src/revparse.c

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #include "common.h"
   9
  10 #include "buffer.h"
  11 #include "tree.h"
  12 #include "refdb.h"
  13 #include "regexp.h"
  14
  15 #include "git2.h"
  16
  17 static int maybe_sha_or_abbrev(git_object** out, git_repository *repo, const char *spec, size_t speclen)
  18 {
  19         git_oid oid;
  20
  21         if (git_oid_fromstrn(&oid, spec, speclen) < 0)
  22                 return GIT_ENOTFOUND;
  23
  24         return git_object_lookup_prefix(out, repo, &oid, speclen, GIT_OBJECT_ANY);
  25 }
  26
  27 static int maybe_sha(git_object** out, git_repository *repo, const char *spec)
  28 {
  29         size_t speclen = strlen(spec);
  30
  31         if (speclen != GIT_OID_HEXSZ)
  32                 return GIT_ENOTFOUND;
  33
  34         return maybe_sha_or_abbrev(out, repo, spec, speclen);
  35 }
  36
  37 static int maybe_abbrev(git_object** out, git_repository *repo, const char *spec)
  38 {
  39         size_t speclen = strlen(spec);
  40
  41         return maybe_sha_or_abbrev(out, repo, spec, speclen);
  42 }
  43
  44 static int build_regex(git_regexp *regex, const char *pattern)
  45 {
  46         int error;
  47
  48         if (*pattern == '\0') {
  49                 git_error_set(GIT_ERROR_REGEX, "empty pattern");
  50                 return GIT_EINVALIDSPEC;
  51         }
  52
  53         error = git_regexp_compile(regex, pattern, 0);
  54         if (!error)
  55                 return 0;
  56
  57         git_regexp_dispose(regex);
  58
  59         return error;
  60 }
  61
  62 static int maybe_describe(git_object**out, git_repository *repo, const char *spec)
  63 {
  64         const char *substr;
  65         int error;
  66         git_regexp regex;
  67
  68         substr = strstr(spec, "-g");
  69
  70         if (substr == NULL)
  71                 return GIT_ENOTFOUND;
  72
  73         if (build_regex(&regex, ".+-[0-9]+-g[0-9a-fA-F]+") < 0)
  74                 return -1;
  75
  76         error = git_regexp_match(&regex, spec);
  77         git_regexp_dispose(&regex);
  78
  79         if (error)
  80                 return GIT_ENOTFOUND;
  81
  82         return maybe_abbrev(out, repo, substr+2);
  83 }
  84
  85 static int revparse_lookup_object(
  86         git_object **object_out,
  87         git_reference **reference_out,
  88         git_repository *repo,
  89         const char *spec)
  90 {
  91         int error;
  92         git_reference *ref;
  93
  94         if ((error = maybe_sha(object_out, repo, spec)) != GIT_ENOTFOUND)
  95                 return error;
  96
  97         error = git_reference_dwim(&ref, repo, spec);
  98         if (!error) {
  99
 100                 error = git_object_lookup(
 101                         object_out, repo, git_reference_target(ref), GIT_OBJECT_ANY);
 102
 103                 if (!error)
 104                         *reference_out = ref;
 105
 106                 return error;
 107         }
 108
 109         if (error != GIT_ENOTFOUND)
 110                 return error;
 111
 112         if ((strlen(spec) < GIT_OID_HEXSZ) &&
 113                 ((error = maybe_abbrev(object_out, repo, spec)) != GIT_ENOTFOUND))
 114                         return error;
 115
 116         if ((error = maybe_describe(object_out, repo, spec)) != GIT_ENOTFOUND)
 117                 return error;
 118
 119         git_error_set(GIT_ERROR_REFERENCE, "revspec '%s' not found", spec);
 120         return GIT_ENOTFOUND;
 121 }
 122
 123 static int try_parse_numeric(int *n, const char *curly_braces_content)
 124 {
 125         int32_t content;
 126         const char *end_ptr;
 127
 128         if (git__strntol32(&content, curly_braces_content, strlen(curly_braces_content),
 129                            &end_ptr, 10) < 0)
 130                 return -1;
 131
 132         if (*end_ptr != '\0')
 133                 return -1;
 134
 135         *n = (int)content;
 136         return 0;
 137 }
 138
 139 static int retrieve_previously_checked_out_branch_or_revision(git_object **out, git_reference **base_ref, git_repository *repo, const char *identifier, size_t position)
 140 {
 141         git_reference *ref = NULL;
 142         git_reflog *reflog = NULL;
 143         git_regexp preg;
 144         int error = -1;
 145         size_t i, numentries, cur;
 146         const git_reflog_entry *entry;
 147         const char *msg;
 148         git_buf buf = GIT_BUF_INIT;
 149
 150         cur = position;
 151
 152         if (*identifier != '\0' || *base_ref != NULL)
 153                 return GIT_EINVALIDSPEC;
 154
 155         if (build_regex(&preg, "checkout: moving from (.*) to .*") < 0)
 156                 return -1;
 157
 158         if (git_reference_lookup(&ref, repo, GIT_HEAD_FILE) < 0)
 159                 goto cleanup;
 160
 161         if (git_reflog_read(&reflog, repo, GIT_HEAD_FILE) < 0)
 162                 goto cleanup;
 163
 164         numentries  = git_reflog_entrycount(reflog);
 165
 166         for (i = 0; i < numentries; i++) {
 167                 git_regmatch regexmatches[2];
 168
 169                 entry = git_reflog_entry_byindex(reflog, i);
 170                 msg = git_reflog_entry_message(entry);
 171                 if (!msg)
 172                         continue;
 173
 174                 if (git_regexp_search(&preg, msg, 2, regexmatches) < 0)
 175                         continue;
 176
 177                 cur--;
 178
 179                 if (cur > 0)
 180                         continue;
 181
 182                 if ((git_buf_put(&buf, msg+regexmatches[1].start, regexmatches[1].end - regexmatches[1].start)) < 0)
 183                         goto cleanup;
 184
 185                 if ((error = git_reference_dwim(base_ref, repo, git_buf_cstr(&buf))) == 0)
 186                         goto cleanup;
 187
 188                 if (error < 0 && error != GIT_ENOTFOUND)
 189                         goto cleanup;
 190
 191                 error = maybe_abbrev(out, repo, git_buf_cstr(&buf));
 192
 193                 goto cleanup;
 194         }
 195
 196         error = GIT_ENOTFOUND;
 197
 198 cleanup:
 199         git_reference_free(ref);
 200         git_buf_dispose(&buf);
 201         git_regexp_dispose(&preg);
 202         git_reflog_free(reflog);
 203         return error;
 204 }
 205
 206 static int retrieve_oid_from_reflog(git_oid *oid, git_reference *ref, size_t identifier)
 207 {
 208         git_reflog *reflog;
 209         size_t numentries;
 210         const git_reflog_entry *entry;
 211         bool search_by_pos = (identifier <= 100000000);
 212
 213         if (git_reflog_read(&reflog, git_reference_owner(ref), git_reference_name(ref)) < 0)
 214                 return -1;
 215
 216         numentries = git_reflog_entrycount(reflog);
 217
 218         if (search_by_pos) {
 219                 if (numentries < identifier + 1)
 220                         goto notfound;
 221
 222                 entry = git_reflog_entry_byindex(reflog, identifier);
 223                 git_oid_cpy(oid, git_reflog_entry_id_new(entry));
 224         } else {
 225                 size_t i;
 226                 git_time commit_time;
 227
 228                 for (i = 0; i < numentries; i++) {
 229                         entry = git_reflog_entry_byindex(reflog, i);
 230                         commit_time = git_reflog_entry_committer(entry)->when;
 231
 232                         if (commit_time.time > (git_time_t)identifier)
 233                                 continue;
 234
 235                         git_oid_cpy(oid, git_reflog_entry_id_new(entry));
 236                         break;
 237                 }
 238
 239                 if (i == numentries)
 240                         goto notfound;
 241         }
 242
 243         git_reflog_free(reflog);
 244         return 0;
 245
 246 notfound:
 247         git_error_set(
 248                 GIT_ERROR_REFERENCE,
 249                 "reflog for '%s' has only %"PRIuZ" entries, asked for %"PRIuZ,
 250                 git_reference_name(ref), numentries, identifier);
 251
 252         git_reflog_free(reflog);
 253         return GIT_ENOTFOUND;
 254 }
 255
 256 static int retrieve_revobject_from_reflog(git_object **out, git_reference **base_ref, git_repository *repo, const char *identifier, size_t position)
 257 {
 258         git_reference *ref;
 259         git_oid oid;
 260         int error = -1;
 261
 262         if (*base_ref == NULL) {
 263                 if ((error = git_reference_dwim(&ref, repo, identifier)) < 0)
 264                         return error;
 265         } else {
 266                 ref = *base_ref;
 267                 *base_ref = NULL;
 268         }
 269
 270         if (position == 0) {
 271                 error = git_object_lookup(out, repo, git_reference_target(ref), GIT_OBJECT_ANY);
 272                 goto cleanup;
 273         }
 274
 275         if ((error = retrieve_oid_from_reflog(&oid, ref, position)) < 0)
 276                 goto cleanup;
 277
 278         error = git_object_lookup(out, repo, &oid, GIT_OBJECT_ANY);
 279
 280 cleanup:
 281         git_reference_free(ref);
 282         return error;
 283 }
 284
 285 static int retrieve_remote_tracking_reference(git_reference **base_ref, const char *identifier, git_repository *repo)
 286 {
 287         git_reference *tracking, *ref;
 288         int error = -1;
 289
 290         if (*base_ref == NULL) {
 291                 if ((error = git_reference_dwim(&ref, repo, identifier)) < 0)
 292                         return error;
 293         } else {
 294                 ref = *base_ref;
 295                 *base_ref = NULL;
 296         }
 297
 298         if (!git_reference_is_branch(ref)) {
 299                 error = GIT_EINVALIDSPEC;
 300                 goto cleanup;
 301         }
 302
 303         if ((error = git_branch_upstream(&tracking, ref)) < 0)
 304                 goto cleanup;
 305
 306         *base_ref = tracking;
 307
 308 cleanup:
 309         git_reference_free(ref);
 310         return error;
 311 }
 312
 313 static int handle_at_syntax(git_object **out, git_reference **ref, const char *spec, size_t identifier_len, git_repository* repo, const char *curly_braces_content)
 314 {
 315         bool is_numeric;
 316         int parsed = 0, error = -1;
 317         git_buf identifier = GIT_BUF_INIT;
 318         git_time_t timestamp;
 319
 320         assert(*out == NULL);
 321
 322         if (git_buf_put(&identifier, spec, identifier_len) < 0)
 323                 return -1;
 324
 325         is_numeric = !try_parse_numeric(&parsed, curly_braces_content);
 326
 327         if (*curly_braces_content == '-' && (!is_numeric || parsed == 0)) {
 328                 error = GIT_EINVALIDSPEC;
 329                 goto cleanup;
 330         }
 331
 332         if (is_numeric) {
 333                 if (parsed < 0)
 334                         error = retrieve_previously_checked_out_branch_or_revision(out, ref, repo, git_buf_cstr(&identifier), -parsed);
 335                 else
 336                         error = retrieve_revobject_from_reflog(out, ref, repo, git_buf_cstr(&identifier), parsed);
 337
 338                 goto cleanup;
 339         }
 340
 341         if (!strcmp(curly_braces_content, "u") || !strcmp(curly_braces_content, "upstream")) {
 342                 error = retrieve_remote_tracking_reference(ref, git_buf_cstr(&identifier), repo);
 343
 344                 goto cleanup;
 345         }
 346
 347         if (git__date_parse(&timestamp, curly_braces_content) < 0)
 348                 goto cleanup;
 349
 350         error = retrieve_revobject_from_reflog(out, ref, repo, git_buf_cstr(&identifier), (size_t)timestamp);
 351
 352 cleanup:
 353         git_buf_dispose(&identifier);
 354         return error;
 355 }
 356
 357 static git_object_t parse_obj_type(const char *str)
 358 {
 359         if (!strcmp(str, "commit"))
 360                 return GIT_OBJECT_COMMIT;
 361
 362         if (!strcmp(str, "tree"))
 363                 return GIT_OBJECT_TREE;
 364
 365         if (!strcmp(str, "blob"))
 366                 return GIT_OBJECT_BLOB;
 367
 368         if (!strcmp(str, "tag"))
 369                 return GIT_OBJECT_TAG;
 370
 371         return GIT_OBJECT_INVALID;
 372 }
 373
 374 static int dereference_to_non_tag(git_object **out, git_object *obj)
 375 {
 376         if (git_object_type(obj) == GIT_OBJECT_TAG)
 377                 return git_tag_peel(out, (git_tag *)obj);
 378
 379         return git_object_dup(out, obj);
 380 }
 381
 382 static int handle_caret_parent_syntax(git_object **out, git_object *obj, int n)
 383 {
 384         git_object *temp_commit = NULL;
 385         int error;
 386
 387         if ((error = git_object_peel(&temp_commit, obj, GIT_OBJECT_COMMIT)) < 0)
 388                 return (error == GIT_EAMBIGUOUS || error == GIT_ENOTFOUND) ?
 389                         GIT_EINVALIDSPEC : error;
 390
 391         if (n == 0) {
 392                 *out = temp_commit;
 393                 return 0;
 394         }
 395
 396         error = git_commit_parent((git_commit **)out, (git_commit*)temp_commit, n - 1);
 397
 398         git_object_free(temp_commit);
 399         return error;
 400 }
 401
 402 static int handle_linear_syntax(git_object **out, git_object *obj, int n)
 403 {
 404         git_object *temp_commit = NULL;
 405         int error;
 406
 407         if ((error = git_object_peel(&temp_commit, obj, GIT_OBJECT_COMMIT)) < 0)
 408                 return (error == GIT_EAMBIGUOUS || error == GIT_ENOTFOUND) ?
 409                         GIT_EINVALIDSPEC : error;
 410
 411         error = git_commit_nth_gen_ancestor((git_commit **)out, (git_commit*)temp_commit, n);
 412
 413         git_object_free(temp_commit);
 414         return error;
 415 }
 416
 417 static int handle_colon_syntax(
 418         git_object **out,
 419         git_object *obj,
 420         const char *path)
 421 {
 422         git_object *tree;
 423         int error = -1;
 424         git_tree_entry *entry = NULL;
 425
 426         if ((error = git_object_peel(&tree, obj, GIT_OBJECT_TREE)) < 0)
 427                 return error == GIT_ENOTFOUND ? GIT_EINVALIDSPEC : error;
 428
 429         if (*path == '\0') {
 430                 *out = tree;
 431                 return 0;
 432         }
 433
 434         /*
 435          * TODO: Handle the relative path syntax
 436          * (:./relative/path and :../relative/path)
 437          */
 438         if ((error = git_tree_entry_bypath(&entry, (git_tree *)tree, path)) < 0)
 439                 goto cleanup;
 440
 441         error = git_tree_entry_to_object(out, git_object_owner(tree), entry);
 442
 443 cleanup:
 444         git_tree_entry_free(entry);
 445         git_object_free(tree);
 446
 447         return error;
 448 }
 449
 450 static int walk_and_search(git_object **out, git_revwalk *walk, git_regexp *regex)
 451 {
 452         int error;
 453         git_oid oid;
 454         git_object *obj;
 455
 456         while (!(error = git_revwalk_next(&oid, walk))) {
 457
 458                 error = git_object_lookup(&obj, git_revwalk_repository(walk), &oid, GIT_OBJECT_COMMIT);
 459                 if ((error < 0) && (error != GIT_ENOTFOUND))
 460                         return -1;
 461
 462                 if (!git_regexp_match(regex, git_commit_message((git_commit*)obj))) {
 463                         *out = obj;
 464                         return 0;
 465                 }
 466
 467                 git_object_free(obj);
 468         }
 469
 470         if (error < 0 && error == GIT_ITEROVER)
 471                 error = GIT_ENOTFOUND;
 472
 473         return error;
 474 }
 475
 476 static int handle_grep_syntax(git_object **out, git_repository *repo, const git_oid *spec_oid, const char *pattern)
 477 {
 478         git_regexp preg;
 479         git_revwalk *walk = NULL;
 480         int error;
 481
 482         if ((error = build_regex(&preg, pattern)) < 0)
 483                 return error;
 484
 485         if ((error = git_revwalk_new(&walk, repo)) < 0)
 486                 goto cleanup;
 487
 488         git_revwalk_sorting(walk, GIT_SORT_TIME);
 489
 490         if (spec_oid == NULL) {
 491                 if ((error = git_revwalk_push_glob(walk, "refs/*")) < 0)
 492                         goto cleanup;
 493         } else if ((error = git_revwalk_push(walk, spec_oid)) < 0)
 494                         goto cleanup;
 495
 496         error = walk_and_search(out, walk, &preg);
 497
 498 cleanup:
 499         git_regexp_dispose(&preg);
 500         git_revwalk_free(walk);
 501
 502         return error;
 503 }
 504
 505 static int handle_caret_curly_syntax(git_object **out, git_object *obj, const char *curly_braces_content)
 506 {
 507         git_object_t expected_type;
 508
 509         if (*curly_braces_content == '\0')
 510                 return dereference_to_non_tag(out, obj);
 511
 512         if (*curly_braces_content == '/')
 513                 return handle_grep_syntax(out, git_object_owner(obj), git_object_id(obj), curly_braces_content + 1);
 514
 515         expected_type = parse_obj_type(curly_braces_content);
 516
 517         if (expected_type == GIT_OBJECT_INVALID)
 518                 return GIT_EINVALIDSPEC;
 519
 520         return git_object_peel(out, obj, expected_type);
 521 }
 522
 523 static int extract_curly_braces_content(git_buf *buf, const char *spec, size_t *pos)
 524 {
 525         git_buf_clear(buf);
 526
 527         assert(spec[*pos] == '^' || spec[*pos] == '@');
 528
 529         (*pos)++;
 530
 531         if (spec[*pos] == '\0' || spec[*pos] != '{')
 532                 return GIT_EINVALIDSPEC;
 533
 534         (*pos)++;
 535
 536         while (spec[*pos] != '}') {
 537                 if (spec[*pos] == '\0')
 538                         return GIT_EINVALIDSPEC;
 539
 540                 if (git_buf_putc(buf, spec[(*pos)++]) < 0)
 541                         return -1;
 542         }
 543
 544         (*pos)++;
 545
 546         return 0;
 547 }
 548
 549 static int extract_path(git_buf *buf, const char *spec, size_t *pos)
 550 {
 551         git_buf_clear(buf);
 552
 553         assert(spec[*pos] == ':');
 554
 555         (*pos)++;
 556
 557         if (git_buf_puts(buf, spec + *pos) < 0)
 558                 return -1;
 559
 560         *pos += git_buf_len(buf);
 561
 562         return 0;
 563 }
 564
 565 static int extract_how_many(int *n, const char *spec, size_t *pos)
 566 {
 567         const char *end_ptr;
 568         int parsed, accumulated;
 569         char kind = spec[*pos];
 570
 571         assert(spec[*pos] == '^' || spec[*pos] == '~');
 572
 573         accumulated = 0;
 574
 575         do {
 576                 do {
 577                         (*pos)++;
 578                         accumulated++;
 579                 } while (spec[(*pos)] == kind && kind == '~');
 580
 581                 if (git__isdigit(spec[*pos])) {
 582                         if (git__strntol32(&parsed, spec + *pos, strlen(spec + *pos), &end_ptr, 10) < 0)
 583                                 return GIT_EINVALIDSPEC;
 584
 585                         accumulated += (parsed - 1);
 586                         *pos = end_ptr - spec;
 587                 }
 588
 589         } while (spec[(*pos)] == kind && kind == '~');
 590
 591         *n = accumulated;
 592
 593         return 0;
 594 }
 595
 596 static int object_from_reference(git_object **object, git_reference *reference)
 597 {
 598         git_reference *resolved = NULL;
 599         int error;
 600
 601         if (git_reference_resolve(&resolved, reference) < 0)
 602                 return -1;
 603
 604         error = git_object_lookup(object, reference->db->repo, git_reference_target(resolved), GIT_OBJECT_ANY);
 605         git_reference_free(resolved);
 606
 607         return error;
 608 }
 609
 610 static int ensure_base_rev_loaded(git_object **object, git_reference **reference, const char *spec, size_t identifier_len, git_repository *repo, bool allow_empty_identifier)
 611 {
 612         int error;
 613         git_buf identifier = GIT_BUF_INIT;
 614
 615         if (*object != NULL)
 616                 return 0;
 617
 618         if (*reference != NULL)
 619                 return object_from_reference(object, *reference);
 620
 621         if (!allow_empty_identifier && identifier_len == 0)
 622                 return GIT_EINVALIDSPEC;
 623
 624         if (git_buf_put(&identifier, spec, identifier_len) < 0)
 625                 return -1;
 626
 627         error = revparse_lookup_object(object, reference, repo, git_buf_cstr(&identifier));
 628         git_buf_dispose(&identifier);
 629
 630         return error;
 631 }
 632
 633 static int ensure_base_rev_is_not_known_yet(git_object *object)
 634 {
 635         if (object == NULL)
 636                 return 0;
 637
 638         return GIT_EINVALIDSPEC;
 639 }
 640
 641 static bool any_left_hand_identifier(git_object *object, git_reference *reference, size_t identifier_len)
 642 {
 643         if (object != NULL)
 644                 return true;
 645
 646         if (reference != NULL)
 647                 return true;
 648
 649         if (identifier_len > 0)
 650                 return true;
 651
 652         return false;
 653 }
 654
 655 static int ensure_left_hand_identifier_is_not_known_yet(git_object *object, git_reference *reference)
 656 {
 657         if (!ensure_base_rev_is_not_known_yet(object) && reference == NULL)
 658                 return 0;
 659
 660         return GIT_EINVALIDSPEC;
 661 }
 662
 663 static int revparse(
 664         git_object **object_out,
 665         git_reference **reference_out,
 666         size_t *identifier_len_out,
 667         git_repository *repo,
 668         const char *spec)
 669 {
 670         size_t pos = 0, identifier_len = 0;
 671         int error = -1, n;
 672         git_buf buf = GIT_BUF_INIT;
 673
 674         git_reference *reference = NULL;
 675         git_object *base_rev = NULL;
 676
 677         bool should_return_reference = true;
 678
 679         assert(object_out && reference_out && repo && spec);
 680
 681         *object_out = NULL;
 682         *reference_out = NULL;
 683
 684         while (spec[pos]) {
 685                 switch (spec[pos]) {
 686                 case '^':
 687                         should_return_reference = false;
 688
 689                         if ((error = ensure_base_rev_loaded(&base_rev, &reference, spec, identifier_len, repo, false)) < 0)
 690                                 goto cleanup;
 691
 692                         if (spec[pos+1] == '{') {
 693                                 git_object *temp_object = NULL;
 694
 695                                 if ((error = extract_curly_braces_content(&buf, spec, &pos)) < 0)
 696                                         goto cleanup;
 697
 698                                 if ((error = handle_caret_curly_syntax(&temp_object, base_rev, git_buf_cstr(&buf))) < 0)
 699                                         goto cleanup;
 700
 701                                 git_object_free(base_rev);
 702                                 base_rev = temp_object;
 703                         } else {
 704                                 git_object *temp_object = NULL;
 705
 706                                 if ((error = extract_how_many(&n, spec, &pos)) < 0)
 707                                         goto cleanup;
 708
 709                                 if ((error = handle_caret_parent_syntax(&temp_object, base_rev, n)) < 0)
 710                                         goto cleanup;
 711
 712                                 git_object_free(base_rev);
 713                                 base_rev = temp_object;
 714                         }
 715                         break;
 716
 717                 case '~':
 718                 {
 719                         git_object *temp_object = NULL;
 720
 721                         should_return_reference = false;
 722
 723                         if ((error = extract_how_many(&n, spec, &pos)) < 0)
 724                                 goto cleanup;
 725
 726                         if ((error = ensure_base_rev_loaded(&base_rev, &reference, spec, identifier_len, repo, false)) < 0)
 727                                 goto cleanup;
 728
 729                         if ((error = handle_linear_syntax(&temp_object, base_rev, n)) < 0)
 730                                 goto cleanup;
 731
 732                         git_object_free(base_rev);
 733                         base_rev = temp_object;
 734                         break;
 735                 }
 736
 737                 case ':':
 738                 {
 739                         git_object *temp_object = NULL;
 740
 741                         should_return_reference = false;
 742
 743                         if ((error = extract_path(&buf, spec, &pos)) < 0)
 744                                 goto cleanup;
 745
 746                         if (any_left_hand_identifier(base_rev, reference, identifier_len)) {
 747                                 if ((error = ensure_base_rev_loaded(&base_rev, &reference, spec, identifier_len, repo, true)) < 0)
 748                                         goto cleanup;
 749
 750                                 if ((error = handle_colon_syntax(&temp_object, base_rev, git_buf_cstr(&buf))) < 0)
 751                                         goto cleanup;
 752                         } else {
 753                                 if (*git_buf_cstr(&buf) == '/') {
 754                                         if ((error = handle_grep_syntax(&temp_object, repo, NULL, git_buf_cstr(&buf) + 1)) < 0)
 755                                                 goto cleanup;
 756                                 } else {
 757
 758                                         /*
 759                                          * TODO: support merge-stage path lookup (":2:Makefile")
 760                                          * and plain index blob lookup (:i-am/a/blob)
 761                                          */
 762                                         git_error_set(GIT_ERROR_INVALID, "unimplemented");
 763                                         error = GIT_ERROR;
 764                                         goto cleanup;
 765                                 }
 766                         }
 767
 768                         git_object_free(base_rev);
 769                         base_rev = temp_object;
 770                         break;
 771                 }
 772
 773                 case '@':
 774                         if (spec[pos+1] == '{') {
 775                                 git_object *temp_object = NULL;
 776
 777                                 if ((error = extract_curly_braces_content(&buf, spec, &pos)) < 0)
 778                                         goto cleanup;
 779
 780                                 if ((error = ensure_base_rev_is_not_known_yet(base_rev)) < 0)
 781                                         goto cleanup;
 782
 783                                 if ((error = handle_at_syntax(&temp_object, &reference, spec, identifier_len, repo, git_buf_cstr(&buf))) < 0)
 784                                         goto cleanup;
 785
 786                                 if (temp_object != NULL)
 787                                         base_rev = temp_object;
 788                                 break;
 789                         }
 790                         /* fall through */
 791
 792                 default:
 793                         if ((error = ensure_left_hand_identifier_is_not_known_yet(base_rev, reference)) < 0)
 794                                 goto cleanup;
 795
 796                         pos++;
 797                         identifier_len++;
 798                 }
 799         }
 800
 801         if ((error = ensure_base_rev_loaded(&base_rev, &reference, spec, identifier_len, repo, false)) < 0)
 802                 goto cleanup;
 803
 804         if (!should_return_reference) {
 805                 git_reference_free(reference);
 806                 reference = NULL;
 807         }
 808
 809         *object_out = base_rev;
 810         *reference_out = reference;
 811         *identifier_len_out = identifier_len;
 812         error = 0;
 813
 814 cleanup:
 815         if (error) {
 816                 if (error == GIT_EINVALIDSPEC)
 817                         git_error_set(GIT_ERROR_INVALID,
 818                                 "failed to parse revision specifier - Invalid pattern '%s'", spec);
 819
 820                 git_object_free(base_rev);
 821                 git_reference_free(reference);
 822         }
 823
 824         git_buf_dispose(&buf);
 825         return error;
 826 }
 827
 828 int git_revparse_ext(
 829         git_object **object_out,
 830         git_reference **reference_out,
 831         git_repository *repo,
 832         const char *spec)
 833 {
 834         int error;
 835         size_t identifier_len;
 836         git_object *obj = NULL;
 837         git_reference *ref = NULL;
 838
 839         if ((error = revparse(&obj, &ref, &identifier_len, repo, spec)) < 0)
 840                 goto cleanup;
 841
 842         *object_out = obj;
 843         *reference_out = ref;
 844         GIT_UNUSED(identifier_len);
 845
 846         return 0;
 847
 848 cleanup:
 849         git_object_free(obj);
 850         git_reference_free(ref);
 851         return error;
 852 }
 853
 854 int git_revparse_single(git_object **out, git_repository *repo, const char *spec)
 855 {
 856         int error;
 857         git_object *obj = NULL;
 858         git_reference *ref = NULL;
 859
 860         *out = NULL;
 861
 862         if ((error = git_revparse_ext(&obj, &ref, repo, spec)) < 0)
 863                 goto cleanup;
 864
 865         git_reference_free(ref);
 866
 867         *out = obj;
 868
 869         return 0;
 870
 871 cleanup:
 872         git_object_free(obj);
 873         git_reference_free(ref);
 874         return error;
 875 }
 876
 877 int git_revparse(
 878         git_revspec *revspec,
 879         git_repository *repo,
 880         const char *spec)
 881 {
 882         const char *dotdot;
 883         int error = 0;
 884
 885         assert(revspec && repo && spec);
 886
 887         memset(revspec, 0x0, sizeof(*revspec));
 888
 889         if ((dotdot = strstr(spec, "..")) != NULL) {
 890                 char *lstr;
 891                 const char *rstr;
 892                 revspec->flags = GIT_REVPARSE_RANGE;
 893
 894                 /*
 895                  * Following git.git, don't allow '..' because it makes command line
 896                  * arguments which can be either paths or revisions ambiguous when the
 897                  * path is almost certainly intended. The empty range '...' is still
 898                  * allowed.
 899                  */
 900                 if (!git__strcmp(spec, "..")) {
 901                         git_error_set(GIT_ERROR_INVALID, "Invalid pattern '..'");
 902                         return GIT_EINVALIDSPEC;
 903                 }
 904
 905                 lstr = git__substrdup(spec, dotdot - spec);
 906                 rstr = dotdot + 2;
 907                 if (dotdot[2] == '.') {
 908                         revspec->flags |= GIT_REVPARSE_MERGE_BASE;
 909                         rstr++;
 910                 }
 911
 912                 error = git_revparse_single(
 913                         &revspec->from,
 914                         repo,
 915                         *lstr == '\0' ? "HEAD" : lstr);
 916
 917                 if (!error) {
 918                         error = git_revparse_single(
 919                                 &revspec->to,
 920                                 repo,
 921                                 *rstr == '\0' ? "HEAD" : rstr);
 922                 }
 923
 924                 git__free((void*)lstr);
 925         } else {
 926                 revspec->flags = GIT_REVPARSE_SINGLE;
 927                 error = git_revparse_single(&revspec->from, repo, spec);
 928         }
 929
 930         return error;
 931 }