Merge branch 'bb/doc-eol-dirty'
[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 "config.h"
11 #include "parse-options.h"
12 #include "builtin.h"
13 #include "lockfile.h"
14 #include "run-command.h"
15 #include "diff.h"
16 #include "refs.h"
17 #include "commit.h"
18 #include "diffcore.h"
19 #include "revision.h"
20 #include "unpack-trees.h"
21 #include "cache-tree.h"
22 #include "dir.h"
23 #include "utf8.h"
24 #include "log-tree.h"
25 #include "color.h"
26 #include "rerere.h"
27 #include "help.h"
28 #include "merge-recursive.h"
29 #include "resolve-undo.h"
30 #include "remote.h"
31 #include "fmt-merge-msg.h"
32 #include "gpg-interface.h"
33 #include "sequencer.h"
34 #include "string-list.h"
35 #include "packfile.h"
36
37 #define DEFAULT_TWOHEAD (1<<0)
38 #define DEFAULT_OCTOPUS (1<<1)
39 #define NO_FAST_FORWARD (1<<2)
40 #define NO_TRIVIAL      (1<<3)
41
42 struct strategy {
43         const char *name;
44         unsigned attr;
45 };
46
47 static const char * const builtin_merge_usage[] = {
48         N_("git merge [<options>] [<commit>...]"),
49         N_("git merge --abort"),
50         N_("git merge --continue"),
51         NULL
52 };
53
54 static int show_diffstat = 1, shortlog_len = -1, squash;
55 static int option_commit = 1;
56 static int option_edit = -1;
57 static int allow_trivial = 1, have_message, verify_signatures;
58 static int overwrite_ignore = 1;
59 static struct strbuf merge_msg = STRBUF_INIT;
60 static struct strategy **use_strategies;
61 static size_t use_strategies_nr, use_strategies_alloc;
62 static const char **xopts;
63 static size_t xopts_nr, xopts_alloc;
64 static const char *branch;
65 static char *branch_mergeoptions;
66 static int option_renormalize;
67 static int verbosity;
68 static int allow_rerere_auto;
69 static int abort_current_merge;
70 static int continue_current_merge;
71 static int allow_unrelated_histories;
72 static int show_progress = -1;
73 static int default_to_upstream = 1;
74 static int signoff;
75 static const char *sign_commit;
76
77 static struct strategy all_strategy[] = {
78         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
79         { "octopus",    DEFAULT_OCTOPUS },
80         { "resolve",    0 },
81         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
82         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
83 };
84
85 static const char *pull_twohead, *pull_octopus;
86
87 enum ff_type {
88         FF_NO,
89         FF_ALLOW,
90         FF_ONLY
91 };
92
93 static enum ff_type fast_forward = FF_ALLOW;
94
95 static int option_parse_message(const struct option *opt,
96                                 const char *arg, int unset)
97 {
98         struct strbuf *buf = opt->value;
99
100         if (unset)
101                 strbuf_setlen(buf, 0);
102         else if (arg) {
103                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
104                 have_message = 1;
105         } else
106                 return error(_("switch `m' requires a value"));
107         return 0;
108 }
109
110 static struct strategy *get_strategy(const char *name)
111 {
112         int i;
113         struct strategy *ret;
114         static struct cmdnames main_cmds, other_cmds;
115         static int loaded;
116
117         if (!name)
118                 return NULL;
119
120         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
121                 if (!strcmp(name, all_strategy[i].name))
122                         return &all_strategy[i];
123
124         if (!loaded) {
125                 struct cmdnames not_strategies;
126                 loaded = 1;
127
128                 memset(&not_strategies, 0, sizeof(struct cmdnames));
129                 load_command_list("git-merge-", &main_cmds, &other_cmds);
130                 for (i = 0; i < main_cmds.cnt; i++) {
131                         int j, found = 0;
132                         struct cmdname *ent = main_cmds.names[i];
133                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
134                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
135                                                 && !all_strategy[j].name[ent->len])
136                                         found = 1;
137                         if (!found)
138                                 add_cmdname(&not_strategies, ent->name, ent->len);
139                 }
140                 exclude_cmds(&main_cmds, &not_strategies);
141         }
142         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
143                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
144                 fprintf(stderr, _("Available strategies are:"));
145                 for (i = 0; i < main_cmds.cnt; i++)
146                         fprintf(stderr, " %s", main_cmds.names[i]->name);
147                 fprintf(stderr, ".\n");
148                 if (other_cmds.cnt) {
149                         fprintf(stderr, _("Available custom strategies are:"));
150                         for (i = 0; i < other_cmds.cnt; i++)
151                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
152                         fprintf(stderr, ".\n");
153                 }
154                 exit(1);
155         }
156
157         ret = xcalloc(1, sizeof(struct strategy));
158         ret->name = xstrdup(name);
159         ret->attr = NO_TRIVIAL;
160         return ret;
161 }
162
163 static void append_strategy(struct strategy *s)
164 {
165         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
166         use_strategies[use_strategies_nr++] = s;
167 }
168
169 static int option_parse_strategy(const struct option *opt,
170                                  const char *name, int unset)
171 {
172         if (unset)
173                 return 0;
174
175         append_strategy(get_strategy(name));
176         return 0;
177 }
178
179 static int option_parse_x(const struct option *opt,
180                           const char *arg, int unset)
181 {
182         if (unset)
183                 return 0;
184
185         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
186         xopts[xopts_nr++] = xstrdup(arg);
187         return 0;
188 }
189
190 static int option_parse_n(const struct option *opt,
191                           const char *arg, int unset)
192 {
193         show_diffstat = unset;
194         return 0;
195 }
196
197 static struct option builtin_merge_options[] = {
198         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
199                 N_("do not show a diffstat at the end of the merge"),
200                 PARSE_OPT_NOARG, option_parse_n },
201         OPT_BOOL(0, "stat", &show_diffstat,
202                 N_("show a diffstat at the end of the merge")),
203         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
204         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
205           N_("add (at most <n>) entries from shortlog to merge commit message"),
206           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
207         OPT_BOOL(0, "squash", &squash,
208                 N_("create a single commit instead of doing a merge")),
209         OPT_BOOL(0, "commit", &option_commit,
210                 N_("perform a commit if the merge succeeds (default)")),
211         OPT_BOOL('e', "edit", &option_edit,
212                 N_("edit message before committing")),
213         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
214         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
215                 N_("abort if fast-forward is not possible"),
216                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
217         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
218         OPT_BOOL(0, "verify-signatures", &verify_signatures,
219                 N_("verify that the named commit has a valid GPG signature")),
220         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
221                 N_("merge strategy to use"), option_parse_strategy),
222         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
223                 N_("option for selected merge strategy"), option_parse_x),
224         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
225                 N_("merge commit message (for a non-fast-forward merge)"),
226                 option_parse_message),
227         OPT__VERBOSITY(&verbosity),
228         OPT_BOOL(0, "abort", &abort_current_merge,
229                 N_("abort the current in-progress merge")),
230         OPT_BOOL(0, "continue", &continue_current_merge,
231                 N_("continue the current in-progress merge")),
232         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
233                  N_("allow merging unrelated histories")),
234         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
235         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
236           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
237         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
238         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
239         OPT_END()
240 };
241
242 /* Cleans up metadata that is uninteresting after a succeeded merge. */
243 static void drop_save(void)
244 {
245         unlink(git_path_merge_head());
246         unlink(git_path_merge_msg());
247         unlink(git_path_merge_mode());
248 }
249
250 static int save_state(struct object_id *stash)
251 {
252         int len;
253         struct child_process cp = CHILD_PROCESS_INIT;
254         struct strbuf buffer = STRBUF_INIT;
255         const char *argv[] = {"stash", "create", NULL};
256
257         cp.argv = argv;
258         cp.out = -1;
259         cp.git_cmd = 1;
260
261         if (start_command(&cp))
262                 die(_("could not run stash."));
263         len = strbuf_read(&buffer, cp.out, 1024);
264         close(cp.out);
265
266         if (finish_command(&cp) || len < 0)
267                 die(_("stash failed"));
268         else if (!len)          /* no changes */
269                 return -1;
270         strbuf_setlen(&buffer, buffer.len-1);
271         if (get_oid(buffer.buf, stash))
272                 die(_("not a valid object: %s"), buffer.buf);
273         return 0;
274 }
275
276 static void read_empty(unsigned const char *sha1, int verbose)
277 {
278         int i = 0;
279         const char *args[7];
280
281         args[i++] = "read-tree";
282         if (verbose)
283                 args[i++] = "-v";
284         args[i++] = "-m";
285         args[i++] = "-u";
286         args[i++] = EMPTY_TREE_SHA1_HEX;
287         args[i++] = sha1_to_hex(sha1);
288         args[i] = NULL;
289
290         if (run_command_v_opt(args, RUN_GIT_CMD))
291                 die(_("read-tree failed"));
292 }
293
294 static void reset_hard(unsigned const char *sha1, int verbose)
295 {
296         int i = 0;
297         const char *args[6];
298
299         args[i++] = "read-tree";
300         if (verbose)
301                 args[i++] = "-v";
302         args[i++] = "--reset";
303         args[i++] = "-u";
304         args[i++] = sha1_to_hex(sha1);
305         args[i] = NULL;
306
307         if (run_command_v_opt(args, RUN_GIT_CMD))
308                 die(_("read-tree failed"));
309 }
310
311 static void restore_state(const struct object_id *head,
312                           const struct object_id *stash)
313 {
314         struct strbuf sb = STRBUF_INIT;
315         const char *args[] = { "stash", "apply", NULL, NULL };
316
317         if (is_null_oid(stash))
318                 return;
319
320         reset_hard(head->hash, 1);
321
322         args[2] = oid_to_hex(stash);
323
324         /*
325          * It is OK to ignore error here, for example when there was
326          * nothing to restore.
327          */
328         run_command_v_opt(args, RUN_GIT_CMD);
329
330         strbuf_release(&sb);
331         refresh_cache(REFRESH_QUIET);
332 }
333
334 /* This is called when no merge was necessary. */
335 static void finish_up_to_date(const char *msg)
336 {
337         if (verbosity >= 0)
338                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
339         drop_save();
340 }
341
342 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
343 {
344         struct rev_info rev;
345         struct strbuf out = STRBUF_INIT;
346         struct commit_list *j;
347         struct pretty_print_context ctx = {0};
348
349         printf(_("Squash commit -- not updating HEAD\n"));
350
351         init_revisions(&rev, NULL);
352         rev.ignore_merges = 1;
353         rev.commit_format = CMIT_FMT_MEDIUM;
354
355         commit->object.flags |= UNINTERESTING;
356         add_pending_object(&rev, &commit->object, NULL);
357
358         for (j = remoteheads; j; j = j->next)
359                 add_pending_object(&rev, &j->item->object, NULL);
360
361         setup_revisions(0, NULL, &rev, NULL);
362         if (prepare_revision_walk(&rev))
363                 die(_("revision walk setup failed"));
364
365         ctx.abbrev = rev.abbrev;
366         ctx.date_mode = rev.date_mode;
367         ctx.fmt = rev.commit_format;
368
369         strbuf_addstr(&out, "Squashed commit of the following:\n");
370         while ((commit = get_revision(&rev)) != NULL) {
371                 strbuf_addch(&out, '\n');
372                 strbuf_addf(&out, "commit %s\n",
373                         oid_to_hex(&commit->object.oid));
374                 pretty_print_commit(&ctx, commit, &out);
375         }
376         write_file_buf(git_path_squash_msg(), out.buf, out.len);
377         strbuf_release(&out);
378 }
379
380 static void finish(struct commit *head_commit,
381                    struct commit_list *remoteheads,
382                    const struct object_id *new_head, const char *msg)
383 {
384         struct strbuf reflog_message = STRBUF_INIT;
385         const struct object_id *head = &head_commit->object.oid;
386
387         if (!msg)
388                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
389         else {
390                 if (verbosity >= 0)
391                         printf("%s\n", msg);
392                 strbuf_addf(&reflog_message, "%s: %s",
393                         getenv("GIT_REFLOG_ACTION"), msg);
394         }
395         if (squash) {
396                 squash_message(head_commit, remoteheads);
397         } else {
398                 if (verbosity >= 0 && !merge_msg.len)
399                         printf(_("No merge message -- not updating HEAD\n"));
400                 else {
401                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
402                         update_ref(reflog_message.buf, "HEAD",
403                                 new_head->hash, head->hash, 0,
404                                 UPDATE_REFS_DIE_ON_ERR);
405                         /*
406                          * We ignore errors in 'gc --auto', since the
407                          * user should see them.
408                          */
409                         close_all_packs();
410                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
411                 }
412         }
413         if (new_head && show_diffstat) {
414                 struct diff_options opts;
415                 diff_setup(&opts);
416                 opts.stat_width = -1; /* use full terminal width */
417                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
418                 opts.output_format |=
419                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
420                 opts.detect_rename = DIFF_DETECT_RENAME;
421                 diff_setup_done(&opts);
422                 diff_tree_oid(head, new_head, "", &opts);
423                 diffcore_std(&opts);
424                 diff_flush(&opts);
425         }
426
427         /* Run a post-merge hook */
428         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
429
430         strbuf_release(&reflog_message);
431 }
432
433 /* Get the name for the merge commit's message. */
434 static void merge_name(const char *remote, struct strbuf *msg)
435 {
436         struct commit *remote_head;
437         struct object_id branch_head;
438         struct strbuf buf = STRBUF_INIT;
439         struct strbuf bname = STRBUF_INIT;
440         const char *ptr;
441         char *found_ref;
442         int len, early;
443
444         strbuf_branchname(&bname, remote, 0);
445         remote = bname.buf;
446
447         oidclr(&branch_head);
448         remote_head = get_merge_parent(remote);
449         if (!remote_head)
450                 die(_("'%s' does not point to a commit"), remote);
451
452         if (dwim_ref(remote, strlen(remote), branch_head.hash, &found_ref) > 0) {
453                 if (starts_with(found_ref, "refs/heads/")) {
454                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
455                                     oid_to_hex(&branch_head), remote);
456                         goto cleanup;
457                 }
458                 if (starts_with(found_ref, "refs/tags/")) {
459                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
460                                     oid_to_hex(&branch_head), remote);
461                         goto cleanup;
462                 }
463                 if (starts_with(found_ref, "refs/remotes/")) {
464                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
465                                     oid_to_hex(&branch_head), remote);
466                         goto cleanup;
467                 }
468         }
469
470         /* See if remote matches <name>^^^.. or <name>~<number> */
471         for (len = 0, ptr = remote + strlen(remote);
472              remote < ptr && ptr[-1] == '^';
473              ptr--)
474                 len++;
475         if (len)
476                 early = 1;
477         else {
478                 early = 0;
479                 ptr = strrchr(remote, '~');
480                 if (ptr) {
481                         int seen_nonzero = 0;
482
483                         len++; /* count ~ */
484                         while (*++ptr && isdigit(*ptr)) {
485                                 seen_nonzero |= (*ptr != '0');
486                                 len++;
487                         }
488                         if (*ptr)
489                                 len = 0; /* not ...~<number> */
490                         else if (seen_nonzero)
491                                 early = 1;
492                         else if (len == 1)
493                                 early = 1; /* "name~" is "name~1"! */
494                 }
495         }
496         if (len) {
497                 struct strbuf truname = STRBUF_INIT;
498                 strbuf_addf(&truname, "refs/heads/%s", remote);
499                 strbuf_setlen(&truname, truname.len - len);
500                 if (ref_exists(truname.buf)) {
501                         strbuf_addf(msg,
502                                     "%s\t\tbranch '%s'%s of .\n",
503                                     oid_to_hex(&remote_head->object.oid),
504                                     truname.buf + 11,
505                                     (early ? " (early part)" : ""));
506                         strbuf_release(&truname);
507                         goto cleanup;
508                 }
509                 strbuf_release(&truname);
510         }
511
512         if (remote_head->util) {
513                 struct merge_remote_desc *desc;
514                 desc = merge_remote_util(remote_head);
515                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
516                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
517                                     oid_to_hex(&desc->obj->oid),
518                                     typename(desc->obj->type),
519                                     remote);
520                         goto cleanup;
521                 }
522         }
523
524         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
525                 oid_to_hex(&remote_head->object.oid), remote);
526 cleanup:
527         strbuf_release(&buf);
528         strbuf_release(&bname);
529 }
530
531 static void parse_branch_merge_options(char *bmo)
532 {
533         const char **argv;
534         int argc;
535
536         if (!bmo)
537                 return;
538         argc = split_cmdline(bmo, &argv);
539         if (argc < 0)
540                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
541                     split_cmdline_strerror(argc));
542         REALLOC_ARRAY(argv, argc + 2);
543         MOVE_ARRAY(argv + 1, argv, argc + 1);
544         argc++;
545         argv[0] = "branch.*.mergeoptions";
546         parse_options(argc, argv, NULL, builtin_merge_options,
547                       builtin_merge_usage, 0);
548         free(argv);
549 }
550
551 static int git_merge_config(const char *k, const char *v, void *cb)
552 {
553         int status;
554
555         if (branch && starts_with(k, "branch.") &&
556                 starts_with(k + 7, branch) &&
557                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
558                 free(branch_mergeoptions);
559                 branch_mergeoptions = xstrdup(v);
560                 return 0;
561         }
562
563         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
564                 show_diffstat = git_config_bool(k, v);
565         else if (!strcmp(k, "pull.twohead"))
566                 return git_config_string(&pull_twohead, k, v);
567         else if (!strcmp(k, "pull.octopus"))
568                 return git_config_string(&pull_octopus, k, v);
569         else if (!strcmp(k, "merge.renormalize"))
570                 option_renormalize = git_config_bool(k, v);
571         else if (!strcmp(k, "merge.ff")) {
572                 int boolval = git_parse_maybe_bool(v);
573                 if (0 <= boolval) {
574                         fast_forward = boolval ? FF_ALLOW : FF_NO;
575                 } else if (v && !strcmp(v, "only")) {
576                         fast_forward = FF_ONLY;
577                 } /* do not barf on values from future versions of git */
578                 return 0;
579         } else if (!strcmp(k, "merge.defaulttoupstream")) {
580                 default_to_upstream = git_config_bool(k, v);
581                 return 0;
582         } else if (!strcmp(k, "commit.gpgsign")) {
583                 sign_commit = git_config_bool(k, v) ? "" : NULL;
584                 return 0;
585         }
586
587         status = fmt_merge_msg_config(k, v, cb);
588         if (status)
589                 return status;
590         status = git_gpg_config(k, v, NULL);
591         if (status)
592                 return status;
593         return git_diff_ui_config(k, v, cb);
594 }
595
596 static int read_tree_trivial(struct object_id *common, struct object_id *head,
597                              struct object_id *one)
598 {
599         int i, nr_trees = 0;
600         struct tree *trees[MAX_UNPACK_TREES];
601         struct tree_desc t[MAX_UNPACK_TREES];
602         struct unpack_trees_options opts;
603
604         memset(&opts, 0, sizeof(opts));
605         opts.head_idx = 2;
606         opts.src_index = &the_index;
607         opts.dst_index = &the_index;
608         opts.update = 1;
609         opts.verbose_update = 1;
610         opts.trivial_merges_only = 1;
611         opts.merge = 1;
612         trees[nr_trees] = parse_tree_indirect(common);
613         if (!trees[nr_trees++])
614                 return -1;
615         trees[nr_trees] = parse_tree_indirect(head);
616         if (!trees[nr_trees++])
617                 return -1;
618         trees[nr_trees] = parse_tree_indirect(one);
619         if (!trees[nr_trees++])
620                 return -1;
621         opts.fn = threeway_merge;
622         cache_tree_free(&active_cache_tree);
623         for (i = 0; i < nr_trees; i++) {
624                 parse_tree(trees[i]);
625                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
626         }
627         if (unpack_trees(nr_trees, t, &opts))
628                 return -1;
629         return 0;
630 }
631
632 static void write_tree_trivial(struct object_id *oid)
633 {
634         if (write_cache_as_tree(oid->hash, 0, NULL))
635                 die(_("git write-tree failed to write a tree"));
636 }
637
638 static int try_merge_strategy(const char *strategy, struct commit_list *common,
639                               struct commit_list *remoteheads,
640                               struct commit *head)
641 {
642         static struct lock_file lock;
643         const char *head_arg = "HEAD";
644
645         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
646         refresh_cache(REFRESH_QUIET);
647         if (active_cache_changed &&
648             write_locked_index(&the_index, &lock, COMMIT_LOCK))
649                 return error(_("Unable to write index."));
650         rollback_lock_file(&lock);
651
652         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
653                 int clean, x;
654                 struct commit *result;
655                 struct commit_list *reversed = NULL;
656                 struct merge_options o;
657                 struct commit_list *j;
658
659                 if (remoteheads->next) {
660                         error(_("Not handling anything other than two heads merge."));
661                         return 2;
662                 }
663
664                 init_merge_options(&o);
665                 if (!strcmp(strategy, "subtree"))
666                         o.subtree_shift = "";
667
668                 o.renormalize = option_renormalize;
669                 o.show_rename_progress =
670                         show_progress == -1 ? isatty(2) : show_progress;
671
672                 for (x = 0; x < xopts_nr; x++)
673                         if (parse_merge_opt(&o, xopts[x]))
674                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
675
676                 o.branch1 = head_arg;
677                 o.branch2 = merge_remote_util(remoteheads->item)->name;
678
679                 for (j = common; j; j = j->next)
680                         commit_list_insert(j->item, &reversed);
681
682                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
683                 clean = merge_recursive(&o, head,
684                                 remoteheads->item, reversed, &result);
685                 if (clean < 0)
686                         exit(128);
687                 if (active_cache_changed &&
688                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
689                         die (_("unable to write %s"), get_index_file());
690                 rollback_lock_file(&lock);
691                 return clean ? 0 : 1;
692         } else {
693                 return try_merge_command(strategy, xopts_nr, xopts,
694                                                 common, head_arg, remoteheads);
695         }
696 }
697
698 static void count_diff_files(struct diff_queue_struct *q,
699                              struct diff_options *opt, void *data)
700 {
701         int *count = data;
702
703         (*count) += q->nr;
704 }
705
706 static int count_unmerged_entries(void)
707 {
708         int i, ret = 0;
709
710         for (i = 0; i < active_nr; i++)
711                 if (ce_stage(active_cache[i]))
712                         ret++;
713
714         return ret;
715 }
716
717 static void add_strategies(const char *string, unsigned attr)
718 {
719         int i;
720
721         if (string) {
722                 struct string_list list = STRING_LIST_INIT_DUP;
723                 struct string_list_item *item;
724                 string_list_split(&list, string, ' ', -1);
725                 for_each_string_list_item(item, &list)
726                         append_strategy(get_strategy(item->string));
727                 string_list_clear(&list, 0);
728                 return;
729         }
730         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
731                 if (all_strategy[i].attr & attr)
732                         append_strategy(&all_strategy[i]);
733
734 }
735
736 static void read_merge_msg(struct strbuf *msg)
737 {
738         const char *filename = git_path_merge_msg();
739         strbuf_reset(msg);
740         if (strbuf_read_file(msg, filename, 0) < 0)
741                 die_errno(_("Could not read from '%s'"), filename);
742 }
743
744 static void write_merge_state(struct commit_list *);
745 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
746 {
747         if (err_msg)
748                 error("%s", err_msg);
749         fprintf(stderr,
750                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
751         write_merge_state(remoteheads);
752         exit(1);
753 }
754
755 static const char merge_editor_comment[] =
756 N_("Please enter a commit message to explain why this merge is necessary,\n"
757    "especially if it merges an updated upstream into a topic branch.\n"
758    "\n"
759    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
760    "the commit.\n");
761
762 static void write_merge_heads(struct commit_list *);
763 static void prepare_to_commit(struct commit_list *remoteheads)
764 {
765         struct strbuf msg = STRBUF_INIT;
766         strbuf_addbuf(&msg, &merge_msg);
767         strbuf_addch(&msg, '\n');
768         if (squash)
769                 BUG("the control must not reach here under --squash");
770         if (0 < option_edit)
771                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
772         if (signoff)
773                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
774         write_merge_heads(remoteheads);
775         write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
776         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
777                             git_path_merge_msg(), "merge", NULL))
778                 abort_commit(remoteheads, NULL);
779         if (0 < option_edit) {
780                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
781                         abort_commit(remoteheads, NULL);
782         }
783         read_merge_msg(&msg);
784         strbuf_stripspace(&msg, 0 < option_edit);
785         if (!msg.len)
786                 abort_commit(remoteheads, _("Empty commit message."));
787         strbuf_release(&merge_msg);
788         strbuf_addbuf(&merge_msg, &msg);
789         strbuf_release(&msg);
790 }
791
792 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
793 {
794         struct object_id result_tree, result_commit;
795         struct commit_list *parents, **pptr = &parents;
796         static struct lock_file lock;
797
798         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
799         refresh_cache(REFRESH_QUIET);
800         if (active_cache_changed &&
801             write_locked_index(&the_index, &lock, COMMIT_LOCK))
802                 return error(_("Unable to write index."));
803         rollback_lock_file(&lock);
804
805         write_tree_trivial(&result_tree);
806         printf(_("Wonderful.\n"));
807         pptr = commit_list_append(head, pptr);
808         pptr = commit_list_append(remoteheads->item, pptr);
809         prepare_to_commit(remoteheads);
810         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree.hash, parents,
811                         result_commit.hash, NULL, sign_commit))
812                 die(_("failed to write commit object"));
813         finish(head, remoteheads, &result_commit, "In-index merge");
814         drop_save();
815         return 0;
816 }
817
818 static int finish_automerge(struct commit *head,
819                             int head_subsumed,
820                             struct commit_list *common,
821                             struct commit_list *remoteheads,
822                             struct object_id *result_tree,
823                             const char *wt_strategy)
824 {
825         struct commit_list *parents = NULL;
826         struct strbuf buf = STRBUF_INIT;
827         struct object_id result_commit;
828
829         free_commit_list(common);
830         parents = remoteheads;
831         if (!head_subsumed || fast_forward == FF_NO)
832                 commit_list_insert(head, &parents);
833         strbuf_addch(&merge_msg, '\n');
834         prepare_to_commit(remoteheads);
835         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree->hash, parents,
836                         result_commit.hash, NULL, sign_commit))
837                 die(_("failed to write commit object"));
838         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
839         finish(head, remoteheads, &result_commit, buf.buf);
840         strbuf_release(&buf);
841         drop_save();
842         return 0;
843 }
844
845 static int suggest_conflicts(void)
846 {
847         const char *filename;
848         FILE *fp;
849         struct strbuf msgbuf = STRBUF_INIT;
850
851         filename = git_path_merge_msg();
852         fp = xfopen(filename, "a");
853
854         append_conflicts_hint(&msgbuf);
855         fputs(msgbuf.buf, fp);
856         strbuf_release(&msgbuf);
857         fclose(fp);
858         rerere(allow_rerere_auto);
859         printf(_("Automatic merge failed; "
860                         "fix conflicts and then commit the result.\n"));
861         return 1;
862 }
863
864 static int evaluate_result(void)
865 {
866         int cnt = 0;
867         struct rev_info rev;
868
869         /* Check how many files differ. */
870         init_revisions(&rev, "");
871         setup_revisions(0, NULL, &rev, NULL);
872         rev.diffopt.output_format |=
873                 DIFF_FORMAT_CALLBACK;
874         rev.diffopt.format_callback = count_diff_files;
875         rev.diffopt.format_callback_data = &cnt;
876         run_diff_files(&rev, 0);
877
878         /*
879          * Check how many unmerged entries are
880          * there.
881          */
882         cnt += count_unmerged_entries();
883
884         return cnt;
885 }
886
887 /*
888  * Pretend as if the user told us to merge with the remote-tracking
889  * branch we have for the upstream of the current branch
890  */
891 static int setup_with_upstream(const char ***argv)
892 {
893         struct branch *branch = branch_get(NULL);
894         int i;
895         const char **args;
896
897         if (!branch)
898                 die(_("No current branch."));
899         if (!branch->remote_name)
900                 die(_("No remote for the current branch."));
901         if (!branch->merge_nr)
902                 die(_("No default upstream defined for the current branch."));
903
904         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
905         for (i = 0; i < branch->merge_nr; i++) {
906                 if (!branch->merge[i]->dst)
907                         die(_("No remote-tracking branch for %s from %s"),
908                             branch->merge[i]->src, branch->remote_name);
909                 args[i] = branch->merge[i]->dst;
910         }
911         args[i] = NULL;
912         *argv = args;
913         return i;
914 }
915
916 static void write_merge_heads(struct commit_list *remoteheads)
917 {
918         struct commit_list *j;
919         struct strbuf buf = STRBUF_INIT;
920
921         for (j = remoteheads; j; j = j->next) {
922                 struct object_id *oid;
923                 struct commit *c = j->item;
924                 if (c->util && merge_remote_util(c)->obj) {
925                         oid = &merge_remote_util(c)->obj->oid;
926                 } else {
927                         oid = &c->object.oid;
928                 }
929                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
930         }
931         write_file_buf(git_path_merge_head(), buf.buf, buf.len);
932
933         strbuf_reset(&buf);
934         if (fast_forward == FF_NO)
935                 strbuf_addstr(&buf, "no-ff");
936         write_file_buf(git_path_merge_mode(), buf.buf, buf.len);
937 }
938
939 static void write_merge_state(struct commit_list *remoteheads)
940 {
941         write_merge_heads(remoteheads);
942         strbuf_addch(&merge_msg, '\n');
943         write_file_buf(git_path_merge_msg(), merge_msg.buf, merge_msg.len);
944 }
945
946 static int default_edit_option(void)
947 {
948         static const char name[] = "GIT_MERGE_AUTOEDIT";
949         const char *e = getenv(name);
950         struct stat st_stdin, st_stdout;
951
952         if (have_message)
953                 /* an explicit -m msg without --[no-]edit */
954                 return 0;
955
956         if (e) {
957                 int v = git_parse_maybe_bool(e);
958                 if (v < 0)
959                         die(_("Bad value '%s' in environment '%s'"), e, name);
960                 return v;
961         }
962
963         /* Use editor if stdin and stdout are the same and is a tty */
964         return (!fstat(0, &st_stdin) &&
965                 !fstat(1, &st_stdout) &&
966                 isatty(0) && isatty(1) &&
967                 st_stdin.st_dev == st_stdout.st_dev &&
968                 st_stdin.st_ino == st_stdout.st_ino &&
969                 st_stdin.st_mode == st_stdout.st_mode);
970 }
971
972 static struct commit_list *reduce_parents(struct commit *head_commit,
973                                           int *head_subsumed,
974                                           struct commit_list *remoteheads)
975 {
976         struct commit_list *parents, **remotes;
977
978         /*
979          * Is the current HEAD reachable from another commit being
980          * merged?  If so we do not want to record it as a parent of
981          * the resulting merge, unless --no-ff is given.  We will flip
982          * this variable to 0 when we find HEAD among the independent
983          * tips being merged.
984          */
985         *head_subsumed = 1;
986
987         /* Find what parents to record by checking independent ones. */
988         parents = reduce_heads(remoteheads);
989
990         remoteheads = NULL;
991         remotes = &remoteheads;
992         while (parents) {
993                 struct commit *commit = pop_commit(&parents);
994                 if (commit == head_commit)
995                         *head_subsumed = 0;
996                 else
997                         remotes = &commit_list_insert(commit, remotes)->next;
998         }
999         return remoteheads;
1000 }
1001
1002 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1003 {
1004         struct fmt_merge_msg_opts opts;
1005
1006         memset(&opts, 0, sizeof(opts));
1007         opts.add_title = !have_message;
1008         opts.shortlog_len = shortlog_len;
1009         opts.credit_people = (0 < option_edit);
1010
1011         fmt_merge_msg(merge_names, merge_msg, &opts);
1012         if (merge_msg->len)
1013                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1014 }
1015
1016 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1017 {
1018         const char *filename;
1019         int fd, pos, npos;
1020         struct strbuf fetch_head_file = STRBUF_INIT;
1021
1022         if (!merge_names)
1023                 merge_names = &fetch_head_file;
1024
1025         filename = git_path_fetch_head();
1026         fd = open(filename, O_RDONLY);
1027         if (fd < 0)
1028                 die_errno(_("could not open '%s' for reading"), filename);
1029
1030         if (strbuf_read(merge_names, fd, 0) < 0)
1031                 die_errno(_("could not read '%s'"), filename);
1032         if (close(fd) < 0)
1033                 die_errno(_("could not close '%s'"), filename);
1034
1035         for (pos = 0; pos < merge_names->len; pos = npos) {
1036                 struct object_id oid;
1037                 char *ptr;
1038                 struct commit *commit;
1039
1040                 ptr = strchr(merge_names->buf + pos, '\n');
1041                 if (ptr)
1042                         npos = ptr - merge_names->buf + 1;
1043                 else
1044                         npos = merge_names->len;
1045
1046                 if (npos - pos < GIT_SHA1_HEXSZ + 2 ||
1047                     get_oid_hex(merge_names->buf + pos, &oid))
1048                         commit = NULL; /* bad */
1049                 else if (memcmp(merge_names->buf + pos + GIT_SHA1_HEXSZ, "\t\t", 2))
1050                         continue; /* not-for-merge */
1051                 else {
1052                         char saved = merge_names->buf[pos + GIT_SHA1_HEXSZ];
1053                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = '\0';
1054                         commit = get_merge_parent(merge_names->buf + pos);
1055                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = saved;
1056                 }
1057                 if (!commit) {
1058                         if (ptr)
1059                                 *ptr = '\0';
1060                         die(_("not something we can merge in %s: %s"),
1061                             filename, merge_names->buf + pos);
1062                 }
1063                 remotes = &commit_list_insert(commit, remotes)->next;
1064         }
1065
1066         if (merge_names == &fetch_head_file)
1067                 strbuf_release(&fetch_head_file);
1068 }
1069
1070 static struct commit_list *collect_parents(struct commit *head_commit,
1071                                            int *head_subsumed,
1072                                            int argc, const char **argv,
1073                                            struct strbuf *merge_msg)
1074 {
1075         int i;
1076         struct commit_list *remoteheads = NULL;
1077         struct commit_list **remotes = &remoteheads;
1078         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1079
1080         if (merge_msg && (!have_message || shortlog_len))
1081                 autogen = &merge_names;
1082
1083         if (head_commit)
1084                 remotes = &commit_list_insert(head_commit, remotes)->next;
1085
1086         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1087                 handle_fetch_head(remotes, autogen);
1088                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1089         } else {
1090                 for (i = 0; i < argc; i++) {
1091                         struct commit *commit = get_merge_parent(argv[i]);
1092                         if (!commit)
1093                                 help_unknown_ref(argv[i], "merge",
1094                                                  _("not something we can merge"));
1095                         remotes = &commit_list_insert(commit, remotes)->next;
1096                 }
1097                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1098                 if (autogen) {
1099                         struct commit_list *p;
1100                         for (p = remoteheads; p; p = p->next)
1101                                 merge_name(merge_remote_util(p->item)->name, autogen);
1102                 }
1103         }
1104
1105         if (autogen) {
1106                 prepare_merge_message(autogen, merge_msg);
1107                 strbuf_release(autogen);
1108         }
1109
1110         return remoteheads;
1111 }
1112
1113 int cmd_merge(int argc, const char **argv, const char *prefix)
1114 {
1115         struct object_id result_tree, stash, head_oid;
1116         struct commit *head_commit;
1117         struct strbuf buf = STRBUF_INIT;
1118         int i, ret = 0, head_subsumed;
1119         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1120         struct commit_list *common = NULL;
1121         const char *best_strategy = NULL, *wt_strategy = NULL;
1122         struct commit_list *remoteheads, *p;
1123         void *branch_to_free;
1124         int orig_argc = argc;
1125
1126         if (argc == 2 && !strcmp(argv[1], "-h"))
1127                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1128
1129         /*
1130          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1131          * current branch.
1132          */
1133         branch = branch_to_free = resolve_refdup("HEAD", 0, head_oid.hash, NULL);
1134         if (branch)
1135                 skip_prefix(branch, "refs/heads/", &branch);
1136         if (!branch || is_null_oid(&head_oid))
1137                 head_commit = NULL;
1138         else
1139                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1140
1141         init_diff_ui_defaults();
1142         git_config(git_merge_config, NULL);
1143
1144         if (branch_mergeoptions)
1145                 parse_branch_merge_options(branch_mergeoptions);
1146         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1147                         builtin_merge_usage, 0);
1148         if (shortlog_len < 0)
1149                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1150
1151         if (verbosity < 0 && show_progress == -1)
1152                 show_progress = 0;
1153
1154         if (abort_current_merge) {
1155                 int nargc = 2;
1156                 const char *nargv[] = {"reset", "--merge", NULL};
1157
1158                 if (orig_argc != 2)
1159                         usage_msg_opt(_("--abort expects no arguments"),
1160                               builtin_merge_usage, builtin_merge_options);
1161
1162                 if (!file_exists(git_path_merge_head()))
1163                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1164
1165                 /* Invoke 'git reset --merge' */
1166                 ret = cmd_reset(nargc, nargv, prefix);
1167                 goto done;
1168         }
1169
1170         if (continue_current_merge) {
1171                 int nargc = 1;
1172                 const char *nargv[] = {"commit", NULL};
1173
1174                 if (orig_argc != 2)
1175                         usage_msg_opt(_("--continue expects no arguments"),
1176                               builtin_merge_usage, builtin_merge_options);
1177
1178                 if (!file_exists(git_path_merge_head()))
1179                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1180
1181                 /* Invoke 'git commit' */
1182                 ret = cmd_commit(nargc, nargv, prefix);
1183                 goto done;
1184         }
1185
1186         if (read_cache_unmerged())
1187                 die_resolve_conflict("merge");
1188
1189         if (file_exists(git_path_merge_head())) {
1190                 /*
1191                  * There is no unmerged entry, don't advise 'git
1192                  * add/rm <file>', just 'git commit'.
1193                  */
1194                 if (advice_resolve_conflict)
1195                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1196                                   "Please, commit your changes before you merge."));
1197                 else
1198                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1199         }
1200         if (file_exists(git_path_cherry_pick_head())) {
1201                 if (advice_resolve_conflict)
1202                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1203                             "Please, commit your changes before you merge."));
1204                 else
1205                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1206         }
1207         resolve_undo_clear();
1208
1209         if (verbosity < 0)
1210                 show_diffstat = 0;
1211
1212         if (squash) {
1213                 if (fast_forward == FF_NO)
1214                         die(_("You cannot combine --squash with --no-ff."));
1215                 option_commit = 0;
1216         }
1217
1218         if (!argc) {
1219                 if (default_to_upstream)
1220                         argc = setup_with_upstream(&argv);
1221                 else
1222                         die(_("No commit specified and merge.defaultToUpstream not set."));
1223         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1224                 argv[0] = "@{-1}";
1225         }
1226
1227         if (!argc)
1228                 usage_with_options(builtin_merge_usage,
1229                         builtin_merge_options);
1230
1231         if (!head_commit) {
1232                 /*
1233                  * If the merged head is a valid one there is no reason
1234                  * to forbid "git merge" into a branch yet to be born.
1235                  * We do the same for "git pull".
1236                  */
1237                 struct object_id *remote_head_oid;
1238                 if (squash)
1239                         die(_("Squash commit into empty head not supported yet"));
1240                 if (fast_forward == FF_NO)
1241                         die(_("Non-fast-forward commit does not make sense into "
1242                             "an empty head"));
1243                 remoteheads = collect_parents(head_commit, &head_subsumed,
1244                                               argc, argv, NULL);
1245                 if (!remoteheads)
1246                         die(_("%s - not something we can merge"), argv[0]);
1247                 if (remoteheads->next)
1248                         die(_("Can merge only exactly one commit into empty head"));
1249                 remote_head_oid = &remoteheads->item->object.oid;
1250                 read_empty(remote_head_oid->hash, 0);
1251                 update_ref("initial pull", "HEAD", remote_head_oid->hash,
1252                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1253                 goto done;
1254         }
1255
1256         /*
1257          * All the rest are the commits being merged; prepare
1258          * the standard merge summary message to be appended
1259          * to the given message.
1260          */
1261         remoteheads = collect_parents(head_commit, &head_subsumed,
1262                                       argc, argv, &merge_msg);
1263
1264         if (!head_commit || !argc)
1265                 usage_with_options(builtin_merge_usage,
1266                         builtin_merge_options);
1267
1268         if (verify_signatures) {
1269                 for (p = remoteheads; p; p = p->next) {
1270                         struct commit *commit = p->item;
1271                         char hex[GIT_MAX_HEXSZ + 1];
1272                         struct signature_check signature_check;
1273                         memset(&signature_check, 0, sizeof(signature_check));
1274
1275                         check_commit_signature(commit, &signature_check);
1276
1277                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1278                         switch (signature_check.result) {
1279                         case 'G':
1280                                 break;
1281                         case 'U':
1282                                 die(_("Commit %s has an untrusted GPG signature, "
1283                                       "allegedly by %s."), hex, signature_check.signer);
1284                         case 'B':
1285                                 die(_("Commit %s has a bad GPG signature "
1286                                       "allegedly by %s."), hex, signature_check.signer);
1287                         default: /* 'N' */
1288                                 die(_("Commit %s does not have a GPG signature."), hex);
1289                         }
1290                         if (verbosity >= 0 && signature_check.result == 'G')
1291                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1292                                        hex, signature_check.signer);
1293
1294                         signature_check_clear(&signature_check);
1295                 }
1296         }
1297
1298         strbuf_addstr(&buf, "merge");
1299         for (p = remoteheads; p; p = p->next)
1300                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1301         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1302         strbuf_reset(&buf);
1303
1304         for (p = remoteheads; p; p = p->next) {
1305                 struct commit *commit = p->item;
1306                 strbuf_addf(&buf, "GITHEAD_%s",
1307                             oid_to_hex(&commit->object.oid));
1308                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1309                 strbuf_reset(&buf);
1310                 if (fast_forward != FF_ONLY &&
1311                     merge_remote_util(commit) &&
1312                     merge_remote_util(commit)->obj &&
1313                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1314                         fast_forward = FF_NO;
1315         }
1316
1317         if (option_edit < 0)
1318                 option_edit = default_edit_option();
1319
1320         if (!use_strategies) {
1321                 if (!remoteheads)
1322                         ; /* already up-to-date */
1323                 else if (!remoteheads->next)
1324                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1325                 else
1326                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1327         }
1328
1329         for (i = 0; i < use_strategies_nr; i++) {
1330                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1331                         fast_forward = FF_NO;
1332                 if (use_strategies[i]->attr & NO_TRIVIAL)
1333                         allow_trivial = 0;
1334         }
1335
1336         if (!remoteheads)
1337                 ; /* already up-to-date */
1338         else if (!remoteheads->next)
1339                 common = get_merge_bases(head_commit, remoteheads->item);
1340         else {
1341                 struct commit_list *list = remoteheads;
1342                 commit_list_insert(head_commit, &list);
1343                 common = get_octopus_merge_bases(list);
1344                 free(list);
1345         }
1346
1347         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.oid.hash,
1348                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1349
1350         if (remoteheads && !common) {
1351                 /* No common ancestors found. */
1352                 if (!allow_unrelated_histories)
1353                         die(_("refusing to merge unrelated histories"));
1354                 /* otherwise, we need a real merge. */
1355         } else if (!remoteheads ||
1356                  (!remoteheads->next && !common->next &&
1357                   common->item == remoteheads->item)) {
1358                 /*
1359                  * If head can reach all the merge then we are up to date.
1360                  * but first the most common case of merging one remote.
1361                  */
1362                 finish_up_to_date(_("Already up to date."));
1363                 goto done;
1364         } else if (fast_forward != FF_NO && !remoteheads->next &&
1365                         !common->next &&
1366                         !oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
1367                 /* Again the most common case of merging one remote. */
1368                 struct strbuf msg = STRBUF_INIT;
1369                 struct commit *commit;
1370
1371                 if (verbosity >= 0) {
1372                         printf(_("Updating %s..%s\n"),
1373                                find_unique_abbrev(head_commit->object.oid.hash,
1374                                                   DEFAULT_ABBREV),
1375                                find_unique_abbrev(remoteheads->item->object.oid.hash,
1376                                                   DEFAULT_ABBREV));
1377                 }
1378                 strbuf_addstr(&msg, "Fast-forward");
1379                 if (have_message)
1380                         strbuf_addstr(&msg,
1381                                 " (no commit created; -m option ignored)");
1382                 commit = remoteheads->item;
1383                 if (!commit) {
1384                         ret = 1;
1385                         goto done;
1386                 }
1387
1388                 if (checkout_fast_forward(&head_commit->object.oid,
1389                                           &commit->object.oid,
1390                                           overwrite_ignore)) {
1391                         ret = 1;
1392                         goto done;
1393                 }
1394
1395                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1396                 drop_save();
1397                 goto done;
1398         } else if (!remoteheads->next && common->next)
1399                 ;
1400                 /*
1401                  * We are not doing octopus and not fast-forward.  Need
1402                  * a real merge.
1403                  */
1404         else if (!remoteheads->next && !common->next && option_commit) {
1405                 /*
1406                  * We are not doing octopus, not fast-forward, and have
1407                  * only one common.
1408                  */
1409                 refresh_cache(REFRESH_QUIET);
1410                 if (allow_trivial && fast_forward != FF_ONLY) {
1411                         /* See if it is really trivial. */
1412                         git_committer_info(IDENT_STRICT);
1413                         printf(_("Trying really trivial in-index merge...\n"));
1414                         if (!read_tree_trivial(&common->item->object.oid,
1415                                                &head_commit->object.oid,
1416                                                &remoteheads->item->object.oid)) {
1417                                 ret = merge_trivial(head_commit, remoteheads);
1418                                 goto done;
1419                         }
1420                         printf(_("Nope.\n"));
1421                 }
1422         } else {
1423                 /*
1424                  * An octopus.  If we can reach all the remote we are up
1425                  * to date.
1426                  */
1427                 int up_to_date = 1;
1428                 struct commit_list *j;
1429
1430                 for (j = remoteheads; j; j = j->next) {
1431                         struct commit_list *common_one;
1432
1433                         /*
1434                          * Here we *have* to calculate the individual
1435                          * merge_bases again, otherwise "git merge HEAD^
1436                          * HEAD^^" would be missed.
1437                          */
1438                         common_one = get_merge_bases(head_commit, j->item);
1439                         if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
1440                                 up_to_date = 0;
1441                                 break;
1442                         }
1443                 }
1444                 if (up_to_date) {
1445                         finish_up_to_date(_("Already up to date. Yeeah!"));
1446                         goto done;
1447                 }
1448         }
1449
1450         if (fast_forward == FF_ONLY)
1451                 die(_("Not possible to fast-forward, aborting."));
1452
1453         /* We are going to make a new commit. */
1454         git_committer_info(IDENT_STRICT);
1455
1456         /*
1457          * At this point, we need a real merge.  No matter what strategy
1458          * we use, it would operate on the index, possibly affecting the
1459          * working tree, and when resolved cleanly, have the desired
1460          * tree in the index -- this means that the index must be in
1461          * sync with the head commit.  The strategies are responsible
1462          * to ensure this.
1463          */
1464         if (use_strategies_nr == 1 ||
1465             /*
1466              * Stash away the local changes so that we can try more than one.
1467              */
1468             save_state(&stash))
1469                 oidclr(&stash);
1470
1471         for (i = 0; i < use_strategies_nr; i++) {
1472                 int ret;
1473                 if (i) {
1474                         printf(_("Rewinding the tree to pristine...\n"));
1475                         restore_state(&head_commit->object.oid, &stash);
1476                 }
1477                 if (use_strategies_nr != 1)
1478                         printf(_("Trying merge strategy %s...\n"),
1479                                 use_strategies[i]->name);
1480                 /*
1481                  * Remember which strategy left the state in the working
1482                  * tree.
1483                  */
1484                 wt_strategy = use_strategies[i]->name;
1485
1486                 ret = try_merge_strategy(use_strategies[i]->name,
1487                                          common, remoteheads,
1488                                          head_commit);
1489                 if (!option_commit && !ret) {
1490                         merge_was_ok = 1;
1491                         /*
1492                          * This is necessary here just to avoid writing
1493                          * the tree, but later we will *not* exit with
1494                          * status code 1 because merge_was_ok is set.
1495                          */
1496                         ret = 1;
1497                 }
1498
1499                 if (ret) {
1500                         /*
1501                          * The backend exits with 1 when conflicts are
1502                          * left to be resolved, with 2 when it does not
1503                          * handle the given merge at all.
1504                          */
1505                         if (ret == 1) {
1506                                 int cnt = evaluate_result();
1507
1508                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1509                                         best_strategy = use_strategies[i]->name;
1510                                         best_cnt = cnt;
1511                                 }
1512                         }
1513                         if (merge_was_ok)
1514                                 break;
1515                         else
1516                                 continue;
1517                 }
1518
1519                 /* Automerge succeeded. */
1520                 write_tree_trivial(&result_tree);
1521                 automerge_was_ok = 1;
1522                 break;
1523         }
1524
1525         /*
1526          * If we have a resulting tree, that means the strategy module
1527          * auto resolved the merge cleanly.
1528          */
1529         if (automerge_was_ok) {
1530                 ret = finish_automerge(head_commit, head_subsumed,
1531                                        common, remoteheads,
1532                                        &result_tree, wt_strategy);
1533                 goto done;
1534         }
1535
1536         /*
1537          * Pick the result from the best strategy and have the user fix
1538          * it up.
1539          */
1540         if (!best_strategy) {
1541                 restore_state(&head_commit->object.oid, &stash);
1542                 if (use_strategies_nr > 1)
1543                         fprintf(stderr,
1544                                 _("No merge strategy handled the merge.\n"));
1545                 else
1546                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1547                                 use_strategies[0]->name);
1548                 ret = 2;
1549                 goto done;
1550         } else if (best_strategy == wt_strategy)
1551                 ; /* We already have its result in the working tree. */
1552         else {
1553                 printf(_("Rewinding the tree to pristine...\n"));
1554                 restore_state(&head_commit->object.oid, &stash);
1555                 printf(_("Using the %s to prepare resolving by hand.\n"),
1556                         best_strategy);
1557                 try_merge_strategy(best_strategy, common, remoteheads,
1558                                    head_commit);
1559         }
1560
1561         if (squash)
1562                 finish(head_commit, remoteheads, NULL, NULL);
1563         else
1564                 write_merge_state(remoteheads);
1565
1566         if (merge_was_ok)
1567                 fprintf(stderr, _("Automatic merge went well; "
1568                         "stopped before committing as requested\n"));
1569         else
1570                 ret = suggest_conflicts();
1571
1572 done:
1573         free(branch_to_free);
1574         return ret;
1575 }