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