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         struct strbuf sb = STRBUF_INIT;
 379         const char *args[] = { "stash", "apply", NULL, NULL };
 380
 381         if (is_null_oid(stash))
 382                 return;
 383
 384         reset_hard(head, 1);
 385
 386         args[2] = oid_to_hex(stash);
 387
 388         /*
 389          * It is OK to ignore error here, for example when there was
 390          * nothing to restore.
 391          */
 392         run_command_v_opt(args, RUN_GIT_CMD);
 393
 394         strbuf_release(&sb);
 395         refresh_cache(REFRESH_QUIET);
 396 }
 397
 398 /* This is called when no merge was necessary. */
 399 static void finish_up_to_date(void)
 400 {
 401         if (verbosity >= 0) {
 402                 if (squash)
 403                         puts(_("Already up to date. (nothing to squash)"));
 404                 else
 405                         puts(_("Already up to date."));
 406         }
 407         remove_merge_branch_state(the_repository);
 408 }
 409
 410 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 411 {
 412         struct rev_info rev;
 413         struct strbuf out = STRBUF_INIT;
 414         struct commit_list *j;
 415         struct pretty_print_context ctx = {0};
 416
 417         printf(_("Squash commit -- not updating HEAD\n"));
 418
 419         repo_init_revisions(the_repository, &rev, NULL);
 420         diff_merges_suppress(&rev);
 421         rev.commit_format = CMIT_FMT_MEDIUM;
 422
 423         commit->object.flags |= UNINTERESTING;
 424         add_pending_object(&rev, &commit->object, NULL);
 425
 426         for (j = remoteheads; j; j = j->next)
 427                 add_pending_object(&rev, &j->item->object, NULL);
 428
 429         setup_revisions(0, NULL, &rev, NULL);
 430         if (prepare_revision_walk(&rev))
 431                 die(_("revision walk setup failed"));
 432
 433         ctx.abbrev = rev.abbrev;
 434         ctx.date_mode = rev.date_mode;
 435         ctx.fmt = rev.commit_format;
 436
 437         strbuf_addstr(&out, "Squashed commit of the following:\n");
 438         while ((commit = get_revision(&rev)) != NULL) {
 439                 strbuf_addch(&out, '\n');
 440                 strbuf_addf(&out, "commit %s\n",
 441                         oid_to_hex(&commit->object.oid));
 442                 pretty_print_commit(&ctx, commit, &out);
 443         }
 444         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 445         strbuf_release(&out);
 446 }
 447
 448 static void finish(struct commit *head_commit,
 449                    struct commit_list *remoteheads,
 450                    const struct object_id *new_head, const char *msg)
 451 {
 452         struct strbuf reflog_message = STRBUF_INIT;
 453         const struct object_id *head = &head_commit->object.oid;
 454
 455         if (!msg)
 456                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 457         else {
 458                 if (verbosity >= 0)
 459                         printf("%s\n", msg);
 460                 strbuf_addf(&reflog_message, "%s: %s",
 461                         getenv("GIT_REFLOG_ACTION"), msg);
 462         }
 463         if (squash) {
 464                 squash_message(head_commit, remoteheads);
 465         } else {
 466                 if (verbosity >= 0 && !merge_msg.len)
 467                         printf(_("No merge message -- not updating HEAD\n"));
 468                 else {
 469                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 470                                    0, UPDATE_REFS_DIE_ON_ERR);
 471                         /*
 472                          * We ignore errors in 'gc --auto', since the
 473                          * user should see them.
 474                          */
 475                         run_auto_maintenance(verbosity < 0);
 476                 }
 477         }
 478         if (new_head && show_diffstat) {
 479                 struct diff_options opts;
 480                 repo_diff_setup(the_repository, &opts);
 481                 opts.stat_width = -1; /* use full terminal width */
 482                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 483                 opts.output_format |=
 484                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 485                 opts.detect_rename = DIFF_DETECT_RENAME;
 486                 diff_setup_done(&opts);
 487                 diff_tree_oid(head, new_head, "", &opts);
 488                 diffcore_std(&opts);
 489                 diff_flush(&opts);
 490         }
 491
 492         /* Run a post-merge hook */
 493         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 494
 495         apply_autostash(git_path_merge_autostash(the_repository));
 496         strbuf_release(&reflog_message);
 497 }
 498
 499 /* Get the name for the merge commit's message. */
 500 static void merge_name(const char *remote, struct strbuf *msg)
 501 {
 502         struct commit *remote_head;
 503         struct object_id branch_head;
 504         struct strbuf buf = STRBUF_INIT;
 505         struct strbuf bname = STRBUF_INIT;
 506         struct merge_remote_desc *desc;
 507         const char *ptr;
 508         char *found_ref = NULL;
 509         int len, early;
 510
 511         strbuf_branchname(&bname, remote, 0);
 512         remote = bname.buf;
 513
 514         oidclr(&branch_head);
 515         remote_head = get_merge_parent(remote);
 516         if (!remote_head)
 517                 die(_("'%s' does not point to a commit"), remote);
 518
 519         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
 520                 if (starts_with(found_ref, "refs/heads/")) {
 521                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 522                                     oid_to_hex(&branch_head), remote);
 523                         goto cleanup;
 524                 }
 525                 if (starts_with(found_ref, "refs/tags/")) {
 526                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 527                                     oid_to_hex(&branch_head), remote);
 528                         goto cleanup;
 529                 }
 530                 if (starts_with(found_ref, "refs/remotes/")) {
 531                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 532                                     oid_to_hex(&branch_head), remote);
 533                         goto cleanup;
 534                 }
 535         }
 536
 537         /* See if remote matches <name>^^^.. or <name>~<number> */
 538         for (len = 0, ptr = remote + strlen(remote);
 539              remote < ptr && ptr[-1] == '^';
 540              ptr--)
 541                 len++;
 542         if (len)
 543                 early = 1;
 544         else {
 545                 early = 0;
 546                 ptr = strrchr(remote, '~');
 547                 if (ptr) {
 548                         int seen_nonzero = 0;
 549
 550                         len++; /* count ~ */
 551                         while (*++ptr && isdigit(*ptr)) {
 552                                 seen_nonzero |= (*ptr != '0');
 553                                 len++;
 554                         }
 555                         if (*ptr)
 556                                 len = 0; /* not ...~<number> */
 557                         else if (seen_nonzero)
 558                                 early = 1;
 559                         else if (len == 1)
 560                                 early = 1; /* "name~" is "name~1"! */
 561                 }
 562         }
 563         if (len) {
 564                 struct strbuf truname = STRBUF_INIT;
 565                 strbuf_addf(&truname, "refs/heads/%s", remote);
 566                 strbuf_setlen(&truname, truname.len - len);
 567                 if (ref_exists(truname.buf)) {
 568                         strbuf_addf(msg,
 569                                     "%s\t\tbranch '%s'%s of .\n",
 570                                     oid_to_hex(&remote_head->object.oid),
 571                                     truname.buf + 11,
 572                                     (early ? " (early part)" : ""));
 573                         strbuf_release(&truname);
 574                         goto cleanup;
 575                 }
 576                 strbuf_release(&truname);
 577         }
 578
 579         desc = merge_remote_util(remote_head);
 580         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 581                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 582                             oid_to_hex(&desc->obj->oid),
 583                             type_name(desc->obj->type),
 584                             remote);
 585                 goto cleanup;
 586         }
 587
 588         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 589                 oid_to_hex(&remote_head->object.oid), remote);
 590 cleanup:
 591         free(found_ref);
 592         strbuf_release(&buf);
 593         strbuf_release(&bname);
 594 }
 595
 596 static void parse_branch_merge_options(char *bmo)
 597 {
 598         const char **argv;
 599         int argc;
 600
 601         if (!bmo)
 602                 return;
 603         argc = split_cmdline(bmo, &argv);
 604         if (argc < 0)
 605                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 606                     _(split_cmdline_strerror(argc)));
 607         REALLOC_ARRAY(argv, argc + 2);
 608         MOVE_ARRAY(argv + 1, argv, argc + 1);
 609         argc++;
 610         argv[0] = "branch.*.mergeoptions";
 611         parse_options(argc, argv, NULL, builtin_merge_options,
 612                       builtin_merge_usage, 0);
 613         free(argv);
 614 }
 615
 616 static int git_merge_config(const char *k, const char *v, void *cb)
 617 {
 618         int status;
 619         const char *str;
 620
 621         if (branch &&
 622             skip_prefix(k, "branch.", &str) &&
 623             skip_prefix(str, branch, &str) &&
 624             !strcmp(str, ".mergeoptions")) {
 625                 free(branch_mergeoptions);
 626                 branch_mergeoptions = xstrdup(v);
 627                 return 0;
 628         }
 629
 630         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 631                 show_diffstat = git_config_bool(k, v);
 632         else if (!strcmp(k, "merge.verifysignatures"))
 633                 verify_signatures = git_config_bool(k, v);
 634         else if (!strcmp(k, "pull.twohead"))
 635                 return git_config_string(&pull_twohead, k, v);
 636         else if (!strcmp(k, "pull.octopus"))
 637                 return git_config_string(&pull_octopus, k, v);
 638         else if (!strcmp(k, "commit.cleanup"))
 639                 return git_config_string(&cleanup_arg, k, v);
 640         else if (!strcmp(k, "merge.ff")) {
 641                 int boolval = git_parse_maybe_bool(v);
 642                 if (0 <= boolval) {
 643                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 644                 } else if (v && !strcmp(v, "only")) {
 645                         fast_forward = FF_ONLY;
 646                 } /* do not barf on values from future versions of git */
 647                 return 0;
 648         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 649                 default_to_upstream = git_config_bool(k, v);
 650                 return 0;
 651         } else if (!strcmp(k, "commit.gpgsign")) {
 652                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 653                 return 0;
 654         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 655                 check_trust_level = 0;
 656         } else if (!strcmp(k, "merge.autostash")) {
 657                 autostash = git_config_bool(k, v);
 658                 return 0;
 659         }
 660
 661         status = fmt_merge_msg_config(k, v, cb);
 662         if (status)
 663                 return status;
 664         status = git_gpg_config(k, v, NULL);
 665         if (status)
 666                 return status;
 667         return git_diff_ui_config(k, v, cb);
 668 }
 669
 670 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 671                              struct object_id *one)
 672 {
 673         int i, nr_trees = 0;
 674         struct tree *trees[MAX_UNPACK_TREES];
 675         struct tree_desc t[MAX_UNPACK_TREES];
 676         struct unpack_trees_options opts;
 677
 678         memset(&opts, 0, sizeof(opts));
 679         opts.head_idx = 2;
 680         opts.src_index = &the_index;
 681         opts.dst_index = &the_index;
 682         opts.update = 1;
 683         opts.verbose_update = 1;
 684         opts.trivial_merges_only = 1;
 685         opts.merge = 1;
 686         opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 687         trees[nr_trees] = parse_tree_indirect(common);
 688         if (!trees[nr_trees++])
 689                 return -1;
 690         trees[nr_trees] = parse_tree_indirect(head);
 691         if (!trees[nr_trees++])
 692                 return -1;
 693         trees[nr_trees] = parse_tree_indirect(one);
 694         if (!trees[nr_trees++])
 695                 return -1;
 696         opts.fn = threeway_merge;
 697         cache_tree_free(&active_cache_tree);
 698         for (i = 0; i < nr_trees; i++) {
 699                 parse_tree(trees[i]);
 700                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 701         }
 702         if (unpack_trees(nr_trees, t, &opts))
 703                 return -1;
 704         return 0;
 705 }
 706
 707 static void write_tree_trivial(struct object_id *oid)
 708 {
 709         if (write_cache_as_tree(oid, 0, NULL))
 710                 die(_("git write-tree failed to write a tree"));
 711 }
 712
 713 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 714                               struct commit_list *remoteheads,
 715                               struct commit *head)
 716 {
 717         const char *head_arg = "HEAD";
 718
 719         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 720                 return error(_("Unable to write index."));
 721
 722         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
 723             !strcmp(strategy, "ort")) {
 724                 struct lock_file lock = LOCK_INIT;
 725                 int clean, x;
 726                 struct commit *result;
 727                 struct commit_list *reversed = NULL;
 728                 struct merge_options o;
 729                 struct commit_list *j;
 730
 731                 if (remoteheads->next) {
 732                         error(_("Not handling anything other than two heads merge."));
 733                         return 2;
 734                 }
 735
 736                 init_merge_options(&o, the_repository);
 737                 if (!strcmp(strategy, "subtree"))
 738                         o.subtree_shift = "";
 739
 740                 o.show_rename_progress =
 741                         show_progress == -1 ? isatty(2) : show_progress;
 742
 743                 for (x = 0; x < xopts_nr; x++)
 744                         if (parse_merge_opt(&o, xopts[x]))
 745                                 die(_("unknown strategy option: -X%s"), xopts[x]);
 746
 747                 o.branch1 = head_arg;
 748                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 749
 750                 for (j = common; j; j = j->next)
 751                         commit_list_insert(j->item, &reversed);
 752
 753                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 754                 if (!strcmp(strategy, "ort"))
 755                         clean = merge_ort_recursive(&o, head, remoteheads->item,
 756                                                     reversed, &result);
 757                 else
 758                         clean = merge_recursive(&o, head, remoteheads->item,
 759                                                 reversed, &result);
 760                 if (clean < 0)
 761                         exit(128);
 762                 if (write_locked_index(&the_index, &lock,
 763                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 764                         die(_("unable to write %s"), get_index_file());
 765                 return clean ? 0 : 1;
 766         } else {
 767                 return try_merge_command(the_repository,
 768                                          strategy, xopts_nr, xopts,
 769                                          common, head_arg, remoteheads);
 770         }
 771 }
 772
 773 static void count_diff_files(struct diff_queue_struct *q,
 774                              struct diff_options *opt, void *data)
 775 {
 776         int *count = data;
 777
 778         (*count) += q->nr;
 779 }
 780
 781 static int count_unmerged_entries(void)
 782 {
 783         int i, ret = 0;
 784
 785         for (i = 0; i < active_nr; i++)
 786                 if (ce_stage(active_cache[i]))
 787                         ret++;
 788
 789         return ret;
 790 }
 791
 792 static void add_strategies(const char *string, unsigned attr)
 793 {
 794         int i;
 795
 796         if (string) {
 797                 struct string_list list = STRING_LIST_INIT_DUP;
 798                 struct string_list_item *item;
 799                 string_list_split(&list, string, ' ', -1);
 800                 for_each_string_list_item(item, &list)
 801                         append_strategy(get_strategy(item->string));
 802                 string_list_clear(&list, 0);
 803                 return;
 804         }
 805         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 806                 if (all_strategy[i].attr & attr)
 807                         append_strategy(&all_strategy[i]);
 808
 809 }
 810
 811 static void read_merge_msg(struct strbuf *msg)
 812 {
 813         const char *filename = git_path_merge_msg(the_repository);
 814         strbuf_reset(msg);
 815         if (strbuf_read_file(msg, filename, 0) < 0)
 816                 die_errno(_("Could not read from '%s'"), filename);
 817 }
 818
 819 static void write_merge_state(struct commit_list *);
 820 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 821 {
 822         if (err_msg)
 823                 error("%s", err_msg);
 824         fprintf(stderr,
 825                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 826         write_merge_state(remoteheads);
 827         exit(1);
 828 }
 829
 830 static const char merge_editor_comment[] =
 831 N_("Please enter a commit message to explain why this merge is necessary,\n"
 832    "especially if it merges an updated upstream into a topic branch.\n"
 833    "\n");
 834
 835 static const char scissors_editor_comment[] =
 836 N_("An empty message aborts the commit.\n");
 837
 838 static const char no_scissors_editor_comment[] =
 839 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 840    "the commit.\n");
 841
 842 static void write_merge_heads(struct commit_list *);
 843 static void prepare_to_commit(struct commit_list *remoteheads)
 844 {
 845         struct strbuf msg = STRBUF_INIT;
 846         const char *index_file = get_index_file();
 847
 848         if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
 849                 abort_commit(remoteheads, NULL);
 850         /*
 851          * Re-read the index as pre-merge-commit hook could have updated it,
 852          * and write it out as a tree.  We must do this before we invoke
 853          * the editor and after we invoke run_status above.
 854          */
 855         if (hook_exists("pre-merge-commit"))
 856                 discard_cache();
 857         read_cache_from(index_file);
 858         strbuf_addbuf(&msg, &merge_msg);
 859         if (squash)
 860                 BUG("the control must not reach here under --squash");
 861         if (0 < option_edit) {
 862                 strbuf_addch(&msg, '\n');
 863                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 864                         wt_status_append_cut_line(&msg);
 865                         strbuf_commented_addf(&msg, "\n");
 866                 }
 867                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 868                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
 869                         strbuf_commented_addf(&msg, _(scissors_editor_comment));
 870                 else
 871                         strbuf_commented_addf(&msg,
 872                                 _(no_scissors_editor_comment), comment_line_char);
 873         }
 874         if (signoff)
 875                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 876         write_merge_heads(remoteheads);
 877         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 878         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 879                             git_path_merge_msg(the_repository), "merge", NULL))
 880                 abort_commit(remoteheads, NULL);
 881         if (0 < option_edit) {
 882                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 883                         abort_commit(remoteheads, NULL);
 884         }
 885
 886         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 887                                           "commit-msg",
 888                                           git_path_merge_msg(the_repository), NULL))
 889                 abort_commit(remoteheads, NULL);
 890
 891         read_merge_msg(&msg);
 892         cleanup_message(&msg, cleanup_mode, 0);
 893         if (!msg.len)
 894                 abort_commit(remoteheads, _("Empty commit message."));
 895         strbuf_release(&merge_msg);
 896         strbuf_addbuf(&merge_msg, &msg);
 897         strbuf_release(&msg);
 898 }
 899
 900 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 901 {
 902         struct object_id result_tree, result_commit;
 903         struct commit_list *parents, **pptr = &parents;
 904
 905         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 906                 return error(_("Unable to write index."));
 907
 908         write_tree_trivial(&result_tree);
 909         printf(_("Wonderful.\n"));
 910         pptr = commit_list_append(head, pptr);
 911         pptr = commit_list_append(remoteheads->item, pptr);
 912         prepare_to_commit(remoteheads);
 913         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 914                         &result_commit, NULL, sign_commit))
 915                 die(_("failed to write commit object"));
 916         finish(head, remoteheads, &result_commit, "In-index merge");
 917         remove_merge_branch_state(the_repository);
 918         return 0;
 919 }
 920
 921 static int finish_automerge(struct commit *head,
 922                             int head_subsumed,
 923                             struct commit_list *common,
 924                             struct commit_list *remoteheads,
 925                             struct object_id *result_tree,
 926                             const char *wt_strategy)
 927 {
 928         struct commit_list *parents = NULL;
 929         struct strbuf buf = STRBUF_INIT;
 930         struct object_id result_commit;
 931
 932         write_tree_trivial(result_tree);
 933         free_commit_list(common);
 934         parents = remoteheads;
 935         if (!head_subsumed || fast_forward == FF_NO)
 936                 commit_list_insert(head, &parents);
 937         prepare_to_commit(remoteheads);
 938         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 939                         &result_commit, NULL, sign_commit))
 940                 die(_("failed to write commit object"));
 941         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 942         finish(head, remoteheads, &result_commit, buf.buf);
 943         strbuf_release(&buf);
 944         remove_merge_branch_state(the_repository);
 945         return 0;
 946 }
 947
 948 static int suggest_conflicts(void)
 949 {
 950         const char *filename;
 951         FILE *fp;
 952         struct strbuf msgbuf = STRBUF_INIT;
 953
 954         filename = git_path_merge_msg(the_repository);
 955         fp = xfopen(filename, "a");
 956
 957         /*
 958          * We can't use cleanup_mode because if we're not using the editor,
 959          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 960          * though the message is meant to be processed later by git-commit.
 961          * Thus, we will get the cleanup mode which is returned when we _are_
 962          * using an editor.
 963          */
 964         append_conflicts_hint(&the_index, &msgbuf,
 965                               get_cleanup_mode(cleanup_arg, 1));
 966         fputs(msgbuf.buf, fp);
 967         strbuf_release(&msgbuf);
 968         fclose(fp);
 969         repo_rerere(the_repository, allow_rerere_auto);
 970         printf(_("Automatic merge failed; "
 971                         "fix conflicts and then commit the result.\n"));
 972         return 1;
 973 }
 974
 975 static int evaluate_result(void)
 976 {
 977         int cnt = 0;
 978         struct rev_info rev;
 979
 980         /* Check how many files differ. */
 981         repo_init_revisions(the_repository, &rev, "");
 982         setup_revisions(0, NULL, &rev, NULL);
 983         rev.diffopt.output_format |=
 984                 DIFF_FORMAT_CALLBACK;
 985         rev.diffopt.format_callback = count_diff_files;
 986         rev.diffopt.format_callback_data = &cnt;
 987         run_diff_files(&rev, 0);
 988
 989         /*
 990          * Check how many unmerged entries are
 991          * there.
 992          */
 993         cnt += count_unmerged_entries();
 994
 995         return cnt;
 996 }
 997
 998 /*
 999  * Pretend as if the user told us to merge with the remote-tracking
1000  * branch we have for the upstream of the current branch
1001  */
1002 static int setup_with_upstream(const char ***argv)
1003 {
1004         struct branch *branch = branch_get(NULL);
1005         int i;
1006         const char **args;
1007
1008         if (!branch)
1009                 die(_("No current branch."));
1010         if (!branch->remote_name)
1011                 die(_("No remote for the current branch."));
1012         if (!branch->merge_nr)
1013                 die(_("No default upstream defined for the current branch."));
1014
1015         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
1016         for (i = 0; i < branch->merge_nr; i++) {
1017                 if (!branch->merge[i]->dst)
1018                         die(_("No remote-tracking branch for %s from %s"),
1019                             branch->merge[i]->src, branch->remote_name);
1020                 args[i] = branch->merge[i]->dst;
1021         }
1022         args[i] = NULL;
1023         *argv = args;
1024         return i;
1025 }
1026
1027 static void write_merge_heads(struct commit_list *remoteheads)
1028 {
1029         struct commit_list *j;
1030         struct strbuf buf = STRBUF_INIT;
1031
1032         for (j = remoteheads; j; j = j->next) {
1033                 struct object_id *oid;
1034                 struct commit *c = j->item;
1035                 struct merge_remote_desc *desc;
1036
1037                 desc = merge_remote_util(c);
1038                 if (desc && desc->obj) {
1039                         oid = &desc->obj->oid;
1040                 } else {
1041                         oid = &c->object.oid;
1042                 }
1043                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1044         }
1045         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1046
1047         strbuf_reset(&buf);
1048         if (fast_forward == FF_NO)
1049                 strbuf_addstr(&buf, "no-ff");
1050         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1051         strbuf_release(&buf);
1052 }
1053
1054 static void write_merge_state(struct commit_list *remoteheads)
1055 {
1056         write_merge_heads(remoteheads);
1057         strbuf_addch(&merge_msg, '\n');
1058         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1059                        merge_msg.len);
1060 }
1061
1062 static int default_edit_option(void)
1063 {
1064         static const char name[] = "GIT_MERGE_AUTOEDIT";
1065         const char *e = getenv(name);
1066         struct stat st_stdin, st_stdout;
1067
1068         if (have_message)
1069                 /* an explicit -m msg without --[no-]edit */
1070                 return 0;
1071
1072         if (e) {
1073                 int v = git_parse_maybe_bool(e);
1074                 if (v < 0)
1075                         die(_("Bad value '%s' in environment '%s'"), e, name);
1076                 return v;
1077         }
1078
1079         /* Use editor if stdin and stdout are the same and is a tty */
1080         return (!fstat(0, &st_stdin) &&
1081                 !fstat(1, &st_stdout) &&
1082                 isatty(0) && isatty(1) &&
1083                 st_stdin.st_dev == st_stdout.st_dev &&
1084                 st_stdin.st_ino == st_stdout.st_ino &&
1085                 st_stdin.st_mode == st_stdout.st_mode);
1086 }
1087
1088 static struct commit_list *reduce_parents(struct commit *head_commit,
1089                                           int *head_subsumed,
1090                                           struct commit_list *remoteheads)
1091 {
1092         struct commit_list *parents, **remotes;
1093
1094         /*
1095          * Is the current HEAD reachable from another commit being
1096          * merged?  If so we do not want to record it as a parent of
1097          * the resulting merge, unless --no-ff is given.  We will flip
1098          * this variable to 0 when we find HEAD among the independent
1099          * tips being merged.
1100          */
1101         *head_subsumed = 1;
1102
1103         /* Find what parents to record by checking independent ones. */
1104         parents = reduce_heads(remoteheads);
1105         free_commit_list(remoteheads);
1106
1107         remoteheads = NULL;
1108         remotes = &remoteheads;
1109         while (parents) {
1110                 struct commit *commit = pop_commit(&parents);
1111                 if (commit == head_commit)
1112                         *head_subsumed = 0;
1113                 else
1114                         remotes = &commit_list_insert(commit, remotes)->next;
1115         }
1116         return remoteheads;
1117 }
1118
1119 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1120 {
1121         struct fmt_merge_msg_opts opts;
1122
1123         memset(&opts, 0, sizeof(opts));
1124         opts.add_title = !have_message;
1125         opts.shortlog_len = shortlog_len;
1126         opts.credit_people = (0 < option_edit);
1127         opts.into_name = into_name;
1128
1129         fmt_merge_msg(merge_names, merge_msg, &opts);
1130         if (merge_msg->len)
1131                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1132 }
1133
1134 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1135 {
1136         const char *filename;
1137         int fd, pos, npos;
1138         struct strbuf fetch_head_file = STRBUF_INIT;
1139         const unsigned hexsz = the_hash_algo->hexsz;
1140
1141         if (!merge_names)
1142                 merge_names = &fetch_head_file;
1143
1144         filename = git_path_fetch_head(the_repository);
1145         fd = xopen(filename, O_RDONLY);
1146
1147         if (strbuf_read(merge_names, fd, 0) < 0)
1148                 die_errno(_("could not read '%s'"), filename);
1149         if (close(fd) < 0)
1150                 die_errno(_("could not close '%s'"), filename);
1151
1152         for (pos = 0; pos < merge_names->len; pos = npos) {
1153                 struct object_id oid;
1154                 char *ptr;
1155                 struct commit *commit;
1156
1157                 ptr = strchr(merge_names->buf + pos, '\n');
1158                 if (ptr)
1159                         npos = ptr - merge_names->buf + 1;
1160                 else
1161                         npos = merge_names->len;
1162
1163                 if (npos - pos < hexsz + 2 ||
1164                     get_oid_hex(merge_names->buf + pos, &oid))
1165                         commit = NULL; /* bad */
1166                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1167                         continue; /* not-for-merge */
1168                 else {
1169                         char saved = merge_names->buf[pos + hexsz];
1170                         merge_names->buf[pos + hexsz] = '\0';
1171                         commit = get_merge_parent(merge_names->buf + pos);
1172                         merge_names->buf[pos + hexsz] = saved;
1173                 }
1174                 if (!commit) {
1175                         if (ptr)
1176                                 *ptr = '\0';
1177                         die(_("not something we can merge in %s: %s"),
1178                             filename, merge_names->buf + pos);
1179                 }
1180                 remotes = &commit_list_insert(commit, remotes)->next;
1181         }
1182
1183         if (merge_names == &fetch_head_file)
1184                 strbuf_release(&fetch_head_file);
1185 }
1186
1187 static struct commit_list *collect_parents(struct commit *head_commit,
1188                                            int *head_subsumed,
1189                                            int argc, const char **argv,
1190                                            struct strbuf *merge_msg)
1191 {
1192         int i;
1193         struct commit_list *remoteheads = NULL;
1194         struct commit_list **remotes = &remoteheads;
1195         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1196
1197         if (merge_msg && (!have_message || shortlog_len))
1198                 autogen = &merge_names;
1199
1200         if (head_commit)
1201                 remotes = &commit_list_insert(head_commit, remotes)->next;
1202
1203         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1204                 handle_fetch_head(remotes, autogen);
1205                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1206         } else {
1207                 for (i = 0; i < argc; i++) {
1208                         struct commit *commit = get_merge_parent(argv[i]);
1209                         if (!commit)
1210                                 help_unknown_ref(argv[i], "merge",
1211                                                  _("not something we can merge"));
1212                         remotes = &commit_list_insert(commit, remotes)->next;
1213                 }
1214                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1215                 if (autogen) {
1216                         struct commit_list *p;
1217                         for (p = remoteheads; p; p = p->next)
1218                                 merge_name(merge_remote_util(p->item)->name, autogen);
1219                 }
1220         }
1221
1222         if (autogen) {
1223                 prepare_merge_message(autogen, merge_msg);
1224                 strbuf_release(autogen);
1225         }
1226
1227         return remoteheads;
1228 }
1229
1230 static int merging_a_throwaway_tag(struct commit *commit)
1231 {
1232         char *tag_ref;
1233         struct object_id oid;
1234         int is_throwaway_tag = 0;
1235
1236         /* Are we merging a tag? */
1237         if (!merge_remote_util(commit) ||
1238             !merge_remote_util(commit)->obj ||
1239             merge_remote_util(commit)->obj->type != OBJ_TAG)
1240                 return is_throwaway_tag;
1241
1242         /*
1243          * Now we know we are merging a tag object.  Are we downstream
1244          * and following the tags from upstream?  If so, we must have
1245          * the tag object pointed at by "refs/tags/$T" where $T is the
1246          * tagname recorded in the tag object.  We want to allow such
1247          * a "just to catch up" merge to fast-forward.
1248          *
1249          * Otherwise, we are playing an integrator's role, making a
1250          * merge with a throw-away tag from a contributor with
1251          * something like "git pull $contributor $signed_tag".
1252          * We want to forbid such a merge from fast-forwarding
1253          * by default; otherwise we would not keep the signature
1254          * anywhere.
1255          */
1256         tag_ref = xstrfmt("refs/tags/%s",
1257                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1258         if (!read_ref(tag_ref, &oid) &&
1259             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1260                 is_throwaway_tag = 0;
1261         else
1262                 is_throwaway_tag = 1;
1263         free(tag_ref);
1264         return is_throwaway_tag;
1265 }
1266
1267 int cmd_merge(int argc, const char **argv, const char *prefix)
1268 {
1269         struct object_id result_tree, stash, head_oid;
1270         struct commit *head_commit;
1271         struct strbuf buf = STRBUF_INIT;
1272         int i, ret = 0, head_subsumed;
1273         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1274         struct commit_list *common = NULL;
1275         const char *best_strategy = NULL, *wt_strategy = NULL;
1276         struct commit_list *remoteheads, *p;
1277         void *branch_to_free;
1278         int orig_argc = argc;
1279
1280         if (argc == 2 && !strcmp(argv[1], "-h"))
1281                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1282
1283         prepare_repo_settings(the_repository);
1284         the_repository->settings.command_requires_full_index = 0;
1285
1286         /*
1287          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1288          * current branch.
1289          */
1290         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1291         if (branch)
1292                 skip_prefix(branch, "refs/heads/", &branch);
1293
1294         if (!pull_twohead) {
1295                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1296                 if (default_strategy && !strcmp(default_strategy, "ort"))
1297                         pull_twohead = "ort";
1298         }
1299
1300         init_diff_ui_defaults();
1301         git_config(git_merge_config, NULL);
1302
1303         if (!branch || is_null_oid(&head_oid))
1304                 head_commit = NULL;
1305         else
1306                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1307
1308         if (branch_mergeoptions)
1309                 parse_branch_merge_options(branch_mergeoptions);
1310         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1311                         builtin_merge_usage, 0);
1312         if (shortlog_len < 0)
1313                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1314
1315         if (verbosity < 0 && show_progress == -1)
1316                 show_progress = 0;
1317
1318         if (abort_current_merge) {
1319                 int nargc = 2;
1320                 const char *nargv[] = {"reset", "--merge", NULL};
1321                 struct strbuf stash_oid = STRBUF_INIT;
1322
1323                 if (orig_argc != 2)
1324                         usage_msg_opt(_("--abort expects no arguments"),
1325                               builtin_merge_usage, builtin_merge_options);
1326
1327                 if (!file_exists(git_path_merge_head(the_repository)))
1328                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1329
1330                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1331                     READ_ONELINER_SKIP_IF_EMPTY))
1332                         unlink(git_path_merge_autostash(the_repository));
1333
1334                 /* Invoke 'git reset --merge' */
1335                 ret = cmd_reset(nargc, nargv, prefix);
1336
1337                 if (stash_oid.len)
1338                         apply_autostash_oid(stash_oid.buf);
1339
1340                 strbuf_release(&stash_oid);
1341                 goto done;
1342         }
1343
1344         if (quit_current_merge) {
1345                 if (orig_argc != 2)
1346                         usage_msg_opt(_("--quit expects no arguments"),
1347                                       builtin_merge_usage,
1348                                       builtin_merge_options);
1349
1350                 remove_merge_branch_state(the_repository);
1351                 goto done;
1352         }
1353
1354         if (continue_current_merge) {
1355                 int nargc = 1;
1356                 const char *nargv[] = {"commit", NULL};
1357
1358                 if (orig_argc != 2)
1359                         usage_msg_opt(_("--continue expects no arguments"),
1360                               builtin_merge_usage, builtin_merge_options);
1361
1362                 if (!file_exists(git_path_merge_head(the_repository)))
1363                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1364
1365                 /* Invoke 'git commit' */
1366                 ret = cmd_commit(nargc, nargv, prefix);
1367                 goto done;
1368         }
1369
1370         if (read_cache_unmerged())
1371                 die_resolve_conflict("merge");
1372
1373         if (file_exists(git_path_merge_head(the_repository))) {
1374                 /*
1375                  * There is no unmerged entry, don't advise 'git
1376                  * add/rm <file>', just 'git commit'.
1377                  */
1378                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1379                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1380                                   "Please, commit your changes before you merge."));
1381                 else
1382                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1383         }
1384         if (ref_exists("CHERRY_PICK_HEAD")) {
1385                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1386                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1387                             "Please, commit your changes before you merge."));
1388                 else
1389                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1390         }
1391         resolve_undo_clear();
1392
1393         if (option_edit < 0)
1394                 option_edit = default_edit_option();
1395
1396         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1397
1398         if (verbosity < 0)
1399                 show_diffstat = 0;
1400
1401         if (squash) {
1402                 if (fast_forward == FF_NO)
1403                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--no-ff.");
1404                 if (option_commit > 0)
1405                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--commit.");
1406                 /*
1407                  * squash can now silently disable option_commit - this is not
1408                  * a problem as it is only overriding the default, not a user
1409                  * supplied option.
1410                  */
1411                 option_commit = 0;
1412         }
1413
1414         if (option_commit < 0)
1415                 option_commit = 1;
1416
1417         if (!argc) {
1418                 if (default_to_upstream)
1419                         argc = setup_with_upstream(&argv);
1420                 else
1421                         die(_("No commit specified and merge.defaultToUpstream not set."));
1422         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1423                 argv[0] = "@{-1}";
1424         }
1425
1426         if (!argc)
1427                 usage_with_options(builtin_merge_usage,
1428                         builtin_merge_options);
1429
1430         if (!head_commit) {
1431                 /*
1432                  * If the merged head is a valid one there is no reason
1433                  * to forbid "git merge" into a branch yet to be born.
1434                  * We do the same for "git pull".
1435                  */
1436                 struct object_id *remote_head_oid;
1437                 if (squash)
1438                         die(_("Squash commit into empty head not supported yet"));
1439                 if (fast_forward == FF_NO)
1440                         die(_("Non-fast-forward commit does not make sense into "
1441                             "an empty head"));
1442                 remoteheads = collect_parents(head_commit, &head_subsumed,
1443                                               argc, argv, NULL);
1444                 if (!remoteheads)
1445                         die(_("%s - not something we can merge"), argv[0]);
1446                 if (remoteheads->next)
1447                         die(_("Can merge only exactly one commit into empty head"));
1448
1449                 if (verify_signatures)
1450                         verify_merge_signature(remoteheads->item, verbosity,
1451                                                check_trust_level);
1452
1453                 remote_head_oid = &remoteheads->item->object.oid;
1454                 read_empty(remote_head_oid, 0);
1455                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1456                            UPDATE_REFS_DIE_ON_ERR);
1457                 goto done;
1458         }
1459
1460         /*
1461          * All the rest are the commits being merged; prepare
1462          * the standard merge summary message to be appended
1463          * to the given message.
1464          */
1465         remoteheads = collect_parents(head_commit, &head_subsumed,
1466                                       argc, argv, &merge_msg);
1467
1468         if (!head_commit || !argc)
1469                 usage_with_options(builtin_merge_usage,
1470                         builtin_merge_options);
1471
1472         if (verify_signatures) {
1473                 for (p = remoteheads; p; p = p->next) {
1474                         verify_merge_signature(p->item, verbosity,
1475                                                check_trust_level);
1476                 }
1477         }
1478
1479         strbuf_addstr(&buf, "merge");
1480         for (p = remoteheads; p; p = p->next)
1481                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1482         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1483         strbuf_reset(&buf);
1484
1485         for (p = remoteheads; p; p = p->next) {
1486                 struct commit *commit = p->item;
1487                 strbuf_addf(&buf, "GITHEAD_%s",
1488                             oid_to_hex(&commit->object.oid));
1489                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1490                 strbuf_reset(&buf);
1491                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1492                         fast_forward = FF_NO;
1493         }
1494
1495         if (!use_strategies && !pull_twohead &&
1496             remoteheads && !remoteheads->next) {
1497                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1498                 if (default_strategy)
1499                         append_strategy(get_strategy(default_strategy));
1500         }
1501         if (!use_strategies) {
1502                 if (!remoteheads)
1503                         ; /* already up-to-date */
1504                 else if (!remoteheads->next)
1505                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1506                 else
1507                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1508         }
1509
1510         for (i = 0; i < use_strategies_nr; i++) {
1511                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1512                         fast_forward = FF_NO;
1513                 if (use_strategies[i]->attr & NO_TRIVIAL)
1514                         allow_trivial = 0;
1515         }
1516
1517         if (!remoteheads)
1518                 ; /* already up-to-date */
1519         else if (!remoteheads->next)
1520                 common = get_merge_bases(head_commit, remoteheads->item);
1521         else {
1522                 struct commit_list *list = remoteheads;
1523                 commit_list_insert(head_commit, &list);
1524                 common = get_octopus_merge_bases(list);
1525                 free(list);
1526         }
1527
1528         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1529                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1530
1531         if (remoteheads && !common) {
1532                 /* No common ancestors found. */
1533                 if (!allow_unrelated_histories)
1534                         die(_("refusing to merge unrelated histories"));
1535                 /* otherwise, we need a real merge. */
1536         } else if (!remoteheads ||
1537                  (!remoteheads->next && !common->next &&
1538                   common->item == remoteheads->item)) {
1539                 /*
1540                  * If head can reach all the merge then we are up to date.
1541                  * but first the most common case of merging one remote.
1542                  */
1543                 finish_up_to_date();
1544                 goto done;
1545         } else if (fast_forward != FF_NO && !remoteheads->next &&
1546                         !common->next &&
1547                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1548                 /* Again the most common case of merging one remote. */
1549                 struct strbuf msg = STRBUF_INIT;
1550                 struct commit *commit;
1551
1552                 if (verbosity >= 0) {
1553                         printf(_("Updating %s..%s\n"),
1554                                find_unique_abbrev(&head_commit->object.oid,
1555                                                   DEFAULT_ABBREV),
1556                                find_unique_abbrev(&remoteheads->item->object.oid,
1557                                                   DEFAULT_ABBREV));
1558                 }
1559                 strbuf_addstr(&msg, "Fast-forward");
1560                 if (have_message)
1561                         strbuf_addstr(&msg,
1562                                 " (no commit created; -m option ignored)");
1563                 commit = remoteheads->item;
1564                 if (!commit) {
1565                         ret = 1;
1566                         goto done;
1567                 }
1568
1569                 if (autostash)
1570                         create_autostash(the_repository,
1571                                          git_path_merge_autostash(the_repository),
1572                                          "merge");
1573                 if (checkout_fast_forward(the_repository,
1574                                           &head_commit->object.oid,
1575                                           &commit->object.oid,
1576                                           overwrite_ignore)) {
1577                         apply_autostash(git_path_merge_autostash(the_repository));
1578                         ret = 1;
1579                         goto done;
1580                 }
1581
1582                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1583                 remove_merge_branch_state(the_repository);
1584                 strbuf_release(&msg);
1585                 goto done;
1586         } else if (!remoteheads->next && common->next)
1587                 ;
1588                 /*
1589                  * We are not doing octopus and not fast-forward.  Need
1590                  * a real merge.
1591                  */
1592         else if (!remoteheads->next && !common->next && option_commit) {
1593                 /*
1594                  * We are not doing octopus, not fast-forward, and have
1595                  * only one common.
1596                  */
1597                 refresh_cache(REFRESH_QUIET);
1598                 if (allow_trivial && fast_forward != FF_ONLY) {
1599                         /* See if it is really trivial. */
1600                         git_committer_info(IDENT_STRICT);
1601                         printf(_("Trying really trivial in-index merge...\n"));
1602                         if (!read_tree_trivial(&common->item->object.oid,
1603                                                &head_commit->object.oid,
1604                                                &remoteheads->item->object.oid)) {
1605                                 ret = merge_trivial(head_commit, remoteheads);
1606                                 goto done;
1607                         }
1608                         printf(_("Nope.\n"));
1609                 }
1610         } else {
1611                 /*
1612                  * An octopus.  If we can reach all the remote we are up
1613                  * to date.
1614                  */
1615                 int up_to_date = 1;
1616                 struct commit_list *j;
1617
1618                 for (j = remoteheads; j; j = j->next) {
1619                         struct commit_list *common_one;
1620
1621                         /*
1622                          * Here we *have* to calculate the individual
1623                          * merge_bases again, otherwise "git merge HEAD^
1624                          * HEAD^^" would be missed.
1625                          */
1626                         common_one = get_merge_bases(head_commit, j->item);
1627                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1628                                 up_to_date = 0;
1629                                 break;
1630                         }
1631                 }
1632                 if (up_to_date) {
1633                         finish_up_to_date();
1634                         goto done;
1635                 }
1636         }
1637
1638         if (fast_forward == FF_ONLY)
1639                 die_ff_impossible();
1640
1641         if (autostash)
1642                 create_autostash(the_repository,
1643                                  git_path_merge_autostash(the_repository),
1644                                  "merge");
1645
1646         /* We are going to make a new commit. */
1647         git_committer_info(IDENT_STRICT);
1648
1649         /*
1650          * At this point, we need a real merge.  No matter what strategy
1651          * we use, it would operate on the index, possibly affecting the
1652          * working tree, and when resolved cleanly, have the desired
1653          * tree in the index -- this means that the index must be in
1654          * sync with the head commit.  The strategies are responsible
1655          * to ensure this.
1656          */
1657         if (use_strategies_nr == 1 ||
1658             /*
1659              * Stash away the local changes so that we can try more than one.
1660              */
1661             save_state(&stash))
1662                 oidclr(&stash);
1663
1664         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1665                 int ret, cnt;
1666                 if (i) {
1667                         printf(_("Rewinding the tree to pristine...\n"));
1668                         restore_state(&head_commit->object.oid, &stash);
1669                 }
1670                 if (use_strategies_nr != 1)
1671                         printf(_("Trying merge strategy %s...\n"),
1672                                 use_strategies[i]->name);
1673                 /*
1674                  * Remember which strategy left the state in the working
1675                  * tree.
1676                  */
1677                 wt_strategy = use_strategies[i]->name;
1678
1679                 ret = try_merge_strategy(use_strategies[i]->name,
1680                                          common, remoteheads,
1681                                          head_commit);
1682                 /*
1683                  * The backend exits with 1 when conflicts are
1684                  * left to be resolved, with 2 when it does not
1685                  * handle the given merge at all.
1686                  */
1687                 if (ret < 2) {
1688                         if (!ret) {
1689                                 if (option_commit) {
1690                                         /* Automerge succeeded. */
1691                                         automerge_was_ok = 1;
1692                                         break;
1693                                 }
1694                                 merge_was_ok = 1;
1695                         }
1696                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1697                         if (best_cnt <= 0 || cnt <= best_cnt) {
1698                                 best_strategy = use_strategies[i]->name;
1699                                 best_cnt = cnt;
1700                         }
1701                 }
1702         }
1703
1704         /*
1705          * If we have a resulting tree, that means the strategy module
1706          * auto resolved the merge cleanly.
1707          */
1708         if (automerge_was_ok) {
1709                 ret = finish_automerge(head_commit, head_subsumed,
1710                                        common, remoteheads,
1711                                        &result_tree, wt_strategy);
1712                 goto done;
1713         }
1714
1715         /*
1716          * Pick the result from the best strategy and have the user fix
1717          * it up.
1718          */
1719         if (!best_strategy) {
1720                 restore_state(&head_commit->object.oid, &stash);
1721                 if (use_strategies_nr > 1)
1722                         fprintf(stderr,
1723                                 _("No merge strategy handled the merge.\n"));
1724                 else
1725                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1726                                 use_strategies[0]->name);
1727                 apply_autostash(git_path_merge_autostash(the_repository));
1728                 ret = 2;
1729                 goto done;
1730         } else if (best_strategy == wt_strategy)
1731                 ; /* We already have its result in the working tree. */
1732         else {
1733                 printf(_("Rewinding the tree to pristine...\n"));
1734                 restore_state(&head_commit->object.oid, &stash);
1735                 printf(_("Using the %s strategy to prepare resolving by hand.\n"),
1736                         best_strategy);
1737                 try_merge_strategy(best_strategy, common, remoteheads,
1738                                    head_commit);
1739         }
1740
1741         if (squash) {
1742                 finish(head_commit, remoteheads, NULL, NULL);
1743
1744                 git_test_write_commit_graph_or_die();
1745         } else
1746                 write_merge_state(remoteheads);
1747
1748         if (merge_was_ok)
1749                 fprintf(stderr, _("Automatic merge went well; "
1750                         "stopped before committing as requested\n"));
1751         else
1752                 ret = suggest_conflicts();
1753
1754 done:
1755         strbuf_release(&buf);
1756         free(branch_to_free);
1757         return ret;
1758 }