Merge branch 'maint'
[git] / notes-merge.c
1 #include "cache.h"
2 #include "commit.h"
3 #include "refs.h"
4 #include "diff.h"
5 #include "diffcore.h"
6 #include "xdiff-interface.h"
7 #include "ll-merge.h"
8 #include "dir.h"
9 #include "notes.h"
10 #include "notes-merge.h"
11 #include "strbuf.h"
12
13 struct notes_merge_pair {
14         unsigned char obj[20], base[20], local[20], remote[20];
15 };
16
17 void init_notes_merge_options(struct notes_merge_options *o)
18 {
19         memset(o, 0, sizeof(struct notes_merge_options));
20         strbuf_init(&(o->commit_msg), 0);
21         o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
22 }
23
24 static int path_to_sha1(const char *path, unsigned char *sha1)
25 {
26         char hex_sha1[40];
27         int i = 0;
28         while (*path && i < 40) {
29                 if (*path != '/')
30                         hex_sha1[i++] = *path;
31                 path++;
32         }
33         if (*path || i != 40)
34                 return -1;
35         return get_sha1_hex(hex_sha1, sha1);
36 }
37
38 static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
39 {
40         switch (p->status) {
41         case DIFF_STATUS_MODIFIED:
42                 assert(p->one->mode == p->two->mode);
43                 assert(!is_null_sha1(p->one->sha1));
44                 assert(!is_null_sha1(p->two->sha1));
45                 break;
46         case DIFF_STATUS_ADDED:
47                 assert(is_null_sha1(p->one->sha1));
48                 break;
49         case DIFF_STATUS_DELETED:
50                 assert(is_null_sha1(p->two->sha1));
51                 break;
52         default:
53                 return -1;
54         }
55         assert(!strcmp(p->one->path, p->two->path));
56         return path_to_sha1(p->one->path, sha1);
57 }
58
59 static struct notes_merge_pair *find_notes_merge_pair_pos(
60                 struct notes_merge_pair *list, int len, unsigned char *obj,
61                 int insert_new, int *occupied)
62 {
63         /*
64          * Both diff_tree_remote() and diff_tree_local() tend to process
65          * merge_pairs in ascending order. Therefore, cache last returned
66          * index, and search sequentially from there until the appropriate
67          * position is found.
68          *
69          * Since inserts only happen from diff_tree_remote() (which mainly
70          * _appends_), we don't care that inserting into the middle of the
71          * list is expensive (using memmove()).
72          */
73         static int last_index;
74         int i = last_index < len ? last_index : len - 1;
75         int prev_cmp = 0, cmp = -1;
76         while (i >= 0 && i < len) {
77                 cmp = hashcmp(obj, list[i].obj);
78                 if (!cmp) /* obj belongs @ i */
79                         break;
80                 else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
81                         i--;
82                 else if (cmp < 0) /* obj belongs between i-1 and i */
83                         break;
84                 else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
85                         i++;
86                 else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
87                         i++;
88                         break;
89                 }
90                 prev_cmp = cmp;
91         }
92         if (i < 0)
93                 i = 0;
94         /* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
95
96         if (!cmp)
97                 *occupied = 1;
98         else {
99                 *occupied = 0;
100                 if (insert_new && i < len) {
101                         memmove(list + i + 1, list + i,
102                                 (len - i) * sizeof(struct notes_merge_pair));
103                         memset(list + i, 0, sizeof(struct notes_merge_pair));
104                 }
105         }
106         last_index = i;
107         return list + i;
108 }
109
110 static unsigned char uninitialized[20] =
111         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
112         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
113
114 static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
115                                                  const unsigned char *base,
116                                                  const unsigned char *remote,
117                                                  int *num_changes)
118 {
119         struct diff_options opt;
120         struct notes_merge_pair *changes;
121         int i, len = 0;
122
123         trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
124                sha1_to_hex(base), sha1_to_hex(remote));
125
126         diff_setup(&opt);
127         DIFF_OPT_SET(&opt, RECURSIVE);
128         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
129         if (diff_setup_done(&opt) < 0)
130                 die("diff_setup_done failed");
131         diff_tree_sha1(base, remote, "", &opt);
132         diffcore_std(&opt);
133
134         changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
135
136         for (i = 0; i < diff_queued_diff.nr; i++) {
137                 struct diff_filepair *p = diff_queued_diff.queue[i];
138                 struct notes_merge_pair *mp;
139                 int occupied;
140                 unsigned char obj[20];
141
142                 if (verify_notes_filepair(p, obj)) {
143                         trace_printf("\t\tCannot merge entry '%s' (%c): "
144                                "%.7s -> %.7s. Skipping!\n", p->one->path,
145                                p->status, sha1_to_hex(p->one->sha1),
146                                sha1_to_hex(p->two->sha1));
147                         continue;
148                 }
149                 mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
150                 if (occupied) {
151                         /* We've found an addition/deletion pair */
152                         assert(!hashcmp(mp->obj, obj));
153                         if (is_null_sha1(p->one->sha1)) { /* addition */
154                                 assert(is_null_sha1(mp->remote));
155                                 hashcpy(mp->remote, p->two->sha1);
156                         } else if (is_null_sha1(p->two->sha1)) { /* deletion */
157                                 assert(is_null_sha1(mp->base));
158                                 hashcpy(mp->base, p->one->sha1);
159                         } else
160                                 assert(!"Invalid existing change recorded");
161                 } else {
162                         hashcpy(mp->obj, obj);
163                         hashcpy(mp->base, p->one->sha1);
164                         hashcpy(mp->local, uninitialized);
165                         hashcpy(mp->remote, p->two->sha1);
166                         len++;
167                 }
168                 trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
169                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
170                        sha1_to_hex(mp->remote));
171         }
172         diff_flush(&opt);
173         diff_tree_release_paths(&opt);
174
175         *num_changes = len;
176         return changes;
177 }
178
179 static void diff_tree_local(struct notes_merge_options *o,
180                             struct notes_merge_pair *changes, int len,
181                             const unsigned char *base,
182                             const unsigned char *local)
183 {
184         struct diff_options opt;
185         int i;
186
187         trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
188                len, sha1_to_hex(base), sha1_to_hex(local));
189
190         diff_setup(&opt);
191         DIFF_OPT_SET(&opt, RECURSIVE);
192         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
193         if (diff_setup_done(&opt) < 0)
194                 die("diff_setup_done failed");
195         diff_tree_sha1(base, local, "", &opt);
196         diffcore_std(&opt);
197
198         for (i = 0; i < diff_queued_diff.nr; i++) {
199                 struct diff_filepair *p = diff_queued_diff.queue[i];
200                 struct notes_merge_pair *mp;
201                 int match;
202                 unsigned char obj[20];
203
204                 if (verify_notes_filepair(p, obj)) {
205                         trace_printf("\t\tCannot merge entry '%s' (%c): "
206                                "%.7s -> %.7s. Skipping!\n", p->one->path,
207                                p->status, sha1_to_hex(p->one->sha1),
208                                sha1_to_hex(p->two->sha1));
209                         continue;
210                 }
211                 mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
212                 if (!match) {
213                         trace_printf("\t\tIgnoring local-only change for %s: "
214                                "%.7s -> %.7s\n", sha1_to_hex(obj),
215                                sha1_to_hex(p->one->sha1),
216                                sha1_to_hex(p->two->sha1));
217                         continue;
218                 }
219
220                 assert(!hashcmp(mp->obj, obj));
221                 if (is_null_sha1(p->two->sha1)) { /* deletion */
222                         /*
223                          * Either this is a true deletion (1), or it is part
224                          * of an A/D pair (2), or D/A pair (3):
225                          *
226                          * (1) mp->local is uninitialized; set it to null_sha1
227                          * (2) mp->local is not uninitialized; don't touch it
228                          * (3) mp->local is uninitialized; set it to null_sha1
229                          *     (will be overwritten by following addition)
230                          */
231                         if (!hashcmp(mp->local, uninitialized))
232                                 hashclr(mp->local);
233                 } else if (is_null_sha1(p->one->sha1)) { /* addition */
234                         /*
235                          * Either this is a true addition (1), or it is part
236                          * of an A/D pair (2), or D/A pair (3):
237                          *
238                          * (1) mp->local is uninitialized; set to p->two->sha1
239                          * (2) mp->local is uninitialized; set to p->two->sha1
240                          * (3) mp->local is null_sha1;     set to p->two->sha1
241                          */
242                         assert(is_null_sha1(mp->local) ||
243                                !hashcmp(mp->local, uninitialized));
244                         hashcpy(mp->local, p->two->sha1);
245                 } else { /* modification */
246                         /*
247                          * This is a true modification. p->one->sha1 shall
248                          * match mp->base, and mp->local shall be uninitialized.
249                          * Set mp->local to p->two->sha1.
250                          */
251                         assert(!hashcmp(p->one->sha1, mp->base));
252                         assert(!hashcmp(mp->local, uninitialized));
253                         hashcpy(mp->local, p->two->sha1);
254                 }
255                 trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
256                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
257                        sha1_to_hex(mp->local));
258         }
259         diff_flush(&opt);
260         diff_tree_release_paths(&opt);
261 }
262
263 static void check_notes_merge_worktree(struct notes_merge_options *o)
264 {
265         if (!o->has_worktree) {
266                 /*
267                  * Must establish NOTES_MERGE_WORKTREE.
268                  * Abort if NOTES_MERGE_WORKTREE already exists
269                  */
270                 if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
271                         if (advice_resolve_conflict)
272                                 die("You have not concluded your previous "
273                                     "notes merge (%s exists).\nPlease, use "
274                                     "'git notes merge --commit' or 'git notes "
275                                     "merge --abort' to commit/abort the "
276                                     "previous merge before you start a new "
277                                     "notes merge.", git_path("NOTES_MERGE_*"));
278                         else
279                                 die("You have not concluded your notes merge "
280                                     "(%s exists).", git_path("NOTES_MERGE_*"));
281                 }
282
283                 if (safe_create_leading_directories(git_path(
284                                 NOTES_MERGE_WORKTREE "/.test")))
285                         die_errno("unable to create directory %s",
286                                   git_path(NOTES_MERGE_WORKTREE));
287                 o->has_worktree = 1;
288         } else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
289                 /* NOTES_MERGE_WORKTREE should already be established */
290                 die("missing '%s'. This should not happen",
291                     git_path(NOTES_MERGE_WORKTREE));
292 }
293
294 static void write_buf_to_worktree(const unsigned char *obj,
295                                   const char *buf, unsigned long size)
296 {
297         int fd;
298         char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
299         if (safe_create_leading_directories(path))
300                 die_errno("unable to create directory for '%s'", path);
301         if (file_exists(path))
302                 die("found existing file at '%s'", path);
303
304         fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0666);
305         if (fd < 0)
306                 die_errno("failed to open '%s'", path);
307
308         while (size > 0) {
309                 long ret = write_in_full(fd, buf, size);
310                 if (ret < 0) {
311                         /* Ignore epipe */
312                         if (errno == EPIPE)
313                                 break;
314                         die_errno("notes-merge");
315                 } else if (!ret) {
316                         die("notes-merge: disk full?");
317                 }
318                 size -= ret;
319                 buf += ret;
320         }
321
322         close(fd);
323 }
324
325 static void write_note_to_worktree(const unsigned char *obj,
326                                    const unsigned char *note)
327 {
328         enum object_type type;
329         unsigned long size;
330         void *buf = read_sha1_file(note, &type, &size);
331
332         if (!buf)
333                 die("cannot read note %s for object %s",
334                     sha1_to_hex(note), sha1_to_hex(obj));
335         if (type != OBJ_BLOB)
336                 die("blob expected in note %s for object %s",
337                     sha1_to_hex(note), sha1_to_hex(obj));
338         write_buf_to_worktree(obj, buf, size);
339         free(buf);
340 }
341
342 static int ll_merge_in_worktree(struct notes_merge_options *o,
343                                 struct notes_merge_pair *p)
344 {
345         mmbuffer_t result_buf;
346         mmfile_t base, local, remote;
347         int status;
348
349         read_mmblob(&base, p->base);
350         read_mmblob(&local, p->local);
351         read_mmblob(&remote, p->remote);
352
353         status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
354                           &local, o->local_ref, &remote, o->remote_ref, NULL);
355
356         free(base.ptr);
357         free(local.ptr);
358         free(remote.ptr);
359
360         if ((status < 0) || !result_buf.ptr)
361                 die("Failed to execute internal merge");
362
363         write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
364         free(result_buf.ptr);
365
366         return status;
367 }
368
369 static int merge_one_change_manual(struct notes_merge_options *o,
370                                    struct notes_merge_pair *p,
371                                    struct notes_tree *t)
372 {
373         const char *lref = o->local_ref ? o->local_ref : "local version";
374         const char *rref = o->remote_ref ? o->remote_ref : "remote version";
375
376         trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
377                "local = %.7s, remote = %.7s)\n",
378                sha1_to_hex(p->obj), sha1_to_hex(p->base),
379                sha1_to_hex(p->local), sha1_to_hex(p->remote));
380
381         /* add "Conflicts:" section to commit message first time through */
382         if (!o->has_worktree)
383                 strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
384
385         strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
386
387         if (o->verbosity >= 2)
388                 printf("Auto-merging notes for %s\n", sha1_to_hex(p->obj));
389         check_notes_merge_worktree(o);
390         if (is_null_sha1(p->local)) {
391                 /* D/F conflict, checkout p->remote */
392                 assert(!is_null_sha1(p->remote));
393                 if (o->verbosity >= 1)
394                         printf("CONFLICT (delete/modify): Notes for object %s "
395                                 "deleted in %s and modified in %s. Version from %s "
396                                 "left in tree.\n",
397                                 sha1_to_hex(p->obj), lref, rref, rref);
398                 write_note_to_worktree(p->obj, p->remote);
399         } else if (is_null_sha1(p->remote)) {
400                 /* D/F conflict, checkout p->local */
401                 assert(!is_null_sha1(p->local));
402                 if (o->verbosity >= 1)
403                         printf("CONFLICT (delete/modify): Notes for object %s "
404                                 "deleted in %s and modified in %s. Version from %s "
405                                 "left in tree.\n",
406                                 sha1_to_hex(p->obj), rref, lref, lref);
407                 write_note_to_worktree(p->obj, p->local);
408         } else {
409                 /* "regular" conflict, checkout result of ll_merge() */
410                 const char *reason = "content";
411                 if (is_null_sha1(p->base))
412                         reason = "add/add";
413                 assert(!is_null_sha1(p->local));
414                 assert(!is_null_sha1(p->remote));
415                 if (o->verbosity >= 1)
416                         printf("CONFLICT (%s): Merge conflict in notes for "
417                                 "object %s\n", reason, sha1_to_hex(p->obj));
418                 ll_merge_in_worktree(o, p);
419         }
420
421         trace_printf("\t\t\tremoving from partial merge result\n");
422         remove_note(t, p->obj);
423
424         return 1;
425 }
426
427 static int merge_one_change(struct notes_merge_options *o,
428                             struct notes_merge_pair *p, struct notes_tree *t)
429 {
430         /*
431          * Return 0 if change is successfully resolved (stored in notes_tree).
432          * Return 1 is change results in a conflict (NOT stored in notes_tree,
433          * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
434          */
435         switch (o->strategy) {
436         case NOTES_MERGE_RESOLVE_MANUAL:
437                 return merge_one_change_manual(o, p, t);
438         case NOTES_MERGE_RESOLVE_OURS:
439                 if (o->verbosity >= 2)
440                         printf("Using local notes for %s\n",
441                                                 sha1_to_hex(p->obj));
442                 /* nothing to do */
443                 return 0;
444         case NOTES_MERGE_RESOLVE_THEIRS:
445                 if (o->verbosity >= 2)
446                         printf("Using remote notes for %s\n",
447                                                 sha1_to_hex(p->obj));
448                 if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
449                         die("BUG: combine_notes_overwrite failed");
450                 return 0;
451         case NOTES_MERGE_RESOLVE_UNION:
452                 if (o->verbosity >= 2)
453                         printf("Concatenating local and remote notes for %s\n",
454                                                         sha1_to_hex(p->obj));
455                 if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
456                         die("failed to concatenate notes "
457                             "(combine_notes_concatenate)");
458                 return 0;
459         case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
460                 if (o->verbosity >= 2)
461                         printf("Concatenating unique lines in local and remote "
462                                 "notes for %s\n", sha1_to_hex(p->obj));
463                 if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
464                         die("failed to concatenate notes "
465                             "(combine_notes_cat_sort_uniq)");
466                 return 0;
467         }
468         die("Unknown strategy (%i).", o->strategy);
469 }
470
471 static int merge_changes(struct notes_merge_options *o,
472                          struct notes_merge_pair *changes, int *num_changes,
473                          struct notes_tree *t)
474 {
475         int i, conflicts = 0;
476
477         trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
478         for (i = 0; i < *num_changes; i++) {
479                 struct notes_merge_pair *p = changes + i;
480                 trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
481                        sha1_to_hex(p->obj), sha1_to_hex(p->base),
482                        sha1_to_hex(p->local), sha1_to_hex(p->remote));
483
484                 if (!hashcmp(p->base, p->remote)) {
485                         /* no remote change; nothing to do */
486                         trace_printf("\t\t\tskipping (no remote change)\n");
487                 } else if (!hashcmp(p->local, p->remote)) {
488                         /* same change in local and remote; nothing to do */
489                         trace_printf("\t\t\tskipping (local == remote)\n");
490                 } else if (!hashcmp(p->local, uninitialized) ||
491                            !hashcmp(p->local, p->base)) {
492                         /* no local change; adopt remote change */
493                         trace_printf("\t\t\tno local change, adopted remote\n");
494                         if (add_note(t, p->obj, p->remote,
495                                      combine_notes_overwrite))
496                                 die("BUG: combine_notes_overwrite failed");
497                 } else {
498                         /* need file-level merge between local and remote */
499                         trace_printf("\t\t\tneed content-level merge\n");
500                         conflicts += merge_one_change(o, p, t);
501                 }
502         }
503
504         return conflicts;
505 }
506
507 static int merge_from_diffs(struct notes_merge_options *o,
508                             const unsigned char *base,
509                             const unsigned char *local,
510                             const unsigned char *remote, struct notes_tree *t)
511 {
512         struct notes_merge_pair *changes;
513         int num_changes, conflicts;
514
515         trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
516                "remote = %.7s)\n", sha1_to_hex(base), sha1_to_hex(local),
517                sha1_to_hex(remote));
518
519         changes = diff_tree_remote(o, base, remote, &num_changes);
520         diff_tree_local(o, changes, num_changes, base, local);
521
522         conflicts = merge_changes(o, changes, &num_changes, t);
523         free(changes);
524
525         if (o->verbosity >= 4)
526                 printf("Merge result: %i unmerged notes and a %s notes tree\n",
527                         conflicts, t->dirty ? "dirty" : "clean");
528
529         return conflicts ? -1 : 1;
530 }
531
532 void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
533                          const char *msg, unsigned char *result_sha1)
534 {
535         unsigned char tree_sha1[20];
536
537         assert(t->initialized);
538
539         if (write_notes_tree(t, tree_sha1))
540                 die("Failed to write notes tree to database");
541
542         if (!parents) {
543                 /* Deduce parent commit from t->ref */
544                 unsigned char parent_sha1[20];
545                 if (!read_ref(t->ref, parent_sha1)) {
546                         struct commit *parent = lookup_commit(parent_sha1);
547                         if (!parent || parse_commit(parent))
548                                 die("Failed to find/parse commit %s", t->ref);
549                         commit_list_insert(parent, &parents);
550                 }
551                 /* else: t->ref points to nothing, assume root/orphan commit */
552         }
553
554         if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
555                 die("Failed to commit notes tree to database");
556 }
557
558 int notes_merge(struct notes_merge_options *o,
559                 struct notes_tree *local_tree,
560                 unsigned char *result_sha1)
561 {
562         unsigned char local_sha1[20], remote_sha1[20];
563         struct commit *local, *remote;
564         struct commit_list *bases = NULL;
565         const unsigned char *base_sha1, *base_tree_sha1;
566         int result = 0;
567
568         assert(o->local_ref && o->remote_ref);
569         assert(!strcmp(o->local_ref, local_tree->ref));
570         hashclr(result_sha1);
571
572         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
573                o->local_ref, o->remote_ref);
574
575         /* Dereference o->local_ref into local_sha1 */
576         if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
577                 die("Failed to resolve local notes ref '%s'", o->local_ref);
578         else if (!check_refname_format(o->local_ref, 0) &&
579                 is_null_sha1(local_sha1))
580                 local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
581         else if (!(local = lookup_commit_reference(local_sha1)))
582                 die("Could not parse local commit %s (%s)",
583                     sha1_to_hex(local_sha1), o->local_ref);
584         trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
585
586         /* Dereference o->remote_ref into remote_sha1 */
587         if (get_sha1(o->remote_ref, remote_sha1)) {
588                 /*
589                  * Failed to get remote_sha1. If o->remote_ref looks like an
590                  * unborn ref, perform the merge using an empty notes tree.
591                  */
592                 if (!check_refname_format(o->remote_ref, 0)) {
593                         hashclr(remote_sha1);
594                         remote = NULL;
595                 } else {
596                         die("Failed to resolve remote notes ref '%s'",
597                             o->remote_ref);
598                 }
599         } else if (!(remote = lookup_commit_reference(remote_sha1))) {
600                 die("Could not parse remote commit %s (%s)",
601                     sha1_to_hex(remote_sha1), o->remote_ref);
602         }
603         trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
604
605         if (!local && !remote)
606                 die("Cannot merge empty notes ref (%s) into empty notes ref "
607                     "(%s)", o->remote_ref, o->local_ref);
608         if (!local) {
609                 /* result == remote commit */
610                 hashcpy(result_sha1, remote_sha1);
611                 goto found_result;
612         }
613         if (!remote) {
614                 /* result == local commit */
615                 hashcpy(result_sha1, local_sha1);
616                 goto found_result;
617         }
618         assert(local && remote);
619
620         /* Find merge bases */
621         bases = get_merge_bases(local, remote, 1);
622         if (!bases) {
623                 base_sha1 = null_sha1;
624                 base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
625                 if (o->verbosity >= 4)
626                         printf("No merge base found; doing history-less merge\n");
627         } else if (!bases->next) {
628                 base_sha1 = bases->item->object.sha1;
629                 base_tree_sha1 = bases->item->tree->object.sha1;
630                 if (o->verbosity >= 4)
631                         printf("One merge base found (%.7s)\n",
632                                 sha1_to_hex(base_sha1));
633         } else {
634                 /* TODO: How to handle multiple merge-bases? */
635                 base_sha1 = bases->item->object.sha1;
636                 base_tree_sha1 = bases->item->tree->object.sha1;
637                 if (o->verbosity >= 3)
638                         printf("Multiple merge bases found. Using the first "
639                                 "(%.7s)\n", sha1_to_hex(base_sha1));
640         }
641
642         if (o->verbosity >= 4)
643                 printf("Merging remote commit %.7s into local commit %.7s with "
644                         "merge-base %.7s\n", sha1_to_hex(remote->object.sha1),
645                         sha1_to_hex(local->object.sha1),
646                         sha1_to_hex(base_sha1));
647
648         if (!hashcmp(remote->object.sha1, base_sha1)) {
649                 /* Already merged; result == local commit */
650                 if (o->verbosity >= 2)
651                         printf("Already up-to-date!\n");
652                 hashcpy(result_sha1, local->object.sha1);
653                 goto found_result;
654         }
655         if (!hashcmp(local->object.sha1, base_sha1)) {
656                 /* Fast-forward; result == remote commit */
657                 if (o->verbosity >= 2)
658                         printf("Fast-forward\n");
659                 hashcpy(result_sha1, remote->object.sha1);
660                 goto found_result;
661         }
662
663         result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
664                                   remote->tree->object.sha1, local_tree);
665
666         if (result != 0) { /* non-trivial merge (with or without conflicts) */
667                 /* Commit (partial) result */
668                 struct commit_list *parents = NULL;
669                 commit_list_insert(remote, &parents); /* LIFO order */
670                 commit_list_insert(local, &parents);
671                 create_notes_commit(local_tree, parents, o->commit_msg.buf,
672                                     result_sha1);
673         }
674
675 found_result:
676         free_commit_list(bases);
677         strbuf_release(&(o->commit_msg));
678         trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
679                result, sha1_to_hex(result_sha1));
680         return result;
681 }
682
683 int notes_merge_commit(struct notes_merge_options *o,
684                        struct notes_tree *partial_tree,
685                        struct commit *partial_commit,
686                        unsigned char *result_sha1)
687 {
688         /*
689          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
690          * found notes to 'partial_tree'. Write the updates notes tree to
691          * the DB, and commit the resulting tree object while reusing the
692          * commit message and parents from 'partial_commit'.
693          * Finally store the new commit object SHA1 into 'result_sha1'.
694          */
695         struct dir_struct dir;
696         char *path = xstrdup(git_path(NOTES_MERGE_WORKTREE "/"));
697         int path_len = strlen(path), i;
698         const char *msg = strstr(partial_commit->buffer, "\n\n");
699
700         if (o->verbosity >= 3)
701                 printf("Committing notes in notes merge worktree at %.*s\n",
702                         path_len - 1, path);
703
704         if (!msg || msg[2] == '\0')
705                 die("partial notes commit has empty message");
706         msg += 2;
707
708         memset(&dir, 0, sizeof(dir));
709         read_directory(&dir, path, path_len, NULL);
710         for (i = 0; i < dir.nr; i++) {
711                 struct dir_entry *ent = dir.entries[i];
712                 struct stat st;
713                 const char *relpath = ent->name + path_len;
714                 unsigned char obj_sha1[20], blob_sha1[20];
715
716                 if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
717                         if (o->verbosity >= 3)
718                                 printf("Skipping non-SHA1 entry '%s'\n",
719                                                                 ent->name);
720                         continue;
721                 }
722
723                 /* write file as blob, and add to partial_tree */
724                 if (stat(ent->name, &st))
725                         die_errno("Failed to stat '%s'", ent->name);
726                 if (index_path(blob_sha1, ent->name, &st, HASH_WRITE_OBJECT))
727                         die("Failed to write blob object from '%s'", ent->name);
728                 if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
729                         die("Failed to add resolved note '%s' to notes tree",
730                             ent->name);
731                 if (o->verbosity >= 4)
732                         printf("Added resolved note for object %s: %s\n",
733                                 sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
734         }
735
736         create_notes_commit(partial_tree, partial_commit->parents, msg,
737                             result_sha1);
738         if (o->verbosity >= 4)
739                 printf("Finalized notes merge commit: %s\n",
740                         sha1_to_hex(result_sha1));
741         free(path);
742         return 0;
743 }
744
745 int notes_merge_abort(struct notes_merge_options *o)
746 {
747         /* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
748         struct strbuf buf = STRBUF_INIT;
749         int ret;
750
751         strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
752         if (o->verbosity >= 3)
753                 printf("Removing notes merge worktree at %s\n", buf.buf);
754         ret = remove_dir_recursively(&buf, 0);
755         strbuf_release(&buf);
756         return ret;
757 }