Merge branch 'so/rebase-doc-fork-point'
[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         N_("git merge [options] [<commit>...]"),
44         N_("git merge [options] <msg> HEAD <commit>"),
45         N_("git merge --abort"),
46         NULL
47 };
48
49 static int show_diffstat = 1, shortlog_len = -1, squash;
50 static int option_commit = 1;
51 static int option_edit = -1;
52 static int allow_trivial = 1, have_message, verify_signatures;
53 static int overwrite_ignore = 1;
54 static struct strbuf merge_msg = STRBUF_INIT;
55 static struct strategy **use_strategies;
56 static size_t use_strategies_nr, use_strategies_alloc;
57 static const char **xopts;
58 static size_t xopts_nr, xopts_alloc;
59 static const char *branch;
60 static char *branch_mergeoptions;
61 static int option_renormalize;
62 static int verbosity;
63 static int allow_rerere_auto;
64 static int abort_current_merge;
65 static int show_progress = -1;
66 static int default_to_upstream = 1;
67 static const char *sign_commit;
68
69 static struct strategy all_strategy[] = {
70         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
71         { "octopus",    DEFAULT_OCTOPUS },
72         { "resolve",    0 },
73         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
74         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
75 };
76
77 static const char *pull_twohead, *pull_octopus;
78
79 enum ff_type {
80         FF_NO,
81         FF_ALLOW,
82         FF_ONLY
83 };
84
85 static enum ff_type fast_forward = FF_ALLOW;
86
87 static int option_parse_message(const struct option *opt,
88                                 const char *arg, int unset)
89 {
90         struct strbuf *buf = opt->value;
91
92         if (unset)
93                 strbuf_setlen(buf, 0);
94         else if (arg) {
95                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
96                 have_message = 1;
97         } else
98                 return error(_("switch `m' requires a value"));
99         return 0;
100 }
101
102 static struct strategy *get_strategy(const char *name)
103 {
104         int i;
105         struct strategy *ret;
106         static struct cmdnames main_cmds, other_cmds;
107         static int loaded;
108
109         if (!name)
110                 return NULL;
111
112         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
113                 if (!strcmp(name, all_strategy[i].name))
114                         return &all_strategy[i];
115
116         if (!loaded) {
117                 struct cmdnames not_strategies;
118                 loaded = 1;
119
120                 memset(&not_strategies, 0, sizeof(struct cmdnames));
121                 load_command_list("git-merge-", &main_cmds, &other_cmds);
122                 for (i = 0; i < main_cmds.cnt; i++) {
123                         int j, found = 0;
124                         struct cmdname *ent = main_cmds.names[i];
125                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
126                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
127                                                 && !all_strategy[j].name[ent->len])
128                                         found = 1;
129                         if (!found)
130                                 add_cmdname(&not_strategies, ent->name, ent->len);
131                 }
132                 exclude_cmds(&main_cmds, &not_strategies);
133         }
134         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
135                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
136                 fprintf(stderr, _("Available strategies are:"));
137                 for (i = 0; i < main_cmds.cnt; i++)
138                         fprintf(stderr, " %s", main_cmds.names[i]->name);
139                 fprintf(stderr, ".\n");
140                 if (other_cmds.cnt) {
141                         fprintf(stderr, _("Available custom strategies are:"));
142                         for (i = 0; i < other_cmds.cnt; i++)
143                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
144                         fprintf(stderr, ".\n");
145                 }
146                 exit(1);
147         }
148
149         ret = xcalloc(1, sizeof(struct strategy));
150         ret->name = xstrdup(name);
151         ret->attr = NO_TRIVIAL;
152         return ret;
153 }
154
155 static void append_strategy(struct strategy *s)
156 {
157         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
158         use_strategies[use_strategies_nr++] = s;
159 }
160
161 static int option_parse_strategy(const struct option *opt,
162                                  const char *name, int unset)
163 {
164         if (unset)
165                 return 0;
166
167         append_strategy(get_strategy(name));
168         return 0;
169 }
170
171 static int option_parse_x(const struct option *opt,
172                           const char *arg, int unset)
173 {
174         if (unset)
175                 return 0;
176
177         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
178         xopts[xopts_nr++] = xstrdup(arg);
179         return 0;
180 }
181
182 static int option_parse_n(const struct option *opt,
183                           const char *arg, int unset)
184 {
185         show_diffstat = unset;
186         return 0;
187 }
188
189 static struct option builtin_merge_options[] = {
190         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
191                 N_("do not show a diffstat at the end of the merge"),
192                 PARSE_OPT_NOARG, option_parse_n },
193         OPT_BOOL(0, "stat", &show_diffstat,
194                 N_("show a diffstat at the end of the merge")),
195         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
196         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
197           N_("add (at most <n>) entries from shortlog to merge commit message"),
198           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
199         OPT_BOOL(0, "squash", &squash,
200                 N_("create a single commit instead of doing a merge")),
201         OPT_BOOL(0, "commit", &option_commit,
202                 N_("perform a commit if the merge succeeds (default)")),
203         OPT_BOOL('e', "edit", &option_edit,
204                 N_("edit message before committing")),
205         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
206         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
207                 N_("abort if fast-forward is not possible"),
208                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
209         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
210         OPT_BOOL(0, "verify-signatures", &verify_signatures,
211                 N_("Verify that the named commit has a valid GPG signature")),
212         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
213                 N_("merge strategy to use"), option_parse_strategy),
214         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
215                 N_("option for selected merge strategy"), option_parse_x),
216         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
217                 N_("merge commit message (for a non-fast-forward merge)"),
218                 option_parse_message),
219         OPT__VERBOSITY(&verbosity),
220         OPT_BOOL(0, "abort", &abort_current_merge,
221                 N_("abort the current in-progress merge")),
222         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
223         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
224           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
225         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
226         OPT_END()
227 };
228
229 /* Cleans up metadata that is uninteresting after a succeeded merge. */
230 static void drop_save(void)
231 {
232         unlink(git_path("MERGE_HEAD"));
233         unlink(git_path("MERGE_MSG"));
234         unlink(git_path("MERGE_MODE"));
235 }
236
237 static int save_state(unsigned char *stash)
238 {
239         int len;
240         struct child_process cp = CHILD_PROCESS_INIT;
241         struct strbuf buffer = STRBUF_INIT;
242         const char *argv[] = {"stash", "create", NULL};
243
244         cp.argv = argv;
245         cp.out = -1;
246         cp.git_cmd = 1;
247
248         if (start_command(&cp))
249                 die(_("could not run stash."));
250         len = strbuf_read(&buffer, cp.out, 1024);
251         close(cp.out);
252
253         if (finish_command(&cp) || len < 0)
254                 die(_("stash failed"));
255         else if (!len)          /* no changes */
256                 return -1;
257         strbuf_setlen(&buffer, buffer.len-1);
258         if (get_sha1(buffer.buf, stash))
259                 die(_("not a valid object: %s"), buffer.buf);
260         return 0;
261 }
262
263 static void read_empty(unsigned const char *sha1, int verbose)
264 {
265         int i = 0;
266         const char *args[7];
267
268         args[i++] = "read-tree";
269         if (verbose)
270                 args[i++] = "-v";
271         args[i++] = "-m";
272         args[i++] = "-u";
273         args[i++] = EMPTY_TREE_SHA1_HEX;
274         args[i++] = sha1_to_hex(sha1);
275         args[i] = NULL;
276
277         if (run_command_v_opt(args, RUN_GIT_CMD))
278                 die(_("read-tree failed"));
279 }
280
281 static void reset_hard(unsigned const char *sha1, int verbose)
282 {
283         int i = 0;
284         const char *args[6];
285
286         args[i++] = "read-tree";
287         if (verbose)
288                 args[i++] = "-v";
289         args[i++] = "--reset";
290         args[i++] = "-u";
291         args[i++] = sha1_to_hex(sha1);
292         args[i] = NULL;
293
294         if (run_command_v_opt(args, RUN_GIT_CMD))
295                 die(_("read-tree failed"));
296 }
297
298 static void restore_state(const unsigned char *head,
299                           const unsigned char *stash)
300 {
301         struct strbuf sb = STRBUF_INIT;
302         const char *args[] = { "stash", "apply", NULL, NULL };
303
304         if (is_null_sha1(stash))
305                 return;
306
307         reset_hard(head, 1);
308
309         args[2] = sha1_to_hex(stash);
310
311         /*
312          * It is OK to ignore error here, for example when there was
313          * nothing to restore.
314          */
315         run_command_v_opt(args, RUN_GIT_CMD);
316
317         strbuf_release(&sb);
318         refresh_cache(REFRESH_QUIET);
319 }
320
321 /* This is called when no merge was necessary. */
322 static void finish_up_to_date(const char *msg)
323 {
324         if (verbosity >= 0)
325                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
326         drop_save();
327 }
328
329 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
330 {
331         struct rev_info rev;
332         struct strbuf out = STRBUF_INIT;
333         struct commit_list *j;
334         const char *filename;
335         int fd;
336         struct pretty_print_context ctx = {0};
337
338         printf(_("Squash commit -- not updating HEAD\n"));
339         filename = git_path("SQUASH_MSG");
340         fd = open(filename, O_WRONLY | O_CREAT, 0666);
341         if (fd < 0)
342                 die_errno(_("Could not write to '%s'"), filename);
343
344         init_revisions(&rev, NULL);
345         rev.ignore_merges = 1;
346         rev.commit_format = CMIT_FMT_MEDIUM;
347
348         commit->object.flags |= UNINTERESTING;
349         add_pending_object(&rev, &commit->object, NULL);
350
351         for (j = remoteheads; j; j = j->next)
352                 add_pending_object(&rev, &j->item->object, NULL);
353
354         setup_revisions(0, NULL, &rev, NULL);
355         if (prepare_revision_walk(&rev))
356                 die(_("revision walk setup failed"));
357
358         ctx.abbrev = rev.abbrev;
359         ctx.date_mode = rev.date_mode;
360         ctx.fmt = rev.commit_format;
361
362         strbuf_addstr(&out, "Squashed commit of the following:\n");
363         while ((commit = get_revision(&rev)) != NULL) {
364                 strbuf_addch(&out, '\n');
365                 strbuf_addf(&out, "commit %s\n",
366                         sha1_to_hex(commit->object.sha1));
367                 pretty_print_commit(&ctx, commit, &out);
368         }
369         if (write_in_full(fd, out.buf, out.len) != out.len)
370                 die_errno(_("Writing SQUASH_MSG"));
371         if (close(fd))
372                 die_errno(_("Finishing SQUASH_MSG"));
373         strbuf_release(&out);
374 }
375
376 static void finish(struct commit *head_commit,
377                    struct commit_list *remoteheads,
378                    const unsigned char *new_head, const char *msg)
379 {
380         struct strbuf reflog_message = STRBUF_INIT;
381         const unsigned char *head = head_commit->object.sha1;
382
383         if (!msg)
384                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
385         else {
386                 if (verbosity >= 0)
387                         printf("%s\n", msg);
388                 strbuf_addf(&reflog_message, "%s: %s",
389                         getenv("GIT_REFLOG_ACTION"), msg);
390         }
391         if (squash) {
392                 squash_message(head_commit, remoteheads);
393         } else {
394                 if (verbosity >= 0 && !merge_msg.len)
395                         printf(_("No merge message -- not updating HEAD\n"));
396                 else {
397                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
398                         update_ref(reflog_message.buf, "HEAD",
399                                 new_head, head, 0,
400                                 UPDATE_REFS_DIE_ON_ERR);
401                         /*
402                          * We ignore errors in 'gc --auto', since the
403                          * user should see them.
404                          */
405                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
406                 }
407         }
408         if (new_head && show_diffstat) {
409                 struct diff_options opts;
410                 diff_setup(&opts);
411                 opts.stat_width = -1; /* use full terminal width */
412                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
413                 opts.output_format |=
414                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
415                 opts.detect_rename = DIFF_DETECT_RENAME;
416                 diff_setup_done(&opts);
417                 diff_tree_sha1(head, new_head, "", &opts);
418                 diffcore_std(&opts);
419                 diff_flush(&opts);
420         }
421
422         /* Run a post-merge hook */
423         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
424
425         strbuf_release(&reflog_message);
426 }
427
428 /* Get the name for the merge commit's message. */
429 static void merge_name(const char *remote, struct strbuf *msg)
430 {
431         struct commit *remote_head;
432         unsigned char branch_head[20];
433         struct strbuf buf = STRBUF_INIT;
434         struct strbuf bname = STRBUF_INIT;
435         const char *ptr;
436         char *found_ref;
437         int len, early;
438
439         strbuf_branchname(&bname, remote);
440         remote = bname.buf;
441
442         memset(branch_head, 0, sizeof(branch_head));
443         remote_head = get_merge_parent(remote);
444         if (!remote_head)
445                 die(_("'%s' does not point to a commit"), remote);
446
447         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
448                 if (starts_with(found_ref, "refs/heads/")) {
449                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
450                                     sha1_to_hex(branch_head), remote);
451                         goto cleanup;
452                 }
453                 if (starts_with(found_ref, "refs/tags/")) {
454                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
455                                     sha1_to_hex(branch_head), remote);
456                         goto cleanup;
457                 }
458                 if (starts_with(found_ref, "refs/remotes/")) {
459                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
460                                     sha1_to_hex(branch_head), remote);
461                         goto cleanup;
462                 }
463         }
464
465         /* See if remote matches <name>^^^.. or <name>~<number> */
466         for (len = 0, ptr = remote + strlen(remote);
467              remote < ptr && ptr[-1] == '^';
468              ptr--)
469                 len++;
470         if (len)
471                 early = 1;
472         else {
473                 early = 0;
474                 ptr = strrchr(remote, '~');
475                 if (ptr) {
476                         int seen_nonzero = 0;
477
478                         len++; /* count ~ */
479                         while (*++ptr && isdigit(*ptr)) {
480                                 seen_nonzero |= (*ptr != '0');
481                                 len++;
482                         }
483                         if (*ptr)
484                                 len = 0; /* not ...~<number> */
485                         else if (seen_nonzero)
486                                 early = 1;
487                         else if (len == 1)
488                                 early = 1; /* "name~" is "name~1"! */
489                 }
490         }
491         if (len) {
492                 struct strbuf truname = STRBUF_INIT;
493                 strbuf_addstr(&truname, "refs/heads/");
494                 strbuf_addstr(&truname, remote);
495                 strbuf_setlen(&truname, truname.len - len);
496                 if (ref_exists(truname.buf)) {
497                         strbuf_addf(msg,
498                                     "%s\t\tbranch '%s'%s of .\n",
499                                     sha1_to_hex(remote_head->object.sha1),
500                                     truname.buf + 11,
501                                     (early ? " (early part)" : ""));
502                         strbuf_release(&truname);
503                         goto cleanup;
504                 }
505         }
506
507         if (!strcmp(remote, "FETCH_HEAD") &&
508                         !access(git_path("FETCH_HEAD"), R_OK)) {
509                 const char *filename;
510                 FILE *fp;
511                 struct strbuf line = STRBUF_INIT;
512                 char *ptr;
513
514                 filename = git_path("FETCH_HEAD");
515                 fp = fopen(filename, "r");
516                 if (!fp)
517                         die_errno(_("could not open '%s' for reading"),
518                                   filename);
519                 strbuf_getline(&line, fp, '\n');
520                 fclose(fp);
521                 ptr = strstr(line.buf, "\tnot-for-merge\t");
522                 if (ptr)
523                         strbuf_remove(&line, ptr-line.buf+1, 13);
524                 strbuf_addbuf(msg, &line);
525                 strbuf_release(&line);
526                 goto cleanup;
527         }
528
529         if (remote_head->util) {
530                 struct merge_remote_desc *desc;
531                 desc = merge_remote_util(remote_head);
532                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
533                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
534                                     sha1_to_hex(desc->obj->sha1),
535                                     typename(desc->obj->type),
536                                     remote);
537                         goto cleanup;
538                 }
539         }
540
541         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
542                 sha1_to_hex(remote_head->object.sha1), remote);
543 cleanup:
544         strbuf_release(&buf);
545         strbuf_release(&bname);
546 }
547
548 static void parse_branch_merge_options(char *bmo)
549 {
550         const char **argv;
551         int argc;
552
553         if (!bmo)
554                 return;
555         argc = split_cmdline(bmo, &argv);
556         if (argc < 0)
557                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
558                     split_cmdline_strerror(argc));
559         REALLOC_ARRAY(argv, argc + 2);
560         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
561         argc++;
562         argv[0] = "branch.*.mergeoptions";
563         parse_options(argc, argv, NULL, builtin_merge_options,
564                       builtin_merge_usage, 0);
565         free(argv);
566 }
567
568 static int git_merge_config(const char *k, const char *v, void *cb)
569 {
570         int status;
571
572         if (branch && starts_with(k, "branch.") &&
573                 starts_with(k + 7, branch) &&
574                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
575                 free(branch_mergeoptions);
576                 branch_mergeoptions = xstrdup(v);
577                 return 0;
578         }
579
580         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
581                 show_diffstat = git_config_bool(k, v);
582         else if (!strcmp(k, "pull.twohead"))
583                 return git_config_string(&pull_twohead, k, v);
584         else if (!strcmp(k, "pull.octopus"))
585                 return git_config_string(&pull_octopus, k, v);
586         else if (!strcmp(k, "merge.renormalize"))
587                 option_renormalize = git_config_bool(k, v);
588         else if (!strcmp(k, "merge.ff")) {
589                 int boolval = git_config_maybe_bool(k, v);
590                 if (0 <= boolval) {
591                         fast_forward = boolval ? FF_ALLOW : FF_NO;
592                 } else if (v && !strcmp(v, "only")) {
593                         fast_forward = FF_ONLY;
594                 } /* do not barf on values from future versions of git */
595                 return 0;
596         } else if (!strcmp(k, "merge.defaulttoupstream")) {
597                 default_to_upstream = git_config_bool(k, v);
598                 return 0;
599         } else if (!strcmp(k, "commit.gpgsign")) {
600                 sign_commit = git_config_bool(k, v) ? "" : NULL;
601                 return 0;
602         }
603
604         status = fmt_merge_msg_config(k, v, cb);
605         if (status)
606                 return status;
607         status = git_gpg_config(k, v, NULL);
608         if (status)
609                 return status;
610         return git_diff_ui_config(k, v, cb);
611 }
612
613 static int read_tree_trivial(unsigned char *common, unsigned char *head,
614                              unsigned char *one)
615 {
616         int i, nr_trees = 0;
617         struct tree *trees[MAX_UNPACK_TREES];
618         struct tree_desc t[MAX_UNPACK_TREES];
619         struct unpack_trees_options opts;
620
621         memset(&opts, 0, sizeof(opts));
622         opts.head_idx = 2;
623         opts.src_index = &the_index;
624         opts.dst_index = &the_index;
625         opts.update = 1;
626         opts.verbose_update = 1;
627         opts.trivial_merges_only = 1;
628         opts.merge = 1;
629         trees[nr_trees] = parse_tree_indirect(common);
630         if (!trees[nr_trees++])
631                 return -1;
632         trees[nr_trees] = parse_tree_indirect(head);
633         if (!trees[nr_trees++])
634                 return -1;
635         trees[nr_trees] = parse_tree_indirect(one);
636         if (!trees[nr_trees++])
637                 return -1;
638         opts.fn = threeway_merge;
639         cache_tree_free(&active_cache_tree);
640         for (i = 0; i < nr_trees; i++) {
641                 parse_tree(trees[i]);
642                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
643         }
644         if (unpack_trees(nr_trees, t, &opts))
645                 return -1;
646         return 0;
647 }
648
649 static void write_tree_trivial(unsigned char *sha1)
650 {
651         if (write_cache_as_tree(sha1, 0, NULL))
652                 die(_("git write-tree failed to write a tree"));
653 }
654
655 static int try_merge_strategy(const char *strategy, struct commit_list *common,
656                               struct commit_list *remoteheads,
657                               struct commit *head, const char *head_arg)
658 {
659         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
660
661         hold_locked_index(lock, 1);
662         refresh_cache(REFRESH_QUIET);
663         if (active_cache_changed &&
664             write_locked_index(&the_index, lock, COMMIT_LOCK))
665                 return error(_("Unable to write index."));
666         rollback_lock_file(lock);
667
668         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
669                 int clean, x;
670                 struct commit *result;
671                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
672                 struct commit_list *reversed = NULL;
673                 struct merge_options o;
674                 struct commit_list *j;
675
676                 if (remoteheads->next) {
677                         error(_("Not handling anything other than two heads merge."));
678                         return 2;
679                 }
680
681                 init_merge_options(&o);
682                 if (!strcmp(strategy, "subtree"))
683                         o.subtree_shift = "";
684
685                 o.renormalize = option_renormalize;
686                 o.show_rename_progress =
687                         show_progress == -1 ? isatty(2) : show_progress;
688
689                 for (x = 0; x < xopts_nr; x++)
690                         if (parse_merge_opt(&o, xopts[x]))
691                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
692
693                 o.branch1 = head_arg;
694                 o.branch2 = merge_remote_util(remoteheads->item)->name;
695
696                 for (j = common; j; j = j->next)
697                         commit_list_insert(j->item, &reversed);
698
699                 hold_locked_index(lock, 1);
700                 clean = merge_recursive(&o, head,
701                                 remoteheads->item, reversed, &result);
702                 if (active_cache_changed &&
703                     write_locked_index(&the_index, lock, COMMIT_LOCK))
704                         die (_("unable to write %s"), get_index_file());
705                 rollback_lock_file(lock);
706                 return clean ? 0 : 1;
707         } else {
708                 return try_merge_command(strategy, xopts_nr, xopts,
709                                                 common, head_arg, remoteheads);
710         }
711 }
712
713 static void count_diff_files(struct diff_queue_struct *q,
714                              struct diff_options *opt, void *data)
715 {
716         int *count = data;
717
718         (*count) += q->nr;
719 }
720
721 static int count_unmerged_entries(void)
722 {
723         int i, ret = 0;
724
725         for (i = 0; i < active_nr; i++)
726                 if (ce_stage(active_cache[i]))
727                         ret++;
728
729         return ret;
730 }
731
732 static void split_merge_strategies(const char *string, struct strategy **list,
733                                    int *nr, int *alloc)
734 {
735         char *p, *q, *buf;
736
737         if (!string)
738                 return;
739
740         buf = xstrdup(string);
741         q = buf;
742         for (;;) {
743                 p = strchr(q, ' ');
744                 if (!p) {
745                         ALLOC_GROW(*list, *nr + 1, *alloc);
746                         (*list)[(*nr)++].name = xstrdup(q);
747                         free(buf);
748                         return;
749                 } else {
750                         *p = '\0';
751                         ALLOC_GROW(*list, *nr + 1, *alloc);
752                         (*list)[(*nr)++].name = xstrdup(q);
753                         q = ++p;
754                 }
755         }
756 }
757
758 static void add_strategies(const char *string, unsigned attr)
759 {
760         struct strategy *list = NULL;
761         int list_alloc = 0, list_nr = 0, i;
762
763         memset(&list, 0, sizeof(list));
764         split_merge_strategies(string, &list, &list_nr, &list_alloc);
765         if (list) {
766                 for (i = 0; i < list_nr; i++)
767                         append_strategy(get_strategy(list[i].name));
768                 return;
769         }
770         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
771                 if (all_strategy[i].attr & attr)
772                         append_strategy(&all_strategy[i]);
773
774 }
775
776 static void write_merge_msg(struct strbuf *msg)
777 {
778         const char *filename = git_path("MERGE_MSG");
779         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
780         if (fd < 0)
781                 die_errno(_("Could not open '%s' for writing"),
782                           filename);
783         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
784                 die_errno(_("Could not write to '%s'"), filename);
785         close(fd);
786 }
787
788 static void read_merge_msg(struct strbuf *msg)
789 {
790         const char *filename = git_path("MERGE_MSG");
791         strbuf_reset(msg);
792         if (strbuf_read_file(msg, filename, 0) < 0)
793                 die_errno(_("Could not read from '%s'"), filename);
794 }
795
796 static void write_merge_state(struct commit_list *);
797 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
798 {
799         if (err_msg)
800                 error("%s", err_msg);
801         fprintf(stderr,
802                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
803         write_merge_state(remoteheads);
804         exit(1);
805 }
806
807 static const char merge_editor_comment[] =
808 N_("Please enter a commit message to explain why this merge is necessary,\n"
809    "especially if it merges an updated upstream into a topic branch.\n"
810    "\n"
811    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
812    "the commit.\n");
813
814 static void prepare_to_commit(struct commit_list *remoteheads)
815 {
816         struct strbuf msg = STRBUF_INIT;
817         strbuf_addbuf(&msg, &merge_msg);
818         strbuf_addch(&msg, '\n');
819         if (0 < option_edit)
820                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
821         write_merge_msg(&msg);
822         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
823                             git_path("MERGE_MSG"), "merge", NULL))
824                 abort_commit(remoteheads, NULL);
825         if (0 < option_edit) {
826                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
827                         abort_commit(remoteheads, NULL);
828         }
829         read_merge_msg(&msg);
830         stripspace(&msg, 0 < option_edit);
831         if (!msg.len)
832                 abort_commit(remoteheads, _("Empty commit message."));
833         strbuf_release(&merge_msg);
834         strbuf_addbuf(&merge_msg, &msg);
835         strbuf_release(&msg);
836 }
837
838 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
839 {
840         unsigned char result_tree[20], result_commit[20];
841         struct commit_list *parents, **pptr = &parents;
842
843         write_tree_trivial(result_tree);
844         printf(_("Wonderful.\n"));
845         pptr = commit_list_append(head, pptr);
846         pptr = commit_list_append(remoteheads->item, pptr);
847         prepare_to_commit(remoteheads);
848         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
849                         result_commit, NULL, sign_commit))
850                 die(_("failed to write commit object"));
851         finish(head, remoteheads, result_commit, "In-index merge");
852         drop_save();
853         return 0;
854 }
855
856 static int finish_automerge(struct commit *head,
857                             int head_subsumed,
858                             struct commit_list *common,
859                             struct commit_list *remoteheads,
860                             unsigned char *result_tree,
861                             const char *wt_strategy)
862 {
863         struct commit_list *parents = NULL;
864         struct strbuf buf = STRBUF_INIT;
865         unsigned char result_commit[20];
866
867         free_commit_list(common);
868         parents = remoteheads;
869         if (!head_subsumed || fast_forward == FF_NO)
870                 commit_list_insert(head, &parents);
871         strbuf_addch(&merge_msg, '\n');
872         prepare_to_commit(remoteheads);
873         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
874                         result_commit, NULL, sign_commit))
875                 die(_("failed to write commit object"));
876         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
877         finish(head, remoteheads, result_commit, buf.buf);
878         strbuf_release(&buf);
879         drop_save();
880         return 0;
881 }
882
883 static int suggest_conflicts(int renormalizing)
884 {
885         const char *filename;
886         FILE *fp;
887         int pos;
888
889         filename = git_path("MERGE_MSG");
890         fp = fopen(filename, "a");
891         if (!fp)
892                 die_errno(_("Could not open '%s' for writing"), filename);
893         fprintf(fp, "\nConflicts:\n");
894         for (pos = 0; pos < active_nr; pos++) {
895                 const struct cache_entry *ce = active_cache[pos];
896
897                 if (ce_stage(ce)) {
898                         fprintf(fp, "\t%s\n", ce->name);
899                         while (pos + 1 < active_nr &&
900                                         !strcmp(ce->name,
901                                                 active_cache[pos + 1]->name))
902                                 pos++;
903                 }
904         }
905         fclose(fp);
906         rerere(allow_rerere_auto);
907         printf(_("Automatic merge failed; "
908                         "fix conflicts and then commit the result.\n"));
909         return 1;
910 }
911
912 static struct commit *is_old_style_invocation(int argc, const char **argv,
913                                               const unsigned char *head)
914 {
915         struct commit *second_token = NULL;
916         if (argc > 2) {
917                 unsigned char second_sha1[20];
918
919                 if (get_sha1(argv[1], second_sha1))
920                         return NULL;
921                 second_token = lookup_commit_reference_gently(second_sha1, 0);
922                 if (!second_token)
923                         die(_("'%s' is not a commit"), argv[1]);
924                 if (hashcmp(second_token->object.sha1, head))
925                         return NULL;
926         }
927         return second_token;
928 }
929
930 static int evaluate_result(void)
931 {
932         int cnt = 0;
933         struct rev_info rev;
934
935         /* Check how many files differ. */
936         init_revisions(&rev, "");
937         setup_revisions(0, NULL, &rev, NULL);
938         rev.diffopt.output_format |=
939                 DIFF_FORMAT_CALLBACK;
940         rev.diffopt.format_callback = count_diff_files;
941         rev.diffopt.format_callback_data = &cnt;
942         run_diff_files(&rev, 0);
943
944         /*
945          * Check how many unmerged entries are
946          * there.
947          */
948         cnt += count_unmerged_entries();
949
950         return cnt;
951 }
952
953 /*
954  * Pretend as if the user told us to merge with the remote-tracking
955  * branch we have for the upstream of the current branch
956  */
957 static int setup_with_upstream(const char ***argv)
958 {
959         struct branch *branch = branch_get(NULL);
960         int i;
961         const char **args;
962
963         if (!branch)
964                 die(_("No current branch."));
965         if (!branch->remote)
966                 die(_("No remote for the current branch."));
967         if (!branch->merge_nr)
968                 die(_("No default upstream defined for the current branch."));
969
970         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
971         for (i = 0; i < branch->merge_nr; i++) {
972                 if (!branch->merge[i]->dst)
973                         die(_("No remote-tracking branch for %s from %s"),
974                             branch->merge[i]->src, branch->remote_name);
975                 args[i] = branch->merge[i]->dst;
976         }
977         args[i] = NULL;
978         *argv = args;
979         return i;
980 }
981
982 static void write_merge_state(struct commit_list *remoteheads)
983 {
984         const char *filename;
985         int fd;
986         struct commit_list *j;
987         struct strbuf buf = STRBUF_INIT;
988
989         for (j = remoteheads; j; j = j->next) {
990                 unsigned const char *sha1;
991                 struct commit *c = j->item;
992                 if (c->util && merge_remote_util(c)->obj) {
993                         sha1 = merge_remote_util(c)->obj->sha1;
994                 } else {
995                         sha1 = c->object.sha1;
996                 }
997                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
998         }
999         filename = git_path("MERGE_HEAD");
1000         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1001         if (fd < 0)
1002                 die_errno(_("Could not open '%s' for writing"), filename);
1003         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1004                 die_errno(_("Could not write to '%s'"), filename);
1005         close(fd);
1006         strbuf_addch(&merge_msg, '\n');
1007         write_merge_msg(&merge_msg);
1008
1009         filename = git_path("MERGE_MODE");
1010         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1011         if (fd < 0)
1012                 die_errno(_("Could not open '%s' for writing"), filename);
1013         strbuf_reset(&buf);
1014         if (fast_forward == FF_NO)
1015                 strbuf_addf(&buf, "no-ff");
1016         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1017                 die_errno(_("Could not write to '%s'"), filename);
1018         close(fd);
1019 }
1020
1021 static int default_edit_option(void)
1022 {
1023         static const char name[] = "GIT_MERGE_AUTOEDIT";
1024         const char *e = getenv(name);
1025         struct stat st_stdin, st_stdout;
1026
1027         if (have_message)
1028                 /* an explicit -m msg without --[no-]edit */
1029                 return 0;
1030
1031         if (e) {
1032                 int v = git_config_maybe_bool(name, e);
1033                 if (v < 0)
1034                         die("Bad value '%s' in environment '%s'", e, name);
1035                 return v;
1036         }
1037
1038         /* Use editor if stdin and stdout are the same and is a tty */
1039         return (!fstat(0, &st_stdin) &&
1040                 !fstat(1, &st_stdout) &&
1041                 isatty(0) && isatty(1) &&
1042                 st_stdin.st_dev == st_stdout.st_dev &&
1043                 st_stdin.st_ino == st_stdout.st_ino &&
1044                 st_stdin.st_mode == st_stdout.st_mode);
1045 }
1046
1047 static struct commit_list *collect_parents(struct commit *head_commit,
1048                                            int *head_subsumed,
1049                                            int argc, const char **argv)
1050 {
1051         int i;
1052         struct commit_list *remoteheads = NULL, *parents, *next;
1053         struct commit_list **remotes = &remoteheads;
1054
1055         if (head_commit)
1056                 remotes = &commit_list_insert(head_commit, remotes)->next;
1057         for (i = 0; i < argc; i++) {
1058                 struct commit *commit = get_merge_parent(argv[i]);
1059                 if (!commit)
1060                         help_unknown_ref(argv[i], "merge",
1061                                          "not something we can merge");
1062                 remotes = &commit_list_insert(commit, remotes)->next;
1063         }
1064         *remotes = NULL;
1065
1066         parents = reduce_heads(remoteheads);
1067
1068         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1069         for (remoteheads = NULL, remotes = &remoteheads;
1070              parents;
1071              parents = next) {
1072                 struct commit *commit = parents->item;
1073                 next = parents->next;
1074                 if (commit == head_commit)
1075                         *head_subsumed = 0;
1076                 else
1077                         remotes = &commit_list_insert(commit, remotes)->next;
1078         }
1079         return remoteheads;
1080 }
1081
1082 int cmd_merge(int argc, const char **argv, const char *prefix)
1083 {
1084         unsigned char result_tree[20];
1085         unsigned char stash[20];
1086         unsigned char head_sha1[20];
1087         struct commit *head_commit;
1088         struct strbuf buf = STRBUF_INIT;
1089         const char *head_arg;
1090         int flag, i, ret = 0, head_subsumed;
1091         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1092         struct commit_list *common = NULL;
1093         const char *best_strategy = NULL, *wt_strategy = NULL;
1094         struct commit_list *remoteheads, *p;
1095         void *branch_to_free;
1096
1097         if (argc == 2 && !strcmp(argv[1], "-h"))
1098                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1099
1100         /*
1101          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1102          * current branch.
1103          */
1104         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1105         if (branch && starts_with(branch, "refs/heads/"))
1106                 branch += 11;
1107         if (!branch || is_null_sha1(head_sha1))
1108                 head_commit = NULL;
1109         else
1110                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1111
1112         git_config(git_merge_config, NULL);
1113
1114         if (branch_mergeoptions)
1115                 parse_branch_merge_options(branch_mergeoptions);
1116         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1117                         builtin_merge_usage, 0);
1118         if (shortlog_len < 0)
1119                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1120
1121         if (verbosity < 0 && show_progress == -1)
1122                 show_progress = 0;
1123
1124         if (abort_current_merge) {
1125                 int nargc = 2;
1126                 const char *nargv[] = {"reset", "--merge", NULL};
1127
1128                 if (!file_exists(git_path("MERGE_HEAD")))
1129                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1130
1131                 /* Invoke 'git reset --merge' */
1132                 ret = cmd_reset(nargc, nargv, prefix);
1133                 goto done;
1134         }
1135
1136         if (read_cache_unmerged())
1137                 die_resolve_conflict("merge");
1138
1139         if (file_exists(git_path("MERGE_HEAD"))) {
1140                 /*
1141                  * There is no unmerged entry, don't advise 'git
1142                  * add/rm <file>', just 'git commit'.
1143                  */
1144                 if (advice_resolve_conflict)
1145                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1146                                   "Please, commit your changes before you merge."));
1147                 else
1148                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1149         }
1150         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1151                 if (advice_resolve_conflict)
1152                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1153                             "Please, commit your changes before you merge."));
1154                 else
1155                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1156         }
1157         resolve_undo_clear();
1158
1159         if (verbosity < 0)
1160                 show_diffstat = 0;
1161
1162         if (squash) {
1163                 if (fast_forward == FF_NO)
1164                         die(_("You cannot combine --squash with --no-ff."));
1165                 option_commit = 0;
1166         }
1167
1168         if (!abort_current_merge) {
1169                 if (!argc) {
1170                         if (default_to_upstream)
1171                                 argc = setup_with_upstream(&argv);
1172                         else
1173                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1174                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1175                         argv[0] = "@{-1}";
1176         }
1177         if (!argc)
1178                 usage_with_options(builtin_merge_usage,
1179                         builtin_merge_options);
1180
1181         /*
1182          * This could be traditional "merge <msg> HEAD <commit>..."  and
1183          * the way we can tell it is to see if the second token is HEAD,
1184          * but some people might have misused the interface and used a
1185          * commit-ish that is the same as HEAD there instead.
1186          * Traditional format never would have "-m" so it is an
1187          * additional safety measure to check for it.
1188          */
1189
1190         if (!have_message && head_commit &&
1191             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1192                 strbuf_addstr(&merge_msg, argv[0]);
1193                 head_arg = argv[1];
1194                 argv += 2;
1195                 argc -= 2;
1196                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1197         } else if (!head_commit) {
1198                 struct commit *remote_head;
1199                 /*
1200                  * If the merged head is a valid one there is no reason
1201                  * to forbid "git merge" into a branch yet to be born.
1202                  * We do the same for "git pull".
1203                  */
1204                 if (argc != 1)
1205                         die(_("Can merge only exactly one commit into "
1206                                 "empty head"));
1207                 if (squash)
1208                         die(_("Squash commit into empty head not supported yet"));
1209                 if (fast_forward == FF_NO)
1210                         die(_("Non-fast-forward commit does not make sense into "
1211                             "an empty head"));
1212                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1213                 remote_head = remoteheads->item;
1214                 if (!remote_head)
1215                         die(_("%s - not something we can merge"), argv[0]);
1216                 read_empty(remote_head->object.sha1, 0);
1217                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1218                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1219                 goto done;
1220         } else {
1221                 struct strbuf merge_names = STRBUF_INIT;
1222
1223                 /* We are invoked directly as the first-class UI. */
1224                 head_arg = "HEAD";
1225
1226                 /*
1227                  * All the rest are the commits being merged; prepare
1228                  * the standard merge summary message to be appended
1229                  * to the given message.
1230                  */
1231                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1232                 for (p = remoteheads; p; p = p->next)
1233                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1234
1235                 if (!have_message || shortlog_len) {
1236                         struct fmt_merge_msg_opts opts;
1237                         memset(&opts, 0, sizeof(opts));
1238                         opts.add_title = !have_message;
1239                         opts.shortlog_len = shortlog_len;
1240                         opts.credit_people = (0 < option_edit);
1241
1242                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1243                         if (merge_msg.len)
1244                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1245                 }
1246         }
1247
1248         if (!head_commit || !argc)
1249                 usage_with_options(builtin_merge_usage,
1250                         builtin_merge_options);
1251
1252         if (verify_signatures) {
1253                 for (p = remoteheads; p; p = p->next) {
1254                         struct commit *commit = p->item;
1255                         char hex[41];
1256                         struct signature_check signature_check;
1257                         memset(&signature_check, 0, sizeof(signature_check));
1258
1259                         check_commit_signature(commit, &signature_check);
1260
1261                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1262                         switch (signature_check.result) {
1263                         case 'G':
1264                                 break;
1265                         case 'U':
1266                                 die(_("Commit %s has an untrusted GPG signature, "
1267                                       "allegedly by %s."), hex, signature_check.signer);
1268                         case 'B':
1269                                 die(_("Commit %s has a bad GPG signature "
1270                                       "allegedly by %s."), hex, signature_check.signer);
1271                         default: /* 'N' */
1272                                 die(_("Commit %s does not have a GPG signature."), hex);
1273                         }
1274                         if (verbosity >= 0 && signature_check.result == 'G')
1275                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1276                                        hex, signature_check.signer);
1277
1278                         signature_check_clear(&signature_check);
1279                 }
1280         }
1281
1282         strbuf_addstr(&buf, "merge");
1283         for (p = remoteheads; p; p = p->next)
1284                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1285         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1286         strbuf_reset(&buf);
1287
1288         for (p = remoteheads; p; p = p->next) {
1289                 struct commit *commit = p->item;
1290                 strbuf_addf(&buf, "GITHEAD_%s",
1291                             sha1_to_hex(commit->object.sha1));
1292                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1293                 strbuf_reset(&buf);
1294                 if (fast_forward != FF_ONLY &&
1295                     merge_remote_util(commit) &&
1296                     merge_remote_util(commit)->obj &&
1297                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1298                         fast_forward = FF_NO;
1299         }
1300
1301         if (option_edit < 0)
1302                 option_edit = default_edit_option();
1303
1304         if (!use_strategies) {
1305                 if (!remoteheads)
1306                         ; /* already up-to-date */
1307                 else if (!remoteheads->next)
1308                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1309                 else
1310                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1311         }
1312
1313         for (i = 0; i < use_strategies_nr; i++) {
1314                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1315                         fast_forward = FF_NO;
1316                 if (use_strategies[i]->attr & NO_TRIVIAL)
1317                         allow_trivial = 0;
1318         }
1319
1320         if (!remoteheads)
1321                 ; /* already up-to-date */
1322         else if (!remoteheads->next)
1323                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1324         else {
1325                 struct commit_list *list = remoteheads;
1326                 commit_list_insert(head_commit, &list);
1327                 common = get_octopus_merge_bases(list);
1328                 free(list);
1329         }
1330
1331         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1332                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1333
1334         if (remoteheads && !common)
1335                 ; /* No common ancestors found. We need a real merge. */
1336         else if (!remoteheads ||
1337                  (!remoteheads->next && !common->next &&
1338                   common->item == remoteheads->item)) {
1339                 /*
1340                  * If head can reach all the merge then we are up to date.
1341                  * but first the most common case of merging one remote.
1342                  */
1343                 finish_up_to_date("Already up-to-date.");
1344                 goto done;
1345         } else if (fast_forward != FF_NO && !remoteheads->next &&
1346                         !common->next &&
1347                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1348                 /* Again the most common case of merging one remote. */
1349                 struct strbuf msg = STRBUF_INIT;
1350                 struct commit *commit;
1351                 char hex[41];
1352
1353                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1354
1355                 if (verbosity >= 0)
1356                         printf(_("Updating %s..%s\n"),
1357                                 hex,
1358                                 find_unique_abbrev(remoteheads->item->object.sha1,
1359                                 DEFAULT_ABBREV));
1360                 strbuf_addstr(&msg, "Fast-forward");
1361                 if (have_message)
1362                         strbuf_addstr(&msg,
1363                                 " (no commit created; -m option ignored)");
1364                 commit = remoteheads->item;
1365                 if (!commit) {
1366                         ret = 1;
1367                         goto done;
1368                 }
1369
1370                 if (checkout_fast_forward(head_commit->object.sha1,
1371                                           commit->object.sha1,
1372                                           overwrite_ignore)) {
1373                         ret = 1;
1374                         goto done;
1375                 }
1376
1377                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1378                 drop_save();
1379                 goto done;
1380         } else if (!remoteheads->next && common->next)
1381                 ;
1382                 /*
1383                  * We are not doing octopus and not fast-forward.  Need
1384                  * a real merge.
1385                  */
1386         else if (!remoteheads->next && !common->next && option_commit) {
1387                 /*
1388                  * We are not doing octopus, not fast-forward, and have
1389                  * only one common.
1390                  */
1391                 refresh_cache(REFRESH_QUIET);
1392                 if (allow_trivial && fast_forward != FF_ONLY) {
1393                         /* See if it is really trivial. */
1394                         git_committer_info(IDENT_STRICT);
1395                         printf(_("Trying really trivial in-index merge...\n"));
1396                         if (!read_tree_trivial(common->item->object.sha1,
1397                                                head_commit->object.sha1,
1398                                                remoteheads->item->object.sha1)) {
1399                                 ret = merge_trivial(head_commit, remoteheads);
1400                                 goto done;
1401                         }
1402                         printf(_("Nope.\n"));
1403                 }
1404         } else {
1405                 /*
1406                  * An octopus.  If we can reach all the remote we are up
1407                  * to date.
1408                  */
1409                 int up_to_date = 1;
1410                 struct commit_list *j;
1411
1412                 for (j = remoteheads; j; j = j->next) {
1413                         struct commit_list *common_one;
1414
1415                         /*
1416                          * Here we *have* to calculate the individual
1417                          * merge_bases again, otherwise "git merge HEAD^
1418                          * HEAD^^" would be missed.
1419                          */
1420                         common_one = get_merge_bases(head_commit, j->item, 1);
1421                         if (hashcmp(common_one->item->object.sha1,
1422                                 j->item->object.sha1)) {
1423                                 up_to_date = 0;
1424                                 break;
1425                         }
1426                 }
1427                 if (up_to_date) {
1428                         finish_up_to_date("Already up-to-date. Yeeah!");
1429                         goto done;
1430                 }
1431         }
1432
1433         if (fast_forward == FF_ONLY)
1434                 die(_("Not possible to fast-forward, aborting."));
1435
1436         /* We are going to make a new commit. */
1437         git_committer_info(IDENT_STRICT);
1438
1439         /*
1440          * At this point, we need a real merge.  No matter what strategy
1441          * we use, it would operate on the index, possibly affecting the
1442          * working tree, and when resolved cleanly, have the desired
1443          * tree in the index -- this means that the index must be in
1444          * sync with the head commit.  The strategies are responsible
1445          * to ensure this.
1446          */
1447         if (use_strategies_nr == 1 ||
1448             /*
1449              * Stash away the local changes so that we can try more than one.
1450              */
1451             save_state(stash))
1452                 hashcpy(stash, null_sha1);
1453
1454         for (i = 0; i < use_strategies_nr; i++) {
1455                 int ret;
1456                 if (i) {
1457                         printf(_("Rewinding the tree to pristine...\n"));
1458                         restore_state(head_commit->object.sha1, stash);
1459                 }
1460                 if (use_strategies_nr != 1)
1461                         printf(_("Trying merge strategy %s...\n"),
1462                                 use_strategies[i]->name);
1463                 /*
1464                  * Remember which strategy left the state in the working
1465                  * tree.
1466                  */
1467                 wt_strategy = use_strategies[i]->name;
1468
1469                 ret = try_merge_strategy(use_strategies[i]->name,
1470                                          common, remoteheads,
1471                                          head_commit, head_arg);
1472                 if (!option_commit && !ret) {
1473                         merge_was_ok = 1;
1474                         /*
1475                          * This is necessary here just to avoid writing
1476                          * the tree, but later we will *not* exit with
1477                          * status code 1 because merge_was_ok is set.
1478                          */
1479                         ret = 1;
1480                 }
1481
1482                 if (ret) {
1483                         /*
1484                          * The backend exits with 1 when conflicts are
1485                          * left to be resolved, with 2 when it does not
1486                          * handle the given merge at all.
1487                          */
1488                         if (ret == 1) {
1489                                 int cnt = evaluate_result();
1490
1491                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1492                                         best_strategy = use_strategies[i]->name;
1493                                         best_cnt = cnt;
1494                                 }
1495                         }
1496                         if (merge_was_ok)
1497                                 break;
1498                         else
1499                                 continue;
1500                 }
1501
1502                 /* Automerge succeeded. */
1503                 write_tree_trivial(result_tree);
1504                 automerge_was_ok = 1;
1505                 break;
1506         }
1507
1508         /*
1509          * If we have a resulting tree, that means the strategy module
1510          * auto resolved the merge cleanly.
1511          */
1512         if (automerge_was_ok) {
1513                 ret = finish_automerge(head_commit, head_subsumed,
1514                                        common, remoteheads,
1515                                        result_tree, wt_strategy);
1516                 goto done;
1517         }
1518
1519         /*
1520          * Pick the result from the best strategy and have the user fix
1521          * it up.
1522          */
1523         if (!best_strategy) {
1524                 restore_state(head_commit->object.sha1, stash);
1525                 if (use_strategies_nr > 1)
1526                         fprintf(stderr,
1527                                 _("No merge strategy handled the merge.\n"));
1528                 else
1529                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1530                                 use_strategies[0]->name);
1531                 ret = 2;
1532                 goto done;
1533         } else if (best_strategy == wt_strategy)
1534                 ; /* We already have its result in the working tree. */
1535         else {
1536                 printf(_("Rewinding the tree to pristine...\n"));
1537                 restore_state(head_commit->object.sha1, stash);
1538                 printf(_("Using the %s to prepare resolving by hand.\n"),
1539                         best_strategy);
1540                 try_merge_strategy(best_strategy, common, remoteheads,
1541                                    head_commit, head_arg);
1542         }
1543
1544         if (squash)
1545                 finish(head_commit, remoteheads, NULL, NULL);
1546         else
1547                 write_merge_state(remoteheads);
1548
1549         if (merge_was_ok)
1550                 fprintf(stderr, _("Automatic merge went well; "
1551                         "stopped before committing as requested\n"));
1552         else
1553                 ret = suggest_conflicts(option_renormalize);
1554
1555 done:
1556         free(branch_to_free);
1557         return ret;
1558 }