Merge branch 'maint'
[git] / builtin-merge.c
1 /*
2  * Builtin "git merge"
3  *
4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
5  *
6  * Based on git-merge.sh by Junio C Hamano.
7  */
8
9 #include "cache.h"
10 #include "parse-options.h"
11 #include "builtin.h"
12 #include "run-command.h"
13 #include "diff.h"
14 #include "refs.h"
15 #include "commit.h"
16 #include "diffcore.h"
17 #include "revision.h"
18 #include "unpack-trees.h"
19 #include "cache-tree.h"
20 #include "dir.h"
21 #include "utf8.h"
22 #include "log-tree.h"
23 #include "color.h"
24 #include "rerere.h"
25 #include "help.h"
26 #include "merge-recursive.h"
27 #include "resolve-undo.h"
28
29 #define DEFAULT_TWOHEAD (1<<0)
30 #define DEFAULT_OCTOPUS (1<<1)
31 #define NO_FAST_FORWARD (1<<2)
32 #define NO_TRIVIAL      (1<<3)
33
34 struct strategy {
35         const char *name;
36         unsigned attr;
37 };
38
39 static const char * const builtin_merge_usage[] = {
40         "git merge [options] <remote>...",
41         "git merge [options] <msg> HEAD <remote>",
42         NULL
43 };
44
45 static int show_diffstat = 1, option_log, squash;
46 static int option_commit = 1, allow_fast_forward = 1;
47 static int fast_forward_only;
48 static int allow_trivial = 1, have_message;
49 static struct strbuf merge_msg;
50 static struct commit_list *remoteheads;
51 static unsigned char head[20], stash[20];
52 static struct strategy **use_strategies;
53 static size_t use_strategies_nr, use_strategies_alloc;
54 static const char **xopts;
55 static size_t xopts_nr, xopts_alloc;
56 static const char *branch;
57 static int verbosity;
58 static int allow_rerere_auto;
59
60 static struct strategy all_strategy[] = {
61         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
62         { "octopus",    DEFAULT_OCTOPUS },
63         { "resolve",    0 },
64         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
65         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
66 };
67
68 static const char *pull_twohead, *pull_octopus;
69
70 static int option_parse_message(const struct option *opt,
71                                 const char *arg, int unset)
72 {
73         struct strbuf *buf = opt->value;
74
75         if (unset)
76                 strbuf_setlen(buf, 0);
77         else if (arg) {
78                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
79                 have_message = 1;
80         } else
81                 return error("switch `m' requires a value");
82         return 0;
83 }
84
85 static struct strategy *get_strategy(const char *name)
86 {
87         int i;
88         struct strategy *ret;
89         static struct cmdnames main_cmds, other_cmds;
90         static int loaded;
91
92         if (!name)
93                 return NULL;
94
95         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
96                 if (!strcmp(name, all_strategy[i].name))
97                         return &all_strategy[i];
98
99         if (!loaded) {
100                 struct cmdnames not_strategies;
101                 loaded = 1;
102
103                 memset(&not_strategies, 0, sizeof(struct cmdnames));
104                 load_command_list("git-merge-", &main_cmds, &other_cmds);
105                 for (i = 0; i < main_cmds.cnt; i++) {
106                         int j, found = 0;
107                         struct cmdname *ent = main_cmds.names[i];
108                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
109                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
110                                                 && !all_strategy[j].name[ent->len])
111                                         found = 1;
112                         if (!found)
113                                 add_cmdname(&not_strategies, ent->name, ent->len);
114                 }
115                 exclude_cmds(&main_cmds, &not_strategies);
116         }
117         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
118                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
119                 fprintf(stderr, "Available strategies are:");
120                 for (i = 0; i < main_cmds.cnt; i++)
121                         fprintf(stderr, " %s", main_cmds.names[i]->name);
122                 fprintf(stderr, ".\n");
123                 if (other_cmds.cnt) {
124                         fprintf(stderr, "Available custom strategies are:");
125                         for (i = 0; i < other_cmds.cnt; i++)
126                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
127                         fprintf(stderr, ".\n");
128                 }
129                 exit(1);
130         }
131
132         ret = xcalloc(1, sizeof(struct strategy));
133         ret->name = xstrdup(name);
134         return ret;
135 }
136
137 static void append_strategy(struct strategy *s)
138 {
139         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
140         use_strategies[use_strategies_nr++] = s;
141 }
142
143 static int option_parse_strategy(const struct option *opt,
144                                  const char *name, int unset)
145 {
146         if (unset)
147                 return 0;
148
149         append_strategy(get_strategy(name));
150         return 0;
151 }
152
153 static int option_parse_x(const struct option *opt,
154                           const char *arg, int unset)
155 {
156         if (unset)
157                 return 0;
158
159         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
160         xopts[xopts_nr++] = xstrdup(arg);
161         return 0;
162 }
163
164 static int option_parse_n(const struct option *opt,
165                           const char *arg, int unset)
166 {
167         show_diffstat = unset;
168         return 0;
169 }
170
171 static struct option builtin_merge_options[] = {
172         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
173                 "do not show a diffstat at the end of the merge",
174                 PARSE_OPT_NOARG, option_parse_n },
175         OPT_BOOLEAN(0, "stat", &show_diffstat,
176                 "show a diffstat at the end of the merge"),
177         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
178         OPT_BOOLEAN(0, "log", &option_log,
179                 "add list of one-line log to merge commit message"),
180         OPT_BOOLEAN(0, "squash", &squash,
181                 "create a single commit instead of doing a merge"),
182         OPT_BOOLEAN(0, "commit", &option_commit,
183                 "perform a commit if the merge succeeds (default)"),
184         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
185                 "allow fast-forward (default)"),
186         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
187                 "abort if fast-forward is not possible"),
188         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
189         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
190                 "merge strategy to use", option_parse_strategy),
191         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
192                 "option for selected merge strategy", option_parse_x),
193         OPT_CALLBACK('m', "message", &merge_msg, "message",
194                 "message to be used for the merge commit (if any)",
195                 option_parse_message),
196         OPT__VERBOSITY(&verbosity),
197         OPT_END()
198 };
199
200 /* Cleans up metadata that is uninteresting after a succeeded merge. */
201 static void drop_save(void)
202 {
203         unlink(git_path("MERGE_HEAD"));
204         unlink(git_path("MERGE_MSG"));
205         unlink(git_path("MERGE_MODE"));
206 }
207
208 static void save_state(void)
209 {
210         int len;
211         struct child_process cp;
212         struct strbuf buffer = STRBUF_INIT;
213         const char *argv[] = {"stash", "create", NULL};
214
215         memset(&cp, 0, sizeof(cp));
216         cp.argv = argv;
217         cp.out = -1;
218         cp.git_cmd = 1;
219
220         if (start_command(&cp))
221                 die("could not run stash.");
222         len = strbuf_read(&buffer, cp.out, 1024);
223         close(cp.out);
224
225         if (finish_command(&cp) || len < 0)
226                 die("stash failed");
227         else if (!len)
228                 return;
229         strbuf_setlen(&buffer, buffer.len-1);
230         if (get_sha1(buffer.buf, stash))
231                 die("not a valid object: %s", buffer.buf);
232 }
233
234 static void reset_hard(unsigned const char *sha1, int verbose)
235 {
236         int i = 0;
237         const char *args[6];
238
239         args[i++] = "read-tree";
240         if (verbose)
241                 args[i++] = "-v";
242         args[i++] = "--reset";
243         args[i++] = "-u";
244         args[i++] = sha1_to_hex(sha1);
245         args[i] = NULL;
246
247         if (run_command_v_opt(args, RUN_GIT_CMD))
248                 die("read-tree failed");
249 }
250
251 static void restore_state(void)
252 {
253         struct strbuf sb = STRBUF_INIT;
254         const char *args[] = { "stash", "apply", NULL, NULL };
255
256         if (is_null_sha1(stash))
257                 return;
258
259         reset_hard(head, 1);
260
261         args[2] = sha1_to_hex(stash);
262
263         /*
264          * It is OK to ignore error here, for example when there was
265          * nothing to restore.
266          */
267         run_command_v_opt(args, RUN_GIT_CMD);
268
269         strbuf_release(&sb);
270         refresh_cache(REFRESH_QUIET);
271 }
272
273 /* This is called when no merge was necessary. */
274 static void finish_up_to_date(const char *msg)
275 {
276         if (verbosity >= 0)
277                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
278         drop_save();
279 }
280
281 static void squash_message(void)
282 {
283         struct rev_info rev;
284         struct commit *commit;
285         struct strbuf out = STRBUF_INIT;
286         struct commit_list *j;
287         int fd;
288         struct pretty_print_context ctx = {0};
289
290         printf("Squash commit -- not updating HEAD\n");
291         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
292         if (fd < 0)
293                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
294
295         init_revisions(&rev, NULL);
296         rev.ignore_merges = 1;
297         rev.commit_format = CMIT_FMT_MEDIUM;
298
299         commit = lookup_commit(head);
300         commit->object.flags |= UNINTERESTING;
301         add_pending_object(&rev, &commit->object, NULL);
302
303         for (j = remoteheads; j; j = j->next)
304                 add_pending_object(&rev, &j->item->object, NULL);
305
306         setup_revisions(0, NULL, &rev, NULL);
307         if (prepare_revision_walk(&rev))
308                 die("revision walk setup failed");
309
310         ctx.abbrev = rev.abbrev;
311         ctx.date_mode = rev.date_mode;
312
313         strbuf_addstr(&out, "Squashed commit of the following:\n");
314         while ((commit = get_revision(&rev)) != NULL) {
315                 strbuf_addch(&out, '\n');
316                 strbuf_addf(&out, "commit %s\n",
317                         sha1_to_hex(commit->object.sha1));
318                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
319         }
320         if (write(fd, out.buf, out.len) < 0)
321                 die_errno("Writing SQUASH_MSG");
322         if (close(fd))
323                 die_errno("Finishing SQUASH_MSG");
324         strbuf_release(&out);
325 }
326
327 static void finish(const unsigned char *new_head, const char *msg)
328 {
329         struct strbuf reflog_message = STRBUF_INIT;
330
331         if (!msg)
332                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
333         else {
334                 if (verbosity >= 0)
335                         printf("%s\n", msg);
336                 strbuf_addf(&reflog_message, "%s: %s",
337                         getenv("GIT_REFLOG_ACTION"), msg);
338         }
339         if (squash) {
340                 squash_message();
341         } else {
342                 if (verbosity >= 0 && !merge_msg.len)
343                         printf("No merge message -- not updating HEAD\n");
344                 else {
345                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
346                         update_ref(reflog_message.buf, "HEAD",
347                                 new_head, head, 0,
348                                 DIE_ON_ERR);
349                         /*
350                          * We ignore errors in 'gc --auto', since the
351                          * user should see them.
352                          */
353                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
354                 }
355         }
356         if (new_head && show_diffstat) {
357                 struct diff_options opts;
358                 diff_setup(&opts);
359                 opts.output_format |=
360                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
361                 opts.detect_rename = DIFF_DETECT_RENAME;
362                 if (diff_use_color_default > 0)
363                         DIFF_OPT_SET(&opts, COLOR_DIFF);
364                 if (diff_setup_done(&opts) < 0)
365                         die("diff_setup_done failed");
366                 diff_tree_sha1(head, new_head, "", &opts);
367                 diffcore_std(&opts);
368                 diff_flush(&opts);
369         }
370
371         /* Run a post-merge hook */
372         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
373
374         strbuf_release(&reflog_message);
375 }
376
377 /* Get the name for the merge commit's message. */
378 static void merge_name(const char *remote, struct strbuf *msg)
379 {
380         struct object *remote_head;
381         unsigned char branch_head[20], buf_sha[20];
382         struct strbuf buf = STRBUF_INIT;
383         struct strbuf bname = STRBUF_INIT;
384         const char *ptr;
385         char *found_ref;
386         int len, early;
387
388         strbuf_branchname(&bname, remote);
389         remote = bname.buf;
390
391         memset(branch_head, 0, sizeof(branch_head));
392         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
393         if (!remote_head)
394                 die("'%s' does not point to a commit", remote);
395
396         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
397                 if (!prefixcmp(found_ref, "refs/heads/")) {
398                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
399                                     sha1_to_hex(branch_head), remote);
400                         goto cleanup;
401                 }
402                 if (!prefixcmp(found_ref, "refs/remotes/")) {
403                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
404                                     sha1_to_hex(branch_head), remote);
405                         goto cleanup;
406                 }
407         }
408
409         /* See if remote matches <name>^^^.. or <name>~<number> */
410         for (len = 0, ptr = remote + strlen(remote);
411              remote < ptr && ptr[-1] == '^';
412              ptr--)
413                 len++;
414         if (len)
415                 early = 1;
416         else {
417                 early = 0;
418                 ptr = strrchr(remote, '~');
419                 if (ptr) {
420                         int seen_nonzero = 0;
421
422                         len++; /* count ~ */
423                         while (*++ptr && isdigit(*ptr)) {
424                                 seen_nonzero |= (*ptr != '0');
425                                 len++;
426                         }
427                         if (*ptr)
428                                 len = 0; /* not ...~<number> */
429                         else if (seen_nonzero)
430                                 early = 1;
431                         else if (len == 1)
432                                 early = 1; /* "name~" is "name~1"! */
433                 }
434         }
435         if (len) {
436                 struct strbuf truname = STRBUF_INIT;
437                 strbuf_addstr(&truname, "refs/heads/");
438                 strbuf_addstr(&truname, remote);
439                 strbuf_setlen(&truname, truname.len - len);
440                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
441                         strbuf_addf(msg,
442                                     "%s\t\tbranch '%s'%s of .\n",
443                                     sha1_to_hex(remote_head->sha1),
444                                     truname.buf + 11,
445                                     (early ? " (early part)" : ""));
446                         strbuf_release(&truname);
447                         goto cleanup;
448                 }
449         }
450
451         if (!strcmp(remote, "FETCH_HEAD") &&
452                         !access(git_path("FETCH_HEAD"), R_OK)) {
453                 FILE *fp;
454                 struct strbuf line = STRBUF_INIT;
455                 char *ptr;
456
457                 fp = fopen(git_path("FETCH_HEAD"), "r");
458                 if (!fp)
459                         die_errno("could not open '%s' for reading",
460                                   git_path("FETCH_HEAD"));
461                 strbuf_getline(&line, fp, '\n');
462                 fclose(fp);
463                 ptr = strstr(line.buf, "\tnot-for-merge\t");
464                 if (ptr)
465                         strbuf_remove(&line, ptr-line.buf+1, 13);
466                 strbuf_addbuf(msg, &line);
467                 strbuf_release(&line);
468                 goto cleanup;
469         }
470         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
471                 sha1_to_hex(remote_head->sha1), remote);
472 cleanup:
473         strbuf_release(&buf);
474         strbuf_release(&bname);
475 }
476
477 static int git_merge_config(const char *k, const char *v, void *cb)
478 {
479         if (branch && !prefixcmp(k, "branch.") &&
480                 !prefixcmp(k + 7, branch) &&
481                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
482                 const char **argv;
483                 int argc;
484                 char *buf;
485
486                 buf = xstrdup(v);
487                 argc = split_cmdline(buf, &argv);
488                 if (argc < 0)
489                         die("Bad branch.%s.mergeoptions string", branch);
490                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
491                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
492                 argc++;
493                 parse_options(argc, argv, NULL, builtin_merge_options,
494                               builtin_merge_usage, 0);
495                 free(buf);
496         }
497
498         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
499                 show_diffstat = git_config_bool(k, v);
500         else if (!strcmp(k, "pull.twohead"))
501                 return git_config_string(&pull_twohead, k, v);
502         else if (!strcmp(k, "pull.octopus"))
503                 return git_config_string(&pull_octopus, k, v);
504         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
505                 option_log = git_config_bool(k, v);
506         return git_diff_ui_config(k, v, cb);
507 }
508
509 static int read_tree_trivial(unsigned char *common, unsigned char *head,
510                              unsigned char *one)
511 {
512         int i, nr_trees = 0;
513         struct tree *trees[MAX_UNPACK_TREES];
514         struct tree_desc t[MAX_UNPACK_TREES];
515         struct unpack_trees_options opts;
516
517         memset(&opts, 0, sizeof(opts));
518         opts.head_idx = 2;
519         opts.src_index = &the_index;
520         opts.dst_index = &the_index;
521         opts.update = 1;
522         opts.verbose_update = 1;
523         opts.trivial_merges_only = 1;
524         opts.merge = 1;
525         trees[nr_trees] = parse_tree_indirect(common);
526         if (!trees[nr_trees++])
527                 return -1;
528         trees[nr_trees] = parse_tree_indirect(head);
529         if (!trees[nr_trees++])
530                 return -1;
531         trees[nr_trees] = parse_tree_indirect(one);
532         if (!trees[nr_trees++])
533                 return -1;
534         opts.fn = threeway_merge;
535         cache_tree_free(&active_cache_tree);
536         for (i = 0; i < nr_trees; i++) {
537                 parse_tree(trees[i]);
538                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
539         }
540         if (unpack_trees(nr_trees, t, &opts))
541                 return -1;
542         return 0;
543 }
544
545 static void write_tree_trivial(unsigned char *sha1)
546 {
547         if (write_cache_as_tree(sha1, 0, NULL))
548                 die("git write-tree failed to write a tree");
549 }
550
551 static int try_merge_strategy(const char *strategy, struct commit_list *common,
552                               const char *head_arg)
553 {
554         const char **args;
555         int i = 0, x = 0, ret;
556         struct commit_list *j;
557         struct strbuf buf = STRBUF_INIT;
558         int index_fd;
559         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
560
561         index_fd = hold_locked_index(lock, 1);
562         refresh_cache(REFRESH_QUIET);
563         if (active_cache_changed &&
564                         (write_cache(index_fd, active_cache, active_nr) ||
565                          commit_locked_index(lock)))
566                 return error("Unable to write index.");
567         rollback_lock_file(lock);
568
569         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
570                 int clean;
571                 struct commit *result;
572                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
573                 int index_fd;
574                 struct commit_list *reversed = NULL;
575                 struct merge_options o;
576
577                 if (remoteheads->next) {
578                         error("Not handling anything other than two heads merge.");
579                         return 2;
580                 }
581
582                 init_merge_options(&o);
583                 if (!strcmp(strategy, "subtree"))
584                         o.subtree_shift = "";
585
586                 for (x = 0; x < xopts_nr; x++) {
587                         if (!strcmp(xopts[x], "ours"))
588                                 o.recursive_variant = MERGE_RECURSIVE_OURS;
589                         else if (!strcmp(xopts[x], "theirs"))
590                                 o.recursive_variant = MERGE_RECURSIVE_THEIRS;
591                         else if (!strcmp(xopts[x], "subtree"))
592                                 o.subtree_shift = "";
593                         else if (!prefixcmp(xopts[x], "subtree="))
594                                 o.subtree_shift = xopts[x]+8;
595                         else
596                                 die("Unknown option for merge-recursive: -X%s", xopts[x]);
597                 }
598
599                 o.branch1 = head_arg;
600                 o.branch2 = remoteheads->item->util;
601
602                 for (j = common; j; j = j->next)
603                         commit_list_insert(j->item, &reversed);
604
605                 index_fd = hold_locked_index(lock, 1);
606                 clean = merge_recursive(&o, lookup_commit(head),
607                                 remoteheads->item, reversed, &result);
608                 if (active_cache_changed &&
609                                 (write_cache(index_fd, active_cache, active_nr) ||
610                                  commit_locked_index(lock)))
611                         die ("unable to write %s", get_index_file());
612                 rollback_lock_file(lock);
613                 return clean ? 0 : 1;
614         } else {
615                 args = xmalloc((4 + xopts_nr + commit_list_count(common) +
616                                         commit_list_count(remoteheads)) * sizeof(char *));
617                 strbuf_addf(&buf, "merge-%s", strategy);
618                 args[i++] = buf.buf;
619                 for (x = 0; x < xopts_nr; x++) {
620                         char *s = xmalloc(strlen(xopts[x])+2+1);
621                         strcpy(s, "--");
622                         strcpy(s+2, xopts[x]);
623                         args[i++] = s;
624                 }
625                 for (j = common; j; j = j->next)
626                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
627                 args[i++] = "--";
628                 args[i++] = head_arg;
629                 for (j = remoteheads; j; j = j->next)
630                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
631                 args[i] = NULL;
632                 ret = run_command_v_opt(args, RUN_GIT_CMD);
633                 strbuf_release(&buf);
634                 i = 1;
635                 for (x = 0; x < xopts_nr; x++)
636                         free((void *)args[i++]);
637                 for (j = common; j; j = j->next)
638                         free((void *)args[i++]);
639                 i += 2;
640                 for (j = remoteheads; j; j = j->next)
641                         free((void *)args[i++]);
642                 free(args);
643                 discard_cache();
644                 if (read_cache() < 0)
645                         die("failed to read the cache");
646                 resolve_undo_clear();
647                 return ret;
648         }
649 }
650
651 static void count_diff_files(struct diff_queue_struct *q,
652                              struct diff_options *opt, void *data)
653 {
654         int *count = data;
655
656         (*count) += q->nr;
657 }
658
659 static int count_unmerged_entries(void)
660 {
661         int i, ret = 0;
662
663         for (i = 0; i < active_nr; i++)
664                 if (ce_stage(active_cache[i]))
665                         ret++;
666
667         return ret;
668 }
669
670 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
671 {
672         struct tree *trees[MAX_UNPACK_TREES];
673         struct unpack_trees_options opts;
674         struct tree_desc t[MAX_UNPACK_TREES];
675         int i, fd, nr_trees = 0;
676         struct dir_struct dir;
677         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
678
679         refresh_cache(REFRESH_QUIET);
680
681         fd = hold_locked_index(lock_file, 1);
682
683         memset(&trees, 0, sizeof(trees));
684         memset(&opts, 0, sizeof(opts));
685         memset(&t, 0, sizeof(t));
686         memset(&dir, 0, sizeof(dir));
687         dir.flags |= DIR_SHOW_IGNORED;
688         dir.exclude_per_dir = ".gitignore";
689         opts.dir = &dir;
690
691         opts.head_idx = 1;
692         opts.src_index = &the_index;
693         opts.dst_index = &the_index;
694         opts.update = 1;
695         opts.verbose_update = 1;
696         opts.merge = 1;
697         opts.fn = twoway_merge;
698         opts.msgs = get_porcelain_error_msgs();
699
700         trees[nr_trees] = parse_tree_indirect(head);
701         if (!trees[nr_trees++])
702                 return -1;
703         trees[nr_trees] = parse_tree_indirect(remote);
704         if (!trees[nr_trees++])
705                 return -1;
706         for (i = 0; i < nr_trees; i++) {
707                 parse_tree(trees[i]);
708                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
709         }
710         if (unpack_trees(nr_trees, t, &opts))
711                 return -1;
712         if (write_cache(fd, active_cache, active_nr) ||
713                 commit_locked_index(lock_file))
714                 die("unable to write new index file");
715         return 0;
716 }
717
718 static void split_merge_strategies(const char *string, struct strategy **list,
719                                    int *nr, int *alloc)
720 {
721         char *p, *q, *buf;
722
723         if (!string)
724                 return;
725
726         buf = xstrdup(string);
727         q = buf;
728         for (;;) {
729                 p = strchr(q, ' ');
730                 if (!p) {
731                         ALLOC_GROW(*list, *nr + 1, *alloc);
732                         (*list)[(*nr)++].name = xstrdup(q);
733                         free(buf);
734                         return;
735                 } else {
736                         *p = '\0';
737                         ALLOC_GROW(*list, *nr + 1, *alloc);
738                         (*list)[(*nr)++].name = xstrdup(q);
739                         q = ++p;
740                 }
741         }
742 }
743
744 static void add_strategies(const char *string, unsigned attr)
745 {
746         struct strategy *list = NULL;
747         int list_alloc = 0, list_nr = 0, i;
748
749         memset(&list, 0, sizeof(list));
750         split_merge_strategies(string, &list, &list_nr, &list_alloc);
751         if (list) {
752                 for (i = 0; i < list_nr; i++)
753                         append_strategy(get_strategy(list[i].name));
754                 return;
755         }
756         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
757                 if (all_strategy[i].attr & attr)
758                         append_strategy(&all_strategy[i]);
759
760 }
761
762 static int merge_trivial(void)
763 {
764         unsigned char result_tree[20], result_commit[20];
765         struct commit_list *parent = xmalloc(sizeof(*parent));
766
767         write_tree_trivial(result_tree);
768         printf("Wonderful.\n");
769         parent->item = lookup_commit(head);
770         parent->next = xmalloc(sizeof(*parent->next));
771         parent->next->item = remoteheads->item;
772         parent->next->next = NULL;
773         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
774         finish(result_commit, "In-index merge");
775         drop_save();
776         return 0;
777 }
778
779 static int finish_automerge(struct commit_list *common,
780                             unsigned char *result_tree,
781                             const char *wt_strategy)
782 {
783         struct commit_list *parents = NULL, *j;
784         struct strbuf buf = STRBUF_INIT;
785         unsigned char result_commit[20];
786
787         free_commit_list(common);
788         if (allow_fast_forward) {
789                 parents = remoteheads;
790                 commit_list_insert(lookup_commit(head), &parents);
791                 parents = reduce_heads(parents);
792         } else {
793                 struct commit_list **pptr = &parents;
794
795                 pptr = &commit_list_insert(lookup_commit(head),
796                                 pptr)->next;
797                 for (j = remoteheads; j; j = j->next)
798                         pptr = &commit_list_insert(j->item, pptr)->next;
799         }
800         free_commit_list(remoteheads);
801         strbuf_addch(&merge_msg, '\n');
802         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
803         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
804         finish(result_commit, buf.buf);
805         strbuf_release(&buf);
806         drop_save();
807         return 0;
808 }
809
810 static int suggest_conflicts(void)
811 {
812         FILE *fp;
813         int pos;
814
815         fp = fopen(git_path("MERGE_MSG"), "a");
816         if (!fp)
817                 die_errno("Could not open '%s' for writing",
818                           git_path("MERGE_MSG"));
819         fprintf(fp, "\nConflicts:\n");
820         for (pos = 0; pos < active_nr; pos++) {
821                 struct cache_entry *ce = active_cache[pos];
822
823                 if (ce_stage(ce)) {
824                         fprintf(fp, "\t%s\n", ce->name);
825                         while (pos + 1 < active_nr &&
826                                         !strcmp(ce->name,
827                                                 active_cache[pos + 1]->name))
828                                 pos++;
829                 }
830         }
831         fclose(fp);
832         rerere(allow_rerere_auto);
833         printf("Automatic merge failed; "
834                         "fix conflicts and then commit the result.\n");
835         return 1;
836 }
837
838 static struct commit *is_old_style_invocation(int argc, const char **argv)
839 {
840         struct commit *second_token = NULL;
841         if (argc > 2) {
842                 unsigned char second_sha1[20];
843
844                 if (get_sha1(argv[1], second_sha1))
845                         return NULL;
846                 second_token = lookup_commit_reference_gently(second_sha1, 0);
847                 if (!second_token)
848                         die("'%s' is not a commit", argv[1]);
849                 if (hashcmp(second_token->object.sha1, head))
850                         return NULL;
851         }
852         return second_token;
853 }
854
855 static int evaluate_result(void)
856 {
857         int cnt = 0;
858         struct rev_info rev;
859
860         /* Check how many files differ. */
861         init_revisions(&rev, "");
862         setup_revisions(0, NULL, &rev, NULL);
863         rev.diffopt.output_format |=
864                 DIFF_FORMAT_CALLBACK;
865         rev.diffopt.format_callback = count_diff_files;
866         rev.diffopt.format_callback_data = &cnt;
867         run_diff_files(&rev, 0);
868
869         /*
870          * Check how many unmerged entries are
871          * there.
872          */
873         cnt += count_unmerged_entries();
874
875         return cnt;
876 }
877
878 int cmd_merge(int argc, const char **argv, const char *prefix)
879 {
880         unsigned char result_tree[20];
881         struct strbuf buf = STRBUF_INIT;
882         const char *head_arg;
883         int flag, head_invalid = 0, i;
884         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
885         struct commit_list *common = NULL;
886         const char *best_strategy = NULL, *wt_strategy = NULL;
887         struct commit_list **remotes = &remoteheads;
888
889         if (read_cache_unmerged()) {
890                 die_resolve_conflict("merge");
891         }
892         if (file_exists(git_path("MERGE_HEAD"))) {
893                 /*
894                  * There is no unmerged entry, don't advise 'git
895                  * add/rm <file>', just 'git commit'.
896                  */
897                 if (advice_resolve_conflict)
898                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
899                             "Please, commit your changes before you can merge.");
900                 else
901                         die("You have not concluded your merge (MERGE_HEAD exists).");
902         }
903
904         resolve_undo_clear();
905         /*
906          * Check if we are _not_ on a detached HEAD, i.e. if there is a
907          * current branch.
908          */
909         branch = resolve_ref("HEAD", head, 0, &flag);
910         if (branch && !prefixcmp(branch, "refs/heads/"))
911                 branch += 11;
912         if (is_null_sha1(head))
913                 head_invalid = 1;
914
915         git_config(git_merge_config, NULL);
916
917         /* for color.ui */
918         if (diff_use_color_default == -1)
919                 diff_use_color_default = git_use_color_default;
920
921         argc = parse_options(argc, argv, prefix, builtin_merge_options,
922                         builtin_merge_usage, 0);
923         if (verbosity < 0)
924                 show_diffstat = 0;
925
926         if (squash) {
927                 if (!allow_fast_forward)
928                         die("You cannot combine --squash with --no-ff.");
929                 option_commit = 0;
930         }
931
932         if (!allow_fast_forward && fast_forward_only)
933                 die("You cannot combine --no-ff with --ff-only.");
934
935         if (!argc)
936                 usage_with_options(builtin_merge_usage,
937                         builtin_merge_options);
938
939         /*
940          * This could be traditional "merge <msg> HEAD <commit>..."  and
941          * the way we can tell it is to see if the second token is HEAD,
942          * but some people might have misused the interface and used a
943          * committish that is the same as HEAD there instead.
944          * Traditional format never would have "-m" so it is an
945          * additional safety measure to check for it.
946          */
947
948         if (!have_message && is_old_style_invocation(argc, argv)) {
949                 strbuf_addstr(&merge_msg, argv[0]);
950                 head_arg = argv[1];
951                 argv += 2;
952                 argc -= 2;
953         } else if (head_invalid) {
954                 struct object *remote_head;
955                 /*
956                  * If the merged head is a valid one there is no reason
957                  * to forbid "git merge" into a branch yet to be born.
958                  * We do the same for "git pull".
959                  */
960                 if (argc != 1)
961                         die("Can merge only exactly one commit into "
962                                 "empty head");
963                 if (squash)
964                         die("Squash commit into empty head not supported yet");
965                 if (!allow_fast_forward)
966                         die("Non-fast-forward commit does not make sense into "
967                             "an empty head");
968                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
969                 if (!remote_head)
970                         die("%s - not something we can merge", argv[0]);
971                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
972                                 DIE_ON_ERR);
973                 reset_hard(remote_head->sha1, 0);
974                 return 0;
975         } else {
976                 struct strbuf msg = STRBUF_INIT;
977
978                 /* We are invoked directly as the first-class UI. */
979                 head_arg = "HEAD";
980
981                 /*
982                  * All the rest are the commits being merged;
983                  * prepare the standard merge summary message to
984                  * be appended to the given message.  If remote
985                  * is invalid we will die later in the common
986                  * codepath so we discard the error in this
987                  * loop.
988                  */
989                 if (!have_message) {
990                         for (i = 0; i < argc; i++)
991                                 merge_name(argv[i], &msg);
992                         fmt_merge_msg(option_log, &msg, &merge_msg);
993                         if (merge_msg.len)
994                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
995                 }
996         }
997
998         if (head_invalid || !argc)
999                 usage_with_options(builtin_merge_usage,
1000                         builtin_merge_options);
1001
1002         strbuf_addstr(&buf, "merge");
1003         for (i = 0; i < argc; i++)
1004                 strbuf_addf(&buf, " %s", argv[i]);
1005         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1006         strbuf_reset(&buf);
1007
1008         for (i = 0; i < argc; i++) {
1009                 struct object *o;
1010                 struct commit *commit;
1011
1012                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1013                 if (!o)
1014                         die("%s - not something we can merge", argv[i]);
1015                 commit = lookup_commit(o->sha1);
1016                 commit->util = (void *)argv[i];
1017                 remotes = &commit_list_insert(commit, remotes)->next;
1018
1019                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1020                 setenv(buf.buf, argv[i], 1);
1021                 strbuf_reset(&buf);
1022         }
1023
1024         if (!use_strategies) {
1025                 if (!remoteheads->next)
1026                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1027                 else
1028                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1029         }
1030
1031         for (i = 0; i < use_strategies_nr; i++) {
1032                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1033                         allow_fast_forward = 0;
1034                 if (use_strategies[i]->attr & NO_TRIVIAL)
1035                         allow_trivial = 0;
1036         }
1037
1038         if (!remoteheads->next)
1039                 common = get_merge_bases(lookup_commit(head),
1040                                 remoteheads->item, 1);
1041         else {
1042                 struct commit_list *list = remoteheads;
1043                 commit_list_insert(lookup_commit(head), &list);
1044                 common = get_octopus_merge_bases(list);
1045                 free(list);
1046         }
1047
1048         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1049                 DIE_ON_ERR);
1050
1051         if (!common)
1052                 ; /* No common ancestors found. We need a real merge. */
1053         else if (!remoteheads->next && !common->next &&
1054                         common->item == remoteheads->item) {
1055                 /*
1056                  * If head can reach all the merge then we are up to date.
1057                  * but first the most common case of merging one remote.
1058                  */
1059                 finish_up_to_date("Already up-to-date.");
1060                 return 0;
1061         } else if (allow_fast_forward && !remoteheads->next &&
1062                         !common->next &&
1063                         !hashcmp(common->item->object.sha1, head)) {
1064                 /* Again the most common case of merging one remote. */
1065                 struct strbuf msg = STRBUF_INIT;
1066                 struct object *o;
1067                 char hex[41];
1068
1069                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1070
1071                 if (verbosity >= 0)
1072                         printf("Updating %s..%s\n",
1073                                 hex,
1074                                 find_unique_abbrev(remoteheads->item->object.sha1,
1075                                 DEFAULT_ABBREV));
1076                 strbuf_addstr(&msg, "Fast-forward");
1077                 if (have_message)
1078                         strbuf_addstr(&msg,
1079                                 " (no commit created; -m option ignored)");
1080                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1081                         0, NULL, OBJ_COMMIT);
1082                 if (!o)
1083                         return 1;
1084
1085                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1086                         return 1;
1087
1088                 finish(o->sha1, msg.buf);
1089                 drop_save();
1090                 return 0;
1091         } else if (!remoteheads->next && common->next)
1092                 ;
1093                 /*
1094                  * We are not doing octopus and not fast-forward.  Need
1095                  * a real merge.
1096                  */
1097         else if (!remoteheads->next && !common->next && option_commit) {
1098                 /*
1099                  * We are not doing octopus, not fast-forward, and have
1100                  * only one common.
1101                  */
1102                 refresh_cache(REFRESH_QUIET);
1103                 if (allow_trivial && !fast_forward_only) {
1104                         /* See if it is really trivial. */
1105                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1106                         printf("Trying really trivial in-index merge...\n");
1107                         if (!read_tree_trivial(common->item->object.sha1,
1108                                         head, remoteheads->item->object.sha1))
1109                                 return merge_trivial();
1110                         printf("Nope.\n");
1111                 }
1112         } else {
1113                 /*
1114                  * An octopus.  If we can reach all the remote we are up
1115                  * to date.
1116                  */
1117                 int up_to_date = 1;
1118                 struct commit_list *j;
1119
1120                 for (j = remoteheads; j; j = j->next) {
1121                         struct commit_list *common_one;
1122
1123                         /*
1124                          * Here we *have* to calculate the individual
1125                          * merge_bases again, otherwise "git merge HEAD^
1126                          * HEAD^^" would be missed.
1127                          */
1128                         common_one = get_merge_bases(lookup_commit(head),
1129                                 j->item, 1);
1130                         if (hashcmp(common_one->item->object.sha1,
1131                                 j->item->object.sha1)) {
1132                                 up_to_date = 0;
1133                                 break;
1134                         }
1135                 }
1136                 if (up_to_date) {
1137                         finish_up_to_date("Already up-to-date. Yeeah!");
1138                         return 0;
1139                 }
1140         }
1141
1142         if (fast_forward_only)
1143                 die("Not possible to fast-forward, aborting.");
1144
1145         /* We are going to make a new commit. */
1146         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1147
1148         /*
1149          * At this point, we need a real merge.  No matter what strategy
1150          * we use, it would operate on the index, possibly affecting the
1151          * working tree, and when resolved cleanly, have the desired
1152          * tree in the index -- this means that the index must be in
1153          * sync with the head commit.  The strategies are responsible
1154          * to ensure this.
1155          */
1156         if (use_strategies_nr != 1) {
1157                 /*
1158                  * Stash away the local changes so that we can try more
1159                  * than one.
1160                  */
1161                 save_state();
1162         } else {
1163                 memcpy(stash, null_sha1, 20);
1164         }
1165
1166         for (i = 0; i < use_strategies_nr; i++) {
1167                 int ret;
1168                 if (i) {
1169                         printf("Rewinding the tree to pristine...\n");
1170                         restore_state();
1171                 }
1172                 if (use_strategies_nr != 1)
1173                         printf("Trying merge strategy %s...\n",
1174                                 use_strategies[i]->name);
1175                 /*
1176                  * Remember which strategy left the state in the working
1177                  * tree.
1178                  */
1179                 wt_strategy = use_strategies[i]->name;
1180
1181                 ret = try_merge_strategy(use_strategies[i]->name,
1182                         common, head_arg);
1183                 if (!option_commit && !ret) {
1184                         merge_was_ok = 1;
1185                         /*
1186                          * This is necessary here just to avoid writing
1187                          * the tree, but later we will *not* exit with
1188                          * status code 1 because merge_was_ok is set.
1189                          */
1190                         ret = 1;
1191                 }
1192
1193                 if (ret) {
1194                         /*
1195                          * The backend exits with 1 when conflicts are
1196                          * left to be resolved, with 2 when it does not
1197                          * handle the given merge at all.
1198                          */
1199                         if (ret == 1) {
1200                                 int cnt = evaluate_result();
1201
1202                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1203                                         best_strategy = use_strategies[i]->name;
1204                                         best_cnt = cnt;
1205                                 }
1206                         }
1207                         if (merge_was_ok)
1208                                 break;
1209                         else
1210                                 continue;
1211                 }
1212
1213                 /* Automerge succeeded. */
1214                 write_tree_trivial(result_tree);
1215                 automerge_was_ok = 1;
1216                 break;
1217         }
1218
1219         /*
1220          * If we have a resulting tree, that means the strategy module
1221          * auto resolved the merge cleanly.
1222          */
1223         if (automerge_was_ok)
1224                 return finish_automerge(common, result_tree, wt_strategy);
1225
1226         /*
1227          * Pick the result from the best strategy and have the user fix
1228          * it up.
1229          */
1230         if (!best_strategy) {
1231                 restore_state();
1232                 if (use_strategies_nr > 1)
1233                         fprintf(stderr,
1234                                 "No merge strategy handled the merge.\n");
1235                 else
1236                         fprintf(stderr, "Merge with strategy %s failed.\n",
1237                                 use_strategies[0]->name);
1238                 return 2;
1239         } else if (best_strategy == wt_strategy)
1240                 ; /* We already have its result in the working tree. */
1241         else {
1242                 printf("Rewinding the tree to pristine...\n");
1243                 restore_state();
1244                 printf("Using the %s to prepare resolving by hand.\n",
1245                         best_strategy);
1246                 try_merge_strategy(best_strategy, common, head_arg);
1247         }
1248
1249         if (squash)
1250                 finish(NULL, NULL);
1251         else {
1252                 int fd;
1253                 struct commit_list *j;
1254
1255                 for (j = remoteheads; j; j = j->next)
1256                         strbuf_addf(&buf, "%s\n",
1257                                 sha1_to_hex(j->item->object.sha1));
1258                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1259                 if (fd < 0)
1260                         die_errno("Could not open '%s' for writing",
1261                                   git_path("MERGE_HEAD"));
1262                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1263                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1264                 close(fd);
1265                 strbuf_addch(&merge_msg, '\n');
1266                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1267                 if (fd < 0)
1268                         die_errno("Could not open '%s' for writing",
1269                                   git_path("MERGE_MSG"));
1270                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1271                         merge_msg.len)
1272                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1273                 close(fd);
1274                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1275                 if (fd < 0)
1276                         die_errno("Could not open '%s' for writing",
1277                                   git_path("MERGE_MODE"));
1278                 strbuf_reset(&buf);
1279                 if (!allow_fast_forward)
1280                         strbuf_addf(&buf, "no-ff");
1281                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1282                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1283                 close(fd);
1284         }
1285
1286         if (merge_was_ok) {
1287                 fprintf(stderr, "Automatic merge went well; "
1288                         "stopped before committing as requested\n");
1289                 return 0;
1290         } else
1291                 return suggest_conflicts();
1292 }