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