git.el: Fix typo in git-update-saved-file error handling.
[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;
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(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
340 {
341         struct tree_entry_list **posns;
342         int i;
343         struct tree_entry_list df_conflict_list;
344         static struct cache_entry *dfc;
345
346         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
347         df_conflict_list.next = &df_conflict_list;
348         memset(&state, 0, sizeof(state));
349         state.base_dir = "";
350         state.force = 1;
351         state.quiet = 1;
352         state.refresh_cache = 1;
353
354         o->merge_size = len;
355
356         if (!dfc)
357                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
358         o->df_conflict_entry = dfc;
359
360         if (len) {
361                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
362                 for (i = 0; i < len; i++)
363                         posns[i] = create_tree_entry_list(t+i);
364
365                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
366                                      o, &df_conflict_list))
367                         return -1;
368         }
369
370         if (o->trivial_merges_only && o->nontrivial_merge)
371                 die("Merge requires file-level merging");
372
373         check_updates(active_cache, active_nr, o);
374         return 0;
375 }
376
377 /* Here come the merge functions */
378
379 static void reject_merge(struct cache_entry *ce)
380 {
381         die("Entry '%s' would be overwritten by merge. Cannot merge.",
382             ce->name);
383 }
384
385 static int same(struct cache_entry *a, struct cache_entry *b)
386 {
387         if (!!a != !!b)
388                 return 0;
389         if (!a && !b)
390                 return 1;
391         return a->ce_mode == b->ce_mode &&
392                !hashcmp(a->sha1, b->sha1);
393 }
394
395
396 /*
397  * When a CE gets turned into an unmerged entry, we
398  * want it to be up-to-date
399  */
400 static void verify_uptodate(struct cache_entry *ce,
401                 struct unpack_trees_options *o)
402 {
403         struct stat st;
404
405         if (o->index_only || o->reset)
406                 return;
407
408         if (!lstat(ce->name, &st)) {
409                 unsigned changed = ce_match_stat(ce, &st, 1);
410                 if (!changed)
411                         return;
412                 /*
413                  * NEEDSWORK: the current default policy is to allow
414                  * submodule to be out of sync wrt the supermodule
415                  * index.  This needs to be tightened later for
416                  * submodules that are marked to be automatically
417                  * checked out.
418                  */
419                 if (S_ISGITLINK(ntohl(ce->ce_mode)))
420                         return;
421                 errno = 0;
422         }
423         if (errno == ENOENT)
424                 return;
425         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
426 }
427
428 static void invalidate_ce_path(struct cache_entry *ce)
429 {
430         if (ce)
431                 cache_tree_invalidate_path(active_cache_tree, ce->name);
432 }
433
434 /*
435  * Check that checking out ce->sha1 in subdir ce->name is not
436  * going to overwrite any working files.
437  *
438  * Currently, git does not checkout subprojects during a superproject
439  * checkout, so it is not going to overwrite anything.
440  */
441 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
442                                       struct unpack_trees_options *o)
443 {
444         return 0;
445 }
446
447 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
448                                       struct unpack_trees_options *o)
449 {
450         /*
451          * we are about to extract "ce->name"; we would not want to lose
452          * anything in the existing directory there.
453          */
454         int namelen;
455         int pos, i;
456         struct dir_struct d;
457         char *pathbuf;
458         int cnt = 0;
459         unsigned char sha1[20];
460
461         if (S_ISGITLINK(ntohl(ce->ce_mode)) &&
462             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
463                 /* If we are not going to update the submodule, then
464                  * we don't care.
465                  */
466                 if (!hashcmp(sha1, ce->sha1))
467                         return 0;
468                 return verify_clean_submodule(ce, action, o);
469         }
470
471         /*
472          * First let's make sure we do not have a local modification
473          * in that directory.
474          */
475         namelen = strlen(ce->name);
476         pos = cache_name_pos(ce->name, namelen);
477         if (0 <= pos)
478                 return cnt; /* we have it as nondirectory */
479         pos = -pos - 1;
480         for (i = pos; i < active_nr; i++) {
481                 struct cache_entry *ce = active_cache[i];
482                 int len = ce_namelen(ce);
483                 if (len < namelen ||
484                     strncmp(ce->name, ce->name, namelen) ||
485                     ce->name[namelen] != '/')
486                         break;
487                 /*
488                  * ce->name is an entry in the subdirectory.
489                  */
490                 if (!ce_stage(ce)) {
491                         verify_uptodate(ce, o);
492                         ce->ce_mode = 0;
493                 }
494                 cnt++;
495         }
496
497         /*
498          * Then we need to make sure that we do not lose a locally
499          * present file that is not ignored.
500          */
501         pathbuf = xmalloc(namelen + 2);
502         memcpy(pathbuf, ce->name, namelen);
503         strcpy(pathbuf+namelen, "/");
504
505         memset(&d, 0, sizeof(d));
506         if (o->dir)
507                 d.exclude_per_dir = o->dir->exclude_per_dir;
508         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
509         if (i)
510                 die("Updating '%s' would lose untracked files in it",
511                     ce->name);
512         free(pathbuf);
513         return cnt;
514 }
515
516 /*
517  * We do not want to remove or overwrite a working tree file that
518  * is not tracked, unless it is ignored.
519  */
520 static void verify_absent(struct cache_entry *ce, const char *action,
521                 struct unpack_trees_options *o)
522 {
523         struct stat st;
524
525         if (o->index_only || o->reset || !o->update)
526                 return;
527
528         if (has_symlink_leading_path(ce->name, NULL))
529                 return;
530
531         if (!lstat(ce->name, &st)) {
532                 int cnt;
533
534                 if (o->dir && excluded(o->dir, ce->name))
535                         /*
536                          * ce->name is explicitly excluded, so it is Ok to
537                          * overwrite it.
538                          */
539                         return;
540                 if (S_ISDIR(st.st_mode)) {
541                         /*
542                          * We are checking out path "foo" and
543                          * found "foo/." in the working tree.
544                          * This is tricky -- if we have modified
545                          * files that are in "foo/" we would lose
546                          * it.
547                          */
548                         cnt = verify_clean_subdirectory(ce, action, o);
549
550                         /*
551                          * If this removed entries from the index,
552                          * what that means is:
553                          *
554                          * (1) the caller unpack_trees_rec() saw path/foo
555                          * in the index, and it has not removed it because
556                          * it thinks it is handling 'path' as blob with
557                          * D/F conflict;
558                          * (2) we will return "ok, we placed a merged entry
559                          * in the index" which would cause o->pos to be
560                          * incremented by one;
561                          * (3) however, original o->pos now has 'path/foo'
562                          * marked with "to be removed".
563                          *
564                          * We need to increment it by the number of
565                          * deleted entries here.
566                          */
567                         o->pos += cnt;
568                         return;
569                 }
570
571                 /*
572                  * The previous round may already have decided to
573                  * delete this path, which is in a subdirectory that
574                  * is being replaced with a blob.
575                  */
576                 cnt = cache_name_pos(ce->name, strlen(ce->name));
577                 if (0 <= cnt) {
578                         struct cache_entry *ce = active_cache[cnt];
579                         if (!ce_stage(ce) && !ce->ce_mode)
580                                 return;
581                 }
582
583                 die("Untracked working tree file '%s' "
584                     "would be %s by merge.", ce->name, action);
585         }
586 }
587
588 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
589                 struct unpack_trees_options *o)
590 {
591         merge->ce_flags |= htons(CE_UPDATE);
592         if (old) {
593                 /*
594                  * See if we can re-use the old CE directly?
595                  * That way we get the uptodate stat info.
596                  *
597                  * This also removes the UPDATE flag on
598                  * a match.
599                  */
600                 if (same(old, merge)) {
601                         *merge = *old;
602                 } else {
603                         verify_uptodate(old, o);
604                         invalidate_ce_path(old);
605                 }
606         }
607         else {
608                 verify_absent(merge, "overwritten", o);
609                 invalidate_ce_path(merge);
610         }
611
612         merge->ce_flags &= ~htons(CE_STAGEMASK);
613         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
614         return 1;
615 }
616
617 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
618                 struct unpack_trees_options *o)
619 {
620         if (old)
621                 verify_uptodate(old, o);
622         else
623                 verify_absent(ce, "removed", o);
624         ce->ce_mode = 0;
625         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
626         invalidate_ce_path(ce);
627         return 1;
628 }
629
630 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
631 {
632         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
633         return 1;
634 }
635
636 #if DBRT_DEBUG
637 static void show_stage_entry(FILE *o,
638                              const char *label, const struct cache_entry *ce)
639 {
640         if (!ce)
641                 fprintf(o, "%s (missing)\n", label);
642         else
643                 fprintf(o, "%s%06o %s %d\t%s\n",
644                         label,
645                         ntohl(ce->ce_mode),
646                         sha1_to_hex(ce->sha1),
647                         ce_stage(ce),
648                         ce->name);
649 }
650 #endif
651
652 int threeway_merge(struct cache_entry **stages,
653                 struct unpack_trees_options *o,
654                 int remove)
655 {
656         struct cache_entry *index;
657         struct cache_entry *head;
658         struct cache_entry *remote = stages[o->head_idx + 1];
659         int count;
660         int head_match = 0;
661         int remote_match = 0;
662
663         int df_conflict_head = 0;
664         int df_conflict_remote = 0;
665
666         int any_anc_missing = 0;
667         int no_anc_exists = 1;
668         int i;
669
670         for (i = 1; i < o->head_idx; i++) {
671                 if (!stages[i] || stages[i] == o->df_conflict_entry)
672                         any_anc_missing = 1;
673                 else
674                         no_anc_exists = 0;
675         }
676
677         index = stages[0];
678         head = stages[o->head_idx];
679
680         if (head == o->df_conflict_entry) {
681                 df_conflict_head = 1;
682                 head = NULL;
683         }
684
685         if (remote == o->df_conflict_entry) {
686                 df_conflict_remote = 1;
687                 remote = NULL;
688         }
689
690         /* First, if there's a #16 situation, note that to prevent #13
691          * and #14.
692          */
693         if (!same(remote, head)) {
694                 for (i = 1; i < o->head_idx; i++) {
695                         if (same(stages[i], head)) {
696                                 head_match = i;
697                         }
698                         if (same(stages[i], remote)) {
699                                 remote_match = i;
700                         }
701                 }
702         }
703
704         /* We start with cases where the index is allowed to match
705          * something other than the head: #14(ALT) and #2ALT, where it
706          * is permitted to match the result instead.
707          */
708         /* #14, #14ALT, #2ALT */
709         if (remote && !df_conflict_head && head_match && !remote_match) {
710                 if (index && !same(index, remote) && !same(index, head))
711                         reject_merge(index);
712                 return merged_entry(remote, index, o);
713         }
714         /*
715          * If we have an entry in the index cache, then we want to
716          * make sure that it matches head.
717          */
718         if (index && !same(index, head)) {
719                 reject_merge(index);
720         }
721
722         if (head) {
723                 /* #5ALT, #15 */
724                 if (same(head, remote))
725                         return merged_entry(head, index, o);
726                 /* #13, #3ALT */
727                 if (!df_conflict_remote && remote_match && !head_match)
728                         return merged_entry(head, index, o);
729         }
730
731         /* #1 */
732         if (!head && !remote && any_anc_missing) {
733                 remove_entry(remove);
734                 return 0;
735         }
736
737         /* Under the new "aggressive" rule, we resolve mostly trivial
738          * cases that we historically had git-merge-one-file resolve.
739          */
740         if (o->aggressive) {
741                 int head_deleted = !head && !df_conflict_head;
742                 int remote_deleted = !remote && !df_conflict_remote;
743                 struct cache_entry *ce = NULL;
744
745                 if (index)
746                         ce = index;
747                 else if (head)
748                         ce = head;
749                 else if (remote)
750                         ce = remote;
751                 else {
752                         for (i = 1; i < o->head_idx; i++) {
753                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
754                                         ce = stages[i];
755                                         break;
756                                 }
757                         }
758                 }
759
760                 /*
761                  * Deleted in both.
762                  * Deleted in one and unchanged in the other.
763                  */
764                 if ((head_deleted && remote_deleted) ||
765                     (head_deleted && remote && remote_match) ||
766                     (remote_deleted && head && head_match)) {
767                         remove_entry(remove);
768                         if (index)
769                                 return deleted_entry(index, index, o);
770                         else if (ce && !head_deleted)
771                                 verify_absent(ce, "removed", o);
772                         return 0;
773                 }
774                 /*
775                  * Added in both, identically.
776                  */
777                 if (no_anc_exists && head && remote && same(head, remote))
778                         return merged_entry(head, index, o);
779
780         }
781
782         /* Below are "no merge" cases, which require that the index be
783          * up-to-date to avoid the files getting overwritten with
784          * conflict resolution files.
785          */
786         if (index) {
787                 verify_uptodate(index, o);
788         }
789
790         remove_entry(remove);
791         o->nontrivial_merge = 1;
792
793         /* #2, #3, #4, #6, #7, #9, #10, #11. */
794         count = 0;
795         if (!head_match || !remote_match) {
796                 for (i = 1; i < o->head_idx; i++) {
797                         if (stages[i] && stages[i] != o->df_conflict_entry) {
798                                 keep_entry(stages[i], o);
799                                 count++;
800                                 break;
801                         }
802                 }
803         }
804 #if DBRT_DEBUG
805         else {
806                 fprintf(stderr, "read-tree: warning #16 detected\n");
807                 show_stage_entry(stderr, "head   ", stages[head_match]);
808                 show_stage_entry(stderr, "remote ", stages[remote_match]);
809         }
810 #endif
811         if (head) { count += keep_entry(head, o); }
812         if (remote) { count += keep_entry(remote, o); }
813         return count;
814 }
815
816 /*
817  * Two-way merge.
818  *
819  * The rule is to "carry forward" what is in the index without losing
820  * information across a "fast forward", favoring a successful merge
821  * over a merge failure when it makes sense.  For details of the
822  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
823  *
824  */
825 int twoway_merge(struct cache_entry **src,
826                 struct unpack_trees_options *o,
827                 int remove)
828 {
829         struct cache_entry *current = src[0];
830         struct cache_entry *oldtree = src[1];
831         struct cache_entry *newtree = src[2];
832
833         if (o->merge_size != 2)
834                 return error("Cannot do a twoway merge of %d trees",
835                              o->merge_size);
836
837         if (oldtree == o->df_conflict_entry)
838                 oldtree = NULL;
839         if (newtree == o->df_conflict_entry)
840                 newtree = NULL;
841
842         if (current) {
843                 if ((!oldtree && !newtree) || /* 4 and 5 */
844                     (!oldtree && newtree &&
845                      same(current, newtree)) || /* 6 and 7 */
846                     (oldtree && newtree &&
847                      same(oldtree, newtree)) || /* 14 and 15 */
848                     (oldtree && newtree &&
849                      !same(oldtree, newtree) && /* 18 and 19 */
850                      same(current, newtree))) {
851                         return keep_entry(current, o);
852                 }
853                 else if (oldtree && !newtree && same(current, oldtree)) {
854                         /* 10 or 11 */
855                         remove_entry(remove);
856                         return deleted_entry(oldtree, current, o);
857                 }
858                 else if (oldtree && newtree &&
859                          same(current, oldtree) && !same(current, newtree)) {
860                         /* 20 or 21 */
861                         return merged_entry(newtree, current, o);
862                 }
863                 else {
864                         /* all other failures */
865                         remove_entry(remove);
866                         if (oldtree)
867                                 reject_merge(oldtree);
868                         if (current)
869                                 reject_merge(current);
870                         if (newtree)
871                                 reject_merge(newtree);
872                         return -1;
873                 }
874         }
875         else if (newtree)
876                 return merged_entry(newtree, current, o);
877         remove_entry(remove);
878         return deleted_entry(oldtree, current, o);
879 }
880
881 /*
882  * Bind merge.
883  *
884  * Keep the index entries at stage0, collapse stage1 but make sure
885  * stage0 does not have anything there.
886  */
887 int bind_merge(struct cache_entry **src,
888                 struct unpack_trees_options *o,
889                 int remove)
890 {
891         struct cache_entry *old = src[0];
892         struct cache_entry *a = src[1];
893
894         if (o->merge_size != 1)
895                 return error("Cannot do a bind merge of %d trees\n",
896                              o->merge_size);
897         if (a && old)
898                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
899         if (!a)
900                 return keep_entry(old, o);
901         else
902                 return merged_entry(a, NULL, o);
903 }
904
905 /*
906  * One-way merge.
907  *
908  * The rule is:
909  * - take the stat information from stage0, take the data from stage1
910  */
911 int oneway_merge(struct cache_entry **src,
912                 struct unpack_trees_options *o,
913                 int remove)
914 {
915         struct cache_entry *old = src[0];
916         struct cache_entry *a = src[1];
917
918         if (o->merge_size != 1)
919                 return error("Cannot do a oneway merge of %d trees",
920                              o->merge_size);
921
922         if (!a) {
923                 remove_entry(remove);
924                 return deleted_entry(old, old, o);
925         }
926         if (old && same(old, a)) {
927                 if (o->reset) {
928                         struct stat st;
929                         if (lstat(old->name, &st) ||
930                             ce_match_stat(old, &st, 1))
931                                 old->ce_flags |= htons(CE_UPDATE);
932                 }
933                 return keep_entry(old, o);
934         }
935         return merged_entry(a, old, o);
936 }