Merge branch 'jk/parse-object-cached'
[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 "run-command.h"
13 #include "diff.h"
14 #include "refs.h"
15 #include "commit.h"
16 #include "diffcore.h"
17 #include "revision.h"
18 #include "unpack-trees.h"
19 #include "cache-tree.h"
20 #include "dir.h"
21 #include "utf8.h"
22 #include "log-tree.h"
23 #include "color.h"
24 #include "rerere.h"
25 #include "help.h"
26 #include "merge-recursive.h"
27 #include "resolve-undo.h"
28 #include "remote.h"
29 #include "fmt-merge-msg.h"
30 #include "gpg-interface.h"
31
32 #define DEFAULT_TWOHEAD (1<<0)
33 #define DEFAULT_OCTOPUS (1<<1)
34 #define NO_FAST_FORWARD (1<<2)
35 #define NO_TRIVIAL      (1<<3)
36
37 struct strategy {
38         const char *name;
39         unsigned attr;
40 };
41
42 static const char * const builtin_merge_usage[] = {
43         "git merge [options] [<commit>...]",
44         "git merge [options] <msg> HEAD <commit>",
45         "git merge --abort",
46         NULL
47 };
48
49 static int show_diffstat = 1, shortlog_len = -1, squash;
50 static int option_commit = 1, allow_fast_forward = 1;
51 static int fast_forward_only, option_edit;
52 static int allow_trivial = 1, have_message;
53 static int overwrite_ignore = 1;
54 static struct strbuf merge_msg = STRBUF_INIT;
55 static struct commit_list *remoteheads;
56 static struct strategy **use_strategies;
57 static size_t use_strategies_nr, use_strategies_alloc;
58 static const char **xopts;
59 static size_t xopts_nr, xopts_alloc;
60 static const char *branch;
61 static char *branch_mergeoptions;
62 static int option_renormalize;
63 static int verbosity;
64 static int allow_rerere_auto;
65 static int abort_current_merge;
66 static int show_progress = -1;
67 static int default_to_upstream;
68 static const char *sign_commit;
69
70 static struct strategy all_strategy[] = {
71         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
72         { "octopus",    DEFAULT_OCTOPUS },
73         { "resolve",    0 },
74         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
75         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
76 };
77
78 static const char *pull_twohead, *pull_octopus;
79
80 static int option_parse_message(const struct option *opt,
81                                 const char *arg, int unset)
82 {
83         struct strbuf *buf = opt->value;
84
85         if (unset)
86                 strbuf_setlen(buf, 0);
87         else if (arg) {
88                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
89                 have_message = 1;
90         } else
91                 return error(_("switch `m' requires a value"));
92         return 0;
93 }
94
95 static struct strategy *get_strategy(const char *name)
96 {
97         int i;
98         struct strategy *ret;
99         static struct cmdnames main_cmds, other_cmds;
100         static int loaded;
101
102         if (!name)
103                 return NULL;
104
105         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
106                 if (!strcmp(name, all_strategy[i].name))
107                         return &all_strategy[i];
108
109         if (!loaded) {
110                 struct cmdnames not_strategies;
111                 loaded = 1;
112
113                 memset(&not_strategies, 0, sizeof(struct cmdnames));
114                 load_command_list("git-merge-", &main_cmds, &other_cmds);
115                 for (i = 0; i < main_cmds.cnt; i++) {
116                         int j, found = 0;
117                         struct cmdname *ent = main_cmds.names[i];
118                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
119                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
120                                                 && !all_strategy[j].name[ent->len])
121                                         found = 1;
122                         if (!found)
123                                 add_cmdname(&not_strategies, ent->name, ent->len);
124                 }
125                 exclude_cmds(&main_cmds, &not_strategies);
126         }
127         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
128                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
129                 fprintf(stderr, _("Available strategies are:"));
130                 for (i = 0; i < main_cmds.cnt; i++)
131                         fprintf(stderr, " %s", main_cmds.names[i]->name);
132                 fprintf(stderr, ".\n");
133                 if (other_cmds.cnt) {
134                         fprintf(stderr, _("Available custom strategies are:"));
135                         for (i = 0; i < other_cmds.cnt; i++)
136                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
137                         fprintf(stderr, ".\n");
138                 }
139                 exit(1);
140         }
141
142         ret = xcalloc(1, sizeof(struct strategy));
143         ret->name = xstrdup(name);
144         ret->attr = NO_TRIVIAL;
145         return ret;
146 }
147
148 static void append_strategy(struct strategy *s)
149 {
150         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
151         use_strategies[use_strategies_nr++] = s;
152 }
153
154 static int option_parse_strategy(const struct option *opt,
155                                  const char *name, int unset)
156 {
157         if (unset)
158                 return 0;
159
160         append_strategy(get_strategy(name));
161         return 0;
162 }
163
164 static int option_parse_x(const struct option *opt,
165                           const char *arg, int unset)
166 {
167         if (unset)
168                 return 0;
169
170         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
171         xopts[xopts_nr++] = xstrdup(arg);
172         return 0;
173 }
174
175 static int option_parse_n(const struct option *opt,
176                           const char *arg, int unset)
177 {
178         show_diffstat = unset;
179         return 0;
180 }
181
182 static struct option builtin_merge_options[] = {
183         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
184                 "do not show a diffstat at the end of the merge",
185                 PARSE_OPT_NOARG, option_parse_n },
186         OPT_BOOLEAN(0, "stat", &show_diffstat,
187                 "show a diffstat at the end of the merge"),
188         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
189         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
190           "add (at most <n>) entries from shortlog to merge commit message",
191           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
192         OPT_BOOLEAN(0, "squash", &squash,
193                 "create a single commit instead of doing a merge"),
194         OPT_BOOLEAN(0, "commit", &option_commit,
195                 "perform a commit if the merge succeeds (default)"),
196         OPT_BOOLEAN('e', "edit", &option_edit,
197                 "edit message before committing"),
198         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
199                 "allow fast-forward (default)"),
200         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
201                 "abort if fast-forward is not possible"),
202         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
203         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
204                 "merge strategy to use", option_parse_strategy),
205         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
206                 "option for selected merge strategy", option_parse_x),
207         OPT_CALLBACK('m', "message", &merge_msg, "message",
208                 "merge commit message (for a non-fast-forward merge)",
209                 option_parse_message),
210         OPT__VERBOSITY(&verbosity),
211         OPT_BOOLEAN(0, "abort", &abort_current_merge,
212                 "abort the current in-progress merge"),
213         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
214         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, "key id",
215           "GPG sign commit", PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
216         OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
217         OPT_END()
218 };
219
220 /* Cleans up metadata that is uninteresting after a succeeded merge. */
221 static void drop_save(void)
222 {
223         unlink(git_path("MERGE_HEAD"));
224         unlink(git_path("MERGE_MSG"));
225         unlink(git_path("MERGE_MODE"));
226 }
227
228 static int save_state(unsigned char *stash)
229 {
230         int len;
231         struct child_process cp;
232         struct strbuf buffer = STRBUF_INIT;
233         const char *argv[] = {"stash", "create", NULL};
234
235         memset(&cp, 0, sizeof(cp));
236         cp.argv = argv;
237         cp.out = -1;
238         cp.git_cmd = 1;
239
240         if (start_command(&cp))
241                 die(_("could not run stash."));
242         len = strbuf_read(&buffer, cp.out, 1024);
243         close(cp.out);
244
245         if (finish_command(&cp) || len < 0)
246                 die(_("stash failed"));
247         else if (!len)          /* no changes */
248                 return -1;
249         strbuf_setlen(&buffer, buffer.len-1);
250         if (get_sha1(buffer.buf, stash))
251                 die(_("not a valid object: %s"), buffer.buf);
252         return 0;
253 }
254
255 static void read_empty(unsigned const char *sha1, int verbose)
256 {
257         int i = 0;
258         const char *args[7];
259
260         args[i++] = "read-tree";
261         if (verbose)
262                 args[i++] = "-v";
263         args[i++] = "-m";
264         args[i++] = "-u";
265         args[i++] = EMPTY_TREE_SHA1_HEX;
266         args[i++] = sha1_to_hex(sha1);
267         args[i] = NULL;
268
269         if (run_command_v_opt(args, RUN_GIT_CMD))
270                 die(_("read-tree failed"));
271 }
272
273 static void reset_hard(unsigned const char *sha1, int verbose)
274 {
275         int i = 0;
276         const char *args[6];
277
278         args[i++] = "read-tree";
279         if (verbose)
280                 args[i++] = "-v";
281         args[i++] = "--reset";
282         args[i++] = "-u";
283         args[i++] = sha1_to_hex(sha1);
284         args[i] = NULL;
285
286         if (run_command_v_opt(args, RUN_GIT_CMD))
287                 die(_("read-tree failed"));
288 }
289
290 static void restore_state(const unsigned char *head,
291                           const unsigned char *stash)
292 {
293         struct strbuf sb = STRBUF_INIT;
294         const char *args[] = { "stash", "apply", NULL, NULL };
295
296         if (is_null_sha1(stash))
297                 return;
298
299         reset_hard(head, 1);
300
301         args[2] = sha1_to_hex(stash);
302
303         /*
304          * It is OK to ignore error here, for example when there was
305          * nothing to restore.
306          */
307         run_command_v_opt(args, RUN_GIT_CMD);
308
309         strbuf_release(&sb);
310         refresh_cache(REFRESH_QUIET);
311 }
312
313 /* This is called when no merge was necessary. */
314 static void finish_up_to_date(const char *msg)
315 {
316         if (verbosity >= 0)
317                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
318         drop_save();
319 }
320
321 static void squash_message(struct commit *commit)
322 {
323         struct rev_info rev;
324         struct strbuf out = STRBUF_INIT;
325         struct commit_list *j;
326         const char *filename;
327         int fd;
328         struct pretty_print_context ctx = {0};
329
330         printf(_("Squash commit -- not updating HEAD\n"));
331         filename = git_path("SQUASH_MSG");
332         fd = open(filename, O_WRONLY | O_CREAT, 0666);
333         if (fd < 0)
334                 die_errno(_("Could not write to '%s'"), filename);
335
336         init_revisions(&rev, NULL);
337         rev.ignore_merges = 1;
338         rev.commit_format = CMIT_FMT_MEDIUM;
339
340         commit->object.flags |= UNINTERESTING;
341         add_pending_object(&rev, &commit->object, NULL);
342
343         for (j = remoteheads; j; j = j->next)
344                 add_pending_object(&rev, &j->item->object, NULL);
345
346         setup_revisions(0, NULL, &rev, NULL);
347         if (prepare_revision_walk(&rev))
348                 die(_("revision walk setup failed"));
349
350         ctx.abbrev = rev.abbrev;
351         ctx.date_mode = rev.date_mode;
352         ctx.fmt = rev.commit_format;
353
354         strbuf_addstr(&out, "Squashed commit of the following:\n");
355         while ((commit = get_revision(&rev)) != NULL) {
356                 strbuf_addch(&out, '\n');
357                 strbuf_addf(&out, "commit %s\n",
358                         sha1_to_hex(commit->object.sha1));
359                 pretty_print_commit(&ctx, commit, &out);
360         }
361         if (write(fd, out.buf, out.len) < 0)
362                 die_errno(_("Writing SQUASH_MSG"));
363         if (close(fd))
364                 die_errno(_("Finishing SQUASH_MSG"));
365         strbuf_release(&out);
366 }
367
368 static void finish(struct commit *head_commit,
369                    const unsigned char *new_head, const char *msg)
370 {
371         struct strbuf reflog_message = STRBUF_INIT;
372         const unsigned char *head = head_commit->object.sha1;
373
374         if (!msg)
375                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
376         else {
377                 if (verbosity >= 0)
378                         printf("%s\n", msg);
379                 strbuf_addf(&reflog_message, "%s: %s",
380                         getenv("GIT_REFLOG_ACTION"), msg);
381         }
382         if (squash) {
383                 squash_message(head_commit);
384         } else {
385                 if (verbosity >= 0 && !merge_msg.len)
386                         printf(_("No merge message -- not updating HEAD\n"));
387                 else {
388                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
389                         update_ref(reflog_message.buf, "HEAD",
390                                 new_head, head, 0,
391                                 DIE_ON_ERR);
392                         /*
393                          * We ignore errors in 'gc --auto', since the
394                          * user should see them.
395                          */
396                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
397                 }
398         }
399         if (new_head && show_diffstat) {
400                 struct diff_options opts;
401                 diff_setup(&opts);
402                 opts.output_format |=
403                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
404                 opts.detect_rename = DIFF_DETECT_RENAME;
405                 if (diff_setup_done(&opts) < 0)
406                         die(_("diff_setup_done failed"));
407                 diff_tree_sha1(head, new_head, "", &opts);
408                 diffcore_std(&opts);
409                 diff_flush(&opts);
410         }
411
412         /* Run a post-merge hook */
413         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
414
415         strbuf_release(&reflog_message);
416 }
417
418 /* Get the name for the merge commit's message. */
419 static void merge_name(const char *remote, struct strbuf *msg)
420 {
421         struct commit *remote_head;
422         unsigned char branch_head[20];
423         struct strbuf buf = STRBUF_INIT;
424         struct strbuf bname = STRBUF_INIT;
425         const char *ptr;
426         char *found_ref;
427         int len, early;
428
429         strbuf_branchname(&bname, remote);
430         remote = bname.buf;
431
432         memset(branch_head, 0, sizeof(branch_head));
433         remote_head = get_merge_parent(remote);
434         if (!remote_head)
435                 die(_("'%s' does not point to a commit"), remote);
436
437         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
438                 if (!prefixcmp(found_ref, "refs/heads/")) {
439                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
440                                     sha1_to_hex(branch_head), remote);
441                         goto cleanup;
442                 }
443                 if (!prefixcmp(found_ref, "refs/tags/")) {
444                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
445                                     sha1_to_hex(branch_head), remote);
446                         goto cleanup;
447                 }
448                 if (!prefixcmp(found_ref, "refs/remotes/")) {
449                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
450                                     sha1_to_hex(branch_head), remote);
451                         goto cleanup;
452                 }
453         }
454
455         /* See if remote matches <name>^^^.. or <name>~<number> */
456         for (len = 0, ptr = remote + strlen(remote);
457              remote < ptr && ptr[-1] == '^';
458              ptr--)
459                 len++;
460         if (len)
461                 early = 1;
462         else {
463                 early = 0;
464                 ptr = strrchr(remote, '~');
465                 if (ptr) {
466                         int seen_nonzero = 0;
467
468                         len++; /* count ~ */
469                         while (*++ptr && isdigit(*ptr)) {
470                                 seen_nonzero |= (*ptr != '0');
471                                 len++;
472                         }
473                         if (*ptr)
474                                 len = 0; /* not ...~<number> */
475                         else if (seen_nonzero)
476                                 early = 1;
477                         else if (len == 1)
478                                 early = 1; /* "name~" is "name~1"! */
479                 }
480         }
481         if (len) {
482                 struct strbuf truname = STRBUF_INIT;
483                 strbuf_addstr(&truname, "refs/heads/");
484                 strbuf_addstr(&truname, remote);
485                 strbuf_setlen(&truname, truname.len - len);
486                 if (ref_exists(truname.buf)) {
487                         strbuf_addf(msg,
488                                     "%s\t\tbranch '%s'%s of .\n",
489                                     sha1_to_hex(remote_head->object.sha1),
490                                     truname.buf + 11,
491                                     (early ? " (early part)" : ""));
492                         strbuf_release(&truname);
493                         goto cleanup;
494                 }
495         }
496
497         if (!strcmp(remote, "FETCH_HEAD") &&
498                         !access(git_path("FETCH_HEAD"), R_OK)) {
499                 const char *filename;
500                 FILE *fp;
501                 struct strbuf line = STRBUF_INIT;
502                 char *ptr;
503
504                 filename = git_path("FETCH_HEAD");
505                 fp = fopen(filename, "r");
506                 if (!fp)
507                         die_errno(_("could not open '%s' for reading"),
508                                   filename);
509                 strbuf_getline(&line, fp, '\n');
510                 fclose(fp);
511                 ptr = strstr(line.buf, "\tnot-for-merge\t");
512                 if (ptr)
513                         strbuf_remove(&line, ptr-line.buf+1, 13);
514                 strbuf_addbuf(msg, &line);
515                 strbuf_release(&line);
516                 goto cleanup;
517         }
518         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
519                 sha1_to_hex(remote_head->object.sha1), remote);
520 cleanup:
521         strbuf_release(&buf);
522         strbuf_release(&bname);
523 }
524
525 static void parse_branch_merge_options(char *bmo)
526 {
527         const char **argv;
528         int argc;
529
530         if (!bmo)
531                 return;
532         argc = split_cmdline(bmo, &argv);
533         if (argc < 0)
534                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
535                     split_cmdline_strerror(argc));
536         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
537         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
538         argc++;
539         argv[0] = "branch.*.mergeoptions";
540         parse_options(argc, argv, NULL, builtin_merge_options,
541                       builtin_merge_usage, 0);
542         free(argv);
543 }
544
545 static int git_merge_config(const char *k, const char *v, void *cb)
546 {
547         int status;
548
549         if (branch && !prefixcmp(k, "branch.") &&
550                 !prefixcmp(k + 7, branch) &&
551                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
552                 free(branch_mergeoptions);
553                 branch_mergeoptions = xstrdup(v);
554                 return 0;
555         }
556
557         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
558                 show_diffstat = git_config_bool(k, v);
559         else if (!strcmp(k, "pull.twohead"))
560                 return git_config_string(&pull_twohead, k, v);
561         else if (!strcmp(k, "pull.octopus"))
562                 return git_config_string(&pull_octopus, k, v);
563         else if (!strcmp(k, "merge.renormalize"))
564                 option_renormalize = git_config_bool(k, v);
565         else if (!strcmp(k, "merge.ff")) {
566                 int boolval = git_config_maybe_bool(k, v);
567                 if (0 <= boolval) {
568                         allow_fast_forward = boolval;
569                 } else if (v && !strcmp(v, "only")) {
570                         allow_fast_forward = 1;
571                         fast_forward_only = 1;
572                 } /* do not barf on values from future versions of git */
573                 return 0;
574         } else if (!strcmp(k, "merge.defaulttoupstream")) {
575                 default_to_upstream = git_config_bool(k, v);
576                 return 0;
577         }
578
579         status = fmt_merge_msg_config(k, v, cb);
580         if (status)
581                 return status;
582         status = git_gpg_config(k, v, NULL);
583         if (status)
584                 return status;
585         return git_diff_ui_config(k, v, cb);
586 }
587
588 static int read_tree_trivial(unsigned char *common, unsigned char *head,
589                              unsigned char *one)
590 {
591         int i, nr_trees = 0;
592         struct tree *trees[MAX_UNPACK_TREES];
593         struct tree_desc t[MAX_UNPACK_TREES];
594         struct unpack_trees_options opts;
595
596         memset(&opts, 0, sizeof(opts));
597         opts.head_idx = 2;
598         opts.src_index = &the_index;
599         opts.dst_index = &the_index;
600         opts.update = 1;
601         opts.verbose_update = 1;
602         opts.trivial_merges_only = 1;
603         opts.merge = 1;
604         trees[nr_trees] = parse_tree_indirect(common);
605         if (!trees[nr_trees++])
606                 return -1;
607         trees[nr_trees] = parse_tree_indirect(head);
608         if (!trees[nr_trees++])
609                 return -1;
610         trees[nr_trees] = parse_tree_indirect(one);
611         if (!trees[nr_trees++])
612                 return -1;
613         opts.fn = threeway_merge;
614         cache_tree_free(&active_cache_tree);
615         for (i = 0; i < nr_trees; i++) {
616                 parse_tree(trees[i]);
617                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
618         }
619         if (unpack_trees(nr_trees, t, &opts))
620                 return -1;
621         return 0;
622 }
623
624 static void write_tree_trivial(unsigned char *sha1)
625 {
626         if (write_cache_as_tree(sha1, 0, NULL))
627                 die(_("git write-tree failed to write a tree"));
628 }
629
630 static const char *merge_argument(struct commit *commit)
631 {
632         if (commit)
633                 return sha1_to_hex(commit->object.sha1);
634         else
635                 return EMPTY_TREE_SHA1_HEX;
636 }
637
638 int try_merge_command(const char *strategy, size_t xopts_nr,
639                       const char **xopts, struct commit_list *common,
640                       const char *head_arg, struct commit_list *remotes)
641 {
642         const char **args;
643         int i = 0, x = 0, ret;
644         struct commit_list *j;
645         struct strbuf buf = STRBUF_INIT;
646
647         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
648                         commit_list_count(remotes)) * sizeof(char *));
649         strbuf_addf(&buf, "merge-%s", strategy);
650         args[i++] = buf.buf;
651         for (x = 0; x < xopts_nr; x++) {
652                 char *s = xmalloc(strlen(xopts[x])+2+1);
653                 strcpy(s, "--");
654                 strcpy(s+2, xopts[x]);
655                 args[i++] = s;
656         }
657         for (j = common; j; j = j->next)
658                 args[i++] = xstrdup(merge_argument(j->item));
659         args[i++] = "--";
660         args[i++] = head_arg;
661         for (j = remotes; j; j = j->next)
662                 args[i++] = xstrdup(merge_argument(j->item));
663         args[i] = NULL;
664         ret = run_command_v_opt(args, RUN_GIT_CMD);
665         strbuf_release(&buf);
666         i = 1;
667         for (x = 0; x < xopts_nr; x++)
668                 free((void *)args[i++]);
669         for (j = common; j; j = j->next)
670                 free((void *)args[i++]);
671         i += 2;
672         for (j = remotes; j; j = j->next)
673                 free((void *)args[i++]);
674         free(args);
675         discard_cache();
676         if (read_cache() < 0)
677                 die(_("failed to read the cache"));
678         resolve_undo_clear();
679
680         return ret;
681 }
682
683 static int try_merge_strategy(const char *strategy, struct commit_list *common,
684                               struct commit *head, const char *head_arg)
685 {
686         int index_fd;
687         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
688
689         index_fd = hold_locked_index(lock, 1);
690         refresh_cache(REFRESH_QUIET);
691         if (active_cache_changed &&
692                         (write_cache(index_fd, active_cache, active_nr) ||
693                          commit_locked_index(lock)))
694                 return error(_("Unable to write index."));
695         rollback_lock_file(lock);
696
697         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
698                 int clean, x;
699                 struct commit *result;
700                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
701                 int index_fd;
702                 struct commit_list *reversed = NULL;
703                 struct merge_options o;
704                 struct commit_list *j;
705
706                 if (remoteheads->next) {
707                         error(_("Not handling anything other than two heads merge."));
708                         return 2;
709                 }
710
711                 init_merge_options(&o);
712                 if (!strcmp(strategy, "subtree"))
713                         o.subtree_shift = "";
714
715                 o.renormalize = option_renormalize;
716                 o.show_rename_progress =
717                         show_progress == -1 ? isatty(2) : show_progress;
718
719                 for (x = 0; x < xopts_nr; x++)
720                         if (parse_merge_opt(&o, xopts[x]))
721                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
722
723                 o.branch1 = head_arg;
724                 o.branch2 = merge_remote_util(remoteheads->item)->name;
725
726                 for (j = common; j; j = j->next)
727                         commit_list_insert(j->item, &reversed);
728
729                 index_fd = hold_locked_index(lock, 1);
730                 clean = merge_recursive(&o, head,
731                                 remoteheads->item, reversed, &result);
732                 if (active_cache_changed &&
733                                 (write_cache(index_fd, active_cache, active_nr) ||
734                                  commit_locked_index(lock)))
735                         die (_("unable to write %s"), get_index_file());
736                 rollback_lock_file(lock);
737                 return clean ? 0 : 1;
738         } else {
739                 return try_merge_command(strategy, xopts_nr, xopts,
740                                                 common, head_arg, remoteheads);
741         }
742 }
743
744 static void count_diff_files(struct diff_queue_struct *q,
745                              struct diff_options *opt, void *data)
746 {
747         int *count = data;
748
749         (*count) += q->nr;
750 }
751
752 static int count_unmerged_entries(void)
753 {
754         int i, ret = 0;
755
756         for (i = 0; i < active_nr; i++)
757                 if (ce_stage(active_cache[i]))
758                         ret++;
759
760         return ret;
761 }
762
763 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
764 {
765         struct tree *trees[MAX_UNPACK_TREES];
766         struct unpack_trees_options opts;
767         struct tree_desc t[MAX_UNPACK_TREES];
768         int i, fd, nr_trees = 0;
769         struct dir_struct dir;
770         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
771
772         refresh_cache(REFRESH_QUIET);
773
774         fd = hold_locked_index(lock_file, 1);
775
776         memset(&trees, 0, sizeof(trees));
777         memset(&opts, 0, sizeof(opts));
778         memset(&t, 0, sizeof(t));
779         if (overwrite_ignore) {
780                 memset(&dir, 0, sizeof(dir));
781                 dir.flags |= DIR_SHOW_IGNORED;
782                 setup_standard_excludes(&dir);
783                 opts.dir = &dir;
784         }
785
786         opts.head_idx = 1;
787         opts.src_index = &the_index;
788         opts.dst_index = &the_index;
789         opts.update = 1;
790         opts.verbose_update = 1;
791         opts.merge = 1;
792         opts.fn = twoway_merge;
793         setup_unpack_trees_porcelain(&opts, "merge");
794
795         trees[nr_trees] = parse_tree_indirect(head);
796         if (!trees[nr_trees++])
797                 return -1;
798         trees[nr_trees] = parse_tree_indirect(remote);
799         if (!trees[nr_trees++])
800                 return -1;
801         for (i = 0; i < nr_trees; i++) {
802                 parse_tree(trees[i]);
803                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
804         }
805         if (unpack_trees(nr_trees, t, &opts))
806                 return -1;
807         if (write_cache(fd, active_cache, active_nr) ||
808                 commit_locked_index(lock_file))
809                 die(_("unable to write new index file"));
810         return 0;
811 }
812
813 static void split_merge_strategies(const char *string, struct strategy **list,
814                                    int *nr, int *alloc)
815 {
816         char *p, *q, *buf;
817
818         if (!string)
819                 return;
820
821         buf = xstrdup(string);
822         q = buf;
823         for (;;) {
824                 p = strchr(q, ' ');
825                 if (!p) {
826                         ALLOC_GROW(*list, *nr + 1, *alloc);
827                         (*list)[(*nr)++].name = xstrdup(q);
828                         free(buf);
829                         return;
830                 } else {
831                         *p = '\0';
832                         ALLOC_GROW(*list, *nr + 1, *alloc);
833                         (*list)[(*nr)++].name = xstrdup(q);
834                         q = ++p;
835                 }
836         }
837 }
838
839 static void add_strategies(const char *string, unsigned attr)
840 {
841         struct strategy *list = NULL;
842         int list_alloc = 0, list_nr = 0, i;
843
844         memset(&list, 0, sizeof(list));
845         split_merge_strategies(string, &list, &list_nr, &list_alloc);
846         if (list) {
847                 for (i = 0; i < list_nr; i++)
848                         append_strategy(get_strategy(list[i].name));
849                 return;
850         }
851         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
852                 if (all_strategy[i].attr & attr)
853                         append_strategy(&all_strategy[i]);
854
855 }
856
857 static void write_merge_msg(struct strbuf *msg)
858 {
859         const char *filename = git_path("MERGE_MSG");
860         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
861         if (fd < 0)
862                 die_errno(_("Could not open '%s' for writing"),
863                           filename);
864         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
865                 die_errno(_("Could not write to '%s'"), filename);
866         close(fd);
867 }
868
869 static void read_merge_msg(struct strbuf *msg)
870 {
871         const char *filename = git_path("MERGE_MSG");
872         strbuf_reset(msg);
873         if (strbuf_read_file(msg, filename, 0) < 0)
874                 die_errno(_("Could not read from '%s'"), filename);
875 }
876
877 static void write_merge_state(void);
878 static void abort_commit(const char *err_msg)
879 {
880         if (err_msg)
881                 error("%s", err_msg);
882         fprintf(stderr,
883                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
884         write_merge_state();
885         exit(1);
886 }
887
888 static void prepare_to_commit(void)
889 {
890         struct strbuf msg = STRBUF_INIT;
891         strbuf_addbuf(&msg, &merge_msg);
892         strbuf_addch(&msg, '\n');
893         write_merge_msg(&msg);
894         run_hook(get_index_file(), "prepare-commit-msg",
895                  git_path("MERGE_MSG"), "merge", NULL, NULL);
896         if (option_edit) {
897                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
898                         abort_commit(NULL);
899         }
900         read_merge_msg(&msg);
901         stripspace(&msg, option_edit);
902         if (!msg.len)
903                 abort_commit(_("Empty commit message."));
904         strbuf_release(&merge_msg);
905         strbuf_addbuf(&merge_msg, &msg);
906         strbuf_release(&msg);
907 }
908
909 static int merge_trivial(struct commit *head)
910 {
911         unsigned char result_tree[20], result_commit[20];
912         struct commit_list *parent = xmalloc(sizeof(*parent));
913
914         write_tree_trivial(result_tree);
915         printf(_("Wonderful.\n"));
916         parent->item = head;
917         parent->next = xmalloc(sizeof(*parent->next));
918         parent->next->item = remoteheads->item;
919         parent->next->next = NULL;
920         prepare_to_commit();
921         if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
922                         sign_commit))
923                 die(_("failed to write commit object"));
924         finish(head, result_commit, "In-index merge");
925         drop_save();
926         return 0;
927 }
928
929 static int finish_automerge(struct commit *head,
930                             struct commit_list *common,
931                             unsigned char *result_tree,
932                             const char *wt_strategy)
933 {
934         struct commit_list *parents = NULL, *j;
935         struct strbuf buf = STRBUF_INIT;
936         unsigned char result_commit[20];
937
938         free_commit_list(common);
939         if (allow_fast_forward) {
940                 parents = remoteheads;
941                 commit_list_insert(head, &parents);
942                 parents = reduce_heads(parents);
943         } else {
944                 struct commit_list **pptr = &parents;
945
946                 pptr = &commit_list_insert(head,
947                                 pptr)->next;
948                 for (j = remoteheads; j; j = j->next)
949                         pptr = &commit_list_insert(j->item, pptr)->next;
950         }
951         strbuf_addch(&merge_msg, '\n');
952         prepare_to_commit();
953         free_commit_list(remoteheads);
954         if (commit_tree(&merge_msg, result_tree, parents, result_commit,
955                         NULL, sign_commit))
956                 die(_("failed to write commit object"));
957         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
958         finish(head, result_commit, buf.buf);
959         strbuf_release(&buf);
960         drop_save();
961         return 0;
962 }
963
964 static int suggest_conflicts(int renormalizing)
965 {
966         const char *filename;
967         FILE *fp;
968         int pos;
969
970         filename = git_path("MERGE_MSG");
971         fp = fopen(filename, "a");
972         if (!fp)
973                 die_errno(_("Could not open '%s' for writing"), filename);
974         fprintf(fp, "\nConflicts:\n");
975         for (pos = 0; pos < active_nr; pos++) {
976                 struct cache_entry *ce = active_cache[pos];
977
978                 if (ce_stage(ce)) {
979                         fprintf(fp, "\t%s\n", ce->name);
980                         while (pos + 1 < active_nr &&
981                                         !strcmp(ce->name,
982                                                 active_cache[pos + 1]->name))
983                                 pos++;
984                 }
985         }
986         fclose(fp);
987         rerere(allow_rerere_auto);
988         printf(_("Automatic merge failed; "
989                         "fix conflicts and then commit the result.\n"));
990         return 1;
991 }
992
993 static struct commit *is_old_style_invocation(int argc, const char **argv,
994                                               const unsigned char *head)
995 {
996         struct commit *second_token = NULL;
997         if (argc > 2) {
998                 unsigned char second_sha1[20];
999
1000                 if (get_sha1(argv[1], second_sha1))
1001                         return NULL;
1002                 second_token = lookup_commit_reference_gently(second_sha1, 0);
1003                 if (!second_token)
1004                         die(_("'%s' is not a commit"), argv[1]);
1005                 if (hashcmp(second_token->object.sha1, head))
1006                         return NULL;
1007         }
1008         return second_token;
1009 }
1010
1011 static int evaluate_result(void)
1012 {
1013         int cnt = 0;
1014         struct rev_info rev;
1015
1016         /* Check how many files differ. */
1017         init_revisions(&rev, "");
1018         setup_revisions(0, NULL, &rev, NULL);
1019         rev.diffopt.output_format |=
1020                 DIFF_FORMAT_CALLBACK;
1021         rev.diffopt.format_callback = count_diff_files;
1022         rev.diffopt.format_callback_data = &cnt;
1023         run_diff_files(&rev, 0);
1024
1025         /*
1026          * Check how many unmerged entries are
1027          * there.
1028          */
1029         cnt += count_unmerged_entries();
1030
1031         return cnt;
1032 }
1033
1034 /*
1035  * Pretend as if the user told us to merge with the tracking
1036  * branch we have for the upstream of the current branch
1037  */
1038 static int setup_with_upstream(const char ***argv)
1039 {
1040         struct branch *branch = branch_get(NULL);
1041         int i;
1042         const char **args;
1043
1044         if (!branch)
1045                 die(_("No current branch."));
1046         if (!branch->remote)
1047                 die(_("No remote for the current branch."));
1048         if (!branch->merge_nr)
1049                 die(_("No default upstream defined for the current branch."));
1050
1051         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1052         for (i = 0; i < branch->merge_nr; i++) {
1053                 if (!branch->merge[i]->dst)
1054                         die(_("No remote tracking branch for %s from %s"),
1055                             branch->merge[i]->src, branch->remote_name);
1056                 args[i] = branch->merge[i]->dst;
1057         }
1058         args[i] = NULL;
1059         *argv = args;
1060         return i;
1061 }
1062
1063 static void write_merge_state(void)
1064 {
1065         const char *filename;
1066         int fd;
1067         struct commit_list *j;
1068         struct strbuf buf = STRBUF_INIT;
1069
1070         for (j = remoteheads; j; j = j->next) {
1071                 unsigned const char *sha1;
1072                 struct commit *c = j->item;
1073                 if (c->util && merge_remote_util(c)->obj) {
1074                         sha1 = merge_remote_util(c)->obj->sha1;
1075                 } else {
1076                         sha1 = c->object.sha1;
1077                 }
1078                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1079         }
1080         filename = git_path("MERGE_HEAD");
1081         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1082         if (fd < 0)
1083                 die_errno(_("Could not open '%s' for writing"), filename);
1084         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1085                 die_errno(_("Could not write to '%s'"), filename);
1086         close(fd);
1087         strbuf_addch(&merge_msg, '\n');
1088         write_merge_msg(&merge_msg);
1089
1090         filename = git_path("MERGE_MODE");
1091         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1092         if (fd < 0)
1093                 die_errno(_("Could not open '%s' for writing"), filename);
1094         strbuf_reset(&buf);
1095         if (!allow_fast_forward)
1096                 strbuf_addf(&buf, "no-ff");
1097         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1098                 die_errno(_("Could not write to '%s'"), filename);
1099         close(fd);
1100 }
1101
1102 int cmd_merge(int argc, const char **argv, const char *prefix)
1103 {
1104         unsigned char result_tree[20];
1105         unsigned char stash[20];
1106         unsigned char head_sha1[20];
1107         struct commit *head_commit;
1108         struct strbuf buf = STRBUF_INIT;
1109         const char *head_arg;
1110         int flag, i, ret = 0;
1111         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1112         struct commit_list *common = NULL;
1113         const char *best_strategy = NULL, *wt_strategy = NULL;
1114         struct commit_list **remotes = &remoteheads;
1115         void *branch_to_free;
1116
1117         if (argc == 2 && !strcmp(argv[1], "-h"))
1118                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1119
1120         /*
1121          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1122          * current branch.
1123          */
1124         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1125         if (branch && !prefixcmp(branch, "refs/heads/"))
1126                 branch += 11;
1127         if (!branch || is_null_sha1(head_sha1))
1128                 head_commit = NULL;
1129         else
1130                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1131
1132         git_config(git_merge_config, NULL);
1133
1134         if (branch_mergeoptions)
1135                 parse_branch_merge_options(branch_mergeoptions);
1136         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1137                         builtin_merge_usage, 0);
1138         if (shortlog_len < 0)
1139                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1140
1141         if (verbosity < 0 && show_progress == -1)
1142                 show_progress = 0;
1143
1144         if (abort_current_merge) {
1145                 int nargc = 2;
1146                 const char *nargv[] = {"reset", "--merge", NULL};
1147
1148                 if (!file_exists(git_path("MERGE_HEAD")))
1149                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1150
1151                 /* Invoke 'git reset --merge' */
1152                 ret = cmd_reset(nargc, nargv, prefix);
1153                 goto done;
1154         }
1155
1156         if (read_cache_unmerged())
1157                 die_resolve_conflict("merge");
1158
1159         if (file_exists(git_path("MERGE_HEAD"))) {
1160                 /*
1161                  * There is no unmerged entry, don't advise 'git
1162                  * add/rm <file>', just 'git commit'.
1163                  */
1164                 if (advice_resolve_conflict)
1165                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1166                                   "Please, commit your changes before you can merge."));
1167                 else
1168                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1169         }
1170         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1171                 if (advice_resolve_conflict)
1172                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1173                             "Please, commit your changes before you can merge."));
1174                 else
1175                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1176         }
1177         resolve_undo_clear();
1178
1179         if (verbosity < 0)
1180                 show_diffstat = 0;
1181
1182         if (squash) {
1183                 if (!allow_fast_forward)
1184                         die(_("You cannot combine --squash with --no-ff."));
1185                 option_commit = 0;
1186         }
1187
1188         if (!allow_fast_forward && fast_forward_only)
1189                 die(_("You cannot combine --no-ff with --ff-only."));
1190
1191         if (!abort_current_merge) {
1192                 if (!argc) {
1193                         if (default_to_upstream)
1194                                 argc = setup_with_upstream(&argv);
1195                         else
1196                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1197                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1198                         argv[0] = "@{-1}";
1199         }
1200         if (!argc)
1201                 usage_with_options(builtin_merge_usage,
1202                         builtin_merge_options);
1203
1204         /*
1205          * This could be traditional "merge <msg> HEAD <commit>..."  and
1206          * the way we can tell it is to see if the second token is HEAD,
1207          * but some people might have misused the interface and used a
1208          * committish that is the same as HEAD there instead.
1209          * Traditional format never would have "-m" so it is an
1210          * additional safety measure to check for it.
1211          */
1212
1213         if (!have_message && head_commit &&
1214             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1215                 strbuf_addstr(&merge_msg, argv[0]);
1216                 head_arg = argv[1];
1217                 argv += 2;
1218                 argc -= 2;
1219         } else if (!head_commit) {
1220                 struct commit *remote_head;
1221                 /*
1222                  * If the merged head is a valid one there is no reason
1223                  * to forbid "git merge" into a branch yet to be born.
1224                  * We do the same for "git pull".
1225                  */
1226                 if (argc != 1)
1227                         die(_("Can merge only exactly one commit into "
1228                                 "empty head"));
1229                 if (squash)
1230                         die(_("Squash commit into empty head not supported yet"));
1231                 if (!allow_fast_forward)
1232                         die(_("Non-fast-forward commit does not make sense into "
1233                             "an empty head"));
1234                 remote_head = get_merge_parent(argv[0]);
1235                 if (!remote_head)
1236                         die(_("%s - not something we can merge"), argv[0]);
1237                 read_empty(remote_head->object.sha1, 0);
1238                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1239                            NULL, 0, DIE_ON_ERR);
1240                 goto done;
1241         } else {
1242                 struct strbuf merge_names = STRBUF_INIT;
1243
1244                 /* We are invoked directly as the first-class UI. */
1245                 head_arg = "HEAD";
1246
1247                 /*
1248                  * All the rest are the commits being merged; prepare
1249                  * the standard merge summary message to be appended
1250                  * to the given message.
1251                  */
1252                 for (i = 0; i < argc; i++)
1253                         merge_name(argv[i], &merge_names);
1254
1255                 if (!have_message || shortlog_len) {
1256                         struct fmt_merge_msg_opts opts;
1257                         memset(&opts, 0, sizeof(opts));
1258                         opts.add_title = !have_message;
1259                         opts.shortlog_len = shortlog_len;
1260
1261                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1262                         if (merge_msg.len)
1263                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1264                 }
1265         }
1266
1267         if (!head_commit || !argc)
1268                 usage_with_options(builtin_merge_usage,
1269                         builtin_merge_options);
1270
1271         strbuf_addstr(&buf, "merge");
1272         for (i = 0; i < argc; i++)
1273                 strbuf_addf(&buf, " %s", argv[i]);
1274         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1275         strbuf_reset(&buf);
1276
1277         for (i = 0; i < argc; i++) {
1278                 struct commit *commit = get_merge_parent(argv[i]);
1279                 if (!commit)
1280                         die(_("%s - not something we can merge"), argv[i]);
1281                 remotes = &commit_list_insert(commit, remotes)->next;
1282                 strbuf_addf(&buf, "GITHEAD_%s",
1283                             sha1_to_hex(commit->object.sha1));
1284                 setenv(buf.buf, argv[i], 1);
1285                 strbuf_reset(&buf);
1286                 if (merge_remote_util(commit) &&
1287                     merge_remote_util(commit)->obj &&
1288                     merge_remote_util(commit)->obj->type == OBJ_TAG) {
1289                         option_edit = 1;
1290                         allow_fast_forward = 0;
1291                 }
1292         }
1293
1294         if (!use_strategies) {
1295                 if (!remoteheads->next)
1296                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1297                 else
1298                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1299         }
1300
1301         for (i = 0; i < use_strategies_nr; i++) {
1302                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1303                         allow_fast_forward = 0;
1304                 if (use_strategies[i]->attr & NO_TRIVIAL)
1305                         allow_trivial = 0;
1306         }
1307
1308         if (!remoteheads->next)
1309                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1310         else {
1311                 struct commit_list *list = remoteheads;
1312                 commit_list_insert(head_commit, &list);
1313                 common = get_octopus_merge_bases(list);
1314                 free(list);
1315         }
1316
1317         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1318                    NULL, 0, DIE_ON_ERR);
1319
1320         if (!common)
1321                 ; /* No common ancestors found. We need a real merge. */
1322         else if (!remoteheads->next && !common->next &&
1323                         common->item == remoteheads->item) {
1324                 /*
1325                  * If head can reach all the merge then we are up to date.
1326                  * but first the most common case of merging one remote.
1327                  */
1328                 finish_up_to_date("Already up-to-date.");
1329                 goto done;
1330         } else if (allow_fast_forward && !remoteheads->next &&
1331                         !common->next &&
1332                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1333                 /* Again the most common case of merging one remote. */
1334                 struct strbuf msg = STRBUF_INIT;
1335                 struct commit *commit;
1336                 char hex[41];
1337
1338                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1339
1340                 if (verbosity >= 0)
1341                         printf(_("Updating %s..%s\n"),
1342                                 hex,
1343                                 find_unique_abbrev(remoteheads->item->object.sha1,
1344                                 DEFAULT_ABBREV));
1345                 strbuf_addstr(&msg, "Fast-forward");
1346                 if (have_message)
1347                         strbuf_addstr(&msg,
1348                                 " (no commit created; -m option ignored)");
1349                 commit = remoteheads->item;
1350                 if (!commit) {
1351                         ret = 1;
1352                         goto done;
1353                 }
1354
1355                 if (checkout_fast_forward(head_commit->object.sha1,
1356                                           commit->object.sha1)) {
1357                         ret = 1;
1358                         goto done;
1359                 }
1360
1361                 finish(head_commit, commit->object.sha1, msg.buf);
1362                 drop_save();
1363                 goto done;
1364         } else if (!remoteheads->next && common->next)
1365                 ;
1366                 /*
1367                  * We are not doing octopus and not fast-forward.  Need
1368                  * a real merge.
1369                  */
1370         else if (!remoteheads->next && !common->next && option_commit) {
1371                 /*
1372                  * We are not doing octopus, not fast-forward, and have
1373                  * only one common.
1374                  */
1375                 refresh_cache(REFRESH_QUIET);
1376                 if (allow_trivial && !fast_forward_only) {
1377                         /* See if it is really trivial. */
1378                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1379                         printf(_("Trying really trivial in-index merge...\n"));
1380                         if (!read_tree_trivial(common->item->object.sha1,
1381                                                head_commit->object.sha1,
1382                                                remoteheads->item->object.sha1)) {
1383                                 ret = merge_trivial(head_commit);
1384                                 goto done;
1385                         }
1386                         printf(_("Nope.\n"));
1387                 }
1388         } else {
1389                 /*
1390                  * An octopus.  If we can reach all the remote we are up
1391                  * to date.
1392                  */
1393                 int up_to_date = 1;
1394                 struct commit_list *j;
1395
1396                 for (j = remoteheads; j; j = j->next) {
1397                         struct commit_list *common_one;
1398
1399                         /*
1400                          * Here we *have* to calculate the individual
1401                          * merge_bases again, otherwise "git merge HEAD^
1402                          * HEAD^^" would be missed.
1403                          */
1404                         common_one = get_merge_bases(head_commit, j->item, 1);
1405                         if (hashcmp(common_one->item->object.sha1,
1406                                 j->item->object.sha1)) {
1407                                 up_to_date = 0;
1408                                 break;
1409                         }
1410                 }
1411                 if (up_to_date) {
1412                         finish_up_to_date("Already up-to-date. Yeeah!");
1413                         goto done;
1414                 }
1415         }
1416
1417         if (fast_forward_only)
1418                 die(_("Not possible to fast-forward, aborting."));
1419
1420         /* We are going to make a new commit. */
1421         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1422
1423         /*
1424          * At this point, we need a real merge.  No matter what strategy
1425          * we use, it would operate on the index, possibly affecting the
1426          * working tree, and when resolved cleanly, have the desired
1427          * tree in the index -- this means that the index must be in
1428          * sync with the head commit.  The strategies are responsible
1429          * to ensure this.
1430          */
1431         if (use_strategies_nr == 1 ||
1432             /*
1433              * Stash away the local changes so that we can try more than one.
1434              */
1435             save_state(stash))
1436                 hashcpy(stash, null_sha1);
1437
1438         for (i = 0; i < use_strategies_nr; i++) {
1439                 int ret;
1440                 if (i) {
1441                         printf(_("Rewinding the tree to pristine...\n"));
1442                         restore_state(head_commit->object.sha1, stash);
1443                 }
1444                 if (use_strategies_nr != 1)
1445                         printf(_("Trying merge strategy %s...\n"),
1446                                 use_strategies[i]->name);
1447                 /*
1448                  * Remember which strategy left the state in the working
1449                  * tree.
1450                  */
1451                 wt_strategy = use_strategies[i]->name;
1452
1453                 ret = try_merge_strategy(use_strategies[i]->name,
1454                                          common, head_commit, head_arg);
1455                 if (!option_commit && !ret) {
1456                         merge_was_ok = 1;
1457                         /*
1458                          * This is necessary here just to avoid writing
1459                          * the tree, but later we will *not* exit with
1460                          * status code 1 because merge_was_ok is set.
1461                          */
1462                         ret = 1;
1463                 }
1464
1465                 if (ret) {
1466                         /*
1467                          * The backend exits with 1 when conflicts are
1468                          * left to be resolved, with 2 when it does not
1469                          * handle the given merge at all.
1470                          */
1471                         if (ret == 1) {
1472                                 int cnt = evaluate_result();
1473
1474                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1475                                         best_strategy = use_strategies[i]->name;
1476                                         best_cnt = cnt;
1477                                 }
1478                         }
1479                         if (merge_was_ok)
1480                                 break;
1481                         else
1482                                 continue;
1483                 }
1484
1485                 /* Automerge succeeded. */
1486                 write_tree_trivial(result_tree);
1487                 automerge_was_ok = 1;
1488                 break;
1489         }
1490
1491         /*
1492          * If we have a resulting tree, that means the strategy module
1493          * auto resolved the merge cleanly.
1494          */
1495         if (automerge_was_ok) {
1496                 ret = finish_automerge(head_commit, common, result_tree,
1497                                        wt_strategy);
1498                 goto done;
1499         }
1500
1501         /*
1502          * Pick the result from the best strategy and have the user fix
1503          * it up.
1504          */
1505         if (!best_strategy) {
1506                 restore_state(head_commit->object.sha1, stash);
1507                 if (use_strategies_nr > 1)
1508                         fprintf(stderr,
1509                                 _("No merge strategy handled the merge.\n"));
1510                 else
1511                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1512                                 use_strategies[0]->name);
1513                 ret = 2;
1514                 goto done;
1515         } else if (best_strategy == wt_strategy)
1516                 ; /* We already have its result in the working tree. */
1517         else {
1518                 printf(_("Rewinding the tree to pristine...\n"));
1519                 restore_state(head_commit->object.sha1, stash);
1520                 printf(_("Using the %s to prepare resolving by hand.\n"),
1521                         best_strategy);
1522                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1523         }
1524
1525         if (squash)
1526                 finish(head_commit, NULL, NULL);
1527         else
1528                 write_merge_state();
1529
1530         if (merge_was_ok)
1531                 fprintf(stderr, _("Automatic merge went well; "
1532                         "stopped before committing as requested\n"));
1533         else
1534                 ret = suggest_conflicts(option_renormalize);
1535
1536 done:
1537         free(branch_to_free);
1538         return ret;
1539 }