builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29
  30 #define DEFAULT_TWOHEAD (1<<0)
  31 #define DEFAULT_OCTOPUS (1<<1)
  32 #define NO_FAST_FORWARD (1<<2)
  33 #define NO_TRIVIAL      (1<<3)
  34
  35 struct strategy {
  36         const char *name;
  37         unsigned attr;
  38 };
  39
  40 static const char * const builtin_merge_usage[] = {
  41         "git merge [options] [<commit>...]",
  42         "git merge [options] <msg> HEAD <commit>",
  43         "git merge --abort",
  44         NULL
  45 };
  46
  47 static int show_diffstat = 1, shortlog_len, squash;
  48 static int option_commit = 1, allow_fast_forward = 1;
  49 static int fast_forward_only;
  50 static int allow_trivial = 1, have_message;
  51 static struct strbuf merge_msg;
  52 static struct commit_list *remoteheads;
  53 static unsigned char head[20], stash[20];
  54 static struct strategy **use_strategies;
  55 static size_t use_strategies_nr, use_strategies_alloc;
  56 static const char **xopts;
  57 static size_t xopts_nr, xopts_alloc;
  58 static const char *branch;
  59 static int option_renormalize;
  60 static int verbosity;
  61 static int allow_rerere_auto;
  62 static int abort_current_merge;
  63 static int show_progress = -1;
  64 static int default_to_upstream;
  65
  66 static struct strategy all_strategy[] = {
  67         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  68         { "octopus",    DEFAULT_OCTOPUS },
  69         { "resolve",    0 },
  70         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  71         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  72 };
  73
  74 static const char *pull_twohead, *pull_octopus;
  75
  76 static int option_parse_message(const struct option *opt,
  77                                 const char *arg, int unset)
  78 {
  79         struct strbuf *buf = opt->value;
  80
  81         if (unset)
  82                 strbuf_setlen(buf, 0);
  83         else if (arg) {
  84                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  85                 have_message = 1;
  86         } else
  87                 return error(_("switch `m' requires a value"));
  88         return 0;
  89 }
  90
  91 static struct strategy *get_strategy(const char *name)
  92 {
  93         int i;
  94         struct strategy *ret;
  95         static struct cmdnames main_cmds, other_cmds;
  96         static int loaded;
  97
  98         if (!name)
  99                 return NULL;
 100
 101         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 102                 if (!strcmp(name, all_strategy[i].name))
 103                         return &all_strategy[i];
 104
 105         if (!loaded) {
 106                 struct cmdnames not_strategies;
 107                 loaded = 1;
 108
 109                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 110                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 111                 for (i = 0; i < main_cmds.cnt; i++) {
 112                         int j, found = 0;
 113                         struct cmdname *ent = main_cmds.names[i];
 114                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 115                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 116                                                 && !all_strategy[j].name[ent->len])
 117                                         found = 1;
 118                         if (!found)
 119                                 add_cmdname(&not_strategies, ent->name, ent->len);
 120                 }
 121                 exclude_cmds(&main_cmds, &not_strategies);
 122         }
 123         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 124                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 125                 fprintf(stderr, _("Available strategies are:"));
 126                 for (i = 0; i < main_cmds.cnt; i++)
 127                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 128                 fprintf(stderr, ".\n");
 129                 if (other_cmds.cnt) {
 130                         fprintf(stderr, _("Available custom strategies are:"));
 131                         for (i = 0; i < other_cmds.cnt; i++)
 132                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 133                         fprintf(stderr, ".\n");
 134                 }
 135                 exit(1);
 136         }
 137
 138         ret = xcalloc(1, sizeof(struct strategy));
 139         ret->name = xstrdup(name);
 140         ret->attr = NO_TRIVIAL;
 141         return ret;
 142 }
 143
 144 static void append_strategy(struct strategy *s)
 145 {
 146         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 147         use_strategies[use_strategies_nr++] = s;
 148 }
 149
 150 static int option_parse_strategy(const struct option *opt,
 151                                  const char *name, int unset)
 152 {
 153         if (unset)
 154                 return 0;
 155
 156         append_strategy(get_strategy(name));
 157         return 0;
 158 }
 159
 160 static int option_parse_x(const struct option *opt,
 161                           const char *arg, int unset)
 162 {
 163         if (unset)
 164                 return 0;
 165
 166         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 167         xopts[xopts_nr++] = xstrdup(arg);
 168         return 0;
 169 }
 170
 171 static int option_parse_n(const struct option *opt,
 172                           const char *arg, int unset)
 173 {
 174         show_diffstat = unset;
 175         return 0;
 176 }
 177
 178 static struct option builtin_merge_options[] = {
 179         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 180                 "do not show a diffstat at the end of the merge",
 181                 PARSE_OPT_NOARG, option_parse_n },
 182         OPT_BOOLEAN(0, "stat", &show_diffstat,
 183                 "show a diffstat at the end of the merge"),
 184         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 185         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 186           "add (at most <n>) entries from shortlog to merge commit message",
 187           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 188         OPT_BOOLEAN(0, "squash", &squash,
 189                 "create a single commit instead of doing a merge"),
 190         OPT_BOOLEAN(0, "commit", &option_commit,
 191                 "perform a commit if the merge succeeds (default)"),
 192         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 193                 "allow fast-forward (default)"),
 194         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 195                 "abort if fast-forward is not possible"),
 196         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 197         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 198                 "merge strategy to use", option_parse_strategy),
 199         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 200                 "option for selected merge strategy", option_parse_x),
 201         OPT_CALLBACK('m', "message", &merge_msg, "message",
 202                 "merge commit message (for a non-fast-forward merge)",
 203                 option_parse_message),
 204         OPT__VERBOSITY(&verbosity),
 205         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 206                 "abort the current in-progress merge"),
 207         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 208         OPT_END()
 209 };
 210
 211 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 212 static void drop_save(void)
 213 {
 214         unlink(git_path("MERGE_HEAD"));
 215         unlink(git_path("MERGE_MSG"));
 216         unlink(git_path("MERGE_MODE"));
 217 }
 218
 219 static void save_state(void)
 220 {
 221         int len;
 222         struct child_process cp;
 223         struct strbuf buffer = STRBUF_INIT;
 224         const char *argv[] = {"stash", "create", NULL};
 225
 226         memset(&cp, 0, sizeof(cp));
 227         cp.argv = argv;
 228         cp.out = -1;
 229         cp.git_cmd = 1;
 230
 231         if (start_command(&cp))
 232                 die(_("could not run stash."));
 233         len = strbuf_read(&buffer, cp.out, 1024);
 234         close(cp.out);
 235
 236         if (finish_command(&cp) || len < 0)
 237                 die(_("stash failed"));
 238         else if (!len)
 239                 return;
 240         strbuf_setlen(&buffer, buffer.len-1);
 241         if (get_sha1(buffer.buf, stash))
 242                 die(_("not a valid object: %s"), buffer.buf);
 243 }
 244
 245 static void read_empty(unsigned const char *sha1, int verbose)
 246 {
 247         int i = 0;
 248         const char *args[7];
 249
 250         args[i++] = "read-tree";
 251         if (verbose)
 252                 args[i++] = "-v";
 253         args[i++] = "-m";
 254         args[i++] = "-u";
 255         args[i++] = EMPTY_TREE_SHA1_HEX;
 256         args[i++] = sha1_to_hex(sha1);
 257         args[i] = NULL;
 258
 259         if (run_command_v_opt(args, RUN_GIT_CMD))
 260                 die(_("read-tree failed"));
 261 }
 262
 263 static void reset_hard(unsigned const char *sha1, int verbose)
 264 {
 265         int i = 0;
 266         const char *args[6];
 267
 268         args[i++] = "read-tree";
 269         if (verbose)
 270                 args[i++] = "-v";
 271         args[i++] = "--reset";
 272         args[i++] = "-u";
 273         args[i++] = sha1_to_hex(sha1);
 274         args[i] = NULL;
 275
 276         if (run_command_v_opt(args, RUN_GIT_CMD))
 277                 die(_("read-tree failed"));
 278 }
 279
 280 static void restore_state(void)
 281 {
 282         struct strbuf sb = STRBUF_INIT;
 283         const char *args[] = { "stash", "apply", NULL, NULL };
 284
 285         if (is_null_sha1(stash))
 286                 return;
 287
 288         reset_hard(head, 1);
 289
 290         args[2] = sha1_to_hex(stash);
 291
 292         /*
 293          * It is OK to ignore error here, for example when there was
 294          * nothing to restore.
 295          */
 296         run_command_v_opt(args, RUN_GIT_CMD);
 297
 298         strbuf_release(&sb);
 299         refresh_cache(REFRESH_QUIET);
 300 }
 301
 302 /* This is called when no merge was necessary. */
 303 static void finish_up_to_date(const char *msg)
 304 {
 305         if (verbosity >= 0)
 306                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 307         drop_save();
 308 }
 309
 310 static void squash_message(void)
 311 {
 312         struct rev_info rev;
 313         struct commit *commit;
 314         struct strbuf out = STRBUF_INIT;
 315         struct commit_list *j;
 316         int fd;
 317         struct pretty_print_context ctx = {0};
 318
 319         printf(_("Squash commit -- not updating HEAD\n"));
 320         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 321         if (fd < 0)
 322                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 323
 324         init_revisions(&rev, NULL);
 325         rev.ignore_merges = 1;
 326         rev.commit_format = CMIT_FMT_MEDIUM;
 327
 328         commit = lookup_commit(head);
 329         commit->object.flags |= UNINTERESTING;
 330         add_pending_object(&rev, &commit->object, NULL);
 331
 332         for (j = remoteheads; j; j = j->next)
 333                 add_pending_object(&rev, &j->item->object, NULL);
 334
 335         setup_revisions(0, NULL, &rev, NULL);
 336         if (prepare_revision_walk(&rev))
 337                 die(_("revision walk setup failed"));
 338
 339         ctx.abbrev = rev.abbrev;
 340         ctx.date_mode = rev.date_mode;
 341
 342         strbuf_addstr(&out, "Squashed commit of the following:\n");
 343         while ((commit = get_revision(&rev)) != NULL) {
 344                 strbuf_addch(&out, '\n');
 345                 strbuf_addf(&out, "commit %s\n",
 346                         sha1_to_hex(commit->object.sha1));
 347                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 348         }
 349         if (write(fd, out.buf, out.len) < 0)
 350                 die_errno(_("Writing SQUASH_MSG"));
 351         if (close(fd))
 352                 die_errno(_("Finishing SQUASH_MSG"));
 353         strbuf_release(&out);
 354 }
 355
 356 static void finish(const unsigned char *new_head, const char *msg)
 357 {
 358         struct strbuf reflog_message = STRBUF_INIT;
 359
 360         if (!msg)
 361                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 362         else {
 363                 if (verbosity >= 0)
 364                         printf("%s\n", msg);
 365                 strbuf_addf(&reflog_message, "%s: %s",
 366                         getenv("GIT_REFLOG_ACTION"), msg);
 367         }
 368         if (squash) {
 369                 squash_message();
 370         } else {
 371                 if (verbosity >= 0 && !merge_msg.len)
 372                         printf(_("No merge message -- not updating HEAD\n"));
 373                 else {
 374                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 375                         update_ref(reflog_message.buf, "HEAD",
 376                                 new_head, head, 0,
 377                                 DIE_ON_ERR);
 378                         /*
 379                          * We ignore errors in 'gc --auto', since the
 380                          * user should see them.
 381                          */
 382                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 383                 }
 384         }
 385         if (new_head && show_diffstat) {
 386                 struct diff_options opts;
 387                 diff_setup(&opts);
 388                 opts.output_format |=
 389                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 390                 opts.detect_rename = DIFF_DETECT_RENAME;
 391                 if (diff_use_color_default > 0)
 392                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 393                 if (diff_setup_done(&opts) < 0)
 394                         die(_("diff_setup_done failed"));
 395                 diff_tree_sha1(head, new_head, "", &opts);
 396                 diffcore_std(&opts);
 397                 diff_flush(&opts);
 398         }
 399
 400         /* Run a post-merge hook */
 401         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 402
 403         strbuf_release(&reflog_message);
 404 }
 405
 406 /* Get the name for the merge commit's message. */
 407 static void merge_name(const char *remote, struct strbuf *msg)
 408 {
 409         struct object *remote_head;
 410         unsigned char branch_head[20], buf_sha[20];
 411         struct strbuf buf = STRBUF_INIT;
 412         struct strbuf bname = STRBUF_INIT;
 413         const char *ptr;
 414         char *found_ref;
 415         int len, early;
 416
 417         strbuf_branchname(&bname, remote);
 418         remote = bname.buf;
 419
 420         memset(branch_head, 0, sizeof(branch_head));
 421         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 422         if (!remote_head)
 423                 die(_("'%s' does not point to a commit"), remote);
 424
 425         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 426                 if (!prefixcmp(found_ref, "refs/heads/")) {
 427                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 428                                     sha1_to_hex(branch_head), remote);
 429                         goto cleanup;
 430                 }
 431                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 432                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 433                                     sha1_to_hex(branch_head), remote);
 434                         goto cleanup;
 435                 }
 436         }
 437
 438         /* See if remote matches <name>^^^.. or <name>~<number> */
 439         for (len = 0, ptr = remote + strlen(remote);
 440              remote < ptr && ptr[-1] == '^';
 441              ptr--)
 442                 len++;
 443         if (len)
 444                 early = 1;
 445         else {
 446                 early = 0;
 447                 ptr = strrchr(remote, '~');
 448                 if (ptr) {
 449                         int seen_nonzero = 0;
 450
 451                         len++; /* count ~ */
 452                         while (*++ptr && isdigit(*ptr)) {
 453                                 seen_nonzero |= (*ptr != '0');
 454                                 len++;
 455                         }
 456                         if (*ptr)
 457                                 len = 0; /* not ...~<number> */
 458                         else if (seen_nonzero)
 459                                 early = 1;
 460                         else if (len == 1)
 461                                 early = 1; /* "name~" is "name~1"! */
 462                 }
 463         }
 464         if (len) {
 465                 struct strbuf truname = STRBUF_INIT;
 466                 strbuf_addstr(&truname, "refs/heads/");
 467                 strbuf_addstr(&truname, remote);
 468                 strbuf_setlen(&truname, truname.len - len);
 469                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 470                         strbuf_addf(msg,
 471                                     "%s\t\tbranch '%s'%s of .\n",
 472                                     sha1_to_hex(remote_head->sha1),
 473                                     truname.buf + 11,
 474                                     (early ? " (early part)" : ""));
 475                         strbuf_release(&truname);
 476                         goto cleanup;
 477                 }
 478         }
 479
 480         if (!strcmp(remote, "FETCH_HEAD") &&
 481                         !access(git_path("FETCH_HEAD"), R_OK)) {
 482                 FILE *fp;
 483                 struct strbuf line = STRBUF_INIT;
 484                 char *ptr;
 485
 486                 fp = fopen(git_path("FETCH_HEAD"), "r");
 487                 if (!fp)
 488                         die_errno(_("could not open '%s' for reading"),
 489                                   git_path("FETCH_HEAD"));
 490                 strbuf_getline(&line, fp, '\n');
 491                 fclose(fp);
 492                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 493                 if (ptr)
 494                         strbuf_remove(&line, ptr-line.buf+1, 13);
 495                 strbuf_addbuf(msg, &line);
 496                 strbuf_release(&line);
 497                 goto cleanup;
 498         }
 499         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 500                 sha1_to_hex(remote_head->sha1), remote);
 501 cleanup:
 502         strbuf_release(&buf);
 503         strbuf_release(&bname);
 504 }
 505
 506 static int git_merge_config(const char *k, const char *v, void *cb)
 507 {
 508         if (branch && !prefixcmp(k, "branch.") &&
 509                 !prefixcmp(k + 7, branch) &&
 510                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 511                 const char **argv;
 512                 int argc;
 513                 char *buf;
 514
 515                 buf = xstrdup(v);
 516                 argc = split_cmdline(buf, &argv);
 517                 if (argc < 0)
 518                         die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 519                             split_cmdline_strerror(argc));
 520                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 521                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 522                 argc++;
 523                 parse_options(argc, argv, NULL, builtin_merge_options,
 524                               builtin_merge_usage, 0);
 525                 free(buf);
 526         }
 527
 528         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 529                 show_diffstat = git_config_bool(k, v);
 530         else if (!strcmp(k, "pull.twohead"))
 531                 return git_config_string(&pull_twohead, k, v);
 532         else if (!strcmp(k, "pull.octopus"))
 533                 return git_config_string(&pull_octopus, k, v);
 534         else if (!strcmp(k, "merge.renormalize"))
 535                 option_renormalize = git_config_bool(k, v);
 536         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 537                 int is_bool;
 538                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 539                 if (!is_bool && shortlog_len < 0)
 540                         return error(_("%s: negative length %s"), k, v);
 541                 if (is_bool && shortlog_len)
 542                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 543                 return 0;
 544         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 545                 default_to_upstream = git_config_bool(k, v);
 546                 return 0;
 547         }
 548         return git_diff_ui_config(k, v, cb);
 549 }
 550
 551 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 552                              unsigned char *one)
 553 {
 554         int i, nr_trees = 0;
 555         struct tree *trees[MAX_UNPACK_TREES];
 556         struct tree_desc t[MAX_UNPACK_TREES];
 557         struct unpack_trees_options opts;
 558
 559         memset(&opts, 0, sizeof(opts));
 560         opts.head_idx = 2;
 561         opts.src_index = &the_index;
 562         opts.dst_index = &the_index;
 563         opts.update = 1;
 564         opts.verbose_update = 1;
 565         opts.trivial_merges_only = 1;
 566         opts.merge = 1;
 567         trees[nr_trees] = parse_tree_indirect(common);
 568         if (!trees[nr_trees++])
 569                 return -1;
 570         trees[nr_trees] = parse_tree_indirect(head);
 571         if (!trees[nr_trees++])
 572                 return -1;
 573         trees[nr_trees] = parse_tree_indirect(one);
 574         if (!trees[nr_trees++])
 575                 return -1;
 576         opts.fn = threeway_merge;
 577         cache_tree_free(&active_cache_tree);
 578         for (i = 0; i < nr_trees; i++) {
 579                 parse_tree(trees[i]);
 580                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 581         }
 582         if (unpack_trees(nr_trees, t, &opts))
 583                 return -1;
 584         return 0;
 585 }
 586
 587 static void write_tree_trivial(unsigned char *sha1)
 588 {
 589         if (write_cache_as_tree(sha1, 0, NULL))
 590                 die(_("git write-tree failed to write a tree"));
 591 }
 592
 593 static const char *merge_argument(struct commit *commit)
 594 {
 595         if (commit)
 596                 return sha1_to_hex(commit->object.sha1);
 597         else
 598                 return EMPTY_TREE_SHA1_HEX;
 599 }
 600
 601 int try_merge_command(const char *strategy, size_t xopts_nr,
 602                       const char **xopts, struct commit_list *common,
 603                       const char *head_arg, struct commit_list *remotes)
 604 {
 605         const char **args;
 606         int i = 0, x = 0, ret;
 607         struct commit_list *j;
 608         struct strbuf buf = STRBUF_INIT;
 609
 610         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 611                         commit_list_count(remotes)) * sizeof(char *));
 612         strbuf_addf(&buf, "merge-%s", strategy);
 613         args[i++] = buf.buf;
 614         for (x = 0; x < xopts_nr; x++) {
 615                 char *s = xmalloc(strlen(xopts[x])+2+1);
 616                 strcpy(s, "--");
 617                 strcpy(s+2, xopts[x]);
 618                 args[i++] = s;
 619         }
 620         for (j = common; j; j = j->next)
 621                 args[i++] = xstrdup(merge_argument(j->item));
 622         args[i++] = "--";
 623         args[i++] = head_arg;
 624         for (j = remotes; j; j = j->next)
 625                 args[i++] = xstrdup(merge_argument(j->item));
 626         args[i] = NULL;
 627         ret = run_command_v_opt(args, RUN_GIT_CMD);
 628         strbuf_release(&buf);
 629         i = 1;
 630         for (x = 0; x < xopts_nr; x++)
 631                 free((void *)args[i++]);
 632         for (j = common; j; j = j->next)
 633                 free((void *)args[i++]);
 634         i += 2;
 635         for (j = remotes; j; j = j->next)
 636                 free((void *)args[i++]);
 637         free(args);
 638         discard_cache();
 639         if (read_cache() < 0)
 640                 die(_("failed to read the cache"));
 641         resolve_undo_clear();
 642
 643         return ret;
 644 }
 645
 646 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 647                               const char *head_arg)
 648 {
 649         int index_fd;
 650         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 651
 652         index_fd = hold_locked_index(lock, 1);
 653         refresh_cache(REFRESH_QUIET);
 654         if (active_cache_changed &&
 655                         (write_cache(index_fd, active_cache, active_nr) ||
 656                          commit_locked_index(lock)))
 657                 return error(_("Unable to write index."));
 658         rollback_lock_file(lock);
 659
 660         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 661                 int clean, x;
 662                 struct commit *result;
 663                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 664                 int index_fd;
 665                 struct commit_list *reversed = NULL;
 666                 struct merge_options o;
 667                 struct commit_list *j;
 668
 669                 if (remoteheads->next) {
 670                         error(_("Not handling anything other than two heads merge."));
 671                         return 2;
 672                 }
 673
 674                 init_merge_options(&o);
 675                 if (!strcmp(strategy, "subtree"))
 676                         o.subtree_shift = "";
 677
 678                 o.renormalize = option_renormalize;
 679                 o.show_rename_progress =
 680                         show_progress == -1 ? isatty(2) : show_progress;
 681
 682                 for (x = 0; x < xopts_nr; x++)
 683                         if (parse_merge_opt(&o, xopts[x]))
 684                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 685
 686                 o.branch1 = head_arg;
 687                 o.branch2 = remoteheads->item->util;
 688
 689                 for (j = common; j; j = j->next)
 690                         commit_list_insert(j->item, &reversed);
 691
 692                 index_fd = hold_locked_index(lock, 1);
 693                 clean = merge_recursive(&o, lookup_commit(head),
 694                                 remoteheads->item, reversed, &result);
 695                 if (active_cache_changed &&
 696                                 (write_cache(index_fd, active_cache, active_nr) ||
 697                                  commit_locked_index(lock)))
 698                         die (_("unable to write %s"), get_index_file());
 699                 rollback_lock_file(lock);
 700                 return clean ? 0 : 1;
 701         } else {
 702                 return try_merge_command(strategy, xopts_nr, xopts,
 703                                                 common, head_arg, remoteheads);
 704         }
 705 }
 706
 707 static void count_diff_files(struct diff_queue_struct *q,
 708                              struct diff_options *opt, void *data)
 709 {
 710         int *count = data;
 711
 712         (*count) += q->nr;
 713 }
 714
 715 static int count_unmerged_entries(void)
 716 {
 717         int i, ret = 0;
 718
 719         for (i = 0; i < active_nr; i++)
 720                 if (ce_stage(active_cache[i]))
 721                         ret++;
 722
 723         return ret;
 724 }
 725
 726 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 727 {
 728         struct tree *trees[MAX_UNPACK_TREES];
 729         struct unpack_trees_options opts;
 730         struct tree_desc t[MAX_UNPACK_TREES];
 731         int i, fd, nr_trees = 0;
 732         struct dir_struct dir;
 733         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 734
 735         refresh_cache(REFRESH_QUIET);
 736
 737         fd = hold_locked_index(lock_file, 1);
 738
 739         memset(&trees, 0, sizeof(trees));
 740         memset(&opts, 0, sizeof(opts));
 741         memset(&t, 0, sizeof(t));
 742         memset(&dir, 0, sizeof(dir));
 743         dir.flags |= DIR_SHOW_IGNORED;
 744         dir.exclude_per_dir = ".gitignore";
 745         opts.dir = &dir;
 746
 747         opts.head_idx = 1;
 748         opts.src_index = &the_index;
 749         opts.dst_index = &the_index;
 750         opts.update = 1;
 751         opts.verbose_update = 1;
 752         opts.merge = 1;
 753         opts.fn = twoway_merge;
 754         setup_unpack_trees_porcelain(&opts, "merge");
 755
 756         trees[nr_trees] = parse_tree_indirect(head);
 757         if (!trees[nr_trees++])
 758                 return -1;
 759         trees[nr_trees] = parse_tree_indirect(remote);
 760         if (!trees[nr_trees++])
 761                 return -1;
 762         for (i = 0; i < nr_trees; i++) {
 763                 parse_tree(trees[i]);
 764                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 765         }
 766         if (unpack_trees(nr_trees, t, &opts))
 767                 return -1;
 768         if (write_cache(fd, active_cache, active_nr) ||
 769                 commit_locked_index(lock_file))
 770                 die(_("unable to write new index file"));
 771         return 0;
 772 }
 773
 774 static void split_merge_strategies(const char *string, struct strategy **list,
 775                                    int *nr, int *alloc)
 776 {
 777         char *p, *q, *buf;
 778
 779         if (!string)
 780                 return;
 781
 782         buf = xstrdup(string);
 783         q = buf;
 784         for (;;) {
 785                 p = strchr(q, ' ');
 786                 if (!p) {
 787                         ALLOC_GROW(*list, *nr + 1, *alloc);
 788                         (*list)[(*nr)++].name = xstrdup(q);
 789                         free(buf);
 790                         return;
 791                 } else {
 792                         *p = '\0';
 793                         ALLOC_GROW(*list, *nr + 1, *alloc);
 794                         (*list)[(*nr)++].name = xstrdup(q);
 795                         q = ++p;
 796                 }
 797         }
 798 }
 799
 800 static void add_strategies(const char *string, unsigned attr)
 801 {
 802         struct strategy *list = NULL;
 803         int list_alloc = 0, list_nr = 0, i;
 804
 805         memset(&list, 0, sizeof(list));
 806         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 807         if (list) {
 808                 for (i = 0; i < list_nr; i++)
 809                         append_strategy(get_strategy(list[i].name));
 810                 return;
 811         }
 812         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 813                 if (all_strategy[i].attr & attr)
 814                         append_strategy(&all_strategy[i]);
 815
 816 }
 817
 818 static void write_merge_msg(void)
 819 {
 820         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 821         if (fd < 0)
 822                 die_errno(_("Could not open '%s' for writing"),
 823                           git_path("MERGE_MSG"));
 824         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 825                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 826         close(fd);
 827 }
 828
 829 static void read_merge_msg(void)
 830 {
 831         strbuf_reset(&merge_msg);
 832         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 833                 die_errno("Could not read from '%s'", git_path("MERGE_MSG"));
 834 }
 835
 836 static void run_prepare_commit_msg(void)
 837 {
 838         write_merge_msg();
 839         run_hook(get_index_file(), "prepare-commit-msg",
 840                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 841         read_merge_msg();
 842 }
 843
 844 static int merge_trivial(void)
 845 {
 846         unsigned char result_tree[20], result_commit[20];
 847         struct commit_list *parent = xmalloc(sizeof(*parent));
 848
 849         write_tree_trivial(result_tree);
 850         printf(_("Wonderful.\n"));
 851         parent->item = lookup_commit(head);
 852         parent->next = xmalloc(sizeof(*parent->next));
 853         parent->next->item = remoteheads->item;
 854         parent->next->next = NULL;
 855         run_prepare_commit_msg();
 856         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 857         finish(result_commit, "In-index merge");
 858         drop_save();
 859         return 0;
 860 }
 861
 862 static int finish_automerge(struct commit_list *common,
 863                             unsigned char *result_tree,
 864                             const char *wt_strategy)
 865 {
 866         struct commit_list *parents = NULL, *j;
 867         struct strbuf buf = STRBUF_INIT;
 868         unsigned char result_commit[20];
 869
 870         free_commit_list(common);
 871         if (allow_fast_forward) {
 872                 parents = remoteheads;
 873                 commit_list_insert(lookup_commit(head), &parents);
 874                 parents = reduce_heads(parents);
 875         } else {
 876                 struct commit_list **pptr = &parents;
 877
 878                 pptr = &commit_list_insert(lookup_commit(head),
 879                                 pptr)->next;
 880                 for (j = remoteheads; j; j = j->next)
 881                         pptr = &commit_list_insert(j->item, pptr)->next;
 882         }
 883         free_commit_list(remoteheads);
 884         strbuf_addch(&merge_msg, '\n');
 885         run_prepare_commit_msg();
 886         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 887         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 888         finish(result_commit, buf.buf);
 889         strbuf_release(&buf);
 890         drop_save();
 891         return 0;
 892 }
 893
 894 static int suggest_conflicts(int renormalizing)
 895 {
 896         FILE *fp;
 897         int pos;
 898
 899         fp = fopen(git_path("MERGE_MSG"), "a");
 900         if (!fp)
 901                 die_errno(_("Could not open '%s' for writing"),
 902                           git_path("MERGE_MSG"));
 903         fprintf(fp, "\nConflicts:\n");
 904         for (pos = 0; pos < active_nr; pos++) {
 905                 struct cache_entry *ce = active_cache[pos];
 906
 907                 if (ce_stage(ce)) {
 908                         fprintf(fp, "\t%s\n", ce->name);
 909                         while (pos + 1 < active_nr &&
 910                                         !strcmp(ce->name,
 911                                                 active_cache[pos + 1]->name))
 912                                 pos++;
 913                 }
 914         }
 915         fclose(fp);
 916         rerere(allow_rerere_auto);
 917         printf(_("Automatic merge failed; "
 918                         "fix conflicts and then commit the result.\n"));
 919         return 1;
 920 }
 921
 922 static struct commit *is_old_style_invocation(int argc, const char **argv)
 923 {
 924         struct commit *second_token = NULL;
 925         if (argc > 2) {
 926                 unsigned char second_sha1[20];
 927
 928                 if (get_sha1(argv[1], second_sha1))
 929                         return NULL;
 930                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 931                 if (!second_token)
 932                         die(_("'%s' is not a commit"), argv[1]);
 933                 if (hashcmp(second_token->object.sha1, head))
 934                         return NULL;
 935         }
 936         return second_token;
 937 }
 938
 939 static int evaluate_result(void)
 940 {
 941         int cnt = 0;
 942         struct rev_info rev;
 943
 944         /* Check how many files differ. */
 945         init_revisions(&rev, "");
 946         setup_revisions(0, NULL, &rev, NULL);
 947         rev.diffopt.output_format |=
 948                 DIFF_FORMAT_CALLBACK;
 949         rev.diffopt.format_callback = count_diff_files;
 950         rev.diffopt.format_callback_data = &cnt;
 951         run_diff_files(&rev, 0);
 952
 953         /*
 954          * Check how many unmerged entries are
 955          * there.
 956          */
 957         cnt += count_unmerged_entries();
 958
 959         return cnt;
 960 }
 961
 962 /*
 963  * Pretend as if the user told us to merge with the tracking
 964  * branch we have for the upstream of the current branch
 965  */
 966 static int setup_with_upstream(const char ***argv)
 967 {
 968         struct branch *branch = branch_get(NULL);
 969         int i;
 970         const char **args;
 971
 972         if (!branch)
 973                 die("No current branch.");
 974         if (!branch->remote)
 975                 die("No remote for the current branch.");
 976         if (!branch->merge_nr)
 977                 die("No default upstream defined for the current branch.");
 978
 979         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 980         for (i = 0; i < branch->merge_nr; i++) {
 981                 if (!branch->merge[i]->dst)
 982                         die("No remote tracking branch for %s from %s",
 983                             branch->merge[i]->src, branch->remote_name);
 984                 args[i] = branch->merge[i]->dst;
 985         }
 986         args[i] = NULL;
 987         *argv = args;
 988         return i;
 989 }
 990
 991 int cmd_merge(int argc, const char **argv, const char *prefix)
 992 {
 993         unsigned char result_tree[20];
 994         struct strbuf buf = STRBUF_INIT;
 995         const char *head_arg;
 996         int flag, head_invalid = 0, i;
 997         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 998         struct commit_list *common = NULL;
 999         const char *best_strategy = NULL, *wt_strategy = NULL;
1000         struct commit_list **remotes = &remoteheads;
1001
1002         if (argc == 2 && !strcmp(argv[1], "-h"))
1003                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1004
1005         /*
1006          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1007          * current branch.
1008          */
1009         branch = resolve_ref("HEAD", head, 0, &flag);
1010         if (branch && !prefixcmp(branch, "refs/heads/"))
1011                 branch += 11;
1012         if (is_null_sha1(head))
1013                 head_invalid = 1;
1014
1015         git_config(git_merge_config, NULL);
1016
1017         /* for color.ui */
1018         if (diff_use_color_default == -1)
1019                 diff_use_color_default = git_use_color_default;
1020
1021         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1022                         builtin_merge_usage, 0);
1023
1024         if (verbosity < 0 && show_progress == -1)
1025                 show_progress = 0;
1026
1027         if (abort_current_merge) {
1028                 int nargc = 2;
1029                 const char *nargv[] = {"reset", "--merge", NULL};
1030
1031                 if (!file_exists(git_path("MERGE_HEAD")))
1032                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1033
1034                 /* Invoke 'git reset --merge' */
1035                 return cmd_reset(nargc, nargv, prefix);
1036         }
1037
1038         if (read_cache_unmerged())
1039                 die_resolve_conflict("merge");
1040
1041         if (file_exists(git_path("MERGE_HEAD"))) {
1042                 /*
1043                  * There is no unmerged entry, don't advise 'git
1044                  * add/rm <file>', just 'git commit'.
1045                  */
1046                 if (advice_resolve_conflict)
1047                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1048                                   "Please, commit your changes before you can merge."));
1049                 else
1050                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1051         }
1052         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1053                 if (advice_resolve_conflict)
1054                         die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1055                             "Please, commit your changes before you can merge.");
1056                 else
1057                         die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).");
1058         }
1059         resolve_undo_clear();
1060
1061         if (verbosity < 0)
1062                 show_diffstat = 0;
1063
1064         if (squash) {
1065                 if (!allow_fast_forward)
1066                         die(_("You cannot combine --squash with --no-ff."));
1067                 option_commit = 0;
1068         }
1069
1070         if (!allow_fast_forward && fast_forward_only)
1071                 die(_("You cannot combine --no-ff with --ff-only."));
1072
1073         if (!argc && !abort_current_merge && default_to_upstream)
1074                 argc = setup_with_upstream(&argv);
1075
1076         if (!argc)
1077                 usage_with_options(builtin_merge_usage,
1078                         builtin_merge_options);
1079
1080         /*
1081          * This could be traditional "merge <msg> HEAD <commit>..."  and
1082          * the way we can tell it is to see if the second token is HEAD,
1083          * but some people might have misused the interface and used a
1084          * committish that is the same as HEAD there instead.
1085          * Traditional format never would have "-m" so it is an
1086          * additional safety measure to check for it.
1087          */
1088
1089         if (!have_message && is_old_style_invocation(argc, argv)) {
1090                 strbuf_addstr(&merge_msg, argv[0]);
1091                 head_arg = argv[1];
1092                 argv += 2;
1093                 argc -= 2;
1094         } else if (head_invalid) {
1095                 struct object *remote_head;
1096                 /*
1097                  * If the merged head is a valid one there is no reason
1098                  * to forbid "git merge" into a branch yet to be born.
1099                  * We do the same for "git pull".
1100                  */
1101                 if (argc != 1)
1102                         die(_("Can merge only exactly one commit into "
1103                                 "empty head"));
1104                 if (squash)
1105                         die(_("Squash commit into empty head not supported yet"));
1106                 if (!allow_fast_forward)
1107                         die(_("Non-fast-forward commit does not make sense into "
1108                             "an empty head"));
1109                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1110                 if (!remote_head)
1111                         die(_("%s - not something we can merge"), argv[0]);
1112                 read_empty(remote_head->sha1, 0);
1113                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1114                                 DIE_ON_ERR);
1115                 return 0;
1116         } else {
1117                 struct strbuf merge_names = STRBUF_INIT;
1118
1119                 /* We are invoked directly as the first-class UI. */
1120                 head_arg = "HEAD";
1121
1122                 /*
1123                  * All the rest are the commits being merged;
1124                  * prepare the standard merge summary message to
1125                  * be appended to the given message.  If remote
1126                  * is invalid we will die later in the common
1127                  * codepath so we discard the error in this
1128                  * loop.
1129                  */
1130                 for (i = 0; i < argc; i++)
1131                         merge_name(argv[i], &merge_names);
1132
1133                 if (!have_message || shortlog_len) {
1134                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1135                                       shortlog_len);
1136                         if (merge_msg.len)
1137                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1138                 }
1139         }
1140
1141         if (head_invalid || !argc)
1142                 usage_with_options(builtin_merge_usage,
1143                         builtin_merge_options);
1144
1145         strbuf_addstr(&buf, "merge");
1146         for (i = 0; i < argc; i++)
1147                 strbuf_addf(&buf, " %s", argv[i]);
1148         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1149         strbuf_reset(&buf);
1150
1151         for (i = 0; i < argc; i++) {
1152                 struct object *o;
1153                 struct commit *commit;
1154
1155                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1156                 if (!o)
1157                         die(_("%s - not something we can merge"), argv[i]);
1158                 commit = lookup_commit(o->sha1);
1159                 commit->util = (void *)argv[i];
1160                 remotes = &commit_list_insert(commit, remotes)->next;
1161
1162                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1163                 setenv(buf.buf, argv[i], 1);
1164                 strbuf_reset(&buf);
1165         }
1166
1167         if (!use_strategies) {
1168                 if (!remoteheads->next)
1169                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1170                 else
1171                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1172         }
1173
1174         for (i = 0; i < use_strategies_nr; i++) {
1175                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1176                         allow_fast_forward = 0;
1177                 if (use_strategies[i]->attr & NO_TRIVIAL)
1178                         allow_trivial = 0;
1179         }
1180
1181         if (!remoteheads->next)
1182                 common = get_merge_bases(lookup_commit(head),
1183                                 remoteheads->item, 1);
1184         else {
1185                 struct commit_list *list = remoteheads;
1186                 commit_list_insert(lookup_commit(head), &list);
1187                 common = get_octopus_merge_bases(list);
1188                 free(list);
1189         }
1190
1191         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1192                 DIE_ON_ERR);
1193
1194         if (!common)
1195                 ; /* No common ancestors found. We need a real merge. */
1196         else if (!remoteheads->next && !common->next &&
1197                         common->item == remoteheads->item) {
1198                 /*
1199                  * If head can reach all the merge then we are up to date.
1200                  * but first the most common case of merging one remote.
1201                  */
1202                 finish_up_to_date("Already up-to-date.");
1203                 return 0;
1204         } else if (allow_fast_forward && !remoteheads->next &&
1205                         !common->next &&
1206                         !hashcmp(common->item->object.sha1, head)) {
1207                 /* Again the most common case of merging one remote. */
1208                 struct strbuf msg = STRBUF_INIT;
1209                 struct object *o;
1210                 char hex[41];
1211
1212                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1213
1214                 if (verbosity >= 0)
1215                         printf(_("Updating %s..%s\n"),
1216                                 hex,
1217                                 find_unique_abbrev(remoteheads->item->object.sha1,
1218                                 DEFAULT_ABBREV));
1219                 strbuf_addstr(&msg, "Fast-forward");
1220                 if (have_message)
1221                         strbuf_addstr(&msg,
1222                                 " (no commit created; -m option ignored)");
1223                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1224                         0, NULL, OBJ_COMMIT);
1225                 if (!o)
1226                         return 1;
1227
1228                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1229                         return 1;
1230
1231                 finish(o->sha1, msg.buf);
1232                 drop_save();
1233                 return 0;
1234         } else if (!remoteheads->next && common->next)
1235                 ;
1236                 /*
1237                  * We are not doing octopus and not fast-forward.  Need
1238                  * a real merge.
1239                  */
1240         else if (!remoteheads->next && !common->next && option_commit) {
1241                 /*
1242                  * We are not doing octopus, not fast-forward, and have
1243                  * only one common.
1244                  */
1245                 refresh_cache(REFRESH_QUIET);
1246                 if (allow_trivial && !fast_forward_only) {
1247                         /* See if it is really trivial. */
1248                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1249                         printf(_("Trying really trivial in-index merge...\n"));
1250                         if (!read_tree_trivial(common->item->object.sha1,
1251                                         head, remoteheads->item->object.sha1))
1252                                 return merge_trivial();
1253                         printf(_("Nope.\n"));
1254                 }
1255         } else {
1256                 /*
1257                  * An octopus.  If we can reach all the remote we are up
1258                  * to date.
1259                  */
1260                 int up_to_date = 1;
1261                 struct commit_list *j;
1262
1263                 for (j = remoteheads; j; j = j->next) {
1264                         struct commit_list *common_one;
1265
1266                         /*
1267                          * Here we *have* to calculate the individual
1268                          * merge_bases again, otherwise "git merge HEAD^
1269                          * HEAD^^" would be missed.
1270                          */
1271                         common_one = get_merge_bases(lookup_commit(head),
1272                                 j->item, 1);
1273                         if (hashcmp(common_one->item->object.sha1,
1274                                 j->item->object.sha1)) {
1275                                 up_to_date = 0;
1276                                 break;
1277                         }
1278                 }
1279                 if (up_to_date) {
1280                         finish_up_to_date("Already up-to-date. Yeeah!");
1281                         return 0;
1282                 }
1283         }
1284
1285         if (fast_forward_only)
1286                 die(_("Not possible to fast-forward, aborting."));
1287
1288         /* We are going to make a new commit. */
1289         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1290
1291         /*
1292          * At this point, we need a real merge.  No matter what strategy
1293          * we use, it would operate on the index, possibly affecting the
1294          * working tree, and when resolved cleanly, have the desired
1295          * tree in the index -- this means that the index must be in
1296          * sync with the head commit.  The strategies are responsible
1297          * to ensure this.
1298          */
1299         if (use_strategies_nr != 1) {
1300                 /*
1301                  * Stash away the local changes so that we can try more
1302                  * than one.
1303                  */
1304                 save_state();
1305         } else {
1306                 memcpy(stash, null_sha1, 20);
1307         }
1308
1309         for (i = 0; i < use_strategies_nr; i++) {
1310                 int ret;
1311                 if (i) {
1312                         printf(_("Rewinding the tree to pristine...\n"));
1313                         restore_state();
1314                 }
1315                 if (use_strategies_nr != 1)
1316                         printf(_("Trying merge strategy %s...\n"),
1317                                 use_strategies[i]->name);
1318                 /*
1319                  * Remember which strategy left the state in the working
1320                  * tree.
1321                  */
1322                 wt_strategy = use_strategies[i]->name;
1323
1324                 ret = try_merge_strategy(use_strategies[i]->name,
1325                         common, head_arg);
1326                 if (!option_commit && !ret) {
1327                         merge_was_ok = 1;
1328                         /*
1329                          * This is necessary here just to avoid writing
1330                          * the tree, but later we will *not* exit with
1331                          * status code 1 because merge_was_ok is set.
1332                          */
1333                         ret = 1;
1334                 }
1335
1336                 if (ret) {
1337                         /*
1338                          * The backend exits with 1 when conflicts are
1339                          * left to be resolved, with 2 when it does not
1340                          * handle the given merge at all.
1341                          */
1342                         if (ret == 1) {
1343                                 int cnt = evaluate_result();
1344
1345                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1346                                         best_strategy = use_strategies[i]->name;
1347                                         best_cnt = cnt;
1348                                 }
1349                         }
1350                         if (merge_was_ok)
1351                                 break;
1352                         else
1353                                 continue;
1354                 }
1355
1356                 /* Automerge succeeded. */
1357                 write_tree_trivial(result_tree);
1358                 automerge_was_ok = 1;
1359                 break;
1360         }
1361
1362         /*
1363          * If we have a resulting tree, that means the strategy module
1364          * auto resolved the merge cleanly.
1365          */
1366         if (automerge_was_ok)
1367                 return finish_automerge(common, result_tree, wt_strategy);
1368
1369         /*
1370          * Pick the result from the best strategy and have the user fix
1371          * it up.
1372          */
1373         if (!best_strategy) {
1374                 restore_state();
1375                 if (use_strategies_nr > 1)
1376                         fprintf(stderr,
1377                                 _("No merge strategy handled the merge.\n"));
1378                 else
1379                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1380                                 use_strategies[0]->name);
1381                 return 2;
1382         } else if (best_strategy == wt_strategy)
1383                 ; /* We already have its result in the working tree. */
1384         else {
1385                 printf(_("Rewinding the tree to pristine...\n"));
1386                 restore_state();
1387                 printf(_("Using the %s to prepare resolving by hand.\n"),
1388                         best_strategy);
1389                 try_merge_strategy(best_strategy, common, head_arg);
1390         }
1391
1392         if (squash)
1393                 finish(NULL, NULL);
1394         else {
1395                 int fd;
1396                 struct commit_list *j;
1397
1398                 for (j = remoteheads; j; j = j->next)
1399                         strbuf_addf(&buf, "%s\n",
1400                                 sha1_to_hex(j->item->object.sha1));
1401                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1402                 if (fd < 0)
1403                         die_errno(_("Could not open '%s' for writing"),
1404                                   git_path("MERGE_HEAD"));
1405                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1406                         die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1407                 close(fd);
1408                 strbuf_addch(&merge_msg, '\n');
1409                 write_merge_msg();
1410                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1411                 if (fd < 0)
1412                         die_errno(_("Could not open '%s' for writing"),
1413                                   git_path("MERGE_MODE"));
1414                 strbuf_reset(&buf);
1415                 if (!allow_fast_forward)
1416                         strbuf_addf(&buf, "no-ff");
1417                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1418                         die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1419                 close(fd);
1420         }
1421
1422         if (merge_was_ok) {
1423                 fprintf(stderr, _("Automatic merge went well; "
1424                         "stopped before committing as requested\n"));
1425                 return 0;
1426         } else
1427                 return suggest_conflicts(option_renormalize);
1428 }