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 "hook.h"
  17 #include "diff.h"
  18 #include "diff-merges.h"
  19 #include "refs.h"
  20 #include "refspec.h"
  21 #include "commit.h"
  22 #include "diffcore.h"
  23 #include "revision.h"
  24 #include "unpack-trees.h"
  25 #include "cache-tree.h"
  26 #include "dir.h"
  27 #include "utf8.h"
  28 #include "log-tree.h"
  29 #include "color.h"
  30 #include "rerere.h"
  31 #include "help.h"
  32 #include "merge-recursive.h"
  33 #include "merge-ort-wrappers.h"
  34 #include "resolve-undo.h"
  35 #include "remote.h"
  36 #include "fmt-merge-msg.h"
  37 #include "gpg-interface.h"
  38 #include "sequencer.h"
  39 #include "string-list.h"
  40 #include "packfile.h"
  41 #include "tag.h"
  42 #include "alias.h"
  43 #include "branch.h"
  44 #include "commit-reach.h"
  45 #include "wt-status.h"
  46 #include "commit-graph.h"
  47
  48 #define DEFAULT_TWOHEAD (1<<0)
  49 #define DEFAULT_OCTOPUS (1<<1)
  50 #define NO_FAST_FORWARD (1<<2)
  51 #define NO_TRIVIAL      (1<<3)
  52
  53 struct strategy {
  54         const char *name;
  55         unsigned attr;
  56 };
  57
  58 static const char * const builtin_merge_usage[] = {
  59         N_("git merge [<options>] [<commit>...]"),
  60         "git merge --abort",
  61         "git merge --continue",
  62         NULL
  63 };
  64
  65 static int show_diffstat = 1, shortlog_len = -1, squash;
  66 static int option_commit = -1;
  67 static int option_edit = -1;
  68 static int allow_trivial = 1, have_message, verify_signatures;
  69 static int check_trust_level = 1;
  70 static int overwrite_ignore = 1;
  71 static struct strbuf merge_msg = STRBUF_INIT;
  72 static struct strategy **use_strategies;
  73 static size_t use_strategies_nr, use_strategies_alloc;
  74 static const char **xopts;
  75 static size_t xopts_nr, xopts_alloc;
  76 static const char *branch;
  77 static char *branch_mergeoptions;
  78 static int verbosity;
  79 static int allow_rerere_auto;
  80 static int abort_current_merge;
  81 static int quit_current_merge;
  82 static int continue_current_merge;
  83 static int allow_unrelated_histories;
  84 static int show_progress = -1;
  85 static int default_to_upstream = 1;
  86 static int signoff;
  87 static const char *sign_commit;
  88 static int autostash;
  89 static int no_verify;
  90 static char *into_name;
  91
  92 static struct strategy all_strategy[] = {
  93         { "recursive",  NO_TRIVIAL },
  94         { "octopus",    DEFAULT_OCTOPUS },
  95         { "ort",        DEFAULT_TWOHEAD | NO_TRIVIAL },
  96         { "resolve",    0 },
  97         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  98         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  99 };
 100
 101 static const char *pull_twohead, *pull_octopus;
 102
 103 enum ff_type {
 104         FF_NO,
 105         FF_ALLOW,
 106         FF_ONLY
 107 };
 108
 109 static enum ff_type fast_forward = FF_ALLOW;
 110
 111 static const char *cleanup_arg;
 112 static enum commit_msg_cleanup_mode cleanup_mode;
 113
 114 static int option_parse_message(const struct option *opt,
 115                                 const char *arg, int unset)
 116 {
 117         struct strbuf *buf = opt->value;
 118
 119         if (unset)
 120                 strbuf_setlen(buf, 0);
 121         else if (arg) {
 122                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 123                 have_message = 1;
 124         } else
 125                 return error(_("switch `m' requires a value"));
 126         return 0;
 127 }
 128
 129 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 130                                                  const struct option *opt,
 131                                                  const char *arg_not_used,
 132                                                  int unset)
 133 {
 134         struct strbuf *buf = opt->value;
 135         const char *arg;
 136
 137         BUG_ON_OPT_ARG(arg_not_used);
 138         if (unset)
 139                 BUG("-F cannot be negated");
 140
 141         if (ctx->opt) {
 142                 arg = ctx->opt;
 143                 ctx->opt = NULL;
 144         } else if (ctx->argc > 1) {
 145                 ctx->argc--;
 146                 arg = *++ctx->argv;
 147         } else
 148                 return error(_("option `%s' requires a value"), opt->long_name);
 149
 150         if (buf->len)
 151                 strbuf_addch(buf, '\n');
 152         if (ctx->prefix && !is_absolute_path(arg))
 153                 arg = prefix_filename(ctx->prefix, arg);
 154         if (strbuf_read_file(buf, arg, 0) < 0)
 155                 return error(_("could not read file '%s'"), arg);
 156         have_message = 1;
 157
 158         return 0;
 159 }
 160
 161 static struct strategy *get_strategy(const char *name)
 162 {
 163         int i;
 164         struct strategy *ret;
 165         static struct cmdnames main_cmds, other_cmds;
 166         static int loaded;
 167         char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 168
 169         if (!name)
 170                 return NULL;
 171
 172         if (default_strategy &&
 173             !strcmp(default_strategy, "ort") &&
 174             !strcmp(name, "recursive")) {
 175                 name = "ort";
 176         }
 177
 178         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 179                 if (!strcmp(name, all_strategy[i].name))
 180                         return &all_strategy[i];
 181
 182         if (!loaded) {
 183                 struct cmdnames not_strategies;
 184                 loaded = 1;
 185
 186                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 187                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 188                 for (i = 0; i < main_cmds.cnt; i++) {
 189                         int j, found = 0;
 190                         struct cmdname *ent = main_cmds.names[i];
 191                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 192                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 193                                                 && !all_strategy[j].name[ent->len])
 194                                         found = 1;
 195                         if (!found)
 196                                 add_cmdname(&not_strategies, ent->name, ent->len);
 197                 }
 198                 exclude_cmds(&main_cmds, &not_strategies);
 199         }
 200         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 201                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 202                 fprintf(stderr, _("Available strategies are:"));
 203                 for (i = 0; i < main_cmds.cnt; i++)
 204                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 205                 fprintf(stderr, ".\n");
 206                 if (other_cmds.cnt) {
 207                         fprintf(stderr, _("Available custom strategies are:"));
 208                         for (i = 0; i < other_cmds.cnt; i++)
 209                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 210                         fprintf(stderr, ".\n");
 211                 }
 212                 exit(1);
 213         }
 214
 215         CALLOC_ARRAY(ret, 1);
 216         ret->name = xstrdup(name);
 217         ret->attr = NO_TRIVIAL;
 218         return ret;
 219 }
 220
 221 static void append_strategy(struct strategy *s)
 222 {
 223         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 224         use_strategies[use_strategies_nr++] = s;
 225 }
 226
 227 static int option_parse_strategy(const struct option *opt,
 228                                  const char *name, int unset)
 229 {
 230         if (unset)
 231                 return 0;
 232
 233         append_strategy(get_strategy(name));
 234         return 0;
 235 }
 236
 237 static int option_parse_x(const struct option *opt,
 238                           const char *arg, int unset)
 239 {
 240         if (unset)
 241                 return 0;
 242
 243         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 244         xopts[xopts_nr++] = xstrdup(arg);
 245         return 0;
 246 }
 247
 248 static int option_parse_n(const struct option *opt,
 249                           const char *arg, int unset)
 250 {
 251         BUG_ON_OPT_ARG(arg);
 252         show_diffstat = unset;
 253         return 0;
 254 }
 255
 256 static struct option builtin_merge_options[] = {
 257         OPT_CALLBACK_F('n', NULL, NULL, NULL,
 258                 N_("do not show a diffstat at the end of the merge"),
 259                 PARSE_OPT_NOARG, option_parse_n),
 260         OPT_BOOL(0, "stat", &show_diffstat,
 261                 N_("show a diffstat at the end of the merge")),
 262         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 263         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 264           N_("add (at most <n>) entries from shortlog to merge commit message"),
 265           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 266         OPT_BOOL(0, "squash", &squash,
 267                 N_("create a single commit instead of doing a merge")),
 268         OPT_BOOL(0, "commit", &option_commit,
 269                 N_("perform a commit if the merge succeeds (default)")),
 270         OPT_BOOL('e', "edit", &option_edit,
 271                 N_("edit message before committing")),
 272         OPT_CLEANUP(&cleanup_arg),
 273         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 274         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 275                       N_("abort if fast-forward is not possible"),
 276                       FF_ONLY, PARSE_OPT_NONEG),
 277         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 278         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 279                 N_("verify that the named commit has a valid GPG signature")),
 280         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 281                 N_("merge strategy to use"), option_parse_strategy),
 282         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 283                 N_("option for selected merge strategy"), option_parse_x),
 284         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 285                 N_("merge commit message (for a non-fast-forward merge)"),
 286                 option_parse_message),
 287         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 288                 N_("read message from file"), PARSE_OPT_NONEG,
 289                 NULL, 0, option_read_message },
 290         OPT_STRING(0, "into-name", &into_name, N_("name"),
 291                    N_("use <name> instead of the real target")),
 292         OPT__VERBOSITY(&verbosity),
 293         OPT_BOOL(0, "abort", &abort_current_merge,
 294                 N_("abort the current in-progress merge")),
 295         OPT_BOOL(0, "quit", &quit_current_merge,
 296                 N_("--abort but leave index and working tree alone")),
 297         OPT_BOOL(0, "continue", &continue_current_merge,
 298                 N_("continue the current in-progress merge")),
 299         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 300                  N_("allow merging unrelated histories")),
 301         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 302         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 303           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 304         OPT_AUTOSTASH(&autostash),
 305         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 306         OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
 307         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 308         OPT_END()
 309 };
 310
 311 static int save_state(struct object_id *stash)
 312 {
 313         int len;
 314         struct child_process cp = CHILD_PROCESS_INIT;
 315         struct strbuf buffer = STRBUF_INIT;
 316         int rc = -1;
 317
 318         strvec_pushl(&cp.args, "stash", "create", NULL);
 319         cp.out = -1;
 320         cp.git_cmd = 1;
 321
 322         if (start_command(&cp))
 323                 die(_("could not run stash."));
 324         len = strbuf_read(&buffer, cp.out, 1024);
 325         close(cp.out);
 326
 327         if (finish_command(&cp) || len < 0)
 328                 die(_("stash failed"));
 329         else if (!len)          /* no changes */
 330                 goto out;
 331         strbuf_setlen(&buffer, buffer.len-1);
 332         if (get_oid(buffer.buf, stash))
 333                 die(_("not a valid object: %s"), buffer.buf);
 334         rc = 0;
 335 out:
 336         strbuf_release(&buffer);
 337         return rc;
 338 }
 339
 340 static void read_empty(const struct object_id *oid, int verbose)
 341 {
 342         int i = 0;
 343         const char *args[7];
 344
 345         args[i++] = "read-tree";
 346         if (verbose)
 347                 args[i++] = "-v";
 348         args[i++] = "-m";
 349         args[i++] = "-u";
 350         args[i++] = empty_tree_oid_hex();
 351         args[i++] = oid_to_hex(oid);
 352         args[i] = NULL;
 353
 354         if (run_command_v_opt(args, RUN_GIT_CMD))
 355                 die(_("read-tree failed"));
 356 }
 357
 358 static void reset_hard(const struct object_id *oid, int verbose)
 359 {
 360         int i = 0;
 361         const char *args[6];
 362
 363         args[i++] = "read-tree";
 364         if (verbose)
 365                 args[i++] = "-v";
 366         args[i++] = "--reset";
 367         args[i++] = "-u";
 368         args[i++] = oid_to_hex(oid);
 369         args[i] = NULL;
 370
 371         if (run_command_v_opt(args, RUN_GIT_CMD))
 372                 die(_("read-tree failed"));
 373 }
 374
 375 static void restore_state(const struct object_id *head,
 376                           const struct object_id *stash)
 377 {
 378         const char *args[] = { "stash", "apply", NULL, NULL };
 379
 380         if (is_null_oid(stash))
 381                 return;
 382
 383         reset_hard(head, 1);
 384
 385         args[2] = oid_to_hex(stash);
 386
 387         /*
 388          * It is OK to ignore error here, for example when there was
 389          * nothing to restore.
 390          */
 391         run_command_v_opt(args, RUN_GIT_CMD);
 392
 393         refresh_cache(REFRESH_QUIET);
 394 }
 395
 396 /* This is called when no merge was necessary. */
 397 static void finish_up_to_date(void)
 398 {
 399         if (verbosity >= 0) {
 400                 if (squash)
 401                         puts(_("Already up to date. (nothing to squash)"));
 402                 else
 403                         puts(_("Already up to date."));
 404         }
 405         remove_merge_branch_state(the_repository);
 406 }
 407
 408 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 409 {
 410         struct rev_info rev;
 411         struct strbuf out = STRBUF_INIT;
 412         struct commit_list *j;
 413         struct pretty_print_context ctx = {0};
 414
 415         printf(_("Squash commit -- not updating HEAD\n"));
 416
 417         repo_init_revisions(the_repository, &rev, NULL);
 418         diff_merges_suppress(&rev);
 419         rev.commit_format = CMIT_FMT_MEDIUM;
 420
 421         commit->object.flags |= UNINTERESTING;
 422         add_pending_object(&rev, &commit->object, NULL);
 423
 424         for (j = remoteheads; j; j = j->next)
 425                 add_pending_object(&rev, &j->item->object, NULL);
 426
 427         setup_revisions(0, NULL, &rev, NULL);
 428         if (prepare_revision_walk(&rev))
 429                 die(_("revision walk setup failed"));
 430
 431         ctx.abbrev = rev.abbrev;
 432         ctx.date_mode = rev.date_mode;
 433         ctx.fmt = rev.commit_format;
 434
 435         strbuf_addstr(&out, "Squashed commit of the following:\n");
 436         while ((commit = get_revision(&rev)) != NULL) {
 437                 strbuf_addch(&out, '\n');
 438                 strbuf_addf(&out, "commit %s\n",
 439                         oid_to_hex(&commit->object.oid));
 440                 pretty_print_commit(&ctx, commit, &out);
 441         }
 442         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 443         strbuf_release(&out);
 444         release_revisions(&rev);
 445 }
 446
 447 static void finish(struct commit *head_commit,
 448                    struct commit_list *remoteheads,
 449                    const struct object_id *new_head, const char *msg)
 450 {
 451         struct strbuf reflog_message = STRBUF_INIT;
 452         const struct object_id *head = &head_commit->object.oid;
 453
 454         if (!msg)
 455                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 456         else {
 457                 if (verbosity >= 0)
 458                         printf("%s\n", msg);
 459                 strbuf_addf(&reflog_message, "%s: %s",
 460                         getenv("GIT_REFLOG_ACTION"), msg);
 461         }
 462         if (squash) {
 463                 squash_message(head_commit, remoteheads);
 464         } else {
 465                 if (verbosity >= 0 && !merge_msg.len)
 466                         printf(_("No merge message -- not updating HEAD\n"));
 467                 else {
 468                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 469                                    0, UPDATE_REFS_DIE_ON_ERR);
 470                         /*
 471                          * We ignore errors in 'gc --auto', since the
 472                          * user should see them.
 473                          */
 474                         run_auto_maintenance(verbosity < 0);
 475                 }
 476         }
 477         if (new_head && show_diffstat) {
 478                 struct diff_options opts;
 479                 repo_diff_setup(the_repository, &opts);
 480                 opts.stat_width = -1; /* use full terminal width */
 481                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 482                 opts.output_format |=
 483                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 484                 opts.detect_rename = DIFF_DETECT_RENAME;
 485                 diff_setup_done(&opts);
 486                 diff_tree_oid(head, new_head, "", &opts);
 487                 diffcore_std(&opts);
 488                 diff_flush(&opts);
 489         }
 490
 491         /* Run a post-merge hook */
 492         run_hooks_l("post-merge", squash ? "1" : "0", NULL);
 493
 494         apply_autostash(git_path_merge_autostash(the_repository));
 495         strbuf_release(&reflog_message);
 496 }
 497
 498 /* Get the name for the merge commit's message. */
 499 static void merge_name(const char *remote, struct strbuf *msg)
 500 {
 501         struct commit *remote_head;
 502         struct object_id branch_head;
 503         struct strbuf bname = STRBUF_INIT;
 504         struct merge_remote_desc *desc;
 505         const char *ptr;
 506         char *found_ref = NULL;
 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         free(found_ref);
 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         opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 684         trees[nr_trees] = parse_tree_indirect(common);
 685         if (!trees[nr_trees++])
 686                 return -1;
 687         trees[nr_trees] = parse_tree_indirect(head);
 688         if (!trees[nr_trees++])
 689                 return -1;
 690         trees[nr_trees] = parse_tree_indirect(one);
 691         if (!trees[nr_trees++])
 692                 return -1;
 693         opts.fn = threeway_merge;
 694         cache_tree_free(&active_cache_tree);
 695         for (i = 0; i < nr_trees; i++) {
 696                 parse_tree(trees[i]);
 697                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 698         }
 699         if (unpack_trees(nr_trees, t, &opts))
 700                 return -1;
 701         return 0;
 702 }
 703
 704 static void write_tree_trivial(struct object_id *oid)
 705 {
 706         if (write_cache_as_tree(oid, 0, NULL))
 707                 die(_("git write-tree failed to write a tree"));
 708 }
 709
 710 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 711                               struct commit_list *remoteheads,
 712                               struct commit *head)
 713 {
 714         const char *head_arg = "HEAD";
 715
 716         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 717                 return error(_("Unable to write index."));
 718
 719         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
 720             !strcmp(strategy, "ort")) {
 721                 struct lock_file lock = LOCK_INIT;
 722                 int clean, x;
 723                 struct commit *result;
 724                 struct commit_list *reversed = NULL;
 725                 struct merge_options o;
 726                 struct commit_list *j;
 727
 728                 if (remoteheads->next) {
 729                         error(_("Not handling anything other than two heads merge."));
 730                         return 2;
 731                 }
 732
 733                 init_merge_options(&o, the_repository);
 734                 if (!strcmp(strategy, "subtree"))
 735                         o.subtree_shift = "";
 736
 737                 o.show_rename_progress =
 738                         show_progress == -1 ? isatty(2) : show_progress;
 739
 740                 for (x = 0; x < xopts_nr; x++)
 741                         if (parse_merge_opt(&o, xopts[x]))
 742                                 die(_("unknown strategy option: -X%s"), xopts[x]);
 743
 744                 o.branch1 = head_arg;
 745                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 746
 747                 for (j = common; j; j = j->next)
 748                         commit_list_insert(j->item, &reversed);
 749
 750                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 751                 if (!strcmp(strategy, "ort"))
 752                         clean = merge_ort_recursive(&o, head, remoteheads->item,
 753                                                     reversed, &result);
 754                 else
 755                         clean = merge_recursive(&o, head, remoteheads->item,
 756                                                 reversed, &result);
 757                 if (clean < 0)
 758                         exit(128);
 759                 if (write_locked_index(&the_index, &lock,
 760                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 761                         die(_("unable to write %s"), get_index_file());
 762                 return clean ? 0 : 1;
 763         } else {
 764                 return try_merge_command(the_repository,
 765                                          strategy, xopts_nr, xopts,
 766                                          common, head_arg, remoteheads);
 767         }
 768 }
 769
 770 static void count_diff_files(struct diff_queue_struct *q,
 771                              struct diff_options *opt, void *data)
 772 {
 773         int *count = data;
 774
 775         (*count) += q->nr;
 776 }
 777
 778 static int count_unmerged_entries(void)
 779 {
 780         int i, ret = 0;
 781
 782         for (i = 0; i < active_nr; i++)
 783                 if (ce_stage(active_cache[i]))
 784                         ret++;
 785
 786         return ret;
 787 }
 788
 789 static void add_strategies(const char *string, unsigned attr)
 790 {
 791         int i;
 792
 793         if (string) {
 794                 struct string_list list = STRING_LIST_INIT_DUP;
 795                 struct string_list_item *item;
 796                 string_list_split(&list, string, ' ', -1);
 797                 for_each_string_list_item(item, &list)
 798                         append_strategy(get_strategy(item->string));
 799                 string_list_clear(&list, 0);
 800                 return;
 801         }
 802         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 803                 if (all_strategy[i].attr & attr)
 804                         append_strategy(&all_strategy[i]);
 805
 806 }
 807
 808 static void read_merge_msg(struct strbuf *msg)
 809 {
 810         const char *filename = git_path_merge_msg(the_repository);
 811         strbuf_reset(msg);
 812         if (strbuf_read_file(msg, filename, 0) < 0)
 813                 die_errno(_("Could not read from '%s'"), filename);
 814 }
 815
 816 static void write_merge_state(struct commit_list *);
 817 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 818 {
 819         if (err_msg)
 820                 error("%s", err_msg);
 821         fprintf(stderr,
 822                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 823         write_merge_state(remoteheads);
 824         exit(1);
 825 }
 826
 827 static const char merge_editor_comment[] =
 828 N_("Please enter a commit message to explain why this merge is necessary,\n"
 829    "especially if it merges an updated upstream into a topic branch.\n"
 830    "\n");
 831
 832 static const char scissors_editor_comment[] =
 833 N_("An empty message aborts the commit.\n");
 834
 835 static const char no_scissors_editor_comment[] =
 836 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 837    "the commit.\n");
 838
 839 static void write_merge_heads(struct commit_list *);
 840 static void prepare_to_commit(struct commit_list *remoteheads)
 841 {
 842         struct strbuf msg = STRBUF_INIT;
 843         const char *index_file = get_index_file();
 844
 845         if (!no_verify) {
 846                 int invoked_hook;
 847
 848                 if (run_commit_hook(0 < option_edit, index_file, &invoked_hook,
 849                                     "pre-merge-commit", NULL))
 850                         abort_commit(remoteheads, NULL);
 851                 /*
 852                  * Re-read the index as pre-merge-commit hook could have updated it,
 853                  * and write it out as a tree.  We must do this before we invoke
 854                  * the editor and after we invoke run_status above.
 855                  */
 856                 if (invoked_hook)
 857                         discard_cache();
 858         }
 859         read_cache_from(index_file);
 860         strbuf_addbuf(&msg, &merge_msg);
 861         if (squash)
 862                 BUG("the control must not reach here under --squash");
 863         if (0 < option_edit) {
 864                 strbuf_addch(&msg, '\n');
 865                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 866                         wt_status_append_cut_line(&msg);
 867                         strbuf_commented_addf(&msg, "\n");
 868                 }
 869                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 870                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
 871                         strbuf_commented_addf(&msg, _(scissors_editor_comment));
 872                 else
 873                         strbuf_commented_addf(&msg,
 874                                 _(no_scissors_editor_comment), comment_line_char);
 875         }
 876         if (signoff)
 877                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 878         write_merge_heads(remoteheads);
 879         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 880         if (run_commit_hook(0 < option_edit, get_index_file(), NULL,
 881                             "prepare-commit-msg",
 882                             git_path_merge_msg(the_repository), "merge", NULL))
 883                 abort_commit(remoteheads, NULL);
 884         if (0 < option_edit) {
 885                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 886                         abort_commit(remoteheads, NULL);
 887         }
 888
 889         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 890                                           NULL, "commit-msg",
 891                                           git_path_merge_msg(the_repository), NULL))
 892                 abort_commit(remoteheads, NULL);
 893
 894         read_merge_msg(&msg);
 895         cleanup_message(&msg, cleanup_mode, 0);
 896         if (!msg.len)
 897                 abort_commit(remoteheads, _("Empty commit message."));
 898         strbuf_release(&merge_msg);
 899         strbuf_addbuf(&merge_msg, &msg);
 900         strbuf_release(&msg);
 901 }
 902
 903 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 904 {
 905         struct object_id result_tree, result_commit;
 906         struct commit_list *parents, **pptr = &parents;
 907
 908         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 909                 return error(_("Unable to write index."));
 910
 911         write_tree_trivial(&result_tree);
 912         printf(_("Wonderful.\n"));
 913         pptr = commit_list_append(head, pptr);
 914         pptr = commit_list_append(remoteheads->item, pptr);
 915         prepare_to_commit(remoteheads);
 916         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 917                         &result_commit, NULL, sign_commit))
 918                 die(_("failed to write commit object"));
 919         finish(head, remoteheads, &result_commit, "In-index merge");
 920         remove_merge_branch_state(the_repository);
 921         return 0;
 922 }
 923
 924 static int finish_automerge(struct commit *head,
 925                             int head_subsumed,
 926                             struct commit_list *common,
 927                             struct commit_list *remoteheads,
 928                             struct object_id *result_tree,
 929                             const char *wt_strategy)
 930 {
 931         struct commit_list *parents = NULL;
 932         struct strbuf buf = STRBUF_INIT;
 933         struct object_id result_commit;
 934
 935         write_tree_trivial(result_tree);
 936         free_commit_list(common);
 937         parents = remoteheads;
 938         if (!head_subsumed || fast_forward == FF_NO)
 939                 commit_list_insert(head, &parents);
 940         prepare_to_commit(remoteheads);
 941         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 942                         &result_commit, NULL, sign_commit))
 943                 die(_("failed to write commit object"));
 944         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 945         finish(head, remoteheads, &result_commit, buf.buf);
 946         strbuf_release(&buf);
 947         remove_merge_branch_state(the_repository);
 948         return 0;
 949 }
 950
 951 static int suggest_conflicts(void)
 952 {
 953         const char *filename;
 954         FILE *fp;
 955         struct strbuf msgbuf = STRBUF_INIT;
 956
 957         filename = git_path_merge_msg(the_repository);
 958         fp = xfopen(filename, "a");
 959
 960         /*
 961          * We can't use cleanup_mode because if we're not using the editor,
 962          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 963          * though the message is meant to be processed later by git-commit.
 964          * Thus, we will get the cleanup mode which is returned when we _are_
 965          * using an editor.
 966          */
 967         append_conflicts_hint(&the_index, &msgbuf,
 968                               get_cleanup_mode(cleanup_arg, 1));
 969         fputs(msgbuf.buf, fp);
 970         strbuf_release(&msgbuf);
 971         fclose(fp);
 972         repo_rerere(the_repository, allow_rerere_auto);
 973         printf(_("Automatic merge failed; "
 974                         "fix conflicts and then commit the result.\n"));
 975         return 1;
 976 }
 977
 978 static int evaluate_result(void)
 979 {
 980         int cnt = 0;
 981         struct rev_info rev;
 982
 983         /* Check how many files differ. */
 984         repo_init_revisions(the_repository, &rev, "");
 985         setup_revisions(0, NULL, &rev, NULL);
 986         rev.diffopt.output_format |=
 987                 DIFF_FORMAT_CALLBACK;
 988         rev.diffopt.format_callback = count_diff_files;
 989         rev.diffopt.format_callback_data = &cnt;
 990         run_diff_files(&rev, 0);
 991
 992         /*
 993          * Check how many unmerged entries are
 994          * there.
 995          */
 996         cnt += count_unmerged_entries();
 997
 998         release_revisions(&rev);
 999         return cnt;
1000 }
1001
1002 /*
1003  * Pretend as if the user told us to merge with the remote-tracking
1004  * branch we have for the upstream of the current branch
1005  */
1006 static int setup_with_upstream(const char ***argv)
1007 {
1008         struct branch *branch = branch_get(NULL);
1009         int i;
1010         const char **args;
1011
1012         if (!branch)
1013                 die(_("No current branch."));
1014         if (!branch->remote_name)
1015                 die(_("No remote for the current branch."));
1016         if (!branch->merge_nr)
1017                 die(_("No default upstream defined for the current branch."));
1018
1019         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
1020         for (i = 0; i < branch->merge_nr; i++) {
1021                 if (!branch->merge[i]->dst)
1022                         die(_("No remote-tracking branch for %s from %s"),
1023                             branch->merge[i]->src, branch->remote_name);
1024                 args[i] = branch->merge[i]->dst;
1025         }
1026         args[i] = NULL;
1027         *argv = args;
1028         return i;
1029 }
1030
1031 static void write_merge_heads(struct commit_list *remoteheads)
1032 {
1033         struct commit_list *j;
1034         struct strbuf buf = STRBUF_INIT;
1035
1036         for (j = remoteheads; j; j = j->next) {
1037                 struct object_id *oid;
1038                 struct commit *c = j->item;
1039                 struct merge_remote_desc *desc;
1040
1041                 desc = merge_remote_util(c);
1042                 if (desc && desc->obj) {
1043                         oid = &desc->obj->oid;
1044                 } else {
1045                         oid = &c->object.oid;
1046                 }
1047                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1048         }
1049         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1050
1051         strbuf_reset(&buf);
1052         if (fast_forward == FF_NO)
1053                 strbuf_addstr(&buf, "no-ff");
1054         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1055         strbuf_release(&buf);
1056 }
1057
1058 static void write_merge_state(struct commit_list *remoteheads)
1059 {
1060         write_merge_heads(remoteheads);
1061         strbuf_addch(&merge_msg, '\n');
1062         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1063                        merge_msg.len);
1064 }
1065
1066 static int default_edit_option(void)
1067 {
1068         static const char name[] = "GIT_MERGE_AUTOEDIT";
1069         const char *e = getenv(name);
1070         struct stat st_stdin, st_stdout;
1071
1072         if (have_message)
1073                 /* an explicit -m msg without --[no-]edit */
1074                 return 0;
1075
1076         if (e) {
1077                 int v = git_parse_maybe_bool(e);
1078                 if (v < 0)
1079                         die(_("Bad value '%s' in environment '%s'"), e, name);
1080                 return v;
1081         }
1082
1083         /* Use editor if stdin and stdout are the same and is a tty */
1084         return (!fstat(0, &st_stdin) &&
1085                 !fstat(1, &st_stdout) &&
1086                 isatty(0) && isatty(1) &&
1087                 st_stdin.st_dev == st_stdout.st_dev &&
1088                 st_stdin.st_ino == st_stdout.st_ino &&
1089                 st_stdin.st_mode == st_stdout.st_mode);
1090 }
1091
1092 static struct commit_list *reduce_parents(struct commit *head_commit,
1093                                           int *head_subsumed,
1094                                           struct commit_list *remoteheads)
1095 {
1096         struct commit_list *parents, **remotes;
1097
1098         /*
1099          * Is the current HEAD reachable from another commit being
1100          * merged?  If so we do not want to record it as a parent of
1101          * the resulting merge, unless --no-ff is given.  We will flip
1102          * this variable to 0 when we find HEAD among the independent
1103          * tips being merged.
1104          */
1105         *head_subsumed = 1;
1106
1107         /* Find what parents to record by checking independent ones. */
1108         parents = reduce_heads(remoteheads);
1109         free_commit_list(remoteheads);
1110
1111         remoteheads = NULL;
1112         remotes = &remoteheads;
1113         while (parents) {
1114                 struct commit *commit = pop_commit(&parents);
1115                 if (commit == head_commit)
1116                         *head_subsumed = 0;
1117                 else
1118                         remotes = &commit_list_insert(commit, remotes)->next;
1119         }
1120         return remoteheads;
1121 }
1122
1123 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1124 {
1125         struct fmt_merge_msg_opts opts;
1126
1127         memset(&opts, 0, sizeof(opts));
1128         opts.add_title = !have_message;
1129         opts.shortlog_len = shortlog_len;
1130         opts.credit_people = (0 < option_edit);
1131         opts.into_name = into_name;
1132
1133         fmt_merge_msg(merge_names, merge_msg, &opts);
1134         if (merge_msg->len)
1135                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1136 }
1137
1138 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1139 {
1140         const char *filename;
1141         int fd, pos, npos;
1142         struct strbuf fetch_head_file = STRBUF_INIT;
1143         const unsigned hexsz = the_hash_algo->hexsz;
1144
1145         if (!merge_names)
1146                 merge_names = &fetch_head_file;
1147
1148         filename = git_path_fetch_head(the_repository);
1149         fd = xopen(filename, O_RDONLY);
1150
1151         if (strbuf_read(merge_names, fd, 0) < 0)
1152                 die_errno(_("could not read '%s'"), filename);
1153         if (close(fd) < 0)
1154                 die_errno(_("could not close '%s'"), filename);
1155
1156         for (pos = 0; pos < merge_names->len; pos = npos) {
1157                 struct object_id oid;
1158                 char *ptr;
1159                 struct commit *commit;
1160
1161                 ptr = strchr(merge_names->buf + pos, '\n');
1162                 if (ptr)
1163                         npos = ptr - merge_names->buf + 1;
1164                 else
1165                         npos = merge_names->len;
1166
1167                 if (npos - pos < hexsz + 2 ||
1168                     get_oid_hex(merge_names->buf + pos, &oid))
1169                         commit = NULL; /* bad */
1170                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1171                         continue; /* not-for-merge */
1172                 else {
1173                         char saved = merge_names->buf[pos + hexsz];
1174                         merge_names->buf[pos + hexsz] = '\0';
1175                         commit = get_merge_parent(merge_names->buf + pos);
1176                         merge_names->buf[pos + hexsz] = saved;
1177                 }
1178                 if (!commit) {
1179                         if (ptr)
1180                                 *ptr = '\0';
1181                         die(_("not something we can merge in %s: %s"),
1182                             filename, merge_names->buf + pos);
1183                 }
1184                 remotes = &commit_list_insert(commit, remotes)->next;
1185         }
1186
1187         if (merge_names == &fetch_head_file)
1188                 strbuf_release(&fetch_head_file);
1189 }
1190
1191 static struct commit_list *collect_parents(struct commit *head_commit,
1192                                            int *head_subsumed,
1193                                            int argc, const char **argv,
1194                                            struct strbuf *merge_msg)
1195 {
1196         int i;
1197         struct commit_list *remoteheads = NULL;
1198         struct commit_list **remotes = &remoteheads;
1199         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1200
1201         if (merge_msg && (!have_message || shortlog_len))
1202                 autogen = &merge_names;
1203
1204         if (head_commit)
1205                 remotes = &commit_list_insert(head_commit, remotes)->next;
1206
1207         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1208                 handle_fetch_head(remotes, autogen);
1209                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1210         } else {
1211                 for (i = 0; i < argc; i++) {
1212                         struct commit *commit = get_merge_parent(argv[i]);
1213                         if (!commit)
1214                                 help_unknown_ref(argv[i], "merge",
1215                                                  _("not something we can merge"));
1216                         remotes = &commit_list_insert(commit, remotes)->next;
1217                 }
1218                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1219                 if (autogen) {
1220                         struct commit_list *p;
1221                         for (p = remoteheads; p; p = p->next)
1222                                 merge_name(merge_remote_util(p->item)->name, autogen);
1223                 }
1224         }
1225
1226         if (autogen) {
1227                 prepare_merge_message(autogen, merge_msg);
1228                 strbuf_release(autogen);
1229         }
1230
1231         return remoteheads;
1232 }
1233
1234 static int merging_a_throwaway_tag(struct commit *commit)
1235 {
1236         char *tag_ref;
1237         struct object_id oid;
1238         int is_throwaway_tag = 0;
1239
1240         /* Are we merging a tag? */
1241         if (!merge_remote_util(commit) ||
1242             !merge_remote_util(commit)->obj ||
1243             merge_remote_util(commit)->obj->type != OBJ_TAG)
1244                 return is_throwaway_tag;
1245
1246         /*
1247          * Now we know we are merging a tag object.  Are we downstream
1248          * and following the tags from upstream?  If so, we must have
1249          * the tag object pointed at by "refs/tags/$T" where $T is the
1250          * tagname recorded in the tag object.  We want to allow such
1251          * a "just to catch up" merge to fast-forward.
1252          *
1253          * Otherwise, we are playing an integrator's role, making a
1254          * merge with a throw-away tag from a contributor with
1255          * something like "git pull $contributor $signed_tag".
1256          * We want to forbid such a merge from fast-forwarding
1257          * by default; otherwise we would not keep the signature
1258          * anywhere.
1259          */
1260         tag_ref = xstrfmt("refs/tags/%s",
1261                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1262         if (!read_ref(tag_ref, &oid) &&
1263             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1264                 is_throwaway_tag = 0;
1265         else
1266                 is_throwaway_tag = 1;
1267         free(tag_ref);
1268         return is_throwaway_tag;
1269 }
1270
1271 int cmd_merge(int argc, const char **argv, const char *prefix)
1272 {
1273         struct object_id result_tree, stash, head_oid;
1274         struct commit *head_commit;
1275         struct strbuf buf = STRBUF_INIT;
1276         int i, ret = 0, head_subsumed;
1277         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1278         struct commit_list *common = NULL;
1279         const char *best_strategy = NULL, *wt_strategy = NULL;
1280         struct commit_list *remoteheads = NULL, *p;
1281         void *branch_to_free;
1282         int orig_argc = argc;
1283
1284         if (argc == 2 && !strcmp(argv[1], "-h"))
1285                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1286
1287         prepare_repo_settings(the_repository);
1288         the_repository->settings.command_requires_full_index = 0;
1289
1290         /*
1291          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1292          * current branch.
1293          */
1294         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1295         if (branch)
1296                 skip_prefix(branch, "refs/heads/", &branch);
1297
1298         if (!pull_twohead) {
1299                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1300                 if (default_strategy && !strcmp(default_strategy, "ort"))
1301                         pull_twohead = "ort";
1302         }
1303
1304         init_diff_ui_defaults();
1305         git_config(git_merge_config, NULL);
1306
1307         if (!branch || is_null_oid(&head_oid))
1308                 head_commit = NULL;
1309         else
1310                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1311
1312         if (branch_mergeoptions)
1313                 parse_branch_merge_options(branch_mergeoptions);
1314         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1315                         builtin_merge_usage, 0);
1316         if (shortlog_len < 0)
1317                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1318
1319         if (verbosity < 0 && show_progress == -1)
1320                 show_progress = 0;
1321
1322         if (abort_current_merge) {
1323                 int nargc = 2;
1324                 const char *nargv[] = {"reset", "--merge", NULL};
1325                 struct strbuf stash_oid = STRBUF_INIT;
1326
1327                 if (orig_argc != 2)
1328                         usage_msg_opt(_("--abort expects no arguments"),
1329                               builtin_merge_usage, builtin_merge_options);
1330
1331                 if (!file_exists(git_path_merge_head(the_repository)))
1332                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1333
1334                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1335                     READ_ONELINER_SKIP_IF_EMPTY))
1336                         unlink(git_path_merge_autostash(the_repository));
1337
1338                 /* Invoke 'git reset --merge' */
1339                 ret = cmd_reset(nargc, nargv, prefix);
1340
1341                 if (stash_oid.len)
1342                         apply_autostash_oid(stash_oid.buf);
1343
1344                 strbuf_release(&stash_oid);
1345                 goto done;
1346         }
1347
1348         if (quit_current_merge) {
1349                 if (orig_argc != 2)
1350                         usage_msg_opt(_("--quit expects no arguments"),
1351                                       builtin_merge_usage,
1352                                       builtin_merge_options);
1353
1354                 remove_merge_branch_state(the_repository);
1355                 goto done;
1356         }
1357
1358         if (continue_current_merge) {
1359                 int nargc = 1;
1360                 const char *nargv[] = {"commit", NULL};
1361
1362                 if (orig_argc != 2)
1363                         usage_msg_opt(_("--continue expects no arguments"),
1364                               builtin_merge_usage, builtin_merge_options);
1365
1366                 if (!file_exists(git_path_merge_head(the_repository)))
1367                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1368
1369                 /* Invoke 'git commit' */
1370                 ret = cmd_commit(nargc, nargv, prefix);
1371                 goto done;
1372         }
1373
1374         if (read_cache_unmerged())
1375                 die_resolve_conflict("merge");
1376
1377         if (file_exists(git_path_merge_head(the_repository))) {
1378                 /*
1379                  * There is no unmerged entry, don't advise 'git
1380                  * add/rm <file>', just 'git commit'.
1381                  */
1382                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1383                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1384                                   "Please, commit your changes before you merge."));
1385                 else
1386                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1387         }
1388         if (ref_exists("CHERRY_PICK_HEAD")) {
1389                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1390                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1391                             "Please, commit your changes before you merge."));
1392                 else
1393                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1394         }
1395         resolve_undo_clear();
1396
1397         if (option_edit < 0)
1398                 option_edit = default_edit_option();
1399
1400         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1401
1402         if (verbosity < 0)
1403                 show_diffstat = 0;
1404
1405         if (squash) {
1406                 if (fast_forward == FF_NO)
1407                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--no-ff.");
1408                 if (option_commit > 0)
1409                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--commit.");
1410                 /*
1411                  * squash can now silently disable option_commit - this is not
1412                  * a problem as it is only overriding the default, not a user
1413                  * supplied option.
1414                  */
1415                 option_commit = 0;
1416         }
1417
1418         if (option_commit < 0)
1419                 option_commit = 1;
1420
1421         if (!argc) {
1422                 if (default_to_upstream)
1423                         argc = setup_with_upstream(&argv);
1424                 else
1425                         die(_("No commit specified and merge.defaultToUpstream not set."));
1426         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1427                 argv[0] = "@{-1}";
1428         }
1429
1430         if (!argc)
1431                 usage_with_options(builtin_merge_usage,
1432                         builtin_merge_options);
1433
1434         if (!head_commit) {
1435                 /*
1436                  * If the merged head is a valid one there is no reason
1437                  * to forbid "git merge" into a branch yet to be born.
1438                  * We do the same for "git pull".
1439                  */
1440                 struct object_id *remote_head_oid;
1441                 if (squash)
1442                         die(_("Squash commit into empty head not supported yet"));
1443                 if (fast_forward == FF_NO)
1444                         die(_("Non-fast-forward commit does not make sense into "
1445                             "an empty head"));
1446                 remoteheads = collect_parents(head_commit, &head_subsumed,
1447                                               argc, argv, NULL);
1448                 if (!remoteheads)
1449                         die(_("%s - not something we can merge"), argv[0]);
1450                 if (remoteheads->next)
1451                         die(_("Can merge only exactly one commit into empty head"));
1452
1453                 if (verify_signatures)
1454                         verify_merge_signature(remoteheads->item, verbosity,
1455                                                check_trust_level);
1456
1457                 remote_head_oid = &remoteheads->item->object.oid;
1458                 read_empty(remote_head_oid, 0);
1459                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1460                            UPDATE_REFS_DIE_ON_ERR);
1461                 goto done;
1462         }
1463
1464         /*
1465          * All the rest are the commits being merged; prepare
1466          * the standard merge summary message to be appended
1467          * to the given message.
1468          */
1469         remoteheads = collect_parents(head_commit, &head_subsumed,
1470                                       argc, argv, &merge_msg);
1471
1472         if (!head_commit || !argc)
1473                 usage_with_options(builtin_merge_usage,
1474                         builtin_merge_options);
1475
1476         if (verify_signatures) {
1477                 for (p = remoteheads; p; p = p->next) {
1478                         verify_merge_signature(p->item, verbosity,
1479                                                check_trust_level);
1480                 }
1481         }
1482
1483         strbuf_addstr(&buf, "merge");
1484         for (p = remoteheads; p; p = p->next)
1485                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1486         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1487         strbuf_reset(&buf);
1488
1489         for (p = remoteheads; p; p = p->next) {
1490                 struct commit *commit = p->item;
1491                 strbuf_addf(&buf, "GITHEAD_%s",
1492                             oid_to_hex(&commit->object.oid));
1493                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1494                 strbuf_reset(&buf);
1495                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1496                         fast_forward = FF_NO;
1497         }
1498
1499         if (!use_strategies && !pull_twohead &&
1500             remoteheads && !remoteheads->next) {
1501                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1502                 if (default_strategy)
1503                         append_strategy(get_strategy(default_strategy));
1504         }
1505         if (!use_strategies) {
1506                 if (!remoteheads)
1507                         ; /* already up-to-date */
1508                 else if (!remoteheads->next)
1509                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1510                 else
1511                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1512         }
1513
1514         for (i = 0; i < use_strategies_nr; i++) {
1515                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1516                         fast_forward = FF_NO;
1517                 if (use_strategies[i]->attr & NO_TRIVIAL)
1518                         allow_trivial = 0;
1519         }
1520
1521         if (!remoteheads)
1522                 ; /* already up-to-date */
1523         else if (!remoteheads->next)
1524                 common = get_merge_bases(head_commit, remoteheads->item);
1525         else {
1526                 struct commit_list *list = remoteheads;
1527                 commit_list_insert(head_commit, &list);
1528                 common = get_octopus_merge_bases(list);
1529                 free(list);
1530         }
1531
1532         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1533                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1534
1535         if (remoteheads && !common) {
1536                 /* No common ancestors found. */
1537                 if (!allow_unrelated_histories)
1538                         die(_("refusing to merge unrelated histories"));
1539                 /* otherwise, we need a real merge. */
1540         } else if (!remoteheads ||
1541                  (!remoteheads->next && !common->next &&
1542                   common->item == remoteheads->item)) {
1543                 /*
1544                  * If head can reach all the merge then we are up to date.
1545                  * but first the most common case of merging one remote.
1546                  */
1547                 finish_up_to_date();
1548                 goto done;
1549         } else if (fast_forward != FF_NO && !remoteheads->next &&
1550                         !common->next &&
1551                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1552                 /* Again the most common case of merging one remote. */
1553                 struct strbuf msg = STRBUF_INIT;
1554                 struct commit *commit;
1555
1556                 if (verbosity >= 0) {
1557                         printf(_("Updating %s..%s\n"),
1558                                find_unique_abbrev(&head_commit->object.oid,
1559                                                   DEFAULT_ABBREV),
1560                                find_unique_abbrev(&remoteheads->item->object.oid,
1561                                                   DEFAULT_ABBREV));
1562                 }
1563                 strbuf_addstr(&msg, "Fast-forward");
1564                 if (have_message)
1565                         strbuf_addstr(&msg,
1566                                 " (no commit created; -m option ignored)");
1567                 commit = remoteheads->item;
1568                 if (!commit) {
1569                         ret = 1;
1570                         goto done;
1571                 }
1572
1573                 if (autostash)
1574                         create_autostash(the_repository,
1575                                          git_path_merge_autostash(the_repository));
1576                 if (checkout_fast_forward(the_repository,
1577                                           &head_commit->object.oid,
1578                                           &commit->object.oid,
1579                                           overwrite_ignore)) {
1580                         apply_autostash(git_path_merge_autostash(the_repository));
1581                         ret = 1;
1582                         goto done;
1583                 }
1584
1585                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1586                 remove_merge_branch_state(the_repository);
1587                 strbuf_release(&msg);
1588                 goto done;
1589         } else if (!remoteheads->next && common->next)
1590                 ;
1591                 /*
1592                  * We are not doing octopus and not fast-forward.  Need
1593                  * a real merge.
1594                  */
1595         else if (!remoteheads->next && !common->next && option_commit) {
1596                 /*
1597                  * We are not doing octopus, not fast-forward, and have
1598                  * only one common.
1599                  */
1600                 refresh_cache(REFRESH_QUIET);
1601                 if (allow_trivial && fast_forward != FF_ONLY) {
1602                         /* See if it is really trivial. */
1603                         git_committer_info(IDENT_STRICT);
1604                         printf(_("Trying really trivial in-index merge...\n"));
1605                         if (!read_tree_trivial(&common->item->object.oid,
1606                                                &head_commit->object.oid,
1607                                                &remoteheads->item->object.oid)) {
1608                                 ret = merge_trivial(head_commit, remoteheads);
1609                                 goto done;
1610                         }
1611                         printf(_("Nope.\n"));
1612                 }
1613         } else {
1614                 /*
1615                  * An octopus.  If we can reach all the remote we are up
1616                  * to date.
1617                  */
1618                 int up_to_date = 1;
1619                 struct commit_list *j;
1620
1621                 for (j = remoteheads; j; j = j->next) {
1622                         struct commit_list *common_one;
1623
1624                         /*
1625                          * Here we *have* to calculate the individual
1626                          * merge_bases again, otherwise "git merge HEAD^
1627                          * HEAD^^" would be missed.
1628                          */
1629                         common_one = get_merge_bases(head_commit, j->item);
1630                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1631                                 up_to_date = 0;
1632                                 break;
1633                         }
1634                 }
1635                 if (up_to_date) {
1636                         finish_up_to_date();
1637                         goto done;
1638                 }
1639         }
1640
1641         if (fast_forward == FF_ONLY)
1642                 die_ff_impossible();
1643
1644         if (autostash)
1645                 create_autostash(the_repository,
1646                                  git_path_merge_autostash(the_repository));
1647
1648         /* We are going to make a new commit. */
1649         git_committer_info(IDENT_STRICT);
1650
1651         /*
1652          * At this point, we need a real merge.  No matter what strategy
1653          * we use, it would operate on the index, possibly affecting the
1654          * working tree, and when resolved cleanly, have the desired
1655          * tree in the index -- this means that the index must be in
1656          * sync with the head commit.  The strategies are responsible
1657          * to ensure this.
1658          */
1659         if (use_strategies_nr == 1 ||
1660             /*
1661              * Stash away the local changes so that we can try more than one.
1662              */
1663             save_state(&stash))
1664                 oidclr(&stash);
1665
1666         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1667                 int ret, cnt;
1668                 if (i) {
1669                         printf(_("Rewinding the tree to pristine...\n"));
1670                         restore_state(&head_commit->object.oid, &stash);
1671                 }
1672                 if (use_strategies_nr != 1)
1673                         printf(_("Trying merge strategy %s...\n"),
1674                                 use_strategies[i]->name);
1675                 /*
1676                  * Remember which strategy left the state in the working
1677                  * tree.
1678                  */
1679                 wt_strategy = use_strategies[i]->name;
1680
1681                 ret = try_merge_strategy(use_strategies[i]->name,
1682                                          common, remoteheads,
1683                                          head_commit);
1684                 /*
1685                  * The backend exits with 1 when conflicts are
1686                  * left to be resolved, with 2 when it does not
1687                  * handle the given merge at all.
1688                  */
1689                 if (ret < 2) {
1690                         if (!ret) {
1691                                 if (option_commit) {
1692                                         /* Automerge succeeded. */
1693                                         automerge_was_ok = 1;
1694                                         break;
1695                                 }
1696                                 merge_was_ok = 1;
1697                         }
1698                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1699                         if (best_cnt <= 0 || cnt <= best_cnt) {
1700                                 best_strategy = use_strategies[i]->name;
1701                                 best_cnt = cnt;
1702                         }
1703                 }
1704         }
1705
1706         /*
1707          * If we have a resulting tree, that means the strategy module
1708          * auto resolved the merge cleanly.
1709          */
1710         if (automerge_was_ok) {
1711                 ret = finish_automerge(head_commit, head_subsumed,
1712                                        common, remoteheads,
1713                                        &result_tree, wt_strategy);
1714                 goto done;
1715         }
1716
1717         /*
1718          * Pick the result from the best strategy and have the user fix
1719          * it up.
1720          */
1721         if (!best_strategy) {
1722                 restore_state(&head_commit->object.oid, &stash);
1723                 if (use_strategies_nr > 1)
1724                         fprintf(stderr,
1725                                 _("No merge strategy handled the merge.\n"));
1726                 else
1727                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1728                                 use_strategies[0]->name);
1729                 apply_autostash(git_path_merge_autostash(the_repository));
1730                 ret = 2;
1731                 goto done;
1732         } else if (best_strategy == wt_strategy)
1733                 ; /* We already have its result in the working tree. */
1734         else {
1735                 printf(_("Rewinding the tree to pristine...\n"));
1736                 restore_state(&head_commit->object.oid, &stash);
1737                 printf(_("Using the %s strategy to prepare resolving by hand.\n"),
1738                         best_strategy);
1739                 try_merge_strategy(best_strategy, common, remoteheads,
1740                                    head_commit);
1741         }
1742
1743         if (squash) {
1744                 finish(head_commit, remoteheads, NULL, NULL);
1745
1746                 git_test_write_commit_graph_or_die();
1747         } else
1748                 write_merge_state(remoteheads);
1749
1750         if (merge_was_ok)
1751                 fprintf(stderr, _("Automatic merge went well; "
1752                         "stopped before committing as requested\n"));
1753         else
1754                 ret = suggest_conflicts();
1755
1756 done:
1757         if (!automerge_was_ok) {
1758                 free_commit_list(common);
1759                 free_commit_list(remoteheads);
1760         }
1761         strbuf_release(&buf);
1762         free(branch_to_free);
1763         return ret;
1764 }