builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "refs.h"
  18 #include "refspec.h"
  19 #include "commit.h"
  20 #include "diffcore.h"
  21 #include "revision.h"
  22 #include "unpack-trees.h"
  23 #include "cache-tree.h"
  24 #include "dir.h"
  25 #include "utf8.h"
  26 #include "log-tree.h"
  27 #include "color.h"
  28 #include "rerere.h"
  29 #include "help.h"
  30 #include "merge-recursive.h"
  31 #include "resolve-undo.h"
  32 #include "remote.h"
  33 #include "fmt-merge-msg.h"
  34 #include "gpg-interface.h"
  35 #include "sequencer.h"
  36 #include "string-list.h"
  37 #include "packfile.h"
  38 #include "tag.h"
  39 #include "alias.h"
  40 #include "commit-reach.h"
  41
  42 #define DEFAULT_TWOHEAD (1<<0)
  43 #define DEFAULT_OCTOPUS (1<<1)
  44 #define NO_FAST_FORWARD (1<<2)
  45 #define NO_TRIVIAL      (1<<3)
  46
  47 struct strategy {
  48         const char *name;
  49         unsigned attr;
  50 };
  51
  52 static const char * const builtin_merge_usage[] = {
  53         N_("git merge [<options>] [<commit>...]"),
  54         N_("git merge --abort"),
  55         N_("git merge --continue"),
  56         NULL
  57 };
  58
  59 static int show_diffstat = 1, shortlog_len = -1, squash;
  60 static int option_commit = 1;
  61 static int option_edit = -1;
  62 static int allow_trivial = 1, have_message, verify_signatures;
  63 static int overwrite_ignore = 1;
  64 static struct strbuf merge_msg = STRBUF_INIT;
  65 static struct strategy **use_strategies;
  66 static size_t use_strategies_nr, use_strategies_alloc;
  67 static const char **xopts;
  68 static size_t xopts_nr, xopts_alloc;
  69 static const char *branch;
  70 static char *branch_mergeoptions;
  71 static int option_renormalize;
  72 static int verbosity;
  73 static int allow_rerere_auto;
  74 static int abort_current_merge;
  75 static int continue_current_merge;
  76 static int allow_unrelated_histories;
  77 static int show_progress = -1;
  78 static int default_to_upstream = 1;
  79 static int signoff;
  80 static const char *sign_commit;
  81 static int verify_msg = 1;
  82
  83 static struct strategy all_strategy[] = {
  84         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  85         { "octopus",    DEFAULT_OCTOPUS },
  86         { "resolve",    0 },
  87         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  88         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  89 };
  90
  91 static const char *pull_twohead, *pull_octopus;
  92
  93 enum ff_type {
  94         FF_NO,
  95         FF_ALLOW,
  96         FF_ONLY
  97 };
  98
  99 static enum ff_type fast_forward = FF_ALLOW;
 100
 101 static int option_parse_message(const struct option *opt,
 102                                 const char *arg, int unset)
 103 {
 104         struct strbuf *buf = opt->value;
 105
 106         if (unset)
 107                 strbuf_setlen(buf, 0);
 108         else if (arg) {
 109                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 110                 have_message = 1;
 111         } else
 112                 return error(_("switch `m' requires a value"));
 113         return 0;
 114 }
 115
 116 static int option_read_message(struct parse_opt_ctx_t *ctx,
 117                                const struct option *opt, int unset)
 118 {
 119         struct strbuf *buf = opt->value;
 120         const char *arg;
 121
 122         if (unset)
 123                 BUG("-F cannot be negated");
 124
 125         if (ctx->opt) {
 126                 arg = ctx->opt;
 127                 ctx->opt = NULL;
 128         } else if (ctx->argc > 1) {
 129                 ctx->argc--;
 130                 arg = *++ctx->argv;
 131         } else
 132                 return error(_("option `%s' requires a value"), opt->long_name);
 133
 134         if (buf->len)
 135                 strbuf_addch(buf, '\n');
 136         if (ctx->prefix && !is_absolute_path(arg))
 137                 arg = prefix_filename(ctx->prefix, arg);
 138         if (strbuf_read_file(buf, arg, 0) < 0)
 139                 return error(_("could not read file '%s'"), arg);
 140         have_message = 1;
 141
 142         return 0;
 143 }
 144
 145 static struct strategy *get_strategy(const char *name)
 146 {
 147         int i;
 148         struct strategy *ret;
 149         static struct cmdnames main_cmds, other_cmds;
 150         static int loaded;
 151
 152         if (!name)
 153                 return NULL;
 154
 155         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 156                 if (!strcmp(name, all_strategy[i].name))
 157                         return &all_strategy[i];
 158
 159         if (!loaded) {
 160                 struct cmdnames not_strategies;
 161                 loaded = 1;
 162
 163                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 164                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 165                 for (i = 0; i < main_cmds.cnt; i++) {
 166                         int j, found = 0;
 167                         struct cmdname *ent = main_cmds.names[i];
 168                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 169                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 170                                                 && !all_strategy[j].name[ent->len])
 171                                         found = 1;
 172                         if (!found)
 173                                 add_cmdname(&not_strategies, ent->name, ent->len);
 174                 }
 175                 exclude_cmds(&main_cmds, &not_strategies);
 176         }
 177         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 178                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 179                 fprintf(stderr, _("Available strategies are:"));
 180                 for (i = 0; i < main_cmds.cnt; i++)
 181                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 182                 fprintf(stderr, ".\n");
 183                 if (other_cmds.cnt) {
 184                         fprintf(stderr, _("Available custom strategies are:"));
 185                         for (i = 0; i < other_cmds.cnt; i++)
 186                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 187                         fprintf(stderr, ".\n");
 188                 }
 189                 exit(1);
 190         }
 191
 192         ret = xcalloc(1, sizeof(struct strategy));
 193         ret->name = xstrdup(name);
 194         ret->attr = NO_TRIVIAL;
 195         return ret;
 196 }
 197
 198 static void append_strategy(struct strategy *s)
 199 {
 200         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 201         use_strategies[use_strategies_nr++] = s;
 202 }
 203
 204 static int option_parse_strategy(const struct option *opt,
 205                                  const char *name, int unset)
 206 {
 207         if (unset)
 208                 return 0;
 209
 210         append_strategy(get_strategy(name));
 211         return 0;
 212 }
 213
 214 static int option_parse_x(const struct option *opt,
 215                           const char *arg, int unset)
 216 {
 217         if (unset)
 218                 return 0;
 219
 220         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 221         xopts[xopts_nr++] = xstrdup(arg);
 222         return 0;
 223 }
 224
 225 static int option_parse_n(const struct option *opt,
 226                           const char *arg, int unset)
 227 {
 228         BUG_ON_OPT_ARG(arg);
 229         show_diffstat = unset;
 230         return 0;
 231 }
 232
 233 static struct option builtin_merge_options[] = {
 234         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 235                 N_("do not show a diffstat at the end of the merge"),
 236                 PARSE_OPT_NOARG, option_parse_n },
 237         OPT_BOOL(0, "stat", &show_diffstat,
 238                 N_("show a diffstat at the end of the merge")),
 239         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 240         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 241           N_("add (at most <n>) entries from shortlog to merge commit message"),
 242           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 243         OPT_BOOL(0, "squash", &squash,
 244                 N_("create a single commit instead of doing a merge")),
 245         OPT_BOOL(0, "commit", &option_commit,
 246                 N_("perform a commit if the merge succeeds (default)")),
 247         OPT_BOOL('e', "edit", &option_edit,
 248                 N_("edit message before committing")),
 249         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 250         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 251                       N_("abort if fast-forward is not possible"),
 252                       FF_ONLY, PARSE_OPT_NONEG),
 253         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 254         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 255                 N_("verify that the named commit has a valid GPG signature")),
 256         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 257                 N_("merge strategy to use"), option_parse_strategy),
 258         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 259                 N_("option for selected merge strategy"), option_parse_x),
 260         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 261                 N_("merge commit message (for a non-fast-forward merge)"),
 262                 option_parse_message),
 263         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 264                 N_("read message from file"), PARSE_OPT_NONEG,
 265                 (parse_opt_cb *) option_read_message },
 266         OPT__VERBOSITY(&verbosity),
 267         OPT_BOOL(0, "abort", &abort_current_merge,
 268                 N_("abort the current in-progress merge")),
 269         OPT_BOOL(0, "continue", &continue_current_merge,
 270                 N_("continue the current in-progress merge")),
 271         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 272                  N_("allow merging unrelated histories")),
 273         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 274         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 275           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 276         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 277         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 278         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 279         OPT_END()
 280 };
 281
 282 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 283 static void drop_save(void)
 284 {
 285         unlink(git_path_merge_head(the_repository));
 286         unlink(git_path_merge_msg(the_repository));
 287         unlink(git_path_merge_mode(the_repository));
 288 }
 289
 290 static int save_state(struct object_id *stash)
 291 {
 292         int len;
 293         struct child_process cp = CHILD_PROCESS_INIT;
 294         struct strbuf buffer = STRBUF_INIT;
 295         const char *argv[] = {"stash", "create", NULL};
 296         int rc = -1;
 297
 298         cp.argv = argv;
 299         cp.out = -1;
 300         cp.git_cmd = 1;
 301
 302         if (start_command(&cp))
 303                 die(_("could not run stash."));
 304         len = strbuf_read(&buffer, cp.out, 1024);
 305         close(cp.out);
 306
 307         if (finish_command(&cp) || len < 0)
 308                 die(_("stash failed"));
 309         else if (!len)          /* no changes */
 310                 goto out;
 311         strbuf_setlen(&buffer, buffer.len-1);
 312         if (get_oid(buffer.buf, stash))
 313                 die(_("not a valid object: %s"), buffer.buf);
 314         rc = 0;
 315 out:
 316         strbuf_release(&buffer);
 317         return rc;
 318 }
 319
 320 static void read_empty(const struct object_id *oid, int verbose)
 321 {
 322         int i = 0;
 323         const char *args[7];
 324
 325         args[i++] = "read-tree";
 326         if (verbose)
 327                 args[i++] = "-v";
 328         args[i++] = "-m";
 329         args[i++] = "-u";
 330         args[i++] = empty_tree_oid_hex();
 331         args[i++] = oid_to_hex(oid);
 332         args[i] = NULL;
 333
 334         if (run_command_v_opt(args, RUN_GIT_CMD))
 335                 die(_("read-tree failed"));
 336 }
 337
 338 static void reset_hard(const struct object_id *oid, int verbose)
 339 {
 340         int i = 0;
 341         const char *args[6];
 342
 343         args[i++] = "read-tree";
 344         if (verbose)
 345                 args[i++] = "-v";
 346         args[i++] = "--reset";
 347         args[i++] = "-u";
 348         args[i++] = oid_to_hex(oid);
 349         args[i] = NULL;
 350
 351         if (run_command_v_opt(args, RUN_GIT_CMD))
 352                 die(_("read-tree failed"));
 353 }
 354
 355 static void restore_state(const struct object_id *head,
 356                           const struct object_id *stash)
 357 {
 358         struct strbuf sb = STRBUF_INIT;
 359         const char *args[] = { "stash", "apply", NULL, NULL };
 360
 361         if (is_null_oid(stash))
 362                 return;
 363
 364         reset_hard(head, 1);
 365
 366         args[2] = oid_to_hex(stash);
 367
 368         /*
 369          * It is OK to ignore error here, for example when there was
 370          * nothing to restore.
 371          */
 372         run_command_v_opt(args, RUN_GIT_CMD);
 373
 374         strbuf_release(&sb);
 375         refresh_cache(REFRESH_QUIET);
 376 }
 377
 378 /* This is called when no merge was necessary. */
 379 static void finish_up_to_date(const char *msg)
 380 {
 381         if (verbosity >= 0)
 382                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 383         drop_save();
 384 }
 385
 386 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 387 {
 388         struct rev_info rev;
 389         struct strbuf out = STRBUF_INIT;
 390         struct commit_list *j;
 391         struct pretty_print_context ctx = {0};
 392
 393         printf(_("Squash commit -- not updating HEAD\n"));
 394
 395         repo_init_revisions(the_repository, &rev, NULL);
 396         rev.ignore_merges = 1;
 397         rev.commit_format = CMIT_FMT_MEDIUM;
 398
 399         commit->object.flags |= UNINTERESTING;
 400         add_pending_object(&rev, &commit->object, NULL);
 401
 402         for (j = remoteheads; j; j = j->next)
 403                 add_pending_object(&rev, &j->item->object, NULL);
 404
 405         setup_revisions(0, NULL, &rev, NULL);
 406         if (prepare_revision_walk(&rev))
 407                 die(_("revision walk setup failed"));
 408
 409         ctx.abbrev = rev.abbrev;
 410         ctx.date_mode = rev.date_mode;
 411         ctx.fmt = rev.commit_format;
 412
 413         strbuf_addstr(&out, "Squashed commit of the following:\n");
 414         while ((commit = get_revision(&rev)) != NULL) {
 415                 strbuf_addch(&out, '\n');
 416                 strbuf_addf(&out, "commit %s\n",
 417                         oid_to_hex(&commit->object.oid));
 418                 pretty_print_commit(&ctx, commit, &out);
 419         }
 420         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 421         strbuf_release(&out);
 422 }
 423
 424 static void finish(struct commit *head_commit,
 425                    struct commit_list *remoteheads,
 426                    const struct object_id *new_head, const char *msg)
 427 {
 428         struct strbuf reflog_message = STRBUF_INIT;
 429         const struct object_id *head = &head_commit->object.oid;
 430
 431         if (!msg)
 432                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 433         else {
 434                 if (verbosity >= 0)
 435                         printf("%s\n", msg);
 436                 strbuf_addf(&reflog_message, "%s: %s",
 437                         getenv("GIT_REFLOG_ACTION"), msg);
 438         }
 439         if (squash) {
 440                 squash_message(head_commit, remoteheads);
 441         } else {
 442                 if (verbosity >= 0 && !merge_msg.len)
 443                         printf(_("No merge message -- not updating HEAD\n"));
 444                 else {
 445                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 446                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 447                                    0, UPDATE_REFS_DIE_ON_ERR);
 448                         /*
 449                          * We ignore errors in 'gc --auto', since the
 450                          * user should see them.
 451                          */
 452                         close_all_packs(the_repository->objects);
 453                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 454                 }
 455         }
 456         if (new_head && show_diffstat) {
 457                 struct diff_options opts;
 458                 repo_diff_setup(the_repository, &opts);
 459                 opts.stat_width = -1; /* use full terminal width */
 460                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 461                 opts.output_format |=
 462                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 463                 opts.detect_rename = DIFF_DETECT_RENAME;
 464                 diff_setup_done(&opts);
 465                 diff_tree_oid(head, new_head, "", &opts);
 466                 diffcore_std(&opts);
 467                 diff_flush(&opts);
 468         }
 469
 470         /* Run a post-merge hook */
 471         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 472
 473         strbuf_release(&reflog_message);
 474 }
 475
 476 /* Get the name for the merge commit's message. */
 477 static void merge_name(const char *remote, struct strbuf *msg)
 478 {
 479         struct commit *remote_head;
 480         struct object_id branch_head;
 481         struct strbuf buf = STRBUF_INIT;
 482         struct strbuf bname = STRBUF_INIT;
 483         struct merge_remote_desc *desc;
 484         const char *ptr;
 485         char *found_ref;
 486         int len, early;
 487
 488         strbuf_branchname(&bname, remote, 0);
 489         remote = bname.buf;
 490
 491         oidclr(&branch_head);
 492         remote_head = get_merge_parent(remote);
 493         if (!remote_head)
 494                 die(_("'%s' does not point to a commit"), remote);
 495
 496         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 497                 if (starts_with(found_ref, "refs/heads/")) {
 498                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 499                                     oid_to_hex(&branch_head), remote);
 500                         goto cleanup;
 501                 }
 502                 if (starts_with(found_ref, "refs/tags/")) {
 503                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 504                                     oid_to_hex(&branch_head), remote);
 505                         goto cleanup;
 506                 }
 507                 if (starts_with(found_ref, "refs/remotes/")) {
 508                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 509                                     oid_to_hex(&branch_head), remote);
 510                         goto cleanup;
 511                 }
 512         }
 513
 514         /* See if remote matches <name>^^^.. or <name>~<number> */
 515         for (len = 0, ptr = remote + strlen(remote);
 516              remote < ptr && ptr[-1] == '^';
 517              ptr--)
 518                 len++;
 519         if (len)
 520                 early = 1;
 521         else {
 522                 early = 0;
 523                 ptr = strrchr(remote, '~');
 524                 if (ptr) {
 525                         int seen_nonzero = 0;
 526
 527                         len++; /* count ~ */
 528                         while (*++ptr && isdigit(*ptr)) {
 529                                 seen_nonzero |= (*ptr != '0');
 530                                 len++;
 531                         }
 532                         if (*ptr)
 533                                 len = 0; /* not ...~<number> */
 534                         else if (seen_nonzero)
 535                                 early = 1;
 536                         else if (len == 1)
 537                                 early = 1; /* "name~" is "name~1"! */
 538                 }
 539         }
 540         if (len) {
 541                 struct strbuf truname = STRBUF_INIT;
 542                 strbuf_addf(&truname, "refs/heads/%s", remote);
 543                 strbuf_setlen(&truname, truname.len - len);
 544                 if (ref_exists(truname.buf)) {
 545                         strbuf_addf(msg,
 546                                     "%s\t\tbranch '%s'%s of .\n",
 547                                     oid_to_hex(&remote_head->object.oid),
 548                                     truname.buf + 11,
 549                                     (early ? " (early part)" : ""));
 550                         strbuf_release(&truname);
 551                         goto cleanup;
 552                 }
 553                 strbuf_release(&truname);
 554         }
 555
 556         desc = merge_remote_util(remote_head);
 557         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 558                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 559                             oid_to_hex(&desc->obj->oid),
 560                             type_name(desc->obj->type),
 561                             remote);
 562                 goto cleanup;
 563         }
 564
 565         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 566                 oid_to_hex(&remote_head->object.oid), remote);
 567 cleanup:
 568         strbuf_release(&buf);
 569         strbuf_release(&bname);
 570 }
 571
 572 static void parse_branch_merge_options(char *bmo)
 573 {
 574         const char **argv;
 575         int argc;
 576
 577         if (!bmo)
 578                 return;
 579         argc = split_cmdline(bmo, &argv);
 580         if (argc < 0)
 581                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 582                     _(split_cmdline_strerror(argc)));
 583         REALLOC_ARRAY(argv, argc + 2);
 584         MOVE_ARRAY(argv + 1, argv, argc + 1);
 585         argc++;
 586         argv[0] = "branch.*.mergeoptions";
 587         parse_options(argc, argv, NULL, builtin_merge_options,
 588                       builtin_merge_usage, 0);
 589         free(argv);
 590 }
 591
 592 static int git_merge_config(const char *k, const char *v, void *cb)
 593 {
 594         int status;
 595
 596         if (branch && starts_with(k, "branch.") &&
 597                 starts_with(k + 7, branch) &&
 598                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 599                 free(branch_mergeoptions);
 600                 branch_mergeoptions = xstrdup(v);
 601                 return 0;
 602         }
 603
 604         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 605                 show_diffstat = git_config_bool(k, v);
 606         else if (!strcmp(k, "merge.verifysignatures"))
 607                 verify_signatures = git_config_bool(k, v);
 608         else if (!strcmp(k, "pull.twohead"))
 609                 return git_config_string(&pull_twohead, k, v);
 610         else if (!strcmp(k, "pull.octopus"))
 611                 return git_config_string(&pull_octopus, k, v);
 612         else if (!strcmp(k, "merge.renormalize"))
 613                 option_renormalize = git_config_bool(k, v);
 614         else if (!strcmp(k, "merge.ff")) {
 615                 int boolval = git_parse_maybe_bool(v);
 616                 if (0 <= boolval) {
 617                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 618                 } else if (v && !strcmp(v, "only")) {
 619                         fast_forward = FF_ONLY;
 620                 } /* do not barf on values from future versions of git */
 621                 return 0;
 622         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 623                 default_to_upstream = git_config_bool(k, v);
 624                 return 0;
 625         } else if (!strcmp(k, "commit.gpgsign")) {
 626                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 627                 return 0;
 628         }
 629
 630         status = fmt_merge_msg_config(k, v, cb);
 631         if (status)
 632                 return status;
 633         status = git_gpg_config(k, v, NULL);
 634         if (status)
 635                 return status;
 636         return git_diff_ui_config(k, v, cb);
 637 }
 638
 639 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 640                              struct object_id *one)
 641 {
 642         int i, nr_trees = 0;
 643         struct tree *trees[MAX_UNPACK_TREES];
 644         struct tree_desc t[MAX_UNPACK_TREES];
 645         struct unpack_trees_options opts;
 646
 647         memset(&opts, 0, sizeof(opts));
 648         opts.head_idx = 2;
 649         opts.src_index = &the_index;
 650         opts.dst_index = &the_index;
 651         opts.update = 1;
 652         opts.verbose_update = 1;
 653         opts.trivial_merges_only = 1;
 654         opts.merge = 1;
 655         trees[nr_trees] = parse_tree_indirect(common);
 656         if (!trees[nr_trees++])
 657                 return -1;
 658         trees[nr_trees] = parse_tree_indirect(head);
 659         if (!trees[nr_trees++])
 660                 return -1;
 661         trees[nr_trees] = parse_tree_indirect(one);
 662         if (!trees[nr_trees++])
 663                 return -1;
 664         opts.fn = threeway_merge;
 665         cache_tree_free(&active_cache_tree);
 666         for (i = 0; i < nr_trees; i++) {
 667                 parse_tree(trees[i]);
 668                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 669         }
 670         if (unpack_trees(nr_trees, t, &opts))
 671                 return -1;
 672         return 0;
 673 }
 674
 675 static void write_tree_trivial(struct object_id *oid)
 676 {
 677         if (write_cache_as_tree(oid, 0, NULL))
 678                 die(_("git write-tree failed to write a tree"));
 679 }
 680
 681 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 682                               struct commit_list *remoteheads,
 683                               struct commit *head)
 684 {
 685         struct lock_file lock = LOCK_INIT;
 686         const char *head_arg = "HEAD";
 687
 688         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 689         refresh_cache(REFRESH_QUIET);
 690         if (write_locked_index(&the_index, &lock,
 691                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 692                 return error(_("Unable to write index."));
 693
 694         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 695                 int clean, x;
 696                 struct commit *result;
 697                 struct commit_list *reversed = NULL;
 698                 struct merge_options o;
 699                 struct commit_list *j;
 700
 701                 if (remoteheads->next) {
 702                         error(_("Not handling anything other than two heads merge."));
 703                         return 2;
 704                 }
 705
 706                 init_merge_options(&o, the_repository);
 707                 if (!strcmp(strategy, "subtree"))
 708                         o.subtree_shift = "";
 709
 710                 o.renormalize = option_renormalize;
 711                 o.show_rename_progress =
 712                         show_progress == -1 ? isatty(2) : show_progress;
 713
 714                 for (x = 0; x < xopts_nr; x++)
 715                         if (parse_merge_opt(&o, xopts[x]))
 716                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 717
 718                 o.branch1 = head_arg;
 719                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 720
 721                 for (j = common; j; j = j->next)
 722                         commit_list_insert(j->item, &reversed);
 723
 724                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 725                 clean = merge_recursive(&o, head,
 726                                 remoteheads->item, reversed, &result);
 727                 if (clean < 0)
 728                         exit(128);
 729                 if (write_locked_index(&the_index, &lock,
 730                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 731                         die(_("unable to write %s"), get_index_file());
 732                 return clean ? 0 : 1;
 733         } else {
 734                 return try_merge_command(the_repository,
 735                                          strategy, xopts_nr, xopts,
 736                                          common, head_arg, remoteheads);
 737         }
 738 }
 739
 740 static void count_diff_files(struct diff_queue_struct *q,
 741                              struct diff_options *opt, void *data)
 742 {
 743         int *count = data;
 744
 745         (*count) += q->nr;
 746 }
 747
 748 static int count_unmerged_entries(void)
 749 {
 750         int i, ret = 0;
 751
 752         for (i = 0; i < active_nr; i++)
 753                 if (ce_stage(active_cache[i]))
 754                         ret++;
 755
 756         return ret;
 757 }
 758
 759 static void add_strategies(const char *string, unsigned attr)
 760 {
 761         int i;
 762
 763         if (string) {
 764                 struct string_list list = STRING_LIST_INIT_DUP;
 765                 struct string_list_item *item;
 766                 string_list_split(&list, string, ' ', -1);
 767                 for_each_string_list_item(item, &list)
 768                         append_strategy(get_strategy(item->string));
 769                 string_list_clear(&list, 0);
 770                 return;
 771         }
 772         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 773                 if (all_strategy[i].attr & attr)
 774                         append_strategy(&all_strategy[i]);
 775
 776 }
 777
 778 static void read_merge_msg(struct strbuf *msg)
 779 {
 780         const char *filename = git_path_merge_msg(the_repository);
 781         strbuf_reset(msg);
 782         if (strbuf_read_file(msg, filename, 0) < 0)
 783                 die_errno(_("Could not read from '%s'"), filename);
 784 }
 785
 786 static void write_merge_state(struct commit_list *);
 787 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 788 {
 789         if (err_msg)
 790                 error("%s", err_msg);
 791         fprintf(stderr,
 792                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 793         write_merge_state(remoteheads);
 794         exit(1);
 795 }
 796
 797 static const char merge_editor_comment[] =
 798 N_("Please enter a commit message to explain why this merge is necessary,\n"
 799    "especially if it merges an updated upstream into a topic branch.\n"
 800    "\n"
 801    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 802    "the commit.\n");
 803
 804 static void write_merge_heads(struct commit_list *);
 805 static void prepare_to_commit(struct commit_list *remoteheads)
 806 {
 807         struct strbuf msg = STRBUF_INIT;
 808         strbuf_addbuf(&msg, &merge_msg);
 809         strbuf_addch(&msg, '\n');
 810         if (squash)
 811                 BUG("the control must not reach here under --squash");
 812         if (0 < option_edit)
 813                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 814         if (signoff)
 815                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 816         write_merge_heads(remoteheads);
 817         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 818         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 819                             git_path_merge_msg(the_repository), "merge", NULL))
 820                 abort_commit(remoteheads, NULL);
 821         if (0 < option_edit) {
 822                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 823                         abort_commit(remoteheads, NULL);
 824         }
 825
 826         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 827                                           "commit-msg",
 828                                           git_path_merge_msg(the_repository), NULL))
 829                 abort_commit(remoteheads, NULL);
 830
 831         read_merge_msg(&msg);
 832         strbuf_stripspace(&msg, 0 < option_edit);
 833         if (!msg.len)
 834                 abort_commit(remoteheads, _("Empty commit message."));
 835         strbuf_release(&merge_msg);
 836         strbuf_addbuf(&merge_msg, &msg);
 837         strbuf_release(&msg);
 838 }
 839
 840 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 841 {
 842         struct object_id result_tree, result_commit;
 843         struct commit_list *parents, **pptr = &parents;
 844         struct lock_file lock = LOCK_INIT;
 845
 846         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 847         refresh_cache(REFRESH_QUIET);
 848         if (write_locked_index(&the_index, &lock,
 849                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 850                 return error(_("Unable to write index."));
 851
 852         write_tree_trivial(&result_tree);
 853         printf(_("Wonderful.\n"));
 854         pptr = commit_list_append(head, pptr);
 855         pptr = commit_list_append(remoteheads->item, pptr);
 856         prepare_to_commit(remoteheads);
 857         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 858                         &result_commit, NULL, sign_commit))
 859                 die(_("failed to write commit object"));
 860         finish(head, remoteheads, &result_commit, "In-index merge");
 861         drop_save();
 862         return 0;
 863 }
 864
 865 static int finish_automerge(struct commit *head,
 866                             int head_subsumed,
 867                             struct commit_list *common,
 868                             struct commit_list *remoteheads,
 869                             struct object_id *result_tree,
 870                             const char *wt_strategy)
 871 {
 872         struct commit_list *parents = NULL;
 873         struct strbuf buf = STRBUF_INIT;
 874         struct object_id result_commit;
 875
 876         free_commit_list(common);
 877         parents = remoteheads;
 878         if (!head_subsumed || fast_forward == FF_NO)
 879                 commit_list_insert(head, &parents);
 880         strbuf_addch(&merge_msg, '\n');
 881         prepare_to_commit(remoteheads);
 882         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 883                         &result_commit, NULL, sign_commit))
 884                 die(_("failed to write commit object"));
 885         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 886         finish(head, remoteheads, &result_commit, buf.buf);
 887         strbuf_release(&buf);
 888         drop_save();
 889         return 0;
 890 }
 891
 892 static int suggest_conflicts(void)
 893 {
 894         const char *filename;
 895         FILE *fp;
 896         struct strbuf msgbuf = STRBUF_INIT;
 897
 898         filename = git_path_merge_msg(the_repository);
 899         fp = xfopen(filename, "a");
 900
 901         append_conflicts_hint(&the_index, &msgbuf);
 902         fputs(msgbuf.buf, fp);
 903         strbuf_release(&msgbuf);
 904         fclose(fp);
 905         repo_rerere(the_repository, allow_rerere_auto);
 906         printf(_("Automatic merge failed; "
 907                         "fix conflicts and then commit the result.\n"));
 908         return 1;
 909 }
 910
 911 static int evaluate_result(void)
 912 {
 913         int cnt = 0;
 914         struct rev_info rev;
 915
 916         /* Check how many files differ. */
 917         repo_init_revisions(the_repository, &rev, "");
 918         setup_revisions(0, NULL, &rev, NULL);
 919         rev.diffopt.output_format |=
 920                 DIFF_FORMAT_CALLBACK;
 921         rev.diffopt.format_callback = count_diff_files;
 922         rev.diffopt.format_callback_data = &cnt;
 923         run_diff_files(&rev, 0);
 924
 925         /*
 926          * Check how many unmerged entries are
 927          * there.
 928          */
 929         cnt += count_unmerged_entries();
 930
 931         return cnt;
 932 }
 933
 934 /*
 935  * Pretend as if the user told us to merge with the remote-tracking
 936  * branch we have for the upstream of the current branch
 937  */
 938 static int setup_with_upstream(const char ***argv)
 939 {
 940         struct branch *branch = branch_get(NULL);
 941         int i;
 942         const char **args;
 943
 944         if (!branch)
 945                 die(_("No current branch."));
 946         if (!branch->remote_name)
 947                 die(_("No remote for the current branch."));
 948         if (!branch->merge_nr)
 949                 die(_("No default upstream defined for the current branch."));
 950
 951         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 952         for (i = 0; i < branch->merge_nr; i++) {
 953                 if (!branch->merge[i]->dst)
 954                         die(_("No remote-tracking branch for %s from %s"),
 955                             branch->merge[i]->src, branch->remote_name);
 956                 args[i] = branch->merge[i]->dst;
 957         }
 958         args[i] = NULL;
 959         *argv = args;
 960         return i;
 961 }
 962
 963 static void write_merge_heads(struct commit_list *remoteheads)
 964 {
 965         struct commit_list *j;
 966         struct strbuf buf = STRBUF_INIT;
 967
 968         for (j = remoteheads; j; j = j->next) {
 969                 struct object_id *oid;
 970                 struct commit *c = j->item;
 971                 struct merge_remote_desc *desc;
 972
 973                 desc = merge_remote_util(c);
 974                 if (desc && desc->obj) {
 975                         oid = &desc->obj->oid;
 976                 } else {
 977                         oid = &c->object.oid;
 978                 }
 979                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 980         }
 981         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 982
 983         strbuf_reset(&buf);
 984         if (fast_forward == FF_NO)
 985                 strbuf_addstr(&buf, "no-ff");
 986         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 987         strbuf_release(&buf);
 988 }
 989
 990 static void write_merge_state(struct commit_list *remoteheads)
 991 {
 992         write_merge_heads(remoteheads);
 993         strbuf_addch(&merge_msg, '\n');
 994         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 995                        merge_msg.len);
 996 }
 997
 998 static int default_edit_option(void)
 999 {
1000         static const char name[] = "GIT_MERGE_AUTOEDIT";
1001         const char *e = getenv(name);
1002         struct stat st_stdin, st_stdout;
1003
1004         if (have_message)
1005                 /* an explicit -m msg without --[no-]edit */
1006                 return 0;
1007
1008         if (e) {
1009                 int v = git_parse_maybe_bool(e);
1010                 if (v < 0)
1011                         die(_("Bad value '%s' in environment '%s'"), e, name);
1012                 return v;
1013         }
1014
1015         /* Use editor if stdin and stdout are the same and is a tty */
1016         return (!fstat(0, &st_stdin) &&
1017                 !fstat(1, &st_stdout) &&
1018                 isatty(0) && isatty(1) &&
1019                 st_stdin.st_dev == st_stdout.st_dev &&
1020                 st_stdin.st_ino == st_stdout.st_ino &&
1021                 st_stdin.st_mode == st_stdout.st_mode);
1022 }
1023
1024 static struct commit_list *reduce_parents(struct commit *head_commit,
1025                                           int *head_subsumed,
1026                                           struct commit_list *remoteheads)
1027 {
1028         struct commit_list *parents, **remotes;
1029
1030         /*
1031          * Is the current HEAD reachable from another commit being
1032          * merged?  If so we do not want to record it as a parent of
1033          * the resulting merge, unless --no-ff is given.  We will flip
1034          * this variable to 0 when we find HEAD among the independent
1035          * tips being merged.
1036          */
1037         *head_subsumed = 1;
1038
1039         /* Find what parents to record by checking independent ones. */
1040         parents = reduce_heads(remoteheads);
1041         free_commit_list(remoteheads);
1042
1043         remoteheads = NULL;
1044         remotes = &remoteheads;
1045         while (parents) {
1046                 struct commit *commit = pop_commit(&parents);
1047                 if (commit == head_commit)
1048                         *head_subsumed = 0;
1049                 else
1050                         remotes = &commit_list_insert(commit, remotes)->next;
1051         }
1052         return remoteheads;
1053 }
1054
1055 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1056 {
1057         struct fmt_merge_msg_opts opts;
1058
1059         memset(&opts, 0, sizeof(opts));
1060         opts.add_title = !have_message;
1061         opts.shortlog_len = shortlog_len;
1062         opts.credit_people = (0 < option_edit);
1063
1064         fmt_merge_msg(merge_names, merge_msg, &opts);
1065         if (merge_msg->len)
1066                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1067 }
1068
1069 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1070 {
1071         const char *filename;
1072         int fd, pos, npos;
1073         struct strbuf fetch_head_file = STRBUF_INIT;
1074         const unsigned hexsz = the_hash_algo->hexsz;
1075
1076         if (!merge_names)
1077                 merge_names = &fetch_head_file;
1078
1079         filename = git_path_fetch_head(the_repository);
1080         fd = open(filename, O_RDONLY);
1081         if (fd < 0)
1082                 die_errno(_("could not open '%s' for reading"), filename);
1083
1084         if (strbuf_read(merge_names, fd, 0) < 0)
1085                 die_errno(_("could not read '%s'"), filename);
1086         if (close(fd) < 0)
1087                 die_errno(_("could not close '%s'"), filename);
1088
1089         for (pos = 0; pos < merge_names->len; pos = npos) {
1090                 struct object_id oid;
1091                 char *ptr;
1092                 struct commit *commit;
1093
1094                 ptr = strchr(merge_names->buf + pos, '\n');
1095                 if (ptr)
1096                         npos = ptr - merge_names->buf + 1;
1097                 else
1098                         npos = merge_names->len;
1099
1100                 if (npos - pos < hexsz + 2 ||
1101                     get_oid_hex(merge_names->buf + pos, &oid))
1102                         commit = NULL; /* bad */
1103                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1104                         continue; /* not-for-merge */
1105                 else {
1106                         char saved = merge_names->buf[pos + hexsz];
1107                         merge_names->buf[pos + hexsz] = '\0';
1108                         commit = get_merge_parent(merge_names->buf + pos);
1109                         merge_names->buf[pos + hexsz] = saved;
1110                 }
1111                 if (!commit) {
1112                         if (ptr)
1113                                 *ptr = '\0';
1114                         die(_("not something we can merge in %s: %s"),
1115                             filename, merge_names->buf + pos);
1116                 }
1117                 remotes = &commit_list_insert(commit, remotes)->next;
1118         }
1119
1120         if (merge_names == &fetch_head_file)
1121                 strbuf_release(&fetch_head_file);
1122 }
1123
1124 static struct commit_list *collect_parents(struct commit *head_commit,
1125                                            int *head_subsumed,
1126                                            int argc, const char **argv,
1127                                            struct strbuf *merge_msg)
1128 {
1129         int i;
1130         struct commit_list *remoteheads = NULL;
1131         struct commit_list **remotes = &remoteheads;
1132         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1133
1134         if (merge_msg && (!have_message || shortlog_len))
1135                 autogen = &merge_names;
1136
1137         if (head_commit)
1138                 remotes = &commit_list_insert(head_commit, remotes)->next;
1139
1140         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1141                 handle_fetch_head(remotes, autogen);
1142                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1143         } else {
1144                 for (i = 0; i < argc; i++) {
1145                         struct commit *commit = get_merge_parent(argv[i]);
1146                         if (!commit)
1147                                 help_unknown_ref(argv[i], "merge",
1148                                                  _("not something we can merge"));
1149                         remotes = &commit_list_insert(commit, remotes)->next;
1150                 }
1151                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1152                 if (autogen) {
1153                         struct commit_list *p;
1154                         for (p = remoteheads; p; p = p->next)
1155                                 merge_name(merge_remote_util(p->item)->name, autogen);
1156                 }
1157         }
1158
1159         if (autogen) {
1160                 prepare_merge_message(autogen, merge_msg);
1161                 strbuf_release(autogen);
1162         }
1163
1164         return remoteheads;
1165 }
1166
1167 static int merging_a_throwaway_tag(struct commit *commit)
1168 {
1169         char *tag_ref;
1170         struct object_id oid;
1171         int is_throwaway_tag = 0;
1172
1173         /* Are we merging a tag? */
1174         if (!merge_remote_util(commit) ||
1175             !merge_remote_util(commit)->obj ||
1176             merge_remote_util(commit)->obj->type != OBJ_TAG)
1177                 return is_throwaway_tag;
1178
1179         /*
1180          * Now we know we are merging a tag object.  Are we downstream
1181          * and following the tags from upstream?  If so, we must have
1182          * the tag object pointed at by "refs/tags/$T" where $T is the
1183          * tagname recorded in the tag object.  We want to allow such
1184          * a "just to catch up" merge to fast-forward.
1185          *
1186          * Otherwise, we are playing an integrator's role, making a
1187          * merge with a throw-away tag from a contributor with
1188          * something like "git pull $contributor $signed_tag".
1189          * We want to forbid such a merge from fast-forwarding
1190          * by default; otherwise we would not keep the signature
1191          * anywhere.
1192          */
1193         tag_ref = xstrfmt("refs/tags/%s",
1194                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1195         if (!read_ref(tag_ref, &oid) &&
1196             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1197                 is_throwaway_tag = 0;
1198         else
1199                 is_throwaway_tag = 1;
1200         free(tag_ref);
1201         return is_throwaway_tag;
1202 }
1203
1204 int cmd_merge(int argc, const char **argv, const char *prefix)
1205 {
1206         struct object_id result_tree, stash, head_oid;
1207         struct commit *head_commit;
1208         struct strbuf buf = STRBUF_INIT;
1209         int i, ret = 0, head_subsumed;
1210         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1211         struct commit_list *common = NULL;
1212         const char *best_strategy = NULL, *wt_strategy = NULL;
1213         struct commit_list *remoteheads, *p;
1214         void *branch_to_free;
1215         int orig_argc = argc;
1216
1217         if (argc == 2 && !strcmp(argv[1], "-h"))
1218                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1219
1220         /*
1221          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1222          * current branch.
1223          */
1224         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1225         if (branch)
1226                 skip_prefix(branch, "refs/heads/", &branch);
1227
1228         init_diff_ui_defaults();
1229         git_config(git_merge_config, NULL);
1230
1231         if (!branch || is_null_oid(&head_oid))
1232                 head_commit = NULL;
1233         else
1234                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1235
1236         if (branch_mergeoptions)
1237                 parse_branch_merge_options(branch_mergeoptions);
1238         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1239                         builtin_merge_usage, 0);
1240         if (shortlog_len < 0)
1241                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1242
1243         if (verbosity < 0 && show_progress == -1)
1244                 show_progress = 0;
1245
1246         if (abort_current_merge) {
1247                 int nargc = 2;
1248                 const char *nargv[] = {"reset", "--merge", NULL};
1249
1250                 if (orig_argc != 2)
1251                         usage_msg_opt(_("--abort expects no arguments"),
1252                               builtin_merge_usage, builtin_merge_options);
1253
1254                 if (!file_exists(git_path_merge_head(the_repository)))
1255                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1256
1257                 /* Invoke 'git reset --merge' */
1258                 ret = cmd_reset(nargc, nargv, prefix);
1259                 goto done;
1260         }
1261
1262         if (continue_current_merge) {
1263                 int nargc = 1;
1264                 const char *nargv[] = {"commit", NULL};
1265
1266                 if (orig_argc != 2)
1267                         usage_msg_opt(_("--continue expects no arguments"),
1268                               builtin_merge_usage, builtin_merge_options);
1269
1270                 if (!file_exists(git_path_merge_head(the_repository)))
1271                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1272
1273                 /* Invoke 'git commit' */
1274                 ret = cmd_commit(nargc, nargv, prefix);
1275                 goto done;
1276         }
1277
1278         if (read_cache_unmerged())
1279                 die_resolve_conflict("merge");
1280
1281         if (file_exists(git_path_merge_head(the_repository))) {
1282                 /*
1283                  * There is no unmerged entry, don't advise 'git
1284                  * add/rm <file>', just 'git commit'.
1285                  */
1286                 if (advice_resolve_conflict)
1287                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1288                                   "Please, commit your changes before you merge."));
1289                 else
1290                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1291         }
1292         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1293                 if (advice_resolve_conflict)
1294                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1295                             "Please, commit your changes before you merge."));
1296                 else
1297                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1298         }
1299         resolve_undo_clear();
1300
1301         if (verbosity < 0)
1302                 show_diffstat = 0;
1303
1304         if (squash) {
1305                 if (fast_forward == FF_NO)
1306                         die(_("You cannot combine --squash with --no-ff."));
1307                 option_commit = 0;
1308         }
1309
1310         if (!argc) {
1311                 if (default_to_upstream)
1312                         argc = setup_with_upstream(&argv);
1313                 else
1314                         die(_("No commit specified and merge.defaultToUpstream not set."));
1315         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1316                 argv[0] = "@{-1}";
1317         }
1318
1319         if (!argc)
1320                 usage_with_options(builtin_merge_usage,
1321                         builtin_merge_options);
1322
1323         if (!head_commit) {
1324                 /*
1325                  * If the merged head is a valid one there is no reason
1326                  * to forbid "git merge" into a branch yet to be born.
1327                  * We do the same for "git pull".
1328                  */
1329                 struct object_id *remote_head_oid;
1330                 if (squash)
1331                         die(_("Squash commit into empty head not supported yet"));
1332                 if (fast_forward == FF_NO)
1333                         die(_("Non-fast-forward commit does not make sense into "
1334                             "an empty head"));
1335                 remoteheads = collect_parents(head_commit, &head_subsumed,
1336                                               argc, argv, NULL);
1337                 if (!remoteheads)
1338                         die(_("%s - not something we can merge"), argv[0]);
1339                 if (remoteheads->next)
1340                         die(_("Can merge only exactly one commit into empty head"));
1341
1342                 if (verify_signatures)
1343                         verify_merge_signature(remoteheads->item, verbosity);
1344
1345                 remote_head_oid = &remoteheads->item->object.oid;
1346                 read_empty(remote_head_oid, 0);
1347                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1348                            UPDATE_REFS_DIE_ON_ERR);
1349                 goto done;
1350         }
1351
1352         /*
1353          * All the rest are the commits being merged; prepare
1354          * the standard merge summary message to be appended
1355          * to the given message.
1356          */
1357         remoteheads = collect_parents(head_commit, &head_subsumed,
1358                                       argc, argv, &merge_msg);
1359
1360         if (!head_commit || !argc)
1361                 usage_with_options(builtin_merge_usage,
1362                         builtin_merge_options);
1363
1364         if (verify_signatures) {
1365                 for (p = remoteheads; p; p = p->next) {
1366                         verify_merge_signature(p->item, verbosity);
1367                 }
1368         }
1369
1370         strbuf_addstr(&buf, "merge");
1371         for (p = remoteheads; p; p = p->next)
1372                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1373         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1374         strbuf_reset(&buf);
1375
1376         for (p = remoteheads; p; p = p->next) {
1377                 struct commit *commit = p->item;
1378                 strbuf_addf(&buf, "GITHEAD_%s",
1379                             oid_to_hex(&commit->object.oid));
1380                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1381                 strbuf_reset(&buf);
1382                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1383                         fast_forward = FF_NO;
1384         }
1385
1386         if (option_edit < 0)
1387                 option_edit = default_edit_option();
1388
1389         if (!use_strategies) {
1390                 if (!remoteheads)
1391                         ; /* already up-to-date */
1392                 else if (!remoteheads->next)
1393                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1394                 else
1395                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1396         }
1397
1398         for (i = 0; i < use_strategies_nr; i++) {
1399                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1400                         fast_forward = FF_NO;
1401                 if (use_strategies[i]->attr & NO_TRIVIAL)
1402                         allow_trivial = 0;
1403         }
1404
1405         if (!remoteheads)
1406                 ; /* already up-to-date */
1407         else if (!remoteheads->next)
1408                 common = get_merge_bases(head_commit, remoteheads->item);
1409         else {
1410                 struct commit_list *list = remoteheads;
1411                 commit_list_insert(head_commit, &list);
1412                 common = get_octopus_merge_bases(list);
1413                 free(list);
1414         }
1415
1416         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1417                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1418
1419         if (remoteheads && !common) {
1420                 /* No common ancestors found. */
1421                 if (!allow_unrelated_histories)
1422                         die(_("refusing to merge unrelated histories"));
1423                 /* otherwise, we need a real merge. */
1424         } else if (!remoteheads ||
1425                  (!remoteheads->next && !common->next &&
1426                   common->item == remoteheads->item)) {
1427                 /*
1428                  * If head can reach all the merge then we are up to date.
1429                  * but first the most common case of merging one remote.
1430                  */
1431                 finish_up_to_date(_("Already up to date."));
1432                 goto done;
1433         } else if (fast_forward != FF_NO && !remoteheads->next &&
1434                         !common->next &&
1435                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1436                 /* Again the most common case of merging one remote. */
1437                 struct strbuf msg = STRBUF_INIT;
1438                 struct commit *commit;
1439
1440                 if (verbosity >= 0) {
1441                         printf(_("Updating %s..%s\n"),
1442                                find_unique_abbrev(&head_commit->object.oid,
1443                                                   DEFAULT_ABBREV),
1444                                find_unique_abbrev(&remoteheads->item->object.oid,
1445                                                   DEFAULT_ABBREV));
1446                 }
1447                 strbuf_addstr(&msg, "Fast-forward");
1448                 if (have_message)
1449                         strbuf_addstr(&msg,
1450                                 " (no commit created; -m option ignored)");
1451                 commit = remoteheads->item;
1452                 if (!commit) {
1453                         ret = 1;
1454                         goto done;
1455                 }
1456
1457                 if (checkout_fast_forward(the_repository,
1458                                           &head_commit->object.oid,
1459                                           &commit->object.oid,
1460                                           overwrite_ignore)) {
1461                         ret = 1;
1462                         goto done;
1463                 }
1464
1465                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1466                 drop_save();
1467                 goto done;
1468         } else if (!remoteheads->next && common->next)
1469                 ;
1470                 /*
1471                  * We are not doing octopus and not fast-forward.  Need
1472                  * a real merge.
1473                  */
1474         else if (!remoteheads->next && !common->next && option_commit) {
1475                 /*
1476                  * We are not doing octopus, not fast-forward, and have
1477                  * only one common.
1478                  */
1479                 refresh_cache(REFRESH_QUIET);
1480                 if (allow_trivial && fast_forward != FF_ONLY) {
1481                         /* See if it is really trivial. */
1482                         git_committer_info(IDENT_STRICT);
1483                         printf(_("Trying really trivial in-index merge...\n"));
1484                         if (!read_tree_trivial(&common->item->object.oid,
1485                                                &head_commit->object.oid,
1486                                                &remoteheads->item->object.oid)) {
1487                                 ret = merge_trivial(head_commit, remoteheads);
1488                                 goto done;
1489                         }
1490                         printf(_("Nope.\n"));
1491                 }
1492         } else {
1493                 /*
1494                  * An octopus.  If we can reach all the remote we are up
1495                  * to date.
1496                  */
1497                 int up_to_date = 1;
1498                 struct commit_list *j;
1499
1500                 for (j = remoteheads; j; j = j->next) {
1501                         struct commit_list *common_one;
1502
1503                         /*
1504                          * Here we *have* to calculate the individual
1505                          * merge_bases again, otherwise "git merge HEAD^
1506                          * HEAD^^" would be missed.
1507                          */
1508                         common_one = get_merge_bases(head_commit, j->item);
1509                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1510                                 up_to_date = 0;
1511                                 break;
1512                         }
1513                 }
1514                 if (up_to_date) {
1515                         finish_up_to_date(_("Already up to date. Yeeah!"));
1516                         goto done;
1517                 }
1518         }
1519
1520         if (fast_forward == FF_ONLY)
1521                 die(_("Not possible to fast-forward, aborting."));
1522
1523         /* We are going to make a new commit. */
1524         git_committer_info(IDENT_STRICT);
1525
1526         /*
1527          * At this point, we need a real merge.  No matter what strategy
1528          * we use, it would operate on the index, possibly affecting the
1529          * working tree, and when resolved cleanly, have the desired
1530          * tree in the index -- this means that the index must be in
1531          * sync with the head commit.  The strategies are responsible
1532          * to ensure this.
1533          */
1534         if (use_strategies_nr == 1 ||
1535             /*
1536              * Stash away the local changes so that we can try more than one.
1537              */
1538             save_state(&stash))
1539                 oidclr(&stash);
1540
1541         for (i = 0; i < use_strategies_nr; i++) {
1542                 int ret;
1543                 if (i) {
1544                         printf(_("Rewinding the tree to pristine...\n"));
1545                         restore_state(&head_commit->object.oid, &stash);
1546                 }
1547                 if (use_strategies_nr != 1)
1548                         printf(_("Trying merge strategy %s...\n"),
1549                                 use_strategies[i]->name);
1550                 /*
1551                  * Remember which strategy left the state in the working
1552                  * tree.
1553                  */
1554                 wt_strategy = use_strategies[i]->name;
1555
1556                 ret = try_merge_strategy(use_strategies[i]->name,
1557                                          common, remoteheads,
1558                                          head_commit);
1559                 if (!option_commit && !ret) {
1560                         merge_was_ok = 1;
1561                         /*
1562                          * This is necessary here just to avoid writing
1563                          * the tree, but later we will *not* exit with
1564                          * status code 1 because merge_was_ok is set.
1565                          */
1566                         ret = 1;
1567                 }
1568
1569                 if (ret) {
1570                         /*
1571                          * The backend exits with 1 when conflicts are
1572                          * left to be resolved, with 2 when it does not
1573                          * handle the given merge at all.
1574                          */
1575                         if (ret == 1) {
1576                                 int cnt = evaluate_result();
1577
1578                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1579                                         best_strategy = use_strategies[i]->name;
1580                                         best_cnt = cnt;
1581                                 }
1582                         }
1583                         if (merge_was_ok)
1584                                 break;
1585                         else
1586                                 continue;
1587                 }
1588
1589                 /* Automerge succeeded. */
1590                 write_tree_trivial(&result_tree);
1591                 automerge_was_ok = 1;
1592                 break;
1593         }
1594
1595         /*
1596          * If we have a resulting tree, that means the strategy module
1597          * auto resolved the merge cleanly.
1598          */
1599         if (automerge_was_ok) {
1600                 ret = finish_automerge(head_commit, head_subsumed,
1601                                        common, remoteheads,
1602                                        &result_tree, wt_strategy);
1603                 goto done;
1604         }
1605
1606         /*
1607          * Pick the result from the best strategy and have the user fix
1608          * it up.
1609          */
1610         if (!best_strategy) {
1611                 restore_state(&head_commit->object.oid, &stash);
1612                 if (use_strategies_nr > 1)
1613                         fprintf(stderr,
1614                                 _("No merge strategy handled the merge.\n"));
1615                 else
1616                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1617                                 use_strategies[0]->name);
1618                 ret = 2;
1619                 goto done;
1620         } else if (best_strategy == wt_strategy)
1621                 ; /* We already have its result in the working tree. */
1622         else {
1623                 printf(_("Rewinding the tree to pristine...\n"));
1624                 restore_state(&head_commit->object.oid, &stash);
1625                 printf(_("Using the %s to prepare resolving by hand.\n"),
1626                         best_strategy);
1627                 try_merge_strategy(best_strategy, common, remoteheads,
1628                                    head_commit);
1629         }
1630
1631         if (squash)
1632                 finish(head_commit, remoteheads, NULL, NULL);
1633         else
1634                 write_merge_state(remoteheads);
1635
1636         if (merge_was_ok)
1637                 fprintf(stderr, _("Automatic merge went well; "
1638                         "stopped before committing as requested\n"));
1639         else
1640                 ret = suggest_conflicts();
1641
1642 done:
1643         free(branch_to_free);
1644         return ret;
1645 }