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