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