Add a "git-describe" command
[git.git] / read-tree.c
1 /*
2  * GIT - The information manager from hell
3  *
4  * Copyright (C) Linus Torvalds, 2005
5  */
6 #define DBRT_DEBUG 1
7
8 #include "cache.h"
9
10 #include "object.h"
11 #include "tree.h"
12
13 static int merge = 0;
14 static int update = 0;
15 static int index_only = 0;
16 static int nontrivial_merge = 0;
17 static int trivial_merges_only = 0;
18
19 static int head_idx = -1;
20 static int merge_size = 0;
21
22 static struct object_list *trees = NULL;
23
24 static struct cache_entry df_conflict_entry = { 
25 };
26
27 static struct tree_entry_list df_conflict_list = {
28         .name = NULL,
29         .next = &df_conflict_list
30 };
31
32 typedef int (*merge_fn_t)(struct cache_entry **src);
33
34 static int entcmp(char *name1, int dir1, char *name2, int dir2)
35 {
36         int len1 = strlen(name1);
37         int len2 = strlen(name2);
38         int len = len1 < len2 ? len1 : len2;
39         int ret = memcmp(name1, name2, len);
40         unsigned char c1, c2;
41         if (ret)
42                 return ret;
43         c1 = name1[len];
44         c2 = name2[len];
45         if (!c1 && dir1)
46                 c1 = '/';
47         if (!c2 && dir2)
48                 c2 = '/';
49         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
50         if (c1 && c2 && !ret)
51                 ret = len1 - len2;
52         return ret;
53 }
54
55 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
56                             const char *base, merge_fn_t fn, int *indpos)
57 {
58         int baselen = strlen(base);
59         int src_size = len + 1;
60         do {
61                 int i;
62                 char *first;
63                 int firstdir = 0;
64                 int pathlen;
65                 unsigned ce_size;
66                 struct tree_entry_list **subposns;
67                 struct cache_entry **src;
68                 int any_files = 0;
69                 int any_dirs = 0;
70                 char *cache_name;
71                 int ce_stage;
72
73                 /* Find the first name in the input. */
74
75                 first = NULL;
76                 cache_name = NULL;
77
78                 /* Check the cache */
79                 if (merge && *indpos < active_nr) {
80                         /* This is a bit tricky: */
81                         /* If the index has a subdirectory (with
82                          * contents) as the first name, it'll get a
83                          * filename like "foo/bar". But that's after
84                          * "foo", so the entry in trees will get
85                          * handled first, at which point we'll go into
86                          * "foo", and deal with "bar" from the index,
87                          * because the base will be "foo/". The only
88                          * way we can actually have "foo/bar" first of
89                          * all the things is if the trees don't
90                          * contain "foo" at all, in which case we'll
91                          * handle "foo/bar" without going into the
92                          * directory, but that's fine (and will return
93                          * an error anyway, with the added unknown
94                          * file case.
95                          */
96
97                         cache_name = active_cache[*indpos]->name;
98                         if (strlen(cache_name) > baselen &&
99                             !memcmp(cache_name, base, baselen)) {
100                                 cache_name += baselen;
101                                 first = cache_name;
102                         } else {
103                                 cache_name = NULL;
104                         }
105                 }
106
107 #if DBRT_DEBUG > 1
108                 if (first)
109                         printf("index %s\n", first);
110 #endif
111                 for (i = 0; i < len; i++) {
112                         if (!posns[i] || posns[i] == &df_conflict_list)
113                                 continue;
114 #if DBRT_DEBUG > 1
115                         printf("%d %s\n", i + 1, posns[i]->name);
116 #endif
117                         if (!first || entcmp(first, firstdir,
118                                              posns[i]->name, 
119                                              posns[i]->directory) > 0) {
120                                 first = posns[i]->name;
121                                 firstdir = posns[i]->directory;
122                         }
123                 }
124                 /* No name means we're done */
125                 if (!first)
126                         return 0;
127
128                 pathlen = strlen(first);
129                 ce_size = cache_entry_size(baselen + pathlen);
130
131                 src = xmalloc(sizeof(struct cache_entry *) * src_size);
132                 memset(src, 0, sizeof(struct cache_entry *) * src_size);
133
134                 subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
135                 memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
136
137                 if (cache_name && !strcmp(cache_name, first)) {
138                         any_files = 1;
139                         src[0] = active_cache[*indpos];
140                         remove_cache_entry_at(*indpos);
141                 }
142
143                 for (i = 0; i < len; i++) {
144                         struct cache_entry *ce;
145
146                         if (!posns[i] ||
147                             (posns[i] != &df_conflict_list &&
148                              strcmp(first, posns[i]->name))) {
149                                 continue;
150                         }
151
152                         if (posns[i] == &df_conflict_list) {
153                                 src[i + merge] = &df_conflict_entry;
154                                 continue;
155                         }
156
157                         if (posns[i]->directory) {
158                                 any_dirs = 1;
159                                 parse_tree(posns[i]->item.tree);
160                                 subposns[i] = posns[i]->item.tree->entries;
161                                 posns[i] = posns[i]->next;
162                                 src[i + merge] = &df_conflict_entry;
163                                 continue;
164                         }
165
166                         if (!merge)
167                                 ce_stage = 0;
168                         else if (i + 1 < head_idx)
169                                 ce_stage = 1;
170                         else if (i + 1 > head_idx)
171                                 ce_stage = 3;
172                         else
173                                 ce_stage = 2;
174
175                         ce = xmalloc(ce_size);
176                         memset(ce, 0, ce_size);
177                         ce->ce_mode = create_ce_mode(posns[i]->mode);
178                         ce->ce_flags = create_ce_flags(baselen + pathlen,
179                                                        ce_stage);
180                         memcpy(ce->name, base, baselen);
181                         memcpy(ce->name + baselen, first, pathlen + 1);
182
183                         any_files = 1;
184
185                         memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
186                         src[i + merge] = ce;
187                         subposns[i] = &df_conflict_list;
188                         posns[i] = posns[i]->next;
189                 }
190                 if (any_files) {
191                         if (merge) {
192                                 int ret;
193
194 #if DBRT_DEBUG > 1
195                                 printf("%s:\n", first);
196                                 for (i = 0; i < src_size; i++) {
197                                         printf(" %d ", i);
198                                         if (src[i])
199                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
200                                         else
201                                                 printf("\n");
202                                 }
203 #endif
204                                 ret = fn(src);
205                                 
206 #if DBRT_DEBUG > 1
207                                 printf("Added %d entries\n", ret);
208 #endif
209                                 *indpos += ret;
210                         } else {
211                                 for (i = 0; i < src_size; i++) {
212                                         if (src[i]) {
213                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
214                                         }
215                                 }
216                         }
217                 }
218                 if (any_dirs) {
219                         char *newbase = xmalloc(baselen + 2 + pathlen);
220                         memcpy(newbase, base, baselen);
221                         memcpy(newbase + baselen, first, pathlen);
222                         newbase[baselen + pathlen] = '/';
223                         newbase[baselen + pathlen + 1] = '\0';
224                         if (unpack_trees_rec(subposns, len, newbase, fn,
225                                              indpos))
226                                 return -1;
227                         free(newbase);
228                 }
229                 free(subposns);
230                 free(src);
231         } while (1);
232 }
233
234 static void reject_merge(struct cache_entry *ce)
235 {
236         die("Entry '%s' would be overwritten by merge. Cannot merge.", 
237             ce->name);
238 }
239
240 /* Unlink the last component and attempt to remove leading
241  * directories, in case this unlink is the removal of the
242  * last entry in the directory -- empty directories are removed.
243  */
244 static void unlink_entry(char *name)
245 {
246         char *cp, *prev;
247
248         if (unlink(name))
249                 return;
250         prev = NULL;
251         while (1) {
252                 int status;
253                 cp = strrchr(name, '/');
254                 if (prev)
255                         *prev = '/';
256                 if (!cp)
257                         break;
258
259                 *cp = 0;
260                 status = rmdir(name);
261                 if (status) {
262                         *cp = '/';
263                         break;
264                 }
265                 prev = cp;
266         }
267 }
268
269 static void check_updates(struct cache_entry **src, int nr)
270 {
271         static struct checkout state = {
272                 .base_dir = "",
273                 .force = 1,
274                 .quiet = 1,
275                 .refresh_cache = 1,
276         };
277         unsigned short mask = htons(CE_UPDATE);
278         while (nr--) {
279                 struct cache_entry *ce = *src++;
280                 if (!ce->ce_mode) {
281                         if (update)
282                                 unlink_entry(ce->name);
283                         continue;
284                 }
285                 if (ce->ce_flags & mask) {
286                         ce->ce_flags &= ~mask;
287                         if (update)
288                                 checkout_entry(ce, &state);
289                 }
290         }
291 }
292
293 static int unpack_trees(merge_fn_t fn)
294 {
295         int indpos = 0;
296         unsigned len = object_list_length(trees);
297         struct tree_entry_list **posns;
298         int i;
299         struct object_list *posn = trees;
300         merge_size = len;
301
302         if (len) {
303                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
304                 for (i = 0; i < len; i++) {
305                         posns[i] = ((struct tree *) posn->item)->entries;
306                         posn = posn->next;
307                 }
308                 if (unpack_trees_rec(posns, len, "", fn, &indpos))
309                         return -1;
310         }
311
312         if (trivial_merges_only && nontrivial_merge)
313                 die("Merge requires file-level merging");
314
315         check_updates(active_cache, active_nr);
316         return 0;
317 }
318
319 static int list_tree(unsigned char *sha1)
320 {
321         struct tree *tree = parse_tree_indirect(sha1);
322         if (!tree)
323                 return -1;
324         object_list_append(&tree->object, &trees);
325         return 0;
326 }
327
328 static int same(struct cache_entry *a, struct cache_entry *b)
329 {
330         if (!!a != !!b)
331                 return 0;
332         if (!a && !b)
333                 return 1;
334         return a->ce_mode == b->ce_mode && 
335                 !memcmp(a->sha1, b->sha1, 20);
336 }
337
338
339 /*
340  * When a CE gets turned into an unmerged entry, we
341  * want it to be up-to-date
342  */
343 static void verify_uptodate(struct cache_entry *ce)
344 {
345         struct stat st;
346
347         if (index_only)
348                 return;
349
350         if (!lstat(ce->name, &st)) {
351                 unsigned changed = ce_match_stat(ce, &st);
352                 if (!changed)
353                         return;
354                 errno = 0;
355         }
356         if (errno == ENOENT)
357                 return;
358         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
359 }
360
361 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
362 {
363         merge->ce_flags |= htons(CE_UPDATE);
364         if (old) {
365                 /*
366                  * See if we can re-use the old CE directly?
367                  * That way we get the uptodate stat info.
368                  *
369                  * This also removes the UPDATE flag on
370                  * a match.
371                  */
372                 if (same(old, merge)) {
373                         *merge = *old;
374                 } else {
375                         verify_uptodate(old);
376                 }
377         }
378         merge->ce_flags &= ~htons(CE_STAGEMASK);
379         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
380         return 1;
381 }
382
383 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
384 {
385         if (old)
386                 verify_uptodate(old);
387         ce->ce_mode = 0;
388         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
389         return 1;
390 }
391
392 static int keep_entry(struct cache_entry *ce)
393 {
394         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
395         return 1;
396 }
397
398 #if DBRT_DEBUG
399 static void show_stage_entry(FILE *o,
400                              const char *label, const struct cache_entry *ce)
401 {
402         if (!ce)
403                 fprintf(o, "%s (missing)\n", label);
404         else
405                 fprintf(o, "%s%06o %s %d\t%s\n",
406                         label,
407                         ntohl(ce->ce_mode),
408                         sha1_to_hex(ce->sha1),
409                         ce_stage(ce),
410                         ce->name);
411 }
412 #endif
413
414 static int threeway_merge(struct cache_entry **stages)
415 {
416         struct cache_entry *index;
417         struct cache_entry *head; 
418         struct cache_entry *remote = stages[head_idx + 1];
419         int count;
420         int head_match = 0;
421         int remote_match = 0;
422
423         int df_conflict_head = 0;
424         int df_conflict_remote = 0;
425
426         int any_anc_missing = 0;
427         int i;
428
429         for (i = 1; i < head_idx; i++) {
430                 if (!stages[i])
431                         any_anc_missing = 1;
432         }
433
434         index = stages[0];
435         head = stages[head_idx];
436
437         if (head == &df_conflict_entry) {
438                 df_conflict_head = 1;
439                 head = NULL;
440         }
441
442         if (remote == &df_conflict_entry) {
443                 df_conflict_remote = 1;
444                 remote = NULL;
445         }
446
447         /* First, if there's a #16 situation, note that to prevent #13
448          * and #14. 
449          */
450         if (!same(remote, head)) {
451                 for (i = 1; i < head_idx; i++) {
452                         if (same(stages[i], head)) {
453                                 head_match = i;
454                         }
455                         if (same(stages[i], remote)) {
456                                 remote_match = i;
457                         }
458                 }
459         }
460
461         /* We start with cases where the index is allowed to match
462          * something other than the head: #14(ALT) and #2ALT, where it
463          * is permitted to match the result instead.
464          */
465         /* #14, #14ALT, #2ALT */
466         if (remote && !df_conflict_head && head_match && !remote_match) {
467                 if (index && !same(index, remote) && !same(index, head))
468                         reject_merge(index);
469                 return merged_entry(remote, index);
470         }
471         /*
472          * If we have an entry in the index cache, then we want to
473          * make sure that it matches head.
474          */
475         if (index && !same(index, head)) {
476                 reject_merge(index);
477         }
478
479         if (head) {
480                 /* #5ALT, #15 */
481                 if (same(head, remote))
482                         return merged_entry(head, index);
483                 /* #13, #3ALT */
484                 if (!df_conflict_remote && remote_match && !head_match)
485                         return merged_entry(head, index);
486         }
487
488         /* #1 */
489         if (!head && !remote && any_anc_missing)
490                 return 0;
491
492         /* Below are "no merge" cases, which require that the index be
493          * up-to-date to avoid the files getting overwritten with
494          * conflict resolution files. 
495          */
496         if (index) {
497                 verify_uptodate(index);
498         }
499
500         nontrivial_merge = 1;
501
502         /* #2, #3, #4, #6, #7, #9, #11. */
503         count = 0;
504         if (!head_match || !remote_match) {
505                 for (i = 1; i < head_idx; i++) {
506                         if (stages[i]) {
507                                 keep_entry(stages[i]);
508                                 count++;
509                                 break;
510                         }
511                 }
512         }
513 #if DBRT_DEBUG
514         else {
515                 fprintf(stderr, "read-tree: warning #16 detected\n");
516                 show_stage_entry(stderr, "head   ", stages[head_match]);
517                 show_stage_entry(stderr, "remote ", stages[remote_match]);
518         }
519 #endif
520         if (head) { count += keep_entry(head); }
521         if (remote) { count += keep_entry(remote); }
522         return count;
523 }
524
525 /*
526  * Two-way merge.
527  *
528  * The rule is to "carry forward" what is in the index without losing
529  * information across a "fast forward", favoring a successful merge
530  * over a merge failure when it makes sense.  For details of the
531  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
532  *
533  */
534 static int twoway_merge(struct cache_entry **src)
535 {
536         struct cache_entry *current = src[0];
537         struct cache_entry *oldtree = src[1], *newtree = src[2];
538
539         if (merge_size != 2)
540                 return error("Cannot do a twoway merge of %d trees\n",
541                              merge_size);
542
543         if (current) {
544                 if ((!oldtree && !newtree) || /* 4 and 5 */
545                     (!oldtree && newtree &&
546                      same(current, newtree)) || /* 6 and 7 */
547                     (oldtree && newtree &&
548                      same(oldtree, newtree)) || /* 14 and 15 */
549                     (oldtree && newtree &&
550                      !same(oldtree, newtree) && /* 18 and 19*/
551                      same(current, newtree))) {
552                         return keep_entry(current);
553                 }
554                 else if (oldtree && !newtree && same(current, oldtree)) {
555                         /* 10 or 11 */
556                         return deleted_entry(oldtree, current);
557                 }
558                 else if (oldtree && newtree &&
559                          same(current, oldtree) && !same(current, newtree)) {
560                         /* 20 or 21 */
561                         return merged_entry(newtree, current);
562                 }
563                 else {
564                         /* all other failures */
565                         if (oldtree)
566                                 reject_merge(oldtree);
567                         if (current)
568                                 reject_merge(current);
569                         if (newtree)
570                                 reject_merge(newtree);
571                         return -1;
572                 }
573         }
574         else if (newtree)
575                 return merged_entry(newtree, current);
576         else
577                 return deleted_entry(oldtree, current);
578 }
579
580 /*
581  * One-way merge.
582  *
583  * The rule is:
584  * - take the stat information from stage0, take the data from stage1
585  */
586 static int oneway_merge(struct cache_entry **src)
587 {
588         struct cache_entry *old = src[0];
589         struct cache_entry *a = src[1];
590
591         if (merge_size != 1)
592                 return error("Cannot do a oneway merge of %d trees\n",
593                              merge_size);
594
595         if (!a)
596                 return 0;
597         if (old && same(old, a)) {
598                 return keep_entry(old);
599         }
600         return merged_entry(a, NULL);
601 }
602
603 static int read_cache_unmerged(void)
604 {
605         int i, deleted;
606         struct cache_entry **dst;
607
608         read_cache();
609         dst = active_cache;
610         deleted = 0;
611         for (i = 0; i < active_nr; i++) {
612                 struct cache_entry *ce = active_cache[i];
613                 if (ce_stage(ce)) {
614                         deleted++;
615                         continue;
616                 }
617                 if (deleted)
618                         *dst = ce;
619                 dst++;
620         }
621         active_nr -= deleted;
622         return deleted;
623 }
624
625 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
626
627 static struct cache_file cache_file;
628
629 int main(int argc, char **argv)
630 {
631         int i, newfd, reset, stage = 0;
632         unsigned char sha1[20];
633         merge_fn_t fn = NULL;
634
635         setup_git_directory();
636
637         newfd = hold_index_file_for_update(&cache_file, get_index_file());
638         if (newfd < 0)
639                 die("unable to create new cachefile");
640
641         git_config(git_default_config);
642
643         merge = 0;
644         reset = 0;
645         for (i = 1; i < argc; i++) {
646                 const char *arg = argv[i];
647
648                 /* "-u" means "update", meaning that a merge will update
649                  * the working tree.
650                  */
651                 if (!strcmp(arg, "-u")) {
652                         update = 1;
653                         continue;
654                 }
655
656                 /* "-i" means "index only", meaning that a merge will
657                  * not even look at the working tree.
658                  */
659                 if (!strcmp(arg, "-i")) {
660                         index_only = 1;
661                         continue;
662                 }
663
664                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
665                 if (!strcmp(arg, "--reset")) {
666                         if (stage || merge)
667                                 usage(read_tree_usage);
668                         reset = 1;
669                         merge = 1;
670                         stage = 1;
671                         read_cache_unmerged();
672                         continue;
673                 }
674
675                 if (!strcmp(arg, "--trivial")) {
676                         trivial_merges_only = 1;
677                         continue;
678                 }
679
680                 /* "-m" stands for "merge", meaning we start in stage 1 */
681                 if (!strcmp(arg, "-m")) {
682                         if (stage || merge)
683                                 usage(read_tree_usage);
684                         if (read_cache_unmerged())
685                                 die("you need to resolve your current index first");
686                         stage = 1;
687                         merge = 1;
688                         continue;
689                 }
690
691                 /* using -u and -i at the same time makes no sense */
692                 if (1 < index_only + update)
693                         usage(read_tree_usage);
694
695                 if (get_sha1(arg, sha1) < 0)
696                         usage(read_tree_usage);
697                 if (list_tree(sha1) < 0)
698                         die("failed to unpack tree object %s", arg);
699                 stage++;
700         }
701         if ((update||index_only) && !merge)
702                 usage(read_tree_usage);
703
704         if (merge) {
705                 if (stage < 2)
706                         die("just how do you expect me to merge %d trees?", stage-1);
707                 switch (stage - 1) {
708                 case 1:
709                         fn = oneway_merge;
710                         break;
711                 case 2:
712                         fn = twoway_merge;
713                         break;
714                 case 3:
715                         fn = threeway_merge;
716                         break;
717                 default:
718                         fn = threeway_merge;
719                         break;
720                 }
721
722                 if (stage - 1 >= 3)
723                         head_idx = stage - 2;
724                 else
725                         head_idx = 1;
726         }
727
728         unpack_trees(fn);
729         if (write_cache(newfd, active_cache, active_nr) ||
730             commit_index_file(&cache_file))
731                 die("unable to write new index file");
732         return 0;
733 }