Merge branch 'bc/doc-merge-no-op-revert'
[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;
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;
241         struct strbuf buffer = STRBUF_INIT;
242         const char *argv[] = {"stash", "create", NULL};
243
244         memset(&cp, 0, sizeof(cp));
245         cp.argv = argv;
246         cp.out = -1;
247         cp.git_cmd = 1;
248
249         if (start_command(&cp))
250                 die(_("could not run stash."));
251         len = strbuf_read(&buffer, cp.out, 1024);
252         close(cp.out);
253
254         if (finish_command(&cp) || len < 0)
255                 die(_("stash failed"));
256         else if (!len)          /* no changes */
257                 return -1;
258         strbuf_setlen(&buffer, buffer.len-1);
259         if (get_sha1(buffer.buf, stash))
260                 die(_("not a valid object: %s"), buffer.buf);
261         return 0;
262 }
263
264 static void read_empty(unsigned const char *sha1, int verbose)
265 {
266         int i = 0;
267         const char *args[7];
268
269         args[i++] = "read-tree";
270         if (verbose)
271                 args[i++] = "-v";
272         args[i++] = "-m";
273         args[i++] = "-u";
274         args[i++] = EMPTY_TREE_SHA1_HEX;
275         args[i++] = sha1_to_hex(sha1);
276         args[i] = NULL;
277
278         if (run_command_v_opt(args, RUN_GIT_CMD))
279                 die(_("read-tree failed"));
280 }
281
282 static void reset_hard(unsigned const char *sha1, int verbose)
283 {
284         int i = 0;
285         const char *args[6];
286
287         args[i++] = "read-tree";
288         if (verbose)
289                 args[i++] = "-v";
290         args[i++] = "--reset";
291         args[i++] = "-u";
292         args[i++] = sha1_to_hex(sha1);
293         args[i] = NULL;
294
295         if (run_command_v_opt(args, RUN_GIT_CMD))
296                 die(_("read-tree failed"));
297 }
298
299 static void restore_state(const unsigned char *head,
300                           const unsigned char *stash)
301 {
302         struct strbuf sb = STRBUF_INIT;
303         const char *args[] = { "stash", "apply", NULL, NULL };
304
305         if (is_null_sha1(stash))
306                 return;
307
308         reset_hard(head, 1);
309
310         args[2] = sha1_to_hex(stash);
311
312         /*
313          * It is OK to ignore error here, for example when there was
314          * nothing to restore.
315          */
316         run_command_v_opt(args, RUN_GIT_CMD);
317
318         strbuf_release(&sb);
319         refresh_cache(REFRESH_QUIET);
320 }
321
322 /* This is called when no merge was necessary. */
323 static void finish_up_to_date(const char *msg)
324 {
325         if (verbosity >= 0)
326                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
327         drop_save();
328 }
329
330 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
331 {
332         struct rev_info rev;
333         struct strbuf out = STRBUF_INIT;
334         struct commit_list *j;
335         const char *filename;
336         int fd;
337         struct pretty_print_context ctx = {0};
338
339         printf(_("Squash commit -- not updating HEAD\n"));
340         filename = git_path("SQUASH_MSG");
341         fd = open(filename, O_WRONLY | O_CREAT, 0666);
342         if (fd < 0)
343                 die_errno(_("Could not write to '%s'"), filename);
344
345         init_revisions(&rev, NULL);
346         rev.ignore_merges = 1;
347         rev.commit_format = CMIT_FMT_MEDIUM;
348
349         commit->object.flags |= UNINTERESTING;
350         add_pending_object(&rev, &commit->object, NULL);
351
352         for (j = remoteheads; j; j = j->next)
353                 add_pending_object(&rev, &j->item->object, NULL);
354
355         setup_revisions(0, NULL, &rev, NULL);
356         if (prepare_revision_walk(&rev))
357                 die(_("revision walk setup failed"));
358
359         ctx.abbrev = rev.abbrev;
360         ctx.date_mode = rev.date_mode;
361         ctx.fmt = rev.commit_format;
362
363         strbuf_addstr(&out, "Squashed commit of the following:\n");
364         while ((commit = get_revision(&rev)) != NULL) {
365                 strbuf_addch(&out, '\n');
366                 strbuf_addf(&out, "commit %s\n",
367                         sha1_to_hex(commit->object.sha1));
368                 pretty_print_commit(&ctx, commit, &out);
369         }
370         if (write(fd, out.buf, out.len) < 0)
371                 die_errno(_("Writing SQUASH_MSG"));
372         if (close(fd))
373                 die_errno(_("Finishing SQUASH_MSG"));
374         strbuf_release(&out);
375 }
376
377 static void finish(struct commit *head_commit,
378                    struct commit_list *remoteheads,
379                    const unsigned char *new_head, const char *msg)
380 {
381         struct strbuf reflog_message = STRBUF_INIT;
382         const unsigned char *head = head_commit->object.sha1;
383
384         if (!msg)
385                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
386         else {
387                 if (verbosity >= 0)
388                         printf("%s\n", msg);
389                 strbuf_addf(&reflog_message, "%s: %s",
390                         getenv("GIT_REFLOG_ACTION"), msg);
391         }
392         if (squash) {
393                 squash_message(head_commit, remoteheads);
394         } else {
395                 if (verbosity >= 0 && !merge_msg.len)
396                         printf(_("No merge message -- not updating HEAD\n"));
397                 else {
398                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
399                         update_ref(reflog_message.buf, "HEAD",
400                                 new_head, head, 0,
401                                 DIE_ON_ERR);
402                         /*
403                          * We ignore errors in 'gc --auto', since the
404                          * user should see them.
405                          */
406                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
407                 }
408         }
409         if (new_head && show_diffstat) {
410                 struct diff_options opts;
411                 diff_setup(&opts);
412                 opts.stat_width = -1; /* use full terminal width */
413                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
414                 opts.output_format |=
415                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
416                 opts.detect_rename = DIFF_DETECT_RENAME;
417                 diff_setup_done(&opts);
418                 diff_tree_sha1(head, new_head, "", &opts);
419                 diffcore_std(&opts);
420                 diff_flush(&opts);
421         }
422
423         /* Run a post-merge hook */
424         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
425
426         strbuf_release(&reflog_message);
427 }
428
429 /* Get the name for the merge commit's message. */
430 static void merge_name(const char *remote, struct strbuf *msg)
431 {
432         struct commit *remote_head;
433         unsigned char branch_head[20];
434         struct strbuf buf = STRBUF_INIT;
435         struct strbuf bname = STRBUF_INIT;
436         const char *ptr;
437         char *found_ref;
438         int len, early;
439
440         strbuf_branchname(&bname, remote);
441         remote = bname.buf;
442
443         memset(branch_head, 0, sizeof(branch_head));
444         remote_head = get_merge_parent(remote);
445         if (!remote_head)
446                 die(_("'%s' does not point to a commit"), remote);
447
448         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
449                 if (!prefixcmp(found_ref, "refs/heads/")) {
450                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
451                                     sha1_to_hex(branch_head), remote);
452                         goto cleanup;
453                 }
454                 if (!prefixcmp(found_ref, "refs/tags/")) {
455                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
456                                     sha1_to_hex(branch_head), remote);
457                         goto cleanup;
458                 }
459                 if (!prefixcmp(found_ref, "refs/remotes/")) {
460                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
461                                     sha1_to_hex(branch_head), remote);
462                         goto cleanup;
463                 }
464         }
465
466         /* See if remote matches <name>^^^.. or <name>~<number> */
467         for (len = 0, ptr = remote + strlen(remote);
468              remote < ptr && ptr[-1] == '^';
469              ptr--)
470                 len++;
471         if (len)
472                 early = 1;
473         else {
474                 early = 0;
475                 ptr = strrchr(remote, '~');
476                 if (ptr) {
477                         int seen_nonzero = 0;
478
479                         len++; /* count ~ */
480                         while (*++ptr && isdigit(*ptr)) {
481                                 seen_nonzero |= (*ptr != '0');
482                                 len++;
483                         }
484                         if (*ptr)
485                                 len = 0; /* not ...~<number> */
486                         else if (seen_nonzero)
487                                 early = 1;
488                         else if (len == 1)
489                                 early = 1; /* "name~" is "name~1"! */
490                 }
491         }
492         if (len) {
493                 struct strbuf truname = STRBUF_INIT;
494                 strbuf_addstr(&truname, "refs/heads/");
495                 strbuf_addstr(&truname, remote);
496                 strbuf_setlen(&truname, truname.len - len);
497                 if (ref_exists(truname.buf)) {
498                         strbuf_addf(msg,
499                                     "%s\t\tbranch '%s'%s of .\n",
500                                     sha1_to_hex(remote_head->object.sha1),
501                                     truname.buf + 11,
502                                     (early ? " (early part)" : ""));
503                         strbuf_release(&truname);
504                         goto cleanup;
505                 }
506         }
507
508         if (!strcmp(remote, "FETCH_HEAD") &&
509                         !access(git_path("FETCH_HEAD"), R_OK)) {
510                 const char *filename;
511                 FILE *fp;
512                 struct strbuf line = STRBUF_INIT;
513                 char *ptr;
514
515                 filename = git_path("FETCH_HEAD");
516                 fp = fopen(filename, "r");
517                 if (!fp)
518                         die_errno(_("could not open '%s' for reading"),
519                                   filename);
520                 strbuf_getline(&line, fp, '\n');
521                 fclose(fp);
522                 ptr = strstr(line.buf, "\tnot-for-merge\t");
523                 if (ptr)
524                         strbuf_remove(&line, ptr-line.buf+1, 13);
525                 strbuf_addbuf(msg, &line);
526                 strbuf_release(&line);
527                 goto cleanup;
528         }
529
530         if (remote_head->util) {
531                 struct merge_remote_desc *desc;
532                 desc = merge_remote_util(remote_head);
533                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
534                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
535                                     sha1_to_hex(desc->obj->sha1),
536                                     typename(desc->obj->type),
537                                     remote);
538                         goto cleanup;
539                 }
540         }
541
542         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
543                 sha1_to_hex(remote_head->object.sha1), remote);
544 cleanup:
545         strbuf_release(&buf);
546         strbuf_release(&bname);
547 }
548
549 static void parse_branch_merge_options(char *bmo)
550 {
551         const char **argv;
552         int argc;
553
554         if (!bmo)
555                 return;
556         argc = split_cmdline(bmo, &argv);
557         if (argc < 0)
558                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
559                     split_cmdline_strerror(argc));
560         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
561         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
562         argc++;
563         argv[0] = "branch.*.mergeoptions";
564         parse_options(argc, argv, NULL, builtin_merge_options,
565                       builtin_merge_usage, 0);
566         free(argv);
567 }
568
569 static int git_merge_config(const char *k, const char *v, void *cb)
570 {
571         int status;
572
573         if (branch && !prefixcmp(k, "branch.") &&
574                 !prefixcmp(k + 7, branch) &&
575                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
576                 free(branch_mergeoptions);
577                 branch_mergeoptions = xstrdup(v);
578                 return 0;
579         }
580
581         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
582                 show_diffstat = git_config_bool(k, v);
583         else if (!strcmp(k, "pull.twohead"))
584                 return git_config_string(&pull_twohead, k, v);
585         else if (!strcmp(k, "pull.octopus"))
586                 return git_config_string(&pull_octopus, k, v);
587         else if (!strcmp(k, "merge.renormalize"))
588                 option_renormalize = git_config_bool(k, v);
589         else if (!strcmp(k, "merge.ff")) {
590                 int boolval = git_config_maybe_bool(k, v);
591                 if (0 <= boolval) {
592                         fast_forward = boolval ? FF_ALLOW : FF_NO;
593                 } else if (v && !strcmp(v, "only")) {
594                         fast_forward = FF_ONLY;
595                 } /* do not barf on values from future versions of git */
596                 return 0;
597         } else if (!strcmp(k, "merge.defaulttoupstream")) {
598                 default_to_upstream = git_config_bool(k, v);
599                 return 0;
600         }
601
602         status = fmt_merge_msg_config(k, v, cb);
603         if (status)
604                 return status;
605         status = git_gpg_config(k, v, NULL);
606         if (status)
607                 return status;
608         return git_diff_ui_config(k, v, cb);
609 }
610
611 static int read_tree_trivial(unsigned char *common, unsigned char *head,
612                              unsigned char *one)
613 {
614         int i, nr_trees = 0;
615         struct tree *trees[MAX_UNPACK_TREES];
616         struct tree_desc t[MAX_UNPACK_TREES];
617         struct unpack_trees_options opts;
618
619         memset(&opts, 0, sizeof(opts));
620         opts.head_idx = 2;
621         opts.src_index = &the_index;
622         opts.dst_index = &the_index;
623         opts.update = 1;
624         opts.verbose_update = 1;
625         opts.trivial_merges_only = 1;
626         opts.merge = 1;
627         trees[nr_trees] = parse_tree_indirect(common);
628         if (!trees[nr_trees++])
629                 return -1;
630         trees[nr_trees] = parse_tree_indirect(head);
631         if (!trees[nr_trees++])
632                 return -1;
633         trees[nr_trees] = parse_tree_indirect(one);
634         if (!trees[nr_trees++])
635                 return -1;
636         opts.fn = threeway_merge;
637         cache_tree_free(&active_cache_tree);
638         for (i = 0; i < nr_trees; i++) {
639                 parse_tree(trees[i]);
640                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
641         }
642         if (unpack_trees(nr_trees, t, &opts))
643                 return -1;
644         return 0;
645 }
646
647 static void write_tree_trivial(unsigned char *sha1)
648 {
649         if (write_cache_as_tree(sha1, 0, NULL))
650                 die(_("git write-tree failed to write a tree"));
651 }
652
653 static int try_merge_strategy(const char *strategy, struct commit_list *common,
654                               struct commit_list *remoteheads,
655                               struct commit *head, const char *head_arg)
656 {
657         int index_fd;
658         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
659
660         index_fd = hold_locked_index(lock, 1);
661         refresh_cache(REFRESH_QUIET);
662         if (active_cache_changed &&
663                         (write_cache(index_fd, active_cache, active_nr) ||
664                          commit_locked_index(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                 int index_fd;
673                 struct commit_list *reversed = NULL;
674                 struct merge_options o;
675                 struct commit_list *j;
676
677                 if (remoteheads->next) {
678                         error(_("Not handling anything other than two heads merge."));
679                         return 2;
680                 }
681
682                 init_merge_options(&o);
683                 if (!strcmp(strategy, "subtree"))
684                         o.subtree_shift = "";
685
686                 o.renormalize = option_renormalize;
687                 o.show_rename_progress =
688                         show_progress == -1 ? isatty(2) : show_progress;
689
690                 for (x = 0; x < xopts_nr; x++)
691                         if (parse_merge_opt(&o, xopts[x]))
692                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
693
694                 o.branch1 = head_arg;
695                 o.branch2 = merge_remote_util(remoteheads->item)->name;
696
697                 for (j = common; j; j = j->next)
698                         commit_list_insert(j->item, &reversed);
699
700                 index_fd = hold_locked_index(lock, 1);
701                 clean = merge_recursive(&o, head,
702                                 remoteheads->item, reversed, &result);
703                 if (active_cache_changed &&
704                                 (write_cache(index_fd, active_cache, active_nr) ||
705                                  commit_locked_index(lock)))
706                         die (_("unable to write %s"), get_index_file());
707                 rollback_lock_file(lock);
708                 return clean ? 0 : 1;
709         } else {
710                 return try_merge_command(strategy, xopts_nr, xopts,
711                                                 common, head_arg, remoteheads);
712         }
713 }
714
715 static void count_diff_files(struct diff_queue_struct *q,
716                              struct diff_options *opt, void *data)
717 {
718         int *count = data;
719
720         (*count) += q->nr;
721 }
722
723 static int count_unmerged_entries(void)
724 {
725         int i, ret = 0;
726
727         for (i = 0; i < active_nr; i++)
728                 if (ce_stage(active_cache[i]))
729                         ret++;
730
731         return ret;
732 }
733
734 static void split_merge_strategies(const char *string, struct strategy **list,
735                                    int *nr, int *alloc)
736 {
737         char *p, *q, *buf;
738
739         if (!string)
740                 return;
741
742         buf = xstrdup(string);
743         q = buf;
744         for (;;) {
745                 p = strchr(q, ' ');
746                 if (!p) {
747                         ALLOC_GROW(*list, *nr + 1, *alloc);
748                         (*list)[(*nr)++].name = xstrdup(q);
749                         free(buf);
750                         return;
751                 } else {
752                         *p = '\0';
753                         ALLOC_GROW(*list, *nr + 1, *alloc);
754                         (*list)[(*nr)++].name = xstrdup(q);
755                         q = ++p;
756                 }
757         }
758 }
759
760 static void add_strategies(const char *string, unsigned attr)
761 {
762         struct strategy *list = NULL;
763         int list_alloc = 0, list_nr = 0, i;
764
765         memset(&list, 0, sizeof(list));
766         split_merge_strategies(string, &list, &list_nr, &list_alloc);
767         if (list) {
768                 for (i = 0; i < list_nr; i++)
769                         append_strategy(get_strategy(list[i].name));
770                 return;
771         }
772         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
773                 if (all_strategy[i].attr & attr)
774                         append_strategy(&all_strategy[i]);
775
776 }
777
778 static void write_merge_msg(struct strbuf *msg)
779 {
780         const char *filename = git_path("MERGE_MSG");
781         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
782         if (fd < 0)
783                 die_errno(_("Could not open '%s' for writing"),
784                           filename);
785         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
786                 die_errno(_("Could not write to '%s'"), filename);
787         close(fd);
788 }
789
790 static void read_merge_msg(struct strbuf *msg)
791 {
792         const char *filename = git_path("MERGE_MSG");
793         strbuf_reset(msg);
794         if (strbuf_read_file(msg, filename, 0) < 0)
795                 die_errno(_("Could not read from '%s'"), filename);
796 }
797
798 static void write_merge_state(struct commit_list *);
799 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
800 {
801         if (err_msg)
802                 error("%s", err_msg);
803         fprintf(stderr,
804                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
805         write_merge_state(remoteheads);
806         exit(1);
807 }
808
809 static const char merge_editor_comment[] =
810 N_("Please enter a commit message to explain why this merge is necessary,\n"
811    "especially if it merges an updated upstream into a topic branch.\n"
812    "\n"
813    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
814    "the commit.\n");
815
816 static void prepare_to_commit(struct commit_list *remoteheads)
817 {
818         struct strbuf msg = STRBUF_INIT;
819         strbuf_addbuf(&msg, &merge_msg);
820         strbuf_addch(&msg, '\n');
821         if (0 < option_edit)
822                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
823         write_merge_msg(&msg);
824         if (run_hook(get_index_file(), "prepare-commit-msg",
825                      git_path("MERGE_MSG"), "merge", NULL, NULL))
826                 abort_commit(remoteheads, NULL);
827         if (0 < option_edit) {
828                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
829                         abort_commit(remoteheads, NULL);
830         }
831         read_merge_msg(&msg);
832         stripspace(&msg, 0 < option_edit);
833         if (!msg.len)
834                 abort_commit(remoteheads, _("Empty commit message."));
835         strbuf_release(&merge_msg);
836         strbuf_addbuf(&merge_msg, &msg);
837         strbuf_release(&msg);
838 }
839
840 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
841 {
842         unsigned char result_tree[20], result_commit[20];
843         struct commit_list *parent = xmalloc(sizeof(*parent));
844
845         write_tree_trivial(result_tree);
846         printf(_("Wonderful.\n"));
847         parent->item = head;
848         parent->next = xmalloc(sizeof(*parent->next));
849         parent->next->item = remoteheads->item;
850         parent->next->next = NULL;
851         prepare_to_commit(remoteheads);
852         if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
853                         sign_commit))
854                 die(_("failed to write commit object"));
855         finish(head, remoteheads, result_commit, "In-index merge");
856         drop_save();
857         return 0;
858 }
859
860 static int finish_automerge(struct commit *head,
861                             int head_subsumed,
862                             struct commit_list *common,
863                             struct commit_list *remoteheads,
864                             unsigned char *result_tree,
865                             const char *wt_strategy)
866 {
867         struct commit_list *parents = NULL;
868         struct strbuf buf = STRBUF_INIT;
869         unsigned char result_commit[20];
870
871         free_commit_list(common);
872         parents = remoteheads;
873         if (!head_subsumed || fast_forward == FF_NO)
874                 commit_list_insert(head, &parents);
875         strbuf_addch(&merge_msg, '\n');
876         prepare_to_commit(remoteheads);
877         if (commit_tree(&merge_msg, result_tree, parents, result_commit,
878                         NULL, sign_commit))
879                 die(_("failed to write commit object"));
880         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
881         finish(head, remoteheads, result_commit, buf.buf);
882         strbuf_release(&buf);
883         drop_save();
884         return 0;
885 }
886
887 static int suggest_conflicts(int renormalizing)
888 {
889         const char *filename;
890         FILE *fp;
891         int pos;
892
893         filename = git_path("MERGE_MSG");
894         fp = fopen(filename, "a");
895         if (!fp)
896                 die_errno(_("Could not open '%s' for writing"), filename);
897         fprintf(fp, "\nConflicts:\n");
898         for (pos = 0; pos < active_nr; pos++) {
899                 const struct cache_entry *ce = active_cache[pos];
900
901                 if (ce_stage(ce)) {
902                         fprintf(fp, "\t%s\n", ce->name);
903                         while (pos + 1 < active_nr &&
904                                         !strcmp(ce->name,
905                                                 active_cache[pos + 1]->name))
906                                 pos++;
907                 }
908         }
909         fclose(fp);
910         rerere(allow_rerere_auto);
911         printf(_("Automatic merge failed; "
912                         "fix conflicts and then commit the result.\n"));
913         return 1;
914 }
915
916 static struct commit *is_old_style_invocation(int argc, const char **argv,
917                                               const unsigned char *head)
918 {
919         struct commit *second_token = NULL;
920         if (argc > 2) {
921                 unsigned char second_sha1[20];
922
923                 if (get_sha1(argv[1], second_sha1))
924                         return NULL;
925                 second_token = lookup_commit_reference_gently(second_sha1, 0);
926                 if (!second_token)
927                         die(_("'%s' is not a commit"), argv[1]);
928                 if (hashcmp(second_token->object.sha1, head))
929                         return NULL;
930         }
931         return second_token;
932 }
933
934 static int evaluate_result(void)
935 {
936         int cnt = 0;
937         struct rev_info rev;
938
939         /* Check how many files differ. */
940         init_revisions(&rev, "");
941         setup_revisions(0, NULL, &rev, NULL);
942         rev.diffopt.output_format |=
943                 DIFF_FORMAT_CALLBACK;
944         rev.diffopt.format_callback = count_diff_files;
945         rev.diffopt.format_callback_data = &cnt;
946         run_diff_files(&rev, 0);
947
948         /*
949          * Check how many unmerged entries are
950          * there.
951          */
952         cnt += count_unmerged_entries();
953
954         return cnt;
955 }
956
957 /*
958  * Pretend as if the user told us to merge with the remote-tracking
959  * branch we have for the upstream of the current branch
960  */
961 static int setup_with_upstream(const char ***argv)
962 {
963         struct branch *branch = branch_get(NULL);
964         int i;
965         const char **args;
966
967         if (!branch)
968                 die(_("No current branch."));
969         if (!branch->remote)
970                 die(_("No remote for the current branch."));
971         if (!branch->merge_nr)
972                 die(_("No default upstream defined for the current branch."));
973
974         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
975         for (i = 0; i < branch->merge_nr; i++) {
976                 if (!branch->merge[i]->dst)
977                         die(_("No remote-tracking branch for %s from %s"),
978                             branch->merge[i]->src, branch->remote_name);
979                 args[i] = branch->merge[i]->dst;
980         }
981         args[i] = NULL;
982         *argv = args;
983         return i;
984 }
985
986 static void write_merge_state(struct commit_list *remoteheads)
987 {
988         const char *filename;
989         int fd;
990         struct commit_list *j;
991         struct strbuf buf = STRBUF_INIT;
992
993         for (j = remoteheads; j; j = j->next) {
994                 unsigned const char *sha1;
995                 struct commit *c = j->item;
996                 if (c->util && merge_remote_util(c)->obj) {
997                         sha1 = merge_remote_util(c)->obj->sha1;
998                 } else {
999                         sha1 = c->object.sha1;
1000                 }
1001                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1002         }
1003         filename = git_path("MERGE_HEAD");
1004         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1005         if (fd < 0)
1006                 die_errno(_("Could not open '%s' for writing"), filename);
1007         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1008                 die_errno(_("Could not write to '%s'"), filename);
1009         close(fd);
1010         strbuf_addch(&merge_msg, '\n');
1011         write_merge_msg(&merge_msg);
1012
1013         filename = git_path("MERGE_MODE");
1014         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1015         if (fd < 0)
1016                 die_errno(_("Could not open '%s' for writing"), filename);
1017         strbuf_reset(&buf);
1018         if (fast_forward == FF_NO)
1019                 strbuf_addf(&buf, "no-ff");
1020         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1021                 die_errno(_("Could not write to '%s'"), filename);
1022         close(fd);
1023 }
1024
1025 static int default_edit_option(void)
1026 {
1027         static const char name[] = "GIT_MERGE_AUTOEDIT";
1028         const char *e = getenv(name);
1029         struct stat st_stdin, st_stdout;
1030
1031         if (have_message)
1032                 /* an explicit -m msg without --[no-]edit */
1033                 return 0;
1034
1035         if (e) {
1036                 int v = git_config_maybe_bool(name, e);
1037                 if (v < 0)
1038                         die("Bad value '%s' in environment '%s'", e, name);
1039                 return v;
1040         }
1041
1042         /* Use editor if stdin and stdout are the same and is a tty */
1043         return (!fstat(0, &st_stdin) &&
1044                 !fstat(1, &st_stdout) &&
1045                 isatty(0) && isatty(1) &&
1046                 st_stdin.st_dev == st_stdout.st_dev &&
1047                 st_stdin.st_ino == st_stdout.st_ino &&
1048                 st_stdin.st_mode == st_stdout.st_mode);
1049 }
1050
1051 static struct commit_list *collect_parents(struct commit *head_commit,
1052                                            int *head_subsumed,
1053                                            int argc, const char **argv)
1054 {
1055         int i;
1056         struct commit_list *remoteheads = NULL, *parents, *next;
1057         struct commit_list **remotes = &remoteheads;
1058
1059         if (head_commit)
1060                 remotes = &commit_list_insert(head_commit, remotes)->next;
1061         for (i = 0; i < argc; i++) {
1062                 struct commit *commit = get_merge_parent(argv[i]);
1063                 if (!commit)
1064                         help_unknown_ref(argv[i], "merge",
1065                                          "not something we can merge");
1066                 remotes = &commit_list_insert(commit, remotes)->next;
1067         }
1068         *remotes = NULL;
1069
1070         parents = reduce_heads(remoteheads);
1071
1072         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1073         for (remoteheads = NULL, remotes = &remoteheads;
1074              parents;
1075              parents = next) {
1076                 struct commit *commit = parents->item;
1077                 next = parents->next;
1078                 if (commit == head_commit)
1079                         *head_subsumed = 0;
1080                 else
1081                         remotes = &commit_list_insert(commit, remotes)->next;
1082         }
1083         return remoteheads;
1084 }
1085
1086 int cmd_merge(int argc, const char **argv, const char *prefix)
1087 {
1088         unsigned char result_tree[20];
1089         unsigned char stash[20];
1090         unsigned char head_sha1[20];
1091         struct commit *head_commit;
1092         struct strbuf buf = STRBUF_INIT;
1093         const char *head_arg;
1094         int flag, i, ret = 0, head_subsumed;
1095         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1096         struct commit_list *common = NULL;
1097         const char *best_strategy = NULL, *wt_strategy = NULL;
1098         struct commit_list *remoteheads, *p;
1099         void *branch_to_free;
1100
1101         if (argc == 2 && !strcmp(argv[1], "-h"))
1102                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1103
1104         /*
1105          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1106          * current branch.
1107          */
1108         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1109         if (branch && !prefixcmp(branch, "refs/heads/"))
1110                 branch += 11;
1111         if (!branch || is_null_sha1(head_sha1))
1112                 head_commit = NULL;
1113         else
1114                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1115
1116         git_config(git_merge_config, NULL);
1117
1118         if (branch_mergeoptions)
1119                 parse_branch_merge_options(branch_mergeoptions);
1120         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1121                         builtin_merge_usage, 0);
1122         if (shortlog_len < 0)
1123                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1124
1125         if (verbosity < 0 && show_progress == -1)
1126                 show_progress = 0;
1127
1128         if (abort_current_merge) {
1129                 int nargc = 2;
1130                 const char *nargv[] = {"reset", "--merge", NULL};
1131
1132                 if (!file_exists(git_path("MERGE_HEAD")))
1133                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1134
1135                 /* Invoke 'git reset --merge' */
1136                 ret = cmd_reset(nargc, nargv, prefix);
1137                 goto done;
1138         }
1139
1140         if (read_cache_unmerged())
1141                 die_resolve_conflict("merge");
1142
1143         if (file_exists(git_path("MERGE_HEAD"))) {
1144                 /*
1145                  * There is no unmerged entry, don't advise 'git
1146                  * add/rm <file>', just 'git commit'.
1147                  */
1148                 if (advice_resolve_conflict)
1149                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1150                                   "Please, commit your changes before you can merge."));
1151                 else
1152                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1153         }
1154         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1155                 if (advice_resolve_conflict)
1156                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1157                             "Please, commit your changes before you can merge."));
1158                 else
1159                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1160         }
1161         resolve_undo_clear();
1162
1163         if (verbosity < 0)
1164                 show_diffstat = 0;
1165
1166         if (squash) {
1167                 if (fast_forward == FF_NO)
1168                         die(_("You cannot combine --squash with --no-ff."));
1169                 option_commit = 0;
1170         }
1171
1172         if (!abort_current_merge) {
1173                 if (!argc) {
1174                         if (default_to_upstream)
1175                                 argc = setup_with_upstream(&argv);
1176                         else
1177                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1178                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1179                         argv[0] = "@{-1}";
1180         }
1181         if (!argc)
1182                 usage_with_options(builtin_merge_usage,
1183                         builtin_merge_options);
1184
1185         /*
1186          * This could be traditional "merge <msg> HEAD <commit>..."  and
1187          * the way we can tell it is to see if the second token is HEAD,
1188          * but some people might have misused the interface and used a
1189          * commit-ish that is the same as HEAD there instead.
1190          * Traditional format never would have "-m" so it is an
1191          * additional safety measure to check for it.
1192          */
1193
1194         if (!have_message && head_commit &&
1195             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1196                 strbuf_addstr(&merge_msg, argv[0]);
1197                 head_arg = argv[1];
1198                 argv += 2;
1199                 argc -= 2;
1200                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1201         } else if (!head_commit) {
1202                 struct commit *remote_head;
1203                 /*
1204                  * If the merged head is a valid one there is no reason
1205                  * to forbid "git merge" into a branch yet to be born.
1206                  * We do the same for "git pull".
1207                  */
1208                 if (argc != 1)
1209                         die(_("Can merge only exactly one commit into "
1210                                 "empty head"));
1211                 if (squash)
1212                         die(_("Squash commit into empty head not supported yet"));
1213                 if (fast_forward == FF_NO)
1214                         die(_("Non-fast-forward commit does not make sense into "
1215                             "an empty head"));
1216                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1217                 remote_head = remoteheads->item;
1218                 if (!remote_head)
1219                         die(_("%s - not something we can merge"), argv[0]);
1220                 read_empty(remote_head->object.sha1, 0);
1221                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1222                            NULL, 0, DIE_ON_ERR);
1223                 goto done;
1224         } else {
1225                 struct strbuf merge_names = STRBUF_INIT;
1226
1227                 /* We are invoked directly as the first-class UI. */
1228                 head_arg = "HEAD";
1229
1230                 /*
1231                  * All the rest are the commits being merged; prepare
1232                  * the standard merge summary message to be appended
1233                  * to the given message.
1234                  */
1235                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1236                 for (p = remoteheads; p; p = p->next)
1237                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1238
1239                 if (!have_message || shortlog_len) {
1240                         struct fmt_merge_msg_opts opts;
1241                         memset(&opts, 0, sizeof(opts));
1242                         opts.add_title = !have_message;
1243                         opts.shortlog_len = shortlog_len;
1244                         opts.credit_people = (0 < option_edit);
1245
1246                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1247                         if (merge_msg.len)
1248                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1249                 }
1250         }
1251
1252         if (!head_commit || !argc)
1253                 usage_with_options(builtin_merge_usage,
1254                         builtin_merge_options);
1255
1256         if (verify_signatures) {
1257                 for (p = remoteheads; p; p = p->next) {
1258                         struct commit *commit = p->item;
1259                         char hex[41];
1260                         struct signature_check signature_check;
1261                         memset(&signature_check, 0, sizeof(signature_check));
1262
1263                         check_commit_signature(commit, &signature_check);
1264
1265                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1266                         switch (signature_check.result) {
1267                         case 'G':
1268                                 break;
1269                         case 'U':
1270                                 die(_("Commit %s has an untrusted GPG signature, "
1271                                       "allegedly by %s."), hex, signature_check.signer);
1272                         case 'B':
1273                                 die(_("Commit %s has a bad GPG signature "
1274                                       "allegedly by %s."), hex, signature_check.signer);
1275                         default: /* 'N' */
1276                                 die(_("Commit %s does not have a GPG signature."), hex);
1277                         }
1278                         if (verbosity >= 0 && signature_check.result == 'G')
1279                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1280                                        hex, signature_check.signer);
1281
1282                         free(signature_check.gpg_output);
1283                         free(signature_check.gpg_status);
1284                         free(signature_check.signer);
1285                         free(signature_check.key);
1286                 }
1287         }
1288
1289         strbuf_addstr(&buf, "merge");
1290         for (p = remoteheads; p; p = p->next)
1291                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1292         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1293         strbuf_reset(&buf);
1294
1295         for (p = remoteheads; p; p = p->next) {
1296                 struct commit *commit = p->item;
1297                 strbuf_addf(&buf, "GITHEAD_%s",
1298                             sha1_to_hex(commit->object.sha1));
1299                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1300                 strbuf_reset(&buf);
1301                 if (fast_forward != FF_ONLY &&
1302                     merge_remote_util(commit) &&
1303                     merge_remote_util(commit)->obj &&
1304                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1305                         fast_forward = FF_NO;
1306         }
1307
1308         if (option_edit < 0)
1309                 option_edit = default_edit_option();
1310
1311         if (!use_strategies) {
1312                 if (!remoteheads)
1313                         ; /* already up-to-date */
1314                 else if (!remoteheads->next)
1315                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1316                 else
1317                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1318         }
1319
1320         for (i = 0; i < use_strategies_nr; i++) {
1321                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1322                         fast_forward = FF_NO;
1323                 if (use_strategies[i]->attr & NO_TRIVIAL)
1324                         allow_trivial = 0;
1325         }
1326
1327         if (!remoteheads)
1328                 ; /* already up-to-date */
1329         else if (!remoteheads->next)
1330                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1331         else {
1332                 struct commit_list *list = remoteheads;
1333                 commit_list_insert(head_commit, &list);
1334                 common = get_octopus_merge_bases(list);
1335                 free(list);
1336         }
1337
1338         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1339                    NULL, 0, DIE_ON_ERR);
1340
1341         if (remoteheads && !common)
1342                 ; /* No common ancestors found. We need a real merge. */
1343         else if (!remoteheads ||
1344                  (!remoteheads->next && !common->next &&
1345                   common->item == remoteheads->item)) {
1346                 /*
1347                  * If head can reach all the merge then we are up to date.
1348                  * but first the most common case of merging one remote.
1349                  */
1350                 finish_up_to_date("Already up-to-date.");
1351                 goto done;
1352         } else if (fast_forward != FF_NO && !remoteheads->next &&
1353                         !common->next &&
1354                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1355                 /* Again the most common case of merging one remote. */
1356                 struct strbuf msg = STRBUF_INIT;
1357                 struct commit *commit;
1358                 char hex[41];
1359
1360                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1361
1362                 if (verbosity >= 0)
1363                         printf(_("Updating %s..%s\n"),
1364                                 hex,
1365                                 find_unique_abbrev(remoteheads->item->object.sha1,
1366                                 DEFAULT_ABBREV));
1367                 strbuf_addstr(&msg, "Fast-forward");
1368                 if (have_message)
1369                         strbuf_addstr(&msg,
1370                                 " (no commit created; -m option ignored)");
1371                 commit = remoteheads->item;
1372                 if (!commit) {
1373                         ret = 1;
1374                         goto done;
1375                 }
1376
1377                 if (checkout_fast_forward(head_commit->object.sha1,
1378                                           commit->object.sha1,
1379                                           overwrite_ignore)) {
1380                         ret = 1;
1381                         goto done;
1382                 }
1383
1384                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1385                 drop_save();
1386                 goto done;
1387         } else if (!remoteheads->next && common->next)
1388                 ;
1389                 /*
1390                  * We are not doing octopus and not fast-forward.  Need
1391                  * a real merge.
1392                  */
1393         else if (!remoteheads->next && !common->next && option_commit) {
1394                 /*
1395                  * We are not doing octopus, not fast-forward, and have
1396                  * only one common.
1397                  */
1398                 refresh_cache(REFRESH_QUIET);
1399                 if (allow_trivial && fast_forward != FF_ONLY) {
1400                         /* See if it is really trivial. */
1401                         git_committer_info(IDENT_STRICT);
1402                         printf(_("Trying really trivial in-index merge...\n"));
1403                         if (!read_tree_trivial(common->item->object.sha1,
1404                                                head_commit->object.sha1,
1405                                                remoteheads->item->object.sha1)) {
1406                                 ret = merge_trivial(head_commit, remoteheads);
1407                                 goto done;
1408                         }
1409                         printf(_("Nope.\n"));
1410                 }
1411         } else {
1412                 /*
1413                  * An octopus.  If we can reach all the remote we are up
1414                  * to date.
1415                  */
1416                 int up_to_date = 1;
1417                 struct commit_list *j;
1418
1419                 for (j = remoteheads; j; j = j->next) {
1420                         struct commit_list *common_one;
1421
1422                         /*
1423                          * Here we *have* to calculate the individual
1424                          * merge_bases again, otherwise "git merge HEAD^
1425                          * HEAD^^" would be missed.
1426                          */
1427                         common_one = get_merge_bases(head_commit, j->item, 1);
1428                         if (hashcmp(common_one->item->object.sha1,
1429                                 j->item->object.sha1)) {
1430                                 up_to_date = 0;
1431                                 break;
1432                         }
1433                 }
1434                 if (up_to_date) {
1435                         finish_up_to_date("Already up-to-date. Yeeah!");
1436                         goto done;
1437                 }
1438         }
1439
1440         if (fast_forward == FF_ONLY)
1441                 die(_("Not possible to fast-forward, aborting."));
1442
1443         /* We are going to make a new commit. */
1444         git_committer_info(IDENT_STRICT);
1445
1446         /*
1447          * At this point, we need a real merge.  No matter what strategy
1448          * we use, it would operate on the index, possibly affecting the
1449          * working tree, and when resolved cleanly, have the desired
1450          * tree in the index -- this means that the index must be in
1451          * sync with the head commit.  The strategies are responsible
1452          * to ensure this.
1453          */
1454         if (use_strategies_nr == 1 ||
1455             /*
1456              * Stash away the local changes so that we can try more than one.
1457              */
1458             save_state(stash))
1459                 hashcpy(stash, null_sha1);
1460
1461         for (i = 0; i < use_strategies_nr; i++) {
1462                 int ret;
1463                 if (i) {
1464                         printf(_("Rewinding the tree to pristine...\n"));
1465                         restore_state(head_commit->object.sha1, stash);
1466                 }
1467                 if (use_strategies_nr != 1)
1468                         printf(_("Trying merge strategy %s...\n"),
1469                                 use_strategies[i]->name);
1470                 /*
1471                  * Remember which strategy left the state in the working
1472                  * tree.
1473                  */
1474                 wt_strategy = use_strategies[i]->name;
1475
1476                 ret = try_merge_strategy(use_strategies[i]->name,
1477                                          common, remoteheads,
1478                                          head_commit, head_arg);
1479                 if (!option_commit && !ret) {
1480                         merge_was_ok = 1;
1481                         /*
1482                          * This is necessary here just to avoid writing
1483                          * the tree, but later we will *not* exit with
1484                          * status code 1 because merge_was_ok is set.
1485                          */
1486                         ret = 1;
1487                 }
1488
1489                 if (ret) {
1490                         /*
1491                          * The backend exits with 1 when conflicts are
1492                          * left to be resolved, with 2 when it does not
1493                          * handle the given merge at all.
1494                          */
1495                         if (ret == 1) {
1496                                 int cnt = evaluate_result();
1497
1498                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1499                                         best_strategy = use_strategies[i]->name;
1500                                         best_cnt = cnt;
1501                                 }
1502                         }
1503                         if (merge_was_ok)
1504                                 break;
1505                         else
1506                                 continue;
1507                 }
1508
1509                 /* Automerge succeeded. */
1510                 write_tree_trivial(result_tree);
1511                 automerge_was_ok = 1;
1512                 break;
1513         }
1514
1515         /*
1516          * If we have a resulting tree, that means the strategy module
1517          * auto resolved the merge cleanly.
1518          */
1519         if (automerge_was_ok) {
1520                 ret = finish_automerge(head_commit, head_subsumed,
1521                                        common, remoteheads,
1522                                        result_tree, wt_strategy);
1523                 goto done;
1524         }
1525
1526         /*
1527          * Pick the result from the best strategy and have the user fix
1528          * it up.
1529          */
1530         if (!best_strategy) {
1531                 restore_state(head_commit->object.sha1, stash);
1532                 if (use_strategies_nr > 1)
1533                         fprintf(stderr,
1534                                 _("No merge strategy handled the merge.\n"));
1535                 else
1536                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1537                                 use_strategies[0]->name);
1538                 ret = 2;
1539                 goto done;
1540         } else if (best_strategy == wt_strategy)
1541                 ; /* We already have its result in the working tree. */
1542         else {
1543                 printf(_("Rewinding the tree to pristine...\n"));
1544                 restore_state(head_commit->object.sha1, stash);
1545                 printf(_("Using the %s to prepare resolving by hand.\n"),
1546                         best_strategy);
1547                 try_merge_strategy(best_strategy, common, remoteheads,
1548                                    head_commit, head_arg);
1549         }
1550
1551         if (squash)
1552                 finish(head_commit, remoteheads, NULL, NULL);
1553         else
1554                 write_merge_state(remoteheads);
1555
1556         if (merge_was_ok)
1557                 fprintf(stderr, _("Automatic merge went well; "
1558                         "stopped before committing as requested\n"));
1559         else
1560                 ret = suggest_conflicts(option_renormalize);
1561
1562 done:
1563         free(branch_to_free);
1564         return ret;
1565 }