gitweb: do not choke on recursive symlink
[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 *tree)
20 {
21         struct tree_desc desc;
22         struct name_entry one;
23         struct tree_entry_list *ret = NULL;
24         struct tree_entry_list **list_p = &ret;
25
26         if (!tree->object.parsed)
27                 parse_tree(tree);
28
29         init_tree_desc(&desc, tree->buffer, tree->size);
30
31         while (tree_entry(&desc, &one)) {
32                 struct tree_entry_list *entry;
33
34                 entry = xmalloc(sizeof(struct tree_entry_list));
35                 entry->name = one.path;
36                 entry->sha1 = one.sha1;
37                 entry->mode = one.mode;
38                 entry->next = NULL;
39
40                 *list_p = entry;
41                 list_p = &entry->next;
42         }
43         return ret;
44 }
45
46 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
47 {
48         int len1 = strlen(name1);
49         int len2 = strlen(name2);
50         int len = len1 < len2 ? len1 : len2;
51         int ret = memcmp(name1, name2, len);
52         unsigned char c1, c2;
53         if (ret)
54                 return ret;
55         c1 = name1[len];
56         c2 = name2[len];
57         if (!c1 && dir1)
58                 c1 = '/';
59         if (!c2 && dir2)
60                 c2 = '/';
61         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
62         if (c1 && c2 && !ret)
63                 ret = len1 - len2;
64         return ret;
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 baselen = strlen(base);
72         int src_size = len + 1;
73         int i_stk = i_stk;
74         int retval = 0;
75
76         if (o->dir)
77                 i_stk = push_exclude_per_directory(o->dir, base, strlen(base));
78
79         do {
80                 int i;
81                 const char *first;
82                 int firstdir = 0;
83                 int pathlen;
84                 unsigned ce_size;
85                 struct tree_entry_list **subposns;
86                 struct cache_entry **src;
87                 int any_files = 0;
88                 int any_dirs = 0;
89                 char *cache_name;
90                 int ce_stage;
91
92                 /* Find the first name in the input. */
93
94                 first = NULL;
95                 cache_name = NULL;
96
97                 /* Check the cache */
98                 if (o->merge && o->pos < active_nr) {
99                         /* This is a bit tricky: */
100                         /* If the index has a subdirectory (with
101                          * contents) as the first name, it'll get a
102                          * filename like "foo/bar". But that's after
103                          * "foo", so the entry in trees will get
104                          * handled first, at which point we'll go into
105                          * "foo", and deal with "bar" from the index,
106                          * because the base will be "foo/". The only
107                          * way we can actually have "foo/bar" first of
108                          * all the things is if the trees don't
109                          * contain "foo" at all, in which case we'll
110                          * handle "foo/bar" without going into the
111                          * directory, but that's fine (and will return
112                          * an error anyway, with the added unknown
113                          * file case.
114                          */
115
116                         cache_name = active_cache[o->pos]->name;
117                         if (strlen(cache_name) > baselen &&
118                             !memcmp(cache_name, base, baselen)) {
119                                 cache_name += baselen;
120                                 first = cache_name;
121                         } else {
122                                 cache_name = NULL;
123                         }
124                 }
125
126 #if DBRT_DEBUG > 1
127                 if (first)
128                         printf("index %s\n", first);
129 #endif
130                 for (i = 0; i < len; i++) {
131                         if (!posns[i] || posns[i] == df_conflict_list)
132                                 continue;
133 #if DBRT_DEBUG > 1
134                         printf("%d %s\n", i + 1, posns[i]->name);
135 #endif
136                         if (!first || entcmp(first, firstdir,
137                                              posns[i]->name,
138                                              S_ISDIR(posns[i]->mode)) > 0) {
139                                 first = posns[i]->name;
140                                 firstdir = S_ISDIR(posns[i]->mode);
141                         }
142                 }
143                 /* No name means we're done */
144                 if (!first)
145                         goto leave_directory;
146
147                 pathlen = strlen(first);
148                 ce_size = cache_entry_size(baselen + pathlen);
149
150                 src = xcalloc(src_size, sizeof(struct cache_entry *));
151
152                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
153
154                 if (cache_name && !strcmp(cache_name, first)) {
155                         any_files = 1;
156                         src[0] = active_cache[o->pos];
157                         remove_cache_entry_at(o->pos);
158                 }
159
160                 for (i = 0; i < len; i++) {
161                         struct cache_entry *ce;
162
163                         if (!posns[i] ||
164                             (posns[i] != df_conflict_list &&
165                              strcmp(first, posns[i]->name))) {
166                                 continue;
167                         }
168
169                         if (posns[i] == df_conflict_list) {
170                                 src[i + o->merge] = o->df_conflict_entry;
171                                 continue;
172                         }
173
174                         if (S_ISDIR(posns[i]->mode)) {
175                                 struct tree *tree = lookup_tree(posns[i]->sha1);
176                                 any_dirs = 1;
177                                 parse_tree(tree);
178                                 subposns[i] = create_tree_entry_list(tree);
179                                 posns[i] = posns[i]->next;
180                                 src[i + o->merge] = o->df_conflict_entry;
181                                 continue;
182                         }
183
184                         if (!o->merge)
185                                 ce_stage = 0;
186                         else if (i + 1 < o->head_idx)
187                                 ce_stage = 1;
188                         else if (i + 1 > o->head_idx)
189                                 ce_stage = 3;
190                         else
191                                 ce_stage = 2;
192
193                         ce = xcalloc(1, ce_size);
194                         ce->ce_mode = create_ce_mode(posns[i]->mode);
195                         ce->ce_flags = create_ce_flags(baselen + pathlen,
196                                                        ce_stage);
197                         memcpy(ce->name, base, baselen);
198                         memcpy(ce->name + baselen, first, pathlen + 1);
199
200                         any_files = 1;
201
202                         hashcpy(ce->sha1, posns[i]->sha1);
203                         src[i + o->merge] = ce;
204                         subposns[i] = df_conflict_list;
205                         posns[i] = posns[i]->next;
206                 }
207                 if (any_files) {
208                         if (o->merge) {
209                                 int ret;
210
211 #if DBRT_DEBUG > 1
212                                 printf("%s:\n", first);
213                                 for (i = 0; i < src_size; i++) {
214                                         printf(" %d ", i);
215                                         if (src[i])
216                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
217                                         else
218                                                 printf("\n");
219                                 }
220 #endif
221                                 ret = o->fn(src, o);
222
223 #if DBRT_DEBUG > 1
224                                 printf("Added %d entries\n", ret);
225 #endif
226                                 o->pos += ret;
227                         } else {
228                                 for (i = 0; i < src_size; i++) {
229                                         if (src[i]) {
230                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
231                                         }
232                                 }
233                         }
234                 }
235                 if (any_dirs) {
236                         char *newbase = xmalloc(baselen + 2 + pathlen);
237                         memcpy(newbase, base, baselen);
238                         memcpy(newbase + baselen, first, pathlen);
239                         newbase[baselen + pathlen] = '/';
240                         newbase[baselen + pathlen + 1] = '\0';
241                         if (unpack_trees_rec(subposns, len, newbase, o,
242                                              df_conflict_list)) {
243                                 retval = -1;
244                                 goto leave_directory;
245                         }
246                         free(newbase);
247                 }
248                 free(subposns);
249                 free(src);
250         } while (1);
251
252  leave_directory:
253         if (o->dir)
254                 pop_exclude_per_directory(o->dir, i_stk);
255         return retval;
256 }
257
258 /* Unlink the last component and attempt to remove leading
259  * directories, in case this unlink is the removal of the
260  * last entry in the directory -- empty directories are removed.
261  */
262 static void unlink_entry(char *name, char *last_symlink)
263 {
264         char *cp, *prev;
265
266         if (has_symlink_leading_path(name, last_symlink))
267                 return;
268         if (unlink(name))
269                 return;
270         prev = NULL;
271         while (1) {
272                 int status;
273                 cp = strrchr(name, '/');
274                 if (prev)
275                         *prev = '/';
276                 if (!cp)
277                         break;
278
279                 *cp = 0;
280                 status = rmdir(name);
281                 if (status) {
282                         *cp = '/';
283                         break;
284                 }
285                 prev = cp;
286         }
287 }
288
289 static struct checkout state;
290 static void check_updates(struct cache_entry **src, int nr,
291                         struct unpack_trees_options *o)
292 {
293         unsigned short mask = htons(CE_UPDATE);
294         unsigned cnt = 0, total = 0;
295         struct progress progress;
296         char last_symlink[PATH_MAX];
297
298         if (o->update && o->verbose_update) {
299                 for (total = cnt = 0; cnt < nr; cnt++) {
300                         struct cache_entry *ce = src[cnt];
301                         if (!ce->ce_mode || ce->ce_flags & mask)
302                                 total++;
303                 }
304
305                 start_progress_delay(&progress, "Checking %u files out...",
306                                      "", total, 50, 2);
307                 cnt = 0;
308         }
309
310         *last_symlink = '\0';
311         while (nr--) {
312                 struct cache_entry *ce = *src++;
313
314                 if (total)
315                         if (!ce->ce_mode || ce->ce_flags & mask)
316                                 display_progress(&progress, ++cnt);
317                 if (!ce->ce_mode) {
318                         if (o->update)
319                                 unlink_entry(ce->name, last_symlink);
320                         continue;
321                 }
322                 if (ce->ce_flags & mask) {
323                         ce->ce_flags &= ~mask;
324                         if (o->update) {
325                                 checkout_entry(ce, &state, NULL);
326                                 *last_symlink = '\0';
327                         }
328                 }
329         }
330         if (total)
331                 stop_progress(&progress);;
332 }
333
334 int unpack_trees(struct object_list *trees, struct unpack_trees_options *o)
335 {
336         unsigned len = object_list_length(trees);
337         struct tree_entry_list **posns;
338         int i;
339         struct object_list *posn = trees;
340         struct tree_entry_list df_conflict_list;
341         static struct cache_entry *dfc;
342
343         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
344         df_conflict_list.next = &df_conflict_list;
345         memset(&state, 0, sizeof(state));
346         state.base_dir = "";
347         state.force = 1;
348         state.quiet = 1;
349         state.refresh_cache = 1;
350
351         o->merge_size = len;
352
353         if (!dfc)
354                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
355         o->df_conflict_entry = dfc;
356
357         if (len) {
358                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
359                 for (i = 0; i < len; i++) {
360                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
361                         posn = posn->next;
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                 errno = 0;
411         }
412         if (errno == ENOENT)
413                 return;
414         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
415 }
416
417 static void invalidate_ce_path(struct cache_entry *ce)
418 {
419         if (ce)
420                 cache_tree_invalidate_path(active_cache_tree, ce->name);
421 }
422
423 /*
424  * Check that checking out ce->sha1 in subdir ce->name is not
425  * going to overwrite any working files.
426  *
427  * Currently, git does not checkout subprojects during a superproject
428  * checkout, so it is not going to overwrite anything.
429  */
430 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
431                                       struct unpack_trees_options *o)
432 {
433         return 0;
434 }
435
436 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
437                                       struct unpack_trees_options *o)
438 {
439         /*
440          * we are about to extract "ce->name"; we would not want to lose
441          * anything in the existing directory there.
442          */
443         int namelen;
444         int pos, i;
445         struct dir_struct d;
446         char *pathbuf;
447         int cnt = 0;
448         unsigned char sha1[20];
449
450         if (S_ISGITLINK(ntohl(ce->ce_mode)) &&
451             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
452                 /* If we are not going to update the submodule, then
453                  * we don't care.
454                  */
455                 if (!hashcmp(sha1, ce->sha1))
456                         return 0;
457                 return verify_clean_submodule(ce, action, o);
458         }
459
460         /*
461          * First let's make sure we do not have a local modification
462          * in that directory.
463          */
464         namelen = strlen(ce->name);
465         pos = cache_name_pos(ce->name, namelen);
466         if (0 <= pos)
467                 return cnt; /* we have it as nondirectory */
468         pos = -pos - 1;
469         for (i = pos; i < active_nr; i++) {
470                 struct cache_entry *ce = active_cache[i];
471                 int len = ce_namelen(ce);
472                 if (len < namelen ||
473                     strncmp(ce->name, ce->name, namelen) ||
474                     ce->name[namelen] != '/')
475                         break;
476                 /*
477                  * ce->name is an entry in the subdirectory.
478                  */
479                 if (!ce_stage(ce)) {
480                         verify_uptodate(ce, o);
481                         ce->ce_mode = 0;
482                 }
483                 cnt++;
484         }
485
486         /*
487          * Then we need to make sure that we do not lose a locally
488          * present file that is not ignored.
489          */
490         pathbuf = xmalloc(namelen + 2);
491         memcpy(pathbuf, ce->name, namelen);
492         strcpy(pathbuf+namelen, "/");
493
494         memset(&d, 0, sizeof(d));
495         if (o->dir)
496                 d.exclude_per_dir = o->dir->exclude_per_dir;
497         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
498         if (i)
499                 die("Updating '%s' would lose untracked files in it",
500                     ce->name);
501         free(pathbuf);
502         return cnt;
503 }
504
505 /*
506  * We do not want to remove or overwrite a working tree file that
507  * is not tracked, unless it is ignored.
508  */
509 static void verify_absent(struct cache_entry *ce, const char *action,
510                 struct unpack_trees_options *o)
511 {
512         struct stat st;
513
514         if (o->index_only || o->reset || !o->update)
515                 return;
516
517         if (has_symlink_leading_path(ce->name, NULL))
518                 return;
519
520         if (!lstat(ce->name, &st)) {
521                 int cnt;
522
523                 if (o->dir && excluded(o->dir, ce->name))
524                         /*
525                          * ce->name is explicitly excluded, so it is Ok to
526                          * overwrite it.
527                          */
528                         return;
529                 if (S_ISDIR(st.st_mode)) {
530                         /*
531                          * We are checking out path "foo" and
532                          * found "foo/." in the working tree.
533                          * This is tricky -- if we have modified
534                          * files that are in "foo/" we would lose
535                          * it.
536                          */
537                         cnt = verify_clean_subdirectory(ce, action, o);
538
539                         /*
540                          * If this removed entries from the index,
541                          * what that means is:
542                          *
543                          * (1) the caller unpack_trees_rec() saw path/foo
544                          * in the index, and it has not removed it because
545                          * it thinks it is handling 'path' as blob with
546                          * D/F conflict;
547                          * (2) we will return "ok, we placed a merged entry
548                          * in the index" which would cause o->pos to be
549                          * incremented by one;
550                          * (3) however, original o->pos now has 'path/foo'
551                          * marked with "to be removed".
552                          *
553                          * We need to increment it by the number of
554                          * deleted entries here.
555                          */
556                         o->pos += cnt;
557                         return;
558                 }
559
560                 /*
561                  * The previous round may already have decided to
562                  * delete this path, which is in a subdirectory that
563                  * is being replaced with a blob.
564                  */
565                 cnt = cache_name_pos(ce->name, strlen(ce->name));
566                 if (0 <= cnt) {
567                         struct cache_entry *ce = active_cache[cnt];
568                         if (!ce_stage(ce) && !ce->ce_mode)
569                                 return;
570                 }
571
572                 die("Untracked working tree file '%s' "
573                     "would be %s by merge.", ce->name, action);
574         }
575 }
576
577 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
578                 struct unpack_trees_options *o)
579 {
580         merge->ce_flags |= htons(CE_UPDATE);
581         if (old) {
582                 /*
583                  * See if we can re-use the old CE directly?
584                  * That way we get the uptodate stat info.
585                  *
586                  * This also removes the UPDATE flag on
587                  * a match.
588                  */
589                 if (same(old, merge)) {
590                         *merge = *old;
591                 } else {
592                         verify_uptodate(old, o);
593                         invalidate_ce_path(old);
594                 }
595         }
596         else {
597                 verify_absent(merge, "overwritten", o);
598                 invalidate_ce_path(merge);
599         }
600
601         merge->ce_flags &= ~htons(CE_STAGEMASK);
602         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
603         return 1;
604 }
605
606 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
607                 struct unpack_trees_options *o)
608 {
609         if (old)
610                 verify_uptodate(old, o);
611         else
612                 verify_absent(ce, "removed", o);
613         ce->ce_mode = 0;
614         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
615         invalidate_ce_path(ce);
616         return 1;
617 }
618
619 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
620 {
621         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
622         return 1;
623 }
624
625 #if DBRT_DEBUG
626 static void show_stage_entry(FILE *o,
627                              const char *label, const struct cache_entry *ce)
628 {
629         if (!ce)
630                 fprintf(o, "%s (missing)\n", label);
631         else
632                 fprintf(o, "%s%06o %s %d\t%s\n",
633                         label,
634                         ntohl(ce->ce_mode),
635                         sha1_to_hex(ce->sha1),
636                         ce_stage(ce),
637                         ce->name);
638 }
639 #endif
640
641 int threeway_merge(struct cache_entry **stages,
642                 struct unpack_trees_options *o)
643 {
644         struct cache_entry *index;
645         struct cache_entry *head;
646         struct cache_entry *remote = stages[o->head_idx + 1];
647         int count;
648         int head_match = 0;
649         int remote_match = 0;
650
651         int df_conflict_head = 0;
652         int df_conflict_remote = 0;
653
654         int any_anc_missing = 0;
655         int no_anc_exists = 1;
656         int i;
657
658         for (i = 1; i < o->head_idx; i++) {
659                 if (!stages[i] || stages[i] == o->df_conflict_entry)
660                         any_anc_missing = 1;
661                 else
662                         no_anc_exists = 0;
663         }
664
665         index = stages[0];
666         head = stages[o->head_idx];
667
668         if (head == o->df_conflict_entry) {
669                 df_conflict_head = 1;
670                 head = NULL;
671         }
672
673         if (remote == o->df_conflict_entry) {
674                 df_conflict_remote = 1;
675                 remote = NULL;
676         }
677
678         /* First, if there's a #16 situation, note that to prevent #13
679          * and #14.
680          */
681         if (!same(remote, head)) {
682                 for (i = 1; i < o->head_idx; i++) {
683                         if (same(stages[i], head)) {
684                                 head_match = i;
685                         }
686                         if (same(stages[i], remote)) {
687                                 remote_match = i;
688                         }
689                 }
690         }
691
692         /* We start with cases where the index is allowed to match
693          * something other than the head: #14(ALT) and #2ALT, where it
694          * is permitted to match the result instead.
695          */
696         /* #14, #14ALT, #2ALT */
697         if (remote && !df_conflict_head && head_match && !remote_match) {
698                 if (index && !same(index, remote) && !same(index, head))
699                         reject_merge(index);
700                 return merged_entry(remote, index, o);
701         }
702         /*
703          * If we have an entry in the index cache, then we want to
704          * make sure that it matches head.
705          */
706         if (index && !same(index, head)) {
707                 reject_merge(index);
708         }
709
710         if (head) {
711                 /* #5ALT, #15 */
712                 if (same(head, remote))
713                         return merged_entry(head, index, o);
714                 /* #13, #3ALT */
715                 if (!df_conflict_remote && remote_match && !head_match)
716                         return merged_entry(head, index, o);
717         }
718
719         /* #1 */
720         if (!head && !remote && any_anc_missing)
721                 return 0;
722
723         /* Under the new "aggressive" rule, we resolve mostly trivial
724          * cases that we historically had git-merge-one-file resolve.
725          */
726         if (o->aggressive) {
727                 int head_deleted = !head && !df_conflict_head;
728                 int remote_deleted = !remote && !df_conflict_remote;
729                 struct cache_entry *ce = NULL;
730
731                 if (index)
732                         ce = index;
733                 else if (head)
734                         ce = head;
735                 else if (remote)
736                         ce = remote;
737                 else {
738                         for (i = 1; i < o->head_idx; i++) {
739                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
740                                         ce = stages[i];
741                                         break;
742                                 }
743                         }
744                 }
745
746                 /*
747                  * Deleted in both.
748                  * Deleted in one and unchanged in the other.
749                  */
750                 if ((head_deleted && remote_deleted) ||
751                     (head_deleted && remote && remote_match) ||
752                     (remote_deleted && head && head_match)) {
753                         if (index)
754                                 return deleted_entry(index, index, o);
755                         else if (ce && !head_deleted)
756                                 verify_absent(ce, "removed", o);
757                         return 0;
758                 }
759                 /*
760                  * Added in both, identically.
761                  */
762                 if (no_anc_exists && head && remote && same(head, remote))
763                         return merged_entry(head, index, o);
764
765         }
766
767         /* Below are "no merge" cases, which require that the index be
768          * up-to-date to avoid the files getting overwritten with
769          * conflict resolution files.
770          */
771         if (index) {
772                 verify_uptodate(index, o);
773         }
774
775         o->nontrivial_merge = 1;
776
777         /* #2, #3, #4, #6, #7, #9, #10, #11. */
778         count = 0;
779         if (!head_match || !remote_match) {
780                 for (i = 1; i < o->head_idx; i++) {
781                         if (stages[i] && stages[i] != o->df_conflict_entry) {
782                                 keep_entry(stages[i], o);
783                                 count++;
784                                 break;
785                         }
786                 }
787         }
788 #if DBRT_DEBUG
789         else {
790                 fprintf(stderr, "read-tree: warning #16 detected\n");
791                 show_stage_entry(stderr, "head   ", stages[head_match]);
792                 show_stage_entry(stderr, "remote ", stages[remote_match]);
793         }
794 #endif
795         if (head) { count += keep_entry(head, o); }
796         if (remote) { count += keep_entry(remote, o); }
797         return count;
798 }
799
800 /*
801  * Two-way merge.
802  *
803  * The rule is to "carry forward" what is in the index without losing
804  * information across a "fast forward", favoring a successful merge
805  * over a merge failure when it makes sense.  For details of the
806  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
807  *
808  */
809 int twoway_merge(struct cache_entry **src,
810                 struct unpack_trees_options *o)
811 {
812         struct cache_entry *current = src[0];
813         struct cache_entry *oldtree = src[1];
814         struct cache_entry *newtree = src[2];
815
816         if (o->merge_size != 2)
817                 return error("Cannot do a twoway merge of %d trees",
818                              o->merge_size);
819
820         if (oldtree == o->df_conflict_entry)
821                 oldtree = NULL;
822         if (newtree == o->df_conflict_entry)
823                 newtree = NULL;
824
825         if (current) {
826                 if ((!oldtree && !newtree) || /* 4 and 5 */
827                     (!oldtree && newtree &&
828                      same(current, newtree)) || /* 6 and 7 */
829                     (oldtree && newtree &&
830                      same(oldtree, newtree)) || /* 14 and 15 */
831                     (oldtree && newtree &&
832                      !same(oldtree, newtree) && /* 18 and 19 */
833                      same(current, newtree))) {
834                         return keep_entry(current, o);
835                 }
836                 else if (oldtree && !newtree && same(current, oldtree)) {
837                         /* 10 or 11 */
838                         return deleted_entry(oldtree, current, o);
839                 }
840                 else if (oldtree && newtree &&
841                          same(current, oldtree) && !same(current, newtree)) {
842                         /* 20 or 21 */
843                         return merged_entry(newtree, current, o);
844                 }
845                 else {
846                         /* all other failures */
847                         if (oldtree)
848                                 reject_merge(oldtree);
849                         if (current)
850                                 reject_merge(current);
851                         if (newtree)
852                                 reject_merge(newtree);
853                         return -1;
854                 }
855         }
856         else if (newtree)
857                 return merged_entry(newtree, current, o);
858         else
859                 return deleted_entry(oldtree, current, o);
860 }
861
862 /*
863  * Bind merge.
864  *
865  * Keep the index entries at stage0, collapse stage1 but make sure
866  * stage0 does not have anything there.
867  */
868 int bind_merge(struct cache_entry **src,
869                 struct unpack_trees_options *o)
870 {
871         struct cache_entry *old = src[0];
872         struct cache_entry *a = src[1];
873
874         if (o->merge_size != 1)
875                 return error("Cannot do a bind merge of %d trees\n",
876                              o->merge_size);
877         if (a && old)
878                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
879         if (!a)
880                 return keep_entry(old, o);
881         else
882                 return merged_entry(a, NULL, o);
883 }
884
885 /*
886  * One-way merge.
887  *
888  * The rule is:
889  * - take the stat information from stage0, take the data from stage1
890  */
891 int oneway_merge(struct cache_entry **src,
892                 struct unpack_trees_options *o)
893 {
894         struct cache_entry *old = src[0];
895         struct cache_entry *a = src[1];
896
897         if (o->merge_size != 1)
898                 return error("Cannot do a oneway merge of %d trees",
899                              o->merge_size);
900
901         if (!a)
902                 return deleted_entry(old, old, o);
903         if (old && same(old, a)) {
904                 if (o->reset) {
905                         struct stat st;
906                         if (lstat(old->name, &st) ||
907                             ce_match_stat(old, &st, 1))
908                                 old->ce_flags |= htons(CE_UPDATE);
909                 }
910                 return keep_entry(old, o);
911         }
912         return merged_entry(a, old, o);
913 }