git.oblomov.eu Git - git/blob - builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "refs.h"
  18 #include "refspec.h"
  19 #include "commit.h"
  20 #include "diffcore.h"
  21 #include "revision.h"
  22 #include "unpack-trees.h"
  23 #include "cache-tree.h"
  24 #include "dir.h"
  25 #include "utf8.h"
  26 #include "log-tree.h"
  27 #include "color.h"
  28 #include "rerere.h"
  29 #include "help.h"
  30 #include "merge-recursive.h"
  31 #include "resolve-undo.h"
  32 #include "remote.h"
  33 #include "fmt-merge-msg.h"
  34 #include "gpg-interface.h"
  35 #include "sequencer.h"
  36 #include "string-list.h"
  37 #include "packfile.h"
  38 #include "tag.h"
  39 #include "alias.h"
  40 #include "branch.h"
  41 #include "commit-reach.h"
  42 #include "wt-status.h"
  43 #include "commit-graph.h"
  44
  45 #define DEFAULT_TWOHEAD (1<<0)
  46 #define DEFAULT_OCTOPUS (1<<1)
  47 #define NO_FAST_FORWARD (1<<2)
  48 #define NO_TRIVIAL      (1<<3)
  49
  50 struct strategy {
  51         const char *name;
  52         unsigned attr;
  53 };
  54
  55 static const char * const builtin_merge_usage[] = {
  56         N_("git merge [<options>] [<commit>...]"),
  57         N_("git merge --abort"),
  58         N_("git merge --continue"),
  59         NULL
  60 };
  61
  62 static int show_diffstat = 1, shortlog_len = -1, squash;
  63 static int option_commit = -1;
  64 static int option_edit = -1;
  65 static int allow_trivial = 1, have_message, verify_signatures;
  66 static int check_trust_level = 1;
  67 static int overwrite_ignore = 1;
  68 static struct strbuf merge_msg = STRBUF_INIT;
  69 static struct strategy **use_strategies;
  70 static size_t use_strategies_nr, use_strategies_alloc;
  71 static const char **xopts;
  72 static size_t xopts_nr, xopts_alloc;
  73 static const char *branch;
  74 static char *branch_mergeoptions;
  75 static int verbosity;
  76 static int allow_rerere_auto;
  77 static int abort_current_merge;
  78 static int quit_current_merge;
  79 static int continue_current_merge;
  80 static int allow_unrelated_histories;
  81 static int show_progress = -1;
  82 static int default_to_upstream = 1;
  83 static int signoff;
  84 static const char *sign_commit;
  85 static int autostash;
  86 static int no_verify;
  87
  88 static struct strategy all_strategy[] = {
  89         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  90         { "octopus",    DEFAULT_OCTOPUS },
  91         { "resolve",    0 },
  92         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  93         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  94 };
  95
  96 static const char *pull_twohead, *pull_octopus;
  97
  98 enum ff_type {
  99         FF_NO,
 100         FF_ALLOW,
 101         FF_ONLY
 102 };
 103
 104 static enum ff_type fast_forward = FF_ALLOW;
 105
 106 static const char *cleanup_arg;
 107 static enum commit_msg_cleanup_mode cleanup_mode;
 108
 109 static int option_parse_message(const struct option *opt,
 110                                 const char *arg, int unset)
 111 {
 112         struct strbuf *buf = opt->value;
 113
 114         if (unset)
 115                 strbuf_setlen(buf, 0);
 116         else if (arg) {
 117                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 118                 have_message = 1;
 119         } else
 120                 return error(_("switch `m' requires a value"));
 121         return 0;
 122 }
 123
 124 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 125                                                  const struct option *opt,
 126                                                  const char *arg_not_used,
 127                                                  int unset)
 128 {
 129         struct strbuf *buf = opt->value;
 130         const char *arg;
 131
 132         BUG_ON_OPT_ARG(arg_not_used);
 133         if (unset)
 134                 BUG("-F cannot be negated");
 135
 136         if (ctx->opt) {
 137                 arg = ctx->opt;
 138                 ctx->opt = NULL;
 139         } else if (ctx->argc > 1) {
 140                 ctx->argc--;
 141                 arg = *++ctx->argv;
 142         } else
 143                 return error(_("option `%s' requires a value"), opt->long_name);
 144
 145         if (buf->len)
 146                 strbuf_addch(buf, '\n');
 147         if (ctx->prefix && !is_absolute_path(arg))
 148                 arg = prefix_filename(ctx->prefix, arg);
 149         if (strbuf_read_file(buf, arg, 0) < 0)
 150                 return error(_("could not read file '%s'"), arg);
 151         have_message = 1;
 152
 153         return 0;
 154 }
 155
 156 static struct strategy *get_strategy(const char *name)
 157 {
 158         int i;
 159         struct strategy *ret;
 160         static struct cmdnames main_cmds, other_cmds;
 161         static int loaded;
 162
 163         if (!name)
 164                 return NULL;
 165
 166         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 167                 if (!strcmp(name, all_strategy[i].name))
 168                         return &all_strategy[i];
 169
 170         if (!loaded) {
 171                 struct cmdnames not_strategies;
 172                 loaded = 1;
 173
 174                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 175                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 176                 for (i = 0; i < main_cmds.cnt; i++) {
 177                         int j, found = 0;
 178                         struct cmdname *ent = main_cmds.names[i];
 179                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 180                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 181                                                 && !all_strategy[j].name[ent->len])
 182                                         found = 1;
 183                         if (!found)
 184                                 add_cmdname(&not_strategies, ent->name, ent->len);
 185                 }
 186                 exclude_cmds(&main_cmds, &not_strategies);
 187         }
 188         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 189                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 190                 fprintf(stderr, _("Available strategies are:"));
 191                 for (i = 0; i < main_cmds.cnt; i++)
 192                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 193                 fprintf(stderr, ".\n");
 194                 if (other_cmds.cnt) {
 195                         fprintf(stderr, _("Available custom strategies are:"));
 196                         for (i = 0; i < other_cmds.cnt; i++)
 197                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 198                         fprintf(stderr, ".\n");
 199                 }
 200                 exit(1);
 201         }
 202
 203         ret = xcalloc(1, sizeof(struct strategy));
 204         ret->name = xstrdup(name);
 205         ret->attr = NO_TRIVIAL;
 206         return ret;
 207 }
 208
 209 static void append_strategy(struct strategy *s)
 210 {
 211         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 212         use_strategies[use_strategies_nr++] = s;
 213 }
 214
 215 static int option_parse_strategy(const struct option *opt,
 216                                  const char *name, int unset)
 217 {
 218         if (unset)
 219                 return 0;
 220
 221         append_strategy(get_strategy(name));
 222         return 0;
 223 }
 224
 225 static int option_parse_x(const struct option *opt,
 226                           const char *arg, int unset)
 227 {
 228         if (unset)
 229                 return 0;
 230
 231         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 232         xopts[xopts_nr++] = xstrdup(arg);
 233         return 0;
 234 }
 235
 236 static int option_parse_n(const struct option *opt,
 237                           const char *arg, int unset)
 238 {
 239         BUG_ON_OPT_ARG(arg);
 240         show_diffstat = unset;
 241         return 0;
 242 }
 243
 244 static struct option builtin_merge_options[] = {
 245         OPT_CALLBACK_F('n', NULL, NULL, NULL,
 246                 N_("do not show a diffstat at the end of the merge"),
 247                 PARSE_OPT_NOARG, option_parse_n),
 248         OPT_BOOL(0, "stat", &show_diffstat,
 249                 N_("show a diffstat at the end of the merge")),
 250         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 251         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 252           N_("add (at most <n>) entries from shortlog to merge commit message"),
 253           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 254         OPT_BOOL(0, "squash", &squash,
 255                 N_("create a single commit instead of doing a merge")),
 256         OPT_BOOL(0, "commit", &option_commit,
 257                 N_("perform a commit if the merge succeeds (default)")),
 258         OPT_BOOL('e', "edit", &option_edit,
 259                 N_("edit message before committing")),
 260         OPT_CLEANUP(&cleanup_arg),
 261         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 262         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 263                       N_("abort if fast-forward is not possible"),
 264                       FF_ONLY, PARSE_OPT_NONEG),
 265         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 266         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 267                 N_("verify that the named commit has a valid GPG signature")),
 268         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 269                 N_("merge strategy to use"), option_parse_strategy),
 270         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 271                 N_("option for selected merge strategy"), option_parse_x),
 272         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 273                 N_("merge commit message (for a non-fast-forward merge)"),
 274                 option_parse_message),
 275         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 276                 N_("read message from file"), PARSE_OPT_NONEG,
 277                 NULL, 0, option_read_message },
 278         OPT__VERBOSITY(&verbosity),
 279         OPT_BOOL(0, "abort", &abort_current_merge,
 280                 N_("abort the current in-progress merge")),
 281         OPT_BOOL(0, "quit", &quit_current_merge,
 282                 N_("--abort but leave index and working tree alone")),
 283         OPT_BOOL(0, "continue", &continue_current_merge,
 284                 N_("continue the current in-progress merge")),
 285         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 286                  N_("allow merging unrelated histories")),
 287         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 288         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 289           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 290         OPT_AUTOSTASH(&autostash),
 291         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 292         OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
 293         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 294         OPT_END()
 295 };
 296
 297 static int save_state(struct object_id *stash)
 298 {
 299         int len;
 300         struct child_process cp = CHILD_PROCESS_INIT;
 301         struct strbuf buffer = STRBUF_INIT;
 302         const char *argv[] = {"stash", "create", NULL};
 303         int rc = -1;
 304
 305         cp.argv = argv;
 306         cp.out = -1;
 307         cp.git_cmd = 1;
 308
 309         if (start_command(&cp))
 310                 die(_("could not run stash."));
 311         len = strbuf_read(&buffer, cp.out, 1024);
 312         close(cp.out);
 313
 314         if (finish_command(&cp) || len < 0)
 315                 die(_("stash failed"));
 316         else if (!len)          /* no changes */
 317                 goto out;
 318         strbuf_setlen(&buffer, buffer.len-1);
 319         if (get_oid(buffer.buf, stash))
 320                 die(_("not a valid object: %s"), buffer.buf);
 321         rc = 0;
 322 out:
 323         strbuf_release(&buffer);
 324         return rc;
 325 }
 326
 327 static void read_empty(const struct object_id *oid, int verbose)
 328 {
 329         int i = 0;
 330         const char *args[7];
 331
 332         args[i++] = "read-tree";
 333         if (verbose)
 334                 args[i++] = "-v";
 335         args[i++] = "-m";
 336         args[i++] = "-u";
 337         args[i++] = empty_tree_oid_hex();
 338         args[i++] = oid_to_hex(oid);
 339         args[i] = NULL;
 340
 341         if (run_command_v_opt(args, RUN_GIT_CMD))
 342                 die(_("read-tree failed"));
 343 }
 344
 345 static void reset_hard(const struct object_id *oid, int verbose)
 346 {
 347         int i = 0;
 348         const char *args[6];
 349
 350         args[i++] = "read-tree";
 351         if (verbose)
 352                 args[i++] = "-v";
 353         args[i++] = "--reset";
 354         args[i++] = "-u";
 355         args[i++] = oid_to_hex(oid);
 356         args[i] = NULL;
 357
 358         if (run_command_v_opt(args, RUN_GIT_CMD))
 359                 die(_("read-tree failed"));
 360 }
 361
 362 static void restore_state(const struct object_id *head,
 363                           const struct object_id *stash)
 364 {
 365         struct strbuf sb = STRBUF_INIT;
 366         const char *args[] = { "stash", "apply", NULL, NULL };
 367
 368         if (is_null_oid(stash))
 369                 return;
 370
 371         reset_hard(head, 1);
 372
 373         args[2] = oid_to_hex(stash);
 374
 375         /*
 376          * It is OK to ignore error here, for example when there was
 377          * nothing to restore.
 378          */
 379         run_command_v_opt(args, RUN_GIT_CMD);
 380
 381         strbuf_release(&sb);
 382         refresh_cache(REFRESH_QUIET);
 383 }
 384
 385 /* This is called when no merge was necessary. */
 386 static void finish_up_to_date(const char *msg)
 387 {
 388         if (verbosity >= 0)
 389                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 390         remove_merge_branch_state(the_repository);
 391 }
 392
 393 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 394 {
 395         struct rev_info rev;
 396         struct strbuf out = STRBUF_INIT;
 397         struct commit_list *j;
 398         struct pretty_print_context ctx = {0};
 399
 400         printf(_("Squash commit -- not updating HEAD\n"));
 401
 402         repo_init_revisions(the_repository, &rev, NULL);
 403         rev.ignore_merges = 1;
 404         rev.commit_format = CMIT_FMT_MEDIUM;
 405
 406         commit->object.flags |= UNINTERESTING;
 407         add_pending_object(&rev, &commit->object, NULL);
 408
 409         for (j = remoteheads; j; j = j->next)
 410                 add_pending_object(&rev, &j->item->object, NULL);
 411
 412         setup_revisions(0, NULL, &rev, NULL);
 413         if (prepare_revision_walk(&rev))
 414                 die(_("revision walk setup failed"));
 415
 416         ctx.abbrev = rev.abbrev;
 417         ctx.date_mode = rev.date_mode;
 418         ctx.fmt = rev.commit_format;
 419
 420         strbuf_addstr(&out, "Squashed commit of the following:\n");
 421         while ((commit = get_revision(&rev)) != NULL) {
 422                 strbuf_addch(&out, '\n');
 423                 strbuf_addf(&out, "commit %s\n",
 424                         oid_to_hex(&commit->object.oid));
 425                 pretty_print_commit(&ctx, commit, &out);
 426         }
 427         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 428         strbuf_release(&out);
 429 }
 430
 431 static void finish(struct commit *head_commit,
 432                    struct commit_list *remoteheads,
 433                    const struct object_id *new_head, const char *msg)
 434 {
 435         struct strbuf reflog_message = STRBUF_INIT;
 436         const struct object_id *head = &head_commit->object.oid;
 437
 438         if (!msg)
 439                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 440         else {
 441                 if (verbosity >= 0)
 442                         printf("%s\n", msg);
 443                 strbuf_addf(&reflog_message, "%s: %s",
 444                         getenv("GIT_REFLOG_ACTION"), msg);
 445         }
 446         if (squash) {
 447                 squash_message(head_commit, remoteheads);
 448         } else {
 449                 if (verbosity >= 0 && !merge_msg.len)
 450                         printf(_("No merge message -- not updating HEAD\n"));
 451                 else {
 452                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 453                                    0, UPDATE_REFS_DIE_ON_ERR);
 454                         /*
 455                          * We ignore errors in 'gc --auto', since the
 456                          * user should see them.
 457                          */
 458                         close_object_store(the_repository->objects);
 459                         run_auto_maintenance(verbosity < 0);
 460                 }
 461         }
 462         if (new_head && show_diffstat) {
 463                 struct diff_options opts;
 464                 repo_diff_setup(the_repository, &opts);
 465                 opts.stat_width = -1; /* use full terminal width */
 466                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 467                 opts.output_format |=
 468                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 469                 opts.detect_rename = DIFF_DETECT_RENAME;
 470                 diff_setup_done(&opts);
 471                 diff_tree_oid(head, new_head, "", &opts);
 472                 diffcore_std(&opts);
 473                 diff_flush(&opts);
 474         }
 475
 476         /* Run a post-merge hook */
 477         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 478
 479         apply_autostash(git_path_merge_autostash(the_repository));
 480         strbuf_release(&reflog_message);
 481 }
 482
 483 /* Get the name for the merge commit's message. */
 484 static void merge_name(const char *remote, struct strbuf *msg)
 485 {
 486         struct commit *remote_head;
 487         struct object_id branch_head;
 488         struct strbuf buf = STRBUF_INIT;
 489         struct strbuf bname = STRBUF_INIT;
 490         struct merge_remote_desc *desc;
 491         const char *ptr;
 492         char *found_ref;
 493         int len, early;
 494
 495         strbuf_branchname(&bname, remote, 0);
 496         remote = bname.buf;
 497
 498         oidclr(&branch_head);
 499         remote_head = get_merge_parent(remote);
 500         if (!remote_head)
 501                 die(_("'%s' does not point to a commit"), remote);
 502
 503         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
 504                 if (starts_with(found_ref, "refs/heads/")) {
 505                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 506                                     oid_to_hex(&branch_head), remote);
 507                         goto cleanup;
 508                 }
 509                 if (starts_with(found_ref, "refs/tags/")) {
 510                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 511                                     oid_to_hex(&branch_head), remote);
 512                         goto cleanup;
 513                 }
 514                 if (starts_with(found_ref, "refs/remotes/")) {
 515                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 516                                     oid_to_hex(&branch_head), remote);
 517                         goto cleanup;
 518                 }
 519         }
 520
 521         /* See if remote matches <name>^^^.. or <name>~<number> */
 522         for (len = 0, ptr = remote + strlen(remote);
 523              remote < ptr && ptr[-1] == '^';
 524              ptr--)
 525                 len++;
 526         if (len)
 527                 early = 1;
 528         else {
 529                 early = 0;
 530                 ptr = strrchr(remote, '~');
 531                 if (ptr) {
 532                         int seen_nonzero = 0;
 533
 534                         len++; /* count ~ */
 535                         while (*++ptr && isdigit(*ptr)) {
 536                                 seen_nonzero |= (*ptr != '0');
 537                                 len++;
 538                         }
 539                         if (*ptr)
 540                                 len = 0; /* not ...~<number> */
 541                         else if (seen_nonzero)
 542                                 early = 1;
 543                         else if (len == 1)
 544                                 early = 1; /* "name~" is "name~1"! */
 545                 }
 546         }
 547         if (len) {
 548                 struct strbuf truname = STRBUF_INIT;
 549                 strbuf_addf(&truname, "refs/heads/%s", remote);
 550                 strbuf_setlen(&truname, truname.len - len);
 551                 if (ref_exists(truname.buf)) {
 552                         strbuf_addf(msg,
 553                                     "%s\t\tbranch '%s'%s of .\n",
 554                                     oid_to_hex(&remote_head->object.oid),
 555                                     truname.buf + 11,
 556                                     (early ? " (early part)" : ""));
 557                         strbuf_release(&truname);
 558                         goto cleanup;
 559                 }
 560                 strbuf_release(&truname);
 561         }
 562
 563         desc = merge_remote_util(remote_head);
 564         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 565                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 566                             oid_to_hex(&desc->obj->oid),
 567                             type_name(desc->obj->type),
 568                             remote);
 569                 goto cleanup;
 570         }
 571
 572         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 573                 oid_to_hex(&remote_head->object.oid), remote);
 574 cleanup:
 575         strbuf_release(&buf);
 576         strbuf_release(&bname);
 577 }
 578
 579 static void parse_branch_merge_options(char *bmo)
 580 {
 581         const char **argv;
 582         int argc;
 583
 584         if (!bmo)
 585                 return;
 586         argc = split_cmdline(bmo, &argv);
 587         if (argc < 0)
 588                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 589                     _(split_cmdline_strerror(argc)));
 590         REALLOC_ARRAY(argv, argc + 2);
 591         MOVE_ARRAY(argv + 1, argv, argc + 1);
 592         argc++;
 593         argv[0] = "branch.*.mergeoptions";
 594         parse_options(argc, argv, NULL, builtin_merge_options,
 595                       builtin_merge_usage, 0);
 596         free(argv);
 597 }
 598
 599 static int git_merge_config(const char *k, const char *v, void *cb)
 600 {
 601         int status;
 602         const char *str;
 603
 604         if (branch &&
 605             skip_prefix(k, "branch.", &str) &&
 606             skip_prefix(str, branch, &str) &&
 607             !strcmp(str, ".mergeoptions")) {
 608                 free(branch_mergeoptions);
 609                 branch_mergeoptions = xstrdup(v);
 610                 return 0;
 611         }
 612
 613         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 614                 show_diffstat = git_config_bool(k, v);
 615         else if (!strcmp(k, "merge.verifysignatures"))
 616                 verify_signatures = git_config_bool(k, v);
 617         else if (!strcmp(k, "pull.twohead"))
 618                 return git_config_string(&pull_twohead, k, v);
 619         else if (!strcmp(k, "pull.octopus"))
 620                 return git_config_string(&pull_octopus, k, v);
 621         else if (!strcmp(k, "commit.cleanup"))
 622                 return git_config_string(&cleanup_arg, k, v);
 623         else if (!strcmp(k, "merge.ff")) {
 624                 int boolval = git_parse_maybe_bool(v);
 625                 if (0 <= boolval) {
 626                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 627                 } else if (v && !strcmp(v, "only")) {
 628                         fast_forward = FF_ONLY;
 629                 } /* do not barf on values from future versions of git */
 630                 return 0;
 631         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 632                 default_to_upstream = git_config_bool(k, v);
 633                 return 0;
 634         } else if (!strcmp(k, "commit.gpgsign")) {
 635                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 636                 return 0;
 637         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 638                 check_trust_level = 0;
 639         } else if (!strcmp(k, "merge.autostash")) {
 640                 autostash = git_config_bool(k, v);
 641                 return 0;
 642         }
 643
 644         status = fmt_merge_msg_config(k, v, cb);
 645         if (status)
 646                 return status;
 647         status = git_gpg_config(k, v, NULL);
 648         if (status)
 649                 return status;
 650         return git_diff_ui_config(k, v, cb);
 651 }
 652
 653 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 654                              struct object_id *one)
 655 {
 656         int i, nr_trees = 0;
 657         struct tree *trees[MAX_UNPACK_TREES];
 658         struct tree_desc t[MAX_UNPACK_TREES];
 659         struct unpack_trees_options opts;
 660
 661         memset(&opts, 0, sizeof(opts));
 662         opts.head_idx = 2;
 663         opts.src_index = &the_index;
 664         opts.dst_index = &the_index;
 665         opts.update = 1;
 666         opts.verbose_update = 1;
 667         opts.trivial_merges_only = 1;
 668         opts.merge = 1;
 669         trees[nr_trees] = parse_tree_indirect(common);
 670         if (!trees[nr_trees++])
 671                 return -1;
 672         trees[nr_trees] = parse_tree_indirect(head);
 673         if (!trees[nr_trees++])
 674                 return -1;
 675         trees[nr_trees] = parse_tree_indirect(one);
 676         if (!trees[nr_trees++])
 677                 return -1;
 678         opts.fn = threeway_merge;
 679         cache_tree_free(&active_cache_tree);
 680         for (i = 0; i < nr_trees; i++) {
 681                 parse_tree(trees[i]);
 682                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 683         }
 684         if (unpack_trees(nr_trees, t, &opts))
 685                 return -1;
 686         return 0;
 687 }
 688
 689 static void write_tree_trivial(struct object_id *oid)
 690 {
 691         if (write_cache_as_tree(oid, 0, NULL))
 692                 die(_("git write-tree failed to write a tree"));
 693 }
 694
 695 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 696                               struct commit_list *remoteheads,
 697                               struct commit *head)
 698 {
 699         const char *head_arg = "HEAD";
 700
 701         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 702                 return error(_("Unable to write index."));
 703
 704         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 705                 struct lock_file lock = LOCK_INIT;
 706                 int clean, x;
 707                 struct commit *result;
 708                 struct commit_list *reversed = NULL;
 709                 struct merge_options o;
 710                 struct commit_list *j;
 711
 712                 if (remoteheads->next) {
 713                         error(_("Not handling anything other than two heads merge."));
 714                         return 2;
 715                 }
 716
 717                 init_merge_options(&o, the_repository);
 718                 if (!strcmp(strategy, "subtree"))
 719                         o.subtree_shift = "";
 720
 721                 o.show_rename_progress =
 722                         show_progress == -1 ? isatty(2) : show_progress;
 723
 724                 for (x = 0; x < xopts_nr; x++)
 725                         if (parse_merge_opt(&o, xopts[x]))
 726                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 727
 728                 o.branch1 = head_arg;
 729                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 730
 731                 for (j = common; j; j = j->next)
 732                         commit_list_insert(j->item, &reversed);
 733
 734                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 735                 clean = merge_recursive(&o, head,
 736                                 remoteheads->item, reversed, &result);
 737                 if (clean < 0)
 738                         exit(128);
 739                 if (write_locked_index(&the_index, &lock,
 740                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 741                         die(_("unable to write %s"), get_index_file());
 742                 return clean ? 0 : 1;
 743         } else {
 744                 return try_merge_command(the_repository,
 745                                          strategy, xopts_nr, xopts,
 746                                          common, head_arg, remoteheads);
 747         }
 748 }
 749
 750 static void count_diff_files(struct diff_queue_struct *q,
 751                              struct diff_options *opt, void *data)
 752 {
 753         int *count = data;
 754
 755         (*count) += q->nr;
 756 }
 757
 758 static int count_unmerged_entries(void)
 759 {
 760         int i, ret = 0;
 761
 762         for (i = 0; i < active_nr; i++)
 763                 if (ce_stage(active_cache[i]))
 764                         ret++;
 765
 766         return ret;
 767 }
 768
 769 static void add_strategies(const char *string, unsigned attr)
 770 {
 771         int i;
 772
 773         if (string) {
 774                 struct string_list list = STRING_LIST_INIT_DUP;
 775                 struct string_list_item *item;
 776                 string_list_split(&list, string, ' ', -1);
 777                 for_each_string_list_item(item, &list)
 778                         append_strategy(get_strategy(item->string));
 779                 string_list_clear(&list, 0);
 780                 return;
 781         }
 782         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 783                 if (all_strategy[i].attr & attr)
 784                         append_strategy(&all_strategy[i]);
 785
 786 }
 787
 788 static void read_merge_msg(struct strbuf *msg)
 789 {
 790         const char *filename = git_path_merge_msg(the_repository);
 791         strbuf_reset(msg);
 792         if (strbuf_read_file(msg, filename, 0) < 0)
 793                 die_errno(_("Could not read from '%s'"), filename);
 794 }
 795
 796 static void write_merge_state(struct commit_list *);
 797 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 798 {
 799         if (err_msg)
 800                 error("%s", err_msg);
 801         fprintf(stderr,
 802                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 803         write_merge_state(remoteheads);
 804         exit(1);
 805 }
 806
 807 static const char merge_editor_comment[] =
 808 N_("Please enter a commit message to explain why this merge is necessary,\n"
 809    "especially if it merges an updated upstream into a topic branch.\n"
 810    "\n");
 811
 812 static const char scissors_editor_comment[] =
 813 N_("An empty message aborts the commit.\n");
 814
 815 static const char no_scissors_editor_comment[] =
 816 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 817    "the commit.\n");
 818
 819 static void write_merge_heads(struct commit_list *);
 820 static void prepare_to_commit(struct commit_list *remoteheads)
 821 {
 822         struct strbuf msg = STRBUF_INIT;
 823         const char *index_file = get_index_file();
 824
 825         if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
 826                 abort_commit(remoteheads, NULL);
 827         /*
 828          * Re-read the index as pre-merge-commit hook could have updated it,
 829          * and write it out as a tree.  We must do this before we invoke
 830          * the editor and after we invoke run_status above.
 831          */
 832         if (find_hook("pre-merge-commit"))
 833                 discard_cache();
 834         read_cache_from(index_file);
 835         strbuf_addbuf(&msg, &merge_msg);
 836         if (squash)
 837                 BUG("the control must not reach here under --squash");
 838         if (0 < option_edit) {
 839                 strbuf_addch(&msg, '\n');
 840                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 841                         wt_status_append_cut_line(&msg);
 842                         strbuf_commented_addf(&msg, "\n");
 843                 }
 844                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 845                 strbuf_commented_addf(&msg, _(cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS ?
 846                         scissors_editor_comment :
 847                         no_scissors_editor_comment), comment_line_char);
 848         }
 849         if (signoff)
 850                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 851         write_merge_heads(remoteheads);
 852         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 853         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 854                             git_path_merge_msg(the_repository), "merge", NULL))
 855                 abort_commit(remoteheads, NULL);
 856         if (0 < option_edit) {
 857                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 858                         abort_commit(remoteheads, NULL);
 859         }
 860
 861         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 862                                           "commit-msg",
 863                                           git_path_merge_msg(the_repository), NULL))
 864                 abort_commit(remoteheads, NULL);
 865
 866         read_merge_msg(&msg);
 867         cleanup_message(&msg, cleanup_mode, 0);
 868         if (!msg.len)
 869                 abort_commit(remoteheads, _("Empty commit message."));
 870         strbuf_release(&merge_msg);
 871         strbuf_addbuf(&merge_msg, &msg);
 872         strbuf_release(&msg);
 873 }
 874
 875 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 876 {
 877         struct object_id result_tree, result_commit;
 878         struct commit_list *parents, **pptr = &parents;
 879
 880         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 881                 return error(_("Unable to write index."));
 882
 883         write_tree_trivial(&result_tree);
 884         printf(_("Wonderful.\n"));
 885         pptr = commit_list_append(head, pptr);
 886         pptr = commit_list_append(remoteheads->item, pptr);
 887         prepare_to_commit(remoteheads);
 888         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 889                         &result_commit, NULL, sign_commit))
 890                 die(_("failed to write commit object"));
 891         finish(head, remoteheads, &result_commit, "In-index merge");
 892         remove_merge_branch_state(the_repository);
 893         return 0;
 894 }
 895
 896 static int finish_automerge(struct commit *head,
 897                             int head_subsumed,
 898                             struct commit_list *common,
 899                             struct commit_list *remoteheads,
 900                             struct object_id *result_tree,
 901                             const char *wt_strategy)
 902 {
 903         struct commit_list *parents = NULL;
 904         struct strbuf buf = STRBUF_INIT;
 905         struct object_id result_commit;
 906
 907         write_tree_trivial(result_tree);
 908         free_commit_list(common);
 909         parents = remoteheads;
 910         if (!head_subsumed || fast_forward == FF_NO)
 911                 commit_list_insert(head, &parents);
 912         prepare_to_commit(remoteheads);
 913         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 914                         &result_commit, NULL, sign_commit))
 915                 die(_("failed to write commit object"));
 916         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 917         finish(head, remoteheads, &result_commit, buf.buf);
 918         strbuf_release(&buf);
 919         remove_merge_branch_state(the_repository);
 920         return 0;
 921 }
 922
 923 static int suggest_conflicts(void)
 924 {
 925         const char *filename;
 926         FILE *fp;
 927         struct strbuf msgbuf = STRBUF_INIT;
 928
 929         filename = git_path_merge_msg(the_repository);
 930         fp = xfopen(filename, "a");
 931
 932         /*
 933          * We can't use cleanup_mode because if we're not using the editor,
 934          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 935          * though the message is meant to be processed later by git-commit.
 936          * Thus, we will get the cleanup mode which is returned when we _are_
 937          * using an editor.
 938          */
 939         append_conflicts_hint(&the_index, &msgbuf,
 940                               get_cleanup_mode(cleanup_arg, 1));
 941         fputs(msgbuf.buf, fp);
 942         strbuf_release(&msgbuf);
 943         fclose(fp);
 944         repo_rerere(the_repository, allow_rerere_auto);
 945         printf(_("Automatic merge failed; "
 946                         "fix conflicts and then commit the result.\n"));
 947         return 1;
 948 }
 949
 950 static int evaluate_result(void)
 951 {
 952         int cnt = 0;
 953         struct rev_info rev;
 954
 955         /* Check how many files differ. */
 956         repo_init_revisions(the_repository, &rev, "");
 957         setup_revisions(0, NULL, &rev, NULL);
 958         rev.diffopt.output_format |=
 959                 DIFF_FORMAT_CALLBACK;
 960         rev.diffopt.format_callback = count_diff_files;
 961         rev.diffopt.format_callback_data = &cnt;
 962         run_diff_files(&rev, 0);
 963
 964         /*
 965          * Check how many unmerged entries are
 966          * there.
 967          */
 968         cnt += count_unmerged_entries();
 969
 970         return cnt;
 971 }
 972
 973 /*
 974  * Pretend as if the user told us to merge with the remote-tracking
 975  * branch we have for the upstream of the current branch
 976  */
 977 static int setup_with_upstream(const char ***argv)
 978 {
 979         struct branch *branch = branch_get(NULL);
 980         int i;
 981         const char **args;
 982
 983         if (!branch)
 984                 die(_("No current branch."));
 985         if (!branch->remote_name)
 986                 die(_("No remote for the current branch."));
 987         if (!branch->merge_nr)
 988                 die(_("No default upstream defined for the current branch."));
 989
 990         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 991         for (i = 0; i < branch->merge_nr; i++) {
 992                 if (!branch->merge[i]->dst)
 993                         die(_("No remote-tracking branch for %s from %s"),
 994                             branch->merge[i]->src, branch->remote_name);
 995                 args[i] = branch->merge[i]->dst;
 996         }
 997         args[i] = NULL;
 998         *argv = args;
 999         return i;
1000 }
1001
1002 static void write_merge_heads(struct commit_list *remoteheads)
1003 {
1004         struct commit_list *j;
1005         struct strbuf buf = STRBUF_INIT;
1006
1007         for (j = remoteheads; j; j = j->next) {
1008                 struct object_id *oid;
1009                 struct commit *c = j->item;
1010                 struct merge_remote_desc *desc;
1011
1012                 desc = merge_remote_util(c);
1013                 if (desc && desc->obj) {
1014                         oid = &desc->obj->oid;
1015                 } else {
1016                         oid = &c->object.oid;
1017                 }
1018                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1019         }
1020         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1021
1022         strbuf_reset(&buf);
1023         if (fast_forward == FF_NO)
1024                 strbuf_addstr(&buf, "no-ff");
1025         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1026         strbuf_release(&buf);
1027 }
1028
1029 static void write_merge_state(struct commit_list *remoteheads)
1030 {
1031         write_merge_heads(remoteheads);
1032         strbuf_addch(&merge_msg, '\n');
1033         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1034                        merge_msg.len);
1035 }
1036
1037 static int default_edit_option(void)
1038 {
1039         static const char name[] = "GIT_MERGE_AUTOEDIT";
1040         const char *e = getenv(name);
1041         struct stat st_stdin, st_stdout;
1042
1043         if (have_message)
1044                 /* an explicit -m msg without --[no-]edit */
1045                 return 0;
1046
1047         if (e) {
1048                 int v = git_parse_maybe_bool(e);
1049                 if (v < 0)
1050                         die(_("Bad value '%s' in environment '%s'"), e, name);
1051                 return v;
1052         }
1053
1054         /* Use editor if stdin and stdout are the same and is a tty */
1055         return (!fstat(0, &st_stdin) &&
1056                 !fstat(1, &st_stdout) &&
1057                 isatty(0) && isatty(1) &&
1058                 st_stdin.st_dev == st_stdout.st_dev &&
1059                 st_stdin.st_ino == st_stdout.st_ino &&
1060                 st_stdin.st_mode == st_stdout.st_mode);
1061 }
1062
1063 static struct commit_list *reduce_parents(struct commit *head_commit,
1064                                           int *head_subsumed,
1065                                           struct commit_list *remoteheads)
1066 {
1067         struct commit_list *parents, **remotes;
1068
1069         /*
1070          * Is the current HEAD reachable from another commit being
1071          * merged?  If so we do not want to record it as a parent of
1072          * the resulting merge, unless --no-ff is given.  We will flip
1073          * this variable to 0 when we find HEAD among the independent
1074          * tips being merged.
1075          */
1076         *head_subsumed = 1;
1077
1078         /* Find what parents to record by checking independent ones. */
1079         parents = reduce_heads(remoteheads);
1080         free_commit_list(remoteheads);
1081
1082         remoteheads = NULL;
1083         remotes = &remoteheads;
1084         while (parents) {
1085                 struct commit *commit = pop_commit(&parents);
1086                 if (commit == head_commit)
1087                         *head_subsumed = 0;
1088                 else
1089                         remotes = &commit_list_insert(commit, remotes)->next;
1090         }
1091         return remoteheads;
1092 }
1093
1094 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1095 {
1096         struct fmt_merge_msg_opts opts;
1097
1098         memset(&opts, 0, sizeof(opts));
1099         opts.add_title = !have_message;
1100         opts.shortlog_len = shortlog_len;
1101         opts.credit_people = (0 < option_edit);
1102
1103         fmt_merge_msg(merge_names, merge_msg, &opts);
1104         if (merge_msg->len)
1105                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1106 }
1107
1108 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1109 {
1110         const char *filename;
1111         int fd, pos, npos;
1112         struct strbuf fetch_head_file = STRBUF_INIT;
1113         const unsigned hexsz = the_hash_algo->hexsz;
1114
1115         if (!merge_names)
1116                 merge_names = &fetch_head_file;
1117
1118         filename = git_path_fetch_head(the_repository);
1119         fd = open(filename, O_RDONLY);
1120         if (fd < 0)
1121                 die_errno(_("could not open '%s' for reading"), filename);
1122
1123         if (strbuf_read(merge_names, fd, 0) < 0)
1124                 die_errno(_("could not read '%s'"), filename);
1125         if (close(fd) < 0)
1126                 die_errno(_("could not close '%s'"), filename);
1127
1128         for (pos = 0; pos < merge_names->len; pos = npos) {
1129                 struct object_id oid;
1130                 char *ptr;
1131                 struct commit *commit;
1132
1133                 ptr = strchr(merge_names->buf + pos, '\n');
1134                 if (ptr)
1135                         npos = ptr - merge_names->buf + 1;
1136                 else
1137                         npos = merge_names->len;
1138
1139                 if (npos - pos < hexsz + 2 ||
1140                     get_oid_hex(merge_names->buf + pos, &oid))
1141                         commit = NULL; /* bad */
1142                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1143                         continue; /* not-for-merge */
1144                 else {
1145                         char saved = merge_names->buf[pos + hexsz];
1146                         merge_names->buf[pos + hexsz] = '\0';
1147                         commit = get_merge_parent(merge_names->buf + pos);
1148                         merge_names->buf[pos + hexsz] = saved;
1149                 }
1150                 if (!commit) {
1151                         if (ptr)
1152                                 *ptr = '\0';
1153                         die(_("not something we can merge in %s: %s"),
1154                             filename, merge_names->buf + pos);
1155                 }
1156                 remotes = &commit_list_insert(commit, remotes)->next;
1157         }
1158
1159         if (merge_names == &fetch_head_file)
1160                 strbuf_release(&fetch_head_file);
1161 }
1162
1163 static struct commit_list *collect_parents(struct commit *head_commit,
1164                                            int *head_subsumed,
1165                                            int argc, const char **argv,
1166                                            struct strbuf *merge_msg)
1167 {
1168         int i;
1169         struct commit_list *remoteheads = NULL;
1170         struct commit_list **remotes = &remoteheads;
1171         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1172
1173         if (merge_msg && (!have_message || shortlog_len))
1174                 autogen = &merge_names;
1175
1176         if (head_commit)
1177                 remotes = &commit_list_insert(head_commit, remotes)->next;
1178
1179         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1180                 handle_fetch_head(remotes, autogen);
1181                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1182         } else {
1183                 for (i = 0; i < argc; i++) {
1184                         struct commit *commit = get_merge_parent(argv[i]);
1185                         if (!commit)
1186                                 help_unknown_ref(argv[i], "merge",
1187                                                  _("not something we can merge"));
1188                         remotes = &commit_list_insert(commit, remotes)->next;
1189                 }
1190                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1191                 if (autogen) {
1192                         struct commit_list *p;
1193                         for (p = remoteheads; p; p = p->next)
1194                                 merge_name(merge_remote_util(p->item)->name, autogen);
1195                 }
1196         }
1197
1198         if (autogen) {
1199                 prepare_merge_message(autogen, merge_msg);
1200                 strbuf_release(autogen);
1201         }
1202
1203         return remoteheads;
1204 }
1205
1206 static int merging_a_throwaway_tag(struct commit *commit)
1207 {
1208         char *tag_ref;
1209         struct object_id oid;
1210         int is_throwaway_tag = 0;
1211
1212         /* Are we merging a tag? */
1213         if (!merge_remote_util(commit) ||
1214             !merge_remote_util(commit)->obj ||
1215             merge_remote_util(commit)->obj->type != OBJ_TAG)
1216                 return is_throwaway_tag;
1217
1218         /*
1219          * Now we know we are merging a tag object.  Are we downstream
1220          * and following the tags from upstream?  If so, we must have
1221          * the tag object pointed at by "refs/tags/$T" where $T is the
1222          * tagname recorded in the tag object.  We want to allow such
1223          * a "just to catch up" merge to fast-forward.
1224          *
1225          * Otherwise, we are playing an integrator's role, making a
1226          * merge with a throw-away tag from a contributor with
1227          * something like "git pull $contributor $signed_tag".
1228          * We want to forbid such a merge from fast-forwarding
1229          * by default; otherwise we would not keep the signature
1230          * anywhere.
1231          */
1232         tag_ref = xstrfmt("refs/tags/%s",
1233                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1234         if (!read_ref(tag_ref, &oid) &&
1235             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1236                 is_throwaway_tag = 0;
1237         else
1238                 is_throwaway_tag = 1;
1239         free(tag_ref);
1240         return is_throwaway_tag;
1241 }
1242
1243 int cmd_merge(int argc, const char **argv, const char *prefix)
1244 {
1245         struct object_id result_tree, stash, head_oid;
1246         struct commit *head_commit;
1247         struct strbuf buf = STRBUF_INIT;
1248         int i, ret = 0, head_subsumed;
1249         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1250         struct commit_list *common = NULL;
1251         const char *best_strategy = NULL, *wt_strategy = NULL;
1252         struct commit_list *remoteheads, *p;
1253         void *branch_to_free;
1254         int orig_argc = argc;
1255
1256         if (argc == 2 && !strcmp(argv[1], "-h"))
1257                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1258
1259         /*
1260          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1261          * current branch.
1262          */
1263         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1264         if (branch)
1265                 skip_prefix(branch, "refs/heads/", &branch);
1266
1267         init_diff_ui_defaults();
1268         git_config(git_merge_config, NULL);
1269
1270         if (!branch || is_null_oid(&head_oid))
1271                 head_commit = NULL;
1272         else
1273                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1274
1275         if (branch_mergeoptions)
1276                 parse_branch_merge_options(branch_mergeoptions);
1277         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1278                         builtin_merge_usage, 0);
1279         if (shortlog_len < 0)
1280                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1281
1282         if (verbosity < 0 && show_progress == -1)
1283                 show_progress = 0;
1284
1285         if (abort_current_merge) {
1286                 int nargc = 2;
1287                 const char *nargv[] = {"reset", "--merge", NULL};
1288                 struct strbuf stash_oid = STRBUF_INIT;
1289
1290                 if (orig_argc != 2)
1291                         usage_msg_opt(_("--abort expects no arguments"),
1292                               builtin_merge_usage, builtin_merge_options);
1293
1294                 if (!file_exists(git_path_merge_head(the_repository)))
1295                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1296
1297                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1298                     READ_ONELINER_SKIP_IF_EMPTY))
1299                         unlink(git_path_merge_autostash(the_repository));
1300
1301                 /* Invoke 'git reset --merge' */
1302                 ret = cmd_reset(nargc, nargv, prefix);
1303
1304                 if (stash_oid.len)
1305                         apply_autostash_oid(stash_oid.buf);
1306
1307                 strbuf_release(&stash_oid);
1308                 goto done;
1309         }
1310
1311         if (quit_current_merge) {
1312                 if (orig_argc != 2)
1313                         usage_msg_opt(_("--quit expects no arguments"),
1314                                       builtin_merge_usage,
1315                                       builtin_merge_options);
1316
1317                 remove_merge_branch_state(the_repository);
1318                 goto done;
1319         }
1320
1321         if (continue_current_merge) {
1322                 int nargc = 1;
1323                 const char *nargv[] = {"commit", NULL};
1324
1325                 if (orig_argc != 2)
1326                         usage_msg_opt(_("--continue expects no arguments"),
1327                               builtin_merge_usage, builtin_merge_options);
1328
1329                 if (!file_exists(git_path_merge_head(the_repository)))
1330                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1331
1332                 /* Invoke 'git commit' */
1333                 ret = cmd_commit(nargc, nargv, prefix);
1334                 goto done;
1335         }
1336
1337         if (read_cache_unmerged())
1338                 die_resolve_conflict("merge");
1339
1340         if (file_exists(git_path_merge_head(the_repository))) {
1341                 /*
1342                  * There is no unmerged entry, don't advise 'git
1343                  * add/rm <file>', just 'git commit'.
1344                  */
1345                 if (advice_resolve_conflict)
1346                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1347                                   "Please, commit your changes before you merge."));
1348                 else
1349                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1350         }
1351         if (ref_exists("CHERRY_PICK_HEAD")) {
1352                 if (advice_resolve_conflict)
1353                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1354                             "Please, commit your changes before you merge."));
1355                 else
1356                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1357         }
1358         resolve_undo_clear();
1359
1360         if (option_edit < 0)
1361                 option_edit = default_edit_option();
1362
1363         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1364
1365         if (verbosity < 0)
1366                 show_diffstat = 0;
1367
1368         if (squash) {
1369                 if (fast_forward == FF_NO)
1370                         die(_("You cannot combine --squash with --no-ff."));
1371                 if (option_commit > 0)
1372                         die(_("You cannot combine --squash with --commit."));
1373                 /*
1374                  * squash can now silently disable option_commit - this is not
1375                  * a problem as it is only overriding the default, not a user
1376                  * supplied option.
1377                  */
1378                 option_commit = 0;
1379         }
1380
1381         if (option_commit < 0)
1382                 option_commit = 1;
1383
1384         if (!argc) {
1385                 if (default_to_upstream)
1386                         argc = setup_with_upstream(&argv);
1387                 else
1388                         die(_("No commit specified and merge.defaultToUpstream not set."));
1389         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1390                 argv[0] = "@{-1}";
1391         }
1392
1393         if (!argc)
1394                 usage_with_options(builtin_merge_usage,
1395                         builtin_merge_options);
1396
1397         if (!head_commit) {
1398                 /*
1399                  * If the merged head is a valid one there is no reason
1400                  * to forbid "git merge" into a branch yet to be born.
1401                  * We do the same for "git pull".
1402                  */
1403                 struct object_id *remote_head_oid;
1404                 if (squash)
1405                         die(_("Squash commit into empty head not supported yet"));
1406                 if (fast_forward == FF_NO)
1407                         die(_("Non-fast-forward commit does not make sense into "
1408                             "an empty head"));
1409                 remoteheads = collect_parents(head_commit, &head_subsumed,
1410                                               argc, argv, NULL);
1411                 if (!remoteheads)
1412                         die(_("%s - not something we can merge"), argv[0]);
1413                 if (remoteheads->next)
1414                         die(_("Can merge only exactly one commit into empty head"));
1415
1416                 if (verify_signatures)
1417                         verify_merge_signature(remoteheads->item, verbosity,
1418                                                check_trust_level);
1419
1420                 remote_head_oid = &remoteheads->item->object.oid;
1421                 read_empty(remote_head_oid, 0);
1422                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1423                            UPDATE_REFS_DIE_ON_ERR);
1424                 goto done;
1425         }
1426
1427         /*
1428          * All the rest are the commits being merged; prepare
1429          * the standard merge summary message to be appended
1430          * to the given message.
1431          */
1432         remoteheads = collect_parents(head_commit, &head_subsumed,
1433                                       argc, argv, &merge_msg);
1434
1435         if (!head_commit || !argc)
1436                 usage_with_options(builtin_merge_usage,
1437                         builtin_merge_options);
1438
1439         if (verify_signatures) {
1440                 for (p = remoteheads; p; p = p->next) {
1441                         verify_merge_signature(p->item, verbosity,
1442                                                check_trust_level);
1443                 }
1444         }
1445
1446         strbuf_addstr(&buf, "merge");
1447         for (p = remoteheads; p; p = p->next)
1448                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1449         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1450         strbuf_reset(&buf);
1451
1452         for (p = remoteheads; p; p = p->next) {
1453                 struct commit *commit = p->item;
1454                 strbuf_addf(&buf, "GITHEAD_%s",
1455                             oid_to_hex(&commit->object.oid));
1456                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1457                 strbuf_reset(&buf);
1458                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1459                         fast_forward = FF_NO;
1460         }
1461
1462         if (!use_strategies) {
1463                 if (!remoteheads)
1464                         ; /* already up-to-date */
1465                 else if (!remoteheads->next)
1466                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1467                 else
1468                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1469         }
1470
1471         for (i = 0; i < use_strategies_nr; i++) {
1472                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1473                         fast_forward = FF_NO;
1474                 if (use_strategies[i]->attr & NO_TRIVIAL)
1475                         allow_trivial = 0;
1476         }
1477
1478         if (!remoteheads)
1479                 ; /* already up-to-date */
1480         else if (!remoteheads->next)
1481                 common = get_merge_bases(head_commit, remoteheads->item);
1482         else {
1483                 struct commit_list *list = remoteheads;
1484                 commit_list_insert(head_commit, &list);
1485                 common = get_octopus_merge_bases(list);
1486                 free(list);
1487         }
1488
1489         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1490                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1491
1492         if (remoteheads && !common) {
1493                 /* No common ancestors found. */
1494                 if (!allow_unrelated_histories)
1495                         die(_("refusing to merge unrelated histories"));
1496                 /* otherwise, we need a real merge. */
1497         } else if (!remoteheads ||
1498                  (!remoteheads->next && !common->next &&
1499                   common->item == remoteheads->item)) {
1500                 /*
1501                  * If head can reach all the merge then we are up to date.
1502                  * but first the most common case of merging one remote.
1503                  */
1504                 finish_up_to_date(_("Already up to date."));
1505                 goto done;
1506         } else if (fast_forward != FF_NO && !remoteheads->next &&
1507                         !common->next &&
1508                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1509                 /* Again the most common case of merging one remote. */
1510                 struct strbuf msg = STRBUF_INIT;
1511                 struct commit *commit;
1512
1513                 if (verbosity >= 0) {
1514                         printf(_("Updating %s..%s\n"),
1515                                find_unique_abbrev(&head_commit->object.oid,
1516                                                   DEFAULT_ABBREV),
1517                                find_unique_abbrev(&remoteheads->item->object.oid,
1518                                                   DEFAULT_ABBREV));
1519                 }
1520                 strbuf_addstr(&msg, "Fast-forward");
1521                 if (have_message)
1522                         strbuf_addstr(&msg,
1523                                 " (no commit created; -m option ignored)");
1524                 commit = remoteheads->item;
1525                 if (!commit) {
1526                         ret = 1;
1527                         goto done;
1528                 }
1529
1530                 if (autostash)
1531                         create_autostash(the_repository,
1532                                          git_path_merge_autostash(the_repository),
1533                                          "merge");
1534                 if (checkout_fast_forward(the_repository,
1535                                           &head_commit->object.oid,
1536                                           &commit->object.oid,
1537                                           overwrite_ignore)) {
1538                         ret = 1;
1539                         goto done;
1540                 }
1541
1542                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1543                 remove_merge_branch_state(the_repository);
1544                 goto done;
1545         } else if (!remoteheads->next && common->next)
1546                 ;
1547                 /*
1548                  * We are not doing octopus and not fast-forward.  Need
1549                  * a real merge.
1550                  */
1551         else if (!remoteheads->next && !common->next && option_commit) {
1552                 /*
1553                  * We are not doing octopus, not fast-forward, and have
1554                  * only one common.
1555                  */
1556                 refresh_cache(REFRESH_QUIET);
1557                 if (allow_trivial && fast_forward != FF_ONLY) {
1558                         /* See if it is really trivial. */
1559                         git_committer_info(IDENT_STRICT);
1560                         printf(_("Trying really trivial in-index merge...\n"));
1561                         if (!read_tree_trivial(&common->item->object.oid,
1562                                                &head_commit->object.oid,
1563                                                &remoteheads->item->object.oid)) {
1564                                 ret = merge_trivial(head_commit, remoteheads);
1565                                 goto done;
1566                         }
1567                         printf(_("Nope.\n"));
1568                 }
1569         } else {
1570                 /*
1571                  * An octopus.  If we can reach all the remote we are up
1572                  * to date.
1573                  */
1574                 int up_to_date = 1;
1575                 struct commit_list *j;
1576
1577                 for (j = remoteheads; j; j = j->next) {
1578                         struct commit_list *common_one;
1579
1580                         /*
1581                          * Here we *have* to calculate the individual
1582                          * merge_bases again, otherwise "git merge HEAD^
1583                          * HEAD^^" would be missed.
1584                          */
1585                         common_one = get_merge_bases(head_commit, j->item);
1586                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1587                                 up_to_date = 0;
1588                                 break;
1589                         }
1590                 }
1591                 if (up_to_date) {
1592                         finish_up_to_date(_("Already up to date. Yeeah!"));
1593                         goto done;
1594                 }
1595         }
1596
1597         if (fast_forward == FF_ONLY)
1598                 die(_("Not possible to fast-forward, aborting."));
1599
1600         if (autostash)
1601                 create_autostash(the_repository,
1602                                  git_path_merge_autostash(the_repository),
1603                                  "merge");
1604
1605         /* We are going to make a new commit. */
1606         git_committer_info(IDENT_STRICT);
1607
1608         /*
1609          * At this point, we need a real merge.  No matter what strategy
1610          * we use, it would operate on the index, possibly affecting the
1611          * working tree, and when resolved cleanly, have the desired
1612          * tree in the index -- this means that the index must be in
1613          * sync with the head commit.  The strategies are responsible
1614          * to ensure this.
1615          */
1616         if (use_strategies_nr == 1 ||
1617             /*
1618              * Stash away the local changes so that we can try more than one.
1619              */
1620             save_state(&stash))
1621                 oidclr(&stash);
1622
1623         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1624                 int ret, cnt;
1625                 if (i) {
1626                         printf(_("Rewinding the tree to pristine...\n"));
1627                         restore_state(&head_commit->object.oid, &stash);
1628                 }
1629                 if (use_strategies_nr != 1)
1630                         printf(_("Trying merge strategy %s...\n"),
1631                                 use_strategies[i]->name);
1632                 /*
1633                  * Remember which strategy left the state in the working
1634                  * tree.
1635                  */
1636                 wt_strategy = use_strategies[i]->name;
1637
1638                 ret = try_merge_strategy(use_strategies[i]->name,
1639                                          common, remoteheads,
1640                                          head_commit);
1641                 /*
1642                  * The backend exits with 1 when conflicts are
1643                  * left to be resolved, with 2 when it does not
1644                  * handle the given merge at all.
1645                  */
1646                 if (ret < 2) {
1647                         if (!ret) {
1648                                 if (option_commit) {
1649                                         /* Automerge succeeded. */
1650                                         automerge_was_ok = 1;
1651                                         break;
1652                                 }
1653                                 merge_was_ok = 1;
1654                         }
1655                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1656                         if (best_cnt <= 0 || cnt <= best_cnt) {
1657                                 best_strategy = use_strategies[i]->name;
1658                                 best_cnt = cnt;
1659                         }
1660                 }
1661         }
1662
1663         /*
1664          * If we have a resulting tree, that means the strategy module
1665          * auto resolved the merge cleanly.
1666          */
1667         if (automerge_was_ok) {
1668                 ret = finish_automerge(head_commit, head_subsumed,
1669                                        common, remoteheads,
1670                                        &result_tree, wt_strategy);
1671                 goto done;
1672         }
1673
1674         /*
1675          * Pick the result from the best strategy and have the user fix
1676          * it up.
1677          */
1678         if (!best_strategy) {
1679                 restore_state(&head_commit->object.oid, &stash);
1680                 if (use_strategies_nr > 1)
1681                         fprintf(stderr,
1682                                 _("No merge strategy handled the merge.\n"));
1683                 else
1684                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1685                                 use_strategies[0]->name);
1686                 ret = 2;
1687                 goto done;
1688         } else if (best_strategy == wt_strategy)
1689                 ; /* We already have its result in the working tree. */
1690         else {
1691                 printf(_("Rewinding the tree to pristine...\n"));
1692                 restore_state(&head_commit->object.oid, &stash);
1693                 printf(_("Using the %s to prepare resolving by hand.\n"),
1694                         best_strategy);
1695                 try_merge_strategy(best_strategy, common, remoteheads,
1696                                    head_commit);
1697         }
1698
1699         if (squash) {
1700                 finish(head_commit, remoteheads, NULL, NULL);
1701
1702                 git_test_write_commit_graph_or_die();
1703         } else
1704                 write_merge_state(remoteheads);
1705
1706         if (merge_was_ok)
1707                 fprintf(stderr, _("Automatic merge went well; "
1708                         "stopped before committing as requested\n"));
1709         else
1710                 ret = suggest_conflicts();
1711
1712 done:
1713         free(branch_to_free);
1714         return ret;
1715 }