Code

Merge git://git.kernel.org/pub/scm/gitk/gitk
[git.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"
10 #define DBRT_DEBUG 1
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 };
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;
25         while (tree_entry(desc, &one)) {
26                 struct tree_entry_list *entry;
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;
34                 *list_p = entry;
35                 list_p = &entry->next;
36         }
37         return ret;
38 }
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 }
61 static inline void remove_entry(int remove)
62 {
63         if (remove >= 0)
64                 remove_cache_entry_at(remove);
65 }
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 retval = 0;
76         do {
77                 int i;
78                 const char *first;
79                 int firstdir = 0;
80                 int pathlen;
81                 unsigned ce_size;
82                 struct tree_entry_list **subposns;
83                 struct cache_entry **src;
84                 int any_files = 0;
85                 int any_dirs = 0;
86                 char *cache_name;
87                 int ce_stage;
89                 /* Find the first name in the input. */
91                 first = NULL;
92                 cache_name = NULL;
94                 /* Check the cache */
95                 if (o->merge && o->pos < active_nr) {
96                         /* This is a bit tricky: */
97                         /* If the index has a subdirectory (with
98                          * contents) as the first name, it'll get a
99                          * filename like "foo/bar". But that's after
100                          * "foo", so the entry in trees will get
101                          * handled first, at which point we'll go into
102                          * "foo", and deal with "bar" from the index,
103                          * because the base will be "foo/". The only
104                          * way we can actually have "foo/bar" first of
105                          * all the things is if the trees don't
106                          * contain "foo" at all, in which case we'll
107                          * handle "foo/bar" without going into the
108                          * directory, but that's fine (and will return
109                          * an error anyway, with the added unknown
110                          * file case.
111                          */
113                         cache_name = active_cache[o->pos]->name;
114                         if (strlen(cache_name) > baselen &&
115                             !memcmp(cache_name, base, baselen)) {
116                                 cache_name += baselen;
117                                 first = cache_name;
118                         } else {
119                                 cache_name = NULL;
120                         }
121                 }
123 #if DBRT_DEBUG > 1
124                 if (first)
125                         printf("index %s\n", first);
126 #endif
127                 for (i = 0; i < len; i++) {
128                         if (!posns[i] || posns[i] == df_conflict_list)
129                                 continue;
130 #if DBRT_DEBUG > 1
131                         printf("%d %s\n", i + 1, posns[i]->name);
132 #endif
133                         if (!first || entcmp(first, firstdir,
134                                              posns[i]->name,
135                                              S_ISDIR(posns[i]->mode)) > 0) {
136                                 first = posns[i]->name;
137                                 firstdir = S_ISDIR(posns[i]->mode);
138                         }
139                 }
140                 /* No name means we're done */
141                 if (!first)
142                         goto leave_directory;
144                 pathlen = strlen(first);
145                 ce_size = cache_entry_size(baselen + pathlen);
147                 src = xcalloc(src_size, sizeof(struct cache_entry *));
149                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
151                 remove = -1;
152                 if (cache_name && !strcmp(cache_name, first)) {
153                         any_files = 1;
154                         src[0] = active_cache[o->pos];
155                         remove = o->pos;
156                 }
158                 for (i = 0; i < len; i++) {
159                         struct cache_entry *ce;
161                         if (!posns[i] ||
162                             (posns[i] != df_conflict_list &&
163                              strcmp(first, posns[i]->name))) {
164                                 continue;
165                         }
167                         if (posns[i] == df_conflict_list) {
168                                 src[i + o->merge] = o->df_conflict_entry;
169                                 continue;
170                         }
172                         if (S_ISDIR(posns[i]->mode)) {
173                                 struct tree *tree = lookup_tree(posns[i]->sha1);
174                                 struct tree_desc t;
175                                 any_dirs = 1;
176                                 parse_tree(tree);
177                                 init_tree_desc(&t, tree->buffer, tree->size);
178                                 subposns[i] = create_tree_entry_list(&t);
179                                 posns[i] = posns[i]->next;
180                                 src[i + o->merge] = o->df_conflict_entry;
181                                 continue;
182                         }
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;
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);
200                         any_files = 1;
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;
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, remove);
223 #if DBRT_DEBUG > 1
224                                 printf("Added %d entries\n", ret);
225 #endif
226                                 o->pos += ret;
227                         } else {
228                                 remove_entry(remove);
229                                 for (i = 0; i < src_size; i++) {
230                                         if (src[i]) {
231                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
232                                         }
233                                 }
234                         }
235                 }
236                 if (any_dirs) {
237                         char *newbase = xmalloc(baselen + 2 + pathlen);
238                         memcpy(newbase, base, baselen);
239                         memcpy(newbase + baselen, first, pathlen);
240                         newbase[baselen + pathlen] = '/';
241                         newbase[baselen + pathlen + 1] = '\0';
242                         if (unpack_trees_rec(subposns, len, newbase, o,
243                                              df_conflict_list)) {
244                                 retval = -1;
245                                 goto leave_directory;
246                         }
247                         free(newbase);
248                 }
249                 free(subposns);
250                 free(src);
251         } while (1);
253  leave_directory:
254         return retval;
257 /* Unlink the last component and attempt to remove leading
258  * directories, in case this unlink is the removal of the
259  * last entry in the directory -- empty directories are removed.
260  */
261 static void unlink_entry(char *name, char *last_symlink)
263         char *cp, *prev;
265         if (has_symlink_leading_path(name, last_symlink))
266                 return;
267         if (unlink(name))
268                 return;
269         prev = NULL;
270         while (1) {
271                 int status;
272                 cp = strrchr(name, '/');
273                 if (prev)
274                         *prev = '/';
275                 if (!cp)
276                         break;
278                 *cp = 0;
279                 status = rmdir(name);
280                 if (status) {
281                         *cp = '/';
282                         break;
283                 }
284                 prev = cp;
285         }
288 static struct checkout state;
289 static void check_updates(struct cache_entry **src, int nr,
290                         struct unpack_trees_options *o)
292         unsigned cnt = 0, total = 0;
293         struct progress *progress = NULL;
294         char last_symlink[PATH_MAX];
296         if (o->update && o->verbose_update) {
297                 for (total = cnt = 0; cnt < nr; cnt++) {
298                         struct cache_entry *ce = src[cnt];
299                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
300                                 total++;
301                 }
303                 progress = start_progress_delay("Checking out files",
304                                                 total, 50, 2);
305                 cnt = 0;
306         }
308         *last_symlink = '\0';
309         while (nr--) {
310                 struct cache_entry *ce = *src++;
312                 if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
313                         display_progress(progress, ++cnt);
314                 if (ce->ce_flags & CE_REMOVE) {
315                         if (o->update)
316                                 unlink_entry(ce->name, last_symlink);
317                         continue;
318                 }
319                 if (ce->ce_flags & CE_UPDATE) {
320                         ce->ce_flags &= ~CE_UPDATE;
321                         if (o->update) {
322                                 checkout_entry(ce, &state, NULL);
323                                 *last_symlink = '\0';
324                         }
325                 }
326         }
327         stop_progress(&progress);
330 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
332         struct tree_entry_list **posns;
333         int i;
334         struct tree_entry_list df_conflict_list;
335         static struct cache_entry *dfc;
337         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
338         df_conflict_list.next = &df_conflict_list;
339         memset(&state, 0, sizeof(state));
340         state.base_dir = "";
341         state.force = 1;
342         state.quiet = 1;
343         state.refresh_cache = 1;
345         o->merge_size = len;
347         if (!dfc)
348                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
349         o->df_conflict_entry = dfc;
351         if (len) {
352                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
353                 for (i = 0; i < len; i++)
354                         posns[i] = create_tree_entry_list(t+i);
356                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
357                                      o, &df_conflict_list))
358                         return -1;
359         }
361         if (o->trivial_merges_only && o->nontrivial_merge)
362                 die("Merge requires file-level merging");
364         check_updates(active_cache, active_nr, o);
365         return 0;
368 /* Here come the merge functions */
370 static void reject_merge(struct cache_entry *ce)
372         die("Entry '%s' would be overwritten by merge. Cannot merge.",
373             ce->name);
376 static int same(struct cache_entry *a, struct cache_entry *b)
378         if (!!a != !!b)
379                 return 0;
380         if (!a && !b)
381                 return 1;
382         return a->ce_mode == b->ce_mode &&
383                !hashcmp(a->sha1, b->sha1);
387 /*
388  * When a CE gets turned into an unmerged entry, we
389  * want it to be up-to-date
390  */
391 static void verify_uptodate(struct cache_entry *ce,
392                 struct unpack_trees_options *o)
394         struct stat st;
396         if (o->index_only || o->reset)
397                 return;
399         if (!lstat(ce->name, &st)) {
400                 unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
401                 if (!changed)
402                         return;
403                 /*
404                  * NEEDSWORK: the current default policy is to allow
405                  * submodule to be out of sync wrt the supermodule
406                  * index.  This needs to be tightened later for
407                  * submodules that are marked to be automatically
408                  * checked out.
409                  */
410                 if (S_ISGITLINK(ce->ce_mode))
411                         return;
412                 errno = 0;
413         }
414         if (errno == ENOENT)
415                 return;
416         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
419 static void invalidate_ce_path(struct cache_entry *ce)
421         if (ce)
422                 cache_tree_invalidate_path(active_cache_tree, ce->name);
425 /*
426  * Check that checking out ce->sha1 in subdir ce->name is not
427  * going to overwrite any working files.
428  *
429  * Currently, git does not checkout subprojects during a superproject
430  * checkout, so it is not going to overwrite anything.
431  */
432 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
433                                       struct unpack_trees_options *o)
435         return 0;
438 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
439                                       struct unpack_trees_options *o)
441         /*
442          * we are about to extract "ce->name"; we would not want to lose
443          * anything in the existing directory there.
444          */
445         int namelen;
446         int pos, i;
447         struct dir_struct d;
448         char *pathbuf;
449         int cnt = 0;
450         unsigned char sha1[20];
452         if (S_ISGITLINK(ce->ce_mode) &&
453             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
454                 /* If we are not going to update the submodule, then
455                  * we don't care.
456                  */
457                 if (!hashcmp(sha1, ce->sha1))
458                         return 0;
459                 return verify_clean_submodule(ce, action, o);
460         }
462         /*
463          * First let's make sure we do not have a local modification
464          * in that directory.
465          */
466         namelen = strlen(ce->name);
467         pos = cache_name_pos(ce->name, namelen);
468         if (0 <= pos)
469                 return cnt; /* we have it as nondirectory */
470         pos = -pos - 1;
471         for (i = pos; i < active_nr; i++) {
472                 struct cache_entry *ce = active_cache[i];
473                 int len = ce_namelen(ce);
474                 if (len < namelen ||
475                     strncmp(ce->name, ce->name, namelen) ||
476                     ce->name[namelen] != '/')
477                         break;
478                 /*
479                  * ce->name is an entry in the subdirectory.
480                  */
481                 if (!ce_stage(ce)) {
482                         verify_uptodate(ce, o);
483                         ce->ce_flags |= CE_REMOVE;
484                 }
485                 cnt++;
486         }
488         /*
489          * Then we need to make sure that we do not lose a locally
490          * present file that is not ignored.
491          */
492         pathbuf = xmalloc(namelen + 2);
493         memcpy(pathbuf, ce->name, namelen);
494         strcpy(pathbuf+namelen, "/");
496         memset(&d, 0, sizeof(d));
497         if (o->dir)
498                 d.exclude_per_dir = o->dir->exclude_per_dir;
499         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
500         if (i)
501                 die("Updating '%s' would lose untracked files in it",
502                     ce->name);
503         free(pathbuf);
504         return cnt;
507 /*
508  * We do not want to remove or overwrite a working tree file that
509  * is not tracked, unless it is ignored.
510  */
511 static void verify_absent(struct cache_entry *ce, const char *action,
512                 struct unpack_trees_options *o)
514         struct stat st;
516         if (o->index_only || o->reset || !o->update)
517                 return;
519         if (has_symlink_leading_path(ce->name, NULL))
520                 return;
522         if (!lstat(ce->name, &st)) {
523                 int cnt;
525                 if (o->dir && excluded(o->dir, ce->name))
526                         /*
527                          * ce->name is explicitly excluded, so it is Ok to
528                          * overwrite it.
529                          */
530                         return;
531                 if (S_ISDIR(st.st_mode)) {
532                         /*
533                          * We are checking out path "foo" and
534                          * found "foo/." in the working tree.
535                          * This is tricky -- if we have modified
536                          * files that are in "foo/" we would lose
537                          * it.
538                          */
539                         cnt = verify_clean_subdirectory(ce, action, o);
541                         /*
542                          * If this removed entries from the index,
543                          * what that means is:
544                          *
545                          * (1) the caller unpack_trees_rec() saw path/foo
546                          * in the index, and it has not removed it because
547                          * it thinks it is handling 'path' as blob with
548                          * D/F conflict;
549                          * (2) we will return "ok, we placed a merged entry
550                          * in the index" which would cause o->pos to be
551                          * incremented by one;
552                          * (3) however, original o->pos now has 'path/foo'
553                          * marked with "to be removed".
554                          *
555                          * We need to increment it by the number of
556                          * deleted entries here.
557                          */
558                         o->pos += cnt;
559                         return;
560                 }
562                 /*
563                  * The previous round may already have decided to
564                  * delete this path, which is in a subdirectory that
565                  * is being replaced with a blob.
566                  */
567                 cnt = cache_name_pos(ce->name, strlen(ce->name));
568                 if (0 <= cnt) {
569                         struct cache_entry *ce = active_cache[cnt];
570                         if (ce->ce_flags & CE_REMOVE)
571                                 return;
572                 }
574                 die("Untracked working tree file '%s' "
575                     "would be %s by merge.", ce->name, action);
576         }
579 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
580                 struct unpack_trees_options *o)
582         merge->ce_flags |= CE_UPDATE;
583         if (old) {
584                 /*
585                  * See if we can re-use the old CE directly?
586                  * That way we get the uptodate stat info.
587                  *
588                  * This also removes the UPDATE flag on
589                  * a match.
590                  */
591                 if (same(old, merge)) {
592                         memcpy(merge, old, offsetof(struct cache_entry, name));
593                 } else {
594                         verify_uptodate(old, o);
595                         invalidate_ce_path(old);
596                 }
597         }
598         else {
599                 verify_absent(merge, "overwritten", o);
600                 invalidate_ce_path(merge);
601         }
603         merge->ce_flags &= ~CE_STAGEMASK;
604         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
605         return 1;
608 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
609                 struct unpack_trees_options *o)
611         if (old)
612                 verify_uptodate(old, o);
613         else
614                 verify_absent(ce, "removed", o);
615         ce->ce_flags |= CE_REMOVE;
616         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
617         invalidate_ce_path(ce);
618         return 1;
621 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
623         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
624         return 1;
627 #if DBRT_DEBUG
628 static void show_stage_entry(FILE *o,
629                              const char *label, const struct cache_entry *ce)
631         if (!ce)
632                 fprintf(o, "%s (missing)\n", label);
633         else
634                 fprintf(o, "%s%06o %s %d\t%s\n",
635                         label,
636                         ce->ce_mode,
637                         sha1_to_hex(ce->sha1),
638                         ce_stage(ce),
639                         ce->name);
641 #endif
643 int threeway_merge(struct cache_entry **stages,
644                 struct unpack_trees_options *o,
645                 int remove)
647         struct cache_entry *index;
648         struct cache_entry *head;
649         struct cache_entry *remote = stages[o->head_idx + 1];
650         int count;
651         int head_match = 0;
652         int remote_match = 0;
654         int df_conflict_head = 0;
655         int df_conflict_remote = 0;
657         int any_anc_missing = 0;
658         int no_anc_exists = 1;
659         int i;
661         for (i = 1; i < o->head_idx; i++) {
662                 if (!stages[i] || stages[i] == o->df_conflict_entry)
663                         any_anc_missing = 1;
664                 else
665                         no_anc_exists = 0;
666         }
668         index = stages[0];
669         head = stages[o->head_idx];
671         if (head == o->df_conflict_entry) {
672                 df_conflict_head = 1;
673                 head = NULL;
674         }
676         if (remote == o->df_conflict_entry) {
677                 df_conflict_remote = 1;
678                 remote = NULL;
679         }
681         /* First, if there's a #16 situation, note that to prevent #13
682          * and #14.
683          */
684         if (!same(remote, head)) {
685                 for (i = 1; i < o->head_idx; i++) {
686                         if (same(stages[i], head)) {
687                                 head_match = i;
688                         }
689                         if (same(stages[i], remote)) {
690                                 remote_match = i;
691                         }
692                 }
693         }
695         /* We start with cases where the index is allowed to match
696          * something other than the head: #14(ALT) and #2ALT, where it
697          * is permitted to match the result instead.
698          */
699         /* #14, #14ALT, #2ALT */
700         if (remote && !df_conflict_head && head_match && !remote_match) {
701                 if (index && !same(index, remote) && !same(index, head))
702                         reject_merge(index);
703                 return merged_entry(remote, index, o);
704         }
705         /*
706          * If we have an entry in the index cache, then we want to
707          * make sure that it matches head.
708          */
709         if (index && !same(index, head)) {
710                 reject_merge(index);
711         }
713         if (head) {
714                 /* #5ALT, #15 */
715                 if (same(head, remote))
716                         return merged_entry(head, index, o);
717                 /* #13, #3ALT */
718                 if (!df_conflict_remote && remote_match && !head_match)
719                         return merged_entry(head, index, o);
720         }
722         /* #1 */
723         if (!head && !remote && any_anc_missing) {
724                 remove_entry(remove);
725                 return 0;
726         }
728         /* Under the new "aggressive" rule, we resolve mostly trivial
729          * cases that we historically had git-merge-one-file resolve.
730          */
731         if (o->aggressive) {
732                 int head_deleted = !head && !df_conflict_head;
733                 int remote_deleted = !remote && !df_conflict_remote;
734                 struct cache_entry *ce = NULL;
736                 if (index)
737                         ce = index;
738                 else if (head)
739                         ce = head;
740                 else if (remote)
741                         ce = remote;
742                 else {
743                         for (i = 1; i < o->head_idx; i++) {
744                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
745                                         ce = stages[i];
746                                         break;
747                                 }
748                         }
749                 }
751                 /*
752                  * Deleted in both.
753                  * Deleted in one and unchanged in the other.
754                  */
755                 if ((head_deleted && remote_deleted) ||
756                     (head_deleted && remote && remote_match) ||
757                     (remote_deleted && head && head_match)) {
758                         remove_entry(remove);
759                         if (index)
760                                 return deleted_entry(index, index, o);
761                         else if (ce && !head_deleted)
762                                 verify_absent(ce, "removed", o);
763                         return 0;
764                 }
765                 /*
766                  * Added in both, identically.
767                  */
768                 if (no_anc_exists && head && remote && same(head, remote))
769                         return merged_entry(head, index, o);
771         }
773         /* Below are "no merge" cases, which require that the index be
774          * up-to-date to avoid the files getting overwritten with
775          * conflict resolution files.
776          */
777         if (index) {
778                 verify_uptodate(index, o);
779         }
781         remove_entry(remove);
782         o->nontrivial_merge = 1;
784         /* #2, #3, #4, #6, #7, #9, #10, #11. */
785         count = 0;
786         if (!head_match || !remote_match) {
787                 for (i = 1; i < o->head_idx; i++) {
788                         if (stages[i] && stages[i] != o->df_conflict_entry) {
789                                 keep_entry(stages[i], o);
790                                 count++;
791                                 break;
792                         }
793                 }
794         }
795 #if DBRT_DEBUG
796         else {
797                 fprintf(stderr, "read-tree: warning #16 detected\n");
798                 show_stage_entry(stderr, "head   ", stages[head_match]);
799                 show_stage_entry(stderr, "remote ", stages[remote_match]);
800         }
801 #endif
802         if (head) { count += keep_entry(head, o); }
803         if (remote) { count += keep_entry(remote, o); }
804         return count;
807 /*
808  * Two-way merge.
809  *
810  * The rule is to "carry forward" what is in the index without losing
811  * information across a "fast forward", favoring a successful merge
812  * over a merge failure when it makes sense.  For details of the
813  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
814  *
815  */
816 int twoway_merge(struct cache_entry **src,
817                 struct unpack_trees_options *o,
818                 int remove)
820         struct cache_entry *current = src[0];
821         struct cache_entry *oldtree = src[1];
822         struct cache_entry *newtree = src[2];
824         if (o->merge_size != 2)
825                 return error("Cannot do a twoway merge of %d trees",
826                              o->merge_size);
828         if (oldtree == o->df_conflict_entry)
829                 oldtree = NULL;
830         if (newtree == o->df_conflict_entry)
831                 newtree = NULL;
833         if (current) {
834                 if ((!oldtree && !newtree) || /* 4 and 5 */
835                     (!oldtree && newtree &&
836                      same(current, newtree)) || /* 6 and 7 */
837                     (oldtree && newtree &&
838                      same(oldtree, newtree)) || /* 14 and 15 */
839                     (oldtree && newtree &&
840                      !same(oldtree, newtree) && /* 18 and 19 */
841                      same(current, newtree))) {
842                         return keep_entry(current, o);
843                 }
844                 else if (oldtree && !newtree && same(current, oldtree)) {
845                         /* 10 or 11 */
846                         remove_entry(remove);
847                         return deleted_entry(oldtree, current, o);
848                 }
849                 else if (oldtree && newtree &&
850                          same(current, oldtree) && !same(current, newtree)) {
851                         /* 20 or 21 */
852                         return merged_entry(newtree, current, o);
853                 }
854                 else {
855                         /* all other failures */
856                         remove_entry(remove);
857                         if (oldtree)
858                                 reject_merge(oldtree);
859                         if (current)
860                                 reject_merge(current);
861                         if (newtree)
862                                 reject_merge(newtree);
863                         return -1;
864                 }
865         }
866         else if (newtree)
867                 return merged_entry(newtree, current, o);
868         remove_entry(remove);
869         return deleted_entry(oldtree, current, o);
872 /*
873  * Bind merge.
874  *
875  * Keep the index entries at stage0, collapse stage1 but make sure
876  * stage0 does not have anything there.
877  */
878 int bind_merge(struct cache_entry **src,
879                 struct unpack_trees_options *o,
880                 int remove)
882         struct cache_entry *old = src[0];
883         struct cache_entry *a = src[1];
885         if (o->merge_size != 1)
886                 return error("Cannot do a bind merge of %d trees\n",
887                              o->merge_size);
888         if (a && old)
889                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
890         if (!a)
891                 return keep_entry(old, o);
892         else
893                 return merged_entry(a, NULL, o);
896 /*
897  * One-way merge.
898  *
899  * The rule is:
900  * - take the stat information from stage0, take the data from stage1
901  */
902 int oneway_merge(struct cache_entry **src,
903                 struct unpack_trees_options *o,
904                 int remove)
906         struct cache_entry *old = src[0];
907         struct cache_entry *a = src[1];
909         if (o->merge_size != 1)
910                 return error("Cannot do a oneway merge of %d trees",
911                              o->merge_size);
913         if (!a) {
914                 remove_entry(remove);
915                 return deleted_entry(old, old, o);
916         }
917         if (old && same(old, a)) {
918                 if (o->reset) {
919                         struct stat st;
920                         if (lstat(old->name, &st) ||
921                             ce_match_stat(old, &st, CE_MATCH_IGNORE_VALID))
922                                 old->ce_flags |= CE_UPDATE;
923                 }
924                 return keep_entry(old, o);
925         }
926         return merged_entry(a, old, o);