builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29 #include "fmt-merge-msg.h"
  30
  31 #define DEFAULT_TWOHEAD (1<<0)
  32 #define DEFAULT_OCTOPUS (1<<1)
  33 #define NO_FAST_FORWARD (1<<2)
  34 #define NO_TRIVIAL      (1<<3)
  35
  36 struct strategy {
  37         const char *name;
  38         unsigned attr;
  39 };
  40
  41 static const char * const builtin_merge_usage[] = {
  42         "git merge [options] [<commit>...]",
  43         "git merge [options] <msg> HEAD <commit>",
  44         "git merge --abort",
  45         NULL
  46 };
  47
  48 static int show_diffstat = 1, shortlog_len = -1, squash;
  49 static int option_commit = 1, allow_fast_forward = 1;
  50 static int fast_forward_only, option_edit;
  51 static int allow_trivial = 1, have_message;
  52 static struct strbuf merge_msg;
  53 static struct commit_list *remoteheads;
  54 static struct strategy **use_strategies;
  55 static size_t use_strategies_nr, use_strategies_alloc;
  56 static const char **xopts;
  57 static size_t xopts_nr, xopts_alloc;
  58 static const char *branch;
  59 static char *branch_mergeoptions;
  60 static int option_renormalize;
  61 static int verbosity;
  62 static int allow_rerere_auto;
  63 static int abort_current_merge;
  64 static int show_progress = -1;
  65 static int default_to_upstream;
  66
  67 static struct strategy all_strategy[] = {
  68         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  69         { "octopus",    DEFAULT_OCTOPUS },
  70         { "resolve",    0 },
  71         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  72         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  73 };
  74
  75 static const char *pull_twohead, *pull_octopus;
  76
  77 static int option_parse_message(const struct option *opt,
  78                                 const char *arg, int unset)
  79 {
  80         struct strbuf *buf = opt->value;
  81
  82         if (unset)
  83                 strbuf_setlen(buf, 0);
  84         else if (arg) {
  85                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  86                 have_message = 1;
  87         } else
  88                 return error(_("switch `m' requires a value"));
  89         return 0;
  90 }
  91
  92 static struct strategy *get_strategy(const char *name)
  93 {
  94         int i;
  95         struct strategy *ret;
  96         static struct cmdnames main_cmds, other_cmds;
  97         static int loaded;
  98
  99         if (!name)
 100                 return NULL;
 101
 102         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 103                 if (!strcmp(name, all_strategy[i].name))
 104                         return &all_strategy[i];
 105
 106         if (!loaded) {
 107                 struct cmdnames not_strategies;
 108                 loaded = 1;
 109
 110                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 111                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 112                 for (i = 0; i < main_cmds.cnt; i++) {
 113                         int j, found = 0;
 114                         struct cmdname *ent = main_cmds.names[i];
 115                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 116                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 117                                                 && !all_strategy[j].name[ent->len])
 118                                         found = 1;
 119                         if (!found)
 120                                 add_cmdname(&not_strategies, ent->name, ent->len);
 121                 }
 122                 exclude_cmds(&main_cmds, &not_strategies);
 123         }
 124         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 125                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 126                 fprintf(stderr, _("Available strategies are:"));
 127                 for (i = 0; i < main_cmds.cnt; i++)
 128                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 129                 fprintf(stderr, ".\n");
 130                 if (other_cmds.cnt) {
 131                         fprintf(stderr, _("Available custom strategies are:"));
 132                         for (i = 0; i < other_cmds.cnt; i++)
 133                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 134                         fprintf(stderr, ".\n");
 135                 }
 136                 exit(1);
 137         }
 138
 139         ret = xcalloc(1, sizeof(struct strategy));
 140         ret->name = xstrdup(name);
 141         ret->attr = NO_TRIVIAL;
 142         return ret;
 143 }
 144
 145 static void append_strategy(struct strategy *s)
 146 {
 147         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 148         use_strategies[use_strategies_nr++] = s;
 149 }
 150
 151 static int option_parse_strategy(const struct option *opt,
 152                                  const char *name, int unset)
 153 {
 154         if (unset)
 155                 return 0;
 156
 157         append_strategy(get_strategy(name));
 158         return 0;
 159 }
 160
 161 static int option_parse_x(const struct option *opt,
 162                           const char *arg, int unset)
 163 {
 164         if (unset)
 165                 return 0;
 166
 167         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 168         xopts[xopts_nr++] = xstrdup(arg);
 169         return 0;
 170 }
 171
 172 static int option_parse_n(const struct option *opt,
 173                           const char *arg, int unset)
 174 {
 175         show_diffstat = unset;
 176         return 0;
 177 }
 178
 179 static struct option builtin_merge_options[] = {
 180         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 181                 "do not show a diffstat at the end of the merge",
 182                 PARSE_OPT_NOARG, option_parse_n },
 183         OPT_BOOLEAN(0, "stat", &show_diffstat,
 184                 "show a diffstat at the end of the merge"),
 185         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 186         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 187           "add (at most <n>) entries from shortlog to merge commit message",
 188           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 189         OPT_BOOLEAN(0, "squash", &squash,
 190                 "create a single commit instead of doing a merge"),
 191         OPT_BOOLEAN(0, "commit", &option_commit,
 192                 "perform a commit if the merge succeeds (default)"),
 193         OPT_BOOLEAN('e', "edit", &option_edit,
 194                 "edit message before committing"),
 195         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 196                 "allow fast-forward (default)"),
 197         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 198                 "abort if fast-forward is not possible"),
 199         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 200         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 201                 "merge strategy to use", option_parse_strategy),
 202         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 203                 "option for selected merge strategy", option_parse_x),
 204         OPT_CALLBACK('m', "message", &merge_msg, "message",
 205                 "merge commit message (for a non-fast-forward merge)",
 206                 option_parse_message),
 207         OPT__VERBOSITY(&verbosity),
 208         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 209                 "abort the current in-progress merge"),
 210         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 211         OPT_END()
 212 };
 213
 214 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 215 static void drop_save(void)
 216 {
 217         unlink(git_path("MERGE_HEAD"));
 218         unlink(git_path("MERGE_MSG"));
 219         unlink(git_path("MERGE_MODE"));
 220 }
 221
 222 static int save_state(unsigned char *stash)
 223 {
 224         int len;
 225         struct child_process cp;
 226         struct strbuf buffer = STRBUF_INIT;
 227         const char *argv[] = {"stash", "create", NULL};
 228
 229         memset(&cp, 0, sizeof(cp));
 230         cp.argv = argv;
 231         cp.out = -1;
 232         cp.git_cmd = 1;
 233
 234         if (start_command(&cp))
 235                 die(_("could not run stash."));
 236         len = strbuf_read(&buffer, cp.out, 1024);
 237         close(cp.out);
 238
 239         if (finish_command(&cp) || len < 0)
 240                 die(_("stash failed"));
 241         else if (!len)          /* no changes */
 242                 return -1;
 243         strbuf_setlen(&buffer, buffer.len-1);
 244         if (get_sha1(buffer.buf, stash))
 245                 die(_("not a valid object: %s"), buffer.buf);
 246         return 0;
 247 }
 248
 249 static void read_empty(unsigned const char *sha1, int verbose)
 250 {
 251         int i = 0;
 252         const char *args[7];
 253
 254         args[i++] = "read-tree";
 255         if (verbose)
 256                 args[i++] = "-v";
 257         args[i++] = "-m";
 258         args[i++] = "-u";
 259         args[i++] = EMPTY_TREE_SHA1_HEX;
 260         args[i++] = sha1_to_hex(sha1);
 261         args[i] = NULL;
 262
 263         if (run_command_v_opt(args, RUN_GIT_CMD))
 264                 die(_("read-tree failed"));
 265 }
 266
 267 static void reset_hard(unsigned const char *sha1, int verbose)
 268 {
 269         int i = 0;
 270         const char *args[6];
 271
 272         args[i++] = "read-tree";
 273         if (verbose)
 274                 args[i++] = "-v";
 275         args[i++] = "--reset";
 276         args[i++] = "-u";
 277         args[i++] = sha1_to_hex(sha1);
 278         args[i] = NULL;
 279
 280         if (run_command_v_opt(args, RUN_GIT_CMD))
 281                 die(_("read-tree failed"));
 282 }
 283
 284 static void restore_state(const unsigned char *head,
 285                           const unsigned char *stash)
 286 {
 287         struct strbuf sb = STRBUF_INIT;
 288         const char *args[] = { "stash", "apply", NULL, NULL };
 289
 290         if (is_null_sha1(stash))
 291                 return;
 292
 293         reset_hard(head, 1);
 294
 295         args[2] = sha1_to_hex(stash);
 296
 297         /*
 298          * It is OK to ignore error here, for example when there was
 299          * nothing to restore.
 300          */
 301         run_command_v_opt(args, RUN_GIT_CMD);
 302
 303         strbuf_release(&sb);
 304         refresh_cache(REFRESH_QUIET);
 305 }
 306
 307 /* This is called when no merge was necessary. */
 308 static void finish_up_to_date(const char *msg)
 309 {
 310         if (verbosity >= 0)
 311                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 312         drop_save();
 313 }
 314
 315 static void squash_message(struct commit *commit)
 316 {
 317         struct rev_info rev;
 318         struct strbuf out = STRBUF_INIT;
 319         struct commit_list *j;
 320         const char *filename;
 321         int fd;
 322         struct pretty_print_context ctx = {0};
 323
 324         printf(_("Squash commit -- not updating HEAD\n"));
 325         filename = git_path("SQUASH_MSG");
 326         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 327         if (fd < 0)
 328                 die_errno(_("Could not write to '%s'"), filename);
 329
 330         init_revisions(&rev, NULL);
 331         rev.ignore_merges = 1;
 332         rev.commit_format = CMIT_FMT_MEDIUM;
 333
 334         commit->object.flags |= UNINTERESTING;
 335         add_pending_object(&rev, &commit->object, NULL);
 336
 337         for (j = remoteheads; j; j = j->next)
 338                 add_pending_object(&rev, &j->item->object, NULL);
 339
 340         setup_revisions(0, NULL, &rev, NULL);
 341         if (prepare_revision_walk(&rev))
 342                 die(_("revision walk setup failed"));
 343
 344         ctx.abbrev = rev.abbrev;
 345         ctx.date_mode = rev.date_mode;
 346         ctx.fmt = rev.commit_format;
 347
 348         strbuf_addstr(&out, "Squashed commit of the following:\n");
 349         while ((commit = get_revision(&rev)) != NULL) {
 350                 strbuf_addch(&out, '\n');
 351                 strbuf_addf(&out, "commit %s\n",
 352                         sha1_to_hex(commit->object.sha1));
 353                 pretty_print_commit(&ctx, commit, &out);
 354         }
 355         if (write(fd, out.buf, out.len) < 0)
 356                 die_errno(_("Writing SQUASH_MSG"));
 357         if (close(fd))
 358                 die_errno(_("Finishing SQUASH_MSG"));
 359         strbuf_release(&out);
 360 }
 361
 362 static void finish(struct commit *head_commit,
 363                    const unsigned char *new_head, const char *msg)
 364 {
 365         struct strbuf reflog_message = STRBUF_INIT;
 366         const unsigned char *head = head_commit->object.sha1;
 367
 368         if (!msg)
 369                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 370         else {
 371                 if (verbosity >= 0)
 372                         printf("%s\n", msg);
 373                 strbuf_addf(&reflog_message, "%s: %s",
 374                         getenv("GIT_REFLOG_ACTION"), msg);
 375         }
 376         if (squash) {
 377                 squash_message(head_commit);
 378         } else {
 379                 if (verbosity >= 0 && !merge_msg.len)
 380                         printf(_("No merge message -- not updating HEAD\n"));
 381                 else {
 382                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 383                         update_ref(reflog_message.buf, "HEAD",
 384                                 new_head, head, 0,
 385                                 DIE_ON_ERR);
 386                         /*
 387                          * We ignore errors in 'gc --auto', since the
 388                          * user should see them.
 389                          */
 390                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 391                 }
 392         }
 393         if (new_head && show_diffstat) {
 394                 struct diff_options opts;
 395                 diff_setup(&opts);
 396                 opts.output_format |=
 397                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 398                 opts.detect_rename = DIFF_DETECT_RENAME;
 399                 if (diff_setup_done(&opts) < 0)
 400                         die(_("diff_setup_done failed"));
 401                 diff_tree_sha1(head, new_head, "", &opts);
 402                 diffcore_std(&opts);
 403                 diff_flush(&opts);
 404         }
 405
 406         /* Run a post-merge hook */
 407         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 408
 409         strbuf_release(&reflog_message);
 410 }
 411
 412 static struct object *want_commit(const char *name)
 413 {
 414         struct object *obj;
 415         unsigned char sha1[20];
 416         if (get_sha1(name, sha1))
 417                 return NULL;
 418         obj = parse_object(sha1);
 419         return peel_to_type(name, 0, obj, OBJ_COMMIT);
 420 }
 421
 422 /* Get the name for the merge commit's message. */
 423 static void merge_name(const char *remote, struct strbuf *msg)
 424 {
 425         struct object *remote_head;
 426         unsigned char branch_head[20], buf_sha[20];
 427         struct strbuf buf = STRBUF_INIT;
 428         struct strbuf bname = STRBUF_INIT;
 429         const char *ptr;
 430         char *found_ref;
 431         int len, early;
 432
 433         strbuf_branchname(&bname, remote);
 434         remote = bname.buf;
 435
 436         memset(branch_head, 0, sizeof(branch_head));
 437         remote_head = want_commit(remote);
 438         if (!remote_head)
 439                 die(_("'%s' does not point to a commit"), remote);
 440
 441         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 442                 if (!prefixcmp(found_ref, "refs/heads/")) {
 443                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 444                                     sha1_to_hex(branch_head), remote);
 445                         goto cleanup;
 446                 }
 447                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 448                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 449                                     sha1_to_hex(branch_head), remote);
 450                         goto cleanup;
 451                 }
 452         }
 453
 454         /* See if remote matches <name>^^^.. or <name>~<number> */
 455         for (len = 0, ptr = remote + strlen(remote);
 456              remote < ptr && ptr[-1] == '^';
 457              ptr--)
 458                 len++;
 459         if (len)
 460                 early = 1;
 461         else {
 462                 early = 0;
 463                 ptr = strrchr(remote, '~');
 464                 if (ptr) {
 465                         int seen_nonzero = 0;
 466
 467                         len++; /* count ~ */
 468                         while (*++ptr && isdigit(*ptr)) {
 469                                 seen_nonzero |= (*ptr != '0');
 470                                 len++;
 471                         }
 472                         if (*ptr)
 473                                 len = 0; /* not ...~<number> */
 474                         else if (seen_nonzero)
 475                                 early = 1;
 476                         else if (len == 1)
 477                                 early = 1; /* "name~" is "name~1"! */
 478                 }
 479         }
 480         if (len) {
 481                 struct strbuf truname = STRBUF_INIT;
 482                 strbuf_addstr(&truname, "refs/heads/");
 483                 strbuf_addstr(&truname, remote);
 484                 strbuf_setlen(&truname, truname.len - len);
 485                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 486                         strbuf_addf(msg,
 487                                     "%s\t\tbranch '%s'%s of .\n",
 488                                     sha1_to_hex(remote_head->sha1),
 489                                     truname.buf + 11,
 490                                     (early ? " (early part)" : ""));
 491                         strbuf_release(&truname);
 492                         goto cleanup;
 493                 }
 494         }
 495
 496         if (!strcmp(remote, "FETCH_HEAD") &&
 497                         !access(git_path("FETCH_HEAD"), R_OK)) {
 498                 const char *filename;
 499                 FILE *fp;
 500                 struct strbuf line = STRBUF_INIT;
 501                 char *ptr;
 502
 503                 filename = git_path("FETCH_HEAD");
 504                 fp = fopen(filename, "r");
 505                 if (!fp)
 506                         die_errno(_("could not open '%s' for reading"),
 507                                   filename);
 508                 strbuf_getline(&line, fp, '\n');
 509                 fclose(fp);
 510                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 511                 if (ptr)
 512                         strbuf_remove(&line, ptr-line.buf+1, 13);
 513                 strbuf_addbuf(msg, &line);
 514                 strbuf_release(&line);
 515                 goto cleanup;
 516         }
 517         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 518                 sha1_to_hex(remote_head->sha1), remote);
 519 cleanup:
 520         strbuf_release(&buf);
 521         strbuf_release(&bname);
 522 }
 523
 524 static void parse_branch_merge_options(char *bmo)
 525 {
 526         const char **argv;
 527         int argc;
 528
 529         if (!bmo)
 530                 return;
 531         argc = split_cmdline(bmo, &argv);
 532         if (argc < 0)
 533                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 534                     split_cmdline_strerror(argc));
 535         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 536         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 537         argc++;
 538         argv[0] = "branch.*.mergeoptions";
 539         parse_options(argc, argv, NULL, builtin_merge_options,
 540                       builtin_merge_usage, 0);
 541         free(argv);
 542 }
 543
 544 static int git_merge_config(const char *k, const char *v, void *cb)
 545 {
 546         int status;
 547
 548         if (branch && !prefixcmp(k, "branch.") &&
 549                 !prefixcmp(k + 7, branch) &&
 550                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 551                 free(branch_mergeoptions);
 552                 branch_mergeoptions = xstrdup(v);
 553                 return 0;
 554         }
 555
 556         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 557                 show_diffstat = git_config_bool(k, v);
 558         else if (!strcmp(k, "pull.twohead"))
 559                 return git_config_string(&pull_twohead, k, v);
 560         else if (!strcmp(k, "pull.octopus"))
 561                 return git_config_string(&pull_octopus, k, v);
 562         else if (!strcmp(k, "merge.renormalize"))
 563                 option_renormalize = git_config_bool(k, v);
 564         else if (!strcmp(k, "merge.ff")) {
 565                 int boolval = git_config_maybe_bool(k, v);
 566                 if (0 <= boolval) {
 567                         allow_fast_forward = boolval;
 568                 } else if (v && !strcmp(v, "only")) {
 569                         allow_fast_forward = 1;
 570                         fast_forward_only = 1;
 571                 } /* do not barf on values from future versions of git */
 572                 return 0;
 573         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 574                 default_to_upstream = git_config_bool(k, v);
 575                 return 0;
 576         }
 577         status = fmt_merge_msg_config(k, v, cb);
 578         if (status)
 579                 return status;
 580         return git_diff_ui_config(k, v, cb);
 581 }
 582
 583 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 584                              unsigned char *one)
 585 {
 586         int i, nr_trees = 0;
 587         struct tree *trees[MAX_UNPACK_TREES];
 588         struct tree_desc t[MAX_UNPACK_TREES];
 589         struct unpack_trees_options opts;
 590
 591         memset(&opts, 0, sizeof(opts));
 592         opts.head_idx = 2;
 593         opts.src_index = &the_index;
 594         opts.dst_index = &the_index;
 595         opts.update = 1;
 596         opts.verbose_update = 1;
 597         opts.trivial_merges_only = 1;
 598         opts.merge = 1;
 599         trees[nr_trees] = parse_tree_indirect(common);
 600         if (!trees[nr_trees++])
 601                 return -1;
 602         trees[nr_trees] = parse_tree_indirect(head);
 603         if (!trees[nr_trees++])
 604                 return -1;
 605         trees[nr_trees] = parse_tree_indirect(one);
 606         if (!trees[nr_trees++])
 607                 return -1;
 608         opts.fn = threeway_merge;
 609         cache_tree_free(&active_cache_tree);
 610         for (i = 0; i < nr_trees; i++) {
 611                 parse_tree(trees[i]);
 612                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 613         }
 614         if (unpack_trees(nr_trees, t, &opts))
 615                 return -1;
 616         return 0;
 617 }
 618
 619 static void write_tree_trivial(unsigned char *sha1)
 620 {
 621         if (write_cache_as_tree(sha1, 0, NULL))
 622                 die(_("git write-tree failed to write a tree"));
 623 }
 624
 625 static const char *merge_argument(struct commit *commit)
 626 {
 627         if (commit)
 628                 return sha1_to_hex(commit->object.sha1);
 629         else
 630                 return EMPTY_TREE_SHA1_HEX;
 631 }
 632
 633 int try_merge_command(const char *strategy, size_t xopts_nr,
 634                       const char **xopts, struct commit_list *common,
 635                       const char *head_arg, struct commit_list *remotes)
 636 {
 637         const char **args;
 638         int i = 0, x = 0, ret;
 639         struct commit_list *j;
 640         struct strbuf buf = STRBUF_INIT;
 641
 642         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 643                         commit_list_count(remotes)) * sizeof(char *));
 644         strbuf_addf(&buf, "merge-%s", strategy);
 645         args[i++] = buf.buf;
 646         for (x = 0; x < xopts_nr; x++) {
 647                 char *s = xmalloc(strlen(xopts[x])+2+1);
 648                 strcpy(s, "--");
 649                 strcpy(s+2, xopts[x]);
 650                 args[i++] = s;
 651         }
 652         for (j = common; j; j = j->next)
 653                 args[i++] = xstrdup(merge_argument(j->item));
 654         args[i++] = "--";
 655         args[i++] = head_arg;
 656         for (j = remotes; j; j = j->next)
 657                 args[i++] = xstrdup(merge_argument(j->item));
 658         args[i] = NULL;
 659         ret = run_command_v_opt(args, RUN_GIT_CMD);
 660         strbuf_release(&buf);
 661         i = 1;
 662         for (x = 0; x < xopts_nr; x++)
 663                 free((void *)args[i++]);
 664         for (j = common; j; j = j->next)
 665                 free((void *)args[i++]);
 666         i += 2;
 667         for (j = remotes; j; j = j->next)
 668                 free((void *)args[i++]);
 669         free(args);
 670         discard_cache();
 671         if (read_cache() < 0)
 672                 die(_("failed to read the cache"));
 673         resolve_undo_clear();
 674
 675         return ret;
 676 }
 677
 678 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 679                               struct commit *head, const char *head_arg)
 680 {
 681         int index_fd;
 682         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 683
 684         index_fd = hold_locked_index(lock, 1);
 685         refresh_cache(REFRESH_QUIET);
 686         if (active_cache_changed &&
 687                         (write_cache(index_fd, active_cache, active_nr) ||
 688                          commit_locked_index(lock)))
 689                 return error(_("Unable to write index."));
 690         rollback_lock_file(lock);
 691
 692         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 693                 int clean, x;
 694                 struct commit *result;
 695                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 696                 int index_fd;
 697                 struct commit_list *reversed = NULL;
 698                 struct merge_options o;
 699                 struct commit_list *j;
 700
 701                 if (remoteheads->next) {
 702                         error(_("Not handling anything other than two heads merge."));
 703                         return 2;
 704                 }
 705
 706                 init_merge_options(&o);
 707                 if (!strcmp(strategy, "subtree"))
 708                         o.subtree_shift = "";
 709
 710                 o.renormalize = option_renormalize;
 711                 o.show_rename_progress =
 712                         show_progress == -1 ? isatty(2) : show_progress;
 713
 714                 for (x = 0; x < xopts_nr; x++)
 715                         if (parse_merge_opt(&o, xopts[x]))
 716                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 717
 718                 o.branch1 = head_arg;
 719                 o.branch2 = remoteheads->item->util;
 720
 721                 for (j = common; j; j = j->next)
 722                         commit_list_insert(j->item, &reversed);
 723
 724                 index_fd = hold_locked_index(lock, 1);
 725                 clean = merge_recursive(&o, head,
 726                                 remoteheads->item, reversed, &result);
 727                 if (active_cache_changed &&
 728                                 (write_cache(index_fd, active_cache, active_nr) ||
 729                                  commit_locked_index(lock)))
 730                         die (_("unable to write %s"), get_index_file());
 731                 rollback_lock_file(lock);
 732                 return clean ? 0 : 1;
 733         } else {
 734                 return try_merge_command(strategy, xopts_nr, xopts,
 735                                                 common, head_arg, remoteheads);
 736         }
 737 }
 738
 739 static void count_diff_files(struct diff_queue_struct *q,
 740                              struct diff_options *opt, void *data)
 741 {
 742         int *count = data;
 743
 744         (*count) += q->nr;
 745 }
 746
 747 static int count_unmerged_entries(void)
 748 {
 749         int i, ret = 0;
 750
 751         for (i = 0; i < active_nr; i++)
 752                 if (ce_stage(active_cache[i]))
 753                         ret++;
 754
 755         return ret;
 756 }
 757
 758 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 759 {
 760         struct tree *trees[MAX_UNPACK_TREES];
 761         struct unpack_trees_options opts;
 762         struct tree_desc t[MAX_UNPACK_TREES];
 763         int i, fd, nr_trees = 0;
 764         struct dir_struct dir;
 765         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 766
 767         refresh_cache(REFRESH_QUIET);
 768
 769         fd = hold_locked_index(lock_file, 1);
 770
 771         memset(&trees, 0, sizeof(trees));
 772         memset(&opts, 0, sizeof(opts));
 773         memset(&t, 0, sizeof(t));
 774         memset(&dir, 0, sizeof(dir));
 775         dir.flags |= DIR_SHOW_IGNORED;
 776         setup_standard_excludes(&dir);
 777         opts.dir = &dir;
 778
 779         opts.head_idx = 1;
 780         opts.src_index = &the_index;
 781         opts.dst_index = &the_index;
 782         opts.update = 1;
 783         opts.verbose_update = 1;
 784         opts.merge = 1;
 785         opts.fn = twoway_merge;
 786         setup_unpack_trees_porcelain(&opts, "merge");
 787
 788         trees[nr_trees] = parse_tree_indirect(head);
 789         if (!trees[nr_trees++])
 790                 return -1;
 791         trees[nr_trees] = parse_tree_indirect(remote);
 792         if (!trees[nr_trees++])
 793                 return -1;
 794         for (i = 0; i < nr_trees; i++) {
 795                 parse_tree(trees[i]);
 796                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 797         }
 798         if (unpack_trees(nr_trees, t, &opts))
 799                 return -1;
 800         if (write_cache(fd, active_cache, active_nr) ||
 801                 commit_locked_index(lock_file))
 802                 die(_("unable to write new index file"));
 803         return 0;
 804 }
 805
 806 static void split_merge_strategies(const char *string, struct strategy **list,
 807                                    int *nr, int *alloc)
 808 {
 809         char *p, *q, *buf;
 810
 811         if (!string)
 812                 return;
 813
 814         buf = xstrdup(string);
 815         q = buf;
 816         for (;;) {
 817                 p = strchr(q, ' ');
 818                 if (!p) {
 819                         ALLOC_GROW(*list, *nr + 1, *alloc);
 820                         (*list)[(*nr)++].name = xstrdup(q);
 821                         free(buf);
 822                         return;
 823                 } else {
 824                         *p = '\0';
 825                         ALLOC_GROW(*list, *nr + 1, *alloc);
 826                         (*list)[(*nr)++].name = xstrdup(q);
 827                         q = ++p;
 828                 }
 829         }
 830 }
 831
 832 static void add_strategies(const char *string, unsigned attr)
 833 {
 834         struct strategy *list = NULL;
 835         int list_alloc = 0, list_nr = 0, i;
 836
 837         memset(&list, 0, sizeof(list));
 838         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 839         if (list) {
 840                 for (i = 0; i < list_nr; i++)
 841                         append_strategy(get_strategy(list[i].name));
 842                 return;
 843         }
 844         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 845                 if (all_strategy[i].attr & attr)
 846                         append_strategy(&all_strategy[i]);
 847
 848 }
 849
 850 static void write_merge_msg(struct strbuf *msg)
 851 {
 852         const char *filename = git_path("MERGE_MSG");
 853         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 854         if (fd < 0)
 855                 die_errno(_("Could not open '%s' for writing"),
 856                           filename);
 857         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 858                 die_errno(_("Could not write to '%s'"), filename);
 859         close(fd);
 860 }
 861
 862 static void read_merge_msg(struct strbuf *msg)
 863 {
 864         const char *filename = git_path("MERGE_MSG");
 865         strbuf_reset(msg);
 866         if (strbuf_read_file(msg, filename, 0) < 0)
 867                 die_errno(_("Could not read from '%s'"), filename);
 868 }
 869
 870 static void write_merge_state(void);
 871 static void abort_commit(const char *err_msg)
 872 {
 873         if (err_msg)
 874                 error("%s", err_msg);
 875         fprintf(stderr,
 876                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 877         write_merge_state();
 878         exit(1);
 879 }
 880
 881 static void prepare_to_commit(void)
 882 {
 883         struct strbuf msg = STRBUF_INIT;
 884         strbuf_addbuf(&msg, &merge_msg);
 885         strbuf_addch(&msg, '\n');
 886         write_merge_msg(&msg);
 887         run_hook(get_index_file(), "prepare-commit-msg",
 888                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 889         if (option_edit) {
 890                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 891                         abort_commit(NULL);
 892         }
 893         read_merge_msg(&msg);
 894         stripspace(&msg, option_edit);
 895         if (!msg.len)
 896                 abort_commit(_("Empty commit message."));
 897         strbuf_release(&merge_msg);
 898         strbuf_addbuf(&merge_msg, &msg);
 899         strbuf_release(&msg);
 900 }
 901
 902 static int merge_trivial(struct commit *head)
 903 {
 904         unsigned char result_tree[20], result_commit[20];
 905         struct commit_list *parent = xmalloc(sizeof(*parent));
 906
 907         write_tree_trivial(result_tree);
 908         printf(_("Wonderful.\n"));
 909         parent->item = head;
 910         parent->next = xmalloc(sizeof(*parent->next));
 911         parent->next->item = remoteheads->item;
 912         parent->next->next = NULL;
 913         prepare_to_commit();
 914         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 915         finish(head, result_commit, "In-index merge");
 916         drop_save();
 917         return 0;
 918 }
 919
 920 static int finish_automerge(struct commit *head,
 921                             struct commit_list *common,
 922                             unsigned char *result_tree,
 923                             const char *wt_strategy)
 924 {
 925         struct commit_list *parents = NULL, *j;
 926         struct strbuf buf = STRBUF_INIT;
 927         unsigned char result_commit[20];
 928
 929         free_commit_list(common);
 930         if (allow_fast_forward) {
 931                 parents = remoteheads;
 932                 commit_list_insert(head, &parents);
 933                 parents = reduce_heads(parents);
 934         } else {
 935                 struct commit_list **pptr = &parents;
 936
 937                 pptr = &commit_list_insert(head,
 938                                 pptr)->next;
 939                 for (j = remoteheads; j; j = j->next)
 940                         pptr = &commit_list_insert(j->item, pptr)->next;
 941         }
 942         strbuf_addch(&merge_msg, '\n');
 943         prepare_to_commit();
 944         free_commit_list(remoteheads);
 945         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 946         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 947         finish(head, result_commit, buf.buf);
 948         strbuf_release(&buf);
 949         drop_save();
 950         return 0;
 951 }
 952
 953 static int suggest_conflicts(int renormalizing)
 954 {
 955         const char *filename;
 956         FILE *fp;
 957         int pos;
 958
 959         filename = git_path("MERGE_MSG");
 960         fp = fopen(filename, "a");
 961         if (!fp)
 962                 die_errno(_("Could not open '%s' for writing"), filename);
 963         fprintf(fp, "\nConflicts:\n");
 964         for (pos = 0; pos < active_nr; pos++) {
 965                 struct cache_entry *ce = active_cache[pos];
 966
 967                 if (ce_stage(ce)) {
 968                         fprintf(fp, "\t%s\n", ce->name);
 969                         while (pos + 1 < active_nr &&
 970                                         !strcmp(ce->name,
 971                                                 active_cache[pos + 1]->name))
 972                                 pos++;
 973                 }
 974         }
 975         fclose(fp);
 976         rerere(allow_rerere_auto);
 977         printf(_("Automatic merge failed; "
 978                         "fix conflicts and then commit the result.\n"));
 979         return 1;
 980 }
 981
 982 static struct commit *is_old_style_invocation(int argc, const char **argv,
 983                                               const unsigned char *head)
 984 {
 985         struct commit *second_token = NULL;
 986         if (argc > 2) {
 987                 unsigned char second_sha1[20];
 988
 989                 if (get_sha1(argv[1], second_sha1))
 990                         return NULL;
 991                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 992                 if (!second_token)
 993                         die(_("'%s' is not a commit"), argv[1]);
 994                 if (hashcmp(second_token->object.sha1, head))
 995                         return NULL;
 996         }
 997         return second_token;
 998 }
 999
1000 static int evaluate_result(void)
1001 {
1002         int cnt = 0;
1003         struct rev_info rev;
1004
1005         /* Check how many files differ. */
1006         init_revisions(&rev, "");
1007         setup_revisions(0, NULL, &rev, NULL);
1008         rev.diffopt.output_format |=
1009                 DIFF_FORMAT_CALLBACK;
1010         rev.diffopt.format_callback = count_diff_files;
1011         rev.diffopt.format_callback_data = &cnt;
1012         run_diff_files(&rev, 0);
1013
1014         /*
1015          * Check how many unmerged entries are
1016          * there.
1017          */
1018         cnt += count_unmerged_entries();
1019
1020         return cnt;
1021 }
1022
1023 /*
1024  * Pretend as if the user told us to merge with the tracking
1025  * branch we have for the upstream of the current branch
1026  */
1027 static int setup_with_upstream(const char ***argv)
1028 {
1029         struct branch *branch = branch_get(NULL);
1030         int i;
1031         const char **args;
1032
1033         if (!branch)
1034                 die(_("No current branch."));
1035         if (!branch->remote)
1036                 die(_("No remote for the current branch."));
1037         if (!branch->merge_nr)
1038                 die(_("No default upstream defined for the current branch."));
1039
1040         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1041         for (i = 0; i < branch->merge_nr; i++) {
1042                 if (!branch->merge[i]->dst)
1043                         die(_("No remote tracking branch for %s from %s"),
1044                             branch->merge[i]->src, branch->remote_name);
1045                 args[i] = branch->merge[i]->dst;
1046         }
1047         args[i] = NULL;
1048         *argv = args;
1049         return i;
1050 }
1051
1052 static void write_merge_state(void)
1053 {
1054         const char *filename;
1055         int fd;
1056         struct commit_list *j;
1057         struct strbuf buf = STRBUF_INIT;
1058
1059         for (j = remoteheads; j; j = j->next)
1060                 strbuf_addf(&buf, "%s\n",
1061                         sha1_to_hex(j->item->object.sha1));
1062         filename = git_path("MERGE_HEAD");
1063         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1064         if (fd < 0)
1065                 die_errno(_("Could not open '%s' for writing"), filename);
1066         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1067                 die_errno(_("Could not write to '%s'"), filename);
1068         close(fd);
1069         strbuf_addch(&merge_msg, '\n');
1070         write_merge_msg(&merge_msg);
1071
1072         filename = git_path("MERGE_MODE");
1073         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1074         if (fd < 0)
1075                 die_errno(_("Could not open '%s' for writing"), filename);
1076         strbuf_reset(&buf);
1077         if (!allow_fast_forward)
1078                 strbuf_addf(&buf, "no-ff");
1079         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1080                 die_errno(_("Could not write to '%s'"), filename);
1081         close(fd);
1082 }
1083
1084 int cmd_merge(int argc, const char **argv, const char *prefix)
1085 {
1086         unsigned char result_tree[20];
1087         unsigned char stash[20];
1088         unsigned char head_sha1[20];
1089         struct commit *head_commit;
1090         struct strbuf buf = STRBUF_INIT;
1091         const char *head_arg;
1092         int flag, i;
1093         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1094         struct commit_list *common = NULL;
1095         const char *best_strategy = NULL, *wt_strategy = NULL;
1096         struct commit_list **remotes = &remoteheads;
1097
1098         if (argc == 2 && !strcmp(argv[1], "-h"))
1099                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1100
1101         /*
1102          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1103          * current branch.
1104          */
1105         branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1106         if (branch && !prefixcmp(branch, "refs/heads/"))
1107                 branch += 11;
1108         if (!branch || is_null_sha1(head_sha1))
1109                 head_commit = NULL;
1110         else
1111                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1112
1113         git_config(git_merge_config, NULL);
1114
1115         if (branch_mergeoptions)
1116                 parse_branch_merge_options(branch_mergeoptions);
1117         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1118                         builtin_merge_usage, 0);
1119         if (shortlog_len < 0)
1120                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1121
1122         if (verbosity < 0 && show_progress == -1)
1123                 show_progress = 0;
1124
1125         if (abort_current_merge) {
1126                 int nargc = 2;
1127                 const char *nargv[] = {"reset", "--merge", NULL};
1128
1129                 if (!file_exists(git_path("MERGE_HEAD")))
1130                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1131
1132                 /* Invoke 'git reset --merge' */
1133                 return cmd_reset(nargc, nargv, prefix);
1134         }
1135
1136         if (read_cache_unmerged())
1137                 die_resolve_conflict("merge");
1138
1139         if (file_exists(git_path("MERGE_HEAD"))) {
1140                 /*
1141                  * There is no unmerged entry, don't advise 'git
1142                  * add/rm <file>', just 'git commit'.
1143                  */
1144                 if (advice_resolve_conflict)
1145                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1146                                   "Please, commit your changes before you can merge."));
1147                 else
1148                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1149         }
1150         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1151                 if (advice_resolve_conflict)
1152                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1153                             "Please, commit your changes before you can merge."));
1154                 else
1155                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1156         }
1157         resolve_undo_clear();
1158
1159         if (verbosity < 0)
1160                 show_diffstat = 0;
1161
1162         if (squash) {
1163                 if (!allow_fast_forward)
1164                         die(_("You cannot combine --squash with --no-ff."));
1165                 option_commit = 0;
1166         }
1167
1168         if (!allow_fast_forward && fast_forward_only)
1169                 die(_("You cannot combine --no-ff with --ff-only."));
1170
1171         if (!abort_current_merge) {
1172                 if (!argc) {
1173                         if (default_to_upstream)
1174                                 argc = setup_with_upstream(&argv);
1175                         else
1176                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1177                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1178                         argv[0] = "@{-1}";
1179         }
1180         if (!argc)
1181                 usage_with_options(builtin_merge_usage,
1182                         builtin_merge_options);
1183
1184         /*
1185          * This could be traditional "merge <msg> HEAD <commit>..."  and
1186          * the way we can tell it is to see if the second token is HEAD,
1187          * but some people might have misused the interface and used a
1188          * committish that is the same as HEAD there instead.
1189          * Traditional format never would have "-m" so it is an
1190          * additional safety measure to check for it.
1191          */
1192
1193         if (!have_message && head_commit &&
1194             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1195                 strbuf_addstr(&merge_msg, argv[0]);
1196                 head_arg = argv[1];
1197                 argv += 2;
1198                 argc -= 2;
1199         } else if (!head_commit) {
1200                 struct object *remote_head;
1201                 /*
1202                  * If the merged head is a valid one there is no reason
1203                  * to forbid "git merge" into a branch yet to be born.
1204                  * We do the same for "git pull".
1205                  */
1206                 if (argc != 1)
1207                         die(_("Can merge only exactly one commit into "
1208                                 "empty head"));
1209                 if (squash)
1210                         die(_("Squash commit into empty head not supported yet"));
1211                 if (!allow_fast_forward)
1212                         die(_("Non-fast-forward commit does not make sense into "
1213                             "an empty head"));
1214                 remote_head = want_commit(argv[0]);
1215                 if (!remote_head)
1216                         die(_("%s - not something we can merge"), argv[0]);
1217                 read_empty(remote_head->sha1, 0);
1218                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1219                                 DIE_ON_ERR);
1220                 return 0;
1221         } else {
1222                 struct strbuf merge_names = STRBUF_INIT;
1223
1224                 /* We are invoked directly as the first-class UI. */
1225                 head_arg = "HEAD";
1226
1227                 /*
1228                  * All the rest are the commits being merged;
1229                  * prepare the standard merge summary message to
1230                  * be appended to the given message.  If remote
1231                  * is invalid we will die later in the common
1232                  * codepath so we discard the error in this
1233                  * loop.
1234                  */
1235                 for (i = 0; i < argc; i++)
1236                         merge_name(argv[i], &merge_names);
1237
1238                 if (!have_message || shortlog_len) {
1239                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1240                                       shortlog_len);
1241                         if (merge_msg.len)
1242                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1243                 }
1244         }
1245
1246         if (!head_commit || !argc)
1247                 usage_with_options(builtin_merge_usage,
1248                         builtin_merge_options);
1249
1250         strbuf_addstr(&buf, "merge");
1251         for (i = 0; i < argc; i++)
1252                 strbuf_addf(&buf, " %s", argv[i]);
1253         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1254         strbuf_reset(&buf);
1255
1256         for (i = 0; i < argc; i++) {
1257                 struct object *o;
1258                 struct commit *commit;
1259
1260                 o = want_commit(argv[i]);
1261                 if (!o)
1262                         die(_("%s - not something we can merge"), argv[i]);
1263                 commit = lookup_commit(o->sha1);
1264                 commit->util = (void *)argv[i];
1265                 remotes = &commit_list_insert(commit, remotes)->next;
1266
1267                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1268                 setenv(buf.buf, argv[i], 1);
1269                 strbuf_reset(&buf);
1270         }
1271
1272         if (!use_strategies) {
1273                 if (!remoteheads->next)
1274                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1275                 else
1276                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1277         }
1278
1279         for (i = 0; i < use_strategies_nr; i++) {
1280                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1281                         allow_fast_forward = 0;
1282                 if (use_strategies[i]->attr & NO_TRIVIAL)
1283                         allow_trivial = 0;
1284         }
1285
1286         if (!remoteheads->next)
1287                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1288         else {
1289                 struct commit_list *list = remoteheads;
1290                 commit_list_insert(head_commit, &list);
1291                 common = get_octopus_merge_bases(list);
1292                 free(list);
1293         }
1294
1295         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1296                    NULL, 0, DIE_ON_ERR);
1297
1298         if (!common)
1299                 ; /* No common ancestors found. We need a real merge. */
1300         else if (!remoteheads->next && !common->next &&
1301                         common->item == remoteheads->item) {
1302                 /*
1303                  * If head can reach all the merge then we are up to date.
1304                  * but first the most common case of merging one remote.
1305                  */
1306                 finish_up_to_date("Already up-to-date.");
1307                 return 0;
1308         } else if (allow_fast_forward && !remoteheads->next &&
1309                         !common->next &&
1310                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1311                 /* Again the most common case of merging one remote. */
1312                 struct strbuf msg = STRBUF_INIT;
1313                 struct object *o;
1314                 char hex[41];
1315
1316                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1317
1318                 if (verbosity >= 0)
1319                         printf(_("Updating %s..%s\n"),
1320                                 hex,
1321                                 find_unique_abbrev(remoteheads->item->object.sha1,
1322                                 DEFAULT_ABBREV));
1323                 strbuf_addstr(&msg, "Fast-forward");
1324                 if (have_message)
1325                         strbuf_addstr(&msg,
1326                                 " (no commit created; -m option ignored)");
1327                 o = want_commit(sha1_to_hex(remoteheads->item->object.sha1));
1328                 if (!o)
1329                         return 1;
1330
1331                 if (checkout_fast_forward(head_commit->object.sha1, remoteheads->item->object.sha1))
1332                         return 1;
1333
1334                 finish(head_commit, o->sha1, msg.buf);
1335                 drop_save();
1336                 return 0;
1337         } else if (!remoteheads->next && common->next)
1338                 ;
1339                 /*
1340                  * We are not doing octopus and not fast-forward.  Need
1341                  * a real merge.
1342                  */
1343         else if (!remoteheads->next && !common->next && option_commit) {
1344                 /*
1345                  * We are not doing octopus, not fast-forward, and have
1346                  * only one common.
1347                  */
1348                 refresh_cache(REFRESH_QUIET);
1349                 if (allow_trivial && !fast_forward_only) {
1350                         /* See if it is really trivial. */
1351                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1352                         printf(_("Trying really trivial in-index merge...\n"));
1353                         if (!read_tree_trivial(common->item->object.sha1,
1354                                         head_commit->object.sha1, remoteheads->item->object.sha1))
1355                                 return merge_trivial(head_commit);
1356                         printf(_("Nope.\n"));
1357                 }
1358         } else {
1359                 /*
1360                  * An octopus.  If we can reach all the remote we are up
1361                  * to date.
1362                  */
1363                 int up_to_date = 1;
1364                 struct commit_list *j;
1365
1366                 for (j = remoteheads; j; j = j->next) {
1367                         struct commit_list *common_one;
1368
1369                         /*
1370                          * Here we *have* to calculate the individual
1371                          * merge_bases again, otherwise "git merge HEAD^
1372                          * HEAD^^" would be missed.
1373                          */
1374                         common_one = get_merge_bases(head_commit, j->item, 1);
1375                         if (hashcmp(common_one->item->object.sha1,
1376                                 j->item->object.sha1)) {
1377                                 up_to_date = 0;
1378                                 break;
1379                         }
1380                 }
1381                 if (up_to_date) {
1382                         finish_up_to_date("Already up-to-date. Yeeah!");
1383                         return 0;
1384                 }
1385         }
1386
1387         if (fast_forward_only)
1388                 die(_("Not possible to fast-forward, aborting."));
1389
1390         /* We are going to make a new commit. */
1391         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1392
1393         /*
1394          * At this point, we need a real merge.  No matter what strategy
1395          * we use, it would operate on the index, possibly affecting the
1396          * working tree, and when resolved cleanly, have the desired
1397          * tree in the index -- this means that the index must be in
1398          * sync with the head commit.  The strategies are responsible
1399          * to ensure this.
1400          */
1401         if (use_strategies_nr == 1 ||
1402             /*
1403              * Stash away the local changes so that we can try more than one.
1404              */
1405             save_state(stash))
1406                 hashcpy(stash, null_sha1);
1407
1408         for (i = 0; i < use_strategies_nr; i++) {
1409                 int ret;
1410                 if (i) {
1411                         printf(_("Rewinding the tree to pristine...\n"));
1412                         restore_state(head_commit->object.sha1, stash);
1413                 }
1414                 if (use_strategies_nr != 1)
1415                         printf(_("Trying merge strategy %s...\n"),
1416                                 use_strategies[i]->name);
1417                 /*
1418                  * Remember which strategy left the state in the working
1419                  * tree.
1420                  */
1421                 wt_strategy = use_strategies[i]->name;
1422
1423                 ret = try_merge_strategy(use_strategies[i]->name,
1424                                          common, head_commit, head_arg);
1425                 if (!option_commit && !ret) {
1426                         merge_was_ok = 1;
1427                         /*
1428                          * This is necessary here just to avoid writing
1429                          * the tree, but later we will *not* exit with
1430                          * status code 1 because merge_was_ok is set.
1431                          */
1432                         ret = 1;
1433                 }
1434
1435                 if (ret) {
1436                         /*
1437                          * The backend exits with 1 when conflicts are
1438                          * left to be resolved, with 2 when it does not
1439                          * handle the given merge at all.
1440                          */
1441                         if (ret == 1) {
1442                                 int cnt = evaluate_result();
1443
1444                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1445                                         best_strategy = use_strategies[i]->name;
1446                                         best_cnt = cnt;
1447                                 }
1448                         }
1449                         if (merge_was_ok)
1450                                 break;
1451                         else
1452                                 continue;
1453                 }
1454
1455                 /* Automerge succeeded. */
1456                 write_tree_trivial(result_tree);
1457                 automerge_was_ok = 1;
1458                 break;
1459         }
1460
1461         /*
1462          * If we have a resulting tree, that means the strategy module
1463          * auto resolved the merge cleanly.
1464          */
1465         if (automerge_was_ok)
1466                 return finish_automerge(head_commit, common, result_tree,
1467                                         wt_strategy);
1468
1469         /*
1470          * Pick the result from the best strategy and have the user fix
1471          * it up.
1472          */
1473         if (!best_strategy) {
1474                 restore_state(head_commit->object.sha1, stash);
1475                 if (use_strategies_nr > 1)
1476                         fprintf(stderr,
1477                                 _("No merge strategy handled the merge.\n"));
1478                 else
1479                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1480                                 use_strategies[0]->name);
1481                 return 2;
1482         } else if (best_strategy == wt_strategy)
1483                 ; /* We already have its result in the working tree. */
1484         else {
1485                 printf(_("Rewinding the tree to pristine...\n"));
1486                 restore_state(head_commit->object.sha1, stash);
1487                 printf(_("Using the %s to prepare resolving by hand.\n"),
1488                         best_strategy);
1489                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1490         }
1491
1492         if (squash)
1493                 finish(head_commit, NULL, NULL);
1494         else
1495                 write_merge_state();
1496
1497         if (merge_was_ok) {
1498                 fprintf(stderr, _("Automatic merge went well; "
1499                         "stopped before committing as requested\n"));
1500                 return 0;
1501         } else
1502                 return suggest_conflicts(option_renormalize);
1503 }