Merge branch 'maint-1.7.1' into maint-1.7.2
[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
10 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
11 {
12         struct alternate_object_database *alt;
13         char hex[40];
14         int found = 0;
15         static struct alternate_object_database *fakeent;
16
17         if (!fakeent) {
18                 const char *objdir = get_object_directory();
19                 int objdir_len = strlen(objdir);
20                 int entlen = objdir_len + 43;
21                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
22                 memcpy(fakeent->base, objdir, objdir_len);
23                 fakeent->name = fakeent->base + objdir_len + 1;
24                 fakeent->name[-1] = '/';
25         }
26         fakeent->next = alt_odb_list;
27
28         sprintf(hex, "%.2s", name);
29         for (alt = fakeent; alt && found < 2; alt = alt->next) {
30                 struct dirent *de;
31                 DIR *dir;
32                 sprintf(alt->name, "%.2s/", name);
33                 dir = opendir(alt->base);
34                 if (!dir)
35                         continue;
36                 while ((de = readdir(dir)) != NULL) {
37                         if (strlen(de->d_name) != 38)
38                                 continue;
39                         if (memcmp(de->d_name, name + 2, len - 2))
40                                 continue;
41                         if (!found) {
42                                 memcpy(hex + 2, de->d_name, 38);
43                                 found++;
44                         }
45                         else if (memcmp(hex + 2, de->d_name, 38)) {
46                                 found = 2;
47                                 break;
48                         }
49                 }
50                 closedir(dir);
51         }
52         if (found == 1)
53                 return get_sha1_hex(hex, sha1) == 0;
54         return found;
55 }
56
57 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
58 {
59         do {
60                 if (*a != *b)
61                         return 0;
62                 a++;
63                 b++;
64                 len -= 2;
65         } while (len > 1);
66         if (len)
67                 if ((*a ^ *b) & 0xf0)
68                         return 0;
69         return 1;
70 }
71
72 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
73 {
74         struct packed_git *p;
75         const unsigned char *found_sha1 = NULL;
76         int found = 0;
77
78         prepare_packed_git();
79         for (p = packed_git; p && found < 2; p = p->next) {
80                 uint32_t num, last;
81                 uint32_t first = 0;
82                 open_pack_index(p);
83                 num = p->num_objects;
84                 last = num;
85                 while (first < last) {
86                         uint32_t mid = (first + last) / 2;
87                         const unsigned char *now;
88                         int cmp;
89
90                         now = nth_packed_object_sha1(p, mid);
91                         cmp = hashcmp(match, now);
92                         if (!cmp) {
93                                 first = mid;
94                                 break;
95                         }
96                         if (cmp > 0) {
97                                 first = mid+1;
98                                 continue;
99                         }
100                         last = mid;
101                 }
102                 if (first < num) {
103                         const unsigned char *now, *next;
104                        now = nth_packed_object_sha1(p, first);
105                         if (match_sha(len, match, now)) {
106                                 next = nth_packed_object_sha1(p, first+1);
107                                if (!next|| !match_sha(len, match, next)) {
108                                         /* unique within this pack */
109                                         if (!found) {
110                                                 found_sha1 = now;
111                                                 found++;
112                                         }
113                                         else if (hashcmp(found_sha1, now)) {
114                                                 found = 2;
115                                                 break;
116                                         }
117                                 }
118                                 else {
119                                         /* not even unique within this pack */
120                                         found = 2;
121                                         break;
122                                 }
123                         }
124                 }
125         }
126         if (found == 1)
127                 hashcpy(sha1, found_sha1);
128         return found;
129 }
130
131 #define SHORT_NAME_NOT_FOUND (-1)
132 #define SHORT_NAME_AMBIGUOUS (-2)
133
134 static int find_unique_short_object(int len, char *canonical,
135                                     unsigned char *res, unsigned char *sha1)
136 {
137         int has_unpacked, has_packed;
138         unsigned char unpacked_sha1[20], packed_sha1[20];
139
140         prepare_alt_odb();
141         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
142         has_packed = find_short_packed_object(len, res, packed_sha1);
143         if (!has_unpacked && !has_packed)
144                 return SHORT_NAME_NOT_FOUND;
145         if (1 < has_unpacked || 1 < has_packed)
146                 return SHORT_NAME_AMBIGUOUS;
147         if (has_unpacked != has_packed) {
148                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
149                 return 0;
150         }
151         /* Both have unique ones -- do they match? */
152         if (hashcmp(packed_sha1, unpacked_sha1))
153                 return SHORT_NAME_AMBIGUOUS;
154         hashcpy(sha1, packed_sha1);
155         return 0;
156 }
157
158 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
159                           int quietly)
160 {
161         int i, status;
162         char canonical[40];
163         unsigned char res[20];
164
165         if (len < MINIMUM_ABBREV || len > 40)
166                 return -1;
167         hashclr(res);
168         memset(canonical, 'x', 40);
169         for (i = 0; i < len ;i++) {
170                 unsigned char c = name[i];
171                 unsigned char val;
172                 if (c >= '0' && c <= '9')
173                         val = c - '0';
174                 else if (c >= 'a' && c <= 'f')
175                         val = c - 'a' + 10;
176                 else if (c >= 'A' && c <='F') {
177                         val = c - 'A' + 10;
178                         c -= 'A' - 'a';
179                 }
180                 else
181                         return -1;
182                 canonical[i] = c;
183                 if (!(i & 1))
184                         val <<= 4;
185                 res[i >> 1] |= val;
186         }
187
188         status = find_unique_short_object(i, canonical, res, sha1);
189         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
190                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
191         return status;
192 }
193
194 const char *find_unique_abbrev(const unsigned char *sha1, int len)
195 {
196         int status, exists;
197         static char hex[41];
198
199         exists = has_sha1_file(sha1);
200         memcpy(hex, sha1_to_hex(sha1), 40);
201         if (len == 40 || !len)
202                 return hex;
203         while (len < 40) {
204                 unsigned char sha1_ret[20];
205                 status = get_short_sha1(hex, len, sha1_ret, 1);
206                 if (exists
207                     ? !status
208                     : status == SHORT_NAME_NOT_FOUND) {
209                         hex[len] = 0;
210                         return hex;
211                 }
212                 len++;
213         }
214         return hex;
215 }
216
217 static int ambiguous_path(const char *path, int len)
218 {
219         int slash = 1;
220         int cnt;
221
222         for (cnt = 0; cnt < len; cnt++) {
223                 switch (*path++) {
224                 case '\0':
225                         break;
226                 case '/':
227                         if (slash)
228                                 break;
229                         slash = 1;
230                         continue;
231                 case '.':
232                         continue;
233                 default:
234                         slash = 0;
235                         continue;
236                 }
237                 break;
238         }
239         return slash;
240 }
241
242 /*
243  * *string and *len will only be substituted, and *string returned (for
244  * later free()ing) if the string passed in is a magic short-hand form
245  * to name a branch.
246  */
247 static char *substitute_branch_name(const char **string, int *len)
248 {
249         struct strbuf buf = STRBUF_INIT;
250         int ret = interpret_branch_name(*string, &buf);
251
252         if (ret == *len) {
253                 size_t size;
254                 *string = strbuf_detach(&buf, &size);
255                 *len = size;
256                 return (char *)*string;
257         }
258
259         return NULL;
260 }
261
262 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
263 {
264         char *last_branch = substitute_branch_name(&str, &len);
265         const char **p, *r;
266         int refs_found = 0;
267
268         *ref = NULL;
269         for (p = ref_rev_parse_rules; *p; p++) {
270                 char fullref[PATH_MAX];
271                 unsigned char sha1_from_ref[20];
272                 unsigned char *this_result;
273                 int flag;
274
275                 this_result = refs_found ? sha1_from_ref : sha1;
276                 mksnpath(fullref, sizeof(fullref), *p, len, str);
277                 r = resolve_ref(fullref, this_result, 1, &flag);
278                 if (r) {
279                         if (!refs_found++)
280                                 *ref = xstrdup(r);
281                         if (!warn_ambiguous_refs)
282                                 break;
283                 } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD"))
284                         warning("ignoring dangling symref %s.", fullref);
285         }
286         free(last_branch);
287         return refs_found;
288 }
289
290 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
291 {
292         char *last_branch = substitute_branch_name(&str, &len);
293         const char **p;
294         int logs_found = 0;
295
296         *log = NULL;
297         for (p = ref_rev_parse_rules; *p; p++) {
298                 struct stat st;
299                 unsigned char hash[20];
300                 char path[PATH_MAX];
301                 const char *ref, *it;
302
303                 mksnpath(path, sizeof(path), *p, len, str);
304                 ref = resolve_ref(path, hash, 1, NULL);
305                 if (!ref)
306                         continue;
307                 if (!stat(git_path("logs/%s", path), &st) &&
308                     S_ISREG(st.st_mode))
309                         it = path;
310                 else if (strcmp(ref, path) &&
311                          !stat(git_path("logs/%s", ref), &st) &&
312                          S_ISREG(st.st_mode))
313                         it = ref;
314                 else
315                         continue;
316                 if (!logs_found++) {
317                         *log = xstrdup(it);
318                         hashcpy(sha1, hash);
319                 }
320                 if (!warn_ambiguous_refs)
321                         break;
322         }
323         free(last_branch);
324         return logs_found;
325 }
326
327 static inline int upstream_mark(const char *string, int len)
328 {
329         const char *suffix[] = { "@{upstream}", "@{u}" };
330         int i;
331
332         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
333                 int suffix_len = strlen(suffix[i]);
334                 if (suffix_len <= len
335                     && !memcmp(string, suffix[i], suffix_len))
336                         return suffix_len;
337         }
338         return 0;
339 }
340
341 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
342
343 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
344 {
345         static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
346         char *real_ref = NULL;
347         int refs_found = 0;
348         int at, reflog_len;
349
350         if (len == 40 && !get_sha1_hex(str, sha1))
351                 return 0;
352
353         /* basic@{time or number or -number} format to query ref-log */
354         reflog_len = at = 0;
355         if (len && str[len-1] == '}') {
356                 for (at = len-2; at >= 0; at--) {
357                         if (str[at] == '@' && str[at+1] == '{') {
358                                 if (!upstream_mark(str + at, len - at)) {
359                                         reflog_len = (len-1) - (at+2);
360                                         len = at;
361                                 }
362                                 break;
363                         }
364                 }
365         }
366
367         /* Accept only unambiguous ref paths. */
368         if (len && ambiguous_path(str, len))
369                 return -1;
370
371         if (!len && reflog_len) {
372                 struct strbuf buf = STRBUF_INIT;
373                 int ret;
374                 /* try the @{-N} syntax for n-th checkout */
375                 ret = interpret_branch_name(str+at, &buf);
376                 if (ret > 0) {
377                         /* substitute this branch name and restart */
378                         return get_sha1_1(buf.buf, buf.len, sha1);
379                 } else if (ret == 0) {
380                         return -1;
381                 }
382                 /* allow "@{...}" to mean the current branch reflog */
383                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
384         } else if (reflog_len)
385                 refs_found = dwim_log(str, len, sha1, &real_ref);
386         else
387                 refs_found = dwim_ref(str, len, sha1, &real_ref);
388
389         if (!refs_found)
390                 return -1;
391
392         if (warn_ambiguous_refs && refs_found > 1)
393                 fprintf(stderr, warning, len, str);
394
395         if (reflog_len) {
396                 int nth, i;
397                 unsigned long at_time;
398                 unsigned long co_time;
399                 int co_tz, co_cnt;
400
401                 /* a @{-N} placed anywhere except the start is an error */
402                 if (str[at+2] == '-')
403                         return -1;
404
405                 /* Is it asking for N-th entry, or approxidate? */
406                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
407                         char ch = str[at+2+i];
408                         if ('0' <= ch && ch <= '9')
409                                 nth = nth * 10 + ch - '0';
410                         else
411                                 nth = -1;
412                 }
413                 if (100000000 <= nth) {
414                         at_time = nth;
415                         nth = -1;
416                 } else if (0 <= nth)
417                         at_time = 0;
418                 else {
419                         int errors = 0;
420                         char *tmp = xstrndup(str + at + 2, reflog_len);
421                         at_time = approxidate_careful(tmp, &errors);
422                         free(tmp);
423                         if (errors)
424                                 return -1;
425                 }
426                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
427                                 &co_time, &co_tz, &co_cnt)) {
428                         if (at_time)
429                                 fprintf(stderr,
430                                         "warning: Log for '%.*s' only goes "
431                                         "back to %s.\n", len, str,
432                                         show_date(co_time, co_tz, DATE_RFC2822));
433                         else
434                                 fprintf(stderr,
435                                         "warning: Log for '%.*s' only has "
436                                         "%d entries.\n", len, str, co_cnt);
437                 }
438         }
439
440         free(real_ref);
441         return 0;
442 }
443
444 static int get_parent(const char *name, int len,
445                       unsigned char *result, int idx)
446 {
447         unsigned char sha1[20];
448         int ret = get_sha1_1(name, len, sha1);
449         struct commit *commit;
450         struct commit_list *p;
451
452         if (ret)
453                 return ret;
454         commit = lookup_commit_reference(sha1);
455         if (!commit)
456                 return -1;
457         if (parse_commit(commit))
458                 return -1;
459         if (!idx) {
460                 hashcpy(result, commit->object.sha1);
461                 return 0;
462         }
463         p = commit->parents;
464         while (p) {
465                 if (!--idx) {
466                         hashcpy(result, p->item->object.sha1);
467                         return 0;
468                 }
469                 p = p->next;
470         }
471         return -1;
472 }
473
474 static int get_nth_ancestor(const char *name, int len,
475                             unsigned char *result, int generation)
476 {
477         unsigned char sha1[20];
478         struct commit *commit;
479         int ret;
480
481         ret = get_sha1_1(name, len, sha1);
482         if (ret)
483                 return ret;
484         commit = lookup_commit_reference(sha1);
485         if (!commit)
486                 return -1;
487
488         while (generation--) {
489                 if (parse_commit(commit) || !commit->parents)
490                         return -1;
491                 commit = commit->parents->item;
492         }
493         hashcpy(result, commit->object.sha1);
494         return 0;
495 }
496
497 struct object *peel_to_type(const char *name, int namelen,
498                             struct object *o, enum object_type expected_type)
499 {
500         if (name && !namelen)
501                 namelen = strlen(name);
502         if (!o) {
503                 unsigned char sha1[20];
504                 if (get_sha1_1(name, namelen, sha1))
505                         return NULL;
506                 o = parse_object(sha1);
507         }
508         while (1) {
509                 if (!o || (!o->parsed && !parse_object(o->sha1)))
510                         return NULL;
511                 if (o->type == expected_type)
512                         return o;
513                 if (o->type == OBJ_TAG)
514                         o = ((struct tag*) o)->tagged;
515                 else if (o->type == OBJ_COMMIT)
516                         o = &(((struct commit *) o)->tree->object);
517                 else {
518                         if (name)
519                                 error("%.*s: expected %s type, but the object "
520                                       "dereferences to %s type",
521                                       namelen, name, typename(expected_type),
522                                       typename(o->type));
523                         return NULL;
524                 }
525         }
526 }
527
528 static int peel_onion(const char *name, int len, unsigned char *sha1)
529 {
530         unsigned char outer[20];
531         const char *sp;
532         unsigned int expected_type = 0;
533         struct object *o;
534
535         /*
536          * "ref^{type}" dereferences ref repeatedly until you cannot
537          * dereference anymore, or you get an object of given type,
538          * whichever comes first.  "ref^{}" means just dereference
539          * tags until you get a non-tag.  "ref^0" is a shorthand for
540          * "ref^{commit}".  "commit^{tree}" could be used to find the
541          * top-level tree of the given commit.
542          */
543         if (len < 4 || name[len-1] != '}')
544                 return -1;
545
546         for (sp = name + len - 1; name <= sp; sp--) {
547                 int ch = *sp;
548                 if (ch == '{' && name < sp && sp[-1] == '^')
549                         break;
550         }
551         if (sp <= name)
552                 return -1;
553
554         sp++; /* beginning of type name, or closing brace for empty */
555         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
556                 expected_type = OBJ_COMMIT;
557         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
558                 expected_type = OBJ_TREE;
559         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
560                 expected_type = OBJ_BLOB;
561         else if (sp[0] == '}')
562                 expected_type = OBJ_NONE;
563         else
564                 return -1;
565
566         if (get_sha1_1(name, sp - name - 2, outer))
567                 return -1;
568
569         o = parse_object(outer);
570         if (!o)
571                 return -1;
572         if (!expected_type) {
573                 o = deref_tag(o, name, sp - name - 2);
574                 if (!o || (!o->parsed && !parse_object(o->sha1)))
575                         return -1;
576                 hashcpy(sha1, o->sha1);
577         }
578         else {
579                 /*
580                  * At this point, the syntax look correct, so
581                  * if we do not get the needed object, we should
582                  * barf.
583                  */
584                 o = peel_to_type(name, len, o, expected_type);
585                 if (o) {
586                         hashcpy(sha1, o->sha1);
587                         return 0;
588                 }
589                 return -1;
590         }
591         return 0;
592 }
593
594 static int get_describe_name(const char *name, int len, unsigned char *sha1)
595 {
596         const char *cp;
597
598         for (cp = name + len - 1; name + 2 <= cp; cp--) {
599                 char ch = *cp;
600                 if (hexval(ch) & ~0377) {
601                         /* We must be looking at g in "SOMETHING-g"
602                          * for it to be describe output.
603                          */
604                         if (ch == 'g' && cp[-1] == '-') {
605                                 cp++;
606                                 len -= cp - name;
607                                 return get_short_sha1(cp, len, sha1, 1);
608                         }
609                 }
610         }
611         return -1;
612 }
613
614 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
615 {
616         int ret, has_suffix;
617         const char *cp;
618
619         /*
620          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
621          */
622         has_suffix = 0;
623         for (cp = name + len - 1; name <= cp; cp--) {
624                 int ch = *cp;
625                 if ('0' <= ch && ch <= '9')
626                         continue;
627                 if (ch == '~' || ch == '^')
628                         has_suffix = ch;
629                 break;
630         }
631
632         if (has_suffix) {
633                 int num = 0;
634                 int len1 = cp - name;
635                 cp++;
636                 while (cp < name + len)
637                         num = num * 10 + *cp++ - '0';
638                 if (!num && len1 == len - 1)
639                         num = 1;
640                 if (has_suffix == '^')
641                         return get_parent(name, len1, sha1, num);
642                 /* else if (has_suffix == '~') -- goes without saying */
643                 return get_nth_ancestor(name, len1, sha1, num);
644         }
645
646         ret = peel_onion(name, len, sha1);
647         if (!ret)
648                 return 0;
649
650         ret = get_sha1_basic(name, len, sha1);
651         if (!ret)
652                 return 0;
653
654         /* It could be describe output that is "SOMETHING-gXXXX" */
655         ret = get_describe_name(name, len, sha1);
656         if (!ret)
657                 return 0;
658
659         return get_short_sha1(name, len, sha1, 0);
660 }
661
662 /*
663  * This interprets names like ':/Initial revision of "git"' by searching
664  * through history and returning the first commit whose message starts
665  * the given regular expression.
666  *
667  * For future extension, ':/!' is reserved. If you want to match a message
668  * beginning with a '!', you have to repeat the exclamation mark.
669  */
670 #define ONELINE_SEEN (1u<<20)
671
672 static int handle_one_ref(const char *path,
673                 const unsigned char *sha1, int flag, void *cb_data)
674 {
675         struct commit_list **list = cb_data;
676         struct object *object = parse_object(sha1);
677         if (!object)
678                 return 0;
679         if (object->type == OBJ_TAG) {
680                 object = deref_tag(object, path, strlen(path));
681                 if (!object)
682                         return 0;
683         }
684         if (object->type != OBJ_COMMIT)
685                 return 0;
686         insert_by_date((struct commit *)object, list);
687         object->flags |= ONELINE_SEEN;
688         return 0;
689 }
690
691 static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
692 {
693         struct commit_list *list = NULL, *backup = NULL, *l;
694         int retval = -1;
695         char *temp_commit_buffer = NULL;
696         regex_t regex;
697
698         if (prefix[0] == '!') {
699                 if (prefix[1] != '!')
700                         die ("Invalid search pattern: %s", prefix);
701                 prefix++;
702         }
703
704         if (regcomp(&regex, prefix, REG_EXTENDED))
705                 die("Invalid search pattern: %s", prefix);
706
707         for_each_ref(handle_one_ref, &list);
708         for (l = list; l; l = l->next)
709                 commit_list_insert(l->item, &backup);
710         while (list) {
711                 char *p;
712                 struct commit *commit;
713                 enum object_type type;
714                 unsigned long size;
715
716                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
717                 if (!parse_object(commit->object.sha1))
718                         continue;
719                 free(temp_commit_buffer);
720                 if (commit->buffer)
721                         p = commit->buffer;
722                 else {
723                         p = read_sha1_file(commit->object.sha1, &type, &size);
724                         if (!p)
725                                 continue;
726                         temp_commit_buffer = p;
727                 }
728                 if (!(p = strstr(p, "\n\n")))
729                         continue;
730                 if (!regexec(&regex, p + 2, 0, NULL, 0)) {
731                         hashcpy(sha1, commit->object.sha1);
732                         retval = 0;
733                         break;
734                 }
735         }
736         regfree(&regex);
737         free(temp_commit_buffer);
738         free_commit_list(list);
739         for (l = backup; l; l = l->next)
740                 clear_commit_marks(l->item, ONELINE_SEEN);
741         return retval;
742 }
743
744 struct grab_nth_branch_switch_cbdata {
745         long cnt, alloc;
746         struct strbuf *buf;
747 };
748
749 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
750                                   const char *email, unsigned long timestamp, int tz,
751                                   const char *message, void *cb_data)
752 {
753         struct grab_nth_branch_switch_cbdata *cb = cb_data;
754         const char *match = NULL, *target = NULL;
755         size_t len;
756         int nth;
757
758         if (!prefixcmp(message, "checkout: moving from ")) {
759                 match = message + strlen("checkout: moving from ");
760                 target = strstr(match, " to ");
761         }
762
763         if (!match || !target)
764                 return 0;
765
766         len = target - match;
767         nth = cb->cnt++ % cb->alloc;
768         strbuf_reset(&cb->buf[nth]);
769         strbuf_add(&cb->buf[nth], match, len);
770         return 0;
771 }
772
773 /*
774  * Parse @{-N} syntax, return the number of characters parsed
775  * if successful; otherwise signal an error with negative value.
776  */
777 static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
778 {
779         long nth;
780         int i, retval;
781         struct grab_nth_branch_switch_cbdata cb;
782         const char *brace;
783         char *num_end;
784
785         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
786                 return -1;
787         brace = strchr(name, '}');
788         if (!brace)
789                 return -1;
790         nth = strtol(name+3, &num_end, 10);
791         if (num_end != brace)
792                 return -1;
793         if (nth <= 0)
794                 return -1;
795         cb.alloc = nth;
796         cb.buf = xmalloc(nth * sizeof(struct strbuf));
797         for (i = 0; i < nth; i++)
798                 strbuf_init(&cb.buf[i], 20);
799         cb.cnt = 0;
800         retval = 0;
801         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
802         if (cb.cnt < nth) {
803                 cb.cnt = 0;
804                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
805         }
806         if (cb.cnt < nth)
807                 goto release_return;
808         i = cb.cnt % nth;
809         strbuf_reset(buf);
810         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
811         retval = brace-name+1;
812
813 release_return:
814         for (i = 0; i < nth; i++)
815                 strbuf_release(&cb.buf[i]);
816         free(cb.buf);
817
818         return retval;
819 }
820
821 int get_sha1_mb(const char *name, unsigned char *sha1)
822 {
823         struct commit *one, *two;
824         struct commit_list *mbs;
825         unsigned char sha1_tmp[20];
826         const char *dots;
827         int st;
828
829         dots = strstr(name, "...");
830         if (!dots)
831                 return get_sha1(name, sha1);
832         if (dots == name)
833                 st = get_sha1("HEAD", sha1_tmp);
834         else {
835                 struct strbuf sb;
836                 strbuf_init(&sb, dots - name);
837                 strbuf_add(&sb, name, dots - name);
838                 st = get_sha1(sb.buf, sha1_tmp);
839                 strbuf_release(&sb);
840         }
841         if (st)
842                 return st;
843         one = lookup_commit_reference_gently(sha1_tmp, 0);
844         if (!one)
845                 return -1;
846
847         if (get_sha1(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
848                 return -1;
849         two = lookup_commit_reference_gently(sha1_tmp, 0);
850         if (!two)
851                 return -1;
852         mbs = get_merge_bases(one, two, 1);
853         if (!mbs || mbs->next)
854                 st = -1;
855         else {
856                 st = 0;
857                 hashcpy(sha1, mbs->item->object.sha1);
858         }
859         free_commit_list(mbs);
860         return st;
861 }
862
863 /*
864  * This reads short-hand syntax that not only evaluates to a commit
865  * object name, but also can act as if the end user spelled the name
866  * of the branch from the command line.
867  *
868  * - "@{-N}" finds the name of the Nth previous branch we were on, and
869  *   places the name of the branch in the given buf and returns the
870  *   number of characters parsed if successful.
871  *
872  * - "<branch>@{upstream}" finds the name of the other ref that
873  *   <branch> is configured to merge with (missing <branch> defaults
874  *   to the current branch), and places the name of the branch in the
875  *   given buf and returns the number of characters parsed if
876  *   successful.
877  *
878  * If the input is not of the accepted format, it returns a negative
879  * number to signal an error.
880  *
881  * If the input was ok but there are not N branch switches in the
882  * reflog, it returns 0.
883  */
884 int interpret_branch_name(const char *name, struct strbuf *buf)
885 {
886         char *cp;
887         struct branch *upstream;
888         int namelen = strlen(name);
889         int len = interpret_nth_prior_checkout(name, buf);
890         int tmp_len;
891
892         if (!len)
893                 return len; /* syntax Ok, not enough switches */
894         if (0 < len && len == namelen)
895                 return len; /* consumed all */
896         else if (0 < len) {
897                 /* we have extra data, which might need further processing */
898                 struct strbuf tmp = STRBUF_INIT;
899                 int used = buf->len;
900                 int ret;
901
902                 strbuf_add(buf, name + len, namelen - len);
903                 ret = interpret_branch_name(buf->buf, &tmp);
904                 /* that data was not interpreted, remove our cruft */
905                 if (ret < 0) {
906                         strbuf_setlen(buf, used);
907                         return len;
908                 }
909                 strbuf_reset(buf);
910                 strbuf_addbuf(buf, &tmp);
911                 strbuf_release(&tmp);
912                 /* tweak for size of {-N} versus expanded ref name */
913                 return ret - used + len;
914         }
915
916         cp = strchr(name, '@');
917         if (!cp)
918                 return -1;
919         tmp_len = upstream_mark(cp, namelen - (cp - name));
920         if (!tmp_len)
921                 return -1;
922         len = cp + tmp_len - name;
923         cp = xstrndup(name, cp - name);
924         upstream = branch_get(*cp ? cp : NULL);
925         if (!upstream
926             || !upstream->merge
927             || !upstream->merge[0]->dst)
928                 return error("No upstream branch found for '%s'", cp);
929         free(cp);
930         cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
931         strbuf_reset(buf);
932         strbuf_addstr(buf, cp);
933         free(cp);
934         return len;
935 }
936
937 /*
938  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
939  * notably "xyz^" for "parent of xyz"
940  */
941 int get_sha1(const char *name, unsigned char *sha1)
942 {
943         struct object_context unused;
944         return get_sha1_with_context(name, sha1, &unused);
945 }
946
947 /* Must be called only when object_name:filename doesn't exist. */
948 static void diagnose_invalid_sha1_path(const char *prefix,
949                                        const char *filename,
950                                        const unsigned char *tree_sha1,
951                                        const char *object_name)
952 {
953         struct stat st;
954         unsigned char sha1[20];
955         unsigned mode;
956
957         if (!prefix)
958                 prefix = "";
959
960         if (!lstat(filename, &st))
961                 die("Path '%s' exists on disk, but not in '%s'.",
962                     filename, object_name);
963         if (errno == ENOENT || errno == ENOTDIR) {
964                 char *fullname = xmalloc(strlen(filename)
965                                              + strlen(prefix) + 1);
966                 strcpy(fullname, prefix);
967                 strcat(fullname, filename);
968
969                 if (!get_tree_entry(tree_sha1, fullname,
970                                     sha1, &mode)) {
971                         die("Path '%s' exists, but not '%s'.\n"
972                             "Did you mean '%s:%s'?",
973                             fullname,
974                             filename,
975                             object_name,
976                             fullname);
977                 }
978                 die("Path '%s' does not exist in '%s'",
979                     filename, object_name);
980         }
981 }
982
983 /* Must be called only when :stage:filename doesn't exist. */
984 static void diagnose_invalid_index_path(int stage,
985                                         const char *prefix,
986                                         const char *filename)
987 {
988         struct stat st;
989         struct cache_entry *ce;
990         int pos;
991         unsigned namelen = strlen(filename);
992         unsigned fullnamelen;
993         char *fullname;
994
995         if (!prefix)
996                 prefix = "";
997
998         /* Wrong stage number? */
999         pos = cache_name_pos(filename, namelen);
1000         if (pos < 0)
1001                 pos = -pos - 1;
1002         if (pos < active_nr) {
1003                 ce = active_cache[pos];
1004                 if (ce_namelen(ce) == namelen &&
1005                     !memcmp(ce->name, filename, namelen))
1006                         die("Path '%s' is in the index, but not at stage %d.\n"
1007                             "Did you mean ':%d:%s'?",
1008                             filename, stage,
1009                             ce_stage(ce), filename);
1010         }
1011
1012         /* Confusion between relative and absolute filenames? */
1013         fullnamelen = namelen + strlen(prefix);
1014         fullname = xmalloc(fullnamelen + 1);
1015         strcpy(fullname, prefix);
1016         strcat(fullname, filename);
1017         pos = cache_name_pos(fullname, fullnamelen);
1018         if (pos < 0)
1019                 pos = -pos - 1;
1020         if (pos < active_nr) {
1021                 ce = active_cache[pos];
1022                 if (ce_namelen(ce) == fullnamelen &&
1023                     !memcmp(ce->name, fullname, fullnamelen))
1024                         die("Path '%s' is in the index, but not '%s'.\n"
1025                             "Did you mean ':%d:%s'?",
1026                             fullname, filename,
1027                             ce_stage(ce), fullname);
1028         }
1029
1030         if (!lstat(filename, &st))
1031                 die("Path '%s' exists on disk, but not in the index.", filename);
1032         if (errno == ENOENT || errno == ENOTDIR)
1033                 die("Path '%s' does not exist (neither on disk nor in the index).",
1034                     filename);
1035
1036         free(fullname);
1037 }
1038
1039
1040 int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int gently, const char *prefix)
1041 {
1042         struct object_context oc;
1043         int ret;
1044         ret = get_sha1_with_context_1(name, sha1, &oc, gently, prefix);
1045         *mode = oc.mode;
1046         return ret;
1047 }
1048
1049 int get_sha1_with_context_1(const char *name, unsigned char *sha1,
1050                             struct object_context *oc,
1051                             int gently, const char *prefix)
1052 {
1053         int ret, bracket_depth;
1054         int namelen = strlen(name);
1055         const char *cp;
1056
1057         memset(oc, 0, sizeof(*oc));
1058         oc->mode = S_IFINVALID;
1059         ret = get_sha1_1(name, namelen, sha1);
1060         if (!ret)
1061                 return ret;
1062         /* sha1:path --> object name of path in ent sha1
1063          * :path -> object name of path in index
1064          * :[0-3]:path -> object name of path in index at stage
1065          */
1066         if (name[0] == ':') {
1067                 int stage = 0;
1068                 struct cache_entry *ce;
1069                 int pos;
1070                 if (namelen > 2 && name[1] == '/')
1071                         return get_sha1_oneline(name + 2, sha1);
1072                 if (namelen < 3 ||
1073                     name[2] != ':' ||
1074                     name[1] < '0' || '3' < name[1])
1075                         cp = name + 1;
1076                 else {
1077                         stage = name[1] - '0';
1078                         cp = name + 3;
1079                 }
1080                 namelen = namelen - (cp - name);
1081
1082                 strncpy(oc->path, cp,
1083                         sizeof(oc->path));
1084                 oc->path[sizeof(oc->path)-1] = '\0';
1085
1086                 if (!active_cache)
1087                         read_cache();
1088                 pos = cache_name_pos(cp, namelen);
1089                 if (pos < 0)
1090                         pos = -pos - 1;
1091                 while (pos < active_nr) {
1092                         ce = active_cache[pos];
1093                         if (ce_namelen(ce) != namelen ||
1094                             memcmp(ce->name, cp, namelen))
1095                                 break;
1096                         if (ce_stage(ce) == stage) {
1097                                 hashcpy(sha1, ce->sha1);
1098                                 return 0;
1099                         }
1100                         pos++;
1101                 }
1102                 if (!gently)
1103                         diagnose_invalid_index_path(stage, prefix, cp);
1104                 return -1;
1105         }
1106         for (cp = name, bracket_depth = 0; *cp; cp++) {
1107                 if (*cp == '{')
1108                         bracket_depth++;
1109                 else if (bracket_depth && *cp == '}')
1110                         bracket_depth--;
1111                 else if (!bracket_depth && *cp == ':')
1112                         break;
1113         }
1114         if (*cp == ':') {
1115                 unsigned char tree_sha1[20];
1116                 char *object_name = NULL;
1117                 if (!gently) {
1118                         object_name = xmalloc(cp-name+1);
1119                         strncpy(object_name, name, cp-name);
1120                         object_name[cp-name] = '\0';
1121                 }
1122                 if (!get_sha1_1(name, cp-name, tree_sha1)) {
1123                         const char *filename = cp+1;
1124                         ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
1125                         if (!gently) {
1126                                 diagnose_invalid_sha1_path(prefix, filename,
1127                                                            tree_sha1, object_name);
1128                                 free(object_name);
1129                         }
1130                         hashcpy(oc->tree, tree_sha1);
1131                         strncpy(oc->path, filename,
1132                                 sizeof(oc->path));
1133                         oc->path[sizeof(oc->path)-1] = '\0';
1134
1135                         return ret;
1136                 } else {
1137                         if (!gently)
1138                                 die("Invalid object name '%s'.", object_name);
1139                 }
1140         }
1141         return ret;
1142 }