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 #include "fmt-merge-msg.h"
  30
  31 #define DEFAULT_TWOHEAD (1<<0)
  32 #define DEFAULT_OCTOPUS (1<<1)
  33 #define NO_FAST_FORWARD (1<<2)
  34 #define NO_TRIVIAL      (1<<3)
  35
  36 struct strategy {
  37         const char *name;
  38         unsigned attr;
  39 };
  40
  41 static const char * const builtin_merge_usage[] = {
  42         "git merge [options] [<commit>...]",
  43         "git merge [options] <msg> HEAD <commit>",
  44         "git merge --abort",
  45         NULL
  46 };
  47
  48 static int show_diffstat = 1, shortlog_len = -1, squash;
  49 static int option_commit = 1, allow_fast_forward = 1;
  50 static int fast_forward_only;
  51 static int allow_trivial = 1, have_message;
  52 static struct strbuf merge_msg;
  53 static struct commit_list *remoteheads;
  54 static unsigned char head[20], stash[20];
  55 static struct strategy **use_strategies;
  56 static size_t use_strategies_nr, use_strategies_alloc;
  57 static const char **xopts;
  58 static size_t xopts_nr, xopts_alloc;
  59 static const char *branch;
  60 static char *branch_mergeoptions;
  61 static int option_renormalize;
  62 static int verbosity;
  63 static int allow_rerere_auto;
  64 static int abort_current_merge;
  65 static int show_progress = -1;
  66 static int default_to_upstream;
  67
  68 static struct strategy all_strategy[] = {
  69         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  70         { "octopus",    DEFAULT_OCTOPUS },
  71         { "resolve",    0 },
  72         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  73         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  74 };
  75
  76 static const char *pull_twohead, *pull_octopus;
  77
  78 static int option_parse_message(const struct option *opt,
  79                                 const char *arg, int unset)
  80 {
  81         struct strbuf *buf = opt->value;
  82
  83         if (unset)
  84                 strbuf_setlen(buf, 0);
  85         else if (arg) {
  86                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  87                 have_message = 1;
  88         } else
  89                 return error(_("switch `m' requires a value"));
  90         return 0;
  91 }
  92
  93 static struct strategy *get_strategy(const char *name)
  94 {
  95         int i;
  96         struct strategy *ret;
  97         static struct cmdnames main_cmds, other_cmds;
  98         static int loaded;
  99
 100         if (!name)
 101                 return NULL;
 102
 103         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 104                 if (!strcmp(name, all_strategy[i].name))
 105                         return &all_strategy[i];
 106
 107         if (!loaded) {
 108                 struct cmdnames not_strategies;
 109                 loaded = 1;
 110
 111                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 112                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 113                 for (i = 0; i < main_cmds.cnt; i++) {
 114                         int j, found = 0;
 115                         struct cmdname *ent = main_cmds.names[i];
 116                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 117                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 118                                                 && !all_strategy[j].name[ent->len])
 119                                         found = 1;
 120                         if (!found)
 121                                 add_cmdname(&not_strategies, ent->name, ent->len);
 122                 }
 123                 exclude_cmds(&main_cmds, &not_strategies);
 124         }
 125         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 126                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 127                 fprintf(stderr, _("Available strategies are:"));
 128                 for (i = 0; i < main_cmds.cnt; i++)
 129                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 130                 fprintf(stderr, ".\n");
 131                 if (other_cmds.cnt) {
 132                         fprintf(stderr, _("Available custom strategies are:"));
 133                         for (i = 0; i < other_cmds.cnt; i++)
 134                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 135                         fprintf(stderr, ".\n");
 136                 }
 137                 exit(1);
 138         }
 139
 140         ret = xcalloc(1, sizeof(struct strategy));
 141         ret->name = xstrdup(name);
 142         ret->attr = NO_TRIVIAL;
 143         return ret;
 144 }
 145
 146 static void append_strategy(struct strategy *s)
 147 {
 148         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 149         use_strategies[use_strategies_nr++] = s;
 150 }
 151
 152 static int option_parse_strategy(const struct option *opt,
 153                                  const char *name, int unset)
 154 {
 155         if (unset)
 156                 return 0;
 157
 158         append_strategy(get_strategy(name));
 159         return 0;
 160 }
 161
 162 static int option_parse_x(const struct option *opt,
 163                           const char *arg, int unset)
 164 {
 165         if (unset)
 166                 return 0;
 167
 168         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 169         xopts[xopts_nr++] = xstrdup(arg);
 170         return 0;
 171 }
 172
 173 static int option_parse_n(const struct option *opt,
 174                           const char *arg, int unset)
 175 {
 176         show_diffstat = unset;
 177         return 0;
 178 }
 179
 180 static struct option builtin_merge_options[] = {
 181         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 182                 "do not show a diffstat at the end of the merge",
 183                 PARSE_OPT_NOARG, option_parse_n },
 184         OPT_BOOLEAN(0, "stat", &show_diffstat,
 185                 "show a diffstat at the end of the merge"),
 186         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 187         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 188           "add (at most <n>) entries from shortlog to merge commit message",
 189           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 190         OPT_BOOLEAN(0, "squash", &squash,
 191                 "create a single commit instead of doing a merge"),
 192         OPT_BOOLEAN(0, "commit", &option_commit,
 193                 "perform a commit if the merge succeeds (default)"),
 194         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 195                 "allow fast-forward (default)"),
 196         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 197                 "abort if fast-forward is not possible"),
 198         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 199         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 200                 "merge strategy to use", option_parse_strategy),
 201         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 202                 "option for selected merge strategy", option_parse_x),
 203         OPT_CALLBACK('m', "message", &merge_msg, "message",
 204                 "merge commit message (for a non-fast-forward merge)",
 205                 option_parse_message),
 206         OPT__VERBOSITY(&verbosity),
 207         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 208                 "abort the current in-progress merge"),
 209         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 210         OPT_END()
 211 };
 212
 213 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 214 static void drop_save(void)
 215 {
 216         unlink(git_path("MERGE_HEAD"));
 217         unlink(git_path("MERGE_MSG"));
 218         unlink(git_path("MERGE_MODE"));
 219 }
 220
 221 static void save_state(void)
 222 {
 223         int len;
 224         struct child_process cp;
 225         struct strbuf buffer = STRBUF_INIT;
 226         const char *argv[] = {"stash", "create", NULL};
 227
 228         memset(&cp, 0, sizeof(cp));
 229         cp.argv = argv;
 230         cp.out = -1;
 231         cp.git_cmd = 1;
 232
 233         if (start_command(&cp))
 234                 die(_("could not run stash."));
 235         len = strbuf_read(&buffer, cp.out, 1024);
 236         close(cp.out);
 237
 238         if (finish_command(&cp) || len < 0)
 239                 die(_("stash failed"));
 240         else if (!len)
 241                 return;
 242         strbuf_setlen(&buffer, buffer.len-1);
 243         if (get_sha1(buffer.buf, stash))
 244                 die(_("not a valid object: %s"), buffer.buf);
 245 }
 246
 247 static void read_empty(unsigned const char *sha1, int verbose)
 248 {
 249         int i = 0;
 250         const char *args[7];
 251
 252         args[i++] = "read-tree";
 253         if (verbose)
 254                 args[i++] = "-v";
 255         args[i++] = "-m";
 256         args[i++] = "-u";
 257         args[i++] = EMPTY_TREE_SHA1_HEX;
 258         args[i++] = sha1_to_hex(sha1);
 259         args[i] = NULL;
 260
 261         if (run_command_v_opt(args, RUN_GIT_CMD))
 262                 die(_("read-tree failed"));
 263 }
 264
 265 static void reset_hard(unsigned const char *sha1, int verbose)
 266 {
 267         int i = 0;
 268         const char *args[6];
 269
 270         args[i++] = "read-tree";
 271         if (verbose)
 272                 args[i++] = "-v";
 273         args[i++] = "--reset";
 274         args[i++] = "-u";
 275         args[i++] = sha1_to_hex(sha1);
 276         args[i] = NULL;
 277
 278         if (run_command_v_opt(args, RUN_GIT_CMD))
 279                 die(_("read-tree failed"));
 280 }
 281
 282 static void restore_state(void)
 283 {
 284         struct strbuf sb = STRBUF_INIT;
 285         const char *args[] = { "stash", "apply", NULL, NULL };
 286
 287         if (is_null_sha1(stash))
 288                 return;
 289
 290         reset_hard(head, 1);
 291
 292         args[2] = sha1_to_hex(stash);
 293
 294         /*
 295          * It is OK to ignore error here, for example when there was
 296          * nothing to restore.
 297          */
 298         run_command_v_opt(args, RUN_GIT_CMD);
 299
 300         strbuf_release(&sb);
 301         refresh_cache(REFRESH_QUIET);
 302 }
 303
 304 /* This is called when no merge was necessary. */
 305 static void finish_up_to_date(const char *msg)
 306 {
 307         if (verbosity >= 0)
 308                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 309         drop_save();
 310 }
 311
 312 static void squash_message(void)
 313 {
 314         struct rev_info rev;
 315         struct commit *commit;
 316         struct strbuf out = STRBUF_INIT;
 317         struct commit_list *j;
 318         int fd;
 319         struct pretty_print_context ctx = {0};
 320
 321         printf(_("Squash commit -- not updating HEAD\n"));
 322         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 323         if (fd < 0)
 324                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 325
 326         init_revisions(&rev, NULL);
 327         rev.ignore_merges = 1;
 328         rev.commit_format = CMIT_FMT_MEDIUM;
 329
 330         commit = lookup_commit(head);
 331         commit->object.flags |= UNINTERESTING;
 332         add_pending_object(&rev, &commit->object, NULL);
 333
 334         for (j = remoteheads; j; j = j->next)
 335                 add_pending_object(&rev, &j->item->object, NULL);
 336
 337         setup_revisions(0, NULL, &rev, NULL);
 338         if (prepare_revision_walk(&rev))
 339                 die(_("revision walk setup failed"));
 340
 341         ctx.abbrev = rev.abbrev;
 342         ctx.date_mode = rev.date_mode;
 343         ctx.fmt = rev.commit_format;
 344
 345         strbuf_addstr(&out, "Squashed commit of the following:\n");
 346         while ((commit = get_revision(&rev)) != NULL) {
 347                 strbuf_addch(&out, '\n');
 348                 strbuf_addf(&out, "commit %s\n",
 349                         sha1_to_hex(commit->object.sha1));
 350                 pretty_print_commit(&ctx, commit, &out);
 351         }
 352         if (write(fd, out.buf, out.len) < 0)
 353                 die_errno(_("Writing SQUASH_MSG"));
 354         if (close(fd))
 355                 die_errno(_("Finishing SQUASH_MSG"));
 356         strbuf_release(&out);
 357 }
 358
 359 static void finish(const unsigned char *new_head, const char *msg)
 360 {
 361         struct strbuf reflog_message = STRBUF_INIT;
 362
 363         if (!msg)
 364                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 365         else {
 366                 if (verbosity >= 0)
 367                         printf("%s\n", msg);
 368                 strbuf_addf(&reflog_message, "%s: %s",
 369                         getenv("GIT_REFLOG_ACTION"), msg);
 370         }
 371         if (squash) {
 372                 squash_message();
 373         } else {
 374                 if (verbosity >= 0 && !merge_msg.len)
 375                         printf(_("No merge message -- not updating HEAD\n"));
 376                 else {
 377                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 378                         update_ref(reflog_message.buf, "HEAD",
 379                                 new_head, head, 0,
 380                                 DIE_ON_ERR);
 381                         /*
 382                          * We ignore errors in 'gc --auto', since the
 383                          * user should see them.
 384                          */
 385                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 386                 }
 387         }
 388         if (new_head && show_diffstat) {
 389                 struct diff_options opts;
 390                 diff_setup(&opts);
 391                 opts.output_format |=
 392                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 393                 opts.detect_rename = DIFF_DETECT_RENAME;
 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         int status;
 530
 531         if (branch && !prefixcmp(k, "branch.") &&
 532                 !prefixcmp(k + 7, branch) &&
 533                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 534                 free(branch_mergeoptions);
 535                 branch_mergeoptions = xstrdup(v);
 536                 return 0;
 537         }
 538
 539         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 540                 show_diffstat = git_config_bool(k, v);
 541         else if (!strcmp(k, "pull.twohead"))
 542                 return git_config_string(&pull_twohead, k, v);
 543         else if (!strcmp(k, "pull.octopus"))
 544                 return git_config_string(&pull_octopus, k, v);
 545         else if (!strcmp(k, "merge.renormalize"))
 546                 option_renormalize = git_config_bool(k, v);
 547         else if (!strcmp(k, "merge.ff")) {
 548                 int boolval = git_config_maybe_bool(k, v);
 549                 if (0 <= boolval) {
 550                         allow_fast_forward = boolval;
 551                 } else if (v && !strcmp(v, "only")) {
 552                         allow_fast_forward = 1;
 553                         fast_forward_only = 1;
 554                 } /* do not barf on values from future versions of git */
 555                 return 0;
 556         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 557                 default_to_upstream = git_config_bool(k, v);
 558                 return 0;
 559         }
 560         status = fmt_merge_msg_config(k, v, cb);
 561         if (status)
 562                 return status;
 563         return git_diff_ui_config(k, v, cb);
 564 }
 565
 566 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 567                              unsigned char *one)
 568 {
 569         int i, nr_trees = 0;
 570         struct tree *trees[MAX_UNPACK_TREES];
 571         struct tree_desc t[MAX_UNPACK_TREES];
 572         struct unpack_trees_options opts;
 573
 574         memset(&opts, 0, sizeof(opts));
 575         opts.head_idx = 2;
 576         opts.src_index = &the_index;
 577         opts.dst_index = &the_index;
 578         opts.update = 1;
 579         opts.verbose_update = 1;
 580         opts.trivial_merges_only = 1;
 581         opts.merge = 1;
 582         trees[nr_trees] = parse_tree_indirect(common);
 583         if (!trees[nr_trees++])
 584                 return -1;
 585         trees[nr_trees] = parse_tree_indirect(head);
 586         if (!trees[nr_trees++])
 587                 return -1;
 588         trees[nr_trees] = parse_tree_indirect(one);
 589         if (!trees[nr_trees++])
 590                 return -1;
 591         opts.fn = threeway_merge;
 592         cache_tree_free(&active_cache_tree);
 593         for (i = 0; i < nr_trees; i++) {
 594                 parse_tree(trees[i]);
 595                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 596         }
 597         if (unpack_trees(nr_trees, t, &opts))
 598                 return -1;
 599         return 0;
 600 }
 601
 602 static void write_tree_trivial(unsigned char *sha1)
 603 {
 604         if (write_cache_as_tree(sha1, 0, NULL))
 605                 die(_("git write-tree failed to write a tree"));
 606 }
 607
 608 static const char *merge_argument(struct commit *commit)
 609 {
 610         if (commit)
 611                 return sha1_to_hex(commit->object.sha1);
 612         else
 613                 return EMPTY_TREE_SHA1_HEX;
 614 }
 615
 616 int try_merge_command(const char *strategy, size_t xopts_nr,
 617                       const char **xopts, struct commit_list *common,
 618                       const char *head_arg, struct commit_list *remotes)
 619 {
 620         const char **args;
 621         int i = 0, x = 0, ret;
 622         struct commit_list *j;
 623         struct strbuf buf = STRBUF_INIT;
 624
 625         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 626                         commit_list_count(remotes)) * sizeof(char *));
 627         strbuf_addf(&buf, "merge-%s", strategy);
 628         args[i++] = buf.buf;
 629         for (x = 0; x < xopts_nr; x++) {
 630                 char *s = xmalloc(strlen(xopts[x])+2+1);
 631                 strcpy(s, "--");
 632                 strcpy(s+2, xopts[x]);
 633                 args[i++] = s;
 634         }
 635         for (j = common; j; j = j->next)
 636                 args[i++] = xstrdup(merge_argument(j->item));
 637         args[i++] = "--";
 638         args[i++] = head_arg;
 639         for (j = remotes; j; j = j->next)
 640                 args[i++] = xstrdup(merge_argument(j->item));
 641         args[i] = NULL;
 642         ret = run_command_v_opt(args, RUN_GIT_CMD);
 643         strbuf_release(&buf);
 644         i = 1;
 645         for (x = 0; x < xopts_nr; x++)
 646                 free((void *)args[i++]);
 647         for (j = common; j; j = j->next)
 648                 free((void *)args[i++]);
 649         i += 2;
 650         for (j = remotes; j; j = j->next)
 651                 free((void *)args[i++]);
 652         free(args);
 653         discard_cache();
 654         if (read_cache() < 0)
 655                 die(_("failed to read the cache"));
 656         resolve_undo_clear();
 657
 658         return ret;
 659 }
 660
 661 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 662                               const char *head_arg)
 663 {
 664         int index_fd;
 665         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 666
 667         index_fd = hold_locked_index(lock, 1);
 668         refresh_cache(REFRESH_QUIET);
 669         if (active_cache_changed &&
 670                         (write_cache(index_fd, active_cache, active_nr) ||
 671                          commit_locked_index(lock)))
 672                 return error(_("Unable to write index."));
 673         rollback_lock_file(lock);
 674
 675         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 676                 int clean, x;
 677                 struct commit *result;
 678                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 679                 int index_fd;
 680                 struct commit_list *reversed = NULL;
 681                 struct merge_options o;
 682                 struct commit_list *j;
 683
 684                 if (remoteheads->next) {
 685                         error(_("Not handling anything other than two heads merge."));
 686                         return 2;
 687                 }
 688
 689                 init_merge_options(&o);
 690                 if (!strcmp(strategy, "subtree"))
 691                         o.subtree_shift = "";
 692
 693                 o.renormalize = option_renormalize;
 694                 o.show_rename_progress =
 695                         show_progress == -1 ? isatty(2) : show_progress;
 696
 697                 for (x = 0; x < xopts_nr; x++)
 698                         if (parse_merge_opt(&o, xopts[x]))
 699                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 700
 701                 o.branch1 = head_arg;
 702                 o.branch2 = remoteheads->item->util;
 703
 704                 for (j = common; j; j = j->next)
 705                         commit_list_insert(j->item, &reversed);
 706
 707                 index_fd = hold_locked_index(lock, 1);
 708                 clean = merge_recursive(&o, lookup_commit(head),
 709                                 remoteheads->item, reversed, &result);
 710                 if (active_cache_changed &&
 711                                 (write_cache(index_fd, active_cache, active_nr) ||
 712                                  commit_locked_index(lock)))
 713                         die (_("unable to write %s"), get_index_file());
 714                 rollback_lock_file(lock);
 715                 return clean ? 0 : 1;
 716         } else {
 717                 return try_merge_command(strategy, xopts_nr, xopts,
 718                                                 common, head_arg, remoteheads);
 719         }
 720 }
 721
 722 static void count_diff_files(struct diff_queue_struct *q,
 723                              struct diff_options *opt, void *data)
 724 {
 725         int *count = data;
 726
 727         (*count) += q->nr;
 728 }
 729
 730 static int count_unmerged_entries(void)
 731 {
 732         int i, ret = 0;
 733
 734         for (i = 0; i < active_nr; i++)
 735                 if (ce_stage(active_cache[i]))
 736                         ret++;
 737
 738         return ret;
 739 }
 740
 741 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 742 {
 743         struct tree *trees[MAX_UNPACK_TREES];
 744         struct unpack_trees_options opts;
 745         struct tree_desc t[MAX_UNPACK_TREES];
 746         int i, fd, nr_trees = 0;
 747         struct dir_struct dir;
 748         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 749
 750         refresh_cache(REFRESH_QUIET);
 751
 752         fd = hold_locked_index(lock_file, 1);
 753
 754         memset(&trees, 0, sizeof(trees));
 755         memset(&opts, 0, sizeof(opts));
 756         memset(&t, 0, sizeof(t));
 757         memset(&dir, 0, sizeof(dir));
 758         dir.flags |= DIR_SHOW_IGNORED;
 759         dir.exclude_per_dir = ".gitignore";
 760         opts.dir = &dir;
 761
 762         opts.head_idx = 1;
 763         opts.src_index = &the_index;
 764         opts.dst_index = &the_index;
 765         opts.update = 1;
 766         opts.verbose_update = 1;
 767         opts.merge = 1;
 768         opts.fn = twoway_merge;
 769         setup_unpack_trees_porcelain(&opts, "merge");
 770
 771         trees[nr_trees] = parse_tree_indirect(head);
 772         if (!trees[nr_trees++])
 773                 return -1;
 774         trees[nr_trees] = parse_tree_indirect(remote);
 775         if (!trees[nr_trees++])
 776                 return -1;
 777         for (i = 0; i < nr_trees; i++) {
 778                 parse_tree(trees[i]);
 779                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 780         }
 781         if (unpack_trees(nr_trees, t, &opts))
 782                 return -1;
 783         if (write_cache(fd, active_cache, active_nr) ||
 784                 commit_locked_index(lock_file))
 785                 die(_("unable to write new index file"));
 786         return 0;
 787 }
 788
 789 static void split_merge_strategies(const char *string, struct strategy **list,
 790                                    int *nr, int *alloc)
 791 {
 792         char *p, *q, *buf;
 793
 794         if (!string)
 795                 return;
 796
 797         buf = xstrdup(string);
 798         q = buf;
 799         for (;;) {
 800                 p = strchr(q, ' ');
 801                 if (!p) {
 802                         ALLOC_GROW(*list, *nr + 1, *alloc);
 803                         (*list)[(*nr)++].name = xstrdup(q);
 804                         free(buf);
 805                         return;
 806                 } else {
 807                         *p = '\0';
 808                         ALLOC_GROW(*list, *nr + 1, *alloc);
 809                         (*list)[(*nr)++].name = xstrdup(q);
 810                         q = ++p;
 811                 }
 812         }
 813 }
 814
 815 static void add_strategies(const char *string, unsigned attr)
 816 {
 817         struct strategy *list = NULL;
 818         int list_alloc = 0, list_nr = 0, i;
 819
 820         memset(&list, 0, sizeof(list));
 821         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 822         if (list) {
 823                 for (i = 0; i < list_nr; i++)
 824                         append_strategy(get_strategy(list[i].name));
 825                 return;
 826         }
 827         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 828                 if (all_strategy[i].attr & attr)
 829                         append_strategy(&all_strategy[i]);
 830
 831 }
 832
 833 static void write_merge_msg(void)
 834 {
 835         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 836         if (fd < 0)
 837                 die_errno(_("Could not open '%s' for writing"),
 838                           git_path("MERGE_MSG"));
 839         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 840                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 841         close(fd);
 842 }
 843
 844 static void read_merge_msg(void)
 845 {
 846         strbuf_reset(&merge_msg);
 847         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 848                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 849 }
 850
 851 static void run_prepare_commit_msg(void)
 852 {
 853         write_merge_msg();
 854         run_hook(get_index_file(), "prepare-commit-msg",
 855                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 856         read_merge_msg();
 857 }
 858
 859 static int merge_trivial(void)
 860 {
 861         unsigned char result_tree[20], result_commit[20];
 862         struct commit_list *parent = xmalloc(sizeof(*parent));
 863
 864         write_tree_trivial(result_tree);
 865         printf(_("Wonderful.\n"));
 866         parent->item = lookup_commit(head);
 867         parent->next = xmalloc(sizeof(*parent->next));
 868         parent->next->item = remoteheads->item;
 869         parent->next->next = NULL;
 870         run_prepare_commit_msg();
 871         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 872         finish(result_commit, "In-index merge");
 873         drop_save();
 874         return 0;
 875 }
 876
 877 static int finish_automerge(struct commit_list *common,
 878                             unsigned char *result_tree,
 879                             const char *wt_strategy)
 880 {
 881         struct commit_list *parents = NULL, *j;
 882         struct strbuf buf = STRBUF_INIT;
 883         unsigned char result_commit[20];
 884
 885         free_commit_list(common);
 886         if (allow_fast_forward) {
 887                 parents = remoteheads;
 888                 commit_list_insert(lookup_commit(head), &parents);
 889                 parents = reduce_heads(parents);
 890         } else {
 891                 struct commit_list **pptr = &parents;
 892
 893                 pptr = &commit_list_insert(lookup_commit(head),
 894                                 pptr)->next;
 895                 for (j = remoteheads; j; j = j->next)
 896                         pptr = &commit_list_insert(j->item, pptr)->next;
 897         }
 898         free_commit_list(remoteheads);
 899         strbuf_addch(&merge_msg, '\n');
 900         run_prepare_commit_msg();
 901         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 902         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 903         finish(result_commit, buf.buf);
 904         strbuf_release(&buf);
 905         drop_save();
 906         return 0;
 907 }
 908
 909 static int suggest_conflicts(int renormalizing)
 910 {
 911         FILE *fp;
 912         int pos;
 913
 914         fp = fopen(git_path("MERGE_MSG"), "a");
 915         if (!fp)
 916                 die_errno(_("Could not open '%s' for writing"),
 917                           git_path("MERGE_MSG"));
 918         fprintf(fp, "\nConflicts:\n");
 919         for (pos = 0; pos < active_nr; pos++) {
 920                 struct cache_entry *ce = active_cache[pos];
 921
 922                 if (ce_stage(ce)) {
 923                         fprintf(fp, "\t%s\n", ce->name);
 924                         while (pos + 1 < active_nr &&
 925                                         !strcmp(ce->name,
 926                                                 active_cache[pos + 1]->name))
 927                                 pos++;
 928                 }
 929         }
 930         fclose(fp);
 931         rerere(allow_rerere_auto);
 932         printf(_("Automatic merge failed; "
 933                         "fix conflicts and then commit the result.\n"));
 934         return 1;
 935 }
 936
 937 static struct commit *is_old_style_invocation(int argc, const char **argv)
 938 {
 939         struct commit *second_token = NULL;
 940         if (argc > 2) {
 941                 unsigned char second_sha1[20];
 942
 943                 if (get_sha1(argv[1], second_sha1))
 944                         return NULL;
 945                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 946                 if (!second_token)
 947                         die(_("'%s' is not a commit"), argv[1]);
 948                 if (hashcmp(second_token->object.sha1, head))
 949                         return NULL;
 950         }
 951         return second_token;
 952 }
 953
 954 static int evaluate_result(void)
 955 {
 956         int cnt = 0;
 957         struct rev_info rev;
 958
 959         /* Check how many files differ. */
 960         init_revisions(&rev, "");
 961         setup_revisions(0, NULL, &rev, NULL);
 962         rev.diffopt.output_format |=
 963                 DIFF_FORMAT_CALLBACK;
 964         rev.diffopt.format_callback = count_diff_files;
 965         rev.diffopt.format_callback_data = &cnt;
 966         run_diff_files(&rev, 0);
 967
 968         /*
 969          * Check how many unmerged entries are
 970          * there.
 971          */
 972         cnt += count_unmerged_entries();
 973
 974         return cnt;
 975 }
 976
 977 /*
 978  * Pretend as if the user told us to merge with the tracking
 979  * branch we have for the upstream of the current branch
 980  */
 981 static int setup_with_upstream(const char ***argv)
 982 {
 983         struct branch *branch = branch_get(NULL);
 984         int i;
 985         const char **args;
 986
 987         if (!branch)
 988                 die(_("No current branch."));
 989         if (!branch->remote)
 990                 die(_("No remote for the current branch."));
 991         if (!branch->merge_nr)
 992                 die(_("No default upstream defined for the current branch."));
 993
 994         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 995         for (i = 0; i < branch->merge_nr; i++) {
 996                 if (!branch->merge[i]->dst)
 997                         die(_("No remote tracking branch for %s from %s"),
 998                             branch->merge[i]->src, branch->remote_name);
 999                 args[i] = branch->merge[i]->dst;
1000         }
1001         args[i] = NULL;
1002         *argv = args;
1003         return i;
1004 }
1005
1006 int cmd_merge(int argc, const char **argv, const char *prefix)
1007 {
1008         unsigned char result_tree[20];
1009         struct strbuf buf = STRBUF_INIT;
1010         const char *head_arg;
1011         int flag, head_invalid = 0, i;
1012         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1013         struct commit_list *common = NULL;
1014         const char *best_strategy = NULL, *wt_strategy = NULL;
1015         struct commit_list **remotes = &remoteheads;
1016
1017         if (argc == 2 && !strcmp(argv[1], "-h"))
1018                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1019
1020         /*
1021          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1022          * current branch.
1023          */
1024         branch = resolve_ref("HEAD", head, 0, &flag);
1025         if (branch && !prefixcmp(branch, "refs/heads/"))
1026                 branch += 11;
1027         if (is_null_sha1(head))
1028                 head_invalid = 1;
1029
1030         git_config(git_merge_config, NULL);
1031
1032         if (branch_mergeoptions)
1033                 parse_branch_merge_options(branch_mergeoptions);
1034         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1035                         builtin_merge_usage, 0);
1036         if (shortlog_len < 0)
1037                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1038
1039         if (verbosity < 0 && show_progress == -1)
1040                 show_progress = 0;
1041
1042         if (abort_current_merge) {
1043                 int nargc = 2;
1044                 const char *nargv[] = {"reset", "--merge", NULL};
1045
1046                 if (!file_exists(git_path("MERGE_HEAD")))
1047                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1048
1049                 /* Invoke 'git reset --merge' */
1050                 return cmd_reset(nargc, nargv, prefix);
1051         }
1052
1053         if (read_cache_unmerged())
1054                 die_resolve_conflict("merge");
1055
1056         if (file_exists(git_path("MERGE_HEAD"))) {
1057                 /*
1058                  * There is no unmerged entry, don't advise 'git
1059                  * add/rm <file>', just 'git commit'.
1060                  */
1061                 if (advice_resolve_conflict)
1062                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1063                                   "Please, commit your changes before you can merge."));
1064                 else
1065                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1066         }
1067         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1068                 if (advice_resolve_conflict)
1069                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1070                             "Please, commit your changes before you can merge."));
1071                 else
1072                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1073         }
1074         resolve_undo_clear();
1075
1076         if (verbosity < 0)
1077                 show_diffstat = 0;
1078
1079         if (squash) {
1080                 if (!allow_fast_forward)
1081                         die(_("You cannot combine --squash with --no-ff."));
1082                 option_commit = 0;
1083         }
1084
1085         if (!allow_fast_forward && fast_forward_only)
1086                 die(_("You cannot combine --no-ff with --ff-only."));
1087
1088         if (!abort_current_merge) {
1089                 if (!argc && default_to_upstream)
1090                         argc = setup_with_upstream(&argv);
1091                 else if (argc == 1 && !strcmp(argv[0], "-"))
1092                         argv[0] = "@{-1}";
1093         }
1094         if (!argc)
1095                 usage_with_options(builtin_merge_usage,
1096                         builtin_merge_options);
1097
1098         /*
1099          * This could be traditional "merge <msg> HEAD <commit>..."  and
1100          * the way we can tell it is to see if the second token is HEAD,
1101          * but some people might have misused the interface and used a
1102          * committish that is the same as HEAD there instead.
1103          * Traditional format never would have "-m" so it is an
1104          * additional safety measure to check for it.
1105          */
1106
1107         if (!have_message && is_old_style_invocation(argc, argv)) {
1108                 strbuf_addstr(&merge_msg, argv[0]);
1109                 head_arg = argv[1];
1110                 argv += 2;
1111                 argc -= 2;
1112         } else if (head_invalid) {
1113                 struct object *remote_head;
1114                 /*
1115                  * If the merged head is a valid one there is no reason
1116                  * to forbid "git merge" into a branch yet to be born.
1117                  * We do the same for "git pull".
1118                  */
1119                 if (argc != 1)
1120                         die(_("Can merge only exactly one commit into "
1121                                 "empty head"));
1122                 if (squash)
1123                         die(_("Squash commit into empty head not supported yet"));
1124                 if (!allow_fast_forward)
1125                         die(_("Non-fast-forward commit does not make sense into "
1126                             "an empty head"));
1127                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1128                 if (!remote_head)
1129                         die(_("%s - not something we can merge"), argv[0]);
1130                 read_empty(remote_head->sha1, 0);
1131                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1132                                 DIE_ON_ERR);
1133                 return 0;
1134         } else {
1135                 struct strbuf merge_names = STRBUF_INIT;
1136
1137                 /* We are invoked directly as the first-class UI. */
1138                 head_arg = "HEAD";
1139
1140                 /*
1141                  * All the rest are the commits being merged;
1142                  * prepare the standard merge summary message to
1143                  * be appended to the given message.  If remote
1144                  * is invalid we will die later in the common
1145                  * codepath so we discard the error in this
1146                  * loop.
1147                  */
1148                 for (i = 0; i < argc; i++)
1149                         merge_name(argv[i], &merge_names);
1150
1151                 if (!have_message || shortlog_len) {
1152                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1153                                       shortlog_len);
1154                         if (merge_msg.len)
1155                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1156                 }
1157         }
1158
1159         if (head_invalid || !argc)
1160                 usage_with_options(builtin_merge_usage,
1161                         builtin_merge_options);
1162
1163         strbuf_addstr(&buf, "merge");
1164         for (i = 0; i < argc; i++)
1165                 strbuf_addf(&buf, " %s", argv[i]);
1166         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1167         strbuf_reset(&buf);
1168
1169         for (i = 0; i < argc; i++) {
1170                 struct object *o;
1171                 struct commit *commit;
1172
1173                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1174                 if (!o)
1175                         die(_("%s - not something we can merge"), argv[i]);
1176                 commit = lookup_commit(o->sha1);
1177                 commit->util = (void *)argv[i];
1178                 remotes = &commit_list_insert(commit, remotes)->next;
1179
1180                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1181                 setenv(buf.buf, argv[i], 1);
1182                 strbuf_reset(&buf);
1183         }
1184
1185         if (!use_strategies) {
1186                 if (!remoteheads->next)
1187                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1188                 else
1189                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1190         }
1191
1192         for (i = 0; i < use_strategies_nr; i++) {
1193                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1194                         allow_fast_forward = 0;
1195                 if (use_strategies[i]->attr & NO_TRIVIAL)
1196                         allow_trivial = 0;
1197         }
1198
1199         if (!remoteheads->next)
1200                 common = get_merge_bases(lookup_commit(head),
1201                                 remoteheads->item, 1);
1202         else {
1203                 struct commit_list *list = remoteheads;
1204                 commit_list_insert(lookup_commit(head), &list);
1205                 common = get_octopus_merge_bases(list);
1206                 free(list);
1207         }
1208
1209         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1210                 DIE_ON_ERR);
1211
1212         if (!common)
1213                 ; /* No common ancestors found. We need a real merge. */
1214         else if (!remoteheads->next && !common->next &&
1215                         common->item == remoteheads->item) {
1216                 /*
1217                  * If head can reach all the merge then we are up to date.
1218                  * but first the most common case of merging one remote.
1219                  */
1220                 finish_up_to_date("Already up-to-date.");
1221                 return 0;
1222         } else if (allow_fast_forward && !remoteheads->next &&
1223                         !common->next &&
1224                         !hashcmp(common->item->object.sha1, head)) {
1225                 /* Again the most common case of merging one remote. */
1226                 struct strbuf msg = STRBUF_INIT;
1227                 struct object *o;
1228                 char hex[41];
1229
1230                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1231
1232                 if (verbosity >= 0)
1233                         printf(_("Updating %s..%s\n"),
1234                                 hex,
1235                                 find_unique_abbrev(remoteheads->item->object.sha1,
1236                                 DEFAULT_ABBREV));
1237                 strbuf_addstr(&msg, "Fast-forward");
1238                 if (have_message)
1239                         strbuf_addstr(&msg,
1240                                 " (no commit created; -m option ignored)");
1241                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1242                         0, NULL, OBJ_COMMIT);
1243                 if (!o)
1244                         return 1;
1245
1246                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1247                         return 1;
1248
1249                 finish(o->sha1, msg.buf);
1250                 drop_save();
1251                 return 0;
1252         } else if (!remoteheads->next && common->next)
1253                 ;
1254                 /*
1255                  * We are not doing octopus and not fast-forward.  Need
1256                  * a real merge.
1257                  */
1258         else if (!remoteheads->next && !common->next && option_commit) {
1259                 /*
1260                  * We are not doing octopus, not fast-forward, and have
1261                  * only one common.
1262                  */
1263                 refresh_cache(REFRESH_QUIET);
1264                 if (allow_trivial && !fast_forward_only) {
1265                         /* See if it is really trivial. */
1266                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1267                         printf(_("Trying really trivial in-index merge...\n"));
1268                         if (!read_tree_trivial(common->item->object.sha1,
1269                                         head, remoteheads->item->object.sha1))
1270                                 return merge_trivial();
1271                         printf(_("Nope.\n"));
1272                 }
1273         } else {
1274                 /*
1275                  * An octopus.  If we can reach all the remote we are up
1276                  * to date.
1277                  */
1278                 int up_to_date = 1;
1279                 struct commit_list *j;
1280
1281                 for (j = remoteheads; j; j = j->next) {
1282                         struct commit_list *common_one;
1283
1284                         /*
1285                          * Here we *have* to calculate the individual
1286                          * merge_bases again, otherwise "git merge HEAD^
1287                          * HEAD^^" would be missed.
1288                          */
1289                         common_one = get_merge_bases(lookup_commit(head),
1290                                 j->item, 1);
1291                         if (hashcmp(common_one->item->object.sha1,
1292                                 j->item->object.sha1)) {
1293                                 up_to_date = 0;
1294                                 break;
1295                         }
1296                 }
1297                 if (up_to_date) {
1298                         finish_up_to_date("Already up-to-date. Yeeah!");
1299                         return 0;
1300                 }
1301         }
1302
1303         if (fast_forward_only)
1304                 die(_("Not possible to fast-forward, aborting."));
1305
1306         /* We are going to make a new commit. */
1307         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1308
1309         /*
1310          * At this point, we need a real merge.  No matter what strategy
1311          * we use, it would operate on the index, possibly affecting the
1312          * working tree, and when resolved cleanly, have the desired
1313          * tree in the index -- this means that the index must be in
1314          * sync with the head commit.  The strategies are responsible
1315          * to ensure this.
1316          */
1317         if (use_strategies_nr != 1) {
1318                 /*
1319                  * Stash away the local changes so that we can try more
1320                  * than one.
1321                  */
1322                 save_state();
1323         } else {
1324                 memcpy(stash, null_sha1, 20);
1325         }
1326
1327         for (i = 0; i < use_strategies_nr; i++) {
1328                 int ret;
1329                 if (i) {
1330                         printf(_("Rewinding the tree to pristine...\n"));
1331                         restore_state();
1332                 }
1333                 if (use_strategies_nr != 1)
1334                         printf(_("Trying merge strategy %s...\n"),
1335                                 use_strategies[i]->name);
1336                 /*
1337                  * Remember which strategy left the state in the working
1338                  * tree.
1339                  */
1340                 wt_strategy = use_strategies[i]->name;
1341
1342                 ret = try_merge_strategy(use_strategies[i]->name,
1343                         common, head_arg);
1344                 if (!option_commit && !ret) {
1345                         merge_was_ok = 1;
1346                         /*
1347                          * This is necessary here just to avoid writing
1348                          * the tree, but later we will *not* exit with
1349                          * status code 1 because merge_was_ok is set.
1350                          */
1351                         ret = 1;
1352                 }
1353
1354                 if (ret) {
1355                         /*
1356                          * The backend exits with 1 when conflicts are
1357                          * left to be resolved, with 2 when it does not
1358                          * handle the given merge at all.
1359                          */
1360                         if (ret == 1) {
1361                                 int cnt = evaluate_result();
1362
1363                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1364                                         best_strategy = use_strategies[i]->name;
1365                                         best_cnt = cnt;
1366                                 }
1367                         }
1368                         if (merge_was_ok)
1369                                 break;
1370                         else
1371                                 continue;
1372                 }
1373
1374                 /* Automerge succeeded. */
1375                 write_tree_trivial(result_tree);
1376                 automerge_was_ok = 1;
1377                 break;
1378         }
1379
1380         /*
1381          * If we have a resulting tree, that means the strategy module
1382          * auto resolved the merge cleanly.
1383          */
1384         if (automerge_was_ok)
1385                 return finish_automerge(common, result_tree, wt_strategy);
1386
1387         /*
1388          * Pick the result from the best strategy and have the user fix
1389          * it up.
1390          */
1391         if (!best_strategy) {
1392                 restore_state();
1393                 if (use_strategies_nr > 1)
1394                         fprintf(stderr,
1395                                 _("No merge strategy handled the merge.\n"));
1396                 else
1397                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1398                                 use_strategies[0]->name);
1399                 return 2;
1400         } else if (best_strategy == wt_strategy)
1401                 ; /* We already have its result in the working tree. */
1402         else {
1403                 printf(_("Rewinding the tree to pristine...\n"));
1404                 restore_state();
1405                 printf(_("Using the %s to prepare resolving by hand.\n"),
1406                         best_strategy);
1407                 try_merge_strategy(best_strategy, common, head_arg);
1408         }
1409
1410         if (squash)
1411                 finish(NULL, NULL);
1412         else {
1413                 int fd;
1414                 struct commit_list *j;
1415
1416                 for (j = remoteheads; j; j = j->next)
1417                         strbuf_addf(&buf, "%s\n",
1418                                 sha1_to_hex(j->item->object.sha1));
1419                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1420                 if (fd < 0)
1421                         die_errno(_("Could not open '%s' for writing"),
1422                                   git_path("MERGE_HEAD"));
1423                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1424                         die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1425                 close(fd);
1426                 strbuf_addch(&merge_msg, '\n');
1427                 write_merge_msg();
1428                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1429                 if (fd < 0)
1430                         die_errno(_("Could not open '%s' for writing"),
1431                                   git_path("MERGE_MODE"));
1432                 strbuf_reset(&buf);
1433                 if (!allow_fast_forward)
1434                         strbuf_addf(&buf, "no-ff");
1435                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1436                         die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1437                 close(fd);
1438         }
1439
1440         if (merge_was_ok) {
1441                 fprintf(stderr, _("Automatic merge went well; "
1442                         "stopped before committing as requested\n"));
1443                 return 0;
1444         } else
1445                 return suggest_conflicts(option_renormalize);
1446 }