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