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