Merge branch 'jt/fetch-pack-v2'
[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 "config.h"
11 #include "parse-options.h"
12 #include "builtin.h"
13 #include "lockfile.h"
14 #include "run-command.h"
15 #include "diff.h"
16 #include "refs.h"
17 #include "refspec.h"
18 #include "commit.h"
19 #include "diffcore.h"
20 #include "revision.h"
21 #include "unpack-trees.h"
22 #include "cache-tree.h"
23 #include "dir.h"
24 #include "utf8.h"
25 #include "log-tree.h"
26 #include "color.h"
27 #include "rerere.h"
28 #include "help.h"
29 #include "merge-recursive.h"
30 #include "resolve-undo.h"
31 #include "remote.h"
32 #include "fmt-merge-msg.h"
33 #include "gpg-interface.h"
34 #include "sequencer.h"
35 #include "string-list.h"
36 #include "packfile.h"
37 #include "tag.h"
38 #include "alias.h"
39 #include "commit-reach.h"
40
41 #define DEFAULT_TWOHEAD (1<<0)
42 #define DEFAULT_OCTOPUS (1<<1)
43 #define NO_FAST_FORWARD (1<<2)
44 #define NO_TRIVIAL      (1<<3)
45
46 struct strategy {
47         const char *name;
48         unsigned attr;
49 };
50
51 static const char * const builtin_merge_usage[] = {
52         N_("git merge [<options>] [<commit>...]"),
53         N_("git merge --abort"),
54         N_("git merge --continue"),
55         NULL
56 };
57
58 static int show_diffstat = 1, shortlog_len = -1, squash;
59 static int option_commit = 1;
60 static int option_edit = -1;
61 static int allow_trivial = 1, have_message, verify_signatures;
62 static int overwrite_ignore = 1;
63 static struct strbuf merge_msg = STRBUF_INIT;
64 static struct strategy **use_strategies;
65 static size_t use_strategies_nr, use_strategies_alloc;
66 static const char **xopts;
67 static size_t xopts_nr, xopts_alloc;
68 static const char *branch;
69 static char *branch_mergeoptions;
70 static int option_renormalize;
71 static int verbosity;
72 static int allow_rerere_auto;
73 static int abort_current_merge;
74 static int continue_current_merge;
75 static int allow_unrelated_histories;
76 static int show_progress = -1;
77 static int default_to_upstream = 1;
78 static int signoff;
79 static const char *sign_commit;
80 static int verify_msg = 1;
81
82 static struct strategy all_strategy[] = {
83         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
84         { "octopus",    DEFAULT_OCTOPUS },
85         { "resolve",    0 },
86         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
87         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
88 };
89
90 static const char *pull_twohead, *pull_octopus;
91
92 enum ff_type {
93         FF_NO,
94         FF_ALLOW,
95         FF_ONLY
96 };
97
98 static enum ff_type fast_forward = FF_ALLOW;
99
100 static int option_parse_message(const struct option *opt,
101                                 const char *arg, int unset)
102 {
103         struct strbuf *buf = opt->value;
104
105         if (unset)
106                 strbuf_setlen(buf, 0);
107         else if (arg) {
108                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
109                 have_message = 1;
110         } else
111                 return error(_("switch `m' requires a value"));
112         return 0;
113 }
114
115 static int option_read_message(struct parse_opt_ctx_t *ctx,
116                                const struct option *opt, int unset)
117 {
118         struct strbuf *buf = opt->value;
119         const char *arg;
120
121         if (unset)
122                 BUG("-F cannot be negated");
123
124         if (ctx->opt) {
125                 arg = ctx->opt;
126                 ctx->opt = NULL;
127         } else if (ctx->argc > 1) {
128                 ctx->argc--;
129                 arg = *++ctx->argv;
130         } else
131                 return error(_("option `%s' requires a value"), opt->long_name);
132
133         if (buf->len)
134                 strbuf_addch(buf, '\n');
135         if (ctx->prefix && !is_absolute_path(arg))
136                 arg = prefix_filename(ctx->prefix, arg);
137         if (strbuf_read_file(buf, arg, 0) < 0)
138                 return error(_("could not read file '%s'"), arg);
139         have_message = 1;
140
141         return 0;
142 }
143
144 static struct strategy *get_strategy(const char *name)
145 {
146         int i;
147         struct strategy *ret;
148         static struct cmdnames main_cmds, other_cmds;
149         static int loaded;
150
151         if (!name)
152                 return NULL;
153
154         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
155                 if (!strcmp(name, all_strategy[i].name))
156                         return &all_strategy[i];
157
158         if (!loaded) {
159                 struct cmdnames not_strategies;
160                 loaded = 1;
161
162                 memset(&not_strategies, 0, sizeof(struct cmdnames));
163                 load_command_list("git-merge-", &main_cmds, &other_cmds);
164                 for (i = 0; i < main_cmds.cnt; i++) {
165                         int j, found = 0;
166                         struct cmdname *ent = main_cmds.names[i];
167                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
168                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
169                                                 && !all_strategy[j].name[ent->len])
170                                         found = 1;
171                         if (!found)
172                                 add_cmdname(&not_strategies, ent->name, ent->len);
173                 }
174                 exclude_cmds(&main_cmds, &not_strategies);
175         }
176         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
177                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
178                 fprintf(stderr, _("Available strategies are:"));
179                 for (i = 0; i < main_cmds.cnt; i++)
180                         fprintf(stderr, " %s", main_cmds.names[i]->name);
181                 fprintf(stderr, ".\n");
182                 if (other_cmds.cnt) {
183                         fprintf(stderr, _("Available custom strategies are:"));
184                         for (i = 0; i < other_cmds.cnt; i++)
185                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
186                         fprintf(stderr, ".\n");
187                 }
188                 exit(1);
189         }
190
191         ret = xcalloc(1, sizeof(struct strategy));
192         ret->name = xstrdup(name);
193         ret->attr = NO_TRIVIAL;
194         return ret;
195 }
196
197 static void append_strategy(struct strategy *s)
198 {
199         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
200         use_strategies[use_strategies_nr++] = s;
201 }
202
203 static int option_parse_strategy(const struct option *opt,
204                                  const char *name, int unset)
205 {
206         if (unset)
207                 return 0;
208
209         append_strategy(get_strategy(name));
210         return 0;
211 }
212
213 static int option_parse_x(const struct option *opt,
214                           const char *arg, int unset)
215 {
216         if (unset)
217                 return 0;
218
219         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
220         xopts[xopts_nr++] = xstrdup(arg);
221         return 0;
222 }
223
224 static int option_parse_n(const struct option *opt,
225                           const char *arg, int unset)
226 {
227         BUG_ON_OPT_ARG(arg);
228         show_diffstat = unset;
229         return 0;
230 }
231
232 static struct option builtin_merge_options[] = {
233         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
234                 N_("do not show a diffstat at the end of the merge"),
235                 PARSE_OPT_NOARG, option_parse_n },
236         OPT_BOOL(0, "stat", &show_diffstat,
237                 N_("show a diffstat at the end of the merge")),
238         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
239         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
240           N_("add (at most <n>) entries from shortlog to merge commit message"),
241           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
242         OPT_BOOL(0, "squash", &squash,
243                 N_("create a single commit instead of doing a merge")),
244         OPT_BOOL(0, "commit", &option_commit,
245                 N_("perform a commit if the merge succeeds (default)")),
246         OPT_BOOL('e', "edit", &option_edit,
247                 N_("edit message before committing")),
248         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
249         OPT_SET_INT_F(0, "ff-only", &fast_forward,
250                       N_("abort if fast-forward is not possible"),
251                       FF_ONLY, PARSE_OPT_NONEG),
252         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
253         OPT_BOOL(0, "verify-signatures", &verify_signatures,
254                 N_("verify that the named commit has a valid GPG signature")),
255         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
256                 N_("merge strategy to use"), option_parse_strategy),
257         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
258                 N_("option for selected merge strategy"), option_parse_x),
259         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
260                 N_("merge commit message (for a non-fast-forward merge)"),
261                 option_parse_message),
262         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
263                 N_("read message from file"), PARSE_OPT_NONEG,
264                 (parse_opt_cb *) option_read_message },
265         OPT__VERBOSITY(&verbosity),
266         OPT_BOOL(0, "abort", &abort_current_merge,
267                 N_("abort the current in-progress merge")),
268         OPT_BOOL(0, "continue", &continue_current_merge,
269                 N_("continue the current in-progress merge")),
270         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
271                  N_("allow merging unrelated histories")),
272         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
273         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
274           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
275         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
276         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
277         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
278         OPT_END()
279 };
280
281 /* Cleans up metadata that is uninteresting after a succeeded merge. */
282 static void drop_save(void)
283 {
284         unlink(git_path_merge_head(the_repository));
285         unlink(git_path_merge_msg(the_repository));
286         unlink(git_path_merge_mode(the_repository));
287 }
288
289 static int save_state(struct object_id *stash)
290 {
291         int len;
292         struct child_process cp = CHILD_PROCESS_INIT;
293         struct strbuf buffer = STRBUF_INIT;
294         const char *argv[] = {"stash", "create", NULL};
295         int rc = -1;
296
297         cp.argv = argv;
298         cp.out = -1;
299         cp.git_cmd = 1;
300
301         if (start_command(&cp))
302                 die(_("could not run stash."));
303         len = strbuf_read(&buffer, cp.out, 1024);
304         close(cp.out);
305
306         if (finish_command(&cp) || len < 0)
307                 die(_("stash failed"));
308         else if (!len)          /* no changes */
309                 goto out;
310         strbuf_setlen(&buffer, buffer.len-1);
311         if (get_oid(buffer.buf, stash))
312                 die(_("not a valid object: %s"), buffer.buf);
313         rc = 0;
314 out:
315         strbuf_release(&buffer);
316         return rc;
317 }
318
319 static void read_empty(const struct object_id *oid, int verbose)
320 {
321         int i = 0;
322         const char *args[7];
323
324         args[i++] = "read-tree";
325         if (verbose)
326                 args[i++] = "-v";
327         args[i++] = "-m";
328         args[i++] = "-u";
329         args[i++] = empty_tree_oid_hex();
330         args[i++] = oid_to_hex(oid);
331         args[i] = NULL;
332
333         if (run_command_v_opt(args, RUN_GIT_CMD))
334                 die(_("read-tree failed"));
335 }
336
337 static void reset_hard(const struct object_id *oid, int verbose)
338 {
339         int i = 0;
340         const char *args[6];
341
342         args[i++] = "read-tree";
343         if (verbose)
344                 args[i++] = "-v";
345         args[i++] = "--reset";
346         args[i++] = "-u";
347         args[i++] = oid_to_hex(oid);
348         args[i] = NULL;
349
350         if (run_command_v_opt(args, RUN_GIT_CMD))
351                 die(_("read-tree failed"));
352 }
353
354 static void restore_state(const struct object_id *head,
355                           const struct object_id *stash)
356 {
357         struct strbuf sb = STRBUF_INIT;
358         const char *args[] = { "stash", "apply", NULL, NULL };
359
360         if (is_null_oid(stash))
361                 return;
362
363         reset_hard(head, 1);
364
365         args[2] = oid_to_hex(stash);
366
367         /*
368          * It is OK to ignore error here, for example when there was
369          * nothing to restore.
370          */
371         run_command_v_opt(args, RUN_GIT_CMD);
372
373         strbuf_release(&sb);
374         refresh_cache(REFRESH_QUIET);
375 }
376
377 /* This is called when no merge was necessary. */
378 static void finish_up_to_date(const char *msg)
379 {
380         if (verbosity >= 0)
381                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
382         drop_save();
383 }
384
385 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
386 {
387         struct rev_info rev;
388         struct strbuf out = STRBUF_INIT;
389         struct commit_list *j;
390         struct pretty_print_context ctx = {0};
391
392         printf(_("Squash commit -- not updating HEAD\n"));
393
394         repo_init_revisions(the_repository, &rev, NULL);
395         rev.ignore_merges = 1;
396         rev.commit_format = CMIT_FMT_MEDIUM;
397
398         commit->object.flags |= UNINTERESTING;
399         add_pending_object(&rev, &commit->object, NULL);
400
401         for (j = remoteheads; j; j = j->next)
402                 add_pending_object(&rev, &j->item->object, NULL);
403
404         setup_revisions(0, NULL, &rev, NULL);
405         if (prepare_revision_walk(&rev))
406                 die(_("revision walk setup failed"));
407
408         ctx.abbrev = rev.abbrev;
409         ctx.date_mode = rev.date_mode;
410         ctx.fmt = rev.commit_format;
411
412         strbuf_addstr(&out, "Squashed commit of the following:\n");
413         while ((commit = get_revision(&rev)) != NULL) {
414                 strbuf_addch(&out, '\n');
415                 strbuf_addf(&out, "commit %s\n",
416                         oid_to_hex(&commit->object.oid));
417                 pretty_print_commit(&ctx, commit, &out);
418         }
419         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
420         strbuf_release(&out);
421 }
422
423 static void finish(struct commit *head_commit,
424                    struct commit_list *remoteheads,
425                    const struct object_id *new_head, const char *msg)
426 {
427         struct strbuf reflog_message = STRBUF_INIT;
428         const struct object_id *head = &head_commit->object.oid;
429
430         if (!msg)
431                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
432         else {
433                 if (verbosity >= 0)
434                         printf("%s\n", msg);
435                 strbuf_addf(&reflog_message, "%s: %s",
436                         getenv("GIT_REFLOG_ACTION"), msg);
437         }
438         if (squash) {
439                 squash_message(head_commit, remoteheads);
440         } else {
441                 if (verbosity >= 0 && !merge_msg.len)
442                         printf(_("No merge message -- not updating HEAD\n"));
443                 else {
444                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
445                         update_ref(reflog_message.buf, "HEAD", new_head, head,
446                                    0, UPDATE_REFS_DIE_ON_ERR);
447                         /*
448                          * We ignore errors in 'gc --auto', since the
449                          * user should see them.
450                          */
451                         close_all_packs(the_repository->objects);
452                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
453                 }
454         }
455         if (new_head && show_diffstat) {
456                 struct diff_options opts;
457                 repo_diff_setup(the_repository, &opts);
458                 opts.stat_width = -1; /* use full terminal width */
459                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
460                 opts.output_format |=
461                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
462                 opts.detect_rename = DIFF_DETECT_RENAME;
463                 diff_setup_done(&opts);
464                 diff_tree_oid(head, new_head, "", &opts);
465                 diffcore_std(&opts);
466                 diff_flush(&opts);
467         }
468
469         /* Run a post-merge hook */
470         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
471
472         strbuf_release(&reflog_message);
473 }
474
475 /* Get the name for the merge commit's message. */
476 static void merge_name(const char *remote, struct strbuf *msg)
477 {
478         struct commit *remote_head;
479         struct object_id branch_head;
480         struct strbuf buf = STRBUF_INIT;
481         struct strbuf bname = STRBUF_INIT;
482         struct merge_remote_desc *desc;
483         const char *ptr;
484         char *found_ref;
485         int len, early;
486
487         strbuf_branchname(&bname, remote, 0);
488         remote = bname.buf;
489
490         oidclr(&branch_head);
491         remote_head = get_merge_parent(remote);
492         if (!remote_head)
493                 die(_("'%s' does not point to a commit"), remote);
494
495         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
496                 if (starts_with(found_ref, "refs/heads/")) {
497                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
498                                     oid_to_hex(&branch_head), remote);
499                         goto cleanup;
500                 }
501                 if (starts_with(found_ref, "refs/tags/")) {
502                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
503                                     oid_to_hex(&branch_head), remote);
504                         goto cleanup;
505                 }
506                 if (starts_with(found_ref, "refs/remotes/")) {
507                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
508                                     oid_to_hex(&branch_head), remote);
509                         goto cleanup;
510                 }
511         }
512
513         /* See if remote matches <name>^^^.. or <name>~<number> */
514         for (len = 0, ptr = remote + strlen(remote);
515              remote < ptr && ptr[-1] == '^';
516              ptr--)
517                 len++;
518         if (len)
519                 early = 1;
520         else {
521                 early = 0;
522                 ptr = strrchr(remote, '~');
523                 if (ptr) {
524                         int seen_nonzero = 0;
525
526                         len++; /* count ~ */
527                         while (*++ptr && isdigit(*ptr)) {
528                                 seen_nonzero |= (*ptr != '0');
529                                 len++;
530                         }
531                         if (*ptr)
532                                 len = 0; /* not ...~<number> */
533                         else if (seen_nonzero)
534                                 early = 1;
535                         else if (len == 1)
536                                 early = 1; /* "name~" is "name~1"! */
537                 }
538         }
539         if (len) {
540                 struct strbuf truname = STRBUF_INIT;
541                 strbuf_addf(&truname, "refs/heads/%s", remote);
542                 strbuf_setlen(&truname, truname.len - len);
543                 if (ref_exists(truname.buf)) {
544                         strbuf_addf(msg,
545                                     "%s\t\tbranch '%s'%s of .\n",
546                                     oid_to_hex(&remote_head->object.oid),
547                                     truname.buf + 11,
548                                     (early ? " (early part)" : ""));
549                         strbuf_release(&truname);
550                         goto cleanup;
551                 }
552                 strbuf_release(&truname);
553         }
554
555         desc = merge_remote_util(remote_head);
556         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
557                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
558                             oid_to_hex(&desc->obj->oid),
559                             type_name(desc->obj->type),
560                             remote);
561                 goto cleanup;
562         }
563
564         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
565                 oid_to_hex(&remote_head->object.oid), remote);
566 cleanup:
567         strbuf_release(&buf);
568         strbuf_release(&bname);
569 }
570
571 static void parse_branch_merge_options(char *bmo)
572 {
573         const char **argv;
574         int argc;
575
576         if (!bmo)
577                 return;
578         argc = split_cmdline(bmo, &argv);
579         if (argc < 0)
580                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
581                     _(split_cmdline_strerror(argc)));
582         REALLOC_ARRAY(argv, argc + 2);
583         MOVE_ARRAY(argv + 1, argv, argc + 1);
584         argc++;
585         argv[0] = "branch.*.mergeoptions";
586         parse_options(argc, argv, NULL, builtin_merge_options,
587                       builtin_merge_usage, 0);
588         free(argv);
589 }
590
591 static int git_merge_config(const char *k, const char *v, void *cb)
592 {
593         int status;
594
595         if (branch && starts_with(k, "branch.") &&
596                 starts_with(k + 7, branch) &&
597                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
598                 free(branch_mergeoptions);
599                 branch_mergeoptions = xstrdup(v);
600                 return 0;
601         }
602
603         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
604                 show_diffstat = git_config_bool(k, v);
605         else if (!strcmp(k, "merge.verifysignatures"))
606                 verify_signatures = git_config_bool(k, v);
607         else if (!strcmp(k, "pull.twohead"))
608                 return git_config_string(&pull_twohead, k, v);
609         else if (!strcmp(k, "pull.octopus"))
610                 return git_config_string(&pull_octopus, k, v);
611         else if (!strcmp(k, "merge.renormalize"))
612                 option_renormalize = git_config_bool(k, v);
613         else if (!strcmp(k, "merge.ff")) {
614                 int boolval = git_parse_maybe_bool(v);
615                 if (0 <= boolval) {
616                         fast_forward = boolval ? FF_ALLOW : FF_NO;
617                 } else if (v && !strcmp(v, "only")) {
618                         fast_forward = FF_ONLY;
619                 } /* do not barf on values from future versions of git */
620                 return 0;
621         } else if (!strcmp(k, "merge.defaulttoupstream")) {
622                 default_to_upstream = git_config_bool(k, v);
623                 return 0;
624         } else if (!strcmp(k, "commit.gpgsign")) {
625                 sign_commit = git_config_bool(k, v) ? "" : NULL;
626                 return 0;
627         }
628
629         status = fmt_merge_msg_config(k, v, cb);
630         if (status)
631                 return status;
632         status = git_gpg_config(k, v, NULL);
633         if (status)
634                 return status;
635         return git_diff_ui_config(k, v, cb);
636 }
637
638 static int read_tree_trivial(struct object_id *common, struct object_id *head,
639                              struct object_id *one)
640 {
641         int i, nr_trees = 0;
642         struct tree *trees[MAX_UNPACK_TREES];
643         struct tree_desc t[MAX_UNPACK_TREES];
644         struct unpack_trees_options opts;
645
646         memset(&opts, 0, sizeof(opts));
647         opts.head_idx = 2;
648         opts.src_index = &the_index;
649         opts.dst_index = &the_index;
650         opts.update = 1;
651         opts.verbose_update = 1;
652         opts.trivial_merges_only = 1;
653         opts.merge = 1;
654         trees[nr_trees] = parse_tree_indirect(common);
655         if (!trees[nr_trees++])
656                 return -1;
657         trees[nr_trees] = parse_tree_indirect(head);
658         if (!trees[nr_trees++])
659                 return -1;
660         trees[nr_trees] = parse_tree_indirect(one);
661         if (!trees[nr_trees++])
662                 return -1;
663         opts.fn = threeway_merge;
664         cache_tree_free(&active_cache_tree);
665         for (i = 0; i < nr_trees; i++) {
666                 parse_tree(trees[i]);
667                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
668         }
669         if (unpack_trees(nr_trees, t, &opts))
670                 return -1;
671         return 0;
672 }
673
674 static void write_tree_trivial(struct object_id *oid)
675 {
676         if (write_cache_as_tree(oid, 0, NULL))
677                 die(_("git write-tree failed to write a tree"));
678 }
679
680 static int try_merge_strategy(const char *strategy, struct commit_list *common,
681                               struct commit_list *remoteheads,
682                               struct commit *head)
683 {
684         struct lock_file lock = LOCK_INIT;
685         const char *head_arg = "HEAD";
686
687         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
688         refresh_cache(REFRESH_QUIET);
689         if (write_locked_index(&the_index, &lock,
690                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
691                 return error(_("Unable to write index."));
692
693         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
694                 int clean, x;
695                 struct commit *result;
696                 struct commit_list *reversed = NULL;
697                 struct merge_options o;
698                 struct commit_list *j;
699
700                 if (remoteheads->next) {
701                         error(_("Not handling anything other than two heads merge."));
702                         return 2;
703                 }
704
705                 init_merge_options(&o);
706                 if (!strcmp(strategy, "subtree"))
707                         o.subtree_shift = "";
708
709                 o.renormalize = option_renormalize;
710                 o.show_rename_progress =
711                         show_progress == -1 ? isatty(2) : show_progress;
712
713                 for (x = 0; x < xopts_nr; x++)
714                         if (parse_merge_opt(&o, xopts[x]))
715                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
716
717                 o.branch1 = head_arg;
718                 o.branch2 = merge_remote_util(remoteheads->item)->name;
719
720                 for (j = common; j; j = j->next)
721                         commit_list_insert(j->item, &reversed);
722
723                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
724                 clean = merge_recursive(&o, head,
725                                 remoteheads->item, reversed, &result);
726                 if (clean < 0)
727                         exit(128);
728                 if (write_locked_index(&the_index, &lock,
729                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
730                         die(_("unable to write %s"), get_index_file());
731                 return clean ? 0 : 1;
732         } else {
733                 return try_merge_command(the_repository,
734                                          strategy, xopts_nr, xopts,
735                                          common, head_arg, remoteheads);
736         }
737 }
738
739 static void count_diff_files(struct diff_queue_struct *q,
740                              struct diff_options *opt, void *data)
741 {
742         int *count = data;
743
744         (*count) += q->nr;
745 }
746
747 static int count_unmerged_entries(void)
748 {
749         int i, ret = 0;
750
751         for (i = 0; i < active_nr; i++)
752                 if (ce_stage(active_cache[i]))
753                         ret++;
754
755         return ret;
756 }
757
758 static void add_strategies(const char *string, unsigned attr)
759 {
760         int i;
761
762         if (string) {
763                 struct string_list list = STRING_LIST_INIT_DUP;
764                 struct string_list_item *item;
765                 string_list_split(&list, string, ' ', -1);
766                 for_each_string_list_item(item, &list)
767                         append_strategy(get_strategy(item->string));
768                 string_list_clear(&list, 0);
769                 return;
770         }
771         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
772                 if (all_strategy[i].attr & attr)
773                         append_strategy(&all_strategy[i]);
774
775 }
776
777 static void read_merge_msg(struct strbuf *msg)
778 {
779         const char *filename = git_path_merge_msg(the_repository);
780         strbuf_reset(msg);
781         if (strbuf_read_file(msg, filename, 0) < 0)
782                 die_errno(_("Could not read from '%s'"), filename);
783 }
784
785 static void write_merge_state(struct commit_list *);
786 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
787 {
788         if (err_msg)
789                 error("%s", err_msg);
790         fprintf(stderr,
791                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
792         write_merge_state(remoteheads);
793         exit(1);
794 }
795
796 static const char merge_editor_comment[] =
797 N_("Please enter a commit message to explain why this merge is necessary,\n"
798    "especially if it merges an updated upstream into a topic branch.\n"
799    "\n"
800    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
801    "the commit.\n");
802
803 static void write_merge_heads(struct commit_list *);
804 static void prepare_to_commit(struct commit_list *remoteheads)
805 {
806         struct strbuf msg = STRBUF_INIT;
807         strbuf_addbuf(&msg, &merge_msg);
808         strbuf_addch(&msg, '\n');
809         if (squash)
810                 BUG("the control must not reach here under --squash");
811         if (0 < option_edit)
812                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
813         if (signoff)
814                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
815         write_merge_heads(remoteheads);
816         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
817         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
818                             git_path_merge_msg(the_repository), "merge", NULL))
819                 abort_commit(remoteheads, NULL);
820         if (0 < option_edit) {
821                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
822                         abort_commit(remoteheads, NULL);
823         }
824
825         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
826                                           "commit-msg",
827                                           git_path_merge_msg(the_repository), NULL))
828                 abort_commit(remoteheads, NULL);
829
830         read_merge_msg(&msg);
831         strbuf_stripspace(&msg, 0 < option_edit);
832         if (!msg.len)
833                 abort_commit(remoteheads, _("Empty commit message."));
834         strbuf_release(&merge_msg);
835         strbuf_addbuf(&merge_msg, &msg);
836         strbuf_release(&msg);
837 }
838
839 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
840 {
841         struct object_id result_tree, result_commit;
842         struct commit_list *parents, **pptr = &parents;
843         struct lock_file lock = LOCK_INIT;
844
845         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
846         refresh_cache(REFRESH_QUIET);
847         if (write_locked_index(&the_index, &lock,
848                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
849                 return error(_("Unable to write index."));
850
851         write_tree_trivial(&result_tree);
852         printf(_("Wonderful.\n"));
853         pptr = commit_list_append(head, pptr);
854         pptr = commit_list_append(remoteheads->item, pptr);
855         prepare_to_commit(remoteheads);
856         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
857                         &result_commit, NULL, sign_commit))
858                 die(_("failed to write commit object"));
859         finish(head, remoteheads, &result_commit, "In-index merge");
860         drop_save();
861         return 0;
862 }
863
864 static int finish_automerge(struct commit *head,
865                             int head_subsumed,
866                             struct commit_list *common,
867                             struct commit_list *remoteheads,
868                             struct object_id *result_tree,
869                             const char *wt_strategy)
870 {
871         struct commit_list *parents = NULL;
872         struct strbuf buf = STRBUF_INIT;
873         struct object_id result_commit;
874
875         free_commit_list(common);
876         parents = remoteheads;
877         if (!head_subsumed || fast_forward == FF_NO)
878                 commit_list_insert(head, &parents);
879         strbuf_addch(&merge_msg, '\n');
880         prepare_to_commit(remoteheads);
881         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
882                         &result_commit, NULL, sign_commit))
883                 die(_("failed to write commit object"));
884         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
885         finish(head, remoteheads, &result_commit, buf.buf);
886         strbuf_release(&buf);
887         drop_save();
888         return 0;
889 }
890
891 static int suggest_conflicts(void)
892 {
893         const char *filename;
894         FILE *fp;
895         struct strbuf msgbuf = STRBUF_INIT;
896
897         filename = git_path_merge_msg(the_repository);
898         fp = xfopen(filename, "a");
899
900         append_conflicts_hint(&the_index, &msgbuf);
901         fputs(msgbuf.buf, fp);
902         strbuf_release(&msgbuf);
903         fclose(fp);
904         repo_rerere(the_repository, allow_rerere_auto);
905         printf(_("Automatic merge failed; "
906                         "fix conflicts and then commit the result.\n"));
907         return 1;
908 }
909
910 static int evaluate_result(void)
911 {
912         int cnt = 0;
913         struct rev_info rev;
914
915         /* Check how many files differ. */
916         repo_init_revisions(the_repository, &rev, "");
917         setup_revisions(0, NULL, &rev, NULL);
918         rev.diffopt.output_format |=
919                 DIFF_FORMAT_CALLBACK;
920         rev.diffopt.format_callback = count_diff_files;
921         rev.diffopt.format_callback_data = &cnt;
922         run_diff_files(&rev, 0);
923
924         /*
925          * Check how many unmerged entries are
926          * there.
927          */
928         cnt += count_unmerged_entries();
929
930         return cnt;
931 }
932
933 /*
934  * Pretend as if the user told us to merge with the remote-tracking
935  * branch we have for the upstream of the current branch
936  */
937 static int setup_with_upstream(const char ***argv)
938 {
939         struct branch *branch = branch_get(NULL);
940         int i;
941         const char **args;
942
943         if (!branch)
944                 die(_("No current branch."));
945         if (!branch->remote_name)
946                 die(_("No remote for the current branch."));
947         if (!branch->merge_nr)
948                 die(_("No default upstream defined for the current branch."));
949
950         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
951         for (i = 0; i < branch->merge_nr; i++) {
952                 if (!branch->merge[i]->dst)
953                         die(_("No remote-tracking branch for %s from %s"),
954                             branch->merge[i]->src, branch->remote_name);
955                 args[i] = branch->merge[i]->dst;
956         }
957         args[i] = NULL;
958         *argv = args;
959         return i;
960 }
961
962 static void write_merge_heads(struct commit_list *remoteheads)
963 {
964         struct commit_list *j;
965         struct strbuf buf = STRBUF_INIT;
966
967         for (j = remoteheads; j; j = j->next) {
968                 struct object_id *oid;
969                 struct commit *c = j->item;
970                 struct merge_remote_desc *desc;
971
972                 desc = merge_remote_util(c);
973                 if (desc && desc->obj) {
974                         oid = &desc->obj->oid;
975                 } else {
976                         oid = &c->object.oid;
977                 }
978                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
979         }
980         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
981
982         strbuf_reset(&buf);
983         if (fast_forward == FF_NO)
984                 strbuf_addstr(&buf, "no-ff");
985         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
986         strbuf_release(&buf);
987 }
988
989 static void write_merge_state(struct commit_list *remoteheads)
990 {
991         write_merge_heads(remoteheads);
992         strbuf_addch(&merge_msg, '\n');
993         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
994                        merge_msg.len);
995 }
996
997 static int default_edit_option(void)
998 {
999         static const char name[] = "GIT_MERGE_AUTOEDIT";
1000         const char *e = getenv(name);
1001         struct stat st_stdin, st_stdout;
1002
1003         if (have_message)
1004                 /* an explicit -m msg without --[no-]edit */
1005                 return 0;
1006
1007         if (e) {
1008                 int v = git_parse_maybe_bool(e);
1009                 if (v < 0)
1010                         die(_("Bad value '%s' in environment '%s'"), e, name);
1011                 return v;
1012         }
1013
1014         /* Use editor if stdin and stdout are the same and is a tty */
1015         return (!fstat(0, &st_stdin) &&
1016                 !fstat(1, &st_stdout) &&
1017                 isatty(0) && isatty(1) &&
1018                 st_stdin.st_dev == st_stdout.st_dev &&
1019                 st_stdin.st_ino == st_stdout.st_ino &&
1020                 st_stdin.st_mode == st_stdout.st_mode);
1021 }
1022
1023 static struct commit_list *reduce_parents(struct commit *head_commit,
1024                                           int *head_subsumed,
1025                                           struct commit_list *remoteheads)
1026 {
1027         struct commit_list *parents, **remotes;
1028
1029         /*
1030          * Is the current HEAD reachable from another commit being
1031          * merged?  If so we do not want to record it as a parent of
1032          * the resulting merge, unless --no-ff is given.  We will flip
1033          * this variable to 0 when we find HEAD among the independent
1034          * tips being merged.
1035          */
1036         *head_subsumed = 1;
1037
1038         /* Find what parents to record by checking independent ones. */
1039         parents = reduce_heads(remoteheads);
1040         free_commit_list(remoteheads);
1041
1042         remoteheads = NULL;
1043         remotes = &remoteheads;
1044         while (parents) {
1045                 struct commit *commit = pop_commit(&parents);
1046                 if (commit == head_commit)
1047                         *head_subsumed = 0;
1048                 else
1049                         remotes = &commit_list_insert(commit, remotes)->next;
1050         }
1051         return remoteheads;
1052 }
1053
1054 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1055 {
1056         struct fmt_merge_msg_opts opts;
1057
1058         memset(&opts, 0, sizeof(opts));
1059         opts.add_title = !have_message;
1060         opts.shortlog_len = shortlog_len;
1061         opts.credit_people = (0 < option_edit);
1062
1063         fmt_merge_msg(merge_names, merge_msg, &opts);
1064         if (merge_msg->len)
1065                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1066 }
1067
1068 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1069 {
1070         const char *filename;
1071         int fd, pos, npos;
1072         struct strbuf fetch_head_file = STRBUF_INIT;
1073         const unsigned hexsz = the_hash_algo->hexsz;
1074
1075         if (!merge_names)
1076                 merge_names = &fetch_head_file;
1077
1078         filename = git_path_fetch_head(the_repository);
1079         fd = open(filename, O_RDONLY);
1080         if (fd < 0)
1081                 die_errno(_("could not open '%s' for reading"), filename);
1082
1083         if (strbuf_read(merge_names, fd, 0) < 0)
1084                 die_errno(_("could not read '%s'"), filename);
1085         if (close(fd) < 0)
1086                 die_errno(_("could not close '%s'"), filename);
1087
1088         for (pos = 0; pos < merge_names->len; pos = npos) {
1089                 struct object_id oid;
1090                 char *ptr;
1091                 struct commit *commit;
1092
1093                 ptr = strchr(merge_names->buf + pos, '\n');
1094                 if (ptr)
1095                         npos = ptr - merge_names->buf + 1;
1096                 else
1097                         npos = merge_names->len;
1098
1099                 if (npos - pos < hexsz + 2 ||
1100                     get_oid_hex(merge_names->buf + pos, &oid))
1101                         commit = NULL; /* bad */
1102                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1103                         continue; /* not-for-merge */
1104                 else {
1105                         char saved = merge_names->buf[pos + hexsz];
1106                         merge_names->buf[pos + hexsz] = '\0';
1107                         commit = get_merge_parent(merge_names->buf + pos);
1108                         merge_names->buf[pos + hexsz] = saved;
1109                 }
1110                 if (!commit) {
1111                         if (ptr)
1112                                 *ptr = '\0';
1113                         die(_("not something we can merge in %s: %s"),
1114                             filename, merge_names->buf + pos);
1115                 }
1116                 remotes = &commit_list_insert(commit, remotes)->next;
1117         }
1118
1119         if (merge_names == &fetch_head_file)
1120                 strbuf_release(&fetch_head_file);
1121 }
1122
1123 static struct commit_list *collect_parents(struct commit *head_commit,
1124                                            int *head_subsumed,
1125                                            int argc, const char **argv,
1126                                            struct strbuf *merge_msg)
1127 {
1128         int i;
1129         struct commit_list *remoteheads = NULL;
1130         struct commit_list **remotes = &remoteheads;
1131         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1132
1133         if (merge_msg && (!have_message || shortlog_len))
1134                 autogen = &merge_names;
1135
1136         if (head_commit)
1137                 remotes = &commit_list_insert(head_commit, remotes)->next;
1138
1139         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1140                 handle_fetch_head(remotes, autogen);
1141                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1142         } else {
1143                 for (i = 0; i < argc; i++) {
1144                         struct commit *commit = get_merge_parent(argv[i]);
1145                         if (!commit)
1146                                 help_unknown_ref(argv[i], "merge",
1147                                                  _("not something we can merge"));
1148                         remotes = &commit_list_insert(commit, remotes)->next;
1149                 }
1150                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1151                 if (autogen) {
1152                         struct commit_list *p;
1153                         for (p = remoteheads; p; p = p->next)
1154                                 merge_name(merge_remote_util(p->item)->name, autogen);
1155                 }
1156         }
1157
1158         if (autogen) {
1159                 prepare_merge_message(autogen, merge_msg);
1160                 strbuf_release(autogen);
1161         }
1162
1163         return remoteheads;
1164 }
1165
1166 static int merging_a_throwaway_tag(struct commit *commit)
1167 {
1168         char *tag_ref;
1169         struct object_id oid;
1170         int is_throwaway_tag = 0;
1171
1172         /* Are we merging a tag? */
1173         if (!merge_remote_util(commit) ||
1174             !merge_remote_util(commit)->obj ||
1175             merge_remote_util(commit)->obj->type != OBJ_TAG)
1176                 return is_throwaway_tag;
1177
1178         /*
1179          * Now we know we are merging a tag object.  Are we downstream
1180          * and following the tags from upstream?  If so, we must have
1181          * the tag object pointed at by "refs/tags/$T" where $T is the
1182          * tagname recorded in the tag object.  We want to allow such
1183          * a "just to catch up" merge to fast-forward.
1184          *
1185          * Otherwise, we are playing an integrator's role, making a
1186          * merge with a throw-away tag from a contributor with
1187          * something like "git pull $contributor $signed_tag".
1188          * We want to forbid such a merge from fast-forwarding
1189          * by default; otherwise we would not keep the signature
1190          * anywhere.
1191          */
1192         tag_ref = xstrfmt("refs/tags/%s",
1193                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1194         if (!read_ref(tag_ref, &oid) &&
1195             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1196                 is_throwaway_tag = 0;
1197         else
1198                 is_throwaway_tag = 1;
1199         free(tag_ref);
1200         return is_throwaway_tag;
1201 }
1202
1203 int cmd_merge(int argc, const char **argv, const char *prefix)
1204 {
1205         struct object_id result_tree, stash, head_oid;
1206         struct commit *head_commit;
1207         struct strbuf buf = STRBUF_INIT;
1208         int i, ret = 0, head_subsumed;
1209         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1210         struct commit_list *common = NULL;
1211         const char *best_strategy = NULL, *wt_strategy = NULL;
1212         struct commit_list *remoteheads, *p;
1213         void *branch_to_free;
1214         int orig_argc = argc;
1215
1216         if (argc == 2 && !strcmp(argv[1], "-h"))
1217                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1218
1219         /*
1220          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1221          * current branch.
1222          */
1223         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1224         if (branch)
1225                 skip_prefix(branch, "refs/heads/", &branch);
1226
1227         init_diff_ui_defaults();
1228         git_config(git_merge_config, NULL);
1229
1230         if (!branch || is_null_oid(&head_oid))
1231                 head_commit = NULL;
1232         else
1233                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1234
1235         if (branch_mergeoptions)
1236                 parse_branch_merge_options(branch_mergeoptions);
1237         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1238                         builtin_merge_usage, 0);
1239         if (shortlog_len < 0)
1240                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1241
1242         if (verbosity < 0 && show_progress == -1)
1243                 show_progress = 0;
1244
1245         if (abort_current_merge) {
1246                 int nargc = 2;
1247                 const char *nargv[] = {"reset", "--merge", NULL};
1248
1249                 if (orig_argc != 2)
1250                         usage_msg_opt(_("--abort expects no arguments"),
1251                               builtin_merge_usage, builtin_merge_options);
1252
1253                 if (!file_exists(git_path_merge_head(the_repository)))
1254                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1255
1256                 /* Invoke 'git reset --merge' */
1257                 ret = cmd_reset(nargc, nargv, prefix);
1258                 goto done;
1259         }
1260
1261         if (continue_current_merge) {
1262                 int nargc = 1;
1263                 const char *nargv[] = {"commit", NULL};
1264
1265                 if (orig_argc != 2)
1266                         usage_msg_opt(_("--continue expects no arguments"),
1267                               builtin_merge_usage, builtin_merge_options);
1268
1269                 if (!file_exists(git_path_merge_head(the_repository)))
1270                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1271
1272                 /* Invoke 'git commit' */
1273                 ret = cmd_commit(nargc, nargv, prefix);
1274                 goto done;
1275         }
1276
1277         if (read_cache_unmerged())
1278                 die_resolve_conflict("merge");
1279
1280         if (file_exists(git_path_merge_head(the_repository))) {
1281                 /*
1282                  * There is no unmerged entry, don't advise 'git
1283                  * add/rm <file>', just 'git commit'.
1284                  */
1285                 if (advice_resolve_conflict)
1286                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1287                                   "Please, commit your changes before you merge."));
1288                 else
1289                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1290         }
1291         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1292                 if (advice_resolve_conflict)
1293                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1294                             "Please, commit your changes before you merge."));
1295                 else
1296                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1297         }
1298         resolve_undo_clear();
1299
1300         if (verbosity < 0)
1301                 show_diffstat = 0;
1302
1303         if (squash) {
1304                 if (fast_forward == FF_NO)
1305                         die(_("You cannot combine --squash with --no-ff."));
1306                 option_commit = 0;
1307         }
1308
1309         if (!argc) {
1310                 if (default_to_upstream)
1311                         argc = setup_with_upstream(&argv);
1312                 else
1313                         die(_("No commit specified and merge.defaultToUpstream not set."));
1314         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1315                 argv[0] = "@{-1}";
1316         }
1317
1318         if (!argc)
1319                 usage_with_options(builtin_merge_usage,
1320                         builtin_merge_options);
1321
1322         if (!head_commit) {
1323                 /*
1324                  * If the merged head is a valid one there is no reason
1325                  * to forbid "git merge" into a branch yet to be born.
1326                  * We do the same for "git pull".
1327                  */
1328                 struct object_id *remote_head_oid;
1329                 if (squash)
1330                         die(_("Squash commit into empty head not supported yet"));
1331                 if (fast_forward == FF_NO)
1332                         die(_("Non-fast-forward commit does not make sense into "
1333                             "an empty head"));
1334                 remoteheads = collect_parents(head_commit, &head_subsumed,
1335                                               argc, argv, NULL);
1336                 if (!remoteheads)
1337                         die(_("%s - not something we can merge"), argv[0]);
1338                 if (remoteheads->next)
1339                         die(_("Can merge only exactly one commit into empty head"));
1340
1341                 if (verify_signatures)
1342                         verify_merge_signature(remoteheads->item, verbosity);
1343
1344                 remote_head_oid = &remoteheads->item->object.oid;
1345                 read_empty(remote_head_oid, 0);
1346                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1347                            UPDATE_REFS_DIE_ON_ERR);
1348                 goto done;
1349         }
1350
1351         /*
1352          * All the rest are the commits being merged; prepare
1353          * the standard merge summary message to be appended
1354          * to the given message.
1355          */
1356         remoteheads = collect_parents(head_commit, &head_subsumed,
1357                                       argc, argv, &merge_msg);
1358
1359         if (!head_commit || !argc)
1360                 usage_with_options(builtin_merge_usage,
1361                         builtin_merge_options);
1362
1363         if (verify_signatures) {
1364                 for (p = remoteheads; p; p = p->next) {
1365                         verify_merge_signature(p->item, verbosity);
1366                 }
1367         }
1368
1369         strbuf_addstr(&buf, "merge");
1370         for (p = remoteheads; p; p = p->next)
1371                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1372         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1373         strbuf_reset(&buf);
1374
1375         for (p = remoteheads; p; p = p->next) {
1376                 struct commit *commit = p->item;
1377                 strbuf_addf(&buf, "GITHEAD_%s",
1378                             oid_to_hex(&commit->object.oid));
1379                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1380                 strbuf_reset(&buf);
1381                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1382                         fast_forward = FF_NO;
1383         }
1384
1385         if (option_edit < 0)
1386                 option_edit = default_edit_option();
1387
1388         if (!use_strategies) {
1389                 if (!remoteheads)
1390                         ; /* already up-to-date */
1391                 else if (!remoteheads->next)
1392                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1393                 else
1394                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1395         }
1396
1397         for (i = 0; i < use_strategies_nr; i++) {
1398                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1399                         fast_forward = FF_NO;
1400                 if (use_strategies[i]->attr & NO_TRIVIAL)
1401                         allow_trivial = 0;
1402         }
1403
1404         if (!remoteheads)
1405                 ; /* already up-to-date */
1406         else if (!remoteheads->next)
1407                 common = get_merge_bases(head_commit, remoteheads->item);
1408         else {
1409                 struct commit_list *list = remoteheads;
1410                 commit_list_insert(head_commit, &list);
1411                 common = get_octopus_merge_bases(list);
1412                 free(list);
1413         }
1414
1415         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1416                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1417
1418         if (remoteheads && !common) {
1419                 /* No common ancestors found. */
1420                 if (!allow_unrelated_histories)
1421                         die(_("refusing to merge unrelated histories"));
1422                 /* otherwise, we need a real merge. */
1423         } else if (!remoteheads ||
1424                  (!remoteheads->next && !common->next &&
1425                   common->item == remoteheads->item)) {
1426                 /*
1427                  * If head can reach all the merge then we are up to date.
1428                  * but first the most common case of merging one remote.
1429                  */
1430                 finish_up_to_date(_("Already up to date."));
1431                 goto done;
1432         } else if (fast_forward != FF_NO && !remoteheads->next &&
1433                         !common->next &&
1434                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1435                 /* Again the most common case of merging one remote. */
1436                 struct strbuf msg = STRBUF_INIT;
1437                 struct commit *commit;
1438
1439                 if (verbosity >= 0) {
1440                         printf(_("Updating %s..%s\n"),
1441                                find_unique_abbrev(&head_commit->object.oid,
1442                                                   DEFAULT_ABBREV),
1443                                find_unique_abbrev(&remoteheads->item->object.oid,
1444                                                   DEFAULT_ABBREV));
1445                 }
1446                 strbuf_addstr(&msg, "Fast-forward");
1447                 if (have_message)
1448                         strbuf_addstr(&msg,
1449                                 " (no commit created; -m option ignored)");
1450                 commit = remoteheads->item;
1451                 if (!commit) {
1452                         ret = 1;
1453                         goto done;
1454                 }
1455
1456                 if (checkout_fast_forward(the_repository,
1457                                           &head_commit->object.oid,
1458                                           &commit->object.oid,
1459                                           overwrite_ignore)) {
1460                         ret = 1;
1461                         goto done;
1462                 }
1463
1464                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1465                 drop_save();
1466                 goto done;
1467         } else if (!remoteheads->next && common->next)
1468                 ;
1469                 /*
1470                  * We are not doing octopus and not fast-forward.  Need
1471                  * a real merge.
1472                  */
1473         else if (!remoteheads->next && !common->next && option_commit) {
1474                 /*
1475                  * We are not doing octopus, not fast-forward, and have
1476                  * only one common.
1477                  */
1478                 refresh_cache(REFRESH_QUIET);
1479                 if (allow_trivial && fast_forward != FF_ONLY) {
1480                         /* See if it is really trivial. */
1481                         git_committer_info(IDENT_STRICT);
1482                         printf(_("Trying really trivial in-index merge...\n"));
1483                         if (!read_tree_trivial(&common->item->object.oid,
1484                                                &head_commit->object.oid,
1485                                                &remoteheads->item->object.oid)) {
1486                                 ret = merge_trivial(head_commit, remoteheads);
1487                                 goto done;
1488                         }
1489                         printf(_("Nope.\n"));
1490                 }
1491         } else {
1492                 /*
1493                  * An octopus.  If we can reach all the remote we are up
1494                  * to date.
1495                  */
1496                 int up_to_date = 1;
1497                 struct commit_list *j;
1498
1499                 for (j = remoteheads; j; j = j->next) {
1500                         struct commit_list *common_one;
1501
1502                         /*
1503                          * Here we *have* to calculate the individual
1504                          * merge_bases again, otherwise "git merge HEAD^
1505                          * HEAD^^" would be missed.
1506                          */
1507                         common_one = get_merge_bases(head_commit, j->item);
1508                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1509                                 up_to_date = 0;
1510                                 break;
1511                         }
1512                 }
1513                 if (up_to_date) {
1514                         finish_up_to_date(_("Already up to date. Yeeah!"));
1515                         goto done;
1516                 }
1517         }
1518
1519         if (fast_forward == FF_ONLY)
1520                 die(_("Not possible to fast-forward, aborting."));
1521
1522         /* We are going to make a new commit. */
1523         git_committer_info(IDENT_STRICT);
1524
1525         /*
1526          * At this point, we need a real merge.  No matter what strategy
1527          * we use, it would operate on the index, possibly affecting the
1528          * working tree, and when resolved cleanly, have the desired
1529          * tree in the index -- this means that the index must be in
1530          * sync with the head commit.  The strategies are responsible
1531          * to ensure this.
1532          */
1533         if (use_strategies_nr == 1 ||
1534             /*
1535              * Stash away the local changes so that we can try more than one.
1536              */
1537             save_state(&stash))
1538                 oidclr(&stash);
1539
1540         for (i = 0; i < use_strategies_nr; i++) {
1541                 int ret;
1542                 if (i) {
1543                         printf(_("Rewinding the tree to pristine...\n"));
1544                         restore_state(&head_commit->object.oid, &stash);
1545                 }
1546                 if (use_strategies_nr != 1)
1547                         printf(_("Trying merge strategy %s...\n"),
1548                                 use_strategies[i]->name);
1549                 /*
1550                  * Remember which strategy left the state in the working
1551                  * tree.
1552                  */
1553                 wt_strategy = use_strategies[i]->name;
1554
1555                 ret = try_merge_strategy(use_strategies[i]->name,
1556                                          common, remoteheads,
1557                                          head_commit);
1558                 if (!option_commit && !ret) {
1559                         merge_was_ok = 1;
1560                         /*
1561                          * This is necessary here just to avoid writing
1562                          * the tree, but later we will *not* exit with
1563                          * status code 1 because merge_was_ok is set.
1564                          */
1565                         ret = 1;
1566                 }
1567
1568                 if (ret) {
1569                         /*
1570                          * The backend exits with 1 when conflicts are
1571                          * left to be resolved, with 2 when it does not
1572                          * handle the given merge at all.
1573                          */
1574                         if (ret == 1) {
1575                                 int cnt = evaluate_result();
1576
1577                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1578                                         best_strategy = use_strategies[i]->name;
1579                                         best_cnt = cnt;
1580                                 }
1581                         }
1582                         if (merge_was_ok)
1583                                 break;
1584                         else
1585                                 continue;
1586                 }
1587
1588                 /* Automerge succeeded. */
1589                 write_tree_trivial(&result_tree);
1590                 automerge_was_ok = 1;
1591                 break;
1592         }
1593
1594         /*
1595          * If we have a resulting tree, that means the strategy module
1596          * auto resolved the merge cleanly.
1597          */
1598         if (automerge_was_ok) {
1599                 ret = finish_automerge(head_commit, head_subsumed,
1600                                        common, remoteheads,
1601                                        &result_tree, wt_strategy);
1602                 goto done;
1603         }
1604
1605         /*
1606          * Pick the result from the best strategy and have the user fix
1607          * it up.
1608          */
1609         if (!best_strategy) {
1610                 restore_state(&head_commit->object.oid, &stash);
1611                 if (use_strategies_nr > 1)
1612                         fprintf(stderr,
1613                                 _("No merge strategy handled the merge.\n"));
1614                 else
1615                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1616                                 use_strategies[0]->name);
1617                 ret = 2;
1618                 goto done;
1619         } else if (best_strategy == wt_strategy)
1620                 ; /* We already have its result in the working tree. */
1621         else {
1622                 printf(_("Rewinding the tree to pristine...\n"));
1623                 restore_state(&head_commit->object.oid, &stash);
1624                 printf(_("Using the %s to prepare resolving by hand.\n"),
1625                         best_strategy);
1626                 try_merge_strategy(best_strategy, common, remoteheads,
1627                                    head_commit);
1628         }
1629
1630         if (squash)
1631                 finish(head_commit, remoteheads, NULL, NULL);
1632         else
1633                 write_merge_state(remoteheads);
1634
1635         if (merge_was_ok)
1636                 fprintf(stderr, _("Automatic merge went well; "
1637                         "stopped before committing as requested\n"));
1638         else
1639                 ret = suggest_conflicts();
1640
1641 done:
1642         free(branch_to_free);
1643         return ret;
1644 }