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 #include "dir.h"
  10 #include "sha1-array.h"
  11
  12 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
  13
  14 typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
  15
  16 struct disambiguate_state {
  17         int len; /* length of prefix in hex chars */
  18         char hex_pfx[GIT_MAX_HEXSZ + 1];
  19         struct object_id bin_pfx;
  20
  21         disambiguate_hint_fn fn;
  22         void *cb_data;
  23         struct object_id candidate;
  24         unsigned candidate_exists:1;
  25         unsigned candidate_checked:1;
  26         unsigned candidate_ok:1;
  27         unsigned disambiguate_fn_used:1;
  28         unsigned ambiguous:1;
  29         unsigned always_call_fn:1;
  30 };
  31
  32 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
  33 {
  34         if (ds->always_call_fn) {
  35                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  36                 return;
  37         }
  38         if (!ds->candidate_exists) {
  39                 /* this is the first candidate */
  40                 oidcpy(&ds->candidate, current);
  41                 ds->candidate_exists = 1;
  42                 return;
  43         } else if (!oidcmp(&ds->candidate, current)) {
  44                 /* the same as what we already have seen */
  45                 return;
  46         }
  47
  48         if (!ds->fn) {
  49                 /* cannot disambiguate between ds->candidate and current */
  50                 ds->ambiguous = 1;
  51                 return;
  52         }
  53
  54         if (!ds->candidate_checked) {
  55                 ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
  56                 ds->disambiguate_fn_used = 1;
  57                 ds->candidate_checked = 1;
  58         }
  59
  60         if (!ds->candidate_ok) {
  61                 /* discard the candidate; we know it does not satisfy fn */
  62                 oidcpy(&ds->candidate, current);
  63                 ds->candidate_checked = 0;
  64                 return;
  65         }
  66
  67         /* if we reach this point, we know ds->candidate satisfies fn */
  68         if (ds->fn(current, ds->cb_data)) {
  69                 /*
  70                  * if both current and candidate satisfy fn, we cannot
  71                  * disambiguate.
  72                  */
  73                 ds->candidate_ok = 0;
  74                 ds->ambiguous = 1;
  75         }
  76
  77         /* otherwise, current can be discarded and candidate is still good */
  78 }
  79
  80 static void find_short_object_filename(struct disambiguate_state *ds)
  81 {
  82         struct alternate_object_database *alt;
  83         char hex[GIT_MAX_HEXSZ];
  84         static struct alternate_object_database *fakeent;
  85
  86         if (!fakeent) {
  87                 /*
  88                  * Create a "fake" alternate object database that
  89                  * points to our own object database, to make it
  90                  * easier to get a temporary working space in
  91                  * alt->name/alt->base while iterating over the
  92                  * object databases including our own.
  93                  */
  94                 fakeent = alloc_alt_odb(get_object_directory());
  95         }
  96         fakeent->next = alt_odb_list;
  97
  98         xsnprintf(hex, sizeof(hex), "%.2s", ds->hex_pfx);
  99         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 100                 struct strbuf *buf = alt_scratch_buf(alt);
 101                 struct dirent *de;
 102                 DIR *dir;
 103
 104                 strbuf_addf(buf, "%.2s/", ds->hex_pfx);
 105                 dir = opendir(buf->buf);
 106                 if (!dir)
 107                         continue;
 108
 109                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
 110                         struct object_id oid;
 111
 112                         if (strlen(de->d_name) != GIT_SHA1_HEXSZ - 2)
 113                                 continue;
 114                         if (memcmp(de->d_name, ds->hex_pfx + 2, ds->len - 2))
 115                                 continue;
 116                         memcpy(hex + 2, de->d_name, GIT_SHA1_HEXSZ - 2);
 117                         if (!get_oid_hex(hex, &oid))
 118                                 update_candidates(ds, &oid);
 119                 }
 120                 closedir(dir);
 121         }
 122 }
 123
 124 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 125 {
 126         do {
 127                 if (*a != *b)
 128                         return 0;
 129                 a++;
 130                 b++;
 131                 len -= 2;
 132         } while (len > 1);
 133         if (len)
 134                 if ((*a ^ *b) & 0xf0)
 135                         return 0;
 136         return 1;
 137 }
 138
 139 static void unique_in_pack(struct packed_git *p,
 140                            struct disambiguate_state *ds)
 141 {
 142         uint32_t num, last, i, first = 0;
 143         const struct object_id *current = NULL;
 144
 145         open_pack_index(p);
 146         num = p->num_objects;
 147         last = num;
 148         while (first < last) {
 149                 uint32_t mid = (first + last) / 2;
 150                 const unsigned char *current;
 151                 int cmp;
 152
 153                 current = nth_packed_object_sha1(p, mid);
 154                 cmp = hashcmp(ds->bin_pfx.hash, current);
 155                 if (!cmp) {
 156                         first = mid;
 157                         break;
 158                 }
 159                 if (cmp > 0) {
 160                         first = mid+1;
 161                         continue;
 162                 }
 163                 last = mid;
 164         }
 165
 166         /*
 167          * At this point, "first" is the location of the lowest object
 168          * with an object name that could match "bin_pfx".  See if we have
 169          * 0, 1 or more objects that actually match(es).
 170          */
 171         for (i = first; i < num && !ds->ambiguous; i++) {
 172                 struct object_id oid;
 173                 current = nth_packed_object_oid(&oid, p, i);
 174                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
 175                         break;
 176                 update_candidates(ds, current);
 177         }
 178 }
 179
 180 static void find_short_packed_object(struct disambiguate_state *ds)
 181 {
 182         struct packed_git *p;
 183
 184         prepare_packed_git();
 185         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 186                 unique_in_pack(p, ds);
 187 }
 188
 189 #define SHORT_NAME_NOT_FOUND (-1)
 190 #define SHORT_NAME_AMBIGUOUS (-2)
 191
 192 static int finish_object_disambiguation(struct disambiguate_state *ds,
 193                                         unsigned char *sha1)
 194 {
 195         if (ds->ambiguous)
 196                 return SHORT_NAME_AMBIGUOUS;
 197
 198         if (!ds->candidate_exists)
 199                 return SHORT_NAME_NOT_FOUND;
 200
 201         if (!ds->candidate_checked)
 202                 /*
 203                  * If this is the only candidate, there is no point
 204                  * calling the disambiguation hint callback.
 205                  *
 206                  * On the other hand, if the current candidate
 207                  * replaced an earlier candidate that did _not_ pass
 208                  * the disambiguation hint callback, then we do have
 209                  * more than one objects that match the short name
 210                  * given, so we should make sure this one matches;
 211                  * otherwise, if we discovered this one and the one
 212                  * that we previously discarded in the reverse order,
 213                  * we would end up showing different results in the
 214                  * same repository!
 215                  */
 216                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 217                                     ds->fn(&ds->candidate, ds->cb_data));
 218
 219         if (!ds->candidate_ok)
 220                 return SHORT_NAME_AMBIGUOUS;
 221
 222         hashcpy(sha1, ds->candidate.hash);
 223         return 0;
 224 }
 225
 226 static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
 227 {
 228         int kind = sha1_object_info(oid->hash, NULL);
 229         return kind == OBJ_COMMIT;
 230 }
 231
 232 static int disambiguate_committish_only(const struct object_id *oid, void *cb_data_unused)
 233 {
 234         struct object *obj;
 235         int kind;
 236
 237         kind = sha1_object_info(oid->hash, NULL);
 238         if (kind == OBJ_COMMIT)
 239                 return 1;
 240         if (kind != OBJ_TAG)
 241                 return 0;
 242
 243         /* We need to do this the hard way... */
 244         obj = deref_tag(parse_object(oid->hash), NULL, 0);
 245         if (obj && obj->type == OBJ_COMMIT)
 246                 return 1;
 247         return 0;
 248 }
 249
 250 static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
 251 {
 252         int kind = sha1_object_info(oid->hash, NULL);
 253         return kind == OBJ_TREE;
 254 }
 255
 256 static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
 257 {
 258         struct object *obj;
 259         int kind;
 260
 261         kind = sha1_object_info(oid->hash, NULL);
 262         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 263                 return 1;
 264         if (kind != OBJ_TAG)
 265                 return 0;
 266
 267         /* We need to do this the hard way... */
 268         obj = deref_tag(parse_object(oid->hash), NULL, 0);
 269         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 270                 return 1;
 271         return 0;
 272 }
 273
 274 static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
 275 {
 276         int kind = sha1_object_info(oid->hash, NULL);
 277         return kind == OBJ_BLOB;
 278 }
 279
 280 static disambiguate_hint_fn default_disambiguate_hint;
 281
 282 int set_disambiguate_hint_config(const char *var, const char *value)
 283 {
 284         static const struct {
 285                 const char *name;
 286                 disambiguate_hint_fn fn;
 287         } hints[] = {
 288                 { "none", NULL },
 289                 { "commit", disambiguate_commit_only },
 290                 { "committish", disambiguate_committish_only },
 291                 { "tree", disambiguate_tree_only },
 292                 { "treeish", disambiguate_treeish_only },
 293                 { "blob", disambiguate_blob_only }
 294         };
 295         int i;
 296
 297         if (!value)
 298                 return config_error_nonbool(var);
 299
 300         for (i = 0; i < ARRAY_SIZE(hints); i++) {
 301                 if (!strcasecmp(value, hints[i].name)) {
 302                         default_disambiguate_hint = hints[i].fn;
 303                         return 0;
 304                 }
 305         }
 306
 307         return error("unknown hint type for '%s': %s", var, value);
 308 }
 309
 310 static int init_object_disambiguation(const char *name, int len,
 311                                       struct disambiguate_state *ds)
 312 {
 313         int i;
 314
 315         if (len < MINIMUM_ABBREV || len > GIT_SHA1_HEXSZ)
 316                 return -1;
 317
 318         memset(ds, 0, sizeof(*ds));
 319
 320         for (i = 0; i < len ;i++) {
 321                 unsigned char c = name[i];
 322                 unsigned char val;
 323                 if (c >= '0' && c <= '9')
 324                         val = c - '0';
 325                 else if (c >= 'a' && c <= 'f')
 326                         val = c - 'a' + 10;
 327                 else if (c >= 'A' && c <='F') {
 328                         val = c - 'A' + 10;
 329                         c -= 'A' - 'a';
 330                 }
 331                 else
 332                         return -1;
 333                 ds->hex_pfx[i] = c;
 334                 if (!(i & 1))
 335                         val <<= 4;
 336                 ds->bin_pfx.hash[i >> 1] |= val;
 337         }
 338
 339         ds->len = len;
 340         ds->hex_pfx[len] = '\0';
 341         prepare_alt_odb();
 342         return 0;
 343 }
 344
 345 static int show_ambiguous_object(const struct object_id *oid, void *data)
 346 {
 347         const struct disambiguate_state *ds = data;
 348         struct strbuf desc = STRBUF_INIT;
 349         int type;
 350
 351
 352         if (ds->fn && !ds->fn(oid, ds->cb_data))
 353                 return 0;
 354
 355         type = sha1_object_info(oid->hash, NULL);
 356         if (type == OBJ_COMMIT) {
 357                 struct commit *commit = lookup_commit(oid->hash);
 358                 if (commit) {
 359                         struct pretty_print_context pp = {0};
 360                         pp.date_mode.type = DATE_SHORT;
 361                         format_commit_message(commit, " %ad - %s", &desc, &pp);
 362                 }
 363         } else if (type == OBJ_TAG) {
 364                 struct tag *tag = lookup_tag(oid->hash);
 365                 if (!parse_tag(tag) && tag->tag)
 366                         strbuf_addf(&desc, " %s", tag->tag);
 367         }
 368
 369         advise("  %s %s%s",
 370                find_unique_abbrev(oid->hash, DEFAULT_ABBREV),
 371                typename(type) ? typename(type) : "unknown type",
 372                desc.buf);
 373
 374         strbuf_release(&desc);
 375         return 0;
 376 }
 377
 378 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 379                           unsigned flags)
 380 {
 381         int status;
 382         struct disambiguate_state ds;
 383         int quietly = !!(flags & GET_SHA1_QUIETLY);
 384
 385         if (init_object_disambiguation(name, len, &ds) < 0)
 386                 return -1;
 387
 388         if (HAS_MULTI_BITS(flags & GET_SHA1_DISAMBIGUATORS))
 389                 die("BUG: multiple get_short_sha1 disambiguator flags");
 390
 391         if (flags & GET_SHA1_COMMIT)
 392                 ds.fn = disambiguate_commit_only;
 393         else if (flags & GET_SHA1_COMMITTISH)
 394                 ds.fn = disambiguate_committish_only;
 395         else if (flags & GET_SHA1_TREE)
 396                 ds.fn = disambiguate_tree_only;
 397         else if (flags & GET_SHA1_TREEISH)
 398                 ds.fn = disambiguate_treeish_only;
 399         else if (flags & GET_SHA1_BLOB)
 400                 ds.fn = disambiguate_blob_only;
 401         else
 402                 ds.fn = default_disambiguate_hint;
 403
 404         find_short_object_filename(&ds);
 405         find_short_packed_object(&ds);
 406         status = finish_object_disambiguation(&ds, sha1);
 407
 408         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
 409                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
 410
 411                 /*
 412                  * We may still have ambiguity if we simply saw a series of
 413                  * candidates that did not satisfy our hint function. In
 414                  * that case, we still want to show them, so disable the hint
 415                  * function entirely.
 416                  */
 417                 if (!ds.ambiguous)
 418                         ds.fn = NULL;
 419
 420                 advise(_("The candidates are:"));
 421                 for_each_abbrev(ds.hex_pfx, show_ambiguous_object, &ds);
 422         }
 423
 424         return status;
 425 }
 426
 427 static int collect_ambiguous(const struct object_id *oid, void *data)
 428 {
 429         oid_array_append(data, oid);
 430         return 0;
 431 }
 432
 433 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 434 {
 435         struct oid_array collect = OID_ARRAY_INIT;
 436         struct disambiguate_state ds;
 437         int ret;
 438
 439         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
 440                 return -1;
 441
 442         ds.always_call_fn = 1;
 443         ds.fn = collect_ambiguous;
 444         ds.cb_data = &collect;
 445         find_short_object_filename(&ds);
 446         find_short_packed_object(&ds);
 447
 448         ret = oid_array_for_each_unique(&collect, fn, cb_data);
 449         oid_array_clear(&collect);
 450         return ret;
 451 }
 452
 453 /*
 454  * Return the slot of the most-significant bit set in "val". There are various
 455  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 456  * probably not a big deal here.
 457  */
 458 static unsigned msb(unsigned long val)
 459 {
 460         unsigned r = 0;
 461         while (val >>= 1)
 462                 r++;
 463         return r;
 464 }
 465
 466 int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
 467 {
 468         int status, exists;
 469
 470         if (len < 0) {
 471                 unsigned long count = approximate_object_count();
 472                 /*
 473                  * Add one because the MSB only tells us the highest bit set,
 474                  * not including the value of all the _other_ bits (so "15"
 475                  * is only one off of 2^4, but the MSB is the 3rd bit.
 476                  */
 477                 len = msb(count) + 1;
 478                 /*
 479                  * We now know we have on the order of 2^len objects, which
 480                  * expects a collision at 2^(len/2). But we also care about hex
 481                  * chars, not bits, and there are 4 bits per hex. So all
 482                  * together we need to divide by 2 and round up.
 483                  */
 484                 len = DIV_ROUND_UP(len, 2);
 485                 /*
 486                  * For very small repos, we stick with our regular fallback.
 487                  */
 488                 if (len < FALLBACK_DEFAULT_ABBREV)
 489                         len = FALLBACK_DEFAULT_ABBREV;
 490         }
 491
 492         sha1_to_hex_r(hex, sha1);
 493         if (len == 40 || !len)
 494                 return 40;
 495         exists = has_sha1_file(sha1);
 496         while (len < 40) {
 497                 unsigned char sha1_ret[20];
 498                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
 499                 if (exists
 500                     ? !status
 501                     : status == SHORT_NAME_NOT_FOUND) {
 502                         hex[len] = 0;
 503                         return len;
 504                 }
 505                 len++;
 506         }
 507         return len;
 508 }
 509
 510 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 511 {
 512         static int bufno;
 513         static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
 514         char *hex = hexbuffer[bufno];
 515         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
 516         find_unique_abbrev_r(hex, sha1, len);
 517         return hex;
 518 }
 519
 520 static int ambiguous_path(const char *path, int len)
 521 {
 522         int slash = 1;
 523         int cnt;
 524
 525         for (cnt = 0; cnt < len; cnt++) {
 526                 switch (*path++) {
 527                 case '\0':
 528                         break;
 529                 case '/':
 530                         if (slash)
 531                                 break;
 532                         slash = 1;
 533                         continue;
 534                 case '.':
 535                         continue;
 536                 default:
 537                         slash = 0;
 538                         continue;
 539                 }
 540                 break;
 541         }
 542         return slash;
 543 }
 544
 545 static inline int at_mark(const char *string, int len,
 546                           const char **suffix, int nr)
 547 {
 548         int i;
 549
 550         for (i = 0; i < nr; i++) {
 551                 int suffix_len = strlen(suffix[i]);
 552                 if (suffix_len <= len
 553                     && !strncasecmp(string, suffix[i], suffix_len))
 554                         return suffix_len;
 555         }
 556         return 0;
 557 }
 558
 559 static inline int upstream_mark(const char *string, int len)
 560 {
 561         const char *suffix[] = { "@{upstream}", "@{u}" };
 562         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 563 }
 564
 565 static inline int push_mark(const char *string, int len)
 566 {
 567         const char *suffix[] = { "@{push}" };
 568         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 569 }
 570
 571 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 572 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 573
 574 static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
 575                           unsigned int flags)
 576 {
 577         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 578         static const char *object_name_msg = N_(
 579         "Git normally never creates a ref that ends with 40 hex characters\n"
 580         "because it will be ignored when you just specify 40-hex. These refs\n"
 581         "may be created by mistake. For example,\n"
 582         "\n"
 583         "  git checkout -b $br $(git rev-parse ...)\n"
 584         "\n"
 585         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 586         "examine these refs and maybe delete them. Turn this message off by\n"
 587         "running \"git config advice.objectNameWarning false\"");
 588         unsigned char tmp_sha1[20];
 589         char *real_ref = NULL;
 590         int refs_found = 0;
 591         int at, reflog_len, nth_prior = 0;
 592
 593         if (len == 40 && !get_sha1_hex(str, sha1)) {
 594                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 595                         refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
 596                         if (refs_found > 0) {
 597                                 warning(warn_msg, len, str);
 598                                 if (advice_object_name_warning)
 599                                         fprintf(stderr, "%s\n", _(object_name_msg));
 600                         }
 601                         free(real_ref);
 602                 }
 603                 return 0;
 604         }
 605
 606         /* basic@{time or number or -number} format to query ref-log */
 607         reflog_len = at = 0;
 608         if (len && str[len-1] == '}') {
 609                 for (at = len-4; at >= 0; at--) {
 610                         if (str[at] == '@' && str[at+1] == '{') {
 611                                 if (str[at+2] == '-') {
 612                                         if (at != 0)
 613                                                 /* @{-N} not at start */
 614                                                 return -1;
 615                                         nth_prior = 1;
 616                                         continue;
 617                                 }
 618                                 if (!upstream_mark(str + at, len - at) &&
 619                                     !push_mark(str + at, len - at)) {
 620                                         reflog_len = (len-1) - (at+2);
 621                                         len = at;
 622                                 }
 623                                 break;
 624                         }
 625                 }
 626         }
 627
 628         /* Accept only unambiguous ref paths. */
 629         if (len && ambiguous_path(str, len))
 630                 return -1;
 631
 632         if (nth_prior) {
 633                 struct strbuf buf = STRBUF_INIT;
 634                 int detached;
 635
 636                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
 637                         detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
 638                         strbuf_release(&buf);
 639                         if (detached)
 640                                 return 0;
 641                 }
 642         }
 643
 644         if (!len && reflog_len)
 645                 /* allow "@{...}" to mean the current branch reflog */
 646                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 647         else if (reflog_len)
 648                 refs_found = dwim_log(str, len, sha1, &real_ref);
 649         else
 650                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 651
 652         if (!refs_found)
 653                 return -1;
 654
 655         if (warn_ambiguous_refs && !(flags & GET_SHA1_QUIETLY) &&
 656             (refs_found > 1 ||
 657              !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
 658                 warning(warn_msg, len, str);
 659
 660         if (reflog_len) {
 661                 int nth, i;
 662                 unsigned long at_time;
 663                 unsigned long co_time;
 664                 int co_tz, co_cnt;
 665
 666                 /* Is it asking for N-th entry, or approxidate? */
 667                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 668                         char ch = str[at+2+i];
 669                         if ('0' <= ch && ch <= '9')
 670                                 nth = nth * 10 + ch - '0';
 671                         else
 672                                 nth = -1;
 673                 }
 674                 if (100000000 <= nth) {
 675                         at_time = nth;
 676                         nth = -1;
 677                 } else if (0 <= nth)
 678                         at_time = 0;
 679                 else {
 680                         int errors = 0;
 681                         char *tmp = xstrndup(str + at + 2, reflog_len);
 682                         at_time = approxidate_careful(tmp, &errors);
 683                         free(tmp);
 684                         if (errors) {
 685                                 free(real_ref);
 686                                 return -1;
 687                         }
 688                 }
 689                 if (read_ref_at(real_ref, flags, at_time, nth, sha1, NULL,
 690                                 &co_time, &co_tz, &co_cnt)) {
 691                         if (!len) {
 692                                 if (starts_with(real_ref, "refs/heads/")) {
 693                                         str = real_ref + 11;
 694                                         len = strlen(real_ref + 11);
 695                                 } else {
 696                                         /* detached HEAD */
 697                                         str = "HEAD";
 698                                         len = 4;
 699                                 }
 700                         }
 701                         if (at_time) {
 702                                 if (!(flags & GET_SHA1_QUIETLY)) {
 703                                         warning("Log for '%.*s' only goes "
 704                                                 "back to %s.", len, str,
 705                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
 706                                 }
 707                         } else {
 708                                 if (flags & GET_SHA1_QUIETLY) {
 709                                         exit(128);
 710                                 }
 711                                 die("Log for '%.*s' only has %d entries.",
 712                                     len, str, co_cnt);
 713                         }
 714                 }
 715         }
 716
 717         free(real_ref);
 718         return 0;
 719 }
 720
 721 static int get_parent(const char *name, int len,
 722                       unsigned char *result, int idx)
 723 {
 724         unsigned char sha1[20];
 725         int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 726         struct commit *commit;
 727         struct commit_list *p;
 728
 729         if (ret)
 730                 return ret;
 731         commit = lookup_commit_reference(sha1);
 732         if (parse_commit(commit))
 733                 return -1;
 734         if (!idx) {
 735                 hashcpy(result, commit->object.oid.hash);
 736                 return 0;
 737         }
 738         p = commit->parents;
 739         while (p) {
 740                 if (!--idx) {
 741                         hashcpy(result, p->item->object.oid.hash);
 742                         return 0;
 743                 }
 744                 p = p->next;
 745         }
 746         return -1;
 747 }
 748
 749 static int get_nth_ancestor(const char *name, int len,
 750                             unsigned char *result, int generation)
 751 {
 752         unsigned char sha1[20];
 753         struct commit *commit;
 754         int ret;
 755
 756         ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
 757         if (ret)
 758                 return ret;
 759         commit = lookup_commit_reference(sha1);
 760         if (!commit)
 761                 return -1;
 762
 763         while (generation--) {
 764                 if (parse_commit(commit) || !commit->parents)
 765                         return -1;
 766                 commit = commit->parents->item;
 767         }
 768         hashcpy(result, commit->object.oid.hash);
 769         return 0;
 770 }
 771
 772 struct object *peel_to_type(const char *name, int namelen,
 773                             struct object *o, enum object_type expected_type)
 774 {
 775         if (name && !namelen)
 776                 namelen = strlen(name);
 777         while (1) {
 778                 if (!o || (!o->parsed && !parse_object(o->oid.hash)))
 779                         return NULL;
 780                 if (expected_type == OBJ_ANY || o->type == expected_type)
 781                         return o;
 782                 if (o->type == OBJ_TAG)
 783                         o = ((struct tag*) o)->tagged;
 784                 else if (o->type == OBJ_COMMIT)
 785                         o = &(((struct commit *) o)->tree->object);
 786                 else {
 787                         if (name)
 788                                 error("%.*s: expected %s type, but the object "
 789                                       "dereferences to %s type",
 790                                       namelen, name, typename(expected_type),
 791                                       typename(o->type));
 792                         return NULL;
 793                 }
 794         }
 795 }
 796
 797 static int peel_onion(const char *name, int len, unsigned char *sha1,
 798                       unsigned lookup_flags)
 799 {
 800         unsigned char outer[20];
 801         const char *sp;
 802         unsigned int expected_type = 0;
 803         struct object *o;
 804
 805         /*
 806          * "ref^{type}" dereferences ref repeatedly until you cannot
 807          * dereference anymore, or you get an object of given type,
 808          * whichever comes first.  "ref^{}" means just dereference
 809          * tags until you get a non-tag.  "ref^0" is a shorthand for
 810          * "ref^{commit}".  "commit^{tree}" could be used to find the
 811          * top-level tree of the given commit.
 812          */
 813         if (len < 4 || name[len-1] != '}')
 814                 return -1;
 815
 816         for (sp = name + len - 1; name <= sp; sp--) {
 817                 int ch = *sp;
 818                 if (ch == '{' && name < sp && sp[-1] == '^')
 819                         break;
 820         }
 821         if (sp <= name)
 822                 return -1;
 823
 824         sp++; /* beginning of type name, or closing brace for empty */
 825         if (starts_with(sp, "commit}"))
 826                 expected_type = OBJ_COMMIT;
 827         else if (starts_with(sp, "tag}"))
 828                 expected_type = OBJ_TAG;
 829         else if (starts_with(sp, "tree}"))
 830                 expected_type = OBJ_TREE;
 831         else if (starts_with(sp, "blob}"))
 832                 expected_type = OBJ_BLOB;
 833         else if (starts_with(sp, "object}"))
 834                 expected_type = OBJ_ANY;
 835         else if (sp[0] == '}')
 836                 expected_type = OBJ_NONE;
 837         else if (sp[0] == '/')
 838                 expected_type = OBJ_COMMIT;
 839         else
 840                 return -1;
 841
 842         lookup_flags &= ~GET_SHA1_DISAMBIGUATORS;
 843         if (expected_type == OBJ_COMMIT)
 844                 lookup_flags |= GET_SHA1_COMMITTISH;
 845         else if (expected_type == OBJ_TREE)
 846                 lookup_flags |= GET_SHA1_TREEISH;
 847
 848         if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
 849                 return -1;
 850
 851         o = parse_object(outer);
 852         if (!o)
 853                 return -1;
 854         if (!expected_type) {
 855                 o = deref_tag(o, name, sp - name - 2);
 856                 if (!o || (!o->parsed && !parse_object(o->oid.hash)))
 857                         return -1;
 858                 hashcpy(sha1, o->oid.hash);
 859                 return 0;
 860         }
 861
 862         /*
 863          * At this point, the syntax look correct, so
 864          * if we do not get the needed object, we should
 865          * barf.
 866          */
 867         o = peel_to_type(name, len, o, expected_type);
 868         if (!o)
 869                 return -1;
 870
 871         hashcpy(sha1, o->oid.hash);
 872         if (sp[0] == '/') {
 873                 /* "$commit^{/foo}" */
 874                 char *prefix;
 875                 int ret;
 876                 struct commit_list *list = NULL;
 877
 878                 /*
 879                  * $commit^{/}. Some regex implementation may reject.
 880                  * We don't need regex anyway. '' pattern always matches.
 881                  */
 882                 if (sp[1] == '}')
 883                         return 0;
 884
 885                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
 886                 commit_list_insert((struct commit *)o, &list);
 887                 ret = get_sha1_oneline(prefix, sha1, list);
 888                 free(prefix);
 889                 return ret;
 890         }
 891         return 0;
 892 }
 893
 894 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 895 {
 896         const char *cp;
 897         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 898
 899         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 900                 char ch = *cp;
 901                 if (!isxdigit(ch)) {
 902                         /* We must be looking at g in "SOMETHING-g"
 903                          * for it to be describe output.
 904                          */
 905                         if (ch == 'g' && cp[-1] == '-') {
 906                                 cp++;
 907                                 len -= cp - name;
 908                                 return get_short_sha1(cp, len, sha1, flags);
 909                         }
 910                 }
 911         }
 912         return -1;
 913 }
 914
 915 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
 916 {
 917         int ret, has_suffix;
 918         const char *cp;
 919
 920         /*
 921          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 922          */
 923         has_suffix = 0;
 924         for (cp = name + len - 1; name <= cp; cp--) {
 925                 int ch = *cp;
 926                 if ('0' <= ch && ch <= '9')
 927                         continue;
 928                 if (ch == '~' || ch == '^')
 929                         has_suffix = ch;
 930                 break;
 931         }
 932
 933         if (has_suffix) {
 934                 int num = 0;
 935                 int len1 = cp - name;
 936                 cp++;
 937                 while (cp < name + len)
 938                         num = num * 10 + *cp++ - '0';
 939                 if (!num && len1 == len - 1)
 940                         num = 1;
 941                 if (has_suffix == '^')
 942                         return get_parent(name, len1, sha1, num);
 943                 /* else if (has_suffix == '~') -- goes without saying */
 944                 return get_nth_ancestor(name, len1, sha1, num);
 945         }
 946
 947         ret = peel_onion(name, len, sha1, lookup_flags);
 948         if (!ret)
 949                 return 0;
 950
 951         ret = get_sha1_basic(name, len, sha1, lookup_flags);
 952         if (!ret)
 953                 return 0;
 954
 955         /* It could be describe output that is "SOMETHING-gXXXX" */
 956         ret = get_describe_name(name, len, sha1);
 957         if (!ret)
 958                 return 0;
 959
 960         return get_short_sha1(name, len, sha1, lookup_flags);
 961 }
 962
 963 /*
 964  * This interprets names like ':/Initial revision of "git"' by searching
 965  * through history and returning the first commit whose message starts
 966  * the given regular expression.
 967  *
 968  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
 969  *
 970  * For a literal '!' character at the beginning of a pattern, you have to repeat
 971  * that, like: ':/!!foo'
 972  *
 973  * For future extension, all other sequences beginning with ':/!' are reserved.
 974  */
 975
 976 /* Remember to update object flag allocation in object.h */
 977 #define ONELINE_SEEN (1u<<20)
 978
 979 static int handle_one_ref(const char *path, const struct object_id *oid,
 980                           int flag, void *cb_data)
 981 {
 982         struct commit_list **list = cb_data;
 983         struct object *object = parse_object(oid->hash);
 984         if (!object)
 985                 return 0;
 986         if (object->type == OBJ_TAG) {
 987                 object = deref_tag(object, path, strlen(path));
 988                 if (!object)
 989                         return 0;
 990         }
 991         if (object->type != OBJ_COMMIT)
 992                 return 0;
 993         commit_list_insert((struct commit *)object, list);
 994         return 0;
 995 }
 996
 997 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 998                             struct commit_list *list)
 999 {
1000         struct commit_list *backup = NULL, *l;
1001         int found = 0;
1002         int negative = 0;
1003         regex_t regex;
1004
1005         if (prefix[0] == '!') {
1006                 prefix++;
1007
1008                 if (prefix[0] == '-') {
1009                         prefix++;
1010                         negative = 1;
1011                 } else if (prefix[0] != '!') {
1012                         return -1;
1013                 }
1014         }
1015
1016         if (regcomp(&regex, prefix, REG_EXTENDED))
1017                 return -1;
1018
1019         for (l = list; l; l = l->next) {
1020                 l->item->object.flags |= ONELINE_SEEN;
1021                 commit_list_insert(l->item, &backup);
1022         }
1023         while (list) {
1024                 const char *p, *buf;
1025                 struct commit *commit;
1026                 int matches;
1027
1028                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1029                 if (!parse_object(commit->object.oid.hash))
1030                         continue;
1031                 buf = get_commit_buffer(commit, NULL);
1032                 p = strstr(buf, "\n\n");
1033                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1034                 unuse_commit_buffer(commit, buf);
1035
1036                 if (matches) {
1037                         hashcpy(sha1, commit->object.oid.hash);
1038                         found = 1;
1039                         break;
1040                 }
1041         }
1042         regfree(&regex);
1043         free_commit_list(list);
1044         for (l = backup; l; l = l->next)
1045                 clear_commit_marks(l->item, ONELINE_SEEN);
1046         free_commit_list(backup);
1047         return found ? 0 : -1;
1048 }
1049
1050 struct grab_nth_branch_switch_cbdata {
1051         int remaining;
1052         struct strbuf buf;
1053 };
1054
1055 static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
1056                                   const char *email, unsigned long timestamp, int tz,
1057                                   const char *message, void *cb_data)
1058 {
1059         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1060         const char *match = NULL, *target = NULL;
1061         size_t len;
1062
1063         if (skip_prefix(message, "checkout: moving from ", &match))
1064                 target = strstr(match, " to ");
1065
1066         if (!match || !target)
1067                 return 0;
1068         if (--(cb->remaining) == 0) {
1069                 len = target - match;
1070                 strbuf_reset(&cb->buf);
1071                 strbuf_add(&cb->buf, match, len);
1072                 return 1; /* we are done */
1073         }
1074         return 0;
1075 }
1076
1077 /*
1078  * Parse @{-N} syntax, return the number of characters parsed
1079  * if successful; otherwise signal an error with negative value.
1080  */
1081 static int interpret_nth_prior_checkout(const char *name, int namelen,
1082                                         struct strbuf *buf)
1083 {
1084         long nth;
1085         int retval;
1086         struct grab_nth_branch_switch_cbdata cb;
1087         const char *brace;
1088         char *num_end;
1089
1090         if (namelen < 4)
1091                 return -1;
1092         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1093                 return -1;
1094         brace = memchr(name, '}', namelen);
1095         if (!brace)
1096                 return -1;
1097         nth = strtol(name + 3, &num_end, 10);
1098         if (num_end != brace)
1099                 return -1;
1100         if (nth <= 0)
1101                 return -1;
1102         cb.remaining = nth;
1103         strbuf_init(&cb.buf, 20);
1104
1105         retval = 0;
1106         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1107                 strbuf_reset(buf);
1108                 strbuf_addbuf(buf, &cb.buf);
1109                 retval = brace - name + 1;
1110         }
1111
1112         strbuf_release(&cb.buf);
1113         return retval;
1114 }
1115
1116 int get_oid_mb(const char *name, struct object_id *oid)
1117 {
1118         struct commit *one, *two;
1119         struct commit_list *mbs;
1120         struct object_id oid_tmp;
1121         const char *dots;
1122         int st;
1123
1124         dots = strstr(name, "...");
1125         if (!dots)
1126                 return get_oid(name, oid);
1127         if (dots == name)
1128                 st = get_oid("HEAD", &oid_tmp);
1129         else {
1130                 struct strbuf sb;
1131                 strbuf_init(&sb, dots - name);
1132                 strbuf_add(&sb, name, dots - name);
1133                 st = get_sha1_committish(sb.buf, oid_tmp.hash);
1134                 strbuf_release(&sb);
1135         }
1136         if (st)
1137                 return st;
1138         one = lookup_commit_reference_gently(oid_tmp.hash, 0);
1139         if (!one)
1140                 return -1;
1141
1142         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", oid_tmp.hash))
1143                 return -1;
1144         two = lookup_commit_reference_gently(oid_tmp.hash, 0);
1145         if (!two)
1146                 return -1;
1147         mbs = get_merge_bases(one, two);
1148         if (!mbs || mbs->next)
1149                 st = -1;
1150         else {
1151                 st = 0;
1152                 oidcpy(oid, &mbs->item->object.oid);
1153         }
1154         free_commit_list(mbs);
1155         return st;
1156 }
1157
1158 /* parse @something syntax, when 'something' is not {.*} */
1159 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1160 {
1161         const char *next;
1162
1163         if (len || name[1] == '{')
1164                 return -1;
1165
1166         /* make sure it's a single @, or @@{.*}, not @foo */
1167         next = memchr(name + len + 1, '@', namelen - len - 1);
1168         if (next && next[1] != '{')
1169                 return -1;
1170         if (!next)
1171                 next = name + namelen;
1172         if (next != name + 1)
1173                 return -1;
1174
1175         strbuf_reset(buf);
1176         strbuf_add(buf, "HEAD", 4);
1177         return 1;
1178 }
1179
1180 static int reinterpret(const char *name, int namelen, int len,
1181                        struct strbuf *buf, unsigned allowed)
1182 {
1183         /* we have extra data, which might need further processing */
1184         struct strbuf tmp = STRBUF_INIT;
1185         int used = buf->len;
1186         int ret;
1187
1188         strbuf_add(buf, name + len, namelen - len);
1189         ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
1190         /* that data was not interpreted, remove our cruft */
1191         if (ret < 0) {
1192                 strbuf_setlen(buf, used);
1193                 return len;
1194         }
1195         strbuf_reset(buf);
1196         strbuf_addbuf(buf, &tmp);
1197         strbuf_release(&tmp);
1198         /* tweak for size of {-N} versus expanded ref name */
1199         return ret - used + len;
1200 }
1201
1202 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1203 {
1204         char *s = shorten_unambiguous_ref(ref, 0);
1205         strbuf_reset(buf);
1206         strbuf_addstr(buf, s);
1207         free(s);
1208 }
1209
1210 static int branch_interpret_allowed(const char *refname, unsigned allowed)
1211 {
1212         if (!allowed)
1213                 return 1;
1214
1215         if ((allowed & INTERPRET_BRANCH_LOCAL) &&
1216             starts_with(refname, "refs/heads/"))
1217                 return 1;
1218         if ((allowed & INTERPRET_BRANCH_REMOTE) &&
1219             starts_with(refname, "refs/remotes/"))
1220                 return 1;
1221
1222         return 0;
1223 }
1224
1225 static int interpret_branch_mark(const char *name, int namelen,
1226                                  int at, struct strbuf *buf,
1227                                  int (*get_mark)(const char *, int),
1228                                  const char *(*get_data)(struct branch *,
1229                                                          struct strbuf *),
1230                                  unsigned allowed)
1231 {
1232         int len;
1233         struct branch *branch;
1234         struct strbuf err = STRBUF_INIT;
1235         const char *value;
1236
1237         len = get_mark(name + at, namelen - at);
1238         if (!len)
1239                 return -1;
1240
1241         if (memchr(name, ':', at))
1242                 return -1;
1243
1244         if (at) {
1245                 char *name_str = xmemdupz(name, at);
1246                 branch = branch_get(name_str);
1247                 free(name_str);
1248         } else
1249                 branch = branch_get(NULL);
1250
1251         value = get_data(branch, &err);
1252         if (!value)
1253                 die("%s", err.buf);
1254
1255         if (!branch_interpret_allowed(value, allowed))
1256                 return -1;
1257
1258         set_shortened_ref(buf, value);
1259         return len + at;
1260 }
1261
1262 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
1263                           unsigned allowed)
1264 {
1265         char *at;
1266         const char *start;
1267         int len;
1268
1269         if (!namelen)
1270                 namelen = strlen(name);
1271
1272         if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
1273                 len = interpret_nth_prior_checkout(name, namelen, buf);
1274                 if (!len) {
1275                         return len; /* syntax Ok, not enough switches */
1276                 } else if (len > 0) {
1277                         if (len == namelen)
1278                                 return len; /* consumed all */
1279                         else
1280                                 return reinterpret(name, namelen, len, buf, allowed);
1281                 }
1282         }
1283
1284         for (start = name;
1285              (at = memchr(start, '@', namelen - (start - name)));
1286              start = at + 1) {
1287
1288                 if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
1289                         len = interpret_empty_at(name, namelen, at - name, buf);
1290                         if (len > 0)
1291                                 return reinterpret(name, namelen, len, buf,
1292                                                    allowed);
1293                 }
1294
1295                 len = interpret_branch_mark(name, namelen, at - name, buf,
1296                                             upstream_mark, branch_get_upstream,
1297                                             allowed);
1298                 if (len > 0)
1299                         return len;
1300
1301                 len = interpret_branch_mark(name, namelen, at - name, buf,
1302                                             push_mark, branch_get_push,
1303                                             allowed);
1304                 if (len > 0)
1305                         return len;
1306         }
1307
1308         return -1;
1309 }
1310
1311 void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
1312 {
1313         int len = strlen(name);
1314         int used = interpret_branch_name(name, len, sb, allowed);
1315
1316         if (used < 0)
1317                 used = 0;
1318         strbuf_add(sb, name + used, len - used);
1319 }
1320
1321 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1322 {
1323         strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
1324         if (name[0] == '-')
1325                 return -1;
1326         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1327         return check_refname_format(sb->buf, 0);
1328 }
1329
1330 /*
1331  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1332  * notably "xyz^" for "parent of xyz"
1333  */
1334 int get_sha1(const char *name, unsigned char *sha1)
1335 {
1336         struct object_context unused;
1337         return get_sha1_with_context(name, 0, sha1, &unused);
1338 }
1339
1340 /*
1341  * This is like "get_sha1()", but for struct object_id.
1342  */
1343 int get_oid(const char *name, struct object_id *oid)
1344 {
1345         return get_sha1(name, oid->hash);
1346 }
1347
1348
1349 /*
1350  * Many callers know that the user meant to name a commit-ish by
1351  * syntactical positions where the object name appears.  Calling this
1352  * function allows the machinery to disambiguate shorter-than-unique
1353  * abbreviated object names between commit-ish and others.
1354  *
1355  * Note that this does NOT error out when the named object is not a
1356  * commit-ish. It is merely to give a hint to the disambiguation
1357  * machinery.
1358  */
1359 int get_sha1_committish(const char *name, unsigned char *sha1)
1360 {
1361         struct object_context unused;
1362         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1363                                      sha1, &unused);
1364 }
1365
1366 int get_sha1_treeish(const char *name, unsigned char *sha1)
1367 {
1368         struct object_context unused;
1369         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1370                                      sha1, &unused);
1371 }
1372
1373 int get_sha1_commit(const char *name, unsigned char *sha1)
1374 {
1375         struct object_context unused;
1376         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1377                                      sha1, &unused);
1378 }
1379
1380 int get_sha1_tree(const char *name, unsigned char *sha1)
1381 {
1382         struct object_context unused;
1383         return get_sha1_with_context(name, GET_SHA1_TREE,
1384                                      sha1, &unused);
1385 }
1386
1387 int get_sha1_blob(const char *name, unsigned char *sha1)
1388 {
1389         struct object_context unused;
1390         return get_sha1_with_context(name, GET_SHA1_BLOB,
1391                                      sha1, &unused);
1392 }
1393
1394 /* Must be called only when object_name:filename doesn't exist. */
1395 static void diagnose_invalid_sha1_path(const char *prefix,
1396                                        const char *filename,
1397                                        const unsigned char *tree_sha1,
1398                                        const char *object_name,
1399                                        int object_name_len)
1400 {
1401         unsigned char sha1[20];
1402         unsigned mode;
1403
1404         if (!prefix)
1405                 prefix = "";
1406
1407         if (file_exists(filename))
1408                 die("Path '%s' exists on disk, but not in '%.*s'.",
1409                     filename, object_name_len, object_name);
1410         if (errno == ENOENT || errno == ENOTDIR) {
1411                 char *fullname = xstrfmt("%s%s", prefix, filename);
1412
1413                 if (!get_tree_entry(tree_sha1, fullname,
1414                                     sha1, &mode)) {
1415                         die("Path '%s' exists, but not '%s'.\n"
1416                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1417                             fullname,
1418                             filename,
1419                             object_name_len, object_name,
1420                             fullname,
1421                             object_name_len, object_name,
1422                             filename);
1423                 }
1424                 die("Path '%s' does not exist in '%.*s'",
1425                     filename, object_name_len, object_name);
1426         }
1427 }
1428
1429 /* Must be called only when :stage:filename doesn't exist. */
1430 static void diagnose_invalid_index_path(int stage,
1431                                         const char *prefix,
1432                                         const char *filename)
1433 {
1434         const struct cache_entry *ce;
1435         int pos;
1436         unsigned namelen = strlen(filename);
1437         struct strbuf fullname = STRBUF_INIT;
1438
1439         if (!prefix)
1440                 prefix = "";
1441
1442         /* Wrong stage number? */
1443         pos = cache_name_pos(filename, namelen);
1444         if (pos < 0)
1445                 pos = -pos - 1;
1446         if (pos < active_nr) {
1447                 ce = active_cache[pos];
1448                 if (ce_namelen(ce) == namelen &&
1449                     !memcmp(ce->name, filename, namelen))
1450                         die("Path '%s' is in the index, but not at stage %d.\n"
1451                             "Did you mean ':%d:%s'?",
1452                             filename, stage,
1453                             ce_stage(ce), filename);
1454         }
1455
1456         /* Confusion between relative and absolute filenames? */
1457         strbuf_addstr(&fullname, prefix);
1458         strbuf_addstr(&fullname, filename);
1459         pos = cache_name_pos(fullname.buf, fullname.len);
1460         if (pos < 0)
1461                 pos = -pos - 1;
1462         if (pos < active_nr) {
1463                 ce = active_cache[pos];
1464                 if (ce_namelen(ce) == fullname.len &&
1465                     !memcmp(ce->name, fullname.buf, fullname.len))
1466                         die("Path '%s' is in the index, but not '%s'.\n"
1467                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1468                             fullname.buf, filename,
1469                             ce_stage(ce), fullname.buf,
1470                             ce_stage(ce), filename);
1471         }
1472
1473         if (file_exists(filename))
1474                 die("Path '%s' exists on disk, but not in the index.", filename);
1475         if (errno == ENOENT || errno == ENOTDIR)
1476                 die("Path '%s' does not exist (neither on disk nor in the index).",
1477                     filename);
1478
1479         strbuf_release(&fullname);
1480 }
1481
1482
1483 static char *resolve_relative_path(const char *rel)
1484 {
1485         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1486                 return NULL;
1487
1488         if (!is_inside_work_tree())
1489                 die("relative path syntax can't be used outside working tree.");
1490
1491         /* die() inside prefix_path() if resolved path is outside worktree */
1492         return prefix_path(startup_info->prefix,
1493                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1494                            rel);
1495 }
1496
1497 static int get_sha1_with_context_1(const char *name,
1498                                    unsigned flags,
1499                                    const char *prefix,
1500                                    unsigned char *sha1,
1501                                    struct object_context *oc)
1502 {
1503         int ret, bracket_depth;
1504         int namelen = strlen(name);
1505         const char *cp;
1506         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1507
1508         if (only_to_die)
1509                 flags |= GET_SHA1_QUIETLY;
1510
1511         memset(oc, 0, sizeof(*oc));
1512         oc->mode = S_IFINVALID;
1513         strbuf_init(&oc->symlink_path, 0);
1514         ret = get_sha1_1(name, namelen, sha1, flags);
1515         if (!ret)
1516                 return ret;
1517         /*
1518          * sha1:path --> object name of path in ent sha1
1519          * :path -> object name of absolute path in index
1520          * :./path -> object name of path relative to cwd in index
1521          * :[0-3]:path -> object name of path in index at stage
1522          * :/foo -> recent commit matching foo
1523          */
1524         if (name[0] == ':') {
1525                 int stage = 0;
1526                 const struct cache_entry *ce;
1527                 char *new_path = NULL;
1528                 int pos;
1529                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1530                         struct commit_list *list = NULL;
1531
1532                         for_each_ref(handle_one_ref, &list);
1533                         commit_list_sort_by_date(&list);
1534                         return get_sha1_oneline(name + 2, sha1, list);
1535                 }
1536                 if (namelen < 3 ||
1537                     name[2] != ':' ||
1538                     name[1] < '0' || '3' < name[1])
1539                         cp = name + 1;
1540                 else {
1541                         stage = name[1] - '0';
1542                         cp = name + 3;
1543                 }
1544                 new_path = resolve_relative_path(cp);
1545                 if (!new_path) {
1546                         namelen = namelen - (cp - name);
1547                 } else {
1548                         cp = new_path;
1549                         namelen = strlen(cp);
1550                 }
1551
1552                 if (flags & GET_SHA1_RECORD_PATH)
1553                         oc->path = xstrdup(cp);
1554
1555                 if (!active_cache)
1556                         read_cache();
1557                 pos = cache_name_pos(cp, namelen);
1558                 if (pos < 0)
1559                         pos = -pos - 1;
1560                 while (pos < active_nr) {
1561                         ce = active_cache[pos];
1562                         if (ce_namelen(ce) != namelen ||
1563                             memcmp(ce->name, cp, namelen))
1564                                 break;
1565                         if (ce_stage(ce) == stage) {
1566                                 hashcpy(sha1, ce->oid.hash);
1567                                 oc->mode = ce->ce_mode;
1568                                 free(new_path);
1569                                 return 0;
1570                         }
1571                         pos++;
1572                 }
1573                 if (only_to_die && name[1] && name[1] != '/')
1574                         diagnose_invalid_index_path(stage, prefix, cp);
1575                 free(new_path);
1576                 return -1;
1577         }
1578         for (cp = name, bracket_depth = 0; *cp; cp++) {
1579                 if (*cp == '{')
1580                         bracket_depth++;
1581                 else if (bracket_depth && *cp == '}')
1582                         bracket_depth--;
1583                 else if (!bracket_depth && *cp == ':')
1584                         break;
1585         }
1586         if (*cp == ':') {
1587                 unsigned char tree_sha1[20];
1588                 int len = cp - name;
1589                 unsigned sub_flags = flags;
1590
1591                 sub_flags &= ~GET_SHA1_DISAMBIGUATORS;
1592                 sub_flags |= GET_SHA1_TREEISH;
1593
1594                 if (!get_sha1_1(name, len, tree_sha1, sub_flags)) {
1595                         const char *filename = cp+1;
1596                         char *new_filename = NULL;
1597
1598                         new_filename = resolve_relative_path(filename);
1599                         if (new_filename)
1600                                 filename = new_filename;
1601                         if (flags & GET_SHA1_FOLLOW_SYMLINKS) {
1602                                 ret = get_tree_entry_follow_symlinks(tree_sha1,
1603                                         filename, sha1, &oc->symlink_path,
1604                                         &oc->mode);
1605                         } else {
1606                                 ret = get_tree_entry(tree_sha1, filename,
1607                                                      sha1, &oc->mode);
1608                                 if (ret && only_to_die) {
1609                                         diagnose_invalid_sha1_path(prefix,
1610                                                                    filename,
1611                                                                    tree_sha1,
1612                                                                    name, len);
1613                                 }
1614                         }
1615                         hashcpy(oc->tree, tree_sha1);
1616                         if (flags & GET_SHA1_RECORD_PATH)
1617                                 oc->path = xstrdup(filename);
1618
1619                         free(new_filename);
1620                         return ret;
1621                 } else {
1622                         if (only_to_die)
1623                                 die("Invalid object name '%.*s'.", len, name);
1624                 }
1625         }
1626         return ret;
1627 }
1628
1629 /*
1630  * Call this function when you know "name" given by the end user must
1631  * name an object but it doesn't; the function _may_ die with a better
1632  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1633  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1634  * you have a chance to diagnose the error further.
1635  */
1636 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1637 {
1638         struct object_context oc;
1639         unsigned char sha1[20];
1640         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1641 }
1642
1643 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *oc)
1644 {
1645         if (flags & GET_SHA1_FOLLOW_SYMLINKS && flags & GET_SHA1_ONLY_TO_DIE)
1646                 die("BUG: incompatible flags for get_sha1_with_context");
1647         return get_sha1_with_context_1(str, flags, NULL, sha1, oc);
1648 }