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[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 #include <sys/time.h>
13 #include <signal.h>
14
15 static int merge = 0;
16 static int update = 0;
17 static int index_only = 0;
18 static int nontrivial_merge = 0;
19 static int trivial_merges_only = 0;
20 static int aggressive = 0;
21 static int verbose_update = 0;
22 static volatile int progress_update = 0;
23
24 static int head_idx = -1;
25 static int merge_size = 0;
26
27 static struct object_list *trees = NULL;
28
29 static struct cache_entry df_conflict_entry = { 
30 };
31
32 static struct tree_entry_list df_conflict_list = {
33         .name = NULL,
34         .next = &df_conflict_list
35 };
36
37 typedef int (*merge_fn_t)(struct cache_entry **src);
38
39 static int entcmp(char *name1, int dir1, char *name2, int dir2)
40 {
41         int len1 = strlen(name1);
42         int len2 = strlen(name2);
43         int len = len1 < len2 ? len1 : len2;
44         int ret = memcmp(name1, name2, len);
45         unsigned char c1, c2;
46         if (ret)
47                 return ret;
48         c1 = name1[len];
49         c2 = name2[len];
50         if (!c1 && dir1)
51                 c1 = '/';
52         if (!c2 && dir2)
53                 c2 = '/';
54         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
55         if (c1 && c2 && !ret)
56                 ret = len1 - len2;
57         return ret;
58 }
59
60 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
61                             const char *base, merge_fn_t fn, int *indpos)
62 {
63         int baselen = strlen(base);
64         int src_size = len + 1;
65         do {
66                 int i;
67                 char *first;
68                 int firstdir = 0;
69                 int pathlen;
70                 unsigned ce_size;
71                 struct tree_entry_list **subposns;
72                 struct cache_entry **src;
73                 int any_files = 0;
74                 int any_dirs = 0;
75                 char *cache_name;
76                 int ce_stage;
77
78                 /* Find the first name in the input. */
79
80                 first = NULL;
81                 cache_name = NULL;
82
83                 /* Check the cache */
84                 if (merge && *indpos < active_nr) {
85                         /* This is a bit tricky: */
86                         /* If the index has a subdirectory (with
87                          * contents) as the first name, it'll get a
88                          * filename like "foo/bar". But that's after
89                          * "foo", so the entry in trees will get
90                          * handled first, at which point we'll go into
91                          * "foo", and deal with "bar" from the index,
92                          * because the base will be "foo/". The only
93                          * way we can actually have "foo/bar" first of
94                          * all the things is if the trees don't
95                          * contain "foo" at all, in which case we'll
96                          * handle "foo/bar" without going into the
97                          * directory, but that's fine (and will return
98                          * an error anyway, with the added unknown
99                          * file case.
100                          */
101
102                         cache_name = active_cache[*indpos]->name;
103                         if (strlen(cache_name) > baselen &&
104                             !memcmp(cache_name, base, baselen)) {
105                                 cache_name += baselen;
106                                 first = cache_name;
107                         } else {
108                                 cache_name = NULL;
109                         }
110                 }
111
112 #if DBRT_DEBUG > 1
113                 if (first)
114                         printf("index %s\n", first);
115 #endif
116                 for (i = 0; i < len; i++) {
117                         if (!posns[i] || posns[i] == &df_conflict_list)
118                                 continue;
119 #if DBRT_DEBUG > 1
120                         printf("%d %s\n", i + 1, posns[i]->name);
121 #endif
122                         if (!first || entcmp(first, firstdir,
123                                              posns[i]->name, 
124                                              posns[i]->directory) > 0) {
125                                 first = posns[i]->name;
126                                 firstdir = posns[i]->directory;
127                         }
128                 }
129                 /* No name means we're done */
130                 if (!first)
131                         return 0;
132
133                 pathlen = strlen(first);
134                 ce_size = cache_entry_size(baselen + pathlen);
135
136                 src = xmalloc(sizeof(struct cache_entry *) * src_size);
137                 memset(src, 0, sizeof(struct cache_entry *) * src_size);
138
139                 subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
140                 memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
141
142                 if (cache_name && !strcmp(cache_name, first)) {
143                         any_files = 1;
144                         src[0] = active_cache[*indpos];
145                         remove_cache_entry_at(*indpos);
146                 }
147
148                 for (i = 0; i < len; i++) {
149                         struct cache_entry *ce;
150
151                         if (!posns[i] ||
152                             (posns[i] != &df_conflict_list &&
153                              strcmp(first, posns[i]->name))) {
154                                 continue;
155                         }
156
157                         if (posns[i] == &df_conflict_list) {
158                                 src[i + merge] = &df_conflict_entry;
159                                 continue;
160                         }
161
162                         if (posns[i]->directory) {
163                                 any_dirs = 1;
164                                 parse_tree(posns[i]->item.tree);
165                                 subposns[i] = posns[i]->item.tree->entries;
166                                 posns[i] = posns[i]->next;
167                                 src[i + merge] = &df_conflict_entry;
168                                 continue;
169                         }
170
171                         if (!merge)
172                                 ce_stage = 0;
173                         else if (i + 1 < head_idx)
174                                 ce_stage = 1;
175                         else if (i + 1 > head_idx)
176                                 ce_stage = 3;
177                         else
178                                 ce_stage = 2;
179
180                         ce = xmalloc(ce_size);
181                         memset(ce, 0, ce_size);
182                         ce->ce_mode = create_ce_mode(posns[i]->mode);
183                         ce->ce_flags = create_ce_flags(baselen + pathlen,
184                                                        ce_stage);
185                         memcpy(ce->name, base, baselen);
186                         memcpy(ce->name + baselen, first, pathlen + 1);
187
188                         any_files = 1;
189
190                         memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
191                         src[i + merge] = ce;
192                         subposns[i] = &df_conflict_list;
193                         posns[i] = posns[i]->next;
194                 }
195                 if (any_files) {
196                         if (merge) {
197                                 int ret;
198
199 #if DBRT_DEBUG > 1
200                                 printf("%s:\n", first);
201                                 for (i = 0; i < src_size; i++) {
202                                         printf(" %d ", i);
203                                         if (src[i])
204                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
205                                         else
206                                                 printf("\n");
207                                 }
208 #endif
209                                 ret = fn(src);
210                                 
211 #if DBRT_DEBUG > 1
212                                 printf("Added %d entries\n", ret);
213 #endif
214                                 *indpos += ret;
215                         } else {
216                                 for (i = 0; i < src_size; i++) {
217                                         if (src[i]) {
218                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
219                                         }
220                                 }
221                         }
222                 }
223                 if (any_dirs) {
224                         char *newbase = xmalloc(baselen + 2 + pathlen);
225                         memcpy(newbase, base, baselen);
226                         memcpy(newbase + baselen, first, pathlen);
227                         newbase[baselen + pathlen] = '/';
228                         newbase[baselen + pathlen + 1] = '\0';
229                         if (unpack_trees_rec(subposns, len, newbase, fn,
230                                              indpos))
231                                 return -1;
232                         free(newbase);
233                 }
234                 free(subposns);
235                 free(src);
236         } while (1);
237 }
238
239 static void reject_merge(struct cache_entry *ce)
240 {
241         die("Entry '%s' would be overwritten by merge. Cannot merge.", 
242             ce->name);
243 }
244
245 /* Unlink the last component and attempt to remove leading
246  * directories, in case this unlink is the removal of the
247  * last entry in the directory -- empty directories are removed.
248  */
249 static void unlink_entry(char *name)
250 {
251         char *cp, *prev;
252
253         if (unlink(name))
254                 return;
255         prev = NULL;
256         while (1) {
257                 int status;
258                 cp = strrchr(name, '/');
259                 if (prev)
260                         *prev = '/';
261                 if (!cp)
262                         break;
263
264                 *cp = 0;
265                 status = rmdir(name);
266                 if (status) {
267                         *cp = '/';
268                         break;
269                 }
270                 prev = cp;
271         }
272 }
273
274 static void progress_interval(int signum)
275 {
276         signal(SIGALRM, progress_interval);
277         progress_update = 1;
278 }
279
280 static void check_updates(struct cache_entry **src, int nr)
281 {
282         static struct checkout state = {
283                 .base_dir = "",
284                 .force = 1,
285                 .quiet = 1,
286                 .refresh_cache = 1,
287         };
288         unsigned short mask = htons(CE_UPDATE);
289         unsigned last_percent = 200, cnt = 0, total = 0;
290
291         if (update && verbose_update) {
292                 struct itimerval v;
293
294                 for (total = cnt = 0; cnt < nr; cnt++) {
295                         struct cache_entry *ce = src[cnt];
296                         if (!ce->ce_mode || ce->ce_flags & mask)
297                                 total++;
298                 }
299
300                 /* Don't bother doing this for very small updates */
301                 if (total < 250)
302                         total = 0;
303
304                 if (total) {
305                         v.it_interval.tv_sec = 1;
306                         v.it_interval.tv_usec = 0;
307                         v.it_value = v.it_interval;
308                         signal(SIGALRM, progress_interval);
309                         setitimer(ITIMER_REAL, &v, NULL);
310                         fprintf(stderr, "Checking files out...\n");
311                         progress_update = 1;
312                 }
313                 cnt = 0;
314         }
315
316         while (nr--) {
317                 struct cache_entry *ce = *src++;
318
319                 if (total) {
320                         if (!ce->ce_mode || ce->ce_flags & mask) {
321                                 unsigned percent;
322                                 cnt++;
323                                 percent = (cnt * 100) / total;
324                                 if (percent != last_percent ||
325                                     progress_update) {
326                                         fprintf(stderr, "%4u%% (%u/%u) done\r",
327                                                 percent, cnt, total);
328                                         last_percent = percent;
329                                 }
330                         }
331                 }
332                 if (!ce->ce_mode) {
333                         if (update)
334                                 unlink_entry(ce->name);
335                         continue;
336                 }
337                 if (ce->ce_flags & mask) {
338                         ce->ce_flags &= ~mask;
339                         if (update)
340                                 checkout_entry(ce, &state);
341                 }
342         }
343         if (total) {
344                 fputc('\n', stderr);
345                 signal(SIGALRM, SIG_IGN);
346         }
347 }
348
349 static int unpack_trees(merge_fn_t fn)
350 {
351         int indpos = 0;
352         unsigned len = object_list_length(trees);
353         struct tree_entry_list **posns;
354         int i;
355         struct object_list *posn = trees;
356         merge_size = len;
357
358         if (len) {
359                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
360                 for (i = 0; i < len; i++) {
361                         posns[i] = ((struct tree *) posn->item)->entries;
362                         posn = posn->next;
363                 }
364                 if (unpack_trees_rec(posns, len, "", fn, &indpos))
365                         return -1;
366         }
367
368         if (trivial_merges_only && nontrivial_merge)
369                 die("Merge requires file-level merging");
370
371         check_updates(active_cache, active_nr);
372         return 0;
373 }
374
375 static int list_tree(unsigned char *sha1)
376 {
377         struct tree *tree = parse_tree_indirect(sha1);
378         if (!tree)
379                 return -1;
380         object_list_append(&tree->object, &trees);
381         return 0;
382 }
383
384 static int same(struct cache_entry *a, struct cache_entry *b)
385 {
386         if (!!a != !!b)
387                 return 0;
388         if (!a && !b)
389                 return 1;
390         return a->ce_mode == b->ce_mode && 
391                 !memcmp(a->sha1, b->sha1, 20);
392 }
393
394
395 /*
396  * When a CE gets turned into an unmerged entry, we
397  * want it to be up-to-date
398  */
399 static void verify_uptodate(struct cache_entry *ce)
400 {
401         struct stat st;
402
403         if (index_only)
404                 return;
405
406         if (!lstat(ce->name, &st)) {
407                 unsigned changed = ce_match_stat(ce, &st, 1);
408                 if (!changed)
409                         return;
410                 errno = 0;
411         }
412         if (errno == ENOENT)
413                 return;
414         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
415 }
416
417 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
418 {
419         merge->ce_flags |= htons(CE_UPDATE);
420         if (old) {
421                 /*
422                  * See if we can re-use the old CE directly?
423                  * That way we get the uptodate stat info.
424                  *
425                  * This also removes the UPDATE flag on
426                  * a match.
427                  */
428                 if (same(old, merge)) {
429                         *merge = *old;
430                 } else {
431                         verify_uptodate(old);
432                 }
433         }
434         merge->ce_flags &= ~htons(CE_STAGEMASK);
435         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
436         return 1;
437 }
438
439 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
440 {
441         if (old)
442                 verify_uptodate(old);
443         ce->ce_mode = 0;
444         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
445         return 1;
446 }
447
448 static int keep_entry(struct cache_entry *ce)
449 {
450         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
451         return 1;
452 }
453
454 #if DBRT_DEBUG
455 static void show_stage_entry(FILE *o,
456                              const char *label, const struct cache_entry *ce)
457 {
458         if (!ce)
459                 fprintf(o, "%s (missing)\n", label);
460         else
461                 fprintf(o, "%s%06o %s %d\t%s\n",
462                         label,
463                         ntohl(ce->ce_mode),
464                         sha1_to_hex(ce->sha1),
465                         ce_stage(ce),
466                         ce->name);
467 }
468 #endif
469
470 static int threeway_merge(struct cache_entry **stages)
471 {
472         struct cache_entry *index;
473         struct cache_entry *head; 
474         struct cache_entry *remote = stages[head_idx + 1];
475         int count;
476         int head_match = 0;
477         int remote_match = 0;
478
479         int df_conflict_head = 0;
480         int df_conflict_remote = 0;
481
482         int any_anc_missing = 0;
483         int no_anc_exists = 1;
484         int i;
485
486         for (i = 1; i < head_idx; i++) {
487                 if (!stages[i])
488                         any_anc_missing = 1;
489                 else
490                         no_anc_exists = 0;
491         }
492
493         index = stages[0];
494         head = stages[head_idx];
495
496         if (head == &df_conflict_entry) {
497                 df_conflict_head = 1;
498                 head = NULL;
499         }
500
501         if (remote == &df_conflict_entry) {
502                 df_conflict_remote = 1;
503                 remote = NULL;
504         }
505
506         /* First, if there's a #16 situation, note that to prevent #13
507          * and #14. 
508          */
509         if (!same(remote, head)) {
510                 for (i = 1; i < head_idx; i++) {
511                         if (same(stages[i], head)) {
512                                 head_match = i;
513                         }
514                         if (same(stages[i], remote)) {
515                                 remote_match = i;
516                         }
517                 }
518         }
519
520         /* We start with cases where the index is allowed to match
521          * something other than the head: #14(ALT) and #2ALT, where it
522          * is permitted to match the result instead.
523          */
524         /* #14, #14ALT, #2ALT */
525         if (remote && !df_conflict_head && head_match && !remote_match) {
526                 if (index && !same(index, remote) && !same(index, head))
527                         reject_merge(index);
528                 return merged_entry(remote, index);
529         }
530         /*
531          * If we have an entry in the index cache, then we want to
532          * make sure that it matches head.
533          */
534         if (index && !same(index, head)) {
535                 reject_merge(index);
536         }
537
538         if (head) {
539                 /* #5ALT, #15 */
540                 if (same(head, remote))
541                         return merged_entry(head, index);
542                 /* #13, #3ALT */
543                 if (!df_conflict_remote && remote_match && !head_match)
544                         return merged_entry(head, index);
545         }
546
547         /* #1 */
548         if (!head && !remote && any_anc_missing)
549                 return 0;
550
551         /* Under the new "aggressive" rule, we resolve mostly trivial
552          * cases that we historically had git-merge-one-file resolve.
553          */
554         if (aggressive) {
555                 int head_deleted = !head && !df_conflict_head;
556                 int remote_deleted = !remote && !df_conflict_remote;
557                 /*
558                  * Deleted in both.
559                  * Deleted in one and unchanged in the other.
560                  */
561                 if ((head_deleted && remote_deleted) ||
562                     (head_deleted && remote && remote_match) ||
563                     (remote_deleted && head && head_match))
564                         return 0;
565
566                 /*
567                  * Added in both, identically.
568                  */
569                 if (no_anc_exists && head && remote && same(head, remote))
570                         return merged_entry(head, index);
571
572         }
573
574         /* Below are "no merge" cases, which require that the index be
575          * up-to-date to avoid the files getting overwritten with
576          * conflict resolution files. 
577          */
578         if (index) {
579                 verify_uptodate(index);
580         }
581
582         nontrivial_merge = 1;
583
584         /* #2, #3, #4, #6, #7, #9, #11. */
585         count = 0;
586         if (!head_match || !remote_match) {
587                 for (i = 1; i < head_idx; i++) {
588                         if (stages[i]) {
589                                 keep_entry(stages[i]);
590                                 count++;
591                                 break;
592                         }
593                 }
594         }
595 #if DBRT_DEBUG
596         else {
597                 fprintf(stderr, "read-tree: warning #16 detected\n");
598                 show_stage_entry(stderr, "head   ", stages[head_match]);
599                 show_stage_entry(stderr, "remote ", stages[remote_match]);
600         }
601 #endif
602         if (head) { count += keep_entry(head); }
603         if (remote) { count += keep_entry(remote); }
604         return count;
605 }
606
607 /*
608  * Two-way merge.
609  *
610  * The rule is to "carry forward" what is in the index without losing
611  * information across a "fast forward", favoring a successful merge
612  * over a merge failure when it makes sense.  For details of the
613  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
614  *
615  */
616 static int twoway_merge(struct cache_entry **src)
617 {
618         struct cache_entry *current = src[0];
619         struct cache_entry *oldtree = src[1], *newtree = src[2];
620
621         if (merge_size != 2)
622                 return error("Cannot do a twoway merge of %d trees",
623                              merge_size);
624
625         if (current) {
626                 if ((!oldtree && !newtree) || /* 4 and 5 */
627                     (!oldtree && newtree &&
628                      same(current, newtree)) || /* 6 and 7 */
629                     (oldtree && newtree &&
630                      same(oldtree, newtree)) || /* 14 and 15 */
631                     (oldtree && newtree &&
632                      !same(oldtree, newtree) && /* 18 and 19*/
633                      same(current, newtree))) {
634                         return keep_entry(current);
635                 }
636                 else if (oldtree && !newtree && same(current, oldtree)) {
637                         /* 10 or 11 */
638                         return deleted_entry(oldtree, current);
639                 }
640                 else if (oldtree && newtree &&
641                          same(current, oldtree) && !same(current, newtree)) {
642                         /* 20 or 21 */
643                         return merged_entry(newtree, current);
644                 }
645                 else {
646                         /* all other failures */
647                         if (oldtree)
648                                 reject_merge(oldtree);
649                         if (current)
650                                 reject_merge(current);
651                         if (newtree)
652                                 reject_merge(newtree);
653                         return -1;
654                 }
655         }
656         else if (newtree)
657                 return merged_entry(newtree, current);
658         else
659                 return deleted_entry(oldtree, current);
660 }
661
662 /*
663  * One-way merge.
664  *
665  * The rule is:
666  * - take the stat information from stage0, take the data from stage1
667  */
668 static int oneway_merge(struct cache_entry **src)
669 {
670         struct cache_entry *old = src[0];
671         struct cache_entry *a = src[1];
672
673         if (merge_size != 1)
674                 return error("Cannot do a oneway merge of %d trees",
675                              merge_size);
676
677         if (!a)
678                 return 0;
679         if (old && same(old, a)) {
680                 return keep_entry(old);
681         }
682         return merged_entry(a, NULL);
683 }
684
685 static int read_cache_unmerged(void)
686 {
687         int i, deleted;
688         struct cache_entry **dst;
689
690         read_cache();
691         dst = active_cache;
692         deleted = 0;
693         for (i = 0; i < active_nr; i++) {
694                 struct cache_entry *ce = active_cache[i];
695                 if (ce_stage(ce)) {
696                         deleted++;
697                         continue;
698                 }
699                 if (deleted)
700                         *dst = ce;
701                 dst++;
702         }
703         active_nr -= deleted;
704         return deleted;
705 }
706
707 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
708
709 static struct cache_file cache_file;
710
711 int main(int argc, char **argv)
712 {
713         int i, newfd, reset, stage = 0;
714         unsigned char sha1[20];
715         merge_fn_t fn = NULL;
716
717         setup_git_directory();
718
719         newfd = hold_index_file_for_update(&cache_file, get_index_file());
720         if (newfd < 0)
721                 die("unable to create new cachefile");
722
723         git_config(git_default_config);
724
725         merge = 0;
726         reset = 0;
727         for (i = 1; i < argc; i++) {
728                 const char *arg = argv[i];
729
730                 /* "-u" means "update", meaning that a merge will update
731                  * the working tree.
732                  */
733                 if (!strcmp(arg, "-u")) {
734                         update = 1;
735                         continue;
736                 }
737
738                 if (!strcmp(arg, "-v")) {
739                         verbose_update = 1;
740                         continue;
741                 }
742
743                 /* "-i" means "index only", meaning that a merge will
744                  * not even look at the working tree.
745                  */
746                 if (!strcmp(arg, "-i")) {
747                         index_only = 1;
748                         continue;
749                 }
750
751                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
752                 if (!strcmp(arg, "--reset")) {
753                         if (stage || merge)
754                                 usage(read_tree_usage);
755                         reset = 1;
756                         merge = 1;
757                         stage = 1;
758                         read_cache_unmerged();
759                         continue;
760                 }
761
762                 if (!strcmp(arg, "--trivial")) {
763                         trivial_merges_only = 1;
764                         continue;
765                 }
766
767                 if (!strcmp(arg, "--aggressive")) {
768                         aggressive = 1;
769                         continue;
770                 }
771
772                 /* "-m" stands for "merge", meaning we start in stage 1 */
773                 if (!strcmp(arg, "-m")) {
774                         if (stage || merge)
775                                 usage(read_tree_usage);
776                         if (read_cache_unmerged())
777                                 die("you need to resolve your current index first");
778                         stage = 1;
779                         merge = 1;
780                         continue;
781                 }
782
783                 /* using -u and -i at the same time makes no sense */
784                 if (1 < index_only + update)
785                         usage(read_tree_usage);
786
787                 if (get_sha1(arg, sha1) < 0)
788                         usage(read_tree_usage);
789                 if (list_tree(sha1) < 0)
790                         die("failed to unpack tree object %s", arg);
791                 stage++;
792         }
793         if ((update||index_only) && !merge)
794                 usage(read_tree_usage);
795
796         if (merge) {
797                 if (stage < 2)
798                         die("just how do you expect me to merge %d trees?", stage-1);
799                 switch (stage - 1) {
800                 case 1:
801                         fn = oneway_merge;
802                         break;
803                 case 2:
804                         fn = twoway_merge;
805                         break;
806                 case 3:
807                         fn = threeway_merge;
808                         break;
809                 default:
810                         fn = threeway_merge;
811                         break;
812                 }
813
814                 if (stage - 1 >= 3)
815                         head_idx = stage - 2;
816                 else
817                         head_idx = 1;
818         }
819
820         unpack_trees(fn);
821         if (write_cache(newfd, active_cache, active_nr) ||
822             commit_index_file(&cache_file))
823                 die("unable to write new index file");
824         return 0;
825 }