sha1_name.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tree-walk.h"
   7 #include "refs.h"
   8 #include "remote.h"
   9
  10 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
  11 {
  12         struct alternate_object_database *alt;
  13         char hex[40];
  14         int found = 0;
  15         static struct alternate_object_database *fakeent;
  16
  17         if (!fakeent) {
  18                 const char *objdir = get_object_directory();
  19                 int objdir_len = strlen(objdir);
  20                 int entlen = objdir_len + 43;
  21                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  22                 memcpy(fakeent->base, objdir, objdir_len);
  23                 fakeent->name = fakeent->base + objdir_len + 1;
  24                 fakeent->name[-1] = '/';
  25         }
  26         fakeent->next = alt_odb_list;
  27
  28         sprintf(hex, "%.2s", name);
  29         for (alt = fakeent; alt && found < 2; alt = alt->next) {
  30                 struct dirent *de;
  31                 DIR *dir;
  32                 sprintf(alt->name, "%.2s/", name);
  33                 dir = opendir(alt->base);
  34                 if (!dir)
  35                         continue;
  36                 while ((de = readdir(dir)) != NULL) {
  37                         if (strlen(de->d_name) != 38)
  38                                 continue;
  39                         if (memcmp(de->d_name, name + 2, len - 2))
  40                                 continue;
  41                         if (!found) {
  42                                 memcpy(hex + 2, de->d_name, 38);
  43                                 found++;
  44                         }
  45                         else if (memcmp(hex + 2, de->d_name, 38)) {
  46                                 found = 2;
  47                                 break;
  48                         }
  49                 }
  50                 closedir(dir);
  51         }
  52         if (found == 1)
  53                 return get_sha1_hex(hex, sha1) == 0;
  54         return found;
  55 }
  56
  57 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
  58 {
  59         do {
  60                 if (*a != *b)
  61                         return 0;
  62                 a++;
  63                 b++;
  64                 len -= 2;
  65         } while (len > 1);
  66         if (len)
  67                 if ((*a ^ *b) & 0xf0)
  68                         return 0;
  69         return 1;
  70 }
  71
  72 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
  73 {
  74         struct packed_git *p;
  75         const unsigned char *found_sha1 = NULL;
  76         int found = 0;
  77
  78         prepare_packed_git();
  79         for (p = packed_git; p && found < 2; p = p->next) {
  80                 uint32_t num, last;
  81                 uint32_t first = 0;
  82                 open_pack_index(p);
  83                 num = p->num_objects;
  84                 last = num;
  85                 while (first < last) {
  86                         uint32_t mid = (first + last) / 2;
  87                         const unsigned char *now;
  88                         int cmp;
  89
  90                         now = nth_packed_object_sha1(p, mid);
  91                         cmp = hashcmp(match, now);
  92                         if (!cmp) {
  93                                 first = mid;
  94                                 break;
  95                         }
  96                         if (cmp > 0) {
  97                                 first = mid+1;
  98                                 continue;
  99                         }
 100                         last = mid;
 101                 }
 102                 if (first < num) {
 103                         const unsigned char *now, *next;
 104                        now = nth_packed_object_sha1(p, first);
 105                         if (match_sha(len, match, now)) {
 106                                 next = nth_packed_object_sha1(p, first+1);
 107                                if (!next|| !match_sha(len, match, next)) {
 108                                         /* unique within this pack */
 109                                         if (!found) {
 110                                                 found_sha1 = now;
 111                                                 found++;
 112                                         }
 113                                         else if (hashcmp(found_sha1, now)) {
 114                                                 found = 2;
 115                                                 break;
 116                                         }
 117                                 }
 118                                 else {
 119                                         /* not even unique within this pack */
 120                                         found = 2;
 121                                         break;
 122                                 }
 123                         }
 124                 }
 125         }
 126         if (found == 1)
 127                 hashcpy(sha1, found_sha1);
 128         return found;
 129 }
 130
 131 #define SHORT_NAME_NOT_FOUND (-1)
 132 #define SHORT_NAME_AMBIGUOUS (-2)
 133
 134 static int find_unique_short_object(int len, char *canonical,
 135                                     unsigned char *res, unsigned char *sha1)
 136 {
 137         int has_unpacked, has_packed;
 138         unsigned char unpacked_sha1[20], packed_sha1[20];
 139
 140         prepare_alt_odb();
 141         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
 142         has_packed = find_short_packed_object(len, res, packed_sha1);
 143         if (!has_unpacked && !has_packed)
 144                 return SHORT_NAME_NOT_FOUND;
 145         if (1 < has_unpacked || 1 < has_packed)
 146                 return SHORT_NAME_AMBIGUOUS;
 147         if (has_unpacked != has_packed) {
 148                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
 149                 return 0;
 150         }
 151         /* Both have unique ones -- do they match? */
 152         if (hashcmp(packed_sha1, unpacked_sha1))
 153                 return SHORT_NAME_AMBIGUOUS;
 154         hashcpy(sha1, packed_sha1);
 155         return 0;
 156 }
 157
 158 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 159                           int quietly)
 160 {
 161         int i, status;
 162         char canonical[40];
 163         unsigned char res[20];
 164
 165         if (len < MINIMUM_ABBREV || len > 40)
 166                 return -1;
 167         hashclr(res);
 168         memset(canonical, 'x', 40);
 169         for (i = 0; i < len ;i++) {
 170                 unsigned char c = name[i];
 171                 unsigned char val;
 172                 if (c >= '0' && c <= '9')
 173                         val = c - '0';
 174                 else if (c >= 'a' && c <= 'f')
 175                         val = c - 'a' + 10;
 176                 else if (c >= 'A' && c <='F') {
 177                         val = c - 'A' + 10;
 178                         c -= 'A' - 'a';
 179                 }
 180                 else
 181                         return -1;
 182                 canonical[i] = c;
 183                 if (!(i & 1))
 184                         val <<= 4;
 185                 res[i >> 1] |= val;
 186         }
 187
 188         status = find_unique_short_object(i, canonical, res, sha1);
 189         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 190                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
 191         return status;
 192 }
 193
 194 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 195 {
 196         int status, exists;
 197         static char hex[41];
 198
 199         exists = has_sha1_file(sha1);
 200         memcpy(hex, sha1_to_hex(sha1), 40);
 201         if (len == 40 || !len)
 202                 return hex;
 203         while (len < 40) {
 204                 unsigned char sha1_ret[20];
 205                 status = get_short_sha1(hex, len, sha1_ret, 1);
 206                 if (exists
 207                     ? !status
 208                     : status == SHORT_NAME_NOT_FOUND) {
 209                         hex[len] = 0;
 210                         return hex;
 211                 }
 212                 len++;
 213         }
 214         return hex;
 215 }
 216
 217 static int ambiguous_path(const char *path, int len)
 218 {
 219         int slash = 1;
 220         int cnt;
 221
 222         for (cnt = 0; cnt < len; cnt++) {
 223                 switch (*path++) {
 224                 case '\0':
 225                         break;
 226                 case '/':
 227                         if (slash)
 228                                 break;
 229                         slash = 1;
 230                         continue;
 231                 case '.':
 232                         continue;
 233                 default:
 234                         slash = 0;
 235                         continue;
 236                 }
 237                 break;
 238         }
 239         return slash;
 240 }
 241
 242 /*
 243  * *string and *len will only be substituted, and *string returned (for
 244  * later free()ing) if the string passed in is a magic short-hand form
 245  * to name a branch.
 246  */
 247 static char *substitute_branch_name(const char **string, int *len)
 248 {
 249         struct strbuf buf = STRBUF_INIT;
 250         int ret = interpret_branch_name(*string, &buf);
 251
 252         if (ret == *len) {
 253                 size_t size;
 254                 *string = strbuf_detach(&buf, &size);
 255                 *len = size;
 256                 return (char *)*string;
 257         }
 258
 259         return NULL;
 260 }
 261
 262 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 263 {
 264         char *last_branch = substitute_branch_name(&str, &len);
 265         const char **p, *r;
 266         int refs_found = 0;
 267
 268         *ref = NULL;
 269         for (p = ref_rev_parse_rules; *p; p++) {
 270                 char fullref[PATH_MAX];
 271                 unsigned char sha1_from_ref[20];
 272                 unsigned char *this_result;
 273                 int flag;
 274
 275                 this_result = refs_found ? sha1_from_ref : sha1;
 276                 mksnpath(fullref, sizeof(fullref), *p, len, str);
 277                 r = resolve_ref(fullref, this_result, 1, &flag);
 278                 if (r) {
 279                         if (!refs_found++)
 280                                 *ref = xstrdup(r);
 281                         if (!warn_ambiguous_refs)
 282                                 break;
 283                 } else if ((flag & REF_ISSYMREF) &&
 284                            (len != 4 || strcmp(str, "HEAD")))
 285                         warning("ignoring dangling symref %s.", fullref);
 286         }
 287         free(last_branch);
 288         return refs_found;
 289 }
 290
 291 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 292 {
 293         char *last_branch = substitute_branch_name(&str, &len);
 294         const char **p;
 295         int logs_found = 0;
 296
 297         *log = NULL;
 298         for (p = ref_rev_parse_rules; *p; p++) {
 299                 struct stat st;
 300                 unsigned char hash[20];
 301                 char path[PATH_MAX];
 302                 const char *ref, *it;
 303
 304                 mksnpath(path, sizeof(path), *p, len, str);
 305                 ref = resolve_ref(path, hash, 1, NULL);
 306                 if (!ref)
 307                         continue;
 308                 if (!stat(git_path("logs/%s", path), &st) &&
 309                     S_ISREG(st.st_mode))
 310                         it = path;
 311                 else if (strcmp(ref, path) &&
 312                          !stat(git_path("logs/%s", ref), &st) &&
 313                          S_ISREG(st.st_mode))
 314                         it = ref;
 315                 else
 316                         continue;
 317                 if (!logs_found++) {
 318                         *log = xstrdup(it);
 319                         hashcpy(sha1, hash);
 320                 }
 321                 if (!warn_ambiguous_refs)
 322                         break;
 323         }
 324         free(last_branch);
 325         return logs_found;
 326 }
 327
 328 static inline int upstream_mark(const char *string, int len)
 329 {
 330         const char *suffix[] = { "@{upstream}", "@{u}" };
 331         int i;
 332
 333         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 334                 int suffix_len = strlen(suffix[i]);
 335                 if (suffix_len <= len
 336                     && !memcmp(string, suffix[i], suffix_len))
 337                         return suffix_len;
 338         }
 339         return 0;
 340 }
 341
 342 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 343
 344 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 345 {
 346         static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
 347         char *real_ref = NULL;
 348         int refs_found = 0;
 349         int at, reflog_len;
 350
 351         if (len == 40 && !get_sha1_hex(str, sha1))
 352                 return 0;
 353
 354         /* basic@{time or number or -number} format to query ref-log */
 355         reflog_len = at = 0;
 356         if (len && str[len-1] == '}') {
 357                 for (at = len-2; at >= 0; at--) {
 358                         if (str[at] == '@' && str[at+1] == '{') {
 359                                 if (!upstream_mark(str + at, len - at)) {
 360                                         reflog_len = (len-1) - (at+2);
 361                                         len = at;
 362                                 }
 363                                 break;
 364                         }
 365                 }
 366         }
 367
 368         /* Accept only unambiguous ref paths. */
 369         if (len && ambiguous_path(str, len))
 370                 return -1;
 371
 372         if (!len && reflog_len) {
 373                 struct strbuf buf = STRBUF_INIT;
 374                 int ret;
 375                 /* try the @{-N} syntax for n-th checkout */
 376                 ret = interpret_branch_name(str+at, &buf);
 377                 if (ret > 0) {
 378                         /* substitute this branch name and restart */
 379                         return get_sha1_1(buf.buf, buf.len, sha1);
 380                 } else if (ret == 0) {
 381                         return -1;
 382                 }
 383                 /* allow "@{...}" to mean the current branch reflog */
 384                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 385         } else if (reflog_len)
 386                 refs_found = dwim_log(str, len, sha1, &real_ref);
 387         else
 388                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 389
 390         if (!refs_found)
 391                 return -1;
 392
 393         if (warn_ambiguous_refs && refs_found > 1)
 394                 fprintf(stderr, warning, len, str);
 395
 396         if (reflog_len) {
 397                 int nth, i;
 398                 unsigned long at_time;
 399                 unsigned long co_time;
 400                 int co_tz, co_cnt;
 401
 402                 /* Is it asking for N-th entry, or approxidate? */
 403                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 404                         char ch = str[at+2+i];
 405                         if ('0' <= ch && ch <= '9')
 406                                 nth = nth * 10 + ch - '0';
 407                         else
 408                                 nth = -1;
 409                 }
 410                 if (100000000 <= nth) {
 411                         at_time = nth;
 412                         nth = -1;
 413                 } else if (0 <= nth)
 414                         at_time = 0;
 415                 else {
 416                         char *tmp = xstrndup(str + at + 2, reflog_len);
 417                         at_time = approxidate(tmp);
 418                         free(tmp);
 419                 }
 420                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 421                                 &co_time, &co_tz, &co_cnt)) {
 422                         if (at_time)
 423                                 fprintf(stderr,
 424                                         "warning: Log for '%.*s' only goes "
 425                                         "back to %s.\n", len, str,
 426                                         show_date(co_time, co_tz, DATE_RFC2822));
 427                         else
 428                                 fprintf(stderr,
 429                                         "warning: Log for '%.*s' only has "
 430                                         "%d entries.\n", len, str, co_cnt);
 431                 }
 432         }
 433
 434         free(real_ref);
 435         return 0;
 436 }
 437
 438 static int get_parent(const char *name, int len,
 439                       unsigned char *result, int idx)
 440 {
 441         unsigned char sha1[20];
 442         int ret = get_sha1_1(name, len, sha1);
 443         struct commit *commit;
 444         struct commit_list *p;
 445
 446         if (ret)
 447                 return ret;
 448         commit = lookup_commit_reference(sha1);
 449         if (!commit)
 450                 return -1;
 451         if (parse_commit(commit))
 452                 return -1;
 453         if (!idx) {
 454                 hashcpy(result, commit->object.sha1);
 455                 return 0;
 456         }
 457         p = commit->parents;
 458         while (p) {
 459                 if (!--idx) {
 460                         hashcpy(result, p->item->object.sha1);
 461                         return 0;
 462                 }
 463                 p = p->next;
 464         }
 465         return -1;
 466 }
 467
 468 static int get_nth_ancestor(const char *name, int len,
 469                             unsigned char *result, int generation)
 470 {
 471         unsigned char sha1[20];
 472         struct commit *commit;
 473         int ret;
 474
 475         ret = get_sha1_1(name, len, sha1);
 476         if (ret)
 477                 return ret;
 478         commit = lookup_commit_reference(sha1);
 479         if (!commit)
 480                 return -1;
 481
 482         while (generation--) {
 483                 if (parse_commit(commit) || !commit->parents)
 484                         return -1;
 485                 commit = commit->parents->item;
 486         }
 487         hashcpy(result, commit->object.sha1);
 488         return 0;
 489 }
 490
 491 struct object *peel_to_type(const char *name, int namelen,
 492                             struct object *o, enum object_type expected_type)
 493 {
 494         if (name && !namelen)
 495                 namelen = strlen(name);
 496         if (!o) {
 497                 unsigned char sha1[20];
 498                 if (get_sha1_1(name, namelen, sha1))
 499                         return NULL;
 500                 o = parse_object(sha1);
 501         }
 502         while (1) {
 503                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 504                         return NULL;
 505                 if (o->type == expected_type)
 506                         return o;
 507                 if (o->type == OBJ_TAG)
 508                         o = ((struct tag*) o)->tagged;
 509                 else if (o->type == OBJ_COMMIT)
 510                         o = &(((struct commit *) o)->tree->object);
 511                 else {
 512                         if (name)
 513                                 error("%.*s: expected %s type, but the object "
 514                                       "dereferences to %s type",
 515                                       namelen, name, typename(expected_type),
 516                                       typename(o->type));
 517                         return NULL;
 518                 }
 519         }
 520 }
 521
 522 static int peel_onion(const char *name, int len, unsigned char *sha1)
 523 {
 524         unsigned char outer[20];
 525         const char *sp;
 526         unsigned int expected_type = 0;
 527         struct object *o;
 528
 529         /*
 530          * "ref^{type}" dereferences ref repeatedly until you cannot
 531          * dereference anymore, or you get an object of given type,
 532          * whichever comes first.  "ref^{}" means just dereference
 533          * tags until you get a non-tag.  "ref^0" is a shorthand for
 534          * "ref^{commit}".  "commit^{tree}" could be used to find the
 535          * top-level tree of the given commit.
 536          */
 537         if (len < 4 || name[len-1] != '}')
 538                 return -1;
 539
 540         for (sp = name + len - 1; name <= sp; sp--) {
 541                 int ch = *sp;
 542                 if (ch == '{' && name < sp && sp[-1] == '^')
 543                         break;
 544         }
 545         if (sp <= name)
 546                 return -1;
 547
 548         sp++; /* beginning of type name, or closing brace for empty */
 549         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 550                 expected_type = OBJ_COMMIT;
 551         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 552                 expected_type = OBJ_TREE;
 553         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 554                 expected_type = OBJ_BLOB;
 555         else if (sp[0] == '}')
 556                 expected_type = OBJ_NONE;
 557         else
 558                 return -1;
 559
 560         if (get_sha1_1(name, sp - name - 2, outer))
 561                 return -1;
 562
 563         o = parse_object(outer);
 564         if (!o)
 565                 return -1;
 566         if (!expected_type) {
 567                 o = deref_tag(o, name, sp - name - 2);
 568                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 569                         return -1;
 570                 hashcpy(sha1, o->sha1);
 571         }
 572         else {
 573                 /*
 574                  * At this point, the syntax look correct, so
 575                  * if we do not get the needed object, we should
 576                  * barf.
 577                  */
 578                 o = peel_to_type(name, len, o, expected_type);
 579                 if (o) {
 580                         hashcpy(sha1, o->sha1);
 581                         return 0;
 582                 }
 583                 return -1;
 584         }
 585         return 0;
 586 }
 587
 588 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 589 {
 590         const char *cp;
 591
 592         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 593                 char ch = *cp;
 594                 if (hexval(ch) & ~0377) {
 595                         /* We must be looking at g in "SOMETHING-g"
 596                          * for it to be describe output.
 597                          */
 598                         if (ch == 'g' && cp[-1] == '-') {
 599                                 cp++;
 600                                 len -= cp - name;
 601                                 return get_short_sha1(cp, len, sha1, 1);
 602                         }
 603                 }
 604         }
 605         return -1;
 606 }
 607
 608 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 609 {
 610         int ret, has_suffix;
 611         const char *cp;
 612
 613         /*
 614          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 615          */
 616         has_suffix = 0;
 617         for (cp = name + len - 1; name <= cp; cp--) {
 618                 int ch = *cp;
 619                 if ('0' <= ch && ch <= '9')
 620                         continue;
 621                 if (ch == '~' || ch == '^')
 622                         has_suffix = ch;
 623                 break;
 624         }
 625
 626         if (has_suffix) {
 627                 int num = 0;
 628                 int len1 = cp - name;
 629                 cp++;
 630                 while (cp < name + len)
 631                         num = num * 10 + *cp++ - '0';
 632                 if (!num && len1 == len - 1)
 633                         num = 1;
 634                 if (has_suffix == '^')
 635                         return get_parent(name, len1, sha1, num);
 636                 /* else if (has_suffix == '~') -- goes without saying */
 637                 return get_nth_ancestor(name, len1, sha1, num);
 638         }
 639
 640         ret = peel_onion(name, len, sha1);
 641         if (!ret)
 642                 return 0;
 643
 644         ret = get_sha1_basic(name, len, sha1);
 645         if (!ret)
 646                 return 0;
 647
 648         /* It could be describe output that is "SOMETHING-gXXXX" */
 649         ret = get_describe_name(name, len, sha1);
 650         if (!ret)
 651                 return 0;
 652
 653         return get_short_sha1(name, len, sha1, 0);
 654 }
 655
 656 static int handle_one_ref(const char *path,
 657                 const unsigned char *sha1, int flag, void *cb_data)
 658 {
 659         struct commit_list **list = cb_data;
 660         struct object *object = parse_object(sha1);
 661         if (!object)
 662                 return 0;
 663         if (object->type == OBJ_TAG) {
 664                 object = deref_tag(object, path, strlen(path));
 665                 if (!object)
 666                         return 0;
 667         }
 668         if (object->type != OBJ_COMMIT)
 669                 return 0;
 670         insert_by_date((struct commit *)object, list);
 671         return 0;
 672 }
 673
 674 /*
 675  * This interprets names like ':/Initial revision of "git"' by searching
 676  * through history and returning the first commit whose message starts
 677  * with the given string.
 678  *
 679  * For future extension, ':/!' is reserved. If you want to match a message
 680  * beginning with a '!', you have to repeat the exclamation mark.
 681  */
 682
 683 #define ONELINE_SEEN (1u<<20)
 684 static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 685 {
 686         struct commit_list *list = NULL, *backup = NULL, *l;
 687         int retval = -1;
 688         char *temp_commit_buffer = NULL;
 689
 690         if (prefix[0] == '!') {
 691                 if (prefix[1] != '!')
 692                         die ("Invalid search pattern: %s", prefix);
 693                 prefix++;
 694         }
 695         for_each_ref(handle_one_ref, &list);
 696         for (l = list; l; l = l->next)
 697                 commit_list_insert(l->item, &backup);
 698         while (list) {
 699                 char *p;
 700                 struct commit *commit;
 701                 enum object_type type;
 702                 unsigned long size;
 703
 704                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 705                 if (!parse_object(commit->object.sha1))
 706                         continue;
 707                 free(temp_commit_buffer);
 708                 if (commit->buffer)
 709                         p = commit->buffer;
 710                 else {
 711                         p = read_sha1_file(commit->object.sha1, &type, &size);
 712                         if (!p)
 713                                 continue;
 714                         temp_commit_buffer = p;
 715                 }
 716                 if (!(p = strstr(p, "\n\n")))
 717                         continue;
 718                 if (!prefixcmp(p + 2, prefix)) {
 719                         hashcpy(sha1, commit->object.sha1);
 720                         retval = 0;
 721                         break;
 722                 }
 723         }
 724         free(temp_commit_buffer);
 725         free_commit_list(list);
 726         for (l = backup; l; l = l->next)
 727                 clear_commit_marks(l->item, ONELINE_SEEN);
 728         return retval;
 729 }
 730
 731 struct grab_nth_branch_switch_cbdata {
 732         long cnt, alloc;
 733         struct strbuf *buf;
 734 };
 735
 736 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 737                                   const char *email, unsigned long timestamp, int tz,
 738                                   const char *message, void *cb_data)
 739 {
 740         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 741         const char *match = NULL, *target = NULL;
 742         size_t len;
 743         int nth;
 744
 745         if (!prefixcmp(message, "checkout: moving from ")) {
 746                 match = message + strlen("checkout: moving from ");
 747                 target = strstr(match, " to ");
 748         }
 749
 750         if (!match || !target)
 751                 return 0;
 752
 753         len = target - match;
 754         nth = cb->cnt++ % cb->alloc;
 755         strbuf_reset(&cb->buf[nth]);
 756         strbuf_add(&cb->buf[nth], match, len);
 757         return 0;
 758 }
 759
 760 /*
 761  * Parse @{-N} syntax, return the number of characters parsed
 762  * if successful; otherwise signal an error with negative value.
 763  */
 764 static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
 765 {
 766         long nth;
 767         int i, retval;
 768         struct grab_nth_branch_switch_cbdata cb;
 769         const char *brace;
 770         char *num_end;
 771
 772         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 773                 return -1;
 774         brace = strchr(name, '}');
 775         if (!brace)
 776                 return -1;
 777         nth = strtol(name+3, &num_end, 10);
 778         if (num_end != brace)
 779                 return -1;
 780         if (nth <= 0)
 781                 return -1;
 782         cb.alloc = nth;
 783         cb.buf = xmalloc(nth * sizeof(struct strbuf));
 784         for (i = 0; i < nth; i++)
 785                 strbuf_init(&cb.buf[i], 20);
 786         cb.cnt = 0;
 787         retval = 0;
 788         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 789         if (cb.cnt < nth) {
 790                 cb.cnt = 0;
 791                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 792         }
 793         if (cb.cnt < nth)
 794                 goto release_return;
 795         i = cb.cnt % nth;
 796         strbuf_reset(buf);
 797         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 798         retval = brace-name+1;
 799
 800 release_return:
 801         for (i = 0; i < nth; i++)
 802                 strbuf_release(&cb.buf[i]);
 803         free(cb.buf);
 804
 805         return retval;
 806 }
 807
 808 /*
 809  * This reads short-hand syntax that not only evaluates to a commit
 810  * object name, but also can act as if the end user spelled the name
 811  * of the branch from the command line.
 812  *
 813  * - "@{-N}" finds the name of the Nth previous branch we were on, and
 814  *   places the name of the branch in the given buf and returns the
 815  *   number of characters parsed if successful.
 816  *
 817  * - "<branch>@{upstream}" finds the name of the other ref that
 818  *   <branch> is configured to merge with (missing <branch> defaults
 819  *   to the current branch), and places the name of the branch in the
 820  *   given buf and returns the number of characters parsed if
 821  *   successful.
 822  *
 823  * If the input is not of the accepted format, it returns a negative
 824  * number to signal an error.
 825  *
 826  * If the input was ok but there are not N branch switches in the
 827  * reflog, it returns 0.
 828  */
 829 int interpret_branch_name(const char *name, struct strbuf *buf)
 830 {
 831         char *cp;
 832         struct branch *upstream;
 833         int namelen = strlen(name);
 834         int len = interpret_nth_prior_checkout(name, buf);
 835         int tmp_len;
 836
 837         if (!len)
 838                 return len; /* syntax Ok, not enough switches */
 839         if (0 < len)
 840                 return len; /* consumed from the front */
 841         cp = strchr(name, '@');
 842         if (!cp)
 843                 return -1;
 844         tmp_len = upstream_mark(cp, namelen - (cp - name));
 845         if (!tmp_len)
 846                 return -1;
 847         len = cp + tmp_len - name;
 848         cp = xstrndup(name, cp - name);
 849         upstream = branch_get(*cp ? cp : NULL);
 850         if (!upstream
 851             || !upstream->merge
 852             || !upstream->merge[0]->dst)
 853                 return error("No upstream branch found for '%s'", cp);
 854         free(cp);
 855         cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
 856         strbuf_reset(buf);
 857         strbuf_addstr(buf, cp);
 858         free(cp);
 859         return len;
 860 }
 861
 862 /*
 863  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 864  * notably "xyz^" for "parent of xyz"
 865  */
 866 int get_sha1(const char *name, unsigned char *sha1)
 867 {
 868         unsigned unused;
 869         return get_sha1_with_mode(name, sha1, &unused);
 870 }
 871
 872 int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 873 {
 874         int ret, bracket_depth;
 875         int namelen = strlen(name);
 876         const char *cp;
 877
 878         *mode = S_IFINVALID;
 879         ret = get_sha1_1(name, namelen, sha1);
 880         if (!ret)
 881                 return ret;
 882         /* sha1:path --> object name of path in ent sha1
 883          * :path -> object name of path in index
 884          * :[0-3]:path -> object name of path in index at stage
 885          */
 886         if (name[0] == ':') {
 887                 int stage = 0;
 888                 struct cache_entry *ce;
 889                 int pos;
 890                 if (namelen > 2 && name[1] == '/')
 891                         return get_sha1_oneline(name + 2, sha1);
 892                 if (namelen < 3 ||
 893                     name[2] != ':' ||
 894                     name[1] < '0' || '3' < name[1])
 895                         cp = name + 1;
 896                 else {
 897                         stage = name[1] - '0';
 898                         cp = name + 3;
 899                 }
 900                 namelen = namelen - (cp - name);
 901                 if (!active_cache)
 902                         read_cache();
 903                 pos = cache_name_pos(cp, namelen);
 904                 if (pos < 0)
 905                         pos = -pos - 1;
 906                 while (pos < active_nr) {
 907                         ce = active_cache[pos];
 908                         if (ce_namelen(ce) != namelen ||
 909                             memcmp(ce->name, cp, namelen))
 910                                 break;
 911                         if (ce_stage(ce) == stage) {
 912                                 hashcpy(sha1, ce->sha1);
 913                                 *mode = ce->ce_mode;
 914                                 return 0;
 915                         }
 916                         pos++;
 917                 }
 918                 return -1;
 919         }
 920         for (cp = name, bracket_depth = 0; *cp; cp++) {
 921                 if (*cp == '{')
 922                         bracket_depth++;
 923                 else if (bracket_depth && *cp == '}')
 924                         bracket_depth--;
 925                 else if (!bracket_depth && *cp == ':')
 926                         break;
 927         }
 928         if (*cp == ':') {
 929                 unsigned char tree_sha1[20];
 930                 if (!get_sha1_1(name, cp-name, tree_sha1))
 931                         return get_tree_entry(tree_sha1, cp+1, sha1,
 932                                               mode);
 933         }
 934         return ret;
 935 }