Merge branch 'sp/msysgit'
[git] / builtin-merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "parse-options.h"
11 #include "builtin.h"
12 #include "run-command.h"
13 #include "diff.h"
14 #include "refs.h"
15 #include "commit.h"
16 #include "diffcore.h"
17 #include "revision.h"
18 #include "unpack-trees.h"
19 #include "cache-tree.h"
20 #include "dir.h"
21 #include "utf8.h"
22 #include "log-tree.h"
23 #include "color.h"
24 #include "rerere.h"
25 #include "help.h"
26 #include "merge-recursive.h"
27
28 #define DEFAULT_TWOHEAD (1<<0)
29 #define DEFAULT_OCTOPUS (1<<1)
30 #define NO_FAST_FORWARD (1<<2)
31 #define NO_TRIVIAL      (1<<3)
32
33 struct strategy {
34         const char *name;
35         unsigned attr;
36 };
37
38 static const char * const builtin_merge_usage[] = {
39         "git merge [options] <remote>...",
40         "git merge [options] <msg> HEAD <remote>",
41         NULL
42 };
43
44 static int show_diffstat = 1, option_log, squash;
45 static int option_commit = 1, allow_fast_forward = 1;
46 static int allow_trivial = 1, have_message;
47 static struct strbuf merge_msg;
48 static struct commit_list *remoteheads;
49 static unsigned char head[20], stash[20];
50 static struct strategy **use_strategies;
51 static size_t use_strategies_nr, use_strategies_alloc;
52 static const char *branch;
53 static int verbosity;
54
55 static struct strategy all_strategy[] = {
56         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
57         { "octopus",    DEFAULT_OCTOPUS },
58         { "resolve",    0 },
59         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
60         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
61 };
62
63 static const char *pull_twohead, *pull_octopus;
64
65 static int option_parse_message(const struct option *opt,
66                                 const char *arg, int unset)
67 {
68         struct strbuf *buf = opt->value;
69
70         if (unset)
71                 strbuf_setlen(buf, 0);
72         else if (arg) {
73                 strbuf_addf(buf, "%s\n\n", arg);
74                 have_message = 1;
75         } else
76                 return error("switch `m' requires a value");
77         return 0;
78 }
79
80 static struct strategy *get_strategy(const char *name)
81 {
82         int i;
83         struct strategy *ret;
84         static struct cmdnames main_cmds, other_cmds;
85         static int loaded;
86
87         if (!name)
88                 return NULL;
89
90         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
91                 if (!strcmp(name, all_strategy[i].name))
92                         return &all_strategy[i];
93
94         if (!loaded) {
95                 struct cmdnames not_strategies;
96                 loaded = 1;
97
98                 memset(&not_strategies, 0, sizeof(struct cmdnames));
99                 load_command_list("git-merge-", &main_cmds, &other_cmds);
100                 for (i = 0; i < main_cmds.cnt; i++) {
101                         int j, found = 0;
102                         struct cmdname *ent = main_cmds.names[i];
103                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
104                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
105                                                 && !all_strategy[j].name[ent->len])
106                                         found = 1;
107                         if (!found)
108                                 add_cmdname(&not_strategies, ent->name, ent->len);
109                         exclude_cmds(&main_cmds, &not_strategies);
110                 }
111         }
112         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
113                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
114                 fprintf(stderr, "Available strategies are:");
115                 for (i = 0; i < main_cmds.cnt; i++)
116                         fprintf(stderr, " %s", main_cmds.names[i]->name);
117                 fprintf(stderr, ".\n");
118                 if (other_cmds.cnt) {
119                         fprintf(stderr, "Available custom strategies are:");
120                         for (i = 0; i < other_cmds.cnt; i++)
121                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
122                         fprintf(stderr, ".\n");
123                 }
124                 exit(1);
125         }
126
127         ret = xcalloc(1, sizeof(struct strategy));
128         ret->name = xstrdup(name);
129         return ret;
130 }
131
132 static void append_strategy(struct strategy *s)
133 {
134         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
135         use_strategies[use_strategies_nr++] = s;
136 }
137
138 static int option_parse_strategy(const struct option *opt,
139                                  const char *name, int unset)
140 {
141         if (unset)
142                 return 0;
143
144         append_strategy(get_strategy(name));
145         return 0;
146 }
147
148 static int option_parse_n(const struct option *opt,
149                           const char *arg, int unset)
150 {
151         show_diffstat = unset;
152         return 0;
153 }
154
155 static struct option builtin_merge_options[] = {
156         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
157                 "do not show a diffstat at the end of the merge",
158                 PARSE_OPT_NOARG, option_parse_n },
159         OPT_BOOLEAN(0, "stat", &show_diffstat,
160                 "show a diffstat at the end of the merge"),
161         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
162         OPT_BOOLEAN(0, "log", &option_log,
163                 "add list of one-line log to merge commit message"),
164         OPT_BOOLEAN(0, "squash", &squash,
165                 "create a single commit instead of doing a merge"),
166         OPT_BOOLEAN(0, "commit", &option_commit,
167                 "perform a commit if the merge succeeds (default)"),
168         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
169                 "allow fast forward (default)"),
170         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
171                 "merge strategy to use", option_parse_strategy),
172         OPT_CALLBACK('m', "message", &merge_msg, "message",
173                 "message to be used for the merge commit (if any)",
174                 option_parse_message),
175         OPT__VERBOSITY(&verbosity),
176         OPT_END()
177 };
178
179 /* Cleans up metadata that is uninteresting after a succeeded merge. */
180 static void drop_save(void)
181 {
182         unlink(git_path("MERGE_HEAD"));
183         unlink(git_path("MERGE_MSG"));
184         unlink(git_path("MERGE_MODE"));
185 }
186
187 static void save_state(void)
188 {
189         int len;
190         struct child_process cp;
191         struct strbuf buffer = STRBUF_INIT;
192         const char *argv[] = {"stash", "create", NULL};
193
194         memset(&cp, 0, sizeof(cp));
195         cp.argv = argv;
196         cp.out = -1;
197         cp.git_cmd = 1;
198
199         if (start_command(&cp))
200                 die("could not run stash.");
201         len = strbuf_read(&buffer, cp.out, 1024);
202         close(cp.out);
203
204         if (finish_command(&cp) || len < 0)
205                 die("stash failed");
206         else if (!len)
207                 return;
208         strbuf_setlen(&buffer, buffer.len-1);
209         if (get_sha1(buffer.buf, stash))
210                 die("not a valid object: %s", buffer.buf);
211 }
212
213 static void reset_hard(unsigned const char *sha1, int verbose)
214 {
215         int i = 0;
216         const char *args[6];
217
218         args[i++] = "read-tree";
219         if (verbose)
220                 args[i++] = "-v";
221         args[i++] = "--reset";
222         args[i++] = "-u";
223         args[i++] = sha1_to_hex(sha1);
224         args[i] = NULL;
225
226         if (run_command_v_opt(args, RUN_GIT_CMD))
227                 die("read-tree failed");
228 }
229
230 static void restore_state(void)
231 {
232         struct strbuf sb = STRBUF_INIT;
233         const char *args[] = { "stash", "apply", NULL, NULL };
234
235         if (is_null_sha1(stash))
236                 return;
237
238         reset_hard(head, 1);
239
240         args[2] = sha1_to_hex(stash);
241
242         /*
243          * It is OK to ignore error here, for example when there was
244          * nothing to restore.
245          */
246         run_command_v_opt(args, RUN_GIT_CMD);
247
248         strbuf_release(&sb);
249         refresh_cache(REFRESH_QUIET);
250 }
251
252 /* This is called when no merge was necessary. */
253 static void finish_up_to_date(const char *msg)
254 {
255         if (verbosity >= 0)
256                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
257         drop_save();
258 }
259
260 static void squash_message(void)
261 {
262         struct rev_info rev;
263         struct commit *commit;
264         struct strbuf out = STRBUF_INIT;
265         struct commit_list *j;
266         int fd;
267
268         printf("Squash commit -- not updating HEAD\n");
269         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
270         if (fd < 0)
271                 die("Could not write to %s", git_path("SQUASH_MSG"));
272
273         init_revisions(&rev, NULL);
274         rev.ignore_merges = 1;
275         rev.commit_format = CMIT_FMT_MEDIUM;
276
277         commit = lookup_commit(head);
278         commit->object.flags |= UNINTERESTING;
279         add_pending_object(&rev, &commit->object, NULL);
280
281         for (j = remoteheads; j; j = j->next)
282                 add_pending_object(&rev, &j->item->object, NULL);
283
284         setup_revisions(0, NULL, &rev, NULL);
285         if (prepare_revision_walk(&rev))
286                 die("revision walk setup failed");
287
288         strbuf_addstr(&out, "Squashed commit of the following:\n");
289         while ((commit = get_revision(&rev)) != NULL) {
290                 strbuf_addch(&out, '\n');
291                 strbuf_addf(&out, "commit %s\n",
292                         sha1_to_hex(commit->object.sha1));
293                 pretty_print_commit(rev.commit_format, commit, &out, rev.abbrev,
294                         NULL, NULL, rev.date_mode, 0);
295         }
296         if (write(fd, out.buf, out.len) < 0)
297                 die("Writing SQUASH_MSG: %s", strerror(errno));
298         if (close(fd))
299                 die("Finishing SQUASH_MSG: %s", strerror(errno));
300         strbuf_release(&out);
301 }
302
303 static void finish(const unsigned char *new_head, const char *msg)
304 {
305         struct strbuf reflog_message = STRBUF_INIT;
306
307         if (!msg)
308                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
309         else {
310                 if (verbosity >= 0)
311                         printf("%s\n", msg);
312                 strbuf_addf(&reflog_message, "%s: %s",
313                         getenv("GIT_REFLOG_ACTION"), msg);
314         }
315         if (squash) {
316                 squash_message();
317         } else {
318                 if (verbosity >= 0 && !merge_msg.len)
319                         printf("No merge message -- not updating HEAD\n");
320                 else {
321                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
322                         update_ref(reflog_message.buf, "HEAD",
323                                 new_head, head, 0,
324                                 DIE_ON_ERR);
325                         /*
326                          * We ignore errors in 'gc --auto', since the
327                          * user should see them.
328                          */
329                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
330                 }
331         }
332         if (new_head && show_diffstat) {
333                 struct diff_options opts;
334                 diff_setup(&opts);
335                 opts.output_format |=
336                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
337                 opts.detect_rename = DIFF_DETECT_RENAME;
338                 if (diff_use_color_default > 0)
339                         DIFF_OPT_SET(&opts, COLOR_DIFF);
340                 if (diff_setup_done(&opts) < 0)
341                         die("diff_setup_done failed");
342                 diff_tree_sha1(head, new_head, "", &opts);
343                 diffcore_std(&opts);
344                 diff_flush(&opts);
345         }
346
347         /* Run a post-merge hook */
348         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
349
350         strbuf_release(&reflog_message);
351 }
352
353 /* Get the name for the merge commit's message. */
354 static void merge_name(const char *remote, struct strbuf *msg)
355 {
356         struct object *remote_head;
357         unsigned char branch_head[20], buf_sha[20];
358         struct strbuf buf = STRBUF_INIT;
359         struct strbuf bname = STRBUF_INIT;
360         const char *ptr;
361         int len, early;
362
363         strbuf_branchname(&bname, remote);
364         remote = bname.buf;
365
366         memset(branch_head, 0, sizeof(branch_head));
367         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
368         if (!remote_head)
369                 die("'%s' does not point to a commit", remote);
370
371         strbuf_addstr(&buf, "refs/heads/");
372         strbuf_addstr(&buf, remote);
373         resolve_ref(buf.buf, branch_head, 0, 0);
374
375         if (!hashcmp(remote_head->sha1, branch_head)) {
376                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
377                         sha1_to_hex(branch_head), remote);
378                 goto cleanup;
379         }
380
381         /* See if remote matches <name>^^^.. or <name>~<number> */
382         for (len = 0, ptr = remote + strlen(remote);
383              remote < ptr && ptr[-1] == '^';
384              ptr--)
385                 len++;
386         if (len)
387                 early = 1;
388         else {
389                 early = 0;
390                 ptr = strrchr(remote, '~');
391                 if (ptr) {
392                         int seen_nonzero = 0;
393
394                         len++; /* count ~ */
395                         while (*++ptr && isdigit(*ptr)) {
396                                 seen_nonzero |= (*ptr != '0');
397                                 len++;
398                         }
399                         if (*ptr)
400                                 len = 0; /* not ...~<number> */
401                         else if (seen_nonzero)
402                                 early = 1;
403                         else if (len == 1)
404                                 early = 1; /* "name~" is "name~1"! */
405                 }
406         }
407         if (len) {
408                 struct strbuf truname = STRBUF_INIT;
409                 strbuf_addstr(&truname, "refs/heads/");
410                 strbuf_addstr(&truname, remote);
411                 strbuf_setlen(&truname, truname.len - len);
412                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
413                         strbuf_addf(msg,
414                                     "%s\t\tbranch '%s'%s of .\n",
415                                     sha1_to_hex(remote_head->sha1),
416                                     truname.buf + 11,
417                                     (early ? " (early part)" : ""));
418                         strbuf_release(&truname);
419                         goto cleanup;
420                 }
421         }
422
423         if (!strcmp(remote, "FETCH_HEAD") &&
424                         !access(git_path("FETCH_HEAD"), R_OK)) {
425                 FILE *fp;
426                 struct strbuf line = STRBUF_INIT;
427                 char *ptr;
428
429                 fp = fopen(git_path("FETCH_HEAD"), "r");
430                 if (!fp)
431                         die("could not open %s for reading: %s",
432                                 git_path("FETCH_HEAD"), strerror(errno));
433                 strbuf_getline(&line, fp, '\n');
434                 fclose(fp);
435                 ptr = strstr(line.buf, "\tnot-for-merge\t");
436                 if (ptr)
437                         strbuf_remove(&line, ptr-line.buf+1, 13);
438                 strbuf_addbuf(msg, &line);
439                 strbuf_release(&line);
440                 goto cleanup;
441         }
442         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
443                 sha1_to_hex(remote_head->sha1), remote);
444 cleanup:
445         strbuf_release(&buf);
446         strbuf_release(&bname);
447 }
448
449 static int git_merge_config(const char *k, const char *v, void *cb)
450 {
451         if (branch && !prefixcmp(k, "branch.") &&
452                 !prefixcmp(k + 7, branch) &&
453                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
454                 const char **argv;
455                 int argc;
456                 char *buf;
457
458                 buf = xstrdup(v);
459                 argc = split_cmdline(buf, &argv);
460                 if (argc < 0)
461                         die("Bad branch.%s.mergeoptions string", branch);
462                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
463                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
464                 argc++;
465                 parse_options(argc, argv, NULL, builtin_merge_options,
466                               builtin_merge_usage, 0);
467                 free(buf);
468         }
469
470         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
471                 show_diffstat = git_config_bool(k, v);
472         else if (!strcmp(k, "pull.twohead"))
473                 return git_config_string(&pull_twohead, k, v);
474         else if (!strcmp(k, "pull.octopus"))
475                 return git_config_string(&pull_octopus, k, v);
476         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
477                 option_log = git_config_bool(k, v);
478         return git_diff_ui_config(k, v, cb);
479 }
480
481 static int read_tree_trivial(unsigned char *common, unsigned char *head,
482                              unsigned char *one)
483 {
484         int i, nr_trees = 0;
485         struct tree *trees[MAX_UNPACK_TREES];
486         struct tree_desc t[MAX_UNPACK_TREES];
487         struct unpack_trees_options opts;
488
489         memset(&opts, 0, sizeof(opts));
490         opts.head_idx = 2;
491         opts.src_index = &the_index;
492         opts.dst_index = &the_index;
493         opts.update = 1;
494         opts.verbose_update = 1;
495         opts.trivial_merges_only = 1;
496         opts.merge = 1;
497         trees[nr_trees] = parse_tree_indirect(common);
498         if (!trees[nr_trees++])
499                 return -1;
500         trees[nr_trees] = parse_tree_indirect(head);
501         if (!trees[nr_trees++])
502                 return -1;
503         trees[nr_trees] = parse_tree_indirect(one);
504         if (!trees[nr_trees++])
505                 return -1;
506         opts.fn = threeway_merge;
507         cache_tree_free(&active_cache_tree);
508         for (i = 0; i < nr_trees; i++) {
509                 parse_tree(trees[i]);
510                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
511         }
512         if (unpack_trees(nr_trees, t, &opts))
513                 return -1;
514         return 0;
515 }
516
517 static void write_tree_trivial(unsigned char *sha1)
518 {
519         if (write_cache_as_tree(sha1, 0, NULL))
520                 die("git write-tree failed to write a tree");
521 }
522
523 static int try_merge_strategy(const char *strategy, struct commit_list *common,
524                               const char *head_arg)
525 {
526         const char **args;
527         int i = 0, ret;
528         struct commit_list *j;
529         struct strbuf buf = STRBUF_INIT;
530         int index_fd;
531         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
532
533         index_fd = hold_locked_index(lock, 1);
534         refresh_cache(REFRESH_QUIET);
535         if (active_cache_changed &&
536                         (write_cache(index_fd, active_cache, active_nr) ||
537                          commit_locked_index(lock)))
538                 return error("Unable to write index.");
539         rollback_lock_file(lock);
540
541         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
542                 int clean;
543                 struct commit *result;
544                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
545                 int index_fd;
546                 struct commit_list *reversed = NULL;
547                 struct merge_options o;
548
549                 if (remoteheads->next) {
550                         error("Not handling anything other than two heads merge.");
551                         return 2;
552                 }
553
554                 init_merge_options(&o);
555                 if (!strcmp(strategy, "subtree"))
556                         o.subtree_merge = 1;
557
558                 o.branch1 = head_arg;
559                 o.branch2 = remoteheads->item->util;
560
561                 for (j = common; j; j = j->next)
562                         commit_list_insert(j->item, &reversed);
563
564                 index_fd = hold_locked_index(lock, 1);
565                 clean = merge_recursive(&o, lookup_commit(head),
566                                 remoteheads->item, reversed, &result);
567                 if (active_cache_changed &&
568                                 (write_cache(index_fd, active_cache, active_nr) ||
569                                  commit_locked_index(lock)))
570                         die ("unable to write %s", get_index_file());
571                 rollback_lock_file(lock);
572                 return clean ? 0 : 1;
573         } else {
574                 args = xmalloc((4 + commit_list_count(common) +
575                                         commit_list_count(remoteheads)) * sizeof(char *));
576                 strbuf_addf(&buf, "merge-%s", strategy);
577                 args[i++] = buf.buf;
578                 for (j = common; j; j = j->next)
579                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
580                 args[i++] = "--";
581                 args[i++] = head_arg;
582                 for (j = remoteheads; j; j = j->next)
583                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
584                 args[i] = NULL;
585                 ret = run_command_v_opt(args, RUN_GIT_CMD);
586                 strbuf_release(&buf);
587                 i = 1;
588                 for (j = common; j; j = j->next)
589                         free((void *)args[i++]);
590                 i += 2;
591                 for (j = remoteheads; j; j = j->next)
592                         free((void *)args[i++]);
593                 free(args);
594                 discard_cache();
595                 if (read_cache() < 0)
596                         die("failed to read the cache");
597                 return -ret;
598         }
599 }
600
601 static void count_diff_files(struct diff_queue_struct *q,
602                              struct diff_options *opt, void *data)
603 {
604         int *count = data;
605
606         (*count) += q->nr;
607 }
608
609 static int count_unmerged_entries(void)
610 {
611         const struct index_state *state = &the_index;
612         int i, ret = 0;
613
614         for (i = 0; i < state->cache_nr; i++)
615                 if (ce_stage(state->cache[i]))
616                         ret++;
617
618         return ret;
619 }
620
621 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
622 {
623         struct tree *trees[MAX_UNPACK_TREES];
624         struct unpack_trees_options opts;
625         struct tree_desc t[MAX_UNPACK_TREES];
626         int i, fd, nr_trees = 0;
627         struct dir_struct dir;
628         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
629
630         refresh_cache(REFRESH_QUIET);
631
632         fd = hold_locked_index(lock_file, 1);
633
634         memset(&trees, 0, sizeof(trees));
635         memset(&opts, 0, sizeof(opts));
636         memset(&t, 0, sizeof(t));
637         memset(&dir, 0, sizeof(dir));
638         dir.flags |= DIR_SHOW_IGNORED;
639         dir.exclude_per_dir = ".gitignore";
640         opts.dir = &dir;
641
642         opts.head_idx = 1;
643         opts.src_index = &the_index;
644         opts.dst_index = &the_index;
645         opts.update = 1;
646         opts.verbose_update = 1;
647         opts.merge = 1;
648         opts.fn = twoway_merge;
649
650         trees[nr_trees] = parse_tree_indirect(head);
651         if (!trees[nr_trees++])
652                 return -1;
653         trees[nr_trees] = parse_tree_indirect(remote);
654         if (!trees[nr_trees++])
655                 return -1;
656         for (i = 0; i < nr_trees; i++) {
657                 parse_tree(trees[i]);
658                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
659         }
660         if (unpack_trees(nr_trees, t, &opts))
661                 return -1;
662         if (write_cache(fd, active_cache, active_nr) ||
663                 commit_locked_index(lock_file))
664                 die("unable to write new index file");
665         return 0;
666 }
667
668 static void split_merge_strategies(const char *string, struct strategy **list,
669                                    int *nr, int *alloc)
670 {
671         char *p, *q, *buf;
672
673         if (!string)
674                 return;
675
676         buf = xstrdup(string);
677         q = buf;
678         for (;;) {
679                 p = strchr(q, ' ');
680                 if (!p) {
681                         ALLOC_GROW(*list, *nr + 1, *alloc);
682                         (*list)[(*nr)++].name = xstrdup(q);
683                         free(buf);
684                         return;
685                 } else {
686                         *p = '\0';
687                         ALLOC_GROW(*list, *nr + 1, *alloc);
688                         (*list)[(*nr)++].name = xstrdup(q);
689                         q = ++p;
690                 }
691         }
692 }
693
694 static void add_strategies(const char *string, unsigned attr)
695 {
696         struct strategy *list = NULL;
697         int list_alloc = 0, list_nr = 0, i;
698
699         memset(&list, 0, sizeof(list));
700         split_merge_strategies(string, &list, &list_nr, &list_alloc);
701         if (list) {
702                 for (i = 0; i < list_nr; i++)
703                         append_strategy(get_strategy(list[i].name));
704                 return;
705         }
706         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
707                 if (all_strategy[i].attr & attr)
708                         append_strategy(&all_strategy[i]);
709
710 }
711
712 static int merge_trivial(void)
713 {
714         unsigned char result_tree[20], result_commit[20];
715         struct commit_list *parent = xmalloc(sizeof(*parent));
716
717         write_tree_trivial(result_tree);
718         printf("Wonderful.\n");
719         parent->item = lookup_commit(head);
720         parent->next = xmalloc(sizeof(*parent->next));
721         parent->next->item = remoteheads->item;
722         parent->next->next = NULL;
723         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
724         finish(result_commit, "In-index merge");
725         drop_save();
726         return 0;
727 }
728
729 static int finish_automerge(struct commit_list *common,
730                             unsigned char *result_tree,
731                             const char *wt_strategy)
732 {
733         struct commit_list *parents = NULL, *j;
734         struct strbuf buf = STRBUF_INIT;
735         unsigned char result_commit[20];
736
737         free_commit_list(common);
738         if (allow_fast_forward) {
739                 parents = remoteheads;
740                 commit_list_insert(lookup_commit(head), &parents);
741                 parents = reduce_heads(parents);
742         } else {
743                 struct commit_list **pptr = &parents;
744
745                 pptr = &commit_list_insert(lookup_commit(head),
746                                 pptr)->next;
747                 for (j = remoteheads; j; j = j->next)
748                         pptr = &commit_list_insert(j->item, pptr)->next;
749         }
750         free_commit_list(remoteheads);
751         strbuf_addch(&merge_msg, '\n');
752         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
753         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
754         finish(result_commit, buf.buf);
755         strbuf_release(&buf);
756         drop_save();
757         return 0;
758 }
759
760 static int suggest_conflicts(void)
761 {
762         FILE *fp;
763         int pos;
764
765         fp = fopen(git_path("MERGE_MSG"), "a");
766         if (!fp)
767                 die("Could not open %s for writing", git_path("MERGE_MSG"));
768         fprintf(fp, "\nConflicts:\n");
769         for (pos = 0; pos < active_nr; pos++) {
770                 struct cache_entry *ce = active_cache[pos];
771
772                 if (ce_stage(ce)) {
773                         fprintf(fp, "\t%s\n", ce->name);
774                         while (pos + 1 < active_nr &&
775                                         !strcmp(ce->name,
776                                                 active_cache[pos + 1]->name))
777                                 pos++;
778                 }
779         }
780         fclose(fp);
781         rerere();
782         printf("Automatic merge failed; "
783                         "fix conflicts and then commit the result.\n");
784         return 1;
785 }
786
787 static struct commit *is_old_style_invocation(int argc, const char **argv)
788 {
789         struct commit *second_token = NULL;
790         if (argc > 1) {
791                 unsigned char second_sha1[20];
792
793                 if (get_sha1(argv[1], second_sha1))
794                         return NULL;
795                 second_token = lookup_commit_reference_gently(second_sha1, 0);
796                 if (!second_token)
797                         die("'%s' is not a commit", argv[1]);
798                 if (hashcmp(second_token->object.sha1, head))
799                         return NULL;
800         }
801         return second_token;
802 }
803
804 static int evaluate_result(void)
805 {
806         int cnt = 0;
807         struct rev_info rev;
808
809         /* Check how many files differ. */
810         init_revisions(&rev, "");
811         setup_revisions(0, NULL, &rev, NULL);
812         rev.diffopt.output_format |=
813                 DIFF_FORMAT_CALLBACK;
814         rev.diffopt.format_callback = count_diff_files;
815         rev.diffopt.format_callback_data = &cnt;
816         run_diff_files(&rev, 0);
817
818         /*
819          * Check how many unmerged entries are
820          * there.
821          */
822         cnt += count_unmerged_entries();
823
824         return cnt;
825 }
826
827 int cmd_merge(int argc, const char **argv, const char *prefix)
828 {
829         unsigned char result_tree[20];
830         struct strbuf buf = STRBUF_INIT;
831         const char *head_arg;
832         int flag, head_invalid = 0, i;
833         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
834         struct commit_list *common = NULL;
835         const char *best_strategy = NULL, *wt_strategy = NULL;
836         struct commit_list **remotes = &remoteheads;
837
838         setup_work_tree();
839         if (file_exists(git_path("MERGE_HEAD")))
840                 die("You have not concluded your merge. (MERGE_HEAD exists)");
841         if (read_cache_unmerged())
842                 die("You are in the middle of a conflicted merge."
843                                 " (index unmerged)");
844
845         /*
846          * Check if we are _not_ on a detached HEAD, i.e. if there is a
847          * current branch.
848          */
849         branch = resolve_ref("HEAD", head, 0, &flag);
850         if (branch && !prefixcmp(branch, "refs/heads/"))
851                 branch += 11;
852         if (is_null_sha1(head))
853                 head_invalid = 1;
854
855         git_config(git_merge_config, NULL);
856
857         /* for color.ui */
858         if (diff_use_color_default == -1)
859                 diff_use_color_default = git_use_color_default;
860
861         argc = parse_options(argc, argv, prefix, builtin_merge_options,
862                         builtin_merge_usage, 0);
863         if (verbosity < 0)
864                 show_diffstat = 0;
865
866         if (squash) {
867                 if (!allow_fast_forward)
868                         die("You cannot combine --squash with --no-ff.");
869                 option_commit = 0;
870         }
871
872         if (!argc)
873                 usage_with_options(builtin_merge_usage,
874                         builtin_merge_options);
875
876         /*
877          * This could be traditional "merge <msg> HEAD <commit>..."  and
878          * the way we can tell it is to see if the second token is HEAD,
879          * but some people might have misused the interface and used a
880          * committish that is the same as HEAD there instead.
881          * Traditional format never would have "-m" so it is an
882          * additional safety measure to check for it.
883          */
884
885         if (!have_message && is_old_style_invocation(argc, argv)) {
886                 strbuf_addstr(&merge_msg, argv[0]);
887                 head_arg = argv[1];
888                 argv += 2;
889                 argc -= 2;
890         } else if (head_invalid) {
891                 struct object *remote_head;
892                 /*
893                  * If the merged head is a valid one there is no reason
894                  * to forbid "git merge" into a branch yet to be born.
895                  * We do the same for "git pull".
896                  */
897                 if (argc != 1)
898                         die("Can merge only exactly one commit into "
899                                 "empty head");
900                 if (squash)
901                         die("Squash commit into empty head not supported yet");
902                 if (!allow_fast_forward)
903                         die("Non-fast-forward commit does not make sense into "
904                             "an empty head");
905                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
906                 if (!remote_head)
907                         die("%s - not something we can merge", argv[0]);
908                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
909                                 DIE_ON_ERR);
910                 reset_hard(remote_head->sha1, 0);
911                 return 0;
912         } else {
913                 struct strbuf msg = STRBUF_INIT;
914
915                 /* We are invoked directly as the first-class UI. */
916                 head_arg = "HEAD";
917
918                 /*
919                  * All the rest are the commits being merged;
920                  * prepare the standard merge summary message to
921                  * be appended to the given message.  If remote
922                  * is invalid we will die later in the common
923                  * codepath so we discard the error in this
924                  * loop.
925                  */
926                 for (i = 0; i < argc; i++)
927                         merge_name(argv[i], &msg);
928                 fmt_merge_msg(option_log, &msg, &merge_msg);
929                 if (merge_msg.len)
930                         strbuf_setlen(&merge_msg, merge_msg.len-1);
931         }
932
933         if (head_invalid || !argc)
934                 usage_with_options(builtin_merge_usage,
935                         builtin_merge_options);
936
937         strbuf_addstr(&buf, "merge");
938         for (i = 0; i < argc; i++)
939                 strbuf_addf(&buf, " %s", argv[i]);
940         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
941         strbuf_reset(&buf);
942
943         for (i = 0; i < argc; i++) {
944                 struct object *o;
945                 struct commit *commit;
946
947                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
948                 if (!o)
949                         die("%s - not something we can merge", argv[i]);
950                 commit = lookup_commit(o->sha1);
951                 commit->util = (void *)argv[i];
952                 remotes = &commit_list_insert(commit, remotes)->next;
953
954                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
955                 setenv(buf.buf, argv[i], 1);
956                 strbuf_reset(&buf);
957         }
958
959         if (!use_strategies) {
960                 if (!remoteheads->next)
961                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
962                 else
963                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
964         }
965
966         for (i = 0; i < use_strategies_nr; i++) {
967                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
968                         allow_fast_forward = 0;
969                 if (use_strategies[i]->attr & NO_TRIVIAL)
970                         allow_trivial = 0;
971         }
972
973         if (!remoteheads->next)
974                 common = get_merge_bases(lookup_commit(head),
975                                 remoteheads->item, 1);
976         else {
977                 struct commit_list *list = remoteheads;
978                 commit_list_insert(lookup_commit(head), &list);
979                 common = get_octopus_merge_bases(list);
980                 free(list);
981         }
982
983         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
984                 DIE_ON_ERR);
985
986         if (!common)
987                 ; /* No common ancestors found. We need a real merge. */
988         else if (!remoteheads->next && !common->next &&
989                         common->item == remoteheads->item) {
990                 /*
991                  * If head can reach all the merge then we are up to date.
992                  * but first the most common case of merging one remote.
993                  */
994                 finish_up_to_date("Already up-to-date.");
995                 return 0;
996         } else if (allow_fast_forward && !remoteheads->next &&
997                         !common->next &&
998                         !hashcmp(common->item->object.sha1, head)) {
999                 /* Again the most common case of merging one remote. */
1000                 struct strbuf msg = STRBUF_INIT;
1001                 struct object *o;
1002                 char hex[41];
1003
1004                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1005
1006                 if (verbosity >= 0)
1007                         printf("Updating %s..%s\n",
1008                                 hex,
1009                                 find_unique_abbrev(remoteheads->item->object.sha1,
1010                                 DEFAULT_ABBREV));
1011                 strbuf_addstr(&msg, "Fast forward");
1012                 if (have_message)
1013                         strbuf_addstr(&msg,
1014                                 " (no commit created; -m option ignored)");
1015                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1016                         0, NULL, OBJ_COMMIT);
1017                 if (!o)
1018                         return 1;
1019
1020                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1021                         return 1;
1022
1023                 finish(o->sha1, msg.buf);
1024                 drop_save();
1025                 return 0;
1026         } else if (!remoteheads->next && common->next)
1027                 ;
1028                 /*
1029                  * We are not doing octopus and not fast forward.  Need
1030                  * a real merge.
1031                  */
1032         else if (!remoteheads->next && !common->next && option_commit) {
1033                 /*
1034                  * We are not doing octopus, not fast forward, and have
1035                  * only one common.
1036                  */
1037                 refresh_cache(REFRESH_QUIET);
1038                 if (allow_trivial) {
1039                         /* See if it is really trivial. */
1040                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1041                         printf("Trying really trivial in-index merge...\n");
1042                         if (!read_tree_trivial(common->item->object.sha1,
1043                                         head, remoteheads->item->object.sha1))
1044                                 return merge_trivial();
1045                         printf("Nope.\n");
1046                 }
1047         } else {
1048                 /*
1049                  * An octopus.  If we can reach all the remote we are up
1050                  * to date.
1051                  */
1052                 int up_to_date = 1;
1053                 struct commit_list *j;
1054
1055                 for (j = remoteheads; j; j = j->next) {
1056                         struct commit_list *common_one;
1057
1058                         /*
1059                          * Here we *have* to calculate the individual
1060                          * merge_bases again, otherwise "git merge HEAD^
1061                          * HEAD^^" would be missed.
1062                          */
1063                         common_one = get_merge_bases(lookup_commit(head),
1064                                 j->item, 1);
1065                         if (hashcmp(common_one->item->object.sha1,
1066                                 j->item->object.sha1)) {
1067                                 up_to_date = 0;
1068                                 break;
1069                         }
1070                 }
1071                 if (up_to_date) {
1072                         finish_up_to_date("Already up-to-date. Yeeah!");
1073                         return 0;
1074                 }
1075         }
1076
1077         /* We are going to make a new commit. */
1078         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1079
1080         /*
1081          * At this point, we need a real merge.  No matter what strategy
1082          * we use, it would operate on the index, possibly affecting the
1083          * working tree, and when resolved cleanly, have the desired
1084          * tree in the index -- this means that the index must be in
1085          * sync with the head commit.  The strategies are responsible
1086          * to ensure this.
1087          */
1088         if (use_strategies_nr != 1) {
1089                 /*
1090                  * Stash away the local changes so that we can try more
1091                  * than one.
1092                  */
1093                 save_state();
1094         } else {
1095                 memcpy(stash, null_sha1, 20);
1096         }
1097
1098         for (i = 0; i < use_strategies_nr; i++) {
1099                 int ret;
1100                 if (i) {
1101                         printf("Rewinding the tree to pristine...\n");
1102                         restore_state();
1103                 }
1104                 if (use_strategies_nr != 1)
1105                         printf("Trying merge strategy %s...\n",
1106                                 use_strategies[i]->name);
1107                 /*
1108                  * Remember which strategy left the state in the working
1109                  * tree.
1110                  */
1111                 wt_strategy = use_strategies[i]->name;
1112
1113                 ret = try_merge_strategy(use_strategies[i]->name,
1114                         common, head_arg);
1115                 if (!option_commit && !ret) {
1116                         merge_was_ok = 1;
1117                         /*
1118                          * This is necessary here just to avoid writing
1119                          * the tree, but later we will *not* exit with
1120                          * status code 1 because merge_was_ok is set.
1121                          */
1122                         ret = 1;
1123                 }
1124
1125                 if (ret) {
1126                         /*
1127                          * The backend exits with 1 when conflicts are
1128                          * left to be resolved, with 2 when it does not
1129                          * handle the given merge at all.
1130                          */
1131                         if (ret == 1) {
1132                                 int cnt = evaluate_result();
1133
1134                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1135                                         best_strategy = use_strategies[i]->name;
1136                                         best_cnt = cnt;
1137                                 }
1138                         }
1139                         if (merge_was_ok)
1140                                 break;
1141                         else
1142                                 continue;
1143                 }
1144
1145                 /* Automerge succeeded. */
1146                 write_tree_trivial(result_tree);
1147                 automerge_was_ok = 1;
1148                 break;
1149         }
1150
1151         /*
1152          * If we have a resulting tree, that means the strategy module
1153          * auto resolved the merge cleanly.
1154          */
1155         if (automerge_was_ok)
1156                 return finish_automerge(common, result_tree, wt_strategy);
1157
1158         /*
1159          * Pick the result from the best strategy and have the user fix
1160          * it up.
1161          */
1162         if (!best_strategy) {
1163                 restore_state();
1164                 if (use_strategies_nr > 1)
1165                         fprintf(stderr,
1166                                 "No merge strategy handled the merge.\n");
1167                 else
1168                         fprintf(stderr, "Merge with strategy %s failed.\n",
1169                                 use_strategies[0]->name);
1170                 return 2;
1171         } else if (best_strategy == wt_strategy)
1172                 ; /* We already have its result in the working tree. */
1173         else {
1174                 printf("Rewinding the tree to pristine...\n");
1175                 restore_state();
1176                 printf("Using the %s to prepare resolving by hand.\n",
1177                         best_strategy);
1178                 try_merge_strategy(best_strategy, common, head_arg);
1179         }
1180
1181         if (squash)
1182                 finish(NULL, NULL);
1183         else {
1184                 int fd;
1185                 struct commit_list *j;
1186
1187                 for (j = remoteheads; j; j = j->next)
1188                         strbuf_addf(&buf, "%s\n",
1189                                 sha1_to_hex(j->item->object.sha1));
1190                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1191                 if (fd < 0)
1192                         die("Could open %s for writing",
1193                                 git_path("MERGE_HEAD"));
1194                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1195                         die("Could not write to %s", git_path("MERGE_HEAD"));
1196                 close(fd);
1197                 strbuf_addch(&merge_msg, '\n');
1198                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1199                 if (fd < 0)
1200                         die("Could open %s for writing", git_path("MERGE_MSG"));
1201                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1202                         merge_msg.len)
1203                         die("Could not write to %s", git_path("MERGE_MSG"));
1204                 close(fd);
1205                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1206                 if (fd < 0)
1207                         die("Could open %s for writing", git_path("MERGE_MODE"));
1208                 strbuf_reset(&buf);
1209                 if (!allow_fast_forward)
1210                         strbuf_addf(&buf, "no-ff");
1211                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1212                         die("Could not write to %s", git_path("MERGE_MODE"));
1213                 close(fd);
1214         }
1215
1216         if (merge_was_ok) {
1217                 fprintf(stderr, "Automatic merge went well; "
1218                         "stopped before committing as requested\n");
1219                 return 0;
1220         } else
1221                 return suggest_conflicts();
1222 }