Pileus Git - ~andy/git/blob - sha1_name.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tree-walk.h"
   7 #include "refs.h"
   8 #include "remote.h"
   9
  10 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
  11
  12 typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
  13
  14 struct disambiguate_state {
  15         disambiguate_hint_fn fn;
  16         void *cb_data;
  17         unsigned char candidate[20];
  18         unsigned candidate_exists:1;
  19         unsigned candidate_checked:1;
  20         unsigned candidate_ok:1;
  21         unsigned disambiguate_fn_used:1;
  22         unsigned ambiguous:1;
  23 };
  24
  25 static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
  26 {
  27         if (!ds->candidate_exists) {
  28                 /* this is the first candidate */
  29                 hashcpy(ds->candidate, current);
  30                 ds->candidate_exists = 1;
  31                 return;
  32         } else if (!hashcmp(ds->candidate, current)) {
  33                 /* the same as what we already have seen */
  34                 return;
  35         }
  36
  37         if (!ds->fn) {
  38                 /* cannot disambiguate between ds->candidate and current */
  39                 ds->ambiguous = 1;
  40                 return;
  41         }
  42
  43         if (!ds->candidate_checked) {
  44                 ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
  45                 ds->disambiguate_fn_used = 1;
  46                 ds->candidate_checked = 1;
  47         }
  48
  49         if (!ds->candidate_ok) {
  50                 /* discard the candidate; we know it does not satisify fn */
  51                 hashcpy(ds->candidate, current);
  52                 ds->candidate_checked = 0;
  53                 return;
  54         }
  55
  56         /* if we reach this point, we know ds->candidate satisfies fn */
  57         if (ds->fn(current, ds->cb_data)) {
  58                 /*
  59                  * if both current and candidate satisfy fn, we cannot
  60                  * disambiguate.
  61                  */
  62                 ds->candidate_ok = 0;
  63                 ds->ambiguous = 1;
  64         }
  65
  66         /* otherwise, current can be discarded and candidate is still good */
  67 }
  68
  69 static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
  70 {
  71         struct alternate_object_database *alt;
  72         char hex[40];
  73         static struct alternate_object_database *fakeent;
  74
  75         if (!fakeent) {
  76                 /*
  77                  * Create a "fake" alternate object database that
  78                  * points to our own object database, to make it
  79                  * easier to get a temporary working space in
  80                  * alt->name/alt->base while iterating over the
  81                  * object databases including our own.
  82                  */
  83                 const char *objdir = get_object_directory();
  84                 int objdir_len = strlen(objdir);
  85                 int entlen = objdir_len + 43;
  86                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  87                 memcpy(fakeent->base, objdir, objdir_len);
  88                 fakeent->name = fakeent->base + objdir_len + 1;
  89                 fakeent->name[-1] = '/';
  90         }
  91         fakeent->next = alt_odb_list;
  92
  93         sprintf(hex, "%.2s", hex_pfx);
  94         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
  95                 struct dirent *de;
  96                 DIR *dir;
  97                 sprintf(alt->name, "%.2s/", hex_pfx);
  98                 dir = opendir(alt->base);
  99                 if (!dir)
 100                         continue;
 101
 102                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
 103                         unsigned char sha1[20];
 104
 105                         if (strlen(de->d_name) != 38)
 106                                 continue;
 107                         if (memcmp(de->d_name, hex_pfx + 2, len - 2))
 108                                 continue;
 109                         memcpy(hex + 2, de->d_name, 38);
 110                         if (!get_sha1_hex(hex, sha1))
 111                                 update_candidates(ds, sha1);
 112                 }
 113                 closedir(dir);
 114         }
 115 }
 116
 117 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 118 {
 119         do {
 120                 if (*a != *b)
 121                         return 0;
 122                 a++;
 123                 b++;
 124                 len -= 2;
 125         } while (len > 1);
 126         if (len)
 127                 if ((*a ^ *b) & 0xf0)
 128                         return 0;
 129         return 1;
 130 }
 131
 132 static void unique_in_pack(int len,
 133                           const unsigned char *bin_pfx,
 134                            struct packed_git *p,
 135                            struct disambiguate_state *ds)
 136 {
 137         uint32_t num, last, i, first = 0;
 138         const unsigned char *current = NULL;
 139
 140         open_pack_index(p);
 141         num = p->num_objects;
 142         last = num;
 143         while (first < last) {
 144                 uint32_t mid = (first + last) / 2;
 145                 const unsigned char *current;
 146                 int cmp;
 147
 148                 current = nth_packed_object_sha1(p, mid);
 149                 cmp = hashcmp(bin_pfx, current);
 150                 if (!cmp) {
 151                         first = mid;
 152                         break;
 153                 }
 154                 if (cmp > 0) {
 155                         first = mid+1;
 156                         continue;
 157                 }
 158                 last = mid;
 159         }
 160
 161         /*
 162          * At this point, "first" is the location of the lowest object
 163          * with an object name that could match "bin_pfx".  See if we have
 164          * 0, 1 or more objects that actually match(es).
 165          */
 166         for (i = first; i < num && !ds->ambiguous; i++) {
 167                 current = nth_packed_object_sha1(p, i);
 168                 if (!match_sha(len, bin_pfx, current))
 169                         break;
 170                 update_candidates(ds, current);
 171         }
 172 }
 173
 174 static void find_short_packed_object(int len, const unsigned char *bin_pfx,
 175                                      struct disambiguate_state *ds)
 176 {
 177         struct packed_git *p;
 178
 179         prepare_packed_git();
 180         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 181                 unique_in_pack(len, bin_pfx, p, ds);
 182 }
 183
 184 #define SHORT_NAME_NOT_FOUND (-1)
 185 #define SHORT_NAME_AMBIGUOUS (-2)
 186
 187 static int finish_object_disambiguation(struct disambiguate_state *ds,
 188                                         unsigned char *sha1)
 189 {
 190         if (ds->ambiguous)
 191                 return SHORT_NAME_AMBIGUOUS;
 192
 193         if (!ds->candidate_exists)
 194                 return SHORT_NAME_NOT_FOUND;
 195
 196         if (!ds->candidate_checked)
 197                 /*
 198                  * If this is the only candidate, there is no point
 199                  * calling the disambiguation hint callback.
 200                  *
 201                  * On the other hand, if the current candidate
 202                  * replaced an earlier candidate that did _not_ pass
 203                  * the disambiguation hint callback, then we do have
 204                  * more than one objects that match the short name
 205                  * given, so we should make sure this one matches;
 206                  * otherwise, if we discovered this one and the one
 207                  * that we previously discarded in the reverse order,
 208                  * we would end up showing different results in the
 209                  * same repository!
 210                  */
 211                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 212                                     ds->fn(ds->candidate, ds->cb_data));
 213
 214         if (!ds->candidate_ok)
 215                 return SHORT_NAME_AMBIGUOUS;
 216
 217         hashcpy(sha1, ds->candidate);
 218         return 0;
 219 }
 220
 221 static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
 222 {
 223         int kind = sha1_object_info(sha1, NULL);
 224         return kind == OBJ_COMMIT;
 225 }
 226
 227 static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
 228 {
 229         struct object *obj;
 230         int kind;
 231
 232         kind = sha1_object_info(sha1, NULL);
 233         if (kind == OBJ_COMMIT)
 234                 return 1;
 235         if (kind != OBJ_TAG)
 236                 return 0;
 237
 238         /* We need to do this the hard way... */
 239         obj = deref_tag(lookup_object(sha1), NULL, 0);
 240         if (obj && obj->type == OBJ_COMMIT)
 241                 return 1;
 242         return 0;
 243 }
 244
 245 static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
 246 {
 247         int kind = sha1_object_info(sha1, NULL);
 248         return kind == OBJ_TREE;
 249 }
 250
 251 static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
 252 {
 253         struct object *obj;
 254         int kind;
 255
 256         kind = sha1_object_info(sha1, NULL);
 257         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 258                 return 1;
 259         if (kind != OBJ_TAG)
 260                 return 0;
 261
 262         /* We need to do this the hard way... */
 263         obj = deref_tag(lookup_object(sha1), NULL, 0);
 264         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 265                 return 1;
 266         return 0;
 267 }
 268
 269 static int disambiguate_blob_only(const unsigned char *sha1, void *cb_data_unused)
 270 {
 271         int kind = sha1_object_info(sha1, NULL);
 272         return kind == OBJ_BLOB;
 273 }
 274
 275 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 276                           unsigned flags)
 277 {
 278         int i, status;
 279         char hex_pfx[40];
 280         unsigned char bin_pfx[20];
 281         struct disambiguate_state ds;
 282         int quietly = !!(flags & GET_SHA1_QUIETLY);
 283
 284         if (len < MINIMUM_ABBREV || len > 40)
 285                 return -1;
 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
 307         prepare_alt_odb();
 308
 309         memset(&ds, 0, sizeof(ds));
 310         if (flags & GET_SHA1_COMMIT)
 311                 ds.fn = disambiguate_commit_only;
 312         else if (flags & GET_SHA1_COMMITTISH)
 313                 ds.fn = disambiguate_committish_only;
 314         else if (flags & GET_SHA1_TREE)
 315                 ds.fn = disambiguate_tree_only;
 316         else if (flags & GET_SHA1_TREEISH)
 317                 ds.fn = disambiguate_treeish_only;
 318         else if (flags & GET_SHA1_BLOB)
 319                 ds.fn = disambiguate_blob_only;
 320
 321         find_short_object_filename(len, hex_pfx, &ds);
 322         find_short_packed_object(len, bin_pfx, &ds);
 323         status = finish_object_disambiguation(&ds, sha1);
 324
 325         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 326                 return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
 327         return status;
 328 }
 329
 330 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 331 {
 332         int status, exists;
 333         static char hex[41];
 334
 335         exists = has_sha1_file(sha1);
 336         memcpy(hex, sha1_to_hex(sha1), 40);
 337         if (len == 40 || !len)
 338                 return hex;
 339         while (len < 40) {
 340                 unsigned char sha1_ret[20];
 341                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
 342                 if (exists
 343                     ? !status
 344                     : status == SHORT_NAME_NOT_FOUND) {
 345                         hex[len] = 0;
 346                         return hex;
 347                 }
 348                 len++;
 349         }
 350         return hex;
 351 }
 352
 353 static int ambiguous_path(const char *path, int len)
 354 {
 355         int slash = 1;
 356         int cnt;
 357
 358         for (cnt = 0; cnt < len; cnt++) {
 359                 switch (*path++) {
 360                 case '\0':
 361                         break;
 362                 case '/':
 363                         if (slash)
 364                                 break;
 365                         slash = 1;
 366                         continue;
 367                 case '.':
 368                         continue;
 369                 default:
 370                         slash = 0;
 371                         continue;
 372                 }
 373                 break;
 374         }
 375         return slash;
 376 }
 377
 378 static inline int upstream_mark(const char *string, int len)
 379 {
 380         const char *suffix[] = { "@{upstream}", "@{u}" };
 381         int i;
 382
 383         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 384                 int suffix_len = strlen(suffix[i]);
 385                 if (suffix_len <= len
 386                     && !memcmp(string, suffix[i], suffix_len))
 387                         return suffix_len;
 388         }
 389         return 0;
 390 }
 391
 392 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 393
 394 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 395 {
 396         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 397         char *real_ref = NULL;
 398         int refs_found = 0;
 399         int at, reflog_len;
 400
 401         if (len == 40 && !get_sha1_hex(str, sha1))
 402                 return 0;
 403
 404         /* basic@{time or number or -number} format to query ref-log */
 405         reflog_len = at = 0;
 406         if (len && str[len-1] == '}') {
 407                 for (at = len-2; at >= 0; at--) {
 408                         if (str[at] == '@' && str[at+1] == '{') {
 409                                 if (!upstream_mark(str + at, len - at)) {
 410                                         reflog_len = (len-1) - (at+2);
 411                                         len = at;
 412                                 }
 413                                 break;
 414                         }
 415                 }
 416         }
 417
 418         /* Accept only unambiguous ref paths. */
 419         if (len && ambiguous_path(str, len))
 420                 return -1;
 421
 422         if (!len && reflog_len) {
 423                 struct strbuf buf = STRBUF_INIT;
 424                 int ret;
 425                 /* try the @{-N} syntax for n-th checkout */
 426                 ret = interpret_branch_name(str+at, &buf);
 427                 if (ret > 0) {
 428                         /* substitute this branch name and restart */
 429                         return get_sha1_1(buf.buf, buf.len, sha1, 0);
 430                 } else if (ret == 0) {
 431                         return -1;
 432                 }
 433                 /* allow "@{...}" to mean the current branch reflog */
 434                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 435         } else if (reflog_len)
 436                 refs_found = dwim_log(str, len, sha1, &real_ref);
 437         else
 438                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 439
 440         if (!refs_found)
 441                 return -1;
 442
 443         if (warn_ambiguous_refs && refs_found > 1)
 444                 warning(warn_msg, len, str);
 445
 446         if (reflog_len) {
 447                 int nth, i;
 448                 unsigned long at_time;
 449                 unsigned long co_time;
 450                 int co_tz, co_cnt;
 451
 452                 /* a @{-N} placed anywhere except the start is an error */
 453                 if (str[at+2] == '-')
 454                         return -1;
 455
 456                 /* Is it asking for N-th entry, or approxidate? */
 457                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 458                         char ch = str[at+2+i];
 459                         if ('0' <= ch && ch <= '9')
 460                                 nth = nth * 10 + ch - '0';
 461                         else
 462                                 nth = -1;
 463                 }
 464                 if (100000000 <= nth) {
 465                         at_time = nth;
 466                         nth = -1;
 467                 } else if (0 <= nth)
 468                         at_time = 0;
 469                 else {
 470                         int errors = 0;
 471                         char *tmp = xstrndup(str + at + 2, reflog_len);
 472                         at_time = approxidate_careful(tmp, &errors);
 473                         free(tmp);
 474                         if (errors)
 475                                 return -1;
 476                 }
 477                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 478                                 &co_time, &co_tz, &co_cnt)) {
 479                         if (at_time)
 480                                 warning("Log for '%.*s' only goes "
 481                                         "back to %s.", len, str,
 482                                         show_date(co_time, co_tz, DATE_RFC2822));
 483                         else {
 484                                 free(real_ref);
 485                                 die("Log for '%.*s' only has %d entries.",
 486                                     len, str, co_cnt);
 487                         }
 488                 }
 489         }
 490
 491         free(real_ref);
 492         return 0;
 493 }
 494
 495 static int get_parent(const char *name, int len,
 496                       unsigned char *result, int idx)
 497 {
 498         unsigned char sha1[20];
 499         int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 500         struct commit *commit;
 501         struct commit_list *p;
 502
 503         if (ret)
 504                 return ret;
 505         commit = lookup_commit_reference(sha1);
 506         if (!commit)
 507                 return -1;
 508         if (parse_commit(commit))
 509                 return -1;
 510         if (!idx) {
 511                 hashcpy(result, commit->object.sha1);
 512                 return 0;
 513         }
 514         p = commit->parents;
 515         while (p) {
 516                 if (!--idx) {
 517                         hashcpy(result, p->item->object.sha1);
 518                         return 0;
 519                 }
 520                 p = p->next;
 521         }
 522         return -1;
 523 }
 524
 525 static int get_nth_ancestor(const char *name, int len,
 526                             unsigned char *result, int generation)
 527 {
 528         unsigned char sha1[20];
 529         struct commit *commit;
 530         int ret;
 531
 532         ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 533         if (ret)
 534                 return ret;
 535         commit = lookup_commit_reference(sha1);
 536         if (!commit)
 537                 return -1;
 538
 539         while (generation--) {
 540                 if (parse_commit(commit) || !commit->parents)
 541                         return -1;
 542                 commit = commit->parents->item;
 543         }
 544         hashcpy(result, commit->object.sha1);
 545         return 0;
 546 }
 547
 548 struct object *peel_to_type(const char *name, int namelen,
 549                             struct object *o, enum object_type expected_type)
 550 {
 551         if (name && !namelen)
 552                 namelen = strlen(name);
 553         while (1) {
 554                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 555                         return NULL;
 556                 if (o->type == expected_type)
 557                         return o;
 558                 if (o->type == OBJ_TAG)
 559                         o = ((struct tag*) o)->tagged;
 560                 else if (o->type == OBJ_COMMIT)
 561                         o = &(((struct commit *) o)->tree->object);
 562                 else {
 563                         if (name)
 564                                 error("%.*s: expected %s type, but the object "
 565                                       "dereferences to %s type",
 566                                       namelen, name, typename(expected_type),
 567                                       typename(o->type));
 568                         return NULL;
 569                 }
 570         }
 571 }
 572
 573 static int peel_onion(const char *name, int len, unsigned char *sha1)
 574 {
 575         unsigned char outer[20];
 576         const char *sp;
 577         unsigned int expected_type = 0;
 578         unsigned lookup_flags = 0;
 579         struct object *o;
 580
 581         /*
 582          * "ref^{type}" dereferences ref repeatedly until you cannot
 583          * dereference anymore, or you get an object of given type,
 584          * whichever comes first.  "ref^{}" means just dereference
 585          * tags until you get a non-tag.  "ref^0" is a shorthand for
 586          * "ref^{commit}".  "commit^{tree}" could be used to find the
 587          * top-level tree of the given commit.
 588          */
 589         if (len < 4 || name[len-1] != '}')
 590                 return -1;
 591
 592         for (sp = name + len - 1; name <= sp; sp--) {
 593                 int ch = *sp;
 594                 if (ch == '{' && name < sp && sp[-1] == '^')
 595                         break;
 596         }
 597         if (sp <= name)
 598                 return -1;
 599
 600         sp++; /* beginning of type name, or closing brace for empty */
 601         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 602                 expected_type = OBJ_COMMIT;
 603         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 604                 expected_type = OBJ_TREE;
 605         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 606                 expected_type = OBJ_BLOB;
 607         else if (sp[0] == '}')
 608                 expected_type = OBJ_NONE;
 609         else if (sp[0] == '/')
 610                 expected_type = OBJ_COMMIT;
 611         else
 612                 return -1;
 613
 614         if (expected_type == OBJ_COMMIT)
 615                 lookup_flags = GET_SHA1_COMMITTISH;
 616
 617         if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
 618                 return -1;
 619
 620         o = parse_object(outer);
 621         if (!o)
 622                 return -1;
 623         if (!expected_type) {
 624                 o = deref_tag(o, name, sp - name - 2);
 625                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 626                         return -1;
 627                 hashcpy(sha1, o->sha1);
 628                 return 0;
 629         }
 630
 631         /*
 632          * At this point, the syntax look correct, so
 633          * if we do not get the needed object, we should
 634          * barf.
 635          */
 636         o = peel_to_type(name, len, o, expected_type);
 637         if (!o)
 638                 return -1;
 639
 640         hashcpy(sha1, o->sha1);
 641         if (sp[0] == '/') {
 642                 /* "$commit^{/foo}" */
 643                 char *prefix;
 644                 int ret;
 645                 struct commit_list *list = NULL;
 646
 647                 /*
 648                  * $commit^{/}. Some regex implementation may reject.
 649                  * We don't need regex anyway. '' pattern always matches.
 650                  */
 651                 if (sp[1] == '}')
 652                         return 0;
 653
 654                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
 655                 commit_list_insert((struct commit *)o, &list);
 656                 ret = get_sha1_oneline(prefix, sha1, list);
 657                 free(prefix);
 658                 return ret;
 659         }
 660         return 0;
 661 }
 662
 663 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 664 {
 665         const char *cp;
 666         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 667
 668         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 669                 char ch = *cp;
 670                 if (hexval(ch) & ~0377) {
 671                         /* We must be looking at g in "SOMETHING-g"
 672                          * for it to be describe output.
 673                          */
 674                         if (ch == 'g' && cp[-1] == '-') {
 675                                 cp++;
 676                                 len -= cp - name;
 677                                 return get_short_sha1(cp, len, sha1, flags);
 678                         }
 679                 }
 680         }
 681         return -1;
 682 }
 683
 684 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
 685 {
 686         int ret, has_suffix;
 687         const char *cp;
 688
 689         /*
 690          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 691          */
 692         has_suffix = 0;
 693         for (cp = name + len - 1; name <= cp; cp--) {
 694                 int ch = *cp;
 695                 if ('0' <= ch && ch <= '9')
 696                         continue;
 697                 if (ch == '~' || ch == '^')
 698                         has_suffix = ch;
 699                 break;
 700         }
 701
 702         if (has_suffix) {
 703                 int num = 0;
 704                 int len1 = cp - name;
 705                 cp++;
 706                 while (cp < name + len)
 707                         num = num * 10 + *cp++ - '0';
 708                 if (!num && len1 == len - 1)
 709                         num = 1;
 710                 if (has_suffix == '^')
 711                         return get_parent(name, len1, sha1, num);
 712                 /* else if (has_suffix == '~') -- goes without saying */
 713                 return get_nth_ancestor(name, len1, sha1, num);
 714         }
 715
 716         ret = peel_onion(name, len, sha1);
 717         if (!ret)
 718                 return 0;
 719
 720         ret = get_sha1_basic(name, len, sha1);
 721         if (!ret)
 722                 return 0;
 723
 724         /* It could be describe output that is "SOMETHING-gXXXX" */
 725         ret = get_describe_name(name, len, sha1);
 726         if (!ret)
 727                 return 0;
 728
 729         return get_short_sha1(name, len, sha1, lookup_flags);
 730 }
 731
 732 /*
 733  * This interprets names like ':/Initial revision of "git"' by searching
 734  * through history and returning the first commit whose message starts
 735  * the given regular expression.
 736  *
 737  * For future extension, ':/!' is reserved. If you want to match a message
 738  * beginning with a '!', you have to repeat the exclamation mark.
 739  */
 740 #define ONELINE_SEEN (1u<<20)
 741
 742 static int handle_one_ref(const char *path,
 743                 const unsigned char *sha1, int flag, void *cb_data)
 744 {
 745         struct commit_list **list = cb_data;
 746         struct object *object = parse_object(sha1);
 747         if (!object)
 748                 return 0;
 749         if (object->type == OBJ_TAG) {
 750                 object = deref_tag(object, path, strlen(path));
 751                 if (!object)
 752                         return 0;
 753         }
 754         if (object->type != OBJ_COMMIT)
 755                 return 0;
 756         commit_list_insert_by_date((struct commit *)object, list);
 757         return 0;
 758 }
 759
 760 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 761                             struct commit_list *list)
 762 {
 763         struct commit_list *backup = NULL, *l;
 764         int found = 0;
 765         regex_t regex;
 766
 767         if (prefix[0] == '!') {
 768                 if (prefix[1] != '!')
 769                         die ("Invalid search pattern: %s", prefix);
 770                 prefix++;
 771         }
 772
 773         if (regcomp(&regex, prefix, REG_EXTENDED))
 774                 die("Invalid search pattern: %s", prefix);
 775
 776         for (l = list; l; l = l->next) {
 777                 l->item->object.flags |= ONELINE_SEEN;
 778                 commit_list_insert(l->item, &backup);
 779         }
 780         while (list) {
 781                 char *p, *to_free = NULL;
 782                 struct commit *commit;
 783                 enum object_type type;
 784                 unsigned long size;
 785                 int matches;
 786
 787                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 788                 if (!parse_object(commit->object.sha1))
 789                         continue;
 790                 if (commit->buffer)
 791                         p = commit->buffer;
 792                 else {
 793                         p = read_sha1_file(commit->object.sha1, &type, &size);
 794                         if (!p)
 795                                 continue;
 796                         to_free = p;
 797                 }
 798
 799                 p = strstr(p, "\n\n");
 800                 matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
 801                 free(to_free);
 802
 803                 if (matches) {
 804                         hashcpy(sha1, commit->object.sha1);
 805                         found = 1;
 806                         break;
 807                 }
 808         }
 809         regfree(&regex);
 810         free_commit_list(list);
 811         for (l = backup; l; l = l->next)
 812                 clear_commit_marks(l->item, ONELINE_SEEN);
 813         free_commit_list(backup);
 814         return found ? 0 : -1;
 815 }
 816
 817 struct grab_nth_branch_switch_cbdata {
 818         long cnt, alloc;
 819         struct strbuf *buf;
 820 };
 821
 822 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 823                                   const char *email, unsigned long timestamp, int tz,
 824                                   const char *message, void *cb_data)
 825 {
 826         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 827         const char *match = NULL, *target = NULL;
 828         size_t len;
 829         int nth;
 830
 831         if (!prefixcmp(message, "checkout: moving from ")) {
 832                 match = message + strlen("checkout: moving from ");
 833                 target = strstr(match, " to ");
 834         }
 835
 836         if (!match || !target)
 837                 return 0;
 838
 839         len = target - match;
 840         nth = cb->cnt++ % cb->alloc;
 841         strbuf_reset(&cb->buf[nth]);
 842         strbuf_add(&cb->buf[nth], match, len);
 843         return 0;
 844 }
 845
 846 /*
 847  * Parse @{-N} syntax, return the number of characters parsed
 848  * if successful; otherwise signal an error with negative value.
 849  */
 850 static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
 851 {
 852         long nth;
 853         int i, retval;
 854         struct grab_nth_branch_switch_cbdata cb;
 855         const char *brace;
 856         char *num_end;
 857
 858         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 859                 return -1;
 860         brace = strchr(name, '}');
 861         if (!brace)
 862                 return -1;
 863         nth = strtol(name+3, &num_end, 10);
 864         if (num_end != brace)
 865                 return -1;
 866         if (nth <= 0)
 867                 return -1;
 868         cb.alloc = nth;
 869         cb.buf = xmalloc(nth * sizeof(struct strbuf));
 870         for (i = 0; i < nth; i++)
 871                 strbuf_init(&cb.buf[i], 20);
 872         cb.cnt = 0;
 873         retval = 0;
 874         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 875         if (cb.cnt < nth) {
 876                 cb.cnt = 0;
 877                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 878         }
 879         if (cb.cnt < nth)
 880                 goto release_return;
 881         i = cb.cnt % nth;
 882         strbuf_reset(buf);
 883         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 884         retval = brace-name+1;
 885
 886 release_return:
 887         for (i = 0; i < nth; i++)
 888                 strbuf_release(&cb.buf[i]);
 889         free(cb.buf);
 890
 891         return retval;
 892 }
 893
 894 int get_sha1_mb(const char *name, unsigned char *sha1)
 895 {
 896         struct commit *one, *two;
 897         struct commit_list *mbs;
 898         unsigned char sha1_tmp[20];
 899         const char *dots;
 900         int st;
 901
 902         dots = strstr(name, "...");
 903         if (!dots)
 904                 return get_sha1(name, sha1);
 905         if (dots == name)
 906                 st = get_sha1("HEAD", sha1_tmp);
 907         else {
 908                 struct strbuf sb;
 909                 strbuf_init(&sb, dots - name);
 910                 strbuf_add(&sb, name, dots - name);
 911                 st = get_sha1_committish(sb.buf, sha1_tmp);
 912                 strbuf_release(&sb);
 913         }
 914         if (st)
 915                 return st;
 916         one = lookup_commit_reference_gently(sha1_tmp, 0);
 917         if (!one)
 918                 return -1;
 919
 920         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
 921                 return -1;
 922         two = lookup_commit_reference_gently(sha1_tmp, 0);
 923         if (!two)
 924                 return -1;
 925         mbs = get_merge_bases(one, two, 1);
 926         if (!mbs || mbs->next)
 927                 st = -1;
 928         else {
 929                 st = 0;
 930                 hashcpy(sha1, mbs->item->object.sha1);
 931         }
 932         free_commit_list(mbs);
 933         return st;
 934 }
 935
 936 /*
 937  * This reads short-hand syntax that not only evaluates to a commit
 938  * object name, but also can act as if the end user spelled the name
 939  * of the branch from the command line.
 940  *
 941  * - "@{-N}" finds the name of the Nth previous branch we were on, and
 942  *   places the name of the branch in the given buf and returns the
 943  *   number of characters parsed if successful.
 944  *
 945  * - "<branch>@{upstream}" finds the name of the other ref that
 946  *   <branch> is configured to merge with (missing <branch> defaults
 947  *   to the current branch), and places the name of the branch in the
 948  *   given buf and returns the number of characters parsed if
 949  *   successful.
 950  *
 951  * If the input is not of the accepted format, it returns a negative
 952  * number to signal an error.
 953  *
 954  * If the input was ok but there are not N branch switches in the
 955  * reflog, it returns 0.
 956  */
 957 int interpret_branch_name(const char *name, struct strbuf *buf)
 958 {
 959         char *cp;
 960         struct branch *upstream;
 961         int namelen = strlen(name);
 962         int len = interpret_nth_prior_checkout(name, buf);
 963         int tmp_len;
 964
 965         if (!len)
 966                 return len; /* syntax Ok, not enough switches */
 967         if (0 < len && len == namelen)
 968                 return len; /* consumed all */
 969         else if (0 < len) {
 970                 /* we have extra data, which might need further processing */
 971                 struct strbuf tmp = STRBUF_INIT;
 972                 int used = buf->len;
 973                 int ret;
 974
 975                 strbuf_add(buf, name + len, namelen - len);
 976                 ret = interpret_branch_name(buf->buf, &tmp);
 977                 /* that data was not interpreted, remove our cruft */
 978                 if (ret < 0) {
 979                         strbuf_setlen(buf, used);
 980                         return len;
 981                 }
 982                 strbuf_reset(buf);
 983                 strbuf_addbuf(buf, &tmp);
 984                 strbuf_release(&tmp);
 985                 /* tweak for size of {-N} versus expanded ref name */
 986                 return ret - used + len;
 987         }
 988
 989         cp = strchr(name, '@');
 990         if (!cp)
 991                 return -1;
 992         tmp_len = upstream_mark(cp, namelen - (cp - name));
 993         if (!tmp_len)
 994                 return -1;
 995         len = cp + tmp_len - name;
 996         cp = xstrndup(name, cp - name);
 997         upstream = branch_get(*cp ? cp : NULL);
 998         if (!upstream
 999             || !upstream->merge
1000             || !upstream->merge[0]->dst)
1001                 return error("No upstream branch found for '%s'", cp);
1002         free(cp);
1003         cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
1004         strbuf_reset(buf);
1005         strbuf_addstr(buf, cp);
1006         free(cp);
1007         return len;
1008 }
1009
1010 int strbuf_branchname(struct strbuf *sb, const char *name)
1011 {
1012         int len = strlen(name);
1013         if (interpret_branch_name(name, sb) == len)
1014                 return 0;
1015         strbuf_add(sb, name, len);
1016         return len;
1017 }
1018
1019 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1020 {
1021         strbuf_branchname(sb, name);
1022         if (name[0] == '-')
1023                 return -1;
1024         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1025         return check_refname_format(sb->buf, 0);
1026 }
1027
1028 /*
1029  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1030  * notably "xyz^" for "parent of xyz"
1031  */
1032 int get_sha1(const char *name, unsigned char *sha1)
1033 {
1034         struct object_context unused;
1035         return get_sha1_with_context(name, 0, sha1, &unused);
1036 }
1037
1038 /*
1039  * Many callers know that the user meant to name a committish by
1040  * syntactical positions where the object name appears.  Calling this
1041  * function allows the machinery to disambiguate shorter-than-unique
1042  * abbreviated object names between committish and others.
1043  *
1044  * Note that this does NOT error out when the named object is not a
1045  * committish. It is merely to give a hint to the disambiguation
1046  * machinery.
1047  */
1048 int get_sha1_committish(const char *name, unsigned char *sha1)
1049 {
1050         struct object_context unused;
1051         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1052                                      sha1, &unused);
1053 }
1054
1055 int get_sha1_treeish(const char *name, unsigned char *sha1)
1056 {
1057         struct object_context unused;
1058         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1059                                      sha1, &unused);
1060 }
1061
1062 int get_sha1_commit(const char *name, unsigned char *sha1)
1063 {
1064         struct object_context unused;
1065         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1066                                      sha1, &unused);
1067 }
1068
1069 int get_sha1_tree(const char *name, unsigned char *sha1)
1070 {
1071         struct object_context unused;
1072         return get_sha1_with_context(name, GET_SHA1_TREE,
1073                                      sha1, &unused);
1074 }
1075
1076 int get_sha1_blob(const char *name, unsigned char *sha1)
1077 {
1078         struct object_context unused;
1079         return get_sha1_with_context(name, GET_SHA1_BLOB,
1080                                      sha1, &unused);
1081 }
1082
1083 /* Must be called only when object_name:filename doesn't exist. */
1084 static void diagnose_invalid_sha1_path(const char *prefix,
1085                                        const char *filename,
1086                                        const unsigned char *tree_sha1,
1087                                        const char *object_name)
1088 {
1089         struct stat st;
1090         unsigned char sha1[20];
1091         unsigned mode;
1092
1093         if (!prefix)
1094                 prefix = "";
1095
1096         if (!lstat(filename, &st))
1097                 die("Path '%s' exists on disk, but not in '%s'.",
1098                     filename, object_name);
1099         if (errno == ENOENT || errno == ENOTDIR) {
1100                 char *fullname = xmalloc(strlen(filename)
1101                                              + strlen(prefix) + 1);
1102                 strcpy(fullname, prefix);
1103                 strcat(fullname, filename);
1104
1105                 if (!get_tree_entry(tree_sha1, fullname,
1106                                     sha1, &mode)) {
1107                         die("Path '%s' exists, but not '%s'.\n"
1108                             "Did you mean '%s:%s' aka '%s:./%s'?",
1109                             fullname,
1110                             filename,
1111                             object_name,
1112                             fullname,
1113                             object_name,
1114                             filename);
1115                 }
1116                 die("Path '%s' does not exist in '%s'",
1117                     filename, object_name);
1118         }
1119 }
1120
1121 /* Must be called only when :stage:filename doesn't exist. */
1122 static void diagnose_invalid_index_path(int stage,
1123                                         const char *prefix,
1124                                         const char *filename)
1125 {
1126         struct stat st;
1127         struct cache_entry *ce;
1128         int pos;
1129         unsigned namelen = strlen(filename);
1130         unsigned fullnamelen;
1131         char *fullname;
1132
1133         if (!prefix)
1134                 prefix = "";
1135
1136         /* Wrong stage number? */
1137         pos = cache_name_pos(filename, namelen);
1138         if (pos < 0)
1139                 pos = -pos - 1;
1140         if (pos < active_nr) {
1141                 ce = active_cache[pos];
1142                 if (ce_namelen(ce) == namelen &&
1143                     !memcmp(ce->name, filename, namelen))
1144                         die("Path '%s' is in the index, but not at stage %d.\n"
1145                             "Did you mean ':%d:%s'?",
1146                             filename, stage,
1147                             ce_stage(ce), filename);
1148         }
1149
1150         /* Confusion between relative and absolute filenames? */
1151         fullnamelen = namelen + strlen(prefix);
1152         fullname = xmalloc(fullnamelen + 1);
1153         strcpy(fullname, prefix);
1154         strcat(fullname, filename);
1155         pos = cache_name_pos(fullname, fullnamelen);
1156         if (pos < 0)
1157                 pos = -pos - 1;
1158         if (pos < active_nr) {
1159                 ce = active_cache[pos];
1160                 if (ce_namelen(ce) == fullnamelen &&
1161                     !memcmp(ce->name, fullname, fullnamelen))
1162                         die("Path '%s' is in the index, but not '%s'.\n"
1163                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1164                             fullname, filename,
1165                             ce_stage(ce), fullname,
1166                             ce_stage(ce), filename);
1167         }
1168
1169         if (!lstat(filename, &st))
1170                 die("Path '%s' exists on disk, but not in the index.", filename);
1171         if (errno == ENOENT || errno == ENOTDIR)
1172                 die("Path '%s' does not exist (neither on disk nor in the index).",
1173                     filename);
1174
1175         free(fullname);
1176 }
1177
1178
1179 static char *resolve_relative_path(const char *rel)
1180 {
1181         if (prefixcmp(rel, "./") && prefixcmp(rel, "../"))
1182                 return NULL;
1183
1184         if (!startup_info)
1185                 die("BUG: startup_info struct is not initialized.");
1186
1187         if (!is_inside_work_tree())
1188                 die("relative path syntax can't be used outside working tree.");
1189
1190         /* die() inside prefix_path() if resolved path is outside worktree */
1191         return prefix_path(startup_info->prefix,
1192                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1193                            rel);
1194 }
1195
1196 static int get_sha1_with_context_1(const char *name,
1197                                    unsigned flags,
1198                                    const char *prefix,
1199                                    unsigned char *sha1,
1200                                    struct object_context *oc)
1201 {
1202         int ret, bracket_depth;
1203         int namelen = strlen(name);
1204         const char *cp;
1205         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1206
1207         memset(oc, 0, sizeof(*oc));
1208         oc->mode = S_IFINVALID;
1209         ret = get_sha1_1(name, namelen, sha1, flags);
1210         if (!ret)
1211                 return ret;
1212         /*
1213          * sha1:path --> object name of path in ent sha1
1214          * :path -> object name of absolute path in index
1215          * :./path -> object name of path relative to cwd in index
1216          * :[0-3]:path -> object name of path in index at stage
1217          * :/foo -> recent commit matching foo
1218          */
1219         if (name[0] == ':') {
1220                 int stage = 0;
1221                 struct cache_entry *ce;
1222                 char *new_path = NULL;
1223                 int pos;
1224                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1225                         struct commit_list *list = NULL;
1226                         for_each_ref(handle_one_ref, &list);
1227                         return get_sha1_oneline(name + 2, sha1, list);
1228                 }
1229                 if (namelen < 3 ||
1230                     name[2] != ':' ||
1231                     name[1] < '0' || '3' < name[1])
1232                         cp = name + 1;
1233                 else {
1234                         stage = name[1] - '0';
1235                         cp = name + 3;
1236                 }
1237                 new_path = resolve_relative_path(cp);
1238                 if (!new_path) {
1239                         namelen = namelen - (cp - name);
1240                 } else {
1241                         cp = new_path;
1242                         namelen = strlen(cp);
1243                 }
1244
1245                 strncpy(oc->path, cp,
1246                         sizeof(oc->path));
1247                 oc->path[sizeof(oc->path)-1] = '\0';
1248
1249                 if (!active_cache)
1250                         read_cache();
1251                 pos = cache_name_pos(cp, namelen);
1252                 if (pos < 0)
1253                         pos = -pos - 1;
1254                 while (pos < active_nr) {
1255                         ce = active_cache[pos];
1256                         if (ce_namelen(ce) != namelen ||
1257                             memcmp(ce->name, cp, namelen))
1258                                 break;
1259                         if (ce_stage(ce) == stage) {
1260                                 hashcpy(sha1, ce->sha1);
1261                                 oc->mode = ce->ce_mode;
1262                                 free(new_path);
1263                                 return 0;
1264                         }
1265                         pos++;
1266                 }
1267                 if (only_to_die && name[1] && name[1] != '/')
1268                         diagnose_invalid_index_path(stage, prefix, cp);
1269                 free(new_path);
1270                 return -1;
1271         }
1272         for (cp = name, bracket_depth = 0; *cp; cp++) {
1273                 if (*cp == '{')
1274                         bracket_depth++;
1275                 else if (bracket_depth && *cp == '}')
1276                         bracket_depth--;
1277                 else if (!bracket_depth && *cp == ':')
1278                         break;
1279         }
1280         if (*cp == ':') {
1281                 unsigned char tree_sha1[20];
1282                 char *object_name = NULL;
1283                 if (only_to_die) {
1284                         object_name = xmalloc(cp-name+1);
1285                         strncpy(object_name, name, cp-name);
1286                         object_name[cp-name] = '\0';
1287                 }
1288                 if (!get_sha1_1(name, cp-name, tree_sha1, GET_SHA1_TREEISH)) {
1289                         const char *filename = cp+1;
1290                         char *new_filename = NULL;
1291
1292                         new_filename = resolve_relative_path(filename);
1293                         if (new_filename)
1294                                 filename = new_filename;
1295                         ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
1296                         if (only_to_die) {
1297                                 diagnose_invalid_sha1_path(prefix, filename,
1298                                                            tree_sha1, object_name);
1299                                 free(object_name);
1300                         }
1301                         hashcpy(oc->tree, tree_sha1);
1302                         strncpy(oc->path, filename,
1303                                 sizeof(oc->path));
1304                         oc->path[sizeof(oc->path)-1] = '\0';
1305
1306                         free(new_filename);
1307                         return ret;
1308                 } else {
1309                         if (only_to_die)
1310                                 die("Invalid object name '%s'.", object_name);
1311                 }
1312         }
1313         return ret;
1314 }
1315
1316 /*
1317  * Call this function when you know "name" given by the end user must
1318  * name an object but it doesn't; the function _may_ die with a better
1319  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1320  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1321  * you have a chance to diagnose the error further.
1322  */
1323 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1324 {
1325         struct object_context oc;
1326         unsigned char sha1[20];
1327         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1328 }
1329
1330 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
1331 {
1332         return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
1333 }