sha1_name.con commit lstat_cache(): print a warning if doing ping-pong between cache types (7734f04)
   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
 241/*
 242 * *string and *len will only be substituted, and *string returned (for
 243 * later free()ing) if the string passed in is of the form @{-<n>}.
 244 */
 245static char *substitute_nth_last_branch(const char **string, int *len)
 246{
 247        struct strbuf buf = STRBUF_INIT;
 248        int ret = interpret_nth_last_branch(*string, &buf);
 249
 250        if (ret == *len) {
 251                size_t size;
 252                *string = strbuf_detach(&buf, &size);
 253                *len = size;
 254                return (char *)*string;
 255        }
 256
 257        return NULL;
 258}
 259
 260int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 261{
 262        char *last_branch = substitute_nth_last_branch(&str, &len);
 263        const char **p, *r;
 264        int refs_found = 0;
 265
 266        *ref = NULL;
 267        for (p = ref_rev_parse_rules; *p; p++) {
 268                char fullref[PATH_MAX];
 269                unsigned char sha1_from_ref[20];
 270                unsigned char *this_result;
 271
 272                this_result = refs_found ? sha1_from_ref : sha1;
 273                mksnpath(fullref, sizeof(fullref), *p, len, str);
 274                r = resolve_ref(fullref, this_result, 1, NULL);
 275                if (r) {
 276                        if (!refs_found++)
 277                                *ref = xstrdup(r);
 278                        if (!warn_ambiguous_refs)
 279                                break;
 280                }
 281        }
 282        free(last_branch);
 283        return refs_found;
 284}
 285
 286int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 287{
 288        char *last_branch = substitute_nth_last_branch(&str, &len);
 289        const char **p;
 290        int logs_found = 0;
 291
 292        *log = NULL;
 293        for (p = ref_rev_parse_rules; *p; p++) {
 294                struct stat st;
 295                unsigned char hash[20];
 296                char path[PATH_MAX];
 297                const char *ref, *it;
 298
 299                mksnpath(path, sizeof(path), *p, len, str);
 300                ref = resolve_ref(path, hash, 1, NULL);
 301                if (!ref)
 302                        continue;
 303                if (!stat(git_path("logs/%s", path), &st) &&
 304                    S_ISREG(st.st_mode))
 305                        it = path;
 306                else if (strcmp(ref, path) &&
 307                         !stat(git_path("logs/%s", ref), &st) &&
 308                         S_ISREG(st.st_mode))
 309                        it = ref;
 310                else
 311                        continue;
 312                if (!logs_found++) {
 313                        *log = xstrdup(it);
 314                        hashcpy(sha1, hash);
 315                }
 316                if (!warn_ambiguous_refs)
 317                        break;
 318        }
 319        free(last_branch);
 320        return logs_found;
 321}
 322
 323static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 324
 325static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 326{
 327        static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
 328        char *real_ref = NULL;
 329        int refs_found = 0;
 330        int at, reflog_len;
 331
 332        if (len == 40 && !get_sha1_hex(str, sha1))
 333                return 0;
 334
 335        /* basic@{time or number or -number} format to query ref-log */
 336        reflog_len = at = 0;
 337        if (len && str[len-1] == '}') {
 338                for (at = len-2; at >= 0; at--) {
 339                        if (str[at] == '@' && str[at+1] == '{') {
 340                                reflog_len = (len-1) - (at+2);
 341                                len = at;
 342                                break;
 343                        }
 344                }
 345        }
 346
 347        /* Accept only unambiguous ref paths. */
 348        if (len && ambiguous_path(str, len))
 349                return -1;
 350
 351        if (!len && reflog_len) {
 352                struct strbuf buf = STRBUF_INIT;
 353                int ret;
 354                /* try the @{-N} syntax for n-th checkout */
 355                ret = interpret_nth_last_branch(str+at, &buf);
 356                if (ret > 0) {
 357                        /* substitute this branch name and restart */
 358                        return get_sha1_1(buf.buf, buf.len, sha1);
 359                } else if (ret == 0) {
 360                        return -1;
 361                }
 362                /* allow "@{...}" to mean the current branch reflog */
 363                refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 364        } else if (reflog_len)
 365                refs_found = dwim_log(str, len, sha1, &real_ref);
 366        else
 367                refs_found = dwim_ref(str, len, sha1, &real_ref);
 368
 369        if (!refs_found)
 370                return -1;
 371
 372        if (warn_ambiguous_refs && refs_found > 1)
 373                fprintf(stderr, warning, len, str);
 374
 375        if (reflog_len) {
 376                int nth, i;
 377                unsigned long at_time;
 378                unsigned long co_time;
 379                int co_tz, co_cnt;
 380
 381                /* Is it asking for N-th entry, or approxidate? */
 382                for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 383                        char ch = str[at+2+i];
 384                        if ('0' <= ch && ch <= '9')
 385                                nth = nth * 10 + ch - '0';
 386                        else
 387                                nth = -1;
 388                }
 389                if (100000000 <= nth) {
 390                        at_time = nth;
 391                        nth = -1;
 392                } else if (0 <= nth)
 393                        at_time = 0;
 394                else {
 395                        char *tmp = xstrndup(str + at + 2, reflog_len);
 396                        at_time = approxidate(tmp);
 397                        free(tmp);
 398                }
 399                if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 400                                &co_time, &co_tz, &co_cnt)) {
 401                        if (at_time)
 402                                fprintf(stderr,
 403                                        "warning: Log for '%.*s' only goes "
 404                                        "back to %s.\n", len, str,
 405                                        show_date(co_time, co_tz, DATE_RFC2822));
 406                        else
 407                                fprintf(stderr,
 408                                        "warning: Log for '%.*s' only has "
 409                                        "%d entries.\n", len, str, co_cnt);
 410                }
 411        }
 412
 413        free(real_ref);
 414        return 0;
 415}
 416
 417static int get_parent(const char *name, int len,
 418                      unsigned char *result, int idx)
 419{
 420        unsigned char sha1[20];
 421        int ret = get_sha1_1(name, len, sha1);
 422        struct commit *commit;
 423        struct commit_list *p;
 424
 425        if (ret)
 426                return ret;
 427        commit = lookup_commit_reference(sha1);
 428        if (!commit)
 429                return -1;
 430        if (parse_commit(commit))
 431                return -1;
 432        if (!idx) {
 433                hashcpy(result, commit->object.sha1);
 434                return 0;
 435        }
 436        p = commit->parents;
 437        while (p) {
 438                if (!--idx) {
 439                        hashcpy(result, p->item->object.sha1);
 440                        return 0;
 441                }
 442                p = p->next;
 443        }
 444        return -1;
 445}
 446
 447static int get_nth_ancestor(const char *name, int len,
 448                            unsigned char *result, int generation)
 449{
 450        unsigned char sha1[20];
 451        struct commit *commit;
 452        int ret;
 453
 454        ret = get_sha1_1(name, len, sha1);
 455        if (ret)
 456                return ret;
 457        commit = lookup_commit_reference(sha1);
 458        if (!commit)
 459                return -1;
 460
 461        while (generation--) {
 462                if (parse_commit(commit) || !commit->parents)
 463                        return -1;
 464                commit = commit->parents->item;
 465        }
 466        hashcpy(result, commit->object.sha1);
 467        return 0;
 468}
 469
 470struct object *peel_to_type(const char *name, int namelen,
 471                            struct object *o, enum object_type expected_type)
 472{
 473        if (name && !namelen)
 474                namelen = strlen(name);
 475        if (!o) {
 476                unsigned char sha1[20];
 477                if (get_sha1_1(name, namelen, sha1))
 478                        return NULL;
 479                o = parse_object(sha1);
 480        }
 481        while (1) {
 482                if (!o || (!o->parsed && !parse_object(o->sha1)))
 483                        return NULL;
 484                if (o->type == expected_type)
 485                        return o;
 486                if (o->type == OBJ_TAG)
 487                        o = ((struct tag*) o)->tagged;
 488                else if (o->type == OBJ_COMMIT)
 489                        o = &(((struct commit *) o)->tree->object);
 490                else {
 491                        if (name)
 492                                error("%.*s: expected %s type, but the object "
 493                                      "dereferences to %s type",
 494                                      namelen, name, typename(expected_type),
 495                                      typename(o->type));
 496                        return NULL;
 497                }
 498        }
 499}
 500
 501static int peel_onion(const char *name, int len, unsigned char *sha1)
 502{
 503        unsigned char outer[20];
 504        const char *sp;
 505        unsigned int expected_type = 0;
 506        struct object *o;
 507
 508        /*
 509         * "ref^{type}" dereferences ref repeatedly until you cannot
 510         * dereference anymore, or you get an object of given type,
 511         * whichever comes first.  "ref^{}" means just dereference
 512         * tags until you get a non-tag.  "ref^0" is a shorthand for
 513         * "ref^{commit}".  "commit^{tree}" could be used to find the
 514         * top-level tree of the given commit.
 515         */
 516        if (len < 4 || name[len-1] != '}')
 517                return -1;
 518
 519        for (sp = name + len - 1; name <= sp; sp--) {
 520                int ch = *sp;
 521                if (ch == '{' && name < sp && sp[-1] == '^')
 522                        break;
 523        }
 524        if (sp <= name)
 525                return -1;
 526
 527        sp++; /* beginning of type name, or closing brace for empty */
 528        if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 529                expected_type = OBJ_COMMIT;
 530        else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 531                expected_type = OBJ_TREE;
 532        else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 533                expected_type = OBJ_BLOB;
 534        else if (sp[0] == '}')
 535                expected_type = OBJ_NONE;
 536        else
 537                return -1;
 538
 539        if (get_sha1_1(name, sp - name - 2, outer))
 540                return -1;
 541
 542        o = parse_object(outer);
 543        if (!o)
 544                return -1;
 545        if (!expected_type) {
 546                o = deref_tag(o, name, sp - name - 2);
 547                if (!o || (!o->parsed && !parse_object(o->sha1)))
 548                        return -1;
 549                hashcpy(sha1, o->sha1);
 550        }
 551        else {
 552                /*
 553                 * At this point, the syntax look correct, so
 554                 * if we do not get the needed object, we should
 555                 * barf.
 556                 */
 557                o = peel_to_type(name, len, o, expected_type);
 558                if (o) {
 559                        hashcpy(sha1, o->sha1);
 560                        return 0;
 561                }
 562                return -1;
 563        }
 564        return 0;
 565}
 566
 567static int get_describe_name(const char *name, int len, unsigned char *sha1)
 568{
 569        const char *cp;
 570
 571        for (cp = name + len - 1; name + 2 <= cp; cp--) {
 572                char ch = *cp;
 573                if (hexval(ch) & ~0377) {
 574                        /* We must be looking at g in "SOMETHING-g"
 575                         * for it to be describe output.
 576                         */
 577                        if (ch == 'g' && cp[-1] == '-') {
 578                                cp++;
 579                                len -= cp - name;
 580                                return get_short_sha1(cp, len, sha1, 1);
 581                        }
 582                }
 583        }
 584        return -1;
 585}
 586
 587static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 588{
 589        int ret, has_suffix;
 590        const char *cp;
 591
 592        /*
 593         * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 594         */
 595        has_suffix = 0;
 596        for (cp = name + len - 1; name <= cp; cp--) {
 597                int ch = *cp;
 598                if ('0' <= ch && ch <= '9')
 599                        continue;
 600                if (ch == '~' || ch == '^')
 601                        has_suffix = ch;
 602                break;
 603        }
 604
 605        if (has_suffix) {
 606                int num = 0;
 607                int len1 = cp - name;
 608                cp++;
 609                while (cp < name + len)
 610                        num = num * 10 + *cp++ - '0';
 611                if (!num && len1 == len - 1)
 612                        num = 1;
 613                if (has_suffix == '^')
 614                        return get_parent(name, len1, sha1, num);
 615                /* else if (has_suffix == '~') -- goes without saying */
 616                return get_nth_ancestor(name, len1, sha1, num);
 617        }
 618
 619        ret = peel_onion(name, len, sha1);
 620        if (!ret)
 621                return 0;
 622
 623        ret = get_sha1_basic(name, len, sha1);
 624        if (!ret)
 625                return 0;
 626
 627        /* It could be describe output that is "SOMETHING-gXXXX" */
 628        ret = get_describe_name(name, len, sha1);
 629        if (!ret)
 630                return 0;
 631
 632        return get_short_sha1(name, len, sha1, 0);
 633}
 634
 635static int handle_one_ref(const char *path,
 636                const unsigned char *sha1, int flag, void *cb_data)
 637{
 638        struct commit_list **list = cb_data;
 639        struct object *object = parse_object(sha1);
 640        if (!object)
 641                return 0;
 642        if (object->type == OBJ_TAG) {
 643                object = deref_tag(object, path, strlen(path));
 644                if (!object)
 645                        return 0;
 646        }
 647        if (object->type != OBJ_COMMIT)
 648                return 0;
 649        insert_by_date((struct commit *)object, list);
 650        return 0;
 651}
 652
 653/*
 654 * This interprets names like ':/Initial revision of "git"' by searching
 655 * through history and returning the first commit whose message starts
 656 * with the given string.
 657 *
 658 * For future extension, ':/!' is reserved. If you want to match a message
 659 * beginning with a '!', you have to repeat the exclamation mark.
 660 */
 661
 662#define ONELINE_SEEN (1u<<20)
 663static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 664{
 665        struct commit_list *list = NULL, *backup = NULL, *l;
 666        int retval = -1;
 667        char *temp_commit_buffer = NULL;
 668
 669        if (prefix[0] == '!') {
 670                if (prefix[1] != '!')
 671                        die ("Invalid search pattern: %s", prefix);
 672                prefix++;
 673        }
 674        for_each_ref(handle_one_ref, &list);
 675        for (l = list; l; l = l->next)
 676                commit_list_insert(l->item, &backup);
 677        while (list) {
 678                char *p;
 679                struct commit *commit;
 680                enum object_type type;
 681                unsigned long size;
 682
 683                commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 684                if (!parse_object(commit->object.sha1))
 685                        continue;
 686                free(temp_commit_buffer);
 687                if (commit->buffer)
 688                        p = commit->buffer;
 689                else {
 690                        p = read_sha1_file(commit->object.sha1, &type, &size);
 691                        if (!p)
 692                                continue;
 693                        temp_commit_buffer = p;
 694                }
 695                if (!(p = strstr(p, "\n\n")))
 696                        continue;
 697                if (!prefixcmp(p + 2, prefix)) {
 698                        hashcpy(sha1, commit->object.sha1);
 699                        retval = 0;
 700                        break;
 701                }
 702        }
 703        free(temp_commit_buffer);
 704        free_commit_list(list);
 705        for (l = backup; l; l = l->next)
 706                clear_commit_marks(l->item, ONELINE_SEEN);
 707        return retval;
 708}
 709
 710struct grab_nth_branch_switch_cbdata {
 711        long cnt, alloc;
 712        struct strbuf *buf;
 713};
 714
 715static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 716                                  const char *email, unsigned long timestamp, int tz,
 717                                  const char *message, void *cb_data)
 718{
 719        struct grab_nth_branch_switch_cbdata *cb = cb_data;
 720        const char *match = NULL, *target = NULL;
 721        size_t len;
 722        int nth;
 723
 724        if (!prefixcmp(message, "checkout: moving from ")) {
 725                match = message + strlen("checkout: moving from ");
 726                target = strstr(match, " to ");
 727        }
 728
 729        if (!match || !target)
 730                return 0;
 731
 732        len = target - match;
 733        nth = cb->cnt++ % cb->alloc;
 734        strbuf_reset(&cb->buf[nth]);
 735        strbuf_add(&cb->buf[nth], match, len);
 736        return 0;
 737}
 738
 739/*
 740 * This reads "@{-N}" syntax, finds the name of the Nth previous
 741 * branch we were on, and places the name of the branch in the given
 742 * buf and returns the number of characters parsed if successful.
 743 *
 744 * If the input is not of the accepted format, it returns a negative
 745 * number to signal an error.
 746 *
 747 * If the input was ok but there are not N branch switches in the
 748 * reflog, it returns 0.
 749 */
 750int interpret_nth_last_branch(const char *name, struct strbuf *buf)
 751{
 752        long nth;
 753        int i, retval;
 754        struct grab_nth_branch_switch_cbdata cb;
 755        const char *brace;
 756        char *num_end;
 757
 758        if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 759                return -1;
 760        brace = strchr(name, '}');
 761        if (!brace)
 762                return -1;
 763        nth = strtol(name+3, &num_end, 10);
 764        if (num_end != brace)
 765                return -1;
 766        if (nth <= 0)
 767                return -1;
 768        cb.alloc = nth;
 769        cb.buf = xmalloc(nth * sizeof(struct strbuf));
 770        for (i = 0; i < nth; i++)
 771                strbuf_init(&cb.buf[i], 20);
 772        cb.cnt = 0;
 773        retval = 0;
 774        for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 775        if (cb.cnt < nth) {
 776                cb.cnt = 0;
 777                for (i = 0; i < nth; i++)
 778                        strbuf_release(&cb.buf[i]);
 779                for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 780        }
 781        if (cb.cnt < nth)
 782                goto release_return;
 783        i = cb.cnt % nth;
 784        strbuf_reset(buf);
 785        strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 786        retval = brace-name+1;
 787
 788release_return:
 789        for (i = 0; i < nth; i++)
 790                strbuf_release(&cb.buf[i]);
 791        free(cb.buf);
 792
 793        return retval;
 794}
 795
 796/*
 797 * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 798 * notably "xyz^" for "parent of xyz"
 799 */
 800int get_sha1(const char *name, unsigned char *sha1)
 801{
 802        unsigned unused;
 803        return get_sha1_with_mode(name, sha1, &unused);
 804}
 805
 806int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 807{
 808        int ret, bracket_depth;
 809        int namelen = strlen(name);
 810        const char *cp;
 811
 812        *mode = S_IFINVALID;
 813        ret = get_sha1_1(name, namelen, sha1);
 814        if (!ret)
 815                return ret;
 816        /* sha1:path --> object name of path in ent sha1
 817         * :path -> object name of path in index
 818         * :[0-3]:path -> object name of path in index at stage
 819         */
 820        if (name[0] == ':') {
 821                int stage = 0;
 822                struct cache_entry *ce;
 823                int pos;
 824                if (namelen > 2 && name[1] == '/')
 825                        return get_sha1_oneline(name + 2, sha1);
 826                if (namelen < 3 ||
 827                    name[2] != ':' ||
 828                    name[1] < '0' || '3' < name[1])
 829                        cp = name + 1;
 830                else {
 831                        stage = name[1] - '0';
 832                        cp = name + 3;
 833                }
 834                namelen = namelen - (cp - name);
 835                if (!active_cache)
 836                        read_cache();
 837                pos = cache_name_pos(cp, namelen);
 838                if (pos < 0)
 839                        pos = -pos - 1;
 840                while (pos < active_nr) {
 841                        ce = active_cache[pos];
 842                        if (ce_namelen(ce) != namelen ||
 843                            memcmp(ce->name, cp, namelen))
 844                                break;
 845                        if (ce_stage(ce) == stage) {
 846                                hashcpy(sha1, ce->sha1);
 847                                *mode = ce->ce_mode;
 848                                return 0;
 849                        }
 850                        pos++;
 851                }
 852                return -1;
 853        }
 854        for (cp = name, bracket_depth = 0; *cp; cp++) {
 855                if (*cp == '{')
 856                        bracket_depth++;
 857                else if (bracket_depth && *cp == '}')
 858                        bracket_depth--;
 859                else if (!bracket_depth && *cp == ':')
 860                        break;
 861        }
 862        if (*cp == ':') {
 863                unsigned char tree_sha1[20];
 864                if (!get_sha1_1(name, cp-name, tree_sha1))
 865                        return get_tree_entry(tree_sha1, cp+1, sha1,
 866                                              mode);
 867        }
 868        return ret;
 869}