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