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