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 /* Get the name for the merge commit's message. */
 410 static void merge_name(const char *remote, struct strbuf *msg)
 411 {
 412         struct commit *remote_head;
 413         unsigned char branch_head[20], buf_sha[20];
 414         struct strbuf buf = STRBUF_INIT;
 415         struct strbuf bname = STRBUF_INIT;
 416         const char *ptr;
 417         char *found_ref;
 418         int len, early;
 419
 420         strbuf_branchname(&bname, remote);
 421         remote = bname.buf;
 422
 423         memset(branch_head, 0, sizeof(branch_head));
 424         remote_head = get_merge_parent(remote);
 425         if (!remote_head)
 426                 die(_("'%s' does not point to a commit"), remote);
 427
 428         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 429                 if (!prefixcmp(found_ref, "refs/heads/")) {
 430                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 431                                     sha1_to_hex(branch_head), remote);
 432                         goto cleanup;
 433                 }
 434                 if (!prefixcmp(found_ref, "refs/tags/")) {
 435                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 436                                     sha1_to_hex(branch_head), remote);
 437                         goto cleanup;
 438                 }
 439                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 440                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 441                                     sha1_to_hex(branch_head), remote);
 442                         goto cleanup;
 443                 }
 444         }
 445
 446         /* See if remote matches <name>^^^.. or <name>~<number> */
 447         for (len = 0, ptr = remote + strlen(remote);
 448              remote < ptr && ptr[-1] == '^';
 449              ptr--)
 450                 len++;
 451         if (len)
 452                 early = 1;
 453         else {
 454                 early = 0;
 455                 ptr = strrchr(remote, '~');
 456                 if (ptr) {
 457                         int seen_nonzero = 0;
 458
 459                         len++; /* count ~ */
 460                         while (*++ptr && isdigit(*ptr)) {
 461                                 seen_nonzero |= (*ptr != '0');
 462                                 len++;
 463                         }
 464                         if (*ptr)
 465                                 len = 0; /* not ...~<number> */
 466                         else if (seen_nonzero)
 467                                 early = 1;
 468                         else if (len == 1)
 469                                 early = 1; /* "name~" is "name~1"! */
 470                 }
 471         }
 472         if (len) {
 473                 struct strbuf truname = STRBUF_INIT;
 474                 strbuf_addstr(&truname, "refs/heads/");
 475                 strbuf_addstr(&truname, remote);
 476                 strbuf_setlen(&truname, truname.len - len);
 477                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 478                         strbuf_addf(msg,
 479                                     "%s\t\tbranch '%s'%s of .\n",
 480                                     sha1_to_hex(remote_head->object.sha1),
 481                                     truname.buf + 11,
 482                                     (early ? " (early part)" : ""));
 483                         strbuf_release(&truname);
 484                         goto cleanup;
 485                 }
 486         }
 487
 488         if (!strcmp(remote, "FETCH_HEAD") &&
 489                         !access(git_path("FETCH_HEAD"), R_OK)) {
 490                 FILE *fp;
 491                 struct strbuf line = STRBUF_INIT;
 492                 char *ptr;
 493
 494                 fp = fopen(git_path("FETCH_HEAD"), "r");
 495                 if (!fp)
 496                         die_errno(_("could not open '%s' for reading"),
 497                                   git_path("FETCH_HEAD"));
 498                 strbuf_getline(&line, fp, '\n');
 499                 fclose(fp);
 500                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 501                 if (ptr)
 502                         strbuf_remove(&line, ptr-line.buf+1, 13);
 503                 strbuf_addbuf(msg, &line);
 504                 strbuf_release(&line);
 505                 goto cleanup;
 506         }
 507         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 508                 sha1_to_hex(remote_head->object.sha1), remote);
 509 cleanup:
 510         strbuf_release(&buf);
 511         strbuf_release(&bname);
 512 }
 513
 514 static void parse_branch_merge_options(char *bmo)
 515 {
 516         const char **argv;
 517         int argc;
 518
 519         if (!bmo)
 520                 return;
 521         argc = split_cmdline(bmo, &argv);
 522         if (argc < 0)
 523                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 524                     split_cmdline_strerror(argc));
 525         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 526         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 527         argc++;
 528         argv[0] = "branch.*.mergeoptions";
 529         parse_options(argc, argv, NULL, builtin_merge_options,
 530                       builtin_merge_usage, 0);
 531         free(argv);
 532 }
 533
 534 static int git_merge_config(const char *k, const char *v, void *cb)
 535 {
 536         if (branch && !prefixcmp(k, "branch.") &&
 537                 !prefixcmp(k + 7, branch) &&
 538                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 539                 free(branch_mergeoptions);
 540                 branch_mergeoptions = xstrdup(v);
 541                 return 0;
 542         }
 543
 544         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 545                 show_diffstat = git_config_bool(k, v);
 546         else if (!strcmp(k, "pull.twohead"))
 547                 return git_config_string(&pull_twohead, k, v);
 548         else if (!strcmp(k, "pull.octopus"))
 549                 return git_config_string(&pull_octopus, k, v);
 550         else if (!strcmp(k, "merge.renormalize"))
 551                 option_renormalize = git_config_bool(k, v);
 552         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 553                 int is_bool;
 554                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 555                 if (!is_bool && shortlog_len < 0)
 556                         return error(_("%s: negative length %s"), k, v);
 557                 if (is_bool && shortlog_len)
 558                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 559                 return 0;
 560         } else if (!strcmp(k, "merge.ff")) {
 561                 int boolval = git_config_maybe_bool(k, v);
 562                 if (0 <= boolval) {
 563                         allow_fast_forward = boolval;
 564                 } else if (v && !strcmp(v, "only")) {
 565                         allow_fast_forward = 1;
 566                         fast_forward_only = 1;
 567                 } /* do not barf on values from future versions of git */
 568                 return 0;
 569         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 570                 default_to_upstream = git_config_bool(k, v);
 571                 return 0;
 572         }
 573         return git_diff_ui_config(k, v, cb);
 574 }
 575
 576 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 577                              unsigned char *one)
 578 {
 579         int i, nr_trees = 0;
 580         struct tree *trees[MAX_UNPACK_TREES];
 581         struct tree_desc t[MAX_UNPACK_TREES];
 582         struct unpack_trees_options opts;
 583
 584         memset(&opts, 0, sizeof(opts));
 585         opts.head_idx = 2;
 586         opts.src_index = &the_index;
 587         opts.dst_index = &the_index;
 588         opts.update = 1;
 589         opts.verbose_update = 1;
 590         opts.trivial_merges_only = 1;
 591         opts.merge = 1;
 592         trees[nr_trees] = parse_tree_indirect(common);
 593         if (!trees[nr_trees++])
 594                 return -1;
 595         trees[nr_trees] = parse_tree_indirect(head);
 596         if (!trees[nr_trees++])
 597                 return -1;
 598         trees[nr_trees] = parse_tree_indirect(one);
 599         if (!trees[nr_trees++])
 600                 return -1;
 601         opts.fn = threeway_merge;
 602         cache_tree_free(&active_cache_tree);
 603         for (i = 0; i < nr_trees; i++) {
 604                 parse_tree(trees[i]);
 605                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 606         }
 607         if (unpack_trees(nr_trees, t, &opts))
 608                 return -1;
 609         return 0;
 610 }
 611
 612 static void write_tree_trivial(unsigned char *sha1)
 613 {
 614         if (write_cache_as_tree(sha1, 0, NULL))
 615                 die(_("git write-tree failed to write a tree"));
 616 }
 617
 618 static const char *merge_argument(struct commit *commit)
 619 {
 620         if (commit)
 621                 return sha1_to_hex(commit->object.sha1);
 622         else
 623                 return EMPTY_TREE_SHA1_HEX;
 624 }
 625
 626 int try_merge_command(const char *strategy, size_t xopts_nr,
 627                       const char **xopts, struct commit_list *common,
 628                       const char *head_arg, struct commit_list *remotes)
 629 {
 630         const char **args;
 631         int i = 0, x = 0, ret;
 632         struct commit_list *j;
 633         struct strbuf buf = STRBUF_INIT;
 634
 635         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 636                         commit_list_count(remotes)) * sizeof(char *));
 637         strbuf_addf(&buf, "merge-%s", strategy);
 638         args[i++] = buf.buf;
 639         for (x = 0; x < xopts_nr; x++) {
 640                 char *s = xmalloc(strlen(xopts[x])+2+1);
 641                 strcpy(s, "--");
 642                 strcpy(s+2, xopts[x]);
 643                 args[i++] = s;
 644         }
 645         for (j = common; j; j = j->next)
 646                 args[i++] = xstrdup(merge_argument(j->item));
 647         args[i++] = "--";
 648         args[i++] = head_arg;
 649         for (j = remotes; j; j = j->next)
 650                 args[i++] = xstrdup(merge_argument(j->item));
 651         args[i] = NULL;
 652         ret = run_command_v_opt(args, RUN_GIT_CMD);
 653         strbuf_release(&buf);
 654         i = 1;
 655         for (x = 0; x < xopts_nr; x++)
 656                 free((void *)args[i++]);
 657         for (j = common; j; j = j->next)
 658                 free((void *)args[i++]);
 659         i += 2;
 660         for (j = remotes; j; j = j->next)
 661                 free((void *)args[i++]);
 662         free(args);
 663         discard_cache();
 664         if (read_cache() < 0)
 665                 die(_("failed to read the cache"));
 666         resolve_undo_clear();
 667
 668         return ret;
 669 }
 670
 671 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 672                               struct commit *head, const char *head_arg)
 673 {
 674         int index_fd;
 675         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 676
 677         index_fd = hold_locked_index(lock, 1);
 678         refresh_cache(REFRESH_QUIET);
 679         if (active_cache_changed &&
 680                         (write_cache(index_fd, active_cache, active_nr) ||
 681                          commit_locked_index(lock)))
 682                 return error(_("Unable to write index."));
 683         rollback_lock_file(lock);
 684
 685         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 686                 int clean, x;
 687                 struct commit *result;
 688                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 689                 int index_fd;
 690                 struct commit_list *reversed = NULL;
 691                 struct merge_options o;
 692                 struct commit_list *j;
 693
 694                 if (remoteheads->next) {
 695                         error(_("Not handling anything other than two heads merge."));
 696                         return 2;
 697                 }
 698
 699                 init_merge_options(&o);
 700                 if (!strcmp(strategy, "subtree"))
 701                         o.subtree_shift = "";
 702
 703                 o.renormalize = option_renormalize;
 704                 o.show_rename_progress =
 705                         show_progress == -1 ? isatty(2) : show_progress;
 706
 707                 for (x = 0; x < xopts_nr; x++)
 708                         if (parse_merge_opt(&o, xopts[x]))
 709                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 710
 711                 o.branch1 = head_arg;
 712                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 713
 714                 for (j = common; j; j = j->next)
 715                         commit_list_insert(j->item, &reversed);
 716
 717                 index_fd = hold_locked_index(lock, 1);
 718                 clean = merge_recursive(&o, head,
 719                                 remoteheads->item, reversed, &result);
 720                 if (active_cache_changed &&
 721                                 (write_cache(index_fd, active_cache, active_nr) ||
 722                                  commit_locked_index(lock)))
 723                         die (_("unable to write %s"), get_index_file());
 724                 rollback_lock_file(lock);
 725                 return clean ? 0 : 1;
 726         } else {
 727                 return try_merge_command(strategy, xopts_nr, xopts,
 728                                                 common, head_arg, remoteheads);
 729         }
 730 }
 731
 732 static void count_diff_files(struct diff_queue_struct *q,
 733                              struct diff_options *opt, void *data)
 734 {
 735         int *count = data;
 736
 737         (*count) += q->nr;
 738 }
 739
 740 static int count_unmerged_entries(void)
 741 {
 742         int i, ret = 0;
 743
 744         for (i = 0; i < active_nr; i++)
 745                 if (ce_stage(active_cache[i]))
 746                         ret++;
 747
 748         return ret;
 749 }
 750
 751 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 752 {
 753         struct tree *trees[MAX_UNPACK_TREES];
 754         struct unpack_trees_options opts;
 755         struct tree_desc t[MAX_UNPACK_TREES];
 756         int i, fd, nr_trees = 0;
 757         struct dir_struct dir;
 758         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 759
 760         refresh_cache(REFRESH_QUIET);
 761
 762         fd = hold_locked_index(lock_file, 1);
 763
 764         memset(&trees, 0, sizeof(trees));
 765         memset(&opts, 0, sizeof(opts));
 766         memset(&t, 0, sizeof(t));
 767         memset(&dir, 0, sizeof(dir));
 768         dir.flags |= DIR_SHOW_IGNORED;
 769         dir.exclude_per_dir = ".gitignore";
 770         opts.dir = &dir;
 771
 772         opts.head_idx = 1;
 773         opts.src_index = &the_index;
 774         opts.dst_index = &the_index;
 775         opts.update = 1;
 776         opts.verbose_update = 1;
 777         opts.merge = 1;
 778         opts.fn = twoway_merge;
 779         setup_unpack_trees_porcelain(&opts, "merge");
 780
 781         trees[nr_trees] = parse_tree_indirect(head);
 782         if (!trees[nr_trees++])
 783                 return -1;
 784         trees[nr_trees] = parse_tree_indirect(remote);
 785         if (!trees[nr_trees++])
 786                 return -1;
 787         for (i = 0; i < nr_trees; i++) {
 788                 parse_tree(trees[i]);
 789                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 790         }
 791         if (unpack_trees(nr_trees, t, &opts))
 792                 return -1;
 793         if (write_cache(fd, active_cache, active_nr) ||
 794                 commit_locked_index(lock_file))
 795                 die(_("unable to write new index file"));
 796         return 0;
 797 }
 798
 799 static void split_merge_strategies(const char *string, struct strategy **list,
 800                                    int *nr, int *alloc)
 801 {
 802         char *p, *q, *buf;
 803
 804         if (!string)
 805                 return;
 806
 807         buf = xstrdup(string);
 808         q = buf;
 809         for (;;) {
 810                 p = strchr(q, ' ');
 811                 if (!p) {
 812                         ALLOC_GROW(*list, *nr + 1, *alloc);
 813                         (*list)[(*nr)++].name = xstrdup(q);
 814                         free(buf);
 815                         return;
 816                 } else {
 817                         *p = '\0';
 818                         ALLOC_GROW(*list, *nr + 1, *alloc);
 819                         (*list)[(*nr)++].name = xstrdup(q);
 820                         q = ++p;
 821                 }
 822         }
 823 }
 824
 825 static void add_strategies(const char *string, unsigned attr)
 826 {
 827         struct strategy *list = NULL;
 828         int list_alloc = 0, list_nr = 0, i;
 829
 830         memset(&list, 0, sizeof(list));
 831         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 832         if (list) {
 833                 for (i = 0; i < list_nr; i++)
 834                         append_strategy(get_strategy(list[i].name));
 835                 return;
 836         }
 837         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 838                 if (all_strategy[i].attr & attr)
 839                         append_strategy(&all_strategy[i]);
 840
 841 }
 842
 843 static void write_merge_msg(struct strbuf *msg)
 844 {
 845         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 846         if (fd < 0)
 847                 die_errno(_("Could not open '%s' for writing"),
 848                           git_path("MERGE_MSG"));
 849         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 850                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 851         close(fd);
 852 }
 853
 854 static void read_merge_msg(struct strbuf *msg)
 855 {
 856         strbuf_reset(msg);
 857         if (strbuf_read_file(msg, git_path("MERGE_MSG"), 0) < 0)
 858                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 859 }
 860
 861 static void write_merge_state(void);
 862 static void abort_commit(const char *err_msg)
 863 {
 864         if (err_msg)
 865                 error("%s", err_msg);
 866         fprintf(stderr,
 867                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 868         write_merge_state();
 869         exit(1);
 870 }
 871
 872 static void prepare_to_commit(void)
 873 {
 874         struct strbuf msg = STRBUF_INIT;
 875         strbuf_addbuf(&msg, &merge_msg);
 876         strbuf_addch(&msg, '\n');
 877         write_merge_msg(&msg);
 878         run_hook(get_index_file(), "prepare-commit-msg",
 879                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 880         if (option_edit) {
 881                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 882                         abort_commit(NULL);
 883         }
 884         read_merge_msg(&msg);
 885         stripspace(&msg, option_edit);
 886         if (!msg.len)
 887                 abort_commit(_("Empty commit message."));
 888         strbuf_release(&merge_msg);
 889         strbuf_addbuf(&merge_msg, &msg);
 890         strbuf_release(&msg);
 891 }
 892
 893 static int merge_trivial(struct commit *head)
 894 {
 895         unsigned char result_tree[20], result_commit[20];
 896         struct commit_list *parent = xmalloc(sizeof(*parent));
 897
 898         write_tree_trivial(result_tree);
 899         printf(_("Wonderful.\n"));
 900         parent->item = head;
 901         parent->next = xmalloc(sizeof(*parent->next));
 902         parent->next->item = remoteheads->item;
 903         parent->next->next = NULL;
 904         prepare_to_commit();
 905         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 906         finish(head, result_commit, "In-index merge");
 907         drop_save();
 908         return 0;
 909 }
 910
 911 static int finish_automerge(struct commit *head,
 912                             struct commit_list *common,
 913                             unsigned char *result_tree,
 914                             const char *wt_strategy)
 915 {
 916         struct commit_list *parents = NULL, *j;
 917         struct strbuf buf = STRBUF_INIT;
 918         unsigned char result_commit[20];
 919
 920         free_commit_list(common);
 921         if (allow_fast_forward) {
 922                 parents = remoteheads;
 923                 commit_list_insert(head, &parents);
 924                 parents = reduce_heads(parents);
 925         } else {
 926                 struct commit_list **pptr = &parents;
 927
 928                 pptr = &commit_list_insert(head,
 929                                 pptr)->next;
 930                 for (j = remoteheads; j; j = j->next)
 931                         pptr = &commit_list_insert(j->item, pptr)->next;
 932         }
 933         strbuf_addch(&merge_msg, '\n');
 934         prepare_to_commit();
 935         free_commit_list(remoteheads);
 936         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 937         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 938         finish(head, result_commit, buf.buf);
 939         strbuf_release(&buf);
 940         drop_save();
 941         return 0;
 942 }
 943
 944 static int suggest_conflicts(int renormalizing)
 945 {
 946         FILE *fp;
 947         int pos;
 948
 949         fp = fopen(git_path("MERGE_MSG"), "a");
 950         if (!fp)
 951                 die_errno(_("Could not open '%s' for writing"),
 952                           git_path("MERGE_MSG"));
 953         fprintf(fp, "\nConflicts:\n");
 954         for (pos = 0; pos < active_nr; pos++) {
 955                 struct cache_entry *ce = active_cache[pos];
 956
 957                 if (ce_stage(ce)) {
 958                         fprintf(fp, "\t%s\n", ce->name);
 959                         while (pos + 1 < active_nr &&
 960                                         !strcmp(ce->name,
 961                                                 active_cache[pos + 1]->name))
 962                                 pos++;
 963                 }
 964         }
 965         fclose(fp);
 966         rerere(allow_rerere_auto);
 967         printf(_("Automatic merge failed; "
 968                         "fix conflicts and then commit the result.\n"));
 969         return 1;
 970 }
 971
 972 static struct commit *is_old_style_invocation(int argc, const char **argv,
 973                                               const unsigned char *head)
 974 {
 975         struct commit *second_token = NULL;
 976         if (argc > 2) {
 977                 unsigned char second_sha1[20];
 978
 979                 if (get_sha1(argv[1], second_sha1))
 980                         return NULL;
 981                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 982                 if (!second_token)
 983                         die(_("'%s' is not a commit"), argv[1]);
 984                 if (hashcmp(second_token->object.sha1, head))
 985                         return NULL;
 986         }
 987         return second_token;
 988 }
 989
 990 static int evaluate_result(void)
 991 {
 992         int cnt = 0;
 993         struct rev_info rev;
 994
 995         /* Check how many files differ. */
 996         init_revisions(&rev, "");
 997         setup_revisions(0, NULL, &rev, NULL);
 998         rev.diffopt.output_format |=
 999                 DIFF_FORMAT_CALLBACK;
1000         rev.diffopt.format_callback = count_diff_files;
1001         rev.diffopt.format_callback_data = &cnt;
1002         run_diff_files(&rev, 0);
1003
1004         /*
1005          * Check how many unmerged entries are
1006          * there.
1007          */
1008         cnt += count_unmerged_entries();
1009
1010         return cnt;
1011 }
1012
1013 /*
1014  * Pretend as if the user told us to merge with the tracking
1015  * branch we have for the upstream of the current branch
1016  */
1017 static int setup_with_upstream(const char ***argv)
1018 {
1019         struct branch *branch = branch_get(NULL);
1020         int i;
1021         const char **args;
1022
1023         if (!branch)
1024                 die(_("No current branch."));
1025         if (!branch->remote)
1026                 die(_("No remote for the current branch."));
1027         if (!branch->merge_nr)
1028                 die(_("No default upstream defined for the current branch."));
1029
1030         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1031         for (i = 0; i < branch->merge_nr; i++) {
1032                 if (!branch->merge[i]->dst)
1033                         die(_("No remote tracking branch for %s from %s"),
1034                             branch->merge[i]->src, branch->remote_name);
1035                 args[i] = branch->merge[i]->dst;
1036         }
1037         args[i] = NULL;
1038         *argv = args;
1039         return i;
1040 }
1041
1042 static void write_merge_state(void)
1043 {
1044         int fd;
1045         struct commit_list *j;
1046         struct strbuf buf = STRBUF_INIT;
1047
1048         for (j = remoteheads; j; j = j->next) {
1049                 unsigned const char *sha1;
1050                 struct commit *c = j->item;
1051                 if (c->util && merge_remote_util(c)->obj) {
1052                         sha1 = merge_remote_util(c)->obj->sha1;
1053                 } else {
1054                         sha1 = c->object.sha1;
1055                 }
1056                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1057         }
1058         fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1059         if (fd < 0)
1060                 die_errno(_("Could not open '%s' for writing"),
1061                           git_path("MERGE_HEAD"));
1062         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1063                 die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1064         close(fd);
1065         strbuf_addch(&merge_msg, '\n');
1066         write_merge_msg(&merge_msg);
1067         fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1068         if (fd < 0)
1069                 die_errno(_("Could not open '%s' for writing"),
1070                           git_path("MERGE_MODE"));
1071         strbuf_reset(&buf);
1072         if (!allow_fast_forward)
1073                 strbuf_addf(&buf, "no-ff");
1074         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1075                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1076         close(fd);
1077 }
1078
1079 int cmd_merge(int argc, const char **argv, const char *prefix)
1080 {
1081         unsigned char result_tree[20];
1082         unsigned char stash[20];
1083         unsigned char head_sha1[20];
1084         struct commit *head_commit;
1085         struct strbuf buf = STRBUF_INIT;
1086         const char *head_arg;
1087         int flag, i;
1088         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1089         struct commit_list *common = NULL;
1090         const char *best_strategy = NULL, *wt_strategy = NULL;
1091         struct commit_list **remotes = &remoteheads;
1092
1093         if (argc == 2 && !strcmp(argv[1], "-h"))
1094                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1095
1096         /*
1097          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1098          * current branch.
1099          */
1100         branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1101         if (branch && !prefixcmp(branch, "refs/heads/"))
1102                 branch += 11;
1103         if (!branch || is_null_sha1(head_sha1))
1104                 head_commit = NULL;
1105         else
1106                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1107
1108         git_config(git_merge_config, NULL);
1109
1110         if (branch_mergeoptions)
1111                 parse_branch_merge_options(branch_mergeoptions);
1112         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1113                         builtin_merge_usage, 0);
1114
1115         if (verbosity < 0 && show_progress == -1)
1116                 show_progress = 0;
1117
1118         if (abort_current_merge) {
1119                 int nargc = 2;
1120                 const char *nargv[] = {"reset", "--merge", NULL};
1121
1122                 if (!file_exists(git_path("MERGE_HEAD")))
1123                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1124
1125                 /* Invoke 'git reset --merge' */
1126                 return cmd_reset(nargc, nargv, prefix);
1127         }
1128
1129         if (read_cache_unmerged())
1130                 die_resolve_conflict("merge");
1131
1132         if (file_exists(git_path("MERGE_HEAD"))) {
1133                 /*
1134                  * There is no unmerged entry, don't advise 'git
1135                  * add/rm <file>', just 'git commit'.
1136                  */
1137                 if (advice_resolve_conflict)
1138                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1139                                   "Please, commit your changes before you can merge."));
1140                 else
1141                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1142         }
1143         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1144                 if (advice_resolve_conflict)
1145                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1146                             "Please, commit your changes before you can merge."));
1147                 else
1148                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1149         }
1150         resolve_undo_clear();
1151
1152         if (verbosity < 0)
1153                 show_diffstat = 0;
1154
1155         if (squash) {
1156                 if (!allow_fast_forward)
1157                         die(_("You cannot combine --squash with --no-ff."));
1158                 option_commit = 0;
1159         }
1160
1161         if (!allow_fast_forward && fast_forward_only)
1162                 die(_("You cannot combine --no-ff with --ff-only."));
1163
1164         if (!abort_current_merge) {
1165                 if (!argc && default_to_upstream)
1166                         argc = setup_with_upstream(&argv);
1167                 else if (argc == 1 && !strcmp(argv[0], "-"))
1168                         argv[0] = "@{-1}";
1169         }
1170         if (!argc)
1171                 usage_with_options(builtin_merge_usage,
1172                         builtin_merge_options);
1173
1174         /*
1175          * This could be traditional "merge <msg> HEAD <commit>..."  and
1176          * the way we can tell it is to see if the second token is HEAD,
1177          * but some people might have misused the interface and used a
1178          * committish that is the same as HEAD there instead.
1179          * Traditional format never would have "-m" so it is an
1180          * additional safety measure to check for it.
1181          */
1182
1183         if (!have_message && head_commit &&
1184             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1185                 strbuf_addstr(&merge_msg, argv[0]);
1186                 head_arg = argv[1];
1187                 argv += 2;
1188                 argc -= 2;
1189         } else if (!head_commit) {
1190                 struct commit *remote_head;
1191                 /*
1192                  * If the merged head is a valid one there is no reason
1193                  * to forbid "git merge" into a branch yet to be born.
1194                  * We do the same for "git pull".
1195                  */
1196                 if (argc != 1)
1197                         die(_("Can merge only exactly one commit into "
1198                                 "empty head"));
1199                 if (squash)
1200                         die(_("Squash commit into empty head not supported yet"));
1201                 if (!allow_fast_forward)
1202                         die(_("Non-fast-forward commit does not make sense into "
1203                             "an empty head"));
1204                 remote_head = get_merge_parent(argv[0]);
1205                 if (!remote_head)
1206                         die(_("%s - not something we can merge"), argv[0]);
1207                 read_empty(remote_head->object.sha1, 0);
1208                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1209                            NULL, 0, DIE_ON_ERR);
1210                 return 0;
1211         } else {
1212                 struct strbuf merge_names = STRBUF_INIT;
1213
1214                 /* We are invoked directly as the first-class UI. */
1215                 head_arg = "HEAD";
1216
1217                 /*
1218                  * All the rest are the commits being merged; prepare
1219                  * the standard merge summary message to be appended
1220                  * to the given message.
1221                  */
1222                 for (i = 0; i < argc; i++)
1223                         merge_name(argv[i], &merge_names);
1224
1225                 if (!have_message || shortlog_len) {
1226                         struct fmt_merge_msg_opts opts;
1227                         memset(&opts, 0, sizeof(opts));
1228                         opts.add_title = !have_message;
1229                         opts.shortlog_len = shortlog_len;
1230
1231                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1232                         if (merge_msg.len)
1233                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1234                 }
1235         }
1236
1237         if (!head_commit || !argc)
1238                 usage_with_options(builtin_merge_usage,
1239                         builtin_merge_options);
1240
1241         strbuf_addstr(&buf, "merge");
1242         for (i = 0; i < argc; i++)
1243                 strbuf_addf(&buf, " %s", argv[i]);
1244         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1245         strbuf_reset(&buf);
1246
1247         for (i = 0; i < argc; i++) {
1248                 struct commit *commit = get_merge_parent(argv[i]);
1249                 if (!commit)
1250                         die(_("%s - not something we can merge"), argv[i]);
1251                 remotes = &commit_list_insert(commit, remotes)->next;
1252                 strbuf_addf(&buf, "GITHEAD_%s",
1253                             sha1_to_hex(commit->object.sha1));
1254                 setenv(buf.buf, argv[i], 1);
1255                 strbuf_reset(&buf);
1256                 if (merge_remote_util(commit) &&
1257                     merge_remote_util(commit)->obj &&
1258                     merge_remote_util(commit)->obj->type == OBJ_TAG) {
1259                         option_edit = 1;
1260                         allow_fast_forward = 0;
1261                 }
1262         }
1263
1264         if (!use_strategies) {
1265                 if (!remoteheads->next)
1266                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1267                 else
1268                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1269         }
1270
1271         for (i = 0; i < use_strategies_nr; i++) {
1272                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1273                         allow_fast_forward = 0;
1274                 if (use_strategies[i]->attr & NO_TRIVIAL)
1275                         allow_trivial = 0;
1276         }
1277
1278         if (!remoteheads->next)
1279                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1280         else {
1281                 struct commit_list *list = remoteheads;
1282                 commit_list_insert(head_commit, &list);
1283                 common = get_octopus_merge_bases(list);
1284                 free(list);
1285         }
1286
1287         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1288                    NULL, 0, DIE_ON_ERR);
1289
1290         if (!common)
1291                 ; /* No common ancestors found. We need a real merge. */
1292         else if (!remoteheads->next && !common->next &&
1293                         common->item == remoteheads->item) {
1294                 /*
1295                  * If head can reach all the merge then we are up to date.
1296                  * but first the most common case of merging one remote.
1297                  */
1298                 finish_up_to_date("Already up-to-date.");
1299                 return 0;
1300         } else if (allow_fast_forward && !remoteheads->next &&
1301                         !common->next &&
1302                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1303                 /* Again the most common case of merging one remote. */
1304                 struct strbuf msg = STRBUF_INIT;
1305                 struct commit *commit;
1306                 char hex[41];
1307
1308                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1309
1310                 if (verbosity >= 0)
1311                         printf(_("Updating %s..%s\n"),
1312                                 hex,
1313                                 find_unique_abbrev(remoteheads->item->object.sha1,
1314                                 DEFAULT_ABBREV));
1315                 strbuf_addstr(&msg, "Fast-forward");
1316                 if (have_message)
1317                         strbuf_addstr(&msg,
1318                                 " (no commit created; -m option ignored)");
1319                 commit = remoteheads->item;
1320                 if (!commit)
1321                         return 1;
1322
1323                 if (checkout_fast_forward(head_commit->object.sha1,
1324                                           commit->object.sha1))
1325                         return 1;
1326
1327                 finish(head_commit, commit->object.sha1, msg.buf);
1328                 drop_save();
1329                 return 0;
1330         } else if (!remoteheads->next && common->next)
1331                 ;
1332                 /*
1333                  * We are not doing octopus and not fast-forward.  Need
1334                  * a real merge.
1335                  */
1336         else if (!remoteheads->next && !common->next && option_commit) {
1337                 /*
1338                  * We are not doing octopus, not fast-forward, and have
1339                  * only one common.
1340                  */
1341                 refresh_cache(REFRESH_QUIET);
1342                 if (allow_trivial && !fast_forward_only) {
1343                         /* See if it is really trivial. */
1344                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1345                         printf(_("Trying really trivial in-index merge...\n"));
1346                         if (!read_tree_trivial(common->item->object.sha1,
1347                                         head_commit->object.sha1, remoteheads->item->object.sha1))
1348                                 return merge_trivial(head_commit);
1349                         printf(_("Nope.\n"));
1350                 }
1351         } else {
1352                 /*
1353                  * An octopus.  If we can reach all the remote we are up
1354                  * to date.
1355                  */
1356                 int up_to_date = 1;
1357                 struct commit_list *j;
1358
1359                 for (j = remoteheads; j; j = j->next) {
1360                         struct commit_list *common_one;
1361
1362                         /*
1363                          * Here we *have* to calculate the individual
1364                          * merge_bases again, otherwise "git merge HEAD^
1365                          * HEAD^^" would be missed.
1366                          */
1367                         common_one = get_merge_bases(head_commit, j->item, 1);
1368                         if (hashcmp(common_one->item->object.sha1,
1369                                 j->item->object.sha1)) {
1370                                 up_to_date = 0;
1371                                 break;
1372                         }
1373                 }
1374                 if (up_to_date) {
1375                         finish_up_to_date("Already up-to-date. Yeeah!");
1376                         return 0;
1377                 }
1378         }
1379
1380         if (fast_forward_only)
1381                 die(_("Not possible to fast-forward, aborting."));
1382
1383         /* We are going to make a new commit. */
1384         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1385
1386         /*
1387          * At this point, we need a real merge.  No matter what strategy
1388          * we use, it would operate on the index, possibly affecting the
1389          * working tree, and when resolved cleanly, have the desired
1390          * tree in the index -- this means that the index must be in
1391          * sync with the head commit.  The strategies are responsible
1392          * to ensure this.
1393          */
1394         if (use_strategies_nr == 1 ||
1395             /*
1396              * Stash away the local changes so that we can try more than one.
1397              */
1398             save_state(stash))
1399                 hashcpy(stash, null_sha1);
1400
1401         for (i = 0; i < use_strategies_nr; i++) {
1402                 int ret;
1403                 if (i) {
1404                         printf(_("Rewinding the tree to pristine...\n"));
1405                         restore_state(head_commit->object.sha1, stash);
1406                 }
1407                 if (use_strategies_nr != 1)
1408                         printf(_("Trying merge strategy %s...\n"),
1409                                 use_strategies[i]->name);
1410                 /*
1411                  * Remember which strategy left the state in the working
1412                  * tree.
1413                  */
1414                 wt_strategy = use_strategies[i]->name;
1415
1416                 ret = try_merge_strategy(use_strategies[i]->name,
1417                                          common, head_commit, head_arg);
1418                 if (!option_commit && !ret) {
1419                         merge_was_ok = 1;
1420                         /*
1421                          * This is necessary here just to avoid writing
1422                          * the tree, but later we will *not* exit with
1423                          * status code 1 because merge_was_ok is set.
1424                          */
1425                         ret = 1;
1426                 }
1427
1428                 if (ret) {
1429                         /*
1430                          * The backend exits with 1 when conflicts are
1431                          * left to be resolved, with 2 when it does not
1432                          * handle the given merge at all.
1433                          */
1434                         if (ret == 1) {
1435                                 int cnt = evaluate_result();
1436
1437                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1438                                         best_strategy = use_strategies[i]->name;
1439                                         best_cnt = cnt;
1440                                 }
1441                         }
1442                         if (merge_was_ok)
1443                                 break;
1444                         else
1445                                 continue;
1446                 }
1447
1448                 /* Automerge succeeded. */
1449                 write_tree_trivial(result_tree);
1450                 automerge_was_ok = 1;
1451                 break;
1452         }
1453
1454         /*
1455          * If we have a resulting tree, that means the strategy module
1456          * auto resolved the merge cleanly.
1457          */
1458         if (automerge_was_ok)
1459                 return finish_automerge(head_commit, common, result_tree,
1460                                         wt_strategy);
1461
1462         /*
1463          * Pick the result from the best strategy and have the user fix
1464          * it up.
1465          */
1466         if (!best_strategy) {
1467                 restore_state(head_commit->object.sha1, stash);
1468                 if (use_strategies_nr > 1)
1469                         fprintf(stderr,
1470                                 _("No merge strategy handled the merge.\n"));
1471                 else
1472                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1473                                 use_strategies[0]->name);
1474                 return 2;
1475         } else if (best_strategy == wt_strategy)
1476                 ; /* We already have its result in the working tree. */
1477         else {
1478                 printf(_("Rewinding the tree to pristine...\n"));
1479                 restore_state(head_commit->object.sha1, stash);
1480                 printf(_("Using the %s to prepare resolving by hand.\n"),
1481                         best_strategy);
1482                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1483         }
1484
1485         if (squash)
1486                 finish(head_commit, NULL, NULL);
1487         else
1488                 write_merge_state();
1489
1490         if (merge_was_ok) {
1491                 fprintf(stderr, _("Automatic merge went well; "
1492                         "stopped before committing as requested\n"));
1493                 return 0;
1494         } else
1495                 return suggest_conflicts(option_renormalize);
1496 }