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

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "lockfile.h"
  13 #include "run-command.h"
  14 #include "diff.h"
  15 #include "refs.h"
  16 #include "commit.h"
  17 #include "diffcore.h"
  18 #include "revision.h"
  19 #include "unpack-trees.h"
  20 #include "cache-tree.h"
  21 #include "dir.h"
  22 #include "utf8.h"
  23 #include "log-tree.h"
  24 #include "color.h"
  25 #include "rerere.h"
  26 #include "help.h"
  27 #include "merge-recursive.h"
  28 #include "resolve-undo.h"
  29 #include "remote.h"
  30 #include "fmt-merge-msg.h"
  31 #include "gpg-interface.h"
  32 #include "sequencer.h"
  33
  34 #define DEFAULT_TWOHEAD (1<<0)
  35 #define DEFAULT_OCTOPUS (1<<1)
  36 #define NO_FAST_FORWARD (1<<2)
  37 #define NO_TRIVIAL      (1<<3)
  38
  39 struct strategy {
  40         const char *name;
  41         unsigned attr;
  42 };
  43
  44 static const char * const builtin_merge_usage[] = {
  45         N_("git merge [<options>] [<commit>...]"),
  46         N_("git merge [<options>] <msg> HEAD <commit>"),
  47         N_("git merge --abort"),
  48         NULL
  49 };
  50
  51 static int show_diffstat = 1, shortlog_len = -1, squash;
  52 static int option_commit = 1;
  53 static int option_edit = -1;
  54 static int allow_trivial = 1, have_message, verify_signatures;
  55 static int overwrite_ignore = 1;
  56 static struct strbuf merge_msg = STRBUF_INIT;
  57 static struct strategy **use_strategies;
  58 static size_t use_strategies_nr, use_strategies_alloc;
  59 static const char **xopts;
  60 static size_t xopts_nr, xopts_alloc;
  61 static const char *branch;
  62 static char *branch_mergeoptions;
  63 static int option_renormalize;
  64 static int verbosity;
  65 static int allow_rerere_auto;
  66 static int abort_current_merge;
  67 static int allow_unrelated_histories;
  68 static int show_progress = -1;
  69 static int default_to_upstream = 1;
  70 static const char *sign_commit;
  71
  72 static struct strategy all_strategy[] = {
  73         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  74         { "octopus",    DEFAULT_OCTOPUS },
  75         { "resolve",    0 },
  76         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  77         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  78 };
  79
  80 static const char *pull_twohead, *pull_octopus;
  81
  82 enum ff_type {
  83         FF_NO,
  84         FF_ALLOW,
  85         FF_ONLY
  86 };
  87
  88 static enum ff_type fast_forward = FF_ALLOW;
  89
  90 static int option_parse_message(const struct option *opt,
  91                                 const char *arg, int unset)
  92 {
  93         struct strbuf *buf = opt->value;
  94
  95         if (unset)
  96                 strbuf_setlen(buf, 0);
  97         else if (arg) {
  98                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  99                 have_message = 1;
 100         } else
 101                 return error(_("switch `m' requires a value"));
 102         return 0;
 103 }
 104
 105 static struct strategy *get_strategy(const char *name)
 106 {
 107         int i;
 108         struct strategy *ret;
 109         static struct cmdnames main_cmds, other_cmds;
 110         static int loaded;
 111
 112         if (!name)
 113                 return NULL;
 114
 115         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 116                 if (!strcmp(name, all_strategy[i].name))
 117                         return &all_strategy[i];
 118
 119         if (!loaded) {
 120                 struct cmdnames not_strategies;
 121                 loaded = 1;
 122
 123                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 124                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 125                 for (i = 0; i < main_cmds.cnt; i++) {
 126                         int j, found = 0;
 127                         struct cmdname *ent = main_cmds.names[i];
 128                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 129                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 130                                                 && !all_strategy[j].name[ent->len])
 131                                         found = 1;
 132                         if (!found)
 133                                 add_cmdname(&not_strategies, ent->name, ent->len);
 134                 }
 135                 exclude_cmds(&main_cmds, &not_strategies);
 136         }
 137         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 138                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 139                 fprintf(stderr, _("Available strategies are:"));
 140                 for (i = 0; i < main_cmds.cnt; i++)
 141                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 142                 fprintf(stderr, ".\n");
 143                 if (other_cmds.cnt) {
 144                         fprintf(stderr, _("Available custom strategies are:"));
 145                         for (i = 0; i < other_cmds.cnt; i++)
 146                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 147                         fprintf(stderr, ".\n");
 148                 }
 149                 exit(1);
 150         }
 151
 152         ret = xcalloc(1, sizeof(struct strategy));
 153         ret->name = xstrdup(name);
 154         ret->attr = NO_TRIVIAL;
 155         return ret;
 156 }
 157
 158 static void append_strategy(struct strategy *s)
 159 {
 160         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 161         use_strategies[use_strategies_nr++] = s;
 162 }
 163
 164 static int option_parse_strategy(const struct option *opt,
 165                                  const char *name, int unset)
 166 {
 167         if (unset)
 168                 return 0;
 169
 170         append_strategy(get_strategy(name));
 171         return 0;
 172 }
 173
 174 static int option_parse_x(const struct option *opt,
 175                           const char *arg, int unset)
 176 {
 177         if (unset)
 178                 return 0;
 179
 180         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 181         xopts[xopts_nr++] = xstrdup(arg);
 182         return 0;
 183 }
 184
 185 static int option_parse_n(const struct option *opt,
 186                           const char *arg, int unset)
 187 {
 188         show_diffstat = unset;
 189         return 0;
 190 }
 191
 192 static struct option builtin_merge_options[] = {
 193         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 194                 N_("do not show a diffstat at the end of the merge"),
 195                 PARSE_OPT_NOARG, option_parse_n },
 196         OPT_BOOL(0, "stat", &show_diffstat,
 197                 N_("show a diffstat at the end of the merge")),
 198         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 199         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 200           N_("add (at most <n>) entries from shortlog to merge commit message"),
 201           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 202         OPT_BOOL(0, "squash", &squash,
 203                 N_("create a single commit instead of doing a merge")),
 204         OPT_BOOL(0, "commit", &option_commit,
 205                 N_("perform a commit if the merge succeeds (default)")),
 206         OPT_BOOL('e', "edit", &option_edit,
 207                 N_("edit message before committing")),
 208         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 209         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
 210                 N_("abort if fast-forward is not possible"),
 211                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
 212         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 213         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 214                 N_("Verify that the named commit has a valid GPG signature")),
 215         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 216                 N_("merge strategy to use"), option_parse_strategy),
 217         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 218                 N_("option for selected merge strategy"), option_parse_x),
 219         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 220                 N_("merge commit message (for a non-fast-forward merge)"),
 221                 option_parse_message),
 222         OPT__VERBOSITY(&verbosity),
 223         OPT_BOOL(0, "abort", &abort_current_merge,
 224                 N_("abort the current in-progress merge")),
 225         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 226                  N_("allow merging unrelated histories")),
 227         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 228         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 229           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 230         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 231         OPT_END()
 232 };
 233
 234 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 235 static void drop_save(void)
 236 {
 237         unlink(git_path_merge_head());
 238         unlink(git_path_merge_msg());
 239         unlink(git_path_merge_mode());
 240 }
 241
 242 static int save_state(unsigned char *stash)
 243 {
 244         int len;
 245         struct child_process cp = CHILD_PROCESS_INIT;
 246         struct strbuf buffer = STRBUF_INIT;
 247         const char *argv[] = {"stash", "create", NULL};
 248
 249         cp.argv = argv;
 250         cp.out = -1;
 251         cp.git_cmd = 1;
 252
 253         if (start_command(&cp))
 254                 die(_("could not run stash."));
 255         len = strbuf_read(&buffer, cp.out, 1024);
 256         close(cp.out);
 257
 258         if (finish_command(&cp) || len < 0)
 259                 die(_("stash failed"));
 260         else if (!len)          /* no changes */
 261                 return -1;
 262         strbuf_setlen(&buffer, buffer.len-1);
 263         if (get_sha1(buffer.buf, stash))
 264                 die(_("not a valid object: %s"), buffer.buf);
 265         return 0;
 266 }
 267
 268 static void read_empty(unsigned const char *sha1, int verbose)
 269 {
 270         int i = 0;
 271         const char *args[7];
 272
 273         args[i++] = "read-tree";
 274         if (verbose)
 275                 args[i++] = "-v";
 276         args[i++] = "-m";
 277         args[i++] = "-u";
 278         args[i++] = EMPTY_TREE_SHA1_HEX;
 279         args[i++] = sha1_to_hex(sha1);
 280         args[i] = NULL;
 281
 282         if (run_command_v_opt(args, RUN_GIT_CMD))
 283                 die(_("read-tree failed"));
 284 }
 285
 286 static void reset_hard(unsigned const char *sha1, int verbose)
 287 {
 288         int i = 0;
 289         const char *args[6];
 290
 291         args[i++] = "read-tree";
 292         if (verbose)
 293                 args[i++] = "-v";
 294         args[i++] = "--reset";
 295         args[i++] = "-u";
 296         args[i++] = sha1_to_hex(sha1);
 297         args[i] = NULL;
 298
 299         if (run_command_v_opt(args, RUN_GIT_CMD))
 300                 die(_("read-tree failed"));
 301 }
 302
 303 static void restore_state(const unsigned char *head,
 304                           const unsigned char *stash)
 305 {
 306         struct strbuf sb = STRBUF_INIT;
 307         const char *args[] = { "stash", "apply", NULL, NULL };
 308
 309         if (is_null_sha1(stash))
 310                 return;
 311
 312         reset_hard(head, 1);
 313
 314         args[2] = sha1_to_hex(stash);
 315
 316         /*
 317          * It is OK to ignore error here, for example when there was
 318          * nothing to restore.
 319          */
 320         run_command_v_opt(args, RUN_GIT_CMD);
 321
 322         strbuf_release(&sb);
 323         refresh_cache(REFRESH_QUIET);
 324 }
 325
 326 /* This is called when no merge was necessary. */
 327 static void finish_up_to_date(const char *msg)
 328 {
 329         if (verbosity >= 0)
 330                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 331         drop_save();
 332 }
 333
 334 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 335 {
 336         struct rev_info rev;
 337         struct strbuf out = STRBUF_INIT;
 338         struct commit_list *j;
 339         const char *filename;
 340         int fd;
 341         struct pretty_print_context ctx = {0};
 342
 343         printf(_("Squash commit -- not updating HEAD\n"));
 344         filename = git_path_squash_msg();
 345         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 346         if (fd < 0)
 347                 die_errno(_("Could not write to '%s'"), filename);
 348
 349         init_revisions(&rev, NULL);
 350         rev.ignore_merges = 1;
 351         rev.commit_format = CMIT_FMT_MEDIUM;
 352
 353         commit->object.flags |= UNINTERESTING;
 354         add_pending_object(&rev, &commit->object, NULL);
 355
 356         for (j = remoteheads; j; j = j->next)
 357                 add_pending_object(&rev, &j->item->object, NULL);
 358
 359         setup_revisions(0, NULL, &rev, NULL);
 360         if (prepare_revision_walk(&rev))
 361                 die(_("revision walk setup failed"));
 362
 363         ctx.abbrev = rev.abbrev;
 364         ctx.date_mode = rev.date_mode;
 365         ctx.fmt = rev.commit_format;
 366
 367         strbuf_addstr(&out, "Squashed commit of the following:\n");
 368         while ((commit = get_revision(&rev)) != NULL) {
 369                 strbuf_addch(&out, '\n');
 370                 strbuf_addf(&out, "commit %s\n",
 371                         oid_to_hex(&commit->object.oid));
 372                 pretty_print_commit(&ctx, commit, &out);
 373         }
 374         if (write_in_full(fd, out.buf, out.len) != out.len)
 375                 die_errno(_("Writing SQUASH_MSG"));
 376         if (close(fd))
 377                 die_errno(_("Finishing SQUASH_MSG"));
 378         strbuf_release(&out);
 379 }
 380
 381 static void finish(struct commit *head_commit,
 382                    struct commit_list *remoteheads,
 383                    const unsigned char *new_head, const char *msg)
 384 {
 385         struct strbuf reflog_message = STRBUF_INIT;
 386         const unsigned char *head = head_commit->object.oid.hash;
 387
 388         if (!msg)
 389                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 390         else {
 391                 if (verbosity >= 0)
 392                         printf("%s\n", msg);
 393                 strbuf_addf(&reflog_message, "%s: %s",
 394                         getenv("GIT_REFLOG_ACTION"), msg);
 395         }
 396         if (squash) {
 397                 squash_message(head_commit, remoteheads);
 398         } else {
 399                 if (verbosity >= 0 && !merge_msg.len)
 400                         printf(_("No merge message -- not updating HEAD\n"));
 401                 else {
 402                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 403                         update_ref(reflog_message.buf, "HEAD",
 404                                 new_head, head, 0,
 405                                 UPDATE_REFS_DIE_ON_ERR);
 406                         /*
 407                          * We ignore errors in 'gc --auto', since the
 408                          * user should see them.
 409                          */
 410                         close_all_packs();
 411                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 412                 }
 413         }
 414         if (new_head && show_diffstat) {
 415                 struct diff_options opts;
 416                 diff_setup(&opts);
 417                 opts.stat_width = -1; /* use full terminal width */
 418                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 419                 opts.output_format |=
 420                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 421                 opts.detect_rename = DIFF_DETECT_RENAME;
 422                 diff_setup_done(&opts);
 423                 diff_tree_sha1(head, new_head, "", &opts);
 424                 diffcore_std(&opts);
 425                 diff_flush(&opts);
 426         }
 427
 428         /* Run a post-merge hook */
 429         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 430
 431         strbuf_release(&reflog_message);
 432 }
 433
 434 /* Get the name for the merge commit's message. */
 435 static void merge_name(const char *remote, struct strbuf *msg)
 436 {
 437         struct commit *remote_head;
 438         unsigned char branch_head[20];
 439         struct strbuf buf = STRBUF_INIT;
 440         struct strbuf bname = STRBUF_INIT;
 441         const char *ptr;
 442         char *found_ref;
 443         int len, early;
 444
 445         strbuf_branchname(&bname, remote);
 446         remote = bname.buf;
 447
 448         memset(branch_head, 0, sizeof(branch_head));
 449         remote_head = get_merge_parent(remote);
 450         if (!remote_head)
 451                 die(_("'%s' does not point to a commit"), remote);
 452
 453         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 454                 if (starts_with(found_ref, "refs/heads/")) {
 455                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 456                                     sha1_to_hex(branch_head), remote);
 457                         goto cleanup;
 458                 }
 459                 if (starts_with(found_ref, "refs/tags/")) {
 460                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 461                                     sha1_to_hex(branch_head), remote);
 462                         goto cleanup;
 463                 }
 464                 if (starts_with(found_ref, "refs/remotes/")) {
 465                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 466                                     sha1_to_hex(branch_head), remote);
 467                         goto cleanup;
 468                 }
 469         }
 470
 471         /* See if remote matches <name>^^^.. or <name>~<number> */
 472         for (len = 0, ptr = remote + strlen(remote);
 473              remote < ptr && ptr[-1] == '^';
 474              ptr--)
 475                 len++;
 476         if (len)
 477                 early = 1;
 478         else {
 479                 early = 0;
 480                 ptr = strrchr(remote, '~');
 481                 if (ptr) {
 482                         int seen_nonzero = 0;
 483
 484                         len++; /* count ~ */
 485                         while (*++ptr && isdigit(*ptr)) {
 486                                 seen_nonzero |= (*ptr != '0');
 487                                 len++;
 488                         }
 489                         if (*ptr)
 490                                 len = 0; /* not ...~<number> */
 491                         else if (seen_nonzero)
 492                                 early = 1;
 493                         else if (len == 1)
 494                                 early = 1; /* "name~" is "name~1"! */
 495                 }
 496         }
 497         if (len) {
 498                 struct strbuf truname = STRBUF_INIT;
 499                 strbuf_addf(&truname, "refs/heads/%s", remote);
 500                 strbuf_setlen(&truname, truname.len - len);
 501                 if (ref_exists(truname.buf)) {
 502                         strbuf_addf(msg,
 503                                     "%s\t\tbranch '%s'%s of .\n",
 504                                     sha1_to_hex(remote_head->object.oid.hash),
 505                                     truname.buf + 11,
 506                                     (early ? " (early part)" : ""));
 507                         strbuf_release(&truname);
 508                         goto cleanup;
 509                 }
 510                 strbuf_release(&truname);
 511         }
 512
 513         if (remote_head->util) {
 514                 struct merge_remote_desc *desc;
 515                 desc = merge_remote_util(remote_head);
 516                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 517                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
 518                                     sha1_to_hex(desc->obj->oid.hash),
 519                                     typename(desc->obj->type),
 520                                     remote);
 521                         goto cleanup;
 522                 }
 523         }
 524
 525         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 526                 sha1_to_hex(remote_head->object.oid.hash), remote);
 527 cleanup:
 528         strbuf_release(&buf);
 529         strbuf_release(&bname);
 530 }
 531
 532 static void parse_branch_merge_options(char *bmo)
 533 {
 534         const char **argv;
 535         int argc;
 536
 537         if (!bmo)
 538                 return;
 539         argc = split_cmdline(bmo, &argv);
 540         if (argc < 0)
 541                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 542                     split_cmdline_strerror(argc));
 543         REALLOC_ARRAY(argv, argc + 2);
 544         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 545         argc++;
 546         argv[0] = "branch.*.mergeoptions";
 547         parse_options(argc, argv, NULL, builtin_merge_options,
 548                       builtin_merge_usage, 0);
 549         free(argv);
 550 }
 551
 552 static int git_merge_config(const char *k, const char *v, void *cb)
 553 {
 554         int status;
 555
 556         if (branch && starts_with(k, "branch.") &&
 557                 starts_with(k + 7, branch) &&
 558                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 559                 free(branch_mergeoptions);
 560                 branch_mergeoptions = xstrdup(v);
 561                 return 0;
 562         }
 563
 564         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 565                 show_diffstat = git_config_bool(k, v);
 566         else if (!strcmp(k, "pull.twohead"))
 567                 return git_config_string(&pull_twohead, k, v);
 568         else if (!strcmp(k, "pull.octopus"))
 569                 return git_config_string(&pull_octopus, k, v);
 570         else if (!strcmp(k, "merge.renormalize"))
 571                 option_renormalize = git_config_bool(k, v);
 572         else if (!strcmp(k, "merge.ff")) {
 573                 int boolval = git_config_maybe_bool(k, v);
 574                 if (0 <= boolval) {
 575                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 576                 } else if (v && !strcmp(v, "only")) {
 577                         fast_forward = FF_ONLY;
 578                 } /* do not barf on values from future versions of git */
 579                 return 0;
 580         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 581                 default_to_upstream = git_config_bool(k, v);
 582                 return 0;
 583         } else if (!strcmp(k, "commit.gpgsign")) {
 584                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 585                 return 0;
 586         }
 587
 588         status = fmt_merge_msg_config(k, v, cb);
 589         if (status)
 590                 return status;
 591         status = git_gpg_config(k, v, NULL);
 592         if (status)
 593                 return status;
 594         return git_diff_ui_config(k, v, cb);
 595 }
 596
 597 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 598                              unsigned char *one)
 599 {
 600         int i, nr_trees = 0;
 601         struct tree *trees[MAX_UNPACK_TREES];
 602         struct tree_desc t[MAX_UNPACK_TREES];
 603         struct unpack_trees_options opts;
 604
 605         memset(&opts, 0, sizeof(opts));
 606         opts.head_idx = 2;
 607         opts.src_index = &the_index;
 608         opts.dst_index = &the_index;
 609         opts.update = 1;
 610         opts.verbose_update = 1;
 611         opts.trivial_merges_only = 1;
 612         opts.merge = 1;
 613         trees[nr_trees] = parse_tree_indirect(common);
 614         if (!trees[nr_trees++])
 615                 return -1;
 616         trees[nr_trees] = parse_tree_indirect(head);
 617         if (!trees[nr_trees++])
 618                 return -1;
 619         trees[nr_trees] = parse_tree_indirect(one);
 620         if (!trees[nr_trees++])
 621                 return -1;
 622         opts.fn = threeway_merge;
 623         cache_tree_free(&active_cache_tree);
 624         for (i = 0; i < nr_trees; i++) {
 625                 parse_tree(trees[i]);
 626                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 627         }
 628         if (unpack_trees(nr_trees, t, &opts))
 629                 return -1;
 630         return 0;
 631 }
 632
 633 static void write_tree_trivial(unsigned char *sha1)
 634 {
 635         if (write_cache_as_tree(sha1, 0, NULL))
 636                 die(_("git write-tree failed to write a tree"));
 637 }
 638
 639 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 640                               struct commit_list *remoteheads,
 641                               struct commit *head, const char *head_arg)
 642 {
 643         static struct lock_file lock;
 644
 645         hold_locked_index(&lock, 1);
 646         refresh_cache(REFRESH_QUIET);
 647         if (active_cache_changed &&
 648             write_locked_index(&the_index, &lock, COMMIT_LOCK))
 649                 return error(_("Unable to write index."));
 650         rollback_lock_file(&lock);
 651
 652         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 653                 int clean, x;
 654                 struct commit *result;
 655                 struct commit_list *reversed = NULL;
 656                 struct merge_options o;
 657                 struct commit_list *j;
 658
 659                 if (remoteheads->next) {
 660                         error(_("Not handling anything other than two heads merge."));
 661                         return 2;
 662                 }
 663
 664                 init_merge_options(&o);
 665                 if (!strcmp(strategy, "subtree"))
 666                         o.subtree_shift = "";
 667
 668                 o.renormalize = option_renormalize;
 669                 o.show_rename_progress =
 670                         show_progress == -1 ? isatty(2) : show_progress;
 671
 672                 for (x = 0; x < xopts_nr; x++)
 673                         if (parse_merge_opt(&o, xopts[x]))
 674                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 675
 676                 o.branch1 = head_arg;
 677                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 678
 679                 for (j = common; j; j = j->next)
 680                         commit_list_insert(j->item, &reversed);
 681
 682                 hold_locked_index(&lock, 1);
 683                 clean = merge_recursive(&o, head,
 684                                 remoteheads->item, reversed, &result);
 685                 if (active_cache_changed &&
 686                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
 687                         die (_("unable to write %s"), get_index_file());
 688                 rollback_lock_file(&lock);
 689                 return clean ? 0 : 1;
 690         } else {
 691                 return try_merge_command(strategy, xopts_nr, xopts,
 692                                                 common, head_arg, remoteheads);
 693         }
 694 }
 695
 696 static void count_diff_files(struct diff_queue_struct *q,
 697                              struct diff_options *opt, void *data)
 698 {
 699         int *count = data;
 700
 701         (*count) += q->nr;
 702 }
 703
 704 static int count_unmerged_entries(void)
 705 {
 706         int i, ret = 0;
 707
 708         for (i = 0; i < active_nr; i++)
 709                 if (ce_stage(active_cache[i]))
 710                         ret++;
 711
 712         return ret;
 713 }
 714
 715 static void split_merge_strategies(const char *string, struct strategy **list,
 716                                    int *nr, int *alloc)
 717 {
 718         char *p, *q, *buf;
 719
 720         if (!string)
 721                 return;
 722
 723         buf = xstrdup(string);
 724         q = buf;
 725         for (;;) {
 726                 p = strchr(q, ' ');
 727                 if (!p) {
 728                         ALLOC_GROW(*list, *nr + 1, *alloc);
 729                         (*list)[(*nr)++].name = xstrdup(q);
 730                         free(buf);
 731                         return;
 732                 } else {
 733                         *p = '\0';
 734                         ALLOC_GROW(*list, *nr + 1, *alloc);
 735                         (*list)[(*nr)++].name = xstrdup(q);
 736                         q = ++p;
 737                 }
 738         }
 739 }
 740
 741 static void add_strategies(const char *string, unsigned attr)
 742 {
 743         struct strategy *list = NULL;
 744         int list_alloc = 0, list_nr = 0, i;
 745
 746         memset(&list, 0, sizeof(list));
 747         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 748         if (list) {
 749                 for (i = 0; i < list_nr; i++)
 750                         append_strategy(get_strategy(list[i].name));
 751                 return;
 752         }
 753         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 754                 if (all_strategy[i].attr & attr)
 755                         append_strategy(&all_strategy[i]);
 756
 757 }
 758
 759 static void write_merge_msg(struct strbuf *msg)
 760 {
 761         const char *filename = git_path_merge_msg();
 762         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 763         if (fd < 0)
 764                 die_errno(_("Could not open '%s' for writing"),
 765                           filename);
 766         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 767                 die_errno(_("Could not write to '%s'"), filename);
 768         close(fd);
 769 }
 770
 771 static void read_merge_msg(struct strbuf *msg)
 772 {
 773         const char *filename = git_path_merge_msg();
 774         strbuf_reset(msg);
 775         if (strbuf_read_file(msg, filename, 0) < 0)
 776                 die_errno(_("Could not read from '%s'"), filename);
 777 }
 778
 779 static void write_merge_state(struct commit_list *);
 780 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 781 {
 782         if (err_msg)
 783                 error("%s", err_msg);
 784         fprintf(stderr,
 785                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 786         write_merge_state(remoteheads);
 787         exit(1);
 788 }
 789
 790 static const char merge_editor_comment[] =
 791 N_("Please enter a commit message to explain why this merge is necessary,\n"
 792    "especially if it merges an updated upstream into a topic branch.\n"
 793    "\n"
 794    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 795    "the commit.\n");
 796
 797 static void prepare_to_commit(struct commit_list *remoteheads)
 798 {
 799         struct strbuf msg = STRBUF_INIT;
 800         strbuf_addbuf(&msg, &merge_msg);
 801         strbuf_addch(&msg, '\n');
 802         if (0 < option_edit)
 803                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 804         write_merge_msg(&msg);
 805         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 806                             git_path_merge_msg(), "merge", NULL))
 807                 abort_commit(remoteheads, NULL);
 808         if (0 < option_edit) {
 809                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
 810                         abort_commit(remoteheads, NULL);
 811         }
 812         read_merge_msg(&msg);
 813         strbuf_stripspace(&msg, 0 < option_edit);
 814         if (!msg.len)
 815                 abort_commit(remoteheads, _("Empty commit message."));
 816         strbuf_release(&merge_msg);
 817         strbuf_addbuf(&merge_msg, &msg);
 818         strbuf_release(&msg);
 819 }
 820
 821 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 822 {
 823         unsigned char result_tree[20], result_commit[20];
 824         struct commit_list *parents, **pptr = &parents;
 825
 826         write_tree_trivial(result_tree);
 827         printf(_("Wonderful.\n"));
 828         pptr = commit_list_append(head, pptr);
 829         pptr = commit_list_append(remoteheads->item, pptr);
 830         prepare_to_commit(remoteheads);
 831         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 832                         result_commit, NULL, sign_commit))
 833                 die(_("failed to write commit object"));
 834         finish(head, remoteheads, result_commit, "In-index merge");
 835         drop_save();
 836         return 0;
 837 }
 838
 839 static int finish_automerge(struct commit *head,
 840                             int head_subsumed,
 841                             struct commit_list *common,
 842                             struct commit_list *remoteheads,
 843                             unsigned char *result_tree,
 844                             const char *wt_strategy)
 845 {
 846         struct commit_list *parents = NULL;
 847         struct strbuf buf = STRBUF_INIT;
 848         unsigned char result_commit[20];
 849
 850         free_commit_list(common);
 851         parents = remoteheads;
 852         if (!head_subsumed || fast_forward == FF_NO)
 853                 commit_list_insert(head, &parents);
 854         strbuf_addch(&merge_msg, '\n');
 855         prepare_to_commit(remoteheads);
 856         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 857                         result_commit, NULL, sign_commit))
 858                 die(_("failed to write commit object"));
 859         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 860         finish(head, remoteheads, result_commit, buf.buf);
 861         strbuf_release(&buf);
 862         drop_save();
 863         return 0;
 864 }
 865
 866 static int suggest_conflicts(void)
 867 {
 868         const char *filename;
 869         FILE *fp;
 870         struct strbuf msgbuf = STRBUF_INIT;
 871
 872         filename = git_path_merge_msg();
 873         fp = fopen(filename, "a");
 874         if (!fp)
 875                 die_errno(_("Could not open '%s' for writing"), filename);
 876
 877         append_conflicts_hint(&msgbuf);
 878         fputs(msgbuf.buf, fp);
 879         strbuf_release(&msgbuf);
 880         fclose(fp);
 881         rerere(allow_rerere_auto);
 882         printf(_("Automatic merge failed; "
 883                         "fix conflicts and then commit the result.\n"));
 884         return 1;
 885 }
 886
 887 static struct commit *is_old_style_invocation(int argc, const char **argv,
 888                                               const unsigned char *head)
 889 {
 890         struct commit *second_token = NULL;
 891         if (argc > 2) {
 892                 unsigned char second_sha1[20];
 893
 894                 if (get_sha1(argv[1], second_sha1))
 895                         return NULL;
 896                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 897                 if (!second_token)
 898                         die(_("'%s' is not a commit"), argv[1]);
 899                 if (hashcmp(second_token->object.oid.hash, head))
 900                         return NULL;
 901         }
 902         return second_token;
 903 }
 904
 905 static int evaluate_result(void)
 906 {
 907         int cnt = 0;
 908         struct rev_info rev;
 909
 910         /* Check how many files differ. */
 911         init_revisions(&rev, "");
 912         setup_revisions(0, NULL, &rev, NULL);
 913         rev.diffopt.output_format |=
 914                 DIFF_FORMAT_CALLBACK;
 915         rev.diffopt.format_callback = count_diff_files;
 916         rev.diffopt.format_callback_data = &cnt;
 917         run_diff_files(&rev, 0);
 918
 919         /*
 920          * Check how many unmerged entries are
 921          * there.
 922          */
 923         cnt += count_unmerged_entries();
 924
 925         return cnt;
 926 }
 927
 928 /*
 929  * Pretend as if the user told us to merge with the remote-tracking
 930  * branch we have for the upstream of the current branch
 931  */
 932 static int setup_with_upstream(const char ***argv)
 933 {
 934         struct branch *branch = branch_get(NULL);
 935         int i;
 936         const char **args;
 937
 938         if (!branch)
 939                 die(_("No current branch."));
 940         if (!branch->remote_name)
 941                 die(_("No remote for the current branch."));
 942         if (!branch->merge_nr)
 943                 die(_("No default upstream defined for the current branch."));
 944
 945         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 946         for (i = 0; i < branch->merge_nr; i++) {
 947                 if (!branch->merge[i]->dst)
 948                         die(_("No remote-tracking branch for %s from %s"),
 949                             branch->merge[i]->src, branch->remote_name);
 950                 args[i] = branch->merge[i]->dst;
 951         }
 952         args[i] = NULL;
 953         *argv = args;
 954         return i;
 955 }
 956
 957 static void write_merge_state(struct commit_list *remoteheads)
 958 {
 959         const char *filename;
 960         int fd;
 961         struct commit_list *j;
 962         struct strbuf buf = STRBUF_INIT;
 963
 964         for (j = remoteheads; j; j = j->next) {
 965                 struct object_id *oid;
 966                 struct commit *c = j->item;
 967                 if (c->util && merge_remote_util(c)->obj) {
 968                         oid = &merge_remote_util(c)->obj->oid;
 969                 } else {
 970                         oid = &c->object.oid;
 971                 }
 972                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 973         }
 974         filename = git_path_merge_head();
 975         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 976         if (fd < 0)
 977                 die_errno(_("Could not open '%s' for writing"), filename);
 978         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 979                 die_errno(_("Could not write to '%s'"), filename);
 980         close(fd);
 981         strbuf_addch(&merge_msg, '\n');
 982         write_merge_msg(&merge_msg);
 983
 984         filename = git_path_merge_mode();
 985         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
 986         if (fd < 0)
 987                 die_errno(_("Could not open '%s' for writing"), filename);
 988         strbuf_reset(&buf);
 989         if (fast_forward == FF_NO)
 990                 strbuf_addf(&buf, "no-ff");
 991         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 992                 die_errno(_("Could not write to '%s'"), filename);
 993         close(fd);
 994 }
 995
 996 static int default_edit_option(void)
 997 {
 998         static const char name[] = "GIT_MERGE_AUTOEDIT";
 999         const char *e = getenv(name);
1000         struct stat st_stdin, st_stdout;
1001
1002         if (have_message)
1003                 /* an explicit -m msg without --[no-]edit */
1004                 return 0;
1005
1006         if (e) {
1007                 int v = git_config_maybe_bool(name, e);
1008                 if (v < 0)
1009                         die("Bad value '%s' in environment '%s'", e, name);
1010                 return v;
1011         }
1012
1013         /* Use editor if stdin and stdout are the same and is a tty */
1014         return (!fstat(0, &st_stdin) &&
1015                 !fstat(1, &st_stdout) &&
1016                 isatty(0) && isatty(1) &&
1017                 st_stdin.st_dev == st_stdout.st_dev &&
1018                 st_stdin.st_ino == st_stdout.st_ino &&
1019                 st_stdin.st_mode == st_stdout.st_mode);
1020 }
1021
1022 static struct commit_list *reduce_parents(struct commit *head_commit,
1023                                           int *head_subsumed,
1024                                           struct commit_list *remoteheads)
1025 {
1026         struct commit_list *parents, **remotes;
1027
1028         /*
1029          * Is the current HEAD reachable from another commit being
1030          * merged?  If so we do not want to record it as a parent of
1031          * the resulting merge, unless --no-ff is given.  We will flip
1032          * this variable to 0 when we find HEAD among the independent
1033          * tips being merged.
1034          */
1035         *head_subsumed = 1;
1036
1037         /* Find what parents to record by checking independent ones. */
1038         parents = reduce_heads(remoteheads);
1039
1040         remoteheads = NULL;
1041         remotes = &remoteheads;
1042         while (parents) {
1043                 struct commit *commit = pop_commit(&parents);
1044                 if (commit == head_commit)
1045                         *head_subsumed = 0;
1046                 else
1047                         remotes = &commit_list_insert(commit, remotes)->next;
1048         }
1049         return remoteheads;
1050 }
1051
1052 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1053 {
1054         struct fmt_merge_msg_opts opts;
1055
1056         memset(&opts, 0, sizeof(opts));
1057         opts.add_title = !have_message;
1058         opts.shortlog_len = shortlog_len;
1059         opts.credit_people = (0 < option_edit);
1060
1061         fmt_merge_msg(merge_names, merge_msg, &opts);
1062         if (merge_msg->len)
1063                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1064 }
1065
1066 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1067 {
1068         const char *filename;
1069         int fd, pos, npos;
1070         struct strbuf fetch_head_file = STRBUF_INIT;
1071
1072         if (!merge_names)
1073                 merge_names = &fetch_head_file;
1074
1075         filename = git_path_fetch_head();
1076         fd = open(filename, O_RDONLY);
1077         if (fd < 0)
1078                 die_errno(_("could not open '%s' for reading"), filename);
1079
1080         if (strbuf_read(merge_names, fd, 0) < 0)
1081                 die_errno(_("could not read '%s'"), filename);
1082         if (close(fd) < 0)
1083                 die_errno(_("could not close '%s'"), filename);
1084
1085         for (pos = 0; pos < merge_names->len; pos = npos) {
1086                 unsigned char sha1[20];
1087                 char *ptr;
1088                 struct commit *commit;
1089
1090                 ptr = strchr(merge_names->buf + pos, '\n');
1091                 if (ptr)
1092                         npos = ptr - merge_names->buf + 1;
1093                 else
1094                         npos = merge_names->len;
1095
1096                 if (npos - pos < 40 + 2 ||
1097                     get_sha1_hex(merge_names->buf + pos, sha1))
1098                         commit = NULL; /* bad */
1099                 else if (memcmp(merge_names->buf + pos + 40, "\t\t", 2))
1100                         continue; /* not-for-merge */
1101                 else {
1102                         char saved = merge_names->buf[pos + 40];
1103                         merge_names->buf[pos + 40] = '\0';
1104                         commit = get_merge_parent(merge_names->buf + pos);
1105                         merge_names->buf[pos + 40] = saved;
1106                 }
1107                 if (!commit) {
1108                         if (ptr)
1109                                 *ptr = '\0';
1110                         die("not something we can merge in %s: %s",
1111                             filename, merge_names->buf + pos);
1112                 }
1113                 remotes = &commit_list_insert(commit, remotes)->next;
1114         }
1115
1116         if (merge_names == &fetch_head_file)
1117                 strbuf_release(&fetch_head_file);
1118 }
1119
1120 static struct commit_list *collect_parents(struct commit *head_commit,
1121                                            int *head_subsumed,
1122                                            int argc, const char **argv,
1123                                            struct strbuf *merge_msg)
1124 {
1125         int i;
1126         struct commit_list *remoteheads = NULL;
1127         struct commit_list **remotes = &remoteheads;
1128         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1129
1130         if (merge_msg && (!have_message || shortlog_len))
1131                 autogen = &merge_names;
1132
1133         if (head_commit)
1134                 remotes = &commit_list_insert(head_commit, remotes)->next;
1135
1136         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1137                 handle_fetch_head(remotes, autogen);
1138                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1139         } else {
1140                 for (i = 0; i < argc; i++) {
1141                         struct commit *commit = get_merge_parent(argv[i]);
1142                         if (!commit)
1143                                 help_unknown_ref(argv[i], "merge",
1144                                                  "not something we can merge");
1145                         remotes = &commit_list_insert(commit, remotes)->next;
1146                 }
1147                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1148                 if (autogen) {
1149                         struct commit_list *p;
1150                         for (p = remoteheads; p; p = p->next)
1151                                 merge_name(merge_remote_util(p->item)->name, autogen);
1152                 }
1153         }
1154
1155         if (autogen) {
1156                 prepare_merge_message(autogen, merge_msg);
1157                 strbuf_release(autogen);
1158         }
1159
1160         return remoteheads;
1161 }
1162
1163 int cmd_merge(int argc, const char **argv, const char *prefix)
1164 {
1165         unsigned char result_tree[20];
1166         unsigned char stash[20];
1167         unsigned char head_sha1[20];
1168         struct commit *head_commit;
1169         struct strbuf buf = STRBUF_INIT;
1170         const char *head_arg;
1171         int flag, i, ret = 0, head_subsumed;
1172         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1173         struct commit_list *common = NULL;
1174         const char *best_strategy = NULL, *wt_strategy = NULL;
1175         struct commit_list *remoteheads, *p;
1176         void *branch_to_free;
1177
1178         if (argc == 2 && !strcmp(argv[1], "-h"))
1179                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1180
1181         /*
1182          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1183          * current branch.
1184          */
1185         branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1186         if (branch && starts_with(branch, "refs/heads/"))
1187                 branch += 11;
1188         if (!branch || is_null_sha1(head_sha1))
1189                 head_commit = NULL;
1190         else
1191                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1192
1193         init_diff_ui_defaults();
1194         git_config(git_merge_config, NULL);
1195
1196         if (branch_mergeoptions)
1197                 parse_branch_merge_options(branch_mergeoptions);
1198         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1199                         builtin_merge_usage, 0);
1200         if (shortlog_len < 0)
1201                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1202
1203         if (verbosity < 0 && show_progress == -1)
1204                 show_progress = 0;
1205
1206         if (abort_current_merge) {
1207                 int nargc = 2;
1208                 const char *nargv[] = {"reset", "--merge", NULL};
1209
1210                 if (!file_exists(git_path_merge_head()))
1211                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1212
1213                 /* Invoke 'git reset --merge' */
1214                 ret = cmd_reset(nargc, nargv, prefix);
1215                 goto done;
1216         }
1217
1218         if (read_cache_unmerged())
1219                 die_resolve_conflict("merge");
1220
1221         if (file_exists(git_path_merge_head())) {
1222                 /*
1223                  * There is no unmerged entry, don't advise 'git
1224                  * add/rm <file>', just 'git commit'.
1225                  */
1226                 if (advice_resolve_conflict)
1227                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1228                                   "Please, commit your changes before you merge."));
1229                 else
1230                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1231         }
1232         if (file_exists(git_path_cherry_pick_head())) {
1233                 if (advice_resolve_conflict)
1234                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1235                             "Please, commit your changes before you merge."));
1236                 else
1237                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1238         }
1239         resolve_undo_clear();
1240
1241         if (verbosity < 0)
1242                 show_diffstat = 0;
1243
1244         if (squash) {
1245                 if (fast_forward == FF_NO)
1246                         die(_("You cannot combine --squash with --no-ff."));
1247                 option_commit = 0;
1248         }
1249
1250         if (!argc) {
1251                 if (default_to_upstream)
1252                         argc = setup_with_upstream(&argv);
1253                 else
1254                         die(_("No commit specified and merge.defaultToUpstream not set."));
1255         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1256                 argv[0] = "@{-1}";
1257         }
1258
1259         if (!argc)
1260                 usage_with_options(builtin_merge_usage,
1261                         builtin_merge_options);
1262
1263         if (!head_commit) {
1264                 /*
1265                  * If the merged head is a valid one there is no reason
1266                  * to forbid "git merge" into a branch yet to be born.
1267                  * We do the same for "git pull".
1268                  */
1269                 unsigned char *remote_head_sha1;
1270                 if (squash)
1271                         die(_("Squash commit into empty head not supported yet"));
1272                 if (fast_forward == FF_NO)
1273                         die(_("Non-fast-forward commit does not make sense into "
1274                             "an empty head"));
1275                 remoteheads = collect_parents(head_commit, &head_subsumed,
1276                                               argc, argv, NULL);
1277                 if (!remoteheads)
1278                         die(_("%s - not something we can merge"), argv[0]);
1279                 if (remoteheads->next)
1280                         die(_("Can merge only exactly one commit into empty head"));
1281                 remote_head_sha1 = remoteheads->item->object.oid.hash;
1282                 read_empty(remote_head_sha1, 0);
1283                 update_ref("initial pull", "HEAD", remote_head_sha1,
1284                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1285                 goto done;
1286         }
1287
1288         /*
1289          * This could be traditional "merge <msg> HEAD <commit>..."  and
1290          * the way we can tell it is to see if the second token is HEAD,
1291          * but some people might have misused the interface and used a
1292          * commit-ish that is the same as HEAD there instead.
1293          * Traditional format never would have "-m" so it is an
1294          * additional safety measure to check for it.
1295          */
1296         if (!have_message &&
1297             is_old_style_invocation(argc, argv, head_commit->object.oid.hash)) {
1298                 warning("old-style 'git merge <msg> HEAD <commit>' is deprecated.");
1299                 strbuf_addstr(&merge_msg, argv[0]);
1300                 head_arg = argv[1];
1301                 argv += 2;
1302                 argc -= 2;
1303                 remoteheads = collect_parents(head_commit, &head_subsumed,
1304                                               argc, argv, NULL);
1305         } else {
1306                 /* We are invoked directly as the first-class UI. */
1307                 head_arg = "HEAD";
1308
1309                 /*
1310                  * All the rest are the commits being merged; prepare
1311                  * the standard merge summary message to be appended
1312                  * to the given message.
1313                  */
1314                 remoteheads = collect_parents(head_commit, &head_subsumed,
1315                                               argc, argv, &merge_msg);
1316         }
1317
1318         if (!head_commit || !argc)
1319                 usage_with_options(builtin_merge_usage,
1320                         builtin_merge_options);
1321
1322         if (verify_signatures) {
1323                 for (p = remoteheads; p; p = p->next) {
1324                         struct commit *commit = p->item;
1325                         char hex[GIT_SHA1_HEXSZ + 1];
1326                         struct signature_check signature_check;
1327                         memset(&signature_check, 0, sizeof(signature_check));
1328
1329                         check_commit_signature(commit, &signature_check);
1330
1331                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1332                         switch (signature_check.result) {
1333                         case 'G':
1334                                 break;
1335                         case 'U':
1336                                 die(_("Commit %s has an untrusted GPG signature, "
1337                                       "allegedly by %s."), hex, signature_check.signer);
1338                         case 'B':
1339                                 die(_("Commit %s has a bad GPG signature "
1340                                       "allegedly by %s."), hex, signature_check.signer);
1341                         default: /* 'N' */
1342                                 die(_("Commit %s does not have a GPG signature."), hex);
1343                         }
1344                         if (verbosity >= 0 && signature_check.result == 'G')
1345                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1346                                        hex, signature_check.signer);
1347
1348                         signature_check_clear(&signature_check);
1349                 }
1350         }
1351
1352         strbuf_addstr(&buf, "merge");
1353         for (p = remoteheads; p; p = p->next)
1354                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1355         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1356         strbuf_reset(&buf);
1357
1358         for (p = remoteheads; p; p = p->next) {
1359                 struct commit *commit = p->item;
1360                 strbuf_addf(&buf, "GITHEAD_%s",
1361                             sha1_to_hex(commit->object.oid.hash));
1362                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1363                 strbuf_reset(&buf);
1364                 if (fast_forward != FF_ONLY &&
1365                     merge_remote_util(commit) &&
1366                     merge_remote_util(commit)->obj &&
1367                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1368                         fast_forward = FF_NO;
1369         }
1370
1371         if (option_edit < 0)
1372                 option_edit = default_edit_option();
1373
1374         if (!use_strategies) {
1375                 if (!remoteheads)
1376                         ; /* already up-to-date */
1377                 else if (!remoteheads->next)
1378                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1379                 else
1380                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1381         }
1382
1383         for (i = 0; i < use_strategies_nr; i++) {
1384                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1385                         fast_forward = FF_NO;
1386                 if (use_strategies[i]->attr & NO_TRIVIAL)
1387                         allow_trivial = 0;
1388         }
1389
1390         if (!remoteheads)
1391                 ; /* already up-to-date */
1392         else if (!remoteheads->next)
1393                 common = get_merge_bases(head_commit, remoteheads->item);
1394         else {
1395                 struct commit_list *list = remoteheads;
1396                 commit_list_insert(head_commit, &list);
1397                 common = get_octopus_merge_bases(list);
1398                 free(list);
1399         }
1400
1401         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.oid.hash,
1402                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1403
1404         if (remoteheads && !common) {
1405                 /* No common ancestors found. */
1406                 if (!allow_unrelated_histories)
1407                         die(_("refusing to merge unrelated histories"));
1408                 /* otherwise, we need a real merge. */
1409         } else if (!remoteheads ||
1410                  (!remoteheads->next && !common->next &&
1411                   common->item == remoteheads->item)) {
1412                 /*
1413                  * If head can reach all the merge then we are up to date.
1414                  * but first the most common case of merging one remote.
1415                  */
1416                 finish_up_to_date("Already up-to-date.");
1417                 goto done;
1418         } else if (fast_forward != FF_NO && !remoteheads->next &&
1419                         !common->next &&
1420                         !hashcmp(common->item->object.oid.hash, head_commit->object.oid.hash)) {
1421                 /* Again the most common case of merging one remote. */
1422                 struct strbuf msg = STRBUF_INIT;
1423                 struct commit *commit;
1424
1425                 if (verbosity >= 0) {
1426                         char from[GIT_SHA1_HEXSZ + 1], to[GIT_SHA1_HEXSZ + 1];
1427                         find_unique_abbrev_r(from, head_commit->object.oid.hash,
1428                                               DEFAULT_ABBREV);
1429                         find_unique_abbrev_r(to, remoteheads->item->object.oid.hash,
1430                                               DEFAULT_ABBREV);
1431                         printf(_("Updating %s..%s\n"), from, to);
1432                 }
1433                 strbuf_addstr(&msg, "Fast-forward");
1434                 if (have_message)
1435                         strbuf_addstr(&msg,
1436                                 " (no commit created; -m option ignored)");
1437                 commit = remoteheads->item;
1438                 if (!commit) {
1439                         ret = 1;
1440                         goto done;
1441                 }
1442
1443                 if (checkout_fast_forward(head_commit->object.oid.hash,
1444                                           commit->object.oid.hash,
1445                                           overwrite_ignore)) {
1446                         ret = 1;
1447                         goto done;
1448                 }
1449
1450                 finish(head_commit, remoteheads, commit->object.oid.hash, msg.buf);
1451                 drop_save();
1452                 goto done;
1453         } else if (!remoteheads->next && common->next)
1454                 ;
1455                 /*
1456                  * We are not doing octopus and not fast-forward.  Need
1457                  * a real merge.
1458                  */
1459         else if (!remoteheads->next && !common->next && option_commit) {
1460                 /*
1461                  * We are not doing octopus, not fast-forward, and have
1462                  * only one common.
1463                  */
1464                 refresh_cache(REFRESH_QUIET);
1465                 if (allow_trivial && fast_forward != FF_ONLY) {
1466                         /* See if it is really trivial. */
1467                         git_committer_info(IDENT_STRICT);
1468                         printf(_("Trying really trivial in-index merge...\n"));
1469                         if (!read_tree_trivial(common->item->object.oid.hash,
1470                                                head_commit->object.oid.hash,
1471                                                remoteheads->item->object.oid.hash)) {
1472                                 ret = merge_trivial(head_commit, remoteheads);
1473                                 goto done;
1474                         }
1475                         printf(_("Nope.\n"));
1476                 }
1477         } else {
1478                 /*
1479                  * An octopus.  If we can reach all the remote we are up
1480                  * to date.
1481                  */
1482                 int up_to_date = 1;
1483                 struct commit_list *j;
1484
1485                 for (j = remoteheads; j; j = j->next) {
1486                         struct commit_list *common_one;
1487
1488                         /*
1489                          * Here we *have* to calculate the individual
1490                          * merge_bases again, otherwise "git merge HEAD^
1491                          * HEAD^^" would be missed.
1492                          */
1493                         common_one = get_merge_bases(head_commit, j->item);
1494                         if (hashcmp(common_one->item->object.oid.hash,
1495                                 j->item->object.oid.hash)) {
1496                                 up_to_date = 0;
1497                                 break;
1498                         }
1499                 }
1500                 if (up_to_date) {
1501                         finish_up_to_date("Already up-to-date. Yeeah!");
1502                         goto done;
1503                 }
1504         }
1505
1506         if (fast_forward == FF_ONLY)
1507                 die(_("Not possible to fast-forward, aborting."));
1508
1509         /* We are going to make a new commit. */
1510         git_committer_info(IDENT_STRICT);
1511
1512         /*
1513          * At this point, we need a real merge.  No matter what strategy
1514          * we use, it would operate on the index, possibly affecting the
1515          * working tree, and when resolved cleanly, have the desired
1516          * tree in the index -- this means that the index must be in
1517          * sync with the head commit.  The strategies are responsible
1518          * to ensure this.
1519          */
1520         if (use_strategies_nr == 1 ||
1521             /*
1522              * Stash away the local changes so that we can try more than one.
1523              */
1524             save_state(stash))
1525                 hashcpy(stash, null_sha1);
1526
1527         for (i = 0; i < use_strategies_nr; i++) {
1528                 int ret;
1529                 if (i) {
1530                         printf(_("Rewinding the tree to pristine...\n"));
1531                         restore_state(head_commit->object.oid.hash, stash);
1532                 }
1533                 if (use_strategies_nr != 1)
1534                         printf(_("Trying merge strategy %s...\n"),
1535                                 use_strategies[i]->name);
1536                 /*
1537                  * Remember which strategy left the state in the working
1538                  * tree.
1539                  */
1540                 wt_strategy = use_strategies[i]->name;
1541
1542                 ret = try_merge_strategy(use_strategies[i]->name,
1543                                          common, remoteheads,
1544                                          head_commit, head_arg);
1545                 if (!option_commit && !ret) {
1546                         merge_was_ok = 1;
1547                         /*
1548                          * This is necessary here just to avoid writing
1549                          * the tree, but later we will *not* exit with
1550                          * status code 1 because merge_was_ok is set.
1551                          */
1552                         ret = 1;
1553                 }
1554
1555                 if (ret) {
1556                         /*
1557                          * The backend exits with 1 when conflicts are
1558                          * left to be resolved, with 2 when it does not
1559                          * handle the given merge at all.
1560                          */
1561                         if (ret == 1) {
1562                                 int cnt = evaluate_result();
1563
1564                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1565                                         best_strategy = use_strategies[i]->name;
1566                                         best_cnt = cnt;
1567                                 }
1568                         }
1569                         if (merge_was_ok)
1570                                 break;
1571                         else
1572                                 continue;
1573                 }
1574
1575                 /* Automerge succeeded. */
1576                 write_tree_trivial(result_tree);
1577                 automerge_was_ok = 1;
1578                 break;
1579         }
1580
1581         /*
1582          * If we have a resulting tree, that means the strategy module
1583          * auto resolved the merge cleanly.
1584          */
1585         if (automerge_was_ok) {
1586                 ret = finish_automerge(head_commit, head_subsumed,
1587                                        common, remoteheads,
1588                                        result_tree, wt_strategy);
1589                 goto done;
1590         }
1591
1592         /*
1593          * Pick the result from the best strategy and have the user fix
1594          * it up.
1595          */
1596         if (!best_strategy) {
1597                 restore_state(head_commit->object.oid.hash, stash);
1598                 if (use_strategies_nr > 1)
1599                         fprintf(stderr,
1600                                 _("No merge strategy handled the merge.\n"));
1601                 else
1602                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1603                                 use_strategies[0]->name);
1604                 ret = 2;
1605                 goto done;
1606         } else if (best_strategy == wt_strategy)
1607                 ; /* We already have its result in the working tree. */
1608         else {
1609                 printf(_("Rewinding the tree to pristine...\n"));
1610                 restore_state(head_commit->object.oid.hash, stash);
1611                 printf(_("Using the %s to prepare resolving by hand.\n"),
1612                         best_strategy);
1613                 try_merge_strategy(best_strategy, common, remoteheads,
1614                                    head_commit, head_arg);
1615         }
1616
1617         if (squash)
1618                 finish(head_commit, remoteheads, NULL, NULL);
1619         else
1620                 write_merge_state(remoteheads);
1621
1622         if (merge_was_ok)
1623                 fprintf(stderr, _("Automatic merge went well; "
1624                         "stopped before committing as requested\n"));
1625         else
1626                 ret = suggest_conflicts();
1627
1628 done:
1629         free(branch_to_free);
1630         return ret;
1631 }