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

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "lockfile.h"
  13 #include "run-command.h"
  14 #include "diff.h"
  15 #include "refs.h"
  16 #include "commit.h"
  17 #include "diffcore.h"
  18 #include "revision.h"
  19 #include "unpack-trees.h"
  20 #include "cache-tree.h"
  21 #include "dir.h"
  22 #include "utf8.h"
  23 #include "log-tree.h"
  24 #include "color.h"
  25 #include "rerere.h"
  26 #include "help.h"
  27 #include "merge-recursive.h"
  28 #include "resolve-undo.h"
  29 #include "remote.h"
  30 #include "fmt-merge-msg.h"
  31 #include "gpg-interface.h"
  32 #include "sequencer.h"
  33
  34 #define DEFAULT_TWOHEAD (1<<0)
  35 #define DEFAULT_OCTOPUS (1<<1)
  36 #define NO_FAST_FORWARD (1<<2)
  37 #define NO_TRIVIAL      (1<<3)
  38
  39 struct strategy {
  40         const char *name;
  41         unsigned attr;
  42 };
  43
  44 static const char * const builtin_merge_usage[] = {
  45         N_("git merge [<options>] [<commit>...]"),
  46         N_("git merge [<options>] <msg> HEAD <commit>"),
  47         N_("git merge --abort"),
  48         NULL
  49 };
  50
  51 static int show_diffstat = 1, shortlog_len = -1, squash;
  52 static int option_commit = 1;
  53 static int option_edit = -1;
  54 static int allow_trivial = 1, have_message, verify_signatures;
  55 static int overwrite_ignore = 1;
  56 static struct strbuf merge_msg = STRBUF_INIT;
  57 static struct strategy **use_strategies;
  58 static size_t use_strategies_nr, use_strategies_alloc;
  59 static const char **xopts;
  60 static size_t xopts_nr, xopts_alloc;
  61 static const char *branch;
  62 static char *branch_mergeoptions;
  63 static int option_renormalize;
  64 static int verbosity;
  65 static int allow_rerere_auto;
  66 static int abort_current_merge;
  67 static int show_progress = -1;
  68 static int default_to_upstream = 1;
  69 static const char *sign_commit;
  70 static int reverse_parents;
  71
  72 static struct strategy all_strategy[] = {
  73         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  74         { "octopus",    DEFAULT_OCTOPUS },
  75         { "resolve",    0 },
  76         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  77         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  78 };
  79
  80 static const char *pull_twohead, *pull_octopus;
  81
  82 enum ff_type {
  83         FF_NO,
  84         FF_ALLOW,
  85         FF_ONLY
  86 };
  87
  88 static enum ff_type fast_forward = FF_ALLOW;
  89
  90 static int option_parse_message(const struct option *opt,
  91                                 const char *arg, int unset)
  92 {
  93         struct strbuf *buf = opt->value;
  94
  95         if (unset)
  96                 strbuf_setlen(buf, 0);
  97         else if (arg) {
  98                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  99                 have_message = 1;
 100         } else
 101                 return error(_("switch `m' requires a value"));
 102         return 0;
 103 }
 104
 105 static struct strategy *get_strategy(const char *name)
 106 {
 107         int i;
 108         struct strategy *ret;
 109         static struct cmdnames main_cmds, other_cmds;
 110         static int loaded;
 111
 112         if (!name)
 113                 return NULL;
 114
 115         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 116                 if (!strcmp(name, all_strategy[i].name))
 117                         return &all_strategy[i];
 118
 119         if (!loaded) {
 120                 struct cmdnames not_strategies;
 121                 loaded = 1;
 122
 123                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 124                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 125                 for (i = 0; i < main_cmds.cnt; i++) {
 126                         int j, found = 0;
 127                         struct cmdname *ent = main_cmds.names[i];
 128                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 129                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 130                                                 && !all_strategy[j].name[ent->len])
 131                                         found = 1;
 132                         if (!found)
 133                                 add_cmdname(&not_strategies, ent->name, ent->len);
 134                 }
 135                 exclude_cmds(&main_cmds, &not_strategies);
 136         }
 137         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 138                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 139                 fprintf(stderr, _("Available strategies are:"));
 140                 for (i = 0; i < main_cmds.cnt; i++)
 141                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 142                 fprintf(stderr, ".\n");
 143                 if (other_cmds.cnt) {
 144                         fprintf(stderr, _("Available custom strategies are:"));
 145                         for (i = 0; i < other_cmds.cnt; i++)
 146                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 147                         fprintf(stderr, ".\n");
 148                 }
 149                 exit(1);
 150         }
 151
 152         ret = xcalloc(1, sizeof(struct strategy));
 153         ret->name = xstrdup(name);
 154         ret->attr = NO_TRIVIAL;
 155         return ret;
 156 }
 157
 158 static void append_strategy(struct strategy *s)
 159 {
 160         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 161         use_strategies[use_strategies_nr++] = s;
 162 }
 163
 164 static int option_parse_strategy(const struct option *opt,
 165                                  const char *name, int unset)
 166 {
 167         if (unset)
 168                 return 0;
 169
 170         append_strategy(get_strategy(name));
 171         return 0;
 172 }
 173
 174 static int option_parse_x(const struct option *opt,
 175                           const char *arg, int unset)
 176 {
 177         if (unset)
 178                 return 0;
 179
 180         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 181         xopts[xopts_nr++] = xstrdup(arg);
 182         return 0;
 183 }
 184
 185 static int option_parse_n(const struct option *opt,
 186                           const char *arg, int unset)
 187 {
 188         show_diffstat = unset;
 189         return 0;
 190 }
 191
 192 static struct option builtin_merge_options[] = {
 193         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 194                 N_("do not show a diffstat at the end of the merge"),
 195                 PARSE_OPT_NOARG, option_parse_n },
 196         OPT_BOOL(0, "stat", &show_diffstat,
 197                 N_("show a diffstat at the end of the merge")),
 198         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 199         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 200           N_("add (at most <n>) entries from shortlog to merge commit message"),
 201           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 202         OPT_BOOL(0, "squash", &squash,
 203                 N_("create a single commit instead of doing a merge")),
 204         OPT_BOOL(0, "commit", &option_commit,
 205                 N_("perform a commit if the merge succeeds (default)")),
 206         OPT_BOOL('e', "edit", &option_edit,
 207                 N_("edit message before committing")),
 208         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 209         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
 210                 N_("abort if fast-forward is not possible"),
 211                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
 212         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 213         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 214                 N_("Verify that the named commit has a valid GPG signature")),
 215         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 216                 N_("merge strategy to use"), option_parse_strategy),
 217         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 218                 N_("option for selected merge strategy"), option_parse_x),
 219         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 220                 N_("merge commit message (for a non-fast-forward merge)"),
 221                 option_parse_message),
 222         OPT__VERBOSITY(&verbosity),
 223         OPT_BOOL(0, "abort", &abort_current_merge,
 224                 N_("abort the current in-progress merge")),
 225         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 226         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 227           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 228         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 229         OPT_BOOL(0, "reverse-parents", &reverse_parents,
 230                 N_("reverse the order of parents")),
 231         OPT_END()
 232 };
 233
 234 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 235 static void drop_save(void)
 236 {
 237         unlink(git_path_merge_head());
 238         unlink(git_path_merge_msg());
 239         unlink(git_path_merge_mode());
 240 }
 241
 242 static int save_state(unsigned char *stash)
 243 {
 244         int len;
 245         struct child_process cp = CHILD_PROCESS_INIT;
 246         struct strbuf buffer = STRBUF_INIT;
 247         const char *argv[] = {"stash", "create", NULL};
 248
 249         cp.argv = argv;
 250         cp.out = -1;
 251         cp.git_cmd = 1;
 252
 253         if (start_command(&cp))
 254                 die(_("could not run stash."));
 255         len = strbuf_read(&buffer, cp.out, 1024);
 256         close(cp.out);
 257
 258         if (finish_command(&cp) || len < 0)
 259                 die(_("stash failed"));
 260         else if (!len)          /* no changes */
 261                 return -1;
 262         strbuf_setlen(&buffer, buffer.len-1);
 263         if (get_sha1(buffer.buf, stash))
 264                 die(_("not a valid object: %s"), buffer.buf);
 265         return 0;
 266 }
 267
 268 static void read_empty(unsigned const char *sha1, int verbose)
 269 {
 270         int i = 0;
 271         const char *args[7];
 272
 273         args[i++] = "read-tree";
 274         if (verbose)
 275                 args[i++] = "-v";
 276         args[i++] = "-m";
 277         args[i++] = "-u";
 278         args[i++] = EMPTY_TREE_SHA1_HEX;
 279         args[i++] = sha1_to_hex(sha1);
 280         args[i] = NULL;
 281
 282         if (run_command_v_opt(args, RUN_GIT_CMD))
 283                 die(_("read-tree failed"));
 284 }
 285
 286 static void reset_hard(unsigned const char *sha1, int verbose)
 287 {
 288         int i = 0;
 289         const char *args[6];
 290
 291         args[i++] = "read-tree";
 292         if (verbose)
 293                 args[i++] = "-v";
 294         args[i++] = "--reset";
 295         args[i++] = "-u";
 296         args[i++] = sha1_to_hex(sha1);
 297         args[i] = NULL;
 298
 299         if (run_command_v_opt(args, RUN_GIT_CMD))
 300                 die(_("read-tree failed"));
 301 }
 302
 303 static void restore_state(const unsigned char *head,
 304                           const unsigned char *stash)
 305 {
 306         struct strbuf sb = STRBUF_INIT;
 307         const char *args[] = { "stash", "apply", NULL, NULL };
 308
 309         if (is_null_sha1(stash))
 310                 return;
 311
 312         reset_hard(head, 1);
 313
 314         args[2] = sha1_to_hex(stash);
 315
 316         /*
 317          * It is OK to ignore error here, for example when there was
 318          * nothing to restore.
 319          */
 320         run_command_v_opt(args, RUN_GIT_CMD);
 321
 322         strbuf_release(&sb);
 323         refresh_cache(REFRESH_QUIET);
 324 }
 325
 326 /* This is called when no merge was necessary. */
 327 static void finish_up_to_date(const char *msg)
 328 {
 329         if (verbosity >= 0)
 330                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 331         drop_save();
 332 }
 333
 334 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 335 {
 336         struct rev_info rev;
 337         struct strbuf out = STRBUF_INIT;
 338         struct commit_list *j;
 339         const char *filename;
 340         int fd;
 341         struct pretty_print_context ctx = {0};
 342
 343         printf(_("Squash commit -- not updating HEAD\n"));
 344         filename = git_path_squash_msg();
 345         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 346         if (fd < 0)
 347                 die_errno(_("Could not write to '%s'"), filename);
 348
 349         init_revisions(&rev, NULL);
 350         rev.ignore_merges = 1;
 351         rev.commit_format = CMIT_FMT_MEDIUM;
 352
 353         commit->object.flags |= UNINTERESTING;
 354         add_pending_object(&rev, &commit->object, NULL);
 355
 356         for (j = remoteheads; j; j = j->next)
 357                 add_pending_object(&rev, &j->item->object, NULL);
 358
 359         setup_revisions(0, NULL, &rev, NULL);
 360         if (prepare_revision_walk(&rev))
 361                 die(_("revision walk setup failed"));
 362
 363         ctx.abbrev = rev.abbrev;
 364         ctx.date_mode = rev.date_mode;
 365         ctx.fmt = rev.commit_format;
 366
 367         strbuf_addstr(&out, "Squashed commit of the following:\n");
 368         while ((commit = get_revision(&rev)) != NULL) {
 369                 strbuf_addch(&out, '\n');
 370                 strbuf_addf(&out, "commit %s\n",
 371                         oid_to_hex(&commit->object.oid));
 372                 pretty_print_commit(&ctx, commit, &out);
 373         }
 374         if (write_in_full(fd, out.buf, out.len) != out.len)
 375                 die_errno(_("Writing SQUASH_MSG"));
 376         if (close(fd))
 377                 die_errno(_("Finishing SQUASH_MSG"));
 378         strbuf_release(&out);
 379 }
 380
 381 static void finish(struct commit *head_commit,
 382                    struct commit_list *remoteheads,
 383                    const unsigned char *new_head, const char *msg)
 384 {
 385         struct strbuf reflog_message = STRBUF_INIT;
 386         const unsigned char *head = head_commit->object.oid.hash;
 387
 388         if (!msg)
 389                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 390         else {
 391                 if (verbosity >= 0)
 392                         printf("%s\n", msg);
 393                 strbuf_addf(&reflog_message, "%s: %s",
 394                         getenv("GIT_REFLOG_ACTION"), msg);
 395         }
 396         if (squash) {
 397                 squash_message(head_commit, remoteheads);
 398         } else {
 399                 if (verbosity >= 0 && !merge_msg.len)
 400                         printf(_("No merge message -- not updating HEAD\n"));
 401                 else {
 402                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 403                         update_ref(reflog_message.buf, "HEAD",
 404                                 new_head, head, 0,
 405                                 UPDATE_REFS_DIE_ON_ERR);
 406                         /*
 407                          * We ignore errors in 'gc --auto', since the
 408                          * user should see them.
 409                          */
 410                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 411                 }
 412         }
 413         if (new_head && show_diffstat) {
 414                 struct diff_options opts;
 415                 diff_setup(&opts);
 416                 opts.stat_width = -1; /* use full terminal width */
 417                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 418                 opts.output_format |=
 419                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 420                 opts.detect_rename = DIFF_DETECT_RENAME;
 421                 diff_setup_done(&opts);
 422                 diff_tree_sha1(head, new_head, "", &opts);
 423                 diffcore_std(&opts);
 424                 diff_flush(&opts);
 425         }
 426
 427         /* Run a post-merge hook */
 428         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 429
 430         strbuf_release(&reflog_message);
 431 }
 432
 433 /* Get the name for the merge commit's message. */
 434 static void merge_name(const char *remote, struct strbuf *msg)
 435 {
 436         struct commit *remote_head;
 437         unsigned char branch_head[20];
 438         struct strbuf buf = STRBUF_INIT;
 439         struct strbuf bname = STRBUF_INIT;
 440         const char *ptr;
 441         char *found_ref;
 442         int len, early;
 443
 444         strbuf_branchname(&bname, remote);
 445         remote = bname.buf;
 446
 447         memset(branch_head, 0, sizeof(branch_head));
 448         remote_head = get_merge_parent(remote);
 449         if (!remote_head)
 450                 die(_("'%s' does not point to a commit"), remote);
 451
 452         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 453                 if (starts_with(found_ref, "refs/heads/")) {
 454                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 455                                     sha1_to_hex(branch_head), remote);
 456                         goto cleanup;
 457                 }
 458                 if (starts_with(found_ref, "refs/tags/")) {
 459                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 460                                     sha1_to_hex(branch_head), remote);
 461                         goto cleanup;
 462                 }
 463                 if (starts_with(found_ref, "refs/remotes/")) {
 464                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 465                                     sha1_to_hex(branch_head), remote);
 466                         goto cleanup;
 467                 }
 468         }
 469
 470         /* See if remote matches <name>^^^.. or <name>~<number> */
 471         for (len = 0, ptr = remote + strlen(remote);
 472              remote < ptr && ptr[-1] == '^';
 473              ptr--)
 474                 len++;
 475         if (len)
 476                 early = 1;
 477         else {
 478                 early = 0;
 479                 ptr = strrchr(remote, '~');
 480                 if (ptr) {
 481                         int seen_nonzero = 0;
 482
 483                         len++; /* count ~ */
 484                         while (*++ptr && isdigit(*ptr)) {
 485                                 seen_nonzero |= (*ptr != '0');
 486                                 len++;
 487                         }
 488                         if (*ptr)
 489                                 len = 0; /* not ...~<number> */
 490                         else if (seen_nonzero)
 491                                 early = 1;
 492                         else if (len == 1)
 493                                 early = 1; /* "name~" is "name~1"! */
 494                 }
 495         }
 496         if (len) {
 497                 struct strbuf truname = STRBUF_INIT;
 498                 strbuf_addf(&truname, "refs/heads/%s", remote);
 499                 strbuf_setlen(&truname, truname.len - len);
 500                 if (ref_exists(truname.buf)) {
 501                         strbuf_addf(msg,
 502                                     "%s\t\tbranch '%s'%s of .\n",
 503                                     sha1_to_hex(remote_head->object.oid.hash),
 504                                     truname.buf + 11,
 505                                     (early ? " (early part)" : ""));
 506                         strbuf_release(&truname);
 507                         goto cleanup;
 508                 }
 509                 strbuf_release(&truname);
 510         }
 511
 512         if (remote_head->util) {
 513                 struct merge_remote_desc *desc;
 514                 desc = merge_remote_util(remote_head);
 515                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 516                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
 517                                     sha1_to_hex(desc->obj->oid.hash),
 518                                     typename(desc->obj->type),
 519                                     remote);
 520                         goto cleanup;
 521                 }
 522         }
 523
 524         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 525                 sha1_to_hex(remote_head->object.oid.hash), remote);
 526 cleanup:
 527         strbuf_release(&buf);
 528         strbuf_release(&bname);
 529 }
 530
 531 static void parse_branch_merge_options(char *bmo)
 532 {
 533         const char **argv;
 534         int argc;
 535
 536         if (!bmo)
 537                 return;
 538         argc = split_cmdline(bmo, &argv);
 539         if (argc < 0)
 540                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 541                     split_cmdline_strerror(argc));
 542         REALLOC_ARRAY(argv, argc + 2);
 543         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 544         argc++;
 545         argv[0] = "branch.*.mergeoptions";
 546         parse_options(argc, argv, NULL, builtin_merge_options,
 547                       builtin_merge_usage, 0);
 548         free(argv);
 549 }
 550
 551 static int git_merge_config(const char *k, const char *v, void *cb)
 552 {
 553         int status;
 554
 555         if (branch && starts_with(k, "branch.") &&
 556                 starts_with(k + 7, branch) &&
 557                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 558                 free(branch_mergeoptions);
 559                 branch_mergeoptions = xstrdup(v);
 560                 return 0;
 561         }
 562
 563         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 564                 show_diffstat = git_config_bool(k, v);
 565         else if (!strcmp(k, "pull.twohead"))
 566                 return git_config_string(&pull_twohead, k, v);
 567         else if (!strcmp(k, "pull.octopus"))
 568                 return git_config_string(&pull_octopus, k, v);
 569         else if (!strcmp(k, "merge.renormalize"))
 570                 option_renormalize = git_config_bool(k, v);
 571         else if (!strcmp(k, "merge.ff")) {
 572                 int boolval = git_config_maybe_bool(k, v);
 573                 if (0 <= boolval) {
 574                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 575                 } else if (v && !strcmp(v, "only")) {
 576                         fast_forward = FF_ONLY;
 577                 } /* do not barf on values from future versions of git */
 578                 return 0;
 579         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 580                 default_to_upstream = git_config_bool(k, v);
 581                 return 0;
 582         } else if (!strcmp(k, "commit.gpgsign")) {
 583                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 584                 return 0;
 585         }
 586
 587         status = fmt_merge_msg_config(k, v, cb);
 588         if (status)
 589                 return status;
 590         status = git_gpg_config(k, v, NULL);
 591         if (status)
 592                 return status;
 593         return git_diff_ui_config(k, v, cb);
 594 }
 595
 596 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 597                              unsigned char *one)
 598 {
 599         int i, nr_trees = 0;
 600         struct tree *trees[MAX_UNPACK_TREES];
 601         struct tree_desc t[MAX_UNPACK_TREES];
 602         struct unpack_trees_options opts;
 603
 604         memset(&opts, 0, sizeof(opts));
 605         opts.head_idx = 2;
 606         opts.src_index = &the_index;
 607         opts.dst_index = &the_index;
 608         opts.update = 1;
 609         opts.verbose_update = 1;
 610         opts.trivial_merges_only = 1;
 611         opts.merge = 1;
 612         trees[nr_trees] = parse_tree_indirect(common);
 613         if (!trees[nr_trees++])
 614                 return -1;
 615         trees[nr_trees] = parse_tree_indirect(head);
 616         if (!trees[nr_trees++])
 617                 return -1;
 618         trees[nr_trees] = parse_tree_indirect(one);
 619         if (!trees[nr_trees++])
 620                 return -1;
 621         opts.fn = threeway_merge;
 622         cache_tree_free(&active_cache_tree);
 623         for (i = 0; i < nr_trees; i++) {
 624                 parse_tree(trees[i]);
 625                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 626         }
 627         if (unpack_trees(nr_trees, t, &opts))
 628                 return -1;
 629         return 0;
 630 }
 631
 632 static void write_tree_trivial(unsigned char *sha1)
 633 {
 634         if (write_cache_as_tree(sha1, 0, NULL))
 635                 die(_("git write-tree failed to write a tree"));
 636 }
 637
 638 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 639                               struct commit_list *remoteheads,
 640                               struct commit *head, const char *head_arg)
 641 {
 642         static struct lock_file lock;
 643
 644         hold_locked_index(&lock, 1);
 645         refresh_cache(REFRESH_QUIET);
 646         if (active_cache_changed &&
 647             write_locked_index(&the_index, &lock, COMMIT_LOCK))
 648                 return error(_("Unable to write index."));
 649         rollback_lock_file(&lock);
 650
 651         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 652                 int clean, x;
 653                 struct commit *result;
 654                 struct commit_list *reversed = NULL;
 655                 struct merge_options o;
 656                 struct commit_list *j;
 657
 658                 if (remoteheads->next) {
 659                         error(_("Not handling anything other than two heads merge."));
 660                         return 2;
 661                 }
 662
 663                 init_merge_options(&o);
 664                 if (!strcmp(strategy, "subtree"))
 665                         o.subtree_shift = "";
 666
 667                 o.renormalize = option_renormalize;
 668                 o.show_rename_progress =
 669                         show_progress == -1 ? isatty(2) : show_progress;
 670
 671                 for (x = 0; x < xopts_nr; x++)
 672                         if (parse_merge_opt(&o, xopts[x]))
 673                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 674
 675                 o.branch1 = head_arg;
 676                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 677
 678                 for (j = common; j; j = j->next)
 679                         commit_list_insert(j->item, &reversed);
 680
 681                 hold_locked_index(&lock, 1);
 682                 clean = merge_recursive(&o, head,
 683                                 remoteheads->item, reversed, &result);
 684                 if (active_cache_changed &&
 685                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
 686                         die (_("unable to write %s"), get_index_file());
 687                 rollback_lock_file(&lock);
 688                 return clean ? 0 : 1;
 689         } else {
 690                 return try_merge_command(strategy, xopts_nr, xopts,
 691                                                 common, head_arg, remoteheads);
 692         }
 693 }
 694
 695 static void count_diff_files(struct diff_queue_struct *q,
 696                              struct diff_options *opt, void *data)
 697 {
 698         int *count = data;
 699
 700         (*count) += q->nr;
 701 }
 702
 703 static int count_unmerged_entries(void)
 704 {
 705         int i, ret = 0;
 706
 707         for (i = 0; i < active_nr; i++)
 708                 if (ce_stage(active_cache[i]))
 709                         ret++;
 710
 711         return ret;
 712 }
 713
 714 static void split_merge_strategies(const char *string, struct strategy **list,
 715                                    int *nr, int *alloc)
 716 {
 717         char *p, *q, *buf;
 718
 719         if (!string)
 720                 return;
 721
 722         buf = xstrdup(string);
 723         q = buf;
 724         for (;;) {
 725                 p = strchr(q, ' ');
 726                 if (!p) {
 727                         ALLOC_GROW(*list, *nr + 1, *alloc);
 728                         (*list)[(*nr)++].name = xstrdup(q);
 729                         free(buf);
 730                         return;
 731                 } else {
 732                         *p = '\0';
 733                         ALLOC_GROW(*list, *nr + 1, *alloc);
 734                         (*list)[(*nr)++].name = xstrdup(q);
 735                         q = ++p;
 736                 }
 737         }
 738 }
 739
 740 static void add_strategies(const char *string, unsigned attr)
 741 {
 742         struct strategy *list = NULL;
 743         int list_alloc = 0, list_nr = 0, i;
 744
 745         memset(&list, 0, sizeof(list));
 746         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 747         if (list) {
 748                 for (i = 0; i < list_nr; i++)
 749                         append_strategy(get_strategy(list[i].name));
 750                 return;
 751         }
 752         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 753                 if (all_strategy[i].attr & attr)
 754                         append_strategy(&all_strategy[i]);
 755
 756 }
 757
 758 static void write_merge_msg(struct strbuf *msg)
 759 {
 760         const char *filename = git_path_merge_msg();
 761         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 762         if (fd < 0)
 763                 die_errno(_("Could not open '%s' for writing"),
 764                           filename);
 765         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 766                 die_errno(_("Could not write to '%s'"), filename);
 767         close(fd);
 768 }
 769
 770 static void read_merge_msg(struct strbuf *msg)
 771 {
 772         const char *filename = git_path_merge_msg();
 773         strbuf_reset(msg);
 774         if (strbuf_read_file(msg, filename, 0) < 0)
 775                 die_errno(_("Could not read from '%s'"), filename);
 776 }
 777
 778 static void write_merge_state(struct commit_list *);
 779 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 780 {
 781         if (err_msg)
 782                 error("%s", err_msg);
 783         fprintf(stderr,
 784                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 785         write_merge_state(remoteheads);
 786         exit(1);
 787 }
 788
 789 static const char merge_editor_comment[] =
 790 N_("Please enter a commit message to explain why this merge is necessary,\n"
 791    "especially if it merges an updated upstream into a topic branch.\n"
 792    "\n"
 793    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 794    "the commit.\n");
 795
 796 static void prepare_to_commit(struct commit_list *remoteheads)
 797 {
 798         struct strbuf msg = STRBUF_INIT;
 799         strbuf_addbuf(&msg, &merge_msg);
 800         strbuf_addch(&msg, '\n');
 801         if (0 < option_edit)
 802                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 803         write_merge_msg(&msg);
 804         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 805                             git_path_merge_msg(), "merge", NULL))
 806                 abort_commit(remoteheads, NULL);
 807         if (0 < option_edit) {
 808                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
 809                         abort_commit(remoteheads, NULL);
 810         }
 811         read_merge_msg(&msg);
 812         strbuf_stripspace(&msg, 0 < option_edit);
 813         if (!msg.len)
 814                 abort_commit(remoteheads, _("Empty commit message."));
 815         strbuf_release(&merge_msg);
 816         strbuf_addbuf(&merge_msg, &msg);
 817         strbuf_release(&msg);
 818 }
 819
 820 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 821 {
 822         unsigned char result_tree[20], result_commit[20];
 823         struct commit_list *parents, **pptr = &parents;
 824
 825         write_tree_trivial(result_tree);
 826         printf(_("Wonderful.\n"));
 827         pptr = commit_list_append(head, pptr);
 828         pptr = commit_list_append(remoteheads->item, pptr);
 829         prepare_to_commit(remoteheads);
 830         if (reverse_parents)
 831                 parents = reverse_heads(parents);
 832         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 833                         result_commit, NULL, sign_commit))
 834                 die(_("failed to write commit object"));
 835         finish(head, remoteheads, result_commit, "In-index merge");
 836         drop_save();
 837         return 0;
 838 }
 839
 840 static int finish_automerge(struct commit *head,
 841                             int head_subsumed,
 842                             struct commit_list *common,
 843                             struct commit_list *remoteheads,
 844                             unsigned char *result_tree,
 845                             const char *wt_strategy)
 846 {
 847         struct commit_list *parents = NULL;
 848         struct strbuf buf = STRBUF_INIT;
 849         unsigned char result_commit[20];
 850
 851         free_commit_list(common);
 852         parents = remoteheads;
 853         if (!head_subsumed || fast_forward == FF_NO)
 854                 commit_list_insert(head, &parents);
 855         if (reverse_parents)
 856                 parents = reverse_heads(parents);
 857         strbuf_addch(&merge_msg, '\n');
 858         prepare_to_commit(remoteheads);
 859         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 860                         result_commit, NULL, sign_commit))
 861                 die(_("failed to write commit object"));
 862         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 863         finish(head, remoteheads, result_commit, buf.buf);
 864         strbuf_release(&buf);
 865         drop_save();
 866         return 0;
 867 }
 868
 869 static int suggest_conflicts(void)
 870 {
 871         const char *filename;
 872         FILE *fp;
 873         struct strbuf msgbuf = STRBUF_INIT;
 874
 875         filename = git_path_merge_msg();
 876         fp = fopen(filename, "a");
 877         if (!fp)
 878                 die_errno(_("Could not open '%s' for writing"), filename);
 879
 880         append_conflicts_hint(&msgbuf);
 881         fputs(msgbuf.buf, fp);
 882         strbuf_release(&msgbuf);
 883         fclose(fp);
 884         rerere(allow_rerere_auto);
 885         printf(_("Automatic merge failed; "
 886                         "fix conflicts and then commit the result.\n"));
 887         return 1;
 888 }
 889
 890 static struct commit *is_old_style_invocation(int argc, const char **argv,
 891                                               const unsigned char *head)
 892 {
 893         struct commit *second_token = NULL;
 894         if (argc > 2) {
 895                 unsigned char second_sha1[20];
 896
 897                 if (get_sha1(argv[1], second_sha1))
 898                         return NULL;
 899                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 900                 if (!second_token)
 901                         die(_("'%s' is not a commit"), argv[1]);
 902                 if (hashcmp(second_token->object.oid.hash, head))
 903                         return NULL;
 904         }
 905         return second_token;
 906 }
 907
 908 static int evaluate_result(void)
 909 {
 910         int cnt = 0;
 911         struct rev_info rev;
 912
 913         /* Check how many files differ. */
 914         init_revisions(&rev, "");
 915         setup_revisions(0, NULL, &rev, NULL);
 916         rev.diffopt.output_format |=
 917                 DIFF_FORMAT_CALLBACK;
 918         rev.diffopt.format_callback = count_diff_files;
 919         rev.diffopt.format_callback_data = &cnt;
 920         run_diff_files(&rev, 0);
 921
 922         /*
 923          * Check how many unmerged entries are
 924          * there.
 925          */
 926         cnt += count_unmerged_entries();
 927
 928         return cnt;
 929 }
 930
 931 /*
 932  * Pretend as if the user told us to merge with the remote-tracking
 933  * branch we have for the upstream of the current branch
 934  */
 935 static int setup_with_upstream(const char ***argv)
 936 {
 937         struct branch *branch = branch_get(NULL);
 938         int i;
 939         const char **args;
 940
 941         if (!branch)
 942                 die(_("No current branch."));
 943         if (!branch->remote_name)
 944                 die(_("No remote for the current branch."));
 945         if (!branch->merge_nr)
 946                 die(_("No default upstream defined for the current branch."));
 947
 948         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 949         for (i = 0; i < branch->merge_nr; i++) {
 950                 if (!branch->merge[i]->dst)
 951                         die(_("No remote-tracking branch for %s from %s"),
 952                             branch->merge[i]->src, branch->remote_name);
 953                 args[i] = branch->merge[i]->dst;
 954         }
 955         args[i] = NULL;
 956         *argv = args;
 957         return i;
 958 }
 959
 960 static void write_merge_state(struct commit_list *remoteheads)
 961 {
 962         const char *filename;
 963         int fd;
 964         struct commit_list *j;
 965         struct strbuf buf = STRBUF_INIT;
 966
 967         for (j = remoteheads; j; j = j->next) {
 968                 struct object_id *oid;
 969                 struct commit *c = j->item;
 970                 if (c->util && merge_remote_util(c)->obj) {
 971                         oid = &merge_remote_util(c)->obj->oid;
 972                 } else {
 973                         oid = &c->object.oid;
 974                 }
 975                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 976         }
 977         filename = git_path_merge_head();
 978         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 979         if (fd < 0)
 980                 die_errno(_("Could not open '%s' for writing"), filename);
 981         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 982                 die_errno(_("Could not write to '%s'"), filename);
 983         close(fd);
 984         strbuf_addch(&merge_msg, '\n');
 985         write_merge_msg(&merge_msg);
 986
 987         filename = git_path_merge_mode();
 988         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
 989         if (fd < 0)
 990                 die_errno(_("Could not open '%s' for writing"), filename);
 991         strbuf_reset(&buf);
 992         if (fast_forward == FF_NO)
 993                 strbuf_addf(&buf, "no-ff ");
 994         if (reverse_parents)
 995                 strbuf_addf(&buf, "reverse ");
 996         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 997                 die_errno(_("Could not write to '%s'"), filename);
 998         close(fd);
 999 }
1000
1001 static int default_edit_option(void)
1002 {
1003         static const char name[] = "GIT_MERGE_AUTOEDIT";
1004         const char *e = getenv(name);
1005         struct stat st_stdin, st_stdout;
1006
1007         if (have_message)
1008                 /* an explicit -m msg without --[no-]edit */
1009                 return 0;
1010
1011         if (e) {
1012                 int v = git_config_maybe_bool(name, e);
1013                 if (v < 0)
1014                         die("Bad value '%s' in environment '%s'", e, name);
1015                 return v;
1016         }
1017
1018         /* Use editor if stdin and stdout are the same and is a tty */
1019         return (!fstat(0, &st_stdin) &&
1020                 !fstat(1, &st_stdout) &&
1021                 isatty(0) && isatty(1) &&
1022                 st_stdin.st_dev == st_stdout.st_dev &&
1023                 st_stdin.st_ino == st_stdout.st_ino &&
1024                 st_stdin.st_mode == st_stdout.st_mode);
1025 }
1026
1027 static struct commit_list *reduce_parents(struct commit *head_commit,
1028                                           int *head_subsumed,
1029                                           struct commit_list *remoteheads)
1030 {
1031         struct commit_list *parents, **remotes;
1032
1033         /*
1034          * Is the current HEAD reachable from another commit being
1035          * merged?  If so we do not want to record it as a parent of
1036          * the resulting merge, unless --no-ff is given.  We will flip
1037          * this variable to 0 when we find HEAD among the independent
1038          * tips being merged.
1039          */
1040         *head_subsumed = 1;
1041
1042         /* Find what parents to record by checking independent ones. */
1043         parents = reduce_heads(remoteheads);
1044
1045         remoteheads = NULL;
1046         remotes = &remoteheads;
1047         while (parents) {
1048                 struct commit *commit = pop_commit(&parents);
1049                 if (commit == head_commit)
1050                         *head_subsumed = 0;
1051                 else
1052                         remotes = &commit_list_insert(commit, remotes)->next;
1053         }
1054         return remoteheads;
1055 }
1056
1057 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1058 {
1059         struct fmt_merge_msg_opts opts;
1060
1061         memset(&opts, 0, sizeof(opts));
1062         opts.add_title = !have_message;
1063         opts.shortlog_len = shortlog_len;
1064         opts.credit_people = (0 < option_edit);
1065
1066         fmt_merge_msg(merge_names, merge_msg, &opts);
1067         if (merge_msg->len)
1068                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1069 }
1070
1071 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1072 {
1073         const char *filename;
1074         int fd, pos, npos;
1075         struct strbuf fetch_head_file = STRBUF_INIT;
1076
1077         if (!merge_names)
1078                 merge_names = &fetch_head_file;
1079
1080         filename = git_path_fetch_head();
1081         fd = open(filename, O_RDONLY);
1082         if (fd < 0)
1083                 die_errno(_("could not open '%s' for reading"), filename);
1084
1085         if (strbuf_read(merge_names, fd, 0) < 0)
1086                 die_errno(_("could not read '%s'"), filename);
1087         if (close(fd) < 0)
1088                 die_errno(_("could not close '%s'"), filename);
1089
1090         for (pos = 0; pos < merge_names->len; pos = npos) {
1091                 unsigned char sha1[20];
1092                 char *ptr;
1093                 struct commit *commit;
1094
1095                 ptr = strchr(merge_names->buf + pos, '\n');
1096                 if (ptr)
1097                         npos = ptr - merge_names->buf + 1;
1098                 else
1099                         npos = merge_names->len;
1100
1101                 if (npos - pos < 40 + 2 ||
1102                     get_sha1_hex(merge_names->buf + pos, sha1))
1103                         commit = NULL; /* bad */
1104                 else if (memcmp(merge_names->buf + pos + 40, "\t\t", 2))
1105                         continue; /* not-for-merge */
1106                 else {
1107                         char saved = merge_names->buf[pos + 40];
1108                         merge_names->buf[pos + 40] = '\0';
1109                         commit = get_merge_parent(merge_names->buf + pos);
1110                         merge_names->buf[pos + 40] = saved;
1111                 }
1112                 if (!commit) {
1113                         if (ptr)
1114                                 *ptr = '\0';
1115                         die("not something we can merge in %s: %s",
1116                             filename, merge_names->buf + pos);
1117                 }
1118                 remotes = &commit_list_insert(commit, remotes)->next;
1119         }
1120
1121         if (merge_names == &fetch_head_file)
1122                 strbuf_release(&fetch_head_file);
1123 }
1124
1125 static struct commit_list *collect_parents(struct commit *head_commit,
1126                                            int *head_subsumed,
1127                                            int argc, const char **argv,
1128                                            struct strbuf *merge_msg)
1129 {
1130         int i;
1131         struct commit_list *remoteheads = NULL;
1132         struct commit_list **remotes = &remoteheads;
1133         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1134
1135         if (merge_msg && (!have_message || shortlog_len))
1136                 autogen = &merge_names;
1137
1138         if (head_commit)
1139                 remotes = &commit_list_insert(head_commit, remotes)->next;
1140
1141         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1142                 handle_fetch_head(remotes, autogen);
1143                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1144         } else {
1145                 for (i = 0; i < argc; i++) {
1146                         struct commit *commit = get_merge_parent(argv[i]);
1147                         if (!commit)
1148                                 help_unknown_ref(argv[i], "merge",
1149                                                  "not something we can merge");
1150                         remotes = &commit_list_insert(commit, remotes)->next;
1151                 }
1152                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1153                 if (autogen) {
1154                         struct commit_list *p;
1155                         for (p = remoteheads; p; p = p->next)
1156                                 merge_name(merge_remote_util(p->item)->name, autogen);
1157                 }
1158         }
1159
1160         if (autogen) {
1161                 prepare_merge_message(autogen, merge_msg);
1162                 strbuf_release(autogen);
1163         }
1164
1165         return remoteheads;
1166 }
1167
1168 int cmd_merge(int argc, const char **argv, const char *prefix)
1169 {
1170         unsigned char result_tree[20];
1171         unsigned char stash[20];
1172         unsigned char head_sha1[20];
1173         struct commit *head_commit;
1174         struct strbuf buf = STRBUF_INIT;
1175         const char *head_arg;
1176         int flag, i, ret = 0, head_subsumed;
1177         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1178         struct commit_list *common = NULL;
1179         const char *best_strategy = NULL, *wt_strategy = NULL;
1180         struct commit_list *remoteheads, *p;
1181         void *branch_to_free;
1182
1183         if (argc == 2 && !strcmp(argv[1], "-h"))
1184                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1185
1186         /*
1187          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1188          * current branch.
1189          */
1190         branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1191         if (branch && starts_with(branch, "refs/heads/"))
1192                 branch += 11;
1193         if (!branch || is_null_sha1(head_sha1))
1194                 head_commit = NULL;
1195         else
1196                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1197
1198         git_config(git_merge_config, NULL);
1199
1200         if (branch_mergeoptions)
1201                 parse_branch_merge_options(branch_mergeoptions);
1202         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1203                         builtin_merge_usage, 0);
1204         if (shortlog_len < 0)
1205                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1206
1207         if (verbosity < 0 && show_progress == -1)
1208                 show_progress = 0;
1209
1210         if (abort_current_merge) {
1211                 int nargc = 2;
1212                 const char *nargv[] = {"reset", "--merge", NULL};
1213
1214                 if (!file_exists(git_path_merge_head()))
1215                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1216
1217                 /* Invoke 'git reset --merge' */
1218                 ret = cmd_reset(nargc, nargv, prefix);
1219                 goto done;
1220         }
1221
1222         if (read_cache_unmerged())
1223                 die_resolve_conflict("merge");
1224
1225         if (file_exists(git_path_merge_head())) {
1226                 /*
1227                  * There is no unmerged entry, don't advise 'git
1228                  * add/rm <file>', just 'git commit'.
1229                  */
1230                 if (advice_resolve_conflict)
1231                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1232                                   "Please, commit your changes before you merge."));
1233                 else
1234                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1235         }
1236         if (file_exists(git_path_cherry_pick_head())) {
1237                 if (advice_resolve_conflict)
1238                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1239                             "Please, commit your changes before you merge."));
1240                 else
1241                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1242         }
1243         resolve_undo_clear();
1244
1245         if (verbosity < 0)
1246                 show_diffstat = 0;
1247
1248         if (squash) {
1249                 if (fast_forward == FF_NO)
1250                         die(_("You cannot combine --squash with --no-ff."));
1251                 option_commit = 0;
1252         }
1253
1254         if (!argc) {
1255                 if (default_to_upstream)
1256                         argc = setup_with_upstream(&argv);
1257                 else
1258                         die(_("No commit specified and merge.defaultToUpstream not set."));
1259         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1260                 argv[0] = "@{-1}";
1261         }
1262
1263         if (!argc)
1264                 usage_with_options(builtin_merge_usage,
1265                         builtin_merge_options);
1266
1267         if (!head_commit) {
1268                 struct commit *remote_head;
1269                 /*
1270                  * If the merged head is a valid one there is no reason
1271                  * to forbid "git merge" into a branch yet to be born.
1272                  * We do the same for "git pull".
1273                  */
1274                 if (squash)
1275                         die(_("Squash commit into empty head not supported yet"));
1276                 if (fast_forward == FF_NO)
1277                         die(_("Non-fast-forward commit does not make sense into "
1278                             "an empty head"));
1279                 remoteheads = collect_parents(head_commit, &head_subsumed,
1280                                               argc, argv, NULL);
1281                 remote_head = remoteheads->item;
1282                 if (!remote_head)
1283                         die(_("%s - not something we can merge"), argv[0]);
1284                 if (remoteheads->next)
1285                         die(_("Can merge only exactly one commit into empty head"));
1286                 read_empty(remote_head->object.oid.hash, 0);
1287                 update_ref("initial pull", "HEAD", remote_head->object.oid.hash,
1288                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1289                 goto done;
1290         }
1291
1292         /*
1293          * This could be traditional "merge <msg> HEAD <commit>..."  and
1294          * the way we can tell it is to see if the second token is HEAD,
1295          * but some people might have misused the interface and used a
1296          * commit-ish that is the same as HEAD there instead.
1297          * Traditional format never would have "-m" so it is an
1298          * additional safety measure to check for it.
1299          */
1300         if (!have_message &&
1301             is_old_style_invocation(argc, argv, head_commit->object.oid.hash)) {
1302                 warning("old-style 'git merge <msg> HEAD <commit>' is deprecated.");
1303                 strbuf_addstr(&merge_msg, argv[0]);
1304                 head_arg = argv[1];
1305                 argv += 2;
1306                 argc -= 2;
1307                 remoteheads = collect_parents(head_commit, &head_subsumed,
1308                                               argc, argv, NULL);
1309         } else {
1310                 /* We are invoked directly as the first-class UI. */
1311                 head_arg = "HEAD";
1312
1313                 /*
1314                  * All the rest are the commits being merged; prepare
1315                  * the standard merge summary message to be appended
1316                  * to the given message.
1317                  */
1318                 remoteheads = collect_parents(head_commit, &head_subsumed,
1319                                               argc, argv, &merge_msg);
1320         }
1321
1322         if (!head_commit || !argc)
1323                 usage_with_options(builtin_merge_usage,
1324                         builtin_merge_options);
1325
1326         if (verify_signatures) {
1327                 for (p = remoteheads; p; p = p->next) {
1328                         struct commit *commit = p->item;
1329                         char hex[GIT_SHA1_HEXSZ + 1];
1330                         struct signature_check signature_check;
1331                         memset(&signature_check, 0, sizeof(signature_check));
1332
1333                         check_commit_signature(commit, &signature_check);
1334
1335                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1336                         switch (signature_check.result) {
1337                         case 'G':
1338                                 break;
1339                         case 'U':
1340                                 die(_("Commit %s has an untrusted GPG signature, "
1341                                       "allegedly by %s."), hex, signature_check.signer);
1342                         case 'B':
1343                                 die(_("Commit %s has a bad GPG signature "
1344                                       "allegedly by %s."), hex, signature_check.signer);
1345                         default: /* 'N' */
1346                                 die(_("Commit %s does not have a GPG signature."), hex);
1347                         }
1348                         if (verbosity >= 0 && signature_check.result == 'G')
1349                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1350                                        hex, signature_check.signer);
1351
1352                         signature_check_clear(&signature_check);
1353                 }
1354         }
1355
1356         strbuf_addstr(&buf, "merge");
1357         for (p = remoteheads; p; p = p->next)
1358                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1359         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1360         strbuf_reset(&buf);
1361
1362         for (p = remoteheads; p; p = p->next) {
1363                 struct commit *commit = p->item;
1364                 strbuf_addf(&buf, "GITHEAD_%s",
1365                             sha1_to_hex(commit->object.oid.hash));
1366                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1367                 strbuf_reset(&buf);
1368                 if (fast_forward != FF_ONLY &&
1369                     merge_remote_util(commit) &&
1370                     merge_remote_util(commit)->obj &&
1371                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1372                         fast_forward = FF_NO;
1373         }
1374
1375         if (option_edit < 0)
1376                 option_edit = default_edit_option();
1377
1378         if (!use_strategies) {
1379                 if (!remoteheads)
1380                         ; /* already up-to-date */
1381                 else if (!remoteheads->next)
1382                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1383                 else
1384                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1385         }
1386
1387         for (i = 0; i < use_strategies_nr; i++) {
1388                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1389                         fast_forward = FF_NO;
1390                 if (use_strategies[i]->attr & NO_TRIVIAL)
1391                         allow_trivial = 0;
1392         }
1393
1394         if (!remoteheads)
1395                 ; /* already up-to-date */
1396         else if (!remoteheads->next)
1397                 common = get_merge_bases(head_commit, remoteheads->item);
1398         else {
1399                 struct commit_list *list = remoteheads;
1400                 commit_list_insert(head_commit, &list);
1401                 common = get_octopus_merge_bases(list);
1402                 free(list);
1403         }
1404
1405         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.oid.hash,
1406                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1407
1408         if (remoteheads && !common)
1409                 ; /* No common ancestors found. We need a real merge. */
1410         else if (!remoteheads ||
1411                  (!remoteheads->next && !common->next &&
1412                   common->item == remoteheads->item)) {
1413                 /*
1414                  * If head can reach all the merge then we are up to date.
1415                  * but first the most common case of merging one remote.
1416                  */
1417                 finish_up_to_date("Already up-to-date.");
1418                 goto done;
1419         } else if (fast_forward != FF_NO && !remoteheads->next &&
1420                         !common->next &&
1421                         !hashcmp(common->item->object.oid.hash, head_commit->object.oid.hash)) {
1422                 /* Again the most common case of merging one remote. */
1423                 struct strbuf msg = STRBUF_INIT;
1424                 struct commit *commit;
1425
1426                 if (verbosity >= 0) {
1427                         char from[GIT_SHA1_HEXSZ + 1], to[GIT_SHA1_HEXSZ + 1];
1428                         find_unique_abbrev_r(from, head_commit->object.oid.hash,
1429                                               DEFAULT_ABBREV);
1430                         find_unique_abbrev_r(to, remoteheads->item->object.oid.hash,
1431                                               DEFAULT_ABBREV);
1432                         printf(_("Updating %s..%s\n"), from, to);
1433                 }
1434                 strbuf_addstr(&msg, "Fast-forward");
1435                 if (have_message)
1436                         strbuf_addstr(&msg,
1437                                 " (no commit created; -m option ignored)");
1438                 commit = remoteheads->item;
1439                 if (!commit) {
1440                         ret = 1;
1441                         goto done;
1442                 }
1443
1444                 if (checkout_fast_forward(head_commit->object.oid.hash,
1445                                           commit->object.oid.hash,
1446                                           overwrite_ignore)) {
1447                         ret = 1;
1448                         goto done;
1449                 }
1450
1451                 finish(head_commit, remoteheads, commit->object.oid.hash, msg.buf);
1452                 drop_save();
1453                 goto done;
1454         } else if (!remoteheads->next && common->next)
1455                 ;
1456                 /*
1457                  * We are not doing octopus and not fast-forward.  Need
1458                  * a real merge.
1459                  */
1460         else if (!remoteheads->next && !common->next && option_commit) {
1461                 /*
1462                  * We are not doing octopus, not fast-forward, and have
1463                  * only one common.
1464                  */
1465                 refresh_cache(REFRESH_QUIET);
1466                 if (allow_trivial && fast_forward != FF_ONLY) {
1467                         /* See if it is really trivial. */
1468                         git_committer_info(IDENT_STRICT);
1469                         printf(_("Trying really trivial in-index merge...\n"));
1470                         if (!read_tree_trivial(common->item->object.oid.hash,
1471                                                head_commit->object.oid.hash,
1472                                                remoteheads->item->object.oid.hash)) {
1473                                 ret = merge_trivial(head_commit, remoteheads);
1474                                 goto done;
1475                         }
1476                         printf(_("Nope.\n"));
1477                 }
1478         } else {
1479                 /*
1480                  * An octopus.  If we can reach all the remote we are up
1481                  * to date.
1482                  */
1483                 int up_to_date = 1;
1484                 struct commit_list *j;
1485
1486                 for (j = remoteheads; j; j = j->next) {
1487                         struct commit_list *common_one;
1488
1489                         /*
1490                          * Here we *have* to calculate the individual
1491                          * merge_bases again, otherwise "git merge HEAD^
1492                          * HEAD^^" would be missed.
1493                          */
1494                         common_one = get_merge_bases(head_commit, j->item);
1495                         if (hashcmp(common_one->item->object.oid.hash,
1496                                 j->item->object.oid.hash)) {
1497                                 up_to_date = 0;
1498                                 break;
1499                         }
1500                 }
1501                 if (up_to_date) {
1502                         finish_up_to_date("Already up-to-date. Yeeah!");
1503                         goto done;
1504                 }
1505         }
1506
1507         if (fast_forward == FF_ONLY)
1508                 die(_("Not possible to fast-forward, aborting."));
1509
1510         /* We are going to make a new commit. */
1511         git_committer_info(IDENT_STRICT);
1512
1513         /*
1514          * At this point, we need a real merge.  No matter what strategy
1515          * we use, it would operate on the index, possibly affecting the
1516          * working tree, and when resolved cleanly, have the desired
1517          * tree in the index -- this means that the index must be in
1518          * sync with the head commit.  The strategies are responsible
1519          * to ensure this.
1520          */
1521         if (use_strategies_nr == 1 ||
1522             /*
1523              * Stash away the local changes so that we can try more than one.
1524              */
1525             save_state(stash))
1526                 hashcpy(stash, null_sha1);
1527
1528         for (i = 0; i < use_strategies_nr; i++) {
1529                 int ret;
1530                 if (i) {
1531                         printf(_("Rewinding the tree to pristine...\n"));
1532                         restore_state(head_commit->object.oid.hash, stash);
1533                 }
1534                 if (use_strategies_nr != 1)
1535                         printf(_("Trying merge strategy %s...\n"),
1536                                 use_strategies[i]->name);
1537                 /*
1538                  * Remember which strategy left the state in the working
1539                  * tree.
1540                  */
1541                 wt_strategy = use_strategies[i]->name;
1542
1543                 ret = try_merge_strategy(use_strategies[i]->name,
1544                                          common, remoteheads,
1545                                          head_commit, head_arg);
1546                 if (!option_commit && !ret) {
1547                         merge_was_ok = 1;
1548                         /*
1549                          * This is necessary here just to avoid writing
1550                          * the tree, but later we will *not* exit with
1551                          * status code 1 because merge_was_ok is set.
1552                          */
1553                         ret = 1;
1554                 }
1555
1556                 if (ret) {
1557                         /*
1558                          * The backend exits with 1 when conflicts are
1559                          * left to be resolved, with 2 when it does not
1560                          * handle the given merge at all.
1561                          */
1562                         if (ret == 1) {
1563                                 int cnt = evaluate_result();
1564
1565                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1566                                         best_strategy = use_strategies[i]->name;
1567                                         best_cnt = cnt;
1568                                 }
1569                         }
1570                         if (merge_was_ok)
1571                                 break;
1572                         else
1573                                 continue;
1574                 }
1575
1576                 /* Automerge succeeded. */
1577                 write_tree_trivial(result_tree);
1578                 automerge_was_ok = 1;
1579                 break;
1580         }
1581
1582         /*
1583          * If we have a resulting tree, that means the strategy module
1584          * auto resolved the merge cleanly.
1585          */
1586         if (automerge_was_ok) {
1587                 ret = finish_automerge(head_commit, head_subsumed,
1588                                        common, remoteheads,
1589                                        result_tree, wt_strategy);
1590                 goto done;
1591         }
1592
1593         /*
1594          * Pick the result from the best strategy and have the user fix
1595          * it up.
1596          */
1597         if (!best_strategy) {
1598                 restore_state(head_commit->object.oid.hash, stash);
1599                 if (use_strategies_nr > 1)
1600                         fprintf(stderr,
1601                                 _("No merge strategy handled the merge.\n"));
1602                 else
1603                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1604                                 use_strategies[0]->name);
1605                 ret = 2;
1606                 goto done;
1607         } else if (best_strategy == wt_strategy)
1608                 ; /* We already have its result in the working tree. */
1609         else {
1610                 printf(_("Rewinding the tree to pristine...\n"));
1611                 restore_state(head_commit->object.oid.hash, stash);
1612                 printf(_("Using the %s to prepare resolving by hand.\n"),
1613                         best_strategy);
1614                 try_merge_strategy(best_strategy, common, remoteheads,
1615                                    head_commit, head_arg);
1616         }
1617
1618         if (squash)
1619                 finish(head_commit, remoteheads, NULL, NULL);
1620         else
1621                 write_merge_state(remoteheads);
1622
1623         if (merge_was_ok)
1624                 fprintf(stderr, _("Automatic merge went well; "
1625                         "stopped before committing as requested\n"));
1626         else
1627                 ret = suggest_conflicts();
1628
1629 done:
1630         free(branch_to_free);
1631         return ret;
1632 }