Merge branch 'maint-1.5.6' into maint
[git] / builtin-merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "parse-options.h"
11 #include "builtin.h"
12 #include "run-command.h"
13 #include "diff.h"
14 #include "refs.h"
15 #include "commit.h"
16 #include "diffcore.h"
17 #include "revision.h"
18 #include "unpack-trees.h"
19 #include "cache-tree.h"
20 #include "dir.h"
21 #include "utf8.h"
22 #include "log-tree.h"
23 #include "color.h"
24 #include "rerere.h"
25 #include "help.h"
26 #include "merge-recursive.h"
27
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 int run_hook(const char *name)
304 {
305         struct child_process hook;
306         const char *argv[3], *env[2];
307         char index[PATH_MAX];
308
309         argv[0] = git_path("hooks/%s", name);
310         if (access(argv[0], X_OK) < 0)
311                 return 0;
312
313         snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", get_index_file());
314         env[0] = index;
315         env[1] = NULL;
316
317         if (squash)
318                 argv[1] = "1";
319         else
320                 argv[1] = "0";
321         argv[2] = NULL;
322
323         memset(&hook, 0, sizeof(hook));
324         hook.argv = argv;
325         hook.no_stdin = 1;
326         hook.stdout_to_stderr = 1;
327         hook.env = env;
328
329         return run_command(&hook);
330 }
331
332 static void finish(const unsigned char *new_head, const char *msg)
333 {
334         struct strbuf reflog_message = STRBUF_INIT;
335
336         if (!msg)
337                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
338         else {
339                 if (verbosity >= 0)
340                         printf("%s\n", msg);
341                 strbuf_addf(&reflog_message, "%s: %s",
342                         getenv("GIT_REFLOG_ACTION"), msg);
343         }
344         if (squash) {
345                 squash_message();
346         } else {
347                 if (verbosity >= 0 && !merge_msg.len)
348                         printf("No merge message -- not updating HEAD\n");
349                 else {
350                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
351                         update_ref(reflog_message.buf, "HEAD",
352                                 new_head, head, 0,
353                                 DIE_ON_ERR);
354                         /*
355                          * We ignore errors in 'gc --auto', since the
356                          * user should see them.
357                          */
358                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
359                 }
360         }
361         if (new_head && show_diffstat) {
362                 struct diff_options opts;
363                 diff_setup(&opts);
364                 opts.output_format |=
365                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
366                 opts.detect_rename = DIFF_DETECT_RENAME;
367                 if (diff_use_color_default > 0)
368                         DIFF_OPT_SET(&opts, COLOR_DIFF);
369                 if (diff_setup_done(&opts) < 0)
370                         die("diff_setup_done failed");
371                 diff_tree_sha1(head, new_head, "", &opts);
372                 diffcore_std(&opts);
373                 diff_flush(&opts);
374         }
375
376         /* Run a post-merge hook */
377         run_hook("post-merge");
378
379         strbuf_release(&reflog_message);
380 }
381
382 /* Get the name for the merge commit's message. */
383 static void merge_name(const char *remote, struct strbuf *msg)
384 {
385         struct object *remote_head;
386         unsigned char branch_head[20], buf_sha[20];
387         struct strbuf buf = STRBUF_INIT;
388         const char *ptr;
389         int len, early;
390
391         memset(branch_head, 0, sizeof(branch_head));
392         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
393         if (!remote_head)
394                 die("'%s' does not point to a commit", remote);
395
396         strbuf_addstr(&buf, "refs/heads/");
397         strbuf_addstr(&buf, remote);
398         resolve_ref(buf.buf, branch_head, 0, 0);
399
400         if (!hashcmp(remote_head->sha1, branch_head)) {
401                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
402                         sha1_to_hex(branch_head), remote);
403                 return;
404         }
405
406         /* See if remote matches <name>^^^.. or <name>~<number> */
407         for (len = 0, ptr = remote + strlen(remote);
408              remote < ptr && ptr[-1] == '^';
409              ptr--)
410                 len++;
411         if (len)
412                 early = 1;
413         else {
414                 early = 0;
415                 ptr = strrchr(remote, '~');
416                 if (ptr) {
417                         int seen_nonzero = 0;
418
419                         len++; /* count ~ */
420                         while (*++ptr && isdigit(*ptr)) {
421                                 seen_nonzero |= (*ptr != '0');
422                                 len++;
423                         }
424                         if (*ptr)
425                                 len = 0; /* not ...~<number> */
426                         else if (seen_nonzero)
427                                 early = 1;
428                         else if (len == 1)
429                                 early = 1; /* "name~" is "name~1"! */
430                 }
431         }
432         if (len) {
433                 struct strbuf truname = STRBUF_INIT;
434                 strbuf_addstr(&truname, "refs/heads/");
435                 strbuf_addstr(&truname, remote);
436                 strbuf_setlen(&truname, truname.len - len);
437                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
438                         strbuf_addf(msg,
439                                     "%s\t\tbranch '%s'%s of .\n",
440                                     sha1_to_hex(remote_head->sha1),
441                                     truname.buf + 11,
442                                     (early ? " (early part)" : ""));
443                         return;
444                 }
445         }
446
447         if (!strcmp(remote, "FETCH_HEAD") &&
448                         !access(git_path("FETCH_HEAD"), R_OK)) {
449                 FILE *fp;
450                 struct strbuf line = STRBUF_INIT;
451                 char *ptr;
452
453                 fp = fopen(git_path("FETCH_HEAD"), "r");
454                 if (!fp)
455                         die("could not open %s for reading: %s",
456                                 git_path("FETCH_HEAD"), strerror(errno));
457                 strbuf_getline(&line, fp, '\n');
458                 fclose(fp);
459                 ptr = strstr(line.buf, "\tnot-for-merge\t");
460                 if (ptr)
461                         strbuf_remove(&line, ptr-line.buf+1, 13);
462                 strbuf_addbuf(msg, &line);
463                 strbuf_release(&line);
464                 return;
465         }
466         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
467                 sha1_to_hex(remote_head->sha1), remote);
468 }
469
470 static int git_merge_config(const char *k, const char *v, void *cb)
471 {
472         if (branch && !prefixcmp(k, "branch.") &&
473                 !prefixcmp(k + 7, branch) &&
474                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
475                 const char **argv;
476                 int argc;
477                 char *buf;
478
479                 buf = xstrdup(v);
480                 argc = split_cmdline(buf, &argv);
481                 if (argc < 0)
482                         die("Bad branch.%s.mergeoptions string", branch);
483                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
484                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
485                 argc++;
486                 parse_options(argc, argv, builtin_merge_options,
487                               builtin_merge_usage, 0);
488                 free(buf);
489         }
490
491         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
492                 show_diffstat = git_config_bool(k, v);
493         else if (!strcmp(k, "pull.twohead"))
494                 return git_config_string(&pull_twohead, k, v);
495         else if (!strcmp(k, "pull.octopus"))
496                 return git_config_string(&pull_octopus, k, v);
497         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
498                 option_log = git_config_bool(k, v);
499         return git_diff_ui_config(k, v, cb);
500 }
501
502 static int read_tree_trivial(unsigned char *common, unsigned char *head,
503                              unsigned char *one)
504 {
505         int i, nr_trees = 0;
506         struct tree *trees[MAX_UNPACK_TREES];
507         struct tree_desc t[MAX_UNPACK_TREES];
508         struct unpack_trees_options opts;
509
510         memset(&opts, 0, sizeof(opts));
511         opts.head_idx = 2;
512         opts.src_index = &the_index;
513         opts.dst_index = &the_index;
514         opts.update = 1;
515         opts.verbose_update = 1;
516         opts.trivial_merges_only = 1;
517         opts.merge = 1;
518         trees[nr_trees] = parse_tree_indirect(common);
519         if (!trees[nr_trees++])
520                 return -1;
521         trees[nr_trees] = parse_tree_indirect(head);
522         if (!trees[nr_trees++])
523                 return -1;
524         trees[nr_trees] = parse_tree_indirect(one);
525         if (!trees[nr_trees++])
526                 return -1;
527         opts.fn = threeway_merge;
528         cache_tree_free(&active_cache_tree);
529         for (i = 0; i < nr_trees; i++) {
530                 parse_tree(trees[i]);
531                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
532         }
533         if (unpack_trees(nr_trees, t, &opts))
534                 return -1;
535         return 0;
536 }
537
538 static void write_tree_trivial(unsigned char *sha1)
539 {
540         if (write_cache_as_tree(sha1, 0, NULL))
541                 die("git write-tree failed to write a tree");
542 }
543
544 static int try_merge_strategy(const char *strategy, struct commit_list *common,
545                               const char *head_arg)
546 {
547         const char **args;
548         int i = 0, ret;
549         struct commit_list *j;
550         struct strbuf buf = STRBUF_INIT;
551         int index_fd;
552         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
553
554         index_fd = hold_locked_index(lock, 1);
555         refresh_cache(REFRESH_QUIET);
556         if (active_cache_changed &&
557                         (write_cache(index_fd, active_cache, active_nr) ||
558                          commit_locked_index(lock)))
559                 return error("Unable to write index.");
560         rollback_lock_file(lock);
561
562         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
563                 int clean;
564                 struct commit *result;
565                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
566                 int index_fd;
567                 struct commit_list *reversed = NULL;
568                 struct merge_options o;
569
570                 if (remoteheads->next) {
571                         error("Not handling anything other than two heads merge.");
572                         return 2;
573                 }
574
575                 init_merge_options(&o);
576                 if (!strcmp(strategy, "subtree"))
577                         o.subtree_merge = 1;
578
579                 o.branch1 = head_arg;
580                 o.branch2 = remoteheads->item->util;
581
582                 for (j = common; j; j = j->next)
583                         commit_list_insert(j->item, &reversed);
584
585                 index_fd = hold_locked_index(lock, 1);
586                 clean = merge_recursive(&o, lookup_commit(head),
587                                 remoteheads->item, reversed, &result);
588                 if (active_cache_changed &&
589                                 (write_cache(index_fd, active_cache, active_nr) ||
590                                  commit_locked_index(lock)))
591                         die ("unable to write %s", get_index_file());
592                 rollback_lock_file(lock);
593                 return clean ? 0 : 1;
594         } else {
595                 args = xmalloc((4 + commit_list_count(common) +
596                                         commit_list_count(remoteheads)) * sizeof(char *));
597                 strbuf_addf(&buf, "merge-%s", strategy);
598                 args[i++] = buf.buf;
599                 for (j = common; j; j = j->next)
600                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
601                 args[i++] = "--";
602                 args[i++] = head_arg;
603                 for (j = remoteheads; j; j = j->next)
604                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
605                 args[i] = NULL;
606                 ret = run_command_v_opt(args, RUN_GIT_CMD);
607                 strbuf_release(&buf);
608                 i = 1;
609                 for (j = common; j; j = j->next)
610                         free((void *)args[i++]);
611                 i += 2;
612                 for (j = remoteheads; j; j = j->next)
613                         free((void *)args[i++]);
614                 free(args);
615                 discard_cache();
616                 if (read_cache() < 0)
617                         die("failed to read the cache");
618                 return -ret;
619         }
620 }
621
622 static void count_diff_files(struct diff_queue_struct *q,
623                              struct diff_options *opt, void *data)
624 {
625         int *count = data;
626
627         (*count) += q->nr;
628 }
629
630 static int count_unmerged_entries(void)
631 {
632         const struct index_state *state = &the_index;
633         int i, ret = 0;
634
635         for (i = 0; i < state->cache_nr; i++)
636                 if (ce_stage(state->cache[i]))
637                         ret++;
638
639         return ret;
640 }
641
642 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
643 {
644         struct tree *trees[MAX_UNPACK_TREES];
645         struct unpack_trees_options opts;
646         struct tree_desc t[MAX_UNPACK_TREES];
647         int i, fd, nr_trees = 0;
648         struct dir_struct dir;
649         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
650
651         refresh_cache(REFRESH_QUIET);
652
653         fd = hold_locked_index(lock_file, 1);
654
655         memset(&trees, 0, sizeof(trees));
656         memset(&opts, 0, sizeof(opts));
657         memset(&t, 0, sizeof(t));
658         memset(&dir, 0, sizeof(dir));
659         dir.show_ignored = 1;
660         dir.exclude_per_dir = ".gitignore";
661         opts.dir = &dir;
662
663         opts.head_idx = 1;
664         opts.src_index = &the_index;
665         opts.dst_index = &the_index;
666         opts.update = 1;
667         opts.verbose_update = 1;
668         opts.merge = 1;
669         opts.fn = twoway_merge;
670
671         trees[nr_trees] = parse_tree_indirect(head);
672         if (!trees[nr_trees++])
673                 return -1;
674         trees[nr_trees] = parse_tree_indirect(remote);
675         if (!trees[nr_trees++])
676                 return -1;
677         for (i = 0; i < nr_trees; i++) {
678                 parse_tree(trees[i]);
679                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
680         }
681         if (unpack_trees(nr_trees, t, &opts))
682                 return -1;
683         if (write_cache(fd, active_cache, active_nr) ||
684                 commit_locked_index(lock_file))
685                 die("unable to write new index file");
686         return 0;
687 }
688
689 static void split_merge_strategies(const char *string, struct strategy **list,
690                                    int *nr, int *alloc)
691 {
692         char *p, *q, *buf;
693
694         if (!string)
695                 return;
696
697         buf = xstrdup(string);
698         q = buf;
699         for (;;) {
700                 p = strchr(q, ' ');
701                 if (!p) {
702                         ALLOC_GROW(*list, *nr + 1, *alloc);
703                         (*list)[(*nr)++].name = xstrdup(q);
704                         free(buf);
705                         return;
706                 } else {
707                         *p = '\0';
708                         ALLOC_GROW(*list, *nr + 1, *alloc);
709                         (*list)[(*nr)++].name = xstrdup(q);
710                         q = ++p;
711                 }
712         }
713 }
714
715 static void add_strategies(const char *string, unsigned attr)
716 {
717         struct strategy *list = NULL;
718         int list_alloc = 0, list_nr = 0, i;
719
720         memset(&list, 0, sizeof(list));
721         split_merge_strategies(string, &list, &list_nr, &list_alloc);
722         if (list) {
723                 for (i = 0; i < list_nr; i++)
724                         append_strategy(get_strategy(list[i].name));
725                 return;
726         }
727         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
728                 if (all_strategy[i].attr & attr)
729                         append_strategy(&all_strategy[i]);
730
731 }
732
733 static int merge_trivial(void)
734 {
735         unsigned char result_tree[20], result_commit[20];
736         struct commit_list *parent = xmalloc(sizeof(*parent));
737
738         write_tree_trivial(result_tree);
739         printf("Wonderful.\n");
740         parent->item = lookup_commit(head);
741         parent->next = xmalloc(sizeof(*parent->next));
742         parent->next->item = remoteheads->item;
743         parent->next->next = NULL;
744         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
745         finish(result_commit, "In-index merge");
746         drop_save();
747         return 0;
748 }
749
750 static int finish_automerge(struct commit_list *common,
751                             unsigned char *result_tree,
752                             const char *wt_strategy)
753 {
754         struct commit_list *parents = NULL, *j;
755         struct strbuf buf = STRBUF_INIT;
756         unsigned char result_commit[20];
757
758         free_commit_list(common);
759         if (allow_fast_forward) {
760                 parents = remoteheads;
761                 commit_list_insert(lookup_commit(head), &parents);
762                 parents = reduce_heads(parents);
763         } else {
764                 struct commit_list **pptr = &parents;
765
766                 pptr = &commit_list_insert(lookup_commit(head),
767                                 pptr)->next;
768                 for (j = remoteheads; j; j = j->next)
769                         pptr = &commit_list_insert(j->item, pptr)->next;
770         }
771         free_commit_list(remoteheads);
772         strbuf_addch(&merge_msg, '\n');
773         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
774         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
775         finish(result_commit, buf.buf);
776         strbuf_release(&buf);
777         drop_save();
778         return 0;
779 }
780
781 static int suggest_conflicts(void)
782 {
783         FILE *fp;
784         int pos;
785
786         fp = fopen(git_path("MERGE_MSG"), "a");
787         if (!fp)
788                 die("Could open %s for writing", git_path("MERGE_MSG"));
789         fprintf(fp, "\nConflicts:\n");
790         for (pos = 0; pos < active_nr; pos++) {
791                 struct cache_entry *ce = active_cache[pos];
792
793                 if (ce_stage(ce)) {
794                         fprintf(fp, "\t%s\n", ce->name);
795                         while (pos + 1 < active_nr &&
796                                         !strcmp(ce->name,
797                                                 active_cache[pos + 1]->name))
798                                 pos++;
799                 }
800         }
801         fclose(fp);
802         rerere();
803         printf("Automatic merge failed; "
804                         "fix conflicts and then commit the result.\n");
805         return 1;
806 }
807
808 static struct commit *is_old_style_invocation(int argc, const char **argv)
809 {
810         struct commit *second_token = NULL;
811         if (argc > 1) {
812                 unsigned char second_sha1[20];
813
814                 if (get_sha1(argv[1], second_sha1))
815                         return NULL;
816                 second_token = lookup_commit_reference_gently(second_sha1, 0);
817                 if (!second_token)
818                         die("'%s' is not a commit", argv[1]);
819                 if (hashcmp(second_token->object.sha1, head))
820                         return NULL;
821         }
822         return second_token;
823 }
824
825 static int evaluate_result(void)
826 {
827         int cnt = 0;
828         struct rev_info rev;
829
830         /* Check how many files differ. */
831         init_revisions(&rev, "");
832         setup_revisions(0, NULL, &rev, NULL);
833         rev.diffopt.output_format |=
834                 DIFF_FORMAT_CALLBACK;
835         rev.diffopt.format_callback = count_diff_files;
836         rev.diffopt.format_callback_data = &cnt;
837         run_diff_files(&rev, 0);
838
839         /*
840          * Check how many unmerged entries are
841          * there.
842          */
843         cnt += count_unmerged_entries();
844
845         return cnt;
846 }
847
848 int cmd_merge(int argc, const char **argv, const char *prefix)
849 {
850         unsigned char result_tree[20];
851         struct strbuf buf = STRBUF_INIT;
852         const char *head_arg;
853         int flag, head_invalid = 0, i;
854         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
855         struct commit_list *common = NULL;
856         const char *best_strategy = NULL, *wt_strategy = NULL;
857         struct commit_list **remotes = &remoteheads;
858
859         setup_work_tree();
860         if (read_cache_unmerged())
861                 die("You are in the middle of a conflicted merge.");
862
863         /*
864          * Check if we are _not_ on a detached HEAD, i.e. if there is a
865          * current branch.
866          */
867         branch = resolve_ref("HEAD", head, 0, &flag);
868         if (branch && !prefixcmp(branch, "refs/heads/"))
869                 branch += 11;
870         if (is_null_sha1(head))
871                 head_invalid = 1;
872
873         git_config(git_merge_config, NULL);
874
875         /* for color.ui */
876         if (diff_use_color_default == -1)
877                 diff_use_color_default = git_use_color_default;
878
879         argc = parse_options(argc, argv, builtin_merge_options,
880                         builtin_merge_usage, 0);
881         if (verbosity < 0)
882                 show_diffstat = 0;
883
884         if (squash) {
885                 if (!allow_fast_forward)
886                         die("You cannot combine --squash with --no-ff.");
887                 option_commit = 0;
888         }
889
890         if (!argc)
891                 usage_with_options(builtin_merge_usage,
892                         builtin_merge_options);
893
894         /*
895          * This could be traditional "merge <msg> HEAD <commit>..."  and
896          * the way we can tell it is to see if the second token is HEAD,
897          * but some people might have misused the interface and used a
898          * committish that is the same as HEAD there instead.
899          * Traditional format never would have "-m" so it is an
900          * additional safety measure to check for it.
901          */
902
903         if (!have_message && is_old_style_invocation(argc, argv)) {
904                 strbuf_addstr(&merge_msg, argv[0]);
905                 head_arg = argv[1];
906                 argv += 2;
907                 argc -= 2;
908         } else if (head_invalid) {
909                 struct object *remote_head;
910                 /*
911                  * If the merged head is a valid one there is no reason
912                  * to forbid "git merge" into a branch yet to be born.
913                  * We do the same for "git pull".
914                  */
915                 if (argc != 1)
916                         die("Can merge only exactly one commit into "
917                                 "empty head");
918                 if (squash)
919                         die("Squash commit into empty head not supported yet");
920                 if (!allow_fast_forward)
921                         die("Non-fast-forward commit does not make sense into "
922                             "an empty head");
923                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
924                 if (!remote_head)
925                         die("%s - not something we can merge", argv[0]);
926                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
927                                 DIE_ON_ERR);
928                 reset_hard(remote_head->sha1, 0);
929                 return 0;
930         } else {
931                 struct strbuf msg = STRBUF_INIT;
932
933                 /* We are invoked directly as the first-class UI. */
934                 head_arg = "HEAD";
935
936                 /*
937                  * All the rest are the commits being merged;
938                  * prepare the standard merge summary message to
939                  * be appended to the given message.  If remote
940                  * is invalid we will die later in the common
941                  * codepath so we discard the error in this
942                  * loop.
943                  */
944                 for (i = 0; i < argc; i++)
945                         merge_name(argv[i], &msg);
946                 fmt_merge_msg(option_log, &msg, &merge_msg);
947                 if (merge_msg.len)
948                         strbuf_setlen(&merge_msg, merge_msg.len-1);
949         }
950
951         if (head_invalid || !argc)
952                 usage_with_options(builtin_merge_usage,
953                         builtin_merge_options);
954
955         strbuf_addstr(&buf, "merge");
956         for (i = 0; i < argc; i++)
957                 strbuf_addf(&buf, " %s", argv[i]);
958         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
959         strbuf_reset(&buf);
960
961         for (i = 0; i < argc; i++) {
962                 struct object *o;
963                 struct commit *commit;
964
965                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
966                 if (!o)
967                         die("%s - not something we can merge", argv[i]);
968                 commit = lookup_commit(o->sha1);
969                 commit->util = (void *)argv[i];
970                 remotes = &commit_list_insert(commit, remotes)->next;
971
972                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
973                 setenv(buf.buf, argv[i], 1);
974                 strbuf_reset(&buf);
975         }
976
977         if (!use_strategies) {
978                 if (!remoteheads->next)
979                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
980                 else
981                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
982         }
983
984         for (i = 0; i < use_strategies_nr; i++) {
985                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
986                         allow_fast_forward = 0;
987                 if (use_strategies[i]->attr & NO_TRIVIAL)
988                         allow_trivial = 0;
989         }
990
991         if (!remoteheads->next)
992                 common = get_merge_bases(lookup_commit(head),
993                                 remoteheads->item, 1);
994         else {
995                 struct commit_list *list = remoteheads;
996                 commit_list_insert(lookup_commit(head), &list);
997                 common = get_octopus_merge_bases(list);
998                 free(list);
999         }
1000
1001         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1002                 DIE_ON_ERR);
1003
1004         if (!common)
1005                 ; /* No common ancestors found. We need a real merge. */
1006         else if (!remoteheads->next && !common->next &&
1007                         common->item == remoteheads->item) {
1008                 /*
1009                  * If head can reach all the merge then we are up to date.
1010                  * but first the most common case of merging one remote.
1011                  */
1012                 finish_up_to_date("Already up-to-date.");
1013                 return 0;
1014         } else if (allow_fast_forward && !remoteheads->next &&
1015                         !common->next &&
1016                         !hashcmp(common->item->object.sha1, head)) {
1017                 /* Again the most common case of merging one remote. */
1018                 struct strbuf msg = STRBUF_INIT;
1019                 struct object *o;
1020                 char hex[41];
1021
1022                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1023
1024                 if (verbosity >= 0)
1025                         printf("Updating %s..%s\n",
1026                                 hex,
1027                                 find_unique_abbrev(remoteheads->item->object.sha1,
1028                                 DEFAULT_ABBREV));
1029                 strbuf_addstr(&msg, "Fast forward");
1030                 if (have_message)
1031                         strbuf_addstr(&msg,
1032                                 " (no commit created; -m option ignored)");
1033                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1034                         0, NULL, OBJ_COMMIT);
1035                 if (!o)
1036                         return 1;
1037
1038                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1039                         return 1;
1040
1041                 finish(o->sha1, msg.buf);
1042                 drop_save();
1043                 return 0;
1044         } else if (!remoteheads->next && common->next)
1045                 ;
1046                 /*
1047                  * We are not doing octopus and not fast forward.  Need
1048                  * a real merge.
1049                  */
1050         else if (!remoteheads->next && !common->next && option_commit) {
1051                 /*
1052                  * We are not doing octopus, not fast forward, and have
1053                  * only one common.
1054                  */
1055                 refresh_cache(REFRESH_QUIET);
1056                 if (allow_trivial) {
1057                         /* See if it is really trivial. */
1058                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1059                         printf("Trying really trivial in-index merge...\n");
1060                         if (!read_tree_trivial(common->item->object.sha1,
1061                                         head, remoteheads->item->object.sha1))
1062                                 return merge_trivial();
1063                         printf("Nope.\n");
1064                 }
1065         } else {
1066                 /*
1067                  * An octopus.  If we can reach all the remote we are up
1068                  * to date.
1069                  */
1070                 int up_to_date = 1;
1071                 struct commit_list *j;
1072
1073                 for (j = remoteheads; j; j = j->next) {
1074                         struct commit_list *common_one;
1075
1076                         /*
1077                          * Here we *have* to calculate the individual
1078                          * merge_bases again, otherwise "git merge HEAD^
1079                          * HEAD^^" would be missed.
1080                          */
1081                         common_one = get_merge_bases(lookup_commit(head),
1082                                 j->item, 1);
1083                         if (hashcmp(common_one->item->object.sha1,
1084                                 j->item->object.sha1)) {
1085                                 up_to_date = 0;
1086                                 break;
1087                         }
1088                 }
1089                 if (up_to_date) {
1090                         finish_up_to_date("Already up-to-date. Yeeah!");
1091                         return 0;
1092                 }
1093         }
1094
1095         /* We are going to make a new commit. */
1096         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1097
1098         /*
1099          * At this point, we need a real merge.  No matter what strategy
1100          * we use, it would operate on the index, possibly affecting the
1101          * working tree, and when resolved cleanly, have the desired
1102          * tree in the index -- this means that the index must be in
1103          * sync with the head commit.  The strategies are responsible
1104          * to ensure this.
1105          */
1106         if (use_strategies_nr != 1) {
1107                 /*
1108                  * Stash away the local changes so that we can try more
1109                  * than one.
1110                  */
1111                 save_state();
1112         } else {
1113                 memcpy(stash, null_sha1, 20);
1114         }
1115
1116         for (i = 0; i < use_strategies_nr; i++) {
1117                 int ret;
1118                 if (i) {
1119                         printf("Rewinding the tree to pristine...\n");
1120                         restore_state();
1121                 }
1122                 if (use_strategies_nr != 1)
1123                         printf("Trying merge strategy %s...\n",
1124                                 use_strategies[i]->name);
1125                 /*
1126                  * Remember which strategy left the state in the working
1127                  * tree.
1128                  */
1129                 wt_strategy = use_strategies[i]->name;
1130
1131                 ret = try_merge_strategy(use_strategies[i]->name,
1132                         common, head_arg);
1133                 if (!option_commit && !ret) {
1134                         merge_was_ok = 1;
1135                         /*
1136                          * This is necessary here just to avoid writing
1137                          * the tree, but later we will *not* exit with
1138                          * status code 1 because merge_was_ok is set.
1139                          */
1140                         ret = 1;
1141                 }
1142
1143                 if (ret) {
1144                         /*
1145                          * The backend exits with 1 when conflicts are
1146                          * left to be resolved, with 2 when it does not
1147                          * handle the given merge at all.
1148                          */
1149                         if (ret == 1) {
1150                                 int cnt = evaluate_result();
1151
1152                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1153                                         best_strategy = use_strategies[i]->name;
1154                                         best_cnt = cnt;
1155                                 }
1156                         }
1157                         if (merge_was_ok)
1158                                 break;
1159                         else
1160                                 continue;
1161                 }
1162
1163                 /* Automerge succeeded. */
1164                 write_tree_trivial(result_tree);
1165                 automerge_was_ok = 1;
1166                 break;
1167         }
1168
1169         /*
1170          * If we have a resulting tree, that means the strategy module
1171          * auto resolved the merge cleanly.
1172          */
1173         if (automerge_was_ok)
1174                 return finish_automerge(common, result_tree, wt_strategy);
1175
1176         /*
1177          * Pick the result from the best strategy and have the user fix
1178          * it up.
1179          */
1180         if (!best_strategy) {
1181                 restore_state();
1182                 if (use_strategies_nr > 1)
1183                         fprintf(stderr,
1184                                 "No merge strategy handled the merge.\n");
1185                 else
1186                         fprintf(stderr, "Merge with strategy %s failed.\n",
1187                                 use_strategies[0]->name);
1188                 return 2;
1189         } else if (best_strategy == wt_strategy)
1190                 ; /* We already have its result in the working tree. */
1191         else {
1192                 printf("Rewinding the tree to pristine...\n");
1193                 restore_state();
1194                 printf("Using the %s to prepare resolving by hand.\n",
1195                         best_strategy);
1196                 try_merge_strategy(best_strategy, common, head_arg);
1197         }
1198
1199         if (squash)
1200                 finish(NULL, NULL);
1201         else {
1202                 int fd;
1203                 struct commit_list *j;
1204
1205                 for (j = remoteheads; j; j = j->next)
1206                         strbuf_addf(&buf, "%s\n",
1207                                 sha1_to_hex(j->item->object.sha1));
1208                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1209                 if (fd < 0)
1210                         die("Could open %s for writing",
1211                                 git_path("MERGE_HEAD"));
1212                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1213                         die("Could not write to %s", git_path("MERGE_HEAD"));
1214                 close(fd);
1215                 strbuf_addch(&merge_msg, '\n');
1216                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1217                 if (fd < 0)
1218                         die("Could open %s for writing", git_path("MERGE_MSG"));
1219                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1220                         merge_msg.len)
1221                         die("Could not write to %s", git_path("MERGE_MSG"));
1222                 close(fd);
1223                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1224                 if (fd < 0)
1225                         die("Could open %s for writing", git_path("MERGE_MODE"));
1226                 strbuf_reset(&buf);
1227                 if (!allow_fast_forward)
1228                         strbuf_addf(&buf, "no-ff");
1229                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1230                         die("Could not write to %s", git_path("MERGE_MODE"));
1231                 close(fd);
1232         }
1233
1234         if (merge_was_ok) {
1235                 fprintf(stderr, "Automatic merge went well; "
1236                         "stopped before committing as requested\n");
1237                 return 0;
1238         } else
1239                 return suggest_conflicts();
1240 }