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 "hook.h"
  17 #include "diff.h"
  18 #include "diff-merges.h"
  19 #include "refs.h"
  20 #include "refspec.h"
  21 #include "commit.h"
  22 #include "diffcore.h"
  23 #include "revision.h"
  24 #include "unpack-trees.h"
  25 #include "cache-tree.h"
  26 #include "dir.h"
  27 #include "utf8.h"
  28 #include "log-tree.h"
  29 #include "color.h"
  30 #include "rerere.h"
  31 #include "help.h"
  32 #include "merge-recursive.h"
  33 #include "merge-ort-wrappers.h"
  34 #include "resolve-undo.h"
  35 #include "remote.h"
  36 #include "fmt-merge-msg.h"
  37 #include "gpg-interface.h"
  38 #include "sequencer.h"
  39 #include "string-list.h"
  40 #include "packfile.h"
  41 #include "tag.h"
  42 #include "alias.h"
  43 #include "branch.h"
  44 #include "commit-reach.h"
  45 #include "wt-status.h"
  46 #include "commit-graph.h"
  47
  48 #define DEFAULT_TWOHEAD (1<<0)
  49 #define DEFAULT_OCTOPUS (1<<1)
  50 #define NO_FAST_FORWARD (1<<2)
  51 #define NO_TRIVIAL      (1<<3)
  52
  53 struct strategy {
  54         const char *name;
  55         unsigned attr;
  56 };
  57
  58 static const char * const builtin_merge_usage[] = {
  59         N_("git merge [<options>] [<commit>...]"),
  60         "git merge --abort",
  61         "git merge --continue",
  62         NULL
  63 };
  64
  65 static int show_diffstat = 1, shortlog_len = -1, squash;
  66 static int option_commit = -1;
  67 static int option_edit = -1;
  68 static int allow_trivial = 1, have_message, verify_signatures;
  69 static int check_trust_level = 1;
  70 static int overwrite_ignore = 1;
  71 static struct strbuf merge_msg = STRBUF_INIT;
  72 static struct strategy **use_strategies;
  73 static size_t use_strategies_nr, use_strategies_alloc;
  74 static const char **xopts;
  75 static size_t xopts_nr, xopts_alloc;
  76 static const char *branch;
  77 static char *branch_mergeoptions;
  78 static int verbosity;
  79 static int allow_rerere_auto;
  80 static int abort_current_merge;
  81 static int quit_current_merge;
  82 static int continue_current_merge;
  83 static int allow_unrelated_histories;
  84 static int show_progress = -1;
  85 static int default_to_upstream = 1;
  86 static int signoff;
  87 static const char *sign_commit;
  88 static int autostash;
  89 static int no_verify;
  90
  91 static struct strategy all_strategy[] = {
  92         { "recursive",  NO_TRIVIAL },
  93         { "octopus",    DEFAULT_OCTOPUS },
  94         { "ort",        DEFAULT_TWOHEAD | NO_TRIVIAL },
  95         { "resolve",    0 },
  96         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  97         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  98 };
  99
 100 static const char *pull_twohead, *pull_octopus;
 101
 102 enum ff_type {
 103         FF_NO,
 104         FF_ALLOW,
 105         FF_ONLY
 106 };
 107
 108 static enum ff_type fast_forward = FF_ALLOW;
 109
 110 static const char *cleanup_arg;
 111 static enum commit_msg_cleanup_mode cleanup_mode;
 112
 113 static int option_parse_message(const struct option *opt,
 114                                 const char *arg, int unset)
 115 {
 116         struct strbuf *buf = opt->value;
 117
 118         if (unset)
 119                 strbuf_setlen(buf, 0);
 120         else if (arg) {
 121                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 122                 have_message = 1;
 123         } else
 124                 return error(_("switch `m' requires a value"));
 125         return 0;
 126 }
 127
 128 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 129                                                  const struct option *opt,
 130                                                  const char *arg_not_used,
 131                                                  int unset)
 132 {
 133         struct strbuf *buf = opt->value;
 134         const char *arg;
 135
 136         BUG_ON_OPT_ARG(arg_not_used);
 137         if (unset)
 138                 BUG("-F cannot be negated");
 139
 140         if (ctx->opt) {
 141                 arg = ctx->opt;
 142                 ctx->opt = NULL;
 143         } else if (ctx->argc > 1) {
 144                 ctx->argc--;
 145                 arg = *++ctx->argv;
 146         } else
 147                 return error(_("option `%s' requires a value"), opt->long_name);
 148
 149         if (buf->len)
 150                 strbuf_addch(buf, '\n');
 151         if (ctx->prefix && !is_absolute_path(arg))
 152                 arg = prefix_filename(ctx->prefix, arg);
 153         if (strbuf_read_file(buf, arg, 0) < 0)
 154                 return error(_("could not read file '%s'"), arg);
 155         have_message = 1;
 156
 157         return 0;
 158 }
 159
 160 static struct strategy *get_strategy(const char *name)
 161 {
 162         int i;
 163         struct strategy *ret;
 164         static struct cmdnames main_cmds, other_cmds;
 165         static int loaded;
 166         char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 167
 168         if (!name)
 169                 return NULL;
 170
 171         if (default_strategy &&
 172             !strcmp(default_strategy, "ort") &&
 173             !strcmp(name, "recursive")) {
 174                 name = "ort";
 175         }
 176
 177         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 178                 if (!strcmp(name, all_strategy[i].name))
 179                         return &all_strategy[i];
 180
 181         if (!loaded) {
 182                 struct cmdnames not_strategies;
 183                 loaded = 1;
 184
 185                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 186                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 187                 for (i = 0; i < main_cmds.cnt; i++) {
 188                         int j, found = 0;
 189                         struct cmdname *ent = main_cmds.names[i];
 190                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 191                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 192                                                 && !all_strategy[j].name[ent->len])
 193                                         found = 1;
 194                         if (!found)
 195                                 add_cmdname(&not_strategies, ent->name, ent->len);
 196                 }
 197                 exclude_cmds(&main_cmds, &not_strategies);
 198         }
 199         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 200                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 201                 fprintf(stderr, _("Available strategies are:"));
 202                 for (i = 0; i < main_cmds.cnt; i++)
 203                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 204                 fprintf(stderr, ".\n");
 205                 if (other_cmds.cnt) {
 206                         fprintf(stderr, _("Available custom strategies are:"));
 207                         for (i = 0; i < other_cmds.cnt; i++)
 208                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 209                         fprintf(stderr, ".\n");
 210                 }
 211                 exit(1);
 212         }
 213
 214         CALLOC_ARRAY(ret, 1);
 215         ret->name = xstrdup(name);
 216         ret->attr = NO_TRIVIAL;
 217         return ret;
 218 }
 219
 220 static void append_strategy(struct strategy *s)
 221 {
 222         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 223         use_strategies[use_strategies_nr++] = s;
 224 }
 225
 226 static int option_parse_strategy(const struct option *opt,
 227                                  const char *name, int unset)
 228 {
 229         if (unset)
 230                 return 0;
 231
 232         append_strategy(get_strategy(name));
 233         return 0;
 234 }
 235
 236 static int option_parse_x(const struct option *opt,
 237                           const char *arg, int unset)
 238 {
 239         if (unset)
 240                 return 0;
 241
 242         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 243         xopts[xopts_nr++] = xstrdup(arg);
 244         return 0;
 245 }
 246
 247 static int option_parse_n(const struct option *opt,
 248                           const char *arg, int unset)
 249 {
 250         BUG_ON_OPT_ARG(arg);
 251         show_diffstat = unset;
 252         return 0;
 253 }
 254
 255 static struct option builtin_merge_options[] = {
 256         OPT_CALLBACK_F('n', NULL, NULL, NULL,
 257                 N_("do not show a diffstat at the end of the merge"),
 258                 PARSE_OPT_NOARG, option_parse_n),
 259         OPT_BOOL(0, "stat", &show_diffstat,
 260                 N_("show a diffstat at the end of the merge")),
 261         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 262         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 263           N_("add (at most <n>) entries from shortlog to merge commit message"),
 264           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 265         OPT_BOOL(0, "squash", &squash,
 266                 N_("create a single commit instead of doing a merge")),
 267         OPT_BOOL(0, "commit", &option_commit,
 268                 N_("perform a commit if the merge succeeds (default)")),
 269         OPT_BOOL('e', "edit", &option_edit,
 270                 N_("edit message before committing")),
 271         OPT_CLEANUP(&cleanup_arg),
 272         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 273         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 274                       N_("abort if fast-forward is not possible"),
 275                       FF_ONLY, PARSE_OPT_NONEG),
 276         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 277         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 278                 N_("verify that the named commit has a valid GPG signature")),
 279         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 280                 N_("merge strategy to use"), option_parse_strategy),
 281         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 282                 N_("option for selected merge strategy"), option_parse_x),
 283         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 284                 N_("merge commit message (for a non-fast-forward merge)"),
 285                 option_parse_message),
 286         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 287                 N_("read message from file"), PARSE_OPT_NONEG,
 288                 NULL, 0, option_read_message },
 289         OPT__VERBOSITY(&verbosity),
 290         OPT_BOOL(0, "abort", &abort_current_merge,
 291                 N_("abort the current in-progress merge")),
 292         OPT_BOOL(0, "quit", &quit_current_merge,
 293                 N_("--abort but leave index and working tree alone")),
 294         OPT_BOOL(0, "continue", &continue_current_merge,
 295                 N_("continue the current in-progress merge")),
 296         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 297                  N_("allow merging unrelated histories")),
 298         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 299         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 300           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 301         OPT_AUTOSTASH(&autostash),
 302         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 303         OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
 304         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 305         OPT_END()
 306 };
 307
 308 static int save_state(struct object_id *stash)
 309 {
 310         int len;
 311         struct child_process cp = CHILD_PROCESS_INIT;
 312         struct strbuf buffer = STRBUF_INIT;
 313         const char *argv[] = {"stash", "create", NULL};
 314         int rc = -1;
 315
 316         cp.argv = argv;
 317         cp.out = -1;
 318         cp.git_cmd = 1;
 319
 320         if (start_command(&cp))
 321                 die(_("could not run stash."));
 322         len = strbuf_read(&buffer, cp.out, 1024);
 323         close(cp.out);
 324
 325         if (finish_command(&cp) || len < 0)
 326                 die(_("stash failed"));
 327         else if (!len)          /* no changes */
 328                 goto out;
 329         strbuf_setlen(&buffer, buffer.len-1);
 330         if (get_oid(buffer.buf, stash))
 331                 die(_("not a valid object: %s"), buffer.buf);
 332         rc = 0;
 333 out:
 334         strbuf_release(&buffer);
 335         return rc;
 336 }
 337
 338 static void read_empty(const struct object_id *oid, int verbose)
 339 {
 340         int i = 0;
 341         const char *args[7];
 342
 343         args[i++] = "read-tree";
 344         if (verbose)
 345                 args[i++] = "-v";
 346         args[i++] = "-m";
 347         args[i++] = "-u";
 348         args[i++] = empty_tree_oid_hex();
 349         args[i++] = oid_to_hex(oid);
 350         args[i] = NULL;
 351
 352         if (run_command_v_opt(args, RUN_GIT_CMD))
 353                 die(_("read-tree failed"));
 354 }
 355
 356 static void reset_hard(const struct object_id *oid, int verbose)
 357 {
 358         int i = 0;
 359         const char *args[6];
 360
 361         args[i++] = "read-tree";
 362         if (verbose)
 363                 args[i++] = "-v";
 364         args[i++] = "--reset";
 365         args[i++] = "-u";
 366         args[i++] = oid_to_hex(oid);
 367         args[i] = NULL;
 368
 369         if (run_command_v_opt(args, RUN_GIT_CMD))
 370                 die(_("read-tree failed"));
 371 }
 372
 373 static void restore_state(const struct object_id *head,
 374                           const struct object_id *stash)
 375 {
 376         struct strbuf sb = STRBUF_INIT;
 377         const char *args[] = { "stash", "apply", NULL, NULL };
 378
 379         if (is_null_oid(stash))
 380                 return;
 381
 382         reset_hard(head, 1);
 383
 384         args[2] = oid_to_hex(stash);
 385
 386         /*
 387          * It is OK to ignore error here, for example when there was
 388          * nothing to restore.
 389          */
 390         run_command_v_opt(args, RUN_GIT_CMD);
 391
 392         strbuf_release(&sb);
 393         refresh_cache(REFRESH_QUIET);
 394 }
 395
 396 /* This is called when no merge was necessary. */
 397 static void finish_up_to_date(void)
 398 {
 399         if (verbosity >= 0) {
 400                 if (squash)
 401                         puts(_("Already up to date. (nothing to squash)"));
 402                 else
 403                         puts(_("Already up to date."));
 404         }
 405         remove_merge_branch_state(the_repository);
 406 }
 407
 408 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 409 {
 410         struct rev_info rev;
 411         struct strbuf out = STRBUF_INIT;
 412         struct commit_list *j;
 413         struct pretty_print_context ctx = {0};
 414
 415         printf(_("Squash commit -- not updating HEAD\n"));
 416
 417         repo_init_revisions(the_repository, &rev, NULL);
 418         diff_merges_suppress(&rev);
 419         rev.commit_format = CMIT_FMT_MEDIUM;
 420
 421         commit->object.flags |= UNINTERESTING;
 422         add_pending_object(&rev, &commit->object, NULL);
 423
 424         for (j = remoteheads; j; j = j->next)
 425                 add_pending_object(&rev, &j->item->object, NULL);
 426
 427         setup_revisions(0, NULL, &rev, NULL);
 428         if (prepare_revision_walk(&rev))
 429                 die(_("revision walk setup failed"));
 430
 431         ctx.abbrev = rev.abbrev;
 432         ctx.date_mode = rev.date_mode;
 433         ctx.fmt = rev.commit_format;
 434
 435         strbuf_addstr(&out, "Squashed commit of the following:\n");
 436         while ((commit = get_revision(&rev)) != NULL) {
 437                 strbuf_addch(&out, '\n');
 438                 strbuf_addf(&out, "commit %s\n",
 439                         oid_to_hex(&commit->object.oid));
 440                 pretty_print_commit(&ctx, commit, &out);
 441         }
 442         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 443         strbuf_release(&out);
 444 }
 445
 446 static void finish(struct commit *head_commit,
 447                    struct commit_list *remoteheads,
 448                    const struct object_id *new_head, const char *msg)
 449 {
 450         struct strbuf reflog_message = STRBUF_INIT;
 451         const struct object_id *head = &head_commit->object.oid;
 452
 453         if (!msg)
 454                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 455         else {
 456                 if (verbosity >= 0)
 457                         printf("%s\n", msg);
 458                 strbuf_addf(&reflog_message, "%s: %s",
 459                         getenv("GIT_REFLOG_ACTION"), msg);
 460         }
 461         if (squash) {
 462                 squash_message(head_commit, remoteheads);
 463         } else {
 464                 if (verbosity >= 0 && !merge_msg.len)
 465                         printf(_("No merge message -- not updating HEAD\n"));
 466                 else {
 467                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 468                                    0, UPDATE_REFS_DIE_ON_ERR);
 469                         /*
 470                          * We ignore errors in 'gc --auto', since the
 471                          * user should see them.
 472                          */
 473                         run_auto_maintenance(verbosity < 0);
 474                 }
 475         }
 476         if (new_head && show_diffstat) {
 477                 struct diff_options opts;
 478                 repo_diff_setup(the_repository, &opts);
 479                 opts.stat_width = -1; /* use full terminal width */
 480                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 481                 opts.output_format |=
 482                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 483                 opts.detect_rename = DIFF_DETECT_RENAME;
 484                 diff_setup_done(&opts);
 485                 diff_tree_oid(head, new_head, "", &opts);
 486                 diffcore_std(&opts);
 487                 diff_flush(&opts);
 488         }
 489
 490         /* Run a post-merge hook */
 491         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 492
 493         apply_autostash(git_path_merge_autostash(the_repository));
 494         strbuf_release(&reflog_message);
 495 }
 496
 497 /* Get the name for the merge commit's message. */
 498 static void merge_name(const char *remote, struct strbuf *msg)
 499 {
 500         struct commit *remote_head;
 501         struct object_id branch_head;
 502         struct strbuf buf = STRBUF_INIT;
 503         struct strbuf bname = STRBUF_INIT;
 504         struct merge_remote_desc *desc;
 505         const char *ptr;
 506         char *found_ref = NULL;
 507         int len, early;
 508
 509         strbuf_branchname(&bname, remote, 0);
 510         remote = bname.buf;
 511
 512         oidclr(&branch_head);
 513         remote_head = get_merge_parent(remote);
 514         if (!remote_head)
 515                 die(_("'%s' does not point to a commit"), remote);
 516
 517         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
 518                 if (starts_with(found_ref, "refs/heads/")) {
 519                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 520                                     oid_to_hex(&branch_head), remote);
 521                         goto cleanup;
 522                 }
 523                 if (starts_with(found_ref, "refs/tags/")) {
 524                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 525                                     oid_to_hex(&branch_head), remote);
 526                         goto cleanup;
 527                 }
 528                 if (starts_with(found_ref, "refs/remotes/")) {
 529                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 530                                     oid_to_hex(&branch_head), remote);
 531                         goto cleanup;
 532                 }
 533         }
 534
 535         /* See if remote matches <name>^^^.. or <name>~<number> */
 536         for (len = 0, ptr = remote + strlen(remote);
 537              remote < ptr && ptr[-1] == '^';
 538              ptr--)
 539                 len++;
 540         if (len)
 541                 early = 1;
 542         else {
 543                 early = 0;
 544                 ptr = strrchr(remote, '~');
 545                 if (ptr) {
 546                         int seen_nonzero = 0;
 547
 548                         len++; /* count ~ */
 549                         while (*++ptr && isdigit(*ptr)) {
 550                                 seen_nonzero |= (*ptr != '0');
 551                                 len++;
 552                         }
 553                         if (*ptr)
 554                                 len = 0; /* not ...~<number> */
 555                         else if (seen_nonzero)
 556                                 early = 1;
 557                         else if (len == 1)
 558                                 early = 1; /* "name~" is "name~1"! */
 559                 }
 560         }
 561         if (len) {
 562                 struct strbuf truname = STRBUF_INIT;
 563                 strbuf_addf(&truname, "refs/heads/%s", remote);
 564                 strbuf_setlen(&truname, truname.len - len);
 565                 if (ref_exists(truname.buf)) {
 566                         strbuf_addf(msg,
 567                                     "%s\t\tbranch '%s'%s of .\n",
 568                                     oid_to_hex(&remote_head->object.oid),
 569                                     truname.buf + 11,
 570                                     (early ? " (early part)" : ""));
 571                         strbuf_release(&truname);
 572                         goto cleanup;
 573                 }
 574                 strbuf_release(&truname);
 575         }
 576
 577         desc = merge_remote_util(remote_head);
 578         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 579                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 580                             oid_to_hex(&desc->obj->oid),
 581                             type_name(desc->obj->type),
 582                             remote);
 583                 goto cleanup;
 584         }
 585
 586         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 587                 oid_to_hex(&remote_head->object.oid), remote);
 588 cleanup:
 589         free(found_ref);
 590         strbuf_release(&buf);
 591         strbuf_release(&bname);
 592 }
 593
 594 static void parse_branch_merge_options(char *bmo)
 595 {
 596         const char **argv;
 597         int argc;
 598
 599         if (!bmo)
 600                 return;
 601         argc = split_cmdline(bmo, &argv);
 602         if (argc < 0)
 603                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 604                     _(split_cmdline_strerror(argc)));
 605         REALLOC_ARRAY(argv, argc + 2);
 606         MOVE_ARRAY(argv + 1, argv, argc + 1);
 607         argc++;
 608         argv[0] = "branch.*.mergeoptions";
 609         parse_options(argc, argv, NULL, builtin_merge_options,
 610                       builtin_merge_usage, 0);
 611         free(argv);
 612 }
 613
 614 static int git_merge_config(const char *k, const char *v, void *cb)
 615 {
 616         int status;
 617         const char *str;
 618
 619         if (branch &&
 620             skip_prefix(k, "branch.", &str) &&
 621             skip_prefix(str, branch, &str) &&
 622             !strcmp(str, ".mergeoptions")) {
 623                 free(branch_mergeoptions);
 624                 branch_mergeoptions = xstrdup(v);
 625                 return 0;
 626         }
 627
 628         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 629                 show_diffstat = git_config_bool(k, v);
 630         else if (!strcmp(k, "merge.verifysignatures"))
 631                 verify_signatures = git_config_bool(k, v);
 632         else if (!strcmp(k, "pull.twohead"))
 633                 return git_config_string(&pull_twohead, k, v);
 634         else if (!strcmp(k, "pull.octopus"))
 635                 return git_config_string(&pull_octopus, k, v);
 636         else if (!strcmp(k, "commit.cleanup"))
 637                 return git_config_string(&cleanup_arg, k, v);
 638         else if (!strcmp(k, "merge.ff")) {
 639                 int boolval = git_parse_maybe_bool(v);
 640                 if (0 <= boolval) {
 641                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 642                 } else if (v && !strcmp(v, "only")) {
 643                         fast_forward = FF_ONLY;
 644                 } /* do not barf on values from future versions of git */
 645                 return 0;
 646         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 647                 default_to_upstream = git_config_bool(k, v);
 648                 return 0;
 649         } else if (!strcmp(k, "commit.gpgsign")) {
 650                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 651                 return 0;
 652         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 653                 check_trust_level = 0;
 654         } else if (!strcmp(k, "merge.autostash")) {
 655                 autostash = git_config_bool(k, v);
 656                 return 0;
 657         }
 658
 659         status = fmt_merge_msg_config(k, v, cb);
 660         if (status)
 661                 return status;
 662         status = git_gpg_config(k, v, NULL);
 663         if (status)
 664                 return status;
 665         return git_diff_ui_config(k, v, cb);
 666 }
 667
 668 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 669                              struct object_id *one)
 670 {
 671         int i, nr_trees = 0;
 672         struct tree *trees[MAX_UNPACK_TREES];
 673         struct tree_desc t[MAX_UNPACK_TREES];
 674         struct unpack_trees_options opts;
 675
 676         memset(&opts, 0, sizeof(opts));
 677         opts.head_idx = 2;
 678         opts.src_index = &the_index;
 679         opts.dst_index = &the_index;
 680         opts.update = 1;
 681         opts.verbose_update = 1;
 682         opts.trivial_merges_only = 1;
 683         opts.merge = 1;
 684         opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 685         trees[nr_trees] = parse_tree_indirect(common);
 686         if (!trees[nr_trees++])
 687                 return -1;
 688         trees[nr_trees] = parse_tree_indirect(head);
 689         if (!trees[nr_trees++])
 690                 return -1;
 691         trees[nr_trees] = parse_tree_indirect(one);
 692         if (!trees[nr_trees++])
 693                 return -1;
 694         opts.fn = threeway_merge;
 695         cache_tree_free(&active_cache_tree);
 696         for (i = 0; i < nr_trees; i++) {
 697                 parse_tree(trees[i]);
 698                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 699         }
 700         if (unpack_trees(nr_trees, t, &opts))
 701                 return -1;
 702         return 0;
 703 }
 704
 705 static void write_tree_trivial(struct object_id *oid)
 706 {
 707         if (write_cache_as_tree(oid, 0, NULL))
 708                 die(_("git write-tree failed to write a tree"));
 709 }
 710
 711 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 712                               struct commit_list *remoteheads,
 713                               struct commit *head)
 714 {
 715         const char *head_arg = "HEAD";
 716
 717         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 718                 return error(_("Unable to write index."));
 719
 720         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
 721             !strcmp(strategy, "ort")) {
 722                 struct lock_file lock = LOCK_INIT;
 723                 int clean, x;
 724                 struct commit *result;
 725                 struct commit_list *reversed = NULL;
 726                 struct merge_options o;
 727                 struct commit_list *j;
 728
 729                 if (remoteheads->next) {
 730                         error(_("Not handling anything other than two heads merge."));
 731                         return 2;
 732                 }
 733
 734                 init_merge_options(&o, the_repository);
 735                 if (!strcmp(strategy, "subtree"))
 736                         o.subtree_shift = "";
 737
 738                 o.show_rename_progress =
 739                         show_progress == -1 ? isatty(2) : show_progress;
 740
 741                 for (x = 0; x < xopts_nr; x++)
 742                         if (parse_merge_opt(&o, xopts[x]))
 743                                 die(_("unknown strategy option: -X%s"), xopts[x]);
 744
 745                 o.branch1 = head_arg;
 746                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 747
 748                 for (j = common; j; j = j->next)
 749                         commit_list_insert(j->item, &reversed);
 750
 751                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 752                 if (!strcmp(strategy, "ort"))
 753                         clean = merge_ort_recursive(&o, head, remoteheads->item,
 754                                                     reversed, &result);
 755                 else
 756                         clean = merge_recursive(&o, head, remoteheads->item,
 757                                                 reversed, &result);
 758                 if (clean < 0)
 759                         exit(128);
 760                 if (write_locked_index(&the_index, &lock,
 761                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 762                         die(_("unable to write %s"), get_index_file());
 763                 return clean ? 0 : 1;
 764         } else {
 765                 return try_merge_command(the_repository,
 766                                          strategy, xopts_nr, xopts,
 767                                          common, head_arg, remoteheads);
 768         }
 769 }
 770
 771 static void count_diff_files(struct diff_queue_struct *q,
 772                              struct diff_options *opt, void *data)
 773 {
 774         int *count = data;
 775
 776         (*count) += q->nr;
 777 }
 778
 779 static int count_unmerged_entries(void)
 780 {
 781         int i, ret = 0;
 782
 783         for (i = 0; i < active_nr; i++)
 784                 if (ce_stage(active_cache[i]))
 785                         ret++;
 786
 787         return ret;
 788 }
 789
 790 static void add_strategies(const char *string, unsigned attr)
 791 {
 792         int i;
 793
 794         if (string) {
 795                 struct string_list list = STRING_LIST_INIT_DUP;
 796                 struct string_list_item *item;
 797                 string_list_split(&list, string, ' ', -1);
 798                 for_each_string_list_item(item, &list)
 799                         append_strategy(get_strategy(item->string));
 800                 string_list_clear(&list, 0);
 801                 return;
 802         }
 803         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 804                 if (all_strategy[i].attr & attr)
 805                         append_strategy(&all_strategy[i]);
 806
 807 }
 808
 809 static void read_merge_msg(struct strbuf *msg)
 810 {
 811         const char *filename = git_path_merge_msg(the_repository);
 812         strbuf_reset(msg);
 813         if (strbuf_read_file(msg, filename, 0) < 0)
 814                 die_errno(_("Could not read from '%s'"), filename);
 815 }
 816
 817 static void write_merge_state(struct commit_list *);
 818 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 819 {
 820         if (err_msg)
 821                 error("%s", err_msg);
 822         fprintf(stderr,
 823                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 824         write_merge_state(remoteheads);
 825         exit(1);
 826 }
 827
 828 static const char merge_editor_comment[] =
 829 N_("Please enter a commit message to explain why this merge is necessary,\n"
 830    "especially if it merges an updated upstream into a topic branch.\n"
 831    "\n");
 832
 833 static const char scissors_editor_comment[] =
 834 N_("An empty message aborts the commit.\n");
 835
 836 static const char no_scissors_editor_comment[] =
 837 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 838    "the commit.\n");
 839
 840 static void write_merge_heads(struct commit_list *);
 841 static void prepare_to_commit(struct commit_list *remoteheads)
 842 {
 843         struct strbuf msg = STRBUF_INIT;
 844         const char *index_file = get_index_file();
 845
 846         if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
 847                 abort_commit(remoteheads, NULL);
 848         /*
 849          * Re-read the index as pre-merge-commit hook could have updated it,
 850          * and write it out as a tree.  We must do this before we invoke
 851          * the editor and after we invoke run_status above.
 852          */
 853         if (hook_exists("pre-merge-commit"))
 854                 discard_cache();
 855         read_cache_from(index_file);
 856         strbuf_addbuf(&msg, &merge_msg);
 857         if (squash)
 858                 BUG("the control must not reach here under --squash");
 859         if (0 < option_edit) {
 860                 strbuf_addch(&msg, '\n');
 861                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 862                         wt_status_append_cut_line(&msg);
 863                         strbuf_commented_addf(&msg, "\n");
 864                 }
 865                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 866                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
 867                         strbuf_commented_addf(&msg, _(scissors_editor_comment));
 868                 else
 869                         strbuf_commented_addf(&msg,
 870                                 _(no_scissors_editor_comment), comment_line_char);
 871         }
 872         if (signoff)
 873                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 874         write_merge_heads(remoteheads);
 875         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 876         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 877                             git_path_merge_msg(the_repository), "merge", NULL))
 878                 abort_commit(remoteheads, NULL);
 879         if (0 < option_edit) {
 880                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 881                         abort_commit(remoteheads, NULL);
 882         }
 883
 884         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 885                                           "commit-msg",
 886                                           git_path_merge_msg(the_repository), NULL))
 887                 abort_commit(remoteheads, NULL);
 888
 889         read_merge_msg(&msg);
 890         cleanup_message(&msg, cleanup_mode, 0);
 891         if (!msg.len)
 892                 abort_commit(remoteheads, _("Empty commit message."));
 893         strbuf_release(&merge_msg);
 894         strbuf_addbuf(&merge_msg, &msg);
 895         strbuf_release(&msg);
 896 }
 897
 898 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 899 {
 900         struct object_id result_tree, result_commit;
 901         struct commit_list *parents, **pptr = &parents;
 902
 903         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 904                 return error(_("Unable to write index."));
 905
 906         write_tree_trivial(&result_tree);
 907         printf(_("Wonderful.\n"));
 908         pptr = commit_list_append(head, pptr);
 909         pptr = commit_list_append(remoteheads->item, pptr);
 910         prepare_to_commit(remoteheads);
 911         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 912                         &result_commit, NULL, sign_commit))
 913                 die(_("failed to write commit object"));
 914         finish(head, remoteheads, &result_commit, "In-index merge");
 915         remove_merge_branch_state(the_repository);
 916         return 0;
 917 }
 918
 919 static int finish_automerge(struct commit *head,
 920                             int head_subsumed,
 921                             struct commit_list *common,
 922                             struct commit_list *remoteheads,
 923                             struct object_id *result_tree,
 924                             const char *wt_strategy)
 925 {
 926         struct commit_list *parents = NULL;
 927         struct strbuf buf = STRBUF_INIT;
 928         struct object_id result_commit;
 929
 930         write_tree_trivial(result_tree);
 931         free_commit_list(common);
 932         parents = remoteheads;
 933         if (!head_subsumed || fast_forward == FF_NO)
 934                 commit_list_insert(head, &parents);
 935         prepare_to_commit(remoteheads);
 936         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 937                         &result_commit, NULL, sign_commit))
 938                 die(_("failed to write commit object"));
 939         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 940         finish(head, remoteheads, &result_commit, buf.buf);
 941         strbuf_release(&buf);
 942         remove_merge_branch_state(the_repository);
 943         return 0;
 944 }
 945
 946 static int suggest_conflicts(void)
 947 {
 948         const char *filename;
 949         FILE *fp;
 950         struct strbuf msgbuf = STRBUF_INIT;
 951
 952         filename = git_path_merge_msg(the_repository);
 953         fp = xfopen(filename, "a");
 954
 955         /*
 956          * We can't use cleanup_mode because if we're not using the editor,
 957          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 958          * though the message is meant to be processed later by git-commit.
 959          * Thus, we will get the cleanup mode which is returned when we _are_
 960          * using an editor.
 961          */
 962         append_conflicts_hint(&the_index, &msgbuf,
 963                               get_cleanup_mode(cleanup_arg, 1));
 964         fputs(msgbuf.buf, fp);
 965         strbuf_release(&msgbuf);
 966         fclose(fp);
 967         repo_rerere(the_repository, allow_rerere_auto);
 968         printf(_("Automatic merge failed; "
 969                         "fix conflicts and then commit the result.\n"));
 970         return 1;
 971 }
 972
 973 static int evaluate_result(void)
 974 {
 975         int cnt = 0;
 976         struct rev_info rev;
 977
 978         /* Check how many files differ. */
 979         repo_init_revisions(the_repository, &rev, "");
 980         setup_revisions(0, NULL, &rev, NULL);
 981         rev.diffopt.output_format |=
 982                 DIFF_FORMAT_CALLBACK;
 983         rev.diffopt.format_callback = count_diff_files;
 984         rev.diffopt.format_callback_data = &cnt;
 985         run_diff_files(&rev, 0);
 986
 987         /*
 988          * Check how many unmerged entries are
 989          * there.
 990          */
 991         cnt += count_unmerged_entries();
 992
 993         return cnt;
 994 }
 995
 996 /*
 997  * Pretend as if the user told us to merge with the remote-tracking
 998  * branch we have for the upstream of the current branch
 999  */
1000 static int setup_with_upstream(const char ***argv)
1001 {
1002         struct branch *branch = branch_get(NULL);
1003         int i;
1004         const char **args;
1005
1006         if (!branch)
1007                 die(_("No current branch."));
1008         if (!branch->remote_name)
1009                 die(_("No remote for the current branch."));
1010         if (!branch->merge_nr)
1011                 die(_("No default upstream defined for the current branch."));
1012
1013         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
1014         for (i = 0; i < branch->merge_nr; i++) {
1015                 if (!branch->merge[i]->dst)
1016                         die(_("No remote-tracking branch for %s from %s"),
1017                             branch->merge[i]->src, branch->remote_name);
1018                 args[i] = branch->merge[i]->dst;
1019         }
1020         args[i] = NULL;
1021         *argv = args;
1022         return i;
1023 }
1024
1025 static void write_merge_heads(struct commit_list *remoteheads)
1026 {
1027         struct commit_list *j;
1028         struct strbuf buf = STRBUF_INIT;
1029
1030         for (j = remoteheads; j; j = j->next) {
1031                 struct object_id *oid;
1032                 struct commit *c = j->item;
1033                 struct merge_remote_desc *desc;
1034
1035                 desc = merge_remote_util(c);
1036                 if (desc && desc->obj) {
1037                         oid = &desc->obj->oid;
1038                 } else {
1039                         oid = &c->object.oid;
1040                 }
1041                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1042         }
1043         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1044
1045         strbuf_reset(&buf);
1046         if (fast_forward == FF_NO)
1047                 strbuf_addstr(&buf, "no-ff");
1048         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1049         strbuf_release(&buf);
1050 }
1051
1052 static void write_merge_state(struct commit_list *remoteheads)
1053 {
1054         write_merge_heads(remoteheads);
1055         strbuf_addch(&merge_msg, '\n');
1056         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1057                        merge_msg.len);
1058 }
1059
1060 static int default_edit_option(void)
1061 {
1062         static const char name[] = "GIT_MERGE_AUTOEDIT";
1063         const char *e = getenv(name);
1064         struct stat st_stdin, st_stdout;
1065
1066         if (have_message)
1067                 /* an explicit -m msg without --[no-]edit */
1068                 return 0;
1069
1070         if (e) {
1071                 int v = git_parse_maybe_bool(e);
1072                 if (v < 0)
1073                         die(_("Bad value '%s' in environment '%s'"), e, name);
1074                 return v;
1075         }
1076
1077         /* Use editor if stdin and stdout are the same and is a tty */
1078         return (!fstat(0, &st_stdin) &&
1079                 !fstat(1, &st_stdout) &&
1080                 isatty(0) && isatty(1) &&
1081                 st_stdin.st_dev == st_stdout.st_dev &&
1082                 st_stdin.st_ino == st_stdout.st_ino &&
1083                 st_stdin.st_mode == st_stdout.st_mode);
1084 }
1085
1086 static struct commit_list *reduce_parents(struct commit *head_commit,
1087                                           int *head_subsumed,
1088                                           struct commit_list *remoteheads)
1089 {
1090         struct commit_list *parents, **remotes;
1091
1092         /*
1093          * Is the current HEAD reachable from another commit being
1094          * merged?  If so we do not want to record it as a parent of
1095          * the resulting merge, unless --no-ff is given.  We will flip
1096          * this variable to 0 when we find HEAD among the independent
1097          * tips being merged.
1098          */
1099         *head_subsumed = 1;
1100
1101         /* Find what parents to record by checking independent ones. */
1102         parents = reduce_heads(remoteheads);
1103         free_commit_list(remoteheads);
1104
1105         remoteheads = NULL;
1106         remotes = &remoteheads;
1107         while (parents) {
1108                 struct commit *commit = pop_commit(&parents);
1109                 if (commit == head_commit)
1110                         *head_subsumed = 0;
1111                 else
1112                         remotes = &commit_list_insert(commit, remotes)->next;
1113         }
1114         return remoteheads;
1115 }
1116
1117 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1118 {
1119         struct fmt_merge_msg_opts opts;
1120
1121         memset(&opts, 0, sizeof(opts));
1122         opts.add_title = !have_message;
1123         opts.shortlog_len = shortlog_len;
1124         opts.credit_people = (0 < option_edit);
1125
1126         fmt_merge_msg(merge_names, merge_msg, &opts);
1127         if (merge_msg->len)
1128                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1129 }
1130
1131 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1132 {
1133         const char *filename;
1134         int fd, pos, npos;
1135         struct strbuf fetch_head_file = STRBUF_INIT;
1136         const unsigned hexsz = the_hash_algo->hexsz;
1137
1138         if (!merge_names)
1139                 merge_names = &fetch_head_file;
1140
1141         filename = git_path_fetch_head(the_repository);
1142         fd = xopen(filename, O_RDONLY);
1143
1144         if (strbuf_read(merge_names, fd, 0) < 0)
1145                 die_errno(_("could not read '%s'"), filename);
1146         if (close(fd) < 0)
1147                 die_errno(_("could not close '%s'"), filename);
1148
1149         for (pos = 0; pos < merge_names->len; pos = npos) {
1150                 struct object_id oid;
1151                 char *ptr;
1152                 struct commit *commit;
1153
1154                 ptr = strchr(merge_names->buf + pos, '\n');
1155                 if (ptr)
1156                         npos = ptr - merge_names->buf + 1;
1157                 else
1158                         npos = merge_names->len;
1159
1160                 if (npos - pos < hexsz + 2 ||
1161                     get_oid_hex(merge_names->buf + pos, &oid))
1162                         commit = NULL; /* bad */
1163                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1164                         continue; /* not-for-merge */
1165                 else {
1166                         char saved = merge_names->buf[pos + hexsz];
1167                         merge_names->buf[pos + hexsz] = '\0';
1168                         commit = get_merge_parent(merge_names->buf + pos);
1169                         merge_names->buf[pos + hexsz] = saved;
1170                 }
1171                 if (!commit) {
1172                         if (ptr)
1173                                 *ptr = '\0';
1174                         die(_("not something we can merge in %s: %s"),
1175                             filename, merge_names->buf + pos);
1176                 }
1177                 remotes = &commit_list_insert(commit, remotes)->next;
1178         }
1179
1180         if (merge_names == &fetch_head_file)
1181                 strbuf_release(&fetch_head_file);
1182 }
1183
1184 static struct commit_list *collect_parents(struct commit *head_commit,
1185                                            int *head_subsumed,
1186                                            int argc, const char **argv,
1187                                            struct strbuf *merge_msg)
1188 {
1189         int i;
1190         struct commit_list *remoteheads = NULL;
1191         struct commit_list **remotes = &remoteheads;
1192         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1193
1194         if (merge_msg && (!have_message || shortlog_len))
1195                 autogen = &merge_names;
1196
1197         if (head_commit)
1198                 remotes = &commit_list_insert(head_commit, remotes)->next;
1199
1200         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1201                 handle_fetch_head(remotes, autogen);
1202                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1203         } else {
1204                 for (i = 0; i < argc; i++) {
1205                         struct commit *commit = get_merge_parent(argv[i]);
1206                         if (!commit)
1207                                 help_unknown_ref(argv[i], "merge",
1208                                                  _("not something we can merge"));
1209                         remotes = &commit_list_insert(commit, remotes)->next;
1210                 }
1211                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1212                 if (autogen) {
1213                         struct commit_list *p;
1214                         for (p = remoteheads; p; p = p->next)
1215                                 merge_name(merge_remote_util(p->item)->name, autogen);
1216                 }
1217         }
1218
1219         if (autogen) {
1220                 prepare_merge_message(autogen, merge_msg);
1221                 strbuf_release(autogen);
1222         }
1223
1224         return remoteheads;
1225 }
1226
1227 static int merging_a_throwaway_tag(struct commit *commit)
1228 {
1229         char *tag_ref;
1230         struct object_id oid;
1231         int is_throwaway_tag = 0;
1232
1233         /* Are we merging a tag? */
1234         if (!merge_remote_util(commit) ||
1235             !merge_remote_util(commit)->obj ||
1236             merge_remote_util(commit)->obj->type != OBJ_TAG)
1237                 return is_throwaway_tag;
1238
1239         /*
1240          * Now we know we are merging a tag object.  Are we downstream
1241          * and following the tags from upstream?  If so, we must have
1242          * the tag object pointed at by "refs/tags/$T" where $T is the
1243          * tagname recorded in the tag object.  We want to allow such
1244          * a "just to catch up" merge to fast-forward.
1245          *
1246          * Otherwise, we are playing an integrator's role, making a
1247          * merge with a throw-away tag from a contributor with
1248          * something like "git pull $contributor $signed_tag".
1249          * We want to forbid such a merge from fast-forwarding
1250          * by default; otherwise we would not keep the signature
1251          * anywhere.
1252          */
1253         tag_ref = xstrfmt("refs/tags/%s",
1254                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1255         if (!read_ref(tag_ref, &oid) &&
1256             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1257                 is_throwaway_tag = 0;
1258         else
1259                 is_throwaway_tag = 1;
1260         free(tag_ref);
1261         return is_throwaway_tag;
1262 }
1263
1264 int cmd_merge(int argc, const char **argv, const char *prefix)
1265 {
1266         struct object_id result_tree, stash, head_oid;
1267         struct commit *head_commit;
1268         struct strbuf buf = STRBUF_INIT;
1269         int i, ret = 0, head_subsumed;
1270         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1271         struct commit_list *common = NULL;
1272         const char *best_strategy = NULL, *wt_strategy = NULL;
1273         struct commit_list *remoteheads, *p;
1274         void *branch_to_free;
1275         int orig_argc = argc;
1276
1277         if (argc == 2 && !strcmp(argv[1], "-h"))
1278                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1279
1280         prepare_repo_settings(the_repository);
1281         the_repository->settings.command_requires_full_index = 0;
1282
1283         /*
1284          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1285          * current branch.
1286          */
1287         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1288         if (branch)
1289                 skip_prefix(branch, "refs/heads/", &branch);
1290
1291         if (!pull_twohead) {
1292                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1293                 if (default_strategy && !strcmp(default_strategy, "ort"))
1294                         pull_twohead = "ort";
1295         }
1296
1297         init_diff_ui_defaults();
1298         git_config(git_merge_config, NULL);
1299
1300         if (!branch || is_null_oid(&head_oid))
1301                 head_commit = NULL;
1302         else
1303                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1304
1305         if (branch_mergeoptions)
1306                 parse_branch_merge_options(branch_mergeoptions);
1307         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1308                         builtin_merge_usage, 0);
1309         if (shortlog_len < 0)
1310                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1311
1312         if (verbosity < 0 && show_progress == -1)
1313                 show_progress = 0;
1314
1315         if (abort_current_merge) {
1316                 int nargc = 2;
1317                 const char *nargv[] = {"reset", "--merge", NULL};
1318                 struct strbuf stash_oid = STRBUF_INIT;
1319
1320                 if (orig_argc != 2)
1321                         usage_msg_opt(_("--abort expects no arguments"),
1322                               builtin_merge_usage, builtin_merge_options);
1323
1324                 if (!file_exists(git_path_merge_head(the_repository)))
1325                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1326
1327                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1328                     READ_ONELINER_SKIP_IF_EMPTY))
1329                         unlink(git_path_merge_autostash(the_repository));
1330
1331                 /* Invoke 'git reset --merge' */
1332                 ret = cmd_reset(nargc, nargv, prefix);
1333
1334                 if (stash_oid.len)
1335                         apply_autostash_oid(stash_oid.buf);
1336
1337                 strbuf_release(&stash_oid);
1338                 goto done;
1339         }
1340
1341         if (quit_current_merge) {
1342                 if (orig_argc != 2)
1343                         usage_msg_opt(_("--quit expects no arguments"),
1344                                       builtin_merge_usage,
1345                                       builtin_merge_options);
1346
1347                 remove_merge_branch_state(the_repository);
1348                 goto done;
1349         }
1350
1351         if (continue_current_merge) {
1352                 int nargc = 1;
1353                 const char *nargv[] = {"commit", NULL};
1354
1355                 if (orig_argc != 2)
1356                         usage_msg_opt(_("--continue expects no arguments"),
1357                               builtin_merge_usage, builtin_merge_options);
1358
1359                 if (!file_exists(git_path_merge_head(the_repository)))
1360                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1361
1362                 /* Invoke 'git commit' */
1363                 ret = cmd_commit(nargc, nargv, prefix);
1364                 goto done;
1365         }
1366
1367         if (read_cache_unmerged())
1368                 die_resolve_conflict("merge");
1369
1370         if (file_exists(git_path_merge_head(the_repository))) {
1371                 /*
1372                  * There is no unmerged entry, don't advise 'git
1373                  * add/rm <file>', just 'git commit'.
1374                  */
1375                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1376                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1377                                   "Please, commit your changes before you merge."));
1378                 else
1379                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1380         }
1381         if (ref_exists("CHERRY_PICK_HEAD")) {
1382                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1383                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1384                             "Please, commit your changes before you merge."));
1385                 else
1386                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1387         }
1388         resolve_undo_clear();
1389
1390         if (option_edit < 0)
1391                 option_edit = default_edit_option();
1392
1393         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1394
1395         if (verbosity < 0)
1396                 show_diffstat = 0;
1397
1398         if (squash) {
1399                 if (fast_forward == FF_NO)
1400                         die(_("You cannot combine --squash with --no-ff."));
1401                 if (option_commit > 0)
1402                         die(_("You cannot combine --squash with --commit."));
1403                 /*
1404                  * squash can now silently disable option_commit - this is not
1405                  * a problem as it is only overriding the default, not a user
1406                  * supplied option.
1407                  */
1408                 option_commit = 0;
1409         }
1410
1411         if (option_commit < 0)
1412                 option_commit = 1;
1413
1414         if (!argc) {
1415                 if (default_to_upstream)
1416                         argc = setup_with_upstream(&argv);
1417                 else
1418                         die(_("No commit specified and merge.defaultToUpstream not set."));
1419         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1420                 argv[0] = "@{-1}";
1421         }
1422
1423         if (!argc)
1424                 usage_with_options(builtin_merge_usage,
1425                         builtin_merge_options);
1426
1427         if (!head_commit) {
1428                 /*
1429                  * If the merged head is a valid one there is no reason
1430                  * to forbid "git merge" into a branch yet to be born.
1431                  * We do the same for "git pull".
1432                  */
1433                 struct object_id *remote_head_oid;
1434                 if (squash)
1435                         die(_("Squash commit into empty head not supported yet"));
1436                 if (fast_forward == FF_NO)
1437                         die(_("Non-fast-forward commit does not make sense into "
1438                             "an empty head"));
1439                 remoteheads = collect_parents(head_commit, &head_subsumed,
1440                                               argc, argv, NULL);
1441                 if (!remoteheads)
1442                         die(_("%s - not something we can merge"), argv[0]);
1443                 if (remoteheads->next)
1444                         die(_("Can merge only exactly one commit into empty head"));
1445
1446                 if (verify_signatures)
1447                         verify_merge_signature(remoteheads->item, verbosity,
1448                                                check_trust_level);
1449
1450                 remote_head_oid = &remoteheads->item->object.oid;
1451                 read_empty(remote_head_oid, 0);
1452                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1453                            UPDATE_REFS_DIE_ON_ERR);
1454                 goto done;
1455         }
1456
1457         /*
1458          * All the rest are the commits being merged; prepare
1459          * the standard merge summary message to be appended
1460          * to the given message.
1461          */
1462         remoteheads = collect_parents(head_commit, &head_subsumed,
1463                                       argc, argv, &merge_msg);
1464
1465         if (!head_commit || !argc)
1466                 usage_with_options(builtin_merge_usage,
1467                         builtin_merge_options);
1468
1469         if (verify_signatures) {
1470                 for (p = remoteheads; p; p = p->next) {
1471                         verify_merge_signature(p->item, verbosity,
1472                                                check_trust_level);
1473                 }
1474         }
1475
1476         strbuf_addstr(&buf, "merge");
1477         for (p = remoteheads; p; p = p->next)
1478                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1479         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1480         strbuf_reset(&buf);
1481
1482         for (p = remoteheads; p; p = p->next) {
1483                 struct commit *commit = p->item;
1484                 strbuf_addf(&buf, "GITHEAD_%s",
1485                             oid_to_hex(&commit->object.oid));
1486                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1487                 strbuf_reset(&buf);
1488                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1489                         fast_forward = FF_NO;
1490         }
1491
1492         if (!use_strategies && !pull_twohead &&
1493             remoteheads && !remoteheads->next) {
1494                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1495                 if (default_strategy)
1496                         append_strategy(get_strategy(default_strategy));
1497         }
1498         if (!use_strategies) {
1499                 if (!remoteheads)
1500                         ; /* already up-to-date */
1501                 else if (!remoteheads->next)
1502                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1503                 else
1504                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1505         }
1506
1507         for (i = 0; i < use_strategies_nr; i++) {
1508                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1509                         fast_forward = FF_NO;
1510                 if (use_strategies[i]->attr & NO_TRIVIAL)
1511                         allow_trivial = 0;
1512         }
1513
1514         if (!remoteheads)
1515                 ; /* already up-to-date */
1516         else if (!remoteheads->next)
1517                 common = get_merge_bases(head_commit, remoteheads->item);
1518         else {
1519                 struct commit_list *list = remoteheads;
1520                 commit_list_insert(head_commit, &list);
1521                 common = get_octopus_merge_bases(list);
1522                 free(list);
1523         }
1524
1525         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1526                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1527
1528         if (remoteheads && !common) {
1529                 /* No common ancestors found. */
1530                 if (!allow_unrelated_histories)
1531                         die(_("refusing to merge unrelated histories"));
1532                 /* otherwise, we need a real merge. */
1533         } else if (!remoteheads ||
1534                  (!remoteheads->next && !common->next &&
1535                   common->item == remoteheads->item)) {
1536                 /*
1537                  * If head can reach all the merge then we are up to date.
1538                  * but first the most common case of merging one remote.
1539                  */
1540                 finish_up_to_date();
1541                 goto done;
1542         } else if (fast_forward != FF_NO && !remoteheads->next &&
1543                         !common->next &&
1544                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1545                 /* Again the most common case of merging one remote. */
1546                 struct strbuf msg = STRBUF_INIT;
1547                 struct commit *commit;
1548
1549                 if (verbosity >= 0) {
1550                         printf(_("Updating %s..%s\n"),
1551                                find_unique_abbrev(&head_commit->object.oid,
1552                                                   DEFAULT_ABBREV),
1553                                find_unique_abbrev(&remoteheads->item->object.oid,
1554                                                   DEFAULT_ABBREV));
1555                 }
1556                 strbuf_addstr(&msg, "Fast-forward");
1557                 if (have_message)
1558                         strbuf_addstr(&msg,
1559                                 " (no commit created; -m option ignored)");
1560                 commit = remoteheads->item;
1561                 if (!commit) {
1562                         ret = 1;
1563                         goto done;
1564                 }
1565
1566                 if (autostash)
1567                         create_autostash(the_repository,
1568                                          git_path_merge_autostash(the_repository),
1569                                          "merge");
1570                 if (checkout_fast_forward(the_repository,
1571                                           &head_commit->object.oid,
1572                                           &commit->object.oid,
1573                                           overwrite_ignore)) {
1574                         apply_autostash(git_path_merge_autostash(the_repository));
1575                         ret = 1;
1576                         goto done;
1577                 }
1578
1579                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1580                 remove_merge_branch_state(the_repository);
1581                 strbuf_release(&msg);
1582                 goto done;
1583         } else if (!remoteheads->next && common->next)
1584                 ;
1585                 /*
1586                  * We are not doing octopus and not fast-forward.  Need
1587                  * a real merge.
1588                  */
1589         else if (!remoteheads->next && !common->next && option_commit) {
1590                 /*
1591                  * We are not doing octopus, not fast-forward, and have
1592                  * only one common.
1593                  */
1594                 refresh_cache(REFRESH_QUIET);
1595                 if (allow_trivial && fast_forward != FF_ONLY) {
1596                         /* See if it is really trivial. */
1597                         git_committer_info(IDENT_STRICT);
1598                         printf(_("Trying really trivial in-index merge...\n"));
1599                         if (!read_tree_trivial(&common->item->object.oid,
1600                                                &head_commit->object.oid,
1601                                                &remoteheads->item->object.oid)) {
1602                                 ret = merge_trivial(head_commit, remoteheads);
1603                                 goto done;
1604                         }
1605                         printf(_("Nope.\n"));
1606                 }
1607         } else {
1608                 /*
1609                  * An octopus.  If we can reach all the remote we are up
1610                  * to date.
1611                  */
1612                 int up_to_date = 1;
1613                 struct commit_list *j;
1614
1615                 for (j = remoteheads; j; j = j->next) {
1616                         struct commit_list *common_one;
1617
1618                         /*
1619                          * Here we *have* to calculate the individual
1620                          * merge_bases again, otherwise "git merge HEAD^
1621                          * HEAD^^" would be missed.
1622                          */
1623                         common_one = get_merge_bases(head_commit, j->item);
1624                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1625                                 up_to_date = 0;
1626                                 break;
1627                         }
1628                 }
1629                 if (up_to_date) {
1630                         finish_up_to_date();
1631                         goto done;
1632                 }
1633         }
1634
1635         if (fast_forward == FF_ONLY)
1636                 die_ff_impossible();
1637
1638         if (autostash)
1639                 create_autostash(the_repository,
1640                                  git_path_merge_autostash(the_repository),
1641                                  "merge");
1642
1643         /* We are going to make a new commit. */
1644         git_committer_info(IDENT_STRICT);
1645
1646         /*
1647          * At this point, we need a real merge.  No matter what strategy
1648          * we use, it would operate on the index, possibly affecting the
1649          * working tree, and when resolved cleanly, have the desired
1650          * tree in the index -- this means that the index must be in
1651          * sync with the head commit.  The strategies are responsible
1652          * to ensure this.
1653          */
1654         if (use_strategies_nr == 1 ||
1655             /*
1656              * Stash away the local changes so that we can try more than one.
1657              */
1658             save_state(&stash))
1659                 oidclr(&stash);
1660
1661         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1662                 int ret, cnt;
1663                 if (i) {
1664                         printf(_("Rewinding the tree to pristine...\n"));
1665                         restore_state(&head_commit->object.oid, &stash);
1666                 }
1667                 if (use_strategies_nr != 1)
1668                         printf(_("Trying merge strategy %s...\n"),
1669                                 use_strategies[i]->name);
1670                 /*
1671                  * Remember which strategy left the state in the working
1672                  * tree.
1673                  */
1674                 wt_strategy = use_strategies[i]->name;
1675
1676                 ret = try_merge_strategy(use_strategies[i]->name,
1677                                          common, remoteheads,
1678                                          head_commit);
1679                 /*
1680                  * The backend exits with 1 when conflicts are
1681                  * left to be resolved, with 2 when it does not
1682                  * handle the given merge at all.
1683                  */
1684                 if (ret < 2) {
1685                         if (!ret) {
1686                                 if (option_commit) {
1687                                         /* Automerge succeeded. */
1688                                         automerge_was_ok = 1;
1689                                         break;
1690                                 }
1691                                 merge_was_ok = 1;
1692                         }
1693                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1694                         if (best_cnt <= 0 || cnt <= best_cnt) {
1695                                 best_strategy = use_strategies[i]->name;
1696                                 best_cnt = cnt;
1697                         }
1698                 }
1699         }
1700
1701         /*
1702          * If we have a resulting tree, that means the strategy module
1703          * auto resolved the merge cleanly.
1704          */
1705         if (automerge_was_ok) {
1706                 ret = finish_automerge(head_commit, head_subsumed,
1707                                        common, remoteheads,
1708                                        &result_tree, wt_strategy);
1709                 goto done;
1710         }
1711
1712         /*
1713          * Pick the result from the best strategy and have the user fix
1714          * it up.
1715          */
1716         if (!best_strategy) {
1717                 restore_state(&head_commit->object.oid, &stash);
1718                 if (use_strategies_nr > 1)
1719                         fprintf(stderr,
1720                                 _("No merge strategy handled the merge.\n"));
1721                 else
1722                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1723                                 use_strategies[0]->name);
1724                 apply_autostash(git_path_merge_autostash(the_repository));
1725                 ret = 2;
1726                 goto done;
1727         } else if (best_strategy == wt_strategy)
1728                 ; /* We already have its result in the working tree. */
1729         else {
1730                 printf(_("Rewinding the tree to pristine...\n"));
1731                 restore_state(&head_commit->object.oid, &stash);
1732                 printf(_("Using the %s strategy to prepare resolving by hand.\n"),
1733                         best_strategy);
1734                 try_merge_strategy(best_strategy, common, remoteheads,
1735                                    head_commit);
1736         }
1737
1738         if (squash) {
1739                 finish(head_commit, remoteheads, NULL, NULL);
1740
1741                 git_test_write_commit_graph_or_die();
1742         } else
1743                 write_merge_state(remoteheads);
1744
1745         if (merge_was_ok)
1746                 fprintf(stderr, _("Automatic merge went well; "
1747                         "stopped before committing as requested\n"));
1748         else
1749                 ret = suggest_conflicts();
1750
1751 done:
1752         strbuf_release(&buf);
1753         free(branch_to_free);
1754         return ret;
1755 }