git.oblomov.eu Git - git/blob - 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 char *branch_mergeoptions;
  60 static int option_renormalize;
  61 static int verbosity;
  62 static int allow_rerere_auto;
  63 static int abort_current_merge;
  64 static int show_progress = -1;
  65 static int default_to_upstream;
  66
  67 static struct strategy all_strategy[] = {
  68         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  69         { "octopus",    DEFAULT_OCTOPUS },
  70         { "resolve",    0 },
  71         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  72         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  73 };
  74
  75 static const char *pull_twohead, *pull_octopus;
  76
  77 static int option_parse_message(const struct option *opt,
  78                                 const char *arg, int unset)
  79 {
  80         struct strbuf *buf = opt->value;
  81
  82         if (unset)
  83                 strbuf_setlen(buf, 0);
  84         else if (arg) {
  85                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  86                 have_message = 1;
  87         } else
  88                 return error(_("switch `m' requires a value"));
  89         return 0;
  90 }
  91
  92 static struct strategy *get_strategy(const char *name)
  93 {
  94         int i;
  95         struct strategy *ret;
  96         static struct cmdnames main_cmds, other_cmds;
  97         static int loaded;
  98
  99         if (!name)
 100                 return NULL;
 101
 102         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 103                 if (!strcmp(name, all_strategy[i].name))
 104                         return &all_strategy[i];
 105
 106         if (!loaded) {
 107                 struct cmdnames not_strategies;
 108                 loaded = 1;
 109
 110                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 111                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 112                 for (i = 0; i < main_cmds.cnt; i++) {
 113                         int j, found = 0;
 114                         struct cmdname *ent = main_cmds.names[i];
 115                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 116                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 117                                                 && !all_strategy[j].name[ent->len])
 118                                         found = 1;
 119                         if (!found)
 120                                 add_cmdname(&not_strategies, ent->name, ent->len);
 121                 }
 122                 exclude_cmds(&main_cmds, &not_strategies);
 123         }
 124         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 125                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 126                 fprintf(stderr, _("Available strategies are:"));
 127                 for (i = 0; i < main_cmds.cnt; i++)
 128                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 129                 fprintf(stderr, ".\n");
 130                 if (other_cmds.cnt) {
 131                         fprintf(stderr, _("Available custom strategies are:"));
 132                         for (i = 0; i < other_cmds.cnt; i++)
 133                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 134                         fprintf(stderr, ".\n");
 135                 }
 136                 exit(1);
 137         }
 138
 139         ret = xcalloc(1, sizeof(struct strategy));
 140         ret->name = xstrdup(name);
 141         ret->attr = NO_TRIVIAL;
 142         return ret;
 143 }
 144
 145 static void append_strategy(struct strategy *s)
 146 {
 147         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 148         use_strategies[use_strategies_nr++] = s;
 149 }
 150
 151 static int option_parse_strategy(const struct option *opt,
 152                                  const char *name, int unset)
 153 {
 154         if (unset)
 155                 return 0;
 156
 157         append_strategy(get_strategy(name));
 158         return 0;
 159 }
 160
 161 static int option_parse_x(const struct option *opt,
 162                           const char *arg, int unset)
 163 {
 164         if (unset)
 165                 return 0;
 166
 167         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 168         xopts[xopts_nr++] = xstrdup(arg);
 169         return 0;
 170 }
 171
 172 static int option_parse_n(const struct option *opt,
 173                           const char *arg, int unset)
 174 {
 175         show_diffstat = unset;
 176         return 0;
 177 }
 178
 179 static struct option builtin_merge_options[] = {
 180         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 181                 "do not show a diffstat at the end of the merge",
 182                 PARSE_OPT_NOARG, option_parse_n },
 183         OPT_BOOLEAN(0, "stat", &show_diffstat,
 184                 "show a diffstat at the end of the merge"),
 185         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 186         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 187           "add (at most <n>) entries from shortlog to merge commit message",
 188           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 189         OPT_BOOLEAN(0, "squash", &squash,
 190                 "create a single commit instead of doing a merge"),
 191         OPT_BOOLEAN(0, "commit", &option_commit,
 192                 "perform a commit if the merge succeeds (default)"),
 193         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 194                 "allow fast-forward (default)"),
 195         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 196                 "abort if fast-forward is not possible"),
 197         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 198         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 199                 "merge strategy to use", option_parse_strategy),
 200         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 201                 "option for selected merge strategy", option_parse_x),
 202         OPT_CALLBACK('m', "message", &merge_msg, "message",
 203                 "merge commit message (for a non-fast-forward merge)",
 204                 option_parse_message),
 205         OPT__VERBOSITY(&verbosity),
 206         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 207                 "abort the current in-progress merge"),
 208         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 209         OPT_END()
 210 };
 211
 212 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 213 static void drop_save(void)
 214 {
 215         unlink(git_path("MERGE_HEAD"));
 216         unlink(git_path("MERGE_MSG"));
 217         unlink(git_path("MERGE_MODE"));
 218 }
 219
 220 static void save_state(void)
 221 {
 222         int len;
 223         struct child_process cp;
 224         struct strbuf buffer = STRBUF_INIT;
 225         const char *argv[] = {"stash", "create", NULL};
 226
 227         memset(&cp, 0, sizeof(cp));
 228         cp.argv = argv;
 229         cp.out = -1;
 230         cp.git_cmd = 1;
 231
 232         if (start_command(&cp))
 233                 die(_("could not run stash."));
 234         len = strbuf_read(&buffer, cp.out, 1024);
 235         close(cp.out);
 236
 237         if (finish_command(&cp) || len < 0)
 238                 die(_("stash failed"));
 239         else if (!len)
 240                 return;
 241         strbuf_setlen(&buffer, buffer.len-1);
 242         if (get_sha1(buffer.buf, stash))
 243                 die(_("not a valid object: %s"), buffer.buf);
 244 }
 245
 246 static void read_empty(unsigned const char *sha1, int verbose)
 247 {
 248         int i = 0;
 249         const char *args[7];
 250
 251         args[i++] = "read-tree";
 252         if (verbose)
 253                 args[i++] = "-v";
 254         args[i++] = "-m";
 255         args[i++] = "-u";
 256         args[i++] = EMPTY_TREE_SHA1_HEX;
 257         args[i++] = sha1_to_hex(sha1);
 258         args[i] = NULL;
 259
 260         if (run_command_v_opt(args, RUN_GIT_CMD))
 261                 die(_("read-tree failed"));
 262 }
 263
 264 static void reset_hard(unsigned const char *sha1, int verbose)
 265 {
 266         int i = 0;
 267         const char *args[6];
 268
 269         args[i++] = "read-tree";
 270         if (verbose)
 271                 args[i++] = "-v";
 272         args[i++] = "--reset";
 273         args[i++] = "-u";
 274         args[i++] = sha1_to_hex(sha1);
 275         args[i] = NULL;
 276
 277         if (run_command_v_opt(args, RUN_GIT_CMD))
 278                 die(_("read-tree failed"));
 279 }
 280
 281 static void restore_state(void)
 282 {
 283         struct strbuf sb = STRBUF_INIT;
 284         const char *args[] = { "stash", "apply", NULL, NULL };
 285
 286         if (is_null_sha1(stash))
 287                 return;
 288
 289         reset_hard(head, 1);
 290
 291         args[2] = sha1_to_hex(stash);
 292
 293         /*
 294          * It is OK to ignore error here, for example when there was
 295          * nothing to restore.
 296          */
 297         run_command_v_opt(args, RUN_GIT_CMD);
 298
 299         strbuf_release(&sb);
 300         refresh_cache(REFRESH_QUIET);
 301 }
 302
 303 /* This is called when no merge was necessary. */
 304 static void finish_up_to_date(const char *msg)
 305 {
 306         if (verbosity >= 0)
 307                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 308         drop_save();
 309 }
 310
 311 static void squash_message(void)
 312 {
 313         struct rev_info rev;
 314         struct commit *commit;
 315         struct strbuf out = STRBUF_INIT;
 316         struct commit_list *j;
 317         int fd;
 318         struct pretty_print_context ctx = {0};
 319
 320         printf(_("Squash commit -- not updating HEAD\n"));
 321         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 322         if (fd < 0)
 323                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 324
 325         init_revisions(&rev, NULL);
 326         rev.ignore_merges = 1;
 327         rev.commit_format = CMIT_FMT_MEDIUM;
 328
 329         commit = lookup_commit(head);
 330         commit->object.flags |= UNINTERESTING;
 331         add_pending_object(&rev, &commit->object, NULL);
 332
 333         for (j = remoteheads; j; j = j->next)
 334                 add_pending_object(&rev, &j->item->object, NULL);
 335
 336         setup_revisions(0, NULL, &rev, NULL);
 337         if (prepare_revision_walk(&rev))
 338                 die(_("revision walk setup failed"));
 339
 340         ctx.abbrev = rev.abbrev;
 341         ctx.date_mode = rev.date_mode;
 342
 343         strbuf_addstr(&out, "Squashed commit of the following:\n");
 344         while ((commit = get_revision(&rev)) != NULL) {
 345                 strbuf_addch(&out, '\n');
 346                 strbuf_addf(&out, "commit %s\n",
 347                         sha1_to_hex(commit->object.sha1));
 348                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 349         }
 350         if (write(fd, out.buf, out.len) < 0)
 351                 die_errno(_("Writing SQUASH_MSG"));
 352         if (close(fd))
 353                 die_errno(_("Finishing SQUASH_MSG"));
 354         strbuf_release(&out);
 355 }
 356
 357 static void finish(const unsigned char *new_head, const char *msg)
 358 {
 359         struct strbuf reflog_message = STRBUF_INIT;
 360
 361         if (!msg)
 362                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 363         else {
 364                 if (verbosity >= 0)
 365                         printf("%s\n", msg);
 366                 strbuf_addf(&reflog_message, "%s: %s",
 367                         getenv("GIT_REFLOG_ACTION"), msg);
 368         }
 369         if (squash) {
 370                 squash_message();
 371         } else {
 372                 if (verbosity >= 0 && !merge_msg.len)
 373                         printf(_("No merge message -- not updating HEAD\n"));
 374                 else {
 375                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 376                         update_ref(reflog_message.buf, "HEAD",
 377                                 new_head, head, 0,
 378                                 DIE_ON_ERR);
 379                         /*
 380                          * We ignore errors in 'gc --auto', since the
 381                          * user should see them.
 382                          */
 383                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 384                 }
 385         }
 386         if (new_head && show_diffstat) {
 387                 struct diff_options opts;
 388                 diff_setup(&opts);
 389                 opts.output_format |=
 390                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 391                 opts.detect_rename = DIFF_DETECT_RENAME;
 392                 if (diff_use_color_default > 0)
 393                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 394                 if (diff_setup_done(&opts) < 0)
 395                         die(_("diff_setup_done failed"));
 396                 diff_tree_sha1(head, new_head, "", &opts);
 397                 diffcore_std(&opts);
 398                 diff_flush(&opts);
 399         }
 400
 401         /* Run a post-merge hook */
 402         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 403
 404         strbuf_release(&reflog_message);
 405 }
 406
 407 /* Get the name for the merge commit's message. */
 408 static void merge_name(const char *remote, struct strbuf *msg)
 409 {
 410         struct object *remote_head;
 411         unsigned char branch_head[20], buf_sha[20];
 412         struct strbuf buf = STRBUF_INIT;
 413         struct strbuf bname = STRBUF_INIT;
 414         const char *ptr;
 415         char *found_ref;
 416         int len, early;
 417
 418         strbuf_branchname(&bname, remote);
 419         remote = bname.buf;
 420
 421         memset(branch_head, 0, sizeof(branch_head));
 422         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 423         if (!remote_head)
 424                 die(_("'%s' does not point to a commit"), remote);
 425
 426         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 427                 if (!prefixcmp(found_ref, "refs/heads/")) {
 428                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 429                                     sha1_to_hex(branch_head), remote);
 430                         goto cleanup;
 431                 }
 432                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 433                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 434                                     sha1_to_hex(branch_head), remote);
 435                         goto cleanup;
 436                 }
 437         }
 438
 439         /* See if remote matches <name>^^^.. or <name>~<number> */
 440         for (len = 0, ptr = remote + strlen(remote);
 441              remote < ptr && ptr[-1] == '^';
 442              ptr--)
 443                 len++;
 444         if (len)
 445                 early = 1;
 446         else {
 447                 early = 0;
 448                 ptr = strrchr(remote, '~');
 449                 if (ptr) {
 450                         int seen_nonzero = 0;
 451
 452                         len++; /* count ~ */
 453                         while (*++ptr && isdigit(*ptr)) {
 454                                 seen_nonzero |= (*ptr != '0');
 455                                 len++;
 456                         }
 457                         if (*ptr)
 458                                 len = 0; /* not ...~<number> */
 459                         else if (seen_nonzero)
 460                                 early = 1;
 461                         else if (len == 1)
 462                                 early = 1; /* "name~" is "name~1"! */
 463                 }
 464         }
 465         if (len) {
 466                 struct strbuf truname = STRBUF_INIT;
 467                 strbuf_addstr(&truname, "refs/heads/");
 468                 strbuf_addstr(&truname, remote);
 469                 strbuf_setlen(&truname, truname.len - len);
 470                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 471                         strbuf_addf(msg,
 472                                     "%s\t\tbranch '%s'%s of .\n",
 473                                     sha1_to_hex(remote_head->sha1),
 474                                     truname.buf + 11,
 475                                     (early ? " (early part)" : ""));
 476                         strbuf_release(&truname);
 477                         goto cleanup;
 478                 }
 479         }
 480
 481         if (!strcmp(remote, "FETCH_HEAD") &&
 482                         !access(git_path("FETCH_HEAD"), R_OK)) {
 483                 FILE *fp;
 484                 struct strbuf line = STRBUF_INIT;
 485                 char *ptr;
 486
 487                 fp = fopen(git_path("FETCH_HEAD"), "r");
 488                 if (!fp)
 489                         die_errno(_("could not open '%s' for reading"),
 490                                   git_path("FETCH_HEAD"));
 491                 strbuf_getline(&line, fp, '\n');
 492                 fclose(fp);
 493                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 494                 if (ptr)
 495                         strbuf_remove(&line, ptr-line.buf+1, 13);
 496                 strbuf_addbuf(msg, &line);
 497                 strbuf_release(&line);
 498                 goto cleanup;
 499         }
 500         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 501                 sha1_to_hex(remote_head->sha1), remote);
 502 cleanup:
 503         strbuf_release(&buf);
 504         strbuf_release(&bname);
 505 }
 506
 507 static void parse_branch_merge_options(char *bmo)
 508 {
 509         const char **argv;
 510         int argc;
 511
 512         if (!bmo)
 513                 return;
 514         argc = split_cmdline(bmo, &argv);
 515         if (argc < 0)
 516                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 517                     split_cmdline_strerror(argc));
 518         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 519         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 520         argc++;
 521         argv[0] = "branch.*.mergeoptions";
 522         parse_options(argc, argv, NULL, builtin_merge_options,
 523                       builtin_merge_usage, 0);
 524         free(argv);
 525 }
 526
 527 static int git_merge_config(const char *k, const char *v, void *cb)
 528 {
 529         if (branch && !prefixcmp(k, "branch.") &&
 530                 !prefixcmp(k + 7, branch) &&
 531                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 532                 free(branch_mergeoptions);
 533                 branch_mergeoptions = xstrdup(v);
 534                 return 0;
 535         }
 536
 537         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 538                 show_diffstat = git_config_bool(k, v);
 539         else if (!strcmp(k, "pull.twohead"))
 540                 return git_config_string(&pull_twohead, k, v);
 541         else if (!strcmp(k, "pull.octopus"))
 542                 return git_config_string(&pull_octopus, k, v);
 543         else if (!strcmp(k, "merge.renormalize"))
 544                 option_renormalize = git_config_bool(k, v);
 545         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 546                 int is_bool;
 547                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 548                 if (!is_bool && shortlog_len < 0)
 549                         return error(_("%s: negative length %s"), k, v);
 550                 if (is_bool && shortlog_len)
 551                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 552                 return 0;
 553         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 554                 default_to_upstream = git_config_bool(k, v);
 555                 return 0;
 556         }
 557         return git_diff_ui_config(k, v, cb);
 558 }
 559
 560 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 561                              unsigned char *one)
 562 {
 563         int i, nr_trees = 0;
 564         struct tree *trees[MAX_UNPACK_TREES];
 565         struct tree_desc t[MAX_UNPACK_TREES];
 566         struct unpack_trees_options opts;
 567
 568         memset(&opts, 0, sizeof(opts));
 569         opts.head_idx = 2;
 570         opts.src_index = &the_index;
 571         opts.dst_index = &the_index;
 572         opts.update = 1;
 573         opts.verbose_update = 1;
 574         opts.trivial_merges_only = 1;
 575         opts.merge = 1;
 576         trees[nr_trees] = parse_tree_indirect(common);
 577         if (!trees[nr_trees++])
 578                 return -1;
 579         trees[nr_trees] = parse_tree_indirect(head);
 580         if (!trees[nr_trees++])
 581                 return -1;
 582         trees[nr_trees] = parse_tree_indirect(one);
 583         if (!trees[nr_trees++])
 584                 return -1;
 585         opts.fn = threeway_merge;
 586         cache_tree_free(&active_cache_tree);
 587         for (i = 0; i < nr_trees; i++) {
 588                 parse_tree(trees[i]);
 589                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 590         }
 591         if (unpack_trees(nr_trees, t, &opts))
 592                 return -1;
 593         return 0;
 594 }
 595
 596 static void write_tree_trivial(unsigned char *sha1)
 597 {
 598         if (write_cache_as_tree(sha1, 0, NULL))
 599                 die(_("git write-tree failed to write a tree"));
 600 }
 601
 602 static const char *merge_argument(struct commit *commit)
 603 {
 604         if (commit)
 605                 return sha1_to_hex(commit->object.sha1);
 606         else
 607                 return EMPTY_TREE_SHA1_HEX;
 608 }
 609
 610 int try_merge_command(const char *strategy, size_t xopts_nr,
 611                       const char **xopts, struct commit_list *common,
 612                       const char *head_arg, struct commit_list *remotes)
 613 {
 614         const char **args;
 615         int i = 0, x = 0, ret;
 616         struct commit_list *j;
 617         struct strbuf buf = STRBUF_INIT;
 618
 619         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 620                         commit_list_count(remotes)) * sizeof(char *));
 621         strbuf_addf(&buf, "merge-%s", strategy);
 622         args[i++] = buf.buf;
 623         for (x = 0; x < xopts_nr; x++) {
 624                 char *s = xmalloc(strlen(xopts[x])+2+1);
 625                 strcpy(s, "--");
 626                 strcpy(s+2, xopts[x]);
 627                 args[i++] = s;
 628         }
 629         for (j = common; j; j = j->next)
 630                 args[i++] = xstrdup(merge_argument(j->item));
 631         args[i++] = "--";
 632         args[i++] = head_arg;
 633         for (j = remotes; j; j = j->next)
 634                 args[i++] = xstrdup(merge_argument(j->item));
 635         args[i] = NULL;
 636         ret = run_command_v_opt(args, RUN_GIT_CMD);
 637         strbuf_release(&buf);
 638         i = 1;
 639         for (x = 0; x < xopts_nr; x++)
 640                 free((void *)args[i++]);
 641         for (j = common; j; j = j->next)
 642                 free((void *)args[i++]);
 643         i += 2;
 644         for (j = remotes; j; j = j->next)
 645                 free((void *)args[i++]);
 646         free(args);
 647         discard_cache();
 648         if (read_cache() < 0)
 649                 die(_("failed to read the cache"));
 650         resolve_undo_clear();
 651
 652         return ret;
 653 }
 654
 655 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 656                               const char *head_arg)
 657 {
 658         int index_fd;
 659         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 660
 661         index_fd = hold_locked_index(lock, 1);
 662         refresh_cache(REFRESH_QUIET);
 663         if (active_cache_changed &&
 664                         (write_cache(index_fd, active_cache, active_nr) ||
 665                          commit_locked_index(lock)))
 666                 return error(_("Unable to write index."));
 667         rollback_lock_file(lock);
 668
 669         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 670                 int clean, x;
 671                 struct commit *result;
 672                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 673                 int index_fd;
 674                 struct commit_list *reversed = NULL;
 675                 struct merge_options o;
 676                 struct commit_list *j;
 677
 678                 if (remoteheads->next) {
 679                         error(_("Not handling anything other than two heads merge."));
 680                         return 2;
 681                 }
 682
 683                 init_merge_options(&o);
 684                 if (!strcmp(strategy, "subtree"))
 685                         o.subtree_shift = "";
 686
 687                 o.renormalize = option_renormalize;
 688                 o.show_rename_progress =
 689                         show_progress == -1 ? isatty(2) : show_progress;
 690
 691                 for (x = 0; x < xopts_nr; x++)
 692                         if (parse_merge_opt(&o, xopts[x]))
 693                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 694
 695                 o.branch1 = head_arg;
 696                 o.branch2 = remoteheads->item->util;
 697
 698                 for (j = common; j; j = j->next)
 699                         commit_list_insert(j->item, &reversed);
 700
 701                 index_fd = hold_locked_index(lock, 1);
 702                 clean = merge_recursive(&o, lookup_commit(head),
 703                                 remoteheads->item, reversed, &result);
 704                 if (active_cache_changed &&
 705                                 (write_cache(index_fd, active_cache, active_nr) ||
 706                                  commit_locked_index(lock)))
 707                         die (_("unable to write %s"), get_index_file());
 708                 rollback_lock_file(lock);
 709                 return clean ? 0 : 1;
 710         } else {
 711                 return try_merge_command(strategy, xopts_nr, xopts,
 712                                                 common, head_arg, remoteheads);
 713         }
 714 }
 715
 716 static void count_diff_files(struct diff_queue_struct *q,
 717                              struct diff_options *opt, void *data)
 718 {
 719         int *count = data;
 720
 721         (*count) += q->nr;
 722 }
 723
 724 static int count_unmerged_entries(void)
 725 {
 726         int i, ret = 0;
 727
 728         for (i = 0; i < active_nr; i++)
 729                 if (ce_stage(active_cache[i]))
 730                         ret++;
 731
 732         return ret;
 733 }
 734
 735 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 736 {
 737         struct tree *trees[MAX_UNPACK_TREES];
 738         struct unpack_trees_options opts;
 739         struct tree_desc t[MAX_UNPACK_TREES];
 740         int i, fd, nr_trees = 0;
 741         struct dir_struct dir;
 742         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 743
 744         refresh_cache(REFRESH_QUIET);
 745
 746         fd = hold_locked_index(lock_file, 1);
 747
 748         memset(&trees, 0, sizeof(trees));
 749         memset(&opts, 0, sizeof(opts));
 750         memset(&t, 0, sizeof(t));
 751         memset(&dir, 0, sizeof(dir));
 752         dir.flags |= DIR_SHOW_IGNORED;
 753         dir.exclude_per_dir = ".gitignore";
 754         opts.dir = &dir;
 755
 756         opts.head_idx = 1;
 757         opts.src_index = &the_index;
 758         opts.dst_index = &the_index;
 759         opts.update = 1;
 760         opts.verbose_update = 1;
 761         opts.merge = 1;
 762         opts.fn = twoway_merge;
 763         setup_unpack_trees_porcelain(&opts, "merge");
 764
 765         trees[nr_trees] = parse_tree_indirect(head);
 766         if (!trees[nr_trees++])
 767                 return -1;
 768         trees[nr_trees] = parse_tree_indirect(remote);
 769         if (!trees[nr_trees++])
 770                 return -1;
 771         for (i = 0; i < nr_trees; i++) {
 772                 parse_tree(trees[i]);
 773                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 774         }
 775         if (unpack_trees(nr_trees, t, &opts))
 776                 return -1;
 777         if (write_cache(fd, active_cache, active_nr) ||
 778                 commit_locked_index(lock_file))
 779                 die(_("unable to write new index file"));
 780         return 0;
 781 }
 782
 783 static void split_merge_strategies(const char *string, struct strategy **list,
 784                                    int *nr, int *alloc)
 785 {
 786         char *p, *q, *buf;
 787
 788         if (!string)
 789                 return;
 790
 791         buf = xstrdup(string);
 792         q = buf;
 793         for (;;) {
 794                 p = strchr(q, ' ');
 795                 if (!p) {
 796                         ALLOC_GROW(*list, *nr + 1, *alloc);
 797                         (*list)[(*nr)++].name = xstrdup(q);
 798                         free(buf);
 799                         return;
 800                 } else {
 801                         *p = '\0';
 802                         ALLOC_GROW(*list, *nr + 1, *alloc);
 803                         (*list)[(*nr)++].name = xstrdup(q);
 804                         q = ++p;
 805                 }
 806         }
 807 }
 808
 809 static void add_strategies(const char *string, unsigned attr)
 810 {
 811         struct strategy *list = NULL;
 812         int list_alloc = 0, list_nr = 0, i;
 813
 814         memset(&list, 0, sizeof(list));
 815         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 816         if (list) {
 817                 for (i = 0; i < list_nr; i++)
 818                         append_strategy(get_strategy(list[i].name));
 819                 return;
 820         }
 821         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 822                 if (all_strategy[i].attr & attr)
 823                         append_strategy(&all_strategy[i]);
 824
 825 }
 826
 827 static void write_merge_msg(void)
 828 {
 829         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 830         if (fd < 0)
 831                 die_errno(_("Could not open '%s' for writing"),
 832                           git_path("MERGE_MSG"));
 833         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 834                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 835         close(fd);
 836 }
 837
 838 static void read_merge_msg(void)
 839 {
 840         strbuf_reset(&merge_msg);
 841         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 842                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 843 }
 844
 845 static void run_prepare_commit_msg(void)
 846 {
 847         write_merge_msg();
 848         run_hook(get_index_file(), "prepare-commit-msg",
 849                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 850         read_merge_msg();
 851 }
 852
 853 static int merge_trivial(void)
 854 {
 855         unsigned char result_tree[20], result_commit[20];
 856         struct commit_list *parent = xmalloc(sizeof(*parent));
 857
 858         write_tree_trivial(result_tree);
 859         printf(_("Wonderful.\n"));
 860         parent->item = lookup_commit(head);
 861         parent->next = xmalloc(sizeof(*parent->next));
 862         parent->next->item = remoteheads->item;
 863         parent->next->next = NULL;
 864         run_prepare_commit_msg();
 865         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 866         finish(result_commit, "In-index merge");
 867         drop_save();
 868         return 0;
 869 }
 870
 871 static int finish_automerge(struct commit_list *common,
 872                             unsigned char *result_tree,
 873                             const char *wt_strategy)
 874 {
 875         struct commit_list *parents = NULL, *j;
 876         struct strbuf buf = STRBUF_INIT;
 877         unsigned char result_commit[20];
 878
 879         free_commit_list(common);
 880         if (allow_fast_forward) {
 881                 parents = remoteheads;
 882                 commit_list_insert(lookup_commit(head), &parents);
 883                 parents = reduce_heads(parents);
 884         } else {
 885                 struct commit_list **pptr = &parents;
 886
 887                 pptr = &commit_list_insert(lookup_commit(head),
 888                                 pptr)->next;
 889                 for (j = remoteheads; j; j = j->next)
 890                         pptr = &commit_list_insert(j->item, pptr)->next;
 891         }
 892         free_commit_list(remoteheads);
 893         strbuf_addch(&merge_msg, '\n');
 894         run_prepare_commit_msg();
 895         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 896         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 897         finish(result_commit, buf.buf);
 898         strbuf_release(&buf);
 899         drop_save();
 900         return 0;
 901 }
 902
 903 static int suggest_conflicts(int renormalizing)
 904 {
 905         FILE *fp;
 906         int pos;
 907
 908         fp = fopen(git_path("MERGE_MSG"), "a");
 909         if (!fp)
 910                 die_errno(_("Could not open '%s' for writing"),
 911                           git_path("MERGE_MSG"));
 912         fprintf(fp, "\nConflicts:\n");
 913         for (pos = 0; pos < active_nr; pos++) {
 914                 struct cache_entry *ce = active_cache[pos];
 915
 916                 if (ce_stage(ce)) {
 917                         fprintf(fp, "\t%s\n", ce->name);
 918                         while (pos + 1 < active_nr &&
 919                                         !strcmp(ce->name,
 920                                                 active_cache[pos + 1]->name))
 921                                 pos++;
 922                 }
 923         }
 924         fclose(fp);
 925         rerere(allow_rerere_auto);
 926         printf(_("Automatic merge failed; "
 927                         "fix conflicts and then commit the result.\n"));
 928         return 1;
 929 }
 930
 931 static struct commit *is_old_style_invocation(int argc, const char **argv)
 932 {
 933         struct commit *second_token = NULL;
 934         if (argc > 2) {
 935                 unsigned char second_sha1[20];
 936
 937                 if (get_sha1(argv[1], second_sha1))
 938                         return NULL;
 939                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 940                 if (!second_token)
 941                         die(_("'%s' is not a commit"), argv[1]);
 942                 if (hashcmp(second_token->object.sha1, head))
 943                         return NULL;
 944         }
 945         return second_token;
 946 }
 947
 948 static int evaluate_result(void)
 949 {
 950         int cnt = 0;
 951         struct rev_info rev;
 952
 953         /* Check how many files differ. */
 954         init_revisions(&rev, "");
 955         setup_revisions(0, NULL, &rev, NULL);
 956         rev.diffopt.output_format |=
 957                 DIFF_FORMAT_CALLBACK;
 958         rev.diffopt.format_callback = count_diff_files;
 959         rev.diffopt.format_callback_data = &cnt;
 960         run_diff_files(&rev, 0);
 961
 962         /*
 963          * Check how many unmerged entries are
 964          * there.
 965          */
 966         cnt += count_unmerged_entries();
 967
 968         return cnt;
 969 }
 970
 971 /*
 972  * Pretend as if the user told us to merge with the tracking
 973  * branch we have for the upstream of the current branch
 974  */
 975 static int setup_with_upstream(const char ***argv)
 976 {
 977         struct branch *branch = branch_get(NULL);
 978         int i;
 979         const char **args;
 980
 981         if (!branch)
 982                 die(_("No current branch."));
 983         if (!branch->remote)
 984                 die(_("No remote for the current branch."));
 985         if (!branch->merge_nr)
 986                 die(_("No default upstream defined for the current branch."));
 987
 988         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 989         for (i = 0; i < branch->merge_nr; i++) {
 990                 if (!branch->merge[i]->dst)
 991                         die(_("No remote tracking branch for %s from %s"),
 992                             branch->merge[i]->src, branch->remote_name);
 993                 args[i] = branch->merge[i]->dst;
 994         }
 995         args[i] = NULL;
 996         *argv = args;
 997         return i;
 998 }
 999
1000 int cmd_merge(int argc, const char **argv, const char *prefix)
1001 {
1002         unsigned char result_tree[20];
1003         struct strbuf buf = STRBUF_INIT;
1004         const char *head_arg;
1005         int flag, head_invalid = 0, i;
1006         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1007         struct commit_list *common = NULL;
1008         const char *best_strategy = NULL, *wt_strategy = NULL;
1009         struct commit_list **remotes = &remoteheads;
1010
1011         if (argc == 2 && !strcmp(argv[1], "-h"))
1012                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1013
1014         /*
1015          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1016          * current branch.
1017          */
1018         branch = resolve_ref("HEAD", head, 0, &flag);
1019         if (branch && !prefixcmp(branch, "refs/heads/"))
1020                 branch += 11;
1021         if (is_null_sha1(head))
1022                 head_invalid = 1;
1023
1024         git_config(git_merge_config, NULL);
1025
1026         /* for color.ui */
1027         if (diff_use_color_default == -1)
1028                 diff_use_color_default = git_use_color_default;
1029
1030         if (branch_mergeoptions)
1031                 parse_branch_merge_options(branch_mergeoptions);
1032         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1033                         builtin_merge_usage, 0);
1034
1035         if (verbosity < 0 && show_progress == -1)
1036                 show_progress = 0;
1037
1038         if (abort_current_merge) {
1039                 int nargc = 2;
1040                 const char *nargv[] = {"reset", "--merge", NULL};
1041
1042                 if (!file_exists(git_path("MERGE_HEAD")))
1043                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1044
1045                 /* Invoke 'git reset --merge' */
1046                 return cmd_reset(nargc, nargv, prefix);
1047         }
1048
1049         if (read_cache_unmerged())
1050                 die_resolve_conflict("merge");
1051
1052         if (file_exists(git_path("MERGE_HEAD"))) {
1053                 /*
1054                  * There is no unmerged entry, don't advise 'git
1055                  * add/rm <file>', just 'git commit'.
1056                  */
1057                 if (advice_resolve_conflict)
1058                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1059                                   "Please, commit your changes before you can merge."));
1060                 else
1061                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1062         }
1063         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1064                 if (advice_resolve_conflict)
1065                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1066                             "Please, commit your changes before you can merge."));
1067                 else
1068                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1069         }
1070         resolve_undo_clear();
1071
1072         if (verbosity < 0)
1073                 show_diffstat = 0;
1074
1075         if (squash) {
1076                 if (!allow_fast_forward)
1077                         die(_("You cannot combine --squash with --no-ff."));
1078                 option_commit = 0;
1079         }
1080
1081         if (!allow_fast_forward && fast_forward_only)
1082                 die(_("You cannot combine --no-ff with --ff-only."));
1083
1084         if (!argc && !abort_current_merge && default_to_upstream)
1085                 argc = setup_with_upstream(&argv);
1086
1087         if (!argc)
1088                 usage_with_options(builtin_merge_usage,
1089                         builtin_merge_options);
1090
1091         /*
1092          * This could be traditional "merge <msg> HEAD <commit>..."  and
1093          * the way we can tell it is to see if the second token is HEAD,
1094          * but some people might have misused the interface and used a
1095          * committish that is the same as HEAD there instead.
1096          * Traditional format never would have "-m" so it is an
1097          * additional safety measure to check for it.
1098          */
1099
1100         if (!have_message && is_old_style_invocation(argc, argv)) {
1101                 strbuf_addstr(&merge_msg, argv[0]);
1102                 head_arg = argv[1];
1103                 argv += 2;
1104                 argc -= 2;
1105         } else if (head_invalid) {
1106                 struct object *remote_head;
1107                 /*
1108                  * If the merged head is a valid one there is no reason
1109                  * to forbid "git merge" into a branch yet to be born.
1110                  * We do the same for "git pull".
1111                  */
1112                 if (argc != 1)
1113                         die(_("Can merge only exactly one commit into "
1114                                 "empty head"));
1115                 if (squash)
1116                         die(_("Squash commit into empty head not supported yet"));
1117                 if (!allow_fast_forward)
1118                         die(_("Non-fast-forward commit does not make sense into "
1119                             "an empty head"));
1120                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1121                 if (!remote_head)
1122                         die(_("%s - not something we can merge"), argv[0]);
1123                 read_empty(remote_head->sha1, 0);
1124                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1125                                 DIE_ON_ERR);
1126                 return 0;
1127         } else {
1128                 struct strbuf merge_names = STRBUF_INIT;
1129
1130                 /* We are invoked directly as the first-class UI. */
1131                 head_arg = "HEAD";
1132
1133                 /*
1134                  * All the rest are the commits being merged;
1135                  * prepare the standard merge summary message to
1136                  * be appended to the given message.  If remote
1137                  * is invalid we will die later in the common
1138                  * codepath so we discard the error in this
1139                  * loop.
1140                  */
1141                 for (i = 0; i < argc; i++)
1142                         merge_name(argv[i], &merge_names);
1143
1144                 if (!have_message || shortlog_len) {
1145                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1146                                       shortlog_len);
1147                         if (merge_msg.len)
1148                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1149                 }
1150         }
1151
1152         if (head_invalid || !argc)
1153                 usage_with_options(builtin_merge_usage,
1154                         builtin_merge_options);
1155
1156         strbuf_addstr(&buf, "merge");
1157         for (i = 0; i < argc; i++)
1158                 strbuf_addf(&buf, " %s", argv[i]);
1159         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1160         strbuf_reset(&buf);
1161
1162         for (i = 0; i < argc; i++) {
1163                 struct object *o;
1164                 struct commit *commit;
1165
1166                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1167                 if (!o)
1168                         die(_("%s - not something we can merge"), argv[i]);
1169                 commit = lookup_commit(o->sha1);
1170                 commit->util = (void *)argv[i];
1171                 remotes = &commit_list_insert(commit, remotes)->next;
1172
1173                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1174                 setenv(buf.buf, argv[i], 1);
1175                 strbuf_reset(&buf);
1176         }
1177
1178         if (!use_strategies) {
1179                 if (!remoteheads->next)
1180                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1181                 else
1182                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1183         }
1184
1185         for (i = 0; i < use_strategies_nr; i++) {
1186                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1187                         allow_fast_forward = 0;
1188                 if (use_strategies[i]->attr & NO_TRIVIAL)
1189                         allow_trivial = 0;
1190         }
1191
1192         if (!remoteheads->next)
1193                 common = get_merge_bases(lookup_commit(head),
1194                                 remoteheads->item, 1);
1195         else {
1196                 struct commit_list *list = remoteheads;
1197                 commit_list_insert(lookup_commit(head), &list);
1198                 common = get_octopus_merge_bases(list);
1199                 free(list);
1200         }
1201
1202         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1203                 DIE_ON_ERR);
1204
1205         if (!common)
1206                 ; /* No common ancestors found. We need a real merge. */
1207         else if (!remoteheads->next && !common->next &&
1208                         common->item == remoteheads->item) {
1209                 /*
1210                  * If head can reach all the merge then we are up to date.
1211                  * but first the most common case of merging one remote.
1212                  */
1213                 finish_up_to_date("Already up-to-date.");
1214                 return 0;
1215         } else if (allow_fast_forward && !remoteheads->next &&
1216                         !common->next &&
1217                         !hashcmp(common->item->object.sha1, head)) {
1218                 /* Again the most common case of merging one remote. */
1219                 struct strbuf msg = STRBUF_INIT;
1220                 struct object *o;
1221                 char hex[41];
1222
1223                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1224
1225                 if (verbosity >= 0)
1226                         printf(_("Updating %s..%s\n"),
1227                                 hex,
1228                                 find_unique_abbrev(remoteheads->item->object.sha1,
1229                                 DEFAULT_ABBREV));
1230                 strbuf_addstr(&msg, "Fast-forward");
1231                 if (have_message)
1232                         strbuf_addstr(&msg,
1233                                 " (no commit created; -m option ignored)");
1234                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1235                         0, NULL, OBJ_COMMIT);
1236                 if (!o)
1237                         return 1;
1238
1239                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1240                         return 1;
1241
1242                 finish(o->sha1, msg.buf);
1243                 drop_save();
1244                 return 0;
1245         } else if (!remoteheads->next && common->next)
1246                 ;
1247                 /*
1248                  * We are not doing octopus and not fast-forward.  Need
1249                  * a real merge.
1250                  */
1251         else if (!remoteheads->next && !common->next && option_commit) {
1252                 /*
1253                  * We are not doing octopus, not fast-forward, and have
1254                  * only one common.
1255                  */
1256                 refresh_cache(REFRESH_QUIET);
1257                 if (allow_trivial && !fast_forward_only) {
1258                         /* See if it is really trivial. */
1259                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1260                         printf(_("Trying really trivial in-index merge...\n"));
1261                         if (!read_tree_trivial(common->item->object.sha1,
1262                                         head, remoteheads->item->object.sha1))
1263                                 return merge_trivial();
1264                         printf(_("Nope.\n"));
1265                 }
1266         } else {
1267                 /*
1268                  * An octopus.  If we can reach all the remote we are up
1269                  * to date.
1270                  */
1271                 int up_to_date = 1;
1272                 struct commit_list *j;
1273
1274                 for (j = remoteheads; j; j = j->next) {
1275                         struct commit_list *common_one;
1276
1277                         /*
1278                          * Here we *have* to calculate the individual
1279                          * merge_bases again, otherwise "git merge HEAD^
1280                          * HEAD^^" would be missed.
1281                          */
1282                         common_one = get_merge_bases(lookup_commit(head),
1283                                 j->item, 1);
1284                         if (hashcmp(common_one->item->object.sha1,
1285                                 j->item->object.sha1)) {
1286                                 up_to_date = 0;
1287                                 break;
1288                         }
1289                 }
1290                 if (up_to_date) {
1291                         finish_up_to_date("Already up-to-date. Yeeah!");
1292                         return 0;
1293                 }
1294         }
1295
1296         if (fast_forward_only)
1297                 die(_("Not possible to fast-forward, aborting."));
1298
1299         /* We are going to make a new commit. */
1300         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1301
1302         /*
1303          * At this point, we need a real merge.  No matter what strategy
1304          * we use, it would operate on the index, possibly affecting the
1305          * working tree, and when resolved cleanly, have the desired
1306          * tree in the index -- this means that the index must be in
1307          * sync with the head commit.  The strategies are responsible
1308          * to ensure this.
1309          */
1310         if (use_strategies_nr != 1) {
1311                 /*
1312                  * Stash away the local changes so that we can try more
1313                  * than one.
1314                  */
1315                 save_state();
1316         } else {
1317                 memcpy(stash, null_sha1, 20);
1318         }
1319
1320         for (i = 0; i < use_strategies_nr; i++) {
1321                 int ret;
1322                 if (i) {
1323                         printf(_("Rewinding the tree to pristine...\n"));
1324                         restore_state();
1325                 }
1326                 if (use_strategies_nr != 1)
1327                         printf(_("Trying merge strategy %s...\n"),
1328                                 use_strategies[i]->name);
1329                 /*
1330                  * Remember which strategy left the state in the working
1331                  * tree.
1332                  */
1333                 wt_strategy = use_strategies[i]->name;
1334
1335                 ret = try_merge_strategy(use_strategies[i]->name,
1336                         common, head_arg);
1337                 if (!option_commit && !ret) {
1338                         merge_was_ok = 1;
1339                         /*
1340                          * This is necessary here just to avoid writing
1341                          * the tree, but later we will *not* exit with
1342                          * status code 1 because merge_was_ok is set.
1343                          */
1344                         ret = 1;
1345                 }
1346
1347                 if (ret) {
1348                         /*
1349                          * The backend exits with 1 when conflicts are
1350                          * left to be resolved, with 2 when it does not
1351                          * handle the given merge at all.
1352                          */
1353                         if (ret == 1) {
1354                                 int cnt = evaluate_result();
1355
1356                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1357                                         best_strategy = use_strategies[i]->name;
1358                                         best_cnt = cnt;
1359                                 }
1360                         }
1361                         if (merge_was_ok)
1362                                 break;
1363                         else
1364                                 continue;
1365                 }
1366
1367                 /* Automerge succeeded. */
1368                 write_tree_trivial(result_tree);
1369                 automerge_was_ok = 1;
1370                 break;
1371         }
1372
1373         /*
1374          * If we have a resulting tree, that means the strategy module
1375          * auto resolved the merge cleanly.
1376          */
1377         if (automerge_was_ok)
1378                 return finish_automerge(common, result_tree, wt_strategy);
1379
1380         /*
1381          * Pick the result from the best strategy and have the user fix
1382          * it up.
1383          */
1384         if (!best_strategy) {
1385                 restore_state();
1386                 if (use_strategies_nr > 1)
1387                         fprintf(stderr,
1388                                 _("No merge strategy handled the merge.\n"));
1389                 else
1390                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1391                                 use_strategies[0]->name);
1392                 return 2;
1393         } else if (best_strategy == wt_strategy)
1394                 ; /* We already have its result in the working tree. */
1395         else {
1396                 printf(_("Rewinding the tree to pristine...\n"));
1397                 restore_state();
1398                 printf(_("Using the %s to prepare resolving by hand.\n"),
1399                         best_strategy);
1400                 try_merge_strategy(best_strategy, common, head_arg);
1401         }
1402
1403         if (squash)
1404                 finish(NULL, NULL);
1405         else {
1406                 int fd;
1407                 struct commit_list *j;
1408
1409                 for (j = remoteheads; j; j = j->next)
1410                         strbuf_addf(&buf, "%s\n",
1411                                 sha1_to_hex(j->item->object.sha1));
1412                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1413                 if (fd < 0)
1414                         die_errno(_("Could not open '%s' for writing"),
1415                                   git_path("MERGE_HEAD"));
1416                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1417                         die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1418                 close(fd);
1419                 strbuf_addch(&merge_msg, '\n');
1420                 write_merge_msg();
1421                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1422                 if (fd < 0)
1423                         die_errno(_("Could not open '%s' for writing"),
1424                                   git_path("MERGE_MODE"));
1425                 strbuf_reset(&buf);
1426                 if (!allow_fast_forward)
1427                         strbuf_addf(&buf, "no-ff");
1428                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1429                         die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1430                 close(fd);
1431         }
1432
1433         if (merge_was_ok) {
1434                 fprintf(stderr, _("Automatic merge went well; "
1435                         "stopped before committing as requested\n"));
1436                 return 0;
1437         } else
1438                 return suggest_conflicts(option_renormalize);
1439 }