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