pull: fast-forward "pull --rebase=true"
[git] / 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
11 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
12
13 typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
14
15 struct disambiguate_state {
16         disambiguate_hint_fn fn;
17         void *cb_data;
18         unsigned char candidate[20];
19         unsigned candidate_exists:1;
20         unsigned candidate_checked:1;
21         unsigned candidate_ok:1;
22         unsigned disambiguate_fn_used:1;
23         unsigned ambiguous:1;
24         unsigned always_call_fn:1;
25 };
26
27 static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
28 {
29         if (ds->always_call_fn) {
30                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
31                 return;
32         }
33         if (!ds->candidate_exists) {
34                 /* this is the first candidate */
35                 hashcpy(ds->candidate, current);
36                 ds->candidate_exists = 1;
37                 return;
38         } else if (!hashcmp(ds->candidate, current)) {
39                 /* the same as what we already have seen */
40                 return;
41         }
42
43         if (!ds->fn) {
44                 /* cannot disambiguate between ds->candidate and current */
45                 ds->ambiguous = 1;
46                 return;
47         }
48
49         if (!ds->candidate_checked) {
50                 ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
51                 ds->disambiguate_fn_used = 1;
52                 ds->candidate_checked = 1;
53         }
54
55         if (!ds->candidate_ok) {
56                 /* discard the candidate; we know it does not satisfy fn */
57                 hashcpy(ds->candidate, current);
58                 ds->candidate_checked = 0;
59                 return;
60         }
61
62         /* if we reach this point, we know ds->candidate satisfies fn */
63         if (ds->fn(current, ds->cb_data)) {
64                 /*
65                  * if both current and candidate satisfy fn, we cannot
66                  * disambiguate.
67                  */
68                 ds->candidate_ok = 0;
69                 ds->ambiguous = 1;
70         }
71
72         /* otherwise, current can be discarded and candidate is still good */
73 }
74
75 static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
76 {
77         struct alternate_object_database *alt;
78         char hex[40];
79         static struct alternate_object_database *fakeent;
80
81         if (!fakeent) {
82                 /*
83                  * Create a "fake" alternate object database that
84                  * points to our own object database, to make it
85                  * easier to get a temporary working space in
86                  * alt->name/alt->base while iterating over the
87                  * object databases including our own.
88                  */
89                 const char *objdir = get_object_directory();
90                 int objdir_len = strlen(objdir);
91                 int entlen = objdir_len + 43;
92                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
93                 memcpy(fakeent->base, objdir, objdir_len);
94                 fakeent->name = fakeent->base + objdir_len + 1;
95                 fakeent->name[-1] = '/';
96         }
97         fakeent->next = alt_odb_list;
98
99         sprintf(hex, "%.2s", hex_pfx);
100         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
101                 struct dirent *de;
102                 DIR *dir;
103                 sprintf(alt->name, "%.2s/", hex_pfx);
104                 dir = opendir(alt->base);
105                 if (!dir)
106                         continue;
107
108                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
109                         unsigned char sha1[20];
110
111                         if (strlen(de->d_name) != 38)
112                                 continue;
113                         if (memcmp(de->d_name, hex_pfx + 2, len - 2))
114                                 continue;
115                         memcpy(hex + 2, de->d_name, 38);
116                         if (!get_sha1_hex(hex, sha1))
117                                 update_candidates(ds, sha1);
118                 }
119                 closedir(dir);
120         }
121 }
122
123 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
124 {
125         do {
126                 if (*a != *b)
127                         return 0;
128                 a++;
129                 b++;
130                 len -= 2;
131         } while (len > 1);
132         if (len)
133                 if ((*a ^ *b) & 0xf0)
134                         return 0;
135         return 1;
136 }
137
138 static void unique_in_pack(int len,
139                           const unsigned char *bin_pfx,
140                            struct packed_git *p,
141                            struct disambiguate_state *ds)
142 {
143         uint32_t num, last, i, first = 0;
144         const unsigned char *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(bin_pfx, 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                 current = nth_packed_object_sha1(p, i);
174                 if (!match_sha(len, bin_pfx, current))
175                         break;
176                 update_candidates(ds, current);
177         }
178 }
179
180 static void find_short_packed_object(int len, const unsigned char *bin_pfx,
181                                      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(len, bin_pfx, 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);
224         return 0;
225 }
226
227 static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
228 {
229         int kind = sha1_object_info(sha1, NULL);
230         return kind == OBJ_COMMIT;
231 }
232
233 static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
234 {
235         struct object *obj;
236         int kind;
237
238         kind = sha1_object_info(sha1, 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(sha1), NULL, 0);
246         if (obj && obj->type == OBJ_COMMIT)
247                 return 1;
248         return 0;
249 }
250
251 static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
252 {
253         int kind = sha1_object_info(sha1, NULL);
254         return kind == OBJ_TREE;
255 }
256
257 static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
258 {
259         struct object *obj;
260         int kind;
261
262         kind = sha1_object_info(sha1, 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(lookup_object(sha1), 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 unsigned char *sha1, void *cb_data_unused)
276 {
277         int kind = sha1_object_info(sha1, NULL);
278         return kind == OBJ_BLOB;
279 }
280
281 static int prepare_prefixes(const char *name, int len,
282                             unsigned char *bin_pfx,
283                             char *hex_pfx)
284 {
285         int i;
286
287         hashclr(bin_pfx);
288         memset(hex_pfx, 'x', 40);
289         for (i = 0; i < len ;i++) {
290                 unsigned char c = name[i];
291                 unsigned char val;
292                 if (c >= '0' && c <= '9')
293                         val = c - '0';
294                 else if (c >= 'a' && c <= 'f')
295                         val = c - 'a' + 10;
296                 else if (c >= 'A' && c <='F') {
297                         val = c - 'A' + 10;
298                         c -= 'A' - 'a';
299                 }
300                 else
301                         return -1;
302                 hex_pfx[i] = c;
303                 if (!(i & 1))
304                         val <<= 4;
305                 bin_pfx[i >> 1] |= val;
306         }
307         return 0;
308 }
309
310 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
311                           unsigned flags)
312 {
313         int status;
314         char hex_pfx[40];
315         unsigned char bin_pfx[20];
316         struct disambiguate_state ds;
317         int quietly = !!(flags & GET_SHA1_QUIETLY);
318
319         if (len < MINIMUM_ABBREV || len > 40)
320                 return -1;
321         if (prepare_prefixes(name, len, bin_pfx, hex_pfx) < 0)
322                 return -1;
323
324         prepare_alt_odb();
325
326         memset(&ds, 0, sizeof(ds));
327         if (flags & GET_SHA1_COMMIT)
328                 ds.fn = disambiguate_commit_only;
329         else if (flags & GET_SHA1_COMMITTISH)
330                 ds.fn = disambiguate_committish_only;
331         else if (flags & GET_SHA1_TREE)
332                 ds.fn = disambiguate_tree_only;
333         else if (flags & GET_SHA1_TREEISH)
334                 ds.fn = disambiguate_treeish_only;
335         else if (flags & GET_SHA1_BLOB)
336                 ds.fn = disambiguate_blob_only;
337
338         find_short_object_filename(len, hex_pfx, &ds);
339         find_short_packed_object(len, bin_pfx, &ds);
340         status = finish_object_disambiguation(&ds, sha1);
341
342         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
343                 return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
344         return status;
345 }
346
347 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
348 {
349         char hex_pfx[40];
350         unsigned char bin_pfx[20];
351         struct disambiguate_state ds;
352         int len = strlen(prefix);
353
354         if (len < MINIMUM_ABBREV || len > 40)
355                 return -1;
356         if (prepare_prefixes(prefix, len, bin_pfx, hex_pfx) < 0)
357                 return -1;
358
359         prepare_alt_odb();
360
361         memset(&ds, 0, sizeof(ds));
362         ds.always_call_fn = 1;
363         ds.cb_data = cb_data;
364         ds.fn = fn;
365
366         find_short_object_filename(len, hex_pfx, &ds);
367         find_short_packed_object(len, bin_pfx, &ds);
368         return ds.ambiguous;
369 }
370
371 const char *find_unique_abbrev(const unsigned char *sha1, int len)
372 {
373         int status, exists;
374         static char hex[41];
375
376         memcpy(hex, sha1_to_hex(sha1), 40);
377         if (len == 40 || !len)
378                 return hex;
379         exists = has_sha1_file(sha1);
380         while (len < 40) {
381                 unsigned char sha1_ret[20];
382                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
383                 if (exists
384                     ? !status
385                     : status == SHORT_NAME_NOT_FOUND) {
386                         hex[len] = 0;
387                         return hex;
388                 }
389                 len++;
390         }
391         return hex;
392 }
393
394 static int ambiguous_path(const char *path, int len)
395 {
396         int slash = 1;
397         int cnt;
398
399         for (cnt = 0; cnt < len; cnt++) {
400                 switch (*path++) {
401                 case '\0':
402                         break;
403                 case '/':
404                         if (slash)
405                                 break;
406                         slash = 1;
407                         continue;
408                 case '.':
409                         continue;
410                 default:
411                         slash = 0;
412                         continue;
413                 }
414                 break;
415         }
416         return slash;
417 }
418
419 static inline int at_mark(const char *string, int len,
420                           const char **suffix, int nr)
421 {
422         int i;
423
424         for (i = 0; i < nr; i++) {
425                 int suffix_len = strlen(suffix[i]);
426                 if (suffix_len <= len
427                     && !memcmp(string, suffix[i], suffix_len))
428                         return suffix_len;
429         }
430         return 0;
431 }
432
433 static inline int upstream_mark(const char *string, int len)
434 {
435         const char *suffix[] = { "@{upstream}", "@{u}" };
436         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
437 }
438
439 static inline int push_mark(const char *string, int len)
440 {
441         const char *suffix[] = { "@{push}" };
442         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
443 }
444
445 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
446 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
447
448 static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
449                           unsigned int flags)
450 {
451         static const char *warn_msg = "refname '%.*s' is ambiguous.";
452         static const char *object_name_msg = N_(
453         "Git normally never creates a ref that ends with 40 hex characters\n"
454         "because it will be ignored when you just specify 40-hex. These refs\n"
455         "may be created by mistake. For example,\n"
456         "\n"
457         "  git checkout -b $br $(git rev-parse ...)\n"
458         "\n"
459         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
460         "examine these refs and maybe delete them. Turn this message off by\n"
461         "running \"git config advice.objectNameWarning false\"");
462         unsigned char tmp_sha1[20];
463         char *real_ref = NULL;
464         int refs_found = 0;
465         int at, reflog_len, nth_prior = 0;
466
467         if (len == 40 && !get_sha1_hex(str, sha1)) {
468                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
469                         refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
470                         if (refs_found > 0) {
471                                 warning(warn_msg, len, str);
472                                 if (advice_object_name_warning)
473                                         fprintf(stderr, "%s\n", _(object_name_msg));
474                         }
475                         free(real_ref);
476                 }
477                 return 0;
478         }
479
480         /* basic@{time or number or -number} format to query ref-log */
481         reflog_len = at = 0;
482         if (len && str[len-1] == '}') {
483                 for (at = len-4; at >= 0; at--) {
484                         if (str[at] == '@' && str[at+1] == '{') {
485                                 if (str[at+2] == '-') {
486                                         if (at != 0)
487                                                 /* @{-N} not at start */
488                                                 return -1;
489                                         nth_prior = 1;
490                                         continue;
491                                 }
492                                 if (!upstream_mark(str + at, len - at) &&
493                                     !push_mark(str + at, len - at)) {
494                                         reflog_len = (len-1) - (at+2);
495                                         len = at;
496                                 }
497                                 break;
498                         }
499                 }
500         }
501
502         /* Accept only unambiguous ref paths. */
503         if (len && ambiguous_path(str, len))
504                 return -1;
505
506         if (nth_prior) {
507                 struct strbuf buf = STRBUF_INIT;
508                 int detached;
509
510                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
511                         detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
512                         strbuf_release(&buf);
513                         if (detached)
514                                 return 0;
515                 }
516         }
517
518         if (!len && reflog_len)
519                 /* allow "@{...}" to mean the current branch reflog */
520                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
521         else if (reflog_len)
522                 refs_found = dwim_log(str, len, sha1, &real_ref);
523         else
524                 refs_found = dwim_ref(str, len, sha1, &real_ref);
525
526         if (!refs_found)
527                 return -1;
528
529         if (warn_ambiguous_refs && !(flags & GET_SHA1_QUIETLY) &&
530             (refs_found > 1 ||
531              !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
532                 warning(warn_msg, len, str);
533
534         if (reflog_len) {
535                 int nth, i;
536                 unsigned long at_time;
537                 unsigned long co_time;
538                 int co_tz, co_cnt;
539
540                 /* Is it asking for N-th entry, or approxidate? */
541                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
542                         char ch = str[at+2+i];
543                         if ('0' <= ch && ch <= '9')
544                                 nth = nth * 10 + ch - '0';
545                         else
546                                 nth = -1;
547                 }
548                 if (100000000 <= nth) {
549                         at_time = nth;
550                         nth = -1;
551                 } else if (0 <= nth)
552                         at_time = 0;
553                 else {
554                         int errors = 0;
555                         char *tmp = xstrndup(str + at + 2, reflog_len);
556                         at_time = approxidate_careful(tmp, &errors);
557                         free(tmp);
558                         if (errors) {
559                                 free(real_ref);
560                                 return -1;
561                         }
562                 }
563                 if (read_ref_at(real_ref, flags, at_time, nth, sha1, NULL,
564                                 &co_time, &co_tz, &co_cnt)) {
565                         if (!len) {
566                                 if (starts_with(real_ref, "refs/heads/")) {
567                                         str = real_ref + 11;
568                                         len = strlen(real_ref + 11);
569                                 } else {
570                                         /* detached HEAD */
571                                         str = "HEAD";
572                                         len = 4;
573                                 }
574                         }
575                         if (at_time) {
576                                 if (!(flags & GET_SHA1_QUIETLY)) {
577                                         warning("Log for '%.*s' only goes "
578                                                 "back to %s.", len, str,
579                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
580                                 }
581                         } else {
582                                 if (flags & GET_SHA1_QUIETLY) {
583                                         exit(128);
584                                 }
585                                 die("Log for '%.*s' only has %d entries.",
586                                     len, str, co_cnt);
587                         }
588                 }
589         }
590
591         free(real_ref);
592         return 0;
593 }
594
595 static int get_parent(const char *name, int len,
596                       unsigned char *result, int idx)
597 {
598         unsigned char sha1[20];
599         int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
600         struct commit *commit;
601         struct commit_list *p;
602
603         if (ret)
604                 return ret;
605         commit = lookup_commit_reference(sha1);
606         if (parse_commit(commit))
607                 return -1;
608         if (!idx) {
609                 hashcpy(result, commit->object.sha1);
610                 return 0;
611         }
612         p = commit->parents;
613         while (p) {
614                 if (!--idx) {
615                         hashcpy(result, p->item->object.sha1);
616                         return 0;
617                 }
618                 p = p->next;
619         }
620         return -1;
621 }
622
623 static int get_nth_ancestor(const char *name, int len,
624                             unsigned char *result, int generation)
625 {
626         unsigned char sha1[20];
627         struct commit *commit;
628         int ret;
629
630         ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
631         if (ret)
632                 return ret;
633         commit = lookup_commit_reference(sha1);
634         if (!commit)
635                 return -1;
636
637         while (generation--) {
638                 if (parse_commit(commit) || !commit->parents)
639                         return -1;
640                 commit = commit->parents->item;
641         }
642         hashcpy(result, commit->object.sha1);
643         return 0;
644 }
645
646 struct object *peel_to_type(const char *name, int namelen,
647                             struct object *o, enum object_type expected_type)
648 {
649         if (name && !namelen)
650                 namelen = strlen(name);
651         while (1) {
652                 if (!o || (!o->parsed && !parse_object(o->sha1)))
653                         return NULL;
654                 if (expected_type == OBJ_ANY || o->type == expected_type)
655                         return o;
656                 if (o->type == OBJ_TAG)
657                         o = ((struct tag*) o)->tagged;
658                 else if (o->type == OBJ_COMMIT)
659                         o = &(((struct commit *) o)->tree->object);
660                 else {
661                         if (name)
662                                 error("%.*s: expected %s type, but the object "
663                                       "dereferences to %s type",
664                                       namelen, name, typename(expected_type),
665                                       typename(o->type));
666                         return NULL;
667                 }
668         }
669 }
670
671 static int peel_onion(const char *name, int len, unsigned char *sha1)
672 {
673         unsigned char outer[20];
674         const char *sp;
675         unsigned int expected_type = 0;
676         unsigned lookup_flags = 0;
677         struct object *o;
678
679         /*
680          * "ref^{type}" dereferences ref repeatedly until you cannot
681          * dereference anymore, or you get an object of given type,
682          * whichever comes first.  "ref^{}" means just dereference
683          * tags until you get a non-tag.  "ref^0" is a shorthand for
684          * "ref^{commit}".  "commit^{tree}" could be used to find the
685          * top-level tree of the given commit.
686          */
687         if (len < 4 || name[len-1] != '}')
688                 return -1;
689
690         for (sp = name + len - 1; name <= sp; sp--) {
691                 int ch = *sp;
692                 if (ch == '{' && name < sp && sp[-1] == '^')
693                         break;
694         }
695         if (sp <= name)
696                 return -1;
697
698         sp++; /* beginning of type name, or closing brace for empty */
699         if (starts_with(sp, "commit}"))
700                 expected_type = OBJ_COMMIT;
701         else if (starts_with(sp, "tag}"))
702                 expected_type = OBJ_TAG;
703         else if (starts_with(sp, "tree}"))
704                 expected_type = OBJ_TREE;
705         else if (starts_with(sp, "blob}"))
706                 expected_type = OBJ_BLOB;
707         else if (starts_with(sp, "object}"))
708                 expected_type = OBJ_ANY;
709         else if (sp[0] == '}')
710                 expected_type = OBJ_NONE;
711         else if (sp[0] == '/')
712                 expected_type = OBJ_COMMIT;
713         else
714                 return -1;
715
716         if (expected_type == OBJ_COMMIT)
717                 lookup_flags = GET_SHA1_COMMITTISH;
718         else if (expected_type == OBJ_TREE)
719                 lookup_flags = GET_SHA1_TREEISH;
720
721         if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
722                 return -1;
723
724         o = parse_object(outer);
725         if (!o)
726                 return -1;
727         if (!expected_type) {
728                 o = deref_tag(o, name, sp - name - 2);
729                 if (!o || (!o->parsed && !parse_object(o->sha1)))
730                         return -1;
731                 hashcpy(sha1, o->sha1);
732                 return 0;
733         }
734
735         /*
736          * At this point, the syntax look correct, so
737          * if we do not get the needed object, we should
738          * barf.
739          */
740         o = peel_to_type(name, len, o, expected_type);
741         if (!o)
742                 return -1;
743
744         hashcpy(sha1, o->sha1);
745         if (sp[0] == '/') {
746                 /* "$commit^{/foo}" */
747                 char *prefix;
748                 int ret;
749                 struct commit_list *list = NULL;
750
751                 /*
752                  * $commit^{/}. Some regex implementation may reject.
753                  * We don't need regex anyway. '' pattern always matches.
754                  */
755                 if (sp[1] == '}')
756                         return 0;
757
758                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
759                 commit_list_insert((struct commit *)o, &list);
760                 ret = get_sha1_oneline(prefix, sha1, list);
761                 free(prefix);
762                 return ret;
763         }
764         return 0;
765 }
766
767 static int get_describe_name(const char *name, int len, unsigned char *sha1)
768 {
769         const char *cp;
770         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
771
772         for (cp = name + len - 1; name + 2 <= cp; cp--) {
773                 char ch = *cp;
774                 if (!isxdigit(ch)) {
775                         /* We must be looking at g in "SOMETHING-g"
776                          * for it to be describe output.
777                          */
778                         if (ch == 'g' && cp[-1] == '-') {
779                                 cp++;
780                                 len -= cp - name;
781                                 return get_short_sha1(cp, len, sha1, flags);
782                         }
783                 }
784         }
785         return -1;
786 }
787
788 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
789 {
790         int ret, has_suffix;
791         const char *cp;
792
793         /*
794          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
795          */
796         has_suffix = 0;
797         for (cp = name + len - 1; name <= cp; cp--) {
798                 int ch = *cp;
799                 if ('0' <= ch && ch <= '9')
800                         continue;
801                 if (ch == '~' || ch == '^')
802                         has_suffix = ch;
803                 break;
804         }
805
806         if (has_suffix) {
807                 int num = 0;
808                 int len1 = cp - name;
809                 cp++;
810                 while (cp < name + len)
811                         num = num * 10 + *cp++ - '0';
812                 if (!num && len1 == len - 1)
813                         num = 1;
814                 if (has_suffix == '^')
815                         return get_parent(name, len1, sha1, num);
816                 /* else if (has_suffix == '~') -- goes without saying */
817                 return get_nth_ancestor(name, len1, sha1, num);
818         }
819
820         ret = peel_onion(name, len, sha1);
821         if (!ret)
822                 return 0;
823
824         ret = get_sha1_basic(name, len, sha1, lookup_flags);
825         if (!ret)
826                 return 0;
827
828         /* It could be describe output that is "SOMETHING-gXXXX" */
829         ret = get_describe_name(name, len, sha1);
830         if (!ret)
831                 return 0;
832
833         return get_short_sha1(name, len, sha1, lookup_flags);
834 }
835
836 /*
837  * This interprets names like ':/Initial revision of "git"' by searching
838  * through history and returning the first commit whose message starts
839  * the given regular expression.
840  *
841  * For future extension, ':/!' is reserved. If you want to match a message
842  * beginning with a '!', you have to repeat the exclamation mark.
843  */
844
845 /* Remember to update object flag allocation in object.h */
846 #define ONELINE_SEEN (1u<<20)
847
848 static int handle_one_ref(const char *path, const struct object_id *oid,
849                           int flag, void *cb_data)
850 {
851         struct commit_list **list = cb_data;
852         struct object *object = parse_object(oid->hash);
853         if (!object)
854                 return 0;
855         if (object->type == OBJ_TAG) {
856                 object = deref_tag(object, path, strlen(path));
857                 if (!object)
858                         return 0;
859         }
860         if (object->type != OBJ_COMMIT)
861                 return 0;
862         commit_list_insert((struct commit *)object, list);
863         return 0;
864 }
865
866 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
867                             struct commit_list *list)
868 {
869         struct commit_list *backup = NULL, *l;
870         int found = 0;
871         regex_t regex;
872
873         if (prefix[0] == '!') {
874                 if (prefix[1] != '!')
875                         die ("Invalid search pattern: %s", prefix);
876                 prefix++;
877         }
878
879         if (regcomp(&regex, prefix, REG_EXTENDED))
880                 die("Invalid search pattern: %s", prefix);
881
882         for (l = list; l; l = l->next) {
883                 l->item->object.flags |= ONELINE_SEEN;
884                 commit_list_insert(l->item, &backup);
885         }
886         while (list) {
887                 const char *p, *buf;
888                 struct commit *commit;
889                 int matches;
890
891                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
892                 if (!parse_object(commit->object.sha1))
893                         continue;
894                 buf = get_commit_buffer(commit, NULL);
895                 p = strstr(buf, "\n\n");
896                 matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
897                 unuse_commit_buffer(commit, buf);
898
899                 if (matches) {
900                         hashcpy(sha1, commit->object.sha1);
901                         found = 1;
902                         break;
903                 }
904         }
905         regfree(&regex);
906         free_commit_list(list);
907         for (l = backup; l; l = l->next)
908                 clear_commit_marks(l->item, ONELINE_SEEN);
909         free_commit_list(backup);
910         return found ? 0 : -1;
911 }
912
913 struct grab_nth_branch_switch_cbdata {
914         int remaining;
915         struct strbuf buf;
916 };
917
918 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
919                                   const char *email, unsigned long timestamp, int tz,
920                                   const char *message, void *cb_data)
921 {
922         struct grab_nth_branch_switch_cbdata *cb = cb_data;
923         const char *match = NULL, *target = NULL;
924         size_t len;
925
926         if (skip_prefix(message, "checkout: moving from ", &match))
927                 target = strstr(match, " to ");
928
929         if (!match || !target)
930                 return 0;
931         if (--(cb->remaining) == 0) {
932                 len = target - match;
933                 strbuf_reset(&cb->buf);
934                 strbuf_add(&cb->buf, match, len);
935                 return 1; /* we are done */
936         }
937         return 0;
938 }
939
940 /*
941  * Parse @{-N} syntax, return the number of characters parsed
942  * if successful; otherwise signal an error with negative value.
943  */
944 static int interpret_nth_prior_checkout(const char *name, int namelen,
945                                         struct strbuf *buf)
946 {
947         long nth;
948         int retval;
949         struct grab_nth_branch_switch_cbdata cb;
950         const char *brace;
951         char *num_end;
952
953         if (namelen < 4)
954                 return -1;
955         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
956                 return -1;
957         brace = memchr(name, '}', namelen);
958         if (!brace)
959                 return -1;
960         nth = strtol(name + 3, &num_end, 10);
961         if (num_end != brace)
962                 return -1;
963         if (nth <= 0)
964                 return -1;
965         cb.remaining = nth;
966         strbuf_init(&cb.buf, 20);
967
968         retval = 0;
969         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
970                 strbuf_reset(buf);
971                 strbuf_addbuf(buf, &cb.buf);
972                 retval = brace - name + 1;
973         }
974
975         strbuf_release(&cb.buf);
976         return retval;
977 }
978
979 int get_sha1_mb(const char *name, unsigned char *sha1)
980 {
981         struct commit *one, *two;
982         struct commit_list *mbs;
983         unsigned char sha1_tmp[20];
984         const char *dots;
985         int st;
986
987         dots = strstr(name, "...");
988         if (!dots)
989                 return get_sha1(name, sha1);
990         if (dots == name)
991                 st = get_sha1("HEAD", sha1_tmp);
992         else {
993                 struct strbuf sb;
994                 strbuf_init(&sb, dots - name);
995                 strbuf_add(&sb, name, dots - name);
996                 st = get_sha1_committish(sb.buf, sha1_tmp);
997                 strbuf_release(&sb);
998         }
999         if (st)
1000                 return st;
1001         one = lookup_commit_reference_gently(sha1_tmp, 0);
1002         if (!one)
1003                 return -1;
1004
1005         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
1006                 return -1;
1007         two = lookup_commit_reference_gently(sha1_tmp, 0);
1008         if (!two)
1009                 return -1;
1010         mbs = get_merge_bases(one, two);
1011         if (!mbs || mbs->next)
1012                 st = -1;
1013         else {
1014                 st = 0;
1015                 hashcpy(sha1, mbs->item->object.sha1);
1016         }
1017         free_commit_list(mbs);
1018         return st;
1019 }
1020
1021 /* parse @something syntax, when 'something' is not {.*} */
1022 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1023 {
1024         const char *next;
1025
1026         if (len || name[1] == '{')
1027                 return -1;
1028
1029         /* make sure it's a single @, or @@{.*}, not @foo */
1030         next = memchr(name + len + 1, '@', namelen - len - 1);
1031         if (next && next[1] != '{')
1032                 return -1;
1033         if (!next)
1034                 next = name + namelen;
1035         if (next != name + 1)
1036                 return -1;
1037
1038         strbuf_reset(buf);
1039         strbuf_add(buf, "HEAD", 4);
1040         return 1;
1041 }
1042
1043 static int reinterpret(const char *name, int namelen, int len, struct strbuf *buf)
1044 {
1045         /* we have extra data, which might need further processing */
1046         struct strbuf tmp = STRBUF_INIT;
1047         int used = buf->len;
1048         int ret;
1049
1050         strbuf_add(buf, name + len, namelen - len);
1051         ret = interpret_branch_name(buf->buf, buf->len, &tmp);
1052         /* that data was not interpreted, remove our cruft */
1053         if (ret < 0) {
1054                 strbuf_setlen(buf, used);
1055                 return len;
1056         }
1057         strbuf_reset(buf);
1058         strbuf_addbuf(buf, &tmp);
1059         strbuf_release(&tmp);
1060         /* tweak for size of {-N} versus expanded ref name */
1061         return ret - used + len;
1062 }
1063
1064 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1065 {
1066         char *s = shorten_unambiguous_ref(ref, 0);
1067         strbuf_reset(buf);
1068         strbuf_addstr(buf, s);
1069         free(s);
1070 }
1071
1072 static int interpret_branch_mark(const char *name, int namelen,
1073                                  int at, struct strbuf *buf,
1074                                  int (*get_mark)(const char *, int),
1075                                  const char *(*get_data)(struct branch *,
1076                                                          struct strbuf *))
1077 {
1078         int len;
1079         struct branch *branch;
1080         struct strbuf err = STRBUF_INIT;
1081         const char *value;
1082
1083         len = get_mark(name + at, namelen - at);
1084         if (!len)
1085                 return -1;
1086
1087         if (memchr(name, ':', at))
1088                 return -1;
1089
1090         if (at) {
1091                 char *name_str = xmemdupz(name, at);
1092                 branch = branch_get(name_str);
1093                 free(name_str);
1094         } else
1095                 branch = branch_get(NULL);
1096
1097         value = get_data(branch, &err);
1098         if (!value)
1099                 die("%s", err.buf);
1100
1101         set_shortened_ref(buf, value);
1102         return len + at;
1103 }
1104
1105 /*
1106  * This reads short-hand syntax that not only evaluates to a commit
1107  * object name, but also can act as if the end user spelled the name
1108  * of the branch from the command line.
1109  *
1110  * - "@{-N}" finds the name of the Nth previous branch we were on, and
1111  *   places the name of the branch in the given buf and returns the
1112  *   number of characters parsed if successful.
1113  *
1114  * - "<branch>@{upstream}" finds the name of the other ref that
1115  *   <branch> is configured to merge with (missing <branch> defaults
1116  *   to the current branch), and places the name of the branch in the
1117  *   given buf and returns the number of characters parsed if
1118  *   successful.
1119  *
1120  * If the input is not of the accepted format, it returns a negative
1121  * number to signal an error.
1122  *
1123  * If the input was ok but there are not N branch switches in the
1124  * reflog, it returns 0.
1125  */
1126 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
1127 {
1128         char *at;
1129         const char *start;
1130         int len = interpret_nth_prior_checkout(name, namelen, buf);
1131
1132         if (!namelen)
1133                 namelen = strlen(name);
1134
1135         if (!len) {
1136                 return len; /* syntax Ok, not enough switches */
1137         } else if (len > 0) {
1138                 if (len == namelen)
1139                         return len; /* consumed all */
1140                 else
1141                         return reinterpret(name, namelen, len, buf);
1142         }
1143
1144         for (start = name;
1145              (at = memchr(start, '@', namelen - (start - name)));
1146              start = at + 1) {
1147
1148                 len = interpret_empty_at(name, namelen, at - name, buf);
1149                 if (len > 0)
1150                         return reinterpret(name, namelen, len, buf);
1151
1152                 len = interpret_branch_mark(name, namelen, at - name, buf,
1153                                             upstream_mark, branch_get_upstream);
1154                 if (len > 0)
1155                         return len;
1156
1157                 len = interpret_branch_mark(name, namelen, at - name, buf,
1158                                             push_mark, branch_get_push);
1159                 if (len > 0)
1160                         return len;
1161         }
1162
1163         return -1;
1164 }
1165
1166 int strbuf_branchname(struct strbuf *sb, const char *name)
1167 {
1168         int len = strlen(name);
1169         int used = interpret_branch_name(name, len, sb);
1170
1171         if (used == len)
1172                 return 0;
1173         if (used < 0)
1174                 used = 0;
1175         strbuf_add(sb, name + used, len - used);
1176         return len;
1177 }
1178
1179 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1180 {
1181         strbuf_branchname(sb, name);
1182         if (name[0] == '-')
1183                 return -1;
1184         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1185         return check_refname_format(sb->buf, 0);
1186 }
1187
1188 /*
1189  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1190  * notably "xyz^" for "parent of xyz"
1191  */
1192 int get_sha1(const char *name, unsigned char *sha1)
1193 {
1194         struct object_context unused;
1195         return get_sha1_with_context(name, 0, sha1, &unused);
1196 }
1197
1198 /*
1199  * Many callers know that the user meant to name a commit-ish by
1200  * syntactical positions where the object name appears.  Calling this
1201  * function allows the machinery to disambiguate shorter-than-unique
1202  * abbreviated object names between commit-ish and others.
1203  *
1204  * Note that this does NOT error out when the named object is not a
1205  * commit-ish. It is merely to give a hint to the disambiguation
1206  * machinery.
1207  */
1208 int get_sha1_committish(const char *name, unsigned char *sha1)
1209 {
1210         struct object_context unused;
1211         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1212                                      sha1, &unused);
1213 }
1214
1215 int get_sha1_treeish(const char *name, unsigned char *sha1)
1216 {
1217         struct object_context unused;
1218         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1219                                      sha1, &unused);
1220 }
1221
1222 int get_sha1_commit(const char *name, unsigned char *sha1)
1223 {
1224         struct object_context unused;
1225         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1226                                      sha1, &unused);
1227 }
1228
1229 int get_sha1_tree(const char *name, unsigned char *sha1)
1230 {
1231         struct object_context unused;
1232         return get_sha1_with_context(name, GET_SHA1_TREE,
1233                                      sha1, &unused);
1234 }
1235
1236 int get_sha1_blob(const char *name, unsigned char *sha1)
1237 {
1238         struct object_context unused;
1239         return get_sha1_with_context(name, GET_SHA1_BLOB,
1240                                      sha1, &unused);
1241 }
1242
1243 /* Must be called only when object_name:filename doesn't exist. */
1244 static void diagnose_invalid_sha1_path(const char *prefix,
1245                                        const char *filename,
1246                                        const unsigned char *tree_sha1,
1247                                        const char *object_name,
1248                                        int object_name_len)
1249 {
1250         unsigned char sha1[20];
1251         unsigned mode;
1252
1253         if (!prefix)
1254                 prefix = "";
1255
1256         if (file_exists(filename))
1257                 die("Path '%s' exists on disk, but not in '%.*s'.",
1258                     filename, object_name_len, object_name);
1259         if (errno == ENOENT || errno == ENOTDIR) {
1260                 char *fullname = xstrfmt("%s%s", prefix, filename);
1261
1262                 if (!get_tree_entry(tree_sha1, fullname,
1263                                     sha1, &mode)) {
1264                         die("Path '%s' exists, but not '%s'.\n"
1265                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1266                             fullname,
1267                             filename,
1268                             object_name_len, object_name,
1269                             fullname,
1270                             object_name_len, object_name,
1271                             filename);
1272                 }
1273                 die("Path '%s' does not exist in '%.*s'",
1274                     filename, object_name_len, object_name);
1275         }
1276 }
1277
1278 /* Must be called only when :stage:filename doesn't exist. */
1279 static void diagnose_invalid_index_path(int stage,
1280                                         const char *prefix,
1281                                         const char *filename)
1282 {
1283         const struct cache_entry *ce;
1284         int pos;
1285         unsigned namelen = strlen(filename);
1286         unsigned fullnamelen;
1287         char *fullname;
1288
1289         if (!prefix)
1290                 prefix = "";
1291
1292         /* Wrong stage number? */
1293         pos = cache_name_pos(filename, namelen);
1294         if (pos < 0)
1295                 pos = -pos - 1;
1296         if (pos < active_nr) {
1297                 ce = active_cache[pos];
1298                 if (ce_namelen(ce) == namelen &&
1299                     !memcmp(ce->name, filename, namelen))
1300                         die("Path '%s' is in the index, but not at stage %d.\n"
1301                             "Did you mean ':%d:%s'?",
1302                             filename, stage,
1303                             ce_stage(ce), filename);
1304         }
1305
1306         /* Confusion between relative and absolute filenames? */
1307         fullnamelen = namelen + strlen(prefix);
1308         fullname = xmalloc(fullnamelen + 1);
1309         strcpy(fullname, prefix);
1310         strcat(fullname, filename);
1311         pos = cache_name_pos(fullname, fullnamelen);
1312         if (pos < 0)
1313                 pos = -pos - 1;
1314         if (pos < active_nr) {
1315                 ce = active_cache[pos];
1316                 if (ce_namelen(ce) == fullnamelen &&
1317                     !memcmp(ce->name, fullname, fullnamelen))
1318                         die("Path '%s' is in the index, but not '%s'.\n"
1319                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1320                             fullname, filename,
1321                             ce_stage(ce), fullname,
1322                             ce_stage(ce), filename);
1323         }
1324
1325         if (file_exists(filename))
1326                 die("Path '%s' exists on disk, but not in the index.", filename);
1327         if (errno == ENOENT || errno == ENOTDIR)
1328                 die("Path '%s' does not exist (neither on disk nor in the index).",
1329                     filename);
1330
1331         free(fullname);
1332 }
1333
1334
1335 static char *resolve_relative_path(const char *rel)
1336 {
1337         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1338                 return NULL;
1339
1340         if (!startup_info)
1341                 die("BUG: startup_info struct is not initialized.");
1342
1343         if (!is_inside_work_tree())
1344                 die("relative path syntax can't be used outside working tree.");
1345
1346         /* die() inside prefix_path() if resolved path is outside worktree */
1347         return prefix_path(startup_info->prefix,
1348                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1349                            rel);
1350 }
1351
1352 static int get_sha1_with_context_1(const char *name,
1353                                    unsigned flags,
1354                                    const char *prefix,
1355                                    unsigned char *sha1,
1356                                    struct object_context *oc)
1357 {
1358         int ret, bracket_depth;
1359         int namelen = strlen(name);
1360         const char *cp;
1361         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1362
1363         memset(oc, 0, sizeof(*oc));
1364         oc->mode = S_IFINVALID;
1365         ret = get_sha1_1(name, namelen, sha1, flags);
1366         if (!ret)
1367                 return ret;
1368         /*
1369          * sha1:path --> object name of path in ent sha1
1370          * :path -> object name of absolute path in index
1371          * :./path -> object name of path relative to cwd in index
1372          * :[0-3]:path -> object name of path in index at stage
1373          * :/foo -> recent commit matching foo
1374          */
1375         if (name[0] == ':') {
1376                 int stage = 0;
1377                 const struct cache_entry *ce;
1378                 char *new_path = NULL;
1379                 int pos;
1380                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1381                         struct commit_list *list = NULL;
1382
1383                         for_each_ref(handle_one_ref, &list);
1384                         commit_list_sort_by_date(&list);
1385                         return get_sha1_oneline(name + 2, sha1, list);
1386                 }
1387                 if (namelen < 3 ||
1388                     name[2] != ':' ||
1389                     name[1] < '0' || '3' < name[1])
1390                         cp = name + 1;
1391                 else {
1392                         stage = name[1] - '0';
1393                         cp = name + 3;
1394                 }
1395                 new_path = resolve_relative_path(cp);
1396                 if (!new_path) {
1397                         namelen = namelen - (cp - name);
1398                 } else {
1399                         cp = new_path;
1400                         namelen = strlen(cp);
1401                 }
1402
1403                 strlcpy(oc->path, cp, sizeof(oc->path));
1404
1405                 if (!active_cache)
1406                         read_cache();
1407                 pos = cache_name_pos(cp, namelen);
1408                 if (pos < 0)
1409                         pos = -pos - 1;
1410                 while (pos < active_nr) {
1411                         ce = active_cache[pos];
1412                         if (ce_namelen(ce) != namelen ||
1413                             memcmp(ce->name, cp, namelen))
1414                                 break;
1415                         if (ce_stage(ce) == stage) {
1416                                 hashcpy(sha1, ce->sha1);
1417                                 oc->mode = ce->ce_mode;
1418                                 free(new_path);
1419                                 return 0;
1420                         }
1421                         pos++;
1422                 }
1423                 if (only_to_die && name[1] && name[1] != '/')
1424                         diagnose_invalid_index_path(stage, prefix, cp);
1425                 free(new_path);
1426                 return -1;
1427         }
1428         for (cp = name, bracket_depth = 0; *cp; cp++) {
1429                 if (*cp == '{')
1430                         bracket_depth++;
1431                 else if (bracket_depth && *cp == '}')
1432                         bracket_depth--;
1433                 else if (!bracket_depth && *cp == ':')
1434                         break;
1435         }
1436         if (*cp == ':') {
1437                 unsigned char tree_sha1[20];
1438                 int len = cp - name;
1439                 if (!get_sha1_1(name, len, tree_sha1, GET_SHA1_TREEISH)) {
1440                         const char *filename = cp+1;
1441                         char *new_filename = NULL;
1442
1443                         new_filename = resolve_relative_path(filename);
1444                         if (new_filename)
1445                                 filename = new_filename;
1446                         if (flags & GET_SHA1_FOLLOW_SYMLINKS) {
1447                                 ret = get_tree_entry_follow_symlinks(tree_sha1,
1448                                         filename, sha1, &oc->symlink_path,
1449                                         &oc->mode);
1450                         } else {
1451                                 ret = get_tree_entry(tree_sha1, filename,
1452                                                      sha1, &oc->mode);
1453                                 if (ret && only_to_die) {
1454                                         diagnose_invalid_sha1_path(prefix,
1455                                                                    filename,
1456                                                                    tree_sha1,
1457                                                                    name, len);
1458                                 }
1459                         }
1460                         hashcpy(oc->tree, tree_sha1);
1461                         strlcpy(oc->path, filename, sizeof(oc->path));
1462
1463                         free(new_filename);
1464                         return ret;
1465                 } else {
1466                         if (only_to_die)
1467                                 die("Invalid object name '%.*s'.", len, name);
1468                 }
1469         }
1470         return ret;
1471 }
1472
1473 /*
1474  * Call this function when you know "name" given by the end user must
1475  * name an object but it doesn't; the function _may_ die with a better
1476  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1477  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1478  * you have a chance to diagnose the error further.
1479  */
1480 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1481 {
1482         struct object_context oc;
1483         unsigned char sha1[20];
1484         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1485 }
1486
1487 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
1488 {
1489         if (flags & GET_SHA1_FOLLOW_SYMLINKS && flags & GET_SHA1_ONLY_TO_DIE)
1490                 die("BUG: incompatible flags for get_sha1_with_context");
1491         return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
1492 }