Merge branch 'jc/push-to-checkout'
[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                 o.show_rename_progress =
688                         show_progress == -1 ? isatty(2) : show_progress;
689
690                 for (x = 0; x < xopts_nr; x++)
691                         if (parse_merge_opt(&o, xopts[x]))
692                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
693
694                 o.branch1 = head_arg;
695                 o.branch2 = merge_remote_util(remoteheads->item)->name;
696
697                 for (j = common; j; j = j->next)
698                         commit_list_insert(j->item, &reversed);
699
700                 hold_locked_index(&lock, 1);
701                 clean = merge_recursive(&o, head,
702                                 remoteheads->item, reversed, &result);
703                 if (active_cache_changed &&
704                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
705                         die (_("unable to write %s"), get_index_file());
706                 rollback_lock_file(&lock);
707                 return clean ? 0 : 1;
708         } else {
709                 return try_merge_command(strategy, xopts_nr, xopts,
710                                                 common, head_arg, remoteheads);
711         }
712 }
713
714 static void count_diff_files(struct diff_queue_struct *q,
715                              struct diff_options *opt, void *data)
716 {
717         int *count = data;
718
719         (*count) += q->nr;
720 }
721
722 static int count_unmerged_entries(void)
723 {
724         int i, ret = 0;
725
726         for (i = 0; i < active_nr; i++)
727                 if (ce_stage(active_cache[i]))
728                         ret++;
729
730         return ret;
731 }
732
733 static void split_merge_strategies(const char *string, struct strategy **list,
734                                    int *nr, int *alloc)
735 {
736         char *p, *q, *buf;
737
738         if (!string)
739                 return;
740
741         buf = xstrdup(string);
742         q = buf;
743         for (;;) {
744                 p = strchr(q, ' ');
745                 if (!p) {
746                         ALLOC_GROW(*list, *nr + 1, *alloc);
747                         (*list)[(*nr)++].name = xstrdup(q);
748                         free(buf);
749                         return;
750                 } else {
751                         *p = '\0';
752                         ALLOC_GROW(*list, *nr + 1, *alloc);
753                         (*list)[(*nr)++].name = xstrdup(q);
754                         q = ++p;
755                 }
756         }
757 }
758
759 static void add_strategies(const char *string, unsigned attr)
760 {
761         struct strategy *list = NULL;
762         int list_alloc = 0, list_nr = 0, i;
763
764         memset(&list, 0, sizeof(list));
765         split_merge_strategies(string, &list, &list_nr, &list_alloc);
766         if (list) {
767                 for (i = 0; i < list_nr; i++)
768                         append_strategy(get_strategy(list[i].name));
769                 return;
770         }
771         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
772                 if (all_strategy[i].attr & attr)
773                         append_strategy(&all_strategy[i]);
774
775 }
776
777 static void write_merge_msg(struct strbuf *msg)
778 {
779         const char *filename = git_path("MERGE_MSG");
780         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
781         if (fd < 0)
782                 die_errno(_("Could not open '%s' for writing"),
783                           filename);
784         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
785                 die_errno(_("Could not write to '%s'"), filename);
786         close(fd);
787 }
788
789 static void read_merge_msg(struct strbuf *msg)
790 {
791         const char *filename = git_path("MERGE_MSG");
792         strbuf_reset(msg);
793         if (strbuf_read_file(msg, filename, 0) < 0)
794                 die_errno(_("Could not read from '%s'"), filename);
795 }
796
797 static void write_merge_state(struct commit_list *);
798 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
799 {
800         if (err_msg)
801                 error("%s", err_msg);
802         fprintf(stderr,
803                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
804         write_merge_state(remoteheads);
805         exit(1);
806 }
807
808 static const char merge_editor_comment[] =
809 N_("Please enter a commit message to explain why this merge is necessary,\n"
810    "especially if it merges an updated upstream into a topic branch.\n"
811    "\n"
812    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
813    "the commit.\n");
814
815 static void prepare_to_commit(struct commit_list *remoteheads)
816 {
817         struct strbuf msg = STRBUF_INIT;
818         strbuf_addbuf(&msg, &merge_msg);
819         strbuf_addch(&msg, '\n');
820         if (0 < option_edit)
821                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
822         write_merge_msg(&msg);
823         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
824                             git_path("MERGE_MSG"), "merge", NULL))
825                 abort_commit(remoteheads, NULL);
826         if (0 < option_edit) {
827                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
828                         abort_commit(remoteheads, NULL);
829         }
830         read_merge_msg(&msg);
831         stripspace(&msg, 0 < option_edit);
832         if (!msg.len)
833                 abort_commit(remoteheads, _("Empty commit message."));
834         strbuf_release(&merge_msg);
835         strbuf_addbuf(&merge_msg, &msg);
836         strbuf_release(&msg);
837 }
838
839 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
840 {
841         unsigned char result_tree[20], result_commit[20];
842         struct commit_list *parents, **pptr = &parents;
843
844         write_tree_trivial(result_tree);
845         printf(_("Wonderful.\n"));
846         pptr = commit_list_append(head, pptr);
847         pptr = commit_list_append(remoteheads->item, pptr);
848         prepare_to_commit(remoteheads);
849         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
850                         result_commit, NULL, sign_commit))
851                 die(_("failed to write commit object"));
852         finish(head, remoteheads, result_commit, "In-index merge");
853         drop_save();
854         return 0;
855 }
856
857 static int finish_automerge(struct commit *head,
858                             int head_subsumed,
859                             struct commit_list *common,
860                             struct commit_list *remoteheads,
861                             unsigned char *result_tree,
862                             const char *wt_strategy)
863 {
864         struct commit_list *parents = NULL;
865         struct strbuf buf = STRBUF_INIT;
866         unsigned char result_commit[20];
867
868         free_commit_list(common);
869         parents = remoteheads;
870         if (!head_subsumed || fast_forward == FF_NO)
871                 commit_list_insert(head, &parents);
872         strbuf_addch(&merge_msg, '\n');
873         prepare_to_commit(remoteheads);
874         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
875                         result_commit, NULL, sign_commit))
876                 die(_("failed to write commit object"));
877         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
878         finish(head, remoteheads, result_commit, buf.buf);
879         strbuf_release(&buf);
880         drop_save();
881         return 0;
882 }
883
884 static int suggest_conflicts(void)
885 {
886         const char *filename;
887         FILE *fp;
888         struct strbuf msgbuf = STRBUF_INIT;
889
890         filename = git_path("MERGE_MSG");
891         fp = fopen(filename, "a");
892         if (!fp)
893                 die_errno(_("Could not open '%s' for writing"), filename);
894
895         append_conflicts_hint(&msgbuf);
896         fputs(msgbuf.buf, fp);
897         strbuf_release(&msgbuf);
898         fclose(fp);
899         rerere(allow_rerere_auto);
900         printf(_("Automatic merge failed; "
901                         "fix conflicts and then commit the result.\n"));
902         return 1;
903 }
904
905 static struct commit *is_old_style_invocation(int argc, const char **argv,
906                                               const unsigned char *head)
907 {
908         struct commit *second_token = NULL;
909         if (argc > 2) {
910                 unsigned char second_sha1[20];
911
912                 if (get_sha1(argv[1], second_sha1))
913                         return NULL;
914                 second_token = lookup_commit_reference_gently(second_sha1, 0);
915                 if (!second_token)
916                         die(_("'%s' is not a commit"), argv[1]);
917                 if (hashcmp(second_token->object.sha1, head))
918                         return NULL;
919         }
920         return second_token;
921 }
922
923 static int evaluate_result(void)
924 {
925         int cnt = 0;
926         struct rev_info rev;
927
928         /* Check how many files differ. */
929         init_revisions(&rev, "");
930         setup_revisions(0, NULL, &rev, NULL);
931         rev.diffopt.output_format |=
932                 DIFF_FORMAT_CALLBACK;
933         rev.diffopt.format_callback = count_diff_files;
934         rev.diffopt.format_callback_data = &cnt;
935         run_diff_files(&rev, 0);
936
937         /*
938          * Check how many unmerged entries are
939          * there.
940          */
941         cnt += count_unmerged_entries();
942
943         return cnt;
944 }
945
946 /*
947  * Pretend as if the user told us to merge with the remote-tracking
948  * branch we have for the upstream of the current branch
949  */
950 static int setup_with_upstream(const char ***argv)
951 {
952         struct branch *branch = branch_get(NULL);
953         int i;
954         const char **args;
955
956         if (!branch)
957                 die(_("No current branch."));
958         if (!branch->remote)
959                 die(_("No remote for the current branch."));
960         if (!branch->merge_nr)
961                 die(_("No default upstream defined for the current branch."));
962
963         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
964         for (i = 0; i < branch->merge_nr; i++) {
965                 if (!branch->merge[i]->dst)
966                         die(_("No remote-tracking branch for %s from %s"),
967                             branch->merge[i]->src, branch->remote_name);
968                 args[i] = branch->merge[i]->dst;
969         }
970         args[i] = NULL;
971         *argv = args;
972         return i;
973 }
974
975 static void write_merge_state(struct commit_list *remoteheads)
976 {
977         const char *filename;
978         int fd;
979         struct commit_list *j;
980         struct strbuf buf = STRBUF_INIT;
981
982         for (j = remoteheads; j; j = j->next) {
983                 unsigned const char *sha1;
984                 struct commit *c = j->item;
985                 if (c->util && merge_remote_util(c)->obj) {
986                         sha1 = merge_remote_util(c)->obj->sha1;
987                 } else {
988                         sha1 = c->object.sha1;
989                 }
990                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
991         }
992         filename = git_path("MERGE_HEAD");
993         fd = open(filename, O_WRONLY | O_CREAT, 0666);
994         if (fd < 0)
995                 die_errno(_("Could not open '%s' for writing"), filename);
996         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
997                 die_errno(_("Could not write to '%s'"), filename);
998         close(fd);
999         strbuf_addch(&merge_msg, '\n');
1000         write_merge_msg(&merge_msg);
1001
1002         filename = git_path("MERGE_MODE");
1003         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1004         if (fd < 0)
1005                 die_errno(_("Could not open '%s' for writing"), filename);
1006         strbuf_reset(&buf);
1007         if (fast_forward == FF_NO)
1008                 strbuf_addf(&buf, "no-ff");
1009         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1010                 die_errno(_("Could not write to '%s'"), filename);
1011         close(fd);
1012 }
1013
1014 static int default_edit_option(void)
1015 {
1016         static const char name[] = "GIT_MERGE_AUTOEDIT";
1017         const char *e = getenv(name);
1018         struct stat st_stdin, st_stdout;
1019
1020         if (have_message)
1021                 /* an explicit -m msg without --[no-]edit */
1022                 return 0;
1023
1024         if (e) {
1025                 int v = git_config_maybe_bool(name, e);
1026                 if (v < 0)
1027                         die("Bad value '%s' in environment '%s'", e, name);
1028                 return v;
1029         }
1030
1031         /* Use editor if stdin and stdout are the same and is a tty */
1032         return (!fstat(0, &st_stdin) &&
1033                 !fstat(1, &st_stdout) &&
1034                 isatty(0) && isatty(1) &&
1035                 st_stdin.st_dev == st_stdout.st_dev &&
1036                 st_stdin.st_ino == st_stdout.st_ino &&
1037                 st_stdin.st_mode == st_stdout.st_mode);
1038 }
1039
1040 static struct commit_list *collect_parents(struct commit *head_commit,
1041                                            int *head_subsumed,
1042                                            int argc, const char **argv)
1043 {
1044         int i;
1045         struct commit_list *remoteheads = NULL, *parents, *next;
1046         struct commit_list **remotes = &remoteheads;
1047
1048         if (head_commit)
1049                 remotes = &commit_list_insert(head_commit, remotes)->next;
1050         for (i = 0; i < argc; i++) {
1051                 struct commit *commit = get_merge_parent(argv[i]);
1052                 if (!commit)
1053                         help_unknown_ref(argv[i], "merge",
1054                                          "not something we can merge");
1055                 remotes = &commit_list_insert(commit, remotes)->next;
1056         }
1057         *remotes = NULL;
1058
1059         parents = reduce_heads(remoteheads);
1060
1061         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1062         for (remoteheads = NULL, remotes = &remoteheads;
1063              parents;
1064              parents = next) {
1065                 struct commit *commit = parents->item;
1066                 next = parents->next;
1067                 if (commit == head_commit)
1068                         *head_subsumed = 0;
1069                 else
1070                         remotes = &commit_list_insert(commit, remotes)->next;
1071         }
1072         return remoteheads;
1073 }
1074
1075 int cmd_merge(int argc, const char **argv, const char *prefix)
1076 {
1077         unsigned char result_tree[20];
1078         unsigned char stash[20];
1079         unsigned char head_sha1[20];
1080         struct commit *head_commit;
1081         struct strbuf buf = STRBUF_INIT;
1082         const char *head_arg;
1083         int flag, i, ret = 0, head_subsumed;
1084         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1085         struct commit_list *common = NULL;
1086         const char *best_strategy = NULL, *wt_strategy = NULL;
1087         struct commit_list *remoteheads, *p;
1088         void *branch_to_free;
1089
1090         if (argc == 2 && !strcmp(argv[1], "-h"))
1091                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1092
1093         /*
1094          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1095          * current branch.
1096          */
1097         branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1098         if (branch && starts_with(branch, "refs/heads/"))
1099                 branch += 11;
1100         if (!branch || is_null_sha1(head_sha1))
1101                 head_commit = NULL;
1102         else
1103                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1104
1105         git_config(git_merge_config, NULL);
1106
1107         if (branch_mergeoptions)
1108                 parse_branch_merge_options(branch_mergeoptions);
1109         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1110                         builtin_merge_usage, 0);
1111         if (shortlog_len < 0)
1112                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1113
1114         if (verbosity < 0 && show_progress == -1)
1115                 show_progress = 0;
1116
1117         if (abort_current_merge) {
1118                 int nargc = 2;
1119                 const char *nargv[] = {"reset", "--merge", NULL};
1120
1121                 if (!file_exists(git_path("MERGE_HEAD")))
1122                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1123
1124                 /* Invoke 'git reset --merge' */
1125                 ret = cmd_reset(nargc, nargv, prefix);
1126                 goto done;
1127         }
1128
1129         if (read_cache_unmerged())
1130                 die_resolve_conflict("merge");
1131
1132         if (file_exists(git_path("MERGE_HEAD"))) {
1133                 /*
1134                  * There is no unmerged entry, don't advise 'git
1135                  * add/rm <file>', just 'git commit'.
1136                  */
1137                 if (advice_resolve_conflict)
1138                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1139                                   "Please, commit your changes before you merge."));
1140                 else
1141                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1142         }
1143         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1144                 if (advice_resolve_conflict)
1145                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1146                             "Please, commit your changes before you merge."));
1147                 else
1148                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1149         }
1150         resolve_undo_clear();
1151
1152         if (verbosity < 0)
1153                 show_diffstat = 0;
1154
1155         if (squash) {
1156                 if (fast_forward == FF_NO)
1157                         die(_("You cannot combine --squash with --no-ff."));
1158                 option_commit = 0;
1159         }
1160
1161         if (!abort_current_merge) {
1162                 if (!argc) {
1163                         if (default_to_upstream)
1164                                 argc = setup_with_upstream(&argv);
1165                         else
1166                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1167                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1168                         argv[0] = "@{-1}";
1169         }
1170         if (!argc)
1171                 usage_with_options(builtin_merge_usage,
1172                         builtin_merge_options);
1173
1174         /*
1175          * This could be traditional "merge <msg> HEAD <commit>..."  and
1176          * the way we can tell it is to see if the second token is HEAD,
1177          * but some people might have misused the interface and used a
1178          * commit-ish that is the same as HEAD there instead.
1179          * Traditional format never would have "-m" so it is an
1180          * additional safety measure to check for it.
1181          */
1182
1183         if (!have_message && head_commit &&
1184             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1185                 strbuf_addstr(&merge_msg, argv[0]);
1186                 head_arg = argv[1];
1187                 argv += 2;
1188                 argc -= 2;
1189                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1190         } else if (!head_commit) {
1191                 struct commit *remote_head;
1192                 /*
1193                  * If the merged head is a valid one there is no reason
1194                  * to forbid "git merge" into a branch yet to be born.
1195                  * We do the same for "git pull".
1196                  */
1197                 if (argc != 1)
1198                         die(_("Can merge only exactly one commit into "
1199                                 "empty head"));
1200                 if (squash)
1201                         die(_("Squash commit into empty head not supported yet"));
1202                 if (fast_forward == FF_NO)
1203                         die(_("Non-fast-forward commit does not make sense into "
1204                             "an empty head"));
1205                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1206                 remote_head = remoteheads->item;
1207                 if (!remote_head)
1208                         die(_("%s - not something we can merge"), argv[0]);
1209                 read_empty(remote_head->object.sha1, 0);
1210                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1211                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1212                 goto done;
1213         } else {
1214                 struct strbuf merge_names = STRBUF_INIT;
1215
1216                 /* We are invoked directly as the first-class UI. */
1217                 head_arg = "HEAD";
1218
1219                 /*
1220                  * All the rest are the commits being merged; prepare
1221                  * the standard merge summary message to be appended
1222                  * to the given message.
1223                  */
1224                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1225                 for (p = remoteheads; p; p = p->next)
1226                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1227
1228                 if (!have_message || shortlog_len) {
1229                         struct fmt_merge_msg_opts opts;
1230                         memset(&opts, 0, sizeof(opts));
1231                         opts.add_title = !have_message;
1232                         opts.shortlog_len = shortlog_len;
1233                         opts.credit_people = (0 < option_edit);
1234
1235                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1236                         if (merge_msg.len)
1237                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1238                 }
1239         }
1240
1241         if (!head_commit || !argc)
1242                 usage_with_options(builtin_merge_usage,
1243                         builtin_merge_options);
1244
1245         if (verify_signatures) {
1246                 for (p = remoteheads; p; p = p->next) {
1247                         struct commit *commit = p->item;
1248                         char hex[41];
1249                         struct signature_check signature_check;
1250                         memset(&signature_check, 0, sizeof(signature_check));
1251
1252                         check_commit_signature(commit, &signature_check);
1253
1254                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1255                         switch (signature_check.result) {
1256                         case 'G':
1257                                 break;
1258                         case 'U':
1259                                 die(_("Commit %s has an untrusted GPG signature, "
1260                                       "allegedly by %s."), hex, signature_check.signer);
1261                         case 'B':
1262                                 die(_("Commit %s has a bad GPG signature "
1263                                       "allegedly by %s."), hex, signature_check.signer);
1264                         default: /* 'N' */
1265                                 die(_("Commit %s does not have a GPG signature."), hex);
1266                         }
1267                         if (verbosity >= 0 && signature_check.result == 'G')
1268                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1269                                        hex, signature_check.signer);
1270
1271                         signature_check_clear(&signature_check);
1272                 }
1273         }
1274
1275         strbuf_addstr(&buf, "merge");
1276         for (p = remoteheads; p; p = p->next)
1277                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1278         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1279         strbuf_reset(&buf);
1280
1281         for (p = remoteheads; p; p = p->next) {
1282                 struct commit *commit = p->item;
1283                 strbuf_addf(&buf, "GITHEAD_%s",
1284                             sha1_to_hex(commit->object.sha1));
1285                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1286                 strbuf_reset(&buf);
1287                 if (fast_forward != FF_ONLY &&
1288                     merge_remote_util(commit) &&
1289                     merge_remote_util(commit)->obj &&
1290                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1291                         fast_forward = FF_NO;
1292         }
1293
1294         if (option_edit < 0)
1295                 option_edit = default_edit_option();
1296
1297         if (!use_strategies) {
1298                 if (!remoteheads)
1299                         ; /* already up-to-date */
1300                 else if (!remoteheads->next)
1301                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1302                 else
1303                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1304         }
1305
1306         for (i = 0; i < use_strategies_nr; i++) {
1307                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1308                         fast_forward = FF_NO;
1309                 if (use_strategies[i]->attr & NO_TRIVIAL)
1310                         allow_trivial = 0;
1311         }
1312
1313         if (!remoteheads)
1314                 ; /* already up-to-date */
1315         else if (!remoteheads->next)
1316                 common = get_merge_bases(head_commit, remoteheads->item);
1317         else {
1318                 struct commit_list *list = remoteheads;
1319                 commit_list_insert(head_commit, &list);
1320                 common = get_octopus_merge_bases(list);
1321                 free(list);
1322         }
1323
1324         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1325                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1326
1327         if (remoteheads && !common)
1328                 ; /* No common ancestors found. We need a real merge. */
1329         else if (!remoteheads ||
1330                  (!remoteheads->next && !common->next &&
1331                   common->item == remoteheads->item)) {
1332                 /*
1333                  * If head can reach all the merge then we are up to date.
1334                  * but first the most common case of merging one remote.
1335                  */
1336                 finish_up_to_date("Already up-to-date.");
1337                 goto done;
1338         } else if (fast_forward != FF_NO && !remoteheads->next &&
1339                         !common->next &&
1340                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1341                 /* Again the most common case of merging one remote. */
1342                 struct strbuf msg = STRBUF_INIT;
1343                 struct commit *commit;
1344                 char hex[41];
1345
1346                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1347
1348                 if (verbosity >= 0)
1349                         printf(_("Updating %s..%s\n"),
1350                                 hex,
1351                                 find_unique_abbrev(remoteheads->item->object.sha1,
1352                                 DEFAULT_ABBREV));
1353                 strbuf_addstr(&msg, "Fast-forward");
1354                 if (have_message)
1355                         strbuf_addstr(&msg,
1356                                 " (no commit created; -m option ignored)");
1357                 commit = remoteheads->item;
1358                 if (!commit) {
1359                         ret = 1;
1360                         goto done;
1361                 }
1362
1363                 if (checkout_fast_forward(head_commit->object.sha1,
1364                                           commit->object.sha1,
1365                                           overwrite_ignore)) {
1366                         ret = 1;
1367                         goto done;
1368                 }
1369
1370                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1371                 drop_save();
1372                 goto done;
1373         } else if (!remoteheads->next && common->next)
1374                 ;
1375                 /*
1376                  * We are not doing octopus and not fast-forward.  Need
1377                  * a real merge.
1378                  */
1379         else if (!remoteheads->next && !common->next && option_commit) {
1380                 /*
1381                  * We are not doing octopus, not fast-forward, and have
1382                  * only one common.
1383                  */
1384                 refresh_cache(REFRESH_QUIET);
1385                 if (allow_trivial && fast_forward != FF_ONLY) {
1386                         /* See if it is really trivial. */
1387                         git_committer_info(IDENT_STRICT);
1388                         printf(_("Trying really trivial in-index merge...\n"));
1389                         if (!read_tree_trivial(common->item->object.sha1,
1390                                                head_commit->object.sha1,
1391                                                remoteheads->item->object.sha1)) {
1392                                 ret = merge_trivial(head_commit, remoteheads);
1393                                 goto done;
1394                         }
1395                         printf(_("Nope.\n"));
1396                 }
1397         } else {
1398                 /*
1399                  * An octopus.  If we can reach all the remote we are up
1400                  * to date.
1401                  */
1402                 int up_to_date = 1;
1403                 struct commit_list *j;
1404
1405                 for (j = remoteheads; j; j = j->next) {
1406                         struct commit_list *common_one;
1407
1408                         /*
1409                          * Here we *have* to calculate the individual
1410                          * merge_bases again, otherwise "git merge HEAD^
1411                          * HEAD^^" would be missed.
1412                          */
1413                         common_one = get_merge_bases(head_commit, j->item);
1414                         if (hashcmp(common_one->item->object.sha1,
1415                                 j->item->object.sha1)) {
1416                                 up_to_date = 0;
1417                                 break;
1418                         }
1419                 }
1420                 if (up_to_date) {
1421                         finish_up_to_date("Already up-to-date. Yeeah!");
1422                         goto done;
1423                 }
1424         }
1425
1426         if (fast_forward == FF_ONLY)
1427                 die(_("Not possible to fast-forward, aborting."));
1428
1429         /* We are going to make a new commit. */
1430         git_committer_info(IDENT_STRICT);
1431
1432         /*
1433          * At this point, we need a real merge.  No matter what strategy
1434          * we use, it would operate on the index, possibly affecting the
1435          * working tree, and when resolved cleanly, have the desired
1436          * tree in the index -- this means that the index must be in
1437          * sync with the head commit.  The strategies are responsible
1438          * to ensure this.
1439          */
1440         if (use_strategies_nr == 1 ||
1441             /*
1442              * Stash away the local changes so that we can try more than one.
1443              */
1444             save_state(stash))
1445                 hashcpy(stash, null_sha1);
1446
1447         for (i = 0; i < use_strategies_nr; i++) {
1448                 int ret;
1449                 if (i) {
1450                         printf(_("Rewinding the tree to pristine...\n"));
1451                         restore_state(head_commit->object.sha1, stash);
1452                 }
1453                 if (use_strategies_nr != 1)
1454                         printf(_("Trying merge strategy %s...\n"),
1455                                 use_strategies[i]->name);
1456                 /*
1457                  * Remember which strategy left the state in the working
1458                  * tree.
1459                  */
1460                 wt_strategy = use_strategies[i]->name;
1461
1462                 ret = try_merge_strategy(use_strategies[i]->name,
1463                                          common, remoteheads,
1464                                          head_commit, head_arg);
1465                 if (!option_commit && !ret) {
1466                         merge_was_ok = 1;
1467                         /*
1468                          * This is necessary here just to avoid writing
1469                          * the tree, but later we will *not* exit with
1470                          * status code 1 because merge_was_ok is set.
1471                          */
1472                         ret = 1;
1473                 }
1474
1475                 if (ret) {
1476                         /*
1477                          * The backend exits with 1 when conflicts are
1478                          * left to be resolved, with 2 when it does not
1479                          * handle the given merge at all.
1480                          */
1481                         if (ret == 1) {
1482                                 int cnt = evaluate_result();
1483
1484                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1485                                         best_strategy = use_strategies[i]->name;
1486                                         best_cnt = cnt;
1487                                 }
1488                         }
1489                         if (merge_was_ok)
1490                                 break;
1491                         else
1492                                 continue;
1493                 }
1494
1495                 /* Automerge succeeded. */
1496                 write_tree_trivial(result_tree);
1497                 automerge_was_ok = 1;
1498                 break;
1499         }
1500
1501         /*
1502          * If we have a resulting tree, that means the strategy module
1503          * auto resolved the merge cleanly.
1504          */
1505         if (automerge_was_ok) {
1506                 ret = finish_automerge(head_commit, head_subsumed,
1507                                        common, remoteheads,
1508                                        result_tree, wt_strategy);
1509                 goto done;
1510         }
1511
1512         /*
1513          * Pick the result from the best strategy and have the user fix
1514          * it up.
1515          */
1516         if (!best_strategy) {
1517                 restore_state(head_commit->object.sha1, stash);
1518                 if (use_strategies_nr > 1)
1519                         fprintf(stderr,
1520                                 _("No merge strategy handled the merge.\n"));
1521                 else
1522                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1523                                 use_strategies[0]->name);
1524                 ret = 2;
1525                 goto done;
1526         } else if (best_strategy == wt_strategy)
1527                 ; /* We already have its result in the working tree. */
1528         else {
1529                 printf(_("Rewinding the tree to pristine...\n"));
1530                 restore_state(head_commit->object.sha1, stash);
1531                 printf(_("Using the %s to prepare resolving by hand.\n"),
1532                         best_strategy);
1533                 try_merge_strategy(best_strategy, common, remoteheads,
1534                                    head_commit, head_arg);
1535         }
1536
1537         if (squash)
1538                 finish(head_commit, remoteheads, NULL, NULL);
1539         else
1540                 write_merge_state(remoteheads);
1541
1542         if (merge_was_ok)
1543                 fprintf(stderr, _("Automatic merge went well; "
1544                         "stopped before committing as requested\n"));
1545         else
1546                 ret = suggest_conflicts();
1547
1548 done:
1549         free(branch_to_free);
1550         return ret;
1551 }