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