree_only },
 290                 { "treeish", disambiguate_treeish_only },
 291                 { "blob", disambiguate_blob_only }
 292         };
 293         int i;
 294
 295         if (!value)
 296                 return config_error_nonbool(var);
 297
 298         for (i = 0; i < ARRAY_SIZE(hints); i++) {
 299                 if (!strcasecmp(value, hints[i].name)) {
 300                         default_disambiguate_hint = hints[i].fn;
 301                         return 0;
 302                 }
 303         }
 304
 305         return error("unknown hint type for '%s': %s", var, value);
 306 }
 307
 308 static int init_object_disambiguation(const char *name, int len,
 309                                       struct disambiguate_state *ds)
 310 {
 311         int i;
 312
 313         if (len < MINIMUM_ABBREV || len > the_hash_algo->hexsz)
 314                 return -1;
 315
 316         memset(ds, 0, sizeof(*ds));
 317
 318         for (i = 0; i < len ;i++) {
 319                 unsigned char c = name[i];
 320                 unsigned char val;
 321                 if (c >= '0' && c <= '9')
 322                         val = c - '0';
 323                 else if (c >= 'a' && c <= 'f')
 324                         val = c - 'a' + 10;
 325                 else if (c >= 'A' && c <='F') {
 326                         val = c - 'A' + 10;
 327                         c -= 'A' - 'a';
 328                 }
 329                 else
 330                         return -1;
 331                 ds->hex_pfx[i] = c;
 332                 if (!(i & 1))
 333                         val <<= 4;
 334                 ds->bin_pfx.hash[i >> 1] |= val;
 335         }
 336
 337         ds->len = len;
 338         ds->hex_pfx[len] = '\0';
 339         prepare_alt_odb(the_repository);
 340         return 0;
 341 }
 342
 343 static int show_ambiguous_object(const struct object_id *oid, void *data)
 344 {
 345         const struct disambiguate_state *ds = data;
 346         struct strbuf desc = STRBUF_INIT;
 347         int type;
 348
 349         if (ds->fn && !ds->fn(oid, ds->cb_data))
 350                 return 0;
 351
 352         type = oid_object_info(the_repository, oid, NULL);
 353         if (type == OBJ_COMMIT) {
 354                 struct commit *commit = lookup_commit(oid);
 355                 if (commit) {
 356                         struct pretty_print_context pp = {0};
 357                         pp.date_mode.type = DATE_SHORT;
 358                         format_commit_message(commit, " %ad - %s", &desc, &pp);
 359                 }
 360         } else if (type == OBJ_TAG) {
 361                 struct tag *tag = lookup_tag(oid);
 362                 if (!parse_tag(tag) && tag->tag)
 363                         strbuf_addf(&desc, " %s", tag->tag);
 364         }
 365
 366         advise("  %s %s%s",
 367                find_unique_abbrev(oid, DEFAULT_ABBREV),
 368                type_name(type) ? type_name(type) : "unknown type",
 369                desc.buf);
 370
 371         strbuf_release(&desc);
 372         return 0;
 373 }
 374
 375 static int collect_ambiguous(const struct object_id *oid, void *data)
 376 {
 377         oid_array_append(data, oid);
 378         return 0;
 379 }
 380
 381 static int sort_ambiguous(const void *a, const void *b)
 382 {
 383         int a_type = oid_object_info(the_repository, a, NULL);
 384         int b_type = oid_object_info(the_repository, b, NULL);
 385         int a_type_sort;
 386         int b_type_sort;
 387
 388         /*
 389          * Sorts by hash within the same object type, just as
 390          * oid_array_for_each_unique() would do.
 391          */
 392         if (a_type == b_type)
 393                 return oidcmp(a, b);
 394
 395         /*
 396          * Between object types show tags, then commits, and finally
 397          * trees and blobs.
 398          *
 399          * The object_type enum is commit, tree, blob, tag, but we
 400          * want tag, commit, tree blob. Cleverly (perhaps too
 401          * cleverly) do that with modulus, since the enum assigns 1 to
 402          * commit, so tag becomes 0.
 403          */
 404         a_type_sort = a_type % 4;
 405         b_type_sort = b_type % 4;
 406         return a_type_sort > b_type_sort ? 1 : -1;
 407 }
 408
 409 static int get_short_oid(const char *name, int len, struct object_id *oid,
 410                           unsigned flags)
 411 {
 412         int status;
 413         struct disambiguate_state ds;
 414         int quietly = !!(flags & GET_OID_QUIETLY);
 415
 416         if (init_object_disambiguation(name, len, &ds) < 0)
 417                 return -1;
 418
 419         if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
 420                 BUG("multiple get_short_oid disambiguator flags");
 421
 422         if (flags & GET_OID_COMMIT)
 423                 ds.fn = disambiguate_commit_only;
 424         else if (flags & GET_OID_COMMITTISH)
 425                 ds.fn = disambiguate_committish_only;
 426         else if (flags & GET_OID_TREE)
 427                 ds.fn = disambiguate_tree_only;
 428         else if (flags & GET_OID_TREEISH)
 429                 ds.fn = disambiguate_treeish_only;
 430         else if (flags & GET_OID_BLOB)
 431                 ds.fn = disambiguate_blob_only;
 432         else
 433                 ds.fn = default_disambiguate_hint;
 434
 435         find_short_object_filename(&ds);
 436         find_short_packed_object(&ds);
 437         status = finish_object_disambiguation(&ds, oid);
 438
 439         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
 440                 struct oid_array collect = OID_ARRAY_INIT;
 441
 442                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
 443
 444                 /*
 445                  * We may still have ambiguity if we simply saw a series of
 446                  * candidates that did not satisfy our hint function. In
 447                  * that case, we still want to show them, so disable the hint
 448                  * function entirely.
 449                  */
 450                 if (!ds.ambiguous)
 451                         ds.fn = NULL;
 452
 453                 advise(_("The candidates are:"));
 454                 for_each_abbrev(ds.hex_pfx, collect_ambiguous, &collect);
 455                 QSORT(collect.oid, collect.nr, sort_ambiguous);
 456
 457                 if (oid_array_for_each(&collect, show_ambiguous_object, &ds))
 458                         BUG("show_ambiguous_object shouldn't return non-zero");
 459                 oid_array_clear(&collect);
 460         }
 461
 462         return status;
 463 }
 464
 465 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 466 {
 467         struct oid_array collect = OID_ARRAY_INIT;
 468         struct disambiguate_state ds;
 469         int ret;
 470
 471         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
 472                 return -1;
 473
 474         ds.always_call_fn = 1;
 475         ds.fn = collect_ambiguous;
 476         ds.cb_data = &collect;
 477         find_short_object_filename(&ds);
 478         find_short_packed_object(&ds);
 479
 480         ret = oid_array_for_each_unique(&collect, fn, cb_data);
 481         oid_array_clear(&collect);
 482         return ret;
 483 }
 484
 485 /*
 486  * Return the slot of the most-significant bit set in "val". There are various
 487  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 488  * probably not a big deal here.
 489  */
 490 static unsigned msb(unsigned long val)
 491 {
 492         unsigned r = 0;
 493         while (val >>= 1)
 494                 r++;
 495         return r;
 496 }
 497
 498 struct min_abbrev_data {
 499         unsigned int init_len;
 500         unsigned int cur_len;
 501         char *hex;
 502         const struct object_id *oid;
 503 };
 504
 505 static inline char get_hex_char_from_oid(const struct object_id *oid,
 506                                          unsigned int pos)
 507 {
 508         static const char hex[] = "0123456789abcdef";
 509
 510         if ((pos & 1) == 0)
 511                 return hex[oid->hash[pos >> 1] >> 4];
 512         else
 513                 return hex[oid->hash[pos >> 1] & 0xf];
 514 }
 515
 516 static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
 517 {
 518         struct min_abbrev_data *mad = cb_data;
 519
 520         unsigned int i = mad->init_len;
 521         while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
 522                 i++;
 523
 524         if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
 525                 mad->cur_len = i + 1;
 526
 527         return 0;
 528 }
 529
 530 static void find_abbrev_len_for_pack(struct packed_git *p,
 531                                      struct min_abbrev_data *mad)
 532 {
 533         int match = 0;
 534         uint32_t num, first = 0;
 535         struct object_id oid;
 536         const struct object_id *mad_oid;
 537
 538         if (open_pack_index(p) || !p->num_objects)
 539                 return;
 540
 541         num = p->num_objects;
 542         mad_oid = mad->oid;
 543         match = bsearch_pack(mad_oid, p, &first);
 544
 545         /*
 546          * first is now the position in the packfile where we would insert
 547          * mad->hash if it does not exist (or the position of mad->hash if
 548          * it does exist). Hence, we consider a maximum of two objects
 549          * nearby for the abbreviation length.
 550          */
 551         mad->init_len = 0;
 552         if (!match) {
 553                 if (nth_packed_object_oid(&oid, p, first))
 554                         extend_abbrev_len(&oid, mad);
 555         } else if (first < num - 1) {
 556                 if (nth_packed_object_oid(&oid, p, first + 1))
 557                         extend_abbrev_len(&oid, mad);
 558         }
 559         if (first > 0) {
 560                 if (nth_packed_object_oid(&oid, p, first - 1))
 561                         extend_abbrev_len(&oid, mad);
 562         }
 563         mad->init_len = mad->cur_len;
 564 }
 565
 566 static void find_abbrev_len_packed(struct min_abbrev_data *mad)
 567 {
 568         struct packed_git *p;
 569
 570         for (p = get_packed_git(the_repository); p; p = p->next)
 571                 find_abbrev_len_for_pack(p, mad);
 572 }
 573
 574 int find_unique_abbrev_r(char *hex, const struct object_id *oid, int len)
 575 {
 576         struct disambiguate_state ds;
 577         struct min_abbrev_data mad;
 578         struct object_id oid_ret;
 579         const unsigned hexsz = the_hash_algo->hexsz;
 580
 581         if (len < 0) {
 582                 unsigned long count = approximate_object_count();
 583                 /*
 584                  * Add one because the MSB only tells us the highest bit set,
 585                  * not including the value of all the _other_ bits (so "15"
 586                  * is only one off of 2^4, but the MSB is the 3rd bit.
 587                  */
 588                 len = msb(count) + 1;
 589                 /*
 590                  * We now know we have on the order of 2^len objects, which
 591                  * expects a collision at 2^(len/2). But we also care about hex
 592                  * chars, not bits, and there are 4 bits per hex. So all
 593                  * together we need to divide by 2 and round up.
 594                  */
 595                 len = DIV_ROUND_UP(len, 2);
 596                 /*
 597                  * For very small repos, we stick with our regular fallback.
 598                  */
 599                 if (len < FALLBACK_DEFAULT_ABBREV)
 600                         len = FALLBACK_DEFAULT_ABBREV;
 601         }
 602
 603         oid_to_hex_r(hex, oid);
 604         if (len == hexsz || !len)
 605                 return hexsz;
 606
 607         mad.init_len = len;
 608         mad.cur_len = len;
 609         mad.hex = hex;
 610         mad.oid = oid;
 611
 612         find_abbrev_len_packed(&mad);
 613
 614         if (init_object_disambiguation(hex, mad.cur_len, &ds) < 0)
 615                 return -1;
 616
 617         ds.fn = extend_abbrev_len;
 618         ds.always_call_fn = 1;
 619         ds.cb_data = (void *)&mad;
 620
 621         find_short_object_filename(&ds);
 622         (void)finish_object_disambiguation(&ds, &oid_ret);
 623
 624         hex[mad.cur_len] = 0;
 625         return mad.cur_len;
 626 }
 627
 628 const char *find_unique_abbrev(const struct object_id *oid, int len)
 629 {
 630         static int bufno;
 631         static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
 632         char *hex = hexbuffer[bufno];
 633         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
 634         find_unique_abbrev_r(hex, oid, len);
 635         return hex;
 636 }
 637
 638 static int ambiguous_path(const char *path, int len)
 639 {
 640         int slash = 1;
 641         int cnt;
 642
 643         for (cnt = 0; cnt < len; cnt++) {
 644                 switch (*path++) {
 645                 case '\0':
 646                         break;
 647                 case '/':
 648                         if (slash)
 649                                 break;
 650                         slash = 1;
 651                         continue;
 652                 case '.':
 653                         continue;
 654                 default:
 655                         slash = 0;
 656                         continue;
 657                 }
 658                 break;
 659         }
 660         return slash;
 661 }
 662
 663 static inline int at_mark(const char *string, int len,
 664                           const char **suffix, int nr)
 665 {
 666         int i;
 667
 668         for (i = 0; i < nr; i++) {
 669                 int suffix_len = strlen(suffix[i]);
 670                 if (suffix_len <= len
 671                     && !strncasecmp(string, suffix[i], suffix_len))
 672                         return suffix_len;
 673         }
 674         return 0;
 675 }
 676
 677 static inline int upstream_mark(const char *string, int len)
 678 {
 679         const char *suffix[] = { "@{upstream}", "@{u}" };
 680         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 681 }
 682
 683 static inline int push_mark(const char *string, int len)
 684 {
 685         const char *suffix[] = { "@{push}" };
 686         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 687 }
 688
 689 static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
 690 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 691
 692 static int get_oid_basic(const char *str, int len, struct object_id *oid,
 693                           unsigned int flags)
 694 {
 695         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 696         static const char *object_name_msg = N_(
 697         "Git normally never creates a ref that ends with 40 hex characters\n"
 698         "because it will be ignored when you just specify 40-hex. These refs\n"
 699         "may be created by mistake. For example,\n"
 700         "\n"
 701         "  git checkout -b $br $(git rev-parse ...)\n"
 702         "\n"
 703         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 704         "examine these refs and maybe delete them. Turn this message off by\n"
 705         "running \"git config advice.objectNameWarning false\"");
 706         struct object_id tmp_oid;
 707         char *real_ref = NULL;
 708         int refs_found = 0;
 709         int at, reflog_len, nth_prior = 0;
 710
 711         if (len == the_hash_algo->hexsz && !get_oid_hex(str, oid)) {
 712                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 713                         refs_found = dwim_ref(str, len, &tmp_oid, &real_ref);
 714                         if (refs_found > 0) {
 715                                 warning(warn_msg, len, str);
 716                                 if (advice_object_name_warning)
 717                                         fprintf(stderr, "%s\n", _(object_name_msg));
 718                         }
 719                         free(real_ref);
 720                 }
 721                 return 0;
 722         }
 723
 724         /* basic@{time or number or -number} format to query ref-log */
 725         reflog_len = at = 0;
 726         if (len && str[len-1] == '}') {
 727                 for (at = len-4; at >= 0; at--) {
 728                         if (str[at] == '@' && str[at+1] == '{') {
 729                                 if (str[at+2] == '-') {
 730                                         if (at != 0)
 731                                                 /* @{-N} not at start */
 732                                                 return -1;
 733                                         nth_prior = 1;
 734                                         continue;
 735                                 }
 736                                 if (!upstream_mark(str + at, len - at) &&
 737                                     !push_mark(str + at, len - at)) {
 738                                         reflog_len = (len-1) - (at+2);
 739                                         len = at;
 740                                 }
 741                                 break;
 742                         }
 743                 }
 744         }
 745
 746         /* Accept only unambiguous ref paths. */
 747         if (len && ambiguous_path(str, len))
 748                 return -1;
 749
 750         if (nth_prior) {
 751                 struct strbuf buf = STRBUF_INIT;
 752                 int detached;
 753
 754                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
 755                         detached = (buf.len == the_hash_algo->hexsz && !get_oid_hex(buf.buf, oid));
 756                         strbuf_release(&buf);
 757                         if (detached)
 758                                 return 0;
 759                 }
 760         }
 761
 762         if (!len && reflog_len)
 763                 /* allow "@{...}" to mean the current branch reflog */
 764                 refs_found = dwim_ref("HEAD", 4, oid, &real_ref);
 765         else if (reflog_len)
 766                 refs_found = dwim_log(str, len, oid, &real_ref);
 767         else
 768                 refs_found = dwim_ref(str, len, oid, &real_ref);
 769
 770         if (!refs_found)
 771                 return -1;
 772
 773         if (warn_ambiguous_refs && !(flags & GET_OID_QUIETLY) &&
 774             (refs_found > 1 ||
 775              !get_short_oid(str, len, &tmp_oid, GET_OID_QUIETLY)))
 776                 warning(warn_msg, len, str);
 777
 778         if (reflog_len) {
 779                 int nth, i;
 780                 timestamp_t at_time;
 781                 timestamp_t co_time;
 782                 int co_tz, co_cnt;
 783
 784                 /* Is it asking for N-th entry, or approxidate? */
 785                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 786                         char ch = str[at+2+i];
 787                         if ('0' <= ch && ch <= '9')
 788                                 nth = nth * 10 + ch - '0';
 789                         else
 790                                 nth = -1;
 791                 }
 792                 if (100000000 <= nth) {
 793                         at_time = nth;
 794                         nth = -1;
 795                 } else if (0 <= nth)
 796                         at_time = 0;
 797                 else {
 798                         int errors = 0;
 799                         char *tmp = xstrndup(str + at + 2, reflog_len);
 800                         at_time = approxidate_careful(tmp, &errors);
 801                         free(tmp);
 802                         if (errors) {
 803                                 free(real_ref);
 804                                 return -1;
 805                         }
 806                 }
 807                 if (read_ref_at(real_ref, flags, at_time, nth, oid, NULL,
 808                                 &co_time, &co_tz, &co_cnt)) {
 809                         if (!len) {
 810                                 if (starts_with(real_ref, "refs/heads/")) {
 811                                         str = real_ref + 11;
 812                                         len = strlen(real_ref + 11);
 813                                 } else {
 814                                         /* detached HEAD */
 815                                         str = "HEAD";
 816                                         len = 4;
 817                                 }
 818                         }
 819                         if (at_time) {
 820                                 if (!(flags & GET_OID_QUIETLY)) {
 821                                         warning("Log for '%.*s' only goes "
 822                                                 "back to %s.", len, str,
 823                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
 824                                 }
 825                         } else {
 826                                 if (flags & GET_OID_QUIETLY) {
 827                                         exit(128);
 828                                 }
 829                                 die("Log for '%.*s' only has %d entries.",
 830                                     len, str, co_cnt);
 831                         }
 832                 }
 833         }
 834
 835         free(real_ref);
 836         return 0;
 837 }
 838
 839 static int get_parent(const char *name, int len,
 840                       struct object_id *result, int idx)
 841 {
 842         struct object_id oid;
 843         int ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
 844         struct commit *commit;
 845         struct commit_list *p;
 846
 847         if (ret)
 848                 return ret;
 849         commit = lookup_commit_reference(&oid);
 850         if (parse_commit(commit))
 851                 return -1;
 852         if (!idx) {
 853                 oidcpy(result, &commit->object.oid);
 854                 return 0;
 855         }
 856         p = commit->parents;
 857         while (p) {
 858                 if (!--idx) {
 859                         oidcpy(result, &p->item->object.oid);
 860                         return 0;
 861                 }
 862                 p = p->next;
 863         }
 864         return -1;
 865 }
 866
 867 static int get_nth_ancestor(const char *name, int len,
 868                             struct object_id *result, int generation)
 869 {
 870         struct object_id oid;
 871         struct commit *commit;
 872         int ret;
 873
 874         ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
 875         if (ret)
 876                 return ret;
 877         commit = lookup_commit_reference(&oid);
 878         if (!commit)
 879                 return -1;
 880
 881         while (generation--) {
 882                 if (parse_commit(commit) || !commit->parents)
 883                         return -1;
 884                 commit = commit->parents->item;
 885         }
 886         oidcpy(result, &commit->object.oid);
 887         return 0;
 888 }
 889
 890 struct object *peel_to_type(const char *name, int namelen,
 891                             struct object *o, enum object_type expected_type)
 892 {
 893         if (name && !namelen)
 894                 namelen = strlen(name);
 895         while (1) {
 896                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 897                         return NULL;
 898                 if (expected_type == OBJ_ANY || o->type == expected_type)
 899                         return o;
 900                 if (o->type == OBJ_TAG)
 901                         o = ((struct tag*) o)->tagged;
 902                 else if (o->type == OBJ_COMMIT)
 903                         o = &(get_commit_tree(((struct commit *)o))->object);
 904                 else {
 905                         if (name)
 906                                 error("%.*s: expected %s type, but the object "
 907                                       "dereferences to %s type",
 908                                       namelen, name, type_name(expected_type),
 909                                       type_name(o->type));
 910                         return NULL;
 911                 }
 912         }
 913 }
 914
 915 static int peel_onion(const char *name, int len, struct object_id *oid,
 916                       unsigned lookup_flags)
 917 {
 918         struct object_id outer;
 919         const char *sp;
 920         unsigned int expected_type = 0;
 921         struct object *o;
 922
 923         /*
 924          * "ref^{type}" dereferences ref repeatedly until you cannot
 925          * dereference anymore, or you get an object of given type,
 926          * whichever comes first.  "ref^{}" means just dereference
 927          * tags until you get a non-tag.  "ref^0" is a shorthand for
 928          * "ref^{commit}".  "commit^{tree}" could be used to find the
 929          * top-level tree of the given commit.
 930          */
 931         if (len < 4 || name[len-1] != '}')
 932                 return -1;
 933
 934         for (sp = name + len - 1; name <= sp; sp--) {
 935                 int ch = *sp;
 936                 if (ch == '{' && name < sp && sp[-1] == '^')
 937                         break;
 938         }
 939         if (sp <= name)
 940                 return -1;
 941
 942         sp++; /* beginning of type name, or closing brace for empty */
 943         if (starts_with(sp, "commit}"))
 944                 expected_type = OBJ_COMMIT;
 945         else if (starts_with(sp, "tag}"))
 946                 expected_type = OBJ_TAG;
 947         else if (starts_with(sp, "tree}"))
 948                 expected_type = OBJ_TREE;
 949         else if (starts_with(sp, "blob}"))
 950                 expected_type = OBJ_BLOB;
 951         else if (starts_with(sp, "object}"))
 952                 expected_type = OBJ_ANY;
 953         else if (sp[0] == '}')
 954                 expected_type = OBJ_NONE;
 955         else if (sp[0] == '/')
 956                 expected_type = OBJ_COMMIT;
 957         else
 958                 return -1;
 959
 960         lookup_flags &= ~GET_OID_DISAMBIGUATORS;
 961         if (expected_type == OBJ_COMMIT)
 962                 lookup_flags |= GET_OID_COMMITTISH;
 963         else if (expected_type == OBJ_TREE)
 964                 lookup_flags |= GET_OID_TREEISH;
 965
 966         if (get_oid_1(name, sp - name - 2, &outer, lookup_flags))
 967                 return -1;
 968
 969         o = parse_object(&outer);
 970         if (!o)
 971                 return -1;
 972         if (!expected_type) {
 973                 o = deref_tag(o, name, sp - name - 2);
 974                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 975                         return -1;
 976                 oidcpy(oid, &o->oid);
 977                 return 0;
 978         }
 979
 980         /*
 981          * At this point, the syntax look correct, so
 982          * if we do not get the needed object, we should
 983          * barf.
 984          */
 985         o = peel_to_type(name, len, o, expected_type);
 986         if (!o)
 987                 return -1;
 988
 989         oidcpy(oid, &o->oid);
 990         if (sp[0] == '/') {
 991                 /* "$commit^{/foo}" */
 992                 char *prefix;
 993                 int ret;
 994                 struct commit_list *list = NULL;
 995
 996                 /*
 997                  * $commit^{/}. Some regex implementation may reject.
 998                  * We don't need regex anyway. '' pattern always matches.
 999                  */
1000                 if (sp[1] == '}')
1001                         return 0;
1002
1003                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
1004                 commit_list_insert((struct commit *)o, &list);
1005                 ret = get_oid_oneline(prefix, oid, list);
1006                 free(prefix);
1007                 return ret;
1008         }
1009         return 0;
1010 }
1011
1012 static int get_describe_name(const char *name, int len, struct object_id *oid)
1013 {
1014         const char *cp;
1015         unsigned flags = GET_OID_QUIETLY | GET_OID_COMMIT;
1016
1017         for (cp = name + len - 1; name + 2 <= cp; cp--) {
1018                 char ch = *cp;
1019                 if (!isxdigit(ch)) {
1020                         /* We must be looking at g in "SOMETHING-g"
1021                          * for it to be describe output.
1022                          */
1023                         if (ch == 'g' && cp[-1] == '-') {
1024                                 cp++;
1025                                 len -= cp - name;
1026                                 return get_short_oid(cp, len, oid, flags);
1027                         }
1028                 }
1029         }
1030         return -1;
1031 }
1032
1033 static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags)
1034 {
1035         int ret, has_suffix;
1036         const char *cp;
1037
1038         /*
1039          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
1040          */
1041         has_suffix = 0;
1042         for (cp = name + len - 1; name <= cp; cp--) {
1043                 int ch = *cp;
1044                 if ('0' <= ch && ch <= '9')
1045                         continue;
1046                 if (ch == '~' || ch == '^')
1047                         has_suffix = ch;
1048                 break;
1049         }
1050
1051         if (has_suffix) {
1052                 int num = 0;
1053                 int len1 = cp - name;
1054                 cp++;
1055                 while (cp < name + len)
1056                         num = num * 10 + *cp++ - '0';
1057                 if (!num && len1 == len - 1)
1058                         num = 1;
1059                 if (has_suffix == '^')
1060                         return get_parent(name, len1, oid, num);
1061                 /* else if (has_suffix == '~') -- goes without saying */
1062                 return get_nth_ancestor(name, len1, oid, num);
1063         }
1064
1065         ret = peel_onion(name, len, oid, lookup_flags);
1066         if (!ret)
1067                 return 0;
1068
1069         ret = get_oid_basic(name, len, oid, lookup_flags);
1070         if (!ret)
1071                 return 0;
1072
1073         /* It could be describe output that is "SOMETHING-gXXXX" */
1074         ret = get_describe_name(name, len, oid);
1075         if (!ret)
1076                 return 0;
1077
1078         return get_short_oid(name, len, oid, lookup_flags);
1079 }
1080
1081 /*
1082  * This interprets names like ':/Initial revision of "git"' by searching
1083  * through history and returning the first commit whose message starts
1084  * the given regular expression.
1085  *
1086  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
1087  *
1088  * For a literal '!' character at the beginning of a pattern, you have to repeat
1089  * that, like: ':/!!foo'
1090  *
1091  * For future extension, all other sequences beginning with ':/!' are reserved.
1092  */
1093
1094 /* Remember to update object flag allocation in object.h */
1095 #define ONELINE_SEEN (1u<<20)
1096
1097 static int handle_one_ref(const char *path, const struct object_id *oid,
1098                           int flag, void *cb_data)
1099 {
1100         struct commit_list **list = cb_data;
1101         struct object *object = parse_object(oid);
1102         if (!object)
1103                 return 0;
1104         if (object->type == OBJ_TAG) {
1105                 object = deref_tag(object, path, strlen(path));
1106                 if (!object)
1107                         return 0;
1108         }
1109         if (object->type != OBJ_COMMIT)
1110                 return 0;
1111         commit_list_insert((struct commit *)object, list);
1112         return 0;
1113 }
1114
1115 static int get_oid_oneline(const char *prefix, struct object_id *oid,
1116                             struct commit_list *list)
1117 {
1118         struct commit_list *backup = NULL, *l;
1119         int found = 0;
1120         int negative = 0;
1121         regex_t regex;
1122
1123         if (prefix[0] == '!') {
1124                 prefix++;
1125
1126                 if (prefix[0] == '-') {
1127                         prefix++;
1128                         negative = 1;
1129                 } else if (prefix[0] != '!') {
1130                         return -1;
1131                 }
1132         }
1133
1134         if (regcomp(&regex, prefix, REG_EXTENDED))
1135                 return -1;
1136
1137         for (l = list; l; l = l->next) {
1138                 l->item->object.flags |= ONELINE_SEEN;
1139                 commit_list_insert(l->item, &backup);
1140         }
1141         while (list) {
1142                 const char *p, *buf;
1143                 struct commit *commit;
1144                 int matches;
1145
1146                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1147                 if (!parse_object(&commit->object.oid))
1148                         continue;
1149                 buf = get_commit_buffer(commit, NULL);
1150                 p = strstr(buf, "\n\n");
1151                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1152                 unuse_commit_buffer(commit, buf);
1153
1154                 if (matches) {
1155                         oidcpy(oid, &commit->object.oid);
1156                         found = 1;
1157                         break;
1158                 }
1159         }
1160         regfree(&regex);
1161         free_commit_list(list);
1162         for (l = backup; l; l = l->next)
1163                 clear_commit_marks(l->item, ONELINE_SEEN);
1164         free_commit_list(backup);
1165         return found ? 0 : -1;
1166 }
1167
1168 struct grab_nth_branch_switch_cbdata {
1169         int remaining;
1170         struct strbuf buf;
1171 };
1172
1173 static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
1174                                   const char *email, timestamp_t timestamp, int tz,
1175                                   const char *message, void *cb_data)
1176 {
1177         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1178         const char *match = NULL, *target = NULL;
1179         size_t len;
1180
1181         if (skip_prefix(message, "checkout: moving from ", &match))
1182                 target = strstr(match, " to ");
1183
1184         if (!match || !target)
1185                 return 0;
1186         if (--(cb->remaining) == 0) {
1187                 len = target - match;
1188                 strbuf_reset(&cb->buf);
1189                 strbuf_add(&cb->buf, match, len);
1190                 return 1; /* we are done */
1191         }
1192         return 0;
1193 }
1194
1195 /*
1196  * Parse @{-N} syntax, return the number of characters parsed
1197  * if successful; otherwise signal an error with negative value.
1198  */
1199 static int interpret_nth_prior_checkout(const char *name, int namelen,
1200                                         struct strbuf *buf)
1201 {
1202         long nth;
1203         int retval;
1204         struct grab_nth_branch_switch_cbdata cb;
1205         const char *brace;
1206         char *num_end;
1207
1208         if (namelen < 4)
1209                 return -1;
1210         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1211                 return -1;
1212         brace = memchr(name, '}', namelen);
1213         if (!brace)
1214                 return -1;
1215         nth = strtol(name + 3, &num_end, 10);
1216         if (num_end != brace)
1217                 return -1;
1218         if (nth <= 0)
1219                 return -1;
1220         cb.remaining = nth;
1221         strbuf_init(&cb.buf, 20);
1222
1223         retval = 0;
1224         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1225                 strbuf_reset(buf);
1226                 strbuf_addbuf(buf, &cb.buf);
1227                 retval = brace - name + 1;
1228         }
1229
1230         strbuf_release(&cb.buf);
1231         return retval;
1232 }
1233
1234 int get_oid_mb(const char *name, struct object_id *oid)
1235 {
1236         struct commit *one, *two;
1237         struct commit_list *mbs;
1238         struct object_id oid_tmp;
1239         const char *dots;
1240         int st;
1241
1242         dots = strstr(name, "...");
1243         if (!dots)
1244                 return get_oid(name, oid);
1245         if (dots == name)
1246                 st = get_oid("HEAD", &oid_tmp);
1247         else {
1248                 struct strbuf sb;
1249                 strbuf_init(&sb, dots - name);
1250                 strbuf_add(&sb, name, dots - name);
1251                 st = get_oid_committish(sb.buf, &oid_tmp);
1252                 strbuf_release(&sb);
1253         }
1254         if (st)
1255                 return st;
1256         one = lookup_commit_reference_gently(&oid_tmp, 0);
1257         if (!one)
1258                 return -1;
1259
1260         if (get_oid_committish(dots[3] ? (dots + 3) : "HEAD", &oid_tmp))
1261                 return -1;
1262         two = lookup_commit_reference_gently(&oid_tmp, 0);
1263         if (!two)
1264                 return -1;
1265         mbs = get_merge_bases(one, two);
1266         if (!mbs || mbs->next)
1267                 st = -1;
1268         else {
1269                 st = 0;
1270                 oidcpy(oid, &mbs->item->object.oid);
1271         }
1272         free_commit_list(mbs);
1273         return st;
1274 }
1275
1276 /* parse @something syntax, when 'something' is not {.*} */
1277 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1278 {
1279         const char *next;
1280
1281         if (len || name[1] == '{')
1282                 return -1;
1283
1284         /* make sure it's a single @, or @@{.*}, not @foo */
1285         next = memchr(name + len + 1, '@', namelen - len - 1);
1286         if (next && next[1] != '{')
1287                 return -1;
1288         if (!next)
1289                 next = name + namelen;
1290         if (next != name + 1)
1291                 return -1;
1292
1293         strbuf_reset(buf);
1294         strbuf_add(buf, "HEAD", 4);
1295         return 1;
1296 }
1297
1298 static int reinterpret(const char *name, int namelen, int len,
1299                        struct strbuf *buf, unsigned allowed)
1300 {
1301         /* we have extra data, which might need further processing */
1302         struct strbuf tmp = STRBUF_INIT;
1303         int used = buf->len;
1304         int ret;
1305
1306         strbuf_add(buf, name + len, namelen - len);
1307         ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
1308         /* that data was not interpreted, remove our cruft */
1309         if (ret < 0) {
1310                 strbuf_setlen(buf, used);
1311                 return len;
1312         }
1313         strbuf_reset(buf);
1314         strbuf_addbuf(buf, &tmp);
1315         strbuf_release(&tmp);
1316         /* tweak for size of {-N} versus expanded ref name */
1317         return ret - used + len;
1318 }
1319
1320 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1321 {
1322         char *s = shorten_unambiguous_ref(ref, 0);
1323         strbuf_reset(buf);
1324         strbuf_addstr(buf, s);
1325         free(s);
1326 }
1327
1328 static int branch_interpret_allowed(const char *refname, unsigned allowed)
1329 {
1330         if (!allowed)
1331                 return 1;
1332
1333         if ((allowed & INTERPRET_BRANCH_LOCAL) &&
1334             starts_with(refname, "refs/heads/"))
1335                 return 1;
1336         if ((allowed & INTERPRET_BRANCH_REMOTE) &&
1337             starts_with(refname, "refs/remotes/"))
1338                 return 1;
1339
1340         return 0;
1341 }
1342
1343 static int interpret_branch_mark(const char *name, int namelen,
1344                                  int at, struct strbuf *buf,
1345                                  int (*get_mark)(const char *, int),
1346                                  const char *(*get_data)(struct branch *,
1347                                                          struct strbuf *),
1348                                  unsigned allowed)
1349 {
1350         int len;
1351         struct branch *branch;
1352         struct strbuf err = STRBUF_INIT;
1353         const char *value;
1354
1355         len = get_mark(name + at, namelen - at);
1356         if (!len)
1357                 return -1;
1358
1359         if (memchr(name, ':', at))
1360                 return -1;
1361
1362         if (at) {
1363                 char *name_str = xmemdupz(name, at);
1364                 branch = branch_get(name_str);
1365                 free(name_str);
1366         } else
1367                 branch = branch_get(NULL);
1368
1369         value = get_data(branch, &err);
1370         if (!value)
1371                 die("%s", err.buf);
1372
1373         if (!branch_interpret_allowed(value, allowed))
1374                 return -1;
1375
1376         set_shortened_ref(buf, value);
1377         return len + at;
1378 }
1379
1380 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
1381                           unsigned allowed)
1382 {
1383         char *at;
1384         const char *start;
1385         int len;
1386
1387         if (!namelen)
1388                 namelen = strlen(name);
1389
1390         if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
1391                 len = interpret_nth_prior_checkout(name, namelen, buf);
1392                 if (!len) {
1393                         return len; /* syntax Ok, not enough switches */
1394                 } else if (len > 0) {
1395                         if (len == namelen)
1396                                 return len; /* consumed all */
1397                         else
1398                                 return reinterpret(name, namelen, len, buf, allowed);
1399                 }
1400         }
1401
1402         for (start = name;
1403              (at = memchr(start, '@', namelen - (start - name)));
1404              start = at + 1) {
1405
1406                 if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
1407                         len = interpret_empty_at(name, namelen, at - name, buf);
1408                         if (len > 0)
1409                                 return reinterpret(name, namelen, len, buf,
1410                                                    allowed);
1411                 }
1412
1413                 len = interpret_branch_mark(name, namelen, at - name, buf,
1414                                             upstream_mark, branch_get_upstream,
1415                                             allowed);
1416                 if (len > 0)
1417                         return len;
1418
1419                 len = interpret_branch_mark(name, namelen, at - name, buf,
1420                                             push_mark, branch_get_push,
1421                                             allowed);
1422                 if (len > 0)
1423                         return len;
1424         }
1425
1426         return -1;
1427 }
1428
1429 void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
1430 {
1431         int len = strlen(name);
1432         int used = interpret_branch_name(name, len, sb, allowed);
1433
1434         if (used < 0)
1435                 used = 0;
1436         strbuf_add(sb, name + used, len - used);
1437 }
1438
1439 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1440 {
1441         if (startup_info->have_repository)
1442                 strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
1443         else
1444                 strbuf_addstr(sb, name);
1445
1446         /*
1447          * This splice must be done even if we end up rejecting the
1448          * name; builtin/branch.c::copy_or_rename_branch() still wants
1449          * to see what the name expanded to so that "branch -m" can be
1450          * used as a tool to correct earlier mistakes.
1451          */
1452         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1453
1454         if (*name == '-' ||
1455             !strcmp(sb->buf, "refs/heads/HEAD"))
1456                 return -1;
1457
1458         return check_refname_format(sb->buf, 0);
1459 }
1460
1461 /*
1462  * This is like "get_oid_basic()", except it allows "object ID expressions",
1463  * notably "xyz^" for "parent of xyz"
1464  */
1465 int get_oid(const char *name, struct object_id *oid)
1466 {
1467         struct object_context unused;
1468         return get_oid_with_context(name, 0, oid, &unused);
1469 }
1470
1471
1472 /*
1473  * Many callers know that the user meant to name a commit-ish by
1474  * syntactical positions where the object name appears.  Calling this
1475  * function allows the machinery to disambiguate shorter-than-unique
1476  * abbreviated object names between commit-ish and others.
1477  *
1478  * Note that this does NOT error out when the named object is not a
1479  * commit-ish. It is merely to give a hint to the disambiguation
1480  * machinery.
1481  */
1482 int get_oid_committish(const char *name, struct object_id *oid)
1483 {
1484         struct object_context unused;
1485         return get_oid_with_context(name, GET_OID_COMMITTISH,
1486                                     oid, &unused);
1487 }
1488
1489 int get_oid_treeish(const char *name, struct object_id *oid)
1490 {
1491         struct object_context unused;
1492         return get_oid_with_context(name, GET_OID_TREEISH,
1493                                     oid, &unused);
1494 }
1495
1496 int get_oid_commit(const char *name, struct object_id *oid)
1497 {
1498         struct object_context unused;
1499         return get_oid_with_context(name, GET_OID_COMMIT,
1500                                     oid, &unused);
1501 }
1502
1503 int get_oid_tree(const char *name, struct object_id *oid)
1504 {
1505         struct object_context unused;
1506         return get_oid_with_context(name, GET_OID_TREE,
1507                                     oid, &unused);
1508 }
1509
1510 int get_oid_blob(const char *name, struct object_id *oid)
1511 {
1512         struct object_context unused;
1513         return get_oid_with_context(name, GET_OID_BLOB,
1514                                     oid, &unused);
1515 }
1516
1517 /* Must be called only when object_name:filename doesn't exist. */
1518 static void diagnose_invalid_oid_path(const char *prefix,
1519                                       const char *filename,
1520                                       const struct object_id *tree_oid,
1521                                       const char *object_name,
1522                                       int object_name_len)
1523 {
1524         struct object_id oid;
1525         unsigned mode;
1526
1527         if (!prefix)
1528                 prefix = "";
1529
1530         if (file_exists(filename))
1531                 die("Path '%s' exists on disk, but not in '%.*s'.",
1532                     filename, object_name_len, object_name);
1533         if (is_missing_file_error(errno)) {
1534                 char *fullname = xstrfmt("%s%s", prefix, filename);
1535
1536                 if (!get_tree_entry(tree_oid, fullname, &oid, &mode)) {
1537                         die("Path '%s' exists, but not '%s'.\n"
1538                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1539                             fullname,
1540                             filename,
1541                             object_name_len, object_name,
1542                             fullname,
1543                             object_name_len, object_name,
1544                             filename);
1545                 }
1546                 die("Path '%s' does not exist in '%.*s'",
1547                     filename, object_name_len, object_name);
1548         }
1549 }
1550
1551 /* Must be called only when :stage:filename doesn't exist. */
1552 static void diagnose_invalid_index_path(int stage,
1553                                         const char *prefix,
1554                                         const char *filename)
1555 {
1556         const struct cache_entry *ce;
1557         int pos;
1558         unsigned namelen = strlen(filename);
1559         struct strbuf fullname = STRBUF_INIT;
1560
1561         if (!prefix)
1562                 prefix = "";
1563
1564         /* Wrong stage number? */
1565         pos = cache_name_pos(filename, namelen);
1566         if (pos < 0)
1567                 pos = -pos - 1;
1568         if (pos < active_nr) {
1569                 ce = active_cache[pos];
1570                 if (ce_namelen(ce) == namelen &&
1571                     !memcmp(ce->name, filename, namelen))
1572                         die("Path '%s' is in the index, but not at stage %d.\n"
1573                             "Did you mean ':%d:%s'?",
1574                             filename, stage,
1575                             ce_stage(ce), filename);
1576         }
1577
1578         /* Confusion between relative and absolute filenames? */
1579         strbuf_addstr(&fullname, prefix);
1580         strbuf_addstr(&fullname, filename);
1581         pos = cache_name_pos(fullname.buf, fullname.len);
1582         if (pos < 0)
1583                 pos = -pos - 1;
1584         if (pos < active_nr) {
1585                 ce = active_cache[pos];
1586                 if (ce_namelen(ce) == fullname.len &&
1587                     !memcmp(ce->name, fullname.buf, fullname.len))
1588                         die("Path '%s' is in the index, but not '%s'.\n"
1589                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1590                             fullname.buf, filename,
1591                             ce_stage(ce), fullname.buf,
1592                             ce_stage(ce), filename);
1593         }
1594
1595         if (file_exists(filename))
1596                 die("Path '%s' exists on disk, but not in the index.", filename);
1597         if (is_missing_file_error(errno))
1598                 die("Path '%s' does not exist (neither on disk nor in the index).",
1599                     filename);
1600
1601         strbuf_release(&fullname);
1602 }
1603
1604
1605 static char *resolve_relative_path(const char *rel)
1606 {
1607         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1608                 return NULL;
1609
1610         if (!is_inside_work_tree())
1611                 die("relative path syntax can't be used outside working tree.");
1612
1613         /* die() inside prefix_path() if resolved path is outside worktree */
1614         return prefix_path(startup_info->prefix,
1615                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1616                            rel);
1617 }
1618
1619 static int get_oid_with_context_1(const char *name,
1620                                   unsigned flags,
1621                                   const char *prefix,
1622                                   struct object_id *oid,
1623                                   struct object_context *oc)
1624 {
1625         int ret, bracket_depth;
1626         int namelen = strlen(name);
1627         const char *cp;
1628         int only_to_die = flags & GET_OID_ONLY_TO_DIE;
1629
1630         if (only_to_die)
1631                 flags |= GET_OID_QUIETLY;
1632
1633         memset(oc, 0, sizeof(*oc));
1634         oc->mode = S_IFINVALID;
1635         strbuf_init(&oc->symlink_path, 0);
1636         ret = get_oid_1(name, namelen, oid, flags);
1637         if (!ret)
1638                 return ret;
1639         /*
1640          * sha1:path --> object name of path in ent sha1
1641          * :path -> object name of absolute path in index
1642          * :./path -> object name of path relative to cwd in index
1643          * :[0-3]:path -> object name of path in index at stage
1644          * :/foo -> recent commit matching foo
1645          */
1646         if (name[0] == ':') {
1647                 int stage = 0;
1648                 const struct cache_entry *ce;
1649                 char *new_path = NULL;
1650                 int pos;
1651                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1652                         struct commit_list *list = NULL;
1653
1654                         for_each_ref(handle_one_ref, &list);
1655                         commit_list_sort_by_date(&list);
1656                         return get_oid_oneline(name + 2, oid, list);
1657                 }
1658                 if (namelen < 3 ||
1659                     name[2] != ':' ||
1660                     name[1] < '0' || '3' < name[1])
1661                         cp = name + 1;
1662                 else {
1663                         stage = name[1] - '0';
1664                         cp = name + 3;
1665                 }
1666                 new_path = resolve_relative_path(cp);
1667                 if (!new_path) {
1668                         namelen = namelen - (cp - name);
1669                 } else {
1670                         cp = new_path;
1671                         namelen = strlen(cp);
1672                 }
1673
1674                 if (flags & GET_OID_RECORD_PATH)
1675                         oc->path = xstrdup(cp);
1676
1677                 if (!active_cache)
1678                         read_cache();
1679                 pos = cache_name_pos(cp, namelen);
1680                 if (pos < 0)
1681                         pos = -pos - 1;
1682                 while (pos < active_nr) {
1683                         ce = active_cache[pos];
1684                         if (ce_namelen(ce) != namelen ||
1685                             memcmp(ce->name, cp, namelen))
1686                                 break;
1687                         if (ce_stage(ce) == stage) {
1688                                 oidcpy(oid, &ce->oid);
1689                                 oc->mode = ce->ce_mode;
1690                                 free(new_path);
1691                                 return 0;
1692                         }
1693                         pos++;
1694                 }
1695                 if (only_to_die && name[1] && name[1] != '/')
1696                         diagnose_invalid_index_path(stage, prefix, cp);
1697                 free(new_path);
1698                 return -1;
1699         }
1700         for (cp = name, bracket_depth = 0; *cp; cp++) {
1701                 if (*cp == '{')
1702                         bracket_depth++;
1703                 else if (bracket_depth && *cp == '}')
1704                         bracket_depth--;
1705                 else if (!bracket_depth && *cp == ':')
1706                         break;
1707         }
1708         if (*cp == ':') {
1709                 struct object_id tree_oid;
1710                 int len = cp - name;
1711                 unsigned sub_flags = flags;
1712
1713                 sub_flags &= ~GET_OID_DISAMBIGUATORS;
1714                 sub_flags |= GET_OID_TREEISH;
1715
1716                 if (!get_oid_1(name, len, &tree_oid, sub_flags)) {
1717                         const char *filename = cp+1;
1718                         char *new_filename = NULL;
1719
1720                         new_filename = resolve_relative_path(filename);
1721                         if (new_filename)
1722                                 filename = new_filename;
1723                         if (flags & GET_OID_FOLLOW_SYMLINKS) {
1724                                 ret = get_tree_entry_follow_symlinks(&tree_oid,
1725                                         filename, oid, &oc->symlink_path,
1726                                         &oc->mode);
1727                         } else {
1728                                 ret = get_tree_entry(&tree_oid, filename, oid,
1729                                                      &oc->mode);
1730                                 if (ret && only_to_die) {
1731                                         diagnose_invalid_oid_path(prefix,
1732                                                                    filename,
1733                                                                    &tree_oid,
1734                                                                    name, len);
1735                                 }
1736                         }
1737                         if (flags & GET_OID_RECORD_PATH)
1738                                 oc->path = xstrdup(filename);
1739
1740                         free(new_filename);
1741                         return ret;
1742                 } else {
1743                         if (only_to_die)
1744                                 die("Invalid object name '%.*s'.", len, name);
1745                 }
1746         }
1747         return ret;
1748 }
1749
1750 /*
1751  * Call this function when you know "name" given by the end user must
1752  * name an object but it doesn't; the function _may_ die with a better
1753  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1754  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1755  * you have a chance to diagnose the error further.
1756  */
1757 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1758 {
1759         struct object_context oc;
1760         struct object_id oid;
1761         get_oid_with_context_1(name, GET_OID_ONLY_TO_DIE, prefix, &oid, &oc);
1762 }
1763
1764 int get_oid_with_context(const char *str, unsigned flags, struct object_id *oid, struct object_context *oc)
1765 {
1766         if (flags & GET_OID_FOLLOW_SYMLINKS && flags & GET_OID_ONLY_TO_DIE)
1767                 BUG("incompatible flags for get_sha1_with_context");
1768         return get_oid_with_context_1(str, flags, NULL, oid, oc);
1769 }