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

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