git.oblomov.eu Git - git/blob - 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 #include "wt-status.h"
  42
  43 #define DEFAULT_TWOHEAD (1<<0)
  44 #define DEFAULT_OCTOPUS (1<<1)
  45 #define NO_FAST_FORWARD (1<<2)
  46 #define NO_TRIVIAL      (1<<3)
  47
  48 struct strategy {
  49         const char *name;
  50         unsigned attr;
  51 };
  52
  53 static const char * const builtin_merge_usage[] = {
  54         N_("git merge [<options>] [<commit>...]"),
  55         N_("git merge --abort"),
  56         N_("git merge --continue"),
  57         NULL
  58 };
  59
  60 static int show_diffstat = 1, shortlog_len = -1, squash;
  61 static int option_commit = 1;
  62 static int option_edit = -1;
  63 static int allow_trivial = 1, have_message, verify_signatures;
  64 static int overwrite_ignore = 1;
  65 static struct strbuf merge_msg = STRBUF_INIT;
  66 static struct strategy **use_strategies;
  67 static size_t use_strategies_nr, use_strategies_alloc;
  68 static const char **xopts;
  69 static size_t xopts_nr, xopts_alloc;
  70 static const char *branch;
  71 static char *branch_mergeoptions;
  72 static int option_renormalize;
  73 static int verbosity;
  74 static int allow_rerere_auto;
  75 static int abort_current_merge;
  76 static int continue_current_merge;
  77 static int allow_unrelated_histories;
  78 static int show_progress = -1;
  79 static int default_to_upstream = 1;
  80 static int signoff;
  81 static const char *sign_commit;
  82 static int verify_msg = 1;
  83
  84 static struct strategy all_strategy[] = {
  85         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  86         { "octopus",    DEFAULT_OCTOPUS },
  87         { "resolve",    0 },
  88         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  89         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  90 };
  91
  92 static const char *pull_twohead, *pull_octopus;
  93
  94 enum ff_type {
  95         FF_NO,
  96         FF_ALLOW,
  97         FF_ONLY
  98 };
  99
 100 static enum ff_type fast_forward = FF_ALLOW;
 101
 102 static const char *cleanup_arg;
 103 static enum commit_msg_cleanup_mode cleanup_mode;
 104
 105 static int option_parse_message(const struct option *opt,
 106                                 const char *arg, int unset)
 107 {
 108         struct strbuf *buf = opt->value;
 109
 110         if (unset)
 111                 strbuf_setlen(buf, 0);
 112         else if (arg) {
 113                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 114                 have_message = 1;
 115         } else
 116                 return error(_("switch `m' requires a value"));
 117         return 0;
 118 }
 119
 120 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 121                                                  const struct option *opt,
 122                                                  const char *arg_not_used,
 123                                                  int unset)
 124 {
 125         struct strbuf *buf = opt->value;
 126         const char *arg;
 127
 128         BUG_ON_OPT_ARG(arg_not_used);
 129         if (unset)
 130                 BUG("-F cannot be negated");
 131
 132         if (ctx->opt) {
 133                 arg = ctx->opt;
 134                 ctx->opt = NULL;
 135         } else if (ctx->argc > 1) {
 136                 ctx->argc--;
 137                 arg = *++ctx->argv;
 138         } else
 139                 return error(_("option `%s' requires a value"), opt->long_name);
 140
 141         if (buf->len)
 142                 strbuf_addch(buf, '\n');
 143         if (ctx->prefix && !is_absolute_path(arg))
 144                 arg = prefix_filename(ctx->prefix, arg);
 145         if (strbuf_read_file(buf, arg, 0) < 0)
 146                 return error(_("could not read file '%s'"), arg);
 147         have_message = 1;
 148
 149         return 0;
 150 }
 151
 152 static struct strategy *get_strategy(const char *name)
 153 {
 154         int i;
 155         struct strategy *ret;
 156         static struct cmdnames main_cmds, other_cmds;
 157         static int loaded;
 158
 159         if (!name)
 160                 return NULL;
 161
 162         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 163                 if (!strcmp(name, all_strategy[i].name))
 164                         return &all_strategy[i];
 165
 166         if (!loaded) {
 167                 struct cmdnames not_strategies;
 168                 loaded = 1;
 169
 170                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 171                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 172                 for (i = 0; i < main_cmds.cnt; i++) {
 173                         int j, found = 0;
 174                         struct cmdname *ent = main_cmds.names[i];
 175                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 176                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 177                                                 && !all_strategy[j].name[ent->len])
 178                                         found = 1;
 179                         if (!found)
 180                                 add_cmdname(&not_strategies, ent->name, ent->len);
 181                 }
 182                 exclude_cmds(&main_cmds, &not_strategies);
 183         }
 184         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 185                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 186                 fprintf(stderr, _("Available strategies are:"));
 187                 for (i = 0; i < main_cmds.cnt; i++)
 188                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 189                 fprintf(stderr, ".\n");
 190                 if (other_cmds.cnt) {
 191                         fprintf(stderr, _("Available custom strategies are:"));
 192                         for (i = 0; i < other_cmds.cnt; i++)
 193                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 194                         fprintf(stderr, ".\n");
 195                 }
 196                 exit(1);
 197         }
 198
 199         ret = xcalloc(1, sizeof(struct strategy));
 200         ret->name = xstrdup(name);
 201         ret->attr = NO_TRIVIAL;
 202         return ret;
 203 }
 204
 205 static void append_strategy(struct strategy *s)
 206 {
 207         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 208         use_strategies[use_strategies_nr++] = s;
 209 }
 210
 211 static int option_parse_strategy(const struct option *opt,
 212                                  const char *name, int unset)
 213 {
 214         if (unset)
 215                 return 0;
 216
 217         append_strategy(get_strategy(name));
 218         return 0;
 219 }
 220
 221 static int option_parse_x(const struct option *opt,
 222                           const char *arg, int unset)
 223 {
 224         if (unset)
 225                 return 0;
 226
 227         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 228         xopts[xopts_nr++] = xstrdup(arg);
 229         return 0;
 230 }
 231
 232 static int option_parse_n(const struct option *opt,
 233                           const char *arg, int unset)
 234 {
 235         BUG_ON_OPT_ARG(arg);
 236         show_diffstat = unset;
 237         return 0;
 238 }
 239
 240 static struct option builtin_merge_options[] = {
 241         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 242                 N_("do not show a diffstat at the end of the merge"),
 243                 PARSE_OPT_NOARG, option_parse_n },
 244         OPT_BOOL(0, "stat", &show_diffstat,
 245                 N_("show a diffstat at the end of the merge")),
 246         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 247         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 248           N_("add (at most <n>) entries from shortlog to merge commit message"),
 249           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 250         OPT_BOOL(0, "squash", &squash,
 251                 N_("create a single commit instead of doing a merge")),
 252         OPT_BOOL(0, "commit", &option_commit,
 253                 N_("perform a commit if the merge succeeds (default)")),
 254         OPT_BOOL('e', "edit", &option_edit,
 255                 N_("edit message before committing")),
 256         OPT_CLEANUP(&cleanup_arg),
 257         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 258         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 259                       N_("abort if fast-forward is not possible"),
 260                       FF_ONLY, PARSE_OPT_NONEG),
 261         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 262         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 263                 N_("verify that the named commit has a valid GPG signature")),
 264         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 265                 N_("merge strategy to use"), option_parse_strategy),
 266         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 267                 N_("option for selected merge strategy"), option_parse_x),
 268         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 269                 N_("merge commit message (for a non-fast-forward merge)"),
 270                 option_parse_message),
 271         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 272                 N_("read message from file"), PARSE_OPT_NONEG,
 273                 NULL, 0, option_read_message },
 274         OPT__VERBOSITY(&verbosity),
 275         OPT_BOOL(0, "abort", &abort_current_merge,
 276                 N_("abort the current in-progress merge")),
 277         OPT_BOOL(0, "continue", &continue_current_merge,
 278                 N_("continue the current in-progress merge")),
 279         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 280                  N_("allow merging unrelated histories")),
 281         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 282         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 283           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 284         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 285         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 286         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 287         OPT_END()
 288 };
 289
 290 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 291 static void drop_save(void)
 292 {
 293         unlink(git_path_merge_head(the_repository));
 294         unlink(git_path_merge_msg(the_repository));
 295         unlink(git_path_merge_mode(the_repository));
 296 }
 297
 298 static int save_state(struct object_id *stash)
 299 {
 300         int len;
 301         struct child_process cp = CHILD_PROCESS_INIT;
 302         struct strbuf buffer = STRBUF_INIT;
 303         const char *argv[] = {"stash", "create", NULL};
 304         int rc = -1;
 305
 306         cp.argv = argv;
 307         cp.out = -1;
 308         cp.git_cmd = 1;
 309
 310         if (start_command(&cp))
 311                 die(_("could not run stash."));
 312         len = strbuf_read(&buffer, cp.out, 1024);
 313         close(cp.out);
 314
 315         if (finish_command(&cp) || len < 0)
 316                 die(_("stash failed"));
 317         else if (!len)          /* no changes */
 318                 goto out;
 319         strbuf_setlen(&buffer, buffer.len-1);
 320         if (get_oid(buffer.buf, stash))
 321                 die(_("not a valid object: %s"), buffer.buf);
 322         rc = 0;
 323 out:
 324         strbuf_release(&buffer);
 325         return rc;
 326 }
 327
 328 static void read_empty(const struct object_id *oid, int verbose)
 329 {
 330         int i = 0;
 331         const char *args[7];
 332
 333         args[i++] = "read-tree";
 334         if (verbose)
 335                 args[i++] = "-v";
 336         args[i++] = "-m";
 337         args[i++] = "-u";
 338         args[i++] = empty_tree_oid_hex();
 339         args[i++] = oid_to_hex(oid);
 340         args[i] = NULL;
 341
 342         if (run_command_v_opt(args, RUN_GIT_CMD))
 343                 die(_("read-tree failed"));
 344 }
 345
 346 static void reset_hard(const struct object_id *oid, int verbose)
 347 {
 348         int i = 0;
 349         const char *args[6];
 350
 351         args[i++] = "read-tree";
 352         if (verbose)
 353                 args[i++] = "-v";
 354         args[i++] = "--reset";
 355         args[i++] = "-u";
 356         args[i++] = oid_to_hex(oid);
 357         args[i] = NULL;
 358
 359         if (run_command_v_opt(args, RUN_GIT_CMD))
 360                 die(_("read-tree failed"));
 361 }
 362
 363 static void restore_state(const struct object_id *head,
 364                           const struct object_id *stash)
 365 {
 366         struct strbuf sb = STRBUF_INIT;
 367         const char *args[] = { "stash", "apply", NULL, NULL };
 368
 369         if (is_null_oid(stash))
 370                 return;
 371
 372         reset_hard(head, 1);
 373
 374         args[2] = oid_to_hex(stash);
 375
 376         /*
 377          * It is OK to ignore error here, for example when there was
 378          * nothing to restore.
 379          */
 380         run_command_v_opt(args, RUN_GIT_CMD);
 381
 382         strbuf_release(&sb);
 383         refresh_cache(REFRESH_QUIET);
 384 }
 385
 386 /* This is called when no merge was necessary. */
 387 static void finish_up_to_date(const char *msg)
 388 {
 389         if (verbosity >= 0)
 390                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 391         drop_save();
 392 }
 393
 394 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 395 {
 396         struct rev_info rev;
 397         struct strbuf out = STRBUF_INIT;
 398         struct commit_list *j;
 399         struct pretty_print_context ctx = {0};
 400
 401         printf(_("Squash commit -- not updating HEAD\n"));
 402
 403         repo_init_revisions(the_repository, &rev, NULL);
 404         rev.ignore_merges = 1;
 405         rev.commit_format = CMIT_FMT_MEDIUM;
 406
 407         commit->object.flags |= UNINTERESTING;
 408         add_pending_object(&rev, &commit->object, NULL);
 409
 410         for (j = remoteheads; j; j = j->next)
 411                 add_pending_object(&rev, &j->item->object, NULL);
 412
 413         setup_revisions(0, NULL, &rev, NULL);
 414         if (prepare_revision_walk(&rev))
 415                 die(_("revision walk setup failed"));
 416
 417         ctx.abbrev = rev.abbrev;
 418         ctx.date_mode = rev.date_mode;
 419         ctx.fmt = rev.commit_format;
 420
 421         strbuf_addstr(&out, "Squashed commit of the following:\n");
 422         while ((commit = get_revision(&rev)) != NULL) {
 423                 strbuf_addch(&out, '\n');
 424                 strbuf_addf(&out, "commit %s\n",
 425                         oid_to_hex(&commit->object.oid));
 426                 pretty_print_commit(&ctx, commit, &out);
 427         }
 428         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 429         strbuf_release(&out);
 430 }
 431
 432 static void finish(struct commit *head_commit,
 433                    struct commit_list *remoteheads,
 434                    const struct object_id *new_head, const char *msg)
 435 {
 436         struct strbuf reflog_message = STRBUF_INIT;
 437         const struct object_id *head = &head_commit->object.oid;
 438
 439         if (!msg)
 440                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 441         else {
 442                 if (verbosity >= 0)
 443                         printf("%s\n", msg);
 444                 strbuf_addf(&reflog_message, "%s: %s",
 445                         getenv("GIT_REFLOG_ACTION"), msg);
 446         }
 447         if (squash) {
 448                 squash_message(head_commit, remoteheads);
 449         } else {
 450                 if (verbosity >= 0 && !merge_msg.len)
 451                         printf(_("No merge message -- not updating HEAD\n"));
 452                 else {
 453                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 454                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 455                                    0, UPDATE_REFS_DIE_ON_ERR);
 456                         /*
 457                          * We ignore errors in 'gc --auto', since the
 458                          * user should see them.
 459                          */
 460                         close_all_packs(the_repository->objects);
 461                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 462                 }
 463         }
 464         if (new_head && show_diffstat) {
 465                 struct diff_options opts;
 466                 repo_diff_setup(the_repository, &opts);
 467                 opts.stat_width = -1; /* use full terminal width */
 468                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 469                 opts.output_format |=
 470                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 471                 opts.detect_rename = DIFF_DETECT_RENAME;
 472                 diff_setup_done(&opts);
 473                 diff_tree_oid(head, new_head, "", &opts);
 474                 diffcore_std(&opts);
 475                 diff_flush(&opts);
 476         }
 477
 478         /* Run a post-merge hook */
 479         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 480
 481         strbuf_release(&reflog_message);
 482 }
 483
 484 /* Get the name for the merge commit's message. */
 485 static void merge_name(const char *remote, struct strbuf *msg)
 486 {
 487         struct commit *remote_head;
 488         struct object_id branch_head;
 489         struct strbuf buf = STRBUF_INIT;
 490         struct strbuf bname = STRBUF_INIT;
 491         struct merge_remote_desc *desc;
 492         const char *ptr;
 493         char *found_ref;
 494         int len, early;
 495
 496         strbuf_branchname(&bname, remote, 0);
 497         remote = bname.buf;
 498
 499         oidclr(&branch_head);
 500         remote_head = get_merge_parent(remote);
 501         if (!remote_head)
 502                 die(_("'%s' does not point to a commit"), remote);
 503
 504         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 505                 if (starts_with(found_ref, "refs/heads/")) {
 506                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 507                                     oid_to_hex(&branch_head), remote);
 508                         goto cleanup;
 509                 }
 510                 if (starts_with(found_ref, "refs/tags/")) {
 511                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 512                                     oid_to_hex(&branch_head), remote);
 513                         goto cleanup;
 514                 }
 515                 if (starts_with(found_ref, "refs/remotes/")) {
 516                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 517                                     oid_to_hex(&branch_head), remote);
 518                         goto cleanup;
 519                 }
 520         }
 521
 522         /* See if remote matches <name>^^^.. or <name>~<number> */
 523         for (len = 0, ptr = remote + strlen(remote);
 524              remote < ptr && ptr[-1] == '^';
 525              ptr--)
 526                 len++;
 527         if (len)
 528                 early = 1;
 529         else {
 530                 early = 0;
 531                 ptr = strrchr(remote, '~');
 532                 if (ptr) {
 533                         int seen_nonzero = 0;
 534
 535                         len++; /* count ~ */
 536                         while (*++ptr && isdigit(*ptr)) {
 537                                 seen_nonzero |= (*ptr != '0');
 538                                 len++;
 539                         }
 540                         if (*ptr)
 541                                 len = 0; /* not ...~<number> */
 542                         else if (seen_nonzero)
 543                                 early = 1;
 544                         else if (len == 1)
 545                                 early = 1; /* "name~" is "name~1"! */
 546                 }
 547         }
 548         if (len) {
 549                 struct strbuf truname = STRBUF_INIT;
 550                 strbuf_addf(&truname, "refs/heads/%s", remote);
 551                 strbuf_setlen(&truname, truname.len - len);
 552                 if (ref_exists(truname.buf)) {
 553                         strbuf_addf(msg,
 554                                     "%s\t\tbranch '%s'%s of .\n",
 555                                     oid_to_hex(&remote_head->object.oid),
 556                                     truname.buf + 11,
 557                                     (early ? " (early part)" : ""));
 558                         strbuf_release(&truname);
 559                         goto cleanup;
 560                 }
 561                 strbuf_release(&truname);
 562         }
 563
 564         desc = merge_remote_util(remote_head);
 565         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 566                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 567                             oid_to_hex(&desc->obj->oid),
 568                             type_name(desc->obj->type),
 569                             remote);
 570                 goto cleanup;
 571         }
 572
 573         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 574                 oid_to_hex(&remote_head->object.oid), remote);
 575 cleanup:
 576         strbuf_release(&buf);
 577         strbuf_release(&bname);
 578 }
 579
 580 static void parse_branch_merge_options(char *bmo)
 581 {
 582         const char **argv;
 583         int argc;
 584
 585         if (!bmo)
 586                 return;
 587         argc = split_cmdline(bmo, &argv);
 588         if (argc < 0)
 589                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 590                     _(split_cmdline_strerror(argc)));
 591         REALLOC_ARRAY(argv, argc + 2);
 592         MOVE_ARRAY(argv + 1, argv, argc + 1);
 593         argc++;
 594         argv[0] = "branch.*.mergeoptions";
 595         parse_options(argc, argv, NULL, builtin_merge_options,
 596                       builtin_merge_usage, 0);
 597         free(argv);
 598 }
 599
 600 static int git_merge_config(const char *k, const char *v, void *cb)
 601 {
 602         int status;
 603
 604         if (branch && starts_with(k, "branch.") &&
 605                 starts_with(k + 7, branch) &&
 606                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 607                 free(branch_mergeoptions);
 608                 branch_mergeoptions = xstrdup(v);
 609                 return 0;
 610         }
 611
 612         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 613                 show_diffstat = git_config_bool(k, v);
 614         else if (!strcmp(k, "merge.verifysignatures"))
 615                 verify_signatures = git_config_bool(k, v);
 616         else if (!strcmp(k, "pull.twohead"))
 617                 return git_config_string(&pull_twohead, k, v);
 618         else if (!strcmp(k, "pull.octopus"))
 619                 return git_config_string(&pull_octopus, k, v);
 620         else if (!strcmp(k, "commit.cleanup"))
 621                 return git_config_string(&cleanup_arg, k, v);
 622         else if (!strcmp(k, "merge.renormalize"))
 623                 option_renormalize = git_config_bool(k, v);
 624         else if (!strcmp(k, "merge.ff")) {
 625                 int boolval = git_parse_maybe_bool(v);
 626                 if (0 <= boolval) {
 627                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 628                 } else if (v && !strcmp(v, "only")) {
 629                         fast_forward = FF_ONLY;
 630                 } /* do not barf on values from future versions of git */
 631                 return 0;
 632         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 633                 default_to_upstream = git_config_bool(k, v);
 634                 return 0;
 635         } else if (!strcmp(k, "commit.gpgsign")) {
 636                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 637                 return 0;
 638         }
 639
 640         status = fmt_merge_msg_config(k, v, cb);
 641         if (status)
 642                 return status;
 643         status = git_gpg_config(k, v, NULL);
 644         if (status)
 645                 return status;
 646         return git_diff_ui_config(k, v, cb);
 647 }
 648
 649 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 650                              struct object_id *one)
 651 {
 652         int i, nr_trees = 0;
 653         struct tree *trees[MAX_UNPACK_TREES];
 654         struct tree_desc t[MAX_UNPACK_TREES];
 655         struct unpack_trees_options opts;
 656
 657         memset(&opts, 0, sizeof(opts));
 658         opts.head_idx = 2;
 659         opts.src_index = &the_index;
 660         opts.dst_index = &the_index;
 661         opts.update = 1;
 662         opts.verbose_update = 1;
 663         opts.trivial_merges_only = 1;
 664         opts.merge = 1;
 665         trees[nr_trees] = parse_tree_indirect(common);
 666         if (!trees[nr_trees++])
 667                 return -1;
 668         trees[nr_trees] = parse_tree_indirect(head);
 669         if (!trees[nr_trees++])
 670                 return -1;
 671         trees[nr_trees] = parse_tree_indirect(one);
 672         if (!trees[nr_trees++])
 673                 return -1;
 674         opts.fn = threeway_merge;
 675         cache_tree_free(&active_cache_tree);
 676         for (i = 0; i < nr_trees; i++) {
 677                 parse_tree(trees[i]);
 678                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 679         }
 680         if (unpack_trees(nr_trees, t, &opts))
 681                 return -1;
 682         return 0;
 683 }
 684
 685 static void write_tree_trivial(struct object_id *oid)
 686 {
 687         if (write_cache_as_tree(oid, 0, NULL))
 688                 die(_("git write-tree failed to write a tree"));
 689 }
 690
 691 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 692                               struct commit_list *remoteheads,
 693                               struct commit *head)
 694 {
 695         struct lock_file lock = LOCK_INIT;
 696         const char *head_arg = "HEAD";
 697
 698         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 699         refresh_cache(REFRESH_QUIET);
 700         if (write_locked_index(&the_index, &lock,
 701                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 702                 return error(_("Unable to write index."));
 703
 704         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 705                 int clean, x;
 706                 struct commit *result;
 707                 struct commit_list *reversed = NULL;
 708                 struct merge_options o;
 709                 struct commit_list *j;
 710
 711                 if (remoteheads->next) {
 712                         error(_("Not handling anything other than two heads merge."));
 713                         return 2;
 714                 }
 715
 716                 init_merge_options(&o, the_repository);
 717                 if (!strcmp(strategy, "subtree"))
 718                         o.subtree_shift = "";
 719
 720                 o.renormalize = option_renormalize;
 721                 o.show_rename_progress =
 722                         show_progress == -1 ? isatty(2) : show_progress;
 723
 724                 for (x = 0; x < xopts_nr; x++)
 725                         if (parse_merge_opt(&o, xopts[x]))
 726                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 727
 728                 o.branch1 = head_arg;
 729                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 730
 731                 for (j = common; j; j = j->next)
 732                         commit_list_insert(j->item, &reversed);
 733
 734                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 735                 clean = merge_recursive(&o, head,
 736                                 remoteheads->item, reversed, &result);
 737                 if (clean < 0)
 738                         exit(128);
 739                 if (write_locked_index(&the_index, &lock,
 740                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 741                         die(_("unable to write %s"), get_index_file());
 742                 return clean ? 0 : 1;
 743         } else {
 744                 return try_merge_command(the_repository,
 745                                          strategy, xopts_nr, xopts,
 746                                          common, head_arg, remoteheads);
 747         }
 748 }
 749
 750 static void count_diff_files(struct diff_queue_struct *q,
 751                              struct diff_options *opt, void *data)
 752 {
 753         int *count = data;
 754
 755         (*count) += q->nr;
 756 }
 757
 758 static int count_unmerged_entries(void)
 759 {
 760         int i, ret = 0;
 761
 762         for (i = 0; i < active_nr; i++)
 763                 if (ce_stage(active_cache[i]))
 764                         ret++;
 765
 766         return ret;
 767 }
 768
 769 static void add_strategies(const char *string, unsigned attr)
 770 {
 771         int i;
 772
 773         if (string) {
 774                 struct string_list list = STRING_LIST_INIT_DUP;
 775                 struct string_list_item *item;
 776                 string_list_split(&list, string, ' ', -1);
 777                 for_each_string_list_item(item, &list)
 778                         append_strategy(get_strategy(item->string));
 779                 string_list_clear(&list, 0);
 780                 return;
 781         }
 782         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 783                 if (all_strategy[i].attr & attr)
 784                         append_strategy(&all_strategy[i]);
 785
 786 }
 787
 788 static void read_merge_msg(struct strbuf *msg)
 789 {
 790         const char *filename = git_path_merge_msg(the_repository);
 791         strbuf_reset(msg);
 792         if (strbuf_read_file(msg, filename, 0) < 0)
 793                 die_errno(_("Could not read from '%s'"), filename);
 794 }
 795
 796 static void write_merge_state(struct commit_list *);
 797 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 798 {
 799         if (err_msg)
 800                 error("%s", err_msg);
 801         fprintf(stderr,
 802                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 803         write_merge_state(remoteheads);
 804         exit(1);
 805 }
 806
 807 static const char merge_editor_comment[] =
 808 N_("Please enter a commit message to explain why this merge is necessary,\n"
 809    "especially if it merges an updated upstream into a topic branch.\n"
 810    "\n");
 811
 812 static const char scissors_editor_comment[] =
 813 N_("An empty message aborts the commit.\n");
 814
 815 static const char no_scissors_editor_comment[] =
 816 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 817    "the commit.\n");
 818
 819 static void write_merge_heads(struct commit_list *);
 820 static void prepare_to_commit(struct commit_list *remoteheads)
 821 {
 822         struct strbuf msg = STRBUF_INIT;
 823         strbuf_addbuf(&msg, &merge_msg);
 824         if (squash)
 825                 BUG("the control must not reach here under --squash");
 826         if (0 < option_edit) {
 827                 strbuf_addch(&msg, '\n');
 828                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 829                         wt_status_append_cut_line(&msg);
 830                         strbuf_commented_addf(&msg, "\n");
 831                 }
 832                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 833                 strbuf_commented_addf(&msg, _(cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS ?
 834                         scissors_editor_comment :
 835                         no_scissors_editor_comment), comment_line_char);
 836         }
 837         if (signoff)
 838                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 839         write_merge_heads(remoteheads);
 840         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 841         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 842                             git_path_merge_msg(the_repository), "merge", NULL))
 843                 abort_commit(remoteheads, NULL);
 844         if (0 < option_edit) {
 845                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 846                         abort_commit(remoteheads, NULL);
 847         }
 848
 849         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 850                                           "commit-msg",
 851                                           git_path_merge_msg(the_repository), NULL))
 852                 abort_commit(remoteheads, NULL);
 853
 854         read_merge_msg(&msg);
 855         cleanup_message(&msg, cleanup_mode, 0);
 856         if (!msg.len)
 857                 abort_commit(remoteheads, _("Empty commit message."));
 858         strbuf_release(&merge_msg);
 859         strbuf_addbuf(&merge_msg, &msg);
 860         strbuf_release(&msg);
 861 }
 862
 863 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 864 {
 865         struct object_id result_tree, result_commit;
 866         struct commit_list *parents, **pptr = &parents;
 867         struct lock_file lock = LOCK_INIT;
 868
 869         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 870         refresh_cache(REFRESH_QUIET);
 871         if (write_locked_index(&the_index, &lock,
 872                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 873                 return error(_("Unable to write index."));
 874
 875         write_tree_trivial(&result_tree);
 876         printf(_("Wonderful.\n"));
 877         pptr = commit_list_append(head, pptr);
 878         pptr = commit_list_append(remoteheads->item, pptr);
 879         prepare_to_commit(remoteheads);
 880         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 881                         &result_commit, NULL, sign_commit))
 882                 die(_("failed to write commit object"));
 883         finish(head, remoteheads, &result_commit, "In-index merge");
 884         drop_save();
 885         return 0;
 886 }
 887
 888 static int finish_automerge(struct commit *head,
 889                             int head_subsumed,
 890                             struct commit_list *common,
 891                             struct commit_list *remoteheads,
 892                             struct object_id *result_tree,
 893                             const char *wt_strategy)
 894 {
 895         struct commit_list *parents = NULL;
 896         struct strbuf buf = STRBUF_INIT;
 897         struct object_id result_commit;
 898
 899         free_commit_list(common);
 900         parents = remoteheads;
 901         if (!head_subsumed || fast_forward == FF_NO)
 902                 commit_list_insert(head, &parents);
 903         prepare_to_commit(remoteheads);
 904         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 905                         &result_commit, NULL, sign_commit))
 906                 die(_("failed to write commit object"));
 907         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 908         finish(head, remoteheads, &result_commit, buf.buf);
 909         strbuf_release(&buf);
 910         drop_save();
 911         return 0;
 912 }
 913
 914 static int suggest_conflicts(void)
 915 {
 916         const char *filename;
 917         FILE *fp;
 918         struct strbuf msgbuf = STRBUF_INIT;
 919
 920         filename = git_path_merge_msg(the_repository);
 921         fp = xfopen(filename, "a");
 922
 923         append_conflicts_hint(&the_index, &msgbuf);
 924         fputs(msgbuf.buf, fp);
 925         strbuf_release(&msgbuf);
 926         fclose(fp);
 927         repo_rerere(the_repository, allow_rerere_auto);
 928         printf(_("Automatic merge failed; "
 929                         "fix conflicts and then commit the result.\n"));
 930         return 1;
 931 }
 932
 933 static int evaluate_result(void)
 934 {
 935         int cnt = 0;
 936         struct rev_info rev;
 937
 938         /* Check how many files differ. */
 939         repo_init_revisions(the_repository, &rev, "");
 940         setup_revisions(0, NULL, &rev, NULL);
 941         rev.diffopt.output_format |=
 942                 DIFF_FORMAT_CALLBACK;
 943         rev.diffopt.format_callback = count_diff_files;
 944         rev.diffopt.format_callback_data = &cnt;
 945         run_diff_files(&rev, 0);
 946
 947         /*
 948          * Check how many unmerged entries are
 949          * there.
 950          */
 951         cnt += count_unmerged_entries();
 952
 953         return cnt;
 954 }
 955
 956 /*
 957  * Pretend as if the user told us to merge with the remote-tracking
 958  * branch we have for the upstream of the current branch
 959  */
 960 static int setup_with_upstream(const char ***argv)
 961 {
 962         struct branch *branch = branch_get(NULL);
 963         int i;
 964         const char **args;
 965
 966         if (!branch)
 967                 die(_("No current branch."));
 968         if (!branch->remote_name)
 969                 die(_("No remote for the current branch."));
 970         if (!branch->merge_nr)
 971                 die(_("No default upstream defined for the current branch."));
 972
 973         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 974         for (i = 0; i < branch->merge_nr; i++) {
 975                 if (!branch->merge[i]->dst)
 976                         die(_("No remote-tracking branch for %s from %s"),
 977                             branch->merge[i]->src, branch->remote_name);
 978                 args[i] = branch->merge[i]->dst;
 979         }
 980         args[i] = NULL;
 981         *argv = args;
 982         return i;
 983 }
 984
 985 static void write_merge_heads(struct commit_list *remoteheads)
 986 {
 987         struct commit_list *j;
 988         struct strbuf buf = STRBUF_INIT;
 989
 990         for (j = remoteheads; j; j = j->next) {
 991                 struct object_id *oid;
 992                 struct commit *c = j->item;
 993                 struct merge_remote_desc *desc;
 994
 995                 desc = merge_remote_util(c);
 996                 if (desc && desc->obj) {
 997                         oid = &desc->obj->oid;
 998                 } else {
 999                         oid = &c->object.oid;
1000                 }
1001                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1002         }
1003         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1004
1005         strbuf_reset(&buf);
1006         if (fast_forward == FF_NO)
1007                 strbuf_addstr(&buf, "no-ff");
1008         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1009         strbuf_release(&buf);
1010 }
1011
1012 static void write_merge_state(struct commit_list *remoteheads)
1013 {
1014         write_merge_heads(remoteheads);
1015         strbuf_addch(&merge_msg, '\n');
1016         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1017                        merge_msg.len);
1018 }
1019
1020 static int default_edit_option(void)
1021 {
1022         static const char name[] = "GIT_MERGE_AUTOEDIT";
1023         const char *e = getenv(name);
1024         struct stat st_stdin, st_stdout;
1025
1026         if (have_message)
1027                 /* an explicit -m msg without --[no-]edit */
1028                 return 0;
1029
1030         if (e) {
1031                 int v = git_parse_maybe_bool(e);
1032                 if (v < 0)
1033                         die(_("Bad value '%s' in environment '%s'"), e, name);
1034                 return v;
1035         }
1036
1037         /* Use editor if stdin and stdout are the same and is a tty */
1038         return (!fstat(0, &st_stdin) &&
1039                 !fstat(1, &st_stdout) &&
1040                 isatty(0) && isatty(1) &&
1041                 st_stdin.st_dev == st_stdout.st_dev &&
1042                 st_stdin.st_ino == st_stdout.st_ino &&
1043                 st_stdin.st_mode == st_stdout.st_mode);
1044 }
1045
1046 static struct commit_list *reduce_parents(struct commit *head_commit,
1047                                           int *head_subsumed,
1048                                           struct commit_list *remoteheads)
1049 {
1050         struct commit_list *parents, **remotes;
1051
1052         /*
1053          * Is the current HEAD reachable from another commit being
1054          * merged?  If so we do not want to record it as a parent of
1055          * the resulting merge, unless --no-ff is given.  We will flip
1056          * this variable to 0 when we find HEAD among the independent
1057          * tips being merged.
1058          */
1059         *head_subsumed = 1;
1060
1061         /* Find what parents to record by checking independent ones. */
1062         parents = reduce_heads(remoteheads);
1063         free_commit_list(remoteheads);
1064
1065         remoteheads = NULL;
1066         remotes = &remoteheads;
1067         while (parents) {
1068                 struct commit *commit = pop_commit(&parents);
1069                 if (commit == head_commit)
1070                         *head_subsumed = 0;
1071                 else
1072                         remotes = &commit_list_insert(commit, remotes)->next;
1073         }
1074         return remoteheads;
1075 }
1076
1077 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1078 {
1079         struct fmt_merge_msg_opts opts;
1080
1081         memset(&opts, 0, sizeof(opts));
1082         opts.add_title = !have_message;
1083         opts.shortlog_len = shortlog_len;
1084         opts.credit_people = (0 < option_edit);
1085
1086         fmt_merge_msg(merge_names, merge_msg, &opts);
1087         if (merge_msg->len)
1088                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1089 }
1090
1091 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1092 {
1093         const char *filename;
1094         int fd, pos, npos;
1095         struct strbuf fetch_head_file = STRBUF_INIT;
1096         const unsigned hexsz = the_hash_algo->hexsz;
1097
1098         if (!merge_names)
1099                 merge_names = &fetch_head_file;
1100
1101         filename = git_path_fetch_head(the_repository);
1102         fd = open(filename, O_RDONLY);
1103         if (fd < 0)
1104                 die_errno(_("could not open '%s' for reading"), filename);
1105
1106         if (strbuf_read(merge_names, fd, 0) < 0)
1107                 die_errno(_("could not read '%s'"), filename);
1108         if (close(fd) < 0)
1109                 die_errno(_("could not close '%s'"), filename);
1110
1111         for (pos = 0; pos < merge_names->len; pos = npos) {
1112                 struct object_id oid;
1113                 char *ptr;
1114                 struct commit *commit;
1115
1116                 ptr = strchr(merge_names->buf + pos, '\n');
1117                 if (ptr)
1118                         npos = ptr - merge_names->buf + 1;
1119                 else
1120                         npos = merge_names->len;
1121
1122                 if (npos - pos < hexsz + 2 ||
1123                     get_oid_hex(merge_names->buf + pos, &oid))
1124                         commit = NULL; /* bad */
1125                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1126                         continue; /* not-for-merge */
1127                 else {
1128                         char saved = merge_names->buf[pos + hexsz];
1129                         merge_names->buf[pos + hexsz] = '\0';
1130                         commit = get_merge_parent(merge_names->buf + pos);
1131                         merge_names->buf[pos + hexsz] = saved;
1132                 }
1133                 if (!commit) {
1134                         if (ptr)
1135                                 *ptr = '\0';
1136                         die(_("not something we can merge in %s: %s"),
1137                             filename, merge_names->buf + pos);
1138                 }
1139                 remotes = &commit_list_insert(commit, remotes)->next;
1140         }
1141
1142         if (merge_names == &fetch_head_file)
1143                 strbuf_release(&fetch_head_file);
1144 }
1145
1146 static struct commit_list *collect_parents(struct commit *head_commit,
1147                                            int *head_subsumed,
1148                                            int argc, const char **argv,
1149                                            struct strbuf *merge_msg)
1150 {
1151         int i;
1152         struct commit_list *remoteheads = NULL;
1153         struct commit_list **remotes = &remoteheads;
1154         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1155
1156         if (merge_msg && (!have_message || shortlog_len))
1157                 autogen = &merge_names;
1158
1159         if (head_commit)
1160                 remotes = &commit_list_insert(head_commit, remotes)->next;
1161
1162         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1163                 handle_fetch_head(remotes, autogen);
1164                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1165         } else {
1166                 for (i = 0; i < argc; i++) {
1167                         struct commit *commit = get_merge_parent(argv[i]);
1168                         if (!commit)
1169                                 help_unknown_ref(argv[i], "merge",
1170                                                  _("not something we can merge"));
1171                         remotes = &commit_list_insert(commit, remotes)->next;
1172                 }
1173                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1174                 if (autogen) {
1175                         struct commit_list *p;
1176                         for (p = remoteheads; p; p = p->next)
1177                                 merge_name(merge_remote_util(p->item)->name, autogen);
1178                 }
1179         }
1180
1181         if (autogen) {
1182                 prepare_merge_message(autogen, merge_msg);
1183                 strbuf_release(autogen);
1184         }
1185
1186         return remoteheads;
1187 }
1188
1189 static int merging_a_throwaway_tag(struct commit *commit)
1190 {
1191         char *tag_ref;
1192         struct object_id oid;
1193         int is_throwaway_tag = 0;
1194
1195         /* Are we merging a tag? */
1196         if (!merge_remote_util(commit) ||
1197             !merge_remote_util(commit)->obj ||
1198             merge_remote_util(commit)->obj->type != OBJ_TAG)
1199                 return is_throwaway_tag;
1200
1201         /*
1202          * Now we know we are merging a tag object.  Are we downstream
1203          * and following the tags from upstream?  If so, we must have
1204          * the tag object pointed at by "refs/tags/$T" where $T is the
1205          * tagname recorded in the tag object.  We want to allow such
1206          * a "just to catch up" merge to fast-forward.
1207          *
1208          * Otherwise, we are playing an integrator's role, making a
1209          * merge with a throw-away tag from a contributor with
1210          * something like "git pull $contributor $signed_tag".
1211          * We want to forbid such a merge from fast-forwarding
1212          * by default; otherwise we would not keep the signature
1213          * anywhere.
1214          */
1215         tag_ref = xstrfmt("refs/tags/%s",
1216                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1217         if (!read_ref(tag_ref, &oid) &&
1218             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1219                 is_throwaway_tag = 0;
1220         else
1221                 is_throwaway_tag = 1;
1222         free(tag_ref);
1223         return is_throwaway_tag;
1224 }
1225
1226 int cmd_merge(int argc, const char **argv, const char *prefix)
1227 {
1228         struct object_id result_tree, stash, head_oid;
1229         struct commit *head_commit;
1230         struct strbuf buf = STRBUF_INIT;
1231         int i, ret = 0, head_subsumed;
1232         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1233         struct commit_list *common = NULL;
1234         const char *best_strategy = NULL, *wt_strategy = NULL;
1235         struct commit_list *remoteheads, *p;
1236         void *branch_to_free;
1237         int orig_argc = argc;
1238
1239         if (argc == 2 && !strcmp(argv[1], "-h"))
1240                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1241
1242         /*
1243          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1244          * current branch.
1245          */
1246         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1247         if (branch)
1248                 skip_prefix(branch, "refs/heads/", &branch);
1249
1250         init_diff_ui_defaults();
1251         git_config(git_merge_config, NULL);
1252
1253         if (!branch || is_null_oid(&head_oid))
1254                 head_commit = NULL;
1255         else
1256                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1257
1258         if (branch_mergeoptions)
1259                 parse_branch_merge_options(branch_mergeoptions);
1260         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1261                         builtin_merge_usage, 0);
1262         if (shortlog_len < 0)
1263                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1264
1265         if (verbosity < 0 && show_progress == -1)
1266                 show_progress = 0;
1267
1268         if (abort_current_merge) {
1269                 int nargc = 2;
1270                 const char *nargv[] = {"reset", "--merge", NULL};
1271
1272                 if (orig_argc != 2)
1273                         usage_msg_opt(_("--abort expects no arguments"),
1274                               builtin_merge_usage, builtin_merge_options);
1275
1276                 if (!file_exists(git_path_merge_head(the_repository)))
1277                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1278
1279                 /* Invoke 'git reset --merge' */
1280                 ret = cmd_reset(nargc, nargv, prefix);
1281                 goto done;
1282         }
1283
1284         if (continue_current_merge) {
1285                 int nargc = 1;
1286                 const char *nargv[] = {"commit", NULL};
1287
1288                 if (orig_argc != 2)
1289                         usage_msg_opt(_("--continue expects no arguments"),
1290                               builtin_merge_usage, builtin_merge_options);
1291
1292                 if (!file_exists(git_path_merge_head(the_repository)))
1293                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1294
1295                 /* Invoke 'git commit' */
1296                 ret = cmd_commit(nargc, nargv, prefix);
1297                 goto done;
1298         }
1299
1300         if (read_cache_unmerged())
1301                 die_resolve_conflict("merge");
1302
1303         if (file_exists(git_path_merge_head(the_repository))) {
1304                 /*
1305                  * There is no unmerged entry, don't advise 'git
1306                  * add/rm <file>', just 'git commit'.
1307                  */
1308                 if (advice_resolve_conflict)
1309                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1310                                   "Please, commit your changes before you merge."));
1311                 else
1312                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1313         }
1314         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1315                 if (advice_resolve_conflict)
1316                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1317                             "Please, commit your changes before you merge."));
1318                 else
1319                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1320         }
1321         resolve_undo_clear();
1322
1323         if (option_edit < 0)
1324                 option_edit = default_edit_option();
1325
1326         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1327
1328         if (verbosity < 0)
1329                 show_diffstat = 0;
1330
1331         if (squash) {
1332                 if (fast_forward == FF_NO)
1333                         die(_("You cannot combine --squash with --no-ff."));
1334                 option_commit = 0;
1335         }
1336
1337         if (!argc) {
1338                 if (default_to_upstream)
1339                         argc = setup_with_upstream(&argv);
1340                 else
1341                         die(_("No commit specified and merge.defaultToUpstream not set."));
1342         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1343                 argv[0] = "@{-1}";
1344         }
1345
1346         if (!argc)
1347                 usage_with_options(builtin_merge_usage,
1348                         builtin_merge_options);
1349
1350         if (!head_commit) {
1351                 /*
1352                  * If the merged head is a valid one there is no reason
1353                  * to forbid "git merge" into a branch yet to be born.
1354                  * We do the same for "git pull".
1355                  */
1356                 struct object_id *remote_head_oid;
1357                 if (squash)
1358                         die(_("Squash commit into empty head not supported yet"));
1359                 if (fast_forward == FF_NO)
1360                         die(_("Non-fast-forward commit does not make sense into "
1361                             "an empty head"));
1362                 remoteheads = collect_parents(head_commit, &head_subsumed,
1363                                               argc, argv, NULL);
1364                 if (!remoteheads)
1365                         die(_("%s - not something we can merge"), argv[0]);
1366                 if (remoteheads->next)
1367                         die(_("Can merge only exactly one commit into empty head"));
1368
1369                 if (verify_signatures)
1370                         verify_merge_signature(remoteheads->item, verbosity);
1371
1372                 remote_head_oid = &remoteheads->item->object.oid;
1373                 read_empty(remote_head_oid, 0);
1374                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1375                            UPDATE_REFS_DIE_ON_ERR);
1376                 goto done;
1377         }
1378
1379         /*
1380          * All the rest are the commits being merged; prepare
1381          * the standard merge summary message to be appended
1382          * to the given message.
1383          */
1384         remoteheads = collect_parents(head_commit, &head_subsumed,
1385                                       argc, argv, &merge_msg);
1386
1387         if (!head_commit || !argc)
1388                 usage_with_options(builtin_merge_usage,
1389                         builtin_merge_options);
1390
1391         if (verify_signatures) {
1392                 for (p = remoteheads; p; p = p->next) {
1393                         verify_merge_signature(p->item, verbosity);
1394                 }
1395         }
1396
1397         strbuf_addstr(&buf, "merge");
1398         for (p = remoteheads; p; p = p->next)
1399                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1400         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1401         strbuf_reset(&buf);
1402
1403         for (p = remoteheads; p; p = p->next) {
1404                 struct commit *commit = p->item;
1405                 strbuf_addf(&buf, "GITHEAD_%s",
1406                             oid_to_hex(&commit->object.oid));
1407                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1408                 strbuf_reset(&buf);
1409                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1410                         fast_forward = FF_NO;
1411         }
1412
1413         if (!use_strategies) {
1414                 if (!remoteheads)
1415                         ; /* already up-to-date */
1416                 else if (!remoteheads->next)
1417                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1418                 else
1419                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1420         }
1421
1422         for (i = 0; i < use_strategies_nr; i++) {
1423                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1424                         fast_forward = FF_NO;
1425                 if (use_strategies[i]->attr & NO_TRIVIAL)
1426                         allow_trivial = 0;
1427         }
1428
1429         if (!remoteheads)
1430                 ; /* already up-to-date */
1431         else if (!remoteheads->next)
1432                 common = get_merge_bases(head_commit, remoteheads->item);
1433         else {
1434                 struct commit_list *list = remoteheads;
1435                 commit_list_insert(head_commit, &list);
1436                 common = get_octopus_merge_bases(list);
1437                 free(list);
1438         }
1439
1440         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1441                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1442
1443         if (remoteheads && !common) {
1444                 /* No common ancestors found. */
1445                 if (!allow_unrelated_histories)
1446                         die(_("refusing to merge unrelated histories"));
1447                 /* otherwise, we need a real merge. */
1448         } else if (!remoteheads ||
1449                  (!remoteheads->next && !common->next &&
1450                   common->item == remoteheads->item)) {
1451                 /*
1452                  * If head can reach all the merge then we are up to date.
1453                  * but first the most common case of merging one remote.
1454                  */
1455                 finish_up_to_date(_("Already up to date."));
1456                 goto done;
1457         } else if (fast_forward != FF_NO && !remoteheads->next &&
1458                         !common->next &&
1459                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1460                 /* Again the most common case of merging one remote. */
1461                 struct strbuf msg = STRBUF_INIT;
1462                 struct commit *commit;
1463
1464                 if (verbosity >= 0) {
1465                         printf(_("Updating %s..%s\n"),
1466                                find_unique_abbrev(&head_commit->object.oid,
1467                                                   DEFAULT_ABBREV),
1468                                find_unique_abbrev(&remoteheads->item->object.oid,
1469                                                   DEFAULT_ABBREV));
1470                 }
1471                 strbuf_addstr(&msg, "Fast-forward");
1472                 if (have_message)
1473                         strbuf_addstr(&msg,
1474                                 " (no commit created; -m option ignored)");
1475                 commit = remoteheads->item;
1476                 if (!commit) {
1477                         ret = 1;
1478                         goto done;
1479                 }
1480
1481                 if (checkout_fast_forward(the_repository,
1482                                           &head_commit->object.oid,
1483                                           &commit->object.oid,
1484                                           overwrite_ignore)) {
1485                         ret = 1;
1486                         goto done;
1487                 }
1488
1489                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1490                 drop_save();
1491                 goto done;
1492         } else if (!remoteheads->next && common->next)
1493                 ;
1494                 /*
1495                  * We are not doing octopus and not fast-forward.  Need
1496                  * a real merge.
1497                  */
1498         else if (!remoteheads->next && !common->next && option_commit) {
1499                 /*
1500                  * We are not doing octopus, not fast-forward, and have
1501                  * only one common.
1502                  */
1503                 refresh_cache(REFRESH_QUIET);
1504                 if (allow_trivial && fast_forward != FF_ONLY) {
1505                         /* See if it is really trivial. */
1506                         git_committer_info(IDENT_STRICT);
1507                         printf(_("Trying really trivial in-index merge...\n"));
1508                         if (!read_tree_trivial(&common->item->object.oid,
1509                                                &head_commit->object.oid,
1510                                                &remoteheads->item->object.oid)) {
1511                                 ret = merge_trivial(head_commit, remoteheads);
1512                                 goto done;
1513                         }
1514                         printf(_("Nope.\n"));
1515                 }
1516         } else {
1517                 /*
1518                  * An octopus.  If we can reach all the remote we are up
1519                  * to date.
1520                  */
1521                 int up_to_date = 1;
1522                 struct commit_list *j;
1523
1524                 for (j = remoteheads; j; j = j->next) {
1525                         struct commit_list *common_one;
1526
1527                         /*
1528                          * Here we *have* to calculate the individual
1529                          * merge_bases again, otherwise "git merge HEAD^
1530                          * HEAD^^" would be missed.
1531                          */
1532                         common_one = get_merge_bases(head_commit, j->item);
1533                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1534                                 up_to_date = 0;
1535                                 break;
1536                         }
1537                 }
1538                 if (up_to_date) {
1539                         finish_up_to_date(_("Already up to date. Yeeah!"));
1540                         goto done;
1541                 }
1542         }
1543
1544         if (fast_forward == FF_ONLY)
1545                 die(_("Not possible to fast-forward, aborting."));
1546
1547         /* We are going to make a new commit. */
1548         git_committer_info(IDENT_STRICT);
1549
1550         /*
1551          * At this point, we need a real merge.  No matter what strategy
1552          * we use, it would operate on the index, possibly affecting the
1553          * working tree, and when resolved cleanly, have the desired
1554          * tree in the index -- this means that the index must be in
1555          * sync with the head commit.  The strategies are responsible
1556          * to ensure this.
1557          */
1558         if (use_strategies_nr == 1 ||
1559             /*
1560              * Stash away the local changes so that we can try more than one.
1561              */
1562             save_state(&stash))
1563                 oidclr(&stash);
1564
1565         for (i = 0; i < use_strategies_nr; i++) {
1566                 int ret;
1567                 if (i) {
1568                         printf(_("Rewinding the tree to pristine...\n"));
1569                         restore_state(&head_commit->object.oid, &stash);
1570                 }
1571                 if (use_strategies_nr != 1)
1572                         printf(_("Trying merge strategy %s...\n"),
1573                                 use_strategies[i]->name);
1574                 /*
1575                  * Remember which strategy left the state in the working
1576                  * tree.
1577                  */
1578                 wt_strategy = use_strategies[i]->name;
1579
1580                 ret = try_merge_strategy(use_strategies[i]->name,
1581                                          common, remoteheads,
1582                                          head_commit);
1583                 if (!option_commit && !ret) {
1584                         merge_was_ok = 1;
1585                         /*
1586                          * This is necessary here just to avoid writing
1587                          * the tree, but later we will *not* exit with
1588                          * status code 1 because merge_was_ok is set.
1589                          */
1590                         ret = 1;
1591                 }
1592
1593                 if (ret) {
1594                         /*
1595                          * The backend exits with 1 when conflicts are
1596                          * left to be resolved, with 2 when it does not
1597                          * handle the given merge at all.
1598                          */
1599                         if (ret == 1) {
1600                                 int cnt = evaluate_result();
1601
1602                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1603                                         best_strategy = use_strategies[i]->name;
1604                                         best_cnt = cnt;
1605                                 }
1606                         }
1607                         if (merge_was_ok)
1608                                 break;
1609                         else
1610                                 continue;
1611                 }
1612
1613                 /* Automerge succeeded. */
1614                 write_tree_trivial(&result_tree);
1615                 automerge_was_ok = 1;
1616                 break;
1617         }
1618
1619         /*
1620          * If we have a resulting tree, that means the strategy module
1621          * auto resolved the merge cleanly.
1622          */
1623         if (automerge_was_ok) {
1624                 ret = finish_automerge(head_commit, head_subsumed,
1625                                        common, remoteheads,
1626                                        &result_tree, wt_strategy);
1627                 goto done;
1628         }
1629
1630         /*
1631          * Pick the result from the best strategy and have the user fix
1632          * it up.
1633          */
1634         if (!best_strategy) {
1635                 restore_state(&head_commit->object.oid, &stash);
1636                 if (use_strategies_nr > 1)
1637                         fprintf(stderr,
1638                                 _("No merge strategy handled the merge.\n"));
1639                 else
1640                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1641                                 use_strategies[0]->name);
1642                 ret = 2;
1643                 goto done;
1644         } else if (best_strategy == wt_strategy)
1645                 ; /* We already have its result in the working tree. */
1646         else {
1647                 printf(_("Rewinding the tree to pristine...\n"));
1648                 restore_state(&head_commit->object.oid, &stash);
1649                 printf(_("Using the %s to prepare resolving by hand.\n"),
1650                         best_strategy);
1651                 try_merge_strategy(best_strategy, common, remoteheads,
1652                                    head_commit);
1653         }
1654
1655         if (squash)
1656                 finish(head_commit, remoteheads, NULL, NULL);
1657         else
1658                 write_merge_state(remoteheads);
1659
1660         if (merge_was_ok)
1661                 fprintf(stderr, _("Automatic merge went well; "
1662                         "stopped before committing as requested\n"));
1663         else
1664                 ret = suggest_conflicts();
1665
1666 done:
1667         free(branch_to_free);
1668         return ret;
1669 }