Merge branch 'jk/merge-quiet'
[git] / builtin / merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "parse-options.h"
11 #include "builtin.h"
12 #include "lockfile.h"
13 #include "run-command.h"
14 #include "diff.h"
15 #include "refs.h"
16 #include "commit.h"
17 #include "diffcore.h"
18 #include "revision.h"
19 #include "unpack-trees.h"
20 #include "cache-tree.h"
21 #include "dir.h"
22 #include "utf8.h"
23 #include "log-tree.h"
24 #include "color.h"
25 #include "rerere.h"
26 #include "help.h"
27 #include "merge-recursive.h"
28 #include "resolve-undo.h"
29 #include "remote.h"
30 #include "fmt-merge-msg.h"
31 #include "gpg-interface.h"
32 #include "sequencer.h"
33
34 #define DEFAULT_TWOHEAD (1<<0)
35 #define DEFAULT_OCTOPUS (1<<1)
36 #define NO_FAST_FORWARD (1<<2)
37 #define NO_TRIVIAL      (1<<3)
38
39 struct strategy {
40         const char *name;
41         unsigned attr;
42 };
43
44 static const char * const builtin_merge_usage[] = {
45         N_("git merge [<options>] [<commit>...]"),
46         N_("git merge [<options>] <msg> HEAD <commit>"),
47         N_("git merge --abort"),
48         NULL
49 };
50
51 static int show_diffstat = 1, shortlog_len = -1, squash;
52 static int option_commit = 1;
53 static int option_edit = -1;
54 static int allow_trivial = 1, have_message, verify_signatures;
55 static int overwrite_ignore = 1;
56 static struct strbuf merge_msg = STRBUF_INIT;
57 static struct strategy **use_strategies;
58 static size_t use_strategies_nr, use_strategies_alloc;
59 static const char **xopts;
60 static size_t xopts_nr, xopts_alloc;
61 static const char *branch;
62 static char *branch_mergeoptions;
63 static int option_renormalize;
64 static int verbosity;
65 static int allow_rerere_auto;
66 static int abort_current_merge;
67 static int show_progress = -1;
68 static int default_to_upstream = 1;
69 static const char *sign_commit;
70
71 static struct strategy all_strategy[] = {
72         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
73         { "octopus",    DEFAULT_OCTOPUS },
74         { "resolve",    0 },
75         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
76         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
77 };
78
79 static const char *pull_twohead, *pull_octopus;
80
81 enum ff_type {
82         FF_NO,
83         FF_ALLOW,
84         FF_ONLY
85 };
86
87 static enum ff_type fast_forward = FF_ALLOW;
88
89 static int option_parse_message(const struct option *opt,
90                                 const char *arg, int unset)
91 {
92         struct strbuf *buf = opt->value;
93
94         if (unset)
95                 strbuf_setlen(buf, 0);
96         else if (arg) {
97                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
98                 have_message = 1;
99         } else
100                 return error(_("switch `m' requires a value"));
101         return 0;
102 }
103
104 static struct strategy *get_strategy(const char *name)
105 {
106         int i;
107         struct strategy *ret;
108         static struct cmdnames main_cmds, other_cmds;
109         static int loaded;
110
111         if (!name)
112                 return NULL;
113
114         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
115                 if (!strcmp(name, all_strategy[i].name))
116                         return &all_strategy[i];
117
118         if (!loaded) {
119                 struct cmdnames not_strategies;
120                 loaded = 1;
121
122                 memset(&not_strategies, 0, sizeof(struct cmdnames));
123                 load_command_list("git-merge-", &main_cmds, &other_cmds);
124                 for (i = 0; i < main_cmds.cnt; i++) {
125                         int j, found = 0;
126                         struct cmdname *ent = main_cmds.names[i];
127                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
128                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
129                                                 && !all_strategy[j].name[ent->len])
130                                         found = 1;
131                         if (!found)
132                                 add_cmdname(&not_strategies, ent->name, ent->len);
133                 }
134                 exclude_cmds(&main_cmds, &not_strategies);
135         }
136         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
137                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
138                 fprintf(stderr, _("Available strategies are:"));
139                 for (i = 0; i < main_cmds.cnt; i++)
140                         fprintf(stderr, " %s", main_cmds.names[i]->name);
141                 fprintf(stderr, ".\n");
142                 if (other_cmds.cnt) {
143                         fprintf(stderr, _("Available custom strategies are:"));
144                         for (i = 0; i < other_cmds.cnt; i++)
145                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
146                         fprintf(stderr, ".\n");
147                 }
148                 exit(1);
149         }
150
151         ret = xcalloc(1, sizeof(struct strategy));
152         ret->name = xstrdup(name);
153         ret->attr = NO_TRIVIAL;
154         return ret;
155 }
156
157 static void append_strategy(struct strategy *s)
158 {
159         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
160         use_strategies[use_strategies_nr++] = s;
161 }
162
163 static int option_parse_strategy(const struct option *opt,
164                                  const char *name, int unset)
165 {
166         if (unset)
167                 return 0;
168
169         append_strategy(get_strategy(name));
170         return 0;
171 }
172
173 static int option_parse_x(const struct option *opt,
174                           const char *arg, int unset)
175 {
176         if (unset)
177                 return 0;
178
179         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
180         xopts[xopts_nr++] = xstrdup(arg);
181         return 0;
182 }
183
184 static int option_parse_n(const struct option *opt,
185                           const char *arg, int unset)
186 {
187         show_diffstat = unset;
188         return 0;
189 }
190
191 static struct option builtin_merge_options[] = {
192         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
193                 N_("do not show a diffstat at the end of the merge"),
194                 PARSE_OPT_NOARG, option_parse_n },
195         OPT_BOOL(0, "stat", &show_diffstat,
196                 N_("show a diffstat at the end of the merge")),
197         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
198         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
199           N_("add (at most <n>) entries from shortlog to merge commit message"),
200           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
201         OPT_BOOL(0, "squash", &squash,
202                 N_("create a single commit instead of doing a merge")),
203         OPT_BOOL(0, "commit", &option_commit,
204                 N_("perform a commit if the merge succeeds (default)")),
205         OPT_BOOL('e', "edit", &option_edit,
206                 N_("edit message before committing")),
207         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
208         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
209                 N_("abort if fast-forward is not possible"),
210                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
211         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
212         OPT_BOOL(0, "verify-signatures", &verify_signatures,
213                 N_("Verify that the named commit has a valid GPG signature")),
214         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
215                 N_("merge strategy to use"), option_parse_strategy),
216         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
217                 N_("option for selected merge strategy"), option_parse_x),
218         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
219                 N_("merge commit message (for a non-fast-forward merge)"),
220                 option_parse_message),
221         OPT__VERBOSITY(&verbosity),
222         OPT_BOOL(0, "abort", &abort_current_merge,
223                 N_("abort the current in-progress merge")),
224         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
225         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
226           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
227         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
228         OPT_END()
229 };
230
231 /* Cleans up metadata that is uninteresting after a succeeded merge. */
232 static void drop_save(void)
233 {
234         unlink(git_path("MERGE_HEAD"));
235         unlink(git_path("MERGE_MSG"));
236         unlink(git_path("MERGE_MODE"));
237 }
238
239 static int save_state(unsigned char *stash)
240 {
241         int len;
242         struct child_process cp = CHILD_PROCESS_INIT;
243         struct strbuf buffer = STRBUF_INIT;
244         const char *argv[] = {"stash", "create", NULL};
245
246         cp.argv = argv;
247         cp.out = -1;
248         cp.git_cmd = 1;
249
250         if (start_command(&cp))
251                 die(_("could not run stash."));
252         len = strbuf_read(&buffer, cp.out, 1024);
253         close(cp.out);
254
255         if (finish_command(&cp) || len < 0)
256                 die(_("stash failed"));
257         else if (!len)          /* no changes */
258                 return -1;
259         strbuf_setlen(&buffer, buffer.len-1);
260         if (get_sha1(buffer.buf, stash))
261                 die(_("not a valid object: %s"), buffer.buf);
262         return 0;
263 }
264
265 static void read_empty(unsigned const char *sha1, int verbose)
266 {
267         int i = 0;
268         const char *args[7];
269
270         args[i++] = "read-tree";
271         if (verbose)
272                 args[i++] = "-v";
273         args[i++] = "-m";
274         args[i++] = "-u";
275         args[i++] = EMPTY_TREE_SHA1_HEX;
276         args[i++] = sha1_to_hex(sha1);
277         args[i] = NULL;
278
279         if (run_command_v_opt(args, RUN_GIT_CMD))
280                 die(_("read-tree failed"));
281 }
282
283 static void reset_hard(unsigned const char *sha1, int verbose)
284 {
285         int i = 0;
286         const char *args[6];
287
288         args[i++] = "read-tree";
289         if (verbose)
290                 args[i++] = "-v";
291         args[i++] = "--reset";
292         args[i++] = "-u";
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 restore_state(const unsigned char *head,
301                           const unsigned char *stash)
302 {
303         struct strbuf sb = STRBUF_INIT;
304         const char *args[] = { "stash", "apply", NULL, NULL };
305
306         if (is_null_sha1(stash))
307                 return;
308
309         reset_hard(head, 1);
310
311         args[2] = sha1_to_hex(stash);
312
313         /*
314          * It is OK to ignore error here, for example when there was
315          * nothing to restore.
316          */
317         run_command_v_opt(args, RUN_GIT_CMD);
318
319         strbuf_release(&sb);
320         refresh_cache(REFRESH_QUIET);
321 }
322
323 /* This is called when no merge was necessary. */
324 static void finish_up_to_date(const char *msg)
325 {
326         if (verbosity >= 0)
327                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
328         drop_save();
329 }
330
331 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
332 {
333         struct rev_info rev;
334         struct strbuf out = STRBUF_INIT;
335         struct commit_list *j;
336         const char *filename;
337         int fd;
338         struct pretty_print_context ctx = {0};
339
340         printf(_("Squash commit -- not updating HEAD\n"));
341         filename = git_path("SQUASH_MSG");
342         fd = open(filename, O_WRONLY | O_CREAT, 0666);
343         if (fd < 0)
344                 die_errno(_("Could not write to '%s'"), filename);
345
346         init_revisions(&rev, NULL);
347         rev.ignore_merges = 1;
348         rev.commit_format = CMIT_FMT_MEDIUM;
349
350         commit->object.flags |= UNINTERESTING;
351         add_pending_object(&rev, &commit->object, NULL);
352
353         for (j = remoteheads; j; j = j->next)
354                 add_pending_object(&rev, &j->item->object, NULL);
355
356         setup_revisions(0, NULL, &rev, NULL);
357         if (prepare_revision_walk(&rev))
358                 die(_("revision walk setup failed"));
359
360         ctx.abbrev = rev.abbrev;
361         ctx.date_mode = rev.date_mode;
362         ctx.fmt = rev.commit_format;
363
364         strbuf_addstr(&out, "Squashed commit of the following:\n");
365         while ((commit = get_revision(&rev)) != NULL) {
366                 strbuf_addch(&out, '\n');
367                 strbuf_addf(&out, "commit %s\n",
368                         sha1_to_hex(commit->object.sha1));
369                 pretty_print_commit(&ctx, commit, &out);
370         }
371         if (write_in_full(fd, out.buf, out.len) != out.len)
372                 die_errno(_("Writing SQUASH_MSG"));
373         if (close(fd))
374                 die_errno(_("Finishing SQUASH_MSG"));
375         strbuf_release(&out);
376 }
377
378 static void finish(struct commit *head_commit,
379                    struct commit_list *remoteheads,
380                    const unsigned char *new_head, const char *msg)
381 {
382         struct strbuf reflog_message = STRBUF_INIT;
383         const unsigned char *head = head_commit->object.sha1;
384
385         if (!msg)
386                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
387         else {
388                 if (verbosity >= 0)
389                         printf("%s\n", msg);
390                 strbuf_addf(&reflog_message, "%s: %s",
391                         getenv("GIT_REFLOG_ACTION"), msg);
392         }
393         if (squash) {
394                 squash_message(head_commit, remoteheads);
395         } else {
396                 if (verbosity >= 0 && !merge_msg.len)
397                         printf(_("No merge message -- not updating HEAD\n"));
398                 else {
399                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
400                         update_ref(reflog_message.buf, "HEAD",
401                                 new_head, head, 0,
402                                 UPDATE_REFS_DIE_ON_ERR);
403                         /*
404                          * We ignore errors in 'gc --auto', since the
405                          * user should see them.
406                          */
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_sha1(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         unsigned char branch_head[20];
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);
442         remote = bname.buf;
443
444         memset(branch_head, 0, sizeof(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, &found_ref) > 0) {
450                 if (starts_with(found_ref, "refs/heads/")) {
451                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
452                                     sha1_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                                     sha1_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                                     sha1_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_addstr(&truname, "refs/heads/");
496                 strbuf_addstr(&truname, remote);
497                 strbuf_setlen(&truname, truname.len - len);
498                 if (ref_exists(truname.buf)) {
499                         strbuf_addf(msg,
500                                     "%s\t\tbranch '%s'%s of .\n",
501                                     sha1_to_hex(remote_head->object.sha1),
502                                     truname.buf + 11,
503                                     (early ? " (early part)" : ""));
504                         strbuf_release(&truname);
505                         goto cleanup;
506                 }
507         }
508
509         if (!strcmp(remote, "FETCH_HEAD") &&
510                         !access(git_path("FETCH_HEAD"), R_OK)) {
511                 const char *filename;
512                 FILE *fp;
513                 struct strbuf line = STRBUF_INIT;
514                 char *ptr;
515
516                 filename = git_path("FETCH_HEAD");
517                 fp = fopen(filename, "r");
518                 if (!fp)
519                         die_errno(_("could not open '%s' for reading"),
520                                   filename);
521                 strbuf_getline(&line, fp, '\n');
522                 fclose(fp);
523                 ptr = strstr(line.buf, "\tnot-for-merge\t");
524                 if (ptr)
525                         strbuf_remove(&line, ptr-line.buf+1, 13);
526                 strbuf_addbuf(msg, &line);
527                 strbuf_release(&line);
528                 goto cleanup;
529         }
530
531         if (remote_head->util) {
532                 struct merge_remote_desc *desc;
533                 desc = merge_remote_util(remote_head);
534                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
535                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
536                                     sha1_to_hex(desc->obj->sha1),
537                                     typename(desc->obj->type),
538                                     remote);
539                         goto cleanup;
540                 }
541         }
542
543         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
544                 sha1_to_hex(remote_head->object.sha1), remote);
545 cleanup:
546         strbuf_release(&buf);
547         strbuf_release(&bname);
548 }
549
550 static void parse_branch_merge_options(char *bmo)
551 {
552         const char **argv;
553         int argc;
554
555         if (!bmo)
556                 return;
557         argc = split_cmdline(bmo, &argv);
558         if (argc < 0)
559                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
560                     split_cmdline_strerror(argc));
561         REALLOC_ARRAY(argv, argc + 2);
562         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
563         argc++;
564         argv[0] = "branch.*.mergeoptions";
565         parse_options(argc, argv, NULL, builtin_merge_options,
566                       builtin_merge_usage, 0);
567         free(argv);
568 }
569
570 static int git_merge_config(const char *k, const char *v, void *cb)
571 {
572         int status;
573
574         if (branch && starts_with(k, "branch.") &&
575                 starts_with(k + 7, branch) &&
576                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
577                 free(branch_mergeoptions);
578                 branch_mergeoptions = xstrdup(v);
579                 return 0;
580         }
581
582         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
583                 show_diffstat = git_config_bool(k, v);
584         else if (!strcmp(k, "pull.twohead"))
585                 return git_config_string(&pull_twohead, k, v);
586         else if (!strcmp(k, "pull.octopus"))
587                 return git_config_string(&pull_octopus, k, v);
588         else if (!strcmp(k, "merge.renormalize"))
589                 option_renormalize = git_config_bool(k, v);
590         else if (!strcmp(k, "merge.ff")) {
591                 int boolval = git_config_maybe_bool(k, v);
592                 if (0 <= boolval) {
593                         fast_forward = boolval ? FF_ALLOW : FF_NO;
594                 } else if (v && !strcmp(v, "only")) {
595                         fast_forward = FF_ONLY;
596                 } /* do not barf on values from future versions of git */
597                 return 0;
598         } else if (!strcmp(k, "merge.defaulttoupstream")) {
599                 default_to_upstream = git_config_bool(k, v);
600                 return 0;
601         } else if (!strcmp(k, "commit.gpgsign")) {
602                 sign_commit = git_config_bool(k, v) ? "" : NULL;
603                 return 0;
604         }
605
606         status = fmt_merge_msg_config(k, v, cb);
607         if (status)
608                 return status;
609         status = git_gpg_config(k, v, NULL);
610         if (status)
611                 return status;
612         return git_diff_ui_config(k, v, cb);
613 }
614
615 static int read_tree_trivial(unsigned char *common, unsigned char *head,
616                              unsigned char *one)
617 {
618         int i, nr_trees = 0;
619         struct tree *trees[MAX_UNPACK_TREES];
620         struct tree_desc t[MAX_UNPACK_TREES];
621         struct unpack_trees_options opts;
622
623         memset(&opts, 0, sizeof(opts));
624         opts.head_idx = 2;
625         opts.src_index = &the_index;
626         opts.dst_index = &the_index;
627         opts.update = 1;
628         opts.verbose_update = 1;
629         opts.trivial_merges_only = 1;
630         opts.merge = 1;
631         trees[nr_trees] = parse_tree_indirect(common);
632         if (!trees[nr_trees++])
633                 return -1;
634         trees[nr_trees] = parse_tree_indirect(head);
635         if (!trees[nr_trees++])
636                 return -1;
637         trees[nr_trees] = parse_tree_indirect(one);
638         if (!trees[nr_trees++])
639                 return -1;
640         opts.fn = threeway_merge;
641         cache_tree_free(&active_cache_tree);
642         for (i = 0; i < nr_trees; i++) {
643                 parse_tree(trees[i]);
644                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
645         }
646         if (unpack_trees(nr_trees, t, &opts))
647                 return -1;
648         return 0;
649 }
650
651 static void write_tree_trivial(unsigned char *sha1)
652 {
653         if (write_cache_as_tree(sha1, 0, NULL))
654                 die(_("git write-tree failed to write a tree"));
655 }
656
657 static int try_merge_strategy(const char *strategy, struct commit_list *common,
658                               struct commit_list *remoteheads,
659                               struct commit *head, const char *head_arg)
660 {
661         static struct lock_file lock;
662
663         hold_locked_index(&lock, 1);
664         refresh_cache(REFRESH_QUIET);
665         if (active_cache_changed &&
666             write_locked_index(&the_index, &lock, COMMIT_LOCK))
667                 return error(_("Unable to write index."));
668         rollback_lock_file(&lock);
669
670         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
671                 int clean, x;
672                 struct commit *result;
673                 struct commit_list *reversed = NULL;
674                 struct merge_options o;
675                 struct commit_list *j;
676
677                 if (remoteheads->next) {
678                         error(_("Not handling anything other than two heads merge."));
679                         return 2;
680                 }
681
682                 init_merge_options(&o);
683                 if (!strcmp(strategy, "subtree"))
684                         o.subtree_shift = "";
685
686                 o.renormalize = option_renormalize;
687                 if (verbosity < 0)
688                         o.verbosity = verbosity;
689                 else if (verbosity > 0)
690                         o.verbosity += verbosity;
691                 o.show_rename_progress =
692                         show_progress == -1 ? isatty(2) : show_progress;
693
694                 for (x = 0; x < xopts_nr; x++)
695                         if (parse_merge_opt(&o, xopts[x]))
696                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
697
698                 o.branch1 = head_arg;
699                 o.branch2 = merge_remote_util(remoteheads->item)->name;
700
701                 for (j = common; j; j = j->next)
702                         commit_list_insert(j->item, &reversed);
703
704                 hold_locked_index(&lock, 1);
705                 clean = merge_recursive(&o, head,
706                                 remoteheads->item, reversed, &result);
707                 if (active_cache_changed &&
708                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
709                         die (_("unable to write %s"), get_index_file());
710                 rollback_lock_file(&lock);
711                 return clean ? 0 : 1;
712         } else {
713                 return try_merge_command(strategy, xopts_nr, xopts,
714                                                 common, head_arg, remoteheads);
715         }
716 }
717
718 static void count_diff_files(struct diff_queue_struct *q,
719                              struct diff_options *opt, void *data)
720 {
721         int *count = data;
722
723         (*count) += q->nr;
724 }
725
726 static int count_unmerged_entries(void)
727 {
728         int i, ret = 0;
729
730         for (i = 0; i < active_nr; i++)
731                 if (ce_stage(active_cache[i]))
732                         ret++;
733
734         return ret;
735 }
736
737 static void split_merge_strategies(const char *string, struct strategy **list,
738                                    int *nr, int *alloc)
739 {
740         char *p, *q, *buf;
741
742         if (!string)
743                 return;
744
745         buf = xstrdup(string);
746         q = buf;
747         for (;;) {
748                 p = strchr(q, ' ');
749                 if (!p) {
750                         ALLOC_GROW(*list, *nr + 1, *alloc);
751                         (*list)[(*nr)++].name = xstrdup(q);
752                         free(buf);
753                         return;
754                 } else {
755                         *p = '\0';
756                         ALLOC_GROW(*list, *nr + 1, *alloc);
757                         (*list)[(*nr)++].name = xstrdup(q);
758                         q = ++p;
759                 }
760         }
761 }
762
763 static void add_strategies(const char *string, unsigned attr)
764 {
765         struct strategy *list = NULL;
766         int list_alloc = 0, list_nr = 0, i;
767
768         memset(&list, 0, sizeof(list));
769         split_merge_strategies(string, &list, &list_nr, &list_alloc);
770         if (list) {
771                 for (i = 0; i < list_nr; i++)
772                         append_strategy(get_strategy(list[i].name));
773                 return;
774         }
775         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
776                 if (all_strategy[i].attr & attr)
777                         append_strategy(&all_strategy[i]);
778
779 }
780
781 static void write_merge_msg(struct strbuf *msg)
782 {
783         const char *filename = git_path("MERGE_MSG");
784         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
785         if (fd < 0)
786                 die_errno(_("Could not open '%s' for writing"),
787                           filename);
788         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
789                 die_errno(_("Could not write to '%s'"), filename);
790         close(fd);
791 }
792
793 static void read_merge_msg(struct strbuf *msg)
794 {
795         const char *filename = git_path("MERGE_MSG");
796         strbuf_reset(msg);
797         if (strbuf_read_file(msg, filename, 0) < 0)
798                 die_errno(_("Could not read from '%s'"), filename);
799 }
800
801 static void write_merge_state(struct commit_list *);
802 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
803 {
804         if (err_msg)
805                 error("%s", err_msg);
806         fprintf(stderr,
807                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
808         write_merge_state(remoteheads);
809         exit(1);
810 }
811
812 static const char merge_editor_comment[] =
813 N_("Please enter a commit message to explain why this merge is necessary,\n"
814    "especially if it merges an updated upstream into a topic branch.\n"
815    "\n"
816    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
817    "the commit.\n");
818
819 static void prepare_to_commit(struct commit_list *remoteheads)
820 {
821         struct strbuf msg = STRBUF_INIT;
822         strbuf_addbuf(&msg, &merge_msg);
823         strbuf_addch(&msg, '\n');
824         if (0 < option_edit)
825                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
826         write_merge_msg(&msg);
827         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
828                             git_path("MERGE_MSG"), "merge", NULL))
829                 abort_commit(remoteheads, NULL);
830         if (0 < option_edit) {
831                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
832                         abort_commit(remoteheads, NULL);
833         }
834         read_merge_msg(&msg);
835         stripspace(&msg, 0 < option_edit);
836         if (!msg.len)
837                 abort_commit(remoteheads, _("Empty commit message."));
838         strbuf_release(&merge_msg);
839         strbuf_addbuf(&merge_msg, &msg);
840         strbuf_release(&msg);
841 }
842
843 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
844 {
845         unsigned char result_tree[20], result_commit[20];
846         struct commit_list *parents, **pptr = &parents;
847
848         write_tree_trivial(result_tree);
849         printf(_("Wonderful.\n"));
850         pptr = commit_list_append(head, pptr);
851         pptr = commit_list_append(remoteheads->item, pptr);
852         prepare_to_commit(remoteheads);
853         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
854                         result_commit, NULL, sign_commit))
855                 die(_("failed to write commit object"));
856         finish(head, remoteheads, result_commit, "In-index merge");
857         drop_save();
858         return 0;
859 }
860
861 static int finish_automerge(struct commit *head,
862                             int head_subsumed,
863                             struct commit_list *common,
864                             struct commit_list *remoteheads,
865                             unsigned char *result_tree,
866                             const char *wt_strategy)
867 {
868         struct commit_list *parents = NULL;
869         struct strbuf buf = STRBUF_INIT;
870         unsigned char result_commit[20];
871
872         free_commit_list(common);
873         parents = remoteheads;
874         if (!head_subsumed || fast_forward == FF_NO)
875                 commit_list_insert(head, &parents);
876         strbuf_addch(&merge_msg, '\n');
877         prepare_to_commit(remoteheads);
878         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
879                         result_commit, NULL, sign_commit))
880                 die(_("failed to write commit object"));
881         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
882         finish(head, remoteheads, result_commit, buf.buf);
883         strbuf_release(&buf);
884         drop_save();
885         return 0;
886 }
887
888 static int suggest_conflicts(void)
889 {
890         const char *filename;
891         FILE *fp;
892         struct strbuf msgbuf = STRBUF_INIT;
893
894         filename = git_path("MERGE_MSG");
895         fp = fopen(filename, "a");
896         if (!fp)
897                 die_errno(_("Could not open '%s' for writing"), filename);
898
899         append_conflicts_hint(&msgbuf);
900         fputs(msgbuf.buf, fp);
901         strbuf_release(&msgbuf);
902         fclose(fp);
903         rerere(allow_rerere_auto);
904         printf(_("Automatic merge failed; "
905                         "fix conflicts and then commit the result.\n"));
906         return 1;
907 }
908
909 static struct commit *is_old_style_invocation(int argc, const char **argv,
910                                               const unsigned char *head)
911 {
912         struct commit *second_token = NULL;
913         if (argc > 2) {
914                 unsigned char second_sha1[20];
915
916                 if (get_sha1(argv[1], second_sha1))
917                         return NULL;
918                 second_token = lookup_commit_reference_gently(second_sha1, 0);
919                 if (!second_token)
920                         die(_("'%s' is not a commit"), argv[1]);
921                 if (hashcmp(second_token->object.sha1, head))
922                         return NULL;
923         }
924         return second_token;
925 }
926
927 static int evaluate_result(void)
928 {
929         int cnt = 0;
930         struct rev_info rev;
931
932         /* Check how many files differ. */
933         init_revisions(&rev, "");
934         setup_revisions(0, NULL, &rev, NULL);
935         rev.diffopt.output_format |=
936                 DIFF_FORMAT_CALLBACK;
937         rev.diffopt.format_callback = count_diff_files;
938         rev.diffopt.format_callback_data = &cnt;
939         run_diff_files(&rev, 0);
940
941         /*
942          * Check how many unmerged entries are
943          * there.
944          */
945         cnt += count_unmerged_entries();
946
947         return cnt;
948 }
949
950 /*
951  * Pretend as if the user told us to merge with the remote-tracking
952  * branch we have for the upstream of the current branch
953  */
954 static int setup_with_upstream(const char ***argv)
955 {
956         struct branch *branch = branch_get(NULL);
957         int i;
958         const char **args;
959
960         if (!branch)
961                 die(_("No current branch."));
962         if (!branch->remote)
963                 die(_("No remote for the current branch."));
964         if (!branch->merge_nr)
965                 die(_("No default upstream defined for the current branch."));
966
967         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
968         for (i = 0; i < branch->merge_nr; i++) {
969                 if (!branch->merge[i]->dst)
970                         die(_("No remote-tracking branch for %s from %s"),
971                             branch->merge[i]->src, branch->remote_name);
972                 args[i] = branch->merge[i]->dst;
973         }
974         args[i] = NULL;
975         *argv = args;
976         return i;
977 }
978
979 static void write_merge_state(struct commit_list *remoteheads)
980 {
981         const char *filename;
982         int fd;
983         struct commit_list *j;
984         struct strbuf buf = STRBUF_INIT;
985
986         for (j = remoteheads; j; j = j->next) {
987                 unsigned const char *sha1;
988                 struct commit *c = j->item;
989                 if (c->util && merge_remote_util(c)->obj) {
990                         sha1 = merge_remote_util(c)->obj->sha1;
991                 } else {
992                         sha1 = c->object.sha1;
993                 }
994                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
995         }
996         filename = git_path("MERGE_HEAD");
997         fd = open(filename, O_WRONLY | O_CREAT, 0666);
998         if (fd < 0)
999                 die_errno(_("Could not open '%s' for writing"), filename);
1000         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1001                 die_errno(_("Could not write to '%s'"), filename);
1002         close(fd);
1003         strbuf_addch(&merge_msg, '\n');
1004         write_merge_msg(&merge_msg);
1005
1006         filename = git_path("MERGE_MODE");
1007         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1008         if (fd < 0)
1009                 die_errno(_("Could not open '%s' for writing"), filename);
1010         strbuf_reset(&buf);
1011         if (fast_forward == FF_NO)
1012                 strbuf_addf(&buf, "no-ff");
1013         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1014                 die_errno(_("Could not write to '%s'"), filename);
1015         close(fd);
1016 }
1017
1018 static int default_edit_option(void)
1019 {
1020         static const char name[] = "GIT_MERGE_AUTOEDIT";
1021         const char *e = getenv(name);
1022         struct stat st_stdin, st_stdout;
1023
1024         if (have_message)
1025                 /* an explicit -m msg without --[no-]edit */
1026                 return 0;
1027
1028         if (e) {
1029                 int v = git_config_maybe_bool(name, e);
1030                 if (v < 0)
1031                         die("Bad value '%s' in environment '%s'", e, name);
1032                 return v;
1033         }
1034
1035         /* Use editor if stdin and stdout are the same and is a tty */
1036         return (!fstat(0, &st_stdin) &&
1037                 !fstat(1, &st_stdout) &&
1038                 isatty(0) && isatty(1) &&
1039                 st_stdin.st_dev == st_stdout.st_dev &&
1040                 st_stdin.st_ino == st_stdout.st_ino &&
1041                 st_stdin.st_mode == st_stdout.st_mode);
1042 }
1043
1044 static struct commit_list *collect_parents(struct commit *head_commit,
1045                                            int *head_subsumed,
1046                                            int argc, const char **argv)
1047 {
1048         int i;
1049         struct commit_list *remoteheads = NULL, *parents, *next;
1050         struct commit_list **remotes = &remoteheads;
1051
1052         if (head_commit)
1053                 remotes = &commit_list_insert(head_commit, remotes)->next;
1054         for (i = 0; i < argc; i++) {
1055                 struct commit *commit = get_merge_parent(argv[i]);
1056                 if (!commit)
1057                         help_unknown_ref(argv[i], "merge",
1058                                          "not something we can merge");
1059                 remotes = &commit_list_insert(commit, remotes)->next;
1060         }
1061         *remotes = NULL;
1062
1063         parents = reduce_heads(remoteheads);
1064
1065         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1066         for (remoteheads = NULL, remotes = &remoteheads;
1067              parents;
1068              parents = next) {
1069                 struct commit *commit = parents->item;
1070                 next = parents->next;
1071                 if (commit == head_commit)
1072                         *head_subsumed = 0;
1073                 else
1074                         remotes = &commit_list_insert(commit, remotes)->next;
1075         }
1076         return remoteheads;
1077 }
1078
1079 int cmd_merge(int argc, const char **argv, const char *prefix)
1080 {
1081         unsigned char result_tree[20];
1082         unsigned char stash[20];
1083         unsigned char head_sha1[20];
1084         struct commit *head_commit;
1085         struct strbuf buf = STRBUF_INIT;
1086         const char *head_arg;
1087         int flag, i, ret = 0, head_subsumed;
1088         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1089         struct commit_list *common = NULL;
1090         const char *best_strategy = NULL, *wt_strategy = NULL;
1091         struct commit_list *remoteheads, *p;
1092         void *branch_to_free;
1093
1094         if (argc == 2 && !strcmp(argv[1], "-h"))
1095                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1096
1097         /*
1098          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1099          * current branch.
1100          */
1101         branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1102         if (branch && starts_with(branch, "refs/heads/"))
1103                 branch += 11;
1104         if (!branch || is_null_sha1(head_sha1))
1105                 head_commit = NULL;
1106         else
1107                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1108
1109         git_config(git_merge_config, NULL);
1110
1111         if (branch_mergeoptions)
1112                 parse_branch_merge_options(branch_mergeoptions);
1113         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1114                         builtin_merge_usage, 0);
1115         if (shortlog_len < 0)
1116                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1117
1118         if (verbosity < 0 && show_progress == -1)
1119                 show_progress = 0;
1120
1121         if (abort_current_merge) {
1122                 int nargc = 2;
1123                 const char *nargv[] = {"reset", "--merge", NULL};
1124
1125                 if (!file_exists(git_path("MERGE_HEAD")))
1126                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1127
1128                 /* Invoke 'git reset --merge' */
1129                 ret = cmd_reset(nargc, nargv, prefix);
1130                 goto done;
1131         }
1132
1133         if (read_cache_unmerged())
1134                 die_resolve_conflict("merge");
1135
1136         if (file_exists(git_path("MERGE_HEAD"))) {
1137                 /*
1138                  * There is no unmerged entry, don't advise 'git
1139                  * add/rm <file>', just 'git commit'.
1140                  */
1141                 if (advice_resolve_conflict)
1142                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1143                                   "Please, commit your changes before you merge."));
1144                 else
1145                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1146         }
1147         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1148                 if (advice_resolve_conflict)
1149                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1150                             "Please, commit your changes before you merge."));
1151                 else
1152                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1153         }
1154         resolve_undo_clear();
1155
1156         if (verbosity < 0)
1157                 show_diffstat = 0;
1158
1159         if (squash) {
1160                 if (fast_forward == FF_NO)
1161                         die(_("You cannot combine --squash with --no-ff."));
1162                 option_commit = 0;
1163         }
1164
1165         if (!abort_current_merge) {
1166                 if (!argc) {
1167                         if (default_to_upstream)
1168                                 argc = setup_with_upstream(&argv);
1169                         else
1170                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1171                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1172                         argv[0] = "@{-1}";
1173         }
1174         if (!argc)
1175                 usage_with_options(builtin_merge_usage,
1176                         builtin_merge_options);
1177
1178         /*
1179          * This could be traditional "merge <msg> HEAD <commit>..."  and
1180          * the way we can tell it is to see if the second token is HEAD,
1181          * but some people might have misused the interface and used a
1182          * commit-ish that is the same as HEAD there instead.
1183          * Traditional format never would have "-m" so it is an
1184          * additional safety measure to check for it.
1185          */
1186
1187         if (!have_message && head_commit &&
1188             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1189                 strbuf_addstr(&merge_msg, argv[0]);
1190                 head_arg = argv[1];
1191                 argv += 2;
1192                 argc -= 2;
1193                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1194         } else if (!head_commit) {
1195                 struct commit *remote_head;
1196                 /*
1197                  * If the merged head is a valid one there is no reason
1198                  * to forbid "git merge" into a branch yet to be born.
1199                  * We do the same for "git pull".
1200                  */
1201                 if (argc != 1)
1202                         die(_("Can merge only exactly one commit into "
1203                                 "empty head"));
1204                 if (squash)
1205                         die(_("Squash commit into empty head not supported yet"));
1206                 if (fast_forward == FF_NO)
1207                         die(_("Non-fast-forward commit does not make sense into "
1208                             "an empty head"));
1209                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1210                 remote_head = remoteheads->item;
1211                 if (!remote_head)
1212                         die(_("%s - not something we can merge"), argv[0]);
1213                 read_empty(remote_head->object.sha1, 0);
1214                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1215                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1216                 goto done;
1217         } else {
1218                 struct strbuf merge_names = STRBUF_INIT;
1219
1220                 /* We are invoked directly as the first-class UI. */
1221                 head_arg = "HEAD";
1222
1223                 /*
1224                  * All the rest are the commits being merged; prepare
1225                  * the standard merge summary message to be appended
1226                  * to the given message.
1227                  */
1228                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1229                 for (p = remoteheads; p; p = p->next)
1230                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1231
1232                 if (!have_message || shortlog_len) {
1233                         struct fmt_merge_msg_opts opts;
1234                         memset(&opts, 0, sizeof(opts));
1235                         opts.add_title = !have_message;
1236                         opts.shortlog_len = shortlog_len;
1237                         opts.credit_people = (0 < option_edit);
1238
1239                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1240                         if (merge_msg.len)
1241                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1242                 }
1243         }
1244
1245         if (!head_commit || !argc)
1246                 usage_with_options(builtin_merge_usage,
1247                         builtin_merge_options);
1248
1249         if (verify_signatures) {
1250                 for (p = remoteheads; p; p = p->next) {
1251                         struct commit *commit = p->item;
1252                         char hex[41];
1253                         struct signature_check signature_check;
1254                         memset(&signature_check, 0, sizeof(signature_check));
1255
1256                         check_commit_signature(commit, &signature_check);
1257
1258                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1259                         switch (signature_check.result) {
1260                         case 'G':
1261                                 break;
1262                         case 'U':
1263                                 die(_("Commit %s has an untrusted GPG signature, "
1264                                       "allegedly by %s."), hex, signature_check.signer);
1265                         case 'B':
1266                                 die(_("Commit %s has a bad GPG signature "
1267                                       "allegedly by %s."), hex, signature_check.signer);
1268                         default: /* 'N' */
1269                                 die(_("Commit %s does not have a GPG signature."), hex);
1270                         }
1271                         if (verbosity >= 0 && signature_check.result == 'G')
1272                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1273                                        hex, signature_check.signer);
1274
1275                         signature_check_clear(&signature_check);
1276                 }
1277         }
1278
1279         strbuf_addstr(&buf, "merge");
1280         for (p = remoteheads; p; p = p->next)
1281                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1282         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1283         strbuf_reset(&buf);
1284
1285         for (p = remoteheads; p; p = p->next) {
1286                 struct commit *commit = p->item;
1287                 strbuf_addf(&buf, "GITHEAD_%s",
1288                             sha1_to_hex(commit->object.sha1));
1289                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1290                 strbuf_reset(&buf);
1291                 if (fast_forward != FF_ONLY &&
1292                     merge_remote_util(commit) &&
1293                     merge_remote_util(commit)->obj &&
1294                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1295                         fast_forward = FF_NO;
1296         }
1297
1298         if (option_edit < 0)
1299                 option_edit = default_edit_option();
1300
1301         if (!use_strategies) {
1302                 if (!remoteheads)
1303                         ; /* already up-to-date */
1304                 else if (!remoteheads->next)
1305                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1306                 else
1307                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1308         }
1309
1310         for (i = 0; i < use_strategies_nr; i++) {
1311                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1312                         fast_forward = FF_NO;
1313                 if (use_strategies[i]->attr & NO_TRIVIAL)
1314                         allow_trivial = 0;
1315         }
1316
1317         if (!remoteheads)
1318                 ; /* already up-to-date */
1319         else if (!remoteheads->next)
1320                 common = get_merge_bases(head_commit, remoteheads->item);
1321         else {
1322                 struct commit_list *list = remoteheads;
1323                 commit_list_insert(head_commit, &list);
1324                 common = get_octopus_merge_bases(list);
1325                 free(list);
1326         }
1327
1328         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1329                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1330
1331         if (remoteheads && !common)
1332                 ; /* No common ancestors found. We need a real merge. */
1333         else if (!remoteheads ||
1334                  (!remoteheads->next && !common->next &&
1335                   common->item == remoteheads->item)) {
1336                 /*
1337                  * If head can reach all the merge then we are up to date.
1338                  * but first the most common case of merging one remote.
1339                  */
1340                 finish_up_to_date("Already up-to-date.");
1341                 goto done;
1342         } else if (fast_forward != FF_NO && !remoteheads->next &&
1343                         !common->next &&
1344                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1345                 /* Again the most common case of merging one remote. */
1346                 struct strbuf msg = STRBUF_INIT;
1347                 struct commit *commit;
1348                 char hex[41];
1349
1350                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1351
1352                 if (verbosity >= 0)
1353                         printf(_("Updating %s..%s\n"),
1354                                 hex,
1355                                 find_unique_abbrev(remoteheads->item->object.sha1,
1356                                 DEFAULT_ABBREV));
1357                 strbuf_addstr(&msg, "Fast-forward");
1358                 if (have_message)
1359                         strbuf_addstr(&msg,
1360                                 " (no commit created; -m option ignored)");
1361                 commit = remoteheads->item;
1362                 if (!commit) {
1363                         ret = 1;
1364                         goto done;
1365                 }
1366
1367                 if (checkout_fast_forward(head_commit->object.sha1,
1368                                           commit->object.sha1,
1369                                           overwrite_ignore)) {
1370                         ret = 1;
1371                         goto done;
1372                 }
1373
1374                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1375                 drop_save();
1376                 goto done;
1377         } else if (!remoteheads->next && common->next)
1378                 ;
1379                 /*
1380                  * We are not doing octopus and not fast-forward.  Need
1381                  * a real merge.
1382                  */
1383         else if (!remoteheads->next && !common->next && option_commit) {
1384                 /*
1385                  * We are not doing octopus, not fast-forward, and have
1386                  * only one common.
1387                  */
1388                 refresh_cache(REFRESH_QUIET);
1389                 if (allow_trivial && fast_forward != FF_ONLY) {
1390                         /* See if it is really trivial. */
1391                         git_committer_info(IDENT_STRICT);
1392                         printf(_("Trying really trivial in-index merge...\n"));
1393                         if (!read_tree_trivial(common->item->object.sha1,
1394                                                head_commit->object.sha1,
1395                                                remoteheads->item->object.sha1)) {
1396                                 ret = merge_trivial(head_commit, remoteheads);
1397                                 goto done;
1398                         }
1399                         printf(_("Nope.\n"));
1400                 }
1401         } else {
1402                 /*
1403                  * An octopus.  If we can reach all the remote we are up
1404                  * to date.
1405                  */
1406                 int up_to_date = 1;
1407                 struct commit_list *j;
1408
1409                 for (j = remoteheads; j; j = j->next) {
1410                         struct commit_list *common_one;
1411
1412                         /*
1413                          * Here we *have* to calculate the individual
1414                          * merge_bases again, otherwise "git merge HEAD^
1415                          * HEAD^^" would be missed.
1416                          */
1417                         common_one = get_merge_bases(head_commit, j->item);
1418                         if (hashcmp(common_one->item->object.sha1,
1419                                 j->item->object.sha1)) {
1420                                 up_to_date = 0;
1421                                 break;
1422                         }
1423                 }
1424                 if (up_to_date) {
1425                         finish_up_to_date("Already up-to-date. Yeeah!");
1426                         goto done;
1427                 }
1428         }
1429
1430         if (fast_forward == FF_ONLY)
1431                 die(_("Not possible to fast-forward, aborting."));
1432
1433         /* We are going to make a new commit. */
1434         git_committer_info(IDENT_STRICT);
1435
1436         /*
1437          * At this point, we need a real merge.  No matter what strategy
1438          * we use, it would operate on the index, possibly affecting the
1439          * working tree, and when resolved cleanly, have the desired
1440          * tree in the index -- this means that the index must be in
1441          * sync with the head commit.  The strategies are responsible
1442          * to ensure this.
1443          */
1444         if (use_strategies_nr == 1 ||
1445             /*
1446              * Stash away the local changes so that we can try more than one.
1447              */
1448             save_state(stash))
1449                 hashcpy(stash, null_sha1);
1450
1451         for (i = 0; i < use_strategies_nr; i++) {
1452                 int ret;
1453                 if (i) {
1454                         printf(_("Rewinding the tree to pristine...\n"));
1455                         restore_state(head_commit->object.sha1, stash);
1456                 }
1457                 if (use_strategies_nr != 1)
1458                         printf(_("Trying merge strategy %s...\n"),
1459                                 use_strategies[i]->name);
1460                 /*
1461                  * Remember which strategy left the state in the working
1462                  * tree.
1463                  */
1464                 wt_strategy = use_strategies[i]->name;
1465
1466                 ret = try_merge_strategy(use_strategies[i]->name,
1467                                          common, remoteheads,
1468                                          head_commit, head_arg);
1469                 if (!option_commit && !ret) {
1470                         merge_was_ok = 1;
1471                         /*
1472                          * This is necessary here just to avoid writing
1473                          * the tree, but later we will *not* exit with
1474                          * status code 1 because merge_was_ok is set.
1475                          */
1476                         ret = 1;
1477                 }
1478
1479                 if (ret) {
1480                         /*
1481                          * The backend exits with 1 when conflicts are
1482                          * left to be resolved, with 2 when it does not
1483                          * handle the given merge at all.
1484                          */
1485                         if (ret == 1) {
1486                                 int cnt = evaluate_result();
1487
1488                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1489                                         best_strategy = use_strategies[i]->name;
1490                                         best_cnt = cnt;
1491                                 }
1492                         }
1493                         if (merge_was_ok)
1494                                 break;
1495                         else
1496                                 continue;
1497                 }
1498
1499                 /* Automerge succeeded. */
1500                 write_tree_trivial(result_tree);
1501                 automerge_was_ok = 1;
1502                 break;
1503         }
1504
1505         /*
1506          * If we have a resulting tree, that means the strategy module
1507          * auto resolved the merge cleanly.
1508          */
1509         if (automerge_was_ok) {
1510                 ret = finish_automerge(head_commit, head_subsumed,
1511                                        common, remoteheads,
1512                                        result_tree, wt_strategy);
1513                 goto done;
1514         }
1515
1516         /*
1517          * Pick the result from the best strategy and have the user fix
1518          * it up.
1519          */
1520         if (!best_strategy) {
1521                 restore_state(head_commit->object.sha1, stash);
1522                 if (use_strategies_nr > 1)
1523                         fprintf(stderr,
1524                                 _("No merge strategy handled the merge.\n"));
1525                 else
1526                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1527                                 use_strategies[0]->name);
1528                 ret = 2;
1529                 goto done;
1530         } else if (best_strategy == wt_strategy)
1531                 ; /* We already have its result in the working tree. */
1532         else {
1533                 printf(_("Rewinding the tree to pristine...\n"));
1534                 restore_state(head_commit->object.sha1, stash);
1535                 printf(_("Using the %s to prepare resolving by hand.\n"),
1536                         best_strategy);
1537                 try_merge_strategy(best_strategy, common, remoteheads,
1538                                    head_commit, head_arg);
1539         }
1540
1541         if (squash)
1542                 finish(head_commit, remoteheads, NULL, NULL);
1543         else
1544                 write_merge_state(remoteheads);
1545
1546         if (merge_was_ok)
1547                 fprintf(stderr, _("Automatic merge went well; "
1548                         "stopped before committing as requested\n"));
1549         else
1550                 ret = suggest_conflicts();
1551
1552 done:
1553         free(branch_to_free);
1554         return ret;
1555 }