Merge branch 'ab/drop-scripted-rebase'
[git] / 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 #include "packfile.h"
13 #include "object-store.h"
14 #include "repository.h"
15 #include "midx.h"
16 #include "commit-reach.h"
17
18 static int get_oid_oneline(const char *, struct object_id *, struct commit_list *);
19
20 typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
21
22 struct disambiguate_state {
23         int len; /* length of prefix in hex chars */
24         char hex_pfx[GIT_MAX_HEXSZ + 1];
25         struct object_id bin_pfx;
26
27         disambiguate_hint_fn fn;
28         void *cb_data;
29         struct object_id candidate;
30         unsigned candidate_exists:1;
31         unsigned candidate_checked:1;
32         unsigned candidate_ok:1;
33         unsigned disambiguate_fn_used:1;
34         unsigned ambiguous:1;
35         unsigned always_call_fn:1;
36 };
37
38 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
39 {
40         if (ds->always_call_fn) {
41                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
42                 return;
43         }
44         if (!ds->candidate_exists) {
45                 /* this is the first candidate */
46                 oidcpy(&ds->candidate, current);
47                 ds->candidate_exists = 1;
48                 return;
49         } else if (oideq(&ds->candidate, current)) {
50                 /* the same as what we already have seen */
51                 return;
52         }
53
54         if (!ds->fn) {
55                 /* cannot disambiguate between ds->candidate and current */
56                 ds->ambiguous = 1;
57                 return;
58         }
59
60         if (!ds->candidate_checked) {
61                 ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
62                 ds->disambiguate_fn_used = 1;
63                 ds->candidate_checked = 1;
64         }
65
66         if (!ds->candidate_ok) {
67                 /* discard the candidate; we know it does not satisfy fn */
68                 oidcpy(&ds->candidate, current);
69                 ds->candidate_checked = 0;
70                 return;
71         }
72
73         /* if we reach this point, we know ds->candidate satisfies fn */
74         if (ds->fn(current, ds->cb_data)) {
75                 /*
76                  * if both current and candidate satisfy fn, we cannot
77                  * disambiguate.
78                  */
79                 ds->candidate_ok = 0;
80                 ds->ambiguous = 1;
81         }
82
83         /* otherwise, current can be discarded and candidate is still good */
84 }
85
86 static int match_sha(unsigned, const unsigned char *, const unsigned char *);
87
88 static void find_short_object_filename(struct disambiguate_state *ds)
89 {
90         struct object_directory *odb;
91
92         for (odb = the_repository->objects->odb;
93              odb && !ds->ambiguous;
94              odb = odb->next) {
95                 int pos;
96                 struct oid_array *loose_objects;
97
98                 loose_objects = odb_loose_cache(odb, &ds->bin_pfx);
99                 pos = oid_array_lookup(loose_objects, &ds->bin_pfx);
100                 if (pos < 0)
101                         pos = -1 - pos;
102                 while (!ds->ambiguous && pos < loose_objects->nr) {
103                         const struct object_id *oid;
104                         oid = loose_objects->oid + pos;
105                         if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
106                                 break;
107                         update_candidates(ds, oid);
108                         pos++;
109                 }
110         }
111 }
112
113 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
114 {
115         do {
116                 if (*a != *b)
117                         return 0;
118                 a++;
119                 b++;
120                 len -= 2;
121         } while (len > 1);
122         if (len)
123                 if ((*a ^ *b) & 0xf0)
124                         return 0;
125         return 1;
126 }
127
128 static void unique_in_midx(struct multi_pack_index *m,
129                            struct disambiguate_state *ds)
130 {
131         uint32_t num, i, first = 0;
132         const struct object_id *current = NULL;
133         num = m->num_objects;
134
135         if (!num)
136                 return;
137
138         bsearch_midx(&ds->bin_pfx, m, &first);
139
140         /*
141          * At this point, "first" is the location of the lowest object
142          * with an object name that could match "bin_pfx".  See if we have
143          * 0, 1 or more objects that actually match(es).
144          */
145         for (i = first; i < num && !ds->ambiguous; i++) {
146                 struct object_id oid;
147                 current = nth_midxed_object_oid(&oid, m, i);
148                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
149                         break;
150                 update_candidates(ds, current);
151         }
152 }
153
154 static void unique_in_pack(struct packed_git *p,
155                            struct disambiguate_state *ds)
156 {
157         uint32_t num, i, first = 0;
158         const struct object_id *current = NULL;
159
160         if (open_pack_index(p) || !p->num_objects)
161                 return;
162
163         num = p->num_objects;
164         bsearch_pack(&ds->bin_pfx, p, &first);
165
166         /*
167          * At this point, "first" is the location of the lowest object
168          * with an object name that could match "bin_pfx".  See if we have
169          * 0, 1 or more objects that actually match(es).
170          */
171         for (i = first; i < num && !ds->ambiguous; i++) {
172                 struct object_id oid;
173                 current = nth_packed_object_oid(&oid, p, i);
174                 if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
175                         break;
176                 update_candidates(ds, current);
177         }
178 }
179
180 static void find_short_packed_object(struct disambiguate_state *ds)
181 {
182         struct multi_pack_index *m;
183         struct packed_git *p;
184
185         for (m = get_multi_pack_index(the_repository); m && !ds->ambiguous;
186              m = m->next)
187                 unique_in_midx(m, ds);
188         for (p = get_packed_git(the_repository); p && !ds->ambiguous;
189              p = p->next)
190                 unique_in_pack(p, ds);
191 }
192
193 static int finish_object_disambiguation(struct disambiguate_state *ds,
194                                         struct object_id *oid)
195 {
196         if (ds->ambiguous)
197                 return SHORT_NAME_AMBIGUOUS;
198
199         if (!ds->candidate_exists)
200                 return MISSING_OBJECT;
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         oidcpy(oid, &ds->candidate);
224         return 0;
225 }
226
227 static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
228 {
229         int kind = oid_object_info(the_repository, oid, 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 = oid_object_info(the_repository, oid, 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(the_repository, parse_object(the_repository, oid),
246                         NULL, 0);
247         if (obj && obj->type == OBJ_COMMIT)
248                 return 1;
249         return 0;
250 }
251
252 static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
253 {
254         int kind = oid_object_info(the_repository, oid, NULL);
255         return kind == OBJ_TREE;
256 }
257
258 static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
259 {
260         struct object *obj;
261         int kind;
262
263         kind = oid_object_info(the_repository, oid, NULL);
264         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
265                 return 1;
266         if (kind != OBJ_TAG)
267                 return 0;
268
269         /* We need to do this the hard way... */
270         obj = deref_tag(the_repository, parse_object(the_repository, oid),
271                         NULL, 0);
272         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
273                 return 1;
274         return 0;
275 }
276
277 static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
278 {
279         int kind = oid_object_info(the_repository, oid, NULL);
280         return kind == OBJ_BLOB;
281 }
282
283 static disambiguate_hint_fn default_disambiguate_hint;
284
285 int set_disambiguate_hint_config(const char *var, const char *value)
286 {
287         static const struct {
288                 const char *name;
289                 disambiguate_hint_fn fn;
290         } hints[] = {
291                 { "none", NULL },
292                 { "commit", disambiguate_commit_only },
293                 { "committish", disambiguate_committish_only },
294                 { "tree", disambiguate_tree_only },
295                 { "treeish", disambiguate_treeish_only },
296                 { "blob", disambiguate_blob_only }
297         };
298         int i;
299
300         if (!value)
301                 return config_error_nonbool(var);
302
303         for (i = 0; i < ARRAY_SIZE(hints); i++) {
304                 if (!strcasecmp(value, hints[i].name)) {
305                         default_disambiguate_hint = hints[i].fn;
306                         return 0;
307                 }
308         }
309
310         return error("unknown hint type for '%s': %s", var, value);
311 }
312
313 static int init_object_disambiguation(const char *name, int len,
314                                       struct disambiguate_state *ds)
315 {
316         int i;
317
318         if (len < MINIMUM_ABBREV || len > the_hash_algo->hexsz)
319                 return -1;
320
321         memset(ds, 0, sizeof(*ds));
322
323         for (i = 0; i < len ;i++) {
324                 unsigned char c = name[i];
325                 unsigned char val;
326                 if (c >= '0' && c <= '9')
327                         val = c - '0';
328                 else if (c >= 'a' && c <= 'f')
329                         val = c - 'a' + 10;
330                 else if (c >= 'A' && c <='F') {
331                         val = c - 'A' + 10;
332                         c -= 'A' - 'a';
333                 }
334                 else
335                         return -1;
336                 ds->hex_pfx[i] = c;
337                 if (!(i & 1))
338                         val <<= 4;
339                 ds->bin_pfx.hash[i >> 1] |= val;
340         }
341
342         ds->len = len;
343         ds->hex_pfx[len] = '\0';
344         prepare_alt_odb(the_repository);
345         return 0;
346 }
347
348 static int show_ambiguous_object(const struct object_id *oid, void *data)
349 {
350         const struct disambiguate_state *ds = data;
351         struct strbuf desc = STRBUF_INIT;
352         int type;
353
354         if (ds->fn && !ds->fn(oid, ds->cb_data))
355                 return 0;
356
357         type = oid_object_info(the_repository, oid, NULL);
358         if (type == OBJ_COMMIT) {
359                 struct commit *commit = lookup_commit(the_repository, oid);
360                 if (commit) {
361                         struct pretty_print_context pp = {0};
362                         pp.date_mode.type = DATE_SHORT;
363                         format_commit_message(commit, " %ad - %s", &desc, &pp);
364                 }
365         } else if (type == OBJ_TAG) {
366                 struct tag *tag = lookup_tag(the_repository, oid);
367                 if (!parse_tag(tag) && tag->tag)
368                         strbuf_addf(&desc, " %s", tag->tag);
369         }
370
371         advise("  %s %s%s",
372                find_unique_abbrev(oid, DEFAULT_ABBREV),
373                type_name(type) ? type_name(type) : "unknown type",
374                desc.buf);
375
376         strbuf_release(&desc);
377         return 0;
378 }
379
380 static int collect_ambiguous(const struct object_id *oid, void *data)
381 {
382         oid_array_append(data, oid);
383         return 0;
384 }
385
386 static int sort_ambiguous(const void *a, const void *b)
387 {
388         int a_type = oid_object_info(the_repository, a, NULL);
389         int b_type = oid_object_info(the_repository, b, NULL);
390         int a_type_sort;
391         int b_type_sort;
392
393         /*
394          * Sorts by hash within the same object type, just as
395          * oid_array_for_each_unique() would do.
396          */
397         if (a_type == b_type)
398                 return oidcmp(a, b);
399
400         /*
401          * Between object types show tags, then commits, and finally
402          * trees and blobs.
403          *
404          * The object_type enum is commit, tree, blob, tag, but we
405          * want tag, commit, tree blob. Cleverly (perhaps too
406          * cleverly) do that with modulus, since the enum assigns 1 to
407          * commit, so tag becomes 0.
408          */
409         a_type_sort = a_type % 4;
410         b_type_sort = b_type % 4;
411         return a_type_sort > b_type_sort ? 1 : -1;
412 }
413
414 static enum get_oid_result get_short_oid(const char *name, int len,
415                                          struct object_id *oid,
416                                          unsigned flags)
417 {
418         int status;
419         struct disambiguate_state ds;
420         int quietly = !!(flags & GET_OID_QUIETLY);
421
422         if (init_object_disambiguation(name, len, &ds) < 0)
423                 return -1;
424
425         if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
426                 BUG("multiple get_short_oid disambiguator flags");
427
428         if (flags & GET_OID_COMMIT)
429                 ds.fn = disambiguate_commit_only;
430         else if (flags & GET_OID_COMMITTISH)
431                 ds.fn = disambiguate_committish_only;
432         else if (flags & GET_OID_TREE)
433                 ds.fn = disambiguate_tree_only;
434         else if (flags & GET_OID_TREEISH)
435                 ds.fn = disambiguate_treeish_only;
436         else if (flags & GET_OID_BLOB)
437                 ds.fn = disambiguate_blob_only;
438         else
439                 ds.fn = default_disambiguate_hint;
440
441         find_short_object_filename(&ds);
442         find_short_packed_object(&ds);
443         status = finish_object_disambiguation(&ds, oid);
444
445         /*
446          * If we didn't find it, do the usual reprepare() slow-path,
447          * since the object may have recently been added to the repository
448          * or migrated from loose to packed.
449          */
450         if (status == MISSING_OBJECT) {
451                 reprepare_packed_git(the_repository);
452                 find_short_object_filename(&ds);
453                 find_short_packed_object(&ds);
454                 status = finish_object_disambiguation(&ds, oid);
455         }
456
457         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
458                 struct oid_array collect = OID_ARRAY_INIT;
459
460                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
461
462                 /*
463                  * We may still have ambiguity if we simply saw a series of
464                  * candidates that did not satisfy our hint function. In
465                  * that case, we still want to show them, so disable the hint
466                  * function entirely.
467                  */
468                 if (!ds.ambiguous)
469                         ds.fn = NULL;
470
471                 advise(_("The candidates are:"));
472                 for_each_abbrev(ds.hex_pfx, collect_ambiguous, &collect);
473                 QSORT(collect.oid, collect.nr, sort_ambiguous);
474
475                 if (oid_array_for_each(&collect, show_ambiguous_object, &ds))
476                         BUG("show_ambiguous_object shouldn't return non-zero");
477                 oid_array_clear(&collect);
478         }
479
480         return status;
481 }
482
483 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
484 {
485         struct oid_array collect = OID_ARRAY_INIT;
486         struct disambiguate_state ds;
487         int ret;
488
489         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
490                 return -1;
491
492         ds.always_call_fn = 1;
493         ds.fn = collect_ambiguous;
494         ds.cb_data = &collect;
495         find_short_object_filename(&ds);
496         find_short_packed_object(&ds);
497
498         ret = oid_array_for_each_unique(&collect, fn, cb_data);
499         oid_array_clear(&collect);
500         return ret;
501 }
502
503 /*
504  * Return the slot of the most-significant bit set in "val". There are various
505  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
506  * probably not a big deal here.
507  */
508 static unsigned msb(unsigned long val)
509 {
510         unsigned r = 0;
511         while (val >>= 1)
512                 r++;
513         return r;
514 }
515
516 struct min_abbrev_data {
517         unsigned int init_len;
518         unsigned int cur_len;
519         char *hex;
520         const struct object_id *oid;
521 };
522
523 static inline char get_hex_char_from_oid(const struct object_id *oid,
524                                          unsigned int pos)
525 {
526         static const char hex[] = "0123456789abcdef";
527
528         if ((pos & 1) == 0)
529                 return hex[oid->hash[pos >> 1] >> 4];
530         else
531                 return hex[oid->hash[pos >> 1] & 0xf];
532 }
533
534 static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
535 {
536         struct min_abbrev_data *mad = cb_data;
537
538         unsigned int i = mad->init_len;
539         while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
540                 i++;
541
542         if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
543                 mad->cur_len = i + 1;
544
545         return 0;
546 }
547
548 static void find_abbrev_len_for_midx(struct multi_pack_index *m,
549                                      struct min_abbrev_data *mad)
550 {
551         int match = 0;
552         uint32_t num, first = 0;
553         struct object_id oid;
554         const struct object_id *mad_oid;
555
556         if (!m->num_objects)
557                 return;
558
559         num = m->num_objects;
560         mad_oid = mad->oid;
561         match = bsearch_midx(mad_oid, m, &first);
562
563         /*
564          * first is now the position in the packfile where we would insert
565          * mad->hash if it does not exist (or the position of mad->hash if
566          * it does exist). Hence, we consider a maximum of two objects
567          * nearby for the abbreviation length.
568          */
569         mad->init_len = 0;
570         if (!match) {
571                 if (nth_midxed_object_oid(&oid, m, first))
572                         extend_abbrev_len(&oid, mad);
573         } else if (first < num - 1) {
574                 if (nth_midxed_object_oid(&oid, m, first + 1))
575                         extend_abbrev_len(&oid, mad);
576         }
577         if (first > 0) {
578                 if (nth_midxed_object_oid(&oid, m, first - 1))
579                         extend_abbrev_len(&oid, mad);
580         }
581         mad->init_len = mad->cur_len;
582 }
583
584 static void find_abbrev_len_for_pack(struct packed_git *p,
585                                      struct min_abbrev_data *mad)
586 {
587         int match = 0;
588         uint32_t num, first = 0;
589         struct object_id oid;
590         const struct object_id *mad_oid;
591
592         if (open_pack_index(p) || !p->num_objects)
593                 return;
594
595         num = p->num_objects;
596         mad_oid = mad->oid;
597         match = bsearch_pack(mad_oid, p, &first);
598
599         /*
600          * first is now the position in the packfile where we would insert
601          * mad->hash if it does not exist (or the position of mad->hash if
602          * it does exist). Hence, we consider a maximum of two objects
603          * nearby for the abbreviation length.
604          */
605         mad->init_len = 0;
606         if (!match) {
607                 if (nth_packed_object_oid(&oid, p, first))
608                         extend_abbrev_len(&oid, mad);
609         } else if (first < num - 1) {
610                 if (nth_packed_object_oid(&oid, p, first + 1))
611                         extend_abbrev_len(&oid, mad);
612         }
613         if (first > 0) {
614                 if (nth_packed_object_oid(&oid, p, first - 1))
615                         extend_abbrev_len(&oid, mad);
616         }
617         mad->init_len = mad->cur_len;
618 }
619
620 static void find_abbrev_len_packed(struct min_abbrev_data *mad)
621 {
622         struct multi_pack_index *m;
623         struct packed_git *p;
624
625         for (m = get_multi_pack_index(the_repository); m; m = m->next)
626                 find_abbrev_len_for_midx(m, mad);
627         for (p = get_packed_git(the_repository); p; p = p->next)
628                 find_abbrev_len_for_pack(p, mad);
629 }
630
631 int find_unique_abbrev_r(char *hex, const struct object_id *oid, int len)
632 {
633         struct disambiguate_state ds;
634         struct min_abbrev_data mad;
635         struct object_id oid_ret;
636         const unsigned hexsz = the_hash_algo->hexsz;
637
638         if (len < 0) {
639                 unsigned long count = approximate_object_count();
640                 /*
641                  * Add one because the MSB only tells us the highest bit set,
642                  * not including the value of all the _other_ bits (so "15"
643                  * is only one off of 2^4, but the MSB is the 3rd bit.
644                  */
645                 len = msb(count) + 1;
646                 /*
647                  * We now know we have on the order of 2^len objects, which
648                  * expects a collision at 2^(len/2). But we also care about hex
649                  * chars, not bits, and there are 4 bits per hex. So all
650                  * together we need to divide by 2 and round up.
651                  */
652                 len = DIV_ROUND_UP(len, 2);
653                 /*
654                  * For very small repos, we stick with our regular fallback.
655                  */
656                 if (len < FALLBACK_DEFAULT_ABBREV)
657                         len = FALLBACK_DEFAULT_ABBREV;
658         }
659
660         oid_to_hex_r(hex, oid);
661         if (len == hexsz || !len)
662                 return hexsz;
663
664         mad.init_len = len;
665         mad.cur_len = len;
666         mad.hex = hex;
667         mad.oid = oid;
668
669         find_abbrev_len_packed(&mad);
670
671         if (init_object_disambiguation(hex, mad.cur_len, &ds) < 0)
672                 return -1;
673
674         ds.fn = extend_abbrev_len;
675         ds.always_call_fn = 1;
676         ds.cb_data = (void *)&mad;
677
678         find_short_object_filename(&ds);
679         (void)finish_object_disambiguation(&ds, &oid_ret);
680
681         hex[mad.cur_len] = 0;
682         return mad.cur_len;
683 }
684
685 const char *find_unique_abbrev(const struct object_id *oid, int len)
686 {
687         static int bufno;
688         static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
689         char *hex = hexbuffer[bufno];
690         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
691         find_unique_abbrev_r(hex, oid, len);
692         return hex;
693 }
694
695 static int ambiguous_path(const char *path, int len)
696 {
697         int slash = 1;
698         int cnt;
699
700         for (cnt = 0; cnt < len; cnt++) {
701                 switch (*path++) {
702                 case '\0':
703                         break;
704                 case '/':
705                         if (slash)
706                                 break;
707                         slash = 1;
708                         continue;
709                 case '.':
710                         continue;
711                 default:
712                         slash = 0;
713                         continue;
714                 }
715                 break;
716         }
717         return slash;
718 }
719
720 static inline int at_mark(const char *string, int len,
721                           const char **suffix, int nr)
722 {
723         int i;
724
725         for (i = 0; i < nr; i++) {
726                 int suffix_len = strlen(suffix[i]);
727                 if (suffix_len <= len
728                     && !strncasecmp(string, suffix[i], suffix_len))
729                         return suffix_len;
730         }
731         return 0;
732 }
733
734 static inline int upstream_mark(const char *string, int len)
735 {
736         const char *suffix[] = { "@{upstream}", "@{u}" };
737         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
738 }
739
740 static inline int push_mark(const char *string, int len)
741 {
742         const char *suffix[] = { "@{push}" };
743         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
744 }
745
746 static enum get_oid_result get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
747 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
748
749 static int get_oid_basic(const char *str, int len, struct object_id *oid,
750                           unsigned int flags)
751 {
752         static const char *warn_msg = "refname '%.*s' is ambiguous.";
753         static const char *object_name_msg = N_(
754         "Git normally never creates a ref that ends with 40 hex characters\n"
755         "because it will be ignored when you just specify 40-hex. These refs\n"
756         "may be created by mistake. For example,\n"
757         "\n"
758         "  git checkout -b $br $(git rev-parse ...)\n"
759         "\n"
760         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
761         "examine these refs and maybe delete them. Turn this message off by\n"
762         "running \"git config advice.objectNameWarning false\"");
763         struct object_id tmp_oid;
764         char *real_ref = NULL;
765         int refs_found = 0;
766         int at, reflog_len, nth_prior = 0;
767
768         if (len == the_hash_algo->hexsz && !get_oid_hex(str, oid)) {
769                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
770                         refs_found = dwim_ref(str, len, &tmp_oid, &real_ref);
771                         if (refs_found > 0) {
772                                 warning(warn_msg, len, str);
773                                 if (advice_object_name_warning)
774                                         fprintf(stderr, "%s\n", _(object_name_msg));
775                         }
776                         free(real_ref);
777                 }
778                 return 0;
779         }
780
781         /* basic@{time or number or -number} format to query ref-log */
782         reflog_len = at = 0;
783         if (len && str[len-1] == '}') {
784                 for (at = len-4; at >= 0; at--) {
785                         if (str[at] == '@' && str[at+1] == '{') {
786                                 if (str[at+2] == '-') {
787                                         if (at != 0)
788                                                 /* @{-N} not at start */
789                                                 return -1;
790                                         nth_prior = 1;
791                                         continue;
792                                 }
793                                 if (!upstream_mark(str + at, len - at) &&
794                                     !push_mark(str + at, len - at)) {
795                                         reflog_len = (len-1) - (at+2);
796                                         len = at;
797                                 }
798                                 break;
799                         }
800                 }
801         }
802
803         /* Accept only unambiguous ref paths. */
804         if (len && ambiguous_path(str, len))
805                 return -1;
806
807         if (nth_prior) {
808                 struct strbuf buf = STRBUF_INIT;
809                 int detached;
810
811                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
812                         detached = (buf.len == the_hash_algo->hexsz && !get_oid_hex(buf.buf, oid));
813                         strbuf_release(&buf);
814                         if (detached)
815                                 return 0;
816                 }
817         }
818
819         if (!len && reflog_len)
820                 /* allow "@{...}" to mean the current branch reflog */
821                 refs_found = dwim_ref("HEAD", 4, oid, &real_ref);
822         else if (reflog_len)
823                 refs_found = dwim_log(str, len, oid, &real_ref);
824         else
825                 refs_found = dwim_ref(str, len, oid, &real_ref);
826
827         if (!refs_found)
828                 return -1;
829
830         if (warn_ambiguous_refs && !(flags & GET_OID_QUIETLY) &&
831             (refs_found > 1 ||
832              !get_short_oid(str, len, &tmp_oid, GET_OID_QUIETLY)))
833                 warning(warn_msg, len, str);
834
835         if (reflog_len) {
836                 int nth, i;
837                 timestamp_t at_time;
838                 timestamp_t co_time;
839                 int co_tz, co_cnt;
840
841                 /* Is it asking for N-th entry, or approxidate? */
842                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
843                         char ch = str[at+2+i];
844                         if ('0' <= ch && ch <= '9')
845                                 nth = nth * 10 + ch - '0';
846                         else
847                                 nth = -1;
848                 }
849                 if (100000000 <= nth) {
850                         at_time = nth;
851                         nth = -1;
852                 } else if (0 <= nth)
853                         at_time = 0;
854                 else {
855                         int errors = 0;
856                         char *tmp = xstrndup(str + at + 2, reflog_len);
857                         at_time = approxidate_careful(tmp, &errors);
858                         free(tmp);
859                         if (errors) {
860                                 free(real_ref);
861                                 return -1;
862                         }
863                 }
864                 if (read_ref_at(real_ref, flags, at_time, nth, oid, NULL,
865                                 &co_time, &co_tz, &co_cnt)) {
866                         if (!len) {
867                                 if (starts_with(real_ref, "refs/heads/")) {
868                                         str = real_ref + 11;
869                                         len = strlen(real_ref + 11);
870                                 } else {
871                                         /* detached HEAD */
872                                         str = "HEAD";
873                                         len = 4;
874                                 }
875                         }
876                         if (at_time) {
877                                 if (!(flags & GET_OID_QUIETLY)) {
878                                         warning("Log for '%.*s' only goes "
879                                                 "back to %s.", len, str,
880                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
881                                 }
882                         } else {
883                                 if (flags & GET_OID_QUIETLY) {
884                                         exit(128);
885                                 }
886                                 die("Log for '%.*s' only has %d entries.",
887                                     len, str, co_cnt);
888                         }
889                 }
890         }
891
892         free(real_ref);
893         return 0;
894 }
895
896 static enum get_oid_result get_parent(const char *name, int len,
897                                       struct object_id *result, int idx)
898 {
899         struct object_id oid;
900         enum get_oid_result ret = get_oid_1(name, len, &oid,
901                                             GET_OID_COMMITTISH);
902         struct commit *commit;
903         struct commit_list *p;
904
905         if (ret)
906                 return ret;
907         commit = lookup_commit_reference(the_repository, &oid);
908         if (parse_commit(commit))
909                 return MISSING_OBJECT;
910         if (!idx) {
911                 oidcpy(result, &commit->object.oid);
912                 return FOUND;
913         }
914         p = commit->parents;
915         while (p) {
916                 if (!--idx) {
917                         oidcpy(result, &p->item->object.oid);
918                         return FOUND;
919                 }
920                 p = p->next;
921         }
922         return MISSING_OBJECT;
923 }
924
925 static enum get_oid_result get_nth_ancestor(const char *name, int len,
926                                             struct object_id *result,
927                                             int generation)
928 {
929         struct object_id oid;
930         struct commit *commit;
931         int ret;
932
933         ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
934         if (ret)
935                 return ret;
936         commit = lookup_commit_reference(the_repository, &oid);
937         if (!commit)
938                 return MISSING_OBJECT;
939
940         while (generation--) {
941                 if (parse_commit(commit) || !commit->parents)
942                         return MISSING_OBJECT;
943                 commit = commit->parents->item;
944         }
945         oidcpy(result, &commit->object.oid);
946         return FOUND;
947 }
948
949 struct object *peel_to_type(const char *name, int namelen,
950                             struct object *o, enum object_type expected_type)
951 {
952         if (name && !namelen)
953                 namelen = strlen(name);
954         while (1) {
955                 if (!o || (!o->parsed && !parse_object(the_repository, &o->oid)))
956                         return NULL;
957                 if (expected_type == OBJ_ANY || o->type == expected_type)
958                         return o;
959                 if (o->type == OBJ_TAG)
960                         o = ((struct tag*) o)->tagged;
961                 else if (o->type == OBJ_COMMIT)
962                         o = &(get_commit_tree(((struct commit *)o))->object);
963                 else {
964                         if (name)
965                                 error("%.*s: expected %s type, but the object "
966                                       "dereferences to %s type",
967                                       namelen, name, type_name(expected_type),
968                                       type_name(o->type));
969                         return NULL;
970                 }
971         }
972 }
973
974 static int peel_onion(const char *name, int len, struct object_id *oid,
975                       unsigned lookup_flags)
976 {
977         struct object_id outer;
978         const char *sp;
979         unsigned int expected_type = 0;
980         struct object *o;
981
982         /*
983          * "ref^{type}" dereferences ref repeatedly until you cannot
984          * dereference anymore, or you get an object of given type,
985          * whichever comes first.  "ref^{}" means just dereference
986          * tags until you get a non-tag.  "ref^0" is a shorthand for
987          * "ref^{commit}".  "commit^{tree}" could be used to find the
988          * top-level tree of the given commit.
989          */
990         if (len < 4 || name[len-1] != '}')
991                 return -1;
992
993         for (sp = name + len - 1; name <= sp; sp--) {
994                 int ch = *sp;
995                 if (ch == '{' && name < sp && sp[-1] == '^')
996                         break;
997         }
998         if (sp <= name)
999                 return -1;
1000
1001         sp++; /* beginning of type name, or closing brace for empty */
1002         if (starts_with(sp, "commit}"))
1003                 expected_type = OBJ_COMMIT;
1004         else if (starts_with(sp, "tag}"))
1005                 expected_type = OBJ_TAG;
1006         else if (starts_with(sp, "tree}"))
1007                 expected_type = OBJ_TREE;
1008         else if (starts_with(sp, "blob}"))
1009                 expected_type = OBJ_BLOB;
1010         else if (starts_with(sp, "object}"))
1011                 expected_type = OBJ_ANY;
1012         else if (sp[0] == '}')
1013                 expected_type = OBJ_NONE;
1014         else if (sp[0] == '/')
1015                 expected_type = OBJ_COMMIT;
1016         else
1017                 return -1;
1018
1019         lookup_flags &= ~GET_OID_DISAMBIGUATORS;
1020         if (expected_type == OBJ_COMMIT)
1021                 lookup_flags |= GET_OID_COMMITTISH;
1022         else if (expected_type == OBJ_TREE)
1023                 lookup_flags |= GET_OID_TREEISH;
1024
1025         if (get_oid_1(name, sp - name - 2, &outer, lookup_flags))
1026                 return -1;
1027
1028         o = parse_object(the_repository, &outer);
1029         if (!o)
1030                 return -1;
1031         if (!expected_type) {
1032                 o = deref_tag(the_repository, o, name, sp - name - 2);
1033                 if (!o || (!o->parsed && !parse_object(the_repository, &o->oid)))
1034                         return -1;
1035                 oidcpy(oid, &o->oid);
1036                 return 0;
1037         }
1038
1039         /*
1040          * At this point, the syntax look correct, so
1041          * if we do not get the needed object, we should
1042          * barf.
1043          */
1044         o = peel_to_type(name, len, o, expected_type);
1045         if (!o)
1046                 return -1;
1047
1048         oidcpy(oid, &o->oid);
1049         if (sp[0] == '/') {
1050                 /* "$commit^{/foo}" */
1051                 char *prefix;
1052                 int ret;
1053                 struct commit_list *list = NULL;
1054
1055                 /*
1056                  * $commit^{/}. Some regex implementation may reject.
1057                  * We don't need regex anyway. '' pattern always matches.
1058                  */
1059                 if (sp[1] == '}')
1060                         return 0;
1061
1062                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
1063                 commit_list_insert((struct commit *)o, &list);
1064                 ret = get_oid_oneline(prefix, oid, list);
1065                 free(prefix);
1066                 return ret;
1067         }
1068         return 0;
1069 }
1070
1071 static int get_describe_name(const char *name, int len, struct object_id *oid)
1072 {
1073         const char *cp;
1074         unsigned flags = GET_OID_QUIETLY | GET_OID_COMMIT;
1075
1076         for (cp = name + len - 1; name + 2 <= cp; cp--) {
1077                 char ch = *cp;
1078                 if (!isxdigit(ch)) {
1079                         /* We must be looking at g in "SOMETHING-g"
1080                          * for it to be describe output.
1081                          */
1082                         if (ch == 'g' && cp[-1] == '-') {
1083                                 cp++;
1084                                 len -= cp - name;
1085                                 return get_short_oid(cp, len, oid, flags);
1086                         }
1087                 }
1088         }
1089         return -1;
1090 }
1091
1092 static enum get_oid_result get_oid_1(const char *name, int len,
1093                                      struct object_id *oid,
1094                                      unsigned lookup_flags)
1095 {
1096         int ret, has_suffix;
1097         const char *cp;
1098
1099         /*
1100          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
1101          */
1102         has_suffix = 0;
1103         for (cp = name + len - 1; name <= cp; cp--) {
1104                 int ch = *cp;
1105                 if ('0' <= ch && ch <= '9')
1106                         continue;
1107                 if (ch == '~' || ch == '^')
1108                         has_suffix = ch;
1109                 break;
1110         }
1111
1112         if (has_suffix) {
1113                 int num = 0;
1114                 int len1 = cp - name;
1115                 cp++;
1116                 while (cp < name + len)
1117                         num = num * 10 + *cp++ - '0';
1118                 if (!num && len1 == len - 1)
1119                         num = 1;
1120                 if (has_suffix == '^')
1121                         return get_parent(name, len1, oid, num);
1122                 /* else if (has_suffix == '~') -- goes without saying */
1123                 return get_nth_ancestor(name, len1, oid, num);
1124         }
1125
1126         ret = peel_onion(name, len, oid, lookup_flags);
1127         if (!ret)
1128                 return FOUND;
1129
1130         ret = get_oid_basic(name, len, oid, lookup_flags);
1131         if (!ret)
1132                 return FOUND;
1133
1134         /* It could be describe output that is "SOMETHING-gXXXX" */
1135         ret = get_describe_name(name, len, oid);
1136         if (!ret)
1137                 return FOUND;
1138
1139         return get_short_oid(name, len, oid, lookup_flags);
1140 }
1141
1142 /*
1143  * This interprets names like ':/Initial revision of "git"' by searching
1144  * through history and returning the first commit whose message starts
1145  * the given regular expression.
1146  *
1147  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
1148  *
1149  * For a literal '!' character at the beginning of a pattern, you have to repeat
1150  * that, like: ':/!!foo'
1151  *
1152  * For future extension, all other sequences beginning with ':/!' are reserved.
1153  */
1154
1155 /* Remember to update object flag allocation in object.h */
1156 #define ONELINE_SEEN (1u<<20)
1157
1158 static int handle_one_ref(const char *path, const struct object_id *oid,
1159                           int flag, void *cb_data)
1160 {
1161         struct commit_list **list = cb_data;
1162         struct object *object = parse_object(the_repository, oid);
1163         if (!object)
1164                 return 0;
1165         if (object->type == OBJ_TAG) {
1166                 object = deref_tag(the_repository, object, path,
1167                                    strlen(path));
1168                 if (!object)
1169                         return 0;
1170         }
1171         if (object->type != OBJ_COMMIT)
1172                 return 0;
1173         commit_list_insert((struct commit *)object, list);
1174         return 0;
1175 }
1176
1177 static int get_oid_oneline(const char *prefix, struct object_id *oid,
1178                             struct commit_list *list)
1179 {
1180         struct commit_list *backup = NULL, *l;
1181         int found = 0;
1182         int negative = 0;
1183         regex_t regex;
1184
1185         if (prefix[0] == '!') {
1186                 prefix++;
1187
1188                 if (prefix[0] == '-') {
1189                         prefix++;
1190                         negative = 1;
1191                 } else if (prefix[0] != '!') {
1192                         return -1;
1193                 }
1194         }
1195
1196         if (regcomp(&regex, prefix, REG_EXTENDED))
1197                 return -1;
1198
1199         for (l = list; l; l = l->next) {
1200                 l->item->object.flags |= ONELINE_SEEN;
1201                 commit_list_insert(l->item, &backup);
1202         }
1203         while (list) {
1204                 const char *p, *buf;
1205                 struct commit *commit;
1206                 int matches;
1207
1208                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1209                 if (!parse_object(the_repository, &commit->object.oid))
1210                         continue;
1211                 buf = get_commit_buffer(commit, NULL);
1212                 p = strstr(buf, "\n\n");
1213                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1214                 unuse_commit_buffer(commit, buf);
1215
1216                 if (matches) {
1217                         oidcpy(oid, &commit->object.oid);
1218                         found = 1;
1219                         break;
1220                 }
1221         }
1222         regfree(&regex);
1223         free_commit_list(list);
1224         for (l = backup; l; l = l->next)
1225                 clear_commit_marks(l->item, ONELINE_SEEN);
1226         free_commit_list(backup);
1227         return found ? 0 : -1;
1228 }
1229
1230 struct grab_nth_branch_switch_cbdata {
1231         int remaining;
1232         struct strbuf buf;
1233 };
1234
1235 static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
1236                                   const char *email, timestamp_t timestamp, int tz,
1237                                   const char *message, void *cb_data)
1238 {
1239         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1240         const char *match = NULL, *target = NULL;
1241         size_t len;
1242
1243         if (skip_prefix(message, "checkout: moving from ", &match))
1244                 target = strstr(match, " to ");
1245
1246         if (!match || !target)
1247                 return 0;
1248         if (--(cb->remaining) == 0) {
1249                 len = target - match;
1250                 strbuf_reset(&cb->buf);
1251                 strbuf_add(&cb->buf, match, len);
1252                 return 1; /* we are done */
1253         }
1254         return 0;
1255 }
1256
1257 /*
1258  * Parse @{-N} syntax, return the number of characters parsed
1259  * if successful; otherwise signal an error with negative value.
1260  */
1261 static int interpret_nth_prior_checkout(const char *name, int namelen,
1262                                         struct strbuf *buf)
1263 {
1264         long nth;
1265         int retval;
1266         struct grab_nth_branch_switch_cbdata cb;
1267         const char *brace;
1268         char *num_end;
1269
1270         if (namelen < 4)
1271                 return -1;
1272         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1273                 return -1;
1274         brace = memchr(name, '}', namelen);
1275         if (!brace)
1276                 return -1;
1277         nth = strtol(name + 3, &num_end, 10);
1278         if (num_end != brace)
1279                 return -1;
1280         if (nth <= 0)
1281                 return -1;
1282         cb.remaining = nth;
1283         strbuf_init(&cb.buf, 20);
1284
1285         retval = 0;
1286         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1287                 strbuf_reset(buf);
1288                 strbuf_addbuf(buf, &cb.buf);
1289                 retval = brace - name + 1;
1290         }
1291
1292         strbuf_release(&cb.buf);
1293         return retval;
1294 }
1295
1296 int get_oid_mb(const char *name, struct object_id *oid)
1297 {
1298         struct commit *one, *two;
1299         struct commit_list *mbs;
1300         struct object_id oid_tmp;
1301         const char *dots;
1302         int st;
1303
1304         dots = strstr(name, "...");
1305         if (!dots)
1306                 return get_oid(name, oid);
1307         if (dots == name)
1308                 st = get_oid("HEAD", &oid_tmp);
1309         else {
1310                 struct strbuf sb;
1311                 strbuf_init(&sb, dots - name);
1312                 strbuf_add(&sb, name, dots - name);
1313                 st = get_oid_committish(sb.buf, &oid_tmp);
1314                 strbuf_release(&sb);
1315         }
1316         if (st)
1317                 return st;
1318         one = lookup_commit_reference_gently(the_repository, &oid_tmp, 0);
1319         if (!one)
1320                 return -1;
1321
1322         if (get_oid_committish(dots[3] ? (dots + 3) : "HEAD", &oid_tmp))
1323                 return -1;
1324         two = lookup_commit_reference_gently(the_repository, &oid_tmp, 0);
1325         if (!two)
1326                 return -1;
1327         mbs = get_merge_bases(one, two);
1328         if (!mbs || mbs->next)
1329                 st = -1;
1330         else {
1331                 st = 0;
1332                 oidcpy(oid, &mbs->item->object.oid);
1333         }
1334         free_commit_list(mbs);
1335         return st;
1336 }
1337
1338 /* parse @something syntax, when 'something' is not {.*} */
1339 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1340 {
1341         const char *next;
1342
1343         if (len || name[1] == '{')
1344                 return -1;
1345
1346         /* make sure it's a single @, or @@{.*}, not @foo */
1347         next = memchr(name + len + 1, '@', namelen - len - 1);
1348         if (next && next[1] != '{')
1349                 return -1;
1350         if (!next)
1351                 next = name + namelen;
1352         if (next != name + 1)
1353                 return -1;
1354
1355         strbuf_reset(buf);
1356         strbuf_add(buf, "HEAD", 4);
1357         return 1;
1358 }
1359
1360 static int reinterpret(const char *name, int namelen, int len,
1361                        struct strbuf *buf, unsigned allowed)
1362 {
1363         /* we have extra data, which might need further processing */
1364         struct strbuf tmp = STRBUF_INIT;
1365         int used = buf->len;
1366         int ret;
1367
1368         strbuf_add(buf, name + len, namelen - len);
1369         ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
1370         /* that data was not interpreted, remove our cruft */
1371         if (ret < 0) {
1372                 strbuf_setlen(buf, used);
1373                 return len;
1374         }
1375         strbuf_reset(buf);
1376         strbuf_addbuf(buf, &tmp);
1377         strbuf_release(&tmp);
1378         /* tweak for size of {-N} versus expanded ref name */
1379         return ret - used + len;
1380 }
1381
1382 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1383 {
1384         char *s = shorten_unambiguous_ref(ref, 0);
1385         strbuf_reset(buf);
1386         strbuf_addstr(buf, s);
1387         free(s);
1388 }
1389
1390 static int branch_interpret_allowed(const char *refname, unsigned allowed)
1391 {
1392         if (!allowed)
1393                 return 1;
1394
1395         if ((allowed & INTERPRET_BRANCH_LOCAL) &&
1396             starts_with(refname, "refs/heads/"))
1397                 return 1;
1398         if ((allowed & INTERPRET_BRANCH_REMOTE) &&
1399             starts_with(refname, "refs/remotes/"))
1400                 return 1;
1401
1402         return 0;
1403 }
1404
1405 static int interpret_branch_mark(const char *name, int namelen,
1406                                  int at, struct strbuf *buf,
1407                                  int (*get_mark)(const char *, int),
1408                                  const char *(*get_data)(struct branch *,
1409                                                          struct strbuf *),
1410                                  unsigned allowed)
1411 {
1412         int len;
1413         struct branch *branch;
1414         struct strbuf err = STRBUF_INIT;
1415         const char *value;
1416
1417         len = get_mark(name + at, namelen - at);
1418         if (!len)
1419                 return -1;
1420
1421         if (memchr(name, ':', at))
1422                 return -1;
1423
1424         if (at) {
1425                 char *name_str = xmemdupz(name, at);
1426                 branch = branch_get(name_str);
1427                 free(name_str);
1428         } else
1429                 branch = branch_get(NULL);
1430
1431         value = get_data(branch, &err);
1432         if (!value)
1433                 die("%s", err.buf);
1434
1435         if (!branch_interpret_allowed(value, allowed))
1436                 return -1;
1437
1438         set_shortened_ref(buf, value);
1439         return len + at;
1440 }
1441
1442 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
1443                           unsigned allowed)
1444 {
1445         char *at;
1446         const char *start;
1447         int len;
1448
1449         if (!namelen)
1450                 namelen = strlen(name);
1451
1452         if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
1453                 len = interpret_nth_prior_checkout(name, namelen, buf);
1454                 if (!len) {
1455                         return len; /* syntax Ok, not enough switches */
1456                 } else if (len > 0) {
1457                         if (len == namelen)
1458                                 return len; /* consumed all */
1459                         else
1460                                 return reinterpret(name, namelen, len, buf, allowed);
1461                 }
1462         }
1463
1464         for (start = name;
1465              (at = memchr(start, '@', namelen - (start - name)));
1466              start = at + 1) {
1467
1468                 if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
1469                         len = interpret_empty_at(name, namelen, at - name, buf);
1470                         if (len > 0)
1471                                 return reinterpret(name, namelen, len, buf,
1472                                                    allowed);
1473                 }
1474
1475                 len = interpret_branch_mark(name, namelen, at - name, buf,
1476                                             upstream_mark, branch_get_upstream,
1477                                             allowed);
1478                 if (len > 0)
1479                         return len;
1480
1481                 len = interpret_branch_mark(name, namelen, at - name, buf,
1482                                             push_mark, branch_get_push,
1483                                             allowed);
1484                 if (len > 0)
1485                         return len;
1486         }
1487
1488         return -1;
1489 }
1490
1491 void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
1492 {
1493         int len = strlen(name);
1494         int used = interpret_branch_name(name, len, sb, allowed);
1495
1496         if (used < 0)
1497                 used = 0;
1498         strbuf_add(sb, name + used, len - used);
1499 }
1500
1501 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1502 {
1503         if (startup_info->have_repository)
1504                 strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
1505         else
1506                 strbuf_addstr(sb, name);
1507
1508         /*
1509          * This splice must be done even if we end up rejecting the
1510          * name; builtin/branch.c::copy_or_rename_branch() still wants
1511          * to see what the name expanded to so that "branch -m" can be
1512          * used as a tool to correct earlier mistakes.
1513          */
1514         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1515
1516         if (*name == '-' ||
1517             !strcmp(sb->buf, "refs/heads/HEAD"))
1518                 return -1;
1519
1520         return check_refname_format(sb->buf, 0);
1521 }
1522
1523 /*
1524  * This is like "get_oid_basic()", except it allows "object ID expressions",
1525  * notably "xyz^" for "parent of xyz"
1526  */
1527 int get_oid(const char *name, struct object_id *oid)
1528 {
1529         struct object_context unused;
1530         return get_oid_with_context(the_repository, name, 0, oid, &unused);
1531 }
1532
1533
1534 /*
1535  * Many callers know that the user meant to name a commit-ish by
1536  * syntactical positions where the object name appears.  Calling this
1537  * function allows the machinery to disambiguate shorter-than-unique
1538  * abbreviated object names between commit-ish and others.
1539  *
1540  * Note that this does NOT error out when the named object is not a
1541  * commit-ish. It is merely to give a hint to the disambiguation
1542  * machinery.
1543  */
1544 int get_oid_committish(const char *name, struct object_id *oid)
1545 {
1546         struct object_context unused;
1547         return get_oid_with_context(the_repository,
1548                                     name, GET_OID_COMMITTISH,
1549                                     oid, &unused);
1550 }
1551
1552 int get_oid_treeish(const char *name, struct object_id *oid)
1553 {
1554         struct object_context unused;
1555         return get_oid_with_context(the_repository,
1556                                     name, GET_OID_TREEISH,
1557                                     oid, &unused);
1558 }
1559
1560 int get_oid_commit(const char *name, struct object_id *oid)
1561 {
1562         struct object_context unused;
1563         return get_oid_with_context(the_repository,
1564                                     name, GET_OID_COMMIT,
1565                                     oid, &unused);
1566 }
1567
1568 int get_oid_tree(const char *name, struct object_id *oid)
1569 {
1570         struct object_context unused;
1571         return get_oid_with_context(the_repository,
1572                                     name, GET_OID_TREE,
1573                                     oid, &unused);
1574 }
1575
1576 int get_oid_blob(const char *name, struct object_id *oid)
1577 {
1578         struct object_context unused;
1579         return get_oid_with_context(the_repository,
1580                                     name, GET_OID_BLOB,
1581                                     oid, &unused);
1582 }
1583
1584 /* Must be called only when object_name:filename doesn't exist. */
1585 static void diagnose_invalid_oid_path(const char *prefix,
1586                                       const char *filename,
1587                                       const struct object_id *tree_oid,
1588                                       const char *object_name,
1589                                       int object_name_len)
1590 {
1591         struct object_id oid;
1592         unsigned mode;
1593
1594         if (!prefix)
1595                 prefix = "";
1596
1597         if (file_exists(filename))
1598                 die("Path '%s' exists on disk, but not in '%.*s'.",
1599                     filename, object_name_len, object_name);
1600         if (is_missing_file_error(errno)) {
1601                 char *fullname = xstrfmt("%s%s", prefix, filename);
1602
1603                 if (!get_tree_entry(tree_oid, fullname, &oid, &mode)) {
1604                         die("Path '%s' exists, but not '%s'.\n"
1605                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1606                             fullname,
1607                             filename,
1608                             object_name_len, object_name,
1609                             fullname,
1610                             object_name_len, object_name,
1611                             filename);
1612                 }
1613                 die("Path '%s' does not exist in '%.*s'",
1614                     filename, object_name_len, object_name);
1615         }
1616 }
1617
1618 /* Must be called only when :stage:filename doesn't exist. */
1619 static void diagnose_invalid_index_path(struct index_state *istate,
1620                                         int stage,
1621                                         const char *prefix,
1622                                         const char *filename)
1623 {
1624         const struct cache_entry *ce;
1625         int pos;
1626         unsigned namelen = strlen(filename);
1627         struct strbuf fullname = STRBUF_INIT;
1628
1629         if (!prefix)
1630                 prefix = "";
1631
1632         /* Wrong stage number? */
1633         pos = index_name_pos(istate, filename, namelen);
1634         if (pos < 0)
1635                 pos = -pos - 1;
1636         if (pos < istate->cache_nr) {
1637                 ce = istate->cache[pos];
1638                 if (ce_namelen(ce) == namelen &&
1639                     !memcmp(ce->name, filename, namelen))
1640                         die("Path '%s' is in the index, but not at stage %d.\n"
1641                             "Did you mean ':%d:%s'?",
1642                             filename, stage,
1643                             ce_stage(ce), filename);
1644         }
1645
1646         /* Confusion between relative and absolute filenames? */
1647         strbuf_addstr(&fullname, prefix);
1648         strbuf_addstr(&fullname, filename);
1649         pos = index_name_pos(istate, fullname.buf, fullname.len);
1650         if (pos < 0)
1651                 pos = -pos - 1;
1652         if (pos < istate->cache_nr) {
1653                 ce = istate->cache[pos];
1654                 if (ce_namelen(ce) == fullname.len &&
1655                     !memcmp(ce->name, fullname.buf, fullname.len))
1656                         die("Path '%s' is in the index, but not '%s'.\n"
1657                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1658                             fullname.buf, filename,
1659                             ce_stage(ce), fullname.buf,
1660                             ce_stage(ce), filename);
1661         }
1662
1663         if (file_exists(filename))
1664                 die("Path '%s' exists on disk, but not in the index.", filename);
1665         if (is_missing_file_error(errno))
1666                 die("Path '%s' does not exist (neither on disk nor in the index).",
1667                     filename);
1668
1669         strbuf_release(&fullname);
1670 }
1671
1672
1673 static char *resolve_relative_path(const char *rel)
1674 {
1675         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1676                 return NULL;
1677
1678         if (!is_inside_work_tree())
1679                 die("relative path syntax can't be used outside working tree.");
1680
1681         /* die() inside prefix_path() if resolved path is outside worktree */
1682         return prefix_path(startup_info->prefix,
1683                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1684                            rel);
1685 }
1686
1687 static enum get_oid_result get_oid_with_context_1(struct repository *repo,
1688                                   const char *name,
1689                                   unsigned flags,
1690                                   const char *prefix,
1691                                   struct object_id *oid,
1692                                   struct object_context *oc)
1693 {
1694         int ret, bracket_depth;
1695         int namelen = strlen(name);
1696         const char *cp;
1697         int only_to_die = flags & GET_OID_ONLY_TO_DIE;
1698
1699         if (only_to_die)
1700                 flags |= GET_OID_QUIETLY;
1701
1702         memset(oc, 0, sizeof(*oc));
1703         oc->mode = S_IFINVALID;
1704         strbuf_init(&oc->symlink_path, 0);
1705         ret = get_oid_1(name, namelen, oid, flags);
1706         if (!ret)
1707                 return ret;
1708         /*
1709          * sha1:path --> object name of path in ent sha1
1710          * :path -> object name of absolute path in index
1711          * :./path -> object name of path relative to cwd in index
1712          * :[0-3]:path -> object name of path in index at stage
1713          * :/foo -> recent commit matching foo
1714          */
1715         if (name[0] == ':') {
1716                 int stage = 0;
1717                 const struct cache_entry *ce;
1718                 char *new_path = NULL;
1719                 int pos;
1720                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1721                         struct commit_list *list = NULL;
1722
1723                         for_each_ref(handle_one_ref, &list);
1724                         head_ref(handle_one_ref, &list);
1725                         commit_list_sort_by_date(&list);
1726                         return get_oid_oneline(name + 2, oid, list);
1727                 }
1728                 if (namelen < 3 ||
1729                     name[2] != ':' ||
1730                     name[1] < '0' || '3' < name[1])
1731                         cp = name + 1;
1732                 else {
1733                         stage = name[1] - '0';
1734                         cp = name + 3;
1735                 }
1736                 new_path = resolve_relative_path(cp);
1737                 if (!new_path) {
1738                         namelen = namelen - (cp - name);
1739                 } else {
1740                         cp = new_path;
1741                         namelen = strlen(cp);
1742                 }
1743
1744                 if (flags & GET_OID_RECORD_PATH)
1745                         oc->path = xstrdup(cp);
1746
1747                 if (!repo->index->cache)
1748                         repo_read_index(the_repository);
1749                 pos = index_name_pos(repo->index, cp, namelen);
1750                 if (pos < 0)
1751                         pos = -pos - 1;
1752                 while (pos < repo->index->cache_nr) {
1753                         ce = repo->index->cache[pos];
1754                         if (ce_namelen(ce) != namelen ||
1755                             memcmp(ce->name, cp, namelen))
1756                                 break;
1757                         if (ce_stage(ce) == stage) {
1758                                 oidcpy(oid, &ce->oid);
1759                                 oc->mode = ce->ce_mode;
1760                                 free(new_path);
1761                                 return 0;
1762                         }
1763                         pos++;
1764                 }
1765                 if (only_to_die && name[1] && name[1] != '/')
1766                         diagnose_invalid_index_path(repo->index, stage, prefix, cp);
1767                 free(new_path);
1768                 return -1;
1769         }
1770         for (cp = name, bracket_depth = 0; *cp; cp++) {
1771                 if (*cp == '{')
1772                         bracket_depth++;
1773                 else if (bracket_depth && *cp == '}')
1774                         bracket_depth--;
1775                 else if (!bracket_depth && *cp == ':')
1776                         break;
1777         }
1778         if (*cp == ':') {
1779                 struct object_id tree_oid;
1780                 int len = cp - name;
1781                 unsigned sub_flags = flags;
1782
1783                 sub_flags &= ~GET_OID_DISAMBIGUATORS;
1784                 sub_flags |= GET_OID_TREEISH;
1785
1786                 if (!get_oid_1(name, len, &tree_oid, sub_flags)) {
1787                         const char *filename = cp+1;
1788                         char *new_filename = NULL;
1789
1790                         new_filename = resolve_relative_path(filename);
1791                         if (new_filename)
1792                                 filename = new_filename;
1793                         if (flags & GET_OID_FOLLOW_SYMLINKS) {
1794                                 ret = get_tree_entry_follow_symlinks(&tree_oid,
1795                                         filename, oid, &oc->symlink_path,
1796                                         &oc->mode);
1797                         } else {
1798                                 ret = get_tree_entry(&tree_oid, filename, oid,
1799                                                      &oc->mode);
1800                                 if (ret && only_to_die) {
1801                                         diagnose_invalid_oid_path(prefix,
1802                                                                    filename,
1803                                                                    &tree_oid,
1804                                                                    name, len);
1805                                 }
1806                         }
1807                         if (flags & GET_OID_RECORD_PATH)
1808                                 oc->path = xstrdup(filename);
1809
1810                         free(new_filename);
1811                         return ret;
1812                 } else {
1813                         if (only_to_die)
1814                                 die("Invalid object name '%.*s'.", len, name);
1815                 }
1816         }
1817         return ret;
1818 }
1819
1820 /*
1821  * Call this function when you know "name" given by the end user must
1822  * name an object but it doesn't; the function _may_ die with a better
1823  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1824  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1825  * you have a chance to diagnose the error further.
1826  */
1827 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1828 {
1829         struct object_context oc;
1830         struct object_id oid;
1831         get_oid_with_context_1(the_repository, name, GET_OID_ONLY_TO_DIE,
1832                                prefix, &oid, &oc);
1833 }
1834
1835 enum get_oid_result get_oid_with_context(struct repository *repo,
1836                                          const char *str,
1837                                          unsigned flags,
1838                                          struct object_id *oid,
1839                                          struct object_context *oc)
1840 {
1841         if (flags & GET_OID_FOLLOW_SYMLINKS && flags & GET_OID_ONLY_TO_DIE)
1842                 BUG("incompatible flags for get_sha1_with_context");
1843         return get_oid_with_context_1(repo, str, flags, NULL, oid, oc);
1844 }