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 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "refs.h"
  18 #include "refspec.h"
  19 #include "commit.h"
  20 #include "diffcore.h"
  21 #include "revision.h"
  22 #include "unpack-trees.h"
  23 #include "cache-tree.h"
  24 #include "dir.h"
  25 #include "utf8.h"
  26 #include "log-tree.h"
  27 #include "color.h"
  28 #include "rerere.h"
  29 #include "help.h"
  30 #include "merge-recursive.h"
  31 #include "resolve-undo.h"
  32 #include "remote.h"
  33 #include "fmt-merge-msg.h"
  34 #include "gpg-interface.h"
  35 #include "sequencer.h"
  36 #include "string-list.h"
  37 #include "packfile.h"
  38 #include "tag.h"
  39 #include "alias.h"
  40 #include "commit-reach.h"
  41
  42 #define DEFAULT_TWOHEAD (1<<0)
  43 #define DEFAULT_OCTOPUS (1<<1)
  44 #define NO_FAST_FORWARD (1<<2)
  45 #define NO_TRIVIAL      (1<<3)
  46
  47 struct strategy {
  48         const char *name;
  49         unsigned attr;
  50 };
  51
  52 static const char * const builtin_merge_usage[] = {
  53         N_("git merge [<options>] [<commit>...]"),
  54         N_("git merge --abort"),
  55         N_("git merge --continue"),
  56         NULL
  57 };
  58
  59 static int show_diffstat = 1, shortlog_len = -1, squash;
  60 static int option_commit = 1;
  61 static int option_edit = -1;
  62 static int allow_trivial = 1, have_message, verify_signatures;
  63 static int overwrite_ignore = 1;
  64 static struct strbuf merge_msg = STRBUF_INIT;
  65 static struct strategy **use_strategies;
  66 static size_t use_strategies_nr, use_strategies_alloc;
  67 static const char **xopts;
  68 static size_t xopts_nr, xopts_alloc;
  69 static const char *branch;
  70 static char *branch_mergeoptions;
  71 static int option_renormalize;
  72 static int verbosity;
  73 static int allow_rerere_auto;
  74 static int abort_current_merge;
  75 static int continue_current_merge;
  76 static int allow_unrelated_histories;
  77 static int show_progress = -1;
  78 static int default_to_upstream = 1;
  79 static int signoff;
  80 static const char *sign_commit;
  81 static int verify_msg = 1;
  82
  83 static struct strategy all_strategy[] = {
  84         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  85         { "octopus",    DEFAULT_OCTOPUS },
  86         { "resolve",    0 },
  87         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  88         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  89 };
  90
  91 static const char *pull_twohead, *pull_octopus;
  92
  93 enum ff_type {
  94         FF_NO,
  95         FF_ALLOW,
  96         FF_ONLY
  97 };
  98
  99 static enum ff_type fast_forward = FF_ALLOW;
 100
 101 static int option_parse_message(const struct option *opt,
 102                                 const char *arg, int unset)
 103 {
 104         struct strbuf *buf = opt->value;
 105
 106         if (unset)
 107                 strbuf_setlen(buf, 0);
 108         else if (arg) {
 109                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 110                 have_message = 1;
 111         } else
 112                 return error(_("switch `m' requires a value"));
 113         return 0;
 114 }
 115
 116 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 117                                                  const struct option *opt,
 118                                                  const char *arg_not_used,
 119                                                  int unset)
 120 {
 121         struct strbuf *buf = opt->value;
 122         const char *arg;
 123
 124         BUG_ON_OPT_ARG(arg_not_used);
 125         if (unset)
 126                 BUG("-F cannot be negated");
 127
 128         if (ctx->opt) {
 129                 arg = ctx->opt;
 130                 ctx->opt = NULL;
 131         } else if (ctx->argc > 1) {
 132                 ctx->argc--;
 133                 arg = *++ctx->argv;
 134         } else
 135                 return error(_("option `%s' requires a value"), opt->long_name);
 136
 137         if (buf->len)
 138                 strbuf_addch(buf, '\n');
 139         if (ctx->prefix && !is_absolute_path(arg))
 140                 arg = prefix_filename(ctx->prefix, arg);
 141         if (strbuf_read_file(buf, arg, 0) < 0)
 142                 return error(_("could not read file '%s'"), arg);
 143         have_message = 1;
 144
 145         return 0;
 146 }
 147
 148 static struct strategy *get_strategy(const char *name)
 149 {
 150         int i;
 151         struct strategy *ret;
 152         static struct cmdnames main_cmds, other_cmds;
 153         static int loaded;
 154
 155         if (!name)
 156                 return NULL;
 157
 158         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 159                 if (!strcmp(name, all_strategy[i].name))
 160                         return &all_strategy[i];
 161
 162         if (!loaded) {
 163                 struct cmdnames not_strategies;
 164                 loaded = 1;
 165
 166                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 167                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 168                 for (i = 0; i < main_cmds.cnt; i++) {
 169                         int j, found = 0;
 170                         struct cmdname *ent = main_cmds.names[i];
 171                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 172                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 173                                                 && !all_strategy[j].name[ent->len])
 174                                         found = 1;
 175                         if (!found)
 176                                 add_cmdname(&not_strategies, ent->name, ent->len);
 177                 }
 178                 exclude_cmds(&main_cmds, &not_strategies);
 179         }
 180         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 181                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 182                 fprintf(stderr, _("Available strategies are:"));
 183                 for (i = 0; i < main_cmds.cnt; i++)
 184                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 185                 fprintf(stderr, ".\n");
 186                 if (other_cmds.cnt) {
 187                         fprintf(stderr, _("Available custom strategies are:"));
 188                         for (i = 0; i < other_cmds.cnt; i++)
 189                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 190                         fprintf(stderr, ".\n");
 191                 }
 192                 exit(1);
 193         }
 194
 195         ret = xcalloc(1, sizeof(struct strategy));
 196         ret->name = xstrdup(name);
 197         ret->attr = NO_TRIVIAL;
 198         return ret;
 199 }
 200
 201 static void append_strategy(struct strategy *s)
 202 {
 203         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 204         use_strategies[use_strategies_nr++] = s;
 205 }
 206
 207 static int option_parse_strategy(const struct option *opt,
 208                                  const char *name, int unset)
 209 {
 210         if (unset)
 211                 return 0;
 212
 213         append_strategy(get_strategy(name));
 214         return 0;
 215 }
 216
 217 static int option_parse_x(const struct option *opt,
 218                           const char *arg, int unset)
 219 {
 220         if (unset)
 221                 return 0;
 222
 223         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 224         xopts[xopts_nr++] = xstrdup(arg);
 225         return 0;
 226 }
 227
 228 static int option_parse_n(const struct option *opt,
 229                           const char *arg, int unset)
 230 {
 231         BUG_ON_OPT_ARG(arg);
 232         show_diffstat = unset;
 233         return 0;
 234 }
 235
 236 static struct option builtin_merge_options[] = {
 237         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 238                 N_("do not show a diffstat at the end of the merge"),
 239                 PARSE_OPT_NOARG, option_parse_n },
 240         OPT_BOOL(0, "stat", &show_diffstat,
 241                 N_("show a diffstat at the end of the merge")),
 242         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 243         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 244           N_("add (at most <n>) entries from shortlog to merge commit message"),
 245           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 246         OPT_BOOL(0, "squash", &squash,
 247                 N_("create a single commit instead of doing a merge")),
 248         OPT_BOOL(0, "commit", &option_commit,
 249                 N_("perform a commit if the merge succeeds (default)")),
 250         OPT_BOOL('e', "edit", &option_edit,
 251                 N_("edit message before committing")),
 252         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 253         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 254                       N_("abort if fast-forward is not possible"),
 255                       FF_ONLY, PARSE_OPT_NONEG),
 256         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 257         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 258                 N_("verify that the named commit has a valid GPG signature")),
 259         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 260                 N_("merge strategy to use"), option_parse_strategy),
 261         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 262                 N_("option for selected merge strategy"), option_parse_x),
 263         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 264                 N_("merge commit message (for a non-fast-forward merge)"),
 265                 option_parse_message),
 266         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 267                 N_("read message from file"), PARSE_OPT_NONEG,
 268                 NULL, 0, option_read_message },
 269         OPT__VERBOSITY(&verbosity),
 270         OPT_BOOL(0, "abort", &abort_current_merge,
 271                 N_("abort the current in-progress merge")),
 272         OPT_BOOL(0, "continue", &continue_current_merge,
 273                 N_("continue the current in-progress merge")),
 274         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 275                  N_("allow merging unrelated histories")),
 276         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 277         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 278           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 279         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 280         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 281         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 282         OPT_END()
 283 };
 284
 285 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 286 static void drop_save(void)
 287 {
 288         unlink(git_path_merge_head(the_repository));
 289         unlink(git_path_merge_msg(the_repository));
 290         unlink(git_path_merge_mode(the_repository));
 291 }
 292
 293 static int save_state(struct object_id *stash)
 294 {
 295         int len;
 296         struct child_process cp = CHILD_PROCESS_INIT;
 297         struct strbuf buffer = STRBUF_INIT;
 298         const char *argv[] = {"stash", "create", NULL};
 299         int rc = -1;
 300
 301         cp.argv = argv;
 302         cp.out = -1;
 303         cp.git_cmd = 1;
 304
 305         if (start_command(&cp))
 306                 die(_("could not run stash."));
 307         len = strbuf_read(&buffer, cp.out, 1024);
 308         close(cp.out);
 309
 310         if (finish_command(&cp) || len < 0)
 311                 die(_("stash failed"));
 312         else if (!len)          /* no changes */
 313                 goto out;
 314         strbuf_setlen(&buffer, buffer.len-1);
 315         if (get_oid(buffer.buf, stash))
 316                 die(_("not a valid object: %s"), buffer.buf);
 317         rc = 0;
 318 out:
 319         strbuf_release(&buffer);
 320         return rc;
 321 }
 322
 323 static void read_empty(const struct object_id *oid, int verbose)
 324 {
 325         int i = 0;
 326         const char *args[7];
 327
 328         args[i++] = "read-tree";
 329         if (verbose)
 330                 args[i++] = "-v";
 331         args[i++] = "-m";
 332         args[i++] = "-u";
 333         args[i++] = empty_tree_oid_hex();
 334         args[i++] = oid_to_hex(oid);
 335         args[i] = NULL;
 336
 337         if (run_command_v_opt(args, RUN_GIT_CMD))
 338                 die(_("read-tree failed"));
 339 }
 340
 341 static void reset_hard(const struct object_id *oid, int verbose)
 342 {
 343         int i = 0;
 344         const char *args[6];
 345
 346         args[i++] = "read-tree";
 347         if (verbose)
 348                 args[i++] = "-v";
 349         args[i++] = "--reset";
 350         args[i++] = "-u";
 351         args[i++] = oid_to_hex(oid);
 352         args[i] = NULL;
 353
 354         if (run_command_v_opt(args, RUN_GIT_CMD))
 355                 die(_("read-tree failed"));
 356 }
 357
 358 static void restore_state(const struct object_id *head,
 359                           const struct object_id *stash)
 360 {
 361         struct strbuf sb = STRBUF_INIT;
 362         const char *args[] = { "stash", "apply", NULL, NULL };
 363
 364         if (is_null_oid(stash))
 365                 return;
 366
 367         reset_hard(head, 1);
 368
 369         args[2] = oid_to_hex(stash);
 370
 371         /*
 372          * It is OK to ignore error here, for example when there was
 373          * nothing to restore.
 374          */
 375         run_command_v_opt(args, RUN_GIT_CMD);
 376
 377         strbuf_release(&sb);
 378         refresh_cache(REFRESH_QUIET);
 379 }
 380
 381 /* This is called when no merge was necessary. */
 382 static void finish_up_to_date(const char *msg)
 383 {
 384         if (verbosity >= 0)
 385                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 386         drop_save();
 387 }
 388
 389 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 390 {
 391         struct rev_info rev;
 392         struct strbuf out = STRBUF_INIT;
 393         struct commit_list *j;
 394         struct pretty_print_context ctx = {0};
 395
 396         printf(_("Squash commit -- not updating HEAD\n"));
 397
 398         repo_init_revisions(the_repository, &rev, NULL);
 399         rev.ignore_merges = 1;
 400         rev.commit_format = CMIT_FMT_MEDIUM;
 401
 402         commit->object.flags |= UNINTERESTING;
 403         add_pending_object(&rev, &commit->object, NULL);
 404
 405         for (j = remoteheads; j; j = j->next)
 406                 add_pending_object(&rev, &j->item->object, NULL);
 407
 408         setup_revisions(0, NULL, &rev, NULL);
 409         if (prepare_revision_walk(&rev))
 410                 die(_("revision walk setup failed"));
 411
 412         ctx.abbrev = rev.abbrev;
 413         ctx.date_mode = rev.date_mode;
 414         ctx.fmt = rev.commit_format;
 415
 416         strbuf_addstr(&out, "Squashed commit of the following:\n");
 417         while ((commit = get_revision(&rev)) != NULL) {
 418                 strbuf_addch(&out, '\n');
 419                 strbuf_addf(&out, "commit %s\n",
 420                         oid_to_hex(&commit->object.oid));
 421                 pretty_print_commit(&ctx, commit, &out);
 422         }
 423         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 424         strbuf_release(&out);
 425 }
 426
 427 static void finish(struct commit *head_commit,
 428                    struct commit_list *remoteheads,
 429                    const struct object_id *new_head, const char *msg)
 430 {
 431         struct strbuf reflog_message = STRBUF_INIT;
 432         const struct object_id *head = &head_commit->object.oid;
 433
 434         if (!msg)
 435                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 436         else {
 437                 if (verbosity >= 0)
 438                         printf("%s\n", msg);
 439                 strbuf_addf(&reflog_message, "%s: %s",
 440                         getenv("GIT_REFLOG_ACTION"), msg);
 441         }
 442         if (squash) {
 443                 squash_message(head_commit, remoteheads);
 444         } else {
 445                 if (verbosity >= 0 && !merge_msg.len)
 446                         printf(_("No merge message -- not updating HEAD\n"));
 447                 else {
 448                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 449                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 450                                    0, UPDATE_REFS_DIE_ON_ERR);
 451                         /*
 452                          * We ignore errors in 'gc --auto', since the
 453                          * user should see them.
 454                          */
 455                         close_all_packs(the_repository->objects);
 456                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 457                 }
 458         }
 459         if (new_head && show_diffstat) {
 460                 struct diff_options opts;
 461                 repo_diff_setup(the_repository, &opts);
 462                 opts.stat_width = -1; /* use full terminal width */
 463                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 464                 opts.output_format |=
 465                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 466                 opts.detect_rename = DIFF_DETECT_RENAME;
 467                 diff_setup_done(&opts);
 468                 diff_tree_oid(head, new_head, "", &opts);
 469                 diffcore_std(&opts);
 470                 diff_flush(&opts);
 471         }
 472
 473         /* Run a post-merge hook */
 474         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 475
 476         strbuf_release(&reflog_message);
 477 }
 478
 479 /* Get the name for the merge commit's message. */
 480 static void merge_name(const char *remote, struct strbuf *msg)
 481 {
 482         struct commit *remote_head;
 483         struct object_id branch_head;
 484         struct strbuf buf = STRBUF_INIT;
 485         struct strbuf bname = STRBUF_INIT;
 486         struct merge_remote_desc *desc;
 487         const char *ptr;
 488         char *found_ref;
 489         int len, early;
 490
 491         strbuf_branchname(&bname, remote, 0);
 492         remote = bname.buf;
 493
 494         oidclr(&branch_head);
 495         remote_head = get_merge_parent(remote);
 496         if (!remote_head)
 497                 die(_("'%s' does not point to a commit"), remote);
 498
 499         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 500                 if (starts_with(found_ref, "refs/heads/")) {
 501                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 502                                     oid_to_hex(&branch_head), remote);
 503                         goto cleanup;
 504                 }
 505                 if (starts_with(found_ref, "refs/tags/")) {
 506                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 507                                     oid_to_hex(&branch_head), remote);
 508                         goto cleanup;
 509                 }
 510                 if (starts_with(found_ref, "refs/remotes/")) {
 511                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 512                                     oid_to_hex(&branch_head), remote);
 513                         goto cleanup;
 514                 }
 515         }
 516
 517         /* See if remote matches <name>^^^.. or <name>~<number> */
 518         for (len = 0, ptr = remote + strlen(remote);
 519              remote < ptr && ptr[-1] == '^';
 520              ptr--)
 521                 len++;
 522         if (len)
 523                 early = 1;
 524         else {
 525                 early = 0;
 526                 ptr = strrchr(remote, '~');
 527                 if (ptr) {
 528                         int seen_nonzero = 0;
 529
 530                         len++; /* count ~ */
 531                         while (*++ptr && isdigit(*ptr)) {
 532                                 seen_nonzero |= (*ptr != '0');
 533                                 len++;
 534                         }
 535                         if (*ptr)
 536                                 len = 0; /* not ...~<number> */
 537                         else if (seen_nonzero)
 538                                 early = 1;
 539                         else if (len == 1)
 540                                 early = 1; /* "name~" is "name~1"! */
 541                 }
 542         }
 543         if (len) {
 544                 struct strbuf truname = STRBUF_INIT;
 545                 strbuf_addf(&truname, "refs/heads/%s", remote);
 546                 strbuf_setlen(&truname, truname.len - len);
 547                 if (ref_exists(truname.buf)) {
 548                         strbuf_addf(msg,
 549                                     "%s\t\tbranch '%s'%s of .\n",
 550                                     oid_to_hex(&remote_head->object.oid),
 551                                     truname.buf + 11,
 552                                     (early ? " (early part)" : ""));
 553                         strbuf_release(&truname);
 554                         goto cleanup;
 555                 }
 556                 strbuf_release(&truname);
 557         }
 558
 559         desc = merge_remote_util(remote_head);
 560         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 561                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 562                             oid_to_hex(&desc->obj->oid),
 563                             type_name(desc->obj->type),
 564                             remote);
 565                 goto cleanup;
 566         }
 567
 568         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 569                 oid_to_hex(&remote_head->object.oid), remote);
 570 cleanup:
 571         strbuf_release(&buf);
 572         strbuf_release(&bname);
 573 }
 574
 575 static void parse_branch_merge_options(char *bmo)
 576 {
 577         const char **argv;
 578         int argc;
 579
 580         if (!bmo)
 581                 return;
 582         argc = split_cmdline(bmo, &argv);
 583         if (argc < 0)
 584                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 585                     _(split_cmdline_strerror(argc)));
 586         REALLOC_ARRAY(argv, argc + 2);
 587         MOVE_ARRAY(argv + 1, argv, argc + 1);
 588         argc++;
 589         argv[0] = "branch.*.mergeoptions";
 590         parse_options(argc, argv, NULL, builtin_merge_options,
 591                       builtin_merge_usage, 0);
 592         free(argv);
 593 }
 594
 595 static int git_merge_config(const char *k, const char *v, void *cb)
 596 {
 597         int status;
 598
 599         if (branch && starts_with(k, "branch.") &&
 600                 starts_with(k + 7, branch) &&
 601                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 602                 free(branch_mergeoptions);
 603                 branch_mergeoptions = xstrdup(v);
 604                 return 0;
 605         }
 606
 607         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 608                 show_diffstat = git_config_bool(k, v);
 609         else if (!strcmp(k, "merge.verifysignatures"))
 610                 verify_signatures = git_config_bool(k, v);
 611         else if (!strcmp(k, "pull.twohead"))
 612                 return git_config_string(&pull_twohead, k, v);
 613         else if (!strcmp(k, "pull.octopus"))
 614                 return git_config_string(&pull_octopus, k, v);
 615         else if (!strcmp(k, "merge.renormalize"))
 616                 option_renormalize = git_config_bool(k, v);
 617         else if (!strcmp(k, "merge.ff")) {
 618                 int boolval = git_parse_maybe_bool(v);
 619                 if (0 <= boolval) {
 620                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 621                 } else if (v && !strcmp(v, "only")) {
 622                         fast_forward = FF_ONLY;
 623                 } /* do not barf on values from future versions of git */
 624                 return 0;
 625         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 626                 default_to_upstream = git_config_bool(k, v);
 627                 return 0;
 628         } else if (!strcmp(k, "commit.gpgsign")) {
 629                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 630                 return 0;
 631         }
 632
 633         status = fmt_merge_msg_config(k, v, cb);
 634         if (status)
 635                 return status;
 636         status = git_gpg_config(k, v, NULL);
 637         if (status)
 638                 return status;
 639         return git_diff_ui_config(k, v, cb);
 640 }
 641
 642 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 643                              struct object_id *one)
 644 {
 645         int i, nr_trees = 0;
 646         struct tree *trees[MAX_UNPACK_TREES];
 647         struct tree_desc t[MAX_UNPACK_TREES];
 648         struct unpack_trees_options opts;
 649
 650         memset(&opts, 0, sizeof(opts));
 651         opts.head_idx = 2;
 652         opts.src_index = &the_index;
 653         opts.dst_index = &the_index;
 654         opts.update = 1;
 655         opts.verbose_update = 1;
 656         opts.trivial_merges_only = 1;
 657         opts.merge = 1;
 658         trees[nr_trees] = parse_tree_indirect(common);
 659         if (!trees[nr_trees++])
 660                 return -1;
 661         trees[nr_trees] = parse_tree_indirect(head);
 662         if (!trees[nr_trees++])
 663                 return -1;
 664         trees[nr_trees] = parse_tree_indirect(one);
 665         if (!trees[nr_trees++])
 666                 return -1;
 667         opts.fn = threeway_merge;
 668         cache_tree_free(&active_cache_tree);
 669         for (i = 0; i < nr_trees; i++) {
 670                 parse_tree(trees[i]);
 671                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 672         }
 673         if (unpack_trees(nr_trees, t, &opts))
 674                 return -1;
 675         return 0;
 676 }
 677
 678 static void write_tree_trivial(struct object_id *oid)
 679 {
 680         if (write_cache_as_tree(oid, 0, NULL))
 681                 die(_("git write-tree failed to write a tree"));
 682 }
 683
 684 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 685                               struct commit_list *remoteheads,
 686                               struct commit *head)
 687 {
 688         struct lock_file lock = LOCK_INIT;
 689         const char *head_arg = "HEAD";
 690
 691         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 692         refresh_cache(REFRESH_QUIET);
 693         if (write_locked_index(&the_index, &lock,
 694                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 695                 return error(_("Unable to write index."));
 696
 697         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 698                 int clean, x;
 699                 struct commit *result;
 700                 struct commit_list *reversed = NULL;
 701                 struct merge_options o;
 702                 struct commit_list *j;
 703
 704                 if (remoteheads->next) {
 705                         error(_("Not handling anything other than two heads merge."));
 706                         return 2;
 707                 }
 708
 709                 init_merge_options(&o, the_repository);
 710                 if (!strcmp(strategy, "subtree"))
 711                         o.subtree_shift = "";
 712
 713                 o.renormalize = option_renormalize;
 714                 o.show_rename_progress =
 715                         show_progress == -1 ? isatty(2) : show_progress;
 716
 717                 for (x = 0; x < xopts_nr; x++)
 718                         if (parse_merge_opt(&o, xopts[x]))
 719                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 720
 721                 o.branch1 = head_arg;
 722                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 723
 724                 for (j = common; j; j = j->next)
 725                         commit_list_insert(j->item, &reversed);
 726
 727                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 728                 clean = merge_recursive(&o, head,
 729                                 remoteheads->item, reversed, &result);
 730                 if (clean < 0)
 731                         exit(128);
 732                 if (write_locked_index(&the_index, &lock,
 733                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 734                         die(_("unable to write %s"), get_index_file());
 735                 return clean ? 0 : 1;
 736         } else {
 737                 return try_merge_command(the_repository,
 738                                          strategy, xopts_nr, xopts,
 739                                          common, head_arg, remoteheads);
 740         }
 741 }
 742
 743 static void count_diff_files(struct diff_queue_struct *q,
 744                              struct diff_options *opt, void *data)
 745 {
 746         int *count = data;
 747
 748         (*count) += q->nr;
 749 }
 750
 751 static int count_unmerged_entries(void)
 752 {
 753         int i, ret = 0;
 754
 755         for (i = 0; i < active_nr; i++)
 756                 if (ce_stage(active_cache[i]))
 757                         ret++;
 758
 759         return ret;
 760 }
 761
 762 static void add_strategies(const char *string, unsigned attr)
 763 {
 764         int i;
 765
 766         if (string) {
 767                 struct string_list list = STRING_LIST_INIT_DUP;
 768                 struct string_list_item *item;
 769                 string_list_split(&list, string, ' ', -1);
 770                 for_each_string_list_item(item, &list)
 771                         append_strategy(get_strategy(item->string));
 772                 string_list_clear(&list, 0);
 773                 return;
 774         }
 775         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 776                 if (all_strategy[i].attr & attr)
 777                         append_strategy(&all_strategy[i]);
 778
 779 }
 780
 781 static void read_merge_msg(struct strbuf *msg)
 782 {
 783         const char *filename = git_path_merge_msg(the_repository);
 784         strbuf_reset(msg);
 785         if (strbuf_read_file(msg, filename, 0) < 0)
 786                 die_errno(_("Could not read from '%s'"), filename);
 787 }
 788
 789 static void write_merge_state(struct commit_list *);
 790 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 791 {
 792         if (err_msg)
 793                 error("%s", err_msg);
 794         fprintf(stderr,
 795                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 796         write_merge_state(remoteheads);
 797         exit(1);
 798 }
 799
 800 static const char merge_editor_comment[] =
 801 N_("Please enter a commit message to explain why this merge is necessary,\n"
 802    "especially if it merges an updated upstream into a topic branch.\n"
 803    "\n"
 804    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 805    "the commit.\n");
 806
 807 static void write_merge_heads(struct commit_list *);
 808 static void prepare_to_commit(struct commit_list *remoteheads)
 809 {
 810         struct strbuf msg = STRBUF_INIT;
 811         strbuf_addbuf(&msg, &merge_msg);
 812         strbuf_addch(&msg, '\n');
 813         if (squash)
 814                 BUG("the control must not reach here under --squash");
 815         if (0 < option_edit)
 816                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 817         if (signoff)
 818                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 819         write_merge_heads(remoteheads);
 820         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 821         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 822                             git_path_merge_msg(the_repository), "merge", NULL))
 823                 abort_commit(remoteheads, NULL);
 824         if (0 < option_edit) {
 825                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 826                         abort_commit(remoteheads, NULL);
 827         }
 828
 829         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 830                                           "commit-msg",
 831                                           git_path_merge_msg(the_repository), NULL))
 832                 abort_commit(remoteheads, NULL);
 833
 834         read_merge_msg(&msg);
 835         strbuf_stripspace(&msg, 0 < option_edit);
 836         if (!msg.len)
 837                 abort_commit(remoteheads, _("Empty commit message."));
 838         strbuf_release(&merge_msg);
 839         strbuf_addbuf(&merge_msg, &msg);
 840         strbuf_release(&msg);
 841 }
 842
 843 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 844 {
 845         struct object_id result_tree, result_commit;
 846         struct commit_list *parents, **pptr = &parents;
 847         struct lock_file lock = LOCK_INIT;
 848
 849         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 850         refresh_cache(REFRESH_QUIET);
 851         if (write_locked_index(&the_index, &lock,
 852                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 853                 return error(_("Unable to write index."));
 854
 855         write_tree_trivial(&result_tree);
 856         printf(_("Wonderful.\n"));
 857         pptr = commit_list_append(head, pptr);
 858         pptr = commit_list_append(remoteheads->item, pptr);
 859         prepare_to_commit(remoteheads);
 860         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 861                         &result_commit, NULL, sign_commit))
 862                 die(_("failed to write commit object"));
 863         finish(head, remoteheads, &result_commit, "In-index merge");
 864         drop_save();
 865         return 0;
 866 }
 867
 868 static int finish_automerge(struct commit *head,
 869                             int head_subsumed,
 870                             struct commit_list *common,
 871                             struct commit_list *remoteheads,
 872                             struct object_id *result_tree,
 873                             const char *wt_strategy)
 874 {
 875         struct commit_list *parents = NULL;
 876         struct strbuf buf = STRBUF_INIT;
 877         struct object_id result_commit;
 878
 879         free_commit_list(common);
 880         parents = remoteheads;
 881         if (!head_subsumed || fast_forward == FF_NO)
 882                 commit_list_insert(head, &parents);
 883         strbuf_addch(&merge_msg, '\n');
 884         prepare_to_commit(remoteheads);
 885         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 886                         &result_commit, NULL, sign_commit))
 887                 die(_("failed to write commit object"));
 888         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 889         finish(head, remoteheads, &result_commit, buf.buf);
 890         strbuf_release(&buf);
 891         drop_save();
 892         return 0;
 893 }
 894
 895 static int suggest_conflicts(void)
 896 {
 897         const char *filename;
 898         FILE *fp;
 899         struct strbuf msgbuf = STRBUF_INIT;
 900
 901         filename = git_path_merge_msg(the_repository);
 902         fp = xfopen(filename, "a");
 903
 904         append_conflicts_hint(&the_index, &msgbuf);
 905         fputs(msgbuf.buf, fp);
 906         strbuf_release(&msgbuf);
 907         fclose(fp);
 908         repo_rerere(the_repository, allow_rerere_auto);
 909         printf(_("Automatic merge failed; "
 910                         "fix conflicts and then commit the result.\n"));
 911         return 1;
 912 }
 913
 914 static int evaluate_result(void)
 915 {
 916         int cnt = 0;
 917         struct rev_info rev;
 918
 919         /* Check how many files differ. */
 920         repo_init_revisions(the_repository, &rev, "");
 921         setup_revisions(0, NULL, &rev, NULL);
 922         rev.diffopt.output_format |=
 923                 DIFF_FORMAT_CALLBACK;
 924         rev.diffopt.format_callback = count_diff_files;
 925         rev.diffopt.format_callback_data = &cnt;
 926         run_diff_files(&rev, 0);
 927
 928         /*
 929          * Check how many unmerged entries are
 930          * there.
 931          */
 932         cnt += count_unmerged_entries();
 933
 934         return cnt;
 935 }
 936
 937 /*
 938  * Pretend as if the user told us to merge with the remote-tracking
 939  * branch we have for the upstream of the current branch
 940  */
 941 static int setup_with_upstream(const char ***argv)
 942 {
 943         struct branch *branch = branch_get(NULL);
 944         int i;
 945         const char **args;
 946
 947         if (!branch)
 948                 die(_("No current branch."));
 949         if (!branch->remote_name)
 950                 die(_("No remote for the current branch."));
 951         if (!branch->merge_nr)
 952                 die(_("No default upstream defined for the current branch."));
 953
 954         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 955         for (i = 0; i < branch->merge_nr; i++) {
 956                 if (!branch->merge[i]->dst)
 957                         die(_("No remote-tracking branch for %s from %s"),
 958                             branch->merge[i]->src, branch->remote_name);
 959                 args[i] = branch->merge[i]->dst;
 960         }
 961         args[i] = NULL;
 962         *argv = args;
 963         return i;
 964 }
 965
 966 static void write_merge_heads(struct commit_list *remoteheads)
 967 {
 968         struct commit_list *j;
 969         struct strbuf buf = STRBUF_INIT;
 970
 971         for (j = remoteheads; j; j = j->next) {
 972                 struct object_id *oid;
 973                 struct commit *c = j->item;
 974                 struct merge_remote_desc *desc;
 975
 976                 desc = merge_remote_util(c);
 977                 if (desc && desc->obj) {
 978                         oid = &desc->obj->oid;
 979                 } else {
 980                         oid = &c->object.oid;
 981                 }
 982                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 983         }
 984         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 985
 986         strbuf_reset(&buf);
 987         if (fast_forward == FF_NO)
 988                 strbuf_addstr(&buf, "no-ff");
 989         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 990         strbuf_release(&buf);
 991 }
 992
 993 static void write_merge_state(struct commit_list *remoteheads)
 994 {
 995         write_merge_heads(remoteheads);
 996         strbuf_addch(&merge_msg, '\n');
 997         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 998                        merge_msg.len);
 999 }
1000
1001 static int default_edit_option(void)
1002 {
1003         static const char name[] = "GIT_MERGE_AUTOEDIT";
1004         const char *e = getenv(name);
1005         struct stat st_stdin, st_stdout;
1006
1007         if (have_message)
1008                 /* an explicit -m msg without --[no-]edit */
1009                 return 0;
1010
1011         if (e) {
1012                 int v = git_parse_maybe_bool(e);
1013                 if (v < 0)
1014                         die(_("Bad value '%s' in environment '%s'"), e, name);
1015                 return v;
1016         }
1017
1018         /* Use editor if stdin and stdout are the same and is a tty */
1019         return (!fstat(0, &st_stdin) &&
1020                 !fstat(1, &st_stdout) &&
1021                 isatty(0) && isatty(1) &&
1022                 st_stdin.st_dev == st_stdout.st_dev &&
1023                 st_stdin.st_ino == st_stdout.st_ino &&
1024                 st_stdin.st_mode == st_stdout.st_mode);
1025 }
1026
1027 static struct commit_list *reduce_parents(struct commit *head_commit,
1028                                           int *head_subsumed,
1029                                           struct commit_list *remoteheads)
1030 {
1031         struct commit_list *parents, **remotes;
1032
1033         /*
1034          * Is the current HEAD reachable from another commit being
1035          * merged?  If so we do not want to record it as a parent of
1036          * the resulting merge, unless --no-ff is given.  We will flip
1037          * this variable to 0 when we find HEAD among the independent
1038          * tips being merged.
1039          */
1040         *head_subsumed = 1;
1041
1042         /* Find what parents to record by checking independent ones. */
1043         parents = reduce_heads(remoteheads);
1044         free_commit_list(remoteheads);
1045
1046         remoteheads = NULL;
1047         remotes = &remoteheads;
1048         while (parents) {
1049                 struct commit *commit = pop_commit(&parents);
1050                 if (commit == head_commit)
1051                         *head_subsumed = 0;
1052                 else
1053                         remotes = &commit_list_insert(commit, remotes)->next;
1054         }
1055         return remoteheads;
1056 }
1057
1058 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1059 {
1060         struct fmt_merge_msg_opts opts;
1061
1062         memset(&opts, 0, sizeof(opts));
1063         opts.add_title = !have_message;
1064         opts.shortlog_len = shortlog_len;
1065         opts.credit_people = (0 < option_edit);
1066
1067         fmt_merge_msg(merge_names, merge_msg, &opts);
1068         if (merge_msg->len)
1069                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1070 }
1071
1072 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1073 {
1074         const char *filename;
1075         int fd, pos, npos;
1076         struct strbuf fetch_head_file = STRBUF_INIT;
1077         const unsigned hexsz = the_hash_algo->hexsz;
1078
1079         if (!merge_names)
1080                 merge_names = &fetch_head_file;
1081
1082         filename = git_path_fetch_head(the_repository);
1083         fd = open(filename, O_RDONLY);
1084         if (fd < 0)
1085                 die_errno(_("could not open '%s' for reading"), filename);
1086
1087         if (strbuf_read(merge_names, fd, 0) < 0)
1088                 die_errno(_("could not read '%s'"), filename);
1089         if (close(fd) < 0)
1090                 die_errno(_("could not close '%s'"), filename);
1091
1092         for (pos = 0; pos < merge_names->len; pos = npos) {
1093                 struct object_id oid;
1094                 char *ptr;
1095                 struct commit *commit;
1096
1097                 ptr = strchr(merge_names->buf + pos, '\n');
1098                 if (ptr)
1099                         npos = ptr - merge_names->buf + 1;
1100                 else
1101                         npos = merge_names->len;
1102
1103                 if (npos - pos < hexsz + 2 ||
1104                     get_oid_hex(merge_names->buf + pos, &oid))
1105                         commit = NULL; /* bad */
1106                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1107                         continue; /* not-for-merge */
1108                 else {
1109                         char saved = merge_names->buf[pos + hexsz];
1110                         merge_names->buf[pos + hexsz] = '\0';
1111                         commit = get_merge_parent(merge_names->buf + pos);
1112                         merge_names->buf[pos + hexsz] = saved;
1113                 }
1114                 if (!commit) {
1115                         if (ptr)
1116                                 *ptr = '\0';
1117                         die(_("not something we can merge in %s: %s"),
1118                             filename, merge_names->buf + pos);
1119                 }
1120                 remotes = &commit_list_insert(commit, remotes)->next;
1121         }
1122
1123         if (merge_names == &fetch_head_file)
1124                 strbuf_release(&fetch_head_file);
1125 }
1126
1127 static struct commit_list *collect_parents(struct commit *head_commit,
1128                                            int *head_subsumed,
1129                                            int argc, const char **argv,
1130                                            struct strbuf *merge_msg)
1131 {
1132         int i;
1133         struct commit_list *remoteheads = NULL;
1134         struct commit_list **remotes = &remoteheads;
1135         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1136
1137         if (merge_msg && (!have_message || shortlog_len))
1138                 autogen = &merge_names;
1139
1140         if (head_commit)
1141                 remotes = &commit_list_insert(head_commit, remotes)->next;
1142
1143         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1144                 handle_fetch_head(remotes, autogen);
1145                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1146         } else {
1147                 for (i = 0; i < argc; i++) {
1148                         struct commit *commit = get_merge_parent(argv[i]);
1149                         if (!commit)
1150                                 help_unknown_ref(argv[i], "merge",
1151                                                  _("not something we can merge"));
1152                         remotes = &commit_list_insert(commit, remotes)->next;
1153                 }
1154                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1155                 if (autogen) {
1156                         struct commit_list *p;
1157                         for (p = remoteheads; p; p = p->next)
1158                                 merge_name(merge_remote_util(p->item)->name, autogen);
1159                 }
1160         }
1161
1162         if (autogen) {
1163                 prepare_merge_message(autogen, merge_msg);
1164                 strbuf_release(autogen);
1165         }
1166
1167         return remoteheads;
1168 }
1169
1170 static int merging_a_throwaway_tag(struct commit *commit)
1171 {
1172         char *tag_ref;
1173         struct object_id oid;
1174         int is_throwaway_tag = 0;
1175
1176         /* Are we merging a tag? */
1177         if (!merge_remote_util(commit) ||
1178             !merge_remote_util(commit)->obj ||
1179             merge_remote_util(commit)->obj->type != OBJ_TAG)
1180                 return is_throwaway_tag;
1181
1182         /*
1183          * Now we know we are merging a tag object.  Are we downstream
1184          * and following the tags from upstream?  If so, we must have
1185          * the tag object pointed at by "refs/tags/$T" where $T is the
1186          * tagname recorded in the tag object.  We want to allow such
1187          * a "just to catch up" merge to fast-forward.
1188          *
1189          * Otherwise, we are playing an integrator's role, making a
1190          * merge with a throw-away tag from a contributor with
1191          * something like "git pull $contributor $signed_tag".
1192          * We want to forbid such a merge from fast-forwarding
1193          * by default; otherwise we would not keep the signature
1194          * anywhere.
1195          */
1196         tag_ref = xstrfmt("refs/tags/%s",
1197                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1198         if (!read_ref(tag_ref, &oid) &&
1199             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1200                 is_throwaway_tag = 0;
1201         else
1202                 is_throwaway_tag = 1;
1203         free(tag_ref);
1204         return is_throwaway_tag;
1205 }
1206
1207 int cmd_merge(int argc, const char **argv, const char *prefix)
1208 {
1209         struct object_id result_tree, stash, head_oid;
1210         struct commit *head_commit;
1211         struct strbuf buf = STRBUF_INIT;
1212         int i, ret = 0, head_subsumed;
1213         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1214         struct commit_list *common = NULL;
1215         const char *best_strategy = NULL, *wt_strategy = NULL;
1216         struct commit_list *remoteheads, *p;
1217         void *branch_to_free;
1218         int orig_argc = argc;
1219
1220         if (argc == 2 && !strcmp(argv[1], "-h"))
1221                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1222
1223         /*
1224          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1225          * current branch.
1226          */
1227         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1228         if (branch)
1229                 skip_prefix(branch, "refs/heads/", &branch);
1230
1231         init_diff_ui_defaults();
1232         git_config(git_merge_config, NULL);
1233
1234         if (!branch || is_null_oid(&head_oid))
1235                 head_commit = NULL;
1236         else
1237                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1238
1239         if (branch_mergeoptions)
1240                 parse_branch_merge_options(branch_mergeoptions);
1241         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1242                         builtin_merge_usage, 0);
1243         if (shortlog_len < 0)
1244                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1245
1246         if (verbosity < 0 && show_progress == -1)
1247                 show_progress = 0;
1248
1249         if (abort_current_merge) {
1250                 int nargc = 2;
1251                 const char *nargv[] = {"reset", "--merge", NULL};
1252
1253                 if (orig_argc != 2)
1254                         usage_msg_opt(_("--abort expects no arguments"),
1255                               builtin_merge_usage, builtin_merge_options);
1256
1257                 if (!file_exists(git_path_merge_head(the_repository)))
1258                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1259
1260                 /* Invoke 'git reset --merge' */
1261                 ret = cmd_reset(nargc, nargv, prefix);
1262                 goto done;
1263         }
1264
1265         if (continue_current_merge) {
1266                 int nargc = 1;
1267                 const char *nargv[] = {"commit", NULL};
1268
1269                 if (orig_argc != 2)
1270                         usage_msg_opt(_("--continue expects no arguments"),
1271                               builtin_merge_usage, builtin_merge_options);
1272
1273                 if (!file_exists(git_path_merge_head(the_repository)))
1274                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1275
1276                 /* Invoke 'git commit' */
1277                 ret = cmd_commit(nargc, nargv, prefix);
1278                 goto done;
1279         }
1280
1281         if (read_cache_unmerged())
1282                 die_resolve_conflict("merge");
1283
1284         if (file_exists(git_path_merge_head(the_repository))) {
1285                 /*
1286                  * There is no unmerged entry, don't advise 'git
1287                  * add/rm <file>', just 'git commit'.
1288                  */
1289                 if (advice_resolve_conflict)
1290                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1291                                   "Please, commit your changes before you merge."));
1292                 else
1293                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1294         }
1295         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1296                 if (advice_resolve_conflict)
1297                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1298                             "Please, commit your changes before you merge."));
1299                 else
1300                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1301         }
1302         resolve_undo_clear();
1303
1304         if (verbosity < 0)
1305                 show_diffstat = 0;
1306
1307         if (squash) {
1308                 if (fast_forward == FF_NO)
1309                         die(_("You cannot combine --squash with --no-ff."));
1310                 option_commit = 0;
1311         }
1312
1313         if (!argc) {
1314                 if (default_to_upstream)
1315                         argc = setup_with_upstream(&argv);
1316                 else
1317                         die(_("No commit specified and merge.defaultToUpstream not set."));
1318         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1319                 argv[0] = "@{-1}";
1320         }
1321
1322         if (!argc)
1323                 usage_with_options(builtin_merge_usage,
1324                         builtin_merge_options);
1325
1326         if (!head_commit) {
1327                 /*
1328                  * If the merged head is a valid one there is no reason
1329                  * to forbid "git merge" into a branch yet to be born.
1330                  * We do the same for "git pull".
1331                  */
1332                 struct object_id *remote_head_oid;
1333                 if (squash)
1334                         die(_("Squash commit into empty head not supported yet"));
1335                 if (fast_forward == FF_NO)
1336                         die(_("Non-fast-forward commit does not make sense into "
1337                             "an empty head"));
1338                 remoteheads = collect_parents(head_commit, &head_subsumed,
1339                                               argc, argv, NULL);
1340                 if (!remoteheads)
1341                         die(_("%s - not something we can merge"), argv[0]);
1342                 if (remoteheads->next)
1343                         die(_("Can merge only exactly one commit into empty head"));
1344
1345                 if (verify_signatures)
1346                         verify_merge_signature(remoteheads->item, verbosity);
1347
1348                 remote_head_oid = &remoteheads->item->object.oid;
1349                 read_empty(remote_head_oid, 0);
1350                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1351                            UPDATE_REFS_DIE_ON_ERR);
1352                 goto done;
1353         }
1354
1355         /*
1356          * All the rest are the commits being merged; prepare
1357          * the standard merge summary message to be appended
1358          * to the given message.
1359          */
1360         remoteheads = collect_parents(head_commit, &head_subsumed,
1361                                       argc, argv, &merge_msg);
1362
1363         if (!head_commit || !argc)
1364                 usage_with_options(builtin_merge_usage,
1365                         builtin_merge_options);
1366
1367         if (verify_signatures) {
1368                 for (p = remoteheads; p; p = p->next) {
1369                         verify_merge_signature(p->item, verbosity);
1370                 }
1371         }
1372
1373         strbuf_addstr(&buf, "merge");
1374         for (p = remoteheads; p; p = p->next)
1375                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1376         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1377         strbuf_reset(&buf);
1378
1379         for (p = remoteheads; p; p = p->next) {
1380                 struct commit *commit = p->item;
1381                 strbuf_addf(&buf, "GITHEAD_%s",
1382                             oid_to_hex(&commit->object.oid));
1383                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1384                 strbuf_reset(&buf);
1385                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1386                         fast_forward = FF_NO;
1387         }
1388
1389         if (option_edit < 0)
1390                 option_edit = default_edit_option();
1391
1392         if (!use_strategies) {
1393                 if (!remoteheads)
1394                         ; /* already up-to-date */
1395                 else if (!remoteheads->next)
1396                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1397                 else
1398                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1399         }
1400
1401         for (i = 0; i < use_strategies_nr; i++) {
1402                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1403                         fast_forward = FF_NO;
1404                 if (use_strategies[i]->attr & NO_TRIVIAL)
1405                         allow_trivial = 0;
1406         }
1407
1408         if (!remoteheads)
1409                 ; /* already up-to-date */
1410         else if (!remoteheads->next)
1411                 common = get_merge_bases(head_commit, remoteheads->item);
1412         else {
1413                 struct commit_list *list = remoteheads;
1414                 commit_list_insert(head_commit, &list);
1415                 common = get_octopus_merge_bases(list);
1416                 free(list);
1417         }
1418
1419         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1420                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1421
1422         if (remoteheads && !common) {
1423                 /* No common ancestors found. */
1424                 if (!allow_unrelated_histories)
1425                         die(_("refusing to merge unrelated histories"));
1426                 /* otherwise, we need a real merge. */
1427         } else if (!remoteheads ||
1428                  (!remoteheads->next && !common->next &&
1429                   common->item == remoteheads->item)) {
1430                 /*
1431                  * If head can reach all the merge then we are up to date.
1432                  * but first the most common case of merging one remote.
1433                  */
1434                 finish_up_to_date(_("Already up to date."));
1435                 goto done;
1436         } else if (fast_forward != FF_NO && !remoteheads->next &&
1437                         !common->next &&
1438                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1439                 /* Again the most common case of merging one remote. */
1440                 struct strbuf msg = STRBUF_INIT;
1441                 struct commit *commit;
1442
1443                 if (verbosity >= 0) {
1444                         printf(_("Updating %s..%s\n"),
1445                                find_unique_abbrev(&head_commit->object.oid,
1446                                                   DEFAULT_ABBREV),
1447                                find_unique_abbrev(&remoteheads->item->object.oid,
1448                                                   DEFAULT_ABBREV));
1449                 }
1450                 strbuf_addstr(&msg, "Fast-forward");
1451                 if (have_message)
1452                         strbuf_addstr(&msg,
1453                                 " (no commit created; -m option ignored)");
1454                 commit = remoteheads->item;
1455                 if (!commit) {
1456                         ret = 1;
1457                         goto done;
1458                 }
1459
1460                 if (checkout_fast_forward(the_repository,
1461                                           &head_commit->object.oid,
1462                                           &commit->object.oid,
1463                                           overwrite_ignore)) {
1464                         ret = 1;
1465                         goto done;
1466                 }
1467
1468                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1469                 drop_save();
1470                 goto done;
1471         } else if (!remoteheads->next && common->next)
1472                 ;
1473                 /*
1474                  * We are not doing octopus and not fast-forward.  Need
1475                  * a real merge.
1476                  */
1477         else if (!remoteheads->next && !common->next && option_commit) {
1478                 /*
1479                  * We are not doing octopus, not fast-forward, and have
1480                  * only one common.
1481                  */
1482                 refresh_cache(REFRESH_QUIET);
1483                 if (allow_trivial && fast_forward != FF_ONLY) {
1484                         /* See if it is really trivial. */
1485                         git_committer_info(IDENT_STRICT);
1486                         printf(_("Trying really trivial in-index merge...\n"));
1487                         if (!read_tree_trivial(&common->item->object.oid,
1488                                                &head_commit->object.oid,
1489                                                &remoteheads->item->object.oid)) {
1490                                 ret = merge_trivial(head_commit, remoteheads);
1491                                 goto done;
1492                         }
1493                         printf(_("Nope.\n"));
1494                 }
1495         } else {
1496                 /*
1497                  * An octopus.  If we can reach all the remote we are up
1498                  * to date.
1499                  */
1500                 int up_to_date = 1;
1501                 struct commit_list *j;
1502
1503                 for (j = remoteheads; j; j = j->next) {
1504                         struct commit_list *common_one;
1505
1506                         /*
1507                          * Here we *have* to calculate the individual
1508                          * merge_bases again, otherwise "git merge HEAD^
1509                          * HEAD^^" would be missed.
1510                          */
1511                         common_one = get_merge_bases(head_commit, j->item);
1512                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1513                                 up_to_date = 0;
1514                                 break;
1515                         }
1516                 }
1517                 if (up_to_date) {
1518                         finish_up_to_date(_("Already up to date. Yeeah!"));
1519                         goto done;
1520                 }
1521         }
1522
1523         if (fast_forward == FF_ONLY)
1524                 die(_("Not possible to fast-forward, aborting."));
1525
1526         /* We are going to make a new commit. */
1527         git_committer_info(IDENT_STRICT);
1528
1529         /*
1530          * At this point, we need a real merge.  No matter what strategy
1531          * we use, it would operate on the index, possibly affecting the
1532          * working tree, and when resolved cleanly, have the desired
1533          * tree in the index -- this means that the index must be in
1534          * sync with the head commit.  The strategies are responsible
1535          * to ensure this.
1536          */
1537         if (use_strategies_nr == 1 ||
1538             /*
1539              * Stash away the local changes so that we can try more than one.
1540              */
1541             save_state(&stash))
1542                 oidclr(&stash);
1543
1544         for (i = 0; i < use_strategies_nr; i++) {
1545                 int ret;
1546                 if (i) {
1547                         printf(_("Rewinding the tree to pristine...\n"));
1548                         restore_state(&head_commit->object.oid, &stash);
1549                 }
1550                 if (use_strategies_nr != 1)
1551                         printf(_("Trying merge strategy %s...\n"),
1552                                 use_strategies[i]->name);
1553                 /*
1554                  * Remember which strategy left the state in the working
1555                  * tree.
1556                  */
1557                 wt_strategy = use_strategies[i]->name;
1558
1559                 ret = try_merge_strategy(use_strategies[i]->name,
1560                                          common, remoteheads,
1561                                          head_commit);
1562                 if (!option_commit && !ret) {
1563                         merge_was_ok = 1;
1564                         /*
1565                          * This is necessary here just to avoid writing
1566                          * the tree, but later we will *not* exit with
1567                          * status code 1 because merge_was_ok is set.
1568                          */
1569                         ret = 1;
1570                 }
1571
1572                 if (ret) {
1573                         /*
1574                          * The backend exits with 1 when conflicts are
1575                          * left to be resolved, with 2 when it does not
1576                          * handle the given merge at all.
1577                          */
1578                         if (ret == 1) {
1579                                 int cnt = evaluate_result();
1580
1581                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1582                                         best_strategy = use_strategies[i]->name;
1583                                         best_cnt = cnt;
1584                                 }
1585                         }
1586                         if (merge_was_ok)
1587                                 break;
1588                         else
1589                                 continue;
1590                 }
1591
1592                 /* Automerge succeeded. */
1593                 write_tree_trivial(&result_tree);
1594                 automerge_was_ok = 1;
1595                 break;
1596         }
1597
1598         /*
1599          * If we have a resulting tree, that means the strategy module
1600          * auto resolved the merge cleanly.
1601          */
1602         if (automerge_was_ok) {
1603                 ret = finish_automerge(head_commit, head_subsumed,
1604                                        common, remoteheads,
1605                                        &result_tree, wt_strategy);
1606                 goto done;
1607         }
1608
1609         /*
1610          * Pick the result from the best strategy and have the user fix
1611          * it up.
1612          */
1613         if (!best_strategy) {
1614                 restore_state(&head_commit->object.oid, &stash);
1615                 if (use_strategies_nr > 1)
1616                         fprintf(stderr,
1617                                 _("No merge strategy handled the merge.\n"));
1618                 else
1619                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1620                                 use_strategies[0]->name);
1621                 ret = 2;
1622                 goto done;
1623         } else if (best_strategy == wt_strategy)
1624                 ; /* We already have its result in the working tree. */
1625         else {
1626                 printf(_("Rewinding the tree to pristine...\n"));
1627                 restore_state(&head_commit->object.oid, &stash);
1628                 printf(_("Using the %s to prepare resolving by hand.\n"),
1629                         best_strategy);
1630                 try_merge_strategy(best_strategy, common, remoteheads,
1631                                    head_commit);
1632         }
1633
1634         if (squash)
1635                 finish(head_commit, remoteheads, NULL, NULL);
1636         else
1637                 write_merge_state(remoteheads);
1638
1639         if (merge_was_ok)
1640                 fprintf(stderr, _("Automatic merge went well; "
1641                         "stopped before committing as requested\n"));
1642         else
1643                 ret = suggest_conflicts();
1644
1645 done:
1646         free(branch_to_free);
1647         return ret;
1648 }