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

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