pathspec: simpler logic to prefix original pathspec elements
[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 #include "sha1-array.h"
11
12 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
13
14 typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
15
16 struct disambiguate_state {
17         int len; /* length of prefix in hex chars */
18         char hex_pfx[GIT_SHA1_HEXSZ + 1];
19         unsigned char bin_pfx[GIT_SHA1_RAWSZ];
20
21         disambiguate_hint_fn fn;
22         void *cb_data;
23         unsigned char candidate[GIT_SHA1_RAWSZ];
24         unsigned candidate_exists:1;
25         unsigned candidate_checked:1;
26         unsigned candidate_ok:1;
27         unsigned disambiguate_fn_used:1;
28         unsigned ambiguous:1;
29         unsigned always_call_fn:1;
30 };
31
32 static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
33 {
34         if (ds->always_call_fn) {
35                 ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
36                 return;
37         }
38         if (!ds->candidate_exists) {
39                 /* this is the first candidate */
40                 hashcpy(ds->candidate, current);
41                 ds->candidate_exists = 1;
42                 return;
43         } else if (!hashcmp(ds->candidate, current)) {
44                 /* the same as what we already have seen */
45                 return;
46         }
47
48         if (!ds->fn) {
49                 /* cannot disambiguate between ds->candidate and current */
50                 ds->ambiguous = 1;
51                 return;
52         }
53
54         if (!ds->candidate_checked) {
55                 ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
56                 ds->disambiguate_fn_used = 1;
57                 ds->candidate_checked = 1;
58         }
59
60         if (!ds->candidate_ok) {
61                 /* discard the candidate; we know it does not satisfy fn */
62                 hashcpy(ds->candidate, current);
63                 ds->candidate_checked = 0;
64                 return;
65         }
66
67         /* if we reach this point, we know ds->candidate satisfies fn */
68         if (ds->fn(current, ds->cb_data)) {
69                 /*
70                  * if both current and candidate satisfy fn, we cannot
71                  * disambiguate.
72                  */
73                 ds->candidate_ok = 0;
74                 ds->ambiguous = 1;
75         }
76
77         /* otherwise, current can be discarded and candidate is still good */
78 }
79
80 static void find_short_object_filename(struct disambiguate_state *ds)
81 {
82         struct alternate_object_database *alt;
83         char hex[GIT_SHA1_HEXSZ];
84         static struct alternate_object_database *fakeent;
85
86         if (!fakeent) {
87                 /*
88                  * Create a "fake" alternate object database that
89                  * points to our own object database, to make it
90                  * easier to get a temporary working space in
91                  * alt->name/alt->base while iterating over the
92                  * object databases including our own.
93                  */
94                 fakeent = alloc_alt_odb(get_object_directory());
95         }
96         fakeent->next = alt_odb_list;
97
98         xsnprintf(hex, sizeof(hex), "%.2s", ds->hex_pfx);
99         for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
100                 struct strbuf *buf = alt_scratch_buf(alt);
101                 struct dirent *de;
102                 DIR *dir;
103
104                 strbuf_addf(buf, "%.2s/", ds->hex_pfx);
105                 dir = opendir(buf->buf);
106                 if (!dir)
107                         continue;
108
109                 while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
110                         unsigned char sha1[20];
111
112                         if (strlen(de->d_name) != 38)
113                                 continue;
114                         if (memcmp(de->d_name, ds->hex_pfx + 2, ds->len - 2))
115                                 continue;
116                         memcpy(hex + 2, de->d_name, 38);
117                         if (!get_sha1_hex(hex, sha1))
118                                 update_candidates(ds, sha1);
119                 }
120                 closedir(dir);
121         }
122 }
123
124 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
125 {
126         do {
127                 if (*a != *b)
128                         return 0;
129                 a++;
130                 b++;
131                 len -= 2;
132         } while (len > 1);
133         if (len)
134                 if ((*a ^ *b) & 0xf0)
135                         return 0;
136         return 1;
137 }
138
139 static void unique_in_pack(struct packed_git *p,
140                            struct disambiguate_state *ds)
141 {
142         uint32_t num, last, i, first = 0;
143         const unsigned char *current = NULL;
144
145         open_pack_index(p);
146         num = p->num_objects;
147         last = num;
148         while (first < last) {
149                 uint32_t mid = (first + last) / 2;
150                 const unsigned char *current;
151                 int cmp;
152
153                 current = nth_packed_object_sha1(p, mid);
154                 cmp = hashcmp(ds->bin_pfx, current);
155                 if (!cmp) {
156                         first = mid;
157                         break;
158                 }
159                 if (cmp > 0) {
160                         first = mid+1;
161                         continue;
162                 }
163                 last = mid;
164         }
165
166         /*
167          * At this point, "first" is the location of the lowest object
168          * with an object name that could match "bin_pfx".  See if we have
169          * 0, 1 or more objects that actually match(es).
170          */
171         for (i = first; i < num && !ds->ambiguous; i++) {
172                 current = nth_packed_object_sha1(p, i);
173                 if (!match_sha(ds->len, ds->bin_pfx, current))
174                         break;
175                 update_candidates(ds, current);
176         }
177 }
178
179 static void find_short_packed_object(struct disambiguate_state *ds)
180 {
181         struct packed_git *p;
182
183         prepare_packed_git();
184         for (p = packed_git; p && !ds->ambiguous; p = p->next)
185                 unique_in_pack(p, ds);
186 }
187
188 #define SHORT_NAME_NOT_FOUND (-1)
189 #define SHORT_NAME_AMBIGUOUS (-2)
190
191 static int finish_object_disambiguation(struct disambiguate_state *ds,
192                                         unsigned char *sha1)
193 {
194         if (ds->ambiguous)
195                 return SHORT_NAME_AMBIGUOUS;
196
197         if (!ds->candidate_exists)
198                 return SHORT_NAME_NOT_FOUND;
199
200         if (!ds->candidate_checked)
201                 /*
202                  * If this is the only candidate, there is no point
203                  * calling the disambiguation hint callback.
204                  *
205                  * On the other hand, if the current candidate
206                  * replaced an earlier candidate that did _not_ pass
207                  * the disambiguation hint callback, then we do have
208                  * more than one objects that match the short name
209                  * given, so we should make sure this one matches;
210                  * otherwise, if we discovered this one and the one
211                  * that we previously discarded in the reverse order,
212                  * we would end up showing different results in the
213                  * same repository!
214                  */
215                 ds->candidate_ok = (!ds->disambiguate_fn_used ||
216                                     ds->fn(ds->candidate, ds->cb_data));
217
218         if (!ds->candidate_ok)
219                 return SHORT_NAME_AMBIGUOUS;
220
221         hashcpy(sha1, ds->candidate);
222         return 0;
223 }
224
225 static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
226 {
227         int kind = sha1_object_info(sha1, NULL);
228         return kind == OBJ_COMMIT;
229 }
230
231 static int disambiguate_committish_only(const unsigned char *sha1, void *cb_data_unused)
232 {
233         struct object *obj;
234         int kind;
235
236         kind = sha1_object_info(sha1, NULL);
237         if (kind == OBJ_COMMIT)
238                 return 1;
239         if (kind != OBJ_TAG)
240                 return 0;
241
242         /* We need to do this the hard way... */
243         obj = deref_tag(parse_object(sha1), NULL, 0);
244         if (obj && obj->type == OBJ_COMMIT)
245                 return 1;
246         return 0;
247 }
248
249 static int disambiguate_tree_only(const unsigned char *sha1, void *cb_data_unused)
250 {
251         int kind = sha1_object_info(sha1, NULL);
252         return kind == OBJ_TREE;
253 }
254
255 static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_unused)
256 {
257         struct object *obj;
258         int kind;
259
260         kind = sha1_object_info(sha1, NULL);
261         if (kind == OBJ_TREE || kind == OBJ_COMMIT)
262                 return 1;
263         if (kind != OBJ_TAG)
264                 return 0;
265
266         /* We need to do this the hard way... */
267         obj = deref_tag(parse_object(sha1), NULL, 0);
268         if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
269                 return 1;
270         return 0;
271 }
272
273 static int disambiguate_blob_only(const unsigned char *sha1, void *cb_data_unused)
274 {
275         int kind = sha1_object_info(sha1, NULL);
276         return kind == OBJ_BLOB;
277 }
278
279 static disambiguate_hint_fn default_disambiguate_hint;
280
281 int set_disambiguate_hint_config(const char *var, const char *value)
282 {
283         static const struct {
284                 const char *name;
285                 disambiguate_hint_fn fn;
286         } hints[] = {
287                 { "none", NULL },
288                 { "commit", disambiguate_commit_only },
289                 { "committish", disambiguate_committish_only },
290                 { "tree", disambiguate_tree_only },
291                 { "treeish", disambiguate_treeish_only },
292                 { "blob", disambiguate_blob_only }
293         };
294         int i;
295
296         if (!value)
297                 return config_error_nonbool(var);
298
299         for (i = 0; i < ARRAY_SIZE(hints); i++) {
300                 if (!strcasecmp(value, hints[i].name)) {
301                         default_disambiguate_hint = hints[i].fn;
302                         return 0;
303                 }
304         }
305
306         return error("unknown hint type for '%s': %s", var, value);
307 }
308
309 static int init_object_disambiguation(const char *name, int len,
310                                       struct disambiguate_state *ds)
311 {
312         int i;
313
314         if (len < MINIMUM_ABBREV || len > GIT_SHA1_HEXSZ)
315                 return -1;
316
317         memset(ds, 0, sizeof(*ds));
318
319         for (i = 0; i < len ;i++) {
320                 unsigned char c = name[i];
321                 unsigned char val;
322                 if (c >= '0' && c <= '9')
323                         val = c - '0';
324                 else if (c >= 'a' && c <= 'f')
325                         val = c - 'a' + 10;
326                 else if (c >= 'A' && c <='F') {
327                         val = c - 'A' + 10;
328                         c -= 'A' - 'a';
329                 }
330                 else
331                         return -1;
332                 ds->hex_pfx[i] = c;
333                 if (!(i & 1))
334                         val <<= 4;
335                 ds->bin_pfx[i >> 1] |= val;
336         }
337
338         ds->len = len;
339         ds->hex_pfx[len] = '\0';
340         prepare_alt_odb();
341         return 0;
342 }
343
344 static int show_ambiguous_object(const unsigned char *sha1, void *data)
345 {
346         const struct disambiguate_state *ds = data;
347         struct strbuf desc = STRBUF_INIT;
348         int type;
349
350         if (ds->fn && !ds->fn(sha1, ds->cb_data))
351                 return 0;
352
353         type = sha1_object_info(sha1, NULL);
354         if (type == OBJ_COMMIT) {
355                 struct commit *commit = lookup_commit(sha1);
356                 if (commit) {
357                         struct pretty_print_context pp = {0};
358                         pp.date_mode.type = DATE_SHORT;
359                         format_commit_message(commit, " %ad - %s", &desc, &pp);
360                 }
361         } else if (type == OBJ_TAG) {
362                 struct tag *tag = lookup_tag(sha1);
363                 if (!parse_tag(tag) && tag->tag)
364                         strbuf_addf(&desc, " %s", tag->tag);
365         }
366
367         advise("  %s %s%s",
368                find_unique_abbrev(sha1, DEFAULT_ABBREV),
369                typename(type) ? typename(type) : "unknown type",
370                desc.buf);
371
372         strbuf_release(&desc);
373         return 0;
374 }
375
376 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
377                           unsigned flags)
378 {
379         int status;
380         struct disambiguate_state ds;
381         int quietly = !!(flags & GET_SHA1_QUIETLY);
382
383         if (init_object_disambiguation(name, len, &ds) < 0)
384                 return -1;
385
386         if (HAS_MULTI_BITS(flags & GET_SHA1_DISAMBIGUATORS))
387                 die("BUG: multiple get_short_sha1 disambiguator flags");
388
389         if (flags & GET_SHA1_COMMIT)
390                 ds.fn = disambiguate_commit_only;
391         else if (flags & GET_SHA1_COMMITTISH)
392                 ds.fn = disambiguate_committish_only;
393         else if (flags & GET_SHA1_TREE)
394                 ds.fn = disambiguate_tree_only;
395         else if (flags & GET_SHA1_TREEISH)
396                 ds.fn = disambiguate_treeish_only;
397         else if (flags & GET_SHA1_BLOB)
398                 ds.fn = disambiguate_blob_only;
399         else
400                 ds.fn = default_disambiguate_hint;
401
402         find_short_object_filename(&ds);
403         find_short_packed_object(&ds);
404         status = finish_object_disambiguation(&ds, sha1);
405
406         if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
407                 error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
408
409                 /*
410                  * We may still have ambiguity if we simply saw a series of
411                  * candidates that did not satisfy our hint function. In
412                  * that case, we still want to show them, so disable the hint
413                  * function entirely.
414                  */
415                 if (!ds.ambiguous)
416                         ds.fn = NULL;
417
418                 advise(_("The candidates are:"));
419                 for_each_abbrev(ds.hex_pfx, show_ambiguous_object, &ds);
420         }
421
422         return status;
423 }
424
425 static int collect_ambiguous(const unsigned char *sha1, void *data)
426 {
427         sha1_array_append(data, sha1);
428         return 0;
429 }
430
431 int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
432 {
433         struct sha1_array collect = SHA1_ARRAY_INIT;
434         struct disambiguate_state ds;
435         int ret;
436
437         if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
438                 return -1;
439
440         ds.always_call_fn = 1;
441         ds.fn = collect_ambiguous;
442         ds.cb_data = &collect;
443         find_short_object_filename(&ds);
444         find_short_packed_object(&ds);
445
446         ret = sha1_array_for_each_unique(&collect, fn, cb_data);
447         sha1_array_clear(&collect);
448         return ret;
449 }
450
451 /*
452  * Return the slot of the most-significant bit set in "val". There are various
453  * ways to do this quickly with fls() or __builtin_clzl(), but speed is
454  * probably not a big deal here.
455  */
456 static unsigned msb(unsigned long val)
457 {
458         unsigned r = 0;
459         while (val >>= 1)
460                 r++;
461         return r;
462 }
463
464 int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
465 {
466         int status, exists;
467
468         if (len < 0) {
469                 unsigned long count = approximate_object_count();
470                 /*
471                  * Add one because the MSB only tells us the highest bit set,
472                  * not including the value of all the _other_ bits (so "15"
473                  * is only one off of 2^4, but the MSB is the 3rd bit.
474                  */
475                 len = msb(count) + 1;
476                 /*
477                  * We now know we have on the order of 2^len objects, which
478                  * expects a collision at 2^(len/2). But we also care about hex
479                  * chars, not bits, and there are 4 bits per hex. So all
480                  * together we need to divide by 2; but we also want to round
481                  * odd numbers up, hence adding one before dividing.
482                  */
483                 len = (len + 1) / 2;
484                 /*
485                  * For very small repos, we stick with our regular fallback.
486                  */
487                 if (len < FALLBACK_DEFAULT_ABBREV)
488                         len = FALLBACK_DEFAULT_ABBREV;
489         }
490
491         sha1_to_hex_r(hex, sha1);
492         if (len == 40 || !len)
493                 return 40;
494         exists = has_sha1_file(sha1);
495         while (len < 40) {
496                 unsigned char sha1_ret[20];
497                 status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
498                 if (exists
499                     ? !status
500                     : status == SHORT_NAME_NOT_FOUND) {
501                         hex[len] = 0;
502                         return len;
503                 }
504                 len++;
505         }
506         return len;
507 }
508
509 const char *find_unique_abbrev(const unsigned char *sha1, int len)
510 {
511         static int bufno;
512         static char hexbuffer[4][GIT_SHA1_HEXSZ + 1];
513         char *hex = hexbuffer[bufno];
514         bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
515         find_unique_abbrev_r(hex, sha1, len);
516         return hex;
517 }
518
519 static int ambiguous_path(const char *path, int len)
520 {
521         int slash = 1;
522         int cnt;
523
524         for (cnt = 0; cnt < len; cnt++) {
525                 switch (*path++) {
526                 case '\0':
527                         break;
528                 case '/':
529                         if (slash)
530                                 break;
531                         slash = 1;
532                         continue;
533                 case '.':
534                         continue;
535                 default:
536                         slash = 0;
537                         continue;
538                 }
539                 break;
540         }
541         return slash;
542 }
543
544 static inline int at_mark(const char *string, int len,
545                           const char **suffix, int nr)
546 {
547         int i;
548
549         for (i = 0; i < nr; i++) {
550                 int suffix_len = strlen(suffix[i]);
551                 if (suffix_len <= len
552                     && !memcmp(string, suffix[i], suffix_len))
553                         return suffix_len;
554         }
555         return 0;
556 }
557
558 static inline int upstream_mark(const char *string, int len)
559 {
560         const char *suffix[] = { "@{upstream}", "@{u}" };
561         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
562 }
563
564 static inline int push_mark(const char *string, int len)
565 {
566         const char *suffix[] = { "@{push}" };
567         return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
568 }
569
570 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
571 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
572
573 static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
574                           unsigned int flags)
575 {
576         static const char *warn_msg = "refname '%.*s' is ambiguous.";
577         static const char *object_name_msg = N_(
578         "Git normally never creates a ref that ends with 40 hex characters\n"
579         "because it will be ignored when you just specify 40-hex. These refs\n"
580         "may be created by mistake. For example,\n"
581         "\n"
582         "  git checkout -b $br $(git rev-parse ...)\n"
583         "\n"
584         "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
585         "examine these refs and maybe delete them. Turn this message off by\n"
586         "running \"git config advice.objectNameWarning false\"");
587         unsigned char tmp_sha1[20];
588         char *real_ref = NULL;
589         int refs_found = 0;
590         int at, reflog_len, nth_prior = 0;
591
592         if (len == 40 && !get_sha1_hex(str, sha1)) {
593                 if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
594                         refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
595                         if (refs_found > 0) {
596                                 warning(warn_msg, len, str);
597                                 if (advice_object_name_warning)
598                                         fprintf(stderr, "%s\n", _(object_name_msg));
599                         }
600                         free(real_ref);
601                 }
602                 return 0;
603         }
604
605         /* basic@{time or number or -number} format to query ref-log */
606         reflog_len = at = 0;
607         if (len && str[len-1] == '}') {
608                 for (at = len-4; at >= 0; at--) {
609                         if (str[at] == '@' && str[at+1] == '{') {
610                                 if (str[at+2] == '-') {
611                                         if (at != 0)
612                                                 /* @{-N} not at start */
613                                                 return -1;
614                                         nth_prior = 1;
615                                         continue;
616                                 }
617                                 if (!upstream_mark(str + at, len - at) &&
618                                     !push_mark(str + at, len - at)) {
619                                         reflog_len = (len-1) - (at+2);
620                                         len = at;
621                                 }
622                                 break;
623                         }
624                 }
625         }
626
627         /* Accept only unambiguous ref paths. */
628         if (len && ambiguous_path(str, len))
629                 return -1;
630
631         if (nth_prior) {
632                 struct strbuf buf = STRBUF_INIT;
633                 int detached;
634
635                 if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
636                         detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
637                         strbuf_release(&buf);
638                         if (detached)
639                                 return 0;
640                 }
641         }
642
643         if (!len && reflog_len)
644                 /* allow "@{...}" to mean the current branch reflog */
645                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
646         else if (reflog_len)
647                 refs_found = dwim_log(str, len, sha1, &real_ref);
648         else
649                 refs_found = dwim_ref(str, len, sha1, &real_ref);
650
651         if (!refs_found)
652                 return -1;
653
654         if (warn_ambiguous_refs && !(flags & GET_SHA1_QUIETLY) &&
655             (refs_found > 1 ||
656              !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
657                 warning(warn_msg, len, str);
658
659         if (reflog_len) {
660                 int nth, i;
661                 unsigned long at_time;
662                 unsigned long co_time;
663                 int co_tz, co_cnt;
664
665                 /* Is it asking for N-th entry, or approxidate? */
666                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
667                         char ch = str[at+2+i];
668                         if ('0' <= ch && ch <= '9')
669                                 nth = nth * 10 + ch - '0';
670                         else
671                                 nth = -1;
672                 }
673                 if (100000000 <= nth) {
674                         at_time = nth;
675                         nth = -1;
676                 } else if (0 <= nth)
677                         at_time = 0;
678                 else {
679                         int errors = 0;
680                         char *tmp = xstrndup(str + at + 2, reflog_len);
681                         at_time = approxidate_careful(tmp, &errors);
682                         free(tmp);
683                         if (errors) {
684                                 free(real_ref);
685                                 return -1;
686                         }
687                 }
688                 if (read_ref_at(real_ref, flags, at_time, nth, sha1, NULL,
689                                 &co_time, &co_tz, &co_cnt)) {
690                         if (!len) {
691                                 if (starts_with(real_ref, "refs/heads/")) {
692                                         str = real_ref + 11;
693                                         len = strlen(real_ref + 11);
694                                 } else {
695                                         /* detached HEAD */
696                                         str = "HEAD";
697                                         len = 4;
698                                 }
699                         }
700                         if (at_time) {
701                                 if (!(flags & GET_SHA1_QUIETLY)) {
702                                         warning("Log for '%.*s' only goes "
703                                                 "back to %s.", len, str,
704                                                 show_date(co_time, co_tz, DATE_MODE(RFC2822)));
705                                 }
706                         } else {
707                                 if (flags & GET_SHA1_QUIETLY) {
708                                         exit(128);
709                                 }
710                                 die("Log for '%.*s' only has %d entries.",
711                                     len, str, co_cnt);
712                         }
713                 }
714         }
715
716         free(real_ref);
717         return 0;
718 }
719
720 static int get_parent(const char *name, int len,
721                       unsigned char *result, int idx)
722 {
723         unsigned char sha1[20];
724         int ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
725         struct commit *commit;
726         struct commit_list *p;
727
728         if (ret)
729                 return ret;
730         commit = lookup_commit_reference(sha1);
731         if (parse_commit(commit))
732                 return -1;
733         if (!idx) {
734                 hashcpy(result, commit->object.oid.hash);
735                 return 0;
736         }
737         p = commit->parents;
738         while (p) {
739                 if (!--idx) {
740                         hashcpy(result, p->item->object.oid.hash);
741                         return 0;
742                 }
743                 p = p->next;
744         }
745         return -1;
746 }
747
748 static int get_nth_ancestor(const char *name, int len,
749                             unsigned char *result, int generation)
750 {
751         unsigned char sha1[20];
752         struct commit *commit;
753         int ret;
754
755         ret = get_sha1_1(name, len, sha1, GET_SHA1_COMMITTISH);
756         if (ret)
757                 return ret;
758         commit = lookup_commit_reference(sha1);
759         if (!commit)
760                 return -1;
761
762         while (generation--) {
763                 if (parse_commit(commit) || !commit->parents)
764                         return -1;
765                 commit = commit->parents->item;
766         }
767         hashcpy(result, commit->object.oid.hash);
768         return 0;
769 }
770
771 struct object *peel_to_type(const char *name, int namelen,
772                             struct object *o, enum object_type expected_type)
773 {
774         if (name && !namelen)
775                 namelen = strlen(name);
776         while (1) {
777                 if (!o || (!o->parsed && !parse_object(o->oid.hash)))
778                         return NULL;
779                 if (expected_type == OBJ_ANY || o->type == expected_type)
780                         return o;
781                 if (o->type == OBJ_TAG)
782                         o = ((struct tag*) o)->tagged;
783                 else if (o->type == OBJ_COMMIT)
784                         o = &(((struct commit *) o)->tree->object);
785                 else {
786                         if (name)
787                                 error("%.*s: expected %s type, but the object "
788                                       "dereferences to %s type",
789                                       namelen, name, typename(expected_type),
790                                       typename(o->type));
791                         return NULL;
792                 }
793         }
794 }
795
796 static int peel_onion(const char *name, int len, unsigned char *sha1,
797                       unsigned lookup_flags)
798 {
799         unsigned char outer[20];
800         const char *sp;
801         unsigned int expected_type = 0;
802         struct object *o;
803
804         /*
805          * "ref^{type}" dereferences ref repeatedly until you cannot
806          * dereference anymore, or you get an object of given type,
807          * whichever comes first.  "ref^{}" means just dereference
808          * tags until you get a non-tag.  "ref^0" is a shorthand for
809          * "ref^{commit}".  "commit^{tree}" could be used to find the
810          * top-level tree of the given commit.
811          */
812         if (len < 4 || name[len-1] != '}')
813                 return -1;
814
815         for (sp = name + len - 1; name <= sp; sp--) {
816                 int ch = *sp;
817                 if (ch == '{' && name < sp && sp[-1] == '^')
818                         break;
819         }
820         if (sp <= name)
821                 return -1;
822
823         sp++; /* beginning of type name, or closing brace for empty */
824         if (starts_with(sp, "commit}"))
825                 expected_type = OBJ_COMMIT;
826         else if (starts_with(sp, "tag}"))
827                 expected_type = OBJ_TAG;
828         else if (starts_with(sp, "tree}"))
829                 expected_type = OBJ_TREE;
830         else if (starts_with(sp, "blob}"))
831                 expected_type = OBJ_BLOB;
832         else if (starts_with(sp, "object}"))
833                 expected_type = OBJ_ANY;
834         else if (sp[0] == '}')
835                 expected_type = OBJ_NONE;
836         else if (sp[0] == '/')
837                 expected_type = OBJ_COMMIT;
838         else
839                 return -1;
840
841         lookup_flags &= ~GET_SHA1_DISAMBIGUATORS;
842         if (expected_type == OBJ_COMMIT)
843                 lookup_flags |= GET_SHA1_COMMITTISH;
844         else if (expected_type == OBJ_TREE)
845                 lookup_flags |= GET_SHA1_TREEISH;
846
847         if (get_sha1_1(name, sp - name - 2, outer, lookup_flags))
848                 return -1;
849
850         o = parse_object(outer);
851         if (!o)
852                 return -1;
853         if (!expected_type) {
854                 o = deref_tag(o, name, sp - name - 2);
855                 if (!o || (!o->parsed && !parse_object(o->oid.hash)))
856                         return -1;
857                 hashcpy(sha1, o->oid.hash);
858                 return 0;
859         }
860
861         /*
862          * At this point, the syntax look correct, so
863          * if we do not get the needed object, we should
864          * barf.
865          */
866         o = peel_to_type(name, len, o, expected_type);
867         if (!o)
868                 return -1;
869
870         hashcpy(sha1, o->oid.hash);
871         if (sp[0] == '/') {
872                 /* "$commit^{/foo}" */
873                 char *prefix;
874                 int ret;
875                 struct commit_list *list = NULL;
876
877                 /*
878                  * $commit^{/}. Some regex implementation may reject.
879                  * We don't need regex anyway. '' pattern always matches.
880                  */
881                 if (sp[1] == '}')
882                         return 0;
883
884                 prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
885                 commit_list_insert((struct commit *)o, &list);
886                 ret = get_sha1_oneline(prefix, sha1, list);
887                 free(prefix);
888                 return ret;
889         }
890         return 0;
891 }
892
893 static int get_describe_name(const char *name, int len, unsigned char *sha1)
894 {
895         const char *cp;
896         unsigned flags = GET_SHA1_QUIETLY | GET_SHA1_COMMIT;
897
898         for (cp = name + len - 1; name + 2 <= cp; cp--) {
899                 char ch = *cp;
900                 if (!isxdigit(ch)) {
901                         /* We must be looking at g in "SOMETHING-g"
902                          * for it to be describe output.
903                          */
904                         if (ch == 'g' && cp[-1] == '-') {
905                                 cp++;
906                                 len -= cp - name;
907                                 return get_short_sha1(cp, len, sha1, flags);
908                         }
909                 }
910         }
911         return -1;
912 }
913
914 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags)
915 {
916         int ret, has_suffix;
917         const char *cp;
918
919         /*
920          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
921          */
922         has_suffix = 0;
923         for (cp = name + len - 1; name <= cp; cp--) {
924                 int ch = *cp;
925                 if ('0' <= ch && ch <= '9')
926                         continue;
927                 if (ch == '~' || ch == '^')
928                         has_suffix = ch;
929                 break;
930         }
931
932         if (has_suffix) {
933                 int num = 0;
934                 int len1 = cp - name;
935                 cp++;
936                 while (cp < name + len)
937                         num = num * 10 + *cp++ - '0';
938                 if (!num && len1 == len - 1)
939                         num = 1;
940                 if (has_suffix == '^')
941                         return get_parent(name, len1, sha1, num);
942                 /* else if (has_suffix == '~') -- goes without saying */
943                 return get_nth_ancestor(name, len1, sha1, num);
944         }
945
946         ret = peel_onion(name, len, sha1, lookup_flags);
947         if (!ret)
948                 return 0;
949
950         ret = get_sha1_basic(name, len, sha1, lookup_flags);
951         if (!ret)
952                 return 0;
953
954         /* It could be describe output that is "SOMETHING-gXXXX" */
955         ret = get_describe_name(name, len, sha1);
956         if (!ret)
957                 return 0;
958
959         return get_short_sha1(name, len, sha1, lookup_flags);
960 }
961
962 /*
963  * This interprets names like ':/Initial revision of "git"' by searching
964  * through history and returning the first commit whose message starts
965  * the given regular expression.
966  *
967  * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
968  *
969  * For a literal '!' character at the beginning of a pattern, you have to repeat
970  * that, like: ':/!!foo'
971  *
972  * For future extension, all other sequences beginning with ':/!' are reserved.
973  */
974
975 /* Remember to update object flag allocation in object.h */
976 #define ONELINE_SEEN (1u<<20)
977
978 static int handle_one_ref(const char *path, const struct object_id *oid,
979                           int flag, void *cb_data)
980 {
981         struct commit_list **list = cb_data;
982         struct object *object = parse_object(oid->hash);
983         if (!object)
984                 return 0;
985         if (object->type == OBJ_TAG) {
986                 object = deref_tag(object, path, strlen(path));
987                 if (!object)
988                         return 0;
989         }
990         if (object->type != OBJ_COMMIT)
991                 return 0;
992         commit_list_insert((struct commit *)object, list);
993         return 0;
994 }
995
996 static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
997                             struct commit_list *list)
998 {
999         struct commit_list *backup = NULL, *l;
1000         int found = 0;
1001         int negative = 0;
1002         regex_t regex;
1003
1004         if (prefix[0] == '!') {
1005                 prefix++;
1006
1007                 if (prefix[0] == '-') {
1008                         prefix++;
1009                         negative = 1;
1010                 } else if (prefix[0] != '!') {
1011                         return -1;
1012                 }
1013         }
1014
1015         if (regcomp(&regex, prefix, REG_EXTENDED))
1016                 return -1;
1017
1018         for (l = list; l; l = l->next) {
1019                 l->item->object.flags |= ONELINE_SEEN;
1020                 commit_list_insert(l->item, &backup);
1021         }
1022         while (list) {
1023                 const char *p, *buf;
1024                 struct commit *commit;
1025                 int matches;
1026
1027                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
1028                 if (!parse_object(commit->object.oid.hash))
1029                         continue;
1030                 buf = get_commit_buffer(commit, NULL);
1031                 p = strstr(buf, "\n\n");
1032                 matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
1033                 unuse_commit_buffer(commit, buf);
1034
1035                 if (matches) {
1036                         hashcpy(sha1, commit->object.oid.hash);
1037                         found = 1;
1038                         break;
1039                 }
1040         }
1041         regfree(&regex);
1042         free_commit_list(list);
1043         for (l = backup; l; l = l->next)
1044                 clear_commit_marks(l->item, ONELINE_SEEN);
1045         free_commit_list(backup);
1046         return found ? 0 : -1;
1047 }
1048
1049 struct grab_nth_branch_switch_cbdata {
1050         int remaining;
1051         struct strbuf buf;
1052 };
1053
1054 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
1055                                   const char *email, unsigned long timestamp, int tz,
1056                                   const char *message, void *cb_data)
1057 {
1058         struct grab_nth_branch_switch_cbdata *cb = cb_data;
1059         const char *match = NULL, *target = NULL;
1060         size_t len;
1061
1062         if (skip_prefix(message, "checkout: moving from ", &match))
1063                 target = strstr(match, " to ");
1064
1065         if (!match || !target)
1066                 return 0;
1067         if (--(cb->remaining) == 0) {
1068                 len = target - match;
1069                 strbuf_reset(&cb->buf);
1070                 strbuf_add(&cb->buf, match, len);
1071                 return 1; /* we are done */
1072         }
1073         return 0;
1074 }
1075
1076 /*
1077  * Parse @{-N} syntax, return the number of characters parsed
1078  * if successful; otherwise signal an error with negative value.
1079  */
1080 static int interpret_nth_prior_checkout(const char *name, int namelen,
1081                                         struct strbuf *buf)
1082 {
1083         long nth;
1084         int retval;
1085         struct grab_nth_branch_switch_cbdata cb;
1086         const char *brace;
1087         char *num_end;
1088
1089         if (namelen < 4)
1090                 return -1;
1091         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
1092                 return -1;
1093         brace = memchr(name, '}', namelen);
1094         if (!brace)
1095                 return -1;
1096         nth = strtol(name + 3, &num_end, 10);
1097         if (num_end != brace)
1098                 return -1;
1099         if (nth <= 0)
1100                 return -1;
1101         cb.remaining = nth;
1102         strbuf_init(&cb.buf, 20);
1103
1104         retval = 0;
1105         if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
1106                 strbuf_reset(buf);
1107                 strbuf_addbuf(buf, &cb.buf);
1108                 retval = brace - name + 1;
1109         }
1110
1111         strbuf_release(&cb.buf);
1112         return retval;
1113 }
1114
1115 int get_oid_mb(const char *name, struct object_id *oid)
1116 {
1117         struct commit *one, *two;
1118         struct commit_list *mbs;
1119         struct object_id oid_tmp;
1120         const char *dots;
1121         int st;
1122
1123         dots = strstr(name, "...");
1124         if (!dots)
1125                 return get_oid(name, oid);
1126         if (dots == name)
1127                 st = get_oid("HEAD", &oid_tmp);
1128         else {
1129                 struct strbuf sb;
1130                 strbuf_init(&sb, dots - name);
1131                 strbuf_add(&sb, name, dots - name);
1132                 st = get_sha1_committish(sb.buf, oid_tmp.hash);
1133                 strbuf_release(&sb);
1134         }
1135         if (st)
1136                 return st;
1137         one = lookup_commit_reference_gently(oid_tmp.hash, 0);
1138         if (!one)
1139                 return -1;
1140
1141         if (get_sha1_committish(dots[3] ? (dots + 3) : "HEAD", oid_tmp.hash))
1142                 return -1;
1143         two = lookup_commit_reference_gently(oid_tmp.hash, 0);
1144         if (!two)
1145                 return -1;
1146         mbs = get_merge_bases(one, two);
1147         if (!mbs || mbs->next)
1148                 st = -1;
1149         else {
1150                 st = 0;
1151                 oidcpy(oid, &mbs->item->object.oid);
1152         }
1153         free_commit_list(mbs);
1154         return st;
1155 }
1156
1157 /* parse @something syntax, when 'something' is not {.*} */
1158 static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
1159 {
1160         const char *next;
1161
1162         if (len || name[1] == '{')
1163                 return -1;
1164
1165         /* make sure it's a single @, or @@{.*}, not @foo */
1166         next = memchr(name + len + 1, '@', namelen - len - 1);
1167         if (next && next[1] != '{')
1168                 return -1;
1169         if (!next)
1170                 next = name + namelen;
1171         if (next != name + 1)
1172                 return -1;
1173
1174         strbuf_reset(buf);
1175         strbuf_add(buf, "HEAD", 4);
1176         return 1;
1177 }
1178
1179 static int reinterpret(const char *name, int namelen, int len, struct strbuf *buf)
1180 {
1181         /* we have extra data, which might need further processing */
1182         struct strbuf tmp = STRBUF_INIT;
1183         int used = buf->len;
1184         int ret;
1185
1186         strbuf_add(buf, name + len, namelen - len);
1187         ret = interpret_branch_name(buf->buf, buf->len, &tmp);
1188         /* that data was not interpreted, remove our cruft */
1189         if (ret < 0) {
1190                 strbuf_setlen(buf, used);
1191                 return len;
1192         }
1193         strbuf_reset(buf);
1194         strbuf_addbuf(buf, &tmp);
1195         strbuf_release(&tmp);
1196         /* tweak for size of {-N} versus expanded ref name */
1197         return ret - used + len;
1198 }
1199
1200 static void set_shortened_ref(struct strbuf *buf, const char *ref)
1201 {
1202         char *s = shorten_unambiguous_ref(ref, 0);
1203         strbuf_reset(buf);
1204         strbuf_addstr(buf, s);
1205         free(s);
1206 }
1207
1208 static int interpret_branch_mark(const char *name, int namelen,
1209                                  int at, struct strbuf *buf,
1210                                  int (*get_mark)(const char *, int),
1211                                  const char *(*get_data)(struct branch *,
1212                                                          struct strbuf *))
1213 {
1214         int len;
1215         struct branch *branch;
1216         struct strbuf err = STRBUF_INIT;
1217         const char *value;
1218
1219         len = get_mark(name + at, namelen - at);
1220         if (!len)
1221                 return -1;
1222
1223         if (memchr(name, ':', at))
1224                 return -1;
1225
1226         if (at) {
1227                 char *name_str = xmemdupz(name, at);
1228                 branch = branch_get(name_str);
1229                 free(name_str);
1230         } else
1231                 branch = branch_get(NULL);
1232
1233         value = get_data(branch, &err);
1234         if (!value)
1235                 die("%s", err.buf);
1236
1237         set_shortened_ref(buf, value);
1238         return len + at;
1239 }
1240
1241 /*
1242  * This reads short-hand syntax that not only evaluates to a commit
1243  * object name, but also can act as if the end user spelled the name
1244  * of the branch from the command line.
1245  *
1246  * - "@{-N}" finds the name of the Nth previous branch we were on, and
1247  *   places the name of the branch in the given buf and returns the
1248  *   number of characters parsed if successful.
1249  *
1250  * - "<branch>@{upstream}" finds the name of the other ref that
1251  *   <branch> is configured to merge with (missing <branch> defaults
1252  *   to the current branch), and places the name of the branch in the
1253  *   given buf and returns the number of characters parsed if
1254  *   successful.
1255  *
1256  * If the input is not of the accepted format, it returns a negative
1257  * number to signal an error.
1258  *
1259  * If the input was ok but there are not N branch switches in the
1260  * reflog, it returns 0.
1261  */
1262 int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
1263 {
1264         char *at;
1265         const char *start;
1266         int len = interpret_nth_prior_checkout(name, namelen, buf);
1267
1268         if (!namelen)
1269                 namelen = strlen(name);
1270
1271         if (!len) {
1272                 return len; /* syntax Ok, not enough switches */
1273         } else if (len > 0) {
1274                 if (len == namelen)
1275                         return len; /* consumed all */
1276                 else
1277                         return reinterpret(name, namelen, len, buf);
1278         }
1279
1280         for (start = name;
1281              (at = memchr(start, '@', namelen - (start - name)));
1282              start = at + 1) {
1283
1284                 len = interpret_empty_at(name, namelen, at - name, buf);
1285                 if (len > 0)
1286                         return reinterpret(name, namelen, len, buf);
1287
1288                 len = interpret_branch_mark(name, namelen, at - name, buf,
1289                                             upstream_mark, branch_get_upstream);
1290                 if (len > 0)
1291                         return len;
1292
1293                 len = interpret_branch_mark(name, namelen, at - name, buf,
1294                                             push_mark, branch_get_push);
1295                 if (len > 0)
1296                         return len;
1297         }
1298
1299         return -1;
1300 }
1301
1302 int strbuf_branchname(struct strbuf *sb, const char *name)
1303 {
1304         int len = strlen(name);
1305         int used = interpret_branch_name(name, len, sb);
1306
1307         if (used == len)
1308                 return 0;
1309         if (used < 0)
1310                 used = 0;
1311         strbuf_add(sb, name + used, len - used);
1312         return len;
1313 }
1314
1315 int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
1316 {
1317         strbuf_branchname(sb, name);
1318         if (name[0] == '-')
1319                 return -1;
1320         strbuf_splice(sb, 0, 0, "refs/heads/", 11);
1321         return check_refname_format(sb->buf, 0);
1322 }
1323
1324 /*
1325  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
1326  * notably "xyz^" for "parent of xyz"
1327  */
1328 int get_sha1(const char *name, unsigned char *sha1)
1329 {
1330         struct object_context unused;
1331         return get_sha1_with_context(name, 0, sha1, &unused);
1332 }
1333
1334 /*
1335  * This is like "get_sha1()", but for struct object_id.
1336  */
1337 int get_oid(const char *name, struct object_id *oid)
1338 {
1339         return get_sha1(name, oid->hash);
1340 }
1341
1342
1343 /*
1344  * Many callers know that the user meant to name a commit-ish by
1345  * syntactical positions where the object name appears.  Calling this
1346  * function allows the machinery to disambiguate shorter-than-unique
1347  * abbreviated object names between commit-ish and others.
1348  *
1349  * Note that this does NOT error out when the named object is not a
1350  * commit-ish. It is merely to give a hint to the disambiguation
1351  * machinery.
1352  */
1353 int get_sha1_committish(const char *name, unsigned char *sha1)
1354 {
1355         struct object_context unused;
1356         return get_sha1_with_context(name, GET_SHA1_COMMITTISH,
1357                                      sha1, &unused);
1358 }
1359
1360 int get_sha1_treeish(const char *name, unsigned char *sha1)
1361 {
1362         struct object_context unused;
1363         return get_sha1_with_context(name, GET_SHA1_TREEISH,
1364                                      sha1, &unused);
1365 }
1366
1367 int get_sha1_commit(const char *name, unsigned char *sha1)
1368 {
1369         struct object_context unused;
1370         return get_sha1_with_context(name, GET_SHA1_COMMIT,
1371                                      sha1, &unused);
1372 }
1373
1374 int get_sha1_tree(const char *name, unsigned char *sha1)
1375 {
1376         struct object_context unused;
1377         return get_sha1_with_context(name, GET_SHA1_TREE,
1378                                      sha1, &unused);
1379 }
1380
1381 int get_sha1_blob(const char *name, unsigned char *sha1)
1382 {
1383         struct object_context unused;
1384         return get_sha1_with_context(name, GET_SHA1_BLOB,
1385                                      sha1, &unused);
1386 }
1387
1388 /* Must be called only when object_name:filename doesn't exist. */
1389 static void diagnose_invalid_sha1_path(const char *prefix,
1390                                        const char *filename,
1391                                        const unsigned char *tree_sha1,
1392                                        const char *object_name,
1393                                        int object_name_len)
1394 {
1395         unsigned char sha1[20];
1396         unsigned mode;
1397
1398         if (!prefix)
1399                 prefix = "";
1400
1401         if (file_exists(filename))
1402                 die("Path '%s' exists on disk, but not in '%.*s'.",
1403                     filename, object_name_len, object_name);
1404         if (errno == ENOENT || errno == ENOTDIR) {
1405                 char *fullname = xstrfmt("%s%s", prefix, filename);
1406
1407                 if (!get_tree_entry(tree_sha1, fullname,
1408                                     sha1, &mode)) {
1409                         die("Path '%s' exists, but not '%s'.\n"
1410                             "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
1411                             fullname,
1412                             filename,
1413                             object_name_len, object_name,
1414                             fullname,
1415                             object_name_len, object_name,
1416                             filename);
1417                 }
1418                 die("Path '%s' does not exist in '%.*s'",
1419                     filename, object_name_len, object_name);
1420         }
1421 }
1422
1423 /* Must be called only when :stage:filename doesn't exist. */
1424 static void diagnose_invalid_index_path(int stage,
1425                                         const char *prefix,
1426                                         const char *filename)
1427 {
1428         const struct cache_entry *ce;
1429         int pos;
1430         unsigned namelen = strlen(filename);
1431         struct strbuf fullname = STRBUF_INIT;
1432
1433         if (!prefix)
1434                 prefix = "";
1435
1436         /* Wrong stage number? */
1437         pos = cache_name_pos(filename, namelen);
1438         if (pos < 0)
1439                 pos = -pos - 1;
1440         if (pos < active_nr) {
1441                 ce = active_cache[pos];
1442                 if (ce_namelen(ce) == namelen &&
1443                     !memcmp(ce->name, filename, namelen))
1444                         die("Path '%s' is in the index, but not at stage %d.\n"
1445                             "Did you mean ':%d:%s'?",
1446                             filename, stage,
1447                             ce_stage(ce), filename);
1448         }
1449
1450         /* Confusion between relative and absolute filenames? */
1451         strbuf_addstr(&fullname, prefix);
1452         strbuf_addstr(&fullname, filename);
1453         pos = cache_name_pos(fullname.buf, fullname.len);
1454         if (pos < 0)
1455                 pos = -pos - 1;
1456         if (pos < active_nr) {
1457                 ce = active_cache[pos];
1458                 if (ce_namelen(ce) == fullname.len &&
1459                     !memcmp(ce->name, fullname.buf, fullname.len))
1460                         die("Path '%s' is in the index, but not '%s'.\n"
1461                             "Did you mean ':%d:%s' aka ':%d:./%s'?",
1462                             fullname.buf, filename,
1463                             ce_stage(ce), fullname.buf,
1464                             ce_stage(ce), filename);
1465         }
1466
1467         if (file_exists(filename))
1468                 die("Path '%s' exists on disk, but not in the index.", filename);
1469         if (errno == ENOENT || errno == ENOTDIR)
1470                 die("Path '%s' does not exist (neither on disk nor in the index).",
1471                     filename);
1472
1473         strbuf_release(&fullname);
1474 }
1475
1476
1477 static char *resolve_relative_path(const char *rel)
1478 {
1479         if (!starts_with(rel, "./") && !starts_with(rel, "../"))
1480                 return NULL;
1481
1482         if (!is_inside_work_tree())
1483                 die("relative path syntax can't be used outside working tree.");
1484
1485         /* die() inside prefix_path() if resolved path is outside worktree */
1486         return prefix_path(startup_info->prefix,
1487                            startup_info->prefix ? strlen(startup_info->prefix) : 0,
1488                            rel);
1489 }
1490
1491 static int get_sha1_with_context_1(const char *name,
1492                                    unsigned flags,
1493                                    const char *prefix,
1494                                    unsigned char *sha1,
1495                                    struct object_context *oc)
1496 {
1497         int ret, bracket_depth;
1498         int namelen = strlen(name);
1499         const char *cp;
1500         int only_to_die = flags & GET_SHA1_ONLY_TO_DIE;
1501
1502         if (only_to_die)
1503                 flags |= GET_SHA1_QUIETLY;
1504
1505         memset(oc, 0, sizeof(*oc));
1506         oc->mode = S_IFINVALID;
1507         ret = get_sha1_1(name, namelen, sha1, flags);
1508         if (!ret)
1509                 return ret;
1510         /*
1511          * sha1:path --> object name of path in ent sha1
1512          * :path -> object name of absolute path in index
1513          * :./path -> object name of path relative to cwd in index
1514          * :[0-3]:path -> object name of path in index at stage
1515          * :/foo -> recent commit matching foo
1516          */
1517         if (name[0] == ':') {
1518                 int stage = 0;
1519                 const struct cache_entry *ce;
1520                 char *new_path = NULL;
1521                 int pos;
1522                 if (!only_to_die && namelen > 2 && name[1] == '/') {
1523                         struct commit_list *list = NULL;
1524
1525                         for_each_ref(handle_one_ref, &list);
1526                         commit_list_sort_by_date(&list);
1527                         return get_sha1_oneline(name + 2, sha1, list);
1528                 }
1529                 if (namelen < 3 ||
1530                     name[2] != ':' ||
1531                     name[1] < '0' || '3' < name[1])
1532                         cp = name + 1;
1533                 else {
1534                         stage = name[1] - '0';
1535                         cp = name + 3;
1536                 }
1537                 new_path = resolve_relative_path(cp);
1538                 if (!new_path) {
1539                         namelen = namelen - (cp - name);
1540                 } else {
1541                         cp = new_path;
1542                         namelen = strlen(cp);
1543                 }
1544
1545                 strlcpy(oc->path, cp, sizeof(oc->path));
1546
1547                 if (!active_cache)
1548                         read_cache();
1549                 pos = cache_name_pos(cp, namelen);
1550                 if (pos < 0)
1551                         pos = -pos - 1;
1552                 while (pos < active_nr) {
1553                         ce = active_cache[pos];
1554                         if (ce_namelen(ce) != namelen ||
1555                             memcmp(ce->name, cp, namelen))
1556                                 break;
1557                         if (ce_stage(ce) == stage) {
1558                                 hashcpy(sha1, ce->oid.hash);
1559                                 oc->mode = ce->ce_mode;
1560                                 free(new_path);
1561                                 return 0;
1562                         }
1563                         pos++;
1564                 }
1565                 if (only_to_die && name[1] && name[1] != '/')
1566                         diagnose_invalid_index_path(stage, prefix, cp);
1567                 free(new_path);
1568                 return -1;
1569         }
1570         for (cp = name, bracket_depth = 0; *cp; cp++) {
1571                 if (*cp == '{')
1572                         bracket_depth++;
1573                 else if (bracket_depth && *cp == '}')
1574                         bracket_depth--;
1575                 else if (!bracket_depth && *cp == ':')
1576                         break;
1577         }
1578         if (*cp == ':') {
1579                 unsigned char tree_sha1[20];
1580                 int len = cp - name;
1581                 unsigned sub_flags = flags;
1582
1583                 sub_flags &= ~GET_SHA1_DISAMBIGUATORS;
1584                 sub_flags |= GET_SHA1_TREEISH;
1585
1586                 if (!get_sha1_1(name, len, tree_sha1, sub_flags)) {
1587                         const char *filename = cp+1;
1588                         char *new_filename = NULL;
1589
1590                         new_filename = resolve_relative_path(filename);
1591                         if (new_filename)
1592                                 filename = new_filename;
1593                         if (flags & GET_SHA1_FOLLOW_SYMLINKS) {
1594                                 ret = get_tree_entry_follow_symlinks(tree_sha1,
1595                                         filename, sha1, &oc->symlink_path,
1596                                         &oc->mode);
1597                         } else {
1598                                 ret = get_tree_entry(tree_sha1, filename,
1599                                                      sha1, &oc->mode);
1600                                 if (ret && only_to_die) {
1601                                         diagnose_invalid_sha1_path(prefix,
1602                                                                    filename,
1603                                                                    tree_sha1,
1604                                                                    name, len);
1605                                 }
1606                         }
1607                         hashcpy(oc->tree, tree_sha1);
1608                         strlcpy(oc->path, filename, sizeof(oc->path));
1609
1610                         free(new_filename);
1611                         return ret;
1612                 } else {
1613                         if (only_to_die)
1614                                 die("Invalid object name '%.*s'.", len, name);
1615                 }
1616         }
1617         return ret;
1618 }
1619
1620 /*
1621  * Call this function when you know "name" given by the end user must
1622  * name an object but it doesn't; the function _may_ die with a better
1623  * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
1624  * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
1625  * you have a chance to diagnose the error further.
1626  */
1627 void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
1628 {
1629         struct object_context oc;
1630         unsigned char sha1[20];
1631         get_sha1_with_context_1(name, GET_SHA1_ONLY_TO_DIE, prefix, sha1, &oc);
1632 }
1633
1634 int get_sha1_with_context(const char *str, unsigned flags, unsigned char *sha1, struct object_context *orc)
1635 {
1636         if (flags & GET_SHA1_FOLLOW_SYMLINKS && flags & GET_SHA1_ONLY_TO_DIE)
1637                 die("BUG: incompatible flags for get_sha1_with_context");
1638         return get_sha1_with_context_1(str, flags, NULL, sha1, orc);
1639 }