sha1_name.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "tag.h"
   4 #include "commit.h"
   5 #include "tree.h"
   6 #include "blob.h"
   7 #include "tree-walk.h"
   8 #include "refs.h"
   9 #include "remote.h"
  10 #include "dir.h"
  11 #include "sha1-array.h"
  12
  13 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
  14
  15 typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
  16
  17 struct disambiguate_state {
  18         int len; /* length of prefix in hex chars */
  19         char hex_pfx[GIT_MAX_HEXSZ + 1];
  20         struct object_id bin_pfx;
  21
  22         disambiguate_hint_fn fn;
  23         void *cb_data;
  24         struct object_id candidate;
  25         unsigned candidate_exists:1;
  26         unsigned candidate_checked:1;
  27         unsigned candidate_ok:1;
  28         unsigned disambiguate_fn_used:1;
  29         unsigned ambiguous:1;
  30         unsigned always_call_fn:1;
  31 };
  32
  33 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
  34 {
  35         if (ds->always_call_fn) {
  36                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
  37                 return;
  38         }
  39         if (!ds->candidate_exists) {
  40                 /* this is the first candidate */
  41                 oidcpy(&ds->candidate, current);
  42                 ds->candidate_exists = 1;
  43                 return;
  44         } else if (!oidcmp(&ds->candidate, current)) {
  45                 /* the same as what we already have seen */
  46                 return;
  47         }
  48
  49         if (!ds->fn) {
  50                 /* cannot disambiguate between ds->candidate and current */
  51                 ds->ambiguous = 1;
  52                 return;
  53         }
  54
  55         if (!ds->candidate_checked) {
  56                 ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
  57                 ds->disambiguate_fn_used = 1;
  58                 ds->candidate_checked = 1;
  59         }
  60
  61         if (!ds->candidate_ok) {
  62                 /* discard the candidate; we know it does not satisfy fn */
  63                 oidcpy(&ds->candidate, current);
  64                 ds->candidate_checked = 0;
  65                 return;
  66         }
  67
  68         /* if we reach this point, we know ds->candidate satisfies fn */
  69         if (ds->fn(current, ds->cb_data)) {
  70                 /*
  71                  * if both current and candidate satisfy fn, we cannot
  72                  * disambiguate.
  73                  */
  74                 ds->candidate_ok = 0;
  75                 ds->ambiguous = 1;
  76         }
  77
  78         /* otherwise, current can be discarded and candidate is still good */
  79 }
  80
  81 static void find_short_object_filename(struct disambiguate_state *ds)
  82 {
  83         struct alternate_object_database *alt;
  84         char hex[GIT_MAX_HEXSZ];
  85         static struct alternate_object_database *fakeent;
  86
  87         if (!fakeent) {
  88                 /*
  89                  * Create a "fake" alternate object database that
  90                  * points to our own object database, to make it
  91                  * easier to get a temporary working space in
  92                  * alt->name/alt->base while iterating over the
  93                  * object databases including our own.
  94                  */
  95                 fakeent = alloc_alt_odb(get_object_directory());
  96         }
  97         fakeent->next = alt_odb_list;
  98
  99         xsnprintf(hex, sizeof(hex), "%.2s", ds->hex_pfx);
 100         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 101                 struct strbuf *buf = alt_scratch_buf(alt);
 102                 struct dirent *de;
 103                 DIR *dir;
 104
 105                 strbuf_addf(buf, "%.2s/", ds->hex_pfx);
 106                 dir = opendir(buf->buf);
 107                 if (!dir)
 108                         continue;
 109
 110                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
 111                         struct object_id oid;
 112
 113                         if (strlen(de->d_name) != GIT_SHA1_HEXSZ - 2)
 114                                 continue;
 115                         if (memcmp(de->d_name, ds->hex_pfx + 2, ds->len - 2))
 116                                 continue;
 117                         memcpy(hex + 2, de->d_name, GIT_SHA1_HEXSZ - 2);
 118                         if (!get_oid_hex(hex, &oid))
 119                                 update_candidates(ds, &oid);
 120                 }
 121                 closedir(dir);
 122         }
 123 }
 124
 125 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
 126 {
 127         do {
 128                 if (*a != *b)
 129                         return 0;
 130                 a++;
 131                 b++;
 132                 len -= 2;
 133         } while (len > 1);
 134         if (len)
 135                 if ((*a ^ *b) & 0xf0)
 136                         return 0;
 137         return 1;
 138 }
 139
 140 static void unique_in_pack(struct packed_git *p,
 141                            struct disambiguate_state *ds)
 142 {
 143         uint32_t num, last, i, first = 0;
 144         const struct object_id *current = NULL;
 145
 146         open_pack_index(p);
 147         num = p->num_objects;
 148         last = num;
 149         while (first < last) {
 150                 uint32_t mid = (first + last) / 2;
 151                 const unsigned char *current;
 152                 int cmp;
 153
 154                 current = nth_packed_object_sha1(p, mid);
 155                 cmp = hashcmp(ds->bin_pfx.hash, current);
 156                 if (!cmp) {
 157                         first = mid;
 158                         break;
 159                 }
 160                 if (cmp > 0) {
 161                         first = mid+1;
 162                         continue;
 163                 }
 164                 last = mid;
 165         }
 166
 167         /*
 168          * At this point, "first" is the location of the lowest object
 169          * with an object name that could match "bin_pfx".  See if we have
 170          * 0, 1 or more objects that actually match(es).
 171          */
 172         for (i = first; i < num && !ds->ambiguous; i++) {
 173                 struct object_id oid;
 174                 current = nth_packed_object_oid(&oid, p, i);
 175                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
 176                         break;
 177                 update_candidates(ds, current);
 178         }
 179 }
 180
 181 static void find_short_packed_object(struct disambiguate_state *ds)
 182 {
 183         struct packed_git *p;
 184
 185         prepare_packed_git();
 186         for (p = packed_git; p && !ds->ambiguous; p = p->next)
 187                 unique_in_pack(p, ds);
 188 }
 189
 190 #define SHORT_NAME_NOT_FOUND (-1)
 191 #define SHORT_NAME_AMBIGUOUS (-2)
 192
 193 static int finish_object_disambiguation(struct disambiguate_state *ds,
 194                                         unsigned char *sha1)
 195 {
 196         if (ds->ambiguous)
 197                 return SHORT_NAME_AMBIGUOUS;
 198
 199         if (!ds->candidate_exists)
 200                 return SHORT_NAME_NOT_FOUND;
 201
 202         if (!ds->candidate_checked)
 203                 /*
 204                  * If this is the only candidate, there is no point
 205                  * calling the disambiguation hint callback.
 206                  *
 207                  * On the other hand, if the current candidate
 208                  * replaced an earlier candidate that did _not_ pass
 209                  * the disambiguation hint callback, then we do have
 210                  * more than one objects that match the short name
 211                  * given, so we should make sure this one matches;
 212                  * otherwise, if we discovered this one and the one
 213                  * that we previously discarded in the reverse order,
 214                  * we would end up showing different results in the
 215                  * same repository!
 216                  */
 217                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
 218                                     ds->fn(&ds->candidate, ds->cb_data));
 219
 220         if (!ds->candidate_ok)
 221                 return SHORT_NAME_AMBIGUOUS;
 222
 223         hashcpy(sha1, ds->candidate.hash);
 224         return 0;
 225 }
 226
 227 static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
 228 {
 229         int kind = sha1_object_info(oid->hash, NULL);
 230         return kind == OBJ_COMMIT;
 231 }
 232
 233 static int disambiguate_committish_only(const struct object_id *oid, void *cb_data_unused)
 234 {
 235         struct object *obj;
 236         int kind;
 237
 238         kind = sha1_object_info(oid->hash, NULL);
 239         if (kind == OBJ_COMMIT)
 240                 return 1;
 241         if (kind != OBJ_TAG)
 242                 return 0;
 243
 244         /* We need to do this the hard way... */
 245         obj = deref_tag(parse_object(oid), NULL, 0);
 246         if (obj && obj->type == OBJ_COMMIT)
 247                 return 1;
 248         return 0;
 249 }
 250
 251 static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
 252 {
 253         int kind = sha1_object_info(oid->hash, NULL);
 254         return kind == OBJ_TREE;
 255 }
 256
 257 static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
 258 {
 259         struct object *obj;
 260         int kind;
 261
 262         kind = sha1_object_info(oid->hash, NULL);
 263         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
 264                 return 1;
 265         if (kind != OBJ_TAG)
 266                 return 0;
 267
 268         /* We need to do this the hard way... */
 269         obj = deref_tag(parse_object(oid), NULL, 0);
 270         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 271                 return 1;
 272         return 0;
 273 }
 274
 275 static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
 276 {
 277         int kind = sha1_object_info(oid->hash, NULL);
 278         return kind == OBJ_BLOB;
 279 }
 280
 281 static disambiguate_hint_fn default_disambiguate_hint;
 282
 283 int set_disambiguate_hint_config(const char *var, const char *value)
 284 {
 285         static const struct {
 286                 const char *name;
 287                 disambiguate_hint_fn fn;
 288         } hints[] = {
 289                 { "none", NULL },
 290                 { "commit", disambiguate_commit_only },
 291                 { "committish", disambiguate_committish_only },
 292                 { "tree", disambiguate_tree_only },
 293                 { "treeish", disambiguate_treeish_only },
 294                 { "blob", disambiguate_blob_only }
 295         };
 296         int i;
 297
 298         if (!value)
 299                 return config_error_nonbool(var);
 300
 301         for (i = 0; i < ARRAY_SIZE(hints); i++) {
 302                 if (!strcasecmp(value, hints[i].name)) {
 303                         default_disambiguate_hint = hints[i].fn;
 304                         return 0;
 305                 }
 306         }
 307
 308         return error("unknown hint type for '%s': %s", var, value);
 309 }
 310
 311 static int init_object_disambiguation(const char *name, int len,
 312                                       struct disambiguate_state *ds)
 313 {
 314         int i;
 315
 316         if (len < MINIMUM_ABBREV || len > GIT_SHA1_HEXSZ)
 317                 return -1;
 318
 319         memset(ds, 0, sizeof(*ds));
 320
 321         for (i = 0; i < len ;i++) {
 322                 unsigned char c = name[i];
 323                 unsigned char val;
 324                 if (c >= '0' && c <= '9')
 325                         val = c - '0';
 326                 else if (c >= 'a' && c <= 'f')
 327                         val = c - 'a' + 10;
 328                 else if (c >= 'A' && c <='F') {
 329                         val = c - 'A' + 10;
 330                         c -= 'A' - 'a';
 331                 }
 332                 else
 333                         return -1;
 334                 ds->hex_pfx[i] = c;
 335                 if (!(i & 1))
 336                         val <<= 4;
 337                 ds->bin_pfx.hash[i >> 1] |= val;
 338         }
 339
 340         ds->len = len;
 341         ds->hex_pfx[len] = '\0';
 342         prepare_alt_odb();
 343         return 0;
 344 }
 345
 346 static int show_ambiguous_object(const struct object_id *oid, void *data)
 347 {
 348         const struct disambiguate_state *ds = data;
 349         struct strbuf desc = STRBUF_INIT;
 350         int type;
 351
 352
 353         if (ds->fn && !ds->fn(oid, ds->cb_data))
 354                 return 0;
 355
 356         type = sha1_object_info(oid->hash, NULL);
 357         if (type == OBJ_COMMIT) {
 358                 struct commit *commit = lookup_commit(oid);
 359                 if (commit) {
 360                         struct pretty_print_context pp = {0};
 361                         pp.date_mode.type = DATE_SHORT;
 362                         format_commit_message(commit, " %ad - %s", &desc, &pp);
 363                 }
 364         } else if (type == OBJ_TAG) {
 365                 struct tag *tag = lookup_tag(oid);
 366                 if (!parse_tag(tag) && tag->tag)
 367                         strbuf_addf(&desc, " %s", tag->tag);
 368         }
 369
 370         advise("  %s %s%s",
 371                find_unique_abbrev(oid->hash, DEFAULT_ABBREV),
 372                typename(type) ? typename(type) : "unknown type",
 373                desc.buf);
 374
 375         strbuf_release(&desc);
 376         return 0;
 377 }
 378
 379 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 380                           unsigned flags)
 381 {
 382         int status;
 383         struct disambiguate_state ds;
 384         int quietly = !!(flags & GET_SHA1_QUIETLY);
 385
 386         if (init_object_disambiguation(name, len, &ds) < 0)
 387                 return -1;
 388
 389         if (HAS_MULTI_BITS(flags & GET_SHA1_DISAMBIGUATORS))
 390                 die("BUG: multiple get_short_sha1 disambiguator flags");
 391
 392         if (flags & GET_SHA1_COMMIT)
 393                 ds.fn = disambiguate_commit_only;
 394         else if (flags & GET_SHA1_COMMITTISH)
 395                 ds.fn = disambiguate_committish_only;
 396         else if (flags & GET_SHA1_TREE)
 397                 ds.fn = disambiguate_tree_only;
 398         else if (flags & GET_SHA1_TREEISH)
 399                 ds.fn = disambiguate_treeish_only;
 400         else if (flags & GET_SHA1_BLOB)
 401                 ds.fn = disambiguate_blob_only;
 402         else
 403                 ds.fn = default_disambiguate_hint;
 404
 405         find_short_object_filename(&ds);
 406         find_short_packed_object(&ds);
 407         status = finish_object_disambiguation(&ds, sha1);
 408
 409         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
 410                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
 411
 412                 /*
 413                  * We may still have ambiguity if we simply saw a series of
 414                  * candidates that did not satisfy our hint function. In
 415                  * that case, we still want to show them, so disable the hint
 416                  * function entirely.
 417                  */
 418                 if (!ds.ambiguous)
 419                         ds.fn = NULL;
 420
 421                 advise(_("The candidates are:"));
 422                 for_each_abbrev(ds.hex_pfx, show_ambiguous_object, &ds);
 423         }
 424
 425         return status;
 426 }
 427
 428 static int collect_ambiguous(const struct object_id *oid, void *data)
 429 {
 430         oid_array_append(data, oid);
 431         return 0;
 432 }
 433
 434 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
 435 {
 436         struct oid_array collect = OID_ARRAY_INIT;
 437         struct disambiguate_state ds;
 438         int ret;
 439
 440         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
 441                 return -1;
 442
 443         ds.always_call_fn = 1;
 444         ds.fn = collect_ambiguous;
 445         ds.cb_data = &collect;
 446         find_short_object_filename(&ds);
 447         find_short_packed_object(&ds);
 448
 449         ret = oid_array_for_each_unique(&collect, fn, cb_data);
 450         oid_array_clear(&collect);
 451         return ret;
 452 }
 453
 454 /*
 455  * Return the slot of the most-significant bit set in "val". There are various
 456  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 457  * probably not a big deal here.
 458  */
 459 static unsigned msb(unsigned long val)
 460 {
 461         unsigned r = 0;
 462         while (val >>= 1)
 463                 r++;
 464         return r;
 465 }
 466
 467 int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
 468 {
 469         int status, exists;
 470
 471         if (len < 0) {
 472                 unsigned long count = approximate_object_count();
 473                 /*
 474                  * Add one because the MSB only tells us the highest bit set,
 475                  * not including the value of all the _other_ bits (so "15"
 476                  * is only one off of 2^4, but the MSB is the 3rd bit.
 477                  */
 478                 len = msb(count) + 1;
 479                 /*
 480                  * We now know we have on the order of 2^len objects, which
 481                  * expects a collision at 2^(len/2). But we also care about hex
 482                  * chars, not bits, and there are 4 bits per hex. So all
 483                  * together we need to divide by 2; but we also want to round
 484                  * odd numbers up, hence adding one before dividing.
 485                  */
 486                 len = (len + 1) / 2;
 487                 /*
 488                  * For very small repos, we stick with our regular fallback.
 489                  */
 490                 if (len < FALLBACK_DEFAULT_ABBREV)
 491                         len = FALLBACK_DEFAULT_ABBREV;
 492         }
 493
 494         sha1_to_hex_r(hex, sha1);
 495         if (len == 40 || !len)
 496                 return 40;
 497         exists = has_sha1_file(sha1);
 498         while (len < 40) {
 499                 unsigned char sha1_ret[20];
 500                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
 501                 if (exists
 502                     ? !status
 503                     : status == SHORT_NAME_NOT_FOUND) {
 504                         hex[len] = 0;
 505                         return len;
 506                 }
 507                 len++;
 508         }
 509         return len;
 510 }
 511
 512 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 513 {
 514         static int bufno;
 515         static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
 516         char *hex = hexbuffer[bufno];
 517         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
 518         find_unique_abbrev_r(hex, sha1, len);
 519         return hex;
 520 }
 521
 522 static int ambiguous_path(const char *path, int len)
 523 {
 524         int slash = 1;
 525         int cnt;
 526
 527         for (cnt = 0; cnt < len; cnt++) {
 528                 switch (*path++) {
 529                 case '\0':
 530                         break;
 531                 case '/':
 532                         if (slash)
 533                                 break;
 534                         slash = 1;
 535                         continue;
 536                 case '.':
 537                         continue;
 538                 default:
 539                         slash = 0;
 540                         continue;
 541                 }
 542                 break;
 543         }
 544         return slash;
 545 }
 546
 547 static inline int at_mark(const char *string, int len,
 548                           const char **suffix, int nr)
 549 {
 550         int i;
 551
 552         for (i = 0; i < nr; i++) {
 553                 int suffix_len = strlen(suffix[i]);
 554                 if (suffix_len <= len
 555                     && !strncasecmp(string, suffix[i], suffix_len))
 556                         return suffix_len;
 557         }
 558         return 0;
 559 }
 560
 561 static inline int upstream_mark(const char *string, int len)
 562 {
 563         const char *suffix[] = { "@{upstream}", "@{u}" };
 564         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 565 }
 566
 567 static inline int push_mark(const char *string, int len)
 568 {
 569         const char *suffix[] = { "@{push}" };
 570         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 571 }
 572
 573 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 574 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 575
 576 static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
 577                           unsigned int flags)
 578 {
 579         static const char *warn_msg = "refname '%.*s' is ambiguous.";
 580         static const char *object_name_msg = N_(
 581         "Git normally never creates a ref that ends with 40 hex characters\n"
 582         "because it will be ignored when you just specify 40-hex. These refs\n"
 583         "may be created by mistake. For example,\n"
 584         "\n"
 585         "  git checkout -b $br $(git rev-parse ...)\n"
 586         "\n"
 587         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 588         "examine these refs and maybe delete them. Turn this message off by\n"
 589         "running \"git config advice.objectNameWarning false\"");
 590         unsigned char tmp_sha1[20];
 591         char *real_ref = NULL;
 592         int refs_found = 0;
 593         int at, reflog_len, nth_prior = 0;
 594
 595         if (len == 40 && !get_sha1_hex(str, sha1)) {
 596                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
 597                         refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
 598                         if (refs_found > 0) {
 599                                 warning(warn_msg, len, str);
 600                                 if (advice_object_name_warning)
 601                                         fprintf(stderr, "%s\n", _(object_name_msg));
 602                         }
 603                         free(real_ref);
 604                 }
 605                 return 0;
 606         }
 607
 608         /* basic@{time or number or -number} format to query ref-log */
 609         reflog_len = at = 0;
 610         if (len && str[len-1] == '}') {
 611                 for (at = len-4; at >= 0; at--) {
 612                         if (str[at] == '@' && str[at+1] == '{') {
 613                                 if (str[at+2] == '-') {
 614                                         if (at != 0)
 615                                                 /* @{-N} not at start */
 616                                                 return -1;
 617                                         nth_prior = 1;
 618                                         continue;
 619                                 }
 620                                 if (!upstream_mark(str + at, len - at) &&
 621                                     !push_mark(str + at, len - at)) {
 622                                         reflog_len = (len-1) - (at+2);
 623                                         len = at;
 624                                 }
 625                                 break;
 626                         }
 627                 }
 628         }
 629
 630         /* Accept only unambiguous ref paths. */
 631         if (len && ambiguous_path(str, len))
 632                 return -1;
 633
 634         if (nth_prior) {
 635                 struct strbuf buf = STRBUF_INIT;
 636                 int detached;
 637
 638                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
 639                         detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
 640                         strbuf_release(&buf);
 641                         if (detached)
 642                                 return 0;
 643                 }
 644         }
 645
 646         if (!len && reflog_len)
 647                 /* allow "@{...}" to mean the current branch reflog */
 648                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 649         else if (reflog_len)
 650                 refs_found = dwim_log(str, len, sha1, &real_ref);
 651         else
 652                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 653
 654         if (!refs_found)
 655                 return -1;
 656
 657         if (warn_ambiguous_refs && !(flags & GET_SHA1_QUIETLY) &&
 658             (refs_found > 1 ||
 659              !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
 660                 warning(warn_msg, len, str);
 661
 662         if (reflog_len) {
 663                 int nth, i;
 664                 timestamp_t at_time;
 665                 timestamp_t co_time;
 666                 int co_tz, co_cnt;
 667
 668                 /* Is it asking for N-th entry, or approxidate? */
 669                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 670                         char ch = str[at+2+i];
 671                         if ('0' <= ch && ch <= '9')
 672                                 nth = nth * 10 + ch - '0';
 673                         else
 674                                 nth = -1;
 675                 }
 676                 if (100000000 <= nth) {
 677                         at_time = nth;
 678                         nth = -1;
 679                 } else if (0 <= nth)
 680                         at_time = 0;
 681                 else {
 682                         int errors = 0;
 683                         char *tmp = xstrndup(str + at + 2, reflog_len);
 684                         at_time = approxidate_careful(tmp, &errors);
 685                         free(tmp);
 686                         if (errors) {
 687                                 free(real_ref);
 688                                 return -1;
 689                         }
 690                 }
 691                 if (read_ref_at(real_ref, flags, at_time, nth, sha1, NULL,
 692                                 &co_time, &co_tz, &co_cnt)) {
 693                         if (!len) {
 694                                 if (starts_with(real_ref, "refs/heads/")) {
 695                                         str = real_ref + 11;
 696                                         len = strlen(real_ref + 11);
 697                                 } else {
 698                                         /* detached HEAD */
 699                                         str = "HEAD";
 700                                         len = 4;
 701                                 }
 702                         }
 703                         if (at_time) {
 704                                 if (!(flags & GET_SHA1_QUIETLY)) {
 705                                         warning("Log for '%.*s' only goes "
 706                                                 "back to %s.", len, str,
 707                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
 708                                 }
 709                         } else {
 710                                 if (flags & GET_SHA1_QUIETLY) {
 711                                         exit(128);
 712                                 }
 713                                 die("Log for '%.*s' only has %d entries.",
 714                                     len, str, co_cnt);
 715                         }
 716                 }
 717         }
 718
 719         free(real_ref);
 720         return 0;
 721 }
 722
 723 static int get_parent(const char *name, int len,
 724                       unsigned char *result, int idx)
 725 {
 726         struct object_id oid;
 727         int ret = get_sha1_1(name, len, oid.hash, GET_SHA1_COMMITTISH);
 728         struct commit *commit;
 729         struct commit_list *p;
 730
 731         if (ret)
 732                 return ret;
 733         commit = lookup_commit_reference(&oid);
 734         if (parse_commit(commit))
 735                 return -1;
 736         if (!idx) {
 737                 hashcpy(result, commit->object.oid.hash);
 738                 return 0;
 739         }
 740         p = commit->parents;
 741         while (p) {
 742                 if (!--idx) {
 743                         hashcpy(result, p->item->object.oid.hash);
 744                         return 0;
 745                 }
 746                 p = p->next;
 747         }
 748         return -1;
 749 }
 750
 751 static int get_nth_ancestor(const char *name, int len,
 752                             unsigned char *result, int generation)
 753 {
 754         struct object_id oid;
 755         struct commit *commit;
 756         int ret;
 757
 758         ret = get_sha1_1(name, len, oid.hash, GET_SHA1_COMMITTISH);
 759         if (ret)
 760                 return ret;
 761         commit = lookup_commit_reference(&oid);
 762         if (!commit)
 763                 return -1;
 764
 765         while (generation--) {
 766                 if (parse_commit(commit) || !commit->parents)
 767                         return -1;
 768                 commit = commit->parents->item;
 769         }
 770         hashcpy(result, commit->object.oid.hash);
 771         return 0;
 772 }
 773
 774 struct object *peel_to_type(const char *name, int namelen,
 775                             struct object *o, enum object_type expected_type)
 776 {
 777         if (name && !namelen)
 778                 namelen = strlen(name);
 779         while (1) {
 780                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 781                         return NULL;
 782                 if (expected_type == OBJ_ANY || o->type == expected_type)
 783                         return o;
 784                 if (o->type == OBJ_TAG)
 785                         o = ((struct tag*) o)->tagged;
 786                 else if (o->type == OBJ_COMMIT)
 787                         o = &(((struct commit *) o)->tree->object);
 788                 else {
 789                         if (name)
 790                                 error("%.*s: expected %s type, but the object "
 791                                       "dereferences to %s type",
 792                                       namelen, name, typename(expected_type),
 793                                       typename(o->type));
 794                         return NULL;
 795                 }
 796         }
 797 }
 798
 799 static int peel_onion(const char *name, int len, unsigned char *sha1,
 800                       unsigned lookup_flags)
 801 {
 802         struct object_id outer;
 803         const char *sp;
 804         unsigned int expected_type = 0;
 805         struct object *o;
 806
 807         /*
 808          * "ref^{type}" dereferences ref repeatedly until you cannot
 809          * dereference anymore, or you get an object of given type,
 810          * whichever comes first.  "ref^{}" means just dereference
 811          * tags until you get a non-tag.  "ref^0" is a shorthand for
 812          * "ref^{commit}".  "commit^{tree}" could be used to find the
 813          * top-level tree of the given commit.
 814          */
 815         if (len < 4 || name[len-1] != '}')
 816                 return -1;
 817
 818         for (sp = name + len - 1; name <= sp; sp--) {
 819                 int ch = *sp;
 820                 if (ch == '{' && name < sp && sp[-1] == '^')
 821                         break;
 822         }
 823         if (sp <= name)
 824                 return -1;
 825
 826         sp++; /* beginning of type name, or closing brace for empty */
 827         if (starts_with(sp, "commit}"))
 828                 expected_type = OBJ_COMMIT;
 829         else if (starts_with(sp, "tag}"))
 830                 expected_type = OBJ_TAG;
 831         else if (starts_with(sp, "tree}"))
 832                 expected_type = OBJ_TREE;
 833         else if (starts_with(sp, "blob}"))
 834                 expected_type = OBJ_BLOB;
 835         else if (starts_with(sp, "object}"))
 836                 expected_type = OBJ_ANY;
 837         else if (sp[0] == '}')
 838                 expected_type = OBJ_NONE;
 839         else if (sp[0] == '/')
 840                 expected_type = OBJ_COMMIT;
 841         else
 842                 return -1;
 843
 844         lookup_flags &= ~GET_SHA1_DISAMBIGUATORS;
 845         if (expected_type == OBJ_COMMIT)
 846                 lookup_flags |= GET_SHA1_COMMITTISH;
 847         else if (expected_type == OBJ_TREE)
 848                 lookup_flags |= GET_SHA1_TREEISH;
 849
 850         if (get_sha1_1(name, sp - name - 2, outer.hash, lookup_flags))
 851                 return -1;
 852
 853         o = parse_object(&outer);
 854         if (!o)
 855                 return -1;
 856         if (!expected_type) {
 857                 o = deref_tag(o, name, sp - name - 2);
 858                 if (!o || (!o->parsed && !parse_object(&o->oid)))
 859                         return -1;
 860                 hashcpy(sha1, o->oid.hash);
 861                 return 0;
 862         }
 863
 864         /*
 865          * At this point, the syntax look correct, so
 866          * if we do not get the needed object, we should
 867          * barf.
 868          */
 869         o = peel_to_type(name, len, o, expected_type);
 870         if (!o)
 871                 return -1;
 872
 873         hashcpy(sha1, o->oid.hash);
 874         if (sp[0] == '/') {
 875                 /* "$commit^{/foo}" */
 876                 char *prefix;
 877                 int ret;
 878                 struct commit_list *list = NULL;
 879
 880                 /*
 881                  * $commit^{/}. Some regex implementation may reject.
 882                  * We don't need regex anyway. '' pattern always matches.
 883                  */
 884                 if (sp[1] == '}')
 885                         return 0;
 886
 887                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
 888                 commit_list_insert((struct commit *)o, &list);
 889                 ret = get_sha1_oneline(prefix, sha1, list);
 890                 free(prefix);
 891                 return ret;
 892         }
 893         return 0;
 894 }
 895
 896 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 897 {
 898         const char *cp;
 899         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
 900
 901         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 902                 char ch = *cp;
 903                 if (!isxdigit(ch)) {
 904                         /* We must be looking at g in "SOMETHING-g"
 905                          * for it to be describe output.
 906                          */
 907                         if (ch == 'g' && cp[-1] == '-') {
 908                                 cp++;
 909                                 len -= cp - name;
 910                                 return get_short_sha1(cp, len, sha1, flags);
 911                         }
 912                 }
 913         }
 914         return -1;
 915 }
 916
 917 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
 918 {
 919         int ret, has_suffix;
 920         const char *cp;
 921
 922         /*
 923          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 924          */
 925         has_suffix = 0;
 926         for (cp = name + len - 1; name <= cp; cp--) {
 927                 int ch = *cp;
 928                 if ('0' <= ch && ch <= '9')
 929                         continue;
 930                 if (ch == '~' || ch == '^')
 931                         has_suffix = ch;
 932                 break;
 933         }
 934
 935         if (has_suffix) {
 936                 int num = 0;
 937                 int len1 = cp - name;
 938                 cp++;
 939                 while (cp < name + len)
 940                         num = num * 10 + *cp++ - '0';
 941                 if (!num && len1 == len - 1)
 942                         num = 1;
 943                 if (has_suffix == '^')
 944                         return get_parent(name, len1, sha1, num);
 945                 /* else if (has_suffix == '~') -- goes without saying */
 946                 return get_nth_ancestor(name, len1, sha1, num);
 947         }
 948
 949         ret = peel_onion(name, len, sha1, lookup_flags);
 950         if (!ret)
 951                 return 0;
 952
 953         ret = get_sha1_basic(name, len, sha1, lookup_flags);
 954         if (!ret)
 955                 return 0;
 956
 957         /* It could be describe output that is "SOMETHING-gXXXX" */
 958         ret = get_describe_name(name, len, sha1);
 959         if (!ret)
 960                 return 0;
 961
 962         return get_short_sha1(name, len, sha1, lookup_flags);
 963 }
 964
 965 /*
 966  * This interprets names like ':/Initial revision of "git"' by searching
 967  * through history and returning the first commit whose message starts
 968  * the given regular expression.
 969  *
 970  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
 971  *
 972  * For a literal '!' character at the beginning of a pattern, you have to repeat
 973  * that, like: ':/!!foo'
 974  *
 975  * For future extension, all other sequences beginning with ':/!' are reserved.
 976  */
 977
 978 /* Remember to update object flag allocation in object.h */
 979 #define ONELINE_SEEN (1u<<20)
 980
 981 static int handle_one_ref(const char *path, const struct object_id *oid,
 982                           int flag, void *cb_data)
 983 {
 984         struct commit_list **list = cb_data;
 985         struct object *object = parse_object(oid);
 986         if (!object)
 987                 return 0;
 988         if (object->type == OBJ_TAG) {
 989                 object = deref_tag(object, path, strlen(path));
 990                 if (!object)
 991                         return 0;
 992         }
 993         if (object->type != OBJ_COMMIT)
 994                 return 0;
 995         commit_list_insert((struct commit *)object, list);
 996         return 0;
 997 }
 998
 999 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
1000                             struct commit_list *list)
1001 {
1002         struct commit_list *backup = NULL, *l;
1003         int found = 0;
1004         int negative = 0;
1005         regex_t regex;
1006
1007         if (prefix[0] == '!') {
1008                 prefix++;
1009
1010                 if (prefix[0] == '-') {
1011                         prefix++;
1012                         negative = 1;
1013                 } else if (prefix[0] != '!') {
1014                         return -1;
1015                 }
1016         }
1017
1018         if (regcomp(&regex, prefix, REG_EXTENDED))
1019                 return -1;
1020
1021         for (l = list; l; l = l->next) {
1022                 l->item->object.flags |= ONELINE_SEEN;
1023                 commit_list_insert(l->item, &backup);
1024         }
1025         while (list) {
1026                 const char *p, *buf;
1027                 struct commit *commit;
1028                 int matches;
1029
1030                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1031                 if (!parse_object(&commit->object.oid))
1032                         continue;
1033                 buf = get_commit_buffer(commit, NULL);
1034                 p = strstr(buf, "\n\n");
1035                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1036                 unuse_commit_buffer(commit, buf);
1037
1038                 if (matches) {
1039                         hashcpy(sha1, commit->object.oid.hash);
1040                         found = 1;
1041                         break;
1042                 }
1043         }
1044         regfree(&regex);
1045         free_commit_list(list);
1046         for (l = backup; l; l = l->next)
1047                 clear_commit_marks(l->item, ONELINE_SEEN);
1048         free_commit_list(backup);
1049         return found ? 0 : -1;
1050 }
1051
1052 struct grab_nth_branch_switch_cbdata {
1053         int remaining;
1054         struct strbuf buf;
1055 };
1056
1057 static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
1058                                   const char *email, timestamp_t timestamp, int tz,
1059                                   const char *message, void *cb_data)
1060 {
1061         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1062         const char *match = NULL, *target = NULL;
1063         size_t len;
1064
1065         if (skip_prefix(message, "checkout: moving from ", &match))
1066                 target = strstr(match, " to ");
1067
1068         if (!match || !target)
1069                 return 0;
1070         if (--(cb->remaining) == 0) {
1071                 len = target - match;
1072                 strbuf_reset(&cb->buf);
1073                 strbuf_add(&cb->buf, match, len);
1074                 return 1; /* we are done */
1075         }
1076         return 0;
1077 }
1078
1079 /*
1080  * Parse @{-N} syntax, return the number of characters parsed
1081  * if successful; otherwise signal an error with negative value.
1082  */
1083 static int interpret_nth_prior_checkout(const char *name, int namelen,
1084                                         struct strbuf *buf)
1085 {
1086         long nth;
1087         int retval;
1088         struct grab_nth_branch_switch_cbdata cb;
1089         const char *brace;
1090         char *num_end;
1091
1092         if (namelen < 4)
1093                 return -1;
1094         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1095                 return -1;
1096         brace = memchr(name, '}', namelen);
1097         if (!brace)
1098                 return -1;
1099         nth = strtol(name + 3, &num_end, 10);
1100         if (num_end != brace)
1101                 return -1;
1102         if (nth <= 0)
1103                 return -1;
1104         cb.remaining = nth;
1105         strbuf_init(&cb.buf, 20);
1106
1107         retval = 0;
1108         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1109                 strbuf_reset(buf);
1110                 strbuf_addbuf(buf, &cb.buf);
1111                 retval = brace - name + 1;
1112         }
1113
1114         strbuf_release(&cb.buf);
1115         return retval;
1116 }
1117
1118 int get_oid_mb(const char *name, struct object_id *oid)
1119 {
1120         struct commit *one, *two;
1121         struct commit_list *mbs;
1122         struct object_id oid_tmp;
1123         const char *dots;
1124         int st;
1125
1126         dots = strstr(name, "...");
1127         if (!dots)
1128                 return get_oid(name, oid);
1129         if (dots == name)
1130                 st = get_oid("HEAD", &oid_tmp);
1131         else {
1132                 struct strbuf sb;
1133                 strbuf_init(&sb, dots - name);
1134                 strbuf_add(&sb, name, dots - name);
1135                 st = get_sha1_committish(sb.buf, oid_tmp.hash);
1136                 strbuf_release(&sb);
1137         }
1138         if (st)
1139                 return st;
1140         one = lookup_commit_reference_gently(&oid_tmp, 0);
1141         if (!one)
1142                 return -1;
1143
1144         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", oid_tmp.hash))
1145                 return -1;
1146         two = lookup_commit_reference_gently(&oid_tmp, 0);
1147         if (!two)
1148                 return -1;
1149         mbs = get_merge_bases(one, two);
1150         if (!mbs || mbs->next)
1151                 st = -1;
1152         else {
1153                 st = 0;
1154                 oidcpy(oid, &mbs->item->object.oid);
1155         }
1156         free_commit_list(mbs);
1157         return st;
1158 }
1159
1160 /* parse @something syntax, when 'something' is not {.*} */
1161 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1162 {
1163         const char *next;
1164
1165         if (len || name[1] == '{')
1166                 return -1;
1167
1168         /* make sure it's a single @, or @@{.*}, not @foo */
1169         next = memchr(name + len + 1, '@', namelen - len - 1);
1170         if (next && next[1] != '{')
1171                 return -1;
1172         if (!next)
1173                 next = name + namelen;
1174         if (next != name + 1)
1175                 return -1;
1176
1177         strbuf_reset(buf);
1178         strbuf_add(buf, "HEAD", 4);
1179         return 1;
1180 }
1181
1182 static int reinterpret(const char *name, int namelen, int len,
1183                        struct strbuf *buf, unsigned allowed)
1184 {
1185         /* we have extra data, which might need further processing */
1186         struct strbuf tmp = STRBUF_INIT;
1187         int used = buf->len;
1188         int ret;
1189
1190         strbuf_add(buf, name + len, namelen - len);
1191         ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
1192         /* that data was not interpreted, remove our cruft */
1193         if (ret < 0) {
1194                 strbuf_setlen(buf, used);
1195                 return len;
1196         }
1197         strbuf_reset(buf);
1198         strbuf_addbuf(buf, &tmp);
1199         strbuf_release(&tmp);
1200         /* tweak for size of {-N} versus expanded ref name */
1201         return ret - used + len;
1202 }
1203
1204 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1205 {
1206         char *s = shorten_unambiguous_ref(ref, 0);
1207         strbuf_reset(buf);
1208         strbuf_addstr(buf, s);
1209         free(s);
1210 }
1211
1212 static int branch_interpret_allowed(const char *refname, unsigned allowed)
1213 {
1214         if (!allowed)
1215                 return 1;
1216
1217         if ((allowed & INTERPRET_BRANCH_LOCAL) &&
1218             starts_with(refname, "refs/heads/"))
1219                 return 1;
1220         if ((allowed & INTERPRET_BRANCH_REMOTE) &&
1221             starts_with(refname, "refs/remotes/"))
1222                 return 1;
1223
1224         return 0;
1225 }
1226
1227 static int interpret_branch_mark(const char *name, int namelen,
1228                                  int at, struct strbuf *buf,
1229                                  int (*get_mark)(const char *, int),
1230                                  const char *(*get_data)(struct branch *,
1231                                                          struct strbuf *),
1232                                  unsigned allowed)
1233 {
1234         int len;
1235         struct branch *branch;
1236         struct strbuf err = STRBUF_INIT;
1237         const char *value;
1238
1239         len = get_mark(name + at, namelen - at);
1240         if (!len)
1241                 return -1;
1242
1243         if (memchr(name, ':', at))
1244                 return -1;
1245
1246         if (at) {
1247                 char *name_str = xmemdupz(name, at);
1248                 branch = branch_get(name_str);
1249                 free(name_str);
1250         } else
1251                 branch = branch_get(NULL);
1252
1253         value = get_data(branch, &err);
1254         if (!value)
1255                 die("%s", err.buf);
1256
1257         if (!branch_interpret_allowed(value, allowed))
1258                 return -1;
1259
1260         set_shortened_ref(buf, value);
1261         return len + at;
1262 }
1263
1264 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
1265                           unsigned allowed)
1266 {
1267         char *at;
1268         const char *start;
1269         int len;
1270
1271         if (!namelen)
1272                 namelen = strlen(name);
1273
1274         if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
1275                 len = interpret_nth_prior_checkout(name, namelen, buf);
1276                 if (!len) {
1277                         return len; /* syntax Ok, not enough switches */
1278                 } else if (len > 0) {
1279                         if (len == namelen)
1280                                 return len; /* consumed all */
1281                         else
1282                                 return reinterpret(name, namelen, len, buf, allowed);
1283                 }
1284         }
1285
1286         for (start = name;
1287              (at = memchr(start, '@', namelen - (start - name)));
1288              start = at + 1) {
1289
1290                 if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
1291                         len = interpret_empty_at(name, namelen, at - name, buf);
1292                         if (len > 0)
1293                                 return reinterpret(name, namelen, len, buf,
1294                                                    allowed);
1295                 }
1296
1297                 len = interpret_branch_mark(name, namelen, at - name, buf,
1298                                             upstream_mark, branch_get_upstream,
1299                                             allowed);
1300                 if (len > 0)
1301                         return len;
1302
1303                 len = interpret_branch_mark(name, namelen, at - name, buf,
1304                                             push_mark, branch_get_push,
1305                                             allowed);
1306                 if (len > 0)
1307                         return len;
1308         }
1309
1310         return -1;
1311 }
1312
1313 void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
1314 {
1315         int len = strlen(name);
1316         int used = interpret_branch_name(name, len, sb, allowed);
1317
1318         if (used < 0)
1319                 used = 0;
1320         strbuf_add(sb, name + used, len - used);
1321 }
1322
1323 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1324 {
1325         strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
1326         if (name[0] == '-')
1327                 return -1;
1328         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1329         return check_refname_format(sb->buf, 0);
1330 }
1331
1332 /*
1333  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1334  * notably "xyz^" for "parent of xyz"
1335  */
1336 int get_sha1(const char *name, unsigned char *sha1)
1337 {
1338         struct object_context unused;
1339         return get_sha1_with_context(name, 0, sha1, &unused);
1340 }
1341
1342 /*
1343  * This is like "get_sha1()", but for struct object_id.
1344  */
1345 int get_oid(const char *name, struct object_id *oid)
1346 {
1347         return get_sha1(name, oid->hash);
1348 }
1349
1350
1351 /*
1352  * Many callers know that the user meant to name a commit-ish by
1353  * syntactical positions where the object name appears.  Calling this
1354  * function allows the machinery to disambiguate shorter-than-unique
1355  * abbreviated object names between commit-ish and others.
1356  *
1357  * Note that this does NOT error out when the named object is not a
1358  * commit-ish. It is merely to give a hint to the disambiguation
1359  * machinery.
1360  */
1361 int get_sha1_committish(const char *name, unsigned char *sha1)
1362 {
1363         struct object_context unused;
1364         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1365                                      sha1, &unused);
1366 }
1367
1368 int get_sha1_treeish(const char *name, unsigned char *sha1)
1369 {
1370         struct object_context unused;
1371         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1372                                      sha1, &unused);
1373 }
1374
1375 int get_sha1_commit(const char *name, unsigned char *sha1)
1376 {
1377         struct object_context unused;
1378         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1379                                      sha1, &unused);
1380 }
1381
1382 int get_sha1_tree(const char *name, unsigned char *sha1)
1383 {
1384         struct object_context unused;
1385         return get_sha1_with_context(name, GET_SHA1_TREE,
1386                                      sha1, &unused);
1387 }
1388
1389 int get_sha1_blob(const char *name, unsigned char *sha1)
1390 {
1391         struct object_context unused;
1392         return get_sha1_with_context(name, GET_SHA1_BLOB,
1393                                      sha1, &unused);
1394 }
1395
1396 /* Must be called only when object_name:filename doesn't exist. */
1397 static void diagnose_invalid_sha1_path(const char *prefix,
1398                                        const char *filename,
1399                                        const unsigned char *tree_sha1,
1400                                        const char *object_name,
1401                                        int object_name_len)
1402 {
1403         unsigned char sha1[20];
1404         unsigned mode;
1405
1406         if (!prefix)
1407                 prefix = "";
1408
1409         if (file_exists(filename))
1410                 die("Path '%s' exists on disk, but not in '%.*s'.",
1411                     filename, object_name_len, object_name);
1412         if (is_missing_file_error(errno)) {
1413                 char *fullname = xstrfmt("%s%s", prefix, filename);
1414
1415                 if (!get_tree_entry(tree_sha1, fullname,
1416                                     sha1, &mode)) {
1417                         die("Path '%s' exists, but not '%s'.\n"
1418                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1419                             fullname,
1420                             filename,
1421                             object_name_len, object_name,
1422                             fullname,
1423                             object_name_len, object_name,
1424                             filename);
1425                 }
1426                 die("Path '%s' does not exist in '%.*s'",
1427                     filename, object_name_len, object_name);
1428         }
1429 }
1430
1431 /* Must be called only when :stage:filename doesn't exist. */
1432 static void diagnose_invalid_index_path(int stage,
1433                                         const char *prefix,
1434                                         const char *filename)
1435 {
1436         const struct cache_entry *ce;
1437         int pos;
1438         unsigned namelen = strlen(filename);
1439         struct strbuf fullname = STRBUF_INIT;
1440
1441         if (!prefix)
1442                 prefix = "";
1443
1444         /* Wrong stage number? */
1445         pos = cache_name_pos(filename, namelen);
1446         if (pos < 0)
1447                 pos = -pos - 1;
1448         if (pos < active_nr) {
1449                 ce = active_cache[pos];
1450                 if (ce_namelen(ce) == namelen &&
1451                     !memcmp(ce->name, filename, namelen))
1452                         die("Path '%s' is in the index, but not at stage %d.\n"
1453                             "Did you mean ':%d:%s'?",
1454                             filename, stage,
1455                             ce_stage(ce), filename);
1456         }
1457
1458         /* Confusion between relative and absolute filenames? */
1459         strbuf_addstr(&fullname, prefix);
1460         strbuf_addstr(&fullname, filename);
1461         pos = cache_name_pos(fullname.buf, fullname.len);
1462         if (pos < 0)
1463                 pos = -pos - 1;
1464         if (pos < active_nr) {
1465                 ce = active_cache[pos];
1466                 if (ce_namelen(ce) == fullname.len &&
1467                     !memcmp(ce->name, fullname.buf, fullname.len))
1468                         die("Path '%s' is in the index, but not '%s'.\n"
1469                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1470                             fullname.buf, filename,
1471                             ce_stage(ce), fullname.buf,
1472                             ce_stage(ce), filename);
1473         }
1474
1475         if (file_exists(filename))
1476                 die("Path '%s' exists on disk, but not in the index.", filename);
1477         if (is_missing_file_error(errno))
1478                 die("Path '%s' does not exist (neither on disk nor in the index).",
1479                     filename);
1480
1481         strbuf_release(&fullname);
1482 }
1483
1484
1485 static char *resolve_relative_path(const char *rel)
1486 {
1487         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1488                 return NULL;
1489
1490         if (!is_inside_work_tree())
1491                 die("relative path syntax can't be used outside working tree.");
1492
1493         /* die() inside prefix_path() if resolved path is outside worktree */
1494         return prefix_path(startup_info->prefix,
1495                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1496                            rel);
1497 }
1498
1499 static int get_sha1_with_context_1(const char *name,
1500                                    unsigned flags,
1501                                    const char *prefix,
1502                                    unsigned char *sha1,
1503                                    struct object_context *oc)
1504 {
1505         int ret, bracket_depth;
1506         int namelen = strlen(name);
1507         const char *cp;
1508         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1509
1510         if (only_to_die)
1511                 flags |= GET_SHA1_QUIETLY;
1512
1513         memset(oc, 0, sizeof(*oc));
1514         oc->mode = S_IFINVALID;
1515         strbuf_init(&oc->symlink_path, 0);
1516         ret = get_sha1_1(name, namelen, sha1, flags);
1517         if (!ret)
1518                 return ret;
1519         /*
1520          * sha1:path --> object name of path in ent sha1
1521          * :path -> object name of absolute path in index
1522          * :./path -> object name of path relative to cwd in index
1523          * :[0-3]:path -> object name of path in index at stage
1524          * :/foo -> recent commit matching foo
1525          */
1526         if (name[0] == ':') {
1527                 int stage = 0;
1528                 const struct cache_entry *ce;
1529                 char *new_path = NULL;
1530                 int pos;
1531                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1532                         struct commit_list *list = NULL;
1533
1534                         for_each_ref(handle_one_ref, &list);
1535                         commit_list_sort_by_date(&list);
1536                         return get_sha1_oneline(name + 2, sha1, list);
1537                 }
1538                 if (namelen < 3 ||
1539                     name[2] != ':' ||
1540                     name[1] < '0' || '3' < name[1])
1541                         cp = name + 1;
1542                 else {
1543                         stage = name[1] - '0';
1544                         cp = name + 3;
1545                 }
1546                 new_path = resolve_relative_path(cp);
1547                 if (!new_path) {
1548                         namelen = namelen - (cp - name);
1549                 } else {
1550                         cp = new_path;
1551                         namelen = strlen(cp);
1552                 }
1553
1554                 if (flags & GET_SHA1_RECORD_PATH)
1555                         oc->path = xstrdup(cp);
1556
1557                 if (!active_cache)
1558                         read_cache();
1559                 pos = cache_name_pos(cp, namelen);
1560                 if (pos < 0)
1561                         pos = -pos - 1;
1562                 while (pos < active_nr) {
1563                         ce = active_cache[pos];
1564                         if (ce_namelen(ce) != namelen ||
1565                             memcmp(ce->name, cp, namelen))
1566                                 break;
1567                         if (ce_stage(ce) == stage) {
1568                                 hashcpy(sha1, ce->oid.hash);
1569                                 oc->mode = ce->ce_mode;
1570                                 free(new_path);
1571                                 return 0;
1572                         }
1573                         pos++;
1574                 }
1575                 if (only_to_die && name[1] && name[1] != '/')
1576                         diagnose_invalid_index_path(stage, prefix, cp);
1577                 free(new_path);
1578                 return -1;
1579         }
1580         for (cp = name, bracket_depth = 0; *cp; cp++) {
1581                 if (*cp == '{')
1582                         bracket_depth++;
1583                 else if (bracket_depth && *cp == '}')
1584                         bracket_depth--;
1585                 else if (!bracket_depth && *cp == ':')
1586                         break;
1587         }
1588         if (*cp == ':') {
1589                 unsigned char tree_sha1[20];
1590                 int len = cp - name;
1591                 unsigned sub_flags = flags;
1592
1593                 sub_flags &= ~GET_SHA1_DISAMBIGUATORS;
1594                 sub_flags |= GET_SHA1_TREEISH;
1595
1596                 if (!get_sha1_1(name, len, tree_sha1, sub_flags)) {
1597                         const char *filename = cp+1;
1598                         char *new_filename = NULL;
1599
1600                         new_filename = resolve_relative_path(filename);
1601                         if (new_filename)
1602                                 filename = new_filename;
1603                         if (flags & GET_SHA1_FOLLOW_SYMLINKS) {
1604                                 ret = get_tree_entry_follow_symlinks(tree_sha1,
1605                                         filename, sha1, &oc->symlink_path,
1606                                         &oc->mode);
1607                         } else {
1608                                 ret = get_tree_entry(tree_sha1, filename,
1609                                                      sha1, &oc->mode);
1610                                 if (ret && only_to_die) {
1611                                         diagnose_invalid_sha1_path(prefix,
1612                                                                    filename,
1613                                                                    tree_sha1,
1614                                                                    name, len);
1615                                 }
1616                         }
1617                         hashcpy(oc->tree, tree_sha1);
1618                         if (flags & GET_SHA1_RECORD_PATH)
1619                                 oc->path = xstrdup(filename);
1620
1621                         free(new_filename);
1622                         return ret;
1623                 } else {
1624                         if (only_to_die)
1625                                 die("Invalid object name '%.*s'.", len, name);
1626                 }
1627         }
1628         return ret;
1629 }
1630
1631 /*
1632  * Call this function when you know "name" given by the end user must
1633  * name an object but it doesn't; the function _may_ die with a better
1634  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1635  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1636  * you have a chance to diagnose the error further.
1637  */
1638 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1639 {
1640         struct object_context oc;
1641         unsigned char sha1[20];
1642         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1643 }
1644
1645 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *oc)
1646 {
1647         if (flags & GET_SHA1_FOLLOW_SYMLINKS && flags & GET_SHA1_ONLY_TO_DIE)
1648                 die("BUG: incompatible flags for get_sha1_with_context");
1649         return get_sha1_with_context_1(str, flags, NULL, sha1, oc);
1650 }