Merge branch 'jc/receive-pack-auto'
[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
9 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
10 {
11         struct alternate_object_database *alt;
12         char hex[40];
13         int found = 0;
14         static struct alternate_object_database *fakeent;
15
16         if (!fakeent) {
17                 const char *objdir = get_object_directory();
18                 int objdir_len = strlen(objdir);
19                 int entlen = objdir_len + 43;
20                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
21                 memcpy(fakeent->base, objdir, objdir_len);
22                 fakeent->name = fakeent->base + objdir_len + 1;
23                 fakeent->name[-1] = '/';
24         }
25         fakeent->next = alt_odb_list;
26
27         sprintf(hex, "%.2s", name);
28         for (alt = fakeent; alt && found < 2; alt = alt->next) {
29                 struct dirent *de;
30                 DIR *dir;
31                 sprintf(alt->name, "%.2s/", name);
32                 dir = opendir(alt->base);
33                 if (!dir)
34                         continue;
35                 while ((de = readdir(dir)) != NULL) {
36                         if (strlen(de->d_name) != 38)
37                                 continue;
38                         if (memcmp(de->d_name, name + 2, len - 2))
39                                 continue;
40                         if (!found) {
41                                 memcpy(hex + 2, de->d_name, 38);
42                                 found++;
43                         }
44                         else if (memcmp(hex + 2, de->d_name, 38)) {
45                                 found = 2;
46                                 break;
47                         }
48                 }
49                 closedir(dir);
50         }
51         if (found == 1)
52                 return get_sha1_hex(hex, sha1) == 0;
53         return found;
54 }
55
56 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
57 {
58         do {
59                 if (*a != *b)
60                         return 0;
61                 a++;
62                 b++;
63                 len -= 2;
64         } while (len > 1);
65         if (len)
66                 if ((*a ^ *b) & 0xf0)
67                         return 0;
68         return 1;
69 }
70
71 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
72 {
73         struct packed_git *p;
74         const unsigned char *found_sha1 = NULL;
75         int found = 0;
76
77         prepare_packed_git();
78         for (p = packed_git; p && found < 2; p = p->next) {
79                 uint32_t num, last;
80                 uint32_t first = 0;
81                 open_pack_index(p);
82                 num = p->num_objects;
83                 last = num;
84                 while (first < last) {
85                         uint32_t mid = (first + last) / 2;
86                         const unsigned char *now;
87                         int cmp;
88
89                         now = nth_packed_object_sha1(p, mid);
90                         cmp = hashcmp(match, now);
91                         if (!cmp) {
92                                 first = mid;
93                                 break;
94                         }
95                         if (cmp > 0) {
96                                 first = mid+1;
97                                 continue;
98                         }
99                         last = mid;
100                 }
101                 if (first < num) {
102                         const unsigned char *now, *next;
103                        now = nth_packed_object_sha1(p, first);
104                         if (match_sha(len, match, now)) {
105                                 next = nth_packed_object_sha1(p, first+1);
106                                if (!next|| !match_sha(len, match, next)) {
107                                         /* unique within this pack */
108                                         if (!found) {
109                                                 found_sha1 = now;
110                                                 found++;
111                                         }
112                                         else if (hashcmp(found_sha1, now)) {
113                                                 found = 2;
114                                                 break;
115                                         }
116                                 }
117                                 else {
118                                         /* not even unique within this pack */
119                                         found = 2;
120                                         break;
121                                 }
122                         }
123                 }
124         }
125         if (found == 1)
126                 hashcpy(sha1, found_sha1);
127         return found;
128 }
129
130 #define SHORT_NAME_NOT_FOUND (-1)
131 #define SHORT_NAME_AMBIGUOUS (-2)
132
133 static int find_unique_short_object(int len, char *canonical,
134                                     unsigned char *res, unsigned char *sha1)
135 {
136         int has_unpacked, has_packed;
137         unsigned char unpacked_sha1[20], packed_sha1[20];
138
139         prepare_alt_odb();
140         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
141         has_packed = find_short_packed_object(len, res, packed_sha1);
142         if (!has_unpacked && !has_packed)
143                 return SHORT_NAME_NOT_FOUND;
144         if (1 < has_unpacked || 1 < has_packed)
145                 return SHORT_NAME_AMBIGUOUS;
146         if (has_unpacked != has_packed) {
147                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
148                 return 0;
149         }
150         /* Both have unique ones -- do they match? */
151         if (hashcmp(packed_sha1, unpacked_sha1))
152                 return SHORT_NAME_AMBIGUOUS;
153         hashcpy(sha1, packed_sha1);
154         return 0;
155 }
156
157 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
158                           int quietly)
159 {
160         int i, status;
161         char canonical[40];
162         unsigned char res[20];
163
164         if (len < MINIMUM_ABBREV || len > 40)
165                 return -1;
166         hashclr(res);
167         memset(canonical, 'x', 40);
168         for (i = 0; i < len ;i++) {
169                 unsigned char c = name[i];
170                 unsigned char val;
171                 if (c >= '0' && c <= '9')
172                         val = c - '0';
173                 else if (c >= 'a' && c <= 'f')
174                         val = c - 'a' + 10;
175                 else if (c >= 'A' && c <='F') {
176                         val = c - 'A' + 10;
177                         c -= 'A' - 'a';
178                 }
179                 else
180                         return -1;
181                 canonical[i] = c;
182                 if (!(i & 1))
183                         val <<= 4;
184                 res[i >> 1] |= val;
185         }
186
187         status = find_unique_short_object(i, canonical, res, sha1);
188         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
189                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
190         return status;
191 }
192
193 const char *find_unique_abbrev(const unsigned char *sha1, int len)
194 {
195         int status, exists;
196         static char hex[41];
197
198         exists = has_sha1_file(sha1);
199         memcpy(hex, sha1_to_hex(sha1), 40);
200         if (len == 40 || !len)
201                 return hex;
202         while (len < 40) {
203                 unsigned char sha1_ret[20];
204                 status = get_short_sha1(hex, len, sha1_ret, 1);
205                 if (exists
206                     ? !status
207                     : status == SHORT_NAME_NOT_FOUND) {
208                         hex[len] = 0;
209                         return hex;
210                 }
211                 len++;
212         }
213         return hex;
214 }
215
216 static int ambiguous_path(const char *path, int len)
217 {
218         int slash = 1;
219         int cnt;
220
221         for (cnt = 0; cnt < len; cnt++) {
222                 switch (*path++) {
223                 case '\0':
224                         break;
225                 case '/':
226                         if (slash)
227                                 break;
228                         slash = 1;
229                         continue;
230                 case '.':
231                         continue;
232                 default:
233                         slash = 0;
234                         continue;
235                 }
236                 break;
237         }
238         return slash;
239 }
240
241 /*
242  * *string and *len will only be substituted, and *string returned (for
243  * later free()ing) if the string passed in is of the form @{-<n>}.
244  */
245 static char *substitute_branch_name(const char **string, int *len)
246 {
247         struct strbuf buf = STRBUF_INIT;
248         int ret = interpret_branch_name(*string, &buf);
249
250         if (ret == *len) {
251                 size_t size;
252                 *string = strbuf_detach(&buf, &size);
253                 *len = size;
254                 return (char *)*string;
255         }
256
257         return NULL;
258 }
259
260 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
261 {
262         char *last_branch = substitute_branch_name(&str, &len);
263         const char **p, *r;
264         int refs_found = 0;
265
266         *ref = NULL;
267         for (p = ref_rev_parse_rules; *p; p++) {
268                 char fullref[PATH_MAX];
269                 unsigned char sha1_from_ref[20];
270                 unsigned char *this_result;
271                 int flag;
272
273                 this_result = refs_found ? sha1_from_ref : sha1;
274                 mksnpath(fullref, sizeof(fullref), *p, len, str);
275                 r = resolve_ref(fullref, this_result, 1, &flag);
276                 if (r) {
277                         if (!refs_found++)
278                                 *ref = xstrdup(r);
279                         if (!warn_ambiguous_refs)
280                                 break;
281                 } else if ((flag & REF_ISSYMREF) &&
282                            (len != 4 || strcmp(str, "HEAD")))
283                         warning("ignoring dangling symref %s.", fullref);
284         }
285         free(last_branch);
286         return refs_found;
287 }
288
289 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
290 {
291         char *last_branch = substitute_branch_name(&str, &len);
292         const char **p;
293         int logs_found = 0;
294
295         *log = NULL;
296         for (p = ref_rev_parse_rules; *p; p++) {
297                 struct stat st;
298                 unsigned char hash[20];
299                 char path[PATH_MAX];
300                 const char *ref, *it;
301
302                 mksnpath(path, sizeof(path), *p, len, str);
303                 ref = resolve_ref(path, hash, 1, NULL);
304                 if (!ref)
305                         continue;
306                 if (!stat(git_path("logs/%s", path), &st) &&
307                     S_ISREG(st.st_mode))
308                         it = path;
309                 else if (strcmp(ref, path) &&
310                          !stat(git_path("logs/%s", ref), &st) &&
311                          S_ISREG(st.st_mode))
312                         it = ref;
313                 else
314                         continue;
315                 if (!logs_found++) {
316                         *log = xstrdup(it);
317                         hashcpy(sha1, hash);
318                 }
319                 if (!warn_ambiguous_refs)
320                         break;
321         }
322         free(last_branch);
323         return logs_found;
324 }
325
326 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
327
328 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
329 {
330         static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
331         char *real_ref = NULL;
332         int refs_found = 0;
333         int at, reflog_len;
334
335         if (len == 40 && !get_sha1_hex(str, sha1))
336                 return 0;
337
338         /* basic@{time or number or -number} format to query ref-log */
339         reflog_len = at = 0;
340         if (len && str[len-1] == '}') {
341                 for (at = len-2; at >= 0; at--) {
342                         if (str[at] == '@' && str[at+1] == '{') {
343                                 reflog_len = (len-1) - (at+2);
344                                 len = at;
345                                 break;
346                         }
347                 }
348         }
349
350         /* Accept only unambiguous ref paths. */
351         if (len && ambiguous_path(str, len))
352                 return -1;
353
354         if (!len && reflog_len) {
355                 struct strbuf buf = STRBUF_INIT;
356                 int ret;
357                 /* try the @{-N} syntax for n-th checkout */
358                 ret = interpret_branch_name(str+at, &buf);
359                 if (ret > 0) {
360                         /* substitute this branch name and restart */
361                         return get_sha1_1(buf.buf, buf.len, sha1);
362                 } else if (ret == 0) {
363                         return -1;
364                 }
365                 /* allow "@{...}" to mean the current branch reflog */
366                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
367         } else if (reflog_len)
368                 refs_found = dwim_log(str, len, sha1, &real_ref);
369         else
370                 refs_found = dwim_ref(str, len, sha1, &real_ref);
371
372         if (!refs_found)
373                 return -1;
374
375         if (warn_ambiguous_refs && refs_found > 1)
376                 fprintf(stderr, warning, len, str);
377
378         if (reflog_len) {
379                 int nth, i;
380                 unsigned long at_time;
381                 unsigned long co_time;
382                 int co_tz, co_cnt;
383
384                 /* Is it asking for N-th entry, or approxidate? */
385                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
386                         char ch = str[at+2+i];
387                         if ('0' <= ch && ch <= '9')
388                                 nth = nth * 10 + ch - '0';
389                         else
390                                 nth = -1;
391                 }
392                 if (100000000 <= nth) {
393                         at_time = nth;
394                         nth = -1;
395                 } else if (0 <= nth)
396                         at_time = 0;
397                 else {
398                         char *tmp = xstrndup(str + at + 2, reflog_len);
399                         at_time = approxidate(tmp);
400                         free(tmp);
401                 }
402                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
403                                 &co_time, &co_tz, &co_cnt)) {
404                         if (at_time)
405                                 fprintf(stderr,
406                                         "warning: Log for '%.*s' only goes "
407                                         "back to %s.\n", len, str,
408                                         show_date(co_time, co_tz, DATE_RFC2822));
409                         else
410                                 fprintf(stderr,
411                                         "warning: Log for '%.*s' only has "
412                                         "%d entries.\n", len, str, co_cnt);
413                 }
414         }
415
416         free(real_ref);
417         return 0;
418 }
419
420 static int get_parent(const char *name, int len,
421                       unsigned char *result, int idx)
422 {
423         unsigned char sha1[20];
424         int ret = get_sha1_1(name, len, sha1);
425         struct commit *commit;
426         struct commit_list *p;
427
428         if (ret)
429                 return ret;
430         commit = lookup_commit_reference(sha1);
431         if (!commit)
432                 return -1;
433         if (parse_commit(commit))
434                 return -1;
435         if (!idx) {
436                 hashcpy(result, commit->object.sha1);
437                 return 0;
438         }
439         p = commit->parents;
440         while (p) {
441                 if (!--idx) {
442                         hashcpy(result, p->item->object.sha1);
443                         return 0;
444                 }
445                 p = p->next;
446         }
447         return -1;
448 }
449
450 static int get_nth_ancestor(const char *name, int len,
451                             unsigned char *result, int generation)
452 {
453         unsigned char sha1[20];
454         struct commit *commit;
455         int ret;
456
457         ret = get_sha1_1(name, len, sha1);
458         if (ret)
459                 return ret;
460         commit = lookup_commit_reference(sha1);
461         if (!commit)
462                 return -1;
463
464         while (generation--) {
465                 if (parse_commit(commit) || !commit->parents)
466                         return -1;
467                 commit = commit->parents->item;
468         }
469         hashcpy(result, commit->object.sha1);
470         return 0;
471 }
472
473 struct object *peel_to_type(const char *name, int namelen,
474                             struct object *o, enum object_type expected_type)
475 {
476         if (name && !namelen)
477                 namelen = strlen(name);
478         if (!o) {
479                 unsigned char sha1[20];
480                 if (get_sha1_1(name, namelen, sha1))
481                         return NULL;
482                 o = parse_object(sha1);
483         }
484         while (1) {
485                 if (!o || (!o->parsed && !parse_object(o->sha1)))
486                         return NULL;
487                 if (o->type == expected_type)
488                         return o;
489                 if (o->type == OBJ_TAG)
490                         o = ((struct tag*) o)->tagged;
491                 else if (o->type == OBJ_COMMIT)
492                         o = &(((struct commit *) o)->tree->object);
493                 else {
494                         if (name)
495                                 error("%.*s: expected %s type, but the object "
496                                       "dereferences to %s type",
497                                       namelen, name, typename(expected_type),
498                                       typename(o->type));
499                         return NULL;
500                 }
501         }
502 }
503
504 static int peel_onion(const char *name, int len, unsigned char *sha1)
505 {
506         unsigned char outer[20];
507         const char *sp;
508         unsigned int expected_type = 0;
509         struct object *o;
510
511         /*
512          * "ref^{type}" dereferences ref repeatedly until you cannot
513          * dereference anymore, or you get an object of given type,
514          * whichever comes first.  "ref^{}" means just dereference
515          * tags until you get a non-tag.  "ref^0" is a shorthand for
516          * "ref^{commit}".  "commit^{tree}" could be used to find the
517          * top-level tree of the given commit.
518          */
519         if (len < 4 || name[len-1] != '}')
520                 return -1;
521
522         for (sp = name + len - 1; name <= sp; sp--) {
523                 int ch = *sp;
524                 if (ch == '{' && name < sp && sp[-1] == '^')
525                         break;
526         }
527         if (sp <= name)
528                 return -1;
529
530         sp++; /* beginning of type name, or closing brace for empty */
531         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
532                 expected_type = OBJ_COMMIT;
533         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
534                 expected_type = OBJ_TREE;
535         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
536                 expected_type = OBJ_BLOB;
537         else if (sp[0] == '}')
538                 expected_type = OBJ_NONE;
539         else
540                 return -1;
541
542         if (get_sha1_1(name, sp - name - 2, outer))
543                 return -1;
544
545         o = parse_object(outer);
546         if (!o)
547                 return -1;
548         if (!expected_type) {
549                 o = deref_tag(o, name, sp - name - 2);
550                 if (!o || (!o->parsed && !parse_object(o->sha1)))
551                         return -1;
552                 hashcpy(sha1, o->sha1);
553         }
554         else {
555                 /*
556                  * At this point, the syntax look correct, so
557                  * if we do not get the needed object, we should
558                  * barf.
559                  */
560                 o = peel_to_type(name, len, o, expected_type);
561                 if (o) {
562                         hashcpy(sha1, o->sha1);
563                         return 0;
564                 }
565                 return -1;
566         }
567         return 0;
568 }
569
570 static int get_describe_name(const char *name, int len, unsigned char *sha1)
571 {
572         const char *cp;
573
574         for (cp = name + len - 1; name + 2 <= cp; cp--) {
575                 char ch = *cp;
576                 if (hexval(ch) & ~0377) {
577                         /* We must be looking at g in "SOMETHING-g"
578                          * for it to be describe output.
579                          */
580                         if (ch == 'g' && cp[-1] == '-') {
581                                 cp++;
582                                 len -= cp - name;
583                                 return get_short_sha1(cp, len, sha1, 1);
584                         }
585                 }
586         }
587         return -1;
588 }
589
590 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
591 {
592         int ret, has_suffix;
593         const char *cp;
594
595         /*
596          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
597          */
598         has_suffix = 0;
599         for (cp = name + len - 1; name <= cp; cp--) {
600                 int ch = *cp;
601                 if ('0' <= ch && ch <= '9')
602                         continue;
603                 if (ch == '~' || ch == '^')
604                         has_suffix = ch;
605                 break;
606         }
607
608         if (has_suffix) {
609                 int num = 0;
610                 int len1 = cp - name;
611                 cp++;
612                 while (cp < name + len)
613                         num = num * 10 + *cp++ - '0';
614                 if (!num && len1 == len - 1)
615                         num = 1;
616                 if (has_suffix == '^')
617                         return get_parent(name, len1, sha1, num);
618                 /* else if (has_suffix == '~') -- goes without saying */
619                 return get_nth_ancestor(name, len1, sha1, num);
620         }
621
622         ret = peel_onion(name, len, sha1);
623         if (!ret)
624                 return 0;
625
626         ret = get_sha1_basic(name, len, sha1);
627         if (!ret)
628                 return 0;
629
630         /* It could be describe output that is "SOMETHING-gXXXX" */
631         ret = get_describe_name(name, len, sha1);
632         if (!ret)
633                 return 0;
634
635         return get_short_sha1(name, len, sha1, 0);
636 }
637
638 static int handle_one_ref(const char *path,
639                 const unsigned char *sha1, int flag, void *cb_data)
640 {
641         struct commit_list **list = cb_data;
642         struct object *object = parse_object(sha1);
643         if (!object)
644                 return 0;
645         if (object->type == OBJ_TAG) {
646                 object = deref_tag(object, path, strlen(path));
647                 if (!object)
648                         return 0;
649         }
650         if (object->type != OBJ_COMMIT)
651                 return 0;
652         insert_by_date((struct commit *)object, list);
653         return 0;
654 }
655
656 /*
657  * This interprets names like ':/Initial revision of "git"' by searching
658  * through history and returning the first commit whose message starts
659  * with the given string.
660  *
661  * For future extension, ':/!' is reserved. If you want to match a message
662  * beginning with a '!', you have to repeat the exclamation mark.
663  */
664
665 #define ONELINE_SEEN (1u<<20)
666 static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
667 {
668         struct commit_list *list = NULL, *backup = NULL, *l;
669         int retval = -1;
670         char *temp_commit_buffer = NULL;
671
672         if (prefix[0] == '!') {
673                 if (prefix[1] != '!')
674                         die ("Invalid search pattern: %s", prefix);
675                 prefix++;
676         }
677         for_each_ref(handle_one_ref, &list);
678         for (l = list; l; l = l->next)
679                 commit_list_insert(l->item, &backup);
680         while (list) {
681                 char *p;
682                 struct commit *commit;
683                 enum object_type type;
684                 unsigned long size;
685
686                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
687                 if (!parse_object(commit->object.sha1))
688                         continue;
689                 free(temp_commit_buffer);
690                 if (commit->buffer)
691                         p = commit->buffer;
692                 else {
693                         p = read_sha1_file(commit->object.sha1, &type, &size);
694                         if (!p)
695                                 continue;
696                         temp_commit_buffer = p;
697                 }
698                 if (!(p = strstr(p, "\n\n")))
699                         continue;
700                 if (!prefixcmp(p + 2, prefix)) {
701                         hashcpy(sha1, commit->object.sha1);
702                         retval = 0;
703                         break;
704                 }
705         }
706         free(temp_commit_buffer);
707         free_commit_list(list);
708         for (l = backup; l; l = l->next)
709                 clear_commit_marks(l->item, ONELINE_SEEN);
710         return retval;
711 }
712
713 struct grab_nth_branch_switch_cbdata {
714         long cnt, alloc;
715         struct strbuf *buf;
716 };
717
718 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
719                                   const char *email, unsigned long timestamp, int tz,
720                                   const char *message, void *cb_data)
721 {
722         struct grab_nth_branch_switch_cbdata *cb = cb_data;
723         const char *match = NULL, *target = NULL;
724         size_t len;
725         int nth;
726
727         if (!prefixcmp(message, "checkout: moving from ")) {
728                 match = message + strlen("checkout: moving from ");
729                 target = strstr(match, " to ");
730         }
731
732         if (!match || !target)
733                 return 0;
734
735         len = target - match;
736         nth = cb->cnt++ % cb->alloc;
737         strbuf_reset(&cb->buf[nth]);
738         strbuf_add(&cb->buf[nth], match, len);
739         return 0;
740 }
741
742 /*
743  * This reads "@{-N}" syntax, finds the name of the Nth previous
744  * branch we were on, and places the name of the branch in the given
745  * buf and returns the number of characters parsed if successful.
746  *
747  * If the input is not of the accepted format, it returns a negative
748  * number to signal an error.
749  *
750  * If the input was ok but there are not N branch switches in the
751  * reflog, it returns 0.
752  */
753 int interpret_branch_name(const char *name, struct strbuf *buf)
754 {
755         long nth;
756         int i, retval;
757         struct grab_nth_branch_switch_cbdata cb;
758         const char *brace;
759         char *num_end;
760
761         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
762                 return -1;
763         brace = strchr(name, '}');
764         if (!brace)
765                 return -1;
766         nth = strtol(name+3, &num_end, 10);
767         if (num_end != brace)
768                 return -1;
769         if (nth <= 0)
770                 return -1;
771         cb.alloc = nth;
772         cb.buf = xmalloc(nth * sizeof(struct strbuf));
773         for (i = 0; i < nth; i++)
774                 strbuf_init(&cb.buf[i], 20);
775         cb.cnt = 0;
776         retval = 0;
777         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
778         if (cb.cnt < nth) {
779                 cb.cnt = 0;
780                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
781         }
782         if (cb.cnt < nth)
783                 goto release_return;
784         i = cb.cnt % nth;
785         strbuf_reset(buf);
786         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
787         retval = brace-name+1;
788
789 release_return:
790         for (i = 0; i < nth; i++)
791                 strbuf_release(&cb.buf[i]);
792         free(cb.buf);
793
794         return retval;
795 }
796
797 /*
798  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
799  * notably "xyz^" for "parent of xyz"
800  */
801 int get_sha1(const char *name, unsigned char *sha1)
802 {
803         unsigned unused;
804         return get_sha1_with_mode(name, sha1, &unused);
805 }
806
807 int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
808 {
809         int ret, bracket_depth;
810         int namelen = strlen(name);
811         const char *cp;
812
813         *mode = S_IFINVALID;
814         ret = get_sha1_1(name, namelen, sha1);
815         if (!ret)
816                 return ret;
817         /* sha1:path --> object name of path in ent sha1
818          * :path -> object name of path in index
819          * :[0-3]:path -> object name of path in index at stage
820          */
821         if (name[0] == ':') {
822                 int stage = 0;
823                 struct cache_entry *ce;
824                 int pos;
825                 if (namelen > 2 && name[1] == '/')
826                         return get_sha1_oneline(name + 2, sha1);
827                 if (namelen < 3 ||
828                     name[2] != ':' ||
829                     name[1] < '0' || '3' < name[1])
830                         cp = name + 1;
831                 else {
832                         stage = name[1] - '0';
833                         cp = name + 3;
834                 }
835                 namelen = namelen - (cp - name);
836                 if (!active_cache)
837                         read_cache();
838                 pos = cache_name_pos(cp, namelen);
839                 if (pos < 0)
840                         pos = -pos - 1;
841                 while (pos < active_nr) {
842                         ce = active_cache[pos];
843                         if (ce_namelen(ce) != namelen ||
844                             memcmp(ce->name, cp, namelen))
845                                 break;
846                         if (ce_stage(ce) == stage) {
847                                 hashcpy(sha1, ce->sha1);
848                                 *mode = ce->ce_mode;
849                                 return 0;
850                         }
851                         pos++;
852                 }
853                 return -1;
854         }
855         for (cp = name, bracket_depth = 0; *cp; cp++) {
856                 if (*cp == '{')
857                         bracket_depth++;
858                 else if (bracket_depth && *cp == '}')
859                         bracket_depth--;
860                 else if (!bracket_depth && *cp == ':')
861                         break;
862         }
863         if (*cp == ':') {
864                 unsigned char tree_sha1[20];
865                 if (!get_sha1_1(name, cp-name, tree_sha1))
866                         return get_tree_entry(tree_sha1, cp+1, sha1,
867                                               mode);
868         }
869         return ret;
870 }