Merge branch 'ep/shell-assign-and-export-vars' into maint
[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_in_full(fd, out.buf, out.len) != out.len)
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_le(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 (starts_with(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 (starts_with(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 (starts_with(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 && starts_with(k, "branch.") &&
574                 starts_with(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         } else if (!strcmp(k, "commit.gpgsign")) {
601                 sign_commit = git_config_bool(k, v) ? "" : NULL;
602                 return 0;
603         }
604
605         status = fmt_merge_msg_config(k, v, cb);
606         if (status)
607                 return status;
608         status = git_gpg_config(k, v, NULL);
609         if (status)
610                 return status;
611         return git_diff_ui_config(k, v, cb);
612 }
613
614 static int read_tree_trivial(unsigned char *common, unsigned char *head,
615                              unsigned char *one)
616 {
617         int i, nr_trees = 0;
618         struct tree *trees[MAX_UNPACK_TREES];
619         struct tree_desc t[MAX_UNPACK_TREES];
620         struct unpack_trees_options opts;
621
622         memset(&opts, 0, sizeof(opts));
623         opts.head_idx = 2;
624         opts.src_index = &the_index;
625         opts.dst_index = &the_index;
626         opts.update = 1;
627         opts.verbose_update = 1;
628         opts.trivial_merges_only = 1;
629         opts.merge = 1;
630         trees[nr_trees] = parse_tree_indirect(common);
631         if (!trees[nr_trees++])
632                 return -1;
633         trees[nr_trees] = parse_tree_indirect(head);
634         if (!trees[nr_trees++])
635                 return -1;
636         trees[nr_trees] = parse_tree_indirect(one);
637         if (!trees[nr_trees++])
638                 return -1;
639         opts.fn = threeway_merge;
640         cache_tree_free(&active_cache_tree);
641         for (i = 0; i < nr_trees; i++) {
642                 parse_tree(trees[i]);
643                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
644         }
645         if (unpack_trees(nr_trees, t, &opts))
646                 return -1;
647         return 0;
648 }
649
650 static void write_tree_trivial(unsigned char *sha1)
651 {
652         if (write_cache_as_tree(sha1, 0, NULL))
653                 die(_("git write-tree failed to write a tree"));
654 }
655
656 static int try_merge_strategy(const char *strategy, struct commit_list *common,
657                               struct commit_list *remoteheads,
658                               struct commit *head, const char *head_arg)
659 {
660         int index_fd;
661         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
662
663         index_fd = hold_locked_index(lock, 1);
664         refresh_cache(REFRESH_QUIET);
665         if (active_cache_changed &&
666                         (write_cache(index_fd, active_cache, active_nr) ||
667                          commit_locked_index(lock)))
668                 return error(_("Unable to write index."));
669         rollback_lock_file(lock);
670
671         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
672                 int clean, x;
673                 struct commit *result;
674                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
675                 int index_fd;
676                 struct commit_list *reversed = NULL;
677                 struct merge_options o;
678                 struct commit_list *j;
679
680                 if (remoteheads->next) {
681                         error(_("Not handling anything other than two heads merge."));
682                         return 2;
683                 }
684
685                 init_merge_options(&o);
686                 if (!strcmp(strategy, "subtree"))
687                         o.subtree_shift = "";
688
689                 o.renormalize = option_renormalize;
690                 o.show_rename_progress =
691                         show_progress == -1 ? isatty(2) : show_progress;
692
693                 for (x = 0; x < xopts_nr; x++)
694                         if (parse_merge_opt(&o, xopts[x]))
695                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
696
697                 o.branch1 = head_arg;
698                 o.branch2 = merge_remote_util(remoteheads->item)->name;
699
700                 for (j = common; j; j = j->next)
701                         commit_list_insert(j->item, &reversed);
702
703                 index_fd = hold_locked_index(lock, 1);
704                 clean = merge_recursive(&o, head,
705                                 remoteheads->item, reversed, &result);
706                 if (active_cache_changed &&
707                                 (write_cache(index_fd, active_cache, active_nr) ||
708                                  commit_locked_index(lock)))
709                         die (_("unable to write %s"), get_index_file());
710                 rollback_lock_file(lock);
711                 return clean ? 0 : 1;
712         } else {
713                 return try_merge_command(strategy, xopts_nr, xopts,
714                                                 common, head_arg, remoteheads);
715         }
716 }
717
718 static void count_diff_files(struct diff_queue_struct *q,
719                              struct diff_options *opt, void *data)
720 {
721         int *count = data;
722
723         (*count) += q->nr;
724 }
725
726 static int count_unmerged_entries(void)
727 {
728         int i, ret = 0;
729
730         for (i = 0; i < active_nr; i++)
731                 if (ce_stage(active_cache[i]))
732                         ret++;
733
734         return ret;
735 }
736
737 static void split_merge_strategies(const char *string, struct strategy **list,
738                                    int *nr, int *alloc)
739 {
740         char *p, *q, *buf;
741
742         if (!string)
743                 return;
744
745         buf = xstrdup(string);
746         q = buf;
747         for (;;) {
748                 p = strchr(q, ' ');
749                 if (!p) {
750                         ALLOC_GROW(*list, *nr + 1, *alloc);
751                         (*list)[(*nr)++].name = xstrdup(q);
752                         free(buf);
753                         return;
754                 } else {
755                         *p = '\0';
756                         ALLOC_GROW(*list, *nr + 1, *alloc);
757                         (*list)[(*nr)++].name = xstrdup(q);
758                         q = ++p;
759                 }
760         }
761 }
762
763 static void add_strategies(const char *string, unsigned attr)
764 {
765         struct strategy *list = NULL;
766         int list_alloc = 0, list_nr = 0, i;
767
768         memset(&list, 0, sizeof(list));
769         split_merge_strategies(string, &list, &list_nr, &list_alloc);
770         if (list) {
771                 for (i = 0; i < list_nr; i++)
772                         append_strategy(get_strategy(list[i].name));
773                 return;
774         }
775         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
776                 if (all_strategy[i].attr & attr)
777                         append_strategy(&all_strategy[i]);
778
779 }
780
781 static void write_merge_msg(struct strbuf *msg)
782 {
783         const char *filename = git_path("MERGE_MSG");
784         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
785         if (fd < 0)
786                 die_errno(_("Could not open '%s' for writing"),
787                           filename);
788         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
789                 die_errno(_("Could not write to '%s'"), filename);
790         close(fd);
791 }
792
793 static void read_merge_msg(struct strbuf *msg)
794 {
795         const char *filename = git_path("MERGE_MSG");
796         strbuf_reset(msg);
797         if (strbuf_read_file(msg, filename, 0) < 0)
798                 die_errno(_("Could not read from '%s'"), filename);
799 }
800
801 static void write_merge_state(struct commit_list *);
802 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
803 {
804         if (err_msg)
805                 error("%s", err_msg);
806         fprintf(stderr,
807                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
808         write_merge_state(remoteheads);
809         exit(1);
810 }
811
812 static const char merge_editor_comment[] =
813 N_("Please enter a commit message to explain why this merge is necessary,\n"
814    "especially if it merges an updated upstream into a topic branch.\n"
815    "\n"
816    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
817    "the commit.\n");
818
819 static void prepare_to_commit(struct commit_list *remoteheads)
820 {
821         struct strbuf msg = STRBUF_INIT;
822         strbuf_addbuf(&msg, &merge_msg);
823         strbuf_addch(&msg, '\n');
824         if (0 < option_edit)
825                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
826         write_merge_msg(&msg);
827         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
828                             git_path("MERGE_MSG"), "merge", NULL))
829                 abort_commit(remoteheads, NULL);
830         if (0 < option_edit) {
831                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
832                         abort_commit(remoteheads, NULL);
833         }
834         read_merge_msg(&msg);
835         stripspace(&msg, 0 < option_edit);
836         if (!msg.len)
837                 abort_commit(remoteheads, _("Empty commit message."));
838         strbuf_release(&merge_msg);
839         strbuf_addbuf(&merge_msg, &msg);
840         strbuf_release(&msg);
841 }
842
843 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
844 {
845         unsigned char result_tree[20], result_commit[20];
846         struct commit_list *parent = xmalloc(sizeof(*parent));
847
848         write_tree_trivial(result_tree);
849         printf(_("Wonderful.\n"));
850         parent->item = head;
851         parent->next = xmalloc(sizeof(*parent->next));
852         parent->next->item = remoteheads->item;
853         parent->next->next = NULL;
854         prepare_to_commit(remoteheads);
855         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parent,
856                         result_commit, NULL, sign_commit))
857                 die(_("failed to write commit object"));
858         finish(head, remoteheads, result_commit, "In-index merge");
859         drop_save();
860         return 0;
861 }
862
863 static int finish_automerge(struct commit *head,
864                             int head_subsumed,
865                             struct commit_list *common,
866                             struct commit_list *remoteheads,
867                             unsigned char *result_tree,
868                             const char *wt_strategy)
869 {
870         struct commit_list *parents = NULL;
871         struct strbuf buf = STRBUF_INIT;
872         unsigned char result_commit[20];
873
874         free_commit_list(common);
875         parents = remoteheads;
876         if (!head_subsumed || fast_forward == FF_NO)
877                 commit_list_insert(head, &parents);
878         strbuf_addch(&merge_msg, '\n');
879         prepare_to_commit(remoteheads);
880         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
881                         result_commit, NULL, sign_commit))
882                 die(_("failed to write commit object"));
883         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
884         finish(head, remoteheads, result_commit, buf.buf);
885         strbuf_release(&buf);
886         drop_save();
887         return 0;
888 }
889
890 static int suggest_conflicts(int renormalizing)
891 {
892         const char *filename;
893         FILE *fp;
894         int pos;
895
896         filename = git_path("MERGE_MSG");
897         fp = fopen(filename, "a");
898         if (!fp)
899                 die_errno(_("Could not open '%s' for writing"), filename);
900         fprintf(fp, "\nConflicts:\n");
901         for (pos = 0; pos < active_nr; pos++) {
902                 const struct cache_entry *ce = active_cache[pos];
903
904                 if (ce_stage(ce)) {
905                         fprintf(fp, "\t%s\n", ce->name);
906                         while (pos + 1 < active_nr &&
907                                         !strcmp(ce->name,
908                                                 active_cache[pos + 1]->name))
909                                 pos++;
910                 }
911         }
912         fclose(fp);
913         rerere(allow_rerere_auto);
914         printf(_("Automatic merge failed; "
915                         "fix conflicts and then commit the result.\n"));
916         return 1;
917 }
918
919 static struct commit *is_old_style_invocation(int argc, const char **argv,
920                                               const unsigned char *head)
921 {
922         struct commit *second_token = NULL;
923         if (argc > 2) {
924                 unsigned char second_sha1[20];
925
926                 if (get_sha1(argv[1], second_sha1))
927                         return NULL;
928                 second_token = lookup_commit_reference_gently(second_sha1, 0);
929                 if (!second_token)
930                         die(_("'%s' is not a commit"), argv[1]);
931                 if (hashcmp(second_token->object.sha1, head))
932                         return NULL;
933         }
934         return second_token;
935 }
936
937 static int evaluate_result(void)
938 {
939         int cnt = 0;
940         struct rev_info rev;
941
942         /* Check how many files differ. */
943         init_revisions(&rev, "");
944         setup_revisions(0, NULL, &rev, NULL);
945         rev.diffopt.output_format |=
946                 DIFF_FORMAT_CALLBACK;
947         rev.diffopt.format_callback = count_diff_files;
948         rev.diffopt.format_callback_data = &cnt;
949         run_diff_files(&rev, 0);
950
951         /*
952          * Check how many unmerged entries are
953          * there.
954          */
955         cnt += count_unmerged_entries();
956
957         return cnt;
958 }
959
960 /*
961  * Pretend as if the user told us to merge with the remote-tracking
962  * branch we have for the upstream of the current branch
963  */
964 static int setup_with_upstream(const char ***argv)
965 {
966         struct branch *branch = branch_get(NULL);
967         int i;
968         const char **args;
969
970         if (!branch)
971                 die(_("No current branch."));
972         if (!branch->remote)
973                 die(_("No remote for the current branch."));
974         if (!branch->merge_nr)
975                 die(_("No default upstream defined for the current branch."));
976
977         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
978         for (i = 0; i < branch->merge_nr; i++) {
979                 if (!branch->merge[i]->dst)
980                         die(_("No remote-tracking branch for %s from %s"),
981                             branch->merge[i]->src, branch->remote_name);
982                 args[i] = branch->merge[i]->dst;
983         }
984         args[i] = NULL;
985         *argv = args;
986         return i;
987 }
988
989 static void write_merge_state(struct commit_list *remoteheads)
990 {
991         const char *filename;
992         int fd;
993         struct commit_list *j;
994         struct strbuf buf = STRBUF_INIT;
995
996         for (j = remoteheads; j; j = j->next) {
997                 unsigned const char *sha1;
998                 struct commit *c = j->item;
999                 if (c->util && merge_remote_util(c)->obj) {
1000                         sha1 = merge_remote_util(c)->obj->sha1;
1001                 } else {
1002                         sha1 = c->object.sha1;
1003                 }
1004                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1005         }
1006         filename = git_path("MERGE_HEAD");
1007         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1008         if (fd < 0)
1009                 die_errno(_("Could not open '%s' for writing"), filename);
1010         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1011                 die_errno(_("Could not write to '%s'"), filename);
1012         close(fd);
1013         strbuf_addch(&merge_msg, '\n');
1014         write_merge_msg(&merge_msg);
1015
1016         filename = git_path("MERGE_MODE");
1017         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1018         if (fd < 0)
1019                 die_errno(_("Could not open '%s' for writing"), filename);
1020         strbuf_reset(&buf);
1021         if (fast_forward == FF_NO)
1022                 strbuf_addf(&buf, "no-ff");
1023         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1024                 die_errno(_("Could not write to '%s'"), filename);
1025         close(fd);
1026 }
1027
1028 static int default_edit_option(void)
1029 {
1030         static const char name[] = "GIT_MERGE_AUTOEDIT";
1031         const char *e = getenv(name);
1032         struct stat st_stdin, st_stdout;
1033
1034         if (have_message)
1035                 /* an explicit -m msg without --[no-]edit */
1036                 return 0;
1037
1038         if (e) {
1039                 int v = git_config_maybe_bool(name, e);
1040                 if (v < 0)
1041                         die("Bad value '%s' in environment '%s'", e, name);
1042                 return v;
1043         }
1044
1045         /* Use editor if stdin and stdout are the same and is a tty */
1046         return (!fstat(0, &st_stdin) &&
1047                 !fstat(1, &st_stdout) &&
1048                 isatty(0) && isatty(1) &&
1049                 st_stdin.st_dev == st_stdout.st_dev &&
1050                 st_stdin.st_ino == st_stdout.st_ino &&
1051                 st_stdin.st_mode == st_stdout.st_mode);
1052 }
1053
1054 static struct commit_list *collect_parents(struct commit *head_commit,
1055                                            int *head_subsumed,
1056                                            int argc, const char **argv)
1057 {
1058         int i;
1059         struct commit_list *remoteheads = NULL, *parents, *next;
1060         struct commit_list **remotes = &remoteheads;
1061
1062         if (head_commit)
1063                 remotes = &commit_list_insert(head_commit, remotes)->next;
1064         for (i = 0; i < argc; i++) {
1065                 struct commit *commit = get_merge_parent(argv[i]);
1066                 if (!commit)
1067                         help_unknown_ref(argv[i], "merge",
1068                                          "not something we can merge");
1069                 remotes = &commit_list_insert(commit, remotes)->next;
1070         }
1071         *remotes = NULL;
1072
1073         parents = reduce_heads(remoteheads);
1074
1075         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1076         for (remoteheads = NULL, remotes = &remoteheads;
1077              parents;
1078              parents = next) {
1079                 struct commit *commit = parents->item;
1080                 next = parents->next;
1081                 if (commit == head_commit)
1082                         *head_subsumed = 0;
1083                 else
1084                         remotes = &commit_list_insert(commit, remotes)->next;
1085         }
1086         return remoteheads;
1087 }
1088
1089 int cmd_merge(int argc, const char **argv, const char *prefix)
1090 {
1091         unsigned char result_tree[20];
1092         unsigned char stash[20];
1093         unsigned char head_sha1[20];
1094         struct commit *head_commit;
1095         struct strbuf buf = STRBUF_INIT;
1096         const char *head_arg;
1097         int flag, i, ret = 0, head_subsumed;
1098         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1099         struct commit_list *common = NULL;
1100         const char *best_strategy = NULL, *wt_strategy = NULL;
1101         struct commit_list *remoteheads, *p;
1102         void *branch_to_free;
1103
1104         if (argc == 2 && !strcmp(argv[1], "-h"))
1105                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1106
1107         /*
1108          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1109          * current branch.
1110          */
1111         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1112         if (branch && starts_with(branch, "refs/heads/"))
1113                 branch += 11;
1114         if (!branch || is_null_sha1(head_sha1))
1115                 head_commit = NULL;
1116         else
1117                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1118
1119         git_config(git_merge_config, NULL);
1120
1121         if (branch_mergeoptions)
1122                 parse_branch_merge_options(branch_mergeoptions);
1123         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1124                         builtin_merge_usage, 0);
1125         if (shortlog_len < 0)
1126                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1127
1128         if (verbosity < 0 && show_progress == -1)
1129                 show_progress = 0;
1130
1131         if (abort_current_merge) {
1132                 int nargc = 2;
1133                 const char *nargv[] = {"reset", "--merge", NULL};
1134
1135                 if (!file_exists(git_path("MERGE_HEAD")))
1136                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1137
1138                 /* Invoke 'git reset --merge' */
1139                 ret = cmd_reset(nargc, nargv, prefix);
1140                 goto done;
1141         }
1142
1143         if (read_cache_unmerged())
1144                 die_resolve_conflict("merge");
1145
1146         if (file_exists(git_path("MERGE_HEAD"))) {
1147                 /*
1148                  * There is no unmerged entry, don't advise 'git
1149                  * add/rm <file>', just 'git commit'.
1150                  */
1151                 if (advice_resolve_conflict)
1152                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1153                                   "Please, commit your changes before you can merge."));
1154                 else
1155                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1156         }
1157         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1158                 if (advice_resolve_conflict)
1159                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1160                             "Please, commit your changes before you can merge."));
1161                 else
1162                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1163         }
1164         resolve_undo_clear();
1165
1166         if (verbosity < 0)
1167                 show_diffstat = 0;
1168
1169         if (squash) {
1170                 if (fast_forward == FF_NO)
1171                         die(_("You cannot combine --squash with --no-ff."));
1172                 option_commit = 0;
1173         }
1174
1175         if (!abort_current_merge) {
1176                 if (!argc) {
1177                         if (default_to_upstream)
1178                                 argc = setup_with_upstream(&argv);
1179                         else
1180                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1181                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1182                         argv[0] = "@{-1}";
1183         }
1184         if (!argc)
1185                 usage_with_options(builtin_merge_usage,
1186                         builtin_merge_options);
1187
1188         /*
1189          * This could be traditional "merge <msg> HEAD <commit>..."  and
1190          * the way we can tell it is to see if the second token is HEAD,
1191          * but some people might have misused the interface and used a
1192          * commit-ish that is the same as HEAD there instead.
1193          * Traditional format never would have "-m" so it is an
1194          * additional safety measure to check for it.
1195          */
1196
1197         if (!have_message && head_commit &&
1198             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1199                 strbuf_addstr(&merge_msg, argv[0]);
1200                 head_arg = argv[1];
1201                 argv += 2;
1202                 argc -= 2;
1203                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1204         } else if (!head_commit) {
1205                 struct commit *remote_head;
1206                 /*
1207                  * If the merged head is a valid one there is no reason
1208                  * to forbid "git merge" into a branch yet to be born.
1209                  * We do the same for "git pull".
1210                  */
1211                 if (argc != 1)
1212                         die(_("Can merge only exactly one commit into "
1213                                 "empty head"));
1214                 if (squash)
1215                         die(_("Squash commit into empty head not supported yet"));
1216                 if (fast_forward == FF_NO)
1217                         die(_("Non-fast-forward commit does not make sense into "
1218                             "an empty head"));
1219                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1220                 remote_head = remoteheads->item;
1221                 if (!remote_head)
1222                         die(_("%s - not something we can merge"), argv[0]);
1223                 read_empty(remote_head->object.sha1, 0);
1224                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1225                            NULL, 0, DIE_ON_ERR);
1226                 goto done;
1227         } else {
1228                 struct strbuf merge_names = STRBUF_INIT;
1229
1230                 /* We are invoked directly as the first-class UI. */
1231                 head_arg = "HEAD";
1232
1233                 /*
1234                  * All the rest are the commits being merged; prepare
1235                  * the standard merge summary message to be appended
1236                  * to the given message.
1237                  */
1238                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1239                 for (p = remoteheads; p; p = p->next)
1240                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1241
1242                 if (!have_message || shortlog_len) {
1243                         struct fmt_merge_msg_opts opts;
1244                         memset(&opts, 0, sizeof(opts));
1245                         opts.add_title = !have_message;
1246                         opts.shortlog_len = shortlog_len;
1247                         opts.credit_people = (0 < option_edit);
1248
1249                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1250                         if (merge_msg.len)
1251                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1252                 }
1253         }
1254
1255         if (!head_commit || !argc)
1256                 usage_with_options(builtin_merge_usage,
1257                         builtin_merge_options);
1258
1259         if (verify_signatures) {
1260                 for (p = remoteheads; p; p = p->next) {
1261                         struct commit *commit = p->item;
1262                         char hex[41];
1263                         struct signature_check signature_check;
1264                         memset(&signature_check, 0, sizeof(signature_check));
1265
1266                         check_commit_signature(commit, &signature_check);
1267
1268                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1269                         switch (signature_check.result) {
1270                         case 'G':
1271                                 break;
1272                         case 'U':
1273                                 die(_("Commit %s has an untrusted GPG signature, "
1274                                       "allegedly by %s."), hex, signature_check.signer);
1275                         case 'B':
1276                                 die(_("Commit %s has a bad GPG signature "
1277                                       "allegedly by %s."), hex, signature_check.signer);
1278                         default: /* 'N' */
1279                                 die(_("Commit %s does not have a GPG signature."), hex);
1280                         }
1281                         if (verbosity >= 0 && signature_check.result == 'G')
1282                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1283                                        hex, signature_check.signer);
1284
1285                         free(signature_check.gpg_output);
1286                         free(signature_check.gpg_status);
1287                         free(signature_check.signer);
1288                         free(signature_check.key);
1289                 }
1290         }
1291
1292         strbuf_addstr(&buf, "merge");
1293         for (p = remoteheads; p; p = p->next)
1294                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1295         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1296         strbuf_reset(&buf);
1297
1298         for (p = remoteheads; p; p = p->next) {
1299                 struct commit *commit = p->item;
1300                 strbuf_addf(&buf, "GITHEAD_%s",
1301                             sha1_to_hex(commit->object.sha1));
1302                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1303                 strbuf_reset(&buf);
1304                 if (fast_forward != FF_ONLY &&
1305                     merge_remote_util(commit) &&
1306                     merge_remote_util(commit)->obj &&
1307                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1308                         fast_forward = FF_NO;
1309         }
1310
1311         if (option_edit < 0)
1312                 option_edit = default_edit_option();
1313
1314         if (!use_strategies) {
1315                 if (!remoteheads)
1316                         ; /* already up-to-date */
1317                 else if (!remoteheads->next)
1318                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1319                 else
1320                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1321         }
1322
1323         for (i = 0; i < use_strategies_nr; i++) {
1324                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1325                         fast_forward = FF_NO;
1326                 if (use_strategies[i]->attr & NO_TRIVIAL)
1327                         allow_trivial = 0;
1328         }
1329
1330         if (!remoteheads)
1331                 ; /* already up-to-date */
1332         else if (!remoteheads->next)
1333                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1334         else {
1335                 struct commit_list *list = remoteheads;
1336                 commit_list_insert(head_commit, &list);
1337                 common = get_octopus_merge_bases(list);
1338                 free(list);
1339         }
1340
1341         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1342                    NULL, 0, DIE_ON_ERR);
1343
1344         if (remoteheads && !common)
1345                 ; /* No common ancestors found. We need a real merge. */
1346         else if (!remoteheads ||
1347                  (!remoteheads->next && !common->next &&
1348                   common->item == remoteheads->item)) {
1349                 /*
1350                  * If head can reach all the merge then we are up to date.
1351                  * but first the most common case of merging one remote.
1352                  */
1353                 finish_up_to_date("Already up-to-date.");
1354                 goto done;
1355         } else if (fast_forward != FF_NO && !remoteheads->next &&
1356                         !common->next &&
1357                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1358                 /* Again the most common case of merging one remote. */
1359                 struct strbuf msg = STRBUF_INIT;
1360                 struct commit *commit;
1361                 char hex[41];
1362
1363                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1364
1365                 if (verbosity >= 0)
1366                         printf(_("Updating %s..%s\n"),
1367                                 hex,
1368                                 find_unique_abbrev(remoteheads->item->object.sha1,
1369                                 DEFAULT_ABBREV));
1370                 strbuf_addstr(&msg, "Fast-forward");
1371                 if (have_message)
1372                         strbuf_addstr(&msg,
1373                                 " (no commit created; -m option ignored)");
1374                 commit = remoteheads->item;
1375                 if (!commit) {
1376                         ret = 1;
1377                         goto done;
1378                 }
1379
1380                 if (checkout_fast_forward(head_commit->object.sha1,
1381                                           commit->object.sha1,
1382                                           overwrite_ignore)) {
1383                         ret = 1;
1384                         goto done;
1385                 }
1386
1387                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1388                 drop_save();
1389                 goto done;
1390         } else if (!remoteheads->next && common->next)
1391                 ;
1392                 /*
1393                  * We are not doing octopus and not fast-forward.  Need
1394                  * a real merge.
1395                  */
1396         else if (!remoteheads->next && !common->next && option_commit) {
1397                 /*
1398                  * We are not doing octopus, not fast-forward, and have
1399                  * only one common.
1400                  */
1401                 refresh_cache(REFRESH_QUIET);
1402                 if (allow_trivial && fast_forward != FF_ONLY) {
1403                         /* See if it is really trivial. */
1404                         git_committer_info(IDENT_STRICT);
1405                         printf(_("Trying really trivial in-index merge...\n"));
1406                         if (!read_tree_trivial(common->item->object.sha1,
1407                                                head_commit->object.sha1,
1408                                                remoteheads->item->object.sha1)) {
1409                                 ret = merge_trivial(head_commit, remoteheads);
1410                                 goto done;
1411                         }
1412                         printf(_("Nope.\n"));
1413                 }
1414         } else {
1415                 /*
1416                  * An octopus.  If we can reach all the remote we are up
1417                  * to date.
1418                  */
1419                 int up_to_date = 1;
1420                 struct commit_list *j;
1421
1422                 for (j = remoteheads; j; j = j->next) {
1423                         struct commit_list *common_one;
1424
1425                         /*
1426                          * Here we *have* to calculate the individual
1427                          * merge_bases again, otherwise "git merge HEAD^
1428                          * HEAD^^" would be missed.
1429                          */
1430                         common_one = get_merge_bases(head_commit, j->item, 1);
1431                         if (hashcmp(common_one->item->object.sha1,
1432                                 j->item->object.sha1)) {
1433                                 up_to_date = 0;
1434                                 break;
1435                         }
1436                 }
1437                 if (up_to_date) {
1438                         finish_up_to_date("Already up-to-date. Yeeah!");
1439                         goto done;
1440                 }
1441         }
1442
1443         if (fast_forward == FF_ONLY)
1444                 die(_("Not possible to fast-forward, aborting."));
1445
1446         /* We are going to make a new commit. */
1447         git_committer_info(IDENT_STRICT);
1448
1449         /*
1450          * At this point, we need a real merge.  No matter what strategy
1451          * we use, it would operate on the index, possibly affecting the
1452          * working tree, and when resolved cleanly, have the desired
1453          * tree in the index -- this means that the index must be in
1454          * sync with the head commit.  The strategies are responsible
1455          * to ensure this.
1456          */
1457         if (use_strategies_nr == 1 ||
1458             /*
1459              * Stash away the local changes so that we can try more than one.
1460              */
1461             save_state(stash))
1462                 hashcpy(stash, null_sha1);
1463
1464         for (i = 0; i < use_strategies_nr; i++) {
1465                 int ret;
1466                 if (i) {
1467                         printf(_("Rewinding the tree to pristine...\n"));
1468                         restore_state(head_commit->object.sha1, stash);
1469                 }
1470                 if (use_strategies_nr != 1)
1471                         printf(_("Trying merge strategy %s...\n"),
1472                                 use_strategies[i]->name);
1473                 /*
1474                  * Remember which strategy left the state in the working
1475                  * tree.
1476                  */
1477                 wt_strategy = use_strategies[i]->name;
1478
1479                 ret = try_merge_strategy(use_strategies[i]->name,
1480                                          common, remoteheads,
1481                                          head_commit, head_arg);
1482                 if (!option_commit && !ret) {
1483                         merge_was_ok = 1;
1484                         /*
1485                          * This is necessary here just to avoid writing
1486                          * the tree, but later we will *not* exit with
1487                          * status code 1 because merge_was_ok is set.
1488                          */
1489                         ret = 1;
1490                 }
1491
1492                 if (ret) {
1493                         /*
1494                          * The backend exits with 1 when conflicts are
1495                          * left to be resolved, with 2 when it does not
1496                          * handle the given merge at all.
1497                          */
1498                         if (ret == 1) {
1499                                 int cnt = evaluate_result();
1500
1501                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1502                                         best_strategy = use_strategies[i]->name;
1503                                         best_cnt = cnt;
1504                                 }
1505                         }
1506                         if (merge_was_ok)
1507                                 break;
1508                         else
1509                                 continue;
1510                 }
1511
1512                 /* Automerge succeeded. */
1513                 write_tree_trivial(result_tree);
1514                 automerge_was_ok = 1;
1515                 break;
1516         }
1517
1518         /*
1519          * If we have a resulting tree, that means the strategy module
1520          * auto resolved the merge cleanly.
1521          */
1522         if (automerge_was_ok) {
1523                 ret = finish_automerge(head_commit, head_subsumed,
1524                                        common, remoteheads,
1525                                        result_tree, wt_strategy);
1526                 goto done;
1527         }
1528
1529         /*
1530          * Pick the result from the best strategy and have the user fix
1531          * it up.
1532          */
1533         if (!best_strategy) {
1534                 restore_state(head_commit->object.sha1, stash);
1535                 if (use_strategies_nr > 1)
1536                         fprintf(stderr,
1537                                 _("No merge strategy handled the merge.\n"));
1538                 else
1539                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1540                                 use_strategies[0]->name);
1541                 ret = 2;
1542                 goto done;
1543         } else if (best_strategy == wt_strategy)
1544                 ; /* We already have its result in the working tree. */
1545         else {
1546                 printf(_("Rewinding the tree to pristine...\n"));
1547                 restore_state(head_commit->object.sha1, stash);
1548                 printf(_("Using the %s to prepare resolving by hand.\n"),
1549                         best_strategy);
1550                 try_merge_strategy(best_strategy, common, remoteheads,
1551                                    head_commit, head_arg);
1552         }
1553
1554         if (squash)
1555                 finish(head_commit, remoteheads, NULL, NULL);
1556         else
1557                 write_merge_state(remoteheads);
1558
1559         if (merge_was_ok)
1560                 fprintf(stderr, _("Automatic merge went well; "
1561                         "stopped before committing as requested\n"));
1562         else
1563                 ret = suggest_conflicts(option_renormalize);
1564
1565 done:
1566         free(branch_to_free);
1567         return ret;
1568 }