builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "refs.h"
  18 #include "refspec.h"
  19 #include "commit.h"
  20 #include "diffcore.h"
  21 #include "revision.h"
  22 #include "unpack-trees.h"
  23 #include "cache-tree.h"
  24 #include "dir.h"
  25 #include "utf8.h"
  26 #include "log-tree.h"
  27 #include "color.h"
  28 #include "rerere.h"
  29 #include "help.h"
  30 #include "merge-recursive.h"
  31 #include "resolve-undo.h"
  32 #include "remote.h"
  33 #include "fmt-merge-msg.h"
  34 #include "gpg-interface.h"
  35 #include "sequencer.h"
  36 #include "string-list.h"
  37 #include "packfile.h"
  38 #include "tag.h"
  39 #include "alias.h"
  40 #include "branch.h"
  41 #include "commit-reach.h"
  42 #include "wt-status.h"
  43
  44 #define DEFAULT_TWOHEAD (1<<0)
  45 #define DEFAULT_OCTOPUS (1<<1)
  46 #define NO_FAST_FORWARD (1<<2)
  47 #define NO_TRIVIAL      (1<<3)
  48
  49 struct strategy {
  50         const char *name;
  51         unsigned attr;
  52 };
  53
  54 static const char * const builtin_merge_usage[] = {
  55         N_("git merge [<options>] [<commit>...]"),
  56         N_("git merge --abort"),
  57         N_("git merge --continue"),
  58         NULL
  59 };
  60
  61 static int show_diffstat = 1, shortlog_len = -1, squash;
  62 static int option_commit = -1;
  63 static int option_edit = -1;
  64 static int allow_trivial = 1, have_message, verify_signatures;
  65 static int check_trust_level = 1;
  66 static int overwrite_ignore = 1;
  67 static struct strbuf merge_msg = STRBUF_INIT;
  68 static struct strategy **use_strategies;
  69 static size_t use_strategies_nr, use_strategies_alloc;
  70 static const char **xopts;
  71 static size_t xopts_nr, xopts_alloc;
  72 static const char *branch;
  73 static char *branch_mergeoptions;
  74 static int option_renormalize;
  75 static int verbosity;
  76 static int allow_rerere_auto;
  77 static int abort_current_merge;
  78 static int quit_current_merge;
  79 static int continue_current_merge;
  80 static int allow_unrelated_histories;
  81 static int show_progress = -1;
  82 static int default_to_upstream = 1;
  83 static int signoff;
  84 static const char *sign_commit;
  85 static int no_verify;
  86
  87 static struct strategy all_strategy[] = {
  88         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  89         { "octopus",    DEFAULT_OCTOPUS },
  90         { "resolve",    0 },
  91         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  92         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  93 };
  94
  95 static const char *pull_twohead, *pull_octopus;
  96
  97 enum ff_type {
  98         FF_NO,
  99         FF_ALLOW,
 100         FF_ONLY
 101 };
 102
 103 static enum ff_type fast_forward = FF_ALLOW;
 104
 105 static const char *cleanup_arg;
 106 static enum commit_msg_cleanup_mode cleanup_mode;
 107
 108 static int option_parse_message(const struct option *opt,
 109                                 const char *arg, int unset)
 110 {
 111         struct strbuf *buf = opt->value;
 112
 113         if (unset)
 114                 strbuf_setlen(buf, 0);
 115         else if (arg) {
 116                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 117                 have_message = 1;
 118         } else
 119                 return error(_("switch `m' requires a value"));
 120         return 0;
 121 }
 122
 123 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 124                                                  const struct option *opt,
 125                                                  const char *arg_not_used,
 126                                                  int unset)
 127 {
 128         struct strbuf *buf = opt->value;
 129         const char *arg;
 130
 131         BUG_ON_OPT_ARG(arg_not_used);
 132         if (unset)
 133                 BUG("-F cannot be negated");
 134
 135         if (ctx->opt) {
 136                 arg = ctx->opt;
 137                 ctx->opt = NULL;
 138         } else if (ctx->argc > 1) {
 139                 ctx->argc--;
 140                 arg = *++ctx->argv;
 141         } else
 142                 return error(_("option `%s' requires a value"), opt->long_name);
 143
 144         if (buf->len)
 145                 strbuf_addch(buf, '\n');
 146         if (ctx->prefix && !is_absolute_path(arg))
 147                 arg = prefix_filename(ctx->prefix, arg);
 148         if (strbuf_read_file(buf, arg, 0) < 0)
 149                 return error(_("could not read file '%s'"), arg);
 150         have_message = 1;
 151
 152         return 0;
 153 }
 154
 155 static struct strategy *get_strategy(const char *name)
 156 {
 157         int i;
 158         struct strategy *ret;
 159         static struct cmdnames main_cmds, other_cmds;
 160         static int loaded;
 161
 162         if (!name)
 163                 return NULL;
 164
 165         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 166                 if (!strcmp(name, all_strategy[i].name))
 167                         return &all_strategy[i];
 168
 169         if (!loaded) {
 170                 struct cmdnames not_strategies;
 171                 loaded = 1;
 172
 173                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 174                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 175                 for (i = 0; i < main_cmds.cnt; i++) {
 176                         int j, found = 0;
 177                         struct cmdname *ent = main_cmds.names[i];
 178                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 179                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 180                                                 && !all_strategy[j].name[ent->len])
 181                                         found = 1;
 182                         if (!found)
 183                                 add_cmdname(&not_strategies, ent->name, ent->len);
 184                 }
 185                 exclude_cmds(&main_cmds, &not_strategies);
 186         }
 187         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 188                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 189                 fprintf(stderr, _("Available strategies are:"));
 190                 for (i = 0; i < main_cmds.cnt; i++)
 191                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 192                 fprintf(stderr, ".\n");
 193                 if (other_cmds.cnt) {
 194                         fprintf(stderr, _("Available custom strategies are:"));
 195                         for (i = 0; i < other_cmds.cnt; i++)
 196                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 197                         fprintf(stderr, ".\n");
 198                 }
 199                 exit(1);
 200         }
 201
 202         ret = xcalloc(1, sizeof(struct strategy));
 203         ret->name = xstrdup(name);
 204         ret->attr = NO_TRIVIAL;
 205         return ret;
 206 }
 207
 208 static void append_strategy(struct strategy *s)
 209 {
 210         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 211         use_strategies[use_strategies_nr++] = s;
 212 }
 213
 214 static int option_parse_strategy(const struct option *opt,
 215                                  const char *name, int unset)
 216 {
 217         if (unset)
 218                 return 0;
 219
 220         append_strategy(get_strategy(name));
 221         return 0;
 222 }
 223
 224 static int option_parse_x(const struct option *opt,
 225                           const char *arg, int unset)
 226 {
 227         if (unset)
 228                 return 0;
 229
 230         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 231         xopts[xopts_nr++] = xstrdup(arg);
 232         return 0;
 233 }
 234
 235 static int option_parse_n(const struct option *opt,
 236                           const char *arg, int unset)
 237 {
 238         BUG_ON_OPT_ARG(arg);
 239         show_diffstat = unset;
 240         return 0;
 241 }
 242
 243 static struct option builtin_merge_options[] = {
 244         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 245                 N_("do not show a diffstat at the end of the merge"),
 246                 PARSE_OPT_NOARG, option_parse_n },
 247         OPT_BOOL(0, "stat", &show_diffstat,
 248                 N_("show a diffstat at the end of the merge")),
 249         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 250         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 251           N_("add (at most <n>) entries from shortlog to merge commit message"),
 252           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 253         OPT_BOOL(0, "squash", &squash,
 254                 N_("create a single commit instead of doing a merge")),
 255         OPT_BOOL(0, "commit", &option_commit,
 256                 N_("perform a commit if the merge succeeds (default)")),
 257         OPT_BOOL('e', "edit", &option_edit,
 258                 N_("edit message before committing")),
 259         OPT_CLEANUP(&cleanup_arg),
 260         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 261         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 262                       N_("abort if fast-forward is not possible"),
 263                       FF_ONLY, PARSE_OPT_NONEG),
 264         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 265         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 266                 N_("verify that the named commit has a valid GPG signature")),
 267         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 268                 N_("merge strategy to use"), option_parse_strategy),
 269         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 270                 N_("option for selected merge strategy"), option_parse_x),
 271         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 272                 N_("merge commit message (for a non-fast-forward merge)"),
 273                 option_parse_message),
 274         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 275                 N_("read message from file"), PARSE_OPT_NONEG,
 276                 NULL, 0, option_read_message },
 277         OPT__VERBOSITY(&verbosity),
 278         OPT_BOOL(0, "abort", &abort_current_merge,
 279                 N_("abort the current in-progress merge")),
 280         OPT_BOOL(0, "quit", &quit_current_merge,
 281                 N_("--abort but leave index and working tree alone")),
 282         OPT_BOOL(0, "continue", &continue_current_merge,
 283                 N_("continue the current in-progress merge")),
 284         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 285                  N_("allow merging unrelated histories")),
 286         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 287         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 288           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 289         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 290         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 291         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 292         OPT_END()
 293 };
 294
 295 static int save_state(struct object_id *stash)
 296 {
 297         int len;
 298         struct child_process cp = CHILD_PROCESS_INIT;
 299         struct strbuf buffer = STRBUF_INIT;
 300         const char *argv[] = {"stash", "create", NULL};
 301         int rc = -1;
 302
 303         cp.argv = argv;
 304         cp.out = -1;
 305         cp.git_cmd = 1;
 306
 307         if (start_command(&cp))
 308                 die(_("could not run stash."));
 309         len = strbuf_read(&buffer, cp.out, 1024);
 310         close(cp.out);
 311
 312         if (finish_command(&cp) || len < 0)
 313                 die(_("stash failed"));
 314         else if (!len)          /* no changes */
 315                 goto out;
 316         strbuf_setlen(&buffer, buffer.len-1);
 317         if (get_oid(buffer.buf, stash))
 318                 die(_("not a valid object: %s"), buffer.buf);
 319         rc = 0;
 320 out:
 321         strbuf_release(&buffer);
 322         return rc;
 323 }
 324
 325 static void read_empty(const struct object_id *oid, int verbose)
 326 {
 327         int i = 0;
 328         const char *args[7];
 329
 330         args[i++] = "read-tree";
 331         if (verbose)
 332                 args[i++] = "-v";
 333         args[i++] = "-m";
 334         args[i++] = "-u";
 335         args[i++] = empty_tree_oid_hex();
 336         args[i++] = oid_to_hex(oid);
 337         args[i] = NULL;
 338
 339         if (run_command_v_opt(args, RUN_GIT_CMD))
 340                 die(_("read-tree failed"));
 341 }
 342
 343 static void reset_hard(const struct object_id *oid, int verbose)
 344 {
 345         int i = 0;
 346         const char *args[6];
 347
 348         args[i++] = "read-tree";
 349         if (verbose)
 350                 args[i++] = "-v";
 351         args[i++] = "--reset";
 352         args[i++] = "-u";
 353         args[i++] = oid_to_hex(oid);
 354         args[i] = NULL;
 355
 356         if (run_command_v_opt(args, RUN_GIT_CMD))
 357                 die(_("read-tree failed"));
 358 }
 359
 360 static void restore_state(const struct object_id *head,
 361                           const struct object_id *stash)
 362 {
 363         struct strbuf sb = STRBUF_INIT;
 364         const char *args[] = { "stash", "apply", NULL, NULL };
 365
 366         if (is_null_oid(stash))
 367                 return;
 368
 369         reset_hard(head, 1);
 370
 371         args[2] = oid_to_hex(stash);
 372
 373         /*
 374          * It is OK to ignore error here, for example when there was
 375          * nothing to restore.
 376          */
 377         run_command_v_opt(args, RUN_GIT_CMD);
 378
 379         strbuf_release(&sb);
 380         refresh_cache(REFRESH_QUIET);
 381 }
 382
 383 /* This is called when no merge was necessary. */
 384 static void finish_up_to_date(const char *msg)
 385 {
 386         if (verbosity >= 0)
 387                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 388         remove_merge_branch_state(the_repository);
 389 }
 390
 391 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 392 {
 393         struct rev_info rev;
 394         struct strbuf out = STRBUF_INIT;
 395         struct commit_list *j;
 396         struct pretty_print_context ctx = {0};
 397
 398         printf(_("Squash commit -- not updating HEAD\n"));
 399
 400         repo_init_revisions(the_repository, &rev, NULL);
 401         rev.ignore_merges = 1;
 402         rev.commit_format = CMIT_FMT_MEDIUM;
 403
 404         commit->object.flags |= UNINTERESTING;
 405         add_pending_object(&rev, &commit->object, NULL);
 406
 407         for (j = remoteheads; j; j = j->next)
 408                 add_pending_object(&rev, &j->item->object, NULL);
 409
 410         setup_revisions(0, NULL, &rev, NULL);
 411         if (prepare_revision_walk(&rev))
 412                 die(_("revision walk setup failed"));
 413
 414         ctx.abbrev = rev.abbrev;
 415         ctx.date_mode = rev.date_mode;
 416         ctx.fmt = rev.commit_format;
 417
 418         strbuf_addstr(&out, "Squashed commit of the following:\n");
 419         while ((commit = get_revision(&rev)) != NULL) {
 420                 strbuf_addch(&out, '\n');
 421                 strbuf_addf(&out, "commit %s\n",
 422                         oid_to_hex(&commit->object.oid));
 423                 pretty_print_commit(&ctx, commit, &out);
 424         }
 425         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 426         strbuf_release(&out);
 427 }
 428
 429 static void finish(struct commit *head_commit,
 430                    struct commit_list *remoteheads,
 431                    const struct object_id *new_head, const char *msg)
 432 {
 433         struct strbuf reflog_message = STRBUF_INIT;
 434         const struct object_id *head = &head_commit->object.oid;
 435
 436         if (!msg)
 437                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 438         else {
 439                 if (verbosity >= 0)
 440                         printf("%s\n", msg);
 441                 strbuf_addf(&reflog_message, "%s: %s",
 442                         getenv("GIT_REFLOG_ACTION"), msg);
 443         }
 444         if (squash) {
 445                 squash_message(head_commit, remoteheads);
 446         } else {
 447                 if (verbosity >= 0 && !merge_msg.len)
 448                         printf(_("No merge message -- not updating HEAD\n"));
 449                 else {
 450                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 451                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 452                                    0, UPDATE_REFS_DIE_ON_ERR);
 453                         /*
 454                          * We ignore errors in 'gc --auto', since the
 455                          * user should see them.
 456                          */
 457                         close_object_store(the_repository->objects);
 458                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 459                 }
 460         }
 461         if (new_head && show_diffstat) {
 462                 struct diff_options opts;
 463                 repo_diff_setup(the_repository, &opts);
 464                 opts.stat_width = -1; /* use full terminal width */
 465                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 466                 opts.output_format |=
 467                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 468                 opts.detect_rename = DIFF_DETECT_RENAME;
 469                 diff_setup_done(&opts);
 470                 diff_tree_oid(head, new_head, "", &opts);
 471                 diffcore_std(&opts);
 472                 diff_flush(&opts);
 473         }
 474
 475         /* Run a post-merge hook */
 476         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 477
 478         strbuf_release(&reflog_message);
 479 }
 480
 481 /* Get the name for the merge commit's message. */
 482 static void merge_name(const char *remote, struct strbuf *msg)
 483 {
 484         struct commit *remote_head;
 485         struct object_id branch_head;
 486         struct strbuf buf = STRBUF_INIT;
 487         struct strbuf bname = STRBUF_INIT;
 488         struct merge_remote_desc *desc;
 489         const char *ptr;
 490         char *found_ref;
 491         int len, early;
 492
 493         strbuf_branchname(&bname, remote, 0);
 494         remote = bname.buf;
 495
 496         oidclr(&branch_head);
 497         remote_head = get_merge_parent(remote);
 498         if (!remote_head)
 499                 die(_("'%s' does not point to a commit"), remote);
 500
 501         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 502                 if (starts_with(found_ref, "refs/heads/")) {
 503                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 504                                     oid_to_hex(&branch_head), remote);
 505                         goto cleanup;
 506                 }
 507                 if (starts_with(found_ref, "refs/tags/")) {
 508                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 509                                     oid_to_hex(&branch_head), remote);
 510                         goto cleanup;
 511                 }
 512                 if (starts_with(found_ref, "refs/remotes/")) {
 513                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 514                                     oid_to_hex(&branch_head), remote);
 515                         goto cleanup;
 516                 }
 517         }
 518
 519         /* See if remote matches <name>^^^.. or <name>~<number> */
 520         for (len = 0, ptr = remote + strlen(remote);
 521              remote < ptr && ptr[-1] == '^';
 522              ptr--)
 523                 len++;
 524         if (len)
 525                 early = 1;
 526         else {
 527                 early = 0;
 528                 ptr = strrchr(remote, '~');
 529                 if (ptr) {
 530                         int seen_nonzero = 0;
 531
 532                         len++; /* count ~ */
 533                         while (*++ptr && isdigit(*ptr)) {
 534                                 seen_nonzero |= (*ptr != '0');
 535                                 len++;
 536                         }
 537                         if (*ptr)
 538                                 len = 0; /* not ...~<number> */
 539                         else if (seen_nonzero)
 540                                 early = 1;
 541                         else if (len == 1)
 542                                 early = 1; /* "name~" is "name~1"! */
 543                 }
 544         }
 545         if (len) {
 546                 struct strbuf truname = STRBUF_INIT;
 547                 strbuf_addf(&truname, "refs/heads/%s", remote);
 548                 strbuf_setlen(&truname, truname.len - len);
 549                 if (ref_exists(truname.buf)) {
 550                         strbuf_addf(msg,
 551                                     "%s\t\tbranch '%s'%s of .\n",
 552                                     oid_to_hex(&remote_head->object.oid),
 553                                     truname.buf + 11,
 554                                     (early ? " (early part)" : ""));
 555                         strbuf_release(&truname);
 556                         goto cleanup;
 557                 }
 558                 strbuf_release(&truname);
 559         }
 560
 561         desc = merge_remote_util(remote_head);
 562         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 563                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 564                             oid_to_hex(&desc->obj->oid),
 565                             type_name(desc->obj->type),
 566                             remote);
 567                 goto cleanup;
 568         }
 569
 570         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 571                 oid_to_hex(&remote_head->object.oid), remote);
 572 cleanup:
 573         strbuf_release(&buf);
 574         strbuf_release(&bname);
 575 }
 576
 577 static void parse_branch_merge_options(char *bmo)
 578 {
 579         const char **argv;
 580         int argc;
 581
 582         if (!bmo)
 583                 return;
 584         argc = split_cmdline(bmo, &argv);
 585         if (argc < 0)
 586                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 587                     _(split_cmdline_strerror(argc)));
 588         REALLOC_ARRAY(argv, argc + 2);
 589         MOVE_ARRAY(argv + 1, argv, argc + 1);
 590         argc++;
 591         argv[0] = "branch.*.mergeoptions";
 592         parse_options(argc, argv, NULL, builtin_merge_options,
 593                       builtin_merge_usage, 0);
 594         free(argv);
 595 }
 596
 597 static int git_merge_config(const char *k, const char *v, void *cb)
 598 {
 599         int status;
 600
 601         if (branch && starts_with(k, "branch.") &&
 602                 starts_with(k + 7, branch) &&
 603                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 604                 free(branch_mergeoptions);
 605                 branch_mergeoptions = xstrdup(v);
 606                 return 0;
 607         }
 608
 609         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 610                 show_diffstat = git_config_bool(k, v);
 611         else if (!strcmp(k, "merge.verifysignatures"))
 612                 verify_signatures = git_config_bool(k, v);
 613         else if (!strcmp(k, "pull.twohead"))
 614                 return git_config_string(&pull_twohead, k, v);
 615         else if (!strcmp(k, "pull.octopus"))
 616                 return git_config_string(&pull_octopus, k, v);
 617         else if (!strcmp(k, "commit.cleanup"))
 618                 return git_config_string(&cleanup_arg, k, v);
 619         else if (!strcmp(k, "merge.renormalize"))
 620                 option_renormalize = git_config_bool(k, v);
 621         else if (!strcmp(k, "merge.ff")) {
 622                 int boolval = git_parse_maybe_bool(v);
 623                 if (0 <= boolval) {
 624                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 625                 } else if (v && !strcmp(v, "only")) {
 626                         fast_forward = FF_ONLY;
 627                 } /* do not barf on values from future versions of git */
 628                 return 0;
 629         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 630                 default_to_upstream = git_config_bool(k, v);
 631                 return 0;
 632         } else if (!strcmp(k, "commit.gpgsign")) {
 633                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 634                 return 0;
 635         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 636                 check_trust_level = 0;
 637         }
 638
 639         status = fmt_merge_msg_config(k, v, cb);
 640         if (status)
 641                 return status;
 642         status = git_gpg_config(k, v, NULL);
 643         if (status)
 644                 return status;
 645         return git_diff_ui_config(k, v, cb);
 646 }
 647
 648 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 649                              struct object_id *one)
 650 {
 651         int i, nr_trees = 0;
 652         struct tree *trees[MAX_UNPACK_TREES];
 653         struct tree_desc t[MAX_UNPACK_TREES];
 654         struct unpack_trees_options opts;
 655
 656         memset(&opts, 0, sizeof(opts));
 657         opts.head_idx = 2;
 658         opts.src_index = &the_index;
 659         opts.dst_index = &the_index;
 660         opts.update = 1;
 661         opts.verbose_update = 1;
 662         opts.trivial_merges_only = 1;
 663         opts.merge = 1;
 664         trees[nr_trees] = parse_tree_indirect(common);
 665         if (!trees[nr_trees++])
 666                 return -1;
 667         trees[nr_trees] = parse_tree_indirect(head);
 668         if (!trees[nr_trees++])
 669                 return -1;
 670         trees[nr_trees] = parse_tree_indirect(one);
 671         if (!trees[nr_trees++])
 672                 return -1;
 673         opts.fn = threeway_merge;
 674         cache_tree_free(&active_cache_tree);
 675         for (i = 0; i < nr_trees; i++) {
 676                 parse_tree(trees[i]);
 677                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 678         }
 679         if (unpack_trees(nr_trees, t, &opts))
 680                 return -1;
 681         return 0;
 682 }
 683
 684 static void write_tree_trivial(struct object_id *oid)
 685 {
 686         if (write_cache_as_tree(oid, 0, NULL))
 687                 die(_("git write-tree failed to write a tree"));
 688 }
 689
 690 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 691                               struct commit_list *remoteheads,
 692                               struct commit *head)
 693 {
 694         const char *head_arg = "HEAD";
 695
 696         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 697                 return error(_("Unable to write index."));
 698
 699         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 700                 struct lock_file lock = LOCK_INIT;
 701                 int clean, x;
 702                 struct commit *result;
 703                 struct commit_list *reversed = NULL;
 704                 struct merge_options o;
 705                 struct commit_list *j;
 706
 707                 if (remoteheads->next) {
 708                         error(_("Not handling anything other than two heads merge."));
 709                         return 2;
 710                 }
 711
 712                 init_merge_options(&o, the_repository);
 713                 if (!strcmp(strategy, "subtree"))
 714                         o.subtree_shift = "";
 715
 716                 o.renormalize = option_renormalize;
 717                 o.show_rename_progress =
 718                         show_progress == -1 ? isatty(2) : show_progress;
 719
 720                 for (x = 0; x < xopts_nr; x++)
 721                         if (parse_merge_opt(&o, xopts[x]))
 722                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 723
 724                 o.branch1 = head_arg;
 725                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 726
 727                 for (j = common; j; j = j->next)
 728                         commit_list_insert(j->item, &reversed);
 729
 730                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 731                 clean = merge_recursive(&o, head,
 732                                 remoteheads->item, reversed, &result);
 733                 if (clean < 0)
 734                         exit(128);
 735                 if (write_locked_index(&the_index, &lock,
 736                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 737                         die(_("unable to write %s"), get_index_file());
 738                 return clean ? 0 : 1;
 739         } else {
 740                 return try_merge_command(the_repository,
 741                                          strategy, xopts_nr, xopts,
 742                                          common, head_arg, remoteheads);
 743         }
 744 }
 745
 746 static void count_diff_files(struct diff_queue_struct *q,
 747                              struct diff_options *opt, void *data)
 748 {
 749         int *count = data;
 750
 751         (*count) += q->nr;
 752 }
 753
 754 static int count_unmerged_entries(void)
 755 {
 756         int i, ret = 0;
 757
 758         for (i = 0; i < active_nr; i++)
 759                 if (ce_stage(active_cache[i]))
 760                         ret++;
 761
 762         return ret;
 763 }
 764
 765 static void add_strategies(const char *string, unsigned attr)
 766 {
 767         int i;
 768
 769         if (string) {
 770                 struct string_list list = STRING_LIST_INIT_DUP;
 771                 struct string_list_item *item;
 772                 string_list_split(&list, string, ' ', -1);
 773                 for_each_string_list_item(item, &list)
 774                         append_strategy(get_strategy(item->string));
 775                 string_list_clear(&list, 0);
 776                 return;
 777         }
 778         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 779                 if (all_strategy[i].attr & attr)
 780                         append_strategy(&all_strategy[i]);
 781
 782 }
 783
 784 static void read_merge_msg(struct strbuf *msg)
 785 {
 786         const char *filename = git_path_merge_msg(the_repository);
 787         strbuf_reset(msg);
 788         if (strbuf_read_file(msg, filename, 0) < 0)
 789                 die_errno(_("Could not read from '%s'"), filename);
 790 }
 791
 792 static void write_merge_state(struct commit_list *);
 793 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 794 {
 795         if (err_msg)
 796                 error("%s", err_msg);
 797         fprintf(stderr,
 798                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 799         write_merge_state(remoteheads);
 800         exit(1);
 801 }
 802
 803 static const char merge_editor_comment[] =
 804 N_("Please enter a commit message to explain why this merge is necessary,\n"
 805    "especially if it merges an updated upstream into a topic branch.\n"
 806    "\n");
 807
 808 static const char scissors_editor_comment[] =
 809 N_("An empty message aborts the commit.\n");
 810
 811 static const char no_scissors_editor_comment[] =
 812 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 813    "the commit.\n");
 814
 815 static void write_merge_heads(struct commit_list *);
 816 static void prepare_to_commit(struct commit_list *remoteheads)
 817 {
 818         struct strbuf msg = STRBUF_INIT;
 819         const char *index_file = get_index_file();
 820
 821         if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
 822                 abort_commit(remoteheads, NULL);
 823         /*
 824          * Re-read the index as pre-merge-commit hook could have updated it,
 825          * and write it out as a tree.  We must do this before we invoke
 826          * the editor and after we invoke run_status above.
 827          */
 828         if (find_hook("pre-merge-commit"))
 829                 discard_cache();
 830         read_cache_from(index_file);
 831         strbuf_addbuf(&msg, &merge_msg);
 832         if (squash)
 833                 BUG("the control must not reach here under --squash");
 834         if (0 < option_edit) {
 835                 strbuf_addch(&msg, '\n');
 836                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 837                         wt_status_append_cut_line(&msg);
 838                         strbuf_commented_addf(&msg, "\n");
 839                 }
 840                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 841                 strbuf_commented_addf(&msg, _(cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS ?
 842                         scissors_editor_comment :
 843                         no_scissors_editor_comment), comment_line_char);
 844         }
 845         if (signoff)
 846                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 847         write_merge_heads(remoteheads);
 848         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 849         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 850                             git_path_merge_msg(the_repository), "merge", NULL))
 851                 abort_commit(remoteheads, NULL);
 852         if (0 < option_edit) {
 853                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 854                         abort_commit(remoteheads, NULL);
 855         }
 856
 857         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 858                                           "commit-msg",
 859                                           git_path_merge_msg(the_repository), NULL))
 860                 abort_commit(remoteheads, NULL);
 861
 862         read_merge_msg(&msg);
 863         cleanup_message(&msg, cleanup_mode, 0);
 864         if (!msg.len)
 865                 abort_commit(remoteheads, _("Empty commit message."));
 866         strbuf_release(&merge_msg);
 867         strbuf_addbuf(&merge_msg, &msg);
 868         strbuf_release(&msg);
 869 }
 870
 871 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 872 {
 873         struct object_id result_tree, result_commit;
 874         struct commit_list *parents, **pptr = &parents;
 875
 876         if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 877                 return error(_("Unable to write index."));
 878
 879         write_tree_trivial(&result_tree);
 880         printf(_("Wonderful.\n"));
 881         pptr = commit_list_append(head, pptr);
 882         pptr = commit_list_append(remoteheads->item, pptr);
 883         prepare_to_commit(remoteheads);
 884         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 885                         &result_commit, NULL, sign_commit))
 886                 die(_("failed to write commit object"));
 887         finish(head, remoteheads, &result_commit, "In-index merge");
 888         remove_merge_branch_state(the_repository);
 889         return 0;
 890 }
 891
 892 static int finish_automerge(struct commit *head,
 893                             int head_subsumed,
 894                             struct commit_list *common,
 895                             struct commit_list *remoteheads,
 896                             struct object_id *result_tree,
 897                             const char *wt_strategy)
 898 {
 899         struct commit_list *parents = NULL;
 900         struct strbuf buf = STRBUF_INIT;
 901         struct object_id result_commit;
 902
 903         write_tree_trivial(result_tree);
 904         free_commit_list(common);
 905         parents = remoteheads;
 906         if (!head_subsumed || fast_forward == FF_NO)
 907                 commit_list_insert(head, &parents);
 908         prepare_to_commit(remoteheads);
 909         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 910                         &result_commit, NULL, sign_commit))
 911                 die(_("failed to write commit object"));
 912         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 913         finish(head, remoteheads, &result_commit, buf.buf);
 914         strbuf_release(&buf);
 915         remove_merge_branch_state(the_repository);
 916         return 0;
 917 }
 918
 919 static int suggest_conflicts(void)
 920 {
 921         const char *filename;
 922         FILE *fp;
 923         struct strbuf msgbuf = STRBUF_INIT;
 924
 925         filename = git_path_merge_msg(the_repository);
 926         fp = xfopen(filename, "a");
 927
 928         /*
 929          * We can't use cleanup_mode because if we're not using the editor,
 930          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 931          * though the message is meant to be processed later by git-commit.
 932          * Thus, we will get the cleanup mode which is returned when we _are_
 933          * using an editor.
 934          */
 935         append_conflicts_hint(&the_index, &msgbuf,
 936                               get_cleanup_mode(cleanup_arg, 1));
 937         fputs(msgbuf.buf, fp);
 938         strbuf_release(&msgbuf);
 939         fclose(fp);
 940         repo_rerere(the_repository, allow_rerere_auto);
 941         printf(_("Automatic merge failed; "
 942                         "fix conflicts and then commit the result.\n"));
 943         return 1;
 944 }
 945
 946 static int evaluate_result(void)
 947 {
 948         int cnt = 0;
 949         struct rev_info rev;
 950
 951         /* Check how many files differ. */
 952         repo_init_revisions(the_repository, &rev, "");
 953         setup_revisions(0, NULL, &rev, NULL);
 954         rev.diffopt.output_format |=
 955                 DIFF_FORMAT_CALLBACK;
 956         rev.diffopt.format_callback = count_diff_files;
 957         rev.diffopt.format_callback_data = &cnt;
 958         run_diff_files(&rev, 0);
 959
 960         /*
 961          * Check how many unmerged entries are
 962          * there.
 963          */
 964         cnt += count_unmerged_entries();
 965
 966         return cnt;
 967 }
 968
 969 /*
 970  * Pretend as if the user told us to merge with the remote-tracking
 971  * branch we have for the upstream of the current branch
 972  */
 973 static int setup_with_upstream(const char ***argv)
 974 {
 975         struct branch *branch = branch_get(NULL);
 976         int i;
 977         const char **args;
 978
 979         if (!branch)
 980                 die(_("No current branch."));
 981         if (!branch->remote_name)
 982                 die(_("No remote for the current branch."));
 983         if (!branch->merge_nr)
 984                 die(_("No default upstream defined for the current branch."));
 985
 986         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 987         for (i = 0; i < branch->merge_nr; i++) {
 988                 if (!branch->merge[i]->dst)
 989                         die(_("No remote-tracking branch for %s from %s"),
 990                             branch->merge[i]->src, branch->remote_name);
 991                 args[i] = branch->merge[i]->dst;
 992         }
 993         args[i] = NULL;
 994         *argv = args;
 995         return i;
 996 }
 997
 998 static void write_merge_heads(struct commit_list *remoteheads)
 999 {
1000         struct commit_list *j;
1001         struct strbuf buf = STRBUF_INIT;
1002
1003         for (j = remoteheads; j; j = j->next) {
1004                 struct object_id *oid;
1005                 struct commit *c = j->item;
1006                 struct merge_remote_desc *desc;
1007
1008                 desc = merge_remote_util(c);
1009                 if (desc && desc->obj) {
1010                         oid = &desc->obj->oid;
1011                 } else {
1012                         oid = &c->object.oid;
1013                 }
1014                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1015         }
1016         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1017
1018         strbuf_reset(&buf);
1019         if (fast_forward == FF_NO)
1020                 strbuf_addstr(&buf, "no-ff");
1021         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1022         strbuf_release(&buf);
1023 }
1024
1025 static void write_merge_state(struct commit_list *remoteheads)
1026 {
1027         write_merge_heads(remoteheads);
1028         strbuf_addch(&merge_msg, '\n');
1029         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1030                        merge_msg.len);
1031 }
1032
1033 static int default_edit_option(void)
1034 {
1035         static const char name[] = "GIT_MERGE_AUTOEDIT";
1036         const char *e = getenv(name);
1037         struct stat st_stdin, st_stdout;
1038
1039         if (have_message)
1040                 /* an explicit -m msg without --[no-]edit */
1041                 return 0;
1042
1043         if (e) {
1044                 int v = git_parse_maybe_bool(e);
1045                 if (v < 0)
1046                         die(_("Bad value '%s' in environment '%s'"), e, name);
1047                 return v;
1048         }
1049
1050         /* Use editor if stdin and stdout are the same and is a tty */
1051         return (!fstat(0, &st_stdin) &&
1052                 !fstat(1, &st_stdout) &&
1053                 isatty(0) && isatty(1) &&
1054                 st_stdin.st_dev == st_stdout.st_dev &&
1055                 st_stdin.st_ino == st_stdout.st_ino &&
1056                 st_stdin.st_mode == st_stdout.st_mode);
1057 }
1058
1059 static struct commit_list *reduce_parents(struct commit *head_commit,
1060                                           int *head_subsumed,
1061                                           struct commit_list *remoteheads)
1062 {
1063         struct commit_list *parents, **remotes;
1064
1065         /*
1066          * Is the current HEAD reachable from another commit being
1067          * merged?  If so we do not want to record it as a parent of
1068          * the resulting merge, unless --no-ff is given.  We will flip
1069          * this variable to 0 when we find HEAD among the independent
1070          * tips being merged.
1071          */
1072         *head_subsumed = 1;
1073
1074         /* Find what parents to record by checking independent ones. */
1075         parents = reduce_heads(remoteheads);
1076         free_commit_list(remoteheads);
1077
1078         remoteheads = NULL;
1079         remotes = &remoteheads;
1080         while (parents) {
1081                 struct commit *commit = pop_commit(&parents);
1082                 if (commit == head_commit)
1083                         *head_subsumed = 0;
1084                 else
1085                         remotes = &commit_list_insert(commit, remotes)->next;
1086         }
1087         return remoteheads;
1088 }
1089
1090 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1091 {
1092         struct fmt_merge_msg_opts opts;
1093
1094         memset(&opts, 0, sizeof(opts));
1095         opts.add_title = !have_message;
1096         opts.shortlog_len = shortlog_len;
1097         opts.credit_people = (0 < option_edit);
1098
1099         fmt_merge_msg(merge_names, merge_msg, &opts);
1100         if (merge_msg->len)
1101                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1102 }
1103
1104 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1105 {
1106         const char *filename;
1107         int fd, pos, npos;
1108         struct strbuf fetch_head_file = STRBUF_INIT;
1109         const unsigned hexsz = the_hash_algo->hexsz;
1110
1111         if (!merge_names)
1112                 merge_names = &fetch_head_file;
1113
1114         filename = git_path_fetch_head(the_repository);
1115         fd = open(filename, O_RDONLY);
1116         if (fd < 0)
1117                 die_errno(_("could not open '%s' for reading"), filename);
1118
1119         if (strbuf_read(merge_names, fd, 0) < 0)
1120                 die_errno(_("could not read '%s'"), filename);
1121         if (close(fd) < 0)
1122                 die_errno(_("could not close '%s'"), filename);
1123
1124         for (pos = 0; pos < merge_names->len; pos = npos) {
1125                 struct object_id oid;
1126                 char *ptr;
1127                 struct commit *commit;
1128
1129                 ptr = strchr(merge_names->buf + pos, '\n');
1130                 if (ptr)
1131                         npos = ptr - merge_names->buf + 1;
1132                 else
1133                         npos = merge_names->len;
1134
1135                 if (npos - pos < hexsz + 2 ||
1136                     get_oid_hex(merge_names->buf + pos, &oid))
1137                         commit = NULL; /* bad */
1138                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1139                         continue; /* not-for-merge */
1140                 else {
1141                         char saved = merge_names->buf[pos + hexsz];
1142                         merge_names->buf[pos + hexsz] = '\0';
1143                         commit = get_merge_parent(merge_names->buf + pos);
1144                         merge_names->buf[pos + hexsz] = saved;
1145                 }
1146                 if (!commit) {
1147                         if (ptr)
1148                                 *ptr = '\0';
1149                         die(_("not something we can merge in %s: %s"),
1150                             filename, merge_names->buf + pos);
1151                 }
1152                 remotes = &commit_list_insert(commit, remotes)->next;
1153         }
1154
1155         if (merge_names == &fetch_head_file)
1156                 strbuf_release(&fetch_head_file);
1157 }
1158
1159 static struct commit_list *collect_parents(struct commit *head_commit,
1160                                            int *head_subsumed,
1161                                            int argc, const char **argv,
1162                                            struct strbuf *merge_msg)
1163 {
1164         int i;
1165         struct commit_list *remoteheads = NULL;
1166         struct commit_list **remotes = &remoteheads;
1167         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1168
1169         if (merge_msg && (!have_message || shortlog_len))
1170                 autogen = &merge_names;
1171
1172         if (head_commit)
1173                 remotes = &commit_list_insert(head_commit, remotes)->next;
1174
1175         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1176                 handle_fetch_head(remotes, autogen);
1177                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1178         } else {
1179                 for (i = 0; i < argc; i++) {
1180                         struct commit *commit = get_merge_parent(argv[i]);
1181                         if (!commit)
1182                                 help_unknown_ref(argv[i], "merge",
1183                                                  _("not something we can merge"));
1184                         remotes = &commit_list_insert(commit, remotes)->next;
1185                 }
1186                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1187                 if (autogen) {
1188                         struct commit_list *p;
1189                         for (p = remoteheads; p; p = p->next)
1190                                 merge_name(merge_remote_util(p->item)->name, autogen);
1191                 }
1192         }
1193
1194         if (autogen) {
1195                 prepare_merge_message(autogen, merge_msg);
1196                 strbuf_release(autogen);
1197         }
1198
1199         return remoteheads;
1200 }
1201
1202 static int merging_a_throwaway_tag(struct commit *commit)
1203 {
1204         char *tag_ref;
1205         struct object_id oid;
1206         int is_throwaway_tag = 0;
1207
1208         /* Are we merging a tag? */
1209         if (!merge_remote_util(commit) ||
1210             !merge_remote_util(commit)->obj ||
1211             merge_remote_util(commit)->obj->type != OBJ_TAG)
1212                 return is_throwaway_tag;
1213
1214         /*
1215          * Now we know we are merging a tag object.  Are we downstream
1216          * and following the tags from upstream?  If so, we must have
1217          * the tag object pointed at by "refs/tags/$T" where $T is the
1218          * tagname recorded in the tag object.  We want to allow such
1219          * a "just to catch up" merge to fast-forward.
1220          *
1221          * Otherwise, we are playing an integrator's role, making a
1222          * merge with a throw-away tag from a contributor with
1223          * something like "git pull $contributor $signed_tag".
1224          * We want to forbid such a merge from fast-forwarding
1225          * by default; otherwise we would not keep the signature
1226          * anywhere.
1227          */
1228         tag_ref = xstrfmt("refs/tags/%s",
1229                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1230         if (!read_ref(tag_ref, &oid) &&
1231             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1232                 is_throwaway_tag = 0;
1233         else
1234                 is_throwaway_tag = 1;
1235         free(tag_ref);
1236         return is_throwaway_tag;
1237 }
1238
1239 int cmd_merge(int argc, const char **argv, const char *prefix)
1240 {
1241         struct object_id result_tree, stash, head_oid;
1242         struct commit *head_commit;
1243         struct strbuf buf = STRBUF_INIT;
1244         int i, ret = 0, head_subsumed;
1245         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1246         struct commit_list *common = NULL;
1247         const char *best_strategy = NULL, *wt_strategy = NULL;
1248         struct commit_list *remoteheads, *p;
1249         void *branch_to_free;
1250         int orig_argc = argc;
1251
1252         if (argc == 2 && !strcmp(argv[1], "-h"))
1253                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1254
1255         /*
1256          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1257          * current branch.
1258          */
1259         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1260         if (branch)
1261                 skip_prefix(branch, "refs/heads/", &branch);
1262
1263         init_diff_ui_defaults();
1264         git_config(git_merge_config, NULL);
1265
1266         if (!branch || is_null_oid(&head_oid))
1267                 head_commit = NULL;
1268         else
1269                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1270
1271         if (branch_mergeoptions)
1272                 parse_branch_merge_options(branch_mergeoptions);
1273         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1274                         builtin_merge_usage, 0);
1275         if (shortlog_len < 0)
1276                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1277
1278         if (verbosity < 0 && show_progress == -1)
1279                 show_progress = 0;
1280
1281         if (abort_current_merge) {
1282                 int nargc = 2;
1283                 const char *nargv[] = {"reset", "--merge", NULL};
1284
1285                 if (orig_argc != 2)
1286                         usage_msg_opt(_("--abort expects no arguments"),
1287                               builtin_merge_usage, builtin_merge_options);
1288
1289                 if (!file_exists(git_path_merge_head(the_repository)))
1290                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1291
1292                 /* Invoke 'git reset --merge' */
1293                 ret = cmd_reset(nargc, nargv, prefix);
1294                 goto done;
1295         }
1296
1297         if (quit_current_merge) {
1298                 if (orig_argc != 2)
1299                         usage_msg_opt(_("--quit expects no arguments"),
1300                                       builtin_merge_usage,
1301                                       builtin_merge_options);
1302
1303                 remove_merge_branch_state(the_repository);
1304                 goto done;
1305         }
1306
1307         if (continue_current_merge) {
1308                 int nargc = 1;
1309                 const char *nargv[] = {"commit", NULL};
1310
1311                 if (orig_argc != 2)
1312                         usage_msg_opt(_("--continue expects no arguments"),
1313                               builtin_merge_usage, builtin_merge_options);
1314
1315                 if (!file_exists(git_path_merge_head(the_repository)))
1316                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1317
1318                 /* Invoke 'git commit' */
1319                 ret = cmd_commit(nargc, nargv, prefix);
1320                 goto done;
1321         }
1322
1323         if (read_cache_unmerged())
1324                 die_resolve_conflict("merge");
1325
1326         if (file_exists(git_path_merge_head(the_repository))) {
1327                 /*
1328                  * There is no unmerged entry, don't advise 'git
1329                  * add/rm <file>', just 'git commit'.
1330                  */
1331                 if (advice_resolve_conflict)
1332                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1333                                   "Please, commit your changes before you merge."));
1334                 else
1335                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1336         }
1337         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1338                 if (advice_resolve_conflict)
1339                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1340                             "Please, commit your changes before you merge."));
1341                 else
1342                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1343         }
1344         resolve_undo_clear();
1345
1346         if (option_edit < 0)
1347                 option_edit = default_edit_option();
1348
1349         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1350
1351         if (verbosity < 0)
1352                 show_diffstat = 0;
1353
1354         if (squash) {
1355                 if (fast_forward == FF_NO)
1356                         die(_("You cannot combine --squash with --no-ff."));
1357                 if (option_commit > 0)
1358                         die(_("You cannot combine --squash with --commit."));
1359                 /*
1360                  * squash can now silently disable option_commit - this is not
1361                  * a problem as it is only overriding the default, not a user
1362                  * supplied option.
1363                  */
1364                 option_commit = 0;
1365         }
1366
1367         if (option_commit < 0)
1368                 option_commit = 1;
1369
1370         if (!argc) {
1371                 if (default_to_upstream)
1372                         argc = setup_with_upstream(&argv);
1373                 else
1374                         die(_("No commit specified and merge.defaultToUpstream not set."));
1375         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1376                 argv[0] = "@{-1}";
1377         }
1378
1379         if (!argc)
1380                 usage_with_options(builtin_merge_usage,
1381                         builtin_merge_options);
1382
1383         if (!head_commit) {
1384                 /*
1385                  * If the merged head is a valid one there is no reason
1386                  * to forbid "git merge" into a branch yet to be born.
1387                  * We do the same for "git pull".
1388                  */
1389                 struct object_id *remote_head_oid;
1390                 if (squash)
1391                         die(_("Squash commit into empty head not supported yet"));
1392                 if (fast_forward == FF_NO)
1393                         die(_("Non-fast-forward commit does not make sense into "
1394                             "an empty head"));
1395                 remoteheads = collect_parents(head_commit, &head_subsumed,
1396                                               argc, argv, NULL);
1397                 if (!remoteheads)
1398                         die(_("%s - not something we can merge"), argv[0]);
1399                 if (remoteheads->next)
1400                         die(_("Can merge only exactly one commit into empty head"));
1401
1402                 if (verify_signatures)
1403                         verify_merge_signature(remoteheads->item, verbosity,
1404                                                check_trust_level);
1405
1406                 remote_head_oid = &remoteheads->item->object.oid;
1407                 read_empty(remote_head_oid, 0);
1408                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1409                            UPDATE_REFS_DIE_ON_ERR);
1410                 goto done;
1411         }
1412
1413         /*
1414          * All the rest are the commits being merged; prepare
1415          * the standard merge summary message to be appended
1416          * to the given message.
1417          */
1418         remoteheads = collect_parents(head_commit, &head_subsumed,
1419                                       argc, argv, &merge_msg);
1420
1421         if (!head_commit || !argc)
1422                 usage_with_options(builtin_merge_usage,
1423                         builtin_merge_options);
1424
1425         if (verify_signatures) {
1426                 for (p = remoteheads; p; p = p->next) {
1427                         verify_merge_signature(p->item, verbosity,
1428                                                check_trust_level);
1429                 }
1430         }
1431
1432         strbuf_addstr(&buf, "merge");
1433         for (p = remoteheads; p; p = p->next)
1434                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1435         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1436         strbuf_reset(&buf);
1437
1438         for (p = remoteheads; p; p = p->next) {
1439                 struct commit *commit = p->item;
1440                 strbuf_addf(&buf, "GITHEAD_%s",
1441                             oid_to_hex(&commit->object.oid));
1442                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1443                 strbuf_reset(&buf);
1444                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1445                         fast_forward = FF_NO;
1446         }
1447
1448         if (!use_strategies) {
1449                 if (!remoteheads)
1450                         ; /* already up-to-date */
1451                 else if (!remoteheads->next)
1452                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1453                 else
1454                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1455         }
1456
1457         for (i = 0; i < use_strategies_nr; i++) {
1458                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1459                         fast_forward = FF_NO;
1460                 if (use_strategies[i]->attr & NO_TRIVIAL)
1461                         allow_trivial = 0;
1462         }
1463
1464         if (!remoteheads)
1465                 ; /* already up-to-date */
1466         else if (!remoteheads->next)
1467                 common = get_merge_bases(head_commit, remoteheads->item);
1468         else {
1469                 struct commit_list *list = remoteheads;
1470                 commit_list_insert(head_commit, &list);
1471                 common = get_octopus_merge_bases(list);
1472                 free(list);
1473         }
1474
1475         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1476                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1477
1478         if (remoteheads && !common) {
1479                 /* No common ancestors found. */
1480                 if (!allow_unrelated_histories)
1481                         die(_("refusing to merge unrelated histories"));
1482                 /* otherwise, we need a real merge. */
1483         } else if (!remoteheads ||
1484                  (!remoteheads->next && !common->next &&
1485                   common->item == remoteheads->item)) {
1486                 /*
1487                  * If head can reach all the merge then we are up to date.
1488                  * but first the most common case of merging one remote.
1489                  */
1490                 finish_up_to_date(_("Already up to date."));
1491                 goto done;
1492         } else if (fast_forward != FF_NO && !remoteheads->next &&
1493                         !common->next &&
1494                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1495                 /* Again the most common case of merging one remote. */
1496                 struct strbuf msg = STRBUF_INIT;
1497                 struct commit *commit;
1498
1499                 if (verbosity >= 0) {
1500                         printf(_("Updating %s..%s\n"),
1501                                find_unique_abbrev(&head_commit->object.oid,
1502                                                   DEFAULT_ABBREV),
1503                                find_unique_abbrev(&remoteheads->item->object.oid,
1504                                                   DEFAULT_ABBREV));
1505                 }
1506                 strbuf_addstr(&msg, "Fast-forward");
1507                 if (have_message)
1508                         strbuf_addstr(&msg,
1509                                 " (no commit created; -m option ignored)");
1510                 commit = remoteheads->item;
1511                 if (!commit) {
1512                         ret = 1;
1513                         goto done;
1514                 }
1515
1516                 if (checkout_fast_forward(the_repository,
1517                                           &head_commit->object.oid,
1518                                           &commit->object.oid,
1519                                           overwrite_ignore)) {
1520                         ret = 1;
1521                         goto done;
1522                 }
1523
1524                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1525                 remove_merge_branch_state(the_repository);
1526                 goto done;
1527         } else if (!remoteheads->next && common->next)
1528                 ;
1529                 /*
1530                  * We are not doing octopus and not fast-forward.  Need
1531                  * a real merge.
1532                  */
1533         else if (!remoteheads->next && !common->next && option_commit) {
1534                 /*
1535                  * We are not doing octopus, not fast-forward, and have
1536                  * only one common.
1537                  */
1538                 refresh_cache(REFRESH_QUIET);
1539                 if (allow_trivial && fast_forward != FF_ONLY) {
1540                         /* See if it is really trivial. */
1541                         git_committer_info(IDENT_STRICT);
1542                         printf(_("Trying really trivial in-index merge...\n"));
1543                         if (!read_tree_trivial(&common->item->object.oid,
1544                                                &head_commit->object.oid,
1545                                                &remoteheads->item->object.oid)) {
1546                                 ret = merge_trivial(head_commit, remoteheads);
1547                                 goto done;
1548                         }
1549                         printf(_("Nope.\n"));
1550                 }
1551         } else {
1552                 /*
1553                  * An octopus.  If we can reach all the remote we are up
1554                  * to date.
1555                  */
1556                 int up_to_date = 1;
1557                 struct commit_list *j;
1558
1559                 for (j = remoteheads; j; j = j->next) {
1560                         struct commit_list *common_one;
1561
1562                         /*
1563                          * Here we *have* to calculate the individual
1564                          * merge_bases again, otherwise "git merge HEAD^
1565                          * HEAD^^" would be missed.
1566                          */
1567                         common_one = get_merge_bases(head_commit, j->item);
1568                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1569                                 up_to_date = 0;
1570                                 break;
1571                         }
1572                 }
1573                 if (up_to_date) {
1574                         finish_up_to_date(_("Already up to date. Yeeah!"));
1575                         goto done;
1576                 }
1577         }
1578
1579         if (fast_forward == FF_ONLY)
1580                 die(_("Not possible to fast-forward, aborting."));
1581
1582         /* We are going to make a new commit. */
1583         git_committer_info(IDENT_STRICT);
1584
1585         /*
1586          * At this point, we need a real merge.  No matter what strategy
1587          * we use, it would operate on the index, possibly affecting the
1588          * working tree, and when resolved cleanly, have the desired
1589          * tree in the index -- this means that the index must be in
1590          * sync with the head commit.  The strategies are responsible
1591          * to ensure this.
1592          */
1593         if (use_strategies_nr == 1 ||
1594             /*
1595              * Stash away the local changes so that we can try more than one.
1596              */
1597             save_state(&stash))
1598                 oidclr(&stash);
1599
1600         for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
1601                 int ret, cnt;
1602                 if (i) {
1603                         printf(_("Rewinding the tree to pristine...\n"));
1604                         restore_state(&head_commit->object.oid, &stash);
1605                 }
1606                 if (use_strategies_nr != 1)
1607                         printf(_("Trying merge strategy %s...\n"),
1608                                 use_strategies[i]->name);
1609                 /*
1610                  * Remember which strategy left the state in the working
1611                  * tree.
1612                  */
1613                 wt_strategy = use_strategies[i]->name;
1614
1615                 ret = try_merge_strategy(use_strategies[i]->name,
1616                                          common, remoteheads,
1617                                          head_commit);
1618                 /*
1619                  * The backend exits with 1 when conflicts are
1620                  * left to be resolved, with 2 when it does not
1621                  * handle the given merge at all.
1622                  */
1623                 if (ret < 2) {
1624                         if (!ret) {
1625                                 if (option_commit) {
1626                                         /* Automerge succeeded. */
1627                                         automerge_was_ok = 1;
1628                                         break;
1629                                 }
1630                                 merge_was_ok = 1;
1631                         }
1632                         cnt = evaluate_result();
1633                         if (best_cnt <= 0 || cnt <= best_cnt) {
1634                                 best_strategy = use_strategies[i]->name;
1635                                 best_cnt = cnt;
1636                         }
1637                 }
1638         }
1639
1640         /*
1641          * If we have a resulting tree, that means the strategy module
1642          * auto resolved the merge cleanly.
1643          */
1644         if (automerge_was_ok) {
1645                 ret = finish_automerge(head_commit, head_subsumed,
1646                                        common, remoteheads,
1647                                        &result_tree, wt_strategy);
1648                 goto done;
1649         }
1650
1651         /*
1652          * Pick the result from the best strategy and have the user fix
1653          * it up.
1654          */
1655         if (!best_strategy) {
1656                 restore_state(&head_commit->object.oid, &stash);
1657                 if (use_strategies_nr > 1)
1658                         fprintf(stderr,
1659                                 _("No merge strategy handled the merge.\n"));
1660                 else
1661                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1662                                 use_strategies[0]->name);
1663                 ret = 2;
1664                 goto done;
1665         } else if (best_strategy == wt_strategy)
1666                 ; /* We already have its result in the working tree. */
1667         else {
1668                 printf(_("Rewinding the tree to pristine...\n"));
1669                 restore_state(&head_commit->object.oid, &stash);
1670                 printf(_("Using the %s to prepare resolving by hand.\n"),
1671                         best_strategy);
1672                 try_merge_strategy(best_strategy, common, remoteheads,
1673                                    head_commit);
1674         }
1675
1676         if (squash)
1677                 finish(head_commit, remoteheads, NULL, NULL);
1678         else
1679                 write_merge_state(remoteheads);
1680
1681         if (merge_was_ok)
1682                 fprintf(stderr, _("Automatic merge went well; "
1683                         "stopped before committing as requested\n"));
1684         else
1685                 ret = suggest_conflicts();
1686
1687 done:
1688         free(branch_to_free);
1689         return ret;
1690 }