Teach rebase -i about --preserve-merges
[git] / unpack-trees.c
1 #include "cache.h"
2 #include "dir.h"
3 #include "tree.h"
4 #include "tree-walk.h"
5 #include "cache-tree.h"
6 #include "unpack-trees.h"
7 #include "progress.h"
8
9 #define DBRT_DEBUG 1
10
11 struct tree_entry_list {
12         struct tree_entry_list *next;
13         unsigned directory : 1;
14         unsigned executable : 1;
15         unsigned symlink : 1;
16         unsigned int mode;
17         const char *name;
18         const unsigned char *sha1;
19 };
20
21 static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
22 {
23         struct tree_desc desc;
24         struct name_entry one;
25         struct tree_entry_list *ret = NULL;
26         struct tree_entry_list **list_p = &ret;
27
28         if (!tree->object.parsed)
29                 parse_tree(tree);
30
31         init_tree_desc(&desc, tree->buffer, tree->size);
32
33         while (tree_entry(&desc, &one)) {
34                 struct tree_entry_list *entry;
35
36                 entry = xmalloc(sizeof(struct tree_entry_list));
37                 entry->name = one.path;
38                 entry->sha1 = one.sha1;
39                 entry->mode = one.mode;
40                 entry->directory = S_ISDIR(one.mode) != 0;
41                 entry->executable = (one.mode & S_IXUSR) != 0;
42                 entry->symlink = S_ISLNK(one.mode) != 0;
43                 entry->next = NULL;
44
45                 *list_p = entry;
46                 list_p = &entry->next;
47         }
48         return ret;
49 }
50
51 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
52 {
53         int len1 = strlen(name1);
54         int len2 = strlen(name2);
55         int len = len1 < len2 ? len1 : len2;
56         int ret = memcmp(name1, name2, len);
57         unsigned char c1, c2;
58         if (ret)
59                 return ret;
60         c1 = name1[len];
61         c2 = name2[len];
62         if (!c1 && dir1)
63                 c1 = '/';
64         if (!c2 && dir2)
65                 c2 = '/';
66         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
67         if (c1 && c2 && !ret)
68                 ret = len1 - len2;
69         return ret;
70 }
71
72 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
73                             const char *base, struct unpack_trees_options *o,
74                             struct tree_entry_list *df_conflict_list)
75 {
76         int baselen = strlen(base);
77         int src_size = len + 1;
78         int i_stk = i_stk;
79         int retval = 0;
80
81         if (o->dir)
82                 i_stk = push_exclude_per_directory(o->dir, base, strlen(base));
83
84         do {
85                 int i;
86                 const char *first;
87                 int firstdir = 0;
88                 int pathlen;
89                 unsigned ce_size;
90                 struct tree_entry_list **subposns;
91                 struct cache_entry **src;
92                 int any_files = 0;
93                 int any_dirs = 0;
94                 char *cache_name;
95                 int ce_stage;
96
97                 /* Find the first name in the input. */
98
99                 first = NULL;
100                 cache_name = NULL;
101
102                 /* Check the cache */
103                 if (o->merge && o->pos < active_nr) {
104                         /* This is a bit tricky: */
105                         /* If the index has a subdirectory (with
106                          * contents) as the first name, it'll get a
107                          * filename like "foo/bar". But that's after
108                          * "foo", so the entry in trees will get
109                          * handled first, at which point we'll go into
110                          * "foo", and deal with "bar" from the index,
111                          * because the base will be "foo/". The only
112                          * way we can actually have "foo/bar" first of
113                          * all the things is if the trees don't
114                          * contain "foo" at all, in which case we'll
115                          * handle "foo/bar" without going into the
116                          * directory, but that's fine (and will return
117                          * an error anyway, with the added unknown
118                          * file case.
119                          */
120
121                         cache_name = active_cache[o->pos]->name;
122                         if (strlen(cache_name) > baselen &&
123                             !memcmp(cache_name, base, baselen)) {
124                                 cache_name += baselen;
125                                 first = cache_name;
126                         } else {
127                                 cache_name = NULL;
128                         }
129                 }
130
131 #if DBRT_DEBUG > 1
132                 if (first)
133                         printf("index %s\n", first);
134 #endif
135                 for (i = 0; i < len; i++) {
136                         if (!posns[i] || posns[i] == df_conflict_list)
137                                 continue;
138 #if DBRT_DEBUG > 1
139                         printf("%d %s\n", i + 1, posns[i]->name);
140 #endif
141                         if (!first || entcmp(first, firstdir,
142                                              posns[i]->name,
143                                              posns[i]->directory) > 0) {
144                                 first = posns[i]->name;
145                                 firstdir = posns[i]->directory;
146                         }
147                 }
148                 /* No name means we're done */
149                 if (!first)
150                         goto leave_directory;
151
152                 pathlen = strlen(first);
153                 ce_size = cache_entry_size(baselen + pathlen);
154
155                 src = xcalloc(src_size, sizeof(struct cache_entry *));
156
157                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
158
159                 if (cache_name && !strcmp(cache_name, first)) {
160                         any_files = 1;
161                         src[0] = active_cache[o->pos];
162                         remove_cache_entry_at(o->pos);
163                 }
164
165                 for (i = 0; i < len; i++) {
166                         struct cache_entry *ce;
167
168                         if (!posns[i] ||
169                             (posns[i] != df_conflict_list &&
170                              strcmp(first, posns[i]->name))) {
171                                 continue;
172                         }
173
174                         if (posns[i] == df_conflict_list) {
175                                 src[i + o->merge] = o->df_conflict_entry;
176                                 continue;
177                         }
178
179                         if (posns[i]->directory) {
180                                 struct tree *tree = lookup_tree(posns[i]->sha1);
181                                 any_dirs = 1;
182                                 parse_tree(tree);
183                                 subposns[i] = create_tree_entry_list(tree);
184                                 posns[i] = posns[i]->next;
185                                 src[i + o->merge] = o->df_conflict_entry;
186                                 continue;
187                         }
188
189                         if (!o->merge)
190                                 ce_stage = 0;
191                         else if (i + 1 < o->head_idx)
192                                 ce_stage = 1;
193                         else if (i + 1 > o->head_idx)
194                                 ce_stage = 3;
195                         else
196                                 ce_stage = 2;
197
198                         ce = xcalloc(1, ce_size);
199                         ce->ce_mode = create_ce_mode(posns[i]->mode);
200                         ce->ce_flags = create_ce_flags(baselen + pathlen,
201                                                        ce_stage);
202                         memcpy(ce->name, base, baselen);
203                         memcpy(ce->name + baselen, first, pathlen + 1);
204
205                         any_files = 1;
206
207                         hashcpy(ce->sha1, posns[i]->sha1);
208                         src[i + o->merge] = ce;
209                         subposns[i] = df_conflict_list;
210                         posns[i] = posns[i]->next;
211                 }
212                 if (any_files) {
213                         if (o->merge) {
214                                 int ret;
215
216 #if DBRT_DEBUG > 1
217                                 printf("%s:\n", first);
218                                 for (i = 0; i < src_size; i++) {
219                                         printf(" %d ", i);
220                                         if (src[i])
221                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
222                                         else
223                                                 printf("\n");
224                                 }
225 #endif
226                                 ret = o->fn(src, o);
227
228 #if DBRT_DEBUG > 1
229                                 printf("Added %d entries\n", ret);
230 #endif
231                                 o->pos += ret;
232                         } else {
233                                 for (i = 0; i < src_size; i++) {
234                                         if (src[i]) {
235                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
236                                         }
237                                 }
238                         }
239                 }
240                 if (any_dirs) {
241                         char *newbase = xmalloc(baselen + 2 + pathlen);
242                         memcpy(newbase, base, baselen);
243                         memcpy(newbase + baselen, first, pathlen);
244                         newbase[baselen + pathlen] = '/';
245                         newbase[baselen + pathlen + 1] = '\0';
246                         if (unpack_trees_rec(subposns, len, newbase, o,
247                                              df_conflict_list)) {
248                                 retval = -1;
249                                 goto leave_directory;
250                         }
251                         free(newbase);
252                 }
253                 free(subposns);
254                 free(src);
255         } while (1);
256
257  leave_directory:
258         if (o->dir)
259                 pop_exclude_per_directory(o->dir, i_stk);
260         return retval;
261 }
262
263 /* Unlink the last component and attempt to remove leading
264  * directories, in case this unlink is the removal of the
265  * last entry in the directory -- empty directories are removed.
266  */
267 static void unlink_entry(char *name, char *last_symlink)
268 {
269         char *cp, *prev;
270
271         if (has_symlink_leading_path(name, last_symlink))
272                 return;
273         if (unlink(name))
274                 return;
275         prev = NULL;
276         while (1) {
277                 int status;
278                 cp = strrchr(name, '/');
279                 if (prev)
280                         *prev = '/';
281                 if (!cp)
282                         break;
283
284                 *cp = 0;
285                 status = rmdir(name);
286                 if (status) {
287                         *cp = '/';
288                         break;
289                 }
290                 prev = cp;
291         }
292 }
293
294 static struct checkout state;
295 static void check_updates(struct cache_entry **src, int nr,
296                         struct unpack_trees_options *o)
297 {
298         unsigned short mask = htons(CE_UPDATE);
299         unsigned cnt = 0, total = 0;
300         struct progress progress;
301         char last_symlink[PATH_MAX];
302
303         if (o->update && o->verbose_update) {
304                 for (total = cnt = 0; cnt < nr; cnt++) {
305                         struct cache_entry *ce = src[cnt];
306                         if (!ce->ce_mode || ce->ce_flags & mask)
307                                 total++;
308                 }
309
310                 start_progress_delay(&progress, "Checking %u files out...",
311                                      "", total, 50, 2);
312                 cnt = 0;
313         }
314
315         *last_symlink = '\0';
316         while (nr--) {
317                 struct cache_entry *ce = *src++;
318
319                 if (total)
320                         if (!ce->ce_mode || ce->ce_flags & mask)
321                                 display_progress(&progress, ++cnt);
322                 if (!ce->ce_mode) {
323                         if (o->update)
324                                 unlink_entry(ce->name, last_symlink);
325                         continue;
326                 }
327                 if (ce->ce_flags & mask) {
328                         ce->ce_flags &= ~mask;
329                         if (o->update) {
330                                 checkout_entry(ce, &state, NULL);
331                                 *last_symlink = '\0';
332                         }
333                 }
334         }
335         if (total)
336                 stop_progress(&progress);;
337 }
338
339 int unpack_trees(struct object_list *trees, struct unpack_trees_options *o)
340 {
341         unsigned len = object_list_length(trees);
342         struct tree_entry_list **posns;
343         int i;
344         struct object_list *posn = trees;
345         struct tree_entry_list df_conflict_list;
346         static struct cache_entry *dfc;
347
348         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
349         df_conflict_list.next = &df_conflict_list;
350         memset(&state, 0, sizeof(state));
351         state.base_dir = "";
352         state.force = 1;
353         state.quiet = 1;
354         state.refresh_cache = 1;
355
356         o->merge_size = len;
357
358         if (!dfc)
359                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
360         o->df_conflict_entry = dfc;
361
362         if (len) {
363                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
364                 for (i = 0; i < len; i++) {
365                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
366                         posn = posn->next;
367                 }
368                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
369                                      o, &df_conflict_list))
370                         return -1;
371         }
372
373         if (o->trivial_merges_only && o->nontrivial_merge)
374                 die("Merge requires file-level merging");
375
376         check_updates(active_cache, active_nr, o);
377         return 0;
378 }
379
380 /* Here come the merge functions */
381
382 static void reject_merge(struct cache_entry *ce)
383 {
384         die("Entry '%s' would be overwritten by merge. Cannot merge.",
385             ce->name);
386 }
387
388 static int same(struct cache_entry *a, struct cache_entry *b)
389 {
390         if (!!a != !!b)
391                 return 0;
392         if (!a && !b)
393                 return 1;
394         return a->ce_mode == b->ce_mode &&
395                !hashcmp(a->sha1, b->sha1);
396 }
397
398
399 /*
400  * When a CE gets turned into an unmerged entry, we
401  * want it to be up-to-date
402  */
403 static void verify_uptodate(struct cache_entry *ce,
404                 struct unpack_trees_options *o)
405 {
406         struct stat st;
407
408         if (o->index_only || o->reset)
409                 return;
410
411         if (!lstat(ce->name, &st)) {
412                 unsigned changed = ce_match_stat(ce, &st, 1);
413                 if (!changed)
414                         return;
415                 errno = 0;
416         }
417         if (errno == ENOENT)
418                 return;
419         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
420 }
421
422 static void invalidate_ce_path(struct cache_entry *ce)
423 {
424         if (ce)
425                 cache_tree_invalidate_path(active_cache_tree, ce->name);
426 }
427
428 static int verify_clean_subdirectory(const char *path, const char *action,
429                                       struct unpack_trees_options *o)
430 {
431         /*
432          * we are about to extract "path"; we would not want to lose
433          * anything in the existing directory there.
434          */
435         int namelen;
436         int pos, i;
437         struct dir_struct d;
438         char *pathbuf;
439         int cnt = 0;
440
441         /*
442          * First let's make sure we do not have a local modification
443          * in that directory.
444          */
445         namelen = strlen(path);
446         pos = cache_name_pos(path, namelen);
447         if (0 <= pos)
448                 return cnt; /* we have it as nondirectory */
449         pos = -pos - 1;
450         for (i = pos; i < active_nr; i++) {
451                 struct cache_entry *ce = active_cache[i];
452                 int len = ce_namelen(ce);
453                 if (len < namelen ||
454                     strncmp(path, ce->name, namelen) ||
455                     ce->name[namelen] != '/')
456                         break;
457                 /*
458                  * ce->name is an entry in the subdirectory.
459                  */
460                 if (!ce_stage(ce)) {
461                         verify_uptodate(ce, o);
462                         ce->ce_mode = 0;
463                 }
464                 cnt++;
465         }
466
467         /*
468          * Then we need to make sure that we do not lose a locally
469          * present file that is not ignored.
470          */
471         pathbuf = xmalloc(namelen + 2);
472         memcpy(pathbuf, path, namelen);
473         strcpy(pathbuf+namelen, "/");
474
475         memset(&d, 0, sizeof(d));
476         if (o->dir)
477                 d.exclude_per_dir = o->dir->exclude_per_dir;
478         i = read_directory(&d, path, pathbuf, namelen+1, NULL);
479         if (i)
480                 die("Updating '%s' would lose untracked files in it",
481                     path);
482         free(pathbuf);
483         return cnt;
484 }
485
486 /*
487  * We do not want to remove or overwrite a working tree file that
488  * is not tracked, unless it is ignored.
489  */
490 static void verify_absent(const char *path, const char *action,
491                 struct unpack_trees_options *o)
492 {
493         struct stat st;
494
495         if (o->index_only || o->reset || !o->update)
496                 return;
497
498         if (!lstat(path, &st)) {
499                 int cnt;
500
501                 if (o->dir && excluded(o->dir, path))
502                         /*
503                          * path is explicitly excluded, so it is Ok to
504                          * overwrite it.
505                          */
506                         return;
507                 if (S_ISDIR(st.st_mode)) {
508                         /*
509                          * We are checking out path "foo" and
510                          * found "foo/." in the working tree.
511                          * This is tricky -- if we have modified
512                          * files that are in "foo/" we would lose
513                          * it.
514                          */
515                         cnt = verify_clean_subdirectory(path, action, o);
516
517                         /*
518                          * If this removed entries from the index,
519                          * what that means is:
520                          *
521                          * (1) the caller unpack_trees_rec() saw path/foo
522                          * in the index, and it has not removed it because
523                          * it thinks it is handling 'path' as blob with
524                          * D/F conflict;
525                          * (2) we will return "ok, we placed a merged entry
526                          * in the index" which would cause o->pos to be
527                          * incremented by one;
528                          * (3) however, original o->pos now has 'path/foo'
529                          * marked with "to be removed".
530                          *
531                          * We need to increment it by the number of
532                          * deleted entries here.
533                          */
534                         o->pos += cnt;
535                         return;
536                 }
537
538                 /*
539                  * The previous round may already have decided to
540                  * delete this path, which is in a subdirectory that
541                  * is being replaced with a blob.
542                  */
543                 cnt = cache_name_pos(path, strlen(path));
544                 if (0 <= cnt) {
545                         struct cache_entry *ce = active_cache[cnt];
546                         if (!ce_stage(ce) && !ce->ce_mode)
547                                 return;
548                 }
549
550                 die("Untracked working tree file '%s' "
551                     "would be %s by merge.", path, action);
552         }
553 }
554
555 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
556                 struct unpack_trees_options *o)
557 {
558         merge->ce_flags |= htons(CE_UPDATE);
559         if (old) {
560                 /*
561                  * See if we can re-use the old CE directly?
562                  * That way we get the uptodate stat info.
563                  *
564                  * This also removes the UPDATE flag on
565                  * a match.
566                  */
567                 if (same(old, merge)) {
568                         *merge = *old;
569                 } else {
570                         verify_uptodate(old, o);
571                         invalidate_ce_path(old);
572                 }
573         }
574         else {
575                 verify_absent(merge->name, "overwritten", o);
576                 invalidate_ce_path(merge);
577         }
578
579         merge->ce_flags &= ~htons(CE_STAGEMASK);
580         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
581         return 1;
582 }
583
584 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
585                 struct unpack_trees_options *o)
586 {
587         if (old)
588                 verify_uptodate(old, o);
589         else
590                 verify_absent(ce->name, "removed", o);
591         ce->ce_mode = 0;
592         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
593         invalidate_ce_path(ce);
594         return 1;
595 }
596
597 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
598 {
599         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
600         return 1;
601 }
602
603 #if DBRT_DEBUG
604 static void show_stage_entry(FILE *o,
605                              const char *label, const struct cache_entry *ce)
606 {
607         if (!ce)
608                 fprintf(o, "%s (missing)\n", label);
609         else
610                 fprintf(o, "%s%06o %s %d\t%s\n",
611                         label,
612                         ntohl(ce->ce_mode),
613                         sha1_to_hex(ce->sha1),
614                         ce_stage(ce),
615                         ce->name);
616 }
617 #endif
618
619 int threeway_merge(struct cache_entry **stages,
620                 struct unpack_trees_options *o)
621 {
622         struct cache_entry *index;
623         struct cache_entry *head;
624         struct cache_entry *remote = stages[o->head_idx + 1];
625         int count;
626         int head_match = 0;
627         int remote_match = 0;
628
629         int df_conflict_head = 0;
630         int df_conflict_remote = 0;
631
632         int any_anc_missing = 0;
633         int no_anc_exists = 1;
634         int i;
635
636         for (i = 1; i < o->head_idx; i++) {
637                 if (!stages[i] || stages[i] == o->df_conflict_entry)
638                         any_anc_missing = 1;
639                 else
640                         no_anc_exists = 0;
641         }
642
643         index = stages[0];
644         head = stages[o->head_idx];
645
646         if (head == o->df_conflict_entry) {
647                 df_conflict_head = 1;
648                 head = NULL;
649         }
650
651         if (remote == o->df_conflict_entry) {
652                 df_conflict_remote = 1;
653                 remote = NULL;
654         }
655
656         /* First, if there's a #16 situation, note that to prevent #13
657          * and #14.
658          */
659         if (!same(remote, head)) {
660                 for (i = 1; i < o->head_idx; i++) {
661                         if (same(stages[i], head)) {
662                                 head_match = i;
663                         }
664                         if (same(stages[i], remote)) {
665                                 remote_match = i;
666                         }
667                 }
668         }
669
670         /* We start with cases where the index is allowed to match
671          * something other than the head: #14(ALT) and #2ALT, where it
672          * is permitted to match the result instead.
673          */
674         /* #14, #14ALT, #2ALT */
675         if (remote && !df_conflict_head && head_match && !remote_match) {
676                 if (index && !same(index, remote) && !same(index, head))
677                         reject_merge(index);
678                 return merged_entry(remote, index, o);
679         }
680         /*
681          * If we have an entry in the index cache, then we want to
682          * make sure that it matches head.
683          */
684         if (index && !same(index, head)) {
685                 reject_merge(index);
686         }
687
688         if (head) {
689                 /* #5ALT, #15 */
690                 if (same(head, remote))
691                         return merged_entry(head, index, o);
692                 /* #13, #3ALT */
693                 if (!df_conflict_remote && remote_match && !head_match)
694                         return merged_entry(head, index, o);
695         }
696
697         /* #1 */
698         if (!head && !remote && any_anc_missing)
699                 return 0;
700
701         /* Under the new "aggressive" rule, we resolve mostly trivial
702          * cases that we historically had git-merge-one-file resolve.
703          */
704         if (o->aggressive) {
705                 int head_deleted = !head && !df_conflict_head;
706                 int remote_deleted = !remote && !df_conflict_remote;
707                 const char *path = NULL;
708
709                 if (index)
710                         path = index->name;
711                 else if (head)
712                         path = head->name;
713                 else if (remote)
714                         path = remote->name;
715                 else {
716                         for (i = 1; i < o->head_idx; i++) {
717                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
718                                         path = stages[i]->name;
719                                         break;
720                                 }
721                         }
722                 }
723
724                 /*
725                  * Deleted in both.
726                  * Deleted in one and unchanged in the other.
727                  */
728                 if ((head_deleted && remote_deleted) ||
729                     (head_deleted && remote && remote_match) ||
730                     (remote_deleted && head && head_match)) {
731                         if (index)
732                                 return deleted_entry(index, index, o);
733                         else if (path && !head_deleted)
734                                 verify_absent(path, "removed", o);
735                         return 0;
736                 }
737                 /*
738                  * Added in both, identically.
739                  */
740                 if (no_anc_exists && head && remote && same(head, remote))
741                         return merged_entry(head, index, o);
742
743         }
744
745         /* Below are "no merge" cases, which require that the index be
746          * up-to-date to avoid the files getting overwritten with
747          * conflict resolution files.
748          */
749         if (index) {
750                 verify_uptodate(index, o);
751         }
752
753         o->nontrivial_merge = 1;
754
755         /* #2, #3, #4, #6, #7, #9, #10, #11. */
756         count = 0;
757         if (!head_match || !remote_match) {
758                 for (i = 1; i < o->head_idx; i++) {
759                         if (stages[i] && stages[i] != o->df_conflict_entry) {
760                                 keep_entry(stages[i], o);
761                                 count++;
762                                 break;
763                         }
764                 }
765         }
766 #if DBRT_DEBUG
767         else {
768                 fprintf(stderr, "read-tree: warning #16 detected\n");
769                 show_stage_entry(stderr, "head   ", stages[head_match]);
770                 show_stage_entry(stderr, "remote ", stages[remote_match]);
771         }
772 #endif
773         if (head) { count += keep_entry(head, o); }
774         if (remote) { count += keep_entry(remote, o); }
775         return count;
776 }
777
778 /*
779  * Two-way merge.
780  *
781  * The rule is to "carry forward" what is in the index without losing
782  * information across a "fast forward", favoring a successful merge
783  * over a merge failure when it makes sense.  For details of the
784  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
785  *
786  */
787 int twoway_merge(struct cache_entry **src,
788                 struct unpack_trees_options *o)
789 {
790         struct cache_entry *current = src[0];
791         struct cache_entry *oldtree = src[1];
792         struct cache_entry *newtree = src[2];
793
794         if (o->merge_size != 2)
795                 return error("Cannot do a twoway merge of %d trees",
796                              o->merge_size);
797
798         if (oldtree == o->df_conflict_entry)
799                 oldtree = NULL;
800         if (newtree == o->df_conflict_entry)
801                 newtree = NULL;
802
803         if (current) {
804                 if ((!oldtree && !newtree) || /* 4 and 5 */
805                     (!oldtree && newtree &&
806                      same(current, newtree)) || /* 6 and 7 */
807                     (oldtree && newtree &&
808                      same(oldtree, newtree)) || /* 14 and 15 */
809                     (oldtree && newtree &&
810                      !same(oldtree, newtree) && /* 18 and 19 */
811                      same(current, newtree))) {
812                         return keep_entry(current, o);
813                 }
814                 else if (oldtree && !newtree && same(current, oldtree)) {
815                         /* 10 or 11 */
816                         return deleted_entry(oldtree, current, o);
817                 }
818                 else if (oldtree && newtree &&
819                          same(current, oldtree) && !same(current, newtree)) {
820                         /* 20 or 21 */
821                         return merged_entry(newtree, current, o);
822                 }
823                 else {
824                         /* all other failures */
825                         if (oldtree)
826                                 reject_merge(oldtree);
827                         if (current)
828                                 reject_merge(current);
829                         if (newtree)
830                                 reject_merge(newtree);
831                         return -1;
832                 }
833         }
834         else if (newtree)
835                 return merged_entry(newtree, current, o);
836         else
837                 return deleted_entry(oldtree, current, o);
838 }
839
840 /*
841  * Bind merge.
842  *
843  * Keep the index entries at stage0, collapse stage1 but make sure
844  * stage0 does not have anything there.
845  */
846 int bind_merge(struct cache_entry **src,
847                 struct unpack_trees_options *o)
848 {
849         struct cache_entry *old = src[0];
850         struct cache_entry *a = src[1];
851
852         if (o->merge_size != 1)
853                 return error("Cannot do a bind merge of %d trees\n",
854                              o->merge_size);
855         if (a && old)
856                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
857         if (!a)
858                 return keep_entry(old, o);
859         else
860                 return merged_entry(a, NULL, o);
861 }
862
863 /*
864  * One-way merge.
865  *
866  * The rule is:
867  * - take the stat information from stage0, take the data from stage1
868  */
869 int oneway_merge(struct cache_entry **src,
870                 struct unpack_trees_options *o)
871 {
872         struct cache_entry *old = src[0];
873         struct cache_entry *a = src[1];
874
875         if (o->merge_size != 1)
876                 return error("Cannot do a oneway merge of %d trees",
877                              o->merge_size);
878
879         if (!a)
880                 return deleted_entry(old, old, o);
881         if (old && same(old, a)) {
882                 if (o->reset) {
883                         struct stat st;
884                         if (lstat(old->name, &st) ||
885                             ce_match_stat(old, &st, 1))
886                                 old->ce_flags |= htons(CE_UPDATE);
887                 }
888                 return keep_entry(old, o);
889         }
890         return merged_entry(a, old, o);
891 }