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