Merge branch 'jc/commit-s-subject-is-not-a-footer'
[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         struct pretty_print_context ctx = {0};
268
269         printf("Squash commit -- not updating HEAD\n");
270         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
271         if (fd < 0)
272                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
273
274         init_revisions(&rev, NULL);
275         rev.ignore_merges = 1;
276         rev.commit_format = CMIT_FMT_MEDIUM;
277
278         commit = lookup_commit(head);
279         commit->object.flags |= UNINTERESTING;
280         add_pending_object(&rev, &commit->object, NULL);
281
282         for (j = remoteheads; j; j = j->next)
283                 add_pending_object(&rev, &j->item->object, NULL);
284
285         setup_revisions(0, NULL, &rev, NULL);
286         if (prepare_revision_walk(&rev))
287                 die("revision walk setup failed");
288
289         ctx.abbrev = rev.abbrev;
290         ctx.date_mode = rev.date_mode;
291
292         strbuf_addstr(&out, "Squashed commit of the following:\n");
293         while ((commit = get_revision(&rev)) != NULL) {
294                 strbuf_addch(&out, '\n');
295                 strbuf_addf(&out, "commit %s\n",
296                         sha1_to_hex(commit->object.sha1));
297                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
298         }
299         if (write(fd, out.buf, out.len) < 0)
300                 die_errno("Writing SQUASH_MSG");
301         if (close(fd))
302                 die_errno("Finishing SQUASH_MSG");
303         strbuf_release(&out);
304 }
305
306 static void finish(const unsigned char *new_head, const char *msg)
307 {
308         struct strbuf reflog_message = STRBUF_INIT;
309
310         if (!msg)
311                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
312         else {
313                 if (verbosity >= 0)
314                         printf("%s\n", msg);
315                 strbuf_addf(&reflog_message, "%s: %s",
316                         getenv("GIT_REFLOG_ACTION"), msg);
317         }
318         if (squash) {
319                 squash_message();
320         } else {
321                 if (verbosity >= 0 && !merge_msg.len)
322                         printf("No merge message -- not updating HEAD\n");
323                 else {
324                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
325                         update_ref(reflog_message.buf, "HEAD",
326                                 new_head, head, 0,
327                                 DIE_ON_ERR);
328                         /*
329                          * We ignore errors in 'gc --auto', since the
330                          * user should see them.
331                          */
332                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
333                 }
334         }
335         if (new_head && show_diffstat) {
336                 struct diff_options opts;
337                 diff_setup(&opts);
338                 opts.output_format |=
339                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
340                 opts.detect_rename = DIFF_DETECT_RENAME;
341                 if (diff_use_color_default > 0)
342                         DIFF_OPT_SET(&opts, COLOR_DIFF);
343                 if (diff_setup_done(&opts) < 0)
344                         die("diff_setup_done failed");
345                 diff_tree_sha1(head, new_head, "", &opts);
346                 diffcore_std(&opts);
347                 diff_flush(&opts);
348         }
349
350         /* Run a post-merge hook */
351         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
352
353         strbuf_release(&reflog_message);
354 }
355
356 /* Get the name for the merge commit's message. */
357 static void merge_name(const char *remote, struct strbuf *msg)
358 {
359         struct object *remote_head;
360         unsigned char branch_head[20], buf_sha[20];
361         struct strbuf buf = STRBUF_INIT;
362         struct strbuf bname = STRBUF_INIT;
363         const char *ptr;
364         char *found_ref;
365         int len, early;
366
367         strbuf_branchname(&bname, remote);
368         remote = bname.buf;
369
370         memset(branch_head, 0, sizeof(branch_head));
371         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
372         if (!remote_head)
373                 die("'%s' does not point to a commit", remote);
374
375         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
376                 if (!prefixcmp(found_ref, "refs/heads/")) {
377                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
378                                     sha1_to_hex(branch_head), remote);
379                         goto cleanup;
380                 }
381                 if (!prefixcmp(found_ref, "refs/remotes/")) {
382                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
383                                     sha1_to_hex(branch_head), remote);
384                         goto cleanup;
385                 }
386         }
387
388         /* See if remote matches <name>^^^.. or <name>~<number> */
389         for (len = 0, ptr = remote + strlen(remote);
390              remote < ptr && ptr[-1] == '^';
391              ptr--)
392                 len++;
393         if (len)
394                 early = 1;
395         else {
396                 early = 0;
397                 ptr = strrchr(remote, '~');
398                 if (ptr) {
399                         int seen_nonzero = 0;
400
401                         len++; /* count ~ */
402                         while (*++ptr && isdigit(*ptr)) {
403                                 seen_nonzero |= (*ptr != '0');
404                                 len++;
405                         }
406                         if (*ptr)
407                                 len = 0; /* not ...~<number> */
408                         else if (seen_nonzero)
409                                 early = 1;
410                         else if (len == 1)
411                                 early = 1; /* "name~" is "name~1"! */
412                 }
413         }
414         if (len) {
415                 struct strbuf truname = STRBUF_INIT;
416                 strbuf_addstr(&truname, "refs/heads/");
417                 strbuf_addstr(&truname, remote);
418                 strbuf_setlen(&truname, truname.len - len);
419                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
420                         strbuf_addf(msg,
421                                     "%s\t\tbranch '%s'%s of .\n",
422                                     sha1_to_hex(remote_head->sha1),
423                                     truname.buf + 11,
424                                     (early ? " (early part)" : ""));
425                         strbuf_release(&truname);
426                         goto cleanup;
427                 }
428         }
429
430         if (!strcmp(remote, "FETCH_HEAD") &&
431                         !access(git_path("FETCH_HEAD"), R_OK)) {
432                 FILE *fp;
433                 struct strbuf line = STRBUF_INIT;
434                 char *ptr;
435
436                 fp = fopen(git_path("FETCH_HEAD"), "r");
437                 if (!fp)
438                         die_errno("could not open '%s' for reading",
439                                   git_path("FETCH_HEAD"));
440                 strbuf_getline(&line, fp, '\n');
441                 fclose(fp);
442                 ptr = strstr(line.buf, "\tnot-for-merge\t");
443                 if (ptr)
444                         strbuf_remove(&line, ptr-line.buf+1, 13);
445                 strbuf_addbuf(msg, &line);
446                 strbuf_release(&line);
447                 goto cleanup;
448         }
449         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
450                 sha1_to_hex(remote_head->sha1), remote);
451 cleanup:
452         strbuf_release(&buf);
453         strbuf_release(&bname);
454 }
455
456 static int git_merge_config(const char *k, const char *v, void *cb)
457 {
458         if (branch && !prefixcmp(k, "branch.") &&
459                 !prefixcmp(k + 7, branch) &&
460                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
461                 const char **argv;
462                 int argc;
463                 char *buf;
464
465                 buf = xstrdup(v);
466                 argc = split_cmdline(buf, &argv);
467                 if (argc < 0)
468                         die("Bad branch.%s.mergeoptions string", branch);
469                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
470                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
471                 argc++;
472                 parse_options(argc, argv, NULL, builtin_merge_options,
473                               builtin_merge_usage, 0);
474                 free(buf);
475         }
476
477         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
478                 show_diffstat = git_config_bool(k, v);
479         else if (!strcmp(k, "pull.twohead"))
480                 return git_config_string(&pull_twohead, k, v);
481         else if (!strcmp(k, "pull.octopus"))
482                 return git_config_string(&pull_octopus, k, v);
483         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
484                 option_log = git_config_bool(k, v);
485         return git_diff_ui_config(k, v, cb);
486 }
487
488 static int read_tree_trivial(unsigned char *common, unsigned char *head,
489                              unsigned char *one)
490 {
491         int i, nr_trees = 0;
492         struct tree *trees[MAX_UNPACK_TREES];
493         struct tree_desc t[MAX_UNPACK_TREES];
494         struct unpack_trees_options opts;
495
496         memset(&opts, 0, sizeof(opts));
497         opts.head_idx = 2;
498         opts.src_index = &the_index;
499         opts.dst_index = &the_index;
500         opts.update = 1;
501         opts.verbose_update = 1;
502         opts.trivial_merges_only = 1;
503         opts.merge = 1;
504         trees[nr_trees] = parse_tree_indirect(common);
505         if (!trees[nr_trees++])
506                 return -1;
507         trees[nr_trees] = parse_tree_indirect(head);
508         if (!trees[nr_trees++])
509                 return -1;
510         trees[nr_trees] = parse_tree_indirect(one);
511         if (!trees[nr_trees++])
512                 return -1;
513         opts.fn = threeway_merge;
514         cache_tree_free(&active_cache_tree);
515         for (i = 0; i < nr_trees; i++) {
516                 parse_tree(trees[i]);
517                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
518         }
519         if (unpack_trees(nr_trees, t, &opts))
520                 return -1;
521         return 0;
522 }
523
524 static void write_tree_trivial(unsigned char *sha1)
525 {
526         if (write_cache_as_tree(sha1, 0, NULL))
527                 die("git write-tree failed to write a tree");
528 }
529
530 static int try_merge_strategy(const char *strategy, struct commit_list *common,
531                               const char *head_arg)
532 {
533         const char **args;
534         int i = 0, ret;
535         struct commit_list *j;
536         struct strbuf buf = STRBUF_INIT;
537         int index_fd;
538         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
539
540         index_fd = hold_locked_index(lock, 1);
541         refresh_cache(REFRESH_QUIET);
542         if (active_cache_changed &&
543                         (write_cache(index_fd, active_cache, active_nr) ||
544                          commit_locked_index(lock)))
545                 return error("Unable to write index.");
546         rollback_lock_file(lock);
547
548         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
549                 int clean;
550                 struct commit *result;
551                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
552                 int index_fd;
553                 struct commit_list *reversed = NULL;
554                 struct merge_options o;
555
556                 if (remoteheads->next) {
557                         error("Not handling anything other than two heads merge.");
558                         return 2;
559                 }
560
561                 init_merge_options(&o);
562                 if (!strcmp(strategy, "subtree"))
563                         o.subtree_merge = 1;
564
565                 o.branch1 = head_arg;
566                 o.branch2 = remoteheads->item->util;
567
568                 for (j = common; j; j = j->next)
569                         commit_list_insert(j->item, &reversed);
570
571                 index_fd = hold_locked_index(lock, 1);
572                 clean = merge_recursive(&o, lookup_commit(head),
573                                 remoteheads->item, reversed, &result);
574                 if (active_cache_changed &&
575                                 (write_cache(index_fd, active_cache, active_nr) ||
576                                  commit_locked_index(lock)))
577                         die ("unable to write %s", get_index_file());
578                 rollback_lock_file(lock);
579                 return clean ? 0 : 1;
580         } else {
581                 args = xmalloc((4 + commit_list_count(common) +
582                                         commit_list_count(remoteheads)) * sizeof(char *));
583                 strbuf_addf(&buf, "merge-%s", strategy);
584                 args[i++] = buf.buf;
585                 for (j = common; j; j = j->next)
586                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
587                 args[i++] = "--";
588                 args[i++] = head_arg;
589                 for (j = remoteheads; j; j = j->next)
590                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
591                 args[i] = NULL;
592                 ret = run_command_v_opt(args, RUN_GIT_CMD);
593                 strbuf_release(&buf);
594                 i = 1;
595                 for (j = common; j; j = j->next)
596                         free((void *)args[i++]);
597                 i += 2;
598                 for (j = remoteheads; j; j = j->next)
599                         free((void *)args[i++]);
600                 free(args);
601                 discard_cache();
602                 if (read_cache() < 0)
603                         die("failed to read the cache");
604                 return ret;
605         }
606 }
607
608 static void count_diff_files(struct diff_queue_struct *q,
609                              struct diff_options *opt, void *data)
610 {
611         int *count = data;
612
613         (*count) += q->nr;
614 }
615
616 static int count_unmerged_entries(void)
617 {
618         const struct index_state *state = &the_index;
619         int i, ret = 0;
620
621         for (i = 0; i < state->cache_nr; i++)
622                 if (ce_stage(state->cache[i]))
623                         ret++;
624
625         return ret;
626 }
627
628 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
629 {
630         struct tree *trees[MAX_UNPACK_TREES];
631         struct unpack_trees_options opts;
632         struct tree_desc t[MAX_UNPACK_TREES];
633         int i, fd, nr_trees = 0;
634         struct dir_struct dir;
635         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
636
637         refresh_cache(REFRESH_QUIET);
638
639         fd = hold_locked_index(lock_file, 1);
640
641         memset(&trees, 0, sizeof(trees));
642         memset(&opts, 0, sizeof(opts));
643         memset(&t, 0, sizeof(t));
644         memset(&dir, 0, sizeof(dir));
645         dir.flags |= DIR_SHOW_IGNORED;
646         dir.exclude_per_dir = ".gitignore";
647         opts.dir = &dir;
648
649         opts.head_idx = 1;
650         opts.src_index = &the_index;
651         opts.dst_index = &the_index;
652         opts.update = 1;
653         opts.verbose_update = 1;
654         opts.merge = 1;
655         opts.fn = twoway_merge;
656
657         trees[nr_trees] = parse_tree_indirect(head);
658         if (!trees[nr_trees++])
659                 return -1;
660         trees[nr_trees] = parse_tree_indirect(remote);
661         if (!trees[nr_trees++])
662                 return -1;
663         for (i = 0; i < nr_trees; i++) {
664                 parse_tree(trees[i]);
665                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
666         }
667         if (unpack_trees(nr_trees, t, &opts))
668                 return -1;
669         if (write_cache(fd, active_cache, active_nr) ||
670                 commit_locked_index(lock_file))
671                 die("unable to write new index file");
672         return 0;
673 }
674
675 static void split_merge_strategies(const char *string, struct strategy **list,
676                                    int *nr, int *alloc)
677 {
678         char *p, *q, *buf;
679
680         if (!string)
681                 return;
682
683         buf = xstrdup(string);
684         q = buf;
685         for (;;) {
686                 p = strchr(q, ' ');
687                 if (!p) {
688                         ALLOC_GROW(*list, *nr + 1, *alloc);
689                         (*list)[(*nr)++].name = xstrdup(q);
690                         free(buf);
691                         return;
692                 } else {
693                         *p = '\0';
694                         ALLOC_GROW(*list, *nr + 1, *alloc);
695                         (*list)[(*nr)++].name = xstrdup(q);
696                         q = ++p;
697                 }
698         }
699 }
700
701 static void add_strategies(const char *string, unsigned attr)
702 {
703         struct strategy *list = NULL;
704         int list_alloc = 0, list_nr = 0, i;
705
706         memset(&list, 0, sizeof(list));
707         split_merge_strategies(string, &list, &list_nr, &list_alloc);
708         if (list) {
709                 for (i = 0; i < list_nr; i++)
710                         append_strategy(get_strategy(list[i].name));
711                 return;
712         }
713         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
714                 if (all_strategy[i].attr & attr)
715                         append_strategy(&all_strategy[i]);
716
717 }
718
719 static int merge_trivial(void)
720 {
721         unsigned char result_tree[20], result_commit[20];
722         struct commit_list *parent = xmalloc(sizeof(*parent));
723
724         write_tree_trivial(result_tree);
725         printf("Wonderful.\n");
726         parent->item = lookup_commit(head);
727         parent->next = xmalloc(sizeof(*parent->next));
728         parent->next->item = remoteheads->item;
729         parent->next->next = NULL;
730         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
731         finish(result_commit, "In-index merge");
732         drop_save();
733         return 0;
734 }
735
736 static int finish_automerge(struct commit_list *common,
737                             unsigned char *result_tree,
738                             const char *wt_strategy)
739 {
740         struct commit_list *parents = NULL, *j;
741         struct strbuf buf = STRBUF_INIT;
742         unsigned char result_commit[20];
743
744         free_commit_list(common);
745         if (allow_fast_forward) {
746                 parents = remoteheads;
747                 commit_list_insert(lookup_commit(head), &parents);
748                 parents = reduce_heads(parents);
749         } else {
750                 struct commit_list **pptr = &parents;
751
752                 pptr = &commit_list_insert(lookup_commit(head),
753                                 pptr)->next;
754                 for (j = remoteheads; j; j = j->next)
755                         pptr = &commit_list_insert(j->item, pptr)->next;
756         }
757         free_commit_list(remoteheads);
758         strbuf_addch(&merge_msg, '\n');
759         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
760         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
761         finish(result_commit, buf.buf);
762         strbuf_release(&buf);
763         drop_save();
764         return 0;
765 }
766
767 static int suggest_conflicts(void)
768 {
769         FILE *fp;
770         int pos;
771
772         fp = fopen(git_path("MERGE_MSG"), "a");
773         if (!fp)
774                 die_errno("Could not open '%s' for writing",
775                           git_path("MERGE_MSG"));
776         fprintf(fp, "\nConflicts:\n");
777         for (pos = 0; pos < active_nr; pos++) {
778                 struct cache_entry *ce = active_cache[pos];
779
780                 if (ce_stage(ce)) {
781                         fprintf(fp, "\t%s\n", ce->name);
782                         while (pos + 1 < active_nr &&
783                                         !strcmp(ce->name,
784                                                 active_cache[pos + 1]->name))
785                                 pos++;
786                 }
787         }
788         fclose(fp);
789         rerere();
790         printf("Automatic merge failed; "
791                         "fix conflicts and then commit the result.\n");
792         return 1;
793 }
794
795 static struct commit *is_old_style_invocation(int argc, const char **argv)
796 {
797         struct commit *second_token = NULL;
798         if (argc > 1) {
799                 unsigned char second_sha1[20];
800
801                 if (get_sha1(argv[1], second_sha1))
802                         return NULL;
803                 second_token = lookup_commit_reference_gently(second_sha1, 0);
804                 if (!second_token)
805                         die("'%s' is not a commit", argv[1]);
806                 if (hashcmp(second_token->object.sha1, head))
807                         return NULL;
808         }
809         return second_token;
810 }
811
812 static int evaluate_result(void)
813 {
814         int cnt = 0;
815         struct rev_info rev;
816
817         /* Check how many files differ. */
818         init_revisions(&rev, "");
819         setup_revisions(0, NULL, &rev, NULL);
820         rev.diffopt.output_format |=
821                 DIFF_FORMAT_CALLBACK;
822         rev.diffopt.format_callback = count_diff_files;
823         rev.diffopt.format_callback_data = &cnt;
824         run_diff_files(&rev, 0);
825
826         /*
827          * Check how many unmerged entries are
828          * there.
829          */
830         cnt += count_unmerged_entries();
831
832         return cnt;
833 }
834
835 int cmd_merge(int argc, const char **argv, const char *prefix)
836 {
837         unsigned char result_tree[20];
838         struct strbuf buf = STRBUF_INIT;
839         const char *head_arg;
840         int flag, head_invalid = 0, i;
841         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
842         struct commit_list *common = NULL;
843         const char *best_strategy = NULL, *wt_strategy = NULL;
844         struct commit_list **remotes = &remoteheads;
845
846         setup_work_tree();
847         if (file_exists(git_path("MERGE_HEAD")))
848                 die("You have not concluded your merge. (MERGE_HEAD exists)");
849         if (read_cache_unmerged())
850                 die("You are in the middle of a conflicted merge."
851                                 " (index unmerged)");
852
853         /*
854          * Check if we are _not_ on a detached HEAD, i.e. if there is a
855          * current branch.
856          */
857         branch = resolve_ref("HEAD", head, 0, &flag);
858         if (branch && !prefixcmp(branch, "refs/heads/"))
859                 branch += 11;
860         if (is_null_sha1(head))
861                 head_invalid = 1;
862
863         git_config(git_merge_config, NULL);
864
865         /* for color.ui */
866         if (diff_use_color_default == -1)
867                 diff_use_color_default = git_use_color_default;
868
869         argc = parse_options(argc, argv, prefix, builtin_merge_options,
870                         builtin_merge_usage, 0);
871         if (verbosity < 0)
872                 show_diffstat = 0;
873
874         if (squash) {
875                 if (!allow_fast_forward)
876                         die("You cannot combine --squash with --no-ff.");
877                 option_commit = 0;
878         }
879
880         if (!argc)
881                 usage_with_options(builtin_merge_usage,
882                         builtin_merge_options);
883
884         /*
885          * This could be traditional "merge <msg> HEAD <commit>..."  and
886          * the way we can tell it is to see if the second token is HEAD,
887          * but some people might have misused the interface and used a
888          * committish that is the same as HEAD there instead.
889          * Traditional format never would have "-m" so it is an
890          * additional safety measure to check for it.
891          */
892
893         if (!have_message && is_old_style_invocation(argc, argv)) {
894                 strbuf_addstr(&merge_msg, argv[0]);
895                 head_arg = argv[1];
896                 argv += 2;
897                 argc -= 2;
898         } else if (head_invalid) {
899                 struct object *remote_head;
900                 /*
901                  * If the merged head is a valid one there is no reason
902                  * to forbid "git merge" into a branch yet to be born.
903                  * We do the same for "git pull".
904                  */
905                 if (argc != 1)
906                         die("Can merge only exactly one commit into "
907                                 "empty head");
908                 if (squash)
909                         die("Squash commit into empty head not supported yet");
910                 if (!allow_fast_forward)
911                         die("Non-fast-forward commit does not make sense into "
912                             "an empty head");
913                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
914                 if (!remote_head)
915                         die("%s - not something we can merge", argv[0]);
916                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
917                                 DIE_ON_ERR);
918                 reset_hard(remote_head->sha1, 0);
919                 return 0;
920         } else {
921                 struct strbuf msg = STRBUF_INIT;
922
923                 /* We are invoked directly as the first-class UI. */
924                 head_arg = "HEAD";
925
926                 /*
927                  * All the rest are the commits being merged;
928                  * prepare the standard merge summary message to
929                  * be appended to the given message.  If remote
930                  * is invalid we will die later in the common
931                  * codepath so we discard the error in this
932                  * loop.
933                  */
934                 for (i = 0; i < argc; i++)
935                         merge_name(argv[i], &msg);
936                 fmt_merge_msg(option_log, &msg, &merge_msg);
937                 if (merge_msg.len)
938                         strbuf_setlen(&merge_msg, merge_msg.len-1);
939         }
940
941         if (head_invalid || !argc)
942                 usage_with_options(builtin_merge_usage,
943                         builtin_merge_options);
944
945         strbuf_addstr(&buf, "merge");
946         for (i = 0; i < argc; i++)
947                 strbuf_addf(&buf, " %s", argv[i]);
948         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
949         strbuf_reset(&buf);
950
951         for (i = 0; i < argc; i++) {
952                 struct object *o;
953                 struct commit *commit;
954
955                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
956                 if (!o)
957                         die("%s - not something we can merge", argv[i]);
958                 commit = lookup_commit(o->sha1);
959                 commit->util = (void *)argv[i];
960                 remotes = &commit_list_insert(commit, remotes)->next;
961
962                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
963                 setenv(buf.buf, argv[i], 1);
964                 strbuf_reset(&buf);
965         }
966
967         if (!use_strategies) {
968                 if (!remoteheads->next)
969                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
970                 else
971                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
972         }
973
974         for (i = 0; i < use_strategies_nr; i++) {
975                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
976                         allow_fast_forward = 0;
977                 if (use_strategies[i]->attr & NO_TRIVIAL)
978                         allow_trivial = 0;
979         }
980
981         if (!remoteheads->next)
982                 common = get_merge_bases(lookup_commit(head),
983                                 remoteheads->item, 1);
984         else {
985                 struct commit_list *list = remoteheads;
986                 commit_list_insert(lookup_commit(head), &list);
987                 common = get_octopus_merge_bases(list);
988                 free(list);
989         }
990
991         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
992                 DIE_ON_ERR);
993
994         if (!common)
995                 ; /* No common ancestors found. We need a real merge. */
996         else if (!remoteheads->next && !common->next &&
997                         common->item == remoteheads->item) {
998                 /*
999                  * If head can reach all the merge then we are up to date.
1000                  * but first the most common case of merging one remote.
1001                  */
1002                 finish_up_to_date("Already up-to-date.");
1003                 return 0;
1004         } else if (allow_fast_forward && !remoteheads->next &&
1005                         !common->next &&
1006                         !hashcmp(common->item->object.sha1, head)) {
1007                 /* Again the most common case of merging one remote. */
1008                 struct strbuf msg = STRBUF_INIT;
1009                 struct object *o;
1010                 char hex[41];
1011
1012                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1013
1014                 if (verbosity >= 0)
1015                         printf("Updating %s..%s\n",
1016                                 hex,
1017                                 find_unique_abbrev(remoteheads->item->object.sha1,
1018                                 DEFAULT_ABBREV));
1019                 strbuf_addstr(&msg, "Fast forward");
1020                 if (have_message)
1021                         strbuf_addstr(&msg,
1022                                 " (no commit created; -m option ignored)");
1023                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1024                         0, NULL, OBJ_COMMIT);
1025                 if (!o)
1026                         return 1;
1027
1028                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1029                         return 1;
1030
1031                 finish(o->sha1, msg.buf);
1032                 drop_save();
1033                 return 0;
1034         } else if (!remoteheads->next && common->next)
1035                 ;
1036                 /*
1037                  * We are not doing octopus and not fast forward.  Need
1038                  * a real merge.
1039                  */
1040         else if (!remoteheads->next && !common->next && option_commit) {
1041                 /*
1042                  * We are not doing octopus, not fast forward, and have
1043                  * only one common.
1044                  */
1045                 refresh_cache(REFRESH_QUIET);
1046                 if (allow_trivial) {
1047                         /* See if it is really trivial. */
1048                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1049                         printf("Trying really trivial in-index merge...\n");
1050                         if (!read_tree_trivial(common->item->object.sha1,
1051                                         head, remoteheads->item->object.sha1))
1052                                 return merge_trivial();
1053                         printf("Nope.\n");
1054                 }
1055         } else {
1056                 /*
1057                  * An octopus.  If we can reach all the remote we are up
1058                  * to date.
1059                  */
1060                 int up_to_date = 1;
1061                 struct commit_list *j;
1062
1063                 for (j = remoteheads; j; j = j->next) {
1064                         struct commit_list *common_one;
1065
1066                         /*
1067                          * Here we *have* to calculate the individual
1068                          * merge_bases again, otherwise "git merge HEAD^
1069                          * HEAD^^" would be missed.
1070                          */
1071                         common_one = get_merge_bases(lookup_commit(head),
1072                                 j->item, 1);
1073                         if (hashcmp(common_one->item->object.sha1,
1074                                 j->item->object.sha1)) {
1075                                 up_to_date = 0;
1076                                 break;
1077                         }
1078                 }
1079                 if (up_to_date) {
1080                         finish_up_to_date("Already up-to-date. Yeeah!");
1081                         return 0;
1082                 }
1083         }
1084
1085         /* We are going to make a new commit. */
1086         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1087
1088         /*
1089          * At this point, we need a real merge.  No matter what strategy
1090          * we use, it would operate on the index, possibly affecting the
1091          * working tree, and when resolved cleanly, have the desired
1092          * tree in the index -- this means that the index must be in
1093          * sync with the head commit.  The strategies are responsible
1094          * to ensure this.
1095          */
1096         if (use_strategies_nr != 1) {
1097                 /*
1098                  * Stash away the local changes so that we can try more
1099                  * than one.
1100                  */
1101                 save_state();
1102         } else {
1103                 memcpy(stash, null_sha1, 20);
1104         }
1105
1106         for (i = 0; i < use_strategies_nr; i++) {
1107                 int ret;
1108                 if (i) {
1109                         printf("Rewinding the tree to pristine...\n");
1110                         restore_state();
1111                 }
1112                 if (use_strategies_nr != 1)
1113                         printf("Trying merge strategy %s...\n",
1114                                 use_strategies[i]->name);
1115                 /*
1116                  * Remember which strategy left the state in the working
1117                  * tree.
1118                  */
1119                 wt_strategy = use_strategies[i]->name;
1120
1121                 ret = try_merge_strategy(use_strategies[i]->name,
1122                         common, head_arg);
1123                 if (!option_commit && !ret) {
1124                         merge_was_ok = 1;
1125                         /*
1126                          * This is necessary here just to avoid writing
1127                          * the tree, but later we will *not* exit with
1128                          * status code 1 because merge_was_ok is set.
1129                          */
1130                         ret = 1;
1131                 }
1132
1133                 if (ret) {
1134                         /*
1135                          * The backend exits with 1 when conflicts are
1136                          * left to be resolved, with 2 when it does not
1137                          * handle the given merge at all.
1138                          */
1139                         if (ret == 1) {
1140                                 int cnt = evaluate_result();
1141
1142                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1143                                         best_strategy = use_strategies[i]->name;
1144                                         best_cnt = cnt;
1145                                 }
1146                         }
1147                         if (merge_was_ok)
1148                                 break;
1149                         else
1150                                 continue;
1151                 }
1152
1153                 /* Automerge succeeded. */
1154                 write_tree_trivial(result_tree);
1155                 automerge_was_ok = 1;
1156                 break;
1157         }
1158
1159         /*
1160          * If we have a resulting tree, that means the strategy module
1161          * auto resolved the merge cleanly.
1162          */
1163         if (automerge_was_ok)
1164                 return finish_automerge(common, result_tree, wt_strategy);
1165
1166         /*
1167          * Pick the result from the best strategy and have the user fix
1168          * it up.
1169          */
1170         if (!best_strategy) {
1171                 restore_state();
1172                 if (use_strategies_nr > 1)
1173                         fprintf(stderr,
1174                                 "No merge strategy handled the merge.\n");
1175                 else
1176                         fprintf(stderr, "Merge with strategy %s failed.\n",
1177                                 use_strategies[0]->name);
1178                 return 2;
1179         } else if (best_strategy == wt_strategy)
1180                 ; /* We already have its result in the working tree. */
1181         else {
1182                 printf("Rewinding the tree to pristine...\n");
1183                 restore_state();
1184                 printf("Using the %s to prepare resolving by hand.\n",
1185                         best_strategy);
1186                 try_merge_strategy(best_strategy, common, head_arg);
1187         }
1188
1189         if (squash)
1190                 finish(NULL, NULL);
1191         else {
1192                 int fd;
1193                 struct commit_list *j;
1194
1195                 for (j = remoteheads; j; j = j->next)
1196                         strbuf_addf(&buf, "%s\n",
1197                                 sha1_to_hex(j->item->object.sha1));
1198                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1199                 if (fd < 0)
1200                         die_errno("Could not open '%s' for writing",
1201                                   git_path("MERGE_HEAD"));
1202                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1203                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1204                 close(fd);
1205                 strbuf_addch(&merge_msg, '\n');
1206                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1207                 if (fd < 0)
1208                         die_errno("Could not open '%s' for writing",
1209                                   git_path("MERGE_MSG"));
1210                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1211                         merge_msg.len)
1212                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1213                 close(fd);
1214                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1215                 if (fd < 0)
1216                         die_errno("Could not open '%s' for writing",
1217                                   git_path("MERGE_MODE"));
1218                 strbuf_reset(&buf);
1219                 if (!allow_fast_forward)
1220                         strbuf_addf(&buf, "no-ff");
1221                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1222                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1223                 close(fd);
1224         }
1225
1226         if (merge_was_ok) {
1227                 fprintf(stderr, "Automatic merge went well; "
1228                         "stopped before committing as requested\n");
1229                 return 0;
1230         } else
1231                 return suggest_conflicts();
1232 }