Sync with maint
[git] / builtin / merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "config.h"
11 #include "parse-options.h"
12 #include "builtin.h"
13 #include "lockfile.h"
14 #include "run-command.h"
15 #include "diff.h"
16 #include "refs.h"
17 #include "commit.h"
18 #include "diffcore.h"
19 #include "revision.h"
20 #include "unpack-trees.h"
21 #include "cache-tree.h"
22 #include "dir.h"
23 #include "utf8.h"
24 #include "log-tree.h"
25 #include "color.h"
26 #include "rerere.h"
27 #include "help.h"
28 #include "merge-recursive.h"
29 #include "resolve-undo.h"
30 #include "remote.h"
31 #include "fmt-merge-msg.h"
32 #include "gpg-interface.h"
33 #include "sequencer.h"
34 #include "string-list.h"
35 #include "packfile.h"
36
37 #define DEFAULT_TWOHEAD (1<<0)
38 #define DEFAULT_OCTOPUS (1<<1)
39 #define NO_FAST_FORWARD (1<<2)
40 #define NO_TRIVIAL      (1<<3)
41
42 struct strategy {
43         const char *name;
44         unsigned attr;
45 };
46
47 static const char * const builtin_merge_usage[] = {
48         N_("git merge [<options>] [<commit>...]"),
49         N_("git merge --abort"),
50         N_("git merge --continue"),
51         NULL
52 };
53
54 static int show_diffstat = 1, shortlog_len = -1, squash;
55 static int option_commit = 1;
56 static int option_edit = -1;
57 static int allow_trivial = 1, have_message, verify_signatures;
58 static int overwrite_ignore = 1;
59 static struct strbuf merge_msg = STRBUF_INIT;
60 static struct strategy **use_strategies;
61 static size_t use_strategies_nr, use_strategies_alloc;
62 static const char **xopts;
63 static size_t xopts_nr, xopts_alloc;
64 static const char *branch;
65 static char *branch_mergeoptions;
66 static int option_renormalize;
67 static int verbosity;
68 static int allow_rerere_auto;
69 static int abort_current_merge;
70 static int continue_current_merge;
71 static int allow_unrelated_histories;
72 static int show_progress = -1;
73 static int default_to_upstream = 1;
74 static int signoff;
75 static const char *sign_commit;
76 static int verify_msg = 1;
77
78 static struct strategy all_strategy[] = {
79         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
80         { "octopus",    DEFAULT_OCTOPUS },
81         { "resolve",    0 },
82         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
83         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
84 };
85
86 static const char *pull_twohead, *pull_octopus;
87
88 enum ff_type {
89         FF_NO,
90         FF_ALLOW,
91         FF_ONLY
92 };
93
94 static enum ff_type fast_forward = FF_ALLOW;
95
96 static int option_parse_message(const struct option *opt,
97                                 const char *arg, int unset)
98 {
99         struct strbuf *buf = opt->value;
100
101         if (unset)
102                 strbuf_setlen(buf, 0);
103         else if (arg) {
104                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
105                 have_message = 1;
106         } else
107                 return error(_("switch `m' requires a value"));
108         return 0;
109 }
110
111 static struct strategy *get_strategy(const char *name)
112 {
113         int i;
114         struct strategy *ret;
115         static struct cmdnames main_cmds, other_cmds;
116         static int loaded;
117
118         if (!name)
119                 return NULL;
120
121         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
122                 if (!strcmp(name, all_strategy[i].name))
123                         return &all_strategy[i];
124
125         if (!loaded) {
126                 struct cmdnames not_strategies;
127                 loaded = 1;
128
129                 memset(&not_strategies, 0, sizeof(struct cmdnames));
130                 load_command_list("git-merge-", &main_cmds, &other_cmds);
131                 for (i = 0; i < main_cmds.cnt; i++) {
132                         int j, found = 0;
133                         struct cmdname *ent = main_cmds.names[i];
134                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
135                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
136                                                 && !all_strategy[j].name[ent->len])
137                                         found = 1;
138                         if (!found)
139                                 add_cmdname(&not_strategies, ent->name, ent->len);
140                 }
141                 exclude_cmds(&main_cmds, &not_strategies);
142         }
143         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
144                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
145                 fprintf(stderr, _("Available strategies are:"));
146                 for (i = 0; i < main_cmds.cnt; i++)
147                         fprintf(stderr, " %s", main_cmds.names[i]->name);
148                 fprintf(stderr, ".\n");
149                 if (other_cmds.cnt) {
150                         fprintf(stderr, _("Available custom strategies are:"));
151                         for (i = 0; i < other_cmds.cnt; i++)
152                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
153                         fprintf(stderr, ".\n");
154                 }
155                 exit(1);
156         }
157
158         ret = xcalloc(1, sizeof(struct strategy));
159         ret->name = xstrdup(name);
160         ret->attr = NO_TRIVIAL;
161         return ret;
162 }
163
164 static void append_strategy(struct strategy *s)
165 {
166         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
167         use_strategies[use_strategies_nr++] = s;
168 }
169
170 static int option_parse_strategy(const struct option *opt,
171                                  const char *name, int unset)
172 {
173         if (unset)
174                 return 0;
175
176         append_strategy(get_strategy(name));
177         return 0;
178 }
179
180 static int option_parse_x(const struct option *opt,
181                           const char *arg, int unset)
182 {
183         if (unset)
184                 return 0;
185
186         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
187         xopts[xopts_nr++] = xstrdup(arg);
188         return 0;
189 }
190
191 static int option_parse_n(const struct option *opt,
192                           const char *arg, int unset)
193 {
194         show_diffstat = unset;
195         return 0;
196 }
197
198 static struct option builtin_merge_options[] = {
199         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
200                 N_("do not show a diffstat at the end of the merge"),
201                 PARSE_OPT_NOARG, option_parse_n },
202         OPT_BOOL(0, "stat", &show_diffstat,
203                 N_("show a diffstat at the end of the merge")),
204         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
205         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
206           N_("add (at most <n>) entries from shortlog to merge commit message"),
207           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
208         OPT_BOOL(0, "squash", &squash,
209                 N_("create a single commit instead of doing a merge")),
210         OPT_BOOL(0, "commit", &option_commit,
211                 N_("perform a commit if the merge succeeds (default)")),
212         OPT_BOOL('e', "edit", &option_edit,
213                 N_("edit message before committing")),
214         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
215         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
216                 N_("abort if fast-forward is not possible"),
217                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
218         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
219         OPT_BOOL(0, "verify-signatures", &verify_signatures,
220                 N_("verify that the named commit has a valid GPG signature")),
221         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
222                 N_("merge strategy to use"), option_parse_strategy),
223         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
224                 N_("option for selected merge strategy"), option_parse_x),
225         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
226                 N_("merge commit message (for a non-fast-forward merge)"),
227                 option_parse_message),
228         OPT__VERBOSITY(&verbosity),
229         OPT_BOOL(0, "abort", &abort_current_merge,
230                 N_("abort the current in-progress merge")),
231         OPT_BOOL(0, "continue", &continue_current_merge,
232                 N_("continue the current in-progress merge")),
233         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
234                  N_("allow merging unrelated histories")),
235         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
236         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
237           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
238         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
239         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
240         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
241         OPT_END()
242 };
243
244 /* Cleans up metadata that is uninteresting after a succeeded merge. */
245 static void drop_save(void)
246 {
247         unlink(git_path_merge_head());
248         unlink(git_path_merge_msg());
249         unlink(git_path_merge_mode());
250 }
251
252 static int save_state(struct object_id *stash)
253 {
254         int len;
255         struct child_process cp = CHILD_PROCESS_INIT;
256         struct strbuf buffer = STRBUF_INIT;
257         const char *argv[] = {"stash", "create", NULL};
258         int rc = -1;
259
260         cp.argv = argv;
261         cp.out = -1;
262         cp.git_cmd = 1;
263
264         if (start_command(&cp))
265                 die(_("could not run stash."));
266         len = strbuf_read(&buffer, cp.out, 1024);
267         close(cp.out);
268
269         if (finish_command(&cp) || len < 0)
270                 die(_("stash failed"));
271         else if (!len)          /* no changes */
272                 goto out;
273         strbuf_setlen(&buffer, buffer.len-1);
274         if (get_oid(buffer.buf, stash))
275                 die(_("not a valid object: %s"), buffer.buf);
276         rc = 0;
277 out:
278         strbuf_release(&buffer);
279         return rc;
280 }
281
282 static void read_empty(unsigned const char *sha1, int verbose)
283 {
284         int i = 0;
285         const char *args[7];
286
287         args[i++] = "read-tree";
288         if (verbose)
289                 args[i++] = "-v";
290         args[i++] = "-m";
291         args[i++] = "-u";
292         args[i++] = EMPTY_TREE_SHA1_HEX;
293         args[i++] = sha1_to_hex(sha1);
294         args[i] = NULL;
295
296         if (run_command_v_opt(args, RUN_GIT_CMD))
297                 die(_("read-tree failed"));
298 }
299
300 static void reset_hard(unsigned const char *sha1, int verbose)
301 {
302         int i = 0;
303         const char *args[6];
304
305         args[i++] = "read-tree";
306         if (verbose)
307                 args[i++] = "-v";
308         args[i++] = "--reset";
309         args[i++] = "-u";
310         args[i++] = sha1_to_hex(sha1);
311         args[i] = NULL;
312
313         if (run_command_v_opt(args, RUN_GIT_CMD))
314                 die(_("read-tree failed"));
315 }
316
317 static void restore_state(const struct object_id *head,
318                           const struct object_id *stash)
319 {
320         struct strbuf sb = STRBUF_INIT;
321         const char *args[] = { "stash", "apply", NULL, NULL };
322
323         if (is_null_oid(stash))
324                 return;
325
326         reset_hard(head->hash, 1);
327
328         args[2] = oid_to_hex(stash);
329
330         /*
331          * It is OK to ignore error here, for example when there was
332          * nothing to restore.
333          */
334         run_command_v_opt(args, RUN_GIT_CMD);
335
336         strbuf_release(&sb);
337         refresh_cache(REFRESH_QUIET);
338 }
339
340 /* This is called when no merge was necessary. */
341 static void finish_up_to_date(const char *msg)
342 {
343         if (verbosity >= 0)
344                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
345         drop_save();
346 }
347
348 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
349 {
350         struct rev_info rev;
351         struct strbuf out = STRBUF_INIT;
352         struct commit_list *j;
353         struct pretty_print_context ctx = {0};
354
355         printf(_("Squash commit -- not updating HEAD\n"));
356
357         init_revisions(&rev, NULL);
358         rev.ignore_merges = 1;
359         rev.commit_format = CMIT_FMT_MEDIUM;
360
361         commit->object.flags |= UNINTERESTING;
362         add_pending_object(&rev, &commit->object, NULL);
363
364         for (j = remoteheads; j; j = j->next)
365                 add_pending_object(&rev, &j->item->object, NULL);
366
367         setup_revisions(0, NULL, &rev, NULL);
368         if (prepare_revision_walk(&rev))
369                 die(_("revision walk setup failed"));
370
371         ctx.abbrev = rev.abbrev;
372         ctx.date_mode = rev.date_mode;
373         ctx.fmt = rev.commit_format;
374
375         strbuf_addstr(&out, "Squashed commit of the following:\n");
376         while ((commit = get_revision(&rev)) != NULL) {
377                 strbuf_addch(&out, '\n');
378                 strbuf_addf(&out, "commit %s\n",
379                         oid_to_hex(&commit->object.oid));
380                 pretty_print_commit(&ctx, commit, &out);
381         }
382         write_file_buf(git_path_squash_msg(), out.buf, out.len);
383         strbuf_release(&out);
384 }
385
386 static void finish(struct commit *head_commit,
387                    struct commit_list *remoteheads,
388                    const struct object_id *new_head, const char *msg)
389 {
390         struct strbuf reflog_message = STRBUF_INIT;
391         const struct object_id *head = &head_commit->object.oid;
392
393         if (!msg)
394                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
395         else {
396                 if (verbosity >= 0)
397                         printf("%s\n", msg);
398                 strbuf_addf(&reflog_message, "%s: %s",
399                         getenv("GIT_REFLOG_ACTION"), msg);
400         }
401         if (squash) {
402                 squash_message(head_commit, remoteheads);
403         } else {
404                 if (verbosity >= 0 && !merge_msg.len)
405                         printf(_("No merge message -- not updating HEAD\n"));
406                 else {
407                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
408                         update_ref(reflog_message.buf, "HEAD", new_head, head,
409                                    0, UPDATE_REFS_DIE_ON_ERR);
410                         /*
411                          * We ignore errors in 'gc --auto', since the
412                          * user should see them.
413                          */
414                         close_all_packs();
415                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
416                 }
417         }
418         if (new_head && show_diffstat) {
419                 struct diff_options opts;
420                 diff_setup(&opts);
421                 opts.stat_width = -1; /* use full terminal width */
422                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
423                 opts.output_format |=
424                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
425                 opts.detect_rename = DIFF_DETECT_RENAME;
426                 diff_setup_done(&opts);
427                 diff_tree_oid(head, new_head, "", &opts);
428                 diffcore_std(&opts);
429                 diff_flush(&opts);
430         }
431
432         /* Run a post-merge hook */
433         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
434
435         strbuf_release(&reflog_message);
436 }
437
438 /* Get the name for the merge commit's message. */
439 static void merge_name(const char *remote, struct strbuf *msg)
440 {
441         struct commit *remote_head;
442         struct object_id branch_head;
443         struct strbuf buf = STRBUF_INIT;
444         struct strbuf bname = STRBUF_INIT;
445         const char *ptr;
446         char *found_ref;
447         int len, early;
448
449         strbuf_branchname(&bname, remote, 0);
450         remote = bname.buf;
451
452         oidclr(&branch_head);
453         remote_head = get_merge_parent(remote);
454         if (!remote_head)
455                 die(_("'%s' does not point to a commit"), remote);
456
457         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
458                 if (starts_with(found_ref, "refs/heads/")) {
459                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
460                                     oid_to_hex(&branch_head), remote);
461                         goto cleanup;
462                 }
463                 if (starts_with(found_ref, "refs/tags/")) {
464                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
465                                     oid_to_hex(&branch_head), remote);
466                         goto cleanup;
467                 }
468                 if (starts_with(found_ref, "refs/remotes/")) {
469                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
470                                     oid_to_hex(&branch_head), remote);
471                         goto cleanup;
472                 }
473         }
474
475         /* See if remote matches <name>^^^.. or <name>~<number> */
476         for (len = 0, ptr = remote + strlen(remote);
477              remote < ptr && ptr[-1] == '^';
478              ptr--)
479                 len++;
480         if (len)
481                 early = 1;
482         else {
483                 early = 0;
484                 ptr = strrchr(remote, '~');
485                 if (ptr) {
486                         int seen_nonzero = 0;
487
488                         len++; /* count ~ */
489                         while (*++ptr && isdigit(*ptr)) {
490                                 seen_nonzero |= (*ptr != '0');
491                                 len++;
492                         }
493                         if (*ptr)
494                                 len = 0; /* not ...~<number> */
495                         else if (seen_nonzero)
496                                 early = 1;
497                         else if (len == 1)
498                                 early = 1; /* "name~" is "name~1"! */
499                 }
500         }
501         if (len) {
502                 struct strbuf truname = STRBUF_INIT;
503                 strbuf_addf(&truname, "refs/heads/%s", remote);
504                 strbuf_setlen(&truname, truname.len - len);
505                 if (ref_exists(truname.buf)) {
506                         strbuf_addf(msg,
507                                     "%s\t\tbranch '%s'%s of .\n",
508                                     oid_to_hex(&remote_head->object.oid),
509                                     truname.buf + 11,
510                                     (early ? " (early part)" : ""));
511                         strbuf_release(&truname);
512                         goto cleanup;
513                 }
514                 strbuf_release(&truname);
515         }
516
517         if (remote_head->util) {
518                 struct merge_remote_desc *desc;
519                 desc = merge_remote_util(remote_head);
520                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
521                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
522                                     oid_to_hex(&desc->obj->oid),
523                                     typename(desc->obj->type),
524                                     remote);
525                         goto cleanup;
526                 }
527         }
528
529         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
530                 oid_to_hex(&remote_head->object.oid), remote);
531 cleanup:
532         strbuf_release(&buf);
533         strbuf_release(&bname);
534 }
535
536 static void parse_branch_merge_options(char *bmo)
537 {
538         const char **argv;
539         int argc;
540
541         if (!bmo)
542                 return;
543         argc = split_cmdline(bmo, &argv);
544         if (argc < 0)
545                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
546                     split_cmdline_strerror(argc));
547         REALLOC_ARRAY(argv, argc + 2);
548         MOVE_ARRAY(argv + 1, argv, argc + 1);
549         argc++;
550         argv[0] = "branch.*.mergeoptions";
551         parse_options(argc, argv, NULL, builtin_merge_options,
552                       builtin_merge_usage, 0);
553         free(argv);
554 }
555
556 static int git_merge_config(const char *k, const char *v, void *cb)
557 {
558         int status;
559
560         if (branch && starts_with(k, "branch.") &&
561                 starts_with(k + 7, branch) &&
562                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
563                 free(branch_mergeoptions);
564                 branch_mergeoptions = xstrdup(v);
565                 return 0;
566         }
567
568         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
569                 show_diffstat = git_config_bool(k, v);
570         else if (!strcmp(k, "merge.verifysignatures"))
571                 verify_signatures = git_config_bool(k, v);
572         else if (!strcmp(k, "pull.twohead"))
573                 return git_config_string(&pull_twohead, k, v);
574         else if (!strcmp(k, "pull.octopus"))
575                 return git_config_string(&pull_octopus, k, v);
576         else if (!strcmp(k, "merge.renormalize"))
577                 option_renormalize = git_config_bool(k, v);
578         else if (!strcmp(k, "merge.ff")) {
579                 int boolval = git_parse_maybe_bool(v);
580                 if (0 <= boolval) {
581                         fast_forward = boolval ? FF_ALLOW : FF_NO;
582                 } else if (v && !strcmp(v, "only")) {
583                         fast_forward = FF_ONLY;
584                 } /* do not barf on values from future versions of git */
585                 return 0;
586         } else if (!strcmp(k, "merge.defaulttoupstream")) {
587                 default_to_upstream = git_config_bool(k, v);
588                 return 0;
589         } else if (!strcmp(k, "commit.gpgsign")) {
590                 sign_commit = git_config_bool(k, v) ? "" : NULL;
591                 return 0;
592         }
593
594         status = fmt_merge_msg_config(k, v, cb);
595         if (status)
596                 return status;
597         status = git_gpg_config(k, v, NULL);
598         if (status)
599                 return status;
600         return git_diff_ui_config(k, v, cb);
601 }
602
603 static int read_tree_trivial(struct object_id *common, struct object_id *head,
604                              struct object_id *one)
605 {
606         int i, nr_trees = 0;
607         struct tree *trees[MAX_UNPACK_TREES];
608         struct tree_desc t[MAX_UNPACK_TREES];
609         struct unpack_trees_options opts;
610
611         memset(&opts, 0, sizeof(opts));
612         opts.head_idx = 2;
613         opts.src_index = &the_index;
614         opts.dst_index = &the_index;
615         opts.update = 1;
616         opts.verbose_update = 1;
617         opts.trivial_merges_only = 1;
618         opts.merge = 1;
619         trees[nr_trees] = parse_tree_indirect(common);
620         if (!trees[nr_trees++])
621                 return -1;
622         trees[nr_trees] = parse_tree_indirect(head);
623         if (!trees[nr_trees++])
624                 return -1;
625         trees[nr_trees] = parse_tree_indirect(one);
626         if (!trees[nr_trees++])
627                 return -1;
628         opts.fn = threeway_merge;
629         cache_tree_free(&active_cache_tree);
630         for (i = 0; i < nr_trees; i++) {
631                 parse_tree(trees[i]);
632                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
633         }
634         if (unpack_trees(nr_trees, t, &opts))
635                 return -1;
636         return 0;
637 }
638
639 static void write_tree_trivial(struct object_id *oid)
640 {
641         if (write_cache_as_tree(oid->hash, 0, NULL))
642                 die(_("git write-tree failed to write a tree"));
643 }
644
645 static int try_merge_strategy(const char *strategy, struct commit_list *common,
646                               struct commit_list *remoteheads,
647                               struct commit *head)
648 {
649         static struct lock_file lock;
650         const char *head_arg = "HEAD";
651
652         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
653         refresh_cache(REFRESH_QUIET);
654         if (active_cache_changed &&
655             write_locked_index(&the_index, &lock, COMMIT_LOCK))
656                 return error(_("Unable to write index."));
657         rollback_lock_file(&lock);
658
659         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
660                 int clean, x;
661                 struct commit *result;
662                 struct commit_list *reversed = NULL;
663                 struct merge_options o;
664                 struct commit_list *j;
665
666                 if (remoteheads->next) {
667                         error(_("Not handling anything other than two heads merge."));
668                         return 2;
669                 }
670
671                 init_merge_options(&o);
672                 if (!strcmp(strategy, "subtree"))
673                         o.subtree_shift = "";
674
675                 o.renormalize = option_renormalize;
676                 o.show_rename_progress =
677                         show_progress == -1 ? isatty(2) : show_progress;
678
679                 for (x = 0; x < xopts_nr; x++)
680                         if (parse_merge_opt(&o, xopts[x]))
681                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
682
683                 o.branch1 = head_arg;
684                 o.branch2 = merge_remote_util(remoteheads->item)->name;
685
686                 for (j = common; j; j = j->next)
687                         commit_list_insert(j->item, &reversed);
688
689                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
690                 clean = merge_recursive(&o, head,
691                                 remoteheads->item, reversed, &result);
692                 if (clean < 0)
693                         exit(128);
694                 if (active_cache_changed &&
695                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
696                         die (_("unable to write %s"), get_index_file());
697                 rollback_lock_file(&lock);
698                 return clean ? 0 : 1;
699         } else {
700                 return try_merge_command(strategy, xopts_nr, xopts,
701                                                 common, head_arg, remoteheads);
702         }
703 }
704
705 static void count_diff_files(struct diff_queue_struct *q,
706                              struct diff_options *opt, void *data)
707 {
708         int *count = data;
709
710         (*count) += q->nr;
711 }
712
713 static int count_unmerged_entries(void)
714 {
715         int i, ret = 0;
716
717         for (i = 0; i < active_nr; i++)
718                 if (ce_stage(active_cache[i]))
719                         ret++;
720
721         return ret;
722 }
723
724 static void add_strategies(const char *string, unsigned attr)
725 {
726         int i;
727
728         if (string) {
729                 struct string_list list = STRING_LIST_INIT_DUP;
730                 struct string_list_item *item;
731                 string_list_split(&list, string, ' ', -1);
732                 for_each_string_list_item(item, &list)
733                         append_strategy(get_strategy(item->string));
734                 string_list_clear(&list, 0);
735                 return;
736         }
737         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
738                 if (all_strategy[i].attr & attr)
739                         append_strategy(&all_strategy[i]);
740
741 }
742
743 static void read_merge_msg(struct strbuf *msg)
744 {
745         const char *filename = git_path_merge_msg();
746         strbuf_reset(msg);
747         if (strbuf_read_file(msg, filename, 0) < 0)
748                 die_errno(_("Could not read from '%s'"), filename);
749 }
750
751 static void write_merge_state(struct commit_list *);
752 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
753 {
754         if (err_msg)
755                 error("%s", err_msg);
756         fprintf(stderr,
757                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
758         write_merge_state(remoteheads);
759         exit(1);
760 }
761
762 static const char merge_editor_comment[] =
763 N_("Please enter a commit message to explain why this merge is necessary,\n"
764    "especially if it merges an updated upstream into a topic branch.\n"
765    "\n"
766    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
767    "the commit.\n");
768
769 static void write_merge_heads(struct commit_list *);
770 static void prepare_to_commit(struct commit_list *remoteheads)
771 {
772         struct strbuf msg = STRBUF_INIT;
773         strbuf_addbuf(&msg, &merge_msg);
774         strbuf_addch(&msg, '\n');
775         if (squash)
776                 BUG("the control must not reach here under --squash");
777         if (0 < option_edit)
778                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
779         if (signoff)
780                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
781         write_merge_heads(remoteheads);
782         write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
783         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
784                             git_path_merge_msg(), "merge", NULL))
785                 abort_commit(remoteheads, NULL);
786         if (0 < option_edit) {
787                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
788                         abort_commit(remoteheads, NULL);
789         }
790
791         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
792                                           "commit-msg",
793                                           git_path_merge_msg(), NULL))
794                 abort_commit(remoteheads, NULL);
795
796         read_merge_msg(&msg);
797         strbuf_stripspace(&msg, 0 < option_edit);
798         if (!msg.len)
799                 abort_commit(remoteheads, _("Empty commit message."));
800         strbuf_release(&merge_msg);
801         strbuf_addbuf(&merge_msg, &msg);
802         strbuf_release(&msg);
803 }
804
805 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
806 {
807         struct object_id result_tree, result_commit;
808         struct commit_list *parents, **pptr = &parents;
809         static struct lock_file lock;
810
811         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
812         refresh_cache(REFRESH_QUIET);
813         if (active_cache_changed &&
814             write_locked_index(&the_index, &lock, COMMIT_LOCK))
815                 return error(_("Unable to write index."));
816         rollback_lock_file(&lock);
817
818         write_tree_trivial(&result_tree);
819         printf(_("Wonderful.\n"));
820         pptr = commit_list_append(head, pptr);
821         pptr = commit_list_append(remoteheads->item, pptr);
822         prepare_to_commit(remoteheads);
823         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
824                         &result_commit, NULL, sign_commit))
825                 die(_("failed to write commit object"));
826         finish(head, remoteheads, &result_commit, "In-index merge");
827         drop_save();
828         return 0;
829 }
830
831 static int finish_automerge(struct commit *head,
832                             int head_subsumed,
833                             struct commit_list *common,
834                             struct commit_list *remoteheads,
835                             struct object_id *result_tree,
836                             const char *wt_strategy)
837 {
838         struct commit_list *parents = NULL;
839         struct strbuf buf = STRBUF_INIT;
840         struct object_id result_commit;
841
842         free_commit_list(common);
843         parents = remoteheads;
844         if (!head_subsumed || fast_forward == FF_NO)
845                 commit_list_insert(head, &parents);
846         strbuf_addch(&merge_msg, '\n');
847         prepare_to_commit(remoteheads);
848         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
849                         &result_commit, NULL, sign_commit))
850                 die(_("failed to write commit object"));
851         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
852         finish(head, remoteheads, &result_commit, buf.buf);
853         strbuf_release(&buf);
854         drop_save();
855         return 0;
856 }
857
858 static int suggest_conflicts(void)
859 {
860         const char *filename;
861         FILE *fp;
862         struct strbuf msgbuf = STRBUF_INIT;
863
864         filename = git_path_merge_msg();
865         fp = xfopen(filename, "a");
866
867         append_conflicts_hint(&msgbuf);
868         fputs(msgbuf.buf, fp);
869         strbuf_release(&msgbuf);
870         fclose(fp);
871         rerere(allow_rerere_auto);
872         printf(_("Automatic merge failed; "
873                         "fix conflicts and then commit the result.\n"));
874         return 1;
875 }
876
877 static int evaluate_result(void)
878 {
879         int cnt = 0;
880         struct rev_info rev;
881
882         /* Check how many files differ. */
883         init_revisions(&rev, "");
884         setup_revisions(0, NULL, &rev, NULL);
885         rev.diffopt.output_format |=
886                 DIFF_FORMAT_CALLBACK;
887         rev.diffopt.format_callback = count_diff_files;
888         rev.diffopt.format_callback_data = &cnt;
889         run_diff_files(&rev, 0);
890
891         /*
892          * Check how many unmerged entries are
893          * there.
894          */
895         cnt += count_unmerged_entries();
896
897         return cnt;
898 }
899
900 /*
901  * Pretend as if the user told us to merge with the remote-tracking
902  * branch we have for the upstream of the current branch
903  */
904 static int setup_with_upstream(const char ***argv)
905 {
906         struct branch *branch = branch_get(NULL);
907         int i;
908         const char **args;
909
910         if (!branch)
911                 die(_("No current branch."));
912         if (!branch->remote_name)
913                 die(_("No remote for the current branch."));
914         if (!branch->merge_nr)
915                 die(_("No default upstream defined for the current branch."));
916
917         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
918         for (i = 0; i < branch->merge_nr; i++) {
919                 if (!branch->merge[i]->dst)
920                         die(_("No remote-tracking branch for %s from %s"),
921                             branch->merge[i]->src, branch->remote_name);
922                 args[i] = branch->merge[i]->dst;
923         }
924         args[i] = NULL;
925         *argv = args;
926         return i;
927 }
928
929 static void write_merge_heads(struct commit_list *remoteheads)
930 {
931         struct commit_list *j;
932         struct strbuf buf = STRBUF_INIT;
933
934         for (j = remoteheads; j; j = j->next) {
935                 struct object_id *oid;
936                 struct commit *c = j->item;
937                 if (c->util && merge_remote_util(c)->obj) {
938                         oid = &merge_remote_util(c)->obj->oid;
939                 } else {
940                         oid = &c->object.oid;
941                 }
942                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
943         }
944         write_file_buf(git_path_merge_head(), buf.buf, buf.len);
945
946         strbuf_reset(&buf);
947         if (fast_forward == FF_NO)
948                 strbuf_addstr(&buf, "no-ff");
949         write_file_buf(git_path_merge_mode(), buf.buf, buf.len);
950         strbuf_release(&buf);
951 }
952
953 static void write_merge_state(struct commit_list *remoteheads)
954 {
955         write_merge_heads(remoteheads);
956         strbuf_addch(&merge_msg, '\n');
957         write_file_buf(git_path_merge_msg(), merge_msg.buf, merge_msg.len);
958 }
959
960 static int default_edit_option(void)
961 {
962         static const char name[] = "GIT_MERGE_AUTOEDIT";
963         const char *e = getenv(name);
964         struct stat st_stdin, st_stdout;
965
966         if (have_message)
967                 /* an explicit -m msg without --[no-]edit */
968                 return 0;
969
970         if (e) {
971                 int v = git_parse_maybe_bool(e);
972                 if (v < 0)
973                         die(_("Bad value '%s' in environment '%s'"), e, name);
974                 return v;
975         }
976
977         /* Use editor if stdin and stdout are the same and is a tty */
978         return (!fstat(0, &st_stdin) &&
979                 !fstat(1, &st_stdout) &&
980                 isatty(0) && isatty(1) &&
981                 st_stdin.st_dev == st_stdout.st_dev &&
982                 st_stdin.st_ino == st_stdout.st_ino &&
983                 st_stdin.st_mode == st_stdout.st_mode);
984 }
985
986 static struct commit_list *reduce_parents(struct commit *head_commit,
987                                           int *head_subsumed,
988                                           struct commit_list *remoteheads)
989 {
990         struct commit_list *parents, **remotes;
991
992         /*
993          * Is the current HEAD reachable from another commit being
994          * merged?  If so we do not want to record it as a parent of
995          * the resulting merge, unless --no-ff is given.  We will flip
996          * this variable to 0 when we find HEAD among the independent
997          * tips being merged.
998          */
999         *head_subsumed = 1;
1000
1001         /* Find what parents to record by checking independent ones. */
1002         parents = reduce_heads(remoteheads);
1003         free_commit_list(remoteheads);
1004
1005         remoteheads = NULL;
1006         remotes = &remoteheads;
1007         while (parents) {
1008                 struct commit *commit = pop_commit(&parents);
1009                 if (commit == head_commit)
1010                         *head_subsumed = 0;
1011                 else
1012                         remotes = &commit_list_insert(commit, remotes)->next;
1013         }
1014         return remoteheads;
1015 }
1016
1017 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1018 {
1019         struct fmt_merge_msg_opts opts;
1020
1021         memset(&opts, 0, sizeof(opts));
1022         opts.add_title = !have_message;
1023         opts.shortlog_len = shortlog_len;
1024         opts.credit_people = (0 < option_edit);
1025
1026         fmt_merge_msg(merge_names, merge_msg, &opts);
1027         if (merge_msg->len)
1028                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1029 }
1030
1031 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1032 {
1033         const char *filename;
1034         int fd, pos, npos;
1035         struct strbuf fetch_head_file = STRBUF_INIT;
1036
1037         if (!merge_names)
1038                 merge_names = &fetch_head_file;
1039
1040         filename = git_path_fetch_head();
1041         fd = open(filename, O_RDONLY);
1042         if (fd < 0)
1043                 die_errno(_("could not open '%s' for reading"), filename);
1044
1045         if (strbuf_read(merge_names, fd, 0) < 0)
1046                 die_errno(_("could not read '%s'"), filename);
1047         if (close(fd) < 0)
1048                 die_errno(_("could not close '%s'"), filename);
1049
1050         for (pos = 0; pos < merge_names->len; pos = npos) {
1051                 struct object_id oid;
1052                 char *ptr;
1053                 struct commit *commit;
1054
1055                 ptr = strchr(merge_names->buf + pos, '\n');
1056                 if (ptr)
1057                         npos = ptr - merge_names->buf + 1;
1058                 else
1059                         npos = merge_names->len;
1060
1061                 if (npos - pos < GIT_SHA1_HEXSZ + 2 ||
1062                     get_oid_hex(merge_names->buf + pos, &oid))
1063                         commit = NULL; /* bad */
1064                 else if (memcmp(merge_names->buf + pos + GIT_SHA1_HEXSZ, "\t\t", 2))
1065                         continue; /* not-for-merge */
1066                 else {
1067                         char saved = merge_names->buf[pos + GIT_SHA1_HEXSZ];
1068                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = '\0';
1069                         commit = get_merge_parent(merge_names->buf + pos);
1070                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = saved;
1071                 }
1072                 if (!commit) {
1073                         if (ptr)
1074                                 *ptr = '\0';
1075                         die(_("not something we can merge in %s: %s"),
1076                             filename, merge_names->buf + pos);
1077                 }
1078                 remotes = &commit_list_insert(commit, remotes)->next;
1079         }
1080
1081         if (merge_names == &fetch_head_file)
1082                 strbuf_release(&fetch_head_file);
1083 }
1084
1085 static struct commit_list *collect_parents(struct commit *head_commit,
1086                                            int *head_subsumed,
1087                                            int argc, const char **argv,
1088                                            struct strbuf *merge_msg)
1089 {
1090         int i;
1091         struct commit_list *remoteheads = NULL;
1092         struct commit_list **remotes = &remoteheads;
1093         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1094
1095         if (merge_msg && (!have_message || shortlog_len))
1096                 autogen = &merge_names;
1097
1098         if (head_commit)
1099                 remotes = &commit_list_insert(head_commit, remotes)->next;
1100
1101         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1102                 handle_fetch_head(remotes, autogen);
1103                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1104         } else {
1105                 for (i = 0; i < argc; i++) {
1106                         struct commit *commit = get_merge_parent(argv[i]);
1107                         if (!commit)
1108                                 help_unknown_ref(argv[i], "merge",
1109                                                  _("not something we can merge"));
1110                         remotes = &commit_list_insert(commit, remotes)->next;
1111                 }
1112                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1113                 if (autogen) {
1114                         struct commit_list *p;
1115                         for (p = remoteheads; p; p = p->next)
1116                                 merge_name(merge_remote_util(p->item)->name, autogen);
1117                 }
1118         }
1119
1120         if (autogen) {
1121                 prepare_merge_message(autogen, merge_msg);
1122                 strbuf_release(autogen);
1123         }
1124
1125         return remoteheads;
1126 }
1127
1128 int cmd_merge(int argc, const char **argv, const char *prefix)
1129 {
1130         struct object_id result_tree, stash, head_oid;
1131         struct commit *head_commit;
1132         struct strbuf buf = STRBUF_INIT;
1133         int i, ret = 0, head_subsumed;
1134         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1135         struct commit_list *common = NULL;
1136         const char *best_strategy = NULL, *wt_strategy = NULL;
1137         struct commit_list *remoteheads, *p;
1138         void *branch_to_free;
1139         int orig_argc = argc;
1140
1141         if (argc == 2 && !strcmp(argv[1], "-h"))
1142                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1143
1144         /*
1145          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1146          * current branch.
1147          */
1148         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1149         if (branch)
1150                 skip_prefix(branch, "refs/heads/", &branch);
1151         if (!branch || is_null_oid(&head_oid))
1152                 head_commit = NULL;
1153         else
1154                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1155
1156         init_diff_ui_defaults();
1157         git_config(git_merge_config, NULL);
1158
1159         if (branch_mergeoptions)
1160                 parse_branch_merge_options(branch_mergeoptions);
1161         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1162                         builtin_merge_usage, 0);
1163         if (shortlog_len < 0)
1164                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1165
1166         if (verbosity < 0 && show_progress == -1)
1167                 show_progress = 0;
1168
1169         if (abort_current_merge) {
1170                 int nargc = 2;
1171                 const char *nargv[] = {"reset", "--merge", NULL};
1172
1173                 if (orig_argc != 2)
1174                         usage_msg_opt(_("--abort expects no arguments"),
1175                               builtin_merge_usage, builtin_merge_options);
1176
1177                 if (!file_exists(git_path_merge_head()))
1178                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1179
1180                 /* Invoke 'git reset --merge' */
1181                 ret = cmd_reset(nargc, nargv, prefix);
1182                 goto done;
1183         }
1184
1185         if (continue_current_merge) {
1186                 int nargc = 1;
1187                 const char *nargv[] = {"commit", NULL};
1188
1189                 if (orig_argc != 2)
1190                         usage_msg_opt(_("--continue expects no arguments"),
1191                               builtin_merge_usage, builtin_merge_options);
1192
1193                 if (!file_exists(git_path_merge_head()))
1194                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1195
1196                 /* Invoke 'git commit' */
1197                 ret = cmd_commit(nargc, nargv, prefix);
1198                 goto done;
1199         }
1200
1201         if (read_cache_unmerged())
1202                 die_resolve_conflict("merge");
1203
1204         if (file_exists(git_path_merge_head())) {
1205                 /*
1206                  * There is no unmerged entry, don't advise 'git
1207                  * add/rm <file>', just 'git commit'.
1208                  */
1209                 if (advice_resolve_conflict)
1210                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1211                                   "Please, commit your changes before you merge."));
1212                 else
1213                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1214         }
1215         if (file_exists(git_path_cherry_pick_head())) {
1216                 if (advice_resolve_conflict)
1217                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1218                             "Please, commit your changes before you merge."));
1219                 else
1220                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1221         }
1222         resolve_undo_clear();
1223
1224         if (verbosity < 0)
1225                 show_diffstat = 0;
1226
1227         if (squash) {
1228                 if (fast_forward == FF_NO)
1229                         die(_("You cannot combine --squash with --no-ff."));
1230                 option_commit = 0;
1231         }
1232
1233         if (!argc) {
1234                 if (default_to_upstream)
1235                         argc = setup_with_upstream(&argv);
1236                 else
1237                         die(_("No commit specified and merge.defaultToUpstream not set."));
1238         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1239                 argv[0] = "@{-1}";
1240         }
1241
1242         if (!argc)
1243                 usage_with_options(builtin_merge_usage,
1244                         builtin_merge_options);
1245
1246         if (!head_commit) {
1247                 /*
1248                  * If the merged head is a valid one there is no reason
1249                  * to forbid "git merge" into a branch yet to be born.
1250                  * We do the same for "git pull".
1251                  */
1252                 struct object_id *remote_head_oid;
1253                 if (squash)
1254                         die(_("Squash commit into empty head not supported yet"));
1255                 if (fast_forward == FF_NO)
1256                         die(_("Non-fast-forward commit does not make sense into "
1257                             "an empty head"));
1258                 remoteheads = collect_parents(head_commit, &head_subsumed,
1259                                               argc, argv, NULL);
1260                 if (!remoteheads)
1261                         die(_("%s - not something we can merge"), argv[0]);
1262                 if (remoteheads->next)
1263                         die(_("Can merge only exactly one commit into empty head"));
1264                 remote_head_oid = &remoteheads->item->object.oid;
1265                 read_empty(remote_head_oid->hash, 0);
1266                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1267                            UPDATE_REFS_DIE_ON_ERR);
1268                 goto done;
1269         }
1270
1271         /*
1272          * All the rest are the commits being merged; prepare
1273          * the standard merge summary message to be appended
1274          * to the given message.
1275          */
1276         remoteheads = collect_parents(head_commit, &head_subsumed,
1277                                       argc, argv, &merge_msg);
1278
1279         if (!head_commit || !argc)
1280                 usage_with_options(builtin_merge_usage,
1281                         builtin_merge_options);
1282
1283         if (verify_signatures) {
1284                 for (p = remoteheads; p; p = p->next) {
1285                         struct commit *commit = p->item;
1286                         char hex[GIT_MAX_HEXSZ + 1];
1287                         struct signature_check signature_check;
1288                         memset(&signature_check, 0, sizeof(signature_check));
1289
1290                         check_commit_signature(commit, &signature_check);
1291
1292                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1293                         switch (signature_check.result) {
1294                         case 'G':
1295                                 break;
1296                         case 'U':
1297                                 die(_("Commit %s has an untrusted GPG signature, "
1298                                       "allegedly by %s."), hex, signature_check.signer);
1299                         case 'B':
1300                                 die(_("Commit %s has a bad GPG signature "
1301                                       "allegedly by %s."), hex, signature_check.signer);
1302                         default: /* 'N' */
1303                                 die(_("Commit %s does not have a GPG signature."), hex);
1304                         }
1305                         if (verbosity >= 0 && signature_check.result == 'G')
1306                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1307                                        hex, signature_check.signer);
1308
1309                         signature_check_clear(&signature_check);
1310                 }
1311         }
1312
1313         strbuf_addstr(&buf, "merge");
1314         for (p = remoteheads; p; p = p->next)
1315                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1316         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1317         strbuf_reset(&buf);
1318
1319         for (p = remoteheads; p; p = p->next) {
1320                 struct commit *commit = p->item;
1321                 strbuf_addf(&buf, "GITHEAD_%s",
1322                             oid_to_hex(&commit->object.oid));
1323                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1324                 strbuf_reset(&buf);
1325                 if (fast_forward != FF_ONLY &&
1326                     merge_remote_util(commit) &&
1327                     merge_remote_util(commit)->obj &&
1328                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1329                         fast_forward = FF_NO;
1330         }
1331
1332         if (option_edit < 0)
1333                 option_edit = default_edit_option();
1334
1335         if (!use_strategies) {
1336                 if (!remoteheads)
1337                         ; /* already up-to-date */
1338                 else if (!remoteheads->next)
1339                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1340                 else
1341                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1342         }
1343
1344         for (i = 0; i < use_strategies_nr; i++) {
1345                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1346                         fast_forward = FF_NO;
1347                 if (use_strategies[i]->attr & NO_TRIVIAL)
1348                         allow_trivial = 0;
1349         }
1350
1351         if (!remoteheads)
1352                 ; /* already up-to-date */
1353         else if (!remoteheads->next)
1354                 common = get_merge_bases(head_commit, remoteheads->item);
1355         else {
1356                 struct commit_list *list = remoteheads;
1357                 commit_list_insert(head_commit, &list);
1358                 common = get_octopus_merge_bases(list);
1359                 free(list);
1360         }
1361
1362         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1363                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1364
1365         if (remoteheads && !common) {
1366                 /* No common ancestors found. */
1367                 if (!allow_unrelated_histories)
1368                         die(_("refusing to merge unrelated histories"));
1369                 /* otherwise, we need a real merge. */
1370         } else if (!remoteheads ||
1371                  (!remoteheads->next && !common->next &&
1372                   common->item == remoteheads->item)) {
1373                 /*
1374                  * If head can reach all the merge then we are up to date.
1375                  * but first the most common case of merging one remote.
1376                  */
1377                 finish_up_to_date(_("Already up to date."));
1378                 goto done;
1379         } else if (fast_forward != FF_NO && !remoteheads->next &&
1380                         !common->next &&
1381                         !oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
1382                 /* Again the most common case of merging one remote. */
1383                 struct strbuf msg = STRBUF_INIT;
1384                 struct commit *commit;
1385
1386                 if (verbosity >= 0) {
1387                         printf(_("Updating %s..%s\n"),
1388                                find_unique_abbrev(head_commit->object.oid.hash,
1389                                                   DEFAULT_ABBREV),
1390                                find_unique_abbrev(remoteheads->item->object.oid.hash,
1391                                                   DEFAULT_ABBREV));
1392                 }
1393                 strbuf_addstr(&msg, "Fast-forward");
1394                 if (have_message)
1395                         strbuf_addstr(&msg,
1396                                 " (no commit created; -m option ignored)");
1397                 commit = remoteheads->item;
1398                 if (!commit) {
1399                         ret = 1;
1400                         goto done;
1401                 }
1402
1403                 if (checkout_fast_forward(&head_commit->object.oid,
1404                                           &commit->object.oid,
1405                                           overwrite_ignore)) {
1406                         ret = 1;
1407                         goto done;
1408                 }
1409
1410                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1411                 drop_save();
1412                 goto done;
1413         } else if (!remoteheads->next && common->next)
1414                 ;
1415                 /*
1416                  * We are not doing octopus and not fast-forward.  Need
1417                  * a real merge.
1418                  */
1419         else if (!remoteheads->next && !common->next && option_commit) {
1420                 /*
1421                  * We are not doing octopus, not fast-forward, and have
1422                  * only one common.
1423                  */
1424                 refresh_cache(REFRESH_QUIET);
1425                 if (allow_trivial && fast_forward != FF_ONLY) {
1426                         /* See if it is really trivial. */
1427                         git_committer_info(IDENT_STRICT);
1428                         printf(_("Trying really trivial in-index merge...\n"));
1429                         if (!read_tree_trivial(&common->item->object.oid,
1430                                                &head_commit->object.oid,
1431                                                &remoteheads->item->object.oid)) {
1432                                 ret = merge_trivial(head_commit, remoteheads);
1433                                 goto done;
1434                         }
1435                         printf(_("Nope.\n"));
1436                 }
1437         } else {
1438                 /*
1439                  * An octopus.  If we can reach all the remote we are up
1440                  * to date.
1441                  */
1442                 int up_to_date = 1;
1443                 struct commit_list *j;
1444
1445                 for (j = remoteheads; j; j = j->next) {
1446                         struct commit_list *common_one;
1447
1448                         /*
1449                          * Here we *have* to calculate the individual
1450                          * merge_bases again, otherwise "git merge HEAD^
1451                          * HEAD^^" would be missed.
1452                          */
1453                         common_one = get_merge_bases(head_commit, j->item);
1454                         if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
1455                                 up_to_date = 0;
1456                                 break;
1457                         }
1458                 }
1459                 if (up_to_date) {
1460                         finish_up_to_date(_("Already up to date. Yeeah!"));
1461                         goto done;
1462                 }
1463         }
1464
1465         if (fast_forward == FF_ONLY)
1466                 die(_("Not possible to fast-forward, aborting."));
1467
1468         /* We are going to make a new commit. */
1469         git_committer_info(IDENT_STRICT);
1470
1471         /*
1472          * At this point, we need a real merge.  No matter what strategy
1473          * we use, it would operate on the index, possibly affecting the
1474          * working tree, and when resolved cleanly, have the desired
1475          * tree in the index -- this means that the index must be in
1476          * sync with the head commit.  The strategies are responsible
1477          * to ensure this.
1478          */
1479         if (use_strategies_nr == 1 ||
1480             /*
1481              * Stash away the local changes so that we can try more than one.
1482              */
1483             save_state(&stash))
1484                 oidclr(&stash);
1485
1486         for (i = 0; i < use_strategies_nr; i++) {
1487                 int ret;
1488                 if (i) {
1489                         printf(_("Rewinding the tree to pristine...\n"));
1490                         restore_state(&head_commit->object.oid, &stash);
1491                 }
1492                 if (use_strategies_nr != 1)
1493                         printf(_("Trying merge strategy %s...\n"),
1494                                 use_strategies[i]->name);
1495                 /*
1496                  * Remember which strategy left the state in the working
1497                  * tree.
1498                  */
1499                 wt_strategy = use_strategies[i]->name;
1500
1501                 ret = try_merge_strategy(use_strategies[i]->name,
1502                                          common, remoteheads,
1503                                          head_commit);
1504                 if (!option_commit && !ret) {
1505                         merge_was_ok = 1;
1506                         /*
1507                          * This is necessary here just to avoid writing
1508                          * the tree, but later we will *not* exit with
1509                          * status code 1 because merge_was_ok is set.
1510                          */
1511                         ret = 1;
1512                 }
1513
1514                 if (ret) {
1515                         /*
1516                          * The backend exits with 1 when conflicts are
1517                          * left to be resolved, with 2 when it does not
1518                          * handle the given merge at all.
1519                          */
1520                         if (ret == 1) {
1521                                 int cnt = evaluate_result();
1522
1523                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1524                                         best_strategy = use_strategies[i]->name;
1525                                         best_cnt = cnt;
1526                                 }
1527                         }
1528                         if (merge_was_ok)
1529                                 break;
1530                         else
1531                                 continue;
1532                 }
1533
1534                 /* Automerge succeeded. */
1535                 write_tree_trivial(&result_tree);
1536                 automerge_was_ok = 1;
1537                 break;
1538         }
1539
1540         /*
1541          * If we have a resulting tree, that means the strategy module
1542          * auto resolved the merge cleanly.
1543          */
1544         if (automerge_was_ok) {
1545                 ret = finish_automerge(head_commit, head_subsumed,
1546                                        common, remoteheads,
1547                                        &result_tree, wt_strategy);
1548                 goto done;
1549         }
1550
1551         /*
1552          * Pick the result from the best strategy and have the user fix
1553          * it up.
1554          */
1555         if (!best_strategy) {
1556                 restore_state(&head_commit->object.oid, &stash);
1557                 if (use_strategies_nr > 1)
1558                         fprintf(stderr,
1559                                 _("No merge strategy handled the merge.\n"));
1560                 else
1561                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1562                                 use_strategies[0]->name);
1563                 ret = 2;
1564                 goto done;
1565         } else if (best_strategy == wt_strategy)
1566                 ; /* We already have its result in the working tree. */
1567         else {
1568                 printf(_("Rewinding the tree to pristine...\n"));
1569                 restore_state(&head_commit->object.oid, &stash);
1570                 printf(_("Using the %s to prepare resolving by hand.\n"),
1571                         best_strategy);
1572                 try_merge_strategy(best_strategy, common, remoteheads,
1573                                    head_commit);
1574         }
1575
1576         if (squash)
1577                 finish(head_commit, remoteheads, NULL, NULL);
1578         else
1579                 write_merge_state(remoteheads);
1580
1581         if (merge_was_ok)
1582                 fprintf(stderr, _("Automatic merge went well; "
1583                         "stopped before committing as requested\n"));
1584         else
1585                 ret = suggest_conflicts();
1586
1587 done:
1588         free(branch_to_free);
1589         return ret;
1590 }