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