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, option_edit;
  50 static int allow_trivial = 1, have_message;
  51 static struct strbuf merge_msg;
  52 static struct commit_list *remoteheads;
  53 static struct strategy **use_strategies;
  54 static size_t use_strategies_nr, use_strategies_alloc;
  55 static const char **xopts;
  56 static size_t xopts_nr, xopts_alloc;
  57 static const char *branch;
  58 static char *branch_mergeoptions;
  59 static int option_renormalize;
  60 static int verbosity;
  61 static int allow_rerere_auto;
  62 static int abort_current_merge;
  63 static int show_progress = -1;
  64 static int default_to_upstream;
  65
  66 static struct strategy all_strategy[] = {
  67         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  68         { "octopus",    DEFAULT_OCTOPUS },
  69         { "resolve",    0 },
  70         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  71         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  72 };
  73
  74 static const char *pull_twohead, *pull_octopus;
  75
  76 static int option_parse_message(const struct option *opt,
  77                                 const char *arg, int unset)
  78 {
  79         struct strbuf *buf = opt->value;
  80
  81         if (unset)
  82                 strbuf_setlen(buf, 0);
  83         else if (arg) {
  84                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  85                 have_message = 1;
  86         } else
  87                 return error(_("switch `m' requires a value"));
  88         return 0;
  89 }
  90
  91 static struct strategy *get_strategy(const char *name)
  92 {
  93         int i;
  94         struct strategy *ret;
  95         static struct cmdnames main_cmds, other_cmds;
  96         static int loaded;
  97
  98         if (!name)
  99                 return NULL;
 100
 101         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 102                 if (!strcmp(name, all_strategy[i].name))
 103                         return &all_strategy[i];
 104
 105         if (!loaded) {
 106                 struct cmdnames not_strategies;
 107                 loaded = 1;
 108
 109                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 110                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 111                 for (i = 0; i < main_cmds.cnt; i++) {
 112                         int j, found = 0;
 113                         struct cmdname *ent = main_cmds.names[i];
 114                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 115                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 116                                                 && !all_strategy[j].name[ent->len])
 117                                         found = 1;
 118                         if (!found)
 119                                 add_cmdname(&not_strategies, ent->name, ent->len);
 120                 }
 121                 exclude_cmds(&main_cmds, &not_strategies);
 122         }
 123         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 124                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 125                 fprintf(stderr, _("Available strategies are:"));
 126                 for (i = 0; i < main_cmds.cnt; i++)
 127                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 128                 fprintf(stderr, ".\n");
 129                 if (other_cmds.cnt) {
 130                         fprintf(stderr, _("Available custom strategies are:"));
 131                         for (i = 0; i < other_cmds.cnt; i++)
 132                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 133                         fprintf(stderr, ".\n");
 134                 }
 135                 exit(1);
 136         }
 137
 138         ret = xcalloc(1, sizeof(struct strategy));
 139         ret->name = xstrdup(name);
 140         ret->attr = NO_TRIVIAL;
 141         return ret;
 142 }
 143
 144 static void append_strategy(struct strategy *s)
 145 {
 146         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 147         use_strategies[use_strategies_nr++] = s;
 148 }
 149
 150 static int option_parse_strategy(const struct option *opt,
 151                                  const char *name, int unset)
 152 {
 153         if (unset)
 154                 return 0;
 155
 156         append_strategy(get_strategy(name));
 157         return 0;
 158 }
 159
 160 static int option_parse_x(const struct option *opt,
 161                           const char *arg, int unset)
 162 {
 163         if (unset)
 164                 return 0;
 165
 166         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 167         xopts[xopts_nr++] = xstrdup(arg);
 168         return 0;
 169 }
 170
 171 static int option_parse_n(const struct option *opt,
 172                           const char *arg, int unset)
 173 {
 174         show_diffstat = unset;
 175         return 0;
 176 }
 177
 178 static struct option builtin_merge_options[] = {
 179         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 180                 "do not show a diffstat at the end of the merge",
 181                 PARSE_OPT_NOARG, option_parse_n },
 182         OPT_BOOLEAN(0, "stat", &show_diffstat,
 183                 "show a diffstat at the end of the merge"),
 184         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 185         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 186           "add (at most <n>) entries from shortlog to merge commit message",
 187           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 188         OPT_BOOLEAN(0, "squash", &squash,
 189                 "create a single commit instead of doing a merge"),
 190         OPT_BOOLEAN(0, "commit", &option_commit,
 191                 "perform a commit if the merge succeeds (default)"),
 192         OPT_BOOLEAN('e', "edit", &option_edit,
 193                 "edit message before committing"),
 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 int save_state(unsigned char *stash)
 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)          /* no changes */
 241                 return -1;
 242         strbuf_setlen(&buffer, buffer.len-1);
 243         if (get_sha1(buffer.buf, stash))
 244                 die(_("not a valid object: %s"), buffer.buf);
 245         return 0;
 246 }
 247
 248 static void read_empty(unsigned const char *sha1, int verbose)
 249 {
 250         int i = 0;
 251         const char *args[7];
 252
 253         args[i++] = "read-tree";
 254         if (verbose)
 255                 args[i++] = "-v";
 256         args[i++] = "-m";
 257         args[i++] = "-u";
 258         args[i++] = EMPTY_TREE_SHA1_HEX;
 259         args[i++] = sha1_to_hex(sha1);
 260         args[i] = NULL;
 261
 262         if (run_command_v_opt(args, RUN_GIT_CMD))
 263                 die(_("read-tree failed"));
 264 }
 265
 266 static void reset_hard(unsigned const char *sha1, int verbose)
 267 {
 268         int i = 0;
 269         const char *args[6];
 270
 271         args[i++] = "read-tree";
 272         if (verbose)
 273                 args[i++] = "-v";
 274         args[i++] = "--reset";
 275         args[i++] = "-u";
 276         args[i++] = sha1_to_hex(sha1);
 277         args[i] = NULL;
 278
 279         if (run_command_v_opt(args, RUN_GIT_CMD))
 280                 die(_("read-tree failed"));
 281 }
 282
 283 static void restore_state(const unsigned char *head,
 284                           const unsigned char *stash)
 285 {
 286         struct strbuf sb = STRBUF_INIT;
 287         const char *args[] = { "stash", "apply", NULL, NULL };
 288
 289         if (is_null_sha1(stash))
 290                 return;
 291
 292         reset_hard(head, 1);
 293
 294         args[2] = sha1_to_hex(stash);
 295
 296         /*
 297          * It is OK to ignore error here, for example when there was
 298          * nothing to restore.
 299          */
 300         run_command_v_opt(args, RUN_GIT_CMD);
 301
 302         strbuf_release(&sb);
 303         refresh_cache(REFRESH_QUIET);
 304 }
 305
 306 /* This is called when no merge was necessary. */
 307 static void finish_up_to_date(const char *msg)
 308 {
 309         if (verbosity >= 0)
 310                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 311         drop_save();
 312 }
 313
 314 static void squash_message(struct commit *commit)
 315 {
 316         struct rev_info rev;
 317         struct strbuf out = STRBUF_INIT;
 318         struct commit_list *j;
 319         int fd;
 320         struct pretty_print_context ctx = {0};
 321
 322         printf(_("Squash commit -- not updating HEAD\n"));
 323         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 324         if (fd < 0)
 325                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 326
 327         init_revisions(&rev, NULL);
 328         rev.ignore_merges = 1;
 329         rev.commit_format = CMIT_FMT_MEDIUM;
 330
 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(struct commit *head_commit,
 360                    const unsigned char *new_head, const char *msg)
 361 {
 362         struct strbuf reflog_message = STRBUF_INIT;
 363         const unsigned char *head = head_commit->object.sha1;
 364
 365         if (!msg)
 366                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 367         else {
 368                 if (verbosity >= 0)
 369                         printf("%s\n", msg);
 370                 strbuf_addf(&reflog_message, "%s: %s",
 371                         getenv("GIT_REFLOG_ACTION"), msg);
 372         }
 373         if (squash) {
 374                 squash_message(head_commit);
 375         } else {
 376                 if (verbosity >= 0 && !merge_msg.len)
 377                         printf(_("No merge message -- not updating HEAD\n"));
 378                 else {
 379                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 380                         update_ref(reflog_message.buf, "HEAD",
 381                                 new_head, head, 0,
 382                                 DIE_ON_ERR);
 383                         /*
 384                          * We ignore errors in 'gc --auto', since the
 385                          * user should see them.
 386                          */
 387                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 388                 }
 389         }
 390         if (new_head && show_diffstat) {
 391                 struct diff_options opts;
 392                 diff_setup(&opts);
 393                 opts.output_format |=
 394                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 395                 opts.detect_rename = DIFF_DETECT_RENAME;
 396                 if (diff_setup_done(&opts) < 0)
 397                         die(_("diff_setup_done failed"));
 398                 diff_tree_sha1(head, new_head, "", &opts);
 399                 diffcore_std(&opts);
 400                 diff_flush(&opts);
 401         }
 402
 403         /* Run a post-merge hook */
 404         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 405
 406         strbuf_release(&reflog_message);
 407 }
 408
 409 static struct object *want_commit(const char *name)
 410 {
 411         struct object *obj;
 412         unsigned char sha1[20];
 413         if (get_sha1(name, sha1))
 414                 return NULL;
 415         obj = parse_object(sha1);
 416         return peel_to_type(name, 0, obj, OBJ_COMMIT);
 417 }
 418
 419 /* Get the name for the merge commit's message. */
 420 static void merge_name(const char *remote, struct strbuf *msg)
 421 {
 422         struct object *remote_head;
 423         unsigned char branch_head[20], buf_sha[20];
 424         struct strbuf buf = STRBUF_INIT;
 425         struct strbuf bname = STRBUF_INIT;
 426         const char *ptr;
 427         char *found_ref;
 428         int len, early;
 429
 430         strbuf_branchname(&bname, remote);
 431         remote = bname.buf;
 432
 433         memset(branch_head, 0, sizeof(branch_head));
 434         remote_head = want_commit(remote);
 435         if (!remote_head)
 436                 die(_("'%s' does not point to a commit"), remote);
 437
 438         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 439                 if (!prefixcmp(found_ref, "refs/heads/")) {
 440                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 441                                     sha1_to_hex(branch_head), remote);
 442                         goto cleanup;
 443                 }
 444                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 445                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 446                                     sha1_to_hex(branch_head), remote);
 447                         goto cleanup;
 448                 }
 449         }
 450
 451         /* See if remote matches <name>^^^.. or <name>~<number> */
 452         for (len = 0, ptr = remote + strlen(remote);
 453              remote < ptr && ptr[-1] == '^';
 454              ptr--)
 455                 len++;
 456         if (len)
 457                 early = 1;
 458         else {
 459                 early = 0;
 460                 ptr = strrchr(remote, '~');
 461                 if (ptr) {
 462                         int seen_nonzero = 0;
 463
 464                         len++; /* count ~ */
 465                         while (*++ptr && isdigit(*ptr)) {
 466                                 seen_nonzero |= (*ptr != '0');
 467                                 len++;
 468                         }
 469                         if (*ptr)
 470                                 len = 0; /* not ...~<number> */
 471                         else if (seen_nonzero)
 472                                 early = 1;
 473                         else if (len == 1)
 474                                 early = 1; /* "name~" is "name~1"! */
 475                 }
 476         }
 477         if (len) {
 478                 struct strbuf truname = STRBUF_INIT;
 479                 strbuf_addstr(&truname, "refs/heads/");
 480                 strbuf_addstr(&truname, remote);
 481                 strbuf_setlen(&truname, truname.len - len);
 482                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 483                         strbuf_addf(msg,
 484                                     "%s\t\tbranch '%s'%s of .\n",
 485                                     sha1_to_hex(remote_head->sha1),
 486                                     truname.buf + 11,
 487                                     (early ? " (early part)" : ""));
 488                         strbuf_release(&truname);
 489                         goto cleanup;
 490                 }
 491         }
 492
 493         if (!strcmp(remote, "FETCH_HEAD") &&
 494                         !access(git_path("FETCH_HEAD"), R_OK)) {
 495                 FILE *fp;
 496                 struct strbuf line = STRBUF_INIT;
 497                 char *ptr;
 498
 499                 fp = fopen(git_path("FETCH_HEAD"), "r");
 500                 if (!fp)
 501                         die_errno(_("could not open '%s' for reading"),
 502                                   git_path("FETCH_HEAD"));
 503                 strbuf_getline(&line, fp, '\n');
 504                 fclose(fp);
 505                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 506                 if (ptr)
 507                         strbuf_remove(&line, ptr-line.buf+1, 13);
 508                 strbuf_addbuf(msg, &line);
 509                 strbuf_release(&line);
 510                 goto cleanup;
 511         }
 512         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 513                 sha1_to_hex(remote_head->sha1), remote);
 514 cleanup:
 515         strbuf_release(&buf);
 516         strbuf_release(&bname);
 517 }
 518
 519 static void parse_branch_merge_options(char *bmo)
 520 {
 521         const char **argv;
 522         int argc;
 523
 524         if (!bmo)
 525                 return;
 526         argc = split_cmdline(bmo, &argv);
 527         if (argc < 0)
 528                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 529                     split_cmdline_strerror(argc));
 530         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 531         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 532         argc++;
 533         argv[0] = "branch.*.mergeoptions";
 534         parse_options(argc, argv, NULL, builtin_merge_options,
 535                       builtin_merge_usage, 0);
 536         free(argv);
 537 }
 538
 539 static int git_merge_config(const char *k, const char *v, void *cb)
 540 {
 541         if (branch && !prefixcmp(k, "branch.") &&
 542                 !prefixcmp(k + 7, branch) &&
 543                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 544                 free(branch_mergeoptions);
 545                 branch_mergeoptions = xstrdup(v);
 546                 return 0;
 547         }
 548
 549         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 550                 show_diffstat = git_config_bool(k, v);
 551         else if (!strcmp(k, "pull.twohead"))
 552                 return git_config_string(&pull_twohead, k, v);
 553         else if (!strcmp(k, "pull.octopus"))
 554                 return git_config_string(&pull_octopus, k, v);
 555         else if (!strcmp(k, "merge.renormalize"))
 556                 option_renormalize = git_config_bool(k, v);
 557         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 558                 int is_bool;
 559                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 560                 if (!is_bool && shortlog_len < 0)
 561                         return error(_("%s: negative length %s"), k, v);
 562                 if (is_bool && shortlog_len)
 563                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 564                 return 0;
 565         } else if (!strcmp(k, "merge.ff")) {
 566                 int boolval = git_config_maybe_bool(k, v);
 567                 if (0 <= boolval) {
 568                         allow_fast_forward = boolval;
 569                 } else if (v && !strcmp(v, "only")) {
 570                         allow_fast_forward = 1;
 571                         fast_forward_only = 1;
 572                 } /* do not barf on values from future versions of git */
 573                 return 0;
 574         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 575                 default_to_upstream = git_config_bool(k, v);
 576                 return 0;
 577         }
 578         return git_diff_ui_config(k, v, cb);
 579 }
 580
 581 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 582                              unsigned char *one)
 583 {
 584         int i, nr_trees = 0;
 585         struct tree *trees[MAX_UNPACK_TREES];
 586         struct tree_desc t[MAX_UNPACK_TREES];
 587         struct unpack_trees_options opts;
 588
 589         memset(&opts, 0, sizeof(opts));
 590         opts.head_idx = 2;
 591         opts.src_index = &the_index;
 592         opts.dst_index = &the_index;
 593         opts.update = 1;
 594         opts.verbose_update = 1;
 595         opts.trivial_merges_only = 1;
 596         opts.merge = 1;
 597         trees[nr_trees] = parse_tree_indirect(common);
 598         if (!trees[nr_trees++])
 599                 return -1;
 600         trees[nr_trees] = parse_tree_indirect(head);
 601         if (!trees[nr_trees++])
 602                 return -1;
 603         trees[nr_trees] = parse_tree_indirect(one);
 604         if (!trees[nr_trees++])
 605                 return -1;
 606         opts.fn = threeway_merge;
 607         cache_tree_free(&active_cache_tree);
 608         for (i = 0; i < nr_trees; i++) {
 609                 parse_tree(trees[i]);
 610                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 611         }
 612         if (unpack_trees(nr_trees, t, &opts))
 613                 return -1;
 614         return 0;
 615 }
 616
 617 static void write_tree_trivial(unsigned char *sha1)
 618 {
 619         if (write_cache_as_tree(sha1, 0, NULL))
 620                 die(_("git write-tree failed to write a tree"));
 621 }
 622
 623 static const char *merge_argument(struct commit *commit)
 624 {
 625         if (commit)
 626                 return sha1_to_hex(commit->object.sha1);
 627         else
 628                 return EMPTY_TREE_SHA1_HEX;
 629 }
 630
 631 int try_merge_command(const char *strategy, size_t xopts_nr,
 632                       const char **xopts, struct commit_list *common,
 633                       const char *head_arg, struct commit_list *remotes)
 634 {
 635         const char **args;
 636         int i = 0, x = 0, ret;
 637         struct commit_list *j;
 638         struct strbuf buf = STRBUF_INIT;
 639
 640         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 641                         commit_list_count(remotes)) * sizeof(char *));
 642         strbuf_addf(&buf, "merge-%s", strategy);
 643         args[i++] = buf.buf;
 644         for (x = 0; x < xopts_nr; x++) {
 645                 char *s = xmalloc(strlen(xopts[x])+2+1);
 646                 strcpy(s, "--");
 647                 strcpy(s+2, xopts[x]);
 648                 args[i++] = s;
 649         }
 650         for (j = common; j; j = j->next)
 651                 args[i++] = xstrdup(merge_argument(j->item));
 652         args[i++] = "--";
 653         args[i++] = head_arg;
 654         for (j = remotes; j; j = j->next)
 655                 args[i++] = xstrdup(merge_argument(j->item));
 656         args[i] = NULL;
 657         ret = run_command_v_opt(args, RUN_GIT_CMD);
 658         strbuf_release(&buf);
 659         i = 1;
 660         for (x = 0; x < xopts_nr; x++)
 661                 free((void *)args[i++]);
 662         for (j = common; j; j = j->next)
 663                 free((void *)args[i++]);
 664         i += 2;
 665         for (j = remotes; j; j = j->next)
 666                 free((void *)args[i++]);
 667         free(args);
 668         discard_cache();
 669         if (read_cache() < 0)
 670                 die(_("failed to read the cache"));
 671         resolve_undo_clear();
 672
 673         return ret;
 674 }
 675
 676 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 677                               struct commit *head, const char *head_arg)
 678 {
 679         int index_fd;
 680         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 681
 682         index_fd = hold_locked_index(lock, 1);
 683         refresh_cache(REFRESH_QUIET);
 684         if (active_cache_changed &&
 685                         (write_cache(index_fd, active_cache, active_nr) ||
 686                          commit_locked_index(lock)))
 687                 return error(_("Unable to write index."));
 688         rollback_lock_file(lock);
 689
 690         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 691                 int clean, x;
 692                 struct commit *result;
 693                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 694                 int index_fd;
 695                 struct commit_list *reversed = NULL;
 696                 struct merge_options o;
 697                 struct commit_list *j;
 698
 699                 if (remoteheads->next) {
 700                         error(_("Not handling anything other than two heads merge."));
 701                         return 2;
 702                 }
 703
 704                 init_merge_options(&o);
 705                 if (!strcmp(strategy, "subtree"))
 706                         o.subtree_shift = "";
 707
 708                 o.renormalize = option_renormalize;
 709                 o.show_rename_progress =
 710                         show_progress == -1 ? isatty(2) : show_progress;
 711
 712                 for (x = 0; x < xopts_nr; x++)
 713                         if (parse_merge_opt(&o, xopts[x]))
 714                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 715
 716                 o.branch1 = head_arg;
 717                 o.branch2 = remoteheads->item->util;
 718
 719                 for (j = common; j; j = j->next)
 720                         commit_list_insert(j->item, &reversed);
 721
 722                 index_fd = hold_locked_index(lock, 1);
 723                 clean = merge_recursive(&o, head,
 724                                 remoteheads->item, reversed, &result);
 725                 if (active_cache_changed &&
 726                                 (write_cache(index_fd, active_cache, active_nr) ||
 727                                  commit_locked_index(lock)))
 728                         die (_("unable to write %s"), get_index_file());
 729                 rollback_lock_file(lock);
 730                 return clean ? 0 : 1;
 731         } else {
 732                 return try_merge_command(strategy, xopts_nr, xopts,
 733                                                 common, head_arg, remoteheads);
 734         }
 735 }
 736
 737 static void count_diff_files(struct diff_queue_struct *q,
 738                              struct diff_options *opt, void *data)
 739 {
 740         int *count = data;
 741
 742         (*count) += q->nr;
 743 }
 744
 745 static int count_unmerged_entries(void)
 746 {
 747         int i, ret = 0;
 748
 749         for (i = 0; i < active_nr; i++)
 750                 if (ce_stage(active_cache[i]))
 751                         ret++;
 752
 753         return ret;
 754 }
 755
 756 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 757 {
 758         struct tree *trees[MAX_UNPACK_TREES];
 759         struct unpack_trees_options opts;
 760         struct tree_desc t[MAX_UNPACK_TREES];
 761         int i, fd, nr_trees = 0;
 762         struct dir_struct dir;
 763         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 764
 765         refresh_cache(REFRESH_QUIET);
 766
 767         fd = hold_locked_index(lock_file, 1);
 768
 769         memset(&trees, 0, sizeof(trees));
 770         memset(&opts, 0, sizeof(opts));
 771         memset(&t, 0, sizeof(t));
 772         memset(&dir, 0, sizeof(dir));
 773         dir.flags |= DIR_SHOW_IGNORED;
 774         dir.exclude_per_dir = ".gitignore";
 775         opts.dir = &dir;
 776
 777         opts.head_idx = 1;
 778         opts.src_index = &the_index;
 779         opts.dst_index = &the_index;
 780         opts.update = 1;
 781         opts.verbose_update = 1;
 782         opts.merge = 1;
 783         opts.fn = twoway_merge;
 784         setup_unpack_trees_porcelain(&opts, "merge");
 785
 786         trees[nr_trees] = parse_tree_indirect(head);
 787         if (!trees[nr_trees++])
 788                 return -1;
 789         trees[nr_trees] = parse_tree_indirect(remote);
 790         if (!trees[nr_trees++])
 791                 return -1;
 792         for (i = 0; i < nr_trees; i++) {
 793                 parse_tree(trees[i]);
 794                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 795         }
 796         if (unpack_trees(nr_trees, t, &opts))
 797                 return -1;
 798         if (write_cache(fd, active_cache, active_nr) ||
 799                 commit_locked_index(lock_file))
 800                 die(_("unable to write new index file"));
 801         return 0;
 802 }
 803
 804 static void split_merge_strategies(const char *string, struct strategy **list,
 805                                    int *nr, int *alloc)
 806 {
 807         char *p, *q, *buf;
 808
 809         if (!string)
 810                 return;
 811
 812         buf = xstrdup(string);
 813         q = buf;
 814         for (;;) {
 815                 p = strchr(q, ' ');
 816                 if (!p) {
 817                         ALLOC_GROW(*list, *nr + 1, *alloc);
 818                         (*list)[(*nr)++].name = xstrdup(q);
 819                         free(buf);
 820                         return;
 821                 } else {
 822                         *p = '\0';
 823                         ALLOC_GROW(*list, *nr + 1, *alloc);
 824                         (*list)[(*nr)++].name = xstrdup(q);
 825                         q = ++p;
 826                 }
 827         }
 828 }
 829
 830 static void add_strategies(const char *string, unsigned attr)
 831 {
 832         struct strategy *list = NULL;
 833         int list_alloc = 0, list_nr = 0, i;
 834
 835         memset(&list, 0, sizeof(list));
 836         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 837         if (list) {
 838                 for (i = 0; i < list_nr; i++)
 839                         append_strategy(get_strategy(list[i].name));
 840                 return;
 841         }
 842         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 843                 if (all_strategy[i].attr & attr)
 844                         append_strategy(&all_strategy[i]);
 845
 846 }
 847
 848 static void write_merge_msg(struct strbuf *msg)
 849 {
 850         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 851         if (fd < 0)
 852                 die_errno(_("Could not open '%s' for writing"),
 853                           git_path("MERGE_MSG"));
 854         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 855                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 856         close(fd);
 857 }
 858
 859 static void read_merge_msg(struct strbuf *msg)
 860 {
 861         strbuf_reset(msg);
 862         if (strbuf_read_file(msg, git_path("MERGE_MSG"), 0) < 0)
 863                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 864 }
 865
 866 static void write_merge_state(void);
 867 static void abort_commit(const char *err_msg)
 868 {
 869         if (err_msg)
 870                 error("%s", err_msg);
 871         fprintf(stderr,
 872                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 873         write_merge_state();
 874         exit(1);
 875 }
 876
 877 static void prepare_to_commit(void)
 878 {
 879         struct strbuf msg = STRBUF_INIT;
 880         strbuf_addbuf(&msg, &merge_msg);
 881         strbuf_addch(&msg, '\n');
 882         write_merge_msg(&msg);
 883         run_hook(get_index_file(), "prepare-commit-msg",
 884                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 885         if (option_edit) {
 886                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 887                         abort_commit(NULL);
 888         }
 889         read_merge_msg(&msg);
 890         stripspace(&msg, option_edit);
 891         if (!msg.len)
 892                 abort_commit(_("Empty commit message."));
 893         strbuf_release(&merge_msg);
 894         strbuf_addbuf(&merge_msg, &msg);
 895         strbuf_release(&msg);
 896 }
 897
 898 static int merge_trivial(struct commit *head)
 899 {
 900         unsigned char result_tree[20], result_commit[20];
 901         struct commit_list *parent = xmalloc(sizeof(*parent));
 902
 903         write_tree_trivial(result_tree);
 904         printf(_("Wonderful.\n"));
 905         parent->item = head;
 906         parent->next = xmalloc(sizeof(*parent->next));
 907         parent->next->item = remoteheads->item;
 908         parent->next->next = NULL;
 909         prepare_to_commit();
 910         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 911         finish(head, result_commit, "In-index merge");
 912         drop_save();
 913         return 0;
 914 }
 915
 916 static int finish_automerge(struct commit *head,
 917                             struct commit_list *common,
 918                             unsigned char *result_tree,
 919                             const char *wt_strategy)
 920 {
 921         struct commit_list *parents = NULL, *j;
 922         struct strbuf buf = STRBUF_INIT;
 923         unsigned char result_commit[20];
 924
 925         free_commit_list(common);
 926         if (allow_fast_forward) {
 927                 parents = remoteheads;
 928                 commit_list_insert(head, &parents);
 929                 parents = reduce_heads(parents);
 930         } else {
 931                 struct commit_list **pptr = &parents;
 932
 933                 pptr = &commit_list_insert(head,
 934                                 pptr)->next;
 935                 for (j = remoteheads; j; j = j->next)
 936                         pptr = &commit_list_insert(j->item, pptr)->next;
 937         }
 938         strbuf_addch(&merge_msg, '\n');
 939         prepare_to_commit();
 940         free_commit_list(remoteheads);
 941         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 942         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 943         finish(head, result_commit, buf.buf);
 944         strbuf_release(&buf);
 945         drop_save();
 946         return 0;
 947 }
 948
 949 static int suggest_conflicts(int renormalizing)
 950 {
 951         FILE *fp;
 952         int pos;
 953
 954         fp = fopen(git_path("MERGE_MSG"), "a");
 955         if (!fp)
 956                 die_errno(_("Could not open '%s' for writing"),
 957                           git_path("MERGE_MSG"));
 958         fprintf(fp, "\nConflicts:\n");
 959         for (pos = 0; pos < active_nr; pos++) {
 960                 struct cache_entry *ce = active_cache[pos];
 961
 962                 if (ce_stage(ce)) {
 963                         fprintf(fp, "\t%s\n", ce->name);
 964                         while (pos + 1 < active_nr &&
 965                                         !strcmp(ce->name,
 966                                                 active_cache[pos + 1]->name))
 967                                 pos++;
 968                 }
 969         }
 970         fclose(fp);
 971         rerere(allow_rerere_auto);
 972         printf(_("Automatic merge failed; "
 973                         "fix conflicts and then commit the result.\n"));
 974         return 1;
 975 }
 976
 977 static struct commit *is_old_style_invocation(int argc, const char **argv,
 978                                               const unsigned char *head)
 979 {
 980         struct commit *second_token = NULL;
 981         if (argc > 2) {
 982                 unsigned char second_sha1[20];
 983
 984                 if (get_sha1(argv[1], second_sha1))
 985                         return NULL;
 986                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 987                 if (!second_token)
 988                         die(_("'%s' is not a commit"), argv[1]);
 989                 if (hashcmp(second_token->object.sha1, head))
 990                         return NULL;
 991         }
 992         return second_token;
 993 }
 994
 995 static int evaluate_result(void)
 996 {
 997         int cnt = 0;
 998         struct rev_info rev;
 999
1000         /* Check how many files differ. */
1001         init_revisions(&rev, "");
1002         setup_revisions(0, NULL, &rev, NULL);
1003         rev.diffopt.output_format |=
1004                 DIFF_FORMAT_CALLBACK;
1005         rev.diffopt.format_callback = count_diff_files;
1006         rev.diffopt.format_callback_data = &cnt;
1007         run_diff_files(&rev, 0);
1008
1009         /*
1010          * Check how many unmerged entries are
1011          * there.
1012          */
1013         cnt += count_unmerged_entries();
1014
1015         return cnt;
1016 }
1017
1018 /*
1019  * Pretend as if the user told us to merge with the tracking
1020  * branch we have for the upstream of the current branch
1021  */
1022 static int setup_with_upstream(const char ***argv)
1023 {
1024         struct branch *branch = branch_get(NULL);
1025         int i;
1026         const char **args;
1027
1028         if (!branch)
1029                 die(_("No current branch."));
1030         if (!branch->remote)
1031                 die(_("No remote for the current branch."));
1032         if (!branch->merge_nr)
1033                 die(_("No default upstream defined for the current branch."));
1034
1035         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1036         for (i = 0; i < branch->merge_nr; i++) {
1037                 if (!branch->merge[i]->dst)
1038                         die(_("No remote tracking branch for %s from %s"),
1039                             branch->merge[i]->src, branch->remote_name);
1040                 args[i] = branch->merge[i]->dst;
1041         }
1042         args[i] = NULL;
1043         *argv = args;
1044         return i;
1045 }
1046
1047 static void write_merge_state(void)
1048 {
1049         int fd;
1050         struct commit_list *j;
1051         struct strbuf buf = STRBUF_INIT;
1052
1053         for (j = remoteheads; j; j = j->next)
1054                 strbuf_addf(&buf, "%s\n",
1055                         sha1_to_hex(j->item->object.sha1));
1056         fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1057         if (fd < 0)
1058                 die_errno(_("Could not open '%s' for writing"),
1059                           git_path("MERGE_HEAD"));
1060         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1061                 die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1062         close(fd);
1063         strbuf_addch(&merge_msg, '\n');
1064         write_merge_msg(&merge_msg);
1065         fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1066         if (fd < 0)
1067                 die_errno(_("Could not open '%s' for writing"),
1068                           git_path("MERGE_MODE"));
1069         strbuf_reset(&buf);
1070         if (!allow_fast_forward)
1071                 strbuf_addf(&buf, "no-ff");
1072         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1073                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1074         close(fd);
1075 }
1076
1077 int cmd_merge(int argc, const char **argv, const char *prefix)
1078 {
1079         unsigned char result_tree[20];
1080         unsigned char stash[20];
1081         unsigned char head_sha1[20];
1082         struct commit *head_commit;
1083         struct strbuf buf = STRBUF_INIT;
1084         const char *head_arg;
1085         int flag, i;
1086         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1087         struct commit_list *common = NULL;
1088         const char *best_strategy = NULL, *wt_strategy = NULL;
1089         struct commit_list **remotes = &remoteheads;
1090
1091         if (argc == 2 && !strcmp(argv[1], "-h"))
1092                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1093
1094         /*
1095          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1096          * current branch.
1097          */
1098         branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1099         if (branch && !prefixcmp(branch, "refs/heads/"))
1100                 branch += 11;
1101         if (!branch || is_null_sha1(head_sha1))
1102                 head_commit = NULL;
1103         else
1104                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1105
1106         git_config(git_merge_config, NULL);
1107
1108         if (branch_mergeoptions)
1109                 parse_branch_merge_options(branch_mergeoptions);
1110         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1111                         builtin_merge_usage, 0);
1112
1113         if (verbosity < 0 && show_progress == -1)
1114                 show_progress = 0;
1115
1116         if (abort_current_merge) {
1117                 int nargc = 2;
1118                 const char *nargv[] = {"reset", "--merge", NULL};
1119
1120                 if (!file_exists(git_path("MERGE_HEAD")))
1121                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1122
1123                 /* Invoke 'git reset --merge' */
1124                 return cmd_reset(nargc, nargv, prefix);
1125         }
1126
1127         if (read_cache_unmerged())
1128                 die_resolve_conflict("merge");
1129
1130         if (file_exists(git_path("MERGE_HEAD"))) {
1131                 /*
1132                  * There is no unmerged entry, don't advise 'git
1133                  * add/rm <file>', just 'git commit'.
1134                  */
1135                 if (advice_resolve_conflict)
1136                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1137                                   "Please, commit your changes before you can merge."));
1138                 else
1139                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1140         }
1141         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1142                 if (advice_resolve_conflict)
1143                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1144                             "Please, commit your changes before you can merge."));
1145                 else
1146                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1147         }
1148         resolve_undo_clear();
1149
1150         if (verbosity < 0)
1151                 show_diffstat = 0;
1152
1153         if (squash) {
1154                 if (!allow_fast_forward)
1155                         die(_("You cannot combine --squash with --no-ff."));
1156                 option_commit = 0;
1157         }
1158
1159         if (!allow_fast_forward && fast_forward_only)
1160                 die(_("You cannot combine --no-ff with --ff-only."));
1161
1162         if (!abort_current_merge) {
1163                 if (!argc && default_to_upstream)
1164                         argc = setup_with_upstream(&argv);
1165                 else if (argc == 1 && !strcmp(argv[0], "-"))
1166                         argv[0] = "@{-1}";
1167         }
1168         if (!argc)
1169                 usage_with_options(builtin_merge_usage,
1170                         builtin_merge_options);
1171
1172         /*
1173          * This could be traditional "merge <msg> HEAD <commit>..."  and
1174          * the way we can tell it is to see if the second token is HEAD,
1175          * but some people might have misused the interface and used a
1176          * committish that is the same as HEAD there instead.
1177          * Traditional format never would have "-m" so it is an
1178          * additional safety measure to check for it.
1179          */
1180
1181         if (!have_message && head_commit &&
1182             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1183                 strbuf_addstr(&merge_msg, argv[0]);
1184                 head_arg = argv[1];
1185                 argv += 2;
1186                 argc -= 2;
1187         } else if (!head_commit) {
1188                 struct object *remote_head;
1189                 /*
1190                  * If the merged head is a valid one there is no reason
1191                  * to forbid "git merge" into a branch yet to be born.
1192                  * We do the same for "git pull".
1193                  */
1194                 if (argc != 1)
1195                         die(_("Can merge only exactly one commit into "
1196                                 "empty head"));
1197                 if (squash)
1198                         die(_("Squash commit into empty head not supported yet"));
1199                 if (!allow_fast_forward)
1200                         die(_("Non-fast-forward commit does not make sense into "
1201                             "an empty head"));
1202                 remote_head = want_commit(argv[0]);
1203                 if (!remote_head)
1204                         die(_("%s - not something we can merge"), argv[0]);
1205                 read_empty(remote_head->sha1, 0);
1206                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1207                                 DIE_ON_ERR);
1208                 return 0;
1209         } else {
1210                 struct strbuf merge_names = STRBUF_INIT;
1211
1212                 /* We are invoked directly as the first-class UI. */
1213                 head_arg = "HEAD";
1214
1215                 /*
1216                  * All the rest are the commits being merged;
1217                  * prepare the standard merge summary message to
1218                  * be appended to the given message.  If remote
1219                  * is invalid we will die later in the common
1220                  * codepath so we discard the error in this
1221                  * loop.
1222                  */
1223                 for (i = 0; i < argc; i++)
1224                         merge_name(argv[i], &merge_names);
1225
1226                 if (!have_message || shortlog_len) {
1227                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1228                                       shortlog_len);
1229                         if (merge_msg.len)
1230                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1231                 }
1232         }
1233
1234         if (!head_commit || !argc)
1235                 usage_with_options(builtin_merge_usage,
1236                         builtin_merge_options);
1237
1238         strbuf_addstr(&buf, "merge");
1239         for (i = 0; i < argc; i++)
1240                 strbuf_addf(&buf, " %s", argv[i]);
1241         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1242         strbuf_reset(&buf);
1243
1244         for (i = 0; i < argc; i++) {
1245                 struct object *o;
1246                 struct commit *commit;
1247
1248                 o = want_commit(argv[i]);
1249                 if (!o)
1250                         die(_("%s - not something we can merge"), argv[i]);
1251                 commit = lookup_commit(o->sha1);
1252                 commit->util = (void *)argv[i];
1253                 remotes = &commit_list_insert(commit, remotes)->next;
1254
1255                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1256                 setenv(buf.buf, argv[i], 1);
1257                 strbuf_reset(&buf);
1258         }
1259
1260         if (!use_strategies) {
1261                 if (!remoteheads->next)
1262                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1263                 else
1264                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1265         }
1266
1267         for (i = 0; i < use_strategies_nr; i++) {
1268                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1269                         allow_fast_forward = 0;
1270                 if (use_strategies[i]->attr & NO_TRIVIAL)
1271                         allow_trivial = 0;
1272         }
1273
1274         if (!remoteheads->next)
1275                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1276         else {
1277                 struct commit_list *list = remoteheads;
1278                 commit_list_insert(head_commit, &list);
1279                 common = get_octopus_merge_bases(list);
1280                 free(list);
1281         }
1282
1283         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1284                    NULL, 0, DIE_ON_ERR);
1285
1286         if (!common)
1287                 ; /* No common ancestors found. We need a real merge. */
1288         else if (!remoteheads->next && !common->next &&
1289                         common->item == remoteheads->item) {
1290                 /*
1291                  * If head can reach all the merge then we are up to date.
1292                  * but first the most common case of merging one remote.
1293                  */
1294                 finish_up_to_date("Already up-to-date.");
1295                 return 0;
1296         } else if (allow_fast_forward && !remoteheads->next &&
1297                         !common->next &&
1298                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1299                 /* Again the most common case of merging one remote. */
1300                 struct strbuf msg = STRBUF_INIT;
1301                 struct object *o;
1302                 char hex[41];
1303
1304                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1305
1306                 if (verbosity >= 0)
1307                         printf(_("Updating %s..%s\n"),
1308                                 hex,
1309                                 find_unique_abbrev(remoteheads->item->object.sha1,
1310                                 DEFAULT_ABBREV));
1311                 strbuf_addstr(&msg, "Fast-forward");
1312                 if (have_message)
1313                         strbuf_addstr(&msg,
1314                                 " (no commit created; -m option ignored)");
1315                 o = want_commit(sha1_to_hex(remoteheads->item->object.sha1));
1316                 if (!o)
1317                         return 1;
1318
1319                 if (checkout_fast_forward(head_commit->object.sha1, remoteheads->item->object.sha1))
1320                         return 1;
1321
1322                 finish(head_commit, o->sha1, msg.buf);
1323                 drop_save();
1324                 return 0;
1325         } else if (!remoteheads->next && common->next)
1326                 ;
1327                 /*
1328                  * We are not doing octopus and not fast-forward.  Need
1329                  * a real merge.
1330                  */
1331         else if (!remoteheads->next && !common->next && option_commit) {
1332                 /*
1333                  * We are not doing octopus, not fast-forward, and have
1334                  * only one common.
1335                  */
1336                 refresh_cache(REFRESH_QUIET);
1337                 if (allow_trivial && !fast_forward_only) {
1338                         /* See if it is really trivial. */
1339                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1340                         printf(_("Trying really trivial in-index merge...\n"));
1341                         if (!read_tree_trivial(common->item->object.sha1,
1342                                         head_commit->object.sha1, remoteheads->item->object.sha1))
1343                                 return merge_trivial(head_commit);
1344                         printf(_("Nope.\n"));
1345                 }
1346         } else {
1347                 /*
1348                  * An octopus.  If we can reach all the remote we are up
1349                  * to date.
1350                  */
1351                 int up_to_date = 1;
1352                 struct commit_list *j;
1353
1354                 for (j = remoteheads; j; j = j->next) {
1355                         struct commit_list *common_one;
1356
1357                         /*
1358                          * Here we *have* to calculate the individual
1359                          * merge_bases again, otherwise "git merge HEAD^
1360                          * HEAD^^" would be missed.
1361                          */
1362                         common_one = get_merge_bases(head_commit, j->item, 1);
1363                         if (hashcmp(common_one->item->object.sha1,
1364                                 j->item->object.sha1)) {
1365                                 up_to_date = 0;
1366                                 break;
1367                         }
1368                 }
1369                 if (up_to_date) {
1370                         finish_up_to_date("Already up-to-date. Yeeah!");
1371                         return 0;
1372                 }
1373         }
1374
1375         if (fast_forward_only)
1376                 die(_("Not possible to fast-forward, aborting."));
1377
1378         /* We are going to make a new commit. */
1379         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1380
1381         /*
1382          * At this point, we need a real merge.  No matter what strategy
1383          * we use, it would operate on the index, possibly affecting the
1384          * working tree, and when resolved cleanly, have the desired
1385          * tree in the index -- this means that the index must be in
1386          * sync with the head commit.  The strategies are responsible
1387          * to ensure this.
1388          */
1389         if (use_strategies_nr == 1 ||
1390             /*
1391              * Stash away the local changes so that we can try more than one.
1392              */
1393             save_state(stash))
1394                 hashcpy(stash, null_sha1);
1395
1396         for (i = 0; i < use_strategies_nr; i++) {
1397                 int ret;
1398                 if (i) {
1399                         printf(_("Rewinding the tree to pristine...\n"));
1400                         restore_state(head_commit->object.sha1, stash);
1401                 }
1402                 if (use_strategies_nr != 1)
1403                         printf(_("Trying merge strategy %s...\n"),
1404                                 use_strategies[i]->name);
1405                 /*
1406                  * Remember which strategy left the state in the working
1407                  * tree.
1408                  */
1409                 wt_strategy = use_strategies[i]->name;
1410
1411                 ret = try_merge_strategy(use_strategies[i]->name,
1412                                          common, head_commit, head_arg);
1413                 if (!option_commit && !ret) {
1414                         merge_was_ok = 1;
1415                         /*
1416                          * This is necessary here just to avoid writing
1417                          * the tree, but later we will *not* exit with
1418                          * status code 1 because merge_was_ok is set.
1419                          */
1420                         ret = 1;
1421                 }
1422
1423                 if (ret) {
1424                         /*
1425                          * The backend exits with 1 when conflicts are
1426                          * left to be resolved, with 2 when it does not
1427                          * handle the given merge at all.
1428                          */
1429                         if (ret == 1) {
1430                                 int cnt = evaluate_result();
1431
1432                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1433                                         best_strategy = use_strategies[i]->name;
1434                                         best_cnt = cnt;
1435                                 }
1436                         }
1437                         if (merge_was_ok)
1438                                 break;
1439                         else
1440                                 continue;
1441                 }
1442
1443                 /* Automerge succeeded. */
1444                 write_tree_trivial(result_tree);
1445                 automerge_was_ok = 1;
1446                 break;
1447         }
1448
1449         /*
1450          * If we have a resulting tree, that means the strategy module
1451          * auto resolved the merge cleanly.
1452          */
1453         if (automerge_was_ok)
1454                 return finish_automerge(head_commit, common, result_tree,
1455                                         wt_strategy);
1456
1457         /*
1458          * Pick the result from the best strategy and have the user fix
1459          * it up.
1460          */
1461         if (!best_strategy) {
1462                 restore_state(head_commit->object.sha1, stash);
1463                 if (use_strategies_nr > 1)
1464                         fprintf(stderr,
1465                                 _("No merge strategy handled the merge.\n"));
1466                 else
1467                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1468                                 use_strategies[0]->name);
1469                 return 2;
1470         } else if (best_strategy == wt_strategy)
1471                 ; /* We already have its result in the working tree. */
1472         else {
1473                 printf(_("Rewinding the tree to pristine...\n"));
1474                 restore_state(head_commit->object.sha1, stash);
1475                 printf(_("Using the %s to prepare resolving by hand.\n"),
1476                         best_strategy);
1477                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1478         }
1479
1480         if (squash)
1481                 finish(head_commit, NULL, NULL);
1482         else
1483                 write_merge_state();
1484
1485         if (merge_was_ok) {
1486                 fprintf(stderr, _("Automatic merge went well; "
1487                         "stopped before committing as requested\n"));
1488                 return 0;
1489         } else
1490                 return suggest_conflicts(option_renormalize);
1491 }