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

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "diff-merges.h"
  18 #include "refs.h"
  19 #include "refspec.h"
  20 #include "commit.h"
  21 #include "diffcore.h"
  22 #include "revision.h"
  23 #include "unpack-trees.h"
  24 #include "cache-tree.h"
  25 #include "dir.h"
  26 #include "utf8.h"
  27 #include "log-tree.h"
  28 #include "color.h"
  29 #include "rerere.h"
  30 #include "help.h"
  31 #include "merge-recursive.h"
  32 #include "merge-ort-wrappers.h"
  33 #include "resolve-undo.h"
  34 #include "remote.h"
  35 #include "fmt-merge-msg.h"
  36 #include "gpg-interface.h"
  37 #include "sequencer.h"
  38 #include "string-list.h"
  39 #include "packfile.h"
  40 #include "tag.h"
  41 #include "alias.h"
  42 #include "branch.h"
  43 #include "commit-reach.h"
  44 #include "wt-status.h"
  45 #include "commit-graph.h"
  46
  47 #define DEFAULT_TWOHEAD (1<<0)
  48 #define DEFAULT_OCTOPUS (1<<1)
  49 #define NO_FAST_FORWARD (1<<2)
  50 #define NO_TRIVIAL      (1<<3)
  51
  52 struct strategy {
  53         const char *name;
  54         unsigned attr;
  55 };
  56
  57 static const char * const builtin_merge_usage[] = {
  58         N_("git merge [<options>] [<commit>...]"),
  59         "git merge --abort",
  60         "git merge --continue",
  61         NULL
  62 };
  63
  64 static int show_diffstat = 1, shortlog_len = -1, squash;
  65 static int option_commit = -1;
  66 static int option_edit = -1;
  67 static int allow_trivial = 1, have_message, verify_signatures;
  68 static int check_trust_level = 1;
  69 static int overwrite_ignore = 1;
  70 static struct strbuf merge_msg = STRBUF_INIT;
  71 static struct strategy **use_strategies;
  72 static size_t use_strategies_nr, use_strategies_alloc;
  73 static const char **xopts;
  74 static size_t xopts_nr, xopts_alloc;
  75 static const char *branch;
  76 static char *branch_mergeoptions;
  77 static int verbosity;
  78 static int allow_rerere_auto;
  79 static int abort_current_merge;
  80 static int quit_current_merge;
  81 static int continue_current_merge;
  82 static int allow_unrelated_histories;
  83 static int show_progress = -1;
  84 static int default_to_upstream = 1;
  85 static int signoff;
  86 static const char *sign_commit;
  87 static int autostash;
  88 static int no_verify;
  89
  90 static struct strategy all_strategy[] = {
  91         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  92         { "octopus",    DEFAULT_OCTOPUS },
  93         { "ort",        NO_TRIVIAL },
  94         { "resolve",    0 },
  95         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  96         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  97 };
  98
  99 static const char *pull_twohead, *pull_octopus;
 100
 101 enum ff_type {
 102         FF_NO,
 103         FF_ALLOW,
 104         FF_ONLY
 105 };
 106
 107 static enum ff_type fast_forward = FF_ALLOW;
 108
 109 static const char *cleanup_arg;
 110 static enum commit_msg_cleanup_mode cleanup_mode;
 111
 112 static int option_parse_message(const struct option *opt,
 113                                 const char *arg, int unset)
 114 {
 115         struct strbuf *buf = opt->value;
 116
 117         if (unset)
 118                 strbuf_setlen(buf, 0);
 119         else if (arg) {
 120                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 121                 have_message = 1;
 122         } else
 123                 return error(_("switch `m' requires a value"));
 124         return 0;
 125 }
 126
 127 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 128                                                  const struct option *opt,
 129                                                  const char *arg_not_used,
 130                                                  int unset)
 131 {
 132         struct strbuf *buf = opt->value;
 133         const char *arg;
 134
 135         BUG_ON_OPT_ARG(arg_not_used);
 136         if (unset)
 137                 BUG("-F cannot be negated");
 138
 139         if (ctx->opt) {
 140                 arg = ctx->opt;
 141                 ctx->opt = NULL;
 142         } else if (ctx->argc > 1) {
 143                 ctx->argc--;
 144                 arg = *++ctx->argv;
 145         } else
 146                 return error(_("option `%s' requires a value"), opt->long_name);
 147
 148         if (buf->len)
 149                 strbuf_addch(buf, '\n');
 150         if (ctx->prefix && !is_absolute_path(arg))
 151                 arg = prefix_filename(ctx->prefix, arg);
 152         if (strbuf_read_file(buf, arg, 0) < 0)
 153                 return error(_("could not read file '%s'"), arg);
 154         have_message = 1;
 155
 156         return 0;
 157 }
 158
 159 static struct strategy *get_strategy(const char *name)
 160 {
 161         int i;
 162         struct strategy *ret;
 163         static struct cmdnames main_cmds, other_cmds;
 164         static int loaded;
 165         char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 166
 167         if (!name)
 168                 return NULL;
 169
 170         if (default_strategy &&
 171             !strcmp(default_strategy, "ort") &&
 172             !strcmp(name, "recursive")) {
 173                 name = "ort";
 174         }
 175
 176         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 177                 if (!strcmp(name, all_strategy[i].name))
 178                         return &all_strategy[i];
 179
 180         if (!loaded) {
 181                 struct cmdnames not_strategies;
 182                 loaded = 1;
 183
 184                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 185                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 186                 for (i = 0; i < main_cmds.cnt; i++) {
 187                         int j, found = 0;
 188                         struct cmdname *ent = main_cmds.names[i];
 189                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 190                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 191                                                 && !all_strategy[j].name[ent->len])
 192                                         found = 1;
 193                         if (!found)
 194                                 add_cmdname(&not_strategies, ent->name, ent->len);
 195                 }
 196                 exclude_cmds(&main_cmds, &not_strategies);
 197         }
 198         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 199                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 200                 fprintf(stderr, _("Available strategies are:"));
 201                 for (i = 0; i < main_cmds.cnt; i++)
 202                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 203                 fprintf(stderr, ".\n");
 204                 if (other_cmds.cnt) {
 205                         fprintf(stderr, _("Available custom strategies are:"));
 206                         for (i = 0; i < other_cmds.cnt; i++)
 207                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 208                         fprintf(stderr, ".\n");
 209                 }
 210                 exit(1);
 211         }
 212
 213         CALLOC_ARRAY(ret, 1);
 214         ret->name = xstrdup(name);
 215         ret->attr = NO_TRIVIAL;
 216         return ret;
 217 }
 218
 219 static void append_strategy(struct strategy *s)
 220 {
 221         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 222         use_strategies[use_strategies_nr++] = s;
 223 }
 224
 225 static int option_parse_strategy(const struct option *opt,
 226                                  const char *name, int unset)
 227 {
 228         if (unset)
 229                 return 0;
 230
 231         append_strategy(get_strategy(name));
 232         return 0;
 233 }
 234
 235 static int option_parse_x(const struct option *opt,
 236                           const char *arg, int unset)
 237 {
 238         if (unset)
 239                 return 0;
 240
 241         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 242         xopts[xopts_nr++] = xstrdup(arg);
 243         return 0;
 244 }
 245
 246 static int option_parse_n(const struct option *opt,
 247                           const char *arg, int unset)
 248 {
 249         BUG_ON_OPT_ARG(arg);
 250         show_diffstat = unset;
 251         return 0;
 252 }
 253
 254 static struct option builtin_merge_options[] = {
 255         OPT_CALLBACK_F('n', NULL, NULL, NULL,
 256                 N_("do not show a diffstat at the end of the merge"),
 257                 PARSE_OPT_NOARG, option_parse_n),
 258         OPT_BOOL(0, "stat", &show_diffstat,
 259                 N_("show a diffstat at the end of the merge")),
 260         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 261         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 262           N_("add (at most <n>) entries from shortlog to merge commit message"),
 263           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 264         OPT_BOOL(0, "squash", &squash,
 265                 N_("create a single commit instead of doing a merge")),
 266         OPT_BOOL(0, "commit", &option_commit,
 267                 N_("perform a commit if the merge succeeds (default)")),
 268         OPT_BOOL('e', "edit", &option_edit,
 269                 N_("edit message before committing")),
 270         OPT_CLEANUP(&cleanup_arg),
 271         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 272         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 273                       N_("abort if fast-forward is not possible"),
 274                       FF_ONLY, PARSE_OPT_NONEG),
 275         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 276         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 277                 N_("verify that the named commit has a valid GPG signature")),
 278         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 279                 N_("merge strategy to use"), option_parse_strategy),
 280         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 281                 N_("option for selected merge strategy"), option_parse_x),
 282         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 283                 N_("merge commit message (for a non-fast-forward merge)"),
 284                 option_parse_message),
 285         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 286                 N_("read message from file"), PARSE_OPT_NONEG,
 287                 NULL, 0, option_read_message },
 288         OPT__VERBOSITY(&verbosity),
 289         OPT_BOOL(0, "abort", &abort_current_merge,
 290                 N_("abort the current in-progress merge")),
 291         OPT_BOOL(0, "quit", &quit_current_merge,
 292                 N_("--abort but leave index and working tree alone")),
 293         OPT_BOOL(0, "continue", &continue_current_merge,
 294                 N_("continue the current in-progress merge")),
 295         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 296                  N_("allow merging unrelated histories")),
 297         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 298         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 299           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 300         OPT_AUTOSTASH(&autostash),
 301         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 302         OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
 303         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 304         OPT_END()
 305 };
 306
 307 static int save_state(struct object_id *stash)
 308 {
 309         int len;
 310         struct child_process cp = CHILD_PROCESS_INIT;
 311         struct strbuf buffer = STRBUF_INIT;
 312         const char *argv[] = {"stash", "create", NULL};
 313         int rc = -1;
 314
 315         cp.argv = argv;
 316         cp.out = -1;
 317         cp.git_cmd = 1;
 318
 319         if (start_command(&cp))
 320                 die(_("could not run stash."));
 321         len = strbuf_read(&buffer, cp.out, 1024);
 322         close(cp.out);
 323
 324         if (finish_command(&cp) || len < 0)
 325                 die(_("stash failed"));
 326         else if (!len)          /* no changes */
 327                 goto out;
 328         strbuf_setlen(&buffer, buffer.len-1);
 329         if (get_oid(buffer.buf, stash))
 330                 die(_("not a valid object: %s"), buffer.buf);
 331         rc = 0;
 332 out:
 333         strbuf_release(&buffer);
 334         return rc;
 335 }
 336
 337 static void read_empty(const struct object_id *oid, int verbose)
 338 {
 339         int i = 0;
 340         const char *args[7];
 341
 342         args[i++] = "read-tree";
 343         if (verbose)
 344                 args[i++] = "-v";
 345         args[i++] = "-m";
 346         args[i++] = "-u";
 347         args[i++] = empty_tree_oid_hex();
 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 reset_hard(const struct object_id *oid, int verbose)
 356 {
 357         int i = 0;
 358         const char *args[6];
 359
 360         args[i++] = "read-tree";
 361         if (verbose)
 362                 args[i++] = "-v";
 363         args[i++] = "--reset";
 364         args[i++] = "-u";
 365         args[i++] = oid_to_hex(oid);
 366         args[i] = NULL;
 367
 368         if (run_command_v_opt(args, RUN_GIT_CMD))
 369                 die(_("read-tree failed"));
 370 }
 371
 372 static void restore_state(const struct object_id *head,
 373                           const struct object_id *stash)
 374 {
 375         struct strbuf sb = STRBUF_INIT;
 376         const char *args[] = { "stash", "apply", NULL, NULL };
 377
 378         if (is_null_oid(stash))
 379                 return;
 380
 381         reset_hard(head, 1);
 382
 383         args[2] = oid_to_hex(stash);
 384
 385         /*
 386          * It is OK to ignore error here, for example when there was
 387          * nothing to restore.
 388          */
 389         run_command_v_opt(args, RUN_GIT_CMD);
 390
 391         strbuf_release(&sb);
 392         refresh_cache(REFRESH_QUIET);
 393 }
 394
 395 /* This is called when no merge was necessary. */
 396 static void finish_up_to_date(void)
 397 {
 398         if (verbosity >= 0) {
 399                 if (squash)
 400                         puts(_("Already up to date. (nothing to squash)"));
 401                 else
 402                         puts(_("Already up to date."));
 403         }
 404         remove_merge_branch_state(the_repository);
 405 }
 406
 407 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 408 {
 409         struct rev_info rev;
 410         struct strbuf out = STRBUF_INIT;
 411         struct commit_list *j;
 412         struct pretty_print_context ctx = {0};
 413
 414         printf(_("Squash commit -- not updating HEAD\n"));
 415
 416         repo_init_revisions(the_repository, &rev, NULL);
 417         diff_merges_suppress(&rev);
 418         rev.commit_format = CMIT_FMT_MEDIUM;
 419
 420         commit->object.flags |= UNINTERESTING;
 421         add_pending_object(&rev, &commit->object, NULL);
 422
 423         for (j = remoteheads; j; j = j->next)
 424                 add_pending_object(&rev, &j->item->object, NULL);
 425
 426         setup_revisions(0, NULL, &rev, NULL);
 427         if (prepare_revision_walk(&rev))
 428                 die(_("revision walk setup failed"));
 429
 430         ctx.abbrev = rev.abbrev;
 431         ctx.date_mode = rev.date_mode;
 432         ctx.fmt = rev.commit_format;
 433
 434         strbuf_addstr(&out, "Squashed commit of the following:\n");
 435         while ((commit = get_revision(&rev)) != NULL) {
 436                 strbuf_addch(&out, '\n');
 437                 strbuf_addf(&out, "commit %s\n",
 438                         oid_to_hex(&commit->object.oid));
 439                 pretty_print_commit(&ctx, commit, &out);
 440         }
 441         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 442         strbuf_release(&out);
 443 }
 444
 445 static void finish(struct commit *head_commit,
 446                    struct commit_list *remoteheads,
 447                    const struct object_id *new_head, const char *msg)
 448 {
 449         struct strbuf reflog_message = STRBUF_INIT;
 450         const struct object_id *head = &head_commit->object.oid;
 451
 452         if (!msg)
 453                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 454         else {
 455                 if (verbosity >= 0)
 456                         printf("%s\n", msg);
 457                 strbuf_addf(&reflog_message, "%s: %s",
 458                         getenv("GIT_REFLOG_ACTION"), msg);
 459         }
 460         if (squash) {
 461                 squash_message(head_commit, remoteheads);
 462         } else {
 463                 if (verbosity >= 0 && !merge_msg.len)
 464                         printf(_("No merge message -- not updating HEAD\n"));
 465                 else {
 466                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 467                                    0, UPDATE_REFS_DIE_ON_ERR);
 468                         /*
 469                          * We ignore errors in 'gc --auto', since the
 470                          * user should see them.
 471                          */
 472                         close_object_store(the_repository->objects);
 473                         run_auto_maintenance(verbosity < 0);
 474                 }
 475         }
 476         if (new_head && show_diffstat) {
 477                 struct diff_options opts;
 478                 repo_diff_setup(the_repository, &opts);
 479                 opts.stat_width = -1; /* use full terminal width */
 480                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 481                 opts.output_format |=
 482                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 483                 opts.detect_rename = DIFF_DETECT_RENAME;
 484                 diff_setup_done(&opts);
 485                 diff_tree_oid(head, new_head, "", &opts);
 486                 diffcore_std(&opts);
 487                 diff_flush(&opts);
 488         }
 489
 490         /* Run a post-merge hook */
 491         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 492
 493         apply_autostash(git_path_merge_autostash(the_repository));
 494         strbuf_release(&reflog_message);
 495 }
 496
 497 /* Get the name for the merge commit's message. */
 498 static void merge_name(const char *remote, struct strbuf *msg)
 499 {
 500         struct commit *remote_head;
 501         struct object_id branch_head;
 502         struct strbuf buf = STRBUF_INIT;
 503         struct strbuf bname = STRBUF_INIT;
 504         struct merge_remote_desc *desc;
 505         const char *ptr;
 506         char *found_ref;
 507         int len, early;
 508
 509         strbuf_branchname(&bname, remote, 0);
 510         remote = bname.buf;
 511
 512         oidclr(&branch_head);
 513         remote_head = get_merge_parent(remote);
 514         if (!remote_head)
 515                 die(_("'%s' does not point to a commit"), remote);
 516
 517         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
 518                 if (starts_with(found_ref, "refs/heads/")) {
 519                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 520                                     oid_to_hex(&branch_head), remote);
 521                         goto cleanup;
 522                 }
 523                 if (starts_with(found_ref, "refs/tags/")) {
 524                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 525                                     oid_to_hex(&branch_head), remote);
 526                         goto cleanup;
 527                 }
 528                 if (starts_with(found_ref, "refs/remotes/")) {
 529                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 530                                     oid_to_hex(&branch_head), remote);
 531                         goto cleanup;
 532                 }
 533         }
 534
 535         /* See if remote matches <name>^^^.. or <name>~<number> */
 536         for (len = 0, ptr = remote + strlen(remote);
 537              remote < ptr && ptr[-1] == '^';
 538              ptr--)
 539                 len++;
 540         if (len)
 541                 early = 1;
 542         else {
 543                 early = 0;
 544                 ptr = strrchr(remote, '~');
 545                 if (ptr) {
 546                         int seen_nonzero = 0;
 547
 548                         len++; /* count ~ */
 549                         while (*++ptr && isdigit(*ptr)) {
 550                                 seen_nonzero |= (*ptr != '0');
 551                                 len++;
 552                         }
 553                         if (*ptr)
 554                                 len = 0; /* not ...~<number> */
 555                         else if (seen_nonzero)
 556                                 early = 1;
 557                         else if (len == 1)
 558                                 early = 1; /* "name~" is "name~1"! */
 559                 }
 560         }
 561         if (len) {
 562                 struct strbuf truname = STRBUF_INIT;
 563                 strbuf_addf(&truname, "refs/heads/%s", remote);
 564                 strbuf_setlen(&truname, truname.len - len);
 565                 if (ref_exists(truname.buf)) {
 566                         strbuf_addf(msg,
 567                                     "%s\t\tbranch '%s'%s of .\n",
 568                                     oid_to_hex(&remote_head->object.oid),
 569                                     truname.buf + 11,
 570                                     (early ? " (early part)" : ""));
 571                         strbuf_release(&truname);
 572                         goto cleanup;
 573                 }
 574                 strbuf_release(&truname);
 575         }
 576
 577         desc = merge_remote_util(remote_head);
 578         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 579                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 580                             oid_to_hex(&desc->obj->oid),
 581                             type_name(desc->obj->type),
 582                             remote);
 583                 goto cleanup;
 584         }
 585
 586         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 587                 oid_to_hex(&remote_head->object.oid), remote);
 588 cleanup:
 589         strbuf_release(&buf);
 590         strbuf_release(&bname);
 591 }
 592
 593 static void parse_branch_merge_options(char *bmo)
 594 {
 595         const char **argv;
 596         int argc;
 597
 598         if (!bmo)
 599                 return;
 600         argc = split_cmdline(bmo, &argv);
 601         if (argc < 0)
 602                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 603                     _(split_cmdline_strerror(argc)));
 604         REALLOC_ARRAY(argv, argc + 2);
 605         MOVE_ARRAY(argv + 1, argv, argc + 1);
 606         argc++;
 607         argv[0] = "branch.*.mergeoptions";
 608         parse_options(argc, argv, NULL, builtin_merge_options,
 609                       builtin_merge_usage, 0);
 610         free(argv);
 611 }
 612
 613 static int git_merge_config(const char *k, const char *v, void *cb)
 614 {
 615         int status;
 616         const char *str;
 617
 618         if (branch &&
 619             skip_prefix(k, "branch.", &str) &&
 620             skip_prefix(str, branch, &str) &&
 621             !strcmp(str, ".mergeoptions")) {
 622                 free(branch_mergeoptions);
 623                 branch_mergeoptions = xstrdup(v);
 624                 return 0;
 625         }
 626
 627         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 628                 show_diffstat = git_config_bool(k, v);
 629         else if (!strcmp(k, "merge.verifysignatures"))
 630                 verify_signatures = git_config_bool(k, v);
 631         else if (!strcmp(k, "pull.twohead"))
 632                 return git_config_string(&pull_twohead, k, v);
 633         else if (!strcmp(k, "pull.octopus"))
 634                 return git_config_string(&pull_octopus, k, v);
 635         else if (!strcmp(k, "commit.cleanup"))
 636                 return git_config_string(&cleanup_arg, k, v);
 637         else if (!strcmp(k, "merge.ff")) {
 638                 int boolval = git_parse_maybe_bool(v);
 639                 if (0 <= boolval) {
 640                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 641                 } else if (v && !strcmp(v, "only")) {
 642                         fast_forward = FF_ONLY;
 643                 } /* do not barf on values from future versions of git */
 644                 return 0;
 645         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 646                 default_to_upstream = git_config_bool(k, v);
 647                 return 0;
 648         } else if (!strcmp(k, "commit.gpgsign")) {
 649                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 650                 return 0;
 651         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 652                 check_trust_level = 0;
 653         } else if (!strcmp(k, "merge.autostash")) {
 654                 autostash = git_config_bool(k, v);
 655                 return 0;
 656         }
 657
 658         status = fmt_merge_msg_config(k, v, cb);
 659         if (status)
 660                 return status;
 661         status = git_gpg_config(k, v, NULL);
 662         if (status)
 663                 return status;
 664         return git_diff_ui_config(k, v, cb);
 665 }
 666
 667 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 668                              struct object_id *one)
 669 {
 670         int i, nr_trees = 0;
 671         struct tree *trees[MAX_UNPACK_TREES];
 672         struct tree_desc t[MAX_UNPACK_TREES];
 673         struct unpack_trees_options opts;
 674
 675         memset(&opts, 0, sizeof(opts));
 676         opts.head_idx = 2;
 677         opts.src_index = &the_index;
 678         opts.dst_index = &the_index;
 679         opts.update = 1;
 680         opts.verbose_update = 1;
 681         opts.trivial_merges_only = 1;
 682         opts.merge = 1;
 683         trees[nr_trees] = parse_tree_indirect(common);
 684         if (!trees[nr_trees++])
 685                 return -1;
 686         trees[nr_trees] = parse_tree_indirect(head);
 687         if (!trees[nr_trees++])
 688                 return -1;
 689         trees[nr_trees] = parse_tree_indirect(one);
 690         if (!trees[nr_trees++])
 691                 return -1;
 692         opts.fn = threeway_merge;
 693         cache_tree_free(&active_cache_tree);
 694         for (i = 0; i < nr_trees; i++) {
 695                 parse_tree(trees[i]);
 696                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 697         }
 698         if (unpack_trees(nr_trees, t, &opts))
 699                 return -1;
 700         return 0;
 701 }
 702
 703 static void write_tree_trivial(struct object_id *oid)
 704 {
 705         if (write_cache_as_tree(oid, 0, NULL))
 706                 die(_("git write-tree failed to write a tree"));
 707 }
 708
 709 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 710                               struct commit_list *remoteheads,
 711                               struct commit *head)
 712 {
 713         const char *head_arg = "HEAD";
 714
 715         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 716                 return error(_("Unable to write index."));
 717
 718         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
 719             !strcmp(strategy, "ort")) {
 720                 struct lock_file lock = LOCK_INIT;
 721                 int clean, x;
 722                 struct commit *result;
 723                 struct commit_list *reversed = NULL;
 724                 struct merge_options o;
 725                 struct commit_list *j;
 726
 727                 if (remoteheads->next) {
 728                         error(_("Not handling anything other than two heads merge."));
 729                         return 2;
 730                 }
 731
 732                 init_merge_options(&o, the_repository);
 733                 if (!strcmp(strategy, "subtree"))
 734                         o.subtree_shift = "";
 735
 736                 o.show_rename_progress =
 737                         show_progress == -1 ? isatty(2) : show_progress;
 738
 739                 for (x = 0; x < xopts_nr; x++)
 740                         if (parse_merge_opt(&o, xopts[x]))
 741                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 742
 743                 o.branch1 = head_arg;
 744                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 745
 746                 for (j = common; j; j = j->next)
 747                         commit_list_insert(j->item, &reversed);
 748
 749                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 750                 if (!strcmp(strategy, "ort"))
 751                         clean = merge_ort_recursive(&o, head, remoteheads->item,
 752                                                     reversed, &result);
 753                 else
 754                         clean = merge_recursive(&o, head, remoteheads->item,
 755                                                 reversed, &result);
 756                 if (clean < 0)
 757                         exit(128);
 758                 if (write_locked_index(&the_index, &lock,
 759                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 760                         die(_("unable to write %s"), get_index_file());
 761                 return clean ? 0 : 1;
 762         } else {
 763                 return try_merge_command(the_repository,
 764                                          strategy, xopts_nr, xopts,
 765                                          common, head_arg, remoteheads);
 766         }
 767 }
 768
 769 static void count_diff_files(struct diff_queue_struct *q,
 770                              struct diff_options *opt, void *data)
 771 {
 772         int *count = data;
 773
 774         (*count) += q->nr;
 775 }
 776
 777 static int count_unmerged_entries(void)
 778 {
 779         int i, ret = 0;
 780
 781         for (i = 0; i < active_nr; i++)
 782                 if (ce_stage(active_cache[i]))
 783                         ret++;
 784
 785         return ret;
 786 }
 787
 788 static void add_strategies(const char *string, unsigned attr)
 789 {
 790         int i;
 791
 792         if (string) {
 793                 struct string_list list = STRING_LIST_INIT_DUP;
 794                 struct string_list_item *item;
 795                 string_list_split(&list, string, ' ', -1);
 796                 for_each_string_list_item(item, &list)
 797                         append_strategy(get_strategy(item->string));
 798                 string_list_clear(&list, 0);
 799                 return;
 800         }
 801         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 802                 if (all_strategy[i].attr & attr)
 803                         append_strategy(&all_strategy[i]);
 804
 805 }
 806
 807 static void read_merge_msg(struct strbuf *msg)
 808 {
 809         const char *filename = git_path_merge_msg(the_repository);
 810         strbuf_reset(msg);
 811         if (strbuf_read_file(msg, filename, 0) < 0)
 812                 die_errno(_("Could not read from '%s'"), filename);
 813 }
 814
 815 static void write_merge_state(struct commit_list *);
 816 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 817 {
 818         if (err_msg)
 819                 error("%s", err_msg);
 820         fprintf(stderr,
 821                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 822         write_merge_state(remoteheads);
 823         exit(1);
 824 }
 825
 826 static const char merge_editor_comment[] =
 827 N_("Please enter a commit message to explain why this merge is necessary,\n"
 828    "especially if it merges an updated upstream into a topic branch.\n"
 829    "\n");
 830
 831 static const char scissors_editor_comment[] =
 832 N_("An empty message aborts the commit.\n");
 833
 834 static const char no_scissors_editor_comment[] =
 835 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 836    "the commit.\n");
 837
 838 static void write_merge_heads(struct commit_list *);
 839 static void prepare_to_commit(struct commit_list *remoteheads)
 840 {
 841         struct strbuf msg = STRBUF_INIT;
 842         const char *index_file = get_index_file();
 843
 844         if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
 845                 abort_commit(remoteheads, NULL);
 846         /*
 847          * Re-read the index as pre-merge-commit hook could have updated it,
 848          * and write it out as a tree.  We must do this before we invoke
 849          * the editor and after we invoke run_status above.
 850          */
 851         if (find_hook("pre-merge-commit"))
 852                 discard_cache();
 853         read_cache_from(index_file);
 854         strbuf_addbuf(&msg, &merge_msg);
 855         if (squash)
 856                 BUG("the control must not reach here under --squash");
 857         if (0 < option_edit) {
 858                 strbuf_addch(&msg, '\n');
 859                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 860                         wt_status_append_cut_line(&msg);
 861                         strbuf_commented_addf(&msg, "\n");
 862                 }
 863                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 864                 strbuf_commented_addf(&msg, _(cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS ?
 865                         scissors_editor_comment :
 866                         no_scissors_editor_comment), comment_line_char);
 867         }
 868         if (signoff)
 869                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 870         write_merge_heads(remoteheads);
 871         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 872         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 873                             git_path_merge_msg(the_repository), "merge", NULL))
 874                 abort_commit(remoteheads, NULL);
 875         if (0 < option_edit) {
 876                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 877                         abort_commit(remoteheads, NULL);
 878         }
 879
 880         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 881                                           "commit-msg",
 882                                           git_path_merge_msg(the_repository), NULL))
 883                 abort_commit(remoteheads, NULL);
 884
 885         read_merge_msg(&msg);
 886         cleanup_message(&msg, cleanup_mode, 0);
 887         if (!msg.len)
 888                 abort_commit(remoteheads, _("Empty commit message."));
 889         strbuf_release(&merge_msg);
 890         strbuf_addbuf(&merge_msg, &msg);
 891         strbuf_release(&msg);
 892 }
 893
 894 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 895 {
 896         struct object_id result_tree, result_commit;
 897         struct commit_list *parents, **pptr = &parents;
 898
 899         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 900                 return error(_("Unable to write index."));
 901
 902         write_tree_trivial(&result_tree);
 903         printf(_("Wonderful.\n"));
 904         pptr = commit_list_append(head, pptr);
 905         pptr = commit_list_append(remoteheads->item, pptr);
 906         prepare_to_commit(remoteheads);
 907         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 908                         &result_commit, NULL, sign_commit))
 909                 die(_("failed to write commit object"));
 910         finish(head, remoteheads, &result_commit, "In-index merge");
 911         remove_merge_branch_state(the_repository);
 912         return 0;
 913 }
 914
 915 static int finish_automerge(struct commit *head,
 916                             int head_subsumed,
 917                             struct commit_list *common,
 918                             struct commit_list *remoteheads,
 919                             struct object_id *result_tree,
 920                             const char *wt_strategy)
 921 {
 922         struct commit_list *parents = NULL;
 923         struct strbuf buf = STRBUF_INIT;
 924         struct object_id result_commit;
 925
 926         write_tree_trivial(result_tree);
 927         free_commit_list(common);
 928         parents = remoteheads;
 929         if (!head_subsumed || fast_forward == FF_NO)
 930                 commit_list_insert(head, &parents);
 931         prepare_to_commit(remoteheads);
 932         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 933                         &result_commit, NULL, sign_commit))
 934                 die(_("failed to write commit object"));
 935         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 936         finish(head, remoteheads, &result_commit, buf.buf);
 937         strbuf_release(&buf);
 938         remove_merge_branch_state(the_repository);
 939         return 0;
 940 }
 941
 942 static int suggest_conflicts(void)
 943 {
 944         const char *filename;
 945         FILE *fp;
 946         struct strbuf msgbuf = STRBUF_INIT;
 947
 948         filename = git_path_merge_msg(the_repository);
 949         fp = xfopen(filename, "a");
 950
 951         /*
 952          * We can't use cleanup_mode because if we're not using the editor,
 953          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 954          * though the message is meant to be processed later by git-commit.
 955          * Thus, we will get the cleanup mode which is returned when we _are_
 956          * using an editor.
 957          */
 958         append_conflicts_hint(&the_index, &msgbuf,
 959                               get_cleanup_mode(cleanup_arg, 1));
 960         fputs(msgbuf.buf, fp);
 961         strbuf_release(&msgbuf);
 962         fclose(fp);
 963         repo_rerere(the_repository, allow_rerere_auto);
 964         printf(_("Automatic merge failed; "
 965                         "fix conflicts and then commit the result.\n"));
 966         return 1;
 967 }
 968
 969 static int evaluate_result(void)
 970 {
 971         int cnt = 0;
 972         struct rev_info rev;
 973
 974         /* Check how many files differ. */
 975         repo_init_revisions(the_repository, &rev, "");
 976         setup_revisions(0, NULL, &rev, NULL);
 977         rev.diffopt.output_format |=
 978                 DIFF_FORMAT_CALLBACK;
 979         rev.diffopt.format_callback = count_diff_files;
 980         rev.diffopt.format_callback_data = &cnt;
 981         run_diff_files(&rev, 0);
 982
 983         /*
 984          * Check how many unmerged entries are
 985          * there.
 986          */
 987         cnt += count_unmerged_entries();
 988
 989         return cnt;
 990 }
 991
 992 /*
 993  * Pretend as if the user told us to merge with the remote-tracking
 994  * branch we have for the upstream of the current branch
 995  */
 996 static int setup_with_upstream(const char ***argv)
 997 {
 998         struct branch *branch = branch_get(NULL);
 999         int i;
1000         const char **args;
1001
1002         if (!branch)
1003                 die(_("No current branch."));
1004         if (!branch->remote_name)
1005                 die(_("No remote for the current branch."));
1006         if (!branch->merge_nr)
1007                 die(_("No default upstream defined for the current branch."));
1008
1009         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
1010         for (i = 0; i < branch->merge_nr; i++) {
1011                 if (!branch->merge[i]->dst)
1012                         die(_("No remote-tracking branch for %s from %s"),
1013                             branch->merge[i]->src, branch->remote_name);
1014                 args[i] = branch->merge[i]->dst;
1015         }
1016         args[i] = NULL;
1017         *argv = args;
1018         return i;
1019 }
1020
1021 static void write_merge_heads(struct commit_list *remoteheads)
1022 {
1023         struct commit_list *j;
1024         struct strbuf buf = STRBUF_INIT;
1025
1026         for (j = remoteheads; j; j = j->next) {
1027                 struct object_id *oid;
1028                 struct commit *c = j->item;
1029                 struct merge_remote_desc *desc;
1030
1031                 desc = merge_remote_util(c);
1032                 if (desc && desc->obj) {
1033                         oid = &desc->obj->oid;
1034                 } else {
1035                         oid = &c->object.oid;
1036                 }
1037                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1038         }
1039         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1040
1041         strbuf_reset(&buf);
1042         if (fast_forward == FF_NO)
1043                 strbuf_addstr(&buf, "no-ff");
1044         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1045         strbuf_release(&buf);
1046 }
1047
1048 static void write_merge_state(struct commit_list *remoteheads)
1049 {
1050         write_merge_heads(remoteheads);
1051         strbuf_addch(&merge_msg, '\n');
1052         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1053                        merge_msg.len);
1054 }
1055
1056 static int default_edit_option(void)
1057 {
1058         static const char name[] = "GIT_MERGE_AUTOEDIT";
1059         const char *e = getenv(name);
1060         struct stat st_stdin, st_stdout;
1061
1062         if (have_message)
1063                 /* an explicit -m msg without --[no-]edit */
1064                 return 0;
1065
1066         if (e) {
1067                 int v = git_parse_maybe_bool(e);
1068                 if (v < 0)
1069                         die(_("Bad value '%s' in environment '%s'"), e, name);
1070                 return v;
1071         }
1072
1073         /* Use editor if stdin and stdout are the same and is a tty */
1074         return (!fstat(0, &st_stdin) &&
1075                 !fstat(1, &st_stdout) &&
1076                 isatty(0) && isatty(1) &&
1077                 st_stdin.st_dev == st_stdout.st_dev &&
1078                 st_stdin.st_ino == st_stdout.st_ino &&
1079                 st_stdin.st_mode == st_stdout.st_mode);
1080 }
1081
1082 static struct commit_list *reduce_parents(struct commit *head_commit,
1083                                           int *head_subsumed,
1084                                           struct commit_list *remoteheads)
1085 {
1086         struct commit_list *parents, **remotes;
1087
1088         /*
1089          * Is the current HEAD reachable from another commit being
1090          * merged?  If so we do not want to record it as a parent of
1091          * the resulting merge, unless --no-ff is given.  We will flip
1092          * this variable to 0 when we find HEAD among the independent
1093          * tips being merged.
1094          */
1095         *head_subsumed = 1;
1096
1097         /* Find what parents to record by checking independent ones. */
1098         parents = reduce_heads(remoteheads);
1099         free_commit_list(remoteheads);
1100
1101         remoteheads = NULL;
1102         remotes = &remoteheads;
1103         while (parents) {
1104                 struct commit *commit = pop_commit(&parents);
1105                 if (commit == head_commit)
1106                         *head_subsumed = 0;
1107                 else
1108                         remotes = &commit_list_insert(commit, remotes)->next;
1109         }
1110         return remoteheads;
1111 }
1112
1113 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1114 {
1115         struct fmt_merge_msg_opts opts;
1116
1117         memset(&opts, 0, sizeof(opts));
1118         opts.add_title = !have_message;
1119         opts.shortlog_len = shortlog_len;
1120         opts.credit_people = (0 < option_edit);
1121
1122         fmt_merge_msg(merge_names, merge_msg, &opts);
1123         if (merge_msg->len)
1124                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1125 }
1126
1127 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1128 {
1129         const char *filename;
1130         int fd, pos, npos;
1131         struct strbuf fetch_head_file = STRBUF_INIT;
1132         const unsigned hexsz = the_hash_algo->hexsz;
1133
1134         if (!merge_names)
1135                 merge_names = &fetch_head_file;
1136
1137         filename = git_path_fetch_head(the_repository);
1138         fd = open(filename, O_RDONLY);
1139         if (fd < 0)
1140                 die_errno(_("could not open '%s' for reading"), filename);
1141
1142         if (strbuf_read(merge_names, fd, 0) < 0)
1143                 die_errno(_("could not read '%s'"), filename);
1144         if (close(fd) < 0)
1145                 die_errno(_("could not close '%s'"), filename);
1146
1147         for (pos = 0; pos < merge_names->len; pos = npos) {
1148                 struct object_id oid;
1149                 char *ptr;
1150                 struct commit *commit;
1151
1152                 ptr = strchr(merge_names->buf + pos, '\n');
1153                 if (ptr)
1154                         npos = ptr - merge_names->buf + 1;
1155                 else
1156                         npos = merge_names->len;
1157
1158                 if (npos - pos < hexsz + 2 ||
1159                     get_oid_hex(merge_names->buf + pos, &oid))
1160                         commit = NULL; /* bad */
1161                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1162                         continue; /* not-for-merge */
1163                 else {
1164                         char saved = merge_names->buf[pos + hexsz];
1165                         merge_names->buf[pos + hexsz] = '\0';
1166                         commit = get_merge_parent(merge_names->buf + pos);
1167                         merge_names->buf[pos + hexsz] = saved;
1168                 }
1169                 if (!commit) {
1170                         if (ptr)
1171                                 *ptr = '\0';
1172                         die(_("not something we can merge in %s: %s"),
1173                             filename, merge_names->buf + pos);
1174                 }
1175                 remotes = &commit_list_insert(commit, remotes)->next;
1176         }
1177
1178         if (merge_names == &fetch_head_file)
1179                 strbuf_release(&fetch_head_file);
1180 }
1181
1182 static struct commit_list *collect_parents(struct commit *head_commit,
1183                                            int *head_subsumed,
1184                                            int argc, const char **argv,
1185                                            struct strbuf *merge_msg)
1186 {
1187         int i;
1188         struct commit_list *remoteheads = NULL;
1189         struct commit_list **remotes = &remoteheads;
1190         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1191
1192         if (merge_msg && (!have_message || shortlog_len))
1193                 autogen = &merge_names;
1194
1195         if (head_commit)
1196                 remotes = &commit_list_insert(head_commit, remotes)->next;
1197
1198         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1199                 handle_fetch_head(remotes, autogen);
1200                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1201         } else {
1202                 for (i = 0; i < argc; i++) {
1203                         struct commit *commit = get_merge_parent(argv[i]);
1204                         if (!commit)
1205                                 help_unknown_ref(argv[i], "merge",
1206                                                  _("not something we can merge"));
1207                         remotes = &commit_list_insert(commit, remotes)->next;
1208                 }
1209                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1210                 if (autogen) {
1211                         struct commit_list *p;
1212                         for (p = remoteheads; p; p = p->next)
1213                                 merge_name(merge_remote_util(p->item)->name, autogen);
1214                 }
1215         }
1216
1217         if (autogen) {
1218                 prepare_merge_message(autogen, merge_msg);
1219                 strbuf_release(autogen);
1220         }
1221
1222         return remoteheads;
1223 }
1224
1225 static int merging_a_throwaway_tag(struct commit *commit)
1226 {
1227         char *tag_ref;
1228         struct object_id oid;
1229         int is_throwaway_tag = 0;
1230
1231         /* Are we merging a tag? */
1232         if (!merge_remote_util(commit) ||
1233             !merge_remote_util(commit)->obj ||
1234             merge_remote_util(commit)->obj->type != OBJ_TAG)
1235                 return is_throwaway_tag;
1236
1237         /*
1238          * Now we know we are merging a tag object.  Are we downstream
1239          * and following the tags from upstream?  If so, we must have
1240          * the tag object pointed at by "refs/tags/$T" where $T is the
1241          * tagname recorded in the tag object.  We want to allow such
1242          * a "just to catch up" merge to fast-forward.
1243          *
1244          * Otherwise, we are playing an integrator's role, making a
1245          * merge with a throw-away tag from a contributor with
1246          * something like "git pull $contributor $signed_tag".
1247          * We want to forbid such a merge from fast-forwarding
1248          * by default; otherwise we would not keep the signature
1249          * anywhere.
1250          */
1251         tag_ref = xstrfmt("refs/tags/%s",
1252                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1253         if (!read_ref(tag_ref, &oid) &&
1254             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1255                 is_throwaway_tag = 0;
1256         else
1257                 is_throwaway_tag = 1;
1258         free(tag_ref);
1259         return is_throwaway_tag;
1260 }
1261
1262 int cmd_merge(int argc, const char **argv, const char *prefix)
1263 {
1264         struct object_id result_tree, stash, head_oid;
1265         struct commit *head_commit;
1266         struct strbuf buf = STRBUF_INIT;
1267         int i, ret = 0, head_subsumed;
1268         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1269         struct commit_list *common = NULL;
1270         const char *best_strategy = NULL, *wt_strategy = NULL;
1271         struct commit_list *remoteheads, *p;
1272         void *branch_to_free;
1273         int orig_argc = argc;
1274
1275         if (argc == 2 && !strcmp(argv[1], "-h"))
1276                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1277
1278         /*
1279          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1280          * current branch.
1281          */
1282         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1283         if (branch)
1284                 skip_prefix(branch, "refs/heads/", &branch);
1285
1286         if (!pull_twohead) {
1287                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1288                 if (default_strategy && !strcmp(default_strategy, "ort"))
1289                         pull_twohead = "ort";
1290         }
1291
1292         init_diff_ui_defaults();
1293         git_config(git_merge_config, NULL);
1294
1295         if (!branch || is_null_oid(&head_oid))
1296                 head_commit = NULL;
1297         else
1298                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1299
1300         if (branch_mergeoptions)
1301                 parse_branch_merge_options(branch_mergeoptions);
1302         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1303                         builtin_merge_usage, 0);
1304         if (shortlog_len < 0)
1305                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1306
1307         if (verbosity < 0 && show_progress == -1)
1308                 show_progress = 0;
1309
1310         if (abort_current_merge) {
1311                 int nargc = 2;
1312                 const char *nargv[] = {"reset", "--merge", NULL};
1313                 struct strbuf stash_oid = STRBUF_INIT;
1314
1315                 if (orig_argc != 2)
1316                         usage_msg_opt(_("--abort expects no arguments"),
1317                               builtin_merge_usage, builtin_merge_options);
1318
1319                 if (!file_exists(git_path_merge_head(the_repository)))
1320                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1321
1322                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1323                     READ_ONELINER_SKIP_IF_EMPTY))
1324                         unlink(git_path_merge_autostash(the_repository));
1325
1326                 /* Invoke 'git reset --merge' */
1327                 ret = cmd_reset(nargc, nargv, prefix);
1328
1329                 if (stash_oid.len)
1330                         apply_autostash_oid(stash_oid.buf);
1331
1332                 strbuf_release(&stash_oid);
1333                 goto done;
1334         }
1335
1336         if (quit_current_merge) {
1337                 if (orig_argc != 2)
1338                         usage_msg_opt(_("--quit expects no arguments"),
1339                                       builtin_merge_usage,
1340                                       builtin_merge_options);
1341
1342                 remove_merge_branch_state(the_repository);
1343                 goto done;
1344         }
1345
1346         if (continue_current_merge) {
1347                 int nargc = 1;
1348                 const char *nargv[] = {"commit", NULL};
1349
1350                 if (orig_argc != 2)
1351                         usage_msg_opt(_("--continue expects no arguments"),
1352                               builtin_merge_usage, builtin_merge_options);
1353
1354                 if (!file_exists(git_path_merge_head(the_repository)))
1355                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1356
1357                 /* Invoke 'git commit' */
1358                 ret = cmd_commit(nargc, nargv, prefix);
1359                 goto done;
1360         }
1361
1362         if (read_cache_unmerged())
1363                 die_resolve_conflict("merge");
1364
1365         if (file_exists(git_path_merge_head(the_repository))) {
1366                 /*
1367                  * There is no unmerged entry, don't advise 'git
1368                  * add/rm <file>', just 'git commit'.
1369                  */
1370                 if (advice_resolve_conflict)
1371                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1372                                   "Please, commit your changes before you merge."));
1373                 else
1374                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1375         }
1376         if (ref_exists("CHERRY_PICK_HEAD")) {
1377                 if (advice_resolve_conflict)
1378                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1379                             "Please, commit your changes before you merge."));
1380                 else
1381                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1382         }
1383         resolve_undo_clear();
1384
1385         if (option_edit < 0)
1386                 option_edit = default_edit_option();
1387
1388         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1389
1390         if (verbosity < 0)
1391                 show_diffstat = 0;
1392
1393         if (squash) {
1394                 if (fast_forward == FF_NO)
1395                         die(_("You cannot combine --squash with --no-ff."));
1396                 if (option_commit > 0)
1397                         die(_("You cannot combine --squash with --commit."));
1398                 /*
1399                  * squash can now silently disable option_commit - this is not
1400                  * a problem as it is only overriding the default, not a user
1401                  * supplied option.
1402                  */
1403                 option_commit = 0;
1404         }
1405
1406         if (option_commit < 0)
1407                 option_commit = 1;
1408
1409         if (!argc) {
1410                 if (default_to_upstream)
1411                         argc = setup_with_upstream(&argv);
1412                 else
1413                         die(_("No commit specified and merge.defaultToUpstream not set."));
1414         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1415                 argv[0] = "@{-1}";
1416         }
1417
1418         if (!argc)
1419                 usage_with_options(builtin_merge_usage,
1420                         builtin_merge_options);
1421
1422         if (!head_commit) {
1423                 /*
1424                  * If the merged head is a valid one there is no reason
1425                  * to forbid "git merge" into a branch yet to be born.
1426                  * We do the same for "git pull".
1427                  */
1428                 struct object_id *remote_head_oid;
1429                 if (squash)
1430                         die(_("Squash commit into empty head not supported yet"));
1431                 if (fast_forward == FF_NO)
1432                         die(_("Non-fast-forward commit does not make sense into "
1433                             "an empty head"));
1434                 remoteheads = collect_parents(head_commit, &head_subsumed,
1435                                               argc, argv, NULL);
1436                 if (!remoteheads)
1437                         die(_("%s - not something we can merge"), argv[0]);
1438                 if (remoteheads->next)
1439                         die(_("Can merge only exactly one commit into empty head"));
1440
1441                 if (verify_signatures)
1442                         verify_merge_signature(remoteheads->item, verbosity,
1443                                                check_trust_level);
1444
1445                 remote_head_oid = &remoteheads->item->object.oid;
1446                 read_empty(remote_head_oid, 0);
1447                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1448                            UPDATE_REFS_DIE_ON_ERR);
1449                 goto done;
1450         }
1451
1452         /*
1453          * All the rest are the commits being merged; prepare
1454          * the standard merge summary message to be appended
1455          * to the given message.
1456          */
1457         remoteheads = collect_parents(head_commit, &head_subsumed,
1458                                       argc, argv, &merge_msg);
1459
1460         if (!head_commit || !argc)
1461                 usage_with_options(builtin_merge_usage,
1462                         builtin_merge_options);
1463
1464         if (verify_signatures) {
1465                 for (p = remoteheads; p; p = p->next) {
1466                         verify_merge_signature(p->item, verbosity,
1467                                                check_trust_level);
1468                 }
1469         }
1470
1471         strbuf_addstr(&buf, "merge");
1472         for (p = remoteheads; p; p = p->next)
1473                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1474         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1475         strbuf_reset(&buf);
1476
1477         for (p = remoteheads; p; p = p->next) {
1478                 struct commit *commit = p->item;
1479                 strbuf_addf(&buf, "GITHEAD_%s",
1480                             oid_to_hex(&commit->object.oid));
1481                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1482                 strbuf_reset(&buf);
1483                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1484                         fast_forward = FF_NO;
1485         }
1486
1487         if (!use_strategies) {
1488                 if (!remoteheads)
1489                         ; /* already up-to-date */
1490                 else if (!remoteheads->next)
1491                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1492                 else
1493                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1494         }
1495
1496         for (i = 0; i < use_strategies_nr; i++) {
1497                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1498                         fast_forward = FF_NO;
1499                 if (use_strategies[i]->attr & NO_TRIVIAL)
1500                         allow_trivial = 0;
1501         }
1502
1503         if (!remoteheads)
1504                 ; /* already up-to-date */
1505         else if (!remoteheads->next)
1506                 common = get_merge_bases(head_commit, remoteheads->item);
1507         else {
1508                 struct commit_list *list = remoteheads;
1509                 commit_list_insert(head_commit, &list);
1510                 common = get_octopus_merge_bases(list);
1511                 free(list);
1512         }
1513
1514         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1515                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1516
1517         if (remoteheads && !common) {
1518                 /* No common ancestors found. */
1519                 if (!allow_unrelated_histories)
1520                         die(_("refusing to merge unrelated histories"));
1521                 /* otherwise, we need a real merge. */
1522         } else if (!remoteheads ||
1523                  (!remoteheads->next && !common->next &&
1524                   common->item == remoteheads->item)) {
1525                 /*
1526                  * If head can reach all the merge then we are up to date.
1527                  * but first the most common case of merging one remote.
1528                  */
1529                 finish_up_to_date();
1530                 goto done;
1531         } else if (fast_forward != FF_NO && !remoteheads->next &&
1532                         !common->next &&
1533                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1534                 /* Again the most common case of merging one remote. */
1535                 struct strbuf msg = STRBUF_INIT;
1536                 struct commit *commit;
1537
1538                 if (verbosity >= 0) {
1539                         printf(_("Updating %s..%s\n"),
1540                                find_unique_abbrev(&head_commit->object.oid,
1541                                                   DEFAULT_ABBREV),
1542                                find_unique_abbrev(&remoteheads->item->object.oid,
1543                                                   DEFAULT_ABBREV));
1544                 }
1545                 strbuf_addstr(&msg, "Fast-forward");
1546                 if (have_message)
1547                         strbuf_addstr(&msg,
1548                                 " (no commit created; -m option ignored)");
1549                 commit = remoteheads->item;
1550                 if (!commit) {
1551                         ret = 1;
1552                         goto done;
1553                 }
1554
1555                 if (autostash)
1556                         create_autostash(the_repository,
1557                                          git_path_merge_autostash(the_repository),
1558                                          "merge");
1559                 if (checkout_fast_forward(the_repository,
1560                                           &head_commit->object.oid,
1561                                           &commit->object.oid,
1562                                           overwrite_ignore)) {
1563                         ret = 1;
1564                         goto done;
1565                 }
1566
1567                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1568                 remove_merge_branch_state(the_repository);
1569                 goto done;
1570         } else if (!remoteheads->next && common->next)
1571                 ;
1572                 /*
1573                  * We are not doing octopus and not fast-forward.  Need
1574                  * a real merge.
1575                  */
1576         else if (!remoteheads->next && !common->next && option_commit) {
1577                 /*
1578                  * We are not doing octopus, not fast-forward, and have
1579                  * only one common.
1580                  */
1581                 refresh_cache(REFRESH_QUIET);
1582                 if (allow_trivial && fast_forward != FF_ONLY) {
1583                         /* See if it is really trivial. */
1584                         git_committer_info(IDENT_STRICT);
1585                         printf(_("Trying really trivial in-index merge...\n"));
1586                         if (!read_tree_trivial(&common->item->object.oid,
1587                                                &head_commit->object.oid,
1588                                                &remoteheads->item->object.oid)) {
1589                                 ret = merge_trivial(head_commit, remoteheads);
1590                                 goto done;
1591                         }
1592                         printf(_("Nope.\n"));
1593                 }
1594         } else {
1595                 /*
1596                  * An octopus.  If we can reach all the remote we are up
1597                  * to date.
1598                  */
1599                 int up_to_date = 1;
1600                 struct commit_list *j;
1601
1602                 for (j = remoteheads; j; j = j->next) {
1603                         struct commit_list *common_one;
1604
1605                         /*
1606                          * Here we *have* to calculate the individual
1607                          * merge_bases again, otherwise "git merge HEAD^
1608                          * HEAD^^" would be missed.
1609                          */
1610                         common_one = get_merge_bases(head_commit, j->item);
1611                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1612                                 up_to_date = 0;
1613                                 break;
1614                         }
1615                 }
1616                 if (up_to_date) {
1617                         finish_up_to_date();
1618                         goto done;
1619                 }
1620         }
1621
1622         if (fast_forward == FF_ONLY)
1623                 die(_("Not possible to fast-forward, aborting."));
1624
1625         if (autostash)
1626                 create_autostash(the_repository,
1627                                  git_path_merge_autostash(the_repository),
1628                                  "merge");
1629
1630         /* We are going to make a new commit. */
1631         git_committer_info(IDENT_STRICT);
1632
1633         /*
1634          * At this point, we need a real merge.  No matter what strategy
1635          * we use, it would operate on the index, possibly affecting the
1636          * working tree, and when resolved cleanly, have the desired
1637          * tree in the index -- this means that the index must be in
1638          * sync with the head commit.  The strategies are responsible
1639          * to ensure this.
1640          */
1641         if (use_strategies_nr == 1 ||
1642             /*
1643              * Stash away the local changes so that we can try more than one.
1644              */
1645             save_state(&stash))
1646                 oidclr(&stash);
1647
1648         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1649                 int ret, cnt;
1650                 if (i) {
1651                         printf(_("Rewinding the tree to pristine...\n"));
1652                         restore_state(&head_commit->object.oid, &stash);
1653                 }
1654                 if (use_strategies_nr != 1)
1655                         printf(_("Trying merge strategy %s...\n"),
1656                                 use_strategies[i]->name);
1657                 /*
1658                  * Remember which strategy left the state in the working
1659                  * tree.
1660                  */
1661                 wt_strategy = use_strategies[i]->name;
1662
1663                 ret = try_merge_strategy(use_strategies[i]->name,
1664                                          common, remoteheads,
1665                                          head_commit);
1666                 /*
1667                  * The backend exits with 1 when conflicts are
1668                  * left to be resolved, with 2 when it does not
1669                  * handle the given merge at all.
1670                  */
1671                 if (ret < 2) {
1672                         if (!ret) {
1673                                 if (option_commit) {
1674                                         /* Automerge succeeded. */
1675                                         automerge_was_ok = 1;
1676                                         break;
1677                                 }
1678                                 merge_was_ok = 1;
1679                         }
1680                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1681                         if (best_cnt <= 0 || cnt <= best_cnt) {
1682                                 best_strategy = use_strategies[i]->name;
1683                                 best_cnt = cnt;
1684                         }
1685                 }
1686         }
1687
1688         /*
1689          * If we have a resulting tree, that means the strategy module
1690          * auto resolved the merge cleanly.
1691          */
1692         if (automerge_was_ok) {
1693                 ret = finish_automerge(head_commit, head_subsumed,
1694                                        common, remoteheads,
1695                                        &result_tree, wt_strategy);
1696                 goto done;
1697         }
1698
1699         /*
1700          * Pick the result from the best strategy and have the user fix
1701          * it up.
1702          */
1703         if (!best_strategy) {
1704                 restore_state(&head_commit->object.oid, &stash);
1705                 if (use_strategies_nr > 1)
1706                         fprintf(stderr,
1707                                 _("No merge strategy handled the merge.\n"));
1708                 else
1709                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1710                                 use_strategies[0]->name);
1711                 ret = 2;
1712                 goto done;
1713         } else if (best_strategy == wt_strategy)
1714                 ; /* We already have its result in the working tree. */
1715         else {
1716                 printf(_("Rewinding the tree to pristine...\n"));
1717                 restore_state(&head_commit->object.oid, &stash);
1718                 printf(_("Using the %s to prepare resolving by hand.\n"),
1719                         best_strategy);
1720                 try_merge_strategy(best_strategy, common, remoteheads,
1721                                    head_commit);
1722         }
1723
1724         if (squash) {
1725                 finish(head_commit, remoteheads, NULL, NULL);
1726
1727                 git_test_write_commit_graph_or_die();
1728         } else
1729                 write_merge_state(remoteheads);
1730
1731         if (merge_was_ok)
1732                 fprintf(stderr, _("Automatic merge went well; "
1733                         "stopped before committing as requested\n"));
1734         else
1735                 ret = suggest_conflicts();
1736
1737 done:
1738         free(branch_to_free);
1739         return ret;
1740 }