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 "config.h"
  11 #include "parse-options.h"
  12 #include "builtin.h"
  13 #include "lockfile.h"
  14 #include "run-command.h"
  15 #include "diff.h"
  16 #include "refs.h"
  17 #include "refspec.h"
  18 #include "commit.h"
  19 #include "diffcore.h"
  20 #include "revision.h"
  21 #include "unpack-trees.h"
  22 #include "cache-tree.h"
  23 #include "dir.h"
  24 #include "utf8.h"
  25 #include "log-tree.h"
  26 #include "color.h"
  27 #include "rerere.h"
  28 #include "help.h"
  29 #include "merge-recursive.h"
  30 #include "resolve-undo.h"
  31 #include "remote.h"
  32 #include "fmt-merge-msg.h"
  33 #include "gpg-interface.h"
  34 #include "sequencer.h"
  35 #include "string-list.h"
  36 #include "packfile.h"
  37 #include "tag.h"
  38 #include "alias.h"
  39 #include "commit-reach.h"
  40
  41 #define DEFAULT_TWOHEAD (1<<0)
  42 #define DEFAULT_OCTOPUS (1<<1)
  43 #define NO_FAST_FORWARD (1<<2)
  44 #define NO_TRIVIAL      (1<<3)
  45
  46 struct strategy {
  47         const char *name;
  48         unsigned attr;
  49 };
  50
  51 static const char * const builtin_merge_usage[] = {
  52         N_("git merge [<options>] [<commit>...]"),
  53         N_("git merge --abort"),
  54         N_("git merge --continue"),
  55         NULL
  56 };
  57
  58 static int show_diffstat = 1, shortlog_len = -1, squash;
  59 static int option_commit = 1;
  60 static int option_edit = -1;
  61 static int allow_trivial = 1, have_message, verify_signatures;
  62 static int overwrite_ignore = 1;
  63 static struct strbuf merge_msg = STRBUF_INIT;
  64 static struct strategy **use_strategies;
  65 static size_t use_strategies_nr, use_strategies_alloc;
  66 static const char **xopts;
  67 static size_t xopts_nr, xopts_alloc;
  68 static const char *branch;
  69 static char *branch_mergeoptions;
  70 static int option_renormalize;
  71 static int verbosity;
  72 static int allow_rerere_auto;
  73 static int abort_current_merge;
  74 static int continue_current_merge;
  75 static int allow_unrelated_histories;
  76 static int show_progress = -1;
  77 static int default_to_upstream = 1;
  78 static int signoff;
  79 static const char *sign_commit;
  80 static int verify_msg = 1;
  81
  82 static struct strategy all_strategy[] = {
  83         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  84         { "octopus",    DEFAULT_OCTOPUS },
  85         { "resolve",    0 },
  86         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  87         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  88 };
  89
  90 static const char *pull_twohead, *pull_octopus;
  91
  92 enum ff_type {
  93         FF_NO,
  94         FF_ALLOW,
  95         FF_ONLY
  96 };
  97
  98 static enum ff_type fast_forward = FF_ALLOW;
  99
 100 static int option_parse_message(const struct option *opt,
 101                                 const char *arg, int unset)
 102 {
 103         struct strbuf *buf = opt->value;
 104
 105         if (unset)
 106                 strbuf_setlen(buf, 0);
 107         else if (arg) {
 108                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 109                 have_message = 1;
 110         } else
 111                 return error(_("switch `m' requires a value"));
 112         return 0;
 113 }
 114
 115 static int option_read_message(struct parse_opt_ctx_t *ctx,
 116                                const struct option *opt, int unset)
 117 {
 118         struct strbuf *buf = opt->value;
 119         const char *arg;
 120
 121         if (unset)
 122                 BUG("-F cannot be negated");
 123
 124         if (ctx->opt) {
 125                 arg = ctx->opt;
 126                 ctx->opt = NULL;
 127         } else if (ctx->argc > 1) {
 128                 ctx->argc--;
 129                 arg = *++ctx->argv;
 130         } else
 131                 return opterror(opt, "requires a value", 0);
 132
 133         if (buf->len)
 134                 strbuf_addch(buf, '\n');
 135         if (ctx->prefix && !is_absolute_path(arg))
 136                 arg = prefix_filename(ctx->prefix, arg);
 137         if (strbuf_read_file(buf, arg, 0) < 0)
 138                 return error(_("could not read file '%s'"), arg);
 139         have_message = 1;
 140
 141         return 0;
 142 }
 143
 144 static struct strategy *get_strategy(const char *name)
 145 {
 146         int i;
 147         struct strategy *ret;
 148         static struct cmdnames main_cmds, other_cmds;
 149         static int loaded;
 150
 151         if (!name)
 152                 return NULL;
 153
 154         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 155                 if (!strcmp(name, all_strategy[i].name))
 156                         return &all_strategy[i];
 157
 158         if (!loaded) {
 159                 struct cmdnames not_strategies;
 160                 loaded = 1;
 161
 162                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 163                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 164                 for (i = 0; i < main_cmds.cnt; i++) {
 165                         int j, found = 0;
 166                         struct cmdname *ent = main_cmds.names[i];
 167                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 168                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 169                                                 && !all_strategy[j].name[ent->len])
 170                                         found = 1;
 171                         if (!found)
 172                                 add_cmdname(&not_strategies, ent->name, ent->len);
 173                 }
 174                 exclude_cmds(&main_cmds, &not_strategies);
 175         }
 176         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 177                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 178                 fprintf(stderr, _("Available strategies are:"));
 179                 for (i = 0; i < main_cmds.cnt; i++)
 180                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 181                 fprintf(stderr, ".\n");
 182                 if (other_cmds.cnt) {
 183                         fprintf(stderr, _("Available custom strategies are:"));
 184                         for (i = 0; i < other_cmds.cnt; i++)
 185                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 186                         fprintf(stderr, ".\n");
 187                 }
 188                 exit(1);
 189         }
 190
 191         ret = xcalloc(1, sizeof(struct strategy));
 192         ret->name = xstrdup(name);
 193         ret->attr = NO_TRIVIAL;
 194         return ret;
 195 }
 196
 197 static void append_strategy(struct strategy *s)
 198 {
 199         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 200         use_strategies[use_strategies_nr++] = s;
 201 }
 202
 203 static int option_parse_strategy(const struct option *opt,
 204                                  const char *name, int unset)
 205 {
 206         if (unset)
 207                 return 0;
 208
 209         append_strategy(get_strategy(name));
 210         return 0;
 211 }
 212
 213 static int option_parse_x(const struct option *opt,
 214                           const char *arg, int unset)
 215 {
 216         if (unset)
 217                 return 0;
 218
 219         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 220         xopts[xopts_nr++] = xstrdup(arg);
 221         return 0;
 222 }
 223
 224 static int option_parse_n(const struct option *opt,
 225                           const char *arg, int unset)
 226 {
 227         show_diffstat = unset;
 228         return 0;
 229 }
 230
 231 static struct option builtin_merge_options[] = {
 232         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 233                 N_("do not show a diffstat at the end of the merge"),
 234                 PARSE_OPT_NOARG, option_parse_n },
 235         OPT_BOOL(0, "stat", &show_diffstat,
 236                 N_("show a diffstat at the end of the merge")),
 237         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 238         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 239           N_("add (at most <n>) entries from shortlog to merge commit message"),
 240           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 241         OPT_BOOL(0, "squash", &squash,
 242                 N_("create a single commit instead of doing a merge")),
 243         OPT_BOOL(0, "commit", &option_commit,
 244                 N_("perform a commit if the merge succeeds (default)")),
 245         OPT_BOOL('e', "edit", &option_edit,
 246                 N_("edit message before committing")),
 247         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 248         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 249                       N_("abort if fast-forward is not possible"),
 250                       FF_ONLY, PARSE_OPT_NONEG),
 251         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 252         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 253                 N_("verify that the named commit has a valid GPG signature")),
 254         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 255                 N_("merge strategy to use"), option_parse_strategy),
 256         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 257                 N_("option for selected merge strategy"), option_parse_x),
 258         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 259                 N_("merge commit message (for a non-fast-forward merge)"),
 260                 option_parse_message),
 261         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 262                 N_("read message from file"), PARSE_OPT_NONEG,
 263                 (parse_opt_cb *) option_read_message },
 264         OPT__VERBOSITY(&verbosity),
 265         OPT_BOOL(0, "abort", &abort_current_merge,
 266                 N_("abort the current in-progress merge")),
 267         OPT_BOOL(0, "continue", &continue_current_merge,
 268                 N_("continue the current in-progress merge")),
 269         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 270                  N_("allow merging unrelated histories")),
 271         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 272         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 273           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 274         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 275         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 276         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 277         OPT_END()
 278 };
 279
 280 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 281 static void drop_save(void)
 282 {
 283         unlink(git_path_merge_head(the_repository));
 284         unlink(git_path_merge_msg(the_repository));
 285         unlink(git_path_merge_mode(the_repository));
 286 }
 287
 288 static int save_state(struct object_id *stash)
 289 {
 290         int len;
 291         struct child_process cp = CHILD_PROCESS_INIT;
 292         struct strbuf buffer = STRBUF_INIT;
 293         const char *argv[] = {"stash", "create", NULL};
 294         int rc = -1;
 295
 296         cp.argv = argv;
 297         cp.out = -1;
 298         cp.git_cmd = 1;
 299
 300         if (start_command(&cp))
 301                 die(_("could not run stash."));
 302         len = strbuf_read(&buffer, cp.out, 1024);
 303         close(cp.out);
 304
 305         if (finish_command(&cp) || len < 0)
 306                 die(_("stash failed"));
 307         else if (!len)          /* no changes */
 308                 goto out;
 309         strbuf_setlen(&buffer, buffer.len-1);
 310         if (get_oid(buffer.buf, stash))
 311                 die(_("not a valid object: %s"), buffer.buf);
 312         rc = 0;
 313 out:
 314         strbuf_release(&buffer);
 315         return rc;
 316 }
 317
 318 static void read_empty(const struct object_id *oid, int verbose)
 319 {
 320         int i = 0;
 321         const char *args[7];
 322
 323         args[i++] = "read-tree";
 324         if (verbose)
 325                 args[i++] = "-v";
 326         args[i++] = "-m";
 327         args[i++] = "-u";
 328         args[i++] = empty_tree_oid_hex();
 329         args[i++] = oid_to_hex(oid);
 330         args[i] = NULL;
 331
 332         if (run_command_v_opt(args, RUN_GIT_CMD))
 333                 die(_("read-tree failed"));
 334 }
 335
 336 static void reset_hard(const struct object_id *oid, int verbose)
 337 {
 338         int i = 0;
 339         const char *args[6];
 340
 341         args[i++] = "read-tree";
 342         if (verbose)
 343                 args[i++] = "-v";
 344         args[i++] = "--reset";
 345         args[i++] = "-u";
 346         args[i++] = oid_to_hex(oid);
 347         args[i] = NULL;
 348
 349         if (run_command_v_opt(args, RUN_GIT_CMD))
 350                 die(_("read-tree failed"));
 351 }
 352
 353 static void restore_state(const struct object_id *head,
 354                           const struct object_id *stash)
 355 {
 356         struct strbuf sb = STRBUF_INIT;
 357         const char *args[] = { "stash", "apply", NULL, NULL };
 358
 359         if (is_null_oid(stash))
 360                 return;
 361
 362         reset_hard(head, 1);
 363
 364         args[2] = oid_to_hex(stash);
 365
 366         /*
 367          * It is OK to ignore error here, for example when there was
 368          * nothing to restore.
 369          */
 370         run_command_v_opt(args, RUN_GIT_CMD);
 371
 372         strbuf_release(&sb);
 373         refresh_cache(REFRESH_QUIET);
 374 }
 375
 376 /* This is called when no merge was necessary. */
 377 static void finish_up_to_date(const char *msg)
 378 {
 379         if (verbosity >= 0)
 380                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 381         drop_save();
 382 }
 383
 384 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 385 {
 386         struct rev_info rev;
 387         struct strbuf out = STRBUF_INIT;
 388         struct commit_list *j;
 389         struct pretty_print_context ctx = {0};
 390
 391         printf(_("Squash commit -- not updating HEAD\n"));
 392
 393         init_revisions(&rev, NULL);
 394         rev.ignore_merges = 1;
 395         rev.commit_format = CMIT_FMT_MEDIUM;
 396
 397         commit->object.flags |= UNINTERESTING;
 398         add_pending_object(&rev, &commit->object, NULL);
 399
 400         for (j = remoteheads; j; j = j->next)
 401                 add_pending_object(&rev, &j->item->object, NULL);
 402
 403         setup_revisions(0, NULL, &rev, NULL);
 404         if (prepare_revision_walk(&rev))
 405                 die(_("revision walk setup failed"));
 406
 407         ctx.abbrev = rev.abbrev;
 408         ctx.date_mode = rev.date_mode;
 409         ctx.fmt = rev.commit_format;
 410
 411         strbuf_addstr(&out, "Squashed commit of the following:\n");
 412         while ((commit = get_revision(&rev)) != NULL) {
 413                 strbuf_addch(&out, '\n');
 414                 strbuf_addf(&out, "commit %s\n",
 415                         oid_to_hex(&commit->object.oid));
 416                 pretty_print_commit(&ctx, commit, &out);
 417         }
 418         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 419         strbuf_release(&out);
 420 }
 421
 422 static void finish(struct commit *head_commit,
 423                    struct commit_list *remoteheads,
 424                    const struct object_id *new_head, const char *msg)
 425 {
 426         struct strbuf reflog_message = STRBUF_INIT;
 427         const struct object_id *head = &head_commit->object.oid;
 428
 429         if (!msg)
 430                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 431         else {
 432                 if (verbosity >= 0)
 433                         printf("%s\n", msg);
 434                 strbuf_addf(&reflog_message, "%s: %s",
 435                         getenv("GIT_REFLOG_ACTION"), msg);
 436         }
 437         if (squash) {
 438                 squash_message(head_commit, remoteheads);
 439         } else {
 440                 if (verbosity >= 0 && !merge_msg.len)
 441                         printf(_("No merge message -- not updating HEAD\n"));
 442                 else {
 443                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 444                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 445                                    0, UPDATE_REFS_DIE_ON_ERR);
 446                         /*
 447                          * We ignore errors in 'gc --auto', since the
 448                          * user should see them.
 449                          */
 450                         close_all_packs(the_repository->objects);
 451                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 452                 }
 453         }
 454         if (new_head && show_diffstat) {
 455                 struct diff_options opts;
 456                 diff_setup(&opts);
 457                 opts.stat_width = -1; /* use full terminal width */
 458                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 459                 opts.output_format |=
 460                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 461                 opts.detect_rename = DIFF_DETECT_RENAME;
 462                 diff_setup_done(&opts);
 463                 diff_tree_oid(head, new_head, "", &opts);
 464                 diffcore_std(&opts);
 465                 diff_flush(&opts);
 466         }
 467
 468         /* Run a post-merge hook */
 469         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 470
 471         strbuf_release(&reflog_message);
 472 }
 473
 474 /* Get the name for the merge commit's message. */
 475 static void merge_name(const char *remote, struct strbuf *msg)
 476 {
 477         struct commit *remote_head;
 478         struct object_id branch_head;
 479         struct strbuf buf = STRBUF_INIT;
 480         struct strbuf bname = STRBUF_INIT;
 481         struct merge_remote_desc *desc;
 482         const char *ptr;
 483         char *found_ref;
 484         int len, early;
 485
 486         strbuf_branchname(&bname, remote, 0);
 487         remote = bname.buf;
 488
 489         oidclr(&branch_head);
 490         remote_head = get_merge_parent(remote);
 491         if (!remote_head)
 492                 die(_("'%s' does not point to a commit"), remote);
 493
 494         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 495                 if (starts_with(found_ref, "refs/heads/")) {
 496                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 497                                     oid_to_hex(&branch_head), remote);
 498                         goto cleanup;
 499                 }
 500                 if (starts_with(found_ref, "refs/tags/")) {
 501                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 502                                     oid_to_hex(&branch_head), remote);
 503                         goto cleanup;
 504                 }
 505                 if (starts_with(found_ref, "refs/remotes/")) {
 506                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 507                                     oid_to_hex(&branch_head), remote);
 508                         goto cleanup;
 509                 }
 510         }
 511
 512         /* See if remote matches <name>^^^.. or <name>~<number> */
 513         for (len = 0, ptr = remote + strlen(remote);
 514              remote < ptr && ptr[-1] == '^';
 515              ptr--)
 516                 len++;
 517         if (len)
 518                 early = 1;
 519         else {
 520                 early = 0;
 521                 ptr = strrchr(remote, '~');
 522                 if (ptr) {
 523                         int seen_nonzero = 0;
 524
 525                         len++; /* count ~ */
 526                         while (*++ptr && isdigit(*ptr)) {
 527                                 seen_nonzero |= (*ptr != '0');
 528                                 len++;
 529                         }
 530                         if (*ptr)
 531                                 len = 0; /* not ...~<number> */
 532                         else if (seen_nonzero)
 533                                 early = 1;
 534                         else if (len == 1)
 535                                 early = 1; /* "name~" is "name~1"! */
 536                 }
 537         }
 538         if (len) {
 539                 struct strbuf truname = STRBUF_INIT;
 540                 strbuf_addf(&truname, "refs/heads/%s", remote);
 541                 strbuf_setlen(&truname, truname.len - len);
 542                 if (ref_exists(truname.buf)) {
 543                         strbuf_addf(msg,
 544                                     "%s\t\tbranch '%s'%s of .\n",
 545                                     oid_to_hex(&remote_head->object.oid),
 546                                     truname.buf + 11,
 547                                     (early ? " (early part)" : ""));
 548                         strbuf_release(&truname);
 549                         goto cleanup;
 550                 }
 551                 strbuf_release(&truname);
 552         }
 553
 554         desc = merge_remote_util(remote_head);
 555         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 556                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 557                             oid_to_hex(&desc->obj->oid),
 558                             type_name(desc->obj->type),
 559                             remote);
 560                 goto cleanup;
 561         }
 562
 563         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 564                 oid_to_hex(&remote_head->object.oid), remote);
 565 cleanup:
 566         strbuf_release(&buf);
 567         strbuf_release(&bname);
 568 }
 569
 570 static void parse_branch_merge_options(char *bmo)
 571 {
 572         const char **argv;
 573         int argc;
 574
 575         if (!bmo)
 576                 return;
 577         argc = split_cmdline(bmo, &argv);
 578         if (argc < 0)
 579                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 580                     split_cmdline_strerror(argc));
 581         REALLOC_ARRAY(argv, argc + 2);
 582         MOVE_ARRAY(argv + 1, argv, argc + 1);
 583         argc++;
 584         argv[0] = "branch.*.mergeoptions";
 585         parse_options(argc, argv, NULL, builtin_merge_options,
 586                       builtin_merge_usage, 0);
 587         free(argv);
 588 }
 589
 590 static int git_merge_config(const char *k, const char *v, void *cb)
 591 {
 592         int status;
 593
 594         if (branch && starts_with(k, "branch.") &&
 595                 starts_with(k + 7, branch) &&
 596                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 597                 free(branch_mergeoptions);
 598                 branch_mergeoptions = xstrdup(v);
 599                 return 0;
 600         }
 601
 602         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 603                 show_diffstat = git_config_bool(k, v);
 604         else if (!strcmp(k, "merge.verifysignatures"))
 605                 verify_signatures = git_config_bool(k, v);
 606         else if (!strcmp(k, "pull.twohead"))
 607                 return git_config_string(&pull_twohead, k, v);
 608         else if (!strcmp(k, "pull.octopus"))
 609                 return git_config_string(&pull_octopus, k, v);
 610         else if (!strcmp(k, "merge.renormalize"))
 611                 option_renormalize = git_config_bool(k, v);
 612         else if (!strcmp(k, "merge.ff")) {
 613                 int boolval = git_parse_maybe_bool(v);
 614                 if (0 <= boolval) {
 615                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 616                 } else if (v && !strcmp(v, "only")) {
 617                         fast_forward = FF_ONLY;
 618                 } /* do not barf on values from future versions of git */
 619                 return 0;
 620         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 621                 default_to_upstream = git_config_bool(k, v);
 622                 return 0;
 623         } else if (!strcmp(k, "commit.gpgsign")) {
 624                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 625                 return 0;
 626         }
 627
 628         status = fmt_merge_msg_config(k, v, cb);
 629         if (status)
 630                 return status;
 631         status = git_gpg_config(k, v, NULL);
 632         if (status)
 633                 return status;
 634         return git_diff_ui_config(k, v, cb);
 635 }
 636
 637 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 638                              struct object_id *one)
 639 {
 640         int i, nr_trees = 0;
 641         struct tree *trees[MAX_UNPACK_TREES];
 642         struct tree_desc t[MAX_UNPACK_TREES];
 643         struct unpack_trees_options opts;
 644
 645         memset(&opts, 0, sizeof(opts));
 646         opts.head_idx = 2;
 647         opts.src_index = &the_index;
 648         opts.dst_index = &the_index;
 649         opts.update = 1;
 650         opts.verbose_update = 1;
 651         opts.trivial_merges_only = 1;
 652         opts.merge = 1;
 653         trees[nr_trees] = parse_tree_indirect(common);
 654         if (!trees[nr_trees++])
 655                 return -1;
 656         trees[nr_trees] = parse_tree_indirect(head);
 657         if (!trees[nr_trees++])
 658                 return -1;
 659         trees[nr_trees] = parse_tree_indirect(one);
 660         if (!trees[nr_trees++])
 661                 return -1;
 662         opts.fn = threeway_merge;
 663         cache_tree_free(&active_cache_tree);
 664         for (i = 0; i < nr_trees; i++) {
 665                 parse_tree(trees[i]);
 666                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 667         }
 668         if (unpack_trees(nr_trees, t, &opts))
 669                 return -1;
 670         return 0;
 671 }
 672
 673 static void write_tree_trivial(struct object_id *oid)
 674 {
 675         if (write_cache_as_tree(oid, 0, NULL))
 676                 die(_("git write-tree failed to write a tree"));
 677 }
 678
 679 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 680                               struct commit_list *remoteheads,
 681                               struct commit *head)
 682 {
 683         struct lock_file lock = LOCK_INIT;
 684         const char *head_arg = "HEAD";
 685
 686         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 687         refresh_cache(REFRESH_QUIET);
 688         if (write_locked_index(&the_index, &lock,
 689                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 690                 return error(_("Unable to write index."));
 691
 692         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 693                 int clean, x;
 694                 struct commit *result;
 695                 struct commit_list *reversed = NULL;
 696                 struct merge_options o;
 697                 struct commit_list *j;
 698
 699                 if (remoteheads->next) {
 700                         error(_("Not handling anything other than two heads merge."));
 701                         return 2;
 702                 }
 703
 704                 init_merge_options(&o);
 705                 if (!strcmp(strategy, "subtree"))
 706                         o.subtree_shift = "";
 707
 708                 o.renormalize = option_renormalize;
 709                 o.show_rename_progress =
 710                         show_progress == -1 ? isatty(2) : show_progress;
 711
 712                 for (x = 0; x < xopts_nr; x++)
 713                         if (parse_merge_opt(&o, xopts[x]))
 714                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 715
 716                 o.branch1 = head_arg;
 717                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 718
 719                 for (j = common; j; j = j->next)
 720                         commit_list_insert(j->item, &reversed);
 721
 722                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 723                 clean = merge_recursive(&o, head,
 724                                 remoteheads->item, reversed, &result);
 725                 if (clean < 0)
 726                         exit(128);
 727                 if (write_locked_index(&the_index, &lock,
 728                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 729                         die(_("unable to write %s"), get_index_file());
 730                 return clean ? 0 : 1;
 731         } else {
 732                 return try_merge_command(strategy, xopts_nr, xopts,
 733                                                 common, head_arg, remoteheads);
 734         }
 735 }
 736
 737 static void count_diff_files(struct diff_queue_struct *q,
 738                              struct diff_options *opt, void *data)
 739 {
 740         int *count = data;
 741
 742         (*count) += q->nr;
 743 }
 744
 745 static int count_unmerged_entries(void)
 746 {
 747         int i, ret = 0;
 748
 749         for (i = 0; i < active_nr; i++)
 750                 if (ce_stage(active_cache[i]))
 751                         ret++;
 752
 753         return ret;
 754 }
 755
 756 static void add_strategies(const char *string, unsigned attr)
 757 {
 758         int i;
 759
 760         if (string) {
 761                 struct string_list list = STRING_LIST_INIT_DUP;
 762                 struct string_list_item *item;
 763                 string_list_split(&list, string, ' ', -1);
 764                 for_each_string_list_item(item, &list)
 765                         append_strategy(get_strategy(item->string));
 766                 string_list_clear(&list, 0);
 767                 return;
 768         }
 769         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 770                 if (all_strategy[i].attr & attr)
 771                         append_strategy(&all_strategy[i]);
 772
 773 }
 774
 775 static void read_merge_msg(struct strbuf *msg)
 776 {
 777         const char *filename = git_path_merge_msg(the_repository);
 778         strbuf_reset(msg);
 779         if (strbuf_read_file(msg, filename, 0) < 0)
 780                 die_errno(_("Could not read from '%s'"), filename);
 781 }
 782
 783 static void write_merge_state(struct commit_list *);
 784 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 785 {
 786         if (err_msg)
 787                 error("%s", err_msg);
 788         fprintf(stderr,
 789                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 790         write_merge_state(remoteheads);
 791         exit(1);
 792 }
 793
 794 static const char merge_editor_comment[] =
 795 N_("Please enter a commit message to explain why this merge is necessary,\n"
 796    "especially if it merges an updated upstream into a topic branch.\n"
 797    "\n"
 798    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 799    "the commit.\n");
 800
 801 static void write_merge_heads(struct commit_list *);
 802 static void prepare_to_commit(struct commit_list *remoteheads)
 803 {
 804         struct strbuf msg = STRBUF_INIT;
 805         strbuf_addbuf(&msg, &merge_msg);
 806         strbuf_addch(&msg, '\n');
 807         if (squash)
 808                 BUG("the control must not reach here under --squash");
 809         if (0 < option_edit)
 810                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 811         if (signoff)
 812                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 813         write_merge_heads(remoteheads);
 814         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 815         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 816                             git_path_merge_msg(the_repository), "merge", NULL))
 817                 abort_commit(remoteheads, NULL);
 818         if (0 < option_edit) {
 819                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 820                         abort_commit(remoteheads, NULL);
 821         }
 822
 823         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 824                                           "commit-msg",
 825                                           git_path_merge_msg(the_repository), NULL))
 826                 abort_commit(remoteheads, NULL);
 827
 828         read_merge_msg(&msg);
 829         strbuf_stripspace(&msg, 0 < option_edit);
 830         if (!msg.len)
 831                 abort_commit(remoteheads, _("Empty commit message."));
 832         strbuf_release(&merge_msg);
 833         strbuf_addbuf(&merge_msg, &msg);
 834         strbuf_release(&msg);
 835 }
 836
 837 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 838 {
 839         struct object_id result_tree, result_commit;
 840         struct commit_list *parents, **pptr = &parents;
 841         struct lock_file lock = LOCK_INIT;
 842
 843         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 844         refresh_cache(REFRESH_QUIET);
 845         if (write_locked_index(&the_index, &lock,
 846                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 847                 return error(_("Unable to write index."));
 848
 849         write_tree_trivial(&result_tree);
 850         printf(_("Wonderful.\n"));
 851         pptr = commit_list_append(head, pptr);
 852         pptr = commit_list_append(remoteheads->item, pptr);
 853         prepare_to_commit(remoteheads);
 854         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 855                         &result_commit, NULL, sign_commit))
 856                 die(_("failed to write commit object"));
 857         finish(head, remoteheads, &result_commit, "In-index merge");
 858         drop_save();
 859         return 0;
 860 }
 861
 862 static int finish_automerge(struct commit *head,
 863                             int head_subsumed,
 864                             struct commit_list *common,
 865                             struct commit_list *remoteheads,
 866                             struct object_id *result_tree,
 867                             const char *wt_strategy)
 868 {
 869         struct commit_list *parents = NULL;
 870         struct strbuf buf = STRBUF_INIT;
 871         struct object_id result_commit;
 872
 873         free_commit_list(common);
 874         parents = remoteheads;
 875         if (!head_subsumed || fast_forward == FF_NO)
 876                 commit_list_insert(head, &parents);
 877         strbuf_addch(&merge_msg, '\n');
 878         prepare_to_commit(remoteheads);
 879         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 880                         &result_commit, NULL, sign_commit))
 881                 die(_("failed to write commit object"));
 882         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 883         finish(head, remoteheads, &result_commit, buf.buf);
 884         strbuf_release(&buf);
 885         drop_save();
 886         return 0;
 887 }
 888
 889 static int suggest_conflicts(void)
 890 {
 891         const char *filename;
 892         FILE *fp;
 893         struct strbuf msgbuf = STRBUF_INIT;
 894
 895         filename = git_path_merge_msg(the_repository);
 896         fp = xfopen(filename, "a");
 897
 898         append_conflicts_hint(&msgbuf);
 899         fputs(msgbuf.buf, fp);
 900         strbuf_release(&msgbuf);
 901         fclose(fp);
 902         rerere(allow_rerere_auto);
 903         printf(_("Automatic merge failed; "
 904                         "fix conflicts and then commit the result.\n"));
 905         return 1;
 906 }
 907
 908 static int evaluate_result(void)
 909 {
 910         int cnt = 0;
 911         struct rev_info rev;
 912
 913         /* Check how many files differ. */
 914         init_revisions(&rev, "");
 915         setup_revisions(0, NULL, &rev, NULL);
 916         rev.diffopt.output_format |=
 917                 DIFF_FORMAT_CALLBACK;
 918         rev.diffopt.format_callback = count_diff_files;
 919         rev.diffopt.format_callback_data = &cnt;
 920         run_diff_files(&rev, 0);
 921
 922         /*
 923          * Check how many unmerged entries are
 924          * there.
 925          */
 926         cnt += count_unmerged_entries();
 927
 928         return cnt;
 929 }
 930
 931 /*
 932  * Pretend as if the user told us to merge with the remote-tracking
 933  * branch we have for the upstream of the current branch
 934  */
 935 static int setup_with_upstream(const char ***argv)
 936 {
 937         struct branch *branch = branch_get(NULL);
 938         int i;
 939         const char **args;
 940
 941         if (!branch)
 942                 die(_("No current branch."));
 943         if (!branch->remote_name)
 944                 die(_("No remote for the current branch."));
 945         if (!branch->merge_nr)
 946                 die(_("No default upstream defined for the current branch."));
 947
 948         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 949         for (i = 0; i < branch->merge_nr; i++) {
 950                 if (!branch->merge[i]->dst)
 951                         die(_("No remote-tracking branch for %s from %s"),
 952                             branch->merge[i]->src, branch->remote_name);
 953                 args[i] = branch->merge[i]->dst;
 954         }
 955         args[i] = NULL;
 956         *argv = args;
 957         return i;
 958 }
 959
 960 static void write_merge_heads(struct commit_list *remoteheads)
 961 {
 962         struct commit_list *j;
 963         struct strbuf buf = STRBUF_INIT;
 964
 965         for (j = remoteheads; j; j = j->next) {
 966                 struct object_id *oid;
 967                 struct commit *c = j->item;
 968                 struct merge_remote_desc *desc;
 969
 970                 desc = merge_remote_util(c);
 971                 if (desc && desc->obj) {
 972                         oid = &desc->obj->oid;
 973                 } else {
 974                         oid = &c->object.oid;
 975                 }
 976                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 977         }
 978         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 979
 980         strbuf_reset(&buf);
 981         if (fast_forward == FF_NO)
 982                 strbuf_addstr(&buf, "no-ff");
 983         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 984         strbuf_release(&buf);
 985 }
 986
 987 static void write_merge_state(struct commit_list *remoteheads)
 988 {
 989         write_merge_heads(remoteheads);
 990         strbuf_addch(&merge_msg, '\n');
 991         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 992                        merge_msg.len);
 993 }
 994
 995 static int default_edit_option(void)
 996 {
 997         static const char name[] = "GIT_MERGE_AUTOEDIT";
 998         const char *e = getenv(name);
 999         struct stat st_stdin, st_stdout;
1000
1001         if (have_message)
1002                 /* an explicit -m msg without --[no-]edit */
1003                 return 0;
1004
1005         if (e) {
1006                 int v = git_parse_maybe_bool(e);
1007                 if (v < 0)
1008                         die(_("Bad value '%s' in environment '%s'"), e, name);
1009                 return v;
1010         }
1011
1012         /* Use editor if stdin and stdout are the same and is a tty */
1013         return (!fstat(0, &st_stdin) &&
1014                 !fstat(1, &st_stdout) &&
1015                 isatty(0) && isatty(1) &&
1016                 st_stdin.st_dev == st_stdout.st_dev &&
1017                 st_stdin.st_ino == st_stdout.st_ino &&
1018                 st_stdin.st_mode == st_stdout.st_mode);
1019 }
1020
1021 static struct commit_list *reduce_parents(struct commit *head_commit,
1022                                           int *head_subsumed,
1023                                           struct commit_list *remoteheads)
1024 {
1025         struct commit_list *parents, **remotes;
1026
1027         /*
1028          * Is the current HEAD reachable from another commit being
1029          * merged?  If so we do not want to record it as a parent of
1030          * the resulting merge, unless --no-ff is given.  We will flip
1031          * this variable to 0 when we find HEAD among the independent
1032          * tips being merged.
1033          */
1034         *head_subsumed = 1;
1035
1036         /* Find what parents to record by checking independent ones. */
1037         parents = reduce_heads(remoteheads);
1038         free_commit_list(remoteheads);
1039
1040         remoteheads = NULL;
1041         remotes = &remoteheads;
1042         while (parents) {
1043                 struct commit *commit = pop_commit(&parents);
1044                 if (commit == head_commit)
1045                         *head_subsumed = 0;
1046                 else
1047                         remotes = &commit_list_insert(commit, remotes)->next;
1048         }
1049         return remoteheads;
1050 }
1051
1052 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1053 {
1054         struct fmt_merge_msg_opts opts;
1055
1056         memset(&opts, 0, sizeof(opts));
1057         opts.add_title = !have_message;
1058         opts.shortlog_len = shortlog_len;
1059         opts.credit_people = (0 < option_edit);
1060
1061         fmt_merge_msg(merge_names, merge_msg, &opts);
1062         if (merge_msg->len)
1063                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1064 }
1065
1066 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1067 {
1068         const char *filename;
1069         int fd, pos, npos;
1070         struct strbuf fetch_head_file = STRBUF_INIT;
1071         const unsigned hexsz = the_hash_algo->hexsz;
1072
1073         if (!merge_names)
1074                 merge_names = &fetch_head_file;
1075
1076         filename = git_path_fetch_head(the_repository);
1077         fd = open(filename, O_RDONLY);
1078         if (fd < 0)
1079                 die_errno(_("could not open '%s' for reading"), filename);
1080
1081         if (strbuf_read(merge_names, fd, 0) < 0)
1082                 die_errno(_("could not read '%s'"), filename);
1083         if (close(fd) < 0)
1084                 die_errno(_("could not close '%s'"), filename);
1085
1086         for (pos = 0; pos < merge_names->len; pos = npos) {
1087                 struct object_id oid;
1088                 char *ptr;
1089                 struct commit *commit;
1090
1091                 ptr = strchr(merge_names->buf + pos, '\n');
1092                 if (ptr)
1093                         npos = ptr - merge_names->buf + 1;
1094                 else
1095                         npos = merge_names->len;
1096
1097                 if (npos - pos < hexsz + 2 ||
1098                     get_oid_hex(merge_names->buf + pos, &oid))
1099                         commit = NULL; /* bad */
1100                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1101                         continue; /* not-for-merge */
1102                 else {
1103                         char saved = merge_names->buf[pos + hexsz];
1104                         merge_names->buf[pos + hexsz] = '\0';
1105                         commit = get_merge_parent(merge_names->buf + pos);
1106                         merge_names->buf[pos + hexsz] = saved;
1107                 }
1108                 if (!commit) {
1109                         if (ptr)
1110                                 *ptr = '\0';
1111                         die(_("not something we can merge in %s: %s"),
1112                             filename, merge_names->buf + pos);
1113                 }
1114                 remotes = &commit_list_insert(commit, remotes)->next;
1115         }
1116
1117         if (merge_names == &fetch_head_file)
1118                 strbuf_release(&fetch_head_file);
1119 }
1120
1121 static struct commit_list *collect_parents(struct commit *head_commit,
1122                                            int *head_subsumed,
1123                                            int argc, const char **argv,
1124                                            struct strbuf *merge_msg)
1125 {
1126         int i;
1127         struct commit_list *remoteheads = NULL;
1128         struct commit_list **remotes = &remoteheads;
1129         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1130
1131         if (merge_msg && (!have_message || shortlog_len))
1132                 autogen = &merge_names;
1133
1134         if (head_commit)
1135                 remotes = &commit_list_insert(head_commit, remotes)->next;
1136
1137         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1138                 handle_fetch_head(remotes, autogen);
1139                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1140         } else {
1141                 for (i = 0; i < argc; i++) {
1142                         struct commit *commit = get_merge_parent(argv[i]);
1143                         if (!commit)
1144                                 help_unknown_ref(argv[i], "merge",
1145                                                  _("not something we can merge"));
1146                         remotes = &commit_list_insert(commit, remotes)->next;
1147                 }
1148                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1149                 if (autogen) {
1150                         struct commit_list *p;
1151                         for (p = remoteheads; p; p = p->next)
1152                                 merge_name(merge_remote_util(p->item)->name, autogen);
1153                 }
1154         }
1155
1156         if (autogen) {
1157                 prepare_merge_message(autogen, merge_msg);
1158                 strbuf_release(autogen);
1159         }
1160
1161         return remoteheads;
1162 }
1163
1164 static int merging_a_throwaway_tag(struct commit *commit)
1165 {
1166         char *tag_ref;
1167         struct object_id oid;
1168         int is_throwaway_tag = 0;
1169
1170         /* Are we merging a tag? */
1171         if (!merge_remote_util(commit) ||
1172             !merge_remote_util(commit)->obj ||
1173             merge_remote_util(commit)->obj->type != OBJ_TAG)
1174                 return is_throwaway_tag;
1175
1176         /*
1177          * Now we know we are merging a tag object.  Are we downstream
1178          * and following the tags from upstream?  If so, we must have
1179          * the tag object pointed at by "refs/tags/$T" where $T is the
1180          * tagname recorded in the tag object.  We want to allow such
1181          * a "just to catch up" merge to fast-forward.
1182          *
1183          * Otherwise, we are playing an integrator's role, making a
1184          * merge with a throw-away tag from a contributor with
1185          * something like "git pull $contributor $signed_tag".
1186          * We want to forbid such a merge from fast-forwarding
1187          * by default; otherwise we would not keep the signature
1188          * anywhere.
1189          */
1190         tag_ref = xstrfmt("refs/tags/%s",
1191                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1192         if (!read_ref(tag_ref, &oid) &&
1193             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1194                 is_throwaway_tag = 0;
1195         else
1196                 is_throwaway_tag = 1;
1197         free(tag_ref);
1198         return is_throwaway_tag;
1199 }
1200
1201 int cmd_merge(int argc, const char **argv, const char *prefix)
1202 {
1203         struct object_id result_tree, stash, head_oid;
1204         struct commit *head_commit;
1205         struct strbuf buf = STRBUF_INIT;
1206         int i, ret = 0, head_subsumed;
1207         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1208         struct commit_list *common = NULL;
1209         const char *best_strategy = NULL, *wt_strategy = NULL;
1210         struct commit_list *remoteheads, *p;
1211         void *branch_to_free;
1212         int orig_argc = argc;
1213
1214         if (argc == 2 && !strcmp(argv[1], "-h"))
1215                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1216
1217         /*
1218          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1219          * current branch.
1220          */
1221         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1222         if (branch)
1223                 skip_prefix(branch, "refs/heads/", &branch);
1224
1225         init_diff_ui_defaults();
1226         git_config(git_merge_config, NULL);
1227
1228         if (!branch || is_null_oid(&head_oid))
1229                 head_commit = NULL;
1230         else
1231                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1232
1233         if (branch_mergeoptions)
1234                 parse_branch_merge_options(branch_mergeoptions);
1235         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1236                         builtin_merge_usage, 0);
1237         if (shortlog_len < 0)
1238                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1239
1240         if (verbosity < 0 && show_progress == -1)
1241                 show_progress = 0;
1242
1243         if (abort_current_merge) {
1244                 int nargc = 2;
1245                 const char *nargv[] = {"reset", "--merge", NULL};
1246
1247                 if (orig_argc != 2)
1248                         usage_msg_opt(_("--abort expects no arguments"),
1249                               builtin_merge_usage, builtin_merge_options);
1250
1251                 if (!file_exists(git_path_merge_head(the_repository)))
1252                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1253
1254                 /* Invoke 'git reset --merge' */
1255                 ret = cmd_reset(nargc, nargv, prefix);
1256                 goto done;
1257         }
1258
1259         if (continue_current_merge) {
1260                 int nargc = 1;
1261                 const char *nargv[] = {"commit", NULL};
1262
1263                 if (orig_argc != 2)
1264                         usage_msg_opt(_("--continue expects no arguments"),
1265                               builtin_merge_usage, builtin_merge_options);
1266
1267                 if (!file_exists(git_path_merge_head(the_repository)))
1268                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1269
1270                 /* Invoke 'git commit' */
1271                 ret = cmd_commit(nargc, nargv, prefix);
1272                 goto done;
1273         }
1274
1275         if (read_cache_unmerged())
1276                 die_resolve_conflict("merge");
1277
1278         if (file_exists(git_path_merge_head(the_repository))) {
1279                 /*
1280                  * There is no unmerged entry, don't advise 'git
1281                  * add/rm <file>', just 'git commit'.
1282                  */
1283                 if (advice_resolve_conflict)
1284                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1285                                   "Please, commit your changes before you merge."));
1286                 else
1287                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1288         }
1289         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1290                 if (advice_resolve_conflict)
1291                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1292                             "Please, commit your changes before you merge."));
1293                 else
1294                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1295         }
1296         resolve_undo_clear();
1297
1298         if (verbosity < 0)
1299                 show_diffstat = 0;
1300
1301         if (squash) {
1302                 if (fast_forward == FF_NO)
1303                         die(_("You cannot combine --squash with --no-ff."));
1304                 option_commit = 0;
1305         }
1306
1307         if (!argc) {
1308                 if (default_to_upstream)
1309                         argc = setup_with_upstream(&argv);
1310                 else
1311                         die(_("No commit specified and merge.defaultToUpstream not set."));
1312         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1313                 argv[0] = "@{-1}";
1314         }
1315
1316         if (!argc)
1317                 usage_with_options(builtin_merge_usage,
1318                         builtin_merge_options);
1319
1320         if (!head_commit) {
1321                 /*
1322                  * If the merged head is a valid one there is no reason
1323                  * to forbid "git merge" into a branch yet to be born.
1324                  * We do the same for "git pull".
1325                  */
1326                 struct object_id *remote_head_oid;
1327                 if (squash)
1328                         die(_("Squash commit into empty head not supported yet"));
1329                 if (fast_forward == FF_NO)
1330                         die(_("Non-fast-forward commit does not make sense into "
1331                             "an empty head"));
1332                 remoteheads = collect_parents(head_commit, &head_subsumed,
1333                                               argc, argv, NULL);
1334                 if (!remoteheads)
1335                         die(_("%s - not something we can merge"), argv[0]);
1336                 if (remoteheads->next)
1337                         die(_("Can merge only exactly one commit into empty head"));
1338                 remote_head_oid = &remoteheads->item->object.oid;
1339                 read_empty(remote_head_oid, 0);
1340                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1341                            UPDATE_REFS_DIE_ON_ERR);
1342                 goto done;
1343         }
1344
1345         /*
1346          * All the rest are the commits being merged; prepare
1347          * the standard merge summary message to be appended
1348          * to the given message.
1349          */
1350         remoteheads = collect_parents(head_commit, &head_subsumed,
1351                                       argc, argv, &merge_msg);
1352
1353         if (!head_commit || !argc)
1354                 usage_with_options(builtin_merge_usage,
1355                         builtin_merge_options);
1356
1357         if (verify_signatures) {
1358                 for (p = remoteheads; p; p = p->next) {
1359                         struct commit *commit = p->item;
1360                         char hex[GIT_MAX_HEXSZ + 1];
1361                         struct signature_check signature_check;
1362                         memset(&signature_check, 0, sizeof(signature_check));
1363
1364                         check_commit_signature(commit, &signature_check);
1365
1366                         find_unique_abbrev_r(hex, &commit->object.oid, DEFAULT_ABBREV);
1367                         switch (signature_check.result) {
1368                         case 'G':
1369                                 break;
1370                         case 'U':
1371                                 die(_("Commit %s has an untrusted GPG signature, "
1372                                       "allegedly by %s."), hex, signature_check.signer);
1373                         case 'B':
1374                                 die(_("Commit %s has a bad GPG signature "
1375                                       "allegedly by %s."), hex, signature_check.signer);
1376                         default: /* 'N' */
1377                                 die(_("Commit %s does not have a GPG signature."), hex);
1378                         }
1379                         if (verbosity >= 0 && signature_check.result == 'G')
1380                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1381                                        hex, signature_check.signer);
1382
1383                         signature_check_clear(&signature_check);
1384                 }
1385         }
1386
1387         strbuf_addstr(&buf, "merge");
1388         for (p = remoteheads; p; p = p->next)
1389                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1390         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1391         strbuf_reset(&buf);
1392
1393         for (p = remoteheads; p; p = p->next) {
1394                 struct commit *commit = p->item;
1395                 strbuf_addf(&buf, "GITHEAD_%s",
1396                             oid_to_hex(&commit->object.oid));
1397                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1398                 strbuf_reset(&buf);
1399                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1400                         fast_forward = FF_NO;
1401         }
1402
1403         if (option_edit < 0)
1404                 option_edit = default_edit_option();
1405
1406         if (!use_strategies) {
1407                 if (!remoteheads)
1408                         ; /* already up-to-date */
1409                 else if (!remoteheads->next)
1410                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1411                 else
1412                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1413         }
1414
1415         for (i = 0; i < use_strategies_nr; i++) {
1416                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1417                         fast_forward = FF_NO;
1418                 if (use_strategies[i]->attr & NO_TRIVIAL)
1419                         allow_trivial = 0;
1420         }
1421
1422         if (!remoteheads)
1423                 ; /* already up-to-date */
1424         else if (!remoteheads->next)
1425                 common = get_merge_bases(head_commit, remoteheads->item);
1426         else {
1427                 struct commit_list *list = remoteheads;
1428                 commit_list_insert(head_commit, &list);
1429                 common = get_octopus_merge_bases(list);
1430                 free(list);
1431         }
1432
1433         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1434                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1435
1436         if (remoteheads && !common) {
1437                 /* No common ancestors found. */
1438                 if (!allow_unrelated_histories)
1439                         die(_("refusing to merge unrelated histories"));
1440                 /* otherwise, we need a real merge. */
1441         } else if (!remoteheads ||
1442                  (!remoteheads->next && !common->next &&
1443                   common->item == remoteheads->item)) {
1444                 /*
1445                  * If head can reach all the merge then we are up to date.
1446                  * but first the most common case of merging one remote.
1447                  */
1448                 finish_up_to_date(_("Already up to date."));
1449                 goto done;
1450         } else if (fast_forward != FF_NO && !remoteheads->next &&
1451                         !common->next &&
1452                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1453                 /* Again the most common case of merging one remote. */
1454                 struct strbuf msg = STRBUF_INIT;
1455                 struct commit *commit;
1456
1457                 if (verbosity >= 0) {
1458                         printf(_("Updating %s..%s\n"),
1459                                find_unique_abbrev(&head_commit->object.oid,
1460                                                   DEFAULT_ABBREV),
1461                                find_unique_abbrev(&remoteheads->item->object.oid,
1462                                                   DEFAULT_ABBREV));
1463                 }
1464                 strbuf_addstr(&msg, "Fast-forward");
1465                 if (have_message)
1466                         strbuf_addstr(&msg,
1467                                 " (no commit created; -m option ignored)");
1468                 commit = remoteheads->item;
1469                 if (!commit) {
1470                         ret = 1;
1471                         goto done;
1472                 }
1473
1474                 if (checkout_fast_forward(&head_commit->object.oid,
1475                                           &commit->object.oid,
1476                                           overwrite_ignore)) {
1477                         ret = 1;
1478                         goto done;
1479                 }
1480
1481                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1482                 drop_save();
1483                 goto done;
1484         } else if (!remoteheads->next && common->next)
1485                 ;
1486                 /*
1487                  * We are not doing octopus and not fast-forward.  Need
1488                  * a real merge.
1489                  */
1490         else if (!remoteheads->next && !common->next && option_commit) {
1491                 /*
1492                  * We are not doing octopus, not fast-forward, and have
1493                  * only one common.
1494                  */
1495                 refresh_cache(REFRESH_QUIET);
1496                 if (allow_trivial && fast_forward != FF_ONLY) {
1497                         /* See if it is really trivial. */
1498                         git_committer_info(IDENT_STRICT);
1499                         printf(_("Trying really trivial in-index merge...\n"));
1500                         if (!read_tree_trivial(&common->item->object.oid,
1501                                                &head_commit->object.oid,
1502                                                &remoteheads->item->object.oid)) {
1503                                 ret = merge_trivial(head_commit, remoteheads);
1504                                 goto done;
1505                         }
1506                         printf(_("Nope.\n"));
1507                 }
1508         } else {
1509                 /*
1510                  * An octopus.  If we can reach all the remote we are up
1511                  * to date.
1512                  */
1513                 int up_to_date = 1;
1514                 struct commit_list *j;
1515
1516                 for (j = remoteheads; j; j = j->next) {
1517                         struct commit_list *common_one;
1518
1519                         /*
1520                          * Here we *have* to calculate the individual
1521                          * merge_bases again, otherwise "git merge HEAD^
1522                          * HEAD^^" would be missed.
1523                          */
1524                         common_one = get_merge_bases(head_commit, j->item);
1525                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1526                                 up_to_date = 0;
1527                                 break;
1528                         }
1529                 }
1530                 if (up_to_date) {
1531                         finish_up_to_date(_("Already up to date. Yeeah!"));
1532                         goto done;
1533                 }
1534         }
1535
1536         if (fast_forward == FF_ONLY)
1537                 die(_("Not possible to fast-forward, aborting."));
1538
1539         /* We are going to make a new commit. */
1540         git_committer_info(IDENT_STRICT);
1541
1542         /*
1543          * At this point, we need a real merge.  No matter what strategy
1544          * we use, it would operate on the index, possibly affecting the
1545          * working tree, and when resolved cleanly, have the desired
1546          * tree in the index -- this means that the index must be in
1547          * sync with the head commit.  The strategies are responsible
1548          * to ensure this.
1549          */
1550         if (use_strategies_nr == 1 ||
1551             /*
1552              * Stash away the local changes so that we can try more than one.
1553              */
1554             save_state(&stash))
1555                 oidclr(&stash);
1556
1557         for (i = 0; i < use_strategies_nr; i++) {
1558                 int ret;
1559                 if (i) {
1560                         printf(_("Rewinding the tree to pristine...\n"));
1561                         restore_state(&head_commit->object.oid, &stash);
1562                 }
1563                 if (use_strategies_nr != 1)
1564                         printf(_("Trying merge strategy %s...\n"),
1565                                 use_strategies[i]->name);
1566                 /*
1567                  * Remember which strategy left the state in the working
1568                  * tree.
1569                  */
1570                 wt_strategy = use_strategies[i]->name;
1571
1572                 ret = try_merge_strategy(use_strategies[i]->name,
1573                                          common, remoteheads,
1574                                          head_commit);
1575                 if (!option_commit && !ret) {
1576                         merge_was_ok = 1;
1577                         /*
1578                          * This is necessary here just to avoid writing
1579                          * the tree, but later we will *not* exit with
1580                          * status code 1 because merge_was_ok is set.
1581                          */
1582                         ret = 1;
1583                 }
1584
1585                 if (ret) {
1586                         /*
1587                          * The backend exits with 1 when conflicts are
1588                          * left to be resolved, with 2 when it does not
1589                          * handle the given merge at all.
1590                          */
1591                         if (ret == 1) {
1592                                 int cnt = evaluate_result();
1593
1594                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1595                                         best_strategy = use_strategies[i]->name;
1596                                         best_cnt = cnt;
1597                                 }
1598                         }
1599                         if (merge_was_ok)
1600                                 break;
1601                         else
1602                                 continue;
1603                 }
1604
1605                 /* Automerge succeeded. */
1606                 write_tree_trivial(&result_tree);
1607                 automerge_was_ok = 1;
1608                 break;
1609         }
1610
1611         /*
1612          * If we have a resulting tree, that means the strategy module
1613          * auto resolved the merge cleanly.
1614          */
1615         if (automerge_was_ok) {
1616                 ret = finish_automerge(head_commit, head_subsumed,
1617                                        common, remoteheads,
1618                                        &result_tree, wt_strategy);
1619                 goto done;
1620         }
1621
1622         /*
1623          * Pick the result from the best strategy and have the user fix
1624          * it up.
1625          */
1626         if (!best_strategy) {
1627                 restore_state(&head_commit->object.oid, &stash);
1628                 if (use_strategies_nr > 1)
1629                         fprintf(stderr,
1630                                 _("No merge strategy handled the merge.\n"));
1631                 else
1632                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1633                                 use_strategies[0]->name);
1634                 ret = 2;
1635                 goto done;
1636         } else if (best_strategy == wt_strategy)
1637                 ; /* We already have its result in the working tree. */
1638         else {
1639                 printf(_("Rewinding the tree to pristine...\n"));
1640                 restore_state(&head_commit->object.oid, &stash);
1641                 printf(_("Using the %s to prepare resolving by hand.\n"),
1642                         best_strategy);
1643                 try_merge_strategy(best_strategy, common, remoteheads,
1644                                    head_commit);
1645         }
1646
1647         if (squash)
1648                 finish(head_commit, remoteheads, NULL, NULL);
1649         else
1650                 write_merge_state(remoteheads);
1651
1652         if (merge_was_ok)
1653                 fprintf(stderr, _("Automatic merge went well; "
1654                         "stopped before committing as requested\n"));
1655         else
1656                 ret = suggest_conflicts();
1657
1658 done:
1659         free(branch_to_free);
1660         return ret;
1661 }