Sync with Git 2.25.2
[git] / merge-recursive.c
1 /*
2  * Recursive Merge algorithm stolen from git-merge-recursive.py by
3  * Fredrik Kuivinen.
4  * The thieves were Alex Riesen and Johannes Schindelin, in June/July 2006
5  */
6 #include "cache.h"
7 #include "merge-recursive.h"
8
9 #include "advice.h"
10 #include "alloc.h"
11 #include "attr.h"
12 #include "blob.h"
13 #include "builtin.h"
14 #include "cache-tree.h"
15 #include "commit.h"
16 #include "commit-reach.h"
17 #include "config.h"
18 #include "diff.h"
19 #include "diffcore.h"
20 #include "dir.h"
21 #include "ll-merge.h"
22 #include "lockfile.h"
23 #include "object-store.h"
24 #include "repository.h"
25 #include "revision.h"
26 #include "string-list.h"
27 #include "submodule.h"
28 #include "tag.h"
29 #include "tree-walk.h"
30 #include "unpack-trees.h"
31 #include "xdiff-interface.h"
32
33 struct merge_options_internal {
34         int call_depth;
35         int needed_rename_limit;
36         struct hashmap current_file_dir_set;
37         struct string_list df_conflict_file_set;
38         struct unpack_trees_options unpack_opts;
39         struct index_state orig_index;
40 };
41
42 struct path_hashmap_entry {
43         struct hashmap_entry e;
44         char path[FLEX_ARRAY];
45 };
46
47 static int path_hashmap_cmp(const void *cmp_data,
48                             const struct hashmap_entry *eptr,
49                             const struct hashmap_entry *entry_or_key,
50                             const void *keydata)
51 {
52         const struct path_hashmap_entry *a, *b;
53         const char *key = keydata;
54
55         a = container_of(eptr, const struct path_hashmap_entry, e);
56         b = container_of(entry_or_key, const struct path_hashmap_entry, e);
57
58         if (ignore_case)
59                 return strcasecmp(a->path, key ? key : b->path);
60         else
61                 return strcmp(a->path, key ? key : b->path);
62 }
63
64 static unsigned int path_hash(const char *path)
65 {
66         return ignore_case ? strihash(path) : strhash(path);
67 }
68
69 /*
70  * For dir_rename_entry, directory names are stored as a full path from the
71  * toplevel of the repository and do not include a trailing '/'.  Also:
72  *
73  *   dir:                original name of directory being renamed
74  *   non_unique_new_dir: if true, could not determine new_dir
75  *   new_dir:            final name of directory being renamed
76  *   possible_new_dirs:  temporary used to help determine new_dir; see comments
77  *                       in get_directory_renames() for details
78  */
79 struct dir_rename_entry {
80         struct hashmap_entry ent;
81         char *dir;
82         unsigned non_unique_new_dir:1;
83         struct strbuf new_dir;
84         struct string_list possible_new_dirs;
85 };
86
87 static struct dir_rename_entry *dir_rename_find_entry(struct hashmap *hashmap,
88                                                       char *dir)
89 {
90         struct dir_rename_entry key;
91
92         if (dir == NULL)
93                 return NULL;
94         hashmap_entry_init(&key.ent, strhash(dir));
95         key.dir = dir;
96         return hashmap_get_entry(hashmap, &key, ent, NULL);
97 }
98
99 static int dir_rename_cmp(const void *unused_cmp_data,
100                           const struct hashmap_entry *eptr,
101                           const struct hashmap_entry *entry_or_key,
102                           const void *unused_keydata)
103 {
104         const struct dir_rename_entry *e1, *e2;
105
106         e1 = container_of(eptr, const struct dir_rename_entry, ent);
107         e2 = container_of(entry_or_key, const struct dir_rename_entry, ent);
108
109         return strcmp(e1->dir, e2->dir);
110 }
111
112 static void dir_rename_init(struct hashmap *map)
113 {
114         hashmap_init(map, dir_rename_cmp, NULL, 0);
115 }
116
117 static void dir_rename_entry_init(struct dir_rename_entry *entry,
118                                   char *directory)
119 {
120         hashmap_entry_init(&entry->ent, strhash(directory));
121         entry->dir = directory;
122         entry->non_unique_new_dir = 0;
123         strbuf_init(&entry->new_dir, 0);
124         string_list_init(&entry->possible_new_dirs, 0);
125 }
126
127 struct collision_entry {
128         struct hashmap_entry ent;
129         char *target_file;
130         struct string_list source_files;
131         unsigned reported_already:1;
132 };
133
134 static struct collision_entry *collision_find_entry(struct hashmap *hashmap,
135                                                     char *target_file)
136 {
137         struct collision_entry key;
138
139         hashmap_entry_init(&key.ent, strhash(target_file));
140         key.target_file = target_file;
141         return hashmap_get_entry(hashmap, &key, ent, NULL);
142 }
143
144 static int collision_cmp(const void *unused_cmp_data,
145                          const struct hashmap_entry *eptr,
146                          const struct hashmap_entry *entry_or_key,
147                          const void *unused_keydata)
148 {
149         const struct collision_entry *e1, *e2;
150
151         e1 = container_of(eptr, const struct collision_entry, ent);
152         e2 = container_of(entry_or_key, const struct collision_entry, ent);
153
154         return strcmp(e1->target_file, e2->target_file);
155 }
156
157 static void collision_init(struct hashmap *map)
158 {
159         hashmap_init(map, collision_cmp, NULL, 0);
160 }
161
162 static void flush_output(struct merge_options *opt)
163 {
164         if (opt->buffer_output < 2 && opt->obuf.len) {
165                 fputs(opt->obuf.buf, stdout);
166                 strbuf_reset(&opt->obuf);
167         }
168 }
169
170 static int err(struct merge_options *opt, const char *err, ...)
171 {
172         va_list params;
173
174         if (opt->buffer_output < 2)
175                 flush_output(opt);
176         else {
177                 strbuf_complete(&opt->obuf, '\n');
178                 strbuf_addstr(&opt->obuf, "error: ");
179         }
180         va_start(params, err);
181         strbuf_vaddf(&opt->obuf, err, params);
182         va_end(params);
183         if (opt->buffer_output > 1)
184                 strbuf_addch(&opt->obuf, '\n');
185         else {
186                 error("%s", opt->obuf.buf);
187                 strbuf_reset(&opt->obuf);
188         }
189
190         return -1;
191 }
192
193 static struct tree *shift_tree_object(struct repository *repo,
194                                       struct tree *one, struct tree *two,
195                                       const char *subtree_shift)
196 {
197         struct object_id shifted;
198
199         if (!*subtree_shift) {
200                 shift_tree(repo, &one->object.oid, &two->object.oid, &shifted, 0);
201         } else {
202                 shift_tree_by(repo, &one->object.oid, &two->object.oid, &shifted,
203                               subtree_shift);
204         }
205         if (oideq(&two->object.oid, &shifted))
206                 return two;
207         return lookup_tree(repo, &shifted);
208 }
209
210 static inline void set_commit_tree(struct commit *c, struct tree *t)
211 {
212         c->maybe_tree = t;
213 }
214
215 static struct commit *make_virtual_commit(struct repository *repo,
216                                           struct tree *tree,
217                                           const char *comment)
218 {
219         struct commit *commit = alloc_commit_node(repo);
220
221         set_merge_remote_desc(commit, comment, (struct object *)commit);
222         set_commit_tree(commit, tree);
223         commit->object.parsed = 1;
224         return commit;
225 }
226
227 enum rename_type {
228         RENAME_NORMAL = 0,
229         RENAME_VIA_DIR,
230         RENAME_ADD,
231         RENAME_DELETE,
232         RENAME_ONE_FILE_TO_ONE,
233         RENAME_ONE_FILE_TO_TWO,
234         RENAME_TWO_FILES_TO_ONE
235 };
236
237 /*
238  * Since we want to write the index eventually, we cannot reuse the index
239  * for these (temporary) data.
240  */
241 struct stage_data {
242         struct diff_filespec stages[4]; /* mostly for oid & mode; maybe path */
243         struct rename_conflict_info *rename_conflict_info;
244         unsigned processed:1;
245 };
246
247 struct rename {
248         unsigned processed:1;
249         struct diff_filepair *pair;
250         const char *branch; /* branch that the rename occurred on */
251         /*
252          * If directory rename detection affected this rename, what was its
253          * original type ('A' or 'R') and it's original destination before
254          * the directory rename (otherwise, '\0' and NULL for these two vars).
255          */
256         char dir_rename_original_type;
257         char *dir_rename_original_dest;
258         /*
259          * Purpose of src_entry and dst_entry:
260          *
261          * If 'before' is renamed to 'after' then src_entry will contain
262          * the versions of 'before' from the merge_base, HEAD, and MERGE in
263          * stages 1, 2, and 3; dst_entry will contain the respective
264          * versions of 'after' in corresponding locations.  Thus, we have a
265          * total of six modes and oids, though some will be null.  (Stage 0
266          * is ignored; we're interested in handling conflicts.)
267          *
268          * Since we don't turn on break-rewrites by default, neither
269          * src_entry nor dst_entry can have all three of their stages have
270          * non-null oids, meaning at most four of the six will be non-null.
271          * Also, since this is a rename, both src_entry and dst_entry will
272          * have at least one non-null oid, meaning at least two will be
273          * non-null.  Of the six oids, a typical rename will have three be
274          * non-null.  Only two implies a rename/delete, and four implies a
275          * rename/add.
276          */
277         struct stage_data *src_entry;
278         struct stage_data *dst_entry;
279 };
280
281 struct rename_conflict_info {
282         enum rename_type rename_type;
283         struct rename *ren1;
284         struct rename *ren2;
285 };
286
287 static inline void setup_rename_conflict_info(enum rename_type rename_type,
288                                               struct merge_options *opt,
289                                               struct rename *ren1,
290                                               struct rename *ren2)
291 {
292         struct rename_conflict_info *ci;
293
294         /*
295          * When we have two renames involved, it's easiest to get the
296          * correct things into stage 2 and 3, and to make sure that the
297          * content merge puts HEAD before the other branch if we just
298          * ensure that branch1 == opt->branch1.  So, simply flip arguments
299          * around if we don't have that.
300          */
301         if (ren2 && ren1->branch != opt->branch1) {
302                 setup_rename_conflict_info(rename_type, opt, ren2, ren1);
303                 return;
304         }
305
306         ci = xcalloc(1, sizeof(struct rename_conflict_info));
307         ci->rename_type = rename_type;
308         ci->ren1 = ren1;
309         ci->ren2 = ren2;
310
311         ci->ren1->dst_entry->processed = 0;
312         ci->ren1->dst_entry->rename_conflict_info = ci;
313         if (ren2) {
314                 ci->ren2->dst_entry->rename_conflict_info = ci;
315         }
316 }
317
318 static int show(struct merge_options *opt, int v)
319 {
320         return (!opt->priv->call_depth && opt->verbosity >= v) ||
321                 opt->verbosity >= 5;
322 }
323
324 __attribute__((format (printf, 3, 4)))
325 static void output(struct merge_options *opt, int v, const char *fmt, ...)
326 {
327         va_list ap;
328
329         if (!show(opt, v))
330                 return;
331
332         strbuf_addchars(&opt->obuf, ' ', opt->priv->call_depth * 2);
333
334         va_start(ap, fmt);
335         strbuf_vaddf(&opt->obuf, fmt, ap);
336         va_end(ap);
337
338         strbuf_addch(&opt->obuf, '\n');
339         if (!opt->buffer_output)
340                 flush_output(opt);
341 }
342
343 static void output_commit_title(struct merge_options *opt, struct commit *commit)
344 {
345         struct merge_remote_desc *desc;
346
347         strbuf_addchars(&opt->obuf, ' ', opt->priv->call_depth * 2);
348         desc = merge_remote_util(commit);
349         if (desc)
350                 strbuf_addf(&opt->obuf, "virtual %s\n", desc->name);
351         else {
352                 strbuf_add_unique_abbrev(&opt->obuf, &commit->object.oid,
353                                          DEFAULT_ABBREV);
354                 strbuf_addch(&opt->obuf, ' ');
355                 if (parse_commit(commit) != 0)
356                         strbuf_addstr(&opt->obuf, _("(bad commit)\n"));
357                 else {
358                         const char *title;
359                         const char *msg = get_commit_buffer(commit, NULL);
360                         int len = find_commit_subject(msg, &title);
361                         if (len)
362                                 strbuf_addf(&opt->obuf, "%.*s\n", len, title);
363                         unuse_commit_buffer(commit, msg);
364                 }
365         }
366         flush_output(opt);
367 }
368
369 static int add_cacheinfo(struct merge_options *opt,
370                          const struct diff_filespec *blob,
371                          const char *path, int stage, int refresh, int options)
372 {
373         struct index_state *istate = opt->repo->index;
374         struct cache_entry *ce;
375         int ret;
376
377         ce = make_cache_entry(istate, blob->mode, &blob->oid, path, stage, 0);
378         if (!ce)
379                 return err(opt, _("add_cacheinfo failed for path '%s'; merge aborting."), path);
380
381         ret = add_index_entry(istate, ce, options);
382         if (refresh) {
383                 struct cache_entry *nce;
384
385                 nce = refresh_cache_entry(istate, ce,
386                                           CE_MATCH_REFRESH | CE_MATCH_IGNORE_MISSING);
387                 if (!nce)
388                         return err(opt, _("add_cacheinfo failed to refresh for path '%s'; merge aborting."), path);
389                 if (nce != ce)
390                         ret = add_index_entry(istate, nce, options);
391         }
392         return ret;
393 }
394
395 static inline int merge_detect_rename(struct merge_options *opt)
396 {
397         return (opt->detect_renames >= 0) ? opt->detect_renames : 1;
398 }
399
400 static void init_tree_desc_from_tree(struct tree_desc *desc, struct tree *tree)
401 {
402         parse_tree(tree);
403         init_tree_desc(desc, tree->buffer, tree->size);
404 }
405
406 static int unpack_trees_start(struct merge_options *opt,
407                               struct tree *common,
408                               struct tree *head,
409                               struct tree *merge)
410 {
411         int rc;
412         struct tree_desc t[3];
413         struct index_state tmp_index = { NULL };
414
415         memset(&opt->priv->unpack_opts, 0, sizeof(opt->priv->unpack_opts));
416         if (opt->priv->call_depth)
417                 opt->priv->unpack_opts.index_only = 1;
418         else
419                 opt->priv->unpack_opts.update = 1;
420         opt->priv->unpack_opts.merge = 1;
421         opt->priv->unpack_opts.head_idx = 2;
422         opt->priv->unpack_opts.fn = threeway_merge;
423         opt->priv->unpack_opts.src_index = opt->repo->index;
424         opt->priv->unpack_opts.dst_index = &tmp_index;
425         opt->priv->unpack_opts.aggressive = !merge_detect_rename(opt);
426         setup_unpack_trees_porcelain(&opt->priv->unpack_opts, "merge");
427
428         init_tree_desc_from_tree(t+0, common);
429         init_tree_desc_from_tree(t+1, head);
430         init_tree_desc_from_tree(t+2, merge);
431
432         rc = unpack_trees(3, t, &opt->priv->unpack_opts);
433         cache_tree_free(&opt->repo->index->cache_tree);
434
435         /*
436          * Update opt->repo->index to match the new results, AFTER saving a
437          * copy in opt->priv->orig_index.  Update src_index to point to the
438          * saved copy.  (verify_uptodate() checks src_index, and the original
439          * index is the one that had the necessary modification timestamps.)
440          */
441         opt->priv->orig_index = *opt->repo->index;
442         *opt->repo->index = tmp_index;
443         opt->priv->unpack_opts.src_index = &opt->priv->orig_index;
444
445         return rc;
446 }
447
448 static void unpack_trees_finish(struct merge_options *opt)
449 {
450         discard_index(&opt->priv->orig_index);
451         clear_unpack_trees_porcelain(&opt->priv->unpack_opts);
452 }
453
454 static int save_files_dirs(const struct object_id *oid,
455                            struct strbuf *base, const char *path,
456                            unsigned int mode, int stage, void *context)
457 {
458         struct path_hashmap_entry *entry;
459         int baselen = base->len;
460         struct merge_options *opt = context;
461
462         strbuf_addstr(base, path);
463
464         FLEX_ALLOC_MEM(entry, path, base->buf, base->len);
465         hashmap_entry_init(&entry->e, path_hash(entry->path));
466         hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
467
468         strbuf_setlen(base, baselen);
469         return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
470 }
471
472 static void get_files_dirs(struct merge_options *opt, struct tree *tree)
473 {
474         struct pathspec match_all;
475         memset(&match_all, 0, sizeof(match_all));
476         read_tree_recursive(opt->repo, tree, "", 0, 0,
477                             &match_all, save_files_dirs, opt);
478 }
479
480 static int get_tree_entry_if_blob(struct repository *r,
481                                   const struct object_id *tree,
482                                   const char *path,
483                                   struct diff_filespec *dfs)
484 {
485         int ret;
486
487         ret = get_tree_entry(r, tree, path, &dfs->oid, &dfs->mode);
488         if (S_ISDIR(dfs->mode)) {
489                 oidcpy(&dfs->oid, &null_oid);
490                 dfs->mode = 0;
491         }
492         return ret;
493 }
494
495 /*
496  * Returns an index_entry instance which doesn't have to correspond to
497  * a real cache entry in Git's index.
498  */
499 static struct stage_data *insert_stage_data(struct repository *r,
500                 const char *path,
501                 struct tree *o, struct tree *a, struct tree *b,
502                 struct string_list *entries)
503 {
504         struct string_list_item *item;
505         struct stage_data *e = xcalloc(1, sizeof(struct stage_data));
506         get_tree_entry_if_blob(r, &o->object.oid, path, &e->stages[1]);
507         get_tree_entry_if_blob(r, &a->object.oid, path, &e->stages[2]);
508         get_tree_entry_if_blob(r, &b->object.oid, path, &e->stages[3]);
509         item = string_list_insert(entries, path);
510         item->util = e;
511         return e;
512 }
513
514 /*
515  * Create a dictionary mapping file names to stage_data objects. The
516  * dictionary contains one entry for every path with a non-zero stage entry.
517  */
518 static struct string_list *get_unmerged(struct index_state *istate)
519 {
520         struct string_list *unmerged = xcalloc(1, sizeof(struct string_list));
521         int i;
522
523         unmerged->strdup_strings = 1;
524
525         for (i = 0; i < istate->cache_nr; i++) {
526                 struct string_list_item *item;
527                 struct stage_data *e;
528                 const struct cache_entry *ce = istate->cache[i];
529                 if (!ce_stage(ce))
530                         continue;
531
532                 item = string_list_lookup(unmerged, ce->name);
533                 if (!item) {
534                         item = string_list_insert(unmerged, ce->name);
535                         item->util = xcalloc(1, sizeof(struct stage_data));
536                 }
537                 e = item->util;
538                 e->stages[ce_stage(ce)].mode = ce->ce_mode;
539                 oidcpy(&e->stages[ce_stage(ce)].oid, &ce->oid);
540         }
541
542         return unmerged;
543 }
544
545 static int string_list_df_name_compare(const char *one, const char *two)
546 {
547         int onelen = strlen(one);
548         int twolen = strlen(two);
549         /*
550          * Here we only care that entries for D/F conflicts are
551          * adjacent, in particular with the file of the D/F conflict
552          * appearing before files below the corresponding directory.
553          * The order of the rest of the list is irrelevant for us.
554          *
555          * To achieve this, we sort with df_name_compare and provide
556          * the mode S_IFDIR so that D/F conflicts will sort correctly.
557          * We use the mode S_IFDIR for everything else for simplicity,
558          * since in other cases any changes in their order due to
559          * sorting cause no problems for us.
560          */
561         int cmp = df_name_compare(one, onelen, S_IFDIR,
562                                   two, twolen, S_IFDIR);
563         /*
564          * Now that 'foo' and 'foo/bar' compare equal, we have to make sure
565          * that 'foo' comes before 'foo/bar'.
566          */
567         if (cmp)
568                 return cmp;
569         return onelen - twolen;
570 }
571
572 static void record_df_conflict_files(struct merge_options *opt,
573                                      struct string_list *entries)
574 {
575         /* If there is a D/F conflict and the file for such a conflict
576          * currently exists in the working tree, we want to allow it to be
577          * removed to make room for the corresponding directory if needed.
578          * The files underneath the directories of such D/F conflicts will
579          * be processed before the corresponding file involved in the D/F
580          * conflict.  If the D/F directory ends up being removed by the
581          * merge, then we won't have to touch the D/F file.  If the D/F
582          * directory needs to be written to the working copy, then the D/F
583          * file will simply be removed (in make_room_for_path()) to make
584          * room for the necessary paths.  Note that if both the directory
585          * and the file need to be present, then the D/F file will be
586          * reinstated with a new unique name at the time it is processed.
587          */
588         struct string_list df_sorted_entries = STRING_LIST_INIT_NODUP;
589         const char *last_file = NULL;
590         int last_len = 0;
591         int i;
592
593         /*
594          * If we're merging merge-bases, we don't want to bother with
595          * any working directory changes.
596          */
597         if (opt->priv->call_depth)
598                 return;
599
600         /* Ensure D/F conflicts are adjacent in the entries list. */
601         for (i = 0; i < entries->nr; i++) {
602                 struct string_list_item *next = &entries->items[i];
603                 string_list_append(&df_sorted_entries, next->string)->util =
604                                    next->util;
605         }
606         df_sorted_entries.cmp = string_list_df_name_compare;
607         string_list_sort(&df_sorted_entries);
608
609         string_list_clear(&opt->priv->df_conflict_file_set, 1);
610         for (i = 0; i < df_sorted_entries.nr; i++) {
611                 const char *path = df_sorted_entries.items[i].string;
612                 int len = strlen(path);
613                 struct stage_data *e = df_sorted_entries.items[i].util;
614
615                 /*
616                  * Check if last_file & path correspond to a D/F conflict;
617                  * i.e. whether path is last_file+'/'+<something>.
618                  * If so, record that it's okay to remove last_file to make
619                  * room for path and friends if needed.
620                  */
621                 if (last_file &&
622                     len > last_len &&
623                     memcmp(path, last_file, last_len) == 0 &&
624                     path[last_len] == '/') {
625                         string_list_insert(&opt->priv->df_conflict_file_set, last_file);
626                 }
627
628                 /*
629                  * Determine whether path could exist as a file in the
630                  * working directory as a possible D/F conflict.  This
631                  * will only occur when it exists in stage 2 as a
632                  * file.
633                  */
634                 if (S_ISREG(e->stages[2].mode) || S_ISLNK(e->stages[2].mode)) {
635                         last_file = path;
636                         last_len = len;
637                 } else {
638                         last_file = NULL;
639                 }
640         }
641         string_list_clear(&df_sorted_entries, 0);
642 }
643
644 static int update_stages(struct merge_options *opt, const char *path,
645                          const struct diff_filespec *o,
646                          const struct diff_filespec *a,
647                          const struct diff_filespec *b)
648 {
649
650         /*
651          * NOTE: It is usually a bad idea to call update_stages on a path
652          * before calling update_file on that same path, since it can
653          * sometimes lead to spurious "refusing to lose untracked file..."
654          * messages from update_file (via make_room_for path via
655          * would_lose_untracked).  Instead, reverse the order of the calls
656          * (executing update_file first and then update_stages).
657          */
658         int clear = 1;
659         int options = ADD_CACHE_OK_TO_ADD | ADD_CACHE_SKIP_DFCHECK;
660         if (clear)
661                 if (remove_file_from_index(opt->repo->index, path))
662                         return -1;
663         if (o)
664                 if (add_cacheinfo(opt, o, path, 1, 0, options))
665                         return -1;
666         if (a)
667                 if (add_cacheinfo(opt, a, path, 2, 0, options))
668                         return -1;
669         if (b)
670                 if (add_cacheinfo(opt, b, path, 3, 0, options))
671                         return -1;
672         return 0;
673 }
674
675 static void update_entry(struct stage_data *entry,
676                          struct diff_filespec *o,
677                          struct diff_filespec *a,
678                          struct diff_filespec *b)
679 {
680         entry->processed = 0;
681         entry->stages[1].mode = o->mode;
682         entry->stages[2].mode = a->mode;
683         entry->stages[3].mode = b->mode;
684         oidcpy(&entry->stages[1].oid, &o->oid);
685         oidcpy(&entry->stages[2].oid, &a->oid);
686         oidcpy(&entry->stages[3].oid, &b->oid);
687 }
688
689 static int remove_file(struct merge_options *opt, int clean,
690                        const char *path, int no_wd)
691 {
692         int update_cache = opt->priv->call_depth || clean;
693         int update_working_directory = !opt->priv->call_depth && !no_wd;
694
695         if (update_cache) {
696                 if (remove_file_from_index(opt->repo->index, path))
697                         return -1;
698         }
699         if (update_working_directory) {
700                 if (ignore_case) {
701                         struct cache_entry *ce;
702                         ce = index_file_exists(opt->repo->index, path, strlen(path),
703                                                ignore_case);
704                         if (ce && ce_stage(ce) == 0 && strcmp(path, ce->name))
705                                 return 0;
706                 }
707                 if (remove_path(path))
708                         return -1;
709         }
710         return 0;
711 }
712
713 /* add a string to a strbuf, but converting "/" to "_" */
714 static void add_flattened_path(struct strbuf *out, const char *s)
715 {
716         size_t i = out->len;
717         strbuf_addstr(out, s);
718         for (; i < out->len; i++)
719                 if (out->buf[i] == '/')
720                         out->buf[i] = '_';
721 }
722
723 static char *unique_path(struct merge_options *opt,
724                          const char *path,
725                          const char *branch)
726 {
727         struct path_hashmap_entry *entry;
728         struct strbuf newpath = STRBUF_INIT;
729         int suffix = 0;
730         size_t base_len;
731
732         strbuf_addf(&newpath, "%s~", path);
733         add_flattened_path(&newpath, branch);
734
735         base_len = newpath.len;
736         while (hashmap_get_from_hash(&opt->priv->current_file_dir_set,
737                                      path_hash(newpath.buf), newpath.buf) ||
738                (!opt->priv->call_depth && file_exists(newpath.buf))) {
739                 strbuf_setlen(&newpath, base_len);
740                 strbuf_addf(&newpath, "_%d", suffix++);
741         }
742
743         FLEX_ALLOC_MEM(entry, path, newpath.buf, newpath.len);
744         hashmap_entry_init(&entry->e, path_hash(entry->path));
745         hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
746         return strbuf_detach(&newpath, NULL);
747 }
748
749 /**
750  * Check whether a directory in the index is in the way of an incoming
751  * file.  Return 1 if so.  If check_working_copy is non-zero, also
752  * check the working directory.  If empty_ok is non-zero, also return
753  * 0 in the case where the working-tree dir exists but is empty.
754  */
755 static int dir_in_way(struct index_state *istate, const char *path,
756                       int check_working_copy, int empty_ok)
757 {
758         int pos;
759         struct strbuf dirpath = STRBUF_INIT;
760         struct stat st;
761
762         strbuf_addstr(&dirpath, path);
763         strbuf_addch(&dirpath, '/');
764
765         pos = index_name_pos(istate, dirpath.buf, dirpath.len);
766
767         if (pos < 0)
768                 pos = -1 - pos;
769         if (pos < istate->cache_nr &&
770             !strncmp(dirpath.buf, istate->cache[pos]->name, dirpath.len)) {
771                 strbuf_release(&dirpath);
772                 return 1;
773         }
774
775         strbuf_release(&dirpath);
776         return check_working_copy && !lstat(path, &st) && S_ISDIR(st.st_mode) &&
777                 !(empty_ok && is_empty_dir(path)) &&
778                 !has_symlink_leading_path(path, strlen(path));
779 }
780
781 /*
782  * Returns whether path was tracked in the index before the merge started,
783  * and its oid and mode match the specified values
784  */
785 static int was_tracked_and_matches(struct merge_options *opt, const char *path,
786                                    const struct diff_filespec *blob)
787 {
788         int pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
789         struct cache_entry *ce;
790
791         if (0 > pos)
792                 /* we were not tracking this path before the merge */
793                 return 0;
794
795         /* See if the file we were tracking before matches */
796         ce = opt->priv->orig_index.cache[pos];
797         return (oideq(&ce->oid, &blob->oid) && ce->ce_mode == blob->mode);
798 }
799
800 /*
801  * Returns whether path was tracked in the index before the merge started
802  */
803 static int was_tracked(struct merge_options *opt, const char *path)
804 {
805         int pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
806
807         if (0 <= pos)
808                 /* we were tracking this path before the merge */
809                 return 1;
810
811         return 0;
812 }
813
814 static int would_lose_untracked(struct merge_options *opt, const char *path)
815 {
816         struct index_state *istate = opt->repo->index;
817
818         /*
819          * This may look like it can be simplified to:
820          *   return !was_tracked(opt, path) && file_exists(path)
821          * but it can't.  This function needs to know whether path was in
822          * the working tree due to EITHER having been tracked in the index
823          * before the merge OR having been put into the working copy and
824          * index by unpack_trees().  Due to that either-or requirement, we
825          * check the current index instead of the original one.
826          *
827          * Note that we do not need to worry about merge-recursive itself
828          * updating the index after unpack_trees() and before calling this
829          * function, because we strictly require all code paths in
830          * merge-recursive to update the working tree first and the index
831          * second.  Doing otherwise would break
832          * update_file()/would_lose_untracked(); see every comment in this
833          * file which mentions "update_stages".
834          */
835         int pos = index_name_pos(istate, path, strlen(path));
836
837         if (pos < 0)
838                 pos = -1 - pos;
839         while (pos < istate->cache_nr &&
840                !strcmp(path, istate->cache[pos]->name)) {
841                 /*
842                  * If stage #0, it is definitely tracked.
843                  * If it has stage #2 then it was tracked
844                  * before this merge started.  All other
845                  * cases the path was not tracked.
846                  */
847                 switch (ce_stage(istate->cache[pos])) {
848                 case 0:
849                 case 2:
850                         return 0;
851                 }
852                 pos++;
853         }
854         return file_exists(path);
855 }
856
857 static int was_dirty(struct merge_options *opt, const char *path)
858 {
859         struct cache_entry *ce;
860         int dirty = 1;
861
862         if (opt->priv->call_depth || !was_tracked(opt, path))
863                 return !dirty;
864
865         ce = index_file_exists(opt->priv->unpack_opts.src_index,
866                                path, strlen(path), ignore_case);
867         dirty = verify_uptodate(ce, &opt->priv->unpack_opts) != 0;
868         return dirty;
869 }
870
871 static int make_room_for_path(struct merge_options *opt, const char *path)
872 {
873         int status, i;
874         const char *msg = _("failed to create path '%s'%s");
875
876         /* Unlink any D/F conflict files that are in the way */
877         for (i = 0; i < opt->priv->df_conflict_file_set.nr; i++) {
878                 const char *df_path = opt->priv->df_conflict_file_set.items[i].string;
879                 size_t pathlen = strlen(path);
880                 size_t df_pathlen = strlen(df_path);
881                 if (df_pathlen < pathlen &&
882                     path[df_pathlen] == '/' &&
883                     strncmp(path, df_path, df_pathlen) == 0) {
884                         output(opt, 3,
885                                _("Removing %s to make room for subdirectory\n"),
886                                df_path);
887                         unlink(df_path);
888                         unsorted_string_list_delete_item(&opt->priv->df_conflict_file_set,
889                                                          i, 0);
890                         break;
891                 }
892         }
893
894         /* Make sure leading directories are created */
895         status = safe_create_leading_directories_const(path);
896         if (status) {
897                 if (status == SCLD_EXISTS)
898                         /* something else exists */
899                         return err(opt, msg, path, _(": perhaps a D/F conflict?"));
900                 return err(opt, msg, path, "");
901         }
902
903         /*
904          * Do not unlink a file in the work tree if we are not
905          * tracking it.
906          */
907         if (would_lose_untracked(opt, path))
908                 return err(opt, _("refusing to lose untracked file at '%s'"),
909                            path);
910
911         /* Successful unlink is good.. */
912         if (!unlink(path))
913                 return 0;
914         /* .. and so is no existing file */
915         if (errno == ENOENT)
916                 return 0;
917         /* .. but not some other error (who really cares what?) */
918         return err(opt, msg, path, _(": perhaps a D/F conflict?"));
919 }
920
921 static int update_file_flags(struct merge_options *opt,
922                              const struct diff_filespec *contents,
923                              const char *path,
924                              int update_cache,
925                              int update_wd)
926 {
927         int ret = 0;
928
929         if (opt->priv->call_depth)
930                 update_wd = 0;
931
932         if (update_wd) {
933                 enum object_type type;
934                 void *buf;
935                 unsigned long size;
936
937                 if (S_ISGITLINK(contents->mode)) {
938                         /*
939                          * We may later decide to recursively descend into
940                          * the submodule directory and update its index
941                          * and/or work tree, but we do not do that now.
942                          */
943                         update_wd = 0;
944                         goto update_index;
945                 }
946
947                 buf = read_object_file(&contents->oid, &type, &size);
948                 if (!buf) {
949                         ret = err(opt, _("cannot read object %s '%s'"),
950                                   oid_to_hex(&contents->oid), path);
951                         goto free_buf;
952                 }
953                 if (type != OBJ_BLOB) {
954                         ret = err(opt, _("blob expected for %s '%s'"),
955                                   oid_to_hex(&contents->oid), path);
956                         goto free_buf;
957                 }
958                 if (S_ISREG(contents->mode)) {
959                         struct strbuf strbuf = STRBUF_INIT;
960                         if (convert_to_working_tree(opt->repo->index,
961                                                     path, buf, size, &strbuf)) {
962                                 free(buf);
963                                 size = strbuf.len;
964                                 buf = strbuf_detach(&strbuf, NULL);
965                         }
966                 }
967
968                 if (make_room_for_path(opt, path) < 0) {
969                         update_wd = 0;
970                         goto free_buf;
971                 }
972                 if (S_ISREG(contents->mode) ||
973                     (!has_symlinks && S_ISLNK(contents->mode))) {
974                         int fd;
975                         int mode = (contents->mode & 0100 ? 0777 : 0666);
976
977                         fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
978                         if (fd < 0) {
979                                 ret = err(opt, _("failed to open '%s': %s"),
980                                           path, strerror(errno));
981                                 goto free_buf;
982                         }
983                         write_in_full(fd, buf, size);
984                         close(fd);
985                 } else if (S_ISLNK(contents->mode)) {
986                         char *lnk = xmemdupz(buf, size);
987                         safe_create_leading_directories_const(path);
988                         unlink(path);
989                         if (symlink(lnk, path))
990                                 ret = err(opt, _("failed to symlink '%s': %s"),
991                                           path, strerror(errno));
992                         free(lnk);
993                 } else
994                         ret = err(opt,
995                                   _("do not know what to do with %06o %s '%s'"),
996                                   contents->mode, oid_to_hex(&contents->oid), path);
997         free_buf:
998                 free(buf);
999         }
1000 update_index:
1001         if (!ret && update_cache) {
1002                 int refresh = (!opt->priv->call_depth &&
1003                                contents->mode != S_IFGITLINK);
1004                 if (add_cacheinfo(opt, contents, path, 0, refresh,
1005                                   ADD_CACHE_OK_TO_ADD))
1006                         return -1;
1007         }
1008         return ret;
1009 }
1010
1011 static int update_file(struct merge_options *opt,
1012                        int clean,
1013                        const struct diff_filespec *contents,
1014                        const char *path)
1015 {
1016         return update_file_flags(opt, contents, path,
1017                                  opt->priv->call_depth || clean, !opt->priv->call_depth);
1018 }
1019
1020 /* Low level file merging, update and removal */
1021
1022 struct merge_file_info {
1023         struct diff_filespec blob; /* mostly use oid & mode; sometimes path */
1024         unsigned clean:1,
1025                  merge:1;
1026 };
1027
1028 static int merge_3way(struct merge_options *opt,
1029                       mmbuffer_t *result_buf,
1030                       const struct diff_filespec *o,
1031                       const struct diff_filespec *a,
1032                       const struct diff_filespec *b,
1033                       const char *branch1,
1034                       const char *branch2,
1035                       const int extra_marker_size)
1036 {
1037         mmfile_t orig, src1, src2;
1038         struct ll_merge_options ll_opts = {0};
1039         char *base, *name1, *name2;
1040         int merge_status;
1041
1042         ll_opts.renormalize = opt->renormalize;
1043         ll_opts.extra_marker_size = extra_marker_size;
1044         ll_opts.xdl_opts = opt->xdl_opts;
1045
1046         if (opt->priv->call_depth) {
1047                 ll_opts.virtual_ancestor = 1;
1048                 ll_opts.variant = 0;
1049         } else {
1050                 switch (opt->recursive_variant) {
1051                 case MERGE_VARIANT_OURS:
1052                         ll_opts.variant = XDL_MERGE_FAVOR_OURS;
1053                         break;
1054                 case MERGE_VARIANT_THEIRS:
1055                         ll_opts.variant = XDL_MERGE_FAVOR_THEIRS;
1056                         break;
1057                 default:
1058                         ll_opts.variant = 0;
1059                         break;
1060                 }
1061         }
1062
1063         assert(a->path && b->path && o->path && opt->ancestor);
1064         if (strcmp(a->path, b->path) || strcmp(a->path, o->path) != 0) {
1065                 base  = mkpathdup("%s:%s", opt->ancestor, o->path);
1066                 name1 = mkpathdup("%s:%s", branch1, a->path);
1067                 name2 = mkpathdup("%s:%s", branch2, b->path);
1068         } else {
1069                 base  = mkpathdup("%s", opt->ancestor);
1070                 name1 = mkpathdup("%s", branch1);
1071                 name2 = mkpathdup("%s", branch2);
1072         }
1073
1074         read_mmblob(&orig, &o->oid);
1075         read_mmblob(&src1, &a->oid);
1076         read_mmblob(&src2, &b->oid);
1077
1078         merge_status = ll_merge(result_buf, a->path, &orig, base,
1079                                 &src1, name1, &src2, name2,
1080                                 opt->repo->index, &ll_opts);
1081
1082         free(base);
1083         free(name1);
1084         free(name2);
1085         free(orig.ptr);
1086         free(src1.ptr);
1087         free(src2.ptr);
1088         return merge_status;
1089 }
1090
1091 static int find_first_merges(struct repository *repo,
1092                              struct object_array *result, const char *path,
1093                              struct commit *a, struct commit *b)
1094 {
1095         int i, j;
1096         struct object_array merges = OBJECT_ARRAY_INIT;
1097         struct commit *commit;
1098         int contains_another;
1099
1100         char merged_revision[GIT_MAX_HEXSZ + 2];
1101         const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
1102                                    "--all", merged_revision, NULL };
1103         struct rev_info revs;
1104         struct setup_revision_opt rev_opts;
1105
1106         memset(result, 0, sizeof(struct object_array));
1107         memset(&rev_opts, 0, sizeof(rev_opts));
1108
1109         /* get all revisions that merge commit a */
1110         xsnprintf(merged_revision, sizeof(merged_revision), "^%s",
1111                   oid_to_hex(&a->object.oid));
1112         repo_init_revisions(repo, &revs, NULL);
1113         rev_opts.submodule = path;
1114         /* FIXME: can't handle linked worktrees in submodules yet */
1115         revs.single_worktree = path != NULL;
1116         setup_revisions(ARRAY_SIZE(rev_args)-1, rev_args, &revs, &rev_opts);
1117
1118         /* save all revisions from the above list that contain b */
1119         if (prepare_revision_walk(&revs))
1120                 die("revision walk setup failed");
1121         while ((commit = get_revision(&revs)) != NULL) {
1122                 struct object *o = &(commit->object);
1123                 if (in_merge_bases(b, commit))
1124                         add_object_array(o, NULL, &merges);
1125         }
1126         reset_revision_walk();
1127
1128         /* Now we've got all merges that contain a and b. Prune all
1129          * merges that contain another found merge and save them in
1130          * result.
1131          */
1132         for (i = 0; i < merges.nr; i++) {
1133                 struct commit *m1 = (struct commit *) merges.objects[i].item;
1134
1135                 contains_another = 0;
1136                 for (j = 0; j < merges.nr; j++) {
1137                         struct commit *m2 = (struct commit *) merges.objects[j].item;
1138                         if (i != j && in_merge_bases(m2, m1)) {
1139                                 contains_another = 1;
1140                                 break;
1141                         }
1142                 }
1143
1144                 if (!contains_another)
1145                         add_object_array(merges.objects[i].item, NULL, result);
1146         }
1147
1148         object_array_clear(&merges);
1149         return result->nr;
1150 }
1151
1152 static void print_commit(struct commit *commit)
1153 {
1154         struct strbuf sb = STRBUF_INIT;
1155         struct pretty_print_context ctx = {0};
1156         ctx.date_mode.type = DATE_NORMAL;
1157         format_commit_message(commit, " %h: %m %s", &sb, &ctx);
1158         fprintf(stderr, "%s\n", sb.buf);
1159         strbuf_release(&sb);
1160 }
1161
1162 static int is_valid(const struct diff_filespec *dfs)
1163 {
1164         return dfs->mode != 0 && !is_null_oid(&dfs->oid);
1165 }
1166
1167 static int merge_submodule(struct merge_options *opt,
1168                            struct object_id *result, const char *path,
1169                            const struct object_id *base, const struct object_id *a,
1170                            const struct object_id *b)
1171 {
1172         struct commit *commit_base, *commit_a, *commit_b;
1173         int parent_count;
1174         struct object_array merges;
1175
1176         int i;
1177         int search = !opt->priv->call_depth;
1178
1179         /* store a in result in case we fail */
1180         oidcpy(result, a);
1181
1182         /* we can not handle deletion conflicts */
1183         if (is_null_oid(base))
1184                 return 0;
1185         if (is_null_oid(a))
1186                 return 0;
1187         if (is_null_oid(b))
1188                 return 0;
1189
1190         if (add_submodule_odb(path)) {
1191                 output(opt, 1, _("Failed to merge submodule %s (not checked out)"), path);
1192                 return 0;
1193         }
1194
1195         if (!(commit_base = lookup_commit_reference(opt->repo, base)) ||
1196             !(commit_a = lookup_commit_reference(opt->repo, a)) ||
1197             !(commit_b = lookup_commit_reference(opt->repo, b))) {
1198                 output(opt, 1, _("Failed to merge submodule %s (commits not present)"), path);
1199                 return 0;
1200         }
1201
1202         /* check whether both changes are forward */
1203         if (!in_merge_bases(commit_base, commit_a) ||
1204             !in_merge_bases(commit_base, commit_b)) {
1205                 output(opt, 1, _("Failed to merge submodule %s (commits don't follow merge-base)"), path);
1206                 return 0;
1207         }
1208
1209         /* Case #1: a is contained in b or vice versa */
1210         if (in_merge_bases(commit_a, commit_b)) {
1211                 oidcpy(result, b);
1212                 if (show(opt, 3)) {
1213                         output(opt, 3, _("Fast-forwarding submodule %s to the following commit:"), path);
1214                         output_commit_title(opt, commit_b);
1215                 } else if (show(opt, 2))
1216                         output(opt, 2, _("Fast-forwarding submodule %s"), path);
1217                 else
1218                         ; /* no output */
1219
1220                 return 1;
1221         }
1222         if (in_merge_bases(commit_b, commit_a)) {
1223                 oidcpy(result, a);
1224                 if (show(opt, 3)) {
1225                         output(opt, 3, _("Fast-forwarding submodule %s to the following commit:"), path);
1226                         output_commit_title(opt, commit_a);
1227                 } else if (show(opt, 2))
1228                         output(opt, 2, _("Fast-forwarding submodule %s"), path);
1229                 else
1230                         ; /* no output */
1231
1232                 return 1;
1233         }
1234
1235         /*
1236          * Case #2: There are one or more merges that contain a and b in
1237          * the submodule. If there is only one, then present it as a
1238          * suggestion to the user, but leave it marked unmerged so the
1239          * user needs to confirm the resolution.
1240          */
1241
1242         /* Skip the search if makes no sense to the calling context.  */
1243         if (!search)
1244                 return 0;
1245
1246         /* find commit which merges them */
1247         parent_count = find_first_merges(opt->repo, &merges, path,
1248                                          commit_a, commit_b);
1249         switch (parent_count) {
1250         case 0:
1251                 output(opt, 1, _("Failed to merge submodule %s (merge following commits not found)"), path);
1252                 break;
1253
1254         case 1:
1255                 output(opt, 1, _("Failed to merge submodule %s (not fast-forward)"), path);
1256                 output(opt, 2, _("Found a possible merge resolution for the submodule:\n"));
1257                 print_commit((struct commit *) merges.objects[0].item);
1258                 output(opt, 2, _(
1259                        "If this is correct simply add it to the index "
1260                        "for example\n"
1261                        "by using:\n\n"
1262                        "  git update-index --cacheinfo 160000 %s \"%s\"\n\n"
1263                        "which will accept this suggestion.\n"),
1264                        oid_to_hex(&merges.objects[0].item->oid), path);
1265                 break;
1266
1267         default:
1268                 output(opt, 1, _("Failed to merge submodule %s (multiple merges found)"), path);
1269                 for (i = 0; i < merges.nr; i++)
1270                         print_commit((struct commit *) merges.objects[i].item);
1271         }
1272
1273         object_array_clear(&merges);
1274         return 0;
1275 }
1276
1277 static int merge_mode_and_contents(struct merge_options *opt,
1278                                    const struct diff_filespec *o,
1279                                    const struct diff_filespec *a,
1280                                    const struct diff_filespec *b,
1281                                    const char *filename,
1282                                    const char *branch1,
1283                                    const char *branch2,
1284                                    const int extra_marker_size,
1285                                    struct merge_file_info *result)
1286 {
1287         if (opt->branch1 != branch1) {
1288                 /*
1289                  * It's weird getting a reverse merge with HEAD on the bottom
1290                  * side of the conflict markers and the other branch on the
1291                  * top.  Fix that.
1292                  */
1293                 return merge_mode_and_contents(opt, o, b, a,
1294                                                filename,
1295                                                branch2, branch1,
1296                                                extra_marker_size, result);
1297         }
1298
1299         result->merge = 0;
1300         result->clean = 1;
1301
1302         if ((S_IFMT & a->mode) != (S_IFMT & b->mode)) {
1303                 result->clean = 0;
1304                 if (S_ISREG(a->mode)) {
1305                         result->blob.mode = a->mode;
1306                         oidcpy(&result->blob.oid, &a->oid);
1307                 } else {
1308                         result->blob.mode = b->mode;
1309                         oidcpy(&result->blob.oid, &b->oid);
1310                 }
1311         } else {
1312                 if (!oideq(&a->oid, &o->oid) && !oideq(&b->oid, &o->oid))
1313                         result->merge = 1;
1314
1315                 /*
1316                  * Merge modes
1317                  */
1318                 if (a->mode == b->mode || a->mode == o->mode)
1319                         result->blob.mode = b->mode;
1320                 else {
1321                         result->blob.mode = a->mode;
1322                         if (b->mode != o->mode) {
1323                                 result->clean = 0;
1324                                 result->merge = 1;
1325                         }
1326                 }
1327
1328                 if (oideq(&a->oid, &b->oid) || oideq(&a->oid, &o->oid))
1329                         oidcpy(&result->blob.oid, &b->oid);
1330                 else if (oideq(&b->oid, &o->oid))
1331                         oidcpy(&result->blob.oid, &a->oid);
1332                 else if (S_ISREG(a->mode)) {
1333                         mmbuffer_t result_buf;
1334                         int ret = 0, merge_status;
1335
1336                         merge_status = merge_3way(opt, &result_buf, o, a, b,
1337                                                   branch1, branch2,
1338                                                   extra_marker_size);
1339
1340                         if ((merge_status < 0) || !result_buf.ptr)
1341                                 ret = err(opt, _("Failed to execute internal merge"));
1342
1343                         if (!ret &&
1344                             write_object_file(result_buf.ptr, result_buf.size,
1345                                               blob_type, &result->blob.oid))
1346                                 ret = err(opt, _("Unable to add %s to database"),
1347                                           a->path);
1348
1349                         free(result_buf.ptr);
1350                         if (ret)
1351                                 return ret;
1352                         result->clean = (merge_status == 0);
1353                 } else if (S_ISGITLINK(a->mode)) {
1354                         result->clean = merge_submodule(opt, &result->blob.oid,
1355                                                         o->path,
1356                                                         &o->oid,
1357                                                         &a->oid,
1358                                                         &b->oid);
1359                 } else if (S_ISLNK(a->mode)) {
1360                         switch (opt->recursive_variant) {
1361                         case MERGE_VARIANT_NORMAL:
1362                                 oidcpy(&result->blob.oid, &a->oid);
1363                                 if (!oideq(&a->oid, &b->oid))
1364                                         result->clean = 0;
1365                                 break;
1366                         case MERGE_VARIANT_OURS:
1367                                 oidcpy(&result->blob.oid, &a->oid);
1368                                 break;
1369                         case MERGE_VARIANT_THEIRS:
1370                                 oidcpy(&result->blob.oid, &b->oid);
1371                                 break;
1372                         }
1373                 } else
1374                         BUG("unsupported object type in the tree");
1375         }
1376
1377         if (result->merge)
1378                 output(opt, 2, _("Auto-merging %s"), filename);
1379
1380         return 0;
1381 }
1382
1383 static int handle_rename_via_dir(struct merge_options *opt,
1384                                  struct rename_conflict_info *ci)
1385 {
1386         /*
1387          * Handle file adds that need to be renamed due to directory rename
1388          * detection.  This differs from handle_rename_normal, because
1389          * there is no content merge to do; just move the file into the
1390          * desired final location.
1391          */
1392         const struct rename *ren = ci->ren1;
1393         const struct diff_filespec *dest = ren->pair->two;
1394         char *file_path = dest->path;
1395         int mark_conflicted = (opt->detect_directory_renames ==
1396                                MERGE_DIRECTORY_RENAMES_CONFLICT);
1397         assert(ren->dir_rename_original_dest);
1398
1399         if (!opt->priv->call_depth && would_lose_untracked(opt, dest->path)) {
1400                 mark_conflicted = 1;
1401                 file_path = unique_path(opt, dest->path, ren->branch);
1402                 output(opt, 1, _("Error: Refusing to lose untracked file at %s; "
1403                                  "writing to %s instead."),
1404                        dest->path, file_path);
1405         }
1406
1407         if (mark_conflicted) {
1408                 /*
1409                  * Write the file in worktree at file_path.  In the index,
1410                  * only record the file at dest->path in the appropriate
1411                  * higher stage.
1412                  */
1413                 if (update_file(opt, 0, dest, file_path))
1414                         return -1;
1415                 if (file_path != dest->path)
1416                         free(file_path);
1417                 if (update_stages(opt, dest->path, NULL,
1418                                   ren->branch == opt->branch1 ? dest : NULL,
1419                                   ren->branch == opt->branch1 ? NULL : dest))
1420                         return -1;
1421                 return 0; /* not clean, but conflicted */
1422         } else {
1423                 /* Update dest->path both in index and in worktree */
1424                 if (update_file(opt, 1, dest, dest->path))
1425                         return -1;
1426                 return 1; /* clean */
1427         }
1428 }
1429
1430 static int handle_change_delete(struct merge_options *opt,
1431                                 const char *path, const char *old_path,
1432                                 const struct diff_filespec *o,
1433                                 const struct diff_filespec *changed,
1434                                 const char *change_branch,
1435                                 const char *delete_branch,
1436                                 const char *change, const char *change_past)
1437 {
1438         char *alt_path = NULL;
1439         const char *update_path = path;
1440         int ret = 0;
1441
1442         if (dir_in_way(opt->repo->index, path, !opt->priv->call_depth, 0) ||
1443             (!opt->priv->call_depth && would_lose_untracked(opt, path))) {
1444                 update_path = alt_path = unique_path(opt, path, change_branch);
1445         }
1446
1447         if (opt->priv->call_depth) {
1448                 /*
1449                  * We cannot arbitrarily accept either a_sha or b_sha as
1450                  * correct; since there is no true "middle point" between
1451                  * them, simply reuse the base version for virtual merge base.
1452                  */
1453                 ret = remove_file_from_index(opt->repo->index, path);
1454                 if (!ret)
1455                         ret = update_file(opt, 0, o, update_path);
1456         } else {
1457                 /*
1458                  * Despite the four nearly duplicate messages and argument
1459                  * lists below and the ugliness of the nested if-statements,
1460                  * having complete messages makes the job easier for
1461                  * translators.
1462                  *
1463                  * The slight variance among the cases is due to the fact
1464                  * that:
1465                  *   1) directory/file conflicts (in effect if
1466                  *      !alt_path) could cause us to need to write the
1467                  *      file to a different path.
1468                  *   2) renames (in effect if !old_path) could mean that
1469                  *      there are two names for the path that the user
1470                  *      may know the file by.
1471                  */
1472                 if (!alt_path) {
1473                         if (!old_path) {
1474                                 output(opt, 1, _("CONFLICT (%s/delete): %s deleted in %s "
1475                                        "and %s in %s. Version %s of %s left in tree."),
1476                                        change, path, delete_branch, change_past,
1477                                        change_branch, change_branch, path);
1478                         } else {
1479                                 output(opt, 1, _("CONFLICT (%s/delete): %s deleted in %s "
1480                                        "and %s to %s in %s. Version %s of %s left in tree."),
1481                                        change, old_path, delete_branch, change_past, path,
1482                                        change_branch, change_branch, path);
1483                         }
1484                 } else {
1485                         if (!old_path) {
1486                                 output(opt, 1, _("CONFLICT (%s/delete): %s deleted in %s "
1487                                        "and %s in %s. Version %s of %s left in tree at %s."),
1488                                        change, path, delete_branch, change_past,
1489                                        change_branch, change_branch, path, alt_path);
1490                         } else {
1491                                 output(opt, 1, _("CONFLICT (%s/delete): %s deleted in %s "
1492                                        "and %s to %s in %s. Version %s of %s left in tree at %s."),
1493                                        change, old_path, delete_branch, change_past, path,
1494                                        change_branch, change_branch, path, alt_path);
1495                         }
1496                 }
1497                 /*
1498                  * No need to call update_file() on path when change_branch ==
1499                  * opt->branch1 && !alt_path, since that would needlessly touch
1500                  * path.  We could call update_file_flags() with update_cache=0
1501                  * and update_wd=0, but that's a no-op.
1502                  */
1503                 if (change_branch != opt->branch1 || alt_path)
1504                         ret = update_file(opt, 0, changed, update_path);
1505         }
1506         free(alt_path);
1507
1508         return ret;
1509 }
1510
1511 static int handle_rename_delete(struct merge_options *opt,
1512                                 struct rename_conflict_info *ci)
1513 {
1514         const struct rename *ren = ci->ren1;
1515         const struct diff_filespec *orig = ren->pair->one;
1516         const struct diff_filespec *dest = ren->pair->two;
1517         const char *rename_branch = ren->branch;
1518         const char *delete_branch = (opt->branch1 == ren->branch ?
1519                                      opt->branch2 : opt->branch1);
1520
1521         if (handle_change_delete(opt,
1522                                  opt->priv->call_depth ? orig->path : dest->path,
1523                                  opt->priv->call_depth ? NULL : orig->path,
1524                                  orig, dest,
1525                                  rename_branch, delete_branch,
1526                                  _("rename"), _("renamed")))
1527                 return -1;
1528
1529         if (opt->priv->call_depth)
1530                 return remove_file_from_index(opt->repo->index, dest->path);
1531         else
1532                 return update_stages(opt, dest->path, NULL,
1533                                      rename_branch == opt->branch1 ? dest : NULL,
1534                                      rename_branch == opt->branch1 ? NULL : dest);
1535 }
1536
1537 static int handle_file_collision(struct merge_options *opt,
1538                                  const char *collide_path,
1539                                  const char *prev_path1,
1540                                  const char *prev_path2,
1541                                  const char *branch1, const char *branch2,
1542                                  struct diff_filespec *a,
1543                                  struct diff_filespec *b)
1544 {
1545         struct merge_file_info mfi;
1546         struct diff_filespec null;
1547         char *alt_path = NULL;
1548         const char *update_path = collide_path;
1549
1550         /*
1551          * It's easiest to get the correct things into stage 2 and 3, and
1552          * to make sure that the content merge puts HEAD before the other
1553          * branch if we just ensure that branch1 == opt->branch1.  So, simply
1554          * flip arguments around if we don't have that.
1555          */
1556         if (branch1 != opt->branch1) {
1557                 return handle_file_collision(opt, collide_path,
1558                                              prev_path2, prev_path1,
1559                                              branch2, branch1,
1560                                              b, a);
1561         }
1562
1563         /* Remove rename sources if rename/add or rename/rename(2to1) */
1564         if (prev_path1)
1565                 remove_file(opt, 1, prev_path1,
1566                             opt->priv->call_depth || would_lose_untracked(opt, prev_path1));
1567         if (prev_path2)
1568                 remove_file(opt, 1, prev_path2,
1569                             opt->priv->call_depth || would_lose_untracked(opt, prev_path2));
1570
1571         /*
1572          * Remove the collision path, if it wouldn't cause dirty contents
1573          * or an untracked file to get lost.  We'll either overwrite with
1574          * merged contents, or just write out to differently named files.
1575          */
1576         if (was_dirty(opt, collide_path)) {
1577                 output(opt, 1, _("Refusing to lose dirty file at %s"),
1578                        collide_path);
1579                 update_path = alt_path = unique_path(opt, collide_path, "merged");
1580         } else if (would_lose_untracked(opt, collide_path)) {
1581                 /*
1582                  * Only way we get here is if both renames were from
1583                  * a directory rename AND user had an untracked file
1584                  * at the location where both files end up after the
1585                  * two directory renames.  See testcase 10d of t6043.
1586                  */
1587                 output(opt, 1, _("Refusing to lose untracked file at "
1588                                "%s, even though it's in the way."),
1589                        collide_path);
1590                 update_path = alt_path = unique_path(opt, collide_path, "merged");
1591         } else {
1592                 /*
1593                  * FIXME: It's possible that the two files are identical
1594                  * and that the current working copy happens to match, in
1595                  * which case we are unnecessarily touching the working
1596                  * tree file.  It's not a likely enough scenario that I
1597                  * want to code up the checks for it and a better fix is
1598                  * available if we restructure how unpack_trees() and
1599                  * merge-recursive interoperate anyway, so punting for
1600                  * now...
1601                  */
1602                 remove_file(opt, 0, collide_path, 0);
1603         }
1604
1605         /* Store things in diff_filespecs for functions that need it */
1606         null.path = (char *)collide_path;
1607         oidcpy(&null.oid, &null_oid);
1608         null.mode = 0;
1609
1610         if (merge_mode_and_contents(opt, &null, a, b, collide_path,
1611                                     branch1, branch2, opt->priv->call_depth * 2, &mfi))
1612                 return -1;
1613         mfi.clean &= !alt_path;
1614         if (update_file(opt, mfi.clean, &mfi.blob, update_path))
1615                 return -1;
1616         if (!mfi.clean && !opt->priv->call_depth &&
1617             update_stages(opt, collide_path, NULL, a, b))
1618                 return -1;
1619         free(alt_path);
1620         /*
1621          * FIXME: If both a & b both started with conflicts (only possible
1622          * if they came from a rename/rename(2to1)), but had IDENTICAL
1623          * contents including those conflicts, then in the next line we claim
1624          * it was clean.  If someone cares about this case, we should have the
1625          * caller notify us if we started with conflicts.
1626          */
1627         return mfi.clean;
1628 }
1629
1630 static int handle_rename_add(struct merge_options *opt,
1631                              struct rename_conflict_info *ci)
1632 {
1633         /* a was renamed to c, and a separate c was added. */
1634         struct diff_filespec *a = ci->ren1->pair->one;
1635         struct diff_filespec *c = ci->ren1->pair->two;
1636         char *path = c->path;
1637         char *prev_path_desc;
1638         struct merge_file_info mfi;
1639
1640         const char *rename_branch = ci->ren1->branch;
1641         const char *add_branch = (opt->branch1 == rename_branch ?
1642                                   opt->branch2 : opt->branch1);
1643         int other_stage = (ci->ren1->branch == opt->branch1 ? 3 : 2);
1644
1645         output(opt, 1, _("CONFLICT (rename/add): "
1646                "Rename %s->%s in %s.  Added %s in %s"),
1647                a->path, c->path, rename_branch,
1648                c->path, add_branch);
1649
1650         prev_path_desc = xstrfmt("version of %s from %s", path, a->path);
1651         ci->ren1->src_entry->stages[other_stage].path = a->path;
1652         if (merge_mode_and_contents(opt, a, c,
1653                                     &ci->ren1->src_entry->stages[other_stage],
1654                                     prev_path_desc,
1655                                     opt->branch1, opt->branch2,
1656                                     1 + opt->priv->call_depth * 2, &mfi))
1657                 return -1;
1658         free(prev_path_desc);
1659
1660         ci->ren1->dst_entry->stages[other_stage].path = mfi.blob.path = c->path;
1661         return handle_file_collision(opt,
1662                                      c->path, a->path, NULL,
1663                                      rename_branch, add_branch,
1664                                      &mfi.blob,
1665                                      &ci->ren1->dst_entry->stages[other_stage]);
1666 }
1667
1668 static char *find_path_for_conflict(struct merge_options *opt,
1669                                     const char *path,
1670                                     const char *branch1,
1671                                     const char *branch2)
1672 {
1673         char *new_path = NULL;
1674         if (dir_in_way(opt->repo->index, path, !opt->priv->call_depth, 0)) {
1675                 new_path = unique_path(opt, path, branch1);
1676                 output(opt, 1, _("%s is a directory in %s adding "
1677                                "as %s instead"),
1678                        path, branch2, new_path);
1679         } else if (would_lose_untracked(opt, path)) {
1680                 new_path = unique_path(opt, path, branch1);
1681                 output(opt, 1, _("Refusing to lose untracked file"
1682                                " at %s; adding as %s instead"),
1683                        path, new_path);
1684         }
1685
1686         return new_path;
1687 }
1688
1689 /*
1690  * Toggle the stage number between "ours" and "theirs" (2 and 3).
1691  */
1692 static inline int flip_stage(int stage)
1693 {
1694         return (2 + 3) - stage;
1695 }
1696
1697 static int handle_rename_rename_1to2(struct merge_options *opt,
1698                                      struct rename_conflict_info *ci)
1699 {
1700         /* One file was renamed in both branches, but to different names. */
1701         struct merge_file_info mfi;
1702         struct diff_filespec *add;
1703         struct diff_filespec *o = ci->ren1->pair->one;
1704         struct diff_filespec *a = ci->ren1->pair->two;
1705         struct diff_filespec *b = ci->ren2->pair->two;
1706         char *path_desc;
1707
1708         output(opt, 1, _("CONFLICT (rename/rename): "
1709                "Rename \"%s\"->\"%s\" in branch \"%s\" "
1710                "rename \"%s\"->\"%s\" in \"%s\"%s"),
1711                o->path, a->path, ci->ren1->branch,
1712                o->path, b->path, ci->ren2->branch,
1713                opt->priv->call_depth ? _(" (left unresolved)") : "");
1714
1715         path_desc = xstrfmt("%s and %s, both renamed from %s",
1716                             a->path, b->path, o->path);
1717         if (merge_mode_and_contents(opt, o, a, b, path_desc,
1718                                     ci->ren1->branch, ci->ren2->branch,
1719                                     opt->priv->call_depth * 2, &mfi))
1720                 return -1;
1721         free(path_desc);
1722
1723         if (opt->priv->call_depth)
1724                 remove_file_from_index(opt->repo->index, o->path);
1725
1726         /*
1727          * For each destination path, we need to see if there is a
1728          * rename/add collision.  If not, we can write the file out
1729          * to the specified location.
1730          */
1731         add = &ci->ren1->dst_entry->stages[flip_stage(2)];
1732         if (is_valid(add)) {
1733                 add->path = mfi.blob.path = a->path;
1734                 if (handle_file_collision(opt, a->path,
1735                                           NULL, NULL,
1736                                           ci->ren1->branch,
1737                                           ci->ren2->branch,
1738                                           &mfi.blob, add) < 0)
1739                         return -1;
1740         } else {
1741                 char *new_path = find_path_for_conflict(opt, a->path,
1742                                                         ci->ren1->branch,
1743                                                         ci->ren2->branch);
1744                 if (update_file(opt, 0, &mfi.blob,
1745                                 new_path ? new_path : a->path))
1746                         return -1;
1747                 free(new_path);
1748                 if (!opt->priv->call_depth &&
1749                     update_stages(opt, a->path, NULL, a, NULL))
1750                         return -1;
1751         }
1752
1753         add = &ci->ren2->dst_entry->stages[flip_stage(3)];
1754         if (is_valid(add)) {
1755                 add->path = mfi.blob.path = b->path;
1756                 if (handle_file_collision(opt, b->path,
1757                                           NULL, NULL,
1758                                           ci->ren1->branch,
1759                                           ci->ren2->branch,
1760                                           add, &mfi.blob) < 0)
1761                         return -1;
1762         } else {
1763                 char *new_path = find_path_for_conflict(opt, b->path,
1764                                                         ci->ren2->branch,
1765                                                         ci->ren1->branch);
1766                 if (update_file(opt, 0, &mfi.blob,
1767                                 new_path ? new_path : b->path))
1768                         return -1;
1769                 free(new_path);
1770                 if (!opt->priv->call_depth &&
1771                     update_stages(opt, b->path, NULL, NULL, b))
1772                         return -1;
1773         }
1774
1775         return 0;
1776 }
1777
1778 static int handle_rename_rename_2to1(struct merge_options *opt,
1779                                      struct rename_conflict_info *ci)
1780 {
1781         /* Two files, a & b, were renamed to the same thing, c. */
1782         struct diff_filespec *a = ci->ren1->pair->one;
1783         struct diff_filespec *b = ci->ren2->pair->one;
1784         struct diff_filespec *c1 = ci->ren1->pair->two;
1785         struct diff_filespec *c2 = ci->ren2->pair->two;
1786         char *path = c1->path; /* == c2->path */
1787         char *path_side_1_desc;
1788         char *path_side_2_desc;
1789         struct merge_file_info mfi_c1;
1790         struct merge_file_info mfi_c2;
1791         int ostage1, ostage2;
1792
1793         output(opt, 1, _("CONFLICT (rename/rename): "
1794                "Rename %s->%s in %s. "
1795                "Rename %s->%s in %s"),
1796                a->path, c1->path, ci->ren1->branch,
1797                b->path, c2->path, ci->ren2->branch);
1798
1799         path_side_1_desc = xstrfmt("version of %s from %s", path, a->path);
1800         path_side_2_desc = xstrfmt("version of %s from %s", path, b->path);
1801         ostage1 = ci->ren1->branch == opt->branch1 ? 3 : 2;
1802         ostage2 = flip_stage(ostage1);
1803         ci->ren1->src_entry->stages[ostage1].path = a->path;
1804         ci->ren2->src_entry->stages[ostage2].path = b->path;
1805         if (merge_mode_and_contents(opt, a, c1,
1806                                     &ci->ren1->src_entry->stages[ostage1],
1807                                     path_side_1_desc,
1808                                     opt->branch1, opt->branch2,
1809                                     1 + opt->priv->call_depth * 2, &mfi_c1) ||
1810             merge_mode_and_contents(opt, b,
1811                                     &ci->ren2->src_entry->stages[ostage2],
1812                                     c2, path_side_2_desc,
1813                                     opt->branch1, opt->branch2,
1814                                     1 + opt->priv->call_depth * 2, &mfi_c2))
1815                 return -1;
1816         free(path_side_1_desc);
1817         free(path_side_2_desc);
1818         mfi_c1.blob.path = path;
1819         mfi_c2.blob.path = path;
1820
1821         return handle_file_collision(opt, path, a->path, b->path,
1822                                      ci->ren1->branch, ci->ren2->branch,
1823                                      &mfi_c1.blob, &mfi_c2.blob);
1824 }
1825
1826 /*
1827  * Get the diff_filepairs changed between o_tree and tree.
1828  */
1829 static struct diff_queue_struct *get_diffpairs(struct merge_options *opt,
1830                                                struct tree *o_tree,
1831                                                struct tree *tree)
1832 {
1833         struct diff_queue_struct *ret;
1834         struct diff_options opts;
1835
1836         repo_diff_setup(opt->repo, &opts);
1837         opts.flags.recursive = 1;
1838         opts.flags.rename_empty = 0;
1839         opts.detect_rename = merge_detect_rename(opt);
1840         /*
1841          * We do not have logic to handle the detection of copies.  In
1842          * fact, it may not even make sense to add such logic: would we
1843          * really want a change to a base file to be propagated through
1844          * multiple other files by a merge?
1845          */
1846         if (opts.detect_rename > DIFF_DETECT_RENAME)
1847                 opts.detect_rename = DIFF_DETECT_RENAME;
1848         opts.rename_limit = (opt->rename_limit >= 0) ? opt->rename_limit : 1000;
1849         opts.rename_score = opt->rename_score;
1850         opts.show_rename_progress = opt->show_rename_progress;
1851         opts.output_format = DIFF_FORMAT_NO_OUTPUT;
1852         diff_setup_done(&opts);
1853         diff_tree_oid(&o_tree->object.oid, &tree->object.oid, "", &opts);
1854         diffcore_std(&opts);
1855         if (opts.needed_rename_limit > opt->priv->needed_rename_limit)
1856                 opt->priv->needed_rename_limit = opts.needed_rename_limit;
1857
1858         ret = xmalloc(sizeof(*ret));
1859         *ret = diff_queued_diff;
1860
1861         opts.output_format = DIFF_FORMAT_NO_OUTPUT;
1862         diff_queued_diff.nr = 0;
1863         diff_queued_diff.queue = NULL;
1864         diff_flush(&opts);
1865         return ret;
1866 }
1867
1868 static int tree_has_path(struct repository *r, struct tree *tree,
1869                          const char *path)
1870 {
1871         struct object_id hashy;
1872         unsigned short mode_o;
1873
1874         return !get_tree_entry(r,
1875                                &tree->object.oid, path,
1876                                &hashy, &mode_o);
1877 }
1878
1879 /*
1880  * Return a new string that replaces the beginning portion (which matches
1881  * entry->dir), with entry->new_dir.  In perl-speak:
1882  *   new_path_name = (old_path =~ s/entry->dir/entry->new_dir/);
1883  * NOTE:
1884  *   Caller must ensure that old_path starts with entry->dir + '/'.
1885  */
1886 static char *apply_dir_rename(struct dir_rename_entry *entry,
1887                               const char *old_path)
1888 {
1889         struct strbuf new_path = STRBUF_INIT;
1890         int oldlen, newlen;
1891
1892         if (entry->non_unique_new_dir)
1893                 return NULL;
1894
1895         oldlen = strlen(entry->dir);
1896         if (entry->new_dir.len == 0)
1897                 /*
1898                  * If someone renamed/merged a subdirectory into the root
1899                  * directory (e.g. 'some/subdir' -> ''), then we want to
1900                  * avoid returning
1901                  *     '' + '/filename'
1902                  * as the rename; we need to make old_path + oldlen advance
1903                  * past the '/' character.
1904                  */
1905                 oldlen++;
1906         newlen = entry->new_dir.len + (strlen(old_path) - oldlen) + 1;
1907         strbuf_grow(&new_path, newlen);
1908         strbuf_addbuf(&new_path, &entry->new_dir);
1909         strbuf_addstr(&new_path, &old_path[oldlen]);
1910
1911         return strbuf_detach(&new_path, NULL);
1912 }
1913
1914 static void get_renamed_dir_portion(const char *old_path, const char *new_path,
1915                                     char **old_dir, char **new_dir)
1916 {
1917         char *end_of_old, *end_of_new;
1918
1919         /* Default return values: NULL, meaning no rename */
1920         *old_dir = NULL;
1921         *new_dir = NULL;
1922
1923         /*
1924          * For
1925          *    "a/b/c/d/e/foo.c" -> "a/b/some/thing/else/e/foo.c"
1926          * the "e/foo.c" part is the same, we just want to know that
1927          *    "a/b/c/d" was renamed to "a/b/some/thing/else"
1928          * so, for this example, this function returns "a/b/c/d" in
1929          * *old_dir and "a/b/some/thing/else" in *new_dir.
1930          */
1931
1932         /*
1933          * If the basename of the file changed, we don't care.  We want
1934          * to know which portion of the directory, if any, changed.
1935          */
1936         end_of_old = strrchr(old_path, '/');
1937         end_of_new = strrchr(new_path, '/');
1938
1939         /*
1940          * If end_of_old is NULL, old_path wasn't in a directory, so there
1941          * could not be a directory rename (our rule elsewhere that a
1942          * directory which still exists is not considered to have been
1943          * renamed means the root directory can never be renamed -- because
1944          * the root directory always exists).
1945          */
1946         if (end_of_old == NULL)
1947                 return; /* Note: *old_dir and *new_dir are still NULL */
1948
1949         /*
1950          * If new_path contains no directory (end_of_new is NULL), then we
1951          * have a rename of old_path's directory to the root directory.
1952          */
1953         if (end_of_new == NULL) {
1954                 *old_dir = xstrndup(old_path, end_of_old - old_path);
1955                 *new_dir = xstrdup("");
1956                 return;
1957         }
1958
1959         /* Find the first non-matching character traversing backwards */
1960         while (*--end_of_new == *--end_of_old &&
1961                end_of_old != old_path &&
1962                end_of_new != new_path)
1963                 ; /* Do nothing; all in the while loop */
1964
1965         /*
1966          * If both got back to the beginning of their strings, then the
1967          * directory didn't change at all, only the basename did.
1968          */
1969         if (end_of_old == old_path && end_of_new == new_path &&
1970             *end_of_old == *end_of_new)
1971                 return; /* Note: *old_dir and *new_dir are still NULL */
1972
1973         /*
1974          * If end_of_new got back to the beginning of its string, and
1975          * end_of_old got back to the beginning of some subdirectory, then
1976          * we have a rename/merge of a subdirectory into the root, which
1977          * needs slightly special handling.
1978          *
1979          * Note: There is no need to consider the opposite case, with a
1980          * rename/merge of the root directory into some subdirectory
1981          * because as noted above the root directory always exists so it
1982          * cannot be considered to be renamed.
1983          */
1984         if (end_of_new == new_path &&
1985             end_of_old != old_path && end_of_old[-1] == '/') {
1986                 *old_dir = xstrndup(old_path, --end_of_old - old_path);
1987                 *new_dir = xstrdup("");
1988                 return;
1989         }
1990
1991         /*
1992          * We've found the first non-matching character in the directory
1993          * paths.  That means the current characters we were looking at
1994          * were part of the first non-matching subdir name going back from
1995          * the end of the strings.  Get the whole name by advancing both
1996          * end_of_old and end_of_new to the NEXT '/' character.  That will
1997          * represent the entire directory rename.
1998          *
1999          * The reason for the increment is cases like
2000          *    a/b/star/foo/whatever.c -> a/b/tar/foo/random.c
2001          * After dropping the basename and going back to the first
2002          * non-matching character, we're now comparing:
2003          *    a/b/s          and         a/b/
2004          * and we want to be comparing:
2005          *    a/b/star/      and         a/b/tar/
2006          * but without the pre-increment, the one on the right would stay
2007          * a/b/.
2008          */
2009         end_of_old = strchr(++end_of_old, '/');
2010         end_of_new = strchr(++end_of_new, '/');
2011
2012         /* Copy the old and new directories into *old_dir and *new_dir. */
2013         *old_dir = xstrndup(old_path, end_of_old - old_path);
2014         *new_dir = xstrndup(new_path, end_of_new - new_path);
2015 }
2016
2017 static void remove_hashmap_entries(struct hashmap *dir_renames,
2018                                    struct string_list *items_to_remove)
2019 {
2020         int i;
2021         struct dir_rename_entry *entry;
2022
2023         for (i = 0; i < items_to_remove->nr; i++) {
2024                 entry = items_to_remove->items[i].util;
2025                 hashmap_remove(dir_renames, &entry->ent, NULL);
2026         }
2027         string_list_clear(items_to_remove, 0);
2028 }
2029
2030 /*
2031  * See if there is a directory rename for path, and if there are any file
2032  * level conflicts for the renamed location.  If there is a rename and
2033  * there are no conflicts, return the new name.  Otherwise, return NULL.
2034  */
2035 static char *handle_path_level_conflicts(struct merge_options *opt,
2036                                          const char *path,
2037                                          struct dir_rename_entry *entry,
2038                                          struct hashmap *collisions,
2039                                          struct tree *tree)
2040 {
2041         char *new_path = NULL;
2042         struct collision_entry *collision_ent;
2043         int clean = 1;
2044         struct strbuf collision_paths = STRBUF_INIT;
2045
2046         /*
2047          * entry has the mapping of old directory name to new directory name
2048          * that we want to apply to path.
2049          */
2050         new_path = apply_dir_rename(entry, path);
2051
2052         if (!new_path) {
2053                 /* This should only happen when entry->non_unique_new_dir set */
2054                 if (!entry->non_unique_new_dir)
2055                         BUG("entry->non_unqiue_dir not set and !new_path");
2056                 output(opt, 1, _("CONFLICT (directory rename split): "
2057                                "Unclear where to place %s because directory "
2058                                "%s was renamed to multiple other directories, "
2059                                "with no destination getting a majority of the "
2060                                "files."),
2061                        path, entry->dir);
2062                 clean = 0;
2063                 return NULL;
2064         }
2065
2066         /*
2067          * The caller needs to have ensured that it has pre-populated
2068          * collisions with all paths that map to new_path.  Do a quick check
2069          * to ensure that's the case.
2070          */
2071         collision_ent = collision_find_entry(collisions, new_path);
2072         if (collision_ent == NULL)
2073                 BUG("collision_ent is NULL");
2074
2075         /*
2076          * Check for one-sided add/add/.../add conflicts, i.e.
2077          * where implicit renames from the other side doing
2078          * directory rename(s) can affect this side of history
2079          * to put multiple paths into the same location.  Warn
2080          * and bail on directory renames for such paths.
2081          */
2082         if (collision_ent->reported_already) {
2083                 clean = 0;
2084         } else if (tree_has_path(opt->repo, tree, new_path)) {
2085                 collision_ent->reported_already = 1;
2086                 strbuf_add_separated_string_list(&collision_paths, ", ",
2087                                                  &collision_ent->source_files);
2088                 output(opt, 1, _("CONFLICT (implicit dir rename): Existing "
2089                                "file/dir at %s in the way of implicit "
2090                                "directory rename(s) putting the following "
2091                                "path(s) there: %s."),
2092                        new_path, collision_paths.buf);
2093                 clean = 0;
2094         } else if (collision_ent->source_files.nr > 1) {
2095                 collision_ent->reported_already = 1;
2096                 strbuf_add_separated_string_list(&collision_paths, ", ",
2097                                                  &collision_ent->source_files);
2098                 output(opt, 1, _("CONFLICT (implicit dir rename): Cannot map "
2099                                "more than one path to %s; implicit directory "
2100                                "renames tried to put these paths there: %s"),
2101                        new_path, collision_paths.buf);
2102                 clean = 0;
2103         }
2104
2105         /* Free memory we no longer need */
2106         strbuf_release(&collision_paths);
2107         if (!clean && new_path) {
2108                 free(new_path);
2109                 return NULL;
2110         }
2111
2112         return new_path;
2113 }
2114
2115 /*
2116  * There are a couple things we want to do at the directory level:
2117  *   1. Check for both sides renaming to the same thing, in order to avoid
2118  *      implicit renaming of files that should be left in place.  (See
2119  *      testcase 6b in t6043 for details.)
2120  *   2. Prune directory renames if there are still files left in the
2121  *      the original directory.  These represent a partial directory rename,
2122  *      i.e. a rename where only some of the files within the directory
2123  *      were renamed elsewhere.  (Technically, this could be done earlier
2124  *      in get_directory_renames(), except that would prevent us from
2125  *      doing the previous check and thus failing testcase 6b.)
2126  *   3. Check for rename/rename(1to2) conflicts (at the directory level).
2127  *      In the future, we could potentially record this info as well and
2128  *      omit reporting rename/rename(1to2) conflicts for each path within
2129  *      the affected directories, thus cleaning up the merge output.
2130  *   NOTE: We do NOT check for rename/rename(2to1) conflicts at the
2131  *         directory level, because merging directories is fine.  If it
2132  *         causes conflicts for files within those merged directories, then
2133  *         that should be detected at the individual path level.
2134  */
2135 static void handle_directory_level_conflicts(struct merge_options *opt,
2136                                              struct hashmap *dir_re_head,
2137                                              struct tree *head,
2138                                              struct hashmap *dir_re_merge,
2139                                              struct tree *merge)
2140 {
2141         struct hashmap_iter iter;
2142         struct dir_rename_entry *head_ent;
2143         struct dir_rename_entry *merge_ent;
2144
2145         struct string_list remove_from_head = STRING_LIST_INIT_NODUP;
2146         struct string_list remove_from_merge = STRING_LIST_INIT_NODUP;
2147
2148         hashmap_for_each_entry(dir_re_head, &iter, head_ent,
2149                                 ent /* member name */) {
2150                 merge_ent = dir_rename_find_entry(dir_re_merge, head_ent->dir);
2151                 if (merge_ent &&
2152                     !head_ent->non_unique_new_dir &&
2153                     !merge_ent->non_unique_new_dir &&
2154                     !strbuf_cmp(&head_ent->new_dir, &merge_ent->new_dir)) {
2155                         /* 1. Renamed identically; remove it from both sides */
2156                         string_list_append(&remove_from_head,
2157                                            head_ent->dir)->util = head_ent;
2158                         strbuf_release(&head_ent->new_dir);
2159                         string_list_append(&remove_from_merge,
2160                                            merge_ent->dir)->util = merge_ent;
2161                         strbuf_release(&merge_ent->new_dir);
2162                 } else if (tree_has_path(opt->repo, head, head_ent->dir)) {
2163                         /* 2. This wasn't a directory rename after all */
2164                         string_list_append(&remove_from_head,
2165                                            head_ent->dir)->util = head_ent;
2166                         strbuf_release(&head_ent->new_dir);
2167                 }
2168         }
2169
2170         remove_hashmap_entries(dir_re_head, &remove_from_head);
2171         remove_hashmap_entries(dir_re_merge, &remove_from_merge);
2172
2173         hashmap_for_each_entry(dir_re_merge, &iter, merge_ent,
2174                                 ent /* member name */) {
2175                 head_ent = dir_rename_find_entry(dir_re_head, merge_ent->dir);
2176                 if (tree_has_path(opt->repo, merge, merge_ent->dir)) {
2177                         /* 2. This wasn't a directory rename after all */
2178                         string_list_append(&remove_from_merge,
2179                                            merge_ent->dir)->util = merge_ent;
2180                 } else if (head_ent &&
2181                            !head_ent->non_unique_new_dir &&
2182                            !merge_ent->non_unique_new_dir) {
2183                         /* 3. rename/rename(1to2) */
2184                         /*
2185                          * We can assume it's not rename/rename(1to1) because
2186                          * that was case (1), already checked above.  So we
2187                          * know that head_ent->new_dir and merge_ent->new_dir
2188                          * are different strings.
2189                          */
2190                         output(opt, 1, _("CONFLICT (rename/rename): "
2191                                        "Rename directory %s->%s in %s. "
2192                                        "Rename directory %s->%s in %s"),
2193                                head_ent->dir, head_ent->new_dir.buf, opt->branch1,
2194                                head_ent->dir, merge_ent->new_dir.buf, opt->branch2);
2195                         string_list_append(&remove_from_head,
2196                                            head_ent->dir)->util = head_ent;
2197                         strbuf_release(&head_ent->new_dir);
2198                         string_list_append(&remove_from_merge,
2199                                            merge_ent->dir)->util = merge_ent;
2200                         strbuf_release(&merge_ent->new_dir);
2201                 }
2202         }
2203
2204         remove_hashmap_entries(dir_re_head, &remove_from_head);
2205         remove_hashmap_entries(dir_re_merge, &remove_from_merge);
2206 }
2207
2208 static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
2209 {
2210         struct hashmap *dir_renames;
2211         struct hashmap_iter iter;
2212         struct dir_rename_entry *entry;
2213         int i;
2214
2215         /*
2216          * Typically, we think of a directory rename as all files from a
2217          * certain directory being moved to a target directory.  However,
2218          * what if someone first moved two files from the original
2219          * directory in one commit, and then renamed the directory
2220          * somewhere else in a later commit?  At merge time, we just know
2221          * that files from the original directory went to two different
2222          * places, and that the bulk of them ended up in the same place.
2223          * We want each directory rename to represent where the bulk of the
2224          * files from that directory end up; this function exists to find
2225          * where the bulk of the files went.
2226          *
2227          * The first loop below simply iterates through the list of file
2228          * renames, finding out how often each directory rename pair
2229          * possibility occurs.
2230          */
2231         dir_renames = xmalloc(sizeof(*dir_renames));
2232         dir_rename_init(dir_renames);
2233         for (i = 0; i < pairs->nr; ++i) {
2234                 struct string_list_item *item;
2235                 int *count;
2236                 struct diff_filepair *pair = pairs->queue[i];
2237                 char *old_dir, *new_dir;
2238
2239                 /* File not part of directory rename if it wasn't renamed */
2240                 if (pair->status != 'R')
2241                         continue;
2242
2243                 get_renamed_dir_portion(pair->one->path, pair->two->path,
2244                                         &old_dir,        &new_dir);
2245                 if (!old_dir)
2246                         /* Directory didn't change at all; ignore this one. */
2247                         continue;
2248
2249                 entry = dir_rename_find_entry(dir_renames, old_dir);
2250                 if (!entry) {
2251                         entry = xmalloc(sizeof(*entry));
2252                         dir_rename_entry_init(entry, old_dir);
2253                         hashmap_put(dir_renames, &entry->ent);
2254                 } else {
2255                         free(old_dir);
2256                 }
2257                 item = string_list_lookup(&entry->possible_new_dirs, new_dir);
2258                 if (!item) {
2259                         item = string_list_insert(&entry->possible_new_dirs,
2260                                                   new_dir);
2261                         item->util = xcalloc(1, sizeof(int));
2262                 } else {
2263                         free(new_dir);
2264                 }
2265                 count = item->util;
2266                 *count += 1;
2267         }
2268
2269         /*
2270          * For each directory with files moved out of it, we find out which
2271          * target directory received the most files so we can declare it to
2272          * be the "winning" target location for the directory rename.  This
2273          * winner gets recorded in new_dir.  If there is no winner
2274          * (multiple target directories received the same number of files),
2275          * we set non_unique_new_dir.  Once we've determined the winner (or
2276          * that there is no winner), we no longer need possible_new_dirs.
2277          */
2278         hashmap_for_each_entry(dir_renames, &iter, entry,
2279                                 ent /* member name */) {
2280                 int max = 0;
2281                 int bad_max = 0;
2282                 char *best = NULL;
2283
2284                 for (i = 0; i < entry->possible_new_dirs.nr; i++) {
2285                         int *count = entry->possible_new_dirs.items[i].util;
2286
2287                         if (*count == max)
2288                                 bad_max = max;
2289                         else if (*count > max) {
2290                                 max = *count;
2291                                 best = entry->possible_new_dirs.items[i].string;
2292                         }
2293                 }
2294                 if (bad_max == max)
2295                         entry->non_unique_new_dir = 1;
2296                 else {
2297                         assert(entry->new_dir.len == 0);
2298                         strbuf_addstr(&entry->new_dir, best);
2299                 }
2300                 /*
2301                  * The relevant directory sub-portion of the original full
2302                  * filepaths were xstrndup'ed before inserting into
2303                  * possible_new_dirs, and instead of manually iterating the
2304                  * list and free'ing each, just lie and tell
2305                  * possible_new_dirs that it did the strdup'ing so that it
2306                  * will free them for us.
2307                  */
2308                 entry->possible_new_dirs.strdup_strings = 1;
2309                 string_list_clear(&entry->possible_new_dirs, 1);
2310         }
2311
2312         return dir_renames;
2313 }
2314
2315 static struct dir_rename_entry *check_dir_renamed(const char *path,
2316                                                   struct hashmap *dir_renames)
2317 {
2318         char *temp = xstrdup(path);
2319         char *end;
2320         struct dir_rename_entry *entry = NULL;
2321
2322         while ((end = strrchr(temp, '/'))) {
2323                 *end = '\0';
2324                 entry = dir_rename_find_entry(dir_renames, temp);
2325                 if (entry)
2326                         break;
2327         }
2328         free(temp);
2329         return entry;
2330 }
2331
2332 static void compute_collisions(struct hashmap *collisions,
2333                                struct hashmap *dir_renames,
2334                                struct diff_queue_struct *pairs)
2335 {
2336         int i;
2337
2338         /*
2339          * Multiple files can be mapped to the same path due to directory
2340          * renames done by the other side of history.  Since that other
2341          * side of history could have merged multiple directories into one,
2342          * if our side of history added the same file basename to each of
2343          * those directories, then all N of them would get implicitly
2344          * renamed by the directory rename detection into the same path,
2345          * and we'd get an add/add/.../add conflict, and all those adds
2346          * from *this* side of history.  This is not representable in the
2347          * index, and users aren't going to easily be able to make sense of
2348          * it.  So we need to provide a good warning about what's
2349          * happening, and fall back to no-directory-rename detection
2350          * behavior for those paths.
2351          *
2352          * See testcases 9e and all of section 5 from t6043 for examples.
2353          */
2354         collision_init(collisions);
2355
2356         for (i = 0; i < pairs->nr; ++i) {
2357                 struct dir_rename_entry *dir_rename_ent;
2358                 struct collision_entry *collision_ent;
2359                 char *new_path;
2360                 struct diff_filepair *pair = pairs->queue[i];
2361
2362                 if (pair->status != 'A' && pair->status != 'R')
2363                         continue;
2364                 dir_rename_ent = check_dir_renamed(pair->two->path,
2365                                                    dir_renames);
2366                 if (!dir_rename_ent)
2367                         continue;
2368
2369                 new_path = apply_dir_rename(dir_rename_ent, pair->two->path);
2370                 if (!new_path)
2371                         /*
2372                          * dir_rename_ent->non_unique_new_path is true, which
2373                          * means there is no directory rename for us to use,
2374                          * which means it won't cause us any additional
2375                          * collisions.
2376                          */
2377                         continue;
2378                 collision_ent = collision_find_entry(collisions, new_path);
2379                 if (!collision_ent) {
2380                         collision_ent = xcalloc(1,
2381                                                 sizeof(struct collision_entry));
2382                         hashmap_entry_init(&collision_ent->ent,
2383                                                 strhash(new_path));
2384                         hashmap_put(collisions, &collision_ent->ent);
2385                         collision_ent->target_file = new_path;
2386                 } else {
2387                         free(new_path);
2388                 }
2389                 string_list_insert(&collision_ent->source_files,
2390                                    pair->two->path);
2391         }
2392 }
2393
2394 static char *check_for_directory_rename(struct merge_options *opt,
2395                                         const char *path,
2396                                         struct tree *tree,
2397                                         struct hashmap *dir_renames,
2398                                         struct hashmap *dir_rename_exclusions,
2399                                         struct hashmap *collisions,
2400                                         int *clean_merge)
2401 {
2402         char *new_path = NULL;
2403         struct dir_rename_entry *entry = check_dir_renamed(path, dir_renames);
2404         struct dir_rename_entry *oentry = NULL;
2405
2406         if (!entry)
2407                 return new_path;
2408
2409         /*
2410          * This next part is a little weird.  We do not want to do an
2411          * implicit rename into a directory we renamed on our side, because
2412          * that will result in a spurious rename/rename(1to2) conflict.  An
2413          * example:
2414          *   Base commit: dumbdir/afile, otherdir/bfile
2415          *   Side 1:      smrtdir/afile, otherdir/bfile
2416          *   Side 2:      dumbdir/afile, dumbdir/bfile
2417          * Here, while working on Side 1, we could notice that otherdir was
2418          * renamed/merged to dumbdir, and change the diff_filepair for
2419          * otherdir/bfile into a rename into dumbdir/bfile.  However, Side
2420          * 2 will notice the rename from dumbdir to smrtdir, and do the
2421          * transitive rename to move it from dumbdir/bfile to
2422          * smrtdir/bfile.  That gives us bfile in dumbdir vs being in
2423          * smrtdir, a rename/rename(1to2) conflict.  We really just want
2424          * the file to end up in smrtdir.  And the way to achieve that is
2425          * to not let Side1 do the rename to dumbdir, since we know that is
2426          * the source of one of our directory renames.
2427          *
2428          * That's why oentry and dir_rename_exclusions is here.
2429          *
2430          * As it turns out, this also prevents N-way transient rename
2431          * confusion; See testcases 9c and 9d of t6043.
2432          */
2433         oentry = dir_rename_find_entry(dir_rename_exclusions, entry->new_dir.buf);
2434         if (oentry) {
2435                 output(opt, 1, _("WARNING: Avoiding applying %s -> %s rename "
2436                                "to %s, because %s itself was renamed."),
2437                        entry->dir, entry->new_dir.buf, path, entry->new_dir.buf);
2438         } else {
2439                 new_path = handle_path_level_conflicts(opt, path, entry,
2440                                                        collisions, tree);
2441                 *clean_merge &= (new_path != NULL);
2442         }
2443
2444         return new_path;
2445 }
2446
2447 static void apply_directory_rename_modifications(struct merge_options *opt,
2448                                                  struct diff_filepair *pair,
2449                                                  char *new_path,
2450                                                  struct rename *re,
2451                                                  struct tree *tree,
2452                                                  struct tree *o_tree,
2453                                                  struct tree *a_tree,
2454                                                  struct tree *b_tree,
2455                                                  struct string_list *entries)
2456 {
2457         struct string_list_item *item;
2458         int stage = (tree == a_tree ? 2 : 3);
2459         int update_wd;
2460
2461         /*
2462          * In all cases where we can do directory rename detection,
2463          * unpack_trees() will have read pair->two->path into the
2464          * index and the working copy.  We need to remove it so that
2465          * we can instead place it at new_path.  It is guaranteed to
2466          * not be untracked (unpack_trees() would have errored out
2467          * saying the file would have been overwritten), but it might
2468          * be dirty, though.
2469          */
2470         update_wd = !was_dirty(opt, pair->two->path);
2471         if (!update_wd)
2472                 output(opt, 1, _("Refusing to lose dirty file at %s"),
2473                        pair->two->path);
2474         remove_file(opt, 1, pair->two->path, !update_wd);
2475
2476         /* Find or create a new re->dst_entry */
2477         item = string_list_lookup(entries, new_path);
2478         if (item) {
2479                 /*
2480                  * Since we're renaming on this side of history, and it's
2481                  * due to a directory rename on the other side of history
2482                  * (which we only allow when the directory in question no
2483                  * longer exists on the other side of history), the
2484                  * original entry for re->dst_entry is no longer
2485                  * necessary...
2486                  */
2487                 re->dst_entry->processed = 1;
2488
2489                 /*
2490                  * ...because we'll be using this new one.
2491                  */
2492                 re->dst_entry = item->util;
2493         } else {
2494                 /*
2495                  * re->dst_entry is for the before-dir-rename path, and we
2496                  * need it to hold information for the after-dir-rename
2497                  * path.  Before creating a new entry, we need to mark the
2498                  * old one as unnecessary (...unless it is shared by
2499                  * src_entry, i.e. this didn't use to be a rename, in which
2500                  * case we can just allow the normal processing to happen
2501                  * for it).
2502                  */
2503                 if (pair->status == 'R')
2504                         re->dst_entry->processed = 1;
2505
2506                 re->dst_entry = insert_stage_data(opt->repo, new_path,
2507                                                   o_tree, a_tree, b_tree,
2508                                                   entries);
2509                 item = string_list_insert(entries, new_path);
2510                 item->util = re->dst_entry;
2511         }
2512
2513         /*
2514          * Update the stage_data with the information about the path we are
2515          * moving into place.  That slot will be empty and available for us
2516          * to write to because of the collision checks in
2517          * handle_path_level_conflicts().  In other words,
2518          * re->dst_entry->stages[stage].oid will be the null_oid, so it's
2519          * open for us to write to.
2520          *
2521          * It may be tempting to actually update the index at this point as
2522          * well, using update_stages_for_stage_data(), but as per the big
2523          * "NOTE" in update_stages(), doing so will modify the current
2524          * in-memory index which will break calls to would_lose_untracked()
2525          * that we need to make.  Instead, we need to just make sure that
2526          * the various handle_rename_*() functions update the index
2527          * explicitly rather than relying on unpack_trees() to have done it.
2528          */
2529         get_tree_entry(opt->repo,
2530                        &tree->object.oid,
2531                        pair->two->path,
2532                        &re->dst_entry->stages[stage].oid,
2533                        &re->dst_entry->stages[stage].mode);
2534
2535         /*
2536          * Record the original change status (or 'type' of change).  If it
2537          * was originally an add ('A'), this lets us differentiate later
2538          * between a RENAME_DELETE conflict and RENAME_VIA_DIR (they
2539          * otherwise look the same).  If it was originally a rename ('R'),
2540          * this lets us remember and report accurately about the transitive
2541          * renaming that occurred via the directory rename detection.  Also,
2542          * record the original destination name.
2543          */
2544         re->dir_rename_original_type = pair->status;
2545         re->dir_rename_original_dest = pair->two->path;
2546
2547         /*
2548          * We don't actually look at pair->status again, but it seems
2549          * pedagogically correct to adjust it.
2550          */
2551         pair->status = 'R';
2552
2553         /*
2554          * Finally, record the new location.
2555          */
2556         pair->two->path = new_path;
2557 }
2558
2559 /*
2560  * Get information of all renames which occurred in 'pairs', making use of
2561  * any implicit directory renames inferred from the other side of history.
2562  * We need the three trees in the merge ('o_tree', 'a_tree' and 'b_tree')
2563  * to be able to associate the correct cache entries with the rename
2564  * information; tree is always equal to either a_tree or b_tree.
2565  */
2566 static struct string_list *get_renames(struct merge_options *opt,
2567                                        const char *branch,
2568                                        struct diff_queue_struct *pairs,
2569                                        struct hashmap *dir_renames,
2570                                        struct hashmap *dir_rename_exclusions,
2571                                        struct tree *tree,
2572                                        struct tree *o_tree,
2573                                        struct tree *a_tree,
2574                                        struct tree *b_tree,
2575                                        struct string_list *entries,
2576                                        int *clean_merge)
2577 {
2578         int i;
2579         struct hashmap collisions;
2580         struct hashmap_iter iter;
2581         struct collision_entry *e;
2582         struct string_list *renames;
2583
2584         compute_collisions(&collisions, dir_renames, pairs);
2585         renames = xcalloc(1, sizeof(struct string_list));
2586
2587         for (i = 0; i < pairs->nr; ++i) {
2588                 struct string_list_item *item;
2589                 struct rename *re;
2590                 struct diff_filepair *pair = pairs->queue[i];
2591                 char *new_path; /* non-NULL only with directory renames */
2592
2593                 if (pair->status != 'A' && pair->status != 'R') {
2594                         diff_free_filepair(pair);
2595                         continue;
2596                 }
2597                 new_path = check_for_directory_rename(opt, pair->two->path, tree,
2598                                                       dir_renames,
2599                                                       dir_rename_exclusions,
2600                                                       &collisions,
2601                                                       clean_merge);
2602                 if (pair->status != 'R' && !new_path) {
2603                         diff_free_filepair(pair);
2604                         continue;
2605                 }
2606
2607                 re = xmalloc(sizeof(*re));
2608                 re->processed = 0;
2609                 re->pair = pair;
2610                 re->branch = branch;
2611                 re->dir_rename_original_type = '\0';
2612                 re->dir_rename_original_dest = NULL;
2613                 item = string_list_lookup(entries, re->pair->one->path);
2614                 if (!item)
2615                         re->src_entry = insert_stage_data(opt->repo,
2616                                         re->pair->one->path,
2617                                         o_tree, a_tree, b_tree, entries);
2618                 else
2619                         re->src_entry = item->util;
2620
2621                 item = string_list_lookup(entries, re->pair->two->path);
2622                 if (!item)
2623                         re->dst_entry = insert_stage_data(opt->repo,
2624                                         re->pair->two->path,
2625                                         o_tree, a_tree, b_tree, entries);
2626                 else
2627                         re->dst_entry = item->util;
2628                 item = string_list_insert(renames, pair->one->path);
2629                 item->util = re;
2630                 if (new_path)
2631                         apply_directory_rename_modifications(opt, pair, new_path,
2632                                                              re, tree, o_tree,
2633                                                              a_tree, b_tree,
2634                                                              entries);
2635         }
2636
2637         hashmap_for_each_entry(&collisions, &iter, e,
2638                                 ent /* member name */) {
2639                 free(e->target_file);
2640                 string_list_clear(&e->source_files, 0);
2641         }
2642         hashmap_free_entries(&collisions, struct collision_entry, ent);
2643         return renames;
2644 }
2645
2646 static int process_renames(struct merge_options *opt,
2647                            struct string_list *a_renames,
2648                            struct string_list *b_renames)
2649 {
2650         int clean_merge = 1, i, j;
2651         struct string_list a_by_dst = STRING_LIST_INIT_NODUP;
2652         struct string_list b_by_dst = STRING_LIST_INIT_NODUP;
2653         const struct rename *sre;
2654
2655         for (i = 0; i < a_renames->nr; i++) {
2656                 sre = a_renames->items[i].util;
2657                 string_list_insert(&a_by_dst, sre->pair->two->path)->util
2658                         = (void *)sre;
2659         }
2660         for (i = 0; i < b_renames->nr; i++) {
2661                 sre = b_renames->items[i].util;
2662                 string_list_insert(&b_by_dst, sre->pair->two->path)->util
2663                         = (void *)sre;
2664         }
2665
2666         for (i = 0, j = 0; i < a_renames->nr || j < b_renames->nr;) {
2667                 struct string_list *renames1, *renames2Dst;
2668                 struct rename *ren1 = NULL, *ren2 = NULL;
2669                 const char *ren1_src, *ren1_dst;
2670                 struct string_list_item *lookup;
2671
2672                 if (i >= a_renames->nr) {
2673                         ren2 = b_renames->items[j++].util;
2674                 } else if (j >= b_renames->nr) {
2675                         ren1 = a_renames->items[i++].util;
2676                 } else {
2677                         int compare = strcmp(a_renames->items[i].string,
2678                                              b_renames->items[j].string);
2679                         if (compare <= 0)
2680                                 ren1 = a_renames->items[i++].util;
2681                         if (compare >= 0)
2682                                 ren2 = b_renames->items[j++].util;
2683                 }
2684
2685                 /* TODO: refactor, so that 1/2 are not needed */
2686                 if (ren1) {
2687                         renames1 = a_renames;
2688                         renames2Dst = &b_by_dst;
2689                 } else {
2690                         renames1 = b_renames;
2691                         renames2Dst = &a_by_dst;
2692                         SWAP(ren2, ren1);
2693                 }
2694
2695                 if (ren1->processed)
2696                         continue;
2697                 ren1->processed = 1;
2698                 ren1->dst_entry->processed = 1;
2699                 /* BUG: We should only mark src_entry as processed if we
2700                  * are not dealing with a rename + add-source case.
2701                  */
2702                 ren1->src_entry->processed = 1;
2703
2704                 ren1_src = ren1->pair->one->path;
2705                 ren1_dst = ren1->pair->two->path;
2706
2707                 if (ren2) {
2708                         /* One file renamed on both sides */
2709                         const char *ren2_src = ren2->pair->one->path;
2710                         const char *ren2_dst = ren2->pair->two->path;
2711                         enum rename_type rename_type;
2712                         if (strcmp(ren1_src, ren2_src) != 0)
2713                                 BUG("ren1_src != ren2_src");
2714                         ren2->dst_entry->processed = 1;
2715                         ren2->processed = 1;
2716                         if (strcmp(ren1_dst, ren2_dst) != 0) {
2717                                 rename_type = RENAME_ONE_FILE_TO_TWO;
2718                                 clean_merge = 0;
2719                         } else {
2720                                 rename_type = RENAME_ONE_FILE_TO_ONE;
2721                                 /* BUG: We should only remove ren1_src in
2722                                  * the base stage (think of rename +
2723                                  * add-source cases).
2724                                  */
2725                                 remove_file(opt, 1, ren1_src, 1);
2726                                 update_entry(ren1->dst_entry,
2727                                              ren1->pair->one,
2728                                              ren1->pair->two,
2729                                              ren2->pair->two);
2730                         }
2731                         setup_rename_conflict_info(rename_type, opt, ren1, ren2);
2732                 } else if ((lookup = string_list_lookup(renames2Dst, ren1_dst))) {
2733                         /* Two different files renamed to the same thing */
2734                         char *ren2_dst;
2735                         ren2 = lookup->util;
2736                         ren2_dst = ren2->pair->two->path;
2737                         if (strcmp(ren1_dst, ren2_dst) != 0)
2738                                 BUG("ren1_dst != ren2_dst");
2739
2740                         clean_merge = 0;
2741                         ren2->processed = 1;
2742                         /*
2743                          * BUG: We should only mark src_entry as processed
2744                          * if we are not dealing with a rename + add-source
2745                          * case.
2746                          */
2747                         ren2->src_entry->processed = 1;
2748
2749                         setup_rename_conflict_info(RENAME_TWO_FILES_TO_ONE,
2750                                                    opt, ren1, ren2);
2751                 } else {
2752                         /* Renamed in 1, maybe changed in 2 */
2753                         /* we only use sha1 and mode of these */
2754                         struct diff_filespec src_other, dst_other;
2755                         int try_merge;
2756
2757                         /*
2758                          * unpack_trees loads entries from common-commit
2759                          * into stage 1, from head-commit into stage 2, and
2760                          * from merge-commit into stage 3.  We keep track
2761                          * of which side corresponds to the rename.
2762                          */
2763                         int renamed_stage = a_renames == renames1 ? 2 : 3;
2764                         int other_stage =   a_renames == renames1 ? 3 : 2;
2765
2766                         /* BUG: We should only remove ren1_src in the base
2767                          * stage and in other_stage (think of rename +
2768                          * add-source case).
2769                          */
2770                         remove_file(opt, 1, ren1_src,
2771                                     renamed_stage == 2 || !was_tracked(opt, ren1_src));
2772
2773                         oidcpy(&src_other.oid,
2774                                &ren1->src_entry->stages[other_stage].oid);
2775                         src_other.mode = ren1->src_entry->stages[other_stage].mode;
2776                         oidcpy(&dst_other.oid,
2777                                &ren1->dst_entry->stages[other_stage].oid);
2778                         dst_other.mode = ren1->dst_entry->stages[other_stage].mode;
2779                         try_merge = 0;
2780
2781                         if (oideq(&src_other.oid, &null_oid) &&
2782                             ren1->dir_rename_original_type == 'A') {
2783                                 setup_rename_conflict_info(RENAME_VIA_DIR,
2784                                                            opt, ren1, NULL);
2785                         } else if (oideq(&src_other.oid, &null_oid)) {
2786                                 setup_rename_conflict_info(RENAME_DELETE,
2787                                                            opt, ren1, NULL);
2788                         } else if ((dst_other.mode == ren1->pair->two->mode) &&
2789                                    oideq(&dst_other.oid, &ren1->pair->two->oid)) {
2790                                 /*
2791                                  * Added file on the other side identical to
2792                                  * the file being renamed: clean merge.
2793                                  * Also, there is no need to overwrite the
2794                                  * file already in the working copy, so call
2795                                  * update_file_flags() instead of
2796                                  * update_file().
2797                                  */
2798                                 if (update_file_flags(opt,
2799                                                       ren1->pair->two,
2800                                                       ren1_dst,
2801                                                       1, /* update_cache */
2802                                                       0  /* update_wd    */))
2803                                         clean_merge = -1;
2804                         } else if (!oideq(&dst_other.oid, &null_oid)) {
2805                                 /*
2806                                  * Probably not a clean merge, but it's
2807                                  * premature to set clean_merge to 0 here,
2808                                  * because if the rename merges cleanly and
2809                                  * the merge exactly matches the newly added
2810                                  * file, then the merge will be clean.
2811                                  */
2812                                 setup_rename_conflict_info(RENAME_ADD,
2813                                                            opt, ren1, NULL);
2814                         } else
2815                                 try_merge = 1;
2816
2817                         if (clean_merge < 0)
2818                                 goto cleanup_and_return;
2819                         if (try_merge) {
2820                                 struct diff_filespec *o, *a, *b;
2821                                 src_other.path = (char *)ren1_src;
2822
2823                                 o = ren1->pair->one;
2824                                 if (a_renames == renames1) {
2825                                         a = ren1->pair->two;
2826                                         b = &src_other;
2827                                 } else {
2828                                         b = ren1->pair->two;
2829                                         a = &src_other;
2830                                 }
2831                                 update_entry(ren1->dst_entry, o, a, b);
2832                                 setup_rename_conflict_info(RENAME_NORMAL,
2833                                                            opt, ren1, NULL);
2834                         }
2835                 }
2836         }
2837 cleanup_and_return:
2838         string_list_clear(&a_by_dst, 0);
2839         string_list_clear(&b_by_dst, 0);
2840
2841         return clean_merge;
2842 }
2843
2844 struct rename_info {
2845         struct string_list *head_renames;
2846         struct string_list *merge_renames;
2847 };
2848
2849 static void initial_cleanup_rename(struct diff_queue_struct *pairs,
2850                                    struct hashmap *dir_renames)
2851 {
2852         struct hashmap_iter iter;
2853         struct dir_rename_entry *e;
2854
2855         hashmap_for_each_entry(dir_renames, &iter, e,
2856                                 ent /* member name */) {
2857                 free(e->dir);
2858                 strbuf_release(&e->new_dir);
2859                 /* possible_new_dirs already cleared in get_directory_renames */
2860         }
2861         hashmap_free_entries(dir_renames, struct dir_rename_entry, ent);
2862         free(dir_renames);
2863
2864         free(pairs->queue);
2865         free(pairs);
2866 }
2867
2868 static int detect_and_process_renames(struct merge_options *opt,
2869                                       struct tree *common,
2870                                       struct tree *head,
2871                                       struct tree *merge,
2872                                       struct string_list *entries,
2873                                       struct rename_info *ri)
2874 {
2875         struct diff_queue_struct *head_pairs, *merge_pairs;
2876         struct hashmap *dir_re_head, *dir_re_merge;
2877         int clean = 1;
2878
2879         ri->head_renames = NULL;
2880         ri->merge_renames = NULL;
2881
2882         if (!merge_detect_rename(opt))
2883                 return 1;
2884
2885         head_pairs = get_diffpairs(opt, common, head);
2886         merge_pairs = get_diffpairs(opt, common, merge);
2887
2888         if ((opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE) ||
2889             (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_CONFLICT &&
2890              !opt->priv->call_depth)) {
2891                 dir_re_head = get_directory_renames(head_pairs);
2892                 dir_re_merge = get_directory_renames(merge_pairs);
2893
2894                 handle_directory_level_conflicts(opt,
2895                                                  dir_re_head, head,
2896                                                  dir_re_merge, merge);
2897         } else {
2898                 dir_re_head  = xmalloc(sizeof(*dir_re_head));
2899                 dir_re_merge = xmalloc(sizeof(*dir_re_merge));
2900                 dir_rename_init(dir_re_head);
2901                 dir_rename_init(dir_re_merge);
2902         }
2903
2904         ri->head_renames  = get_renames(opt, opt->branch1, head_pairs,
2905                                         dir_re_merge, dir_re_head, head,
2906                                         common, head, merge, entries,
2907                                         &clean);
2908         if (clean < 0)
2909                 goto cleanup;
2910         ri->merge_renames = get_renames(opt, opt->branch2, merge_pairs,
2911                                         dir_re_head, dir_re_merge, merge,
2912                                         common, head, merge, entries,
2913                                         &clean);
2914         if (clean < 0)
2915                 goto cleanup;
2916         clean &= process_renames(opt, ri->head_renames, ri->merge_renames);
2917
2918 cleanup:
2919         /*
2920          * Some cleanup is deferred until cleanup_renames() because the
2921          * data structures are still needed and referenced in
2922          * process_entry().  But there are a few things we can free now.
2923          */
2924         initial_cleanup_rename(head_pairs, dir_re_head);
2925         initial_cleanup_rename(merge_pairs, dir_re_merge);
2926
2927         return clean;
2928 }
2929
2930 static void final_cleanup_rename(struct string_list *rename)
2931 {
2932         const struct rename *re;
2933         int i;
2934
2935         if (rename == NULL)
2936                 return;
2937
2938         for (i = 0; i < rename->nr; i++) {
2939                 re = rename->items[i].util;
2940                 diff_free_filepair(re->pair);
2941         }
2942         string_list_clear(rename, 1);
2943         free(rename);
2944 }
2945
2946 static void final_cleanup_renames(struct rename_info *re_info)
2947 {
2948         final_cleanup_rename(re_info->head_renames);
2949         final_cleanup_rename(re_info->merge_renames);
2950 }
2951
2952 static int read_oid_strbuf(struct merge_options *opt,
2953                            const struct object_id *oid,
2954                            struct strbuf *dst)
2955 {
2956         void *buf;
2957         enum object_type type;
2958         unsigned long size;
2959         buf = read_object_file(oid, &type, &size);
2960         if (!buf)
2961                 return err(opt, _("cannot read object %s"), oid_to_hex(oid));
2962         if (type != OBJ_BLOB) {
2963                 free(buf);
2964                 return err(opt, _("object %s is not a blob"), oid_to_hex(oid));
2965         }
2966         strbuf_attach(dst, buf, size, size + 1);
2967         return 0;
2968 }
2969
2970 static int blob_unchanged(struct merge_options *opt,
2971                           const struct diff_filespec *o,
2972                           const struct diff_filespec *a,
2973                           int renormalize, const char *path)
2974 {
2975         struct strbuf obuf = STRBUF_INIT;
2976         struct strbuf abuf = STRBUF_INIT;
2977         int ret = 0; /* assume changed for safety */
2978         const struct index_state *idx = opt->repo->index;
2979
2980         if (a->mode != o->mode)
2981                 return 0;
2982         if (oideq(&o->oid, &a->oid))
2983                 return 1;
2984         if (!renormalize)
2985                 return 0;
2986
2987         if (read_oid_strbuf(opt, &o->oid, &obuf) ||
2988             read_oid_strbuf(opt, &a->oid, &abuf))
2989                 goto error_return;
2990         /*
2991          * Note: binary | is used so that both renormalizations are
2992          * performed.  Comparison can be skipped if both files are
2993          * unchanged since their sha1s have already been compared.
2994          */
2995         if (renormalize_buffer(idx, path, obuf.buf, obuf.len, &obuf) |
2996             renormalize_buffer(idx, path, abuf.buf, abuf.len, &abuf))
2997                 ret = (obuf.len == abuf.len && !memcmp(obuf.buf, abuf.buf, obuf.len));
2998
2999 error_return:
3000         strbuf_release(&obuf);
3001         strbuf_release(&abuf);
3002         return ret;
3003 }
3004
3005 static int handle_modify_delete(struct merge_options *opt,
3006                                 const char *path,
3007                                 const struct diff_filespec *o,
3008                                 const struct diff_filespec *a,
3009                                 const struct diff_filespec *b)
3010 {
3011         const char *modify_branch, *delete_branch;
3012         const struct diff_filespec *changed;
3013
3014         if (is_valid(a)) {
3015                 modify_branch = opt->branch1;
3016                 delete_branch = opt->branch2;
3017                 changed = a;
3018         } else {
3019                 modify_branch = opt->branch2;
3020                 delete_branch = opt->branch1;
3021                 changed = b;
3022         }
3023
3024         return handle_change_delete(opt,
3025                                     path, NULL,
3026                                     o, changed,
3027                                     modify_branch, delete_branch,
3028                                     _("modify"), _("modified"));
3029 }
3030
3031 static int handle_content_merge(struct merge_file_info *mfi,
3032                                 struct merge_options *opt,
3033                                 const char *path,
3034                                 int is_dirty,
3035                                 const struct diff_filespec *o,
3036                                 const struct diff_filespec *a,
3037                                 const struct diff_filespec *b,
3038                                 struct rename_conflict_info *ci)
3039 {
3040         const char *reason = _("content");
3041         unsigned df_conflict_remains = 0;
3042
3043         if (!is_valid(o))
3044                 reason = _("add/add");
3045
3046         assert(o->path && a->path && b->path);
3047         if (ci && dir_in_way(opt->repo->index, path, !opt->priv->call_depth,
3048                              S_ISGITLINK(ci->ren1->pair->two->mode)))
3049                 df_conflict_remains = 1;
3050
3051         if (merge_mode_and_contents(opt, o, a, b, path,
3052                                     opt->branch1, opt->branch2,
3053                                     opt->priv->call_depth * 2, mfi))
3054                 return -1;
3055
3056         /*
3057          * We can skip updating the working tree file iff:
3058          *   a) The merge is clean
3059          *   b) The merge matches what was in HEAD (content, mode, pathname)
3060          *   c) The target path is usable (i.e. not involved in D/F conflict)
3061          */
3062         if (mfi->clean && was_tracked_and_matches(opt, path, &mfi->blob) &&
3063             !df_conflict_remains) {
3064                 int pos;
3065                 struct cache_entry *ce;
3066
3067                 output(opt, 3, _("Skipped %s (merged same as existing)"), path);
3068                 if (add_cacheinfo(opt, &mfi->blob, path,
3069                                   0, (!opt->priv->call_depth && !is_dirty), 0))
3070                         return -1;
3071                 /*
3072                  * However, add_cacheinfo() will delete the old cache entry
3073                  * and add a new one.  We need to copy over any skip_worktree
3074                  * flag to avoid making the file appear as if it were
3075                  * deleted by the user.
3076                  */
3077                 pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
3078                 ce = opt->priv->orig_index.cache[pos];
3079                 if (ce_skip_worktree(ce)) {
3080                         pos = index_name_pos(opt->repo->index, path, strlen(path));
3081                         ce = opt->repo->index->cache[pos];
3082                         ce->ce_flags |= CE_SKIP_WORKTREE;
3083                 }
3084                 return mfi->clean;
3085         }
3086
3087         if (!mfi->clean) {
3088                 if (S_ISGITLINK(mfi->blob.mode))
3089                         reason = _("submodule");
3090                 output(opt, 1, _("CONFLICT (%s): Merge conflict in %s"),
3091                                 reason, path);
3092                 if (ci && !df_conflict_remains)
3093                         if (update_stages(opt, path, o, a, b))
3094                                 return -1;
3095         }
3096
3097         if (df_conflict_remains || is_dirty) {
3098                 char *new_path;
3099                 if (opt->priv->call_depth) {
3100                         remove_file_from_index(opt->repo->index, path);
3101                 } else {
3102                         if (!mfi->clean) {
3103                                 if (update_stages(opt, path, o, a, b))
3104                                         return -1;
3105                         } else {
3106                                 int file_from_stage2 = was_tracked(opt, path);
3107
3108                                 if (update_stages(opt, path, NULL,
3109                                                   file_from_stage2 ? &mfi->blob : NULL,
3110                                                   file_from_stage2 ? NULL : &mfi->blob))
3111                                         return -1;
3112                         }
3113
3114                 }
3115                 new_path = unique_path(opt, path, ci->ren1->branch);
3116                 if (is_dirty) {
3117                         output(opt, 1, _("Refusing to lose dirty file at %s"),
3118                                path);
3119                 }
3120                 output(opt, 1, _("Adding as %s instead"), new_path);
3121                 if (update_file(opt, 0, &mfi->blob, new_path)) {
3122                         free(new_path);
3123                         return -1;
3124                 }
3125                 free(new_path);
3126                 mfi->clean = 0;
3127         } else if (update_file(opt, mfi->clean, &mfi->blob, path))
3128                 return -1;
3129         return !is_dirty && mfi->clean;
3130 }
3131
3132 static int handle_rename_normal(struct merge_options *opt,
3133                                 const char *path,
3134                                 const struct diff_filespec *o,
3135                                 const struct diff_filespec *a,
3136                                 const struct diff_filespec *b,
3137                                 struct rename_conflict_info *ci)
3138 {
3139         struct rename *ren = ci->ren1;
3140         struct merge_file_info mfi;
3141         int clean;
3142         int side = (ren->branch == opt->branch1 ? 2 : 3);
3143
3144         /* Merge the content and write it out */
3145         clean = handle_content_merge(&mfi, opt, path, was_dirty(opt, path),
3146                                      o, a, b, ci);
3147
3148         if (clean &&
3149             opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_CONFLICT &&
3150             ren->dir_rename_original_dest) {
3151                 if (update_stages(opt, path,
3152                                   NULL,
3153                                   side == 2 ? &mfi.blob : NULL,
3154                                   side == 2 ? NULL : &mfi.blob))
3155                         return -1;
3156                 clean = 0; /* not clean, but conflicted */
3157         }
3158         return clean;
3159 }
3160
3161 static void dir_rename_warning(const char *msg,
3162                                int is_add,
3163                                int clean,
3164                                struct merge_options *opt,
3165                                struct rename *ren)
3166 {
3167         const char *other_branch;
3168         other_branch = (ren->branch == opt->branch1 ?
3169                         opt->branch2 : opt->branch1);
3170         if (is_add) {
3171                 output(opt, clean ? 2 : 1, msg,
3172                        ren->pair->one->path, ren->branch,
3173                        other_branch, ren->pair->two->path);
3174                 return;
3175         }
3176         output(opt, clean ? 2 : 1, msg,
3177                ren->pair->one->path, ren->dir_rename_original_dest, ren->branch,
3178                other_branch, ren->pair->two->path);
3179 }
3180 static int warn_about_dir_renamed_entries(struct merge_options *opt,
3181                                           struct rename *ren)
3182 {
3183         const char *msg;
3184         int clean = 1, is_add;
3185
3186         if (!ren)
3187                 return clean;
3188
3189         /* Return early if ren was not affected/created by a directory rename */
3190         if (!ren->dir_rename_original_dest)
3191                 return clean;
3192
3193         /* Sanity checks */
3194         assert(opt->detect_directory_renames > MERGE_DIRECTORY_RENAMES_NONE);
3195         assert(ren->dir_rename_original_type == 'A' ||
3196                ren->dir_rename_original_type == 'R');
3197
3198         /* Check whether to treat directory renames as a conflict */
3199         clean = (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE);
3200
3201         is_add = (ren->dir_rename_original_type == 'A');
3202         if (ren->dir_rename_original_type == 'A' && clean) {
3203                 msg = _("Path updated: %s added in %s inside a "
3204                         "directory that was renamed in %s; moving it to %s.");
3205         } else if (ren->dir_rename_original_type == 'A' && !clean) {
3206                 msg = _("CONFLICT (file location): %s added in %s "
3207                         "inside a directory that was renamed in %s, "
3208                         "suggesting it should perhaps be moved to %s.");
3209         } else if (ren->dir_rename_original_type == 'R' && clean) {
3210                 msg = _("Path updated: %s renamed to %s in %s, inside a "
3211                         "directory that was renamed in %s; moving it to %s.");
3212         } else if (ren->dir_rename_original_type == 'R' && !clean) {
3213                 msg = _("CONFLICT (file location): %s renamed to %s in %s, "
3214                         "inside a directory that was renamed in %s, "
3215                         "suggesting it should perhaps be moved to %s.");
3216         } else {
3217                 BUG("Impossible dir_rename_original_type/clean combination");
3218         }
3219         dir_rename_warning(msg, is_add, clean, opt, ren);
3220
3221         return clean;
3222 }
3223
3224 /* Per entry merge function */
3225 static int process_entry(struct merge_options *opt,
3226                          const char *path, struct stage_data *entry)
3227 {
3228         int clean_merge = 1;
3229         int normalize = opt->renormalize;
3230
3231         struct diff_filespec *o = &entry->stages[1];
3232         struct diff_filespec *a = &entry->stages[2];
3233         struct diff_filespec *b = &entry->stages[3];
3234         int o_valid = is_valid(o);
3235         int a_valid = is_valid(a);
3236         int b_valid = is_valid(b);
3237         o->path = a->path = b->path = (char*)path;
3238
3239         entry->processed = 1;
3240         if (entry->rename_conflict_info) {
3241                 struct rename_conflict_info *ci = entry->rename_conflict_info;
3242                 struct diff_filespec *temp;
3243                 int path_clean;
3244
3245                 path_clean = warn_about_dir_renamed_entries(opt, ci->ren1);
3246                 path_clean &= warn_about_dir_renamed_entries(opt, ci->ren2);
3247
3248                 /*
3249                  * For cases with a single rename, {o,a,b}->path have all been
3250                  * set to the rename target path; we need to set two of these
3251                  * back to the rename source.
3252                  * For rename/rename conflicts, we'll manually fix paths below.
3253                  */
3254                 temp = (opt->branch1 == ci->ren1->branch) ? b : a;
3255                 o->path = temp->path = ci->ren1->pair->one->path;
3256                 if (ci->ren2) {
3257                         assert(opt->branch1 == ci->ren1->branch);
3258                 }
3259
3260                 switch (ci->rename_type) {
3261                 case RENAME_NORMAL:
3262                 case RENAME_ONE_FILE_TO_ONE:
3263                         clean_merge = handle_rename_normal(opt, path, o, a, b,
3264                                                            ci);
3265                         break;
3266                 case RENAME_VIA_DIR:
3267                         clean_merge = handle_rename_via_dir(opt, ci);
3268                         break;
3269                 case RENAME_ADD:
3270                         /*
3271                          * Probably unclean merge, but if the renamed file
3272                          * merges cleanly and the result can then be
3273                          * two-way merged cleanly with the added file, I
3274                          * guess it's a clean merge?
3275                          */
3276                         clean_merge = handle_rename_add(opt, ci);
3277                         break;
3278                 case RENAME_DELETE:
3279                         clean_merge = 0;
3280                         if (handle_rename_delete(opt, ci))
3281                                 clean_merge = -1;
3282                         break;
3283                 case RENAME_ONE_FILE_TO_TWO:
3284                         /*
3285                          * Manually fix up paths; note:
3286                          * ren[12]->pair->one->path are equal.
3287                          */
3288                         o->path = ci->ren1->pair->one->path;
3289                         a->path = ci->ren1->pair->two->path;
3290                         b->path = ci->ren2->pair->two->path;
3291
3292                         clean_merge = 0;
3293                         if (handle_rename_rename_1to2(opt, ci))
3294                                 clean_merge = -1;
3295                         break;
3296                 case RENAME_TWO_FILES_TO_ONE:
3297                         /*
3298                          * Manually fix up paths; note,
3299                          * ren[12]->pair->two->path are actually equal.
3300                          */
3301                         o->path = NULL;
3302                         a->path = ci->ren1->pair->two->path;
3303                         b->path = ci->ren2->pair->two->path;
3304
3305                         /*
3306                          * Probably unclean merge, but if the two renamed
3307                          * files merge cleanly and the two resulting files
3308                          * can then be two-way merged cleanly, I guess it's
3309                          * a clean merge?
3310                          */
3311                         clean_merge = handle_rename_rename_2to1(opt, ci);
3312                         break;
3313                 default:
3314                         entry->processed = 0;
3315                         break;
3316                 }
3317                 if (path_clean < clean_merge)
3318                         clean_merge = path_clean;
3319         } else if (o_valid && (!a_valid || !b_valid)) {
3320                 /* Case A: Deleted in one */
3321                 if ((!a_valid && !b_valid) ||
3322                     (!b_valid && blob_unchanged(opt, o, a, normalize, path)) ||
3323                     (!a_valid && blob_unchanged(opt, o, b, normalize, path))) {
3324                         /* Deleted in both or deleted in one and
3325                          * unchanged in the other */
3326                         if (a_valid)
3327                                 output(opt, 2, _("Removing %s"), path);
3328                         /* do not touch working file if it did not exist */
3329                         remove_file(opt, 1, path, !a_valid);
3330                 } else {
3331                         /* Modify/delete; deleted side may have put a directory in the way */
3332                         clean_merge = 0;
3333                         if (handle_modify_delete(opt, path, o, a, b))
3334                                 clean_merge = -1;
3335                 }
3336         } else if ((!o_valid && a_valid && !b_valid) ||
3337                    (!o_valid && !a_valid && b_valid)) {
3338                 /* Case B: Added in one. */
3339                 /* [nothing|directory] -> ([nothing|directory], file) */
3340
3341                 const char *add_branch;
3342                 const char *other_branch;
3343                 const char *conf;
3344                 const struct diff_filespec *contents;
3345
3346                 if (a_valid) {
3347                         add_branch = opt->branch1;
3348                         other_branch = opt->branch2;
3349                         contents = a;
3350                         conf = _("file/directory");
3351                 } else {
3352                         add_branch = opt->branch2;
3353                         other_branch = opt->branch1;
3354                         contents = b;
3355                         conf = _("directory/file");
3356                 }
3357                 if (dir_in_way(opt->repo->index, path,
3358                                !opt->priv->call_depth && !S_ISGITLINK(a->mode),
3359                                0)) {
3360                         char *new_path = unique_path(opt, path, add_branch);
3361                         clean_merge = 0;
3362                         output(opt, 1, _("CONFLICT (%s): There is a directory with name %s in %s. "
3363                                "Adding %s as %s"),
3364                                conf, path, other_branch, path, new_path);
3365                         if (update_file(opt, 0, contents, new_path))
3366                                 clean_merge = -1;
3367                         else if (opt->priv->call_depth)
3368                                 remove_file_from_index(opt->repo->index, path);
3369                         free(new_path);
3370                 } else {
3371                         output(opt, 2, _("Adding %s"), path);
3372                         /* do not overwrite file if already present */
3373                         if (update_file_flags(opt, contents, path, 1, !a_valid))
3374                                 clean_merge = -1;
3375                 }
3376         } else if (a_valid && b_valid) {
3377                 if (!o_valid) {
3378                         /* Case C: Added in both (check for same permissions) */
3379                         output(opt, 1,
3380                                _("CONFLICT (add/add): Merge conflict in %s"),
3381                                path);
3382                         clean_merge = handle_file_collision(opt,
3383                                                             path, NULL, NULL,
3384                                                             opt->branch1,
3385                                                             opt->branch2,
3386                                                             a, b);
3387                 } else {
3388                         /* case D: Modified in both, but differently. */
3389                         struct merge_file_info mfi;
3390                         int is_dirty = 0; /* unpack_trees would have bailed if dirty */
3391                         clean_merge = handle_content_merge(&mfi, opt, path,
3392                                                            is_dirty,
3393                                                            o, a, b, NULL);
3394                 }
3395         } else if (!o_valid && !a_valid && !b_valid) {
3396                 /*
3397                  * this entry was deleted altogether. a_mode == 0 means
3398                  * we had that path and want to actively remove it.
3399                  */
3400                 remove_file(opt, 1, path, !a->mode);
3401         } else
3402                 BUG("fatal merge failure, shouldn't happen.");
3403
3404         return clean_merge;
3405 }
3406
3407 static int merge_trees_internal(struct merge_options *opt,
3408                                 struct tree *head,
3409                                 struct tree *merge,
3410                                 struct tree *merge_base,
3411                                 struct tree **result)
3412 {
3413         struct index_state *istate = opt->repo->index;
3414         int code, clean;
3415
3416         if (opt->subtree_shift) {
3417                 merge = shift_tree_object(opt->repo, head, merge,
3418                                           opt->subtree_shift);
3419                 merge_base = shift_tree_object(opt->repo, head, merge_base,
3420                                                opt->subtree_shift);
3421         }
3422
3423         if (oideq(&merge_base->object.oid, &merge->object.oid)) {
3424                 output(opt, 0, _("Already up to date!"));
3425                 *result = head;
3426                 return 1;
3427         }
3428
3429         code = unpack_trees_start(opt, merge_base, head, merge);
3430
3431         if (code != 0) {
3432                 if (show(opt, 4) || opt->priv->call_depth)
3433                         err(opt, _("merging of trees %s and %s failed"),
3434                             oid_to_hex(&head->object.oid),
3435                             oid_to_hex(&merge->object.oid));
3436                 unpack_trees_finish(opt);
3437                 return -1;
3438         }
3439
3440         if (unmerged_index(istate)) {
3441                 struct string_list *entries;
3442                 struct rename_info re_info;
3443                 int i;
3444                 /*
3445                  * Only need the hashmap while processing entries, so
3446                  * initialize it here and free it when we are done running
3447                  * through the entries. Keeping it in the merge_options as
3448                  * opposed to decaring a local hashmap is for convenience
3449                  * so that we don't have to pass it to around.
3450                  */
3451                 hashmap_init(&opt->priv->current_file_dir_set, path_hashmap_cmp,
3452                              NULL, 512);
3453                 get_files_dirs(opt, head);
3454                 get_files_dirs(opt, merge);
3455
3456                 entries = get_unmerged(opt->repo->index);
3457                 clean = detect_and_process_renames(opt, merge_base, head, merge,
3458                                                    entries, &re_info);
3459                 record_df_conflict_files(opt, entries);
3460                 if (clean < 0)
3461                         goto cleanup;
3462                 for (i = entries->nr-1; 0 <= i; i--) {
3463                         const char *path = entries->items[i].string;
3464                         struct stage_data *e = entries->items[i].util;
3465                         if (!e->processed) {
3466                                 int ret = process_entry(opt, path, e);
3467                                 if (!ret)
3468                                         clean = 0;
3469                                 else if (ret < 0) {
3470                                         clean = ret;
3471                                         goto cleanup;
3472                                 }
3473                         }
3474                 }
3475                 for (i = 0; i < entries->nr; i++) {
3476                         struct stage_data *e = entries->items[i].util;
3477                         if (!e->processed)
3478                                 BUG("unprocessed path??? %s",
3479                                     entries->items[i].string);
3480                 }
3481
3482         cleanup:
3483                 final_cleanup_renames(&re_info);
3484
3485                 string_list_clear(entries, 1);
3486                 free(entries);
3487
3488                 hashmap_free_entries(&opt->priv->current_file_dir_set,
3489                                         struct path_hashmap_entry, e);
3490
3491                 if (clean < 0) {
3492                         unpack_trees_finish(opt);
3493                         return clean;
3494                 }
3495         }
3496         else
3497                 clean = 1;
3498
3499         unpack_trees_finish(opt);
3500
3501         if (opt->priv->call_depth &&
3502             !(*result = write_in_core_index_as_tree(opt->repo)))
3503                 return -1;
3504
3505         return clean;
3506 }
3507
3508 static struct commit_list *reverse_commit_list(struct commit_list *list)
3509 {
3510         struct commit_list *next = NULL, *current, *backup;
3511         for (current = list; current; current = backup) {
3512                 backup = current->next;
3513                 current->next = next;
3514                 next = current;
3515         }
3516         return next;
3517 }
3518
3519 /*
3520  * Merge the commits h1 and h2, return the resulting virtual
3521  * commit object and a flag indicating the cleanness of the merge.
3522  */
3523 static int merge_recursive_internal(struct merge_options *opt,
3524                                     struct commit *h1,
3525                                     struct commit *h2,
3526                                     struct commit_list *merge_bases,
3527                                     struct commit **result)
3528 {
3529         struct commit_list *iter;
3530         struct commit *merged_merge_bases;
3531         struct tree *result_tree;
3532         int clean;
3533         const char *ancestor_name;
3534         struct strbuf merge_base_abbrev = STRBUF_INIT;
3535
3536         if (show(opt, 4)) {
3537                 output(opt, 4, _("Merging:"));
3538                 output_commit_title(opt, h1);
3539                 output_commit_title(opt, h2);
3540         }
3541
3542         if (!merge_bases) {
3543                 merge_bases = get_merge_bases(h1, h2);
3544                 merge_bases = reverse_commit_list(merge_bases);
3545         }
3546
3547         if (show(opt, 5)) {
3548                 unsigned cnt = commit_list_count(merge_bases);
3549
3550                 output(opt, 5, Q_("found %u common ancestor:",
3551                                 "found %u common ancestors:", cnt), cnt);
3552                 for (iter = merge_bases; iter; iter = iter->next)
3553                         output_commit_title(opt, iter->item);
3554         }
3555
3556         merged_merge_bases = pop_commit(&merge_bases);
3557         if (merged_merge_bases == NULL) {
3558                 /* if there is no common ancestor, use an empty tree */
3559                 struct tree *tree;
3560
3561                 tree = lookup_tree(opt->repo, opt->repo->hash_algo->empty_tree);
3562                 merged_merge_bases = make_virtual_commit(opt->repo, tree,
3563                                                          "ancestor");
3564                 ancestor_name = "empty tree";
3565         } else if (opt->ancestor && !opt->priv->call_depth) {
3566                 ancestor_name = opt->ancestor;
3567         } else if (merge_bases) {
3568                 ancestor_name = "merged common ancestors";
3569         } else {
3570                 strbuf_add_unique_abbrev(&merge_base_abbrev,
3571                                          &merged_merge_bases->object.oid,
3572                                          DEFAULT_ABBREV);
3573                 ancestor_name = merge_base_abbrev.buf;
3574         }
3575
3576         for (iter = merge_bases; iter; iter = iter->next) {
3577                 const char *saved_b1, *saved_b2;
3578                 opt->priv->call_depth++;
3579                 /*
3580                  * When the merge fails, the result contains files
3581                  * with conflict markers. The cleanness flag is
3582                  * ignored (unless indicating an error), it was never
3583                  * actually used, as result of merge_trees has always
3584                  * overwritten it: the committed "conflicts" were
3585                  * already resolved.
3586                  */
3587                 discard_index(opt->repo->index);
3588                 saved_b1 = opt->branch1;
3589                 saved_b2 = opt->branch2;
3590                 opt->branch1 = "Temporary merge branch 1";
3591                 opt->branch2 = "Temporary merge branch 2";
3592                 if (merge_recursive_internal(opt, merged_merge_bases, iter->item,
3593                                              NULL, &merged_merge_bases) < 0)
3594                         return -1;
3595                 opt->branch1 = saved_b1;
3596                 opt->branch2 = saved_b2;
3597                 opt->priv->call_depth--;
3598
3599                 if (!merged_merge_bases)
3600                         return err(opt, _("merge returned no commit"));
3601         }
3602
3603         discard_index(opt->repo->index);
3604         if (!opt->priv->call_depth)
3605                 repo_read_index(opt->repo);
3606
3607         opt->ancestor = ancestor_name;
3608         clean = merge_trees_internal(opt,
3609                                      repo_get_commit_tree(opt->repo, h1),
3610                                      repo_get_commit_tree(opt->repo, h2),
3611                                      repo_get_commit_tree(opt->repo,
3612                                                           merged_merge_bases),
3613                                      &result_tree);
3614         strbuf_release(&merge_base_abbrev);
3615         opt->ancestor = NULL;  /* avoid accidental re-use of opt->ancestor */
3616         if (clean < 0) {
3617                 flush_output(opt);
3618                 return clean;
3619         }
3620
3621         if (opt->priv->call_depth) {
3622                 *result = make_virtual_commit(opt->repo, result_tree,
3623                                               "merged tree");
3624                 commit_list_insert(h1, &(*result)->parents);
3625                 commit_list_insert(h2, &(*result)->parents->next);
3626         }
3627         return clean;
3628 }
3629
3630 static int merge_start(struct merge_options *opt, struct tree *head)
3631 {
3632         struct strbuf sb = STRBUF_INIT;
3633
3634         /* Sanity checks on opt */
3635         assert(opt->repo);
3636
3637         assert(opt->branch1 && opt->branch2);
3638
3639         assert(opt->detect_renames >= -1 &&
3640                opt->detect_renames <= DIFF_DETECT_COPY);
3641         assert(opt->detect_directory_renames >= MERGE_DIRECTORY_RENAMES_NONE &&
3642                opt->detect_directory_renames <= MERGE_DIRECTORY_RENAMES_TRUE);
3643         assert(opt->rename_limit >= -1);
3644         assert(opt->rename_score >= 0 && opt->rename_score <= MAX_SCORE);
3645         assert(opt->show_rename_progress >= 0 && opt->show_rename_progress <= 1);
3646
3647         assert(opt->xdl_opts >= 0);
3648         assert(opt->recursive_variant >= MERGE_VARIANT_NORMAL &&
3649                opt->recursive_variant <= MERGE_VARIANT_THEIRS);
3650
3651         assert(opt->verbosity >= 0 && opt->verbosity <= 5);
3652         assert(opt->buffer_output <= 2);
3653         assert(opt->obuf.len == 0);
3654
3655         assert(opt->priv == NULL);
3656
3657         /* Sanity check on repo state; index must match head */
3658         if (repo_index_has_changes(opt->repo, head, &sb)) {
3659                 err(opt, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
3660                     sb.buf);
3661                 strbuf_release(&sb);
3662                 return -1;
3663         }
3664
3665         opt->priv = xcalloc(1, sizeof(*opt->priv));
3666         string_list_init(&opt->priv->df_conflict_file_set, 1);
3667         return 0;
3668 }
3669
3670 static void merge_finalize(struct merge_options *opt)
3671 {
3672         flush_output(opt);
3673         if (!opt->priv->call_depth && opt->buffer_output < 2)
3674                 strbuf_release(&opt->obuf);
3675         if (show(opt, 2))
3676                 diff_warn_rename_limit("merge.renamelimit",
3677                                        opt->priv->needed_rename_limit, 0);
3678         FREE_AND_NULL(opt->priv);
3679 }
3680
3681 int merge_trees(struct merge_options *opt,
3682                 struct tree *head,
3683                 struct tree *merge,
3684                 struct tree *merge_base)
3685 {
3686         int clean;
3687         struct tree *ignored;
3688
3689         assert(opt->ancestor != NULL);
3690
3691         if (merge_start(opt, head))
3692                 return -1;
3693         clean = merge_trees_internal(opt, head, merge, merge_base, &ignored);
3694         merge_finalize(opt);
3695
3696         return clean;
3697 }
3698
3699 int merge_recursive(struct merge_options *opt,
3700                     struct commit *h1,
3701                     struct commit *h2,
3702                     struct commit_list *merge_bases,
3703                     struct commit **result)
3704 {
3705         int clean;
3706
3707         assert(opt->ancestor == NULL ||
3708                !strcmp(opt->ancestor, "constructed merge base"));
3709
3710         if (merge_start(opt, repo_get_commit_tree(opt->repo, h1)))
3711                 return -1;
3712         clean = merge_recursive_internal(opt, h1, h2, merge_bases, result);
3713         merge_finalize(opt);
3714
3715         return clean;
3716 }
3717
3718 static struct commit *get_ref(struct repository *repo,
3719                               const struct object_id *oid,
3720                               const char *name)
3721 {
3722         struct object *object;
3723
3724         object = deref_tag(repo, parse_object(repo, oid),
3725                            name, strlen(name));
3726         if (!object)
3727                 return NULL;
3728         if (object->type == OBJ_TREE)
3729                 return make_virtual_commit(repo, (struct tree*)object, name);
3730         if (object->type != OBJ_COMMIT)
3731                 return NULL;
3732         if (parse_commit((struct commit *)object))
3733                 return NULL;
3734         return (struct commit *)object;
3735 }
3736
3737 int merge_recursive_generic(struct merge_options *opt,
3738                             const struct object_id *head,
3739                             const struct object_id *merge,
3740                             int num_merge_bases,
3741                             const struct object_id **merge_bases,
3742                             struct commit **result)
3743 {
3744         int clean;
3745         struct lock_file lock = LOCK_INIT;
3746         struct commit *head_commit = get_ref(opt->repo, head, opt->branch1);
3747         struct commit *next_commit = get_ref(opt->repo, merge, opt->branch2);
3748         struct commit_list *ca = NULL;
3749
3750         if (merge_bases) {
3751                 int i;
3752                 for (i = 0; i < num_merge_bases; ++i) {
3753                         struct commit *base;
3754                         if (!(base = get_ref(opt->repo, merge_bases[i],
3755                                              oid_to_hex(merge_bases[i]))))
3756                                 return err(opt, _("Could not parse object '%s'"),
3757                                            oid_to_hex(merge_bases[i]));
3758                         commit_list_insert(base, &ca);
3759                 }
3760                 if (num_merge_bases == 1)
3761                         opt->ancestor = "constructed merge base";
3762         }
3763
3764         repo_hold_locked_index(opt->repo, &lock, LOCK_DIE_ON_ERROR);
3765         clean = merge_recursive(opt, head_commit, next_commit, ca,
3766                                 result);
3767         if (clean < 0) {
3768                 rollback_lock_file(&lock);
3769                 return clean;
3770         }
3771
3772         if (write_locked_index(opt->repo->index, &lock,
3773                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
3774                 return err(opt, _("Unable to write index."));
3775
3776         return clean ? 0 : 1;
3777 }
3778
3779 static void merge_recursive_config(struct merge_options *opt)
3780 {
3781         char *value = NULL;
3782         git_config_get_int("merge.verbosity", &opt->verbosity);
3783         git_config_get_int("diff.renamelimit", &opt->rename_limit);
3784         git_config_get_int("merge.renamelimit", &opt->rename_limit);
3785         if (!git_config_get_string("diff.renames", &value)) {
3786                 opt->detect_renames = git_config_rename("diff.renames", value);
3787                 free(value);
3788         }
3789         if (!git_config_get_string("merge.renames", &value)) {
3790                 opt->detect_renames = git_config_rename("merge.renames", value);
3791                 free(value);
3792         }
3793         if (!git_config_get_string("merge.directoryrenames", &value)) {
3794                 int boolval = git_parse_maybe_bool(value);
3795                 if (0 <= boolval) {
3796                         opt->detect_directory_renames = boolval ?
3797                                 MERGE_DIRECTORY_RENAMES_TRUE :
3798                                 MERGE_DIRECTORY_RENAMES_NONE;
3799                 } else if (!strcasecmp(value, "conflict")) {
3800                         opt->detect_directory_renames =
3801                                 MERGE_DIRECTORY_RENAMES_CONFLICT;
3802                 } /* avoid erroring on values from future versions of git */
3803                 free(value);
3804         }
3805         git_config(git_xmerge_config, NULL);
3806 }
3807
3808 void init_merge_options(struct merge_options *opt,
3809                         struct repository *repo)
3810 {
3811         const char *merge_verbosity;
3812         memset(opt, 0, sizeof(struct merge_options));
3813
3814         opt->repo = repo;
3815
3816         opt->detect_renames = -1;
3817         opt->detect_directory_renames = MERGE_DIRECTORY_RENAMES_CONFLICT;
3818         opt->rename_limit = -1;
3819
3820         opt->verbosity = 2;
3821         opt->buffer_output = 1;
3822         strbuf_init(&opt->obuf, 0);
3823
3824         opt->renormalize = 0;
3825
3826         merge_recursive_config(opt);
3827         merge_verbosity = getenv("GIT_MERGE_VERBOSITY");
3828         if (merge_verbosity)
3829                 opt->verbosity = strtol(merge_verbosity, NULL, 10);
3830         if (opt->verbosity >= 5)
3831                 opt->buffer_output = 0;
3832 }
3833
3834 int parse_merge_opt(struct merge_options *opt, const char *s)
3835 {
3836         const char *arg;
3837
3838         if (!s || !*s)
3839                 return -1;
3840         if (!strcmp(s, "ours"))
3841                 opt->recursive_variant = MERGE_VARIANT_OURS;
3842         else if (!strcmp(s, "theirs"))
3843                 opt->recursive_variant = MERGE_VARIANT_THEIRS;
3844         else if (!strcmp(s, "subtree"))
3845                 opt->subtree_shift = "";
3846         else if (skip_prefix(s, "subtree=", &arg))
3847                 opt->subtree_shift = arg;
3848         else if (!strcmp(s, "patience"))
3849                 opt->xdl_opts = DIFF_WITH_ALG(opt, PATIENCE_DIFF);
3850         else if (!strcmp(s, "histogram"))
3851                 opt->xdl_opts = DIFF_WITH_ALG(opt, HISTOGRAM_DIFF);
3852         else if (skip_prefix(s, "diff-algorithm=", &arg)) {
3853                 long value = parse_algorithm_value(arg);
3854                 if (value < 0)
3855                         return -1;
3856                 /* clear out previous settings */
3857                 DIFF_XDL_CLR(opt, NEED_MINIMAL);
3858                 opt->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
3859                 opt->xdl_opts |= value;
3860         }
3861         else if (!strcmp(s, "ignore-space-change"))
3862                 DIFF_XDL_SET(opt, IGNORE_WHITESPACE_CHANGE);
3863         else if (!strcmp(s, "ignore-all-space"))
3864                 DIFF_XDL_SET(opt, IGNORE_WHITESPACE);
3865         else if (!strcmp(s, "ignore-space-at-eol"))
3866                 DIFF_XDL_SET(opt, IGNORE_WHITESPACE_AT_EOL);
3867         else if (!strcmp(s, "ignore-cr-at-eol"))
3868                 DIFF_XDL_SET(opt, IGNORE_CR_AT_EOL);
3869         else if (!strcmp(s, "renormalize"))
3870                 opt->renormalize = 1;
3871         else if (!strcmp(s, "no-renormalize"))
3872                 opt->renormalize = 0;
3873         else if (!strcmp(s, "no-renames"))
3874                 opt->detect_renames = 0;
3875         else if (!strcmp(s, "find-renames")) {
3876                 opt->detect_renames = 1;
3877                 opt->rename_score = 0;
3878         }
3879         else if (skip_prefix(s, "find-renames=", &arg) ||
3880                  skip_prefix(s, "rename-threshold=", &arg)) {
3881                 if ((opt->rename_score = parse_rename_score(&arg)) == -1 || *arg != 0)
3882                         return -1;
3883                 opt->detect_renames = 1;
3884         }
3885         /*
3886          * Please update $__git_merge_strategy_options in
3887          * git-completion.bash when you add new options
3888          */
3889         else
3890                 return -1;
3891         return 0;
3892 }