Andrew's git / gitweb.git / sha1_name.c
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sha1_name.con commit sha1_name: support @{-N} syntax in get_sha1() (d18ba22)
   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
   9static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
  10{
  11        struct alternate_object_database *alt;
  12        char hex[40];
  13        int found = 0;
  14        static struct alternate_object_database *fakeent;
  15
  16        if (!fakeent) {
  17                const char *objdir = get_object_directory();
  18                int objdir_len = strlen(objdir);
  19                int entlen = objdir_len + 43;
  20                fakeent = xmalloc(sizeof(*fakeent) + entlen);
  21                memcpy(fakeent->base, objdir, objdir_len);
  22                fakeent->name = fakeent->base + objdir_len + 1;
  23                fakeent->name[-1] = '/';
  24        }
  25        fakeent->next = alt_odb_list;
  26
  27        sprintf(hex, "%.2s", name);
  28        for (alt = fakeent; alt && found < 2; alt = alt->next) {
  29                struct dirent *de;
  30                DIR *dir;
  31                sprintf(alt->name, "%.2s/", name);
  32                dir = opendir(alt->base);
  33                if (!dir)
  34                        continue;
  35                while ((de = readdir(dir)) != NULL) {
  36                        if (strlen(de->d_name) != 38)
  37                                continue;
  38                        if (memcmp(de->d_name, name + 2, len - 2))
  39                                continue;
  40                        if (!found) {
  41                                memcpy(hex + 2, de->d_name, 38);
  42                                found++;
  43                        }
  44                        else if (memcmp(hex + 2, de->d_name, 38)) {
  45                                found = 2;
  46                                break;
  47                        }
  48                }
  49                closedir(dir);
  50        }
  51        if (found == 1)
  52                return get_sha1_hex(hex, sha1) == 0;
  53        return found;
  54}
  55
  56static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
  57{
  58        do {
  59                if (*a != *b)
  60                        return 0;
  61                a++;
  62                b++;
  63                len -= 2;
  64        } while (len > 1);
  65        if (len)
  66                if ((*a ^ *b) & 0xf0)
  67                        return 0;
  68        return 1;
  69}
  70
  71static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
  72{
  73        struct packed_git *p;
  74        const unsigned char *found_sha1 = NULL;
  75        int found = 0;
  76
  77        prepare_packed_git();
  78        for (p = packed_git; p && found < 2; p = p->next) {
  79                uint32_t num, last;
  80                uint32_t first = 0;
  81                open_pack_index(p);
  82                num = p->num_objects;
  83                last = num;
  84                while (first < last) {
  85                        uint32_t mid = (first + last) / 2;
  86                        const unsigned char *now;
  87                        int cmp;
  88
  89                        now = nth_packed_object_sha1(p, mid);
  90                        cmp = hashcmp(match, now);
  91                        if (!cmp) {
  92                                first = mid;
  93                                break;
  94                        }
  95                        if (cmp > 0) {
  96                                first = mid+1;
  97                                continue;
  98                        }
  99                        last = mid;
 100                }
 101                if (first < num) {
 102                        const unsigned char *now, *next;
 103                       now = nth_packed_object_sha1(p, first);
 104                        if (match_sha(len, match, now)) {
 105                                next = nth_packed_object_sha1(p, first+1);
 106                               if (!next|| !match_sha(len, match, next)) {
 107                                        /* unique within this pack */
 108                                        if (!found) {
 109                                                found_sha1 = now;
 110                                                found++;
 111                                        }
 112                                        else if (hashcmp(found_sha1, now)) {
 113                                                found = 2;
 114                                                break;
 115                                        }
 116                                }
 117                                else {
 118                                        /* not even unique within this pack */
 119                                        found = 2;
 120                                        break;
 121                                }
 122                        }
 123                }
 124        }
 125        if (found == 1)
 126                hashcpy(sha1, found_sha1);
 127        return found;
 128}
 129
 130#define SHORT_NAME_NOT_FOUND (-1)
 131#define SHORT_NAME_AMBIGUOUS (-2)
 132
 133static int find_unique_short_object(int len, char *canonical,
 134                                    unsigned char *res, unsigned char *sha1)
 135{
 136        int has_unpacked, has_packed;
 137        unsigned char unpacked_sha1[20], packed_sha1[20];
 138
 139        prepare_alt_odb();
 140        has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
 141        has_packed = find_short_packed_object(len, res, packed_sha1);
 142        if (!has_unpacked && !has_packed)
 143                return SHORT_NAME_NOT_FOUND;
 144        if (1 < has_unpacked || 1 < has_packed)
 145                return SHORT_NAME_AMBIGUOUS;
 146        if (has_unpacked != has_packed) {
 147                hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
 148                return 0;
 149        }
 150        /* Both have unique ones -- do they match? */
 151        if (hashcmp(packed_sha1, unpacked_sha1))
 152                return SHORT_NAME_AMBIGUOUS;
 153        hashcpy(sha1, packed_sha1);
 154        return 0;
 155}
 156
 157static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 158                          int quietly)
 159{
 160        int i, status;
 161        char canonical[40];
 162        unsigned char res[20];
 163
 164        if (len < MINIMUM_ABBREV || len > 40)
 165                return -1;
 166        hashclr(res);
 167        memset(canonical, 'x', 40);
 168        for (i = 0; i < len ;i++) {
 169                unsigned char c = name[i];
 170                unsigned char val;
 171                if (c >= '0' && c <= '9')
 172                        val = c - '0';
 173                else if (c >= 'a' && c <= 'f')
 174                        val = c - 'a' + 10;
 175                else if (c >= 'A' && c <='F') {
 176                        val = c - 'A' + 10;
 177                        c -= 'A' - 'a';
 178                }
 179                else
 180                        return -1;
 181                canonical[i] = c;
 182                if (!(i & 1))
 183                        val <<= 4;
 184                res[i >> 1] |= val;
 185        }
 186
 187        status = find_unique_short_object(i, canonical, res, sha1);
 188        if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 189                return error("short SHA1 %.*s is ambiguous.", len, canonical);
 190        return status;
 191}
 192
 193const char *find_unique_abbrev(const unsigned char *sha1, int len)
 194{
 195        int status, exists;
 196        static char hex[41];
 197
 198        exists = has_sha1_file(sha1);
 199        memcpy(hex, sha1_to_hex(sha1), 40);
 200        if (len == 40 || !len)
 201                return hex;
 202        while (len < 40) {
 203                unsigned char sha1_ret[20];
 204                status = get_short_sha1(hex, len, sha1_ret, 1);
 205                if (exists
 206                    ? !status
 207                    : status == SHORT_NAME_NOT_FOUND) {
 208                        hex[len] = 0;
 209                        return hex;
 210                }
 211                len++;
 212        }
 213        return hex;
 214}
 215
 216static int ambiguous_path(const char *path, int len)
 217{
 218        int slash = 1;
 219        int cnt;
 220
 221        for (cnt = 0; cnt < len; cnt++) {
 222                switch (*path++) {
 223                case '\0':
 224                        break;
 225                case '/':
 226                        if (slash)
 227                                break;
 228                        slash = 1;
 229                        continue;
 230                case '.':
 231                        continue;
 232                default:
 233                        slash = 0;
 234                        continue;
 235                }
 236                break;
 237        }
 238        return slash;
 239}
 240
 241int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 242{
 243        const char **p, *r;
 244        int refs_found = 0;
 245
 246        *ref = NULL;
 247        for (p = ref_rev_parse_rules; *p; p++) {
 248                char fullref[PATH_MAX];
 249                unsigned char sha1_from_ref[20];
 250                unsigned char *this_result;
 251
 252                this_result = refs_found ? sha1_from_ref : sha1;
 253                mksnpath(fullref, sizeof(fullref), *p, len, str);
 254                r = resolve_ref(fullref, this_result, 1, NULL);
 255                if (r) {
 256                        if (!refs_found++)
 257                                *ref = xstrdup(r);
 258                        if (!warn_ambiguous_refs)
 259                                break;
 260                }
 261        }
 262        return refs_found;
 263}
 264
 265int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 266{
 267        const char **p;
 268        int logs_found = 0;
 269
 270        *log = NULL;
 271        for (p = ref_rev_parse_rules; *p; p++) {
 272                struct stat st;
 273                unsigned char hash[20];
 274                char path[PATH_MAX];
 275                const char *ref, *it;
 276
 277                mksnpath(path, sizeof(path), *p, len, str);
 278                ref = resolve_ref(path, hash, 1, NULL);
 279                if (!ref)
 280                        continue;
 281                if (!stat(git_path("logs/%s", path), &st) &&
 282                    S_ISREG(st.st_mode))
 283                        it = path;
 284                else if (strcmp(ref, path) &&
 285                         !stat(git_path("logs/%s", ref), &st) &&
 286                         S_ISREG(st.st_mode))
 287                        it = ref;
 288                else
 289                        continue;
 290                if (!logs_found++) {
 291                        *log = xstrdup(it);
 292                        hashcpy(sha1, hash);
 293                }
 294                if (!warn_ambiguous_refs)
 295                        break;
 296        }
 297        return logs_found;
 298}
 299
 300static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 301
 302static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 303{
 304        static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
 305        char *real_ref = NULL;
 306        int refs_found = 0;
 307        int at, reflog_len;
 308
 309        if (len == 40 && !get_sha1_hex(str, sha1))
 310                return 0;
 311
 312        /* basic@{time or number or -number} format to query ref-log */
 313        reflog_len = at = 0;
 314        if (str[len-1] == '}') {
 315                for (at = 0; at < len - 1; at++) {
 316                        if (str[at] == '@' && str[at+1] == '{') {
 317                                reflog_len = (len-1) - (at+2);
 318                                len = at;
 319                                break;
 320                        }
 321                }
 322        }
 323
 324        /* Accept only unambiguous ref paths. */
 325        if (len && ambiguous_path(str, len))
 326                return -1;
 327
 328        if (!len && reflog_len) {
 329                struct strbuf buf = STRBUF_INIT;
 330                int ret;
 331                /* try the @{-N} syntax for n-th checkout */
 332                ret = interpret_nth_last_branch(str+at, &buf);
 333                if (ret > 0) {
 334                        /* substitute this branch name and restart */
 335                        return get_sha1_1(buf.buf, buf.len, sha1);
 336                } else if (ret == 0) {
 337                        return -1;
 338                }
 339                /* allow "@{...}" to mean the current branch reflog */
 340                refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 341        } else if (reflog_len)
 342                refs_found = dwim_log(str, len, sha1, &real_ref);
 343        else
 344                refs_found = dwim_ref(str, len, sha1, &real_ref);
 345
 346        if (!refs_found)
 347                return -1;
 348
 349        if (warn_ambiguous_refs && refs_found > 1)
 350                fprintf(stderr, warning, len, str);
 351
 352        if (reflog_len) {
 353                int nth, i;
 354                unsigned long at_time;
 355                unsigned long co_time;
 356                int co_tz, co_cnt;
 357
 358                /* Is it asking for N-th entry, or approxidate? */
 359                for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 360                        char ch = str[at+2+i];
 361                        if ('0' <= ch && ch <= '9')
 362                                nth = nth * 10 + ch - '0';
 363                        else
 364                                nth = -1;
 365                }
 366                if (100000000 <= nth) {
 367                        at_time = nth;
 368                        nth = -1;
 369                } else if (0 <= nth)
 370                        at_time = 0;
 371                else {
 372                        char *tmp = xstrndup(str + at + 2, reflog_len);
 373                        at_time = approxidate(tmp);
 374                        free(tmp);
 375                }
 376                if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 377                                &co_time, &co_tz, &co_cnt)) {
 378                        if (at_time)
 379                                fprintf(stderr,
 380                                        "warning: Log for '%.*s' only goes "
 381                                        "back to %s.\n", len, str,
 382                                        show_date(co_time, co_tz, DATE_RFC2822));
 383                        else
 384                                fprintf(stderr,
 385                                        "warning: Log for '%.*s' only has "
 386                                        "%d entries.\n", len, str, co_cnt);
 387                }
 388        }
 389
 390        free(real_ref);
 391        return 0;
 392}
 393
 394static int get_parent(const char *name, int len,
 395                      unsigned char *result, int idx)
 396{
 397        unsigned char sha1[20];
 398        int ret = get_sha1_1(name, len, sha1);
 399        struct commit *commit;
 400        struct commit_list *p;
 401
 402        if (ret)
 403                return ret;
 404        commit = lookup_commit_reference(sha1);
 405        if (!commit)
 406                return -1;
 407        if (parse_commit(commit))
 408                return -1;
 409        if (!idx) {
 410                hashcpy(result, commit->object.sha1);
 411                return 0;
 412        }
 413        p = commit->parents;
 414        while (p) {
 415                if (!--idx) {
 416                        hashcpy(result, p->item->object.sha1);
 417                        return 0;
 418                }
 419                p = p->next;
 420        }
 421        return -1;
 422}
 423
 424static int get_nth_ancestor(const char *name, int len,
 425                            unsigned char *result, int generation)
 426{
 427        unsigned char sha1[20];
 428        struct commit *commit;
 429        int ret;
 430
 431        ret = get_sha1_1(name, len, sha1);
 432        if (ret)
 433                return ret;
 434        commit = lookup_commit_reference(sha1);
 435        if (!commit)
 436                return -1;
 437
 438        while (generation--) {
 439                if (parse_commit(commit) || !commit->parents)
 440                        return -1;
 441                commit = commit->parents->item;
 442        }
 443        hashcpy(result, commit->object.sha1);
 444        return 0;
 445}
 446
 447struct object *peel_to_type(const char *name, int namelen,
 448                            struct object *o, enum object_type expected_type)
 449{
 450        if (name && !namelen)
 451                namelen = strlen(name);
 452        if (!o) {
 453                unsigned char sha1[20];
 454                if (get_sha1_1(name, namelen, sha1))
 455                        return NULL;
 456                o = parse_object(sha1);
 457        }
 458        while (1) {
 459                if (!o || (!o->parsed && !parse_object(o->sha1)))
 460                        return NULL;
 461                if (o->type == expected_type)
 462                        return o;
 463                if (o->type == OBJ_TAG)
 464                        o = ((struct tag*) o)->tagged;
 465                else if (o->type == OBJ_COMMIT)
 466                        o = &(((struct commit *) o)->tree->object);
 467                else {
 468                        if (name)
 469                                error("%.*s: expected %s type, but the object "
 470                                      "dereferences to %s type",
 471                                      namelen, name, typename(expected_type),
 472                                      typename(o->type));
 473                        return NULL;
 474                }
 475        }
 476}
 477
 478static int peel_onion(const char *name, int len, unsigned char *sha1)
 479{
 480        unsigned char outer[20];
 481        const char *sp;
 482        unsigned int expected_type = 0;
 483        struct object *o;
 484
 485        /*
 486         * "ref^{type}" dereferences ref repeatedly until you cannot
 487         * dereference anymore, or you get an object of given type,
 488         * whichever comes first.  "ref^{}" means just dereference
 489         * tags until you get a non-tag.  "ref^0" is a shorthand for
 490         * "ref^{commit}".  "commit^{tree}" could be used to find the
 491         * top-level tree of the given commit.
 492         */
 493        if (len < 4 || name[len-1] != '}')
 494                return -1;
 495
 496        for (sp = name + len - 1; name <= sp; sp--) {
 497                int ch = *sp;
 498                if (ch == '{' && name < sp && sp[-1] == '^')
 499                        break;
 500        }
 501        if (sp <= name)
 502                return -1;
 503
 504        sp++; /* beginning of type name, or closing brace for empty */
 505        if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 506                expected_type = OBJ_COMMIT;
 507        else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 508                expected_type = OBJ_TREE;
 509        else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 510                expected_type = OBJ_BLOB;
 511        else if (sp[0] == '}')
 512                expected_type = OBJ_NONE;
 513        else
 514                return -1;
 515
 516        if (get_sha1_1(name, sp - name - 2, outer))
 517                return -1;
 518
 519        o = parse_object(outer);
 520        if (!o)
 521                return -1;
 522        if (!expected_type) {
 523                o = deref_tag(o, name, sp - name - 2);
 524                if (!o || (!o->parsed && !parse_object(o->sha1)))
 525                        return -1;
 526                hashcpy(sha1, o->sha1);
 527        }
 528        else {
 529                /*
 530                 * At this point, the syntax look correct, so
 531                 * if we do not get the needed object, we should
 532                 * barf.
 533                 */
 534                o = peel_to_type(name, len, o, expected_type);
 535                if (o) {
 536                        hashcpy(sha1, o->sha1);
 537                        return 0;
 538                }
 539                return -1;
 540        }
 541        return 0;
 542}
 543
 544static int get_describe_name(const char *name, int len, unsigned char *sha1)
 545{
 546        const char *cp;
 547
 548        for (cp = name + len - 1; name + 2 <= cp; cp--) {
 549                char ch = *cp;
 550                if (hexval(ch) & ~0377) {
 551                        /* We must be looking at g in "SOMETHING-g"
 552                         * for it to be describe output.
 553                         */
 554                        if (ch == 'g' && cp[-1] == '-') {
 555                                cp++;
 556                                len -= cp - name;
 557                                return get_short_sha1(cp, len, sha1, 1);
 558                        }
 559                }
 560        }
 561        return -1;
 562}
 563
 564static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 565{
 566        int ret, has_suffix;
 567        const char *cp;
 568
 569        /*
 570         * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 571         */
 572        has_suffix = 0;
 573        for (cp = name + len - 1; name <= cp; cp--) {
 574                int ch = *cp;
 575                if ('0' <= ch && ch <= '9')
 576                        continue;
 577                if (ch == '~' || ch == '^')
 578                        has_suffix = ch;
 579                break;
 580        }
 581
 582        if (has_suffix) {
 583                int num = 0;
 584                int len1 = cp - name;
 585                cp++;
 586                while (cp < name + len)
 587                        num = num * 10 + *cp++ - '0';
 588                if (!num && len1 == len - 1)
 589                        num = 1;
 590                if (has_suffix == '^')
 591                        return get_parent(name, len1, sha1, num);
 592                /* else if (has_suffix == '~') -- goes without saying */
 593                return get_nth_ancestor(name, len1, sha1, num);
 594        }
 595
 596        ret = peel_onion(name, len, sha1);
 597        if (!ret)
 598                return 0;
 599
 600        ret = get_sha1_basic(name, len, sha1);
 601        if (!ret)
 602                return 0;
 603
 604        /* It could be describe output that is "SOMETHING-gXXXX" */
 605        ret = get_describe_name(name, len, sha1);
 606        if (!ret)
 607                return 0;
 608
 609        return get_short_sha1(name, len, sha1, 0);
 610}
 611
 612static int handle_one_ref(const char *path,
 613                const unsigned char *sha1, int flag, void *cb_data)
 614{
 615        struct commit_list **list = cb_data;
 616        struct object *object = parse_object(sha1);
 617        if (!object)
 618                return 0;
 619        if (object->type == OBJ_TAG) {
 620                object = deref_tag(object, path, strlen(path));
 621                if (!object)
 622                        return 0;
 623        }
 624        if (object->type != OBJ_COMMIT)
 625                return 0;
 626        insert_by_date((struct commit *)object, list);
 627        return 0;
 628}
 629
 630/*
 631 * This interprets names like ':/Initial revision of "git"' by searching
 632 * through history and returning the first commit whose message starts
 633 * with the given string.
 634 *
 635 * For future extension, ':/!' is reserved. If you want to match a message
 636 * beginning with a '!', you have to repeat the exclamation mark.
 637 */
 638
 639#define ONELINE_SEEN (1u<<20)
 640static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 641{
 642        struct commit_list *list = NULL, *backup = NULL, *l;
 643        int retval = -1;
 644        char *temp_commit_buffer = NULL;
 645
 646        if (prefix[0] == '!') {
 647                if (prefix[1] != '!')
 648                        die ("Invalid search pattern: %s", prefix);
 649                prefix++;
 650        }
 651        for_each_ref(handle_one_ref, &list);
 652        for (l = list; l; l = l->next)
 653                commit_list_insert(l->item, &backup);
 654        while (list) {
 655                char *p;
 656                struct commit *commit;
 657                enum object_type type;
 658                unsigned long size;
 659
 660                commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 661                if (!parse_object(commit->object.sha1))
 662                        continue;
 663                free(temp_commit_buffer);
 664                if (commit->buffer)
 665                        p = commit->buffer;
 666                else {
 667                        p = read_sha1_file(commit->object.sha1, &type, &size);
 668                        if (!p)
 669                                continue;
 670                        temp_commit_buffer = p;
 671                }
 672                if (!(p = strstr(p, "\n\n")))
 673                        continue;
 674                if (!prefixcmp(p + 2, prefix)) {
 675                        hashcpy(sha1, commit->object.sha1);
 676                        retval = 0;
 677                        break;
 678                }
 679        }
 680        free(temp_commit_buffer);
 681        free_commit_list(list);
 682        for (l = backup; l; l = l->next)
 683                clear_commit_marks(l->item, ONELINE_SEEN);
 684        return retval;
 685}
 686
 687struct grab_nth_branch_switch_cbdata {
 688        int counting;
 689        int nth;
 690        struct strbuf *buf;
 691};
 692
 693static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 694                                  const char *email, unsigned long timestamp, int tz,
 695                                  const char *message, void *cb_data)
 696{
 697        struct grab_nth_branch_switch_cbdata *cb = cb_data;
 698        const char *match = NULL, *target = NULL;
 699        size_t len;
 700
 701        if (!prefixcmp(message, "checkout: moving from ")) {
 702                match = message + strlen("checkout: moving from ");
 703                if ((target = strstr(match, " to ")) != NULL)
 704                        target += 4;
 705        }
 706
 707        if (!match)
 708                return 0;
 709
 710        len = target - match - 4;
 711        if (target[len] == '\n' && !strncmp(match, target, len))
 712                return 0;
 713
 714        if (cb->counting) {
 715                cb->nth++;
 716                return 0;
 717        }
 718
 719        if (cb->nth-- <= 0) {
 720                strbuf_reset(cb->buf);
 721                strbuf_add(cb->buf, match, len);
 722                return 1;
 723        }
 724        return 0;
 725}
 726
 727/*
 728 * This reads "@{-N}" syntax, finds the name of the Nth previous
 729 * branch we were on, and places the name of the branch in the given
 730 * buf and returns the number of characters parsed if successful.
 731 *
 732 * If the input is not of the accepted format, it returns a negative
 733 * number to signal an error.
 734 *
 735 * If the input was ok but there are not N branch switches in the
 736 * reflog, it returns 0.
 737 */
 738int interpret_nth_last_branch(const char *name, struct strbuf *buf)
 739{
 740        int nth;
 741        struct grab_nth_branch_switch_cbdata cb;
 742        const char *brace;
 743        char *num_end;
 744
 745        if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 746                return -1;
 747        brace = strchr(name, '}');
 748        if (!brace)
 749                return -1;
 750        nth = strtol(name+3, &num_end, 10);
 751        if (num_end != brace)
 752                return -1;
 753
 754        cb.counting = 1;
 755        cb.nth = 0;
 756        cb.buf = buf;
 757        for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 758
 759        if (cb.nth < nth)
 760                return 0;
 761
 762        cb.counting = 0;
 763        cb.nth -= nth;
 764        cb.buf = buf;
 765        for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 766
 767        return brace-name+1;
 768}
 769
 770/*
 771 * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 772 * notably "xyz^" for "parent of xyz"
 773 */
 774int get_sha1(const char *name, unsigned char *sha1)
 775{
 776        unsigned unused;
 777        return get_sha1_with_mode(name, sha1, &unused);
 778}
 779
 780int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 781{
 782        int ret, bracket_depth;
 783        int namelen = strlen(name);
 784        const char *cp;
 785
 786        *mode = S_IFINVALID;
 787        ret = get_sha1_1(name, namelen, sha1);
 788        if (!ret)
 789                return ret;
 790        /* sha1:path --> object name of path in ent sha1
 791         * :path -> object name of path in index
 792         * :[0-3]:path -> object name of path in index at stage
 793         */
 794        if (name[0] == ':') {
 795                int stage = 0;
 796                struct cache_entry *ce;
 797                int pos;
 798                if (namelen > 2 && name[1] == '/')
 799                        return get_sha1_oneline(name + 2, sha1);
 800                if (namelen < 3 ||
 801                    name[2] != ':' ||
 802                    name[1] < '0' || '3' < name[1])
 803                        cp = name + 1;
 804                else {
 805                        stage = name[1] - '0';
 806                        cp = name + 3;
 807                }
 808                namelen = namelen - (cp - name);
 809                if (!active_cache)
 810                        read_cache();
 811                pos = cache_name_pos(cp, namelen);
 812                if (pos < 0)
 813                        pos = -pos - 1;
 814                while (pos < active_nr) {
 815                        ce = active_cache[pos];
 816                        if (ce_namelen(ce) != namelen ||
 817                            memcmp(ce->name, cp, namelen))
 818                                break;
 819                        if (ce_stage(ce) == stage) {
 820                                hashcpy(sha1, ce->sha1);
 821                                *mode = ce->ce_mode;
 822                                return 0;
 823                        }
 824                        pos++;
 825                }
 826                return -1;
 827        }
 828        for (cp = name, bracket_depth = 0; *cp; cp++) {
 829                if (*cp == '{')
 830                        bracket_depth++;
 831                else if (bracket_depth && *cp == '}')
 832                        bracket_depth--;
 833                else if (!bracket_depth && *cp == ':')
 834                        break;
 835        }
 836        if (*cp == ':') {
 837                unsigned char tree_sha1[20];
 838                if (!get_sha1_1(name, cp-name, tree_sha1))
 839                        return get_tree_entry(tree_sha1, cp+1, sha1,
 840                                              mode);
 841        }
 842        return ret;
 843}