Merge branch 'rr/cvsexportcommit-w'
[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 #include "refs.h"
9
10 #define DBRT_DEBUG 1
11
12 struct tree_entry_list {
13         struct tree_entry_list *next;
14         unsigned int mode;
15         const char *name;
16         const unsigned char *sha1;
17 };
18
19 static struct tree_entry_list *create_tree_entry_list(struct tree_desc *desc)
20 {
21         struct name_entry one;
22         struct tree_entry_list *ret = NULL;
23         struct tree_entry_list **list_p = &ret;
24
25         while (tree_entry(desc, &one)) {
26                 struct tree_entry_list *entry;
27
28                 entry = xmalloc(sizeof(struct tree_entry_list));
29                 entry->name = one.path;
30                 entry->sha1 = one.sha1;
31                 entry->mode = one.mode;
32                 entry->next = NULL;
33
34                 *list_p = entry;
35                 list_p = &entry->next;
36         }
37         return ret;
38 }
39
40 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
41 {
42         int len1 = strlen(name1);
43         int len2 = strlen(name2);
44         int len = len1 < len2 ? len1 : len2;
45         int ret = memcmp(name1, name2, len);
46         unsigned char c1, c2;
47         if (ret)
48                 return ret;
49         c1 = name1[len];
50         c2 = name2[len];
51         if (!c1 && dir1)
52                 c1 = '/';
53         if (!c2 && dir2)
54                 c2 = '/';
55         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
56         if (c1 && c2 && !ret)
57                 ret = len1 - len2;
58         return ret;
59 }
60
61 static inline void remove_entry(int remove)
62 {
63         if (remove >= 0)
64                 remove_cache_entry_at(remove);
65 }
66
67 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
68                             const char *base, struct unpack_trees_options *o,
69                             struct tree_entry_list *df_conflict_list)
70 {
71         int remove;
72         int baselen = strlen(base);
73         int src_size = len + 1;
74         int i_stk = i_stk;
75         int retval = 0;
76
77         if (o->dir)
78                 i_stk = push_exclude_per_directory(o->dir, base, strlen(base));
79
80         do {
81                 int i;
82                 const char *first;
83                 int firstdir = 0;
84                 int pathlen;
85                 unsigned ce_size;
86                 struct tree_entry_list **subposns;
87                 struct cache_entry **src;
88                 int any_files = 0;
89                 int any_dirs = 0;
90                 char *cache_name;
91                 int ce_stage;
92
93                 /* Find the first name in the input. */
94
95                 first = NULL;
96                 cache_name = NULL;
97
98                 /* Check the cache */
99                 if (o->merge && o->pos < active_nr) {
100                         /* This is a bit tricky: */
101                         /* If the index has a subdirectory (with
102                          * contents) as the first name, it'll get a
103                          * filename like "foo/bar". But that's after
104                          * "foo", so the entry in trees will get
105                          * handled first, at which point we'll go into
106                          * "foo", and deal with "bar" from the index,
107                          * because the base will be "foo/". The only
108                          * way we can actually have "foo/bar" first of
109                          * all the things is if the trees don't
110                          * contain "foo" at all, in which case we'll
111                          * handle "foo/bar" without going into the
112                          * directory, but that's fine (and will return
113                          * an error anyway, with the added unknown
114                          * file case.
115                          */
116
117                         cache_name = active_cache[o->pos]->name;
118                         if (strlen(cache_name) > baselen &&
119                             !memcmp(cache_name, base, baselen)) {
120                                 cache_name += baselen;
121                                 first = cache_name;
122                         } else {
123                                 cache_name = NULL;
124                         }
125                 }
126
127 #if DBRT_DEBUG > 1
128                 if (first)
129                         printf("index %s\n", first);
130 #endif
131                 for (i = 0; i < len; i++) {
132                         if (!posns[i] || posns[i] == df_conflict_list)
133                                 continue;
134 #if DBRT_DEBUG > 1
135                         printf("%d %s\n", i + 1, posns[i]->name);
136 #endif
137                         if (!first || entcmp(first, firstdir,
138                                              posns[i]->name,
139                                              S_ISDIR(posns[i]->mode)) > 0) {
140                                 first = posns[i]->name;
141                                 firstdir = S_ISDIR(posns[i]->mode);
142                         }
143                 }
144                 /* No name means we're done */
145                 if (!first)
146                         goto leave_directory;
147
148                 pathlen = strlen(first);
149                 ce_size = cache_entry_size(baselen + pathlen);
150
151                 src = xcalloc(src_size, sizeof(struct cache_entry *));
152
153                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
154
155                 remove = -1;
156                 if (cache_name && !strcmp(cache_name, first)) {
157                         any_files = 1;
158                         src[0] = active_cache[o->pos];
159                         remove = o->pos;
160                 }
161
162                 for (i = 0; i < len; i++) {
163                         struct cache_entry *ce;
164
165                         if (!posns[i] ||
166                             (posns[i] != df_conflict_list &&
167                              strcmp(first, posns[i]->name))) {
168                                 continue;
169                         }
170
171                         if (posns[i] == df_conflict_list) {
172                                 src[i + o->merge] = o->df_conflict_entry;
173                                 continue;
174                         }
175
176                         if (S_ISDIR(posns[i]->mode)) {
177                                 struct tree *tree = lookup_tree(posns[i]->sha1);
178                                 struct tree_desc t;
179                                 any_dirs = 1;
180                                 parse_tree(tree);
181                                 init_tree_desc(&t, tree->buffer, tree->size);
182                                 subposns[i] = create_tree_entry_list(&t);
183                                 posns[i] = posns[i]->next;
184                                 src[i + o->merge] = o->df_conflict_entry;
185                                 continue;
186                         }
187
188                         if (!o->merge)
189                                 ce_stage = 0;
190                         else if (i + 1 < o->head_idx)
191                                 ce_stage = 1;
192                         else if (i + 1 > o->head_idx)
193                                 ce_stage = 3;
194                         else
195                                 ce_stage = 2;
196
197                         ce = xcalloc(1, ce_size);
198                         ce->ce_mode = create_ce_mode(posns[i]->mode);
199                         ce->ce_flags = create_ce_flags(baselen + pathlen,
200                                                        ce_stage);
201                         memcpy(ce->name, base, baselen);
202                         memcpy(ce->name + baselen, first, pathlen + 1);
203
204                         any_files = 1;
205
206                         hashcpy(ce->sha1, posns[i]->sha1);
207                         src[i + o->merge] = ce;
208                         subposns[i] = df_conflict_list;
209                         posns[i] = posns[i]->next;
210                 }
211                 if (any_files) {
212                         if (o->merge) {
213                                 int ret;
214
215 #if DBRT_DEBUG > 1
216                                 printf("%s:\n", first);
217                                 for (i = 0; i < src_size; i++) {
218                                         printf(" %d ", i);
219                                         if (src[i])
220                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
221                                         else
222                                                 printf("\n");
223                                 }
224 #endif
225                                 ret = o->fn(src, o, remove);
226
227 #if DBRT_DEBUG > 1
228                                 printf("Added %d entries\n", ret);
229 #endif
230                                 o->pos += ret;
231                         } else {
232                                 remove_entry(remove);
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 = NULL;
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                 progress = start_progress_delay("Checking out files",
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 (!ce->ce_mode || ce->ce_flags & mask)
320                         display_progress(progress, ++cnt);
321                 if (!ce->ce_mode) {
322                         if (o->update)
323                                 unlink_entry(ce->name, last_symlink);
324                         continue;
325                 }
326                 if (ce->ce_flags & mask) {
327                         ce->ce_flags &= ~mask;
328                         if (o->update) {
329                                 checkout_entry(ce, &state, NULL);
330                                 *last_symlink = '\0';
331                         }
332                 }
333         }
334         stop_progress(&progress);
335 }
336
337 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
338 {
339         struct tree_entry_list **posns;
340         int i;
341         struct tree_entry_list df_conflict_list;
342         static struct cache_entry *dfc;
343
344         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
345         df_conflict_list.next = &df_conflict_list;
346         memset(&state, 0, sizeof(state));
347         state.base_dir = "";
348         state.force = 1;
349         state.quiet = 1;
350         state.refresh_cache = 1;
351
352         o->merge_size = len;
353
354         if (!dfc)
355                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
356         o->df_conflict_entry = dfc;
357
358         if (len) {
359                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
360                 for (i = 0; i < len; i++)
361                         posns[i] = create_tree_entry_list(t+i);
362
363                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
364                                      o, &df_conflict_list))
365                         return -1;
366         }
367
368         if (o->trivial_merges_only && o->nontrivial_merge)
369                 die("Merge requires file-level merging");
370
371         check_updates(active_cache, active_nr, o);
372         return 0;
373 }
374
375 /* Here come the merge functions */
376
377 static void reject_merge(struct cache_entry *ce)
378 {
379         die("Entry '%s' would be overwritten by merge. Cannot merge.",
380             ce->name);
381 }
382
383 static int same(struct cache_entry *a, struct cache_entry *b)
384 {
385         if (!!a != !!b)
386                 return 0;
387         if (!a && !b)
388                 return 1;
389         return a->ce_mode == b->ce_mode &&
390                !hashcmp(a->sha1, b->sha1);
391 }
392
393
394 /*
395  * When a CE gets turned into an unmerged entry, we
396  * want it to be up-to-date
397  */
398 static void verify_uptodate(struct cache_entry *ce,
399                 struct unpack_trees_options *o)
400 {
401         struct stat st;
402
403         if (o->index_only || o->reset)
404                 return;
405
406         if (!lstat(ce->name, &st)) {
407                 unsigned changed = ce_match_stat(ce, &st, 1);
408                 if (!changed)
409                         return;
410                 /*
411                  * NEEDSWORK: the current default policy is to allow
412                  * submodule to be out of sync wrt the supermodule
413                  * index.  This needs to be tightened later for
414                  * submodules that are marked to be automatically
415                  * checked out.
416                  */
417                 if (S_ISGITLINK(ntohl(ce->ce_mode)))
418                         return;
419                 errno = 0;
420         }
421         if (errno == ENOENT)
422                 return;
423         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
424 }
425
426 static void invalidate_ce_path(struct cache_entry *ce)
427 {
428         if (ce)
429                 cache_tree_invalidate_path(active_cache_tree, ce->name);
430 }
431
432 /*
433  * Check that checking out ce->sha1 in subdir ce->name is not
434  * going to overwrite any working files.
435  *
436  * Currently, git does not checkout subprojects during a superproject
437  * checkout, so it is not going to overwrite anything.
438  */
439 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
440                                       struct unpack_trees_options *o)
441 {
442         return 0;
443 }
444
445 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
446                                       struct unpack_trees_options *o)
447 {
448         /*
449          * we are about to extract "ce->name"; we would not want to lose
450          * anything in the existing directory there.
451          */
452         int namelen;
453         int pos, i;
454         struct dir_struct d;
455         char *pathbuf;
456         int cnt = 0;
457         unsigned char sha1[20];
458
459         if (S_ISGITLINK(ntohl(ce->ce_mode)) &&
460             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
461                 /* If we are not going to update the submodule, then
462                  * we don't care.
463                  */
464                 if (!hashcmp(sha1, ce->sha1))
465                         return 0;
466                 return verify_clean_submodule(ce, action, o);
467         }
468
469         /*
470          * First let's make sure we do not have a local modification
471          * in that directory.
472          */
473         namelen = strlen(ce->name);
474         pos = cache_name_pos(ce->name, namelen);
475         if (0 <= pos)
476                 return cnt; /* we have it as nondirectory */
477         pos = -pos - 1;
478         for (i = pos; i < active_nr; i++) {
479                 struct cache_entry *ce = active_cache[i];
480                 int len = ce_namelen(ce);
481                 if (len < namelen ||
482                     strncmp(ce->name, ce->name, namelen) ||
483                     ce->name[namelen] != '/')
484                         break;
485                 /*
486                  * ce->name is an entry in the subdirectory.
487                  */
488                 if (!ce_stage(ce)) {
489                         verify_uptodate(ce, o);
490                         ce->ce_mode = 0;
491                 }
492                 cnt++;
493         }
494
495         /*
496          * Then we need to make sure that we do not lose a locally
497          * present file that is not ignored.
498          */
499         pathbuf = xmalloc(namelen + 2);
500         memcpy(pathbuf, ce->name, namelen);
501         strcpy(pathbuf+namelen, "/");
502
503         memset(&d, 0, sizeof(d));
504         if (o->dir)
505                 d.exclude_per_dir = o->dir->exclude_per_dir;
506         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
507         if (i)
508                 die("Updating '%s' would lose untracked files in it",
509                     ce->name);
510         free(pathbuf);
511         return cnt;
512 }
513
514 /*
515  * We do not want to remove or overwrite a working tree file that
516  * is not tracked, unless it is ignored.
517  */
518 static void verify_absent(struct cache_entry *ce, const char *action,
519                 struct unpack_trees_options *o)
520 {
521         struct stat st;
522
523         if (o->index_only || o->reset || !o->update)
524                 return;
525
526         if (has_symlink_leading_path(ce->name, NULL))
527                 return;
528
529         if (!lstat(ce->name, &st)) {
530                 int cnt;
531
532                 if (o->dir && excluded(o->dir, ce->name))
533                         /*
534                          * ce->name is explicitly excluded, so it is Ok to
535                          * overwrite it.
536                          */
537                         return;
538                 if (S_ISDIR(st.st_mode)) {
539                         /*
540                          * We are checking out path "foo" and
541                          * found "foo/." in the working tree.
542                          * This is tricky -- if we have modified
543                          * files that are in "foo/" we would lose
544                          * it.
545                          */
546                         cnt = verify_clean_subdirectory(ce, action, o);
547
548                         /*
549                          * If this removed entries from the index,
550                          * what that means is:
551                          *
552                          * (1) the caller unpack_trees_rec() saw path/foo
553                          * in the index, and it has not removed it because
554                          * it thinks it is handling 'path' as blob with
555                          * D/F conflict;
556                          * (2) we will return "ok, we placed a merged entry
557                          * in the index" which would cause o->pos to be
558                          * incremented by one;
559                          * (3) however, original o->pos now has 'path/foo'
560                          * marked with "to be removed".
561                          *
562                          * We need to increment it by the number of
563                          * deleted entries here.
564                          */
565                         o->pos += cnt;
566                         return;
567                 }
568
569                 /*
570                  * The previous round may already have decided to
571                  * delete this path, which is in a subdirectory that
572                  * is being replaced with a blob.
573                  */
574                 cnt = cache_name_pos(ce->name, strlen(ce->name));
575                 if (0 <= cnt) {
576                         struct cache_entry *ce = active_cache[cnt];
577                         if (!ce_stage(ce) && !ce->ce_mode)
578                                 return;
579                 }
580
581                 die("Untracked working tree file '%s' "
582                     "would be %s by merge.", ce->name, action);
583         }
584 }
585
586 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
587                 struct unpack_trees_options *o)
588 {
589         merge->ce_flags |= htons(CE_UPDATE);
590         if (old) {
591                 /*
592                  * See if we can re-use the old CE directly?
593                  * That way we get the uptodate stat info.
594                  *
595                  * This also removes the UPDATE flag on
596                  * a match.
597                  */
598                 if (same(old, merge)) {
599                         *merge = *old;
600                 } else {
601                         verify_uptodate(old, o);
602                         invalidate_ce_path(old);
603                 }
604         }
605         else {
606                 verify_absent(merge, "overwritten", o);
607                 invalidate_ce_path(merge);
608         }
609
610         merge->ce_flags &= ~htons(CE_STAGEMASK);
611         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
612         return 1;
613 }
614
615 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
616                 struct unpack_trees_options *o)
617 {
618         if (old)
619                 verify_uptodate(old, o);
620         else
621                 verify_absent(ce, "removed", o);
622         ce->ce_mode = 0;
623         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
624         invalidate_ce_path(ce);
625         return 1;
626 }
627
628 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
629 {
630         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
631         return 1;
632 }
633
634 #if DBRT_DEBUG
635 static void show_stage_entry(FILE *o,
636                              const char *label, const struct cache_entry *ce)
637 {
638         if (!ce)
639                 fprintf(o, "%s (missing)\n", label);
640         else
641                 fprintf(o, "%s%06o %s %d\t%s\n",
642                         label,
643                         ntohl(ce->ce_mode),
644                         sha1_to_hex(ce->sha1),
645                         ce_stage(ce),
646                         ce->name);
647 }
648 #endif
649
650 int threeway_merge(struct cache_entry **stages,
651                 struct unpack_trees_options *o,
652                 int remove)
653 {
654         struct cache_entry *index;
655         struct cache_entry *head;
656         struct cache_entry *remote = stages[o->head_idx + 1];
657         int count;
658         int head_match = 0;
659         int remote_match = 0;
660
661         int df_conflict_head = 0;
662         int df_conflict_remote = 0;
663
664         int any_anc_missing = 0;
665         int no_anc_exists = 1;
666         int i;
667
668         for (i = 1; i < o->head_idx; i++) {
669                 if (!stages[i] || stages[i] == o->df_conflict_entry)
670                         any_anc_missing = 1;
671                 else
672                         no_anc_exists = 0;
673         }
674
675         index = stages[0];
676         head = stages[o->head_idx];
677
678         if (head == o->df_conflict_entry) {
679                 df_conflict_head = 1;
680                 head = NULL;
681         }
682
683         if (remote == o->df_conflict_entry) {
684                 df_conflict_remote = 1;
685                 remote = NULL;
686         }
687
688         /* First, if there's a #16 situation, note that to prevent #13
689          * and #14.
690          */
691         if (!same(remote, head)) {
692                 for (i = 1; i < o->head_idx; i++) {
693                         if (same(stages[i], head)) {
694                                 head_match = i;
695                         }
696                         if (same(stages[i], remote)) {
697                                 remote_match = i;
698                         }
699                 }
700         }
701
702         /* We start with cases where the index is allowed to match
703          * something other than the head: #14(ALT) and #2ALT, where it
704          * is permitted to match the result instead.
705          */
706         /* #14, #14ALT, #2ALT */
707         if (remote && !df_conflict_head && head_match && !remote_match) {
708                 if (index && !same(index, remote) && !same(index, head))
709                         reject_merge(index);
710                 return merged_entry(remote, index, o);
711         }
712         /*
713          * If we have an entry in the index cache, then we want to
714          * make sure that it matches head.
715          */
716         if (index && !same(index, head)) {
717                 reject_merge(index);
718         }
719
720         if (head) {
721                 /* #5ALT, #15 */
722                 if (same(head, remote))
723                         return merged_entry(head, index, o);
724                 /* #13, #3ALT */
725                 if (!df_conflict_remote && remote_match && !head_match)
726                         return merged_entry(head, index, o);
727         }
728
729         /* #1 */
730         if (!head && !remote && any_anc_missing) {
731                 remove_entry(remove);
732                 return 0;
733         }
734
735         /* Under the new "aggressive" rule, we resolve mostly trivial
736          * cases that we historically had git-merge-one-file resolve.
737          */
738         if (o->aggressive) {
739                 int head_deleted = !head && !df_conflict_head;
740                 int remote_deleted = !remote && !df_conflict_remote;
741                 struct cache_entry *ce = NULL;
742
743                 if (index)
744                         ce = index;
745                 else if (head)
746                         ce = head;
747                 else if (remote)
748                         ce = remote;
749                 else {
750                         for (i = 1; i < o->head_idx; i++) {
751                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
752                                         ce = stages[i];
753                                         break;
754                                 }
755                         }
756                 }
757
758                 /*
759                  * Deleted in both.
760                  * Deleted in one and unchanged in the other.
761                  */
762                 if ((head_deleted && remote_deleted) ||
763                     (head_deleted && remote && remote_match) ||
764                     (remote_deleted && head && head_match)) {
765                         remove_entry(remove);
766                         if (index)
767                                 return deleted_entry(index, index, o);
768                         else if (ce && !head_deleted)
769                                 verify_absent(ce, "removed", o);
770                         return 0;
771                 }
772                 /*
773                  * Added in both, identically.
774                  */
775                 if (no_anc_exists && head && remote && same(head, remote))
776                         return merged_entry(head, index, o);
777
778         }
779
780         /* Below are "no merge" cases, which require that the index be
781          * up-to-date to avoid the files getting overwritten with
782          * conflict resolution files.
783          */
784         if (index) {
785                 verify_uptodate(index, o);
786         }
787
788         remove_entry(remove);
789         o->nontrivial_merge = 1;
790
791         /* #2, #3, #4, #6, #7, #9, #10, #11. */
792         count = 0;
793         if (!head_match || !remote_match) {
794                 for (i = 1; i < o->head_idx; i++) {
795                         if (stages[i] && stages[i] != o->df_conflict_entry) {
796                                 keep_entry(stages[i], o);
797                                 count++;
798                                 break;
799                         }
800                 }
801         }
802 #if DBRT_DEBUG
803         else {
804                 fprintf(stderr, "read-tree: warning #16 detected\n");
805                 show_stage_entry(stderr, "head   ", stages[head_match]);
806                 show_stage_entry(stderr, "remote ", stages[remote_match]);
807         }
808 #endif
809         if (head) { count += keep_entry(head, o); }
810         if (remote) { count += keep_entry(remote, o); }
811         return count;
812 }
813
814 /*
815  * Two-way merge.
816  *
817  * The rule is to "carry forward" what is in the index without losing
818  * information across a "fast forward", favoring a successful merge
819  * over a merge failure when it makes sense.  For details of the
820  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
821  *
822  */
823 int twoway_merge(struct cache_entry **src,
824                 struct unpack_trees_options *o,
825                 int remove)
826 {
827         struct cache_entry *current = src[0];
828         struct cache_entry *oldtree = src[1];
829         struct cache_entry *newtree = src[2];
830
831         if (o->merge_size != 2)
832                 return error("Cannot do a twoway merge of %d trees",
833                              o->merge_size);
834
835         if (oldtree == o->df_conflict_entry)
836                 oldtree = NULL;
837         if (newtree == o->df_conflict_entry)
838                 newtree = NULL;
839
840         if (current) {
841                 if ((!oldtree && !newtree) || /* 4 and 5 */
842                     (!oldtree && newtree &&
843                      same(current, newtree)) || /* 6 and 7 */
844                     (oldtree && newtree &&
845                      same(oldtree, newtree)) || /* 14 and 15 */
846                     (oldtree && newtree &&
847                      !same(oldtree, newtree) && /* 18 and 19 */
848                      same(current, newtree))) {
849                         return keep_entry(current, o);
850                 }
851                 else if (oldtree && !newtree && same(current, oldtree)) {
852                         /* 10 or 11 */
853                         remove_entry(remove);
854                         return deleted_entry(oldtree, current, o);
855                 }
856                 else if (oldtree && newtree &&
857                          same(current, oldtree) && !same(current, newtree)) {
858                         /* 20 or 21 */
859                         return merged_entry(newtree, current, o);
860                 }
861                 else {
862                         /* all other failures */
863                         remove_entry(remove);
864                         if (oldtree)
865                                 reject_merge(oldtree);
866                         if (current)
867                                 reject_merge(current);
868                         if (newtree)
869                                 reject_merge(newtree);
870                         return -1;
871                 }
872         }
873         else if (newtree)
874                 return merged_entry(newtree, current, o);
875         remove_entry(remove);
876         return deleted_entry(oldtree, current, o);
877 }
878
879 /*
880  * Bind merge.
881  *
882  * Keep the index entries at stage0, collapse stage1 but make sure
883  * stage0 does not have anything there.
884  */
885 int bind_merge(struct cache_entry **src,
886                 struct unpack_trees_options *o,
887                 int remove)
888 {
889         struct cache_entry *old = src[0];
890         struct cache_entry *a = src[1];
891
892         if (o->merge_size != 1)
893                 return error("Cannot do a bind merge of %d trees\n",
894                              o->merge_size);
895         if (a && old)
896                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
897         if (!a)
898                 return keep_entry(old, o);
899         else
900                 return merged_entry(a, NULL, o);
901 }
902
903 /*
904  * One-way merge.
905  *
906  * The rule is:
907  * - take the stat information from stage0, take the data from stage1
908  */
909 int oneway_merge(struct cache_entry **src,
910                 struct unpack_trees_options *o,
911                 int remove)
912 {
913         struct cache_entry *old = src[0];
914         struct cache_entry *a = src[1];
915
916         if (o->merge_size != 1)
917                 return error("Cannot do a oneway merge of %d trees",
918                              o->merge_size);
919
920         if (!a) {
921                 remove_entry(remove);
922                 return deleted_entry(old, old, o);
923         }
924         if (old && same(old, a)) {
925                 if (o->reset) {
926                         struct stat st;
927                         if (lstat(old->name, &st) ||
928                             ce_match_stat(old, &st, 1))
929                                 old->ce_flags |= htons(CE_UPDATE);
930                 }
931                 return keep_entry(old, o);
932         }
933         return merged_entry(a, old, o);
934 }