Merge branch 'js/rebase-helper' into next
[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 "lockfile.h"
13 #include "run-command.h"
14 #include "diff.h"
15 #include "refs.h"
16 #include "commit.h"
17 #include "diffcore.h"
18 #include "revision.h"
19 #include "unpack-trees.h"
20 #include "cache-tree.h"
21 #include "dir.h"
22 #include "utf8.h"
23 #include "log-tree.h"
24 #include "color.h"
25 #include "rerere.h"
26 #include "help.h"
27 #include "merge-recursive.h"
28 #include "resolve-undo.h"
29 #include "remote.h"
30 #include "fmt-merge-msg.h"
31 #include "gpg-interface.h"
32 #include "sequencer.h"
33 #include "string-list.h"
34
35 #define DEFAULT_TWOHEAD (1<<0)
36 #define DEFAULT_OCTOPUS (1<<1)
37 #define NO_FAST_FORWARD (1<<2)
38 #define NO_TRIVIAL      (1<<3)
39
40 struct strategy {
41         const char *name;
42         unsigned attr;
43 };
44
45 static const char * const builtin_merge_usage[] = {
46         N_("git merge [<options>] [<commit>...]"),
47         N_("git merge --abort"),
48         N_("git merge --continue"),
49         NULL
50 };
51
52 static int show_diffstat = 1, shortlog_len = -1, squash;
53 static int option_commit = 1;
54 static int option_edit = -1;
55 static int allow_trivial = 1, have_message, verify_signatures;
56 static int overwrite_ignore = 1;
57 static struct strbuf merge_msg = STRBUF_INIT;
58 static struct strategy **use_strategies;
59 static size_t use_strategies_nr, use_strategies_alloc;
60 static const char **xopts;
61 static size_t xopts_nr, xopts_alloc;
62 static const char *branch;
63 static char *branch_mergeoptions;
64 static int option_renormalize;
65 static int verbosity;
66 static int allow_rerere_auto;
67 static int abort_current_merge;
68 static int continue_current_merge;
69 static int allow_unrelated_histories;
70 static int show_progress = -1;
71 static int default_to_upstream = 1;
72 static const char *sign_commit;
73
74 static struct strategy all_strategy[] = {
75         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
76         { "octopus",    DEFAULT_OCTOPUS },
77         { "resolve",    0 },
78         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
79         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
80 };
81
82 static const char *pull_twohead, *pull_octopus;
83
84 enum ff_type {
85         FF_NO,
86         FF_ALLOW,
87         FF_ONLY
88 };
89
90 static enum ff_type fast_forward = FF_ALLOW;
91
92 static int option_parse_message(const struct option *opt,
93                                 const char *arg, int unset)
94 {
95         struct strbuf *buf = opt->value;
96
97         if (unset)
98                 strbuf_setlen(buf, 0);
99         else if (arg) {
100                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
101                 have_message = 1;
102         } else
103                 return error(_("switch `m' requires a value"));
104         return 0;
105 }
106
107 static struct strategy *get_strategy(const char *name)
108 {
109         int i;
110         struct strategy *ret;
111         static struct cmdnames main_cmds, other_cmds;
112         static int loaded;
113
114         if (!name)
115                 return NULL;
116
117         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
118                 if (!strcmp(name, all_strategy[i].name))
119                         return &all_strategy[i];
120
121         if (!loaded) {
122                 struct cmdnames not_strategies;
123                 loaded = 1;
124
125                 memset(&not_strategies, 0, sizeof(struct cmdnames));
126                 load_command_list("git-merge-", &main_cmds, &other_cmds);
127                 for (i = 0; i < main_cmds.cnt; i++) {
128                         int j, found = 0;
129                         struct cmdname *ent = main_cmds.names[i];
130                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
131                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
132                                                 && !all_strategy[j].name[ent->len])
133                                         found = 1;
134                         if (!found)
135                                 add_cmdname(&not_strategies, ent->name, ent->len);
136                 }
137                 exclude_cmds(&main_cmds, &not_strategies);
138         }
139         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
140                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
141                 fprintf(stderr, _("Available strategies are:"));
142                 for (i = 0; i < main_cmds.cnt; i++)
143                         fprintf(stderr, " %s", main_cmds.names[i]->name);
144                 fprintf(stderr, ".\n");
145                 if (other_cmds.cnt) {
146                         fprintf(stderr, _("Available custom strategies are:"));
147                         for (i = 0; i < other_cmds.cnt; i++)
148                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
149                         fprintf(stderr, ".\n");
150                 }
151                 exit(1);
152         }
153
154         ret = xcalloc(1, sizeof(struct strategy));
155         ret->name = xstrdup(name);
156         ret->attr = NO_TRIVIAL;
157         return ret;
158 }
159
160 static void append_strategy(struct strategy *s)
161 {
162         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
163         use_strategies[use_strategies_nr++] = s;
164 }
165
166 static int option_parse_strategy(const struct option *opt,
167                                  const char *name, int unset)
168 {
169         if (unset)
170                 return 0;
171
172         append_strategy(get_strategy(name));
173         return 0;
174 }
175
176 static int option_parse_x(const struct option *opt,
177                           const char *arg, int unset)
178 {
179         if (unset)
180                 return 0;
181
182         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
183         xopts[xopts_nr++] = xstrdup(arg);
184         return 0;
185 }
186
187 static int option_parse_n(const struct option *opt,
188                           const char *arg, int unset)
189 {
190         show_diffstat = unset;
191         return 0;
192 }
193
194 static struct option builtin_merge_options[] = {
195         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
196                 N_("do not show a diffstat at the end of the merge"),
197                 PARSE_OPT_NOARG, option_parse_n },
198         OPT_BOOL(0, "stat", &show_diffstat,
199                 N_("show a diffstat at the end of the merge")),
200         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
201         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
202           N_("add (at most <n>) entries from shortlog to merge commit message"),
203           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
204         OPT_BOOL(0, "squash", &squash,
205                 N_("create a single commit instead of doing a merge")),
206         OPT_BOOL(0, "commit", &option_commit,
207                 N_("perform a commit if the merge succeeds (default)")),
208         OPT_BOOL('e', "edit", &option_edit,
209                 N_("edit message before committing")),
210         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
211         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
212                 N_("abort if fast-forward is not possible"),
213                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
214         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
215         OPT_BOOL(0, "verify-signatures", &verify_signatures,
216                 N_("verify that the named commit has a valid GPG signature")),
217         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
218                 N_("merge strategy to use"), option_parse_strategy),
219         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
220                 N_("option for selected merge strategy"), option_parse_x),
221         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
222                 N_("merge commit message (for a non-fast-forward merge)"),
223                 option_parse_message),
224         OPT__VERBOSITY(&verbosity),
225         OPT_BOOL(0, "abort", &abort_current_merge,
226                 N_("abort the current in-progress merge")),
227         OPT_BOOL(0, "continue", &continue_current_merge,
228                 N_("continue the current in-progress merge")),
229         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
230                  N_("allow merging unrelated histories")),
231         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
232         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
233           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
234         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
235         OPT_END()
236 };
237
238 /* Cleans up metadata that is uninteresting after a succeeded merge. */
239 static void drop_save(void)
240 {
241         unlink(git_path_merge_head());
242         unlink(git_path_merge_msg());
243         unlink(git_path_merge_mode());
244 }
245
246 static int save_state(struct object_id *stash)
247 {
248         int len;
249         struct child_process cp = CHILD_PROCESS_INIT;
250         struct strbuf buffer = STRBUF_INIT;
251         const char *argv[] = {"stash", "create", NULL};
252
253         cp.argv = argv;
254         cp.out = -1;
255         cp.git_cmd = 1;
256
257         if (start_command(&cp))
258                 die(_("could not run stash."));
259         len = strbuf_read(&buffer, cp.out, 1024);
260         close(cp.out);
261
262         if (finish_command(&cp) || len < 0)
263                 die(_("stash failed"));
264         else if (!len)          /* no changes */
265                 return -1;
266         strbuf_setlen(&buffer, buffer.len-1);
267         if (get_oid(buffer.buf, stash))
268                 die(_("not a valid object: %s"), buffer.buf);
269         return 0;
270 }
271
272 static void read_empty(unsigned const char *sha1, int verbose)
273 {
274         int i = 0;
275         const char *args[7];
276
277         args[i++] = "read-tree";
278         if (verbose)
279                 args[i++] = "-v";
280         args[i++] = "-m";
281         args[i++] = "-u";
282         args[i++] = EMPTY_TREE_SHA1_HEX;
283         args[i++] = sha1_to_hex(sha1);
284         args[i] = NULL;
285
286         if (run_command_v_opt(args, RUN_GIT_CMD))
287                 die(_("read-tree failed"));
288 }
289
290 static void reset_hard(unsigned const char *sha1, int verbose)
291 {
292         int i = 0;
293         const char *args[6];
294
295         args[i++] = "read-tree";
296         if (verbose)
297                 args[i++] = "-v";
298         args[i++] = "--reset";
299         args[i++] = "-u";
300         args[i++] = sha1_to_hex(sha1);
301         args[i] = NULL;
302
303         if (run_command_v_opt(args, RUN_GIT_CMD))
304                 die(_("read-tree failed"));
305 }
306
307 static void restore_state(const struct object_id *head,
308                           const struct object_id *stash)
309 {
310         struct strbuf sb = STRBUF_INIT;
311         const char *args[] = { "stash", "apply", NULL, NULL };
312
313         if (is_null_oid(stash))
314                 return;
315
316         reset_hard(head->hash, 1);
317
318         args[2] = oid_to_hex(stash);
319
320         /*
321          * It is OK to ignore error here, for example when there was
322          * nothing to restore.
323          */
324         run_command_v_opt(args, RUN_GIT_CMD);
325
326         strbuf_release(&sb);
327         refresh_cache(REFRESH_QUIET);
328 }
329
330 /* This is called when no merge was necessary. */
331 static void finish_up_to_date(const char *msg)
332 {
333         if (verbosity >= 0)
334                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
335         drop_save();
336 }
337
338 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
339 {
340         struct rev_info rev;
341         struct strbuf out = STRBUF_INIT;
342         struct commit_list *j;
343         struct pretty_print_context ctx = {0};
344
345         printf(_("Squash commit -- not updating HEAD\n"));
346
347         init_revisions(&rev, NULL);
348         rev.ignore_merges = 1;
349         rev.commit_format = CMIT_FMT_MEDIUM;
350
351         commit->object.flags |= UNINTERESTING;
352         add_pending_object(&rev, &commit->object, NULL);
353
354         for (j = remoteheads; j; j = j->next)
355                 add_pending_object(&rev, &j->item->object, NULL);
356
357         setup_revisions(0, NULL, &rev, NULL);
358         if (prepare_revision_walk(&rev))
359                 die(_("revision walk setup failed"));
360
361         ctx.abbrev = rev.abbrev;
362         ctx.date_mode = rev.date_mode;
363         ctx.fmt = rev.commit_format;
364
365         strbuf_addstr(&out, "Squashed commit of the following:\n");
366         while ((commit = get_revision(&rev)) != NULL) {
367                 strbuf_addch(&out, '\n');
368                 strbuf_addf(&out, "commit %s\n",
369                         oid_to_hex(&commit->object.oid));
370                 pretty_print_commit(&ctx, commit, &out);
371         }
372         write_file_buf(git_path_squash_msg(), out.buf, out.len);
373         strbuf_release(&out);
374 }
375
376 static void finish(struct commit *head_commit,
377                    struct commit_list *remoteheads,
378                    const struct object_id *new_head, const char *msg)
379 {
380         struct strbuf reflog_message = STRBUF_INIT;
381         const struct object_id *head = &head_commit->object.oid;
382
383         if (!msg)
384                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
385         else {
386                 if (verbosity >= 0)
387                         printf("%s\n", msg);
388                 strbuf_addf(&reflog_message, "%s: %s",
389                         getenv("GIT_REFLOG_ACTION"), msg);
390         }
391         if (squash) {
392                 squash_message(head_commit, remoteheads);
393         } else {
394                 if (verbosity >= 0 && !merge_msg.len)
395                         printf(_("No merge message -- not updating HEAD\n"));
396                 else {
397                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
398                         update_ref(reflog_message.buf, "HEAD",
399                                 new_head->hash, head->hash, 0,
400                                 UPDATE_REFS_DIE_ON_ERR);
401                         /*
402                          * We ignore errors in 'gc --auto', since the
403                          * user should see them.
404                          */
405                         close_all_packs();
406                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
407                 }
408         }
409         if (new_head && show_diffstat) {
410                 struct diff_options opts;
411                 diff_setup(&opts);
412                 opts.stat_width = -1; /* use full terminal width */
413                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
414                 opts.output_format |=
415                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
416                 opts.detect_rename = DIFF_DETECT_RENAME;
417                 diff_setup_done(&opts);
418                 diff_tree_sha1(head->hash, new_head->hash, "", &opts);
419                 diffcore_std(&opts);
420                 diff_flush(&opts);
421         }
422
423         /* Run a post-merge hook */
424         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
425
426         strbuf_release(&reflog_message);
427 }
428
429 /* Get the name for the merge commit's message. */
430 static void merge_name(const char *remote, struct strbuf *msg)
431 {
432         struct commit *remote_head;
433         struct object_id branch_head;
434         struct strbuf buf = STRBUF_INIT;
435         struct strbuf bname = STRBUF_INIT;
436         const char *ptr;
437         char *found_ref;
438         int len, early;
439
440         strbuf_branchname(&bname, remote, 0);
441         remote = bname.buf;
442
443         oidclr(&branch_head);
444         remote_head = get_merge_parent(remote);
445         if (!remote_head)
446                 die(_("'%s' does not point to a commit"), remote);
447
448         if (dwim_ref(remote, strlen(remote), branch_head.hash, &found_ref) > 0) {
449                 if (starts_with(found_ref, "refs/heads/")) {
450                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
451                                     oid_to_hex(&branch_head), remote);
452                         goto cleanup;
453                 }
454                 if (starts_with(found_ref, "refs/tags/")) {
455                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
456                                     oid_to_hex(&branch_head), remote);
457                         goto cleanup;
458                 }
459                 if (starts_with(found_ref, "refs/remotes/")) {
460                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
461                                     oid_to_hex(&branch_head), remote);
462                         goto cleanup;
463                 }
464         }
465
466         /* See if remote matches <name>^^^.. or <name>~<number> */
467         for (len = 0, ptr = remote + strlen(remote);
468              remote < ptr && ptr[-1] == '^';
469              ptr--)
470                 len++;
471         if (len)
472                 early = 1;
473         else {
474                 early = 0;
475                 ptr = strrchr(remote, '~');
476                 if (ptr) {
477                         int seen_nonzero = 0;
478
479                         len++; /* count ~ */
480                         while (*++ptr && isdigit(*ptr)) {
481                                 seen_nonzero |= (*ptr != '0');
482                                 len++;
483                         }
484                         if (*ptr)
485                                 len = 0; /* not ...~<number> */
486                         else if (seen_nonzero)
487                                 early = 1;
488                         else if (len == 1)
489                                 early = 1; /* "name~" is "name~1"! */
490                 }
491         }
492         if (len) {
493                 struct strbuf truname = STRBUF_INIT;
494                 strbuf_addf(&truname, "refs/heads/%s", remote);
495                 strbuf_setlen(&truname, truname.len - len);
496                 if (ref_exists(truname.buf)) {
497                         strbuf_addf(msg,
498                                     "%s\t\tbranch '%s'%s of .\n",
499                                     oid_to_hex(&remote_head->object.oid),
500                                     truname.buf + 11,
501                                     (early ? " (early part)" : ""));
502                         strbuf_release(&truname);
503                         goto cleanup;
504                 }
505                 strbuf_release(&truname);
506         }
507
508         if (remote_head->util) {
509                 struct merge_remote_desc *desc;
510                 desc = merge_remote_util(remote_head);
511                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
512                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
513                                     oid_to_hex(&desc->obj->oid),
514                                     typename(desc->obj->type),
515                                     remote);
516                         goto cleanup;
517                 }
518         }
519
520         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
521                 oid_to_hex(&remote_head->object.oid), remote);
522 cleanup:
523         strbuf_release(&buf);
524         strbuf_release(&bname);
525 }
526
527 static void parse_branch_merge_options(char *bmo)
528 {
529         const char **argv;
530         int argc;
531
532         if (!bmo)
533                 return;
534         argc = split_cmdline(bmo, &argv);
535         if (argc < 0)
536                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
537                     split_cmdline_strerror(argc));
538         REALLOC_ARRAY(argv, argc + 2);
539         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
540         argc++;
541         argv[0] = "branch.*.mergeoptions";
542         parse_options(argc, argv, NULL, builtin_merge_options,
543                       builtin_merge_usage, 0);
544         free(argv);
545 }
546
547 static int git_merge_config(const char *k, const char *v, void *cb)
548 {
549         int status;
550
551         if (branch && starts_with(k, "branch.") &&
552                 starts_with(k + 7, branch) &&
553                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
554                 free(branch_mergeoptions);
555                 branch_mergeoptions = xstrdup(v);
556                 return 0;
557         }
558
559         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
560                 show_diffstat = git_config_bool(k, v);
561         else if (!strcmp(k, "pull.twohead"))
562                 return git_config_string(&pull_twohead, k, v);
563         else if (!strcmp(k, "pull.octopus"))
564                 return git_config_string(&pull_octopus, k, v);
565         else if (!strcmp(k, "merge.renormalize"))
566                 option_renormalize = git_config_bool(k, v);
567         else if (!strcmp(k, "merge.ff")) {
568                 int boolval = git_config_maybe_bool(k, v);
569                 if (0 <= boolval) {
570                         fast_forward = boolval ? FF_ALLOW : FF_NO;
571                 } else if (v && !strcmp(v, "only")) {
572                         fast_forward = FF_ONLY;
573                 } /* do not barf on values from future versions of git */
574                 return 0;
575         } else if (!strcmp(k, "merge.defaulttoupstream")) {
576                 default_to_upstream = git_config_bool(k, v);
577                 return 0;
578         } else if (!strcmp(k, "commit.gpgsign")) {
579                 sign_commit = git_config_bool(k, v) ? "" : NULL;
580                 return 0;
581         }
582
583         status = fmt_merge_msg_config(k, v, cb);
584         if (status)
585                 return status;
586         status = git_gpg_config(k, v, NULL);
587         if (status)
588                 return status;
589         return git_diff_ui_config(k, v, cb);
590 }
591
592 static int read_tree_trivial(struct object_id *common, struct object_id *head,
593                              struct object_id *one)
594 {
595         int i, nr_trees = 0;
596         struct tree *trees[MAX_UNPACK_TREES];
597         struct tree_desc t[MAX_UNPACK_TREES];
598         struct unpack_trees_options opts;
599
600         memset(&opts, 0, sizeof(opts));
601         opts.head_idx = 2;
602         opts.src_index = &the_index;
603         opts.dst_index = &the_index;
604         opts.update = 1;
605         opts.verbose_update = 1;
606         opts.trivial_merges_only = 1;
607         opts.merge = 1;
608         trees[nr_trees] = parse_tree_indirect(common->hash);
609         if (!trees[nr_trees++])
610                 return -1;
611         trees[nr_trees] = parse_tree_indirect(head->hash);
612         if (!trees[nr_trees++])
613                 return -1;
614         trees[nr_trees] = parse_tree_indirect(one->hash);
615         if (!trees[nr_trees++])
616                 return -1;
617         opts.fn = threeway_merge;
618         cache_tree_free(&active_cache_tree);
619         for (i = 0; i < nr_trees; i++) {
620                 parse_tree(trees[i]);
621                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
622         }
623         if (unpack_trees(nr_trees, t, &opts))
624                 return -1;
625         return 0;
626 }
627
628 static void write_tree_trivial(struct object_id *oid)
629 {
630         if (write_cache_as_tree(oid->hash, 0, NULL))
631                 die(_("git write-tree failed to write a tree"));
632 }
633
634 static int try_merge_strategy(const char *strategy, struct commit_list *common,
635                               struct commit_list *remoteheads,
636                               struct commit *head)
637 {
638         static struct lock_file lock;
639         const char *head_arg = "HEAD";
640
641         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
642         refresh_cache(REFRESH_QUIET);
643         if (active_cache_changed &&
644             write_locked_index(&the_index, &lock, COMMIT_LOCK))
645                 return error(_("Unable to write index."));
646         rollback_lock_file(&lock);
647
648         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
649                 int clean, x;
650                 struct commit *result;
651                 struct commit_list *reversed = NULL;
652                 struct merge_options o;
653                 struct commit_list *j;
654
655                 if (remoteheads->next) {
656                         error(_("Not handling anything other than two heads merge."));
657                         return 2;
658                 }
659
660                 init_merge_options(&o);
661                 if (!strcmp(strategy, "subtree"))
662                         o.subtree_shift = "";
663
664                 o.renormalize = option_renormalize;
665                 o.show_rename_progress =
666                         show_progress == -1 ? isatty(2) : show_progress;
667
668                 for (x = 0; x < xopts_nr; x++)
669                         if (parse_merge_opt(&o, xopts[x]))
670                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
671
672                 o.branch1 = head_arg;
673                 o.branch2 = merge_remote_util(remoteheads->item)->name;
674
675                 for (j = common; j; j = j->next)
676                         commit_list_insert(j->item, &reversed);
677
678                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
679                 clean = merge_recursive(&o, head,
680                                 remoteheads->item, reversed, &result);
681                 if (clean < 0)
682                         exit(128);
683                 if (active_cache_changed &&
684                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
685                         die (_("unable to write %s"), get_index_file());
686                 rollback_lock_file(&lock);
687                 return clean ? 0 : 1;
688         } else {
689                 return try_merge_command(strategy, xopts_nr, xopts,
690                                                 common, head_arg, remoteheads);
691         }
692 }
693
694 static void count_diff_files(struct diff_queue_struct *q,
695                              struct diff_options *opt, void *data)
696 {
697         int *count = data;
698
699         (*count) += q->nr;
700 }
701
702 static int count_unmerged_entries(void)
703 {
704         int i, ret = 0;
705
706         for (i = 0; i < active_nr; i++)
707                 if (ce_stage(active_cache[i]))
708                         ret++;
709
710         return ret;
711 }
712
713 static void add_strategies(const char *string, unsigned attr)
714 {
715         int i;
716
717         if (string) {
718                 struct string_list list = STRING_LIST_INIT_DUP;
719                 struct string_list_item *item;
720                 string_list_split(&list, string, ' ', -1);
721                 for_each_string_list_item(item, &list)
722                         append_strategy(get_strategy(item->string));
723                 string_list_clear(&list, 0);
724                 return;
725         }
726         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
727                 if (all_strategy[i].attr & attr)
728                         append_strategy(&all_strategy[i]);
729
730 }
731
732 static void read_merge_msg(struct strbuf *msg)
733 {
734         const char *filename = git_path_merge_msg();
735         strbuf_reset(msg);
736         if (strbuf_read_file(msg, filename, 0) < 0)
737                 die_errno(_("Could not read from '%s'"), filename);
738 }
739
740 static void write_merge_state(struct commit_list *);
741 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
742 {
743         if (err_msg)
744                 error("%s", err_msg);
745         fprintf(stderr,
746                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
747         write_merge_state(remoteheads);
748         exit(1);
749 }
750
751 static const char merge_editor_comment[] =
752 N_("Please enter a commit message to explain why this merge is necessary,\n"
753    "especially if it merges an updated upstream into a topic branch.\n"
754    "\n"
755    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
756    "the commit.\n");
757
758 static void prepare_to_commit(struct commit_list *remoteheads)
759 {
760         struct strbuf msg = STRBUF_INIT;
761         strbuf_addbuf(&msg, &merge_msg);
762         strbuf_addch(&msg, '\n');
763         if (0 < option_edit)
764                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
765         write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
766         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
767                             git_path_merge_msg(), "merge", NULL))
768                 abort_commit(remoteheads, NULL);
769         if (0 < option_edit) {
770                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
771                         abort_commit(remoteheads, NULL);
772         }
773         read_merge_msg(&msg);
774         strbuf_stripspace(&msg, 0 < option_edit);
775         if (!msg.len)
776                 abort_commit(remoteheads, _("Empty commit message."));
777         strbuf_release(&merge_msg);
778         strbuf_addbuf(&merge_msg, &msg);
779         strbuf_release(&msg);
780 }
781
782 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
783 {
784         struct object_id result_tree, result_commit;
785         struct commit_list *parents, **pptr = &parents;
786         static struct lock_file lock;
787
788         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
789         refresh_cache(REFRESH_QUIET);
790         if (active_cache_changed &&
791             write_locked_index(&the_index, &lock, COMMIT_LOCK))
792                 return error(_("Unable to write index."));
793         rollback_lock_file(&lock);
794
795         write_tree_trivial(&result_tree);
796         printf(_("Wonderful.\n"));
797         pptr = commit_list_append(head, pptr);
798         pptr = commit_list_append(remoteheads->item, pptr);
799         prepare_to_commit(remoteheads);
800         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree.hash, parents,
801                         result_commit.hash, NULL, sign_commit))
802                 die(_("failed to write commit object"));
803         finish(head, remoteheads, &result_commit, "In-index merge");
804         drop_save();
805         return 0;
806 }
807
808 static int finish_automerge(struct commit *head,
809                             int head_subsumed,
810                             struct commit_list *common,
811                             struct commit_list *remoteheads,
812                             struct object_id *result_tree,
813                             const char *wt_strategy)
814 {
815         struct commit_list *parents = NULL;
816         struct strbuf buf = STRBUF_INIT;
817         struct object_id result_commit;
818
819         free_commit_list(common);
820         parents = remoteheads;
821         if (!head_subsumed || fast_forward == FF_NO)
822                 commit_list_insert(head, &parents);
823         strbuf_addch(&merge_msg, '\n');
824         prepare_to_commit(remoteheads);
825         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree->hash, parents,
826                         result_commit.hash, NULL, sign_commit))
827                 die(_("failed to write commit object"));
828         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
829         finish(head, remoteheads, &result_commit, buf.buf);
830         strbuf_release(&buf);
831         drop_save();
832         return 0;
833 }
834
835 static int suggest_conflicts(void)
836 {
837         const char *filename;
838         FILE *fp;
839         struct strbuf msgbuf = STRBUF_INIT;
840
841         filename = git_path_merge_msg();
842         fp = fopen(filename, "a");
843         if (!fp)
844                 die_errno(_("Could not open '%s' for writing"), filename);
845
846         append_conflicts_hint(&msgbuf);
847         fputs(msgbuf.buf, fp);
848         strbuf_release(&msgbuf);
849         fclose(fp);
850         rerere(allow_rerere_auto);
851         printf(_("Automatic merge failed; "
852                         "fix conflicts and then commit the result.\n"));
853         return 1;
854 }
855
856 static int evaluate_result(void)
857 {
858         int cnt = 0;
859         struct rev_info rev;
860
861         /* Check how many files differ. */
862         init_revisions(&rev, "");
863         setup_revisions(0, NULL, &rev, NULL);
864         rev.diffopt.output_format |=
865                 DIFF_FORMAT_CALLBACK;
866         rev.diffopt.format_callback = count_diff_files;
867         rev.diffopt.format_callback_data = &cnt;
868         run_diff_files(&rev, 0);
869
870         /*
871          * Check how many unmerged entries are
872          * there.
873          */
874         cnt += count_unmerged_entries();
875
876         return cnt;
877 }
878
879 /*
880  * Pretend as if the user told us to merge with the remote-tracking
881  * branch we have for the upstream of the current branch
882  */
883 static int setup_with_upstream(const char ***argv)
884 {
885         struct branch *branch = branch_get(NULL);
886         int i;
887         const char **args;
888
889         if (!branch)
890                 die(_("No current branch."));
891         if (!branch->remote_name)
892                 die(_("No remote for the current branch."));
893         if (!branch->merge_nr)
894                 die(_("No default upstream defined for the current branch."));
895
896         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
897         for (i = 0; i < branch->merge_nr; i++) {
898                 if (!branch->merge[i]->dst)
899                         die(_("No remote-tracking branch for %s from %s"),
900                             branch->merge[i]->src, branch->remote_name);
901                 args[i] = branch->merge[i]->dst;
902         }
903         args[i] = NULL;
904         *argv = args;
905         return i;
906 }
907
908 static void write_merge_state(struct commit_list *remoteheads)
909 {
910         struct commit_list *j;
911         struct strbuf buf = STRBUF_INIT;
912
913         for (j = remoteheads; j; j = j->next) {
914                 struct object_id *oid;
915                 struct commit *c = j->item;
916                 if (c->util && merge_remote_util(c)->obj) {
917                         oid = &merge_remote_util(c)->obj->oid;
918                 } else {
919                         oid = &c->object.oid;
920                 }
921                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
922         }
923         write_file_buf(git_path_merge_head(), buf.buf, buf.len);
924         strbuf_addch(&merge_msg, '\n');
925         write_file_buf(git_path_merge_msg(), merge_msg.buf, merge_msg.len);
926
927         strbuf_reset(&buf);
928         if (fast_forward == FF_NO)
929                 strbuf_addstr(&buf, "no-ff");
930         write_file_buf(git_path_merge_mode(), buf.buf, buf.len);
931 }
932
933 static int default_edit_option(void)
934 {
935         static const char name[] = "GIT_MERGE_AUTOEDIT";
936         const char *e = getenv(name);
937         struct stat st_stdin, st_stdout;
938
939         if (have_message)
940                 /* an explicit -m msg without --[no-]edit */
941                 return 0;
942
943         if (e) {
944                 int v = git_config_maybe_bool(name, e);
945                 if (v < 0)
946                         die(_("Bad value '%s' in environment '%s'"), e, name);
947                 return v;
948         }
949
950         /* Use editor if stdin and stdout are the same and is a tty */
951         return (!fstat(0, &st_stdin) &&
952                 !fstat(1, &st_stdout) &&
953                 isatty(0) && isatty(1) &&
954                 st_stdin.st_dev == st_stdout.st_dev &&
955                 st_stdin.st_ino == st_stdout.st_ino &&
956                 st_stdin.st_mode == st_stdout.st_mode);
957 }
958
959 static struct commit_list *reduce_parents(struct commit *head_commit,
960                                           int *head_subsumed,
961                                           struct commit_list *remoteheads)
962 {
963         struct commit_list *parents, **remotes;
964
965         /*
966          * Is the current HEAD reachable from another commit being
967          * merged?  If so we do not want to record it as a parent of
968          * the resulting merge, unless --no-ff is given.  We will flip
969          * this variable to 0 when we find HEAD among the independent
970          * tips being merged.
971          */
972         *head_subsumed = 1;
973
974         /* Find what parents to record by checking independent ones. */
975         parents = reduce_heads(remoteheads);
976
977         remoteheads = NULL;
978         remotes = &remoteheads;
979         while (parents) {
980                 struct commit *commit = pop_commit(&parents);
981                 if (commit == head_commit)
982                         *head_subsumed = 0;
983                 else
984                         remotes = &commit_list_insert(commit, remotes)->next;
985         }
986         return remoteheads;
987 }
988
989 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
990 {
991         struct fmt_merge_msg_opts opts;
992
993         memset(&opts, 0, sizeof(opts));
994         opts.add_title = !have_message;
995         opts.shortlog_len = shortlog_len;
996         opts.credit_people = (0 < option_edit);
997
998         fmt_merge_msg(merge_names, merge_msg, &opts);
999         if (merge_msg->len)
1000                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1001 }
1002
1003 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1004 {
1005         const char *filename;
1006         int fd, pos, npos;
1007         struct strbuf fetch_head_file = STRBUF_INIT;
1008
1009         if (!merge_names)
1010                 merge_names = &fetch_head_file;
1011
1012         filename = git_path_fetch_head();
1013         fd = open(filename, O_RDONLY);
1014         if (fd < 0)
1015                 die_errno(_("could not open '%s' for reading"), filename);
1016
1017         if (strbuf_read(merge_names, fd, 0) < 0)
1018                 die_errno(_("could not read '%s'"), filename);
1019         if (close(fd) < 0)
1020                 die_errno(_("could not close '%s'"), filename);
1021
1022         for (pos = 0; pos < merge_names->len; pos = npos) {
1023                 struct object_id oid;
1024                 char *ptr;
1025                 struct commit *commit;
1026
1027                 ptr = strchr(merge_names->buf + pos, '\n');
1028                 if (ptr)
1029                         npos = ptr - merge_names->buf + 1;
1030                 else
1031                         npos = merge_names->len;
1032
1033                 if (npos - pos < GIT_SHA1_HEXSZ + 2 ||
1034                     get_oid_hex(merge_names->buf + pos, &oid))
1035                         commit = NULL; /* bad */
1036                 else if (memcmp(merge_names->buf + pos + GIT_SHA1_HEXSZ, "\t\t", 2))
1037                         continue; /* not-for-merge */
1038                 else {
1039                         char saved = merge_names->buf[pos + GIT_SHA1_HEXSZ];
1040                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = '\0';
1041                         commit = get_merge_parent(merge_names->buf + pos);
1042                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = saved;
1043                 }
1044                 if (!commit) {
1045                         if (ptr)
1046                                 *ptr = '\0';
1047                         die(_("not something we can merge in %s: %s"),
1048                             filename, merge_names->buf + pos);
1049                 }
1050                 remotes = &commit_list_insert(commit, remotes)->next;
1051         }
1052
1053         if (merge_names == &fetch_head_file)
1054                 strbuf_release(&fetch_head_file);
1055 }
1056
1057 static struct commit_list *collect_parents(struct commit *head_commit,
1058                                            int *head_subsumed,
1059                                            int argc, const char **argv,
1060                                            struct strbuf *merge_msg)
1061 {
1062         int i;
1063         struct commit_list *remoteheads = NULL;
1064         struct commit_list **remotes = &remoteheads;
1065         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1066
1067         if (merge_msg && (!have_message || shortlog_len))
1068                 autogen = &merge_names;
1069
1070         if (head_commit)
1071                 remotes = &commit_list_insert(head_commit, remotes)->next;
1072
1073         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1074                 handle_fetch_head(remotes, autogen);
1075                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1076         } else {
1077                 for (i = 0; i < argc; i++) {
1078                         struct commit *commit = get_merge_parent(argv[i]);
1079                         if (!commit)
1080                                 help_unknown_ref(argv[i], "merge",
1081                                                  _("not something we can merge"));
1082                         remotes = &commit_list_insert(commit, remotes)->next;
1083                 }
1084                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1085                 if (autogen) {
1086                         struct commit_list *p;
1087                         for (p = remoteheads; p; p = p->next)
1088                                 merge_name(merge_remote_util(p->item)->name, autogen);
1089                 }
1090         }
1091
1092         if (autogen) {
1093                 prepare_merge_message(autogen, merge_msg);
1094                 strbuf_release(autogen);
1095         }
1096
1097         return remoteheads;
1098 }
1099
1100 int cmd_merge(int argc, const char **argv, const char *prefix)
1101 {
1102         struct object_id result_tree, stash, head_oid;
1103         struct commit *head_commit;
1104         struct strbuf buf = STRBUF_INIT;
1105         int i, ret = 0, head_subsumed;
1106         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1107         struct commit_list *common = NULL;
1108         const char *best_strategy = NULL, *wt_strategy = NULL;
1109         struct commit_list *remoteheads, *p;
1110         void *branch_to_free;
1111         int orig_argc = argc;
1112
1113         if (argc == 2 && !strcmp(argv[1], "-h"))
1114                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1115
1116         /*
1117          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1118          * current branch.
1119          */
1120         branch = branch_to_free = resolve_refdup("HEAD", 0, head_oid.hash, NULL);
1121         if (branch && starts_with(branch, "refs/heads/"))
1122                 branch += 11;
1123         if (!branch || is_null_oid(&head_oid))
1124                 head_commit = NULL;
1125         else
1126                 head_commit = lookup_commit_or_die(head_oid.hash, "HEAD");
1127
1128         init_diff_ui_defaults();
1129         git_config(git_merge_config, NULL);
1130
1131         if (branch_mergeoptions)
1132                 parse_branch_merge_options(branch_mergeoptions);
1133         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1134                         builtin_merge_usage, 0);
1135         if (shortlog_len < 0)
1136                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1137
1138         if (verbosity < 0 && show_progress == -1)
1139                 show_progress = 0;
1140
1141         if (abort_current_merge) {
1142                 int nargc = 2;
1143                 const char *nargv[] = {"reset", "--merge", NULL};
1144
1145                 if (orig_argc != 2)
1146                         usage_msg_opt(_("--abort expects no arguments"),
1147                               builtin_merge_usage, builtin_merge_options);
1148
1149                 if (!file_exists(git_path_merge_head()))
1150                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1151
1152                 /* Invoke 'git reset --merge' */
1153                 ret = cmd_reset(nargc, nargv, prefix);
1154                 goto done;
1155         }
1156
1157         if (continue_current_merge) {
1158                 int nargc = 1;
1159                 const char *nargv[] = {"commit", NULL};
1160
1161                 if (orig_argc != 2)
1162                         usage_msg_opt(_("--continue expects no arguments"),
1163                               builtin_merge_usage, builtin_merge_options);
1164
1165                 if (!file_exists(git_path_merge_head()))
1166                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1167
1168                 /* Invoke 'git commit' */
1169                 ret = cmd_commit(nargc, nargv, prefix);
1170                 goto done;
1171         }
1172
1173         if (read_cache_unmerged())
1174                 die_resolve_conflict("merge");
1175
1176         if (file_exists(git_path_merge_head())) {
1177                 /*
1178                  * There is no unmerged entry, don't advise 'git
1179                  * add/rm <file>', just 'git commit'.
1180                  */
1181                 if (advice_resolve_conflict)
1182                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1183                                   "Please, commit your changes before you merge."));
1184                 else
1185                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1186         }
1187         if (file_exists(git_path_cherry_pick_head())) {
1188                 if (advice_resolve_conflict)
1189                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1190                             "Please, commit your changes before you merge."));
1191                 else
1192                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1193         }
1194         resolve_undo_clear();
1195
1196         if (verbosity < 0)
1197                 show_diffstat = 0;
1198
1199         if (squash) {
1200                 if (fast_forward == FF_NO)
1201                         die(_("You cannot combine --squash with --no-ff."));
1202                 option_commit = 0;
1203         }
1204
1205         if (!argc) {
1206                 if (default_to_upstream)
1207                         argc = setup_with_upstream(&argv);
1208                 else
1209                         die(_("No commit specified and merge.defaultToUpstream not set."));
1210         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1211                 argv[0] = "@{-1}";
1212         }
1213
1214         if (!argc)
1215                 usage_with_options(builtin_merge_usage,
1216                         builtin_merge_options);
1217
1218         if (!head_commit) {
1219                 /*
1220                  * If the merged head is a valid one there is no reason
1221                  * to forbid "git merge" into a branch yet to be born.
1222                  * We do the same for "git pull".
1223                  */
1224                 struct object_id *remote_head_oid;
1225                 if (squash)
1226                         die(_("Squash commit into empty head not supported yet"));
1227                 if (fast_forward == FF_NO)
1228                         die(_("Non-fast-forward commit does not make sense into "
1229                             "an empty head"));
1230                 remoteheads = collect_parents(head_commit, &head_subsumed,
1231                                               argc, argv, NULL);
1232                 if (!remoteheads)
1233                         die(_("%s - not something we can merge"), argv[0]);
1234                 if (remoteheads->next)
1235                         die(_("Can merge only exactly one commit into empty head"));
1236                 remote_head_oid = &remoteheads->item->object.oid;
1237                 read_empty(remote_head_oid->hash, 0);
1238                 update_ref("initial pull", "HEAD", remote_head_oid->hash,
1239                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1240                 goto done;
1241         }
1242
1243         /*
1244          * All the rest are the commits being merged; prepare
1245          * the standard merge summary message to be appended
1246          * to the given message.
1247          */
1248         remoteheads = collect_parents(head_commit, &head_subsumed,
1249                                       argc, argv, &merge_msg);
1250
1251         if (!head_commit || !argc)
1252                 usage_with_options(builtin_merge_usage,
1253                         builtin_merge_options);
1254
1255         if (verify_signatures) {
1256                 for (p = remoteheads; p; p = p->next) {
1257                         struct commit *commit = p->item;
1258                         char hex[GIT_SHA1_HEXSZ + 1];
1259                         struct signature_check signature_check;
1260                         memset(&signature_check, 0, sizeof(signature_check));
1261
1262                         check_commit_signature(commit, &signature_check);
1263
1264                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1265                         switch (signature_check.result) {
1266                         case 'G':
1267                                 break;
1268                         case 'U':
1269                                 die(_("Commit %s has an untrusted GPG signature, "
1270                                       "allegedly by %s."), hex, signature_check.signer);
1271                         case 'B':
1272                                 die(_("Commit %s has a bad GPG signature "
1273                                       "allegedly by %s."), hex, signature_check.signer);
1274                         default: /* 'N' */
1275                                 die(_("Commit %s does not have a GPG signature."), hex);
1276                         }
1277                         if (verbosity >= 0 && signature_check.result == 'G')
1278                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1279                                        hex, signature_check.signer);
1280
1281                         signature_check_clear(&signature_check);
1282                 }
1283         }
1284
1285         strbuf_addstr(&buf, "merge");
1286         for (p = remoteheads; p; p = p->next)
1287                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1288         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1289         strbuf_reset(&buf);
1290
1291         for (p = remoteheads; p; p = p->next) {
1292                 struct commit *commit = p->item;
1293                 strbuf_addf(&buf, "GITHEAD_%s",
1294                             oid_to_hex(&commit->object.oid));
1295                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1296                 strbuf_reset(&buf);
1297                 if (fast_forward != FF_ONLY &&
1298                     merge_remote_util(commit) &&
1299                     merge_remote_util(commit)->obj &&
1300                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1301                         fast_forward = FF_NO;
1302         }
1303
1304         if (option_edit < 0)
1305                 option_edit = default_edit_option();
1306
1307         if (!use_strategies) {
1308                 if (!remoteheads)
1309                         ; /* already up-to-date */
1310                 else if (!remoteheads->next)
1311                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1312                 else
1313                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1314         }
1315
1316         for (i = 0; i < use_strategies_nr; i++) {
1317                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1318                         fast_forward = FF_NO;
1319                 if (use_strategies[i]->attr & NO_TRIVIAL)
1320                         allow_trivial = 0;
1321         }
1322
1323         if (!remoteheads)
1324                 ; /* already up-to-date */
1325         else if (!remoteheads->next)
1326                 common = get_merge_bases(head_commit, remoteheads->item);
1327         else {
1328                 struct commit_list *list = remoteheads;
1329                 commit_list_insert(head_commit, &list);
1330                 common = get_octopus_merge_bases(list);
1331                 free(list);
1332         }
1333
1334         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.oid.hash,
1335                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1336
1337         if (remoteheads && !common) {
1338                 /* No common ancestors found. */
1339                 if (!allow_unrelated_histories)
1340                         die(_("refusing to merge unrelated histories"));
1341                 /* otherwise, we need a real merge. */
1342         } else if (!remoteheads ||
1343                  (!remoteheads->next && !common->next &&
1344                   common->item == remoteheads->item)) {
1345                 /*
1346                  * If head can reach all the merge then we are up to date.
1347                  * but first the most common case of merging one remote.
1348                  */
1349                 finish_up_to_date(_("Already up-to-date."));
1350                 goto done;
1351         } else if (fast_forward != FF_NO && !remoteheads->next &&
1352                         !common->next &&
1353                         !oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
1354                 /* Again the most common case of merging one remote. */
1355                 struct strbuf msg = STRBUF_INIT;
1356                 struct commit *commit;
1357
1358                 if (verbosity >= 0) {
1359                         printf(_("Updating %s..%s\n"),
1360                                find_unique_abbrev(head_commit->object.oid.hash,
1361                                                   DEFAULT_ABBREV),
1362                                find_unique_abbrev(remoteheads->item->object.oid.hash,
1363                                                   DEFAULT_ABBREV));
1364                 }
1365                 strbuf_addstr(&msg, "Fast-forward");
1366                 if (have_message)
1367                         strbuf_addstr(&msg,
1368                                 " (no commit created; -m option ignored)");
1369                 commit = remoteheads->item;
1370                 if (!commit) {
1371                         ret = 1;
1372                         goto done;
1373                 }
1374
1375                 if (checkout_fast_forward(head_commit->object.oid.hash,
1376                                           commit->object.oid.hash,
1377                                           overwrite_ignore)) {
1378                         ret = 1;
1379                         goto done;
1380                 }
1381
1382                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1383                 drop_save();
1384                 goto done;
1385         } else if (!remoteheads->next && common->next)
1386                 ;
1387                 /*
1388                  * We are not doing octopus and not fast-forward.  Need
1389                  * a real merge.
1390                  */
1391         else if (!remoteheads->next && !common->next && option_commit) {
1392                 /*
1393                  * We are not doing octopus, not fast-forward, and have
1394                  * only one common.
1395                  */
1396                 refresh_cache(REFRESH_QUIET);
1397                 if (allow_trivial && fast_forward != FF_ONLY) {
1398                         /* See if it is really trivial. */
1399                         git_committer_info(IDENT_STRICT);
1400                         printf(_("Trying really trivial in-index merge...\n"));
1401                         if (!read_tree_trivial(&common->item->object.oid,
1402                                                &head_commit->object.oid,
1403                                                &remoteheads->item->object.oid)) {
1404                                 ret = merge_trivial(head_commit, remoteheads);
1405                                 goto done;
1406                         }
1407                         printf(_("Nope.\n"));
1408                 }
1409         } else {
1410                 /*
1411                  * An octopus.  If we can reach all the remote we are up
1412                  * to date.
1413                  */
1414                 int up_to_date = 1;
1415                 struct commit_list *j;
1416
1417                 for (j = remoteheads; j; j = j->next) {
1418                         struct commit_list *common_one;
1419
1420                         /*
1421                          * Here we *have* to calculate the individual
1422                          * merge_bases again, otherwise "git merge HEAD^
1423                          * HEAD^^" would be missed.
1424                          */
1425                         common_one = get_merge_bases(head_commit, j->item);
1426                         if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
1427                                 up_to_date = 0;
1428                                 break;
1429                         }
1430                 }
1431                 if (up_to_date) {
1432                         finish_up_to_date(_("Already up-to-date. Yeeah!"));
1433                         goto done;
1434                 }
1435         }
1436
1437         if (fast_forward == FF_ONLY)
1438                 die(_("Not possible to fast-forward, aborting."));
1439
1440         /* We are going to make a new commit. */
1441         git_committer_info(IDENT_STRICT);
1442
1443         /*
1444          * At this point, we need a real merge.  No matter what strategy
1445          * we use, it would operate on the index, possibly affecting the
1446          * working tree, and when resolved cleanly, have the desired
1447          * tree in the index -- this means that the index must be in
1448          * sync with the head commit.  The strategies are responsible
1449          * to ensure this.
1450          */
1451         if (use_strategies_nr == 1 ||
1452             /*
1453              * Stash away the local changes so that we can try more than one.
1454              */
1455             save_state(&stash))
1456                 oidclr(&stash);
1457
1458         for (i = 0; i < use_strategies_nr; i++) {
1459                 int ret;
1460                 if (i) {
1461                         printf(_("Rewinding the tree to pristine...\n"));
1462                         restore_state(&head_commit->object.oid, &stash);
1463                 }
1464                 if (use_strategies_nr != 1)
1465                         printf(_("Trying merge strategy %s...\n"),
1466                                 use_strategies[i]->name);
1467                 /*
1468                  * Remember which strategy left the state in the working
1469                  * tree.
1470                  */
1471                 wt_strategy = use_strategies[i]->name;
1472
1473                 ret = try_merge_strategy(use_strategies[i]->name,
1474                                          common, remoteheads,
1475                                          head_commit);
1476                 if (!option_commit && !ret) {
1477                         merge_was_ok = 1;
1478                         /*
1479                          * This is necessary here just to avoid writing
1480                          * the tree, but later we will *not* exit with
1481                          * status code 1 because merge_was_ok is set.
1482                          */
1483                         ret = 1;
1484                 }
1485
1486                 if (ret) {
1487                         /*
1488                          * The backend exits with 1 when conflicts are
1489                          * left to be resolved, with 2 when it does not
1490                          * handle the given merge at all.
1491                          */
1492                         if (ret == 1) {
1493                                 int cnt = evaluate_result();
1494
1495                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1496                                         best_strategy = use_strategies[i]->name;
1497                                         best_cnt = cnt;
1498                                 }
1499                         }
1500                         if (merge_was_ok)
1501                                 break;
1502                         else
1503                                 continue;
1504                 }
1505
1506                 /* Automerge succeeded. */
1507                 write_tree_trivial(&result_tree);
1508                 automerge_was_ok = 1;
1509                 break;
1510         }
1511
1512         /*
1513          * If we have a resulting tree, that means the strategy module
1514          * auto resolved the merge cleanly.
1515          */
1516         if (automerge_was_ok) {
1517                 ret = finish_automerge(head_commit, head_subsumed,
1518                                        common, remoteheads,
1519                                        &result_tree, wt_strategy);
1520                 goto done;
1521         }
1522
1523         /*
1524          * Pick the result from the best strategy and have the user fix
1525          * it up.
1526          */
1527         if (!best_strategy) {
1528                 restore_state(&head_commit->object.oid, &stash);
1529                 if (use_strategies_nr > 1)
1530                         fprintf(stderr,
1531                                 _("No merge strategy handled the merge.\n"));
1532                 else
1533                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1534                                 use_strategies[0]->name);
1535                 ret = 2;
1536                 goto done;
1537         } else if (best_strategy == wt_strategy)
1538                 ; /* We already have its result in the working tree. */
1539         else {
1540                 printf(_("Rewinding the tree to pristine...\n"));
1541                 restore_state(&head_commit->object.oid, &stash);
1542                 printf(_("Using the %s to prepare resolving by hand.\n"),
1543                         best_strategy);
1544                 try_merge_strategy(best_strategy, common, remoteheads,
1545                                    head_commit);
1546         }
1547
1548         if (squash)
1549                 finish(head_commit, remoteheads, NULL, NULL);
1550         else
1551                 write_merge_state(remoteheads);
1552
1553         if (merge_was_ok)
1554                 fprintf(stderr, _("Automatic merge went well; "
1555                         "stopped before committing as requested\n"));
1556         else
1557                 ret = suggest_conflicts();
1558
1559 done:
1560         free(branch_to_free);
1561         return ret;
1562 }