Teach --[no-]rerere-autoupdate option to merge, revert and friends
[git] / builtin-merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "parse-options.h"
11 #include "builtin.h"
12 #include "run-command.h"
13 #include "diff.h"
14 #include "refs.h"
15 #include "commit.h"
16 #include "diffcore.h"
17 #include "revision.h"
18 #include "unpack-trees.h"
19 #include "cache-tree.h"
20 #include "dir.h"
21 #include "utf8.h"
22 #include "log-tree.h"
23 #include "color.h"
24 #include "rerere.h"
25 #include "help.h"
26 #include "merge-recursive.h"
27
28 #define DEFAULT_TWOHEAD (1<<0)
29 #define DEFAULT_OCTOPUS (1<<1)
30 #define NO_FAST_FORWARD (1<<2)
31 #define NO_TRIVIAL      (1<<3)
32
33 struct strategy {
34         const char *name;
35         unsigned attr;
36 };
37
38 static const char * const builtin_merge_usage[] = {
39         "git merge [options] <remote>...",
40         "git merge [options] <msg> HEAD <remote>",
41         NULL
42 };
43
44 static int show_diffstat = 1, option_log, squash;
45 static int option_commit = 1, allow_fast_forward = 1;
46 static int fast_forward_only;
47 static int allow_trivial = 1, have_message;
48 static struct strbuf merge_msg;
49 static struct commit_list *remoteheads;
50 static unsigned char head[20], stash[20];
51 static struct strategy **use_strategies;
52 static size_t use_strategies_nr, use_strategies_alloc;
53 static const char *branch;
54 static int verbosity;
55 static int allow_rerere_auto;
56
57 static struct strategy all_strategy[] = {
58         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
59         { "octopus",    DEFAULT_OCTOPUS },
60         { "resolve",    0 },
61         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
62         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
63 };
64
65 static const char *pull_twohead, *pull_octopus;
66
67 static int option_parse_message(const struct option *opt,
68                                 const char *arg, int unset)
69 {
70         struct strbuf *buf = opt->value;
71
72         if (unset)
73                 strbuf_setlen(buf, 0);
74         else if (arg) {
75                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
76                 have_message = 1;
77         } else
78                 return error("switch `m' requires a value");
79         return 0;
80 }
81
82 static struct strategy *get_strategy(const char *name)
83 {
84         int i;
85         struct strategy *ret;
86         static struct cmdnames main_cmds, other_cmds;
87         static int loaded;
88
89         if (!name)
90                 return NULL;
91
92         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
93                 if (!strcmp(name, all_strategy[i].name))
94                         return &all_strategy[i];
95
96         if (!loaded) {
97                 struct cmdnames not_strategies;
98                 loaded = 1;
99
100                 memset(&not_strategies, 0, sizeof(struct cmdnames));
101                 load_command_list("git-merge-", &main_cmds, &other_cmds);
102                 for (i = 0; i < main_cmds.cnt; i++) {
103                         int j, found = 0;
104                         struct cmdname *ent = main_cmds.names[i];
105                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
106                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
107                                                 && !all_strategy[j].name[ent->len])
108                                         found = 1;
109                         if (!found)
110                                 add_cmdname(&not_strategies, ent->name, ent->len);
111                 }
112                 exclude_cmds(&main_cmds, &not_strategies);
113         }
114         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
115                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
116                 fprintf(stderr, "Available strategies are:");
117                 for (i = 0; i < main_cmds.cnt; i++)
118                         fprintf(stderr, " %s", main_cmds.names[i]->name);
119                 fprintf(stderr, ".\n");
120                 if (other_cmds.cnt) {
121                         fprintf(stderr, "Available custom strategies are:");
122                         for (i = 0; i < other_cmds.cnt; i++)
123                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
124                         fprintf(stderr, ".\n");
125                 }
126                 exit(1);
127         }
128
129         ret = xcalloc(1, sizeof(struct strategy));
130         ret->name = xstrdup(name);
131         return ret;
132 }
133
134 static void append_strategy(struct strategy *s)
135 {
136         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
137         use_strategies[use_strategies_nr++] = s;
138 }
139
140 static int option_parse_strategy(const struct option *opt,
141                                  const char *name, int unset)
142 {
143         if (unset)
144                 return 0;
145
146         append_strategy(get_strategy(name));
147         return 0;
148 }
149
150 static int option_parse_n(const struct option *opt,
151                           const char *arg, int unset)
152 {
153         show_diffstat = unset;
154         return 0;
155 }
156
157 static struct option builtin_merge_options[] = {
158         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
159                 "do not show a diffstat at the end of the merge",
160                 PARSE_OPT_NOARG, option_parse_n },
161         OPT_BOOLEAN(0, "stat", &show_diffstat,
162                 "show a diffstat at the end of the merge"),
163         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
164         OPT_BOOLEAN(0, "log", &option_log,
165                 "add list of one-line log to merge commit message"),
166         OPT_BOOLEAN(0, "squash", &squash,
167                 "create a single commit instead of doing a merge"),
168         OPT_BOOLEAN(0, "commit", &option_commit,
169                 "perform a commit if the merge succeeds (default)"),
170         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
171                 "allow fast-forward (default)"),
172         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
173                 "abort if fast-forward is not possible"),
174         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
175         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
176                 "merge strategy to use", option_parse_strategy),
177         OPT_CALLBACK('m', "message", &merge_msg, "message",
178                 "message to be used for the merge commit (if any)",
179                 option_parse_message),
180         OPT__VERBOSITY(&verbosity),
181         OPT_END()
182 };
183
184 /* Cleans up metadata that is uninteresting after a succeeded merge. */
185 static void drop_save(void)
186 {
187         unlink(git_path("MERGE_HEAD"));
188         unlink(git_path("MERGE_MSG"));
189         unlink(git_path("MERGE_MODE"));
190 }
191
192 static void save_state(void)
193 {
194         int len;
195         struct child_process cp;
196         struct strbuf buffer = STRBUF_INIT;
197         const char *argv[] = {"stash", "create", NULL};
198
199         memset(&cp, 0, sizeof(cp));
200         cp.argv = argv;
201         cp.out = -1;
202         cp.git_cmd = 1;
203
204         if (start_command(&cp))
205                 die("could not run stash.");
206         len = strbuf_read(&buffer, cp.out, 1024);
207         close(cp.out);
208
209         if (finish_command(&cp) || len < 0)
210                 die("stash failed");
211         else if (!len)
212                 return;
213         strbuf_setlen(&buffer, buffer.len-1);
214         if (get_sha1(buffer.buf, stash))
215                 die("not a valid object: %s", buffer.buf);
216 }
217
218 static void reset_hard(unsigned const char *sha1, int verbose)
219 {
220         int i = 0;
221         const char *args[6];
222
223         args[i++] = "read-tree";
224         if (verbose)
225                 args[i++] = "-v";
226         args[i++] = "--reset";
227         args[i++] = "-u";
228         args[i++] = sha1_to_hex(sha1);
229         args[i] = NULL;
230
231         if (run_command_v_opt(args, RUN_GIT_CMD))
232                 die("read-tree failed");
233 }
234
235 static void restore_state(void)
236 {
237         struct strbuf sb = STRBUF_INIT;
238         const char *args[] = { "stash", "apply", NULL, NULL };
239
240         if (is_null_sha1(stash))
241                 return;
242
243         reset_hard(head, 1);
244
245         args[2] = sha1_to_hex(stash);
246
247         /*
248          * It is OK to ignore error here, for example when there was
249          * nothing to restore.
250          */
251         run_command_v_opt(args, RUN_GIT_CMD);
252
253         strbuf_release(&sb);
254         refresh_cache(REFRESH_QUIET);
255 }
256
257 /* This is called when no merge was necessary. */
258 static void finish_up_to_date(const char *msg)
259 {
260         if (verbosity >= 0)
261                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
262         drop_save();
263 }
264
265 static void squash_message(void)
266 {
267         struct rev_info rev;
268         struct commit *commit;
269         struct strbuf out = STRBUF_INIT;
270         struct commit_list *j;
271         int fd;
272         struct pretty_print_context ctx = {0};
273
274         printf("Squash commit -- not updating HEAD\n");
275         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
276         if (fd < 0)
277                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
278
279         init_revisions(&rev, NULL);
280         rev.ignore_merges = 1;
281         rev.commit_format = CMIT_FMT_MEDIUM;
282
283         commit = lookup_commit(head);
284         commit->object.flags |= UNINTERESTING;
285         add_pending_object(&rev, &commit->object, NULL);
286
287         for (j = remoteheads; j; j = j->next)
288                 add_pending_object(&rev, &j->item->object, NULL);
289
290         setup_revisions(0, NULL, &rev, NULL);
291         if (prepare_revision_walk(&rev))
292                 die("revision walk setup failed");
293
294         ctx.abbrev = rev.abbrev;
295         ctx.date_mode = rev.date_mode;
296
297         strbuf_addstr(&out, "Squashed commit of the following:\n");
298         while ((commit = get_revision(&rev)) != NULL) {
299                 strbuf_addch(&out, '\n');
300                 strbuf_addf(&out, "commit %s\n",
301                         sha1_to_hex(commit->object.sha1));
302                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
303         }
304         if (write(fd, out.buf, out.len) < 0)
305                 die_errno("Writing SQUASH_MSG");
306         if (close(fd))
307                 die_errno("Finishing SQUASH_MSG");
308         strbuf_release(&out);
309 }
310
311 static void finish(const unsigned char *new_head, const char *msg)
312 {
313         struct strbuf reflog_message = STRBUF_INIT;
314
315         if (!msg)
316                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
317         else {
318                 if (verbosity >= 0)
319                         printf("%s\n", msg);
320                 strbuf_addf(&reflog_message, "%s: %s",
321                         getenv("GIT_REFLOG_ACTION"), msg);
322         }
323         if (squash) {
324                 squash_message();
325         } else {
326                 if (verbosity >= 0 && !merge_msg.len)
327                         printf("No merge message -- not updating HEAD\n");
328                 else {
329                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
330                         update_ref(reflog_message.buf, "HEAD",
331                                 new_head, head, 0,
332                                 DIE_ON_ERR);
333                         /*
334                          * We ignore errors in 'gc --auto', since the
335                          * user should see them.
336                          */
337                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
338                 }
339         }
340         if (new_head && show_diffstat) {
341                 struct diff_options opts;
342                 diff_setup(&opts);
343                 opts.output_format |=
344                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
345                 opts.detect_rename = DIFF_DETECT_RENAME;
346                 if (diff_use_color_default > 0)
347                         DIFF_OPT_SET(&opts, COLOR_DIFF);
348                 if (diff_setup_done(&opts) < 0)
349                         die("diff_setup_done failed");
350                 diff_tree_sha1(head, new_head, "", &opts);
351                 diffcore_std(&opts);
352                 diff_flush(&opts);
353         }
354
355         /* Run a post-merge hook */
356         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
357
358         strbuf_release(&reflog_message);
359 }
360
361 /* Get the name for the merge commit's message. */
362 static void merge_name(const char *remote, struct strbuf *msg)
363 {
364         struct object *remote_head;
365         unsigned char branch_head[20], buf_sha[20];
366         struct strbuf buf = STRBUF_INIT;
367         struct strbuf bname = STRBUF_INIT;
368         const char *ptr;
369         char *found_ref;
370         int len, early;
371
372         strbuf_branchname(&bname, remote);
373         remote = bname.buf;
374
375         memset(branch_head, 0, sizeof(branch_head));
376         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
377         if (!remote_head)
378                 die("'%s' does not point to a commit", remote);
379
380         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
381                 if (!prefixcmp(found_ref, "refs/heads/")) {
382                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
383                                     sha1_to_hex(branch_head), remote);
384                         goto cleanup;
385                 }
386                 if (!prefixcmp(found_ref, "refs/remotes/")) {
387                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
388                                     sha1_to_hex(branch_head), remote);
389                         goto cleanup;
390                 }
391         }
392
393         /* See if remote matches <name>^^^.. or <name>~<number> */
394         for (len = 0, ptr = remote + strlen(remote);
395              remote < ptr && ptr[-1] == '^';
396              ptr--)
397                 len++;
398         if (len)
399                 early = 1;
400         else {
401                 early = 0;
402                 ptr = strrchr(remote, '~');
403                 if (ptr) {
404                         int seen_nonzero = 0;
405
406                         len++; /* count ~ */
407                         while (*++ptr && isdigit(*ptr)) {
408                                 seen_nonzero |= (*ptr != '0');
409                                 len++;
410                         }
411                         if (*ptr)
412                                 len = 0; /* not ...~<number> */
413                         else if (seen_nonzero)
414                                 early = 1;
415                         else if (len == 1)
416                                 early = 1; /* "name~" is "name~1"! */
417                 }
418         }
419         if (len) {
420                 struct strbuf truname = STRBUF_INIT;
421                 strbuf_addstr(&truname, "refs/heads/");
422                 strbuf_addstr(&truname, remote);
423                 strbuf_setlen(&truname, truname.len - len);
424                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
425                         strbuf_addf(msg,
426                                     "%s\t\tbranch '%s'%s of .\n",
427                                     sha1_to_hex(remote_head->sha1),
428                                     truname.buf + 11,
429                                     (early ? " (early part)" : ""));
430                         strbuf_release(&truname);
431                         goto cleanup;
432                 }
433         }
434
435         if (!strcmp(remote, "FETCH_HEAD") &&
436                         !access(git_path("FETCH_HEAD"), R_OK)) {
437                 FILE *fp;
438                 struct strbuf line = STRBUF_INIT;
439                 char *ptr;
440
441                 fp = fopen(git_path("FETCH_HEAD"), "r");
442                 if (!fp)
443                         die_errno("could not open '%s' for reading",
444                                   git_path("FETCH_HEAD"));
445                 strbuf_getline(&line, fp, '\n');
446                 fclose(fp);
447                 ptr = strstr(line.buf, "\tnot-for-merge\t");
448                 if (ptr)
449                         strbuf_remove(&line, ptr-line.buf+1, 13);
450                 strbuf_addbuf(msg, &line);
451                 strbuf_release(&line);
452                 goto cleanup;
453         }
454         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
455                 sha1_to_hex(remote_head->sha1), remote);
456 cleanup:
457         strbuf_release(&buf);
458         strbuf_release(&bname);
459 }
460
461 static int git_merge_config(const char *k, const char *v, void *cb)
462 {
463         if (branch && !prefixcmp(k, "branch.") &&
464                 !prefixcmp(k + 7, branch) &&
465                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
466                 const char **argv;
467                 int argc;
468                 char *buf;
469
470                 buf = xstrdup(v);
471                 argc = split_cmdline(buf, &argv);
472                 if (argc < 0)
473                         die("Bad branch.%s.mergeoptions string", branch);
474                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
475                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
476                 argc++;
477                 parse_options(argc, argv, NULL, builtin_merge_options,
478                               builtin_merge_usage, 0);
479                 free(buf);
480         }
481
482         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
483                 show_diffstat = git_config_bool(k, v);
484         else if (!strcmp(k, "pull.twohead"))
485                 return git_config_string(&pull_twohead, k, v);
486         else if (!strcmp(k, "pull.octopus"))
487                 return git_config_string(&pull_octopus, k, v);
488         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
489                 option_log = git_config_bool(k, v);
490         return git_diff_ui_config(k, v, cb);
491 }
492
493 static int read_tree_trivial(unsigned char *common, unsigned char *head,
494                              unsigned char *one)
495 {
496         int i, nr_trees = 0;
497         struct tree *trees[MAX_UNPACK_TREES];
498         struct tree_desc t[MAX_UNPACK_TREES];
499         struct unpack_trees_options opts;
500
501         memset(&opts, 0, sizeof(opts));
502         opts.head_idx = 2;
503         opts.src_index = &the_index;
504         opts.dst_index = &the_index;
505         opts.update = 1;
506         opts.verbose_update = 1;
507         opts.trivial_merges_only = 1;
508         opts.merge = 1;
509         trees[nr_trees] = parse_tree_indirect(common);
510         if (!trees[nr_trees++])
511                 return -1;
512         trees[nr_trees] = parse_tree_indirect(head);
513         if (!trees[nr_trees++])
514                 return -1;
515         trees[nr_trees] = parse_tree_indirect(one);
516         if (!trees[nr_trees++])
517                 return -1;
518         opts.fn = threeway_merge;
519         cache_tree_free(&active_cache_tree);
520         for (i = 0; i < nr_trees; i++) {
521                 parse_tree(trees[i]);
522                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
523         }
524         if (unpack_trees(nr_trees, t, &opts))
525                 return -1;
526         return 0;
527 }
528
529 static void write_tree_trivial(unsigned char *sha1)
530 {
531         if (write_cache_as_tree(sha1, 0, NULL))
532                 die("git write-tree failed to write a tree");
533 }
534
535 static int try_merge_strategy(const char *strategy, struct commit_list *common,
536                               const char *head_arg)
537 {
538         const char **args;
539         int i = 0, ret;
540         struct commit_list *j;
541         struct strbuf buf = STRBUF_INIT;
542         int index_fd;
543         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
544
545         index_fd = hold_locked_index(lock, 1);
546         refresh_cache(REFRESH_QUIET);
547         if (active_cache_changed &&
548                         (write_cache(index_fd, active_cache, active_nr) ||
549                          commit_locked_index(lock)))
550                 return error("Unable to write index.");
551         rollback_lock_file(lock);
552
553         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
554                 int clean;
555                 struct commit *result;
556                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
557                 int index_fd;
558                 struct commit_list *reversed = NULL;
559                 struct merge_options o;
560
561                 if (remoteheads->next) {
562                         error("Not handling anything other than two heads merge.");
563                         return 2;
564                 }
565
566                 init_merge_options(&o);
567                 if (!strcmp(strategy, "subtree"))
568                         o.subtree_merge = 1;
569
570                 o.branch1 = head_arg;
571                 o.branch2 = remoteheads->item->util;
572
573                 for (j = common; j; j = j->next)
574                         commit_list_insert(j->item, &reversed);
575
576                 index_fd = hold_locked_index(lock, 1);
577                 clean = merge_recursive(&o, lookup_commit(head),
578                                 remoteheads->item, reversed, &result);
579                 if (active_cache_changed &&
580                                 (write_cache(index_fd, active_cache, active_nr) ||
581                                  commit_locked_index(lock)))
582                         die ("unable to write %s", get_index_file());
583                 rollback_lock_file(lock);
584                 return clean ? 0 : 1;
585         } else {
586                 args = xmalloc((4 + commit_list_count(common) +
587                                         commit_list_count(remoteheads)) * sizeof(char *));
588                 strbuf_addf(&buf, "merge-%s", strategy);
589                 args[i++] = buf.buf;
590                 for (j = common; j; j = j->next)
591                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
592                 args[i++] = "--";
593                 args[i++] = head_arg;
594                 for (j = remoteheads; j; j = j->next)
595                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
596                 args[i] = NULL;
597                 ret = run_command_v_opt(args, RUN_GIT_CMD);
598                 strbuf_release(&buf);
599                 i = 1;
600                 for (j = common; j; j = j->next)
601                         free((void *)args[i++]);
602                 i += 2;
603                 for (j = remoteheads; j; j = j->next)
604                         free((void *)args[i++]);
605                 free(args);
606                 discard_cache();
607                 if (read_cache() < 0)
608                         die("failed to read the cache");
609                 return ret;
610         }
611 }
612
613 static void count_diff_files(struct diff_queue_struct *q,
614                              struct diff_options *opt, void *data)
615 {
616         int *count = data;
617
618         (*count) += q->nr;
619 }
620
621 static int count_unmerged_entries(void)
622 {
623         const struct index_state *state = &the_index;
624         int i, ret = 0;
625
626         for (i = 0; i < state->cache_nr; i++)
627                 if (ce_stage(state->cache[i]))
628                         ret++;
629
630         return ret;
631 }
632
633 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
634 {
635         struct tree *trees[MAX_UNPACK_TREES];
636         struct unpack_trees_options opts;
637         struct tree_desc t[MAX_UNPACK_TREES];
638         int i, fd, nr_trees = 0;
639         struct dir_struct dir;
640         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
641
642         refresh_cache(REFRESH_QUIET);
643
644         fd = hold_locked_index(lock_file, 1);
645
646         memset(&trees, 0, sizeof(trees));
647         memset(&opts, 0, sizeof(opts));
648         memset(&t, 0, sizeof(t));
649         memset(&dir, 0, sizeof(dir));
650         dir.flags |= DIR_SHOW_IGNORED;
651         dir.exclude_per_dir = ".gitignore";
652         opts.dir = &dir;
653
654         opts.head_idx = 1;
655         opts.src_index = &the_index;
656         opts.dst_index = &the_index;
657         opts.update = 1;
658         opts.verbose_update = 1;
659         opts.merge = 1;
660         opts.fn = twoway_merge;
661         opts.msgs = get_porcelain_error_msgs();
662
663         trees[nr_trees] = parse_tree_indirect(head);
664         if (!trees[nr_trees++])
665                 return -1;
666         trees[nr_trees] = parse_tree_indirect(remote);
667         if (!trees[nr_trees++])
668                 return -1;
669         for (i = 0; i < nr_trees; i++) {
670                 parse_tree(trees[i]);
671                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
672         }
673         if (unpack_trees(nr_trees, t, &opts))
674                 return -1;
675         if (write_cache(fd, active_cache, active_nr) ||
676                 commit_locked_index(lock_file))
677                 die("unable to write new index file");
678         return 0;
679 }
680
681 static void split_merge_strategies(const char *string, struct strategy **list,
682                                    int *nr, int *alloc)
683 {
684         char *p, *q, *buf;
685
686         if (!string)
687                 return;
688
689         buf = xstrdup(string);
690         q = buf;
691         for (;;) {
692                 p = strchr(q, ' ');
693                 if (!p) {
694                         ALLOC_GROW(*list, *nr + 1, *alloc);
695                         (*list)[(*nr)++].name = xstrdup(q);
696                         free(buf);
697                         return;
698                 } else {
699                         *p = '\0';
700                         ALLOC_GROW(*list, *nr + 1, *alloc);
701                         (*list)[(*nr)++].name = xstrdup(q);
702                         q = ++p;
703                 }
704         }
705 }
706
707 static void add_strategies(const char *string, unsigned attr)
708 {
709         struct strategy *list = NULL;
710         int list_alloc = 0, list_nr = 0, i;
711
712         memset(&list, 0, sizeof(list));
713         split_merge_strategies(string, &list, &list_nr, &list_alloc);
714         if (list) {
715                 for (i = 0; i < list_nr; i++)
716                         append_strategy(get_strategy(list[i].name));
717                 return;
718         }
719         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
720                 if (all_strategy[i].attr & attr)
721                         append_strategy(&all_strategy[i]);
722
723 }
724
725 static int merge_trivial(void)
726 {
727         unsigned char result_tree[20], result_commit[20];
728         struct commit_list *parent = xmalloc(sizeof(*parent));
729
730         write_tree_trivial(result_tree);
731         printf("Wonderful.\n");
732         parent->item = lookup_commit(head);
733         parent->next = xmalloc(sizeof(*parent->next));
734         parent->next->item = remoteheads->item;
735         parent->next->next = NULL;
736         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
737         finish(result_commit, "In-index merge");
738         drop_save();
739         return 0;
740 }
741
742 static int finish_automerge(struct commit_list *common,
743                             unsigned char *result_tree,
744                             const char *wt_strategy)
745 {
746         struct commit_list *parents = NULL, *j;
747         struct strbuf buf = STRBUF_INIT;
748         unsigned char result_commit[20];
749
750         free_commit_list(common);
751         if (allow_fast_forward) {
752                 parents = remoteheads;
753                 commit_list_insert(lookup_commit(head), &parents);
754                 parents = reduce_heads(parents);
755         } else {
756                 struct commit_list **pptr = &parents;
757
758                 pptr = &commit_list_insert(lookup_commit(head),
759                                 pptr)->next;
760                 for (j = remoteheads; j; j = j->next)
761                         pptr = &commit_list_insert(j->item, pptr)->next;
762         }
763         free_commit_list(remoteheads);
764         strbuf_addch(&merge_msg, '\n');
765         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
766         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
767         finish(result_commit, buf.buf);
768         strbuf_release(&buf);
769         drop_save();
770         return 0;
771 }
772
773 static int suggest_conflicts(void)
774 {
775         FILE *fp;
776         int pos;
777
778         fp = fopen(git_path("MERGE_MSG"), "a");
779         if (!fp)
780                 die_errno("Could not open '%s' for writing",
781                           git_path("MERGE_MSG"));
782         fprintf(fp, "\nConflicts:\n");
783         for (pos = 0; pos < active_nr; pos++) {
784                 struct cache_entry *ce = active_cache[pos];
785
786                 if (ce_stage(ce)) {
787                         fprintf(fp, "\t%s\n", ce->name);
788                         while (pos + 1 < active_nr &&
789                                         !strcmp(ce->name,
790                                                 active_cache[pos + 1]->name))
791                                 pos++;
792                 }
793         }
794         fclose(fp);
795         rerere(allow_rerere_auto);
796         printf("Automatic merge failed; "
797                         "fix conflicts and then commit the result.\n");
798         return 1;
799 }
800
801 static const char deprecation_warning[] =
802         "'git merge <msg> HEAD <commit>' is deprecated. Please update\n"
803         "your script to use 'git merge -m <msg> <commit>' instead.\n"
804         "In future versions of git, this syntax will be removed.";
805
806 static struct commit *is_old_style_invocation(int argc, const char **argv)
807 {
808         struct commit *second_token = NULL;
809         if (argc > 2) {
810                 unsigned char second_sha1[20];
811
812                 if (get_sha1(argv[1], second_sha1))
813                         return NULL;
814                 second_token = lookup_commit_reference_gently(second_sha1, 0);
815                 if (!second_token)
816                         die("'%s' is not a commit", argv[1]);
817                 if (hashcmp(second_token->object.sha1, head))
818                         return NULL;
819                 warning(deprecation_warning);
820         }
821         return second_token;
822 }
823
824 static int evaluate_result(void)
825 {
826         int cnt = 0;
827         struct rev_info rev;
828
829         /* Check how many files differ. */
830         init_revisions(&rev, "");
831         setup_revisions(0, NULL, &rev, NULL);
832         rev.diffopt.output_format |=
833                 DIFF_FORMAT_CALLBACK;
834         rev.diffopt.format_callback = count_diff_files;
835         rev.diffopt.format_callback_data = &cnt;
836         run_diff_files(&rev, 0);
837
838         /*
839          * Check how many unmerged entries are
840          * there.
841          */
842         cnt += count_unmerged_entries();
843
844         return cnt;
845 }
846
847 int cmd_merge(int argc, const char **argv, const char *prefix)
848 {
849         unsigned char result_tree[20];
850         struct strbuf buf = STRBUF_INIT;
851         const char *head_arg;
852         int flag, head_invalid = 0, i;
853         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
854         struct commit_list *common = NULL;
855         const char *best_strategy = NULL, *wt_strategy = NULL;
856         struct commit_list **remotes = &remoteheads;
857
858         if (file_exists(git_path("MERGE_HEAD")))
859                 die("You have not concluded your merge. (MERGE_HEAD exists)");
860         if (read_cache_unmerged())
861                 die("You are in the middle of a conflicted merge."
862                                 " (index unmerged)");
863
864         /*
865          * Check if we are _not_ on a detached HEAD, i.e. if there is a
866          * current branch.
867          */
868         branch = resolve_ref("HEAD", head, 0, &flag);
869         if (branch && !prefixcmp(branch, "refs/heads/"))
870                 branch += 11;
871         if (is_null_sha1(head))
872                 head_invalid = 1;
873
874         git_config(git_merge_config, NULL);
875
876         /* for color.ui */
877         if (diff_use_color_default == -1)
878                 diff_use_color_default = git_use_color_default;
879
880         argc = parse_options(argc, argv, prefix, builtin_merge_options,
881                         builtin_merge_usage, 0);
882         if (verbosity < 0)
883                 show_diffstat = 0;
884
885         if (squash) {
886                 if (!allow_fast_forward)
887                         die("You cannot combine --squash with --no-ff.");
888                 option_commit = 0;
889         }
890
891         if (!allow_fast_forward && fast_forward_only)
892                 die("You cannot combine --no-ff with --ff-only.");
893
894         if (!argc)
895                 usage_with_options(builtin_merge_usage,
896                         builtin_merge_options);
897
898         /*
899          * This could be traditional "merge <msg> HEAD <commit>..."  and
900          * the way we can tell it is to see if the second token is HEAD,
901          * but some people might have misused the interface and used a
902          * committish that is the same as HEAD there instead.
903          * Traditional format never would have "-m" so it is an
904          * additional safety measure to check for it.
905          */
906
907         if (!have_message && is_old_style_invocation(argc, argv)) {
908                 strbuf_addstr(&merge_msg, argv[0]);
909                 head_arg = argv[1];
910                 argv += 2;
911                 argc -= 2;
912         } else if (head_invalid) {
913                 struct object *remote_head;
914                 /*
915                  * If the merged head is a valid one there is no reason
916                  * to forbid "git merge" into a branch yet to be born.
917                  * We do the same for "git pull".
918                  */
919                 if (argc != 1)
920                         die("Can merge only exactly one commit into "
921                                 "empty head");
922                 if (squash)
923                         die("Squash commit into empty head not supported yet");
924                 if (!allow_fast_forward)
925                         die("Non-fast-forward commit does not make sense into "
926                             "an empty head");
927                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
928                 if (!remote_head)
929                         die("%s - not something we can merge", argv[0]);
930                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
931                                 DIE_ON_ERR);
932                 reset_hard(remote_head->sha1, 0);
933                 return 0;
934         } else {
935                 struct strbuf msg = STRBUF_INIT;
936
937                 /* We are invoked directly as the first-class UI. */
938                 head_arg = "HEAD";
939
940                 /*
941                  * All the rest are the commits being merged;
942                  * prepare the standard merge summary message to
943                  * be appended to the given message.  If remote
944                  * is invalid we will die later in the common
945                  * codepath so we discard the error in this
946                  * loop.
947                  */
948                 if (!have_message) {
949                         for (i = 0; i < argc; i++)
950                                 merge_name(argv[i], &msg);
951                         fmt_merge_msg(option_log, &msg, &merge_msg);
952                         if (merge_msg.len)
953                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
954                 }
955         }
956
957         if (head_invalid || !argc)
958                 usage_with_options(builtin_merge_usage,
959                         builtin_merge_options);
960
961         strbuf_addstr(&buf, "merge");
962         for (i = 0; i < argc; i++)
963                 strbuf_addf(&buf, " %s", argv[i]);
964         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
965         strbuf_reset(&buf);
966
967         for (i = 0; i < argc; i++) {
968                 struct object *o;
969                 struct commit *commit;
970
971                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
972                 if (!o)
973                         die("%s - not something we can merge", argv[i]);
974                 commit = lookup_commit(o->sha1);
975                 commit->util = (void *)argv[i];
976                 remotes = &commit_list_insert(commit, remotes)->next;
977
978                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
979                 setenv(buf.buf, argv[i], 1);
980                 strbuf_reset(&buf);
981         }
982
983         if (!use_strategies) {
984                 if (!remoteheads->next)
985                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
986                 else
987                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
988         }
989
990         for (i = 0; i < use_strategies_nr; i++) {
991                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
992                         allow_fast_forward = 0;
993                 if (use_strategies[i]->attr & NO_TRIVIAL)
994                         allow_trivial = 0;
995         }
996
997         if (!remoteheads->next)
998                 common = get_merge_bases(lookup_commit(head),
999                                 remoteheads->item, 1);
1000         else {
1001                 struct commit_list *list = remoteheads;
1002                 commit_list_insert(lookup_commit(head), &list);
1003                 common = get_octopus_merge_bases(list);
1004                 free(list);
1005         }
1006
1007         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1008                 DIE_ON_ERR);
1009
1010         if (!common)
1011                 ; /* No common ancestors found. We need a real merge. */
1012         else if (!remoteheads->next && !common->next &&
1013                         common->item == remoteheads->item) {
1014                 /*
1015                  * If head can reach all the merge then we are up to date.
1016                  * but first the most common case of merging one remote.
1017                  */
1018                 finish_up_to_date("Already up-to-date.");
1019                 return 0;
1020         } else if (allow_fast_forward && !remoteheads->next &&
1021                         !common->next &&
1022                         !hashcmp(common->item->object.sha1, head)) {
1023                 /* Again the most common case of merging one remote. */
1024                 struct strbuf msg = STRBUF_INIT;
1025                 struct object *o;
1026                 char hex[41];
1027
1028                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1029
1030                 if (verbosity >= 0)
1031                         printf("Updating %s..%s\n",
1032                                 hex,
1033                                 find_unique_abbrev(remoteheads->item->object.sha1,
1034                                 DEFAULT_ABBREV));
1035                 strbuf_addstr(&msg, "Fast-forward");
1036                 if (have_message)
1037                         strbuf_addstr(&msg,
1038                                 " (no commit created; -m option ignored)");
1039                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1040                         0, NULL, OBJ_COMMIT);
1041                 if (!o)
1042                         return 1;
1043
1044                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1045                         return 1;
1046
1047                 finish(o->sha1, msg.buf);
1048                 drop_save();
1049                 return 0;
1050         } else if (!remoteheads->next && common->next)
1051                 ;
1052                 /*
1053                  * We are not doing octopus and not fast-forward.  Need
1054                  * a real merge.
1055                  */
1056         else if (!remoteheads->next && !common->next && option_commit) {
1057                 /*
1058                  * We are not doing octopus, not fast-forward, and have
1059                  * only one common.
1060                  */
1061                 refresh_cache(REFRESH_QUIET);
1062                 if (allow_trivial && !fast_forward_only) {
1063                         /* See if it is really trivial. */
1064                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1065                         printf("Trying really trivial in-index merge...\n");
1066                         if (!read_tree_trivial(common->item->object.sha1,
1067                                         head, remoteheads->item->object.sha1))
1068                                 return merge_trivial();
1069                         printf("Nope.\n");
1070                 }
1071         } else {
1072                 /*
1073                  * An octopus.  If we can reach all the remote we are up
1074                  * to date.
1075                  */
1076                 int up_to_date = 1;
1077                 struct commit_list *j;
1078
1079                 for (j = remoteheads; j; j = j->next) {
1080                         struct commit_list *common_one;
1081
1082                         /*
1083                          * Here we *have* to calculate the individual
1084                          * merge_bases again, otherwise "git merge HEAD^
1085                          * HEAD^^" would be missed.
1086                          */
1087                         common_one = get_merge_bases(lookup_commit(head),
1088                                 j->item, 1);
1089                         if (hashcmp(common_one->item->object.sha1,
1090                                 j->item->object.sha1)) {
1091                                 up_to_date = 0;
1092                                 break;
1093                         }
1094                 }
1095                 if (up_to_date) {
1096                         finish_up_to_date("Already up-to-date. Yeeah!");
1097                         return 0;
1098                 }
1099         }
1100
1101         if (fast_forward_only)
1102                 die("Not possible to fast-forward, aborting.");
1103
1104         /* We are going to make a new commit. */
1105         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1106
1107         /*
1108          * At this point, we need a real merge.  No matter what strategy
1109          * we use, it would operate on the index, possibly affecting the
1110          * working tree, and when resolved cleanly, have the desired
1111          * tree in the index -- this means that the index must be in
1112          * sync with the head commit.  The strategies are responsible
1113          * to ensure this.
1114          */
1115         if (use_strategies_nr != 1) {
1116                 /*
1117                  * Stash away the local changes so that we can try more
1118                  * than one.
1119                  */
1120                 save_state();
1121         } else {
1122                 memcpy(stash, null_sha1, 20);
1123         }
1124
1125         for (i = 0; i < use_strategies_nr; i++) {
1126                 int ret;
1127                 if (i) {
1128                         printf("Rewinding the tree to pristine...\n");
1129                         restore_state();
1130                 }
1131                 if (use_strategies_nr != 1)
1132                         printf("Trying merge strategy %s...\n",
1133                                 use_strategies[i]->name);
1134                 /*
1135                  * Remember which strategy left the state in the working
1136                  * tree.
1137                  */
1138                 wt_strategy = use_strategies[i]->name;
1139
1140                 ret = try_merge_strategy(use_strategies[i]->name,
1141                         common, head_arg);
1142                 if (!option_commit && !ret) {
1143                         merge_was_ok = 1;
1144                         /*
1145                          * This is necessary here just to avoid writing
1146                          * the tree, but later we will *not* exit with
1147                          * status code 1 because merge_was_ok is set.
1148                          */
1149                         ret = 1;
1150                 }
1151
1152                 if (ret) {
1153                         /*
1154                          * The backend exits with 1 when conflicts are
1155                          * left to be resolved, with 2 when it does not
1156                          * handle the given merge at all.
1157                          */
1158                         if (ret == 1) {
1159                                 int cnt = evaluate_result();
1160
1161                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1162                                         best_strategy = use_strategies[i]->name;
1163                                         best_cnt = cnt;
1164                                 }
1165                         }
1166                         if (merge_was_ok)
1167                                 break;
1168                         else
1169                                 continue;
1170                 }
1171
1172                 /* Automerge succeeded. */
1173                 write_tree_trivial(result_tree);
1174                 automerge_was_ok = 1;
1175                 break;
1176         }
1177
1178         /*
1179          * If we have a resulting tree, that means the strategy module
1180          * auto resolved the merge cleanly.
1181          */
1182         if (automerge_was_ok)
1183                 return finish_automerge(common, result_tree, wt_strategy);
1184
1185         /*
1186          * Pick the result from the best strategy and have the user fix
1187          * it up.
1188          */
1189         if (!best_strategy) {
1190                 restore_state();
1191                 if (use_strategies_nr > 1)
1192                         fprintf(stderr,
1193                                 "No merge strategy handled the merge.\n");
1194                 else
1195                         fprintf(stderr, "Merge with strategy %s failed.\n",
1196                                 use_strategies[0]->name);
1197                 return 2;
1198         } else if (best_strategy == wt_strategy)
1199                 ; /* We already have its result in the working tree. */
1200         else {
1201                 printf("Rewinding the tree to pristine...\n");
1202                 restore_state();
1203                 printf("Using the %s to prepare resolving by hand.\n",
1204                         best_strategy);
1205                 try_merge_strategy(best_strategy, common, head_arg);
1206         }
1207
1208         if (squash)
1209                 finish(NULL, NULL);
1210         else {
1211                 int fd;
1212                 struct commit_list *j;
1213
1214                 for (j = remoteheads; j; j = j->next)
1215                         strbuf_addf(&buf, "%s\n",
1216                                 sha1_to_hex(j->item->object.sha1));
1217                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1218                 if (fd < 0)
1219                         die_errno("Could not open '%s' for writing",
1220                                   git_path("MERGE_HEAD"));
1221                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1222                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1223                 close(fd);
1224                 strbuf_addch(&merge_msg, '\n');
1225                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1226                 if (fd < 0)
1227                         die_errno("Could not open '%s' for writing",
1228                                   git_path("MERGE_MSG"));
1229                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1230                         merge_msg.len)
1231                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1232                 close(fd);
1233                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1234                 if (fd < 0)
1235                         die_errno("Could not open '%s' for writing",
1236                                   git_path("MERGE_MODE"));
1237                 strbuf_reset(&buf);
1238                 if (!allow_fast_forward)
1239                         strbuf_addf(&buf, "no-ff");
1240                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1241                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1242                 close(fd);
1243         }
1244
1245         if (merge_was_ok) {
1246                 fprintf(stderr, "Automatic merge went well; "
1247                         "stopped before committing as requested\n");
1248                 return 0;
1249         } else
1250                 return suggest_conflicts();
1251 }