sha1_name.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tree-walk.h"
   7 #include "refs.h"
   8 #include "remote.h"
   9
  10 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
  11
  12 typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
  13
  14 struct disambiguate_state {
  15         disambiguate_hint_fn fn;
  16         void *cb_data;
  17         unsigned char candidate[20];
  18         unsigned candidate_exists:1;
  19         unsigned candidate_checked:1;
  20         unsigned candidate_ok:1;
  21         unsigned disambiguate_fn_used:1;
  22         unsigned ambiguous:1;
  23         unsigned always_call_fn:1;
  24 };
  25
  26 static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
  27 {
  28         if (ds->always_call_fn) {
  29                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  30                 return;
  31         }
  32         if (!ds->candidate_exists) {
  33                 /* this is the first candidate */
  34                 hashcpy(ds->candidate, current);
  35                 ds->candidate_exists = 1;
  36                 return;
  37         } else if (!hashcmp(ds->candidate, current)) {
  38                 /* the same as what we already have seen */
  39                 return;
  40         }
  41
  42         if (!ds->fn) {
  43                 /* cannot disambiguate between ds->candidate and current */
  44                 ds->ambiguous = 1;
  45                 return;
  46         }
  47
  48         if (!ds->candidate_checked) {
  49                 ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
  50                 ds->disambiguate_fn_used = 1;
  51                 ds->candidate_checked = 1;
  52         }
  53
  54         if (!ds->candidate_ok) {
  55                 /* discard the candidate; we know it does not satisify fn */
  56                 hashcpy(ds->candidate, current);
  57                 ds->candidate_checked = 0;
  58                 return;
  59         }
  60
  61         /* if we reach this point, we know ds->candidate satisfies fn */
  62         if (ds->fn(current, ds->cb_data)) {
  63                 /*
  64                  * if both current and candidate satisfy fn, we cannot
  65                  * disambiguate.
  66                  */
  67                 ds->candidate_ok = 0;
  68                 ds->ambiguous = 1;
  69         }
  70
  71         /* otherwise, current can be discarded and candidate is still good */
  72 }
  73
  74 static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
  75 {
  76         struct alternate_object_database *alt;
  77         char hex[40];
  78         static struct alternate_object_database *fakeent;
  79
  80         if (!fakeent) {
  81                 /*
  82                  * Create a "fake" alternate object database that
  83                  * points to our own object database, to make it
  84                  * easier to get a temporary working space in
  85                  * alt->name/alt->base while iterating over the
  86                  * object databases including our own.
  87                  */
  88                 const char *objdir = get_object_directory();
  89                 int objdir_len = strlen(objdir);
  90                 int entlen = objdir_len + 43;
  91                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  92                 memcpy(fakeent->base, objdir, objdir_len);
  93                 fakeent->name = fakeent->base + objdir_len + 1;
  94                 fakeent->name[-1] = '/';
  95         }
  96         fakeent->next = alt_odb_list;
  97
  98         sprintf(hex, "%.2s", hex_pfx);
  99         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 100                 struct dirent *de;
 101                 DIR *dir;
 102                 sprintf(alt->name, "%.2s/", hex_pfx);
 103                 dir = opendir(alt->base);
 104                 if (!dir)
 105                         continue;
 106
 107                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
 108                         unsigned char sha1[20];
 109
 110                         if (strlen(de->d_name) != 38)
 111                                 continue;
 112                         if (memcmp(de->d_name, hex_pfx + 2, len - 2))
 113                                 continue;
 114                         memcpy(hex + 2, de->d_name, 38);
 115                         if (!get_sha1_hex(hex, sha1))
 116                                 update_candidates(ds, sha1);
 117                 }
 118                 closedir(dir);
 119         }
 120 }
 121
 122 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 123 {
 124         do {
 125                 if (*a != *b)
 126                         return 0;
 127                 a++;
 128                 b++;
 129                 len -= 2;
 130         } while (len > 1);
 131         if (len)
 132                 if ((*a ^ *b) & 0xf0)
 133                         return 0;
 134         return 1;
 135 }
 136
 137 static void unique_in_pack(int len,
 138                           const unsigned char *bin_pfx,
 139                            struct packed_git *p,
 140                            struct disambiguate_state *ds)
 141 {
 142         uint32_t num, last, i, first = 0;
 143         const unsigned char *current = NULL;
 144
 145         open_pack_index(p);
 146         num = p->num_objects;
 147         last = num;
 148         while (first < last) {
 149                 uint32_t mid = (first + last) / 2;
 150                 const unsigned char *current;
 151                 int cmp;
 152
 153                 current = nth_packed_object_sha1(p, mid);
 154                 cmp = hashcmp(bin_pfx, current);
 155                 if (!cmp) {
 156                         first = mid;
 157                         break;
 158                 }
 159                 if (cmp > 0) {
 160                         first = mid+1;
 161                         continue;
 162                 }
 163                 last = mid;
 164         }
 165
 166         /*
 167          * At this point, "first" is the location of the lowest object
 168          * with an object name that could match "bin_pfx".  See if we have
 169          * 0, 1 or more objects that actually match(es).
 170          */
 171         for (i = first; i < num && !ds->ambiguous; i++) {
 172                 current = nth_packed_object_sha1(p, i);
 173                 if (!match_sha(len, bin_pfx, current))
 174                         break;
 175                 update_candidates(ds, current);
 176         }
 177 }
 178
 179 static void find_short_packed_object(int len, const unsigned char *bin_pfx,
 180                                      struct disambiguate_state *ds)
 181 {
 182         struct packed_git *p;
 183
 184         prepare_packed_git();
 185         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 186                 unique_in_pack(len, bin_pfx, p, ds);
 187 }
 188
 189 #define SHORT_NAME_NOT_FOUND (-1)
 190 #define SHORT_NAME_AMBIGUOUS (-2)
 191
 192 static int finish_object_disambiguation(struct disambiguate_state *ds,
 193                                         unsigned char *sha1)
 194 {
 195         if (ds->ambiguous)
 196                 return SHORT_NAME_AMBIGUOUS;
 197
 198         if (!ds->candidate_exists)
 199                 return SHORT_NAME_NOT_FOUND;
 200
 201         if (!ds->candidate_checked)
 202                 /*
 203                  * If this is the only candidate, there is no point
 204                  * calling the disambiguation hint callback.
 205                  *
 206                  * On the other hand, if the current candidate
 207                  * replaced an earlier candidate that did _not_ pass
 208                  * the disambiguation hint callback, then we do have
 209                  * more than one objects that match the short name
 210                  * given, so we should make sure this one matches;
 211                  * otherwise, if we discovered this one and the one
 212                  * that we previously discarded in the reverse order,
 213                  * we would end up showing different results in the
 214                  * same repository!
 215                  */
 216                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 217                                     ds->fn(ds->candidate, ds->cb_data));
 218
 219         if (!ds->candidate_ok)
 220                 return SHORT_NAME_AMBIGUOUS;
 221
 222         hashcpy(sha1, ds->candidate);
 223         return 0;
 224 }
 225
 226 static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
 227 {
 228         int kind = sha1_object_info(sha1, NULL);
 229         return kind == OBJ_COMMIT;
 230 }
 231
 232 static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
 233 {
 234         struct object *obj;
 235         int kind;
 236
 237         kind = sha1_object_info(sha1, NULL);
 238         if (kind == OBJ_COMMIT)
 239                 return 1;
 240         if (kind != OBJ_TAG)
 241                 return 0;
 242
 243         /* We need to do this the hard way... */
 244         obj = deref_tag(lookup_object(sha1), NULL, 0);
 245         if (obj && obj->type == OBJ_COMMIT)
 246                 return 1;
 247         return 0;
 248 }
 249
 250 static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
 251 {
 252         int kind = sha1_object_info(sha1, NULL);
 253         return kind == OBJ_TREE;
 254 }
 255
 256 static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
 257 {
 258         struct object *obj;
 259         int kind;
 260
 261         kind = sha1_object_info(sha1, NULL);
 262         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 263                 return 1;
 264         if (kind != OBJ_TAG)
 265                 return 0;
 266
 267         /* We need to do this the hard way... */
 268         obj = deref_tag(lookup_object(sha1), NULL, 0);
 269         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 270                 return 1;
 271         return 0;
 272 }
 273
 274 static int disambiguate_blob_only(const unsigned char *sha1, void *cb_data_unused)
 275 {
 276         int kind = sha1_object_info(sha1, NULL);
 277         return kind == OBJ_BLOB;
 278 }
 279
 280 static int prepare_prefixes(const char *name, int len,
 281                             unsigned char *bin_pfx,
 282                             char *hex_pfx)
 283 {
 284         int i;
 285
 286         hashclr(bin_pfx);
 287         memset(hex_pfx, 'x', 40);
 288         for (i = 0; i < len ;i++) {
 289                 unsigned char c = name[i];
 290                 unsigned char val;
 291                 if (c >= '0' && c <= '9')
 292                         val = c - '0';
 293                 else if (c >= 'a' && c <= 'f')
 294                         val = c - 'a' + 10;
 295                 else if (c >= 'A' && c <='F') {
 296                         val = c - 'A' + 10;
 297                         c -= 'A' - 'a';
 298                 }
 299                 else
 300                         return -1;
 301                 hex_pfx[i] = c;
 302                 if (!(i & 1))
 303                         val <<= 4;
 304                 bin_pfx[i >> 1] |= val;
 305         }
 306         return 0;
 307 }
 308
 309 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 310                           unsigned flags)
 311 {
 312         int status;
 313         char hex_pfx[40];
 314         unsigned char bin_pfx[20];
 315         struct disambiguate_state ds;
 316         int quietly = !!(flags & GET_SHA1_QUIETLY);
 317
 318         if (len < MINIMUM_ABBREV || len > 40)
 319                 return -1;
 320         if (prepare_prefixes(name, len, bin_pfx, hex_pfx) < 0)
 321                 return -1;
 322
 323         prepare_alt_odb();
 324
 325         memset(&ds, 0, sizeof(ds));
 326         if (flags & GET_SHA1_COMMIT)
 327                 ds.fn = disambiguate_commit_only;
 328         else if (flags & GET_SHA1_COMMITTISH)
 329                 ds.fn = disambiguate_committish_only;
 330         else if (flags & GET_SHA1_TREE)
 331                 ds.fn = disambiguate_tree_only;
 332         else if (flags & GET_SHA1_TREEISH)
 333                 ds.fn = disambiguate_treeish_only;
 334         else if (flags & GET_SHA1_BLOB)
 335                 ds.fn = disambiguate_blob_only;
 336
 337         find_short_object_filename(len, hex_pfx, &ds);
 338         find_short_packed_object(len, bin_pfx, &ds);
 339         status = finish_object_disambiguation(&ds, sha1);
 340
 341         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 342                 return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
 343         return status;
 344 }
 345
 346
 347 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 348 {
 349         char hex_pfx[40];
 350         unsigned char bin_pfx[20];
 351         struct disambiguate_state ds;
 352         int len = strlen(prefix);
 353
 354         if (len < MINIMUM_ABBREV || len > 40)
 355                 return -1;
 356         if (prepare_prefixes(prefix, len, bin_pfx, hex_pfx) < 0)
 357                 return -1;
 358
 359         prepare_alt_odb();
 360
 361         memset(&ds, 0, sizeof(ds));
 362         ds.always_call_fn = 1;
 363         ds.cb_data = cb_data;
 364         ds.fn = fn;
 365
 366         find_short_object_filename(len, hex_pfx, &ds);
 367         find_short_packed_object(len, bin_pfx, &ds);
 368         return ds.ambiguous;
 369 }
 370
 371 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 372 {
 373         int status, exists;
 374         static char hex[41];
 375
 376         exists = has_sha1_file(sha1);
 377         memcpy(hex, sha1_to_hex(sha1), 40);
 378         if (len == 40 || !len)
 379                 return hex;
 380         while (len < 40) {
 381                 unsigned char sha1_ret[20];
 382                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
 383                 if (exists
 384                     ? !status
 385                     : status == SHORT_NAME_NOT_FOUND) {
 386                         hex[len] = 0;
 387                         return hex;
 388                 }
 389                 len++;
 390         }
 391         return hex;
 392 }
 393
 394 static int ambiguous_path(const char *path, int len)
 395 {
 396         int slash = 1;
 397         int cnt;
 398
 399         for (cnt = 0; cnt < len; cnt++) {
 400                 switch (*path++) {
 401                 case '\0':
 402                         break;
 403                 case '/':
 404                         if (slash)
 405                                 break;
 406                         slash = 1;
 407                         continue;
 408                 case '.':
 409                         continue;
 410                 default:
 411                         slash = 0;
 412                         continue;
 413                 }
 414                 break;
 415         }
 416         return slash;
 417 }
 418
 419 static inline int upstream_mark(const char *string, int len)
 420 {
 421         const char *suffix[] = { "@{upstream}", "@{u}" };
 422         int i;
 423
 424         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 425                 int suffix_len = strlen(suffix[i]);
 426                 if (suffix_len <= len
 427                     && !memcmp(string, suffix[i], suffix_len))
 428                         return suffix_len;
 429         }
 430         return 0;
 431 }
 432
 433 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 434
 435 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 436 {
 437         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 438         char *real_ref = NULL;
 439         int refs_found = 0;
 440         int at, reflog_len;
 441
 442         if (len == 40 && !get_sha1_hex(str, sha1))
 443                 return 0;
 444
 445         /* basic@{time or number or -number} format to query ref-log */
 446         reflog_len = at = 0;
 447         if (len && str[len-1] == '}') {
 448                 for (at = len-2; at >= 0; at--) {
 449                         if (str[at] == '@' && str[at+1] == '{') {
 450                                 if (!upstream_mark(str + at, len - at)) {
 451                                         reflog_len = (len-1) - (at+2);
 452                                         len = at;
 453                                 }
 454                                 break;
 455                         }
 456                 }
 457         }
 458
 459         /* Accept only unambiguous ref paths. */
 460         if (len && ambiguous_path(str, len))
 461                 return -1;
 462
 463         if (!len && reflog_len) {
 464                 struct strbuf buf = STRBUF_INIT;
 465                 int ret;
 466                 /* try the @{-N} syntax for n-th checkout */
 467                 ret = interpret_branch_name(str, &buf);
 468                 if (ret > 0)
 469                         /* substitute this branch name and restart */
 470                         return get_sha1_1(buf.buf, buf.len, sha1, 0);
 471                 else if (ret == 0)
 472                         return -1;
 473                 /* allow "@{...}" to mean the current branch reflog */
 474                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 475         } else if (reflog_len)
 476                 refs_found = dwim_log(str, len, sha1, &real_ref);
 477         else
 478                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 479
 480         if (!refs_found)
 481                 return -1;
 482
 483         if (warn_ambiguous_refs && refs_found > 1)
 484                 warning(warn_msg, len, str);
 485
 486         if (reflog_len) {
 487                 int nth, i;
 488                 unsigned long at_time;
 489                 unsigned long co_time;
 490                 int co_tz, co_cnt;
 491
 492                 /* a @{-N} placed anywhere except the start is an error */
 493                 if (str[at+2] == '-')
 494                         return -1;
 495
 496                 /* Is it asking for N-th entry, or approxidate? */
 497                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 498                         char ch = str[at+2+i];
 499                         if ('0' <= ch && ch <= '9')
 500                                 nth = nth * 10 + ch - '0';
 501                         else
 502                                 nth = -1;
 503                 }
 504                 if (100000000 <= nth) {
 505                         at_time = nth;
 506                         nth = -1;
 507                 } else if (0 <= nth)
 508                         at_time = 0;
 509                 else {
 510                         int errors = 0;
 511                         char *tmp = xstrndup(str + at + 2, reflog_len);
 512                         at_time = approxidate_careful(tmp, &errors);
 513                         free(tmp);
 514                         if (errors)
 515                                 return -1;
 516                 }
 517                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 518                                 &co_time, &co_tz, &co_cnt)) {
 519                         if (at_time)
 520                                 warning("Log for '%.*s' only goes "
 521                                         "back to %s.", len, str,
 522                                         show_date(co_time, co_tz, DATE_RFC2822));
 523                         else {
 524                                 free(real_ref);
 525                                 die("Log for '%.*s' only has %d entries.",
 526                                     len, str, co_cnt);
 527                         }
 528                 }
 529         }
 530
 531         free(real_ref);
 532         return 0;
 533 }
 534
 535 static int get_parent(const char *name, int len,
 536                       unsigned char *result, int idx)
 537 {
 538         unsigned char sha1[20];
 539         int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 540         struct commit *commit;
 541         struct commit_list *p;
 542
 543         if (ret)
 544                 return ret;
 545         commit = lookup_commit_reference(sha1);
 546         if (!commit)
 547                 return -1;
 548         if (parse_commit(commit))
 549                 return -1;
 550         if (!idx) {
 551                 hashcpy(result, commit->object.sha1);
 552                 return 0;
 553         }
 554         p = commit->parents;
 555         while (p) {
 556                 if (!--idx) {
 557                         hashcpy(result, p->item->object.sha1);
 558                         return 0;
 559                 }
 560                 p = p->next;
 561         }
 562         return -1;
 563 }
 564
 565 static int get_nth_ancestor(const char *name, int len,
 566                             unsigned char *result, int generation)
 567 {
 568         unsigned char sha1[20];
 569         struct commit *commit;
 570         int ret;
 571
 572         ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 573         if (ret)
 574                 return ret;
 575         commit = lookup_commit_reference(sha1);
 576         if (!commit)
 577                 return -1;
 578
 579         while (generation--) {
 580                 if (parse_commit(commit) || !commit->parents)
 581                         return -1;
 582                 commit = commit->parents->item;
 583         }
 584         hashcpy(result, commit->object.sha1);
 585         return 0;
 586 }
 587
 588 struct object *peel_to_type(const char *name, int namelen,
 589                             struct object *o, enum object_type expected_type)
 590 {
 591         if (name && !namelen)
 592                 namelen = strlen(name);
 593         while (1) {
 594                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 595                         return NULL;
 596                 if (expected_type == OBJ_ANY || o->type == expected_type)
 597                         return o;
 598                 if (o->type == OBJ_TAG)
 599                         o = ((struct tag*) o)->tagged;
 600                 else if (o->type == OBJ_COMMIT)
 601                         o = &(((struct commit *) o)->tree->object);
 602                 else {
 603                         if (name)
 604                                 error("%.*s: expected %s type, but the object "
 605                                       "dereferences to %s type",
 606                                       namelen, name, typename(expected_type),
 607                                       typename(o->type));
 608                         return NULL;
 609                 }
 610         }
 611 }
 612
 613 static int peel_onion(const char *name, int len, unsigned char *sha1)
 614 {
 615         unsigned char outer[20];
 616         const char *sp;
 617         unsigned int expected_type = 0;
 618         unsigned lookup_flags = 0;
 619         struct object *o;
 620
 621         /*
 622          * "ref^{type}" dereferences ref repeatedly until you cannot
 623          * dereference anymore, or you get an object of given type,
 624          * whichever comes first.  "ref^{}" means just dereference
 625          * tags until you get a non-tag.  "ref^0" is a shorthand for
 626          * "ref^{commit}".  "commit^{tree}" could be used to find the
 627          * top-level tree of the given commit.
 628          */
 629         if (len < 4 || name[len-1] != '}')
 630                 return -1;
 631
 632         for (sp = name + len - 1; name <= sp; sp--) {
 633                 int ch = *sp;
 634                 if (ch == '{' && name < sp && sp[-1] == '^')
 635                         break;
 636         }
 637         if (sp <= name)
 638                 return -1;
 639
 640         sp++; /* beginning of type name, or closing brace for empty */
 641         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 642                 expected_type = OBJ_COMMIT;
 643         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 644                 expected_type = OBJ_TREE;
 645         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 646                 expected_type = OBJ_BLOB;
 647         else if (!prefixcmp(sp, "object}"))
 648                 expected_type = OBJ_ANY;
 649         else if (sp[0] == '}')
 650                 expected_type = OBJ_NONE;
 651         else if (sp[0] == '/')
 652                 expected_type = OBJ_COMMIT;
 653         else
 654                 return -1;
 655
 656         if (expected_type == OBJ_COMMIT)
 657                 lookup_flags = GET_SHA1_COMMITTISH;
 658         else if (expected_type == OBJ_TREE)
 659                 lookup_flags = GET_SHA1_TREEISH;
 660
 661         if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
 662                 return -1;
 663
 664         o = parse_object(outer);
 665         if (!o)
 666                 return -1;
 667         if (!expected_type) {
 668                 o = deref_tag(o, name, sp - name - 2);
 669                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 670                         return -1;
 671                 hashcpy(sha1, o->sha1);
 672                 return 0;
 673         }
 674
 675         /*
 676          * At this point, the syntax look correct, so
 677          * if we do not get the needed object, we should
 678          * barf.
 679          */
 680         o = peel_to_type(name, len, o, expected_type);
 681         if (!o)
 682                 return -1;
 683
 684         hashcpy(sha1, o->sha1);
 685         if (sp[0] == '/') {
 686                 /* "$commit^{/foo}" */
 687                 char *prefix;
 688                 int ret;
 689                 struct commit_list *list = NULL;
 690
 691                 /*
 692                  * $commit^{/}. Some regex implementation may reject.
 693                  * We don't need regex anyway. '' pattern always matches.
 694                  */
 695                 if (sp[1] == '}')
 696                         return 0;
 697
 698                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
 699                 commit_list_insert((struct commit *)o, &list);
 700                 ret = get_sha1_oneline(prefix, sha1, list);
 701                 free(prefix);
 702                 return ret;
 703         }
 704         return 0;
 705 }
 706
 707 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 708 {
 709         const char *cp;
 710         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 711
 712         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 713                 char ch = *cp;
 714                 if (hexval(ch) & ~0377) {
 715                         /* We must be looking at g in "SOMETHING-g"
 716                          * for it to be describe output.
 717                          */
 718                         if (ch == 'g' && cp[-1] == '-') {
 719                                 cp++;
 720                                 len -= cp - name;
 721                                 return get_short_sha1(cp, len, sha1, flags);
 722                         }
 723                 }
 724         }
 725         return -1;
 726 }
 727
 728 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
 729 {
 730         int ret, has_suffix;
 731         const char *cp;
 732
 733         /*
 734          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 735          */
 736         has_suffix = 0;
 737         for (cp = name + len - 1; name <= cp; cp--) {
 738                 int ch = *cp;
 739                 if ('0' <= ch && ch <= '9')
 740                         continue;
 741                 if (ch == '~' || ch == '^')
 742                         has_suffix = ch;
 743                 break;
 744         }
 745
 746         if (has_suffix) {
 747                 int num = 0;
 748                 int len1 = cp - name;
 749                 cp++;
 750                 while (cp < name + len)
 751                         num = num * 10 + *cp++ - '0';
 752                 if (!num && len1 == len - 1)
 753                         num = 1;
 754                 if (has_suffix == '^')
 755                         return get_parent(name, len1, sha1, num);
 756                 /* else if (has_suffix == '~') -- goes without saying */
 757                 return get_nth_ancestor(name, len1, sha1, num);
 758         }
 759
 760         ret = peel_onion(name, len, sha1);
 761         if (!ret)
 762                 return 0;
 763
 764         ret = get_sha1_basic(name, len, sha1);
 765         if (!ret)
 766                 return 0;
 767
 768         /* It could be describe output that is "SOMETHING-gXXXX" */
 769         ret = get_describe_name(name, len, sha1);
 770         if (!ret)
 771                 return 0;
 772
 773         return get_short_sha1(name, len, sha1, lookup_flags);
 774 }
 775
 776 /*
 777  * This interprets names like ':/Initial revision of "git"' by searching
 778  * through history and returning the first commit whose message starts
 779  * the given regular expression.
 780  *
 781  * For future extension, ':/!' is reserved. If you want to match a message
 782  * beginning with a '!', you have to repeat the exclamation mark.
 783  */
 784 #define ONELINE_SEEN (1u<<20)
 785
 786 static int handle_one_ref(const char *path,
 787                 const unsigned char *sha1, int flag, void *cb_data)
 788 {
 789         struct commit_list **list = cb_data;
 790         struct object *object = parse_object(sha1);
 791         if (!object)
 792                 return 0;
 793         if (object->type == OBJ_TAG) {
 794                 object = deref_tag(object, path, strlen(path));
 795                 if (!object)
 796                         return 0;
 797         }
 798         if (object->type != OBJ_COMMIT)
 799                 return 0;
 800         commit_list_insert_by_date((struct commit *)object, list);
 801         return 0;
 802 }
 803
 804 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 805                             struct commit_list *list)
 806 {
 807         struct commit_list *backup = NULL, *l;
 808         int found = 0;
 809         regex_t regex;
 810
 811         if (prefix[0] == '!') {
 812                 if (prefix[1] != '!')
 813                         die ("Invalid search pattern: %s", prefix);
 814                 prefix++;
 815         }
 816
 817         if (regcomp(&regex, prefix, REG_EXTENDED))
 818                 die("Invalid search pattern: %s", prefix);
 819
 820         for (l = list; l; l = l->next) {
 821                 l->item->object.flags |= ONELINE_SEEN;
 822                 commit_list_insert(l->item, &backup);
 823         }
 824         while (list) {
 825                 char *p, *to_free = NULL;
 826                 struct commit *commit;
 827                 enum object_type type;
 828                 unsigned long size;
 829                 int matches;
 830
 831                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 832                 if (!parse_object(commit->object.sha1))
 833                         continue;
 834                 if (commit->buffer)
 835                         p = commit->buffer;
 836                 else {
 837                         p = read_sha1_file(commit->object.sha1, &type, &size);
 838                         if (!p)
 839                                 continue;
 840                         to_free = p;
 841                 }
 842
 843                 p = strstr(p, "\n\n");
 844                 matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
 845                 free(to_free);
 846
 847                 if (matches) {
 848                         hashcpy(sha1, commit->object.sha1);
 849                         found = 1;
 850                         break;
 851                 }
 852         }
 853         regfree(&regex);
 854         free_commit_list(list);
 855         for (l = backup; l; l = l->next)
 856                 clear_commit_marks(l->item, ONELINE_SEEN);
 857         free_commit_list(backup);
 858         return found ? 0 : -1;
 859 }
 860
 861 struct grab_nth_branch_switch_cbdata {
 862         int remaining;
 863         struct strbuf buf;
 864 };
 865
 866 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 867                                   const char *email, unsigned long timestamp, int tz,
 868                                   const char *message, void *cb_data)
 869 {
 870         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 871         const char *match = NULL, *target = NULL;
 872         size_t len;
 873
 874         if (!prefixcmp(message, "checkout: moving from ")) {
 875                 match = message + strlen("checkout: moving from ");
 876                 target = strstr(match, " to ");
 877         }
 878
 879         if (!match || !target)
 880                 return 0;
 881         if (--(cb->remaining) == 0) {
 882                 len = target - match;
 883                 strbuf_reset(&cb->buf);
 884                 strbuf_add(&cb->buf, match, len);
 885                 return 1; /* we are done */
 886         }
 887         return 0;
 888 }
 889
 890 /*
 891  * Parse @{-N} syntax, return the number of characters parsed
 892  * if successful; otherwise signal an error with negative value.
 893  */
 894 static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
 895 {
 896         long nth;
 897         int retval;
 898         struct grab_nth_branch_switch_cbdata cb;
 899         const char *brace;
 900         char *num_end;
 901
 902         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 903                 return -1;
 904         brace = strchr(name, '}');
 905         if (!brace)
 906                 return -1;
 907         nth = strtol(name + 3, &num_end, 10);
 908         if (num_end != brace)
 909                 return -1;
 910         if (nth <= 0)
 911                 return -1;
 912         cb.remaining = nth;
 913         strbuf_init(&cb.buf, 20);
 914
 915         retval = 0;
 916         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
 917                 strbuf_reset(buf);
 918                 strbuf_add(buf, cb.buf.buf, cb.buf.len);
 919                 retval = brace - name + 1;
 920         }
 921
 922         strbuf_release(&cb.buf);
 923         return retval;
 924 }
 925
 926 int get_sha1_mb(const char *name, unsigned char *sha1)
 927 {
 928         struct commit *one, *two;
 929         struct commit_list *mbs;
 930         unsigned char sha1_tmp[20];
 931         const char *dots;
 932         int st;
 933
 934         dots = strstr(name, "...");
 935         if (!dots)
 936                 return get_sha1(name, sha1);
 937         if (dots == name)
 938                 st = get_sha1("HEAD", sha1_tmp);
 939         else {
 940                 struct strbuf sb;
 941                 strbuf_init(&sb, dots - name);
 942                 strbuf_add(&sb, name, dots - name);
 943                 st = get_sha1_committish(sb.buf, sha1_tmp);
 944                 strbuf_release(&sb);
 945         }
 946         if (st)
 947                 return st;
 948         one = lookup_commit_reference_gently(sha1_tmp, 0);
 949         if (!one)
 950                 return -1;
 951
 952         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
 953                 return -1;
 954         two = lookup_commit_reference_gently(sha1_tmp, 0);
 955         if (!two)
 956                 return -1;
 957         mbs = get_merge_bases(one, two, 1);
 958         if (!mbs || mbs->next)
 959                 st = -1;
 960         else {
 961                 st = 0;
 962                 hashcpy(sha1, mbs->item->object.sha1);
 963         }
 964         free_commit_list(mbs);
 965         return st;
 966 }
 967
 968 /*
 969  * This reads short-hand syntax that not only evaluates to a commit
 970  * object name, but also can act as if the end user spelled the name
 971  * of the branch from the command line.
 972  *
 973  * - "@{-N}" finds the name of the Nth previous branch we were on, and
 974  *   places the name of the branch in the given buf and returns the
 975  *   number of characters parsed if successful.
 976  *
 977  * - "<branch>@{upstream}" finds the name of the other ref that
 978  *   <branch> is configured to merge with (missing <branch> defaults
 979  *   to the current branch), and places the name of the branch in the
 980  *   given buf and returns the number of characters parsed if
 981  *   successful.
 982  *
 983  * If the input is not of the accepted format, it returns a negative
 984  * number to signal an error.
 985  *
 986  * If the input was ok but there are not N branch switches in the
 987  * reflog, it returns 0.
 988  */
 989 int interpret_branch_name(const char *name, struct strbuf *buf)
 990 {
 991         char *cp;
 992         struct branch *upstream;
 993         int namelen = strlen(name);
 994         int len = interpret_nth_prior_checkout(name, buf);
 995         int tmp_len;
 996
 997         if (!len)
 998                 return len; /* syntax Ok, not enough switches */
 999         if (0 < len && len == namelen)
1000                 return len; /* consumed all */
1001         else if (0 < len) {
1002                 /* we have extra data, which might need further processing */
1003                 struct strbuf tmp = STRBUF_INIT;
1004                 int used = buf->len;
1005                 int ret;
1006
1007                 strbuf_add(buf, name + len, namelen - len);
1008                 ret = interpret_branch_name(buf->buf, &tmp);
1009                 /* that data was not interpreted, remove our cruft */
1010                 if (ret < 0) {
1011                         strbuf_setlen(buf, used);
1012                         return len;
1013                 }
1014                 strbuf_reset(buf);
1015                 strbuf_addbuf(buf, &tmp);
1016                 strbuf_release(&tmp);
1017                 /* tweak for size of {-N} versus expanded ref name */
1018                 return ret - used + len;
1019         }
1020
1021         cp = strchr(name, '@');
1022         if (!cp)
1023                 return -1;
1024         tmp_len = upstream_mark(cp, namelen - (cp - name));
1025         if (!tmp_len)
1026                 return -1;
1027         len = cp + tmp_len - name;
1028         cp = xstrndup(name, cp - name);
1029         upstream = branch_get(*cp ? cp : NULL);
1030         /*
1031          * Upstream can be NULL only if cp refers to HEAD and HEAD
1032          * points to something different than a branch.
1033          */
1034         if (!upstream)
1035                 return error(_("HEAD does not point to a branch"));
1036         if (!upstream->merge || !upstream->merge[0]->dst) {
1037                 if (!ref_exists(upstream->refname))
1038                         return error(_("No such branch: '%s'"), cp);
1039                 if (!upstream->merge)
1040                         return error(_("No upstream configured for branch '%s'"),
1041                                      upstream->name);
1042                 return error(
1043                         _("Upstream branch '%s' not stored as a remote-tracking branch"),
1044                         upstream->merge[0]->src);
1045         }
1046         free(cp);
1047         cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
1048         strbuf_reset(buf);
1049         strbuf_addstr(buf, cp);
1050         free(cp);
1051         return len;
1052 }
1053
1054 int strbuf_branchname(struct strbuf *sb, const char *name)
1055 {
1056         int len = strlen(name);
1057         if (interpret_branch_name(name, sb) == len)
1058                 return 0;
1059         strbuf_add(sb, name, len);
1060         return len;
1061 }
1062
1063 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1064 {
1065         strbuf_branchname(sb, name);
1066         if (name[0] == '-')
1067                 return -1;
1068         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1069         return check_refname_format(sb->buf, 0);
1070 }
1071
1072 /*
1073  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1074  * notably "xyz^" for "parent of xyz"
1075  */
1076 int get_sha1(const char *name, unsigned char *sha1)
1077 {
1078         struct object_context unused;
1079         return get_sha1_with_context(name, 0, sha1, &unused);
1080 }
1081
1082 /*
1083  * Many callers know that the user meant to name a committish by
1084  * syntactical positions where the object name appears.  Calling this
1085  * function allows the machinery to disambiguate shorter-than-unique
1086  * abbreviated object names between committish and others.
1087  *
1088  * Note that this does NOT error out when the named object is not a
1089  * committish. It is merely to give a hint to the disambiguation
1090  * machinery.
1091  */
1092 int get_sha1_committish(const char *name, unsigned char *sha1)
1093 {
1094         struct object_context unused;
1095         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1096                                      sha1, &unused);
1097 }
1098
1099 int get_sha1_treeish(const char *name, unsigned char *sha1)
1100 {
1101         struct object_context unused;
1102         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1103                                      sha1, &unused);
1104 }
1105
1106 int get_sha1_commit(const char *name, unsigned char *sha1)
1107 {
1108         struct object_context unused;
1109         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1110                                      sha1, &unused);
1111 }
1112
1113 int get_sha1_tree(const char *name, unsigned char *sha1)
1114 {
1115         struct object_context unused;
1116         return get_sha1_with_context(name, GET_SHA1_TREE,
1117                                      sha1, &unused);
1118 }
1119
1120 int get_sha1_blob(const char *name, unsigned char *sha1)
1121 {
1122         struct object_context unused;
1123         return get_sha1_with_context(name, GET_SHA1_BLOB,
1124                                      sha1, &unused);
1125 }
1126
1127 /* Must be called only when object_name:filename doesn't exist. */
1128 static void diagnose_invalid_sha1_path(const char *prefix,
1129                                        const char *filename,
1130                                        const unsigned char *tree_sha1,
1131                                        const char *object_name,
1132                                        int object_name_len)
1133 {
1134         struct stat st;
1135         unsigned char sha1[20];
1136         unsigned mode;
1137
1138         if (!prefix)
1139                 prefix = "";
1140
1141         if (!lstat(filename, &st))
1142                 die("Path '%s' exists on disk, but not in '%.*s'.",
1143                     filename, object_name_len, object_name);
1144         if (errno == ENOENT || errno == ENOTDIR) {
1145                 char *fullname = xmalloc(strlen(filename)
1146                                              + strlen(prefix) + 1);
1147                 strcpy(fullname, prefix);
1148                 strcat(fullname, filename);
1149
1150                 if (!get_tree_entry(tree_sha1, fullname,
1151                                     sha1, &mode)) {
1152                         die("Path '%s' exists, but not '%s'.\n"
1153                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1154                             fullname,
1155                             filename,
1156                             object_name_len, object_name,
1157                             fullname,
1158                             object_name_len, object_name,
1159                             filename);
1160                 }
1161                 die("Path '%s' does not exist in '%.*s'",
1162                     filename, object_name_len, object_name);
1163         }
1164 }
1165
1166 /* Must be called only when :stage:filename doesn't exist. */
1167 static void diagnose_invalid_index_path(int stage,
1168                                         const char *prefix,
1169                                         const char *filename)
1170 {
1171         struct stat st;
1172         struct cache_entry *ce;
1173         int pos;
1174         unsigned namelen = strlen(filename);
1175         unsigned fullnamelen;
1176         char *fullname;
1177
1178         if (!prefix)
1179                 prefix = "";
1180
1181         /* Wrong stage number? */
1182         pos = cache_name_pos(filename, namelen);
1183         if (pos < 0)
1184                 pos = -pos - 1;
1185         if (pos < active_nr) {
1186                 ce = active_cache[pos];
1187                 if (ce_namelen(ce) == namelen &&
1188                     !memcmp(ce->name, filename, namelen))
1189                         die("Path '%s' is in the index, but not at stage %d.\n"
1190                             "Did you mean ':%d:%s'?",
1191                             filename, stage,
1192                             ce_stage(ce), filename);
1193         }
1194
1195         /* Confusion between relative and absolute filenames? */
1196         fullnamelen = namelen + strlen(prefix);
1197         fullname = xmalloc(fullnamelen + 1);
1198         strcpy(fullname, prefix);
1199         strcat(fullname, filename);
1200         pos = cache_name_pos(fullname, fullnamelen);
1201         if (pos < 0)
1202                 pos = -pos - 1;
1203         if (pos < active_nr) {
1204                 ce = active_cache[pos];
1205                 if (ce_namelen(ce) == fullnamelen &&
1206                     !memcmp(ce->name, fullname, fullnamelen))
1207                         die("Path '%s' is in the index, but not '%s'.\n"
1208                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1209                             fullname, filename,
1210                             ce_stage(ce), fullname,
1211                             ce_stage(ce), filename);
1212         }
1213
1214         if (!lstat(filename, &st))
1215                 die("Path '%s' exists on disk, but not in the index.", filename);
1216         if (errno == ENOENT || errno == ENOTDIR)
1217                 die("Path '%s' does not exist (neither on disk nor in the index).",
1218                     filename);
1219
1220         free(fullname);
1221 }
1222
1223
1224 static char *resolve_relative_path(const char *rel)
1225 {
1226         if (prefixcmp(rel, "./") && prefixcmp(rel, "../"))
1227                 return NULL;
1228
1229         if (!startup_info)
1230                 die("BUG: startup_info struct is not initialized.");
1231
1232         if (!is_inside_work_tree())
1233                 die("relative path syntax can't be used outside working tree.");
1234
1235         /* die() inside prefix_path() if resolved path is outside worktree */
1236         return prefix_path(startup_info->prefix,
1237                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1238                            rel);
1239 }
1240
1241 static int get_sha1_with_context_1(const char *name,
1242                                    unsigned flags,
1243                                    const char *prefix,
1244                                    unsigned char *sha1,
1245                                    struct object_context *oc)
1246 {
1247         int ret, bracket_depth;
1248         int namelen = strlen(name);
1249         const char *cp;
1250         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1251
1252         memset(oc, 0, sizeof(*oc));
1253         oc->mode = S_IFINVALID;
1254         ret = get_sha1_1(name, namelen, sha1, flags);
1255         if (!ret)
1256                 return ret;
1257         /*
1258          * sha1:path --> object name of path in ent sha1
1259          * :path -> object name of absolute path in index
1260          * :./path -> object name of path relative to cwd in index
1261          * :[0-3]:path -> object name of path in index at stage
1262          * :/foo -> recent commit matching foo
1263          */
1264         if (name[0] == ':') {
1265                 int stage = 0;
1266                 struct cache_entry *ce;
1267                 char *new_path = NULL;
1268                 int pos;
1269                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1270                         struct commit_list *list = NULL;
1271                         for_each_ref(handle_one_ref, &list);
1272                         return get_sha1_oneline(name + 2, sha1, list);
1273                 }
1274                 if (namelen < 3 ||
1275                     name[2] != ':' ||
1276                     name[1] < '0' || '3' < name[1])
1277                         cp = name + 1;
1278                 else {
1279                         stage = name[1] - '0';
1280                         cp = name + 3;
1281                 }
1282                 new_path = resolve_relative_path(cp);
1283                 if (!new_path) {
1284                         namelen = namelen - (cp - name);
1285                 } else {
1286                         cp = new_path;
1287                         namelen = strlen(cp);
1288                 }
1289
1290                 strncpy(oc->path, cp,
1291                         sizeof(oc->path));
1292                 oc->path[sizeof(oc->path)-1] = '\0';
1293
1294                 if (!active_cache)
1295                         read_cache();
1296                 pos = cache_name_pos(cp, namelen);
1297                 if (pos < 0)
1298                         pos = -pos - 1;
1299                 while (pos < active_nr) {
1300                         ce = active_cache[pos];
1301                         if (ce_namelen(ce) != namelen ||
1302                             memcmp(ce->name, cp, namelen))
1303                                 break;
1304                         if (ce_stage(ce) == stage) {
1305                                 hashcpy(sha1, ce->sha1);
1306                                 oc->mode = ce->ce_mode;
1307                                 free(new_path);
1308                                 return 0;
1309                         }
1310                         pos++;
1311                 }
1312                 if (only_to_die && name[1] && name[1] != '/')
1313                         diagnose_invalid_index_path(stage, prefix, cp);
1314                 free(new_path);
1315                 return -1;
1316         }
1317         for (cp = name, bracket_depth = 0; *cp; cp++) {
1318                 if (*cp == '{')
1319                         bracket_depth++;
1320                 else if (bracket_depth && *cp == '}')
1321                         bracket_depth--;
1322                 else if (!bracket_depth && *cp == ':')
1323                         break;
1324         }
1325         if (*cp == ':') {
1326                 unsigned char tree_sha1[20];
1327                 int len = cp - name;
1328                 if (!get_sha1_1(name, len, tree_sha1, GET_SHA1_TREEISH)) {
1329                         const char *filename = cp+1;
1330                         char *new_filename = NULL;
1331
1332                         new_filename = resolve_relative_path(filename);
1333                         if (new_filename)
1334                                 filename = new_filename;
1335                         ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
1336                         if (ret && only_to_die) {
1337                                 diagnose_invalid_sha1_path(prefix, filename,
1338                                                            tree_sha1,
1339                                                            name, len);
1340                         }
1341                         hashcpy(oc->tree, tree_sha1);
1342                         strncpy(oc->path, filename,
1343                                 sizeof(oc->path));
1344                         oc->path[sizeof(oc->path)-1] = '\0';
1345
1346                         free(new_filename);
1347                         return ret;
1348                 } else {
1349                         if (only_to_die)
1350                                 die("Invalid object name '%.*s'.", len, name);
1351                 }
1352         }
1353         return ret;
1354 }
1355
1356 /*
1357  * Call this function when you know "name" given by the end user must
1358  * name an object but it doesn't; the function _may_ die with a better
1359  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1360  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1361  * you have a chance to diagnose the error further.
1362  */
1363 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1364 {
1365         struct object_context oc;
1366         unsigned char sha1[20];
1367         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1368 }
1369
1370 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
1371 {
1372         return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
1373 }