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