Merge branch 'maint-1.6.1' into maint-1.6.2
[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
28 #define DEFAULT_TWOHEAD (1<<0)
29 #define DEFAULT_OCTOPUS (1<<1)
30 #define NO_FAST_FORWARD (1<<2)
31 #define NO_TRIVIAL      (1<<3)
32
33 struct strategy {
34         const char *name;
35         unsigned attr;
36 };
37
38 static const char * const builtin_merge_usage[] = {
39         "git merge [options] <remote>...",
40         "git merge [options] <msg> HEAD <remote>",
41         NULL
42 };
43
44 static int show_diffstat = 1, option_log, squash;
45 static int option_commit = 1, allow_fast_forward = 1;
46 static int allow_trivial = 1, have_message;
47 static struct strbuf merge_msg;
48 static struct commit_list *remoteheads;
49 static unsigned char head[20], stash[20];
50 static struct strategy **use_strategies;
51 static size_t use_strategies_nr, use_strategies_alloc;
52 static const char *branch;
53 static int verbosity;
54
55 static struct strategy all_strategy[] = {
56         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
57         { "octopus",    DEFAULT_OCTOPUS },
58         { "resolve",    0 },
59         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
60         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
61 };
62
63 static const char *pull_twohead, *pull_octopus;
64
65 static int option_parse_message(const struct option *opt,
66                                 const char *arg, int unset)
67 {
68         struct strbuf *buf = opt->value;
69
70         if (unset)
71                 strbuf_setlen(buf, 0);
72         else if (arg) {
73                 strbuf_addf(buf, "%s\n\n", arg);
74                 have_message = 1;
75         } else
76                 return error("switch `m' requires a value");
77         return 0;
78 }
79
80 static struct strategy *get_strategy(const char *name)
81 {
82         int i;
83         struct strategy *ret;
84         static struct cmdnames main_cmds, other_cmds;
85         static int loaded;
86
87         if (!name)
88                 return NULL;
89
90         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
91                 if (!strcmp(name, all_strategy[i].name))
92                         return &all_strategy[i];
93
94         if (!loaded) {
95                 struct cmdnames not_strategies;
96                 loaded = 1;
97
98                 memset(&not_strategies, 0, sizeof(struct cmdnames));
99                 load_command_list("git-merge-", &main_cmds, &other_cmds);
100                 for (i = 0; i < main_cmds.cnt; i++) {
101                         int j, found = 0;
102                         struct cmdname *ent = main_cmds.names[i];
103                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
104                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
105                                                 && !all_strategy[j].name[ent->len])
106                                         found = 1;
107                         if (!found)
108                                 add_cmdname(&not_strategies, ent->name, ent->len);
109                         exclude_cmds(&main_cmds, &not_strategies);
110                 }
111         }
112         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
113                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
114                 fprintf(stderr, "Available strategies are:");
115                 for (i = 0; i < main_cmds.cnt; i++)
116                         fprintf(stderr, " %s", main_cmds.names[i]->name);
117                 fprintf(stderr, ".\n");
118                 if (other_cmds.cnt) {
119                         fprintf(stderr, "Available custom strategies are:");
120                         for (i = 0; i < other_cmds.cnt; i++)
121                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
122                         fprintf(stderr, ".\n");
123                 }
124                 exit(1);
125         }
126
127         ret = xcalloc(1, sizeof(struct strategy));
128         ret->name = xstrdup(name);
129         return ret;
130 }
131
132 static void append_strategy(struct strategy *s)
133 {
134         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
135         use_strategies[use_strategies_nr++] = s;
136 }
137
138 static int option_parse_strategy(const struct option *opt,
139                                  const char *name, int unset)
140 {
141         if (unset)
142                 return 0;
143
144         append_strategy(get_strategy(name));
145         return 0;
146 }
147
148 static int option_parse_n(const struct option *opt,
149                           const char *arg, int unset)
150 {
151         show_diffstat = unset;
152         return 0;
153 }
154
155 static struct option builtin_merge_options[] = {
156         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
157                 "do not show a diffstat at the end of the merge",
158                 PARSE_OPT_NOARG, option_parse_n },
159         OPT_BOOLEAN(0, "stat", &show_diffstat,
160                 "show a diffstat at the end of the merge"),
161         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
162         OPT_BOOLEAN(0, "log", &option_log,
163                 "add list of one-line log to merge commit message"),
164         OPT_BOOLEAN(0, "squash", &squash,
165                 "create a single commit instead of doing a merge"),
166         OPT_BOOLEAN(0, "commit", &option_commit,
167                 "perform a commit if the merge succeeds (default)"),
168         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
169                 "allow fast forward (default)"),
170         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
171                 "merge strategy to use", option_parse_strategy),
172         OPT_CALLBACK('m', "message", &merge_msg, "message",
173                 "message to be used for the merge commit (if any)",
174                 option_parse_message),
175         OPT__VERBOSITY(&verbosity),
176         OPT_END()
177 };
178
179 /* Cleans up metadata that is uninteresting after a succeeded merge. */
180 static void drop_save(void)
181 {
182         unlink(git_path("MERGE_HEAD"));
183         unlink(git_path("MERGE_MSG"));
184         unlink(git_path("MERGE_MODE"));
185 }
186
187 static void save_state(void)
188 {
189         int len;
190         struct child_process cp;
191         struct strbuf buffer = STRBUF_INIT;
192         const char *argv[] = {"stash", "create", NULL};
193
194         memset(&cp, 0, sizeof(cp));
195         cp.argv = argv;
196         cp.out = -1;
197         cp.git_cmd = 1;
198
199         if (start_command(&cp))
200                 die("could not run stash.");
201         len = strbuf_read(&buffer, cp.out, 1024);
202         close(cp.out);
203
204         if (finish_command(&cp) || len < 0)
205                 die("stash failed");
206         else if (!len)
207                 return;
208         strbuf_setlen(&buffer, buffer.len-1);
209         if (get_sha1(buffer.buf, stash))
210                 die("not a valid object: %s", buffer.buf);
211 }
212
213 static void reset_hard(unsigned const char *sha1, int verbose)
214 {
215         int i = 0;
216         const char *args[6];
217
218         args[i++] = "read-tree";
219         if (verbose)
220                 args[i++] = "-v";
221         args[i++] = "--reset";
222         args[i++] = "-u";
223         args[i++] = sha1_to_hex(sha1);
224         args[i] = NULL;
225
226         if (run_command_v_opt(args, RUN_GIT_CMD))
227                 die("read-tree failed");
228 }
229
230 static void restore_state(void)
231 {
232         struct strbuf sb = STRBUF_INIT;
233         const char *args[] = { "stash", "apply", NULL, NULL };
234
235         if (is_null_sha1(stash))
236                 return;
237
238         reset_hard(head, 1);
239
240         args[2] = sha1_to_hex(stash);
241
242         /*
243          * It is OK to ignore error here, for example when there was
244          * nothing to restore.
245          */
246         run_command_v_opt(args, RUN_GIT_CMD);
247
248         strbuf_release(&sb);
249         refresh_cache(REFRESH_QUIET);
250 }
251
252 /* This is called when no merge was necessary. */
253 static void finish_up_to_date(const char *msg)
254 {
255         if (verbosity >= 0)
256                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
257         drop_save();
258 }
259
260 static void squash_message(void)
261 {
262         struct rev_info rev;
263         struct commit *commit;
264         struct strbuf out = STRBUF_INIT;
265         struct commit_list *j;
266         int fd;
267
268         printf("Squash commit -- not updating HEAD\n");
269         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
270         if (fd < 0)
271                 die("Could not write to %s", git_path("SQUASH_MSG"));
272
273         init_revisions(&rev, NULL);
274         rev.ignore_merges = 1;
275         rev.commit_format = CMIT_FMT_MEDIUM;
276
277         commit = lookup_commit(head);
278         commit->object.flags |= UNINTERESTING;
279         add_pending_object(&rev, &commit->object, NULL);
280
281         for (j = remoteheads; j; j = j->next)
282                 add_pending_object(&rev, &j->item->object, NULL);
283
284         setup_revisions(0, NULL, &rev, NULL);
285         if (prepare_revision_walk(&rev))
286                 die("revision walk setup failed");
287
288         strbuf_addstr(&out, "Squashed commit of the following:\n");
289         while ((commit = get_revision(&rev)) != NULL) {
290                 strbuf_addch(&out, '\n');
291                 strbuf_addf(&out, "commit %s\n",
292                         sha1_to_hex(commit->object.sha1));
293                 pretty_print_commit(rev.commit_format, commit, &out, rev.abbrev,
294                         NULL, NULL, rev.date_mode, 0);
295         }
296         if (write(fd, out.buf, out.len) < 0)
297                 die("Writing SQUASH_MSG: %s", strerror(errno));
298         if (close(fd))
299                 die("Finishing SQUASH_MSG: %s", strerror(errno));
300         strbuf_release(&out);
301 }
302
303 static void finish(const unsigned char *new_head, const char *msg)
304 {
305         struct strbuf reflog_message = STRBUF_INIT;
306
307         if (!msg)
308                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
309         else {
310                 if (verbosity >= 0)
311                         printf("%s\n", msg);
312                 strbuf_addf(&reflog_message, "%s: %s",
313                         getenv("GIT_REFLOG_ACTION"), msg);
314         }
315         if (squash) {
316                 squash_message();
317         } else {
318                 if (verbosity >= 0 && !merge_msg.len)
319                         printf("No merge message -- not updating HEAD\n");
320                 else {
321                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
322                         update_ref(reflog_message.buf, "HEAD",
323                                 new_head, head, 0,
324                                 DIE_ON_ERR);
325                         /*
326                          * We ignore errors in 'gc --auto', since the
327                          * user should see them.
328                          */
329                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
330                 }
331         }
332         if (new_head && show_diffstat) {
333                 struct diff_options opts;
334                 diff_setup(&opts);
335                 opts.output_format |=
336                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
337                 opts.detect_rename = DIFF_DETECT_RENAME;
338                 if (diff_use_color_default > 0)
339                         DIFF_OPT_SET(&opts, COLOR_DIFF);
340                 if (diff_setup_done(&opts) < 0)
341                         die("diff_setup_done failed");
342                 diff_tree_sha1(head, new_head, "", &opts);
343                 diffcore_std(&opts);
344                 diff_flush(&opts);
345         }
346
347         /* Run a post-merge hook */
348         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
349
350         strbuf_release(&reflog_message);
351 }
352
353 /* Get the name for the merge commit's message. */
354 static void merge_name(const char *remote, struct strbuf *msg)
355 {
356         struct object *remote_head;
357         unsigned char branch_head[20], buf_sha[20];
358         struct strbuf buf = STRBUF_INIT;
359         struct strbuf bname = STRBUF_INIT;
360         const char *ptr;
361         int len, early;
362
363         len = strlen(remote);
364         if (interpret_nth_last_branch(remote, &bname) == len)
365                 remote = bname.buf;
366
367         memset(branch_head, 0, sizeof(branch_head));
368         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
369         if (!remote_head)
370                 die("'%s' does not point to a commit", remote);
371
372         strbuf_addstr(&buf, "refs/heads/");
373         strbuf_addstr(&buf, remote);
374         resolve_ref(buf.buf, branch_head, 0, 0);
375
376         if (!hashcmp(remote_head->sha1, branch_head)) {
377                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
378                         sha1_to_hex(branch_head), remote);
379                 goto cleanup;
380         }
381
382         /* See if remote matches <name>^^^.. or <name>~<number> */
383         for (len = 0, ptr = remote + strlen(remote);
384              remote < ptr && ptr[-1] == '^';
385              ptr--)
386                 len++;
387         if (len)
388                 early = 1;
389         else {
390                 early = 0;
391                 ptr = strrchr(remote, '~');
392                 if (ptr) {
393                         int seen_nonzero = 0;
394
395                         len++; /* count ~ */
396                         while (*++ptr && isdigit(*ptr)) {
397                                 seen_nonzero |= (*ptr != '0');
398                                 len++;
399                         }
400                         if (*ptr)
401                                 len = 0; /* not ...~<number> */
402                         else if (seen_nonzero)
403                                 early = 1;
404                         else if (len == 1)
405                                 early = 1; /* "name~" is "name~1"! */
406                 }
407         }
408         if (len) {
409                 struct strbuf truname = STRBUF_INIT;
410                 strbuf_addstr(&truname, "refs/heads/");
411                 strbuf_addstr(&truname, remote);
412                 strbuf_setlen(&truname, truname.len - len);
413                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
414                         strbuf_addf(msg,
415                                     "%s\t\tbranch '%s'%s of .\n",
416                                     sha1_to_hex(remote_head->sha1),
417                                     truname.buf + 11,
418                                     (early ? " (early part)" : ""));
419                         strbuf_release(&truname);
420                         goto cleanup;
421                 }
422         }
423
424         if (!strcmp(remote, "FETCH_HEAD") &&
425                         !access(git_path("FETCH_HEAD"), R_OK)) {
426                 FILE *fp;
427                 struct strbuf line = STRBUF_INIT;
428                 char *ptr;
429
430                 fp = fopen(git_path("FETCH_HEAD"), "r");
431                 if (!fp)
432                         die("could not open %s for reading: %s",
433                                 git_path("FETCH_HEAD"), strerror(errno));
434                 strbuf_getline(&line, fp, '\n');
435                 fclose(fp);
436                 ptr = strstr(line.buf, "\tnot-for-merge\t");
437                 if (ptr)
438                         strbuf_remove(&line, ptr-line.buf+1, 13);
439                 strbuf_addbuf(msg, &line);
440                 strbuf_release(&line);
441                 goto cleanup;
442         }
443         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
444                 sha1_to_hex(remote_head->sha1), remote);
445 cleanup:
446         strbuf_release(&buf);
447         strbuf_release(&bname);
448 }
449
450 static int git_merge_config(const char *k, const char *v, void *cb)
451 {
452         if (branch && !prefixcmp(k, "branch.") &&
453                 !prefixcmp(k + 7, branch) &&
454                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
455                 const char **argv;
456                 int argc;
457                 char *buf;
458
459                 buf = xstrdup(v);
460                 argc = split_cmdline(buf, &argv);
461                 if (argc < 0)
462                         die("Bad branch.%s.mergeoptions string", branch);
463                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
464                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
465                 argc++;
466                 parse_options(argc, argv, builtin_merge_options,
467                               builtin_merge_usage, 0);
468                 free(buf);
469         }
470
471         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
472                 show_diffstat = git_config_bool(k, v);
473         else if (!strcmp(k, "pull.twohead"))
474                 return git_config_string(&pull_twohead, k, v);
475         else if (!strcmp(k, "pull.octopus"))
476                 return git_config_string(&pull_octopus, k, v);
477         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
478                 option_log = git_config_bool(k, v);
479         return git_diff_ui_config(k, v, cb);
480 }
481
482 static int read_tree_trivial(unsigned char *common, unsigned char *head,
483                              unsigned char *one)
484 {
485         int i, nr_trees = 0;
486         struct tree *trees[MAX_UNPACK_TREES];
487         struct tree_desc t[MAX_UNPACK_TREES];
488         struct unpack_trees_options opts;
489
490         memset(&opts, 0, sizeof(opts));
491         opts.head_idx = 2;
492         opts.src_index = &the_index;
493         opts.dst_index = &the_index;
494         opts.update = 1;
495         opts.verbose_update = 1;
496         opts.trivial_merges_only = 1;
497         opts.merge = 1;
498         trees[nr_trees] = parse_tree_indirect(common);
499         if (!trees[nr_trees++])
500                 return -1;
501         trees[nr_trees] = parse_tree_indirect(head);
502         if (!trees[nr_trees++])
503                 return -1;
504         trees[nr_trees] = parse_tree_indirect(one);
505         if (!trees[nr_trees++])
506                 return -1;
507         opts.fn = threeway_merge;
508         cache_tree_free(&active_cache_tree);
509         for (i = 0; i < nr_trees; i++) {
510                 parse_tree(trees[i]);
511                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
512         }
513         if (unpack_trees(nr_trees, t, &opts))
514                 return -1;
515         return 0;
516 }
517
518 static void write_tree_trivial(unsigned char *sha1)
519 {
520         if (write_cache_as_tree(sha1, 0, NULL))
521                 die("git write-tree failed to write a tree");
522 }
523
524 static int try_merge_strategy(const char *strategy, struct commit_list *common,
525                               const char *head_arg)
526 {
527         const char **args;
528         int i = 0, ret;
529         struct commit_list *j;
530         struct strbuf buf = STRBUF_INIT;
531         int index_fd;
532         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
533
534         index_fd = hold_locked_index(lock, 1);
535         refresh_cache(REFRESH_QUIET);
536         if (active_cache_changed &&
537                         (write_cache(index_fd, active_cache, active_nr) ||
538                          commit_locked_index(lock)))
539                 return error("Unable to write index.");
540         rollback_lock_file(lock);
541
542         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
543                 int clean;
544                 struct commit *result;
545                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
546                 int index_fd;
547                 struct commit_list *reversed = NULL;
548                 struct merge_options o;
549
550                 if (remoteheads->next) {
551                         error("Not handling anything other than two heads merge.");
552                         return 2;
553                 }
554
555                 init_merge_options(&o);
556                 if (!strcmp(strategy, "subtree"))
557                         o.subtree_merge = 1;
558
559                 o.branch1 = head_arg;
560                 o.branch2 = remoteheads->item->util;
561
562                 for (j = common; j; j = j->next)
563                         commit_list_insert(j->item, &reversed);
564
565                 index_fd = hold_locked_index(lock, 1);
566                 clean = merge_recursive(&o, lookup_commit(head),
567                                 remoteheads->item, reversed, &result);
568                 if (active_cache_changed &&
569                                 (write_cache(index_fd, active_cache, active_nr) ||
570                                  commit_locked_index(lock)))
571                         die ("unable to write %s", get_index_file());
572                 rollback_lock_file(lock);
573                 return clean ? 0 : 1;
574         } else {
575                 args = xmalloc((4 + commit_list_count(common) +
576                                         commit_list_count(remoteheads)) * sizeof(char *));
577                 strbuf_addf(&buf, "merge-%s", strategy);
578                 args[i++] = buf.buf;
579                 for (j = common; j; j = j->next)
580                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
581                 args[i++] = "--";
582                 args[i++] = head_arg;
583                 for (j = remoteheads; j; j = j->next)
584                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
585                 args[i] = NULL;
586                 ret = run_command_v_opt(args, RUN_GIT_CMD);
587                 strbuf_release(&buf);
588                 i = 1;
589                 for (j = common; j; j = j->next)
590                         free((void *)args[i++]);
591                 i += 2;
592                 for (j = remoteheads; j; j = j->next)
593                         free((void *)args[i++]);
594                 free(args);
595                 discard_cache();
596                 if (read_cache() < 0)
597                         die("failed to read the cache");
598                 return -ret;
599         }
600 }
601
602 static void count_diff_files(struct diff_queue_struct *q,
603                              struct diff_options *opt, void *data)
604 {
605         int *count = data;
606
607         (*count) += q->nr;
608 }
609
610 static int count_unmerged_entries(void)
611 {
612         const struct index_state *state = &the_index;
613         int i, ret = 0;
614
615         for (i = 0; i < state->cache_nr; i++)
616                 if (ce_stage(state->cache[i]))
617                         ret++;
618
619         return ret;
620 }
621
622 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
623 {
624         struct tree *trees[MAX_UNPACK_TREES];
625         struct unpack_trees_options opts;
626         struct tree_desc t[MAX_UNPACK_TREES];
627         int i, fd, nr_trees = 0;
628         struct dir_struct dir;
629         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
630
631         refresh_cache(REFRESH_QUIET);
632
633         fd = hold_locked_index(lock_file, 1);
634
635         memset(&trees, 0, sizeof(trees));
636         memset(&opts, 0, sizeof(opts));
637         memset(&t, 0, sizeof(t));
638         memset(&dir, 0, sizeof(dir));
639         dir.show_ignored = 1;
640         dir.exclude_per_dir = ".gitignore";
641         opts.dir = &dir;
642
643         opts.head_idx = 1;
644         opts.src_index = &the_index;
645         opts.dst_index = &the_index;
646         opts.update = 1;
647         opts.verbose_update = 1;
648         opts.merge = 1;
649         opts.fn = twoway_merge;
650
651         trees[nr_trees] = parse_tree_indirect(head);
652         if (!trees[nr_trees++])
653                 return -1;
654         trees[nr_trees] = parse_tree_indirect(remote);
655         if (!trees[nr_trees++])
656                 return -1;
657         for (i = 0; i < nr_trees; i++) {
658                 parse_tree(trees[i]);
659                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
660         }
661         if (unpack_trees(nr_trees, t, &opts))
662                 return -1;
663         if (write_cache(fd, active_cache, active_nr) ||
664                 commit_locked_index(lock_file))
665                 die("unable to write new index file");
666         return 0;
667 }
668
669 static void split_merge_strategies(const char *string, struct strategy **list,
670                                    int *nr, int *alloc)
671 {
672         char *p, *q, *buf;
673
674         if (!string)
675                 return;
676
677         buf = xstrdup(string);
678         q = buf;
679         for (;;) {
680                 p = strchr(q, ' ');
681                 if (!p) {
682                         ALLOC_GROW(*list, *nr + 1, *alloc);
683                         (*list)[(*nr)++].name = xstrdup(q);
684                         free(buf);
685                         return;
686                 } else {
687                         *p = '\0';
688                         ALLOC_GROW(*list, *nr + 1, *alloc);
689                         (*list)[(*nr)++].name = xstrdup(q);
690                         q = ++p;
691                 }
692         }
693 }
694
695 static void add_strategies(const char *string, unsigned attr)
696 {
697         struct strategy *list = NULL;
698         int list_alloc = 0, list_nr = 0, i;
699
700         memset(&list, 0, sizeof(list));
701         split_merge_strategies(string, &list, &list_nr, &list_alloc);
702         if (list) {
703                 for (i = 0; i < list_nr; i++)
704                         append_strategy(get_strategy(list[i].name));
705                 return;
706         }
707         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
708                 if (all_strategy[i].attr & attr)
709                         append_strategy(&all_strategy[i]);
710
711 }
712
713 static int merge_trivial(void)
714 {
715         unsigned char result_tree[20], result_commit[20];
716         struct commit_list *parent = xmalloc(sizeof(*parent));
717
718         write_tree_trivial(result_tree);
719         printf("Wonderful.\n");
720         parent->item = lookup_commit(head);
721         parent->next = xmalloc(sizeof(*parent->next));
722         parent->next->item = remoteheads->item;
723         parent->next->next = NULL;
724         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
725         finish(result_commit, "In-index merge");
726         drop_save();
727         return 0;
728 }
729
730 static int finish_automerge(struct commit_list *common,
731                             unsigned char *result_tree,
732                             const char *wt_strategy)
733 {
734         struct commit_list *parents = NULL, *j;
735         struct strbuf buf = STRBUF_INIT;
736         unsigned char result_commit[20];
737
738         free_commit_list(common);
739         if (allow_fast_forward) {
740                 parents = remoteheads;
741                 commit_list_insert(lookup_commit(head), &parents);
742                 parents = reduce_heads(parents);
743         } else {
744                 struct commit_list **pptr = &parents;
745
746                 pptr = &commit_list_insert(lookup_commit(head),
747                                 pptr)->next;
748                 for (j = remoteheads; j; j = j->next)
749                         pptr = &commit_list_insert(j->item, pptr)->next;
750         }
751         free_commit_list(remoteheads);
752         strbuf_addch(&merge_msg, '\n');
753         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
754         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
755         finish(result_commit, buf.buf);
756         strbuf_release(&buf);
757         drop_save();
758         return 0;
759 }
760
761 static int suggest_conflicts(void)
762 {
763         FILE *fp;
764         int pos;
765
766         fp = fopen(git_path("MERGE_MSG"), "a");
767         if (!fp)
768                 die("Could not open %s for writing", git_path("MERGE_MSG"));
769         fprintf(fp, "\nConflicts:\n");
770         for (pos = 0; pos < active_nr; pos++) {
771                 struct cache_entry *ce = active_cache[pos];
772
773                 if (ce_stage(ce)) {
774                         fprintf(fp, "\t%s\n", ce->name);
775                         while (pos + 1 < active_nr &&
776                                         !strcmp(ce->name,
777                                                 active_cache[pos + 1]->name))
778                                 pos++;
779                 }
780         }
781         fclose(fp);
782         rerere();
783         printf("Automatic merge failed; "
784                         "fix conflicts and then commit the result.\n");
785         return 1;
786 }
787
788 static struct commit *is_old_style_invocation(int argc, const char **argv)
789 {
790         struct commit *second_token = NULL;
791         if (argc > 1) {
792                 unsigned char second_sha1[20];
793
794                 if (get_sha1(argv[1], second_sha1))
795                         return NULL;
796                 second_token = lookup_commit_reference_gently(second_sha1, 0);
797                 if (!second_token)
798                         die("'%s' is not a commit", argv[1]);
799                 if (hashcmp(second_token->object.sha1, head))
800                         return NULL;
801         }
802         return second_token;
803 }
804
805 static int evaluate_result(void)
806 {
807         int cnt = 0;
808         struct rev_info rev;
809
810         /* Check how many files differ. */
811         init_revisions(&rev, "");
812         setup_revisions(0, NULL, &rev, NULL);
813         rev.diffopt.output_format |=
814                 DIFF_FORMAT_CALLBACK;
815         rev.diffopt.format_callback = count_diff_files;
816         rev.diffopt.format_callback_data = &cnt;
817         run_diff_files(&rev, 0);
818
819         /*
820          * Check how many unmerged entries are
821          * there.
822          */
823         cnt += count_unmerged_entries();
824
825         return cnt;
826 }
827
828 int cmd_merge(int argc, const char **argv, const char *prefix)
829 {
830         unsigned char result_tree[20];
831         struct strbuf buf = STRBUF_INIT;
832         const char *head_arg;
833         int flag, head_invalid = 0, i;
834         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
835         struct commit_list *common = NULL;
836         const char *best_strategy = NULL, *wt_strategy = NULL;
837         struct commit_list **remotes = &remoteheads;
838
839         setup_work_tree();
840         if (read_cache_unmerged())
841                 die("You are in the middle of a conflicted merge.");
842
843         /*
844          * Check if we are _not_ on a detached HEAD, i.e. if there is a
845          * current branch.
846          */
847         branch = resolve_ref("HEAD", head, 0, &flag);
848         if (branch && !prefixcmp(branch, "refs/heads/"))
849                 branch += 11;
850         if (is_null_sha1(head))
851                 head_invalid = 1;
852
853         git_config(git_merge_config, NULL);
854
855         /* for color.ui */
856         if (diff_use_color_default == -1)
857                 diff_use_color_default = git_use_color_default;
858
859         argc = parse_options(argc, argv, builtin_merge_options,
860                         builtin_merge_usage, 0);
861         if (verbosity < 0)
862                 show_diffstat = 0;
863
864         if (squash) {
865                 if (!allow_fast_forward)
866                         die("You cannot combine --squash with --no-ff.");
867                 option_commit = 0;
868         }
869
870         if (!argc)
871                 usage_with_options(builtin_merge_usage,
872                         builtin_merge_options);
873
874         /*
875          * This could be traditional "merge <msg> HEAD <commit>..."  and
876          * the way we can tell it is to see if the second token is HEAD,
877          * but some people might have misused the interface and used a
878          * committish that is the same as HEAD there instead.
879          * Traditional format never would have "-m" so it is an
880          * additional safety measure to check for it.
881          */
882
883         if (!have_message && is_old_style_invocation(argc, argv)) {
884                 strbuf_addstr(&merge_msg, argv[0]);
885                 head_arg = argv[1];
886                 argv += 2;
887                 argc -= 2;
888         } else if (head_invalid) {
889                 struct object *remote_head;
890                 /*
891                  * If the merged head is a valid one there is no reason
892                  * to forbid "git merge" into a branch yet to be born.
893                  * We do the same for "git pull".
894                  */
895                 if (argc != 1)
896                         die("Can merge only exactly one commit into "
897                                 "empty head");
898                 if (squash)
899                         die("Squash commit into empty head not supported yet");
900                 if (!allow_fast_forward)
901                         die("Non-fast-forward commit does not make sense into "
902                             "an empty head");
903                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
904                 if (!remote_head)
905                         die("%s - not something we can merge", argv[0]);
906                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
907                                 DIE_ON_ERR);
908                 reset_hard(remote_head->sha1, 0);
909                 return 0;
910         } else {
911                 struct strbuf msg = STRBUF_INIT;
912
913                 /* We are invoked directly as the first-class UI. */
914                 head_arg = "HEAD";
915
916                 /*
917                  * All the rest are the commits being merged;
918                  * prepare the standard merge summary message to
919                  * be appended to the given message.  If remote
920                  * is invalid we will die later in the common
921                  * codepath so we discard the error in this
922                  * loop.
923                  */
924                 for (i = 0; i < argc; i++)
925                         merge_name(argv[i], &msg);
926                 fmt_merge_msg(option_log, &msg, &merge_msg);
927                 if (merge_msg.len)
928                         strbuf_setlen(&merge_msg, merge_msg.len-1);
929         }
930
931         if (head_invalid || !argc)
932                 usage_with_options(builtin_merge_usage,
933                         builtin_merge_options);
934
935         strbuf_addstr(&buf, "merge");
936         for (i = 0; i < argc; i++)
937                 strbuf_addf(&buf, " %s", argv[i]);
938         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
939         strbuf_reset(&buf);
940
941         for (i = 0; i < argc; i++) {
942                 struct object *o;
943                 struct commit *commit;
944
945                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
946                 if (!o)
947                         die("%s - not something we can merge", argv[i]);
948                 commit = lookup_commit(o->sha1);
949                 commit->util = (void *)argv[i];
950                 remotes = &commit_list_insert(commit, remotes)->next;
951
952                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
953                 setenv(buf.buf, argv[i], 1);
954                 strbuf_reset(&buf);
955         }
956
957         if (!use_strategies) {
958                 if (!remoteheads->next)
959                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
960                 else
961                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
962         }
963
964         for (i = 0; i < use_strategies_nr; i++) {
965                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
966                         allow_fast_forward = 0;
967                 if (use_strategies[i]->attr & NO_TRIVIAL)
968                         allow_trivial = 0;
969         }
970
971         if (!remoteheads->next)
972                 common = get_merge_bases(lookup_commit(head),
973                                 remoteheads->item, 1);
974         else {
975                 struct commit_list *list = remoteheads;
976                 commit_list_insert(lookup_commit(head), &list);
977                 common = get_octopus_merge_bases(list);
978                 free(list);
979         }
980
981         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
982                 DIE_ON_ERR);
983
984         if (!common)
985                 ; /* No common ancestors found. We need a real merge. */
986         else if (!remoteheads->next && !common->next &&
987                         common->item == remoteheads->item) {
988                 /*
989                  * If head can reach all the merge then we are up to date.
990                  * but first the most common case of merging one remote.
991                  */
992                 finish_up_to_date("Already up-to-date.");
993                 return 0;
994         } else if (allow_fast_forward && !remoteheads->next &&
995                         !common->next &&
996                         !hashcmp(common->item->object.sha1, head)) {
997                 /* Again the most common case of merging one remote. */
998                 struct strbuf msg = STRBUF_INIT;
999                 struct object *o;
1000                 char hex[41];
1001
1002                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1003
1004                 if (verbosity >= 0)
1005                         printf("Updating %s..%s\n",
1006                                 hex,
1007                                 find_unique_abbrev(remoteheads->item->object.sha1,
1008                                 DEFAULT_ABBREV));
1009                 strbuf_addstr(&msg, "Fast forward");
1010                 if (have_message)
1011                         strbuf_addstr(&msg,
1012                                 " (no commit created; -m option ignored)");
1013                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1014                         0, NULL, OBJ_COMMIT);
1015                 if (!o)
1016                         return 1;
1017
1018                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1019                         return 1;
1020
1021                 finish(o->sha1, msg.buf);
1022                 drop_save();
1023                 return 0;
1024         } else if (!remoteheads->next && common->next)
1025                 ;
1026                 /*
1027                  * We are not doing octopus and not fast forward.  Need
1028                  * a real merge.
1029                  */
1030         else if (!remoteheads->next && !common->next && option_commit) {
1031                 /*
1032                  * We are not doing octopus, not fast forward, and have
1033                  * only one common.
1034                  */
1035                 refresh_cache(REFRESH_QUIET);
1036                 if (allow_trivial) {
1037                         /* See if it is really trivial. */
1038                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1039                         printf("Trying really trivial in-index merge...\n");
1040                         if (!read_tree_trivial(common->item->object.sha1,
1041                                         head, remoteheads->item->object.sha1))
1042                                 return merge_trivial();
1043                         printf("Nope.\n");
1044                 }
1045         } else {
1046                 /*
1047                  * An octopus.  If we can reach all the remote we are up
1048                  * to date.
1049                  */
1050                 int up_to_date = 1;
1051                 struct commit_list *j;
1052
1053                 for (j = remoteheads; j; j = j->next) {
1054                         struct commit_list *common_one;
1055
1056                         /*
1057                          * Here we *have* to calculate the individual
1058                          * merge_bases again, otherwise "git merge HEAD^
1059                          * HEAD^^" would be missed.
1060                          */
1061                         common_one = get_merge_bases(lookup_commit(head),
1062                                 j->item, 1);
1063                         if (hashcmp(common_one->item->object.sha1,
1064                                 j->item->object.sha1)) {
1065                                 up_to_date = 0;
1066                                 break;
1067                         }
1068                 }
1069                 if (up_to_date) {
1070                         finish_up_to_date("Already up-to-date. Yeeah!");
1071                         return 0;
1072                 }
1073         }
1074
1075         /* We are going to make a new commit. */
1076         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1077
1078         /*
1079          * At this point, we need a real merge.  No matter what strategy
1080          * we use, it would operate on the index, possibly affecting the
1081          * working tree, and when resolved cleanly, have the desired
1082          * tree in the index -- this means that the index must be in
1083          * sync with the head commit.  The strategies are responsible
1084          * to ensure this.
1085          */
1086         if (use_strategies_nr != 1) {
1087                 /*
1088                  * Stash away the local changes so that we can try more
1089                  * than one.
1090                  */
1091                 save_state();
1092         } else {
1093                 memcpy(stash, null_sha1, 20);
1094         }
1095
1096         for (i = 0; i < use_strategies_nr; i++) {
1097                 int ret;
1098                 if (i) {
1099                         printf("Rewinding the tree to pristine...\n");
1100                         restore_state();
1101                 }
1102                 if (use_strategies_nr != 1)
1103                         printf("Trying merge strategy %s...\n",
1104                                 use_strategies[i]->name);
1105                 /*
1106                  * Remember which strategy left the state in the working
1107                  * tree.
1108                  */
1109                 wt_strategy = use_strategies[i]->name;
1110
1111                 ret = try_merge_strategy(use_strategies[i]->name,
1112                         common, head_arg);
1113                 if (!option_commit && !ret) {
1114                         merge_was_ok = 1;
1115                         /*
1116                          * This is necessary here just to avoid writing
1117                          * the tree, but later we will *not* exit with
1118                          * status code 1 because merge_was_ok is set.
1119                          */
1120                         ret = 1;
1121                 }
1122
1123                 if (ret) {
1124                         /*
1125                          * The backend exits with 1 when conflicts are
1126                          * left to be resolved, with 2 when it does not
1127                          * handle the given merge at all.
1128                          */
1129                         if (ret == 1) {
1130                                 int cnt = evaluate_result();
1131
1132                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1133                                         best_strategy = use_strategies[i]->name;
1134                                         best_cnt = cnt;
1135                                 }
1136                         }
1137                         if (merge_was_ok)
1138                                 break;
1139                         else
1140                                 continue;
1141                 }
1142
1143                 /* Automerge succeeded. */
1144                 write_tree_trivial(result_tree);
1145                 automerge_was_ok = 1;
1146                 break;
1147         }
1148
1149         /*
1150          * If we have a resulting tree, that means the strategy module
1151          * auto resolved the merge cleanly.
1152          */
1153         if (automerge_was_ok)
1154                 return finish_automerge(common, result_tree, wt_strategy);
1155
1156         /*
1157          * Pick the result from the best strategy and have the user fix
1158          * it up.
1159          */
1160         if (!best_strategy) {
1161                 restore_state();
1162                 if (use_strategies_nr > 1)
1163                         fprintf(stderr,
1164                                 "No merge strategy handled the merge.\n");
1165                 else
1166                         fprintf(stderr, "Merge with strategy %s failed.\n",
1167                                 use_strategies[0]->name);
1168                 return 2;
1169         } else if (best_strategy == wt_strategy)
1170                 ; /* We already have its result in the working tree. */
1171         else {
1172                 printf("Rewinding the tree to pristine...\n");
1173                 restore_state();
1174                 printf("Using the %s to prepare resolving by hand.\n",
1175                         best_strategy);
1176                 try_merge_strategy(best_strategy, common, head_arg);
1177         }
1178
1179         if (squash)
1180                 finish(NULL, NULL);
1181         else {
1182                 int fd;
1183                 struct commit_list *j;
1184
1185                 for (j = remoteheads; j; j = j->next)
1186                         strbuf_addf(&buf, "%s\n",
1187                                 sha1_to_hex(j->item->object.sha1));
1188                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1189                 if (fd < 0)
1190                         die("Could open %s for writing",
1191                                 git_path("MERGE_HEAD"));
1192                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1193                         die("Could not write to %s", git_path("MERGE_HEAD"));
1194                 close(fd);
1195                 strbuf_addch(&merge_msg, '\n');
1196                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1197                 if (fd < 0)
1198                         die("Could open %s for writing", git_path("MERGE_MSG"));
1199                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1200                         merge_msg.len)
1201                         die("Could not write to %s", git_path("MERGE_MSG"));
1202                 close(fd);
1203                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1204                 if (fd < 0)
1205                         die("Could open %s for writing", git_path("MERGE_MODE"));
1206                 strbuf_reset(&buf);
1207                 if (!allow_fast_forward)
1208                         strbuf_addf(&buf, "no-ff");
1209                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1210                         die("Could not write to %s", git_path("MERGE_MODE"));
1211                 close(fd);
1212         }
1213
1214         if (merge_was_ok) {
1215                 fprintf(stderr, "Automatic merge went well; "
1216                         "stopped before committing as requested\n");
1217                 return 0;
1218         } else
1219                 return suggest_conflicts();
1220 }