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 #include "cache.h"
  10 #include "config.h"
  11 #include "parse-options.h"
  12 #include "builtin.h"
  13 #include "lockfile.h"
  14 #include "run-command.h"
  15 #include "diff.h"
  16 #include "refs.h"
  17 #include "refspec.h"
  18 #include "commit.h"
  19 #include "diffcore.h"
  20 #include "revision.h"
  21 #include "unpack-trees.h"
  22 #include "cache-tree.h"
  23 #include "dir.h"
  24 #include "utf8.h"
  25 #include "log-tree.h"
  26 #include "color.h"
  27 #include "rerere.h"
  28 #include "help.h"
  29 #include "merge-recursive.h"
  30 #include "resolve-undo.h"
  31 #include "remote.h"
  32 #include "fmt-merge-msg.h"
  33 #include "gpg-interface.h"
  34 #include "sequencer.h"
  35 #include "string-list.h"
  36 #include "packfile.h"
  37 #include "tag.h"
  38 #include "alias.h"
  39 #include "commit-reach.h"
  40
  41 #define DEFAULT_TWOHEAD (1<<0)
  42 #define DEFAULT_OCTOPUS (1<<1)
  43 #define NO_FAST_FORWARD (1<<2)
  44 #define NO_TRIVIAL      (1<<3)
  45
  46 struct strategy {
  47         const char *name;
  48         unsigned attr;
  49 };
  50
  51 static const char * const builtin_merge_usage[] = {
  52         N_("git merge [<options>] [<commit>...]"),
  53         N_("git merge --abort"),
  54         N_("git merge --continue"),
  55         NULL
  56 };
  57
  58 static int show_diffstat = 1, shortlog_len = -1, squash;
  59 static int option_commit = 1;
  60 static int option_edit = -1;
  61 static int allow_trivial = 1, have_message, verify_signatures;
  62 static int overwrite_ignore = 1;
  63 static struct strbuf merge_msg = STRBUF_INIT;
  64 static struct strategy **use_strategies;
  65 static size_t use_strategies_nr, use_strategies_alloc;
  66 static const char **xopts;
  67 static size_t xopts_nr, xopts_alloc;
  68 static const char *branch;
  69 static char *branch_mergeoptions;
  70 static int option_renormalize;
  71 static int verbosity;
  72 static int allow_rerere_auto;
  73 static int abort_current_merge;
  74 static int continue_current_merge;
  75 static int allow_unrelated_histories;
  76 static int show_progress = -1;
  77 static int default_to_upstream = 1;
  78 static int signoff;
  79 static const char *sign_commit;
  80 static int verify_msg = 1;
  81
  82 static struct strategy all_strategy[] = {
  83         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  84         { "octopus",    DEFAULT_OCTOPUS },
  85         { "resolve",    0 },
  86         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  87         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  88 };
  89
  90 static const char *pull_twohead, *pull_octopus;
  91
  92 enum ff_type {
  93         FF_NO,
  94         FF_ALLOW,
  95         FF_ONLY
  96 };
  97
  98 static enum ff_type fast_forward = FF_ALLOW;
  99
 100 static int option_parse_message(const struct option *opt,
 101                                 const char *arg, int unset)
 102 {
 103         struct strbuf *buf = opt->value;
 104
 105         if (unset)
 106                 strbuf_setlen(buf, 0);
 107         else if (arg) {
 108                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 109                 have_message = 1;
 110         } else
 111                 return error(_("switch `m' requires a value"));
 112         return 0;
 113 }
 114
 115 static struct strategy *get_strategy(const char *name)
 116 {
 117         int i;
 118         struct strategy *ret;
 119         static struct cmdnames main_cmds, other_cmds;
 120         static int loaded;
 121
 122         if (!name)
 123                 return NULL;
 124
 125         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 126                 if (!strcmp(name, all_strategy[i].name))
 127                         return &all_strategy[i];
 128
 129         if (!loaded) {
 130                 struct cmdnames not_strategies;
 131                 loaded = 1;
 132
 133                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 134                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 135                 for (i = 0; i < main_cmds.cnt; i++) {
 136                         int j, found = 0;
 137                         struct cmdname *ent = main_cmds.names[i];
 138                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 139                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 140                                                 && !all_strategy[j].name[ent->len])
 141                                         found = 1;
 142                         if (!found)
 143                                 add_cmdname(&not_strategies, ent->name, ent->len);
 144                 }
 145                 exclude_cmds(&main_cmds, &not_strategies);
 146         }
 147         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 148                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 149                 fprintf(stderr, _("Available strategies are:"));
 150                 for (i = 0; i < main_cmds.cnt; i++)
 151                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 152                 fprintf(stderr, ".\n");
 153                 if (other_cmds.cnt) {
 154                         fprintf(stderr, _("Available custom strategies are:"));
 155                         for (i = 0; i < other_cmds.cnt; i++)
 156                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 157                         fprintf(stderr, ".\n");
 158                 }
 159                 exit(1);
 160         }
 161
 162         ret = xcalloc(1, sizeof(struct strategy));
 163         ret->name = xstrdup(name);
 164         ret->attr = NO_TRIVIAL;
 165         return ret;
 166 }
 167
 168 static void append_strategy(struct strategy *s)
 169 {
 170         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 171         use_strategies[use_strategies_nr++] = s;
 172 }
 173
 174 static int option_parse_strategy(const struct option *opt,
 175                                  const char *name, int unset)
 176 {
 177         if (unset)
 178                 return 0;
 179
 180         append_strategy(get_strategy(name));
 181         return 0;
 182 }
 183
 184 static int option_parse_x(const struct option *opt,
 185                           const char *arg, int unset)
 186 {
 187         if (unset)
 188                 return 0;
 189
 190         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 191         xopts[xopts_nr++] = xstrdup(arg);
 192         return 0;
 193 }
 194
 195 static int option_parse_n(const struct option *opt,
 196                           const char *arg, int unset)
 197 {
 198         show_diffstat = unset;
 199         return 0;
 200 }
 201
 202 static struct option builtin_merge_options[] = {
 203         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 204                 N_("do not show a diffstat at the end of the merge"),
 205                 PARSE_OPT_NOARG, option_parse_n },
 206         OPT_BOOL(0, "stat", &show_diffstat,
 207                 N_("show a diffstat at the end of the merge")),
 208         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 209         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 210           N_("add (at most <n>) entries from shortlog to merge commit message"),
 211           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 212         OPT_BOOL(0, "squash", &squash,
 213                 N_("create a single commit instead of doing a merge")),
 214         OPT_BOOL(0, "commit", &option_commit,
 215                 N_("perform a commit if the merge succeeds (default)")),
 216         OPT_BOOL('e', "edit", &option_edit,
 217                 N_("edit message before committing")),
 218         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 219         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 220                       N_("abort if fast-forward is not possible"),
 221                       FF_ONLY, PARSE_OPT_NONEG),
 222         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 223         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 224                 N_("verify that the named commit has a valid GPG signature")),
 225         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 226                 N_("merge strategy to use"), option_parse_strategy),
 227         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 228                 N_("option for selected merge strategy"), option_parse_x),
 229         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 230                 N_("merge commit message (for a non-fast-forward merge)"),
 231                 option_parse_message),
 232         OPT__VERBOSITY(&verbosity),
 233         OPT_BOOL(0, "abort", &abort_current_merge,
 234                 N_("abort the current in-progress merge")),
 235         OPT_BOOL(0, "continue", &continue_current_merge,
 236                 N_("continue the current in-progress merge")),
 237         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 238                  N_("allow merging unrelated histories")),
 239         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 240         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 241           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 242         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 243         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 244         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 245         OPT_END()
 246 };
 247
 248 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 249 static void drop_save(void)
 250 {
 251         unlink(git_path_merge_head(the_repository));
 252         unlink(git_path_merge_msg(the_repository));
 253         unlink(git_path_merge_mode(the_repository));
 254 }
 255
 256 static int save_state(struct object_id *stash)
 257 {
 258         int len;
 259         struct child_process cp = CHILD_PROCESS_INIT;
 260         struct strbuf buffer = STRBUF_INIT;
 261         const char *argv[] = {"stash", "create", NULL};
 262         int rc = -1;
 263
 264         cp.argv = argv;
 265         cp.out = -1;
 266         cp.git_cmd = 1;
 267
 268         if (start_command(&cp))
 269                 die(_("could not run stash."));
 270         len = strbuf_read(&buffer, cp.out, 1024);
 271         close(cp.out);
 272
 273         if (finish_command(&cp) || len < 0)
 274                 die(_("stash failed"));
 275         else if (!len)          /* no changes */
 276                 goto out;
 277         strbuf_setlen(&buffer, buffer.len-1);
 278         if (get_oid(buffer.buf, stash))
 279                 die(_("not a valid object: %s"), buffer.buf);
 280         rc = 0;
 281 out:
 282         strbuf_release(&buffer);
 283         return rc;
 284 }
 285
 286 static void read_empty(const struct object_id *oid, int verbose)
 287 {
 288         int i = 0;
 289         const char *args[7];
 290
 291         args[i++] = "read-tree";
 292         if (verbose)
 293                 args[i++] = "-v";
 294         args[i++] = "-m";
 295         args[i++] = "-u";
 296         args[i++] = empty_tree_oid_hex();
 297         args[i++] = oid_to_hex(oid);
 298         args[i] = NULL;
 299
 300         if (run_command_v_opt(args, RUN_GIT_CMD))
 301                 die(_("read-tree failed"));
 302 }
 303
 304 static void reset_hard(const struct object_id *oid, int verbose)
 305 {
 306         int i = 0;
 307         const char *args[6];
 308
 309         args[i++] = "read-tree";
 310         if (verbose)
 311                 args[i++] = "-v";
 312         args[i++] = "--reset";
 313         args[i++] = "-u";
 314         args[i++] = oid_to_hex(oid);
 315         args[i] = NULL;
 316
 317         if (run_command_v_opt(args, RUN_GIT_CMD))
 318                 die(_("read-tree failed"));
 319 }
 320
 321 static void restore_state(const struct object_id *head,
 322                           const struct object_id *stash)
 323 {
 324         struct strbuf sb = STRBUF_INIT;
 325         const char *args[] = { "stash", "apply", NULL, NULL };
 326
 327         if (is_null_oid(stash))
 328                 return;
 329
 330         reset_hard(head, 1);
 331
 332         args[2] = oid_to_hex(stash);
 333
 334         /*
 335          * It is OK to ignore error here, for example when there was
 336          * nothing to restore.
 337          */
 338         run_command_v_opt(args, RUN_GIT_CMD);
 339
 340         strbuf_release(&sb);
 341         refresh_cache(REFRESH_QUIET);
 342 }
 343
 344 /* This is called when no merge was necessary. */
 345 static void finish_up_to_date(const char *msg)
 346 {
 347         if (verbosity >= 0)
 348                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 349         drop_save();
 350 }
 351
 352 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 353 {
 354         struct rev_info rev;
 355         struct strbuf out = STRBUF_INIT;
 356         struct commit_list *j;
 357         struct pretty_print_context ctx = {0};
 358
 359         printf(_("Squash commit -- not updating HEAD\n"));
 360
 361         init_revisions(&rev, NULL);
 362         rev.ignore_merges = 1;
 363         rev.commit_format = CMIT_FMT_MEDIUM;
 364
 365         commit->object.flags |= UNINTERESTING;
 366         add_pending_object(&rev, &commit->object, NULL);
 367
 368         for (j = remoteheads; j; j = j->next)
 369                 add_pending_object(&rev, &j->item->object, NULL);
 370
 371         setup_revisions(0, NULL, &rev, NULL);
 372         if (prepare_revision_walk(&rev))
 373                 die(_("revision walk setup failed"));
 374
 375         ctx.abbrev = rev.abbrev;
 376         ctx.date_mode = rev.date_mode;
 377         ctx.fmt = rev.commit_format;
 378
 379         strbuf_addstr(&out, "Squashed commit of the following:\n");
 380         while ((commit = get_revision(&rev)) != NULL) {
 381                 strbuf_addch(&out, '\n');
 382                 strbuf_addf(&out, "commit %s\n",
 383                         oid_to_hex(&commit->object.oid));
 384                 pretty_print_commit(&ctx, commit, &out);
 385         }
 386         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 387         strbuf_release(&out);
 388 }
 389
 390 static void finish(struct commit *head_commit,
 391                    struct commit_list *remoteheads,
 392                    const struct object_id *new_head, const char *msg)
 393 {
 394         struct strbuf reflog_message = STRBUF_INIT;
 395         const struct object_id *head = &head_commit->object.oid;
 396
 397         if (!msg)
 398                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 399         else {
 400                 if (verbosity >= 0)
 401                         printf("%s\n", msg);
 402                 strbuf_addf(&reflog_message, "%s: %s",
 403                         getenv("GIT_REFLOG_ACTION"), msg);
 404         }
 405         if (squash) {
 406                 squash_message(head_commit, remoteheads);
 407         } else {
 408                 if (verbosity >= 0 && !merge_msg.len)
 409                         printf(_("No merge message -- not updating HEAD\n"));
 410                 else {
 411                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 412                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 413                                    0, UPDATE_REFS_DIE_ON_ERR);
 414                         /*
 415                          * We ignore errors in 'gc --auto', since the
 416                          * user should see them.
 417                          */
 418                         close_all_packs(the_repository->objects);
 419                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 420                 }
 421         }
 422         if (new_head && show_diffstat) {
 423                 struct diff_options opts;
 424                 diff_setup(&opts);
 425                 opts.stat_width = -1; /* use full terminal width */
 426                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 427                 opts.output_format |=
 428                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 429                 opts.detect_rename = DIFF_DETECT_RENAME;
 430                 diff_setup_done(&opts);
 431                 diff_tree_oid(head, new_head, "", &opts);
 432                 diffcore_std(&opts);
 433                 diff_flush(&opts);
 434         }
 435
 436         /* Run a post-merge hook */
 437         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 438
 439         strbuf_release(&reflog_message);
 440 }
 441
 442 /* Get the name for the merge commit's message. */
 443 static void merge_name(const char *remote, struct strbuf *msg)
 444 {
 445         struct commit *remote_head;
 446         struct object_id branch_head;
 447         struct strbuf buf = STRBUF_INIT;
 448         struct strbuf bname = STRBUF_INIT;
 449         struct merge_remote_desc *desc;
 450         const char *ptr;
 451         char *found_ref;
 452         int len, early;
 453
 454         strbuf_branchname(&bname, remote, 0);
 455         remote = bname.buf;
 456
 457         oidclr(&branch_head);
 458         remote_head = get_merge_parent(remote);
 459         if (!remote_head)
 460                 die(_("'%s' does not point to a commit"), remote);
 461
 462         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 463                 if (starts_with(found_ref, "refs/heads/")) {
 464                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 465                                     oid_to_hex(&branch_head), remote);
 466                         goto cleanup;
 467                 }
 468                 if (starts_with(found_ref, "refs/tags/")) {
 469                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 470                                     oid_to_hex(&branch_head), remote);
 471                         goto cleanup;
 472                 }
 473                 if (starts_with(found_ref, "refs/remotes/")) {
 474                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 475                                     oid_to_hex(&branch_head), remote);
 476                         goto cleanup;
 477                 }
 478         }
 479
 480         /* See if remote matches <name>^^^.. or <name>~<number> */
 481         for (len = 0, ptr = remote + strlen(remote);
 482              remote < ptr && ptr[-1] == '^';
 483              ptr--)
 484                 len++;
 485         if (len)
 486                 early = 1;
 487         else {
 488                 early = 0;
 489                 ptr = strrchr(remote, '~');
 490                 if (ptr) {
 491                         int seen_nonzero = 0;
 492
 493                         len++; /* count ~ */
 494                         while (*++ptr && isdigit(*ptr)) {
 495                                 seen_nonzero |= (*ptr != '0');
 496                                 len++;
 497                         }
 498                         if (*ptr)
 499                                 len = 0; /* not ...~<number> */
 500                         else if (seen_nonzero)
 501                                 early = 1;
 502                         else if (len == 1)
 503                                 early = 1; /* "name~" is "name~1"! */
 504                 }
 505         }
 506         if (len) {
 507                 struct strbuf truname = STRBUF_INIT;
 508                 strbuf_addf(&truname, "refs/heads/%s", remote);
 509                 strbuf_setlen(&truname, truname.len - len);
 510                 if (ref_exists(truname.buf)) {
 511                         strbuf_addf(msg,
 512                                     "%s\t\tbranch '%s'%s of .\n",
 513                                     oid_to_hex(&remote_head->object.oid),
 514                                     truname.buf + 11,
 515                                     (early ? " (early part)" : ""));
 516                         strbuf_release(&truname);
 517                         goto cleanup;
 518                 }
 519                 strbuf_release(&truname);
 520         }
 521
 522         desc = merge_remote_util(remote_head);
 523         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 524                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 525                             oid_to_hex(&desc->obj->oid),
 526                             type_name(desc->obj->type),
 527                             remote);
 528                 goto cleanup;
 529         }
 530
 531         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 532                 oid_to_hex(&remote_head->object.oid), remote);
 533 cleanup:
 534         strbuf_release(&buf);
 535         strbuf_release(&bname);
 536 }
 537
 538 static void parse_branch_merge_options(char *bmo)
 539 {
 540         const char **argv;
 541         int argc;
 542
 543         if (!bmo)
 544                 return;
 545         argc = split_cmdline(bmo, &argv);
 546         if (argc < 0)
 547                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 548                     split_cmdline_strerror(argc));
 549         REALLOC_ARRAY(argv, argc + 2);
 550         MOVE_ARRAY(argv + 1, argv, argc + 1);
 551         argc++;
 552         argv[0] = "branch.*.mergeoptions";
 553         parse_options(argc, argv, NULL, builtin_merge_options,
 554                       builtin_merge_usage, 0);
 555         free(argv);
 556 }
 557
 558 static int git_merge_config(const char *k, const char *v, void *cb)
 559 {
 560         int status;
 561
 562         if (branch && starts_with(k, "branch.") &&
 563                 starts_with(k + 7, branch) &&
 564                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 565                 free(branch_mergeoptions);
 566                 branch_mergeoptions = xstrdup(v);
 567                 return 0;
 568         }
 569
 570         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 571                 show_diffstat = git_config_bool(k, v);
 572         else if (!strcmp(k, "merge.verifysignatures"))
 573                 verify_signatures = git_config_bool(k, v);
 574         else if (!strcmp(k, "pull.twohead"))
 575                 return git_config_string(&pull_twohead, k, v);
 576         else if (!strcmp(k, "pull.octopus"))
 577                 return git_config_string(&pull_octopus, k, v);
 578         else if (!strcmp(k, "merge.renormalize"))
 579                 option_renormalize = git_config_bool(k, v);
 580         else if (!strcmp(k, "merge.ff")) {
 581                 int boolval = git_parse_maybe_bool(v);
 582                 if (0 <= boolval) {
 583                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 584                 } else if (v && !strcmp(v, "only")) {
 585                         fast_forward = FF_ONLY;
 586                 } /* do not barf on values from future versions of git */
 587                 return 0;
 588         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 589                 default_to_upstream = git_config_bool(k, v);
 590                 return 0;
 591         } else if (!strcmp(k, "commit.gpgsign")) {
 592                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 593                 return 0;
 594         }
 595
 596         status = fmt_merge_msg_config(k, v, cb);
 597         if (status)
 598                 return status;
 599         status = git_gpg_config(k, v, NULL);
 600         if (status)
 601                 return status;
 602         return git_diff_ui_config(k, v, cb);
 603 }
 604
 605 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 606                              struct object_id *one)
 607 {
 608         int i, nr_trees = 0;
 609         struct tree *trees[MAX_UNPACK_TREES];
 610         struct tree_desc t[MAX_UNPACK_TREES];
 611         struct unpack_trees_options opts;
 612
 613         memset(&opts, 0, sizeof(opts));
 614         opts.head_idx = 2;
 615         opts.src_index = &the_index;
 616         opts.dst_index = &the_index;
 617         opts.update = 1;
 618         opts.verbose_update = 1;
 619         opts.trivial_merges_only = 1;
 620         opts.merge = 1;
 621         trees[nr_trees] = parse_tree_indirect(common);
 622         if (!trees[nr_trees++])
 623                 return -1;
 624         trees[nr_trees] = parse_tree_indirect(head);
 625         if (!trees[nr_trees++])
 626                 return -1;
 627         trees[nr_trees] = parse_tree_indirect(one);
 628         if (!trees[nr_trees++])
 629                 return -1;
 630         opts.fn = threeway_merge;
 631         cache_tree_free(&active_cache_tree);
 632         for (i = 0; i < nr_trees; i++) {
 633                 parse_tree(trees[i]);
 634                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 635         }
 636         if (unpack_trees(nr_trees, t, &opts))
 637                 return -1;
 638         return 0;
 639 }
 640
 641 static void write_tree_trivial(struct object_id *oid)
 642 {
 643         if (write_cache_as_tree(oid, 0, NULL))
 644                 die(_("git write-tree failed to write a tree"));
 645 }
 646
 647 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 648                               struct commit_list *remoteheads,
 649                               struct commit *head)
 650 {
 651         struct lock_file lock = LOCK_INIT;
 652         const char *head_arg = "HEAD";
 653
 654         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 655         refresh_cache(REFRESH_QUIET);
 656         if (write_locked_index(&the_index, &lock,
 657                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 658                 return error(_("Unable to write index."));
 659
 660         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 661                 int clean, x;
 662                 struct commit *result;
 663                 struct commit_list *reversed = NULL;
 664                 struct merge_options o;
 665                 struct commit_list *j;
 666
 667                 if (remoteheads->next) {
 668                         error(_("Not handling anything other than two heads merge."));
 669                         return 2;
 670                 }
 671
 672                 init_merge_options(&o);
 673                 if (!strcmp(strategy, "subtree"))
 674                         o.subtree_shift = "";
 675
 676                 o.renormalize = option_renormalize;
 677                 o.show_rename_progress =
 678                         show_progress == -1 ? isatty(2) : show_progress;
 679
 680                 for (x = 0; x < xopts_nr; x++)
 681                         if (parse_merge_opt(&o, xopts[x]))
 682                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 683
 684                 o.branch1 = head_arg;
 685                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 686
 687                 for (j = common; j; j = j->next)
 688                         commit_list_insert(j->item, &reversed);
 689
 690                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 691                 clean = merge_recursive(&o, head,
 692                                 remoteheads->item, reversed, &result);
 693                 if (clean < 0)
 694                         exit(128);
 695                 if (write_locked_index(&the_index, &lock,
 696                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 697                         die (_("unable to write %s"), get_index_file());
 698                 return clean ? 0 : 1;
 699         } else {
 700                 return try_merge_command(strategy, xopts_nr, xopts,
 701                                                 common, head_arg, remoteheads);
 702         }
 703 }
 704
 705 static void count_diff_files(struct diff_queue_struct *q,
 706                              struct diff_options *opt, void *data)
 707 {
 708         int *count = data;
 709
 710         (*count) += q->nr;
 711 }
 712
 713 static int count_unmerged_entries(void)
 714 {
 715         int i, ret = 0;
 716
 717         for (i = 0; i < active_nr; i++)
 718                 if (ce_stage(active_cache[i]))
 719                         ret++;
 720
 721         return ret;
 722 }
 723
 724 static void add_strategies(const char *string, unsigned attr)
 725 {
 726         int i;
 727
 728         if (string) {
 729                 struct string_list list = STRING_LIST_INIT_DUP;
 730                 struct string_list_item *item;
 731                 string_list_split(&list, string, ' ', -1);
 732                 for_each_string_list_item(item, &list)
 733                         append_strategy(get_strategy(item->string));
 734                 string_list_clear(&list, 0);
 735                 return;
 736         }
 737         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 738                 if (all_strategy[i].attr & attr)
 739                         append_strategy(&all_strategy[i]);
 740
 741 }
 742
 743 static void read_merge_msg(struct strbuf *msg)
 744 {
 745         const char *filename = git_path_merge_msg(the_repository);
 746         strbuf_reset(msg);
 747         if (strbuf_read_file(msg, filename, 0) < 0)
 748                 die_errno(_("Could not read from '%s'"), filename);
 749 }
 750
 751 static void write_merge_state(struct commit_list *);
 752 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 753 {
 754         if (err_msg)
 755                 error("%s", err_msg);
 756         fprintf(stderr,
 757                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 758         write_merge_state(remoteheads);
 759         exit(1);
 760 }
 761
 762 static const char merge_editor_comment[] =
 763 N_("Please enter a commit message to explain why this merge is necessary,\n"
 764    "especially if it merges an updated upstream into a topic branch.\n"
 765    "\n"
 766    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 767    "the commit.\n");
 768
 769 static void write_merge_heads(struct commit_list *);
 770 static void prepare_to_commit(struct commit_list *remoteheads)
 771 {
 772         struct strbuf msg = STRBUF_INIT;
 773         strbuf_addbuf(&msg, &merge_msg);
 774         strbuf_addch(&msg, '\n');
 775         if (squash)
 776                 BUG("the control must not reach here under --squash");
 777         if (0 < option_edit)
 778                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 779         if (signoff)
 780                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 781         write_merge_heads(remoteheads);
 782         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 783         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 784                             git_path_merge_msg(the_repository), "merge", NULL))
 785                 abort_commit(remoteheads, NULL);
 786         if (0 < option_edit) {
 787                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 788                         abort_commit(remoteheads, NULL);
 789         }
 790
 791         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 792                                           "commit-msg",
 793                                           git_path_merge_msg(the_repository), NULL))
 794                 abort_commit(remoteheads, NULL);
 795
 796         read_merge_msg(&msg);
 797         strbuf_stripspace(&msg, 0 < option_edit);
 798         if (!msg.len)
 799                 abort_commit(remoteheads, _("Empty commit message."));
 800         strbuf_release(&merge_msg);
 801         strbuf_addbuf(&merge_msg, &msg);
 802         strbuf_release(&msg);
 803 }
 804
 805 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 806 {
 807         struct object_id result_tree, result_commit;
 808         struct commit_list *parents, **pptr = &parents;
 809         struct lock_file lock = LOCK_INIT;
 810
 811         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 812         refresh_cache(REFRESH_QUIET);
 813         if (write_locked_index(&the_index, &lock,
 814                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 815                 return error(_("Unable to write index."));
 816
 817         write_tree_trivial(&result_tree);
 818         printf(_("Wonderful.\n"));
 819         pptr = commit_list_append(head, pptr);
 820         pptr = commit_list_append(remoteheads->item, pptr);
 821         prepare_to_commit(remoteheads);
 822         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 823                         &result_commit, NULL, sign_commit))
 824                 die(_("failed to write commit object"));
 825         finish(head, remoteheads, &result_commit, "In-index merge");
 826         drop_save();
 827         return 0;
 828 }
 829
 830 static int finish_automerge(struct commit *head,
 831                             int head_subsumed,
 832                             struct commit_list *common,
 833                             struct commit_list *remoteheads,
 834                             struct object_id *result_tree,
 835                             const char *wt_strategy)
 836 {
 837         struct commit_list *parents = NULL;
 838         struct strbuf buf = STRBUF_INIT;
 839         struct object_id result_commit;
 840
 841         free_commit_list(common);
 842         parents = remoteheads;
 843         if (!head_subsumed || fast_forward == FF_NO)
 844                 commit_list_insert(head, &parents);
 845         strbuf_addch(&merge_msg, '\n');
 846         prepare_to_commit(remoteheads);
 847         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 848                         &result_commit, NULL, sign_commit))
 849                 die(_("failed to write commit object"));
 850         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 851         finish(head, remoteheads, &result_commit, buf.buf);
 852         strbuf_release(&buf);
 853         drop_save();
 854         return 0;
 855 }
 856
 857 static int suggest_conflicts(void)
 858 {
 859         const char *filename;
 860         FILE *fp;
 861         struct strbuf msgbuf = STRBUF_INIT;
 862
 863         filename = git_path_merge_msg(the_repository);
 864         fp = xfopen(filename, "a");
 865
 866         append_conflicts_hint(&msgbuf);
 867         fputs(msgbuf.buf, fp);
 868         strbuf_release(&msgbuf);
 869         fclose(fp);
 870         rerere(allow_rerere_auto);
 871         printf(_("Automatic merge failed; "
 872                         "fix conflicts and then commit the result.\n"));
 873         return 1;
 874 }
 875
 876 static int evaluate_result(void)
 877 {
 878         int cnt = 0;
 879         struct rev_info rev;
 880
 881         /* Check how many files differ. */
 882         init_revisions(&rev, "");
 883         setup_revisions(0, NULL, &rev, NULL);
 884         rev.diffopt.output_format |=
 885                 DIFF_FORMAT_CALLBACK;
 886         rev.diffopt.format_callback = count_diff_files;
 887         rev.diffopt.format_callback_data = &cnt;
 888         run_diff_files(&rev, 0);
 889
 890         /*
 891          * Check how many unmerged entries are
 892          * there.
 893          */
 894         cnt += count_unmerged_entries();
 895
 896         return cnt;
 897 }
 898
 899 /*
 900  * Pretend as if the user told us to merge with the remote-tracking
 901  * branch we have for the upstream of the current branch
 902  */
 903 static int setup_with_upstream(const char ***argv)
 904 {
 905         struct branch *branch = branch_get(NULL);
 906         int i;
 907         const char **args;
 908
 909         if (!branch)
 910                 die(_("No current branch."));
 911         if (!branch->remote_name)
 912                 die(_("No remote for the current branch."));
 913         if (!branch->merge_nr)
 914                 die(_("No default upstream defined for the current branch."));
 915
 916         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 917         for (i = 0; i < branch->merge_nr; i++) {
 918                 if (!branch->merge[i]->dst)
 919                         die(_("No remote-tracking branch for %s from %s"),
 920                             branch->merge[i]->src, branch->remote_name);
 921                 args[i] = branch->merge[i]->dst;
 922         }
 923         args[i] = NULL;
 924         *argv = args;
 925         return i;
 926 }
 927
 928 static void write_merge_heads(struct commit_list *remoteheads)
 929 {
 930         struct commit_list *j;
 931         struct strbuf buf = STRBUF_INIT;
 932
 933         for (j = remoteheads; j; j = j->next) {
 934                 struct object_id *oid;
 935                 struct commit *c = j->item;
 936                 struct merge_remote_desc *desc;
 937
 938                 desc = merge_remote_util(c);
 939                 if (desc && desc->obj) {
 940                         oid = &desc->obj->oid;
 941                 } else {
 942                         oid = &c->object.oid;
 943                 }
 944                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 945         }
 946         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 947
 948         strbuf_reset(&buf);
 949         if (fast_forward == FF_NO)
 950                 strbuf_addstr(&buf, "no-ff");
 951         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 952         strbuf_release(&buf);
 953 }
 954
 955 static void write_merge_state(struct commit_list *remoteheads)
 956 {
 957         write_merge_heads(remoteheads);
 958         strbuf_addch(&merge_msg, '\n');
 959         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 960                        merge_msg.len);
 961 }
 962
 963 static int default_edit_option(void)
 964 {
 965         static const char name[] = "GIT_MERGE_AUTOEDIT";
 966         const char *e = getenv(name);
 967         struct stat st_stdin, st_stdout;
 968
 969         if (have_message)
 970                 /* an explicit -m msg without --[no-]edit */
 971                 return 0;
 972
 973         if (e) {
 974                 int v = git_parse_maybe_bool(e);
 975                 if (v < 0)
 976                         die(_("Bad value '%s' in environment '%s'"), e, name);
 977                 return v;
 978         }
 979
 980         /* Use editor if stdin and stdout are the same and is a tty */
 981         return (!fstat(0, &st_stdin) &&
 982                 !fstat(1, &st_stdout) &&
 983                 isatty(0) && isatty(1) &&
 984                 st_stdin.st_dev == st_stdout.st_dev &&
 985                 st_stdin.st_ino == st_stdout.st_ino &&
 986                 st_stdin.st_mode == st_stdout.st_mode);
 987 }
 988
 989 static struct commit_list *reduce_parents(struct commit *head_commit,
 990                                           int *head_subsumed,
 991                                           struct commit_list *remoteheads)
 992 {
 993         struct commit_list *parents, **remotes;
 994
 995         /*
 996          * Is the current HEAD reachable from another commit being
 997          * merged?  If so we do not want to record it as a parent of
 998          * the resulting merge, unless --no-ff is given.  We will flip
 999          * this variable to 0 when we find HEAD among the independent
1000          * tips being merged.
1001          */
1002         *head_subsumed = 1;
1003
1004         /* Find what parents to record by checking independent ones. */
1005         parents = reduce_heads(remoteheads);
1006         free_commit_list(remoteheads);
1007
1008         remoteheads = NULL;
1009         remotes = &remoteheads;
1010         while (parents) {
1011                 struct commit *commit = pop_commit(&parents);
1012                 if (commit == head_commit)
1013                         *head_subsumed = 0;
1014                 else
1015                         remotes = &commit_list_insert(commit, remotes)->next;
1016         }
1017         return remoteheads;
1018 }
1019
1020 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1021 {
1022         struct fmt_merge_msg_opts opts;
1023
1024         memset(&opts, 0, sizeof(opts));
1025         opts.add_title = !have_message;
1026         opts.shortlog_len = shortlog_len;
1027         opts.credit_people = (0 < option_edit);
1028
1029         fmt_merge_msg(merge_names, merge_msg, &opts);
1030         if (merge_msg->len)
1031                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1032 }
1033
1034 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1035 {
1036         const char *filename;
1037         int fd, pos, npos;
1038         struct strbuf fetch_head_file = STRBUF_INIT;
1039
1040         if (!merge_names)
1041                 merge_names = &fetch_head_file;
1042
1043         filename = git_path_fetch_head(the_repository);
1044         fd = open(filename, O_RDONLY);
1045         if (fd < 0)
1046                 die_errno(_("could not open '%s' for reading"), filename);
1047
1048         if (strbuf_read(merge_names, fd, 0) < 0)
1049                 die_errno(_("could not read '%s'"), filename);
1050         if (close(fd) < 0)
1051                 die_errno(_("could not close '%s'"), filename);
1052
1053         for (pos = 0; pos < merge_names->len; pos = npos) {
1054                 struct object_id oid;
1055                 char *ptr;
1056                 struct commit *commit;
1057
1058                 ptr = strchr(merge_names->buf + pos, '\n');
1059                 if (ptr)
1060                         npos = ptr - merge_names->buf + 1;
1061                 else
1062                         npos = merge_names->len;
1063
1064                 if (npos - pos < GIT_SHA1_HEXSZ + 2 ||
1065                     get_oid_hex(merge_names->buf + pos, &oid))
1066                         commit = NULL; /* bad */
1067                 else if (memcmp(merge_names->buf + pos + GIT_SHA1_HEXSZ, "\t\t", 2))
1068                         continue; /* not-for-merge */
1069                 else {
1070                         char saved = merge_names->buf[pos + GIT_SHA1_HEXSZ];
1071                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = '\0';
1072                         commit = get_merge_parent(merge_names->buf + pos);
1073                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = saved;
1074                 }
1075                 if (!commit) {
1076                         if (ptr)
1077                                 *ptr = '\0';
1078                         die(_("not something we can merge in %s: %s"),
1079                             filename, merge_names->buf + pos);
1080                 }
1081                 remotes = &commit_list_insert(commit, remotes)->next;
1082         }
1083
1084         if (merge_names == &fetch_head_file)
1085                 strbuf_release(&fetch_head_file);
1086 }
1087
1088 static struct commit_list *collect_parents(struct commit *head_commit,
1089                                            int *head_subsumed,
1090                                            int argc, const char **argv,
1091                                            struct strbuf *merge_msg)
1092 {
1093         int i;
1094         struct commit_list *remoteheads = NULL;
1095         struct commit_list **remotes = &remoteheads;
1096         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1097
1098         if (merge_msg && (!have_message || shortlog_len))
1099                 autogen = &merge_names;
1100
1101         if (head_commit)
1102                 remotes = &commit_list_insert(head_commit, remotes)->next;
1103
1104         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1105                 handle_fetch_head(remotes, autogen);
1106                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1107         } else {
1108                 for (i = 0; i < argc; i++) {
1109                         struct commit *commit = get_merge_parent(argv[i]);
1110                         if (!commit)
1111                                 help_unknown_ref(argv[i], "merge",
1112                                                  _("not something we can merge"));
1113                         remotes = &commit_list_insert(commit, remotes)->next;
1114                 }
1115                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1116                 if (autogen) {
1117                         struct commit_list *p;
1118                         for (p = remoteheads; p; p = p->next)
1119                                 merge_name(merge_remote_util(p->item)->name, autogen);
1120                 }
1121         }
1122
1123         if (autogen) {
1124                 prepare_merge_message(autogen, merge_msg);
1125                 strbuf_release(autogen);
1126         }
1127
1128         return remoteheads;
1129 }
1130
1131 static int merging_a_throwaway_tag(struct commit *commit)
1132 {
1133         char *tag_ref;
1134         struct object_id oid;
1135         int is_throwaway_tag = 0;
1136
1137         /* Are we merging a tag? */
1138         if (!merge_remote_util(commit) ||
1139             !merge_remote_util(commit)->obj ||
1140             merge_remote_util(commit)->obj->type != OBJ_TAG)
1141                 return is_throwaway_tag;
1142
1143         /*
1144          * Now we know we are merging a tag object.  Are we downstream
1145          * and following the tags from upstream?  If so, we must have
1146          * the tag object pointed at by "refs/tags/$T" where $T is the
1147          * tagname recorded in the tag object.  We want to allow such
1148          * a "just to catch up" merge to fast-forward.
1149          *
1150          * Otherwise, we are playing an integrator's role, making a
1151          * merge with a throw-away tag from a contributor with
1152          * something like "git pull $contributor $signed_tag".
1153          * We want to forbid such a merge from fast-forwarding
1154          * by default; otherwise we would not keep the signature
1155          * anywhere.
1156          */
1157         tag_ref = xstrfmt("refs/tags/%s",
1158                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1159         if (!read_ref(tag_ref, &oid) &&
1160             !oidcmp(&oid, &merge_remote_util(commit)->obj->oid))
1161                 is_throwaway_tag = 0;
1162         else
1163                 is_throwaway_tag = 1;
1164         free(tag_ref);
1165         return is_throwaway_tag;
1166 }
1167
1168 int cmd_merge(int argc, const char **argv, const char *prefix)
1169 {
1170         struct object_id result_tree, stash, head_oid;
1171         struct commit *head_commit;
1172         struct strbuf buf = STRBUF_INIT;
1173         int i, ret = 0, head_subsumed;
1174         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1175         struct commit_list *common = NULL;
1176         const char *best_strategy = NULL, *wt_strategy = NULL;
1177         struct commit_list *remoteheads, *p;
1178         void *branch_to_free;
1179         int orig_argc = argc;
1180
1181         if (argc == 2 && !strcmp(argv[1], "-h"))
1182                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1183
1184         /*
1185          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1186          * current branch.
1187          */
1188         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1189         if (branch)
1190                 skip_prefix(branch, "refs/heads/", &branch);
1191
1192         init_diff_ui_defaults();
1193         git_config(git_merge_config, NULL);
1194
1195         if (!branch || is_null_oid(&head_oid))
1196                 head_commit = NULL;
1197         else
1198                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1199
1200         if (branch_mergeoptions)
1201                 parse_branch_merge_options(branch_mergeoptions);
1202         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1203                         builtin_merge_usage, 0);
1204         if (shortlog_len < 0)
1205                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1206
1207         if (verbosity < 0 && show_progress == -1)
1208                 show_progress = 0;
1209
1210         if (abort_current_merge) {
1211                 int nargc = 2;
1212                 const char *nargv[] = {"reset", "--merge", NULL};
1213
1214                 if (orig_argc != 2)
1215                         usage_msg_opt(_("--abort expects no arguments"),
1216                               builtin_merge_usage, builtin_merge_options);
1217
1218                 if (!file_exists(git_path_merge_head(the_repository)))
1219                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1220
1221                 /* Invoke 'git reset --merge' */
1222                 ret = cmd_reset(nargc, nargv, prefix);
1223                 goto done;
1224         }
1225
1226         if (continue_current_merge) {
1227                 int nargc = 1;
1228                 const char *nargv[] = {"commit", NULL};
1229
1230                 if (orig_argc != 2)
1231                         usage_msg_opt(_("--continue expects no arguments"),
1232                               builtin_merge_usage, builtin_merge_options);
1233
1234                 if (!file_exists(git_path_merge_head(the_repository)))
1235                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1236
1237                 /* Invoke 'git commit' */
1238                 ret = cmd_commit(nargc, nargv, prefix);
1239                 goto done;
1240         }
1241
1242         if (read_cache_unmerged())
1243                 die_resolve_conflict("merge");
1244
1245         if (file_exists(git_path_merge_head(the_repository))) {
1246                 /*
1247                  * There is no unmerged entry, don't advise 'git
1248                  * add/rm <file>', just 'git commit'.
1249                  */
1250                 if (advice_resolve_conflict)
1251                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1252                                   "Please, commit your changes before you merge."));
1253                 else
1254                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1255         }
1256         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1257                 if (advice_resolve_conflict)
1258                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1259                             "Please, commit your changes before you merge."));
1260                 else
1261                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1262         }
1263         resolve_undo_clear();
1264
1265         if (verbosity < 0)
1266                 show_diffstat = 0;
1267
1268         if (squash) {
1269                 if (fast_forward == FF_NO)
1270                         die(_("You cannot combine --squash with --no-ff."));
1271                 option_commit = 0;
1272         }
1273
1274         if (!argc) {
1275                 if (default_to_upstream)
1276                         argc = setup_with_upstream(&argv);
1277                 else
1278                         die(_("No commit specified and merge.defaultToUpstream not set."));
1279         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1280                 argv[0] = "@{-1}";
1281         }
1282
1283         if (!argc)
1284                 usage_with_options(builtin_merge_usage,
1285                         builtin_merge_options);
1286
1287         if (!head_commit) {
1288                 /*
1289                  * If the merged head is a valid one there is no reason
1290                  * to forbid "git merge" into a branch yet to be born.
1291                  * We do the same for "git pull".
1292                  */
1293                 struct object_id *remote_head_oid;
1294                 if (squash)
1295                         die(_("Squash commit into empty head not supported yet"));
1296                 if (fast_forward == FF_NO)
1297                         die(_("Non-fast-forward commit does not make sense into "
1298                             "an empty head"));
1299                 remoteheads = collect_parents(head_commit, &head_subsumed,
1300                                               argc, argv, NULL);
1301                 if (!remoteheads)
1302                         die(_("%s - not something we can merge"), argv[0]);
1303                 if (remoteheads->next)
1304                         die(_("Can merge only exactly one commit into empty head"));
1305                 remote_head_oid = &remoteheads->item->object.oid;
1306                 read_empty(remote_head_oid, 0);
1307                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1308                            UPDATE_REFS_DIE_ON_ERR);
1309                 goto done;
1310         }
1311
1312         /*
1313          * All the rest are the commits being merged; prepare
1314          * the standard merge summary message to be appended
1315          * to the given message.
1316          */
1317         remoteheads = collect_parents(head_commit, &head_subsumed,
1318                                       argc, argv, &merge_msg);
1319
1320         if (!head_commit || !argc)
1321                 usage_with_options(builtin_merge_usage,
1322                         builtin_merge_options);
1323
1324         if (verify_signatures) {
1325                 for (p = remoteheads; p; p = p->next) {
1326                         struct commit *commit = p->item;
1327                         char hex[GIT_MAX_HEXSZ + 1];
1328                         struct signature_check signature_check;
1329                         memset(&signature_check, 0, sizeof(signature_check));
1330
1331                         check_commit_signature(commit, &signature_check);
1332
1333                         find_unique_abbrev_r(hex, &commit->object.oid, DEFAULT_ABBREV);
1334                         switch (signature_check.result) {
1335                         case 'G':
1336                                 break;
1337                         case 'U':
1338                                 die(_("Commit %s has an untrusted GPG signature, "
1339                                       "allegedly by %s."), hex, signature_check.signer);
1340                         case 'B':
1341                                 die(_("Commit %s has a bad GPG signature "
1342                                       "allegedly by %s."), hex, signature_check.signer);
1343                         default: /* 'N' */
1344                                 die(_("Commit %s does not have a GPG signature."), hex);
1345                         }
1346                         if (verbosity >= 0 && signature_check.result == 'G')
1347                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1348                                        hex, signature_check.signer);
1349
1350                         signature_check_clear(&signature_check);
1351                 }
1352         }
1353
1354         strbuf_addstr(&buf, "merge");
1355         for (p = remoteheads; p; p = p->next)
1356                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1357         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1358         strbuf_reset(&buf);
1359
1360         for (p = remoteheads; p; p = p->next) {
1361                 struct commit *commit = p->item;
1362                 strbuf_addf(&buf, "GITHEAD_%s",
1363                             oid_to_hex(&commit->object.oid));
1364                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1365                 strbuf_reset(&buf);
1366                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1367                         fast_forward = FF_NO;
1368         }
1369
1370         if (option_edit < 0)
1371                 option_edit = default_edit_option();
1372
1373         if (!use_strategies) {
1374                 if (!remoteheads)
1375                         ; /* already up-to-date */
1376                 else if (!remoteheads->next)
1377                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1378                 else
1379                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1380         }
1381
1382         for (i = 0; i < use_strategies_nr; i++) {
1383                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1384                         fast_forward = FF_NO;
1385                 if (use_strategies[i]->attr & NO_TRIVIAL)
1386                         allow_trivial = 0;
1387         }
1388
1389         if (!remoteheads)
1390                 ; /* already up-to-date */
1391         else if (!remoteheads->next)
1392                 common = get_merge_bases(head_commit, remoteheads->item);
1393         else {
1394                 struct commit_list *list = remoteheads;
1395                 commit_list_insert(head_commit, &list);
1396                 common = get_octopus_merge_bases(list);
1397                 free(list);
1398         }
1399
1400         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1401                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1402
1403         if (remoteheads && !common) {
1404                 /* No common ancestors found. */
1405                 if (!allow_unrelated_histories)
1406                         die(_("refusing to merge unrelated histories"));
1407                 /* otherwise, we need a real merge. */
1408         } else if (!remoteheads ||
1409                  (!remoteheads->next && !common->next &&
1410                   common->item == remoteheads->item)) {
1411                 /*
1412                  * If head can reach all the merge then we are up to date.
1413                  * but first the most common case of merging one remote.
1414                  */
1415                 finish_up_to_date(_("Already up to date."));
1416                 goto done;
1417         } else if (fast_forward != FF_NO && !remoteheads->next &&
1418                         !common->next &&
1419                         !oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
1420                 /* Again the most common case of merging one remote. */
1421                 struct strbuf msg = STRBUF_INIT;
1422                 struct commit *commit;
1423
1424                 if (verbosity >= 0) {
1425                         printf(_("Updating %s..%s\n"),
1426                                find_unique_abbrev(&head_commit->object.oid,
1427                                                   DEFAULT_ABBREV),
1428                                find_unique_abbrev(&remoteheads->item->object.oid,
1429                                                   DEFAULT_ABBREV));
1430                 }
1431                 strbuf_addstr(&msg, "Fast-forward");
1432                 if (have_message)
1433                         strbuf_addstr(&msg,
1434                                 " (no commit created; -m option ignored)");
1435                 commit = remoteheads->item;
1436                 if (!commit) {
1437                         ret = 1;
1438                         goto done;
1439                 }
1440
1441                 if (checkout_fast_forward(&head_commit->object.oid,
1442                                           &commit->object.oid,
1443                                           overwrite_ignore)) {
1444                         ret = 1;
1445                         goto done;
1446                 }
1447
1448                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1449                 drop_save();
1450                 goto done;
1451         } else if (!remoteheads->next && common->next)
1452                 ;
1453                 /*
1454                  * We are not doing octopus and not fast-forward.  Need
1455                  * a real merge.
1456                  */
1457         else if (!remoteheads->next && !common->next && option_commit) {
1458                 /*
1459                  * We are not doing octopus, not fast-forward, and have
1460                  * only one common.
1461                  */
1462                 refresh_cache(REFRESH_QUIET);
1463                 if (allow_trivial && fast_forward != FF_ONLY) {
1464                         /* See if it is really trivial. */
1465                         git_committer_info(IDENT_STRICT);
1466                         printf(_("Trying really trivial in-index merge...\n"));
1467                         if (!read_tree_trivial(&common->item->object.oid,
1468                                                &head_commit->object.oid,
1469                                                &remoteheads->item->object.oid)) {
1470                                 ret = merge_trivial(head_commit, remoteheads);
1471                                 goto done;
1472                         }
1473                         printf(_("Nope.\n"));
1474                 }
1475         } else {
1476                 /*
1477                  * An octopus.  If we can reach all the remote we are up
1478                  * to date.
1479                  */
1480                 int up_to_date = 1;
1481                 struct commit_list *j;
1482
1483                 for (j = remoteheads; j; j = j->next) {
1484                         struct commit_list *common_one;
1485
1486                         /*
1487                          * Here we *have* to calculate the individual
1488                          * merge_bases again, otherwise "git merge HEAD^
1489                          * HEAD^^" would be missed.
1490                          */
1491                         common_one = get_merge_bases(head_commit, j->item);
1492                         if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
1493                                 up_to_date = 0;
1494                                 break;
1495                         }
1496                 }
1497                 if (up_to_date) {
1498                         finish_up_to_date(_("Already up to date. Yeeah!"));
1499                         goto done;
1500                 }
1501         }
1502
1503         if (fast_forward == FF_ONLY)
1504                 die(_("Not possible to fast-forward, aborting."));
1505
1506         /* We are going to make a new commit. */
1507         git_committer_info(IDENT_STRICT);
1508
1509         /*
1510          * At this point, we need a real merge.  No matter what strategy
1511          * we use, it would operate on the index, possibly affecting the
1512          * working tree, and when resolved cleanly, have the desired
1513          * tree in the index -- this means that the index must be in
1514          * sync with the head commit.  The strategies are responsible
1515          * to ensure this.
1516          */
1517         if (use_strategies_nr == 1 ||
1518             /*
1519              * Stash away the local changes so that we can try more than one.
1520              */
1521             save_state(&stash))
1522                 oidclr(&stash);
1523
1524         for (i = 0; i < use_strategies_nr; i++) {
1525                 int ret;
1526                 if (i) {
1527                         printf(_("Rewinding the tree to pristine...\n"));
1528                         restore_state(&head_commit->object.oid, &stash);
1529                 }
1530                 if (use_strategies_nr != 1)
1531                         printf(_("Trying merge strategy %s...\n"),
1532                                 use_strategies[i]->name);
1533                 /*
1534                  * Remember which strategy left the state in the working
1535                  * tree.
1536                  */
1537                 wt_strategy = use_strategies[i]->name;
1538
1539                 ret = try_merge_strategy(use_strategies[i]->name,
1540                                          common, remoteheads,
1541                                          head_commit);
1542                 if (!option_commit && !ret) {
1543                         merge_was_ok = 1;
1544                         /*
1545                          * This is necessary here just to avoid writing
1546                          * the tree, but later we will *not* exit with
1547                          * status code 1 because merge_was_ok is set.
1548                          */
1549                         ret = 1;
1550                 }
1551
1552                 if (ret) {
1553                         /*
1554                          * The backend exits with 1 when conflicts are
1555                          * left to be resolved, with 2 when it does not
1556                          * handle the given merge at all.
1557                          */
1558                         if (ret == 1) {
1559                                 int cnt = evaluate_result();
1560
1561                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1562                                         best_strategy = use_strategies[i]->name;
1563                                         best_cnt = cnt;
1564                                 }
1565                         }
1566                         if (merge_was_ok)
1567                                 break;
1568                         else
1569                                 continue;
1570                 }
1571
1572                 /* Automerge succeeded. */
1573                 write_tree_trivial(&result_tree);
1574                 automerge_was_ok = 1;
1575                 break;
1576         }
1577
1578         /*
1579          * If we have a resulting tree, that means the strategy module
1580          * auto resolved the merge cleanly.
1581          */
1582         if (automerge_was_ok) {
1583                 ret = finish_automerge(head_commit, head_subsumed,
1584                                        common, remoteheads,
1585                                        &result_tree, wt_strategy);
1586                 goto done;
1587         }
1588
1589         /*
1590          * Pick the result from the best strategy and have the user fix
1591          * it up.
1592          */
1593         if (!best_strategy) {
1594                 restore_state(&head_commit->object.oid, &stash);
1595                 if (use_strategies_nr > 1)
1596                         fprintf(stderr,
1597                                 _("No merge strategy handled the merge.\n"));
1598                 else
1599                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1600                                 use_strategies[0]->name);
1601                 ret = 2;
1602                 goto done;
1603         } else if (best_strategy == wt_strategy)
1604                 ; /* We already have its result in the working tree. */
1605         else {
1606                 printf(_("Rewinding the tree to pristine...\n"));
1607                 restore_state(&head_commit->object.oid, &stash);
1608                 printf(_("Using the %s to prepare resolving by hand.\n"),
1609                         best_strategy);
1610                 try_merge_strategy(best_strategy, common, remoteheads,
1611                                    head_commit);
1612         }
1613
1614         if (squash)
1615                 finish(head_commit, remoteheads, NULL, NULL);
1616         else
1617                 write_merge_state(remoteheads);
1618
1619         if (merge_was_ok)
1620                 fprintf(stderr, _("Automatic merge went well; "
1621                         "stopped before committing as requested\n"));
1622         else
1623                 ret = suggest_conflicts();
1624
1625 done:
1626         free(branch_to_free);
1627         return ret;
1628 }