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                         sha1_to_hex(commit->object.sha1));
 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.sha1;
 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                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 408                 }
 409         }
 410         if (new_head && show_diffstat) {
 411                 struct diff_options opts;
 412                 diff_setup(&opts);
 413                 opts.stat_width = -1; /* use full terminal width */
 414                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 415                 opts.output_format |=
 416                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 417                 opts.detect_rename = DIFF_DETECT_RENAME;
 418                 diff_setup_done(&opts);
 419                 diff_tree_sha1(head, new_head, "", &opts);
 420                 diffcore_std(&opts);
 421                 diff_flush(&opts);
 422         }
 423
 424         /* Run a post-merge hook */
 425         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 426
 427         strbuf_release(&reflog_message);
 428 }
 429
 430 /* Get the name for the merge commit's message. */
 431 static void merge_name(const char *remote, struct strbuf *msg)
 432 {
 433         struct commit *remote_head;
 434         unsigned char branch_head[20];
 435         struct strbuf buf = STRBUF_INIT;
 436         struct strbuf bname = STRBUF_INIT;
 437         const char *ptr;
 438         char *found_ref;
 439         int len, early;
 440
 441         strbuf_branchname(&bname, remote);
 442         remote = bname.buf;
 443
 444         memset(branch_head, 0, sizeof(branch_head));
 445         remote_head = get_merge_parent(remote);
 446         if (!remote_head)
 447                 die(_("'%s' does not point to a commit"), remote);
 448
 449         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 450                 if (starts_with(found_ref, "refs/heads/")) {
 451                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 452                                     sha1_to_hex(branch_head), remote);
 453                         goto cleanup;
 454                 }
 455                 if (starts_with(found_ref, "refs/tags/")) {
 456                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 457                                     sha1_to_hex(branch_head), remote);
 458                         goto cleanup;
 459                 }
 460                 if (starts_with(found_ref, "refs/remotes/")) {
 461                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 462                                     sha1_to_hex(branch_head), remote);
 463                         goto cleanup;
 464                 }
 465         }
 466
 467         /* See if remote matches <name>^^^.. or <name>~<number> */
 468         for (len = 0, ptr = remote + strlen(remote);
 469              remote < ptr && ptr[-1] == '^';
 470              ptr--)
 471                 len++;
 472         if (len)
 473                 early = 1;
 474         else {
 475                 early = 0;
 476                 ptr = strrchr(remote, '~');
 477                 if (ptr) {
 478                         int seen_nonzero = 0;
 479
 480                         len++; /* count ~ */
 481                         while (*++ptr && isdigit(*ptr)) {
 482                                 seen_nonzero |= (*ptr != '0');
 483                                 len++;
 484                         }
 485                         if (*ptr)
 486                                 len = 0; /* not ...~<number> */
 487                         else if (seen_nonzero)
 488                                 early = 1;
 489                         else if (len == 1)
 490                                 early = 1; /* "name~" is "name~1"! */
 491                 }
 492         }
 493         if (len) {
 494                 struct strbuf truname = STRBUF_INIT;
 495                 strbuf_addf(&truname, "refs/heads/%s", remote);
 496                 strbuf_setlen(&truname, truname.len - len);
 497                 if (ref_exists(truname.buf)) {
 498                         strbuf_addf(msg,
 499                                     "%s\t\tbranch '%s'%s of .\n",
 500                                     sha1_to_hex(remote_head->object.sha1),
 501                                     truname.buf + 11,
 502                                     (early ? " (early part)" : ""));
 503                         strbuf_release(&truname);
 504                         goto cleanup;
 505                 }
 506                 strbuf_release(&truname);
 507         }
 508
 509         if (remote_head->util) {
 510                 struct merge_remote_desc *desc;
 511                 desc = merge_remote_util(remote_head);
 512                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 513                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
 514                                     sha1_to_hex(desc->obj->sha1),
 515                                     typename(desc->obj->type),
 516                                     remote);
 517                         goto cleanup;
 518                 }
 519         }
 520
 521         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 522                 sha1_to_hex(remote_head->object.sha1), remote);
 523 cleanup:
 524         strbuf_release(&buf);
 525         strbuf_release(&bname);
 526 }
 527
 528 static void parse_branch_merge_options(char *bmo)
 529 {
 530         const char **argv;
 531         int argc;
 532
 533         if (!bmo)
 534                 return;
 535         argc = split_cmdline(bmo, &argv);
 536         if (argc < 0)
 537                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 538                     split_cmdline_strerror(argc));
 539         REALLOC_ARRAY(argv, argc + 2);
 540         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 541         argc++;
 542         argv[0] = "branch.*.mergeoptions";
 543         parse_options(argc, argv, NULL, builtin_merge_options,
 544                       builtin_merge_usage, 0);
 545         free(argv);
 546 }
 547
 548 static int git_merge_config(const char *k, const char *v, void *cb)
 549 {
 550         int status;
 551
 552         if (branch && starts_with(k, "branch.") &&
 553                 starts_with(k + 7, branch) &&
 554                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 555                 free(branch_mergeoptions);
 556                 branch_mergeoptions = xstrdup(v);
 557                 return 0;
 558         }
 559
 560         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 561                 show_diffstat = git_config_bool(k, v);
 562         else if (!strcmp(k, "pull.twohead"))
 563                 return git_config_string(&pull_twohead, k, v);
 564         else if (!strcmp(k, "pull.octopus"))
 565                 return git_config_string(&pull_octopus, k, v);
 566         else if (!strcmp(k, "merge.renormalize"))
 567                 option_renormalize = git_config_bool(k, v);
 568         else if (!strcmp(k, "merge.ff")) {
 569                 int boolval = git_config_maybe_bool(k, v);
 570                 if (0 <= boolval) {
 571                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 572                 } else if (v && !strcmp(v, "only")) {
 573                         fast_forward = FF_ONLY;
 574                 } /* do not barf on values from future versions of git */
 575                 return 0;
 576         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 577                 default_to_upstream = git_config_bool(k, v);
 578                 return 0;
 579         } else if (!strcmp(k, "commit.gpgsign")) {
 580                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 581                 return 0;
 582         }
 583
 584         status = fmt_merge_msg_config(k, v, cb);
 585         if (status)
 586                 return status;
 587         status = git_gpg_config(k, v, NULL);
 588         if (status)
 589                 return status;
 590         return git_diff_ui_config(k, v, cb);
 591 }
 592
 593 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 594                              unsigned char *one)
 595 {
 596         int i, nr_trees = 0;
 597         struct tree *trees[MAX_UNPACK_TREES];
 598         struct tree_desc t[MAX_UNPACK_TREES];
 599         struct unpack_trees_options opts;
 600
 601         memset(&opts, 0, sizeof(opts));
 602         opts.head_idx = 2;
 603         opts.src_index = &the_index;
 604         opts.dst_index = &the_index;
 605         opts.update = 1;
 606         opts.verbose_update = 1;
 607         opts.trivial_merges_only = 1;
 608         opts.merge = 1;
 609         trees[nr_trees] = parse_tree_indirect(common);
 610         if (!trees[nr_trees++])
 611                 return -1;
 612         trees[nr_trees] = parse_tree_indirect(head);
 613         if (!trees[nr_trees++])
 614                 return -1;
 615         trees[nr_trees] = parse_tree_indirect(one);
 616         if (!trees[nr_trees++])
 617                 return -1;
 618         opts.fn = threeway_merge;
 619         cache_tree_free(&active_cache_tree);
 620         for (i = 0; i < nr_trees; i++) {
 621                 parse_tree(trees[i]);
 622                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 623         }
 624         if (unpack_trees(nr_trees, t, &opts))
 625                 return -1;
 626         return 0;
 627 }
 628
 629 static void write_tree_trivial(unsigned char *sha1)
 630 {
 631         if (write_cache_as_tree(sha1, 0, NULL))
 632                 die(_("git write-tree failed to write a tree"));
 633 }
 634
 635 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 636                               struct commit_list *remoteheads,
 637                               struct commit *head, const char *head_arg)
 638 {
 639         static struct lock_file lock;
 640
 641         hold_locked_index(&lock, 1);
 642         refresh_cache(REFRESH_QUIET);
 643         if (active_cache_changed &&
 644             write_locked_index(&the_index, &lock, COMMIT_LOCK))
 645                 return error(_("Unable to write index."));
 646         rollback_lock_file(&lock);
 647
 648         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 649                 int clean, x;
 650                 struct commit *result;
 651                 struct commit_list *reversed = NULL;
 652                 struct merge_options o;
 653                 struct commit_list *j;
 654
 655                 if (remoteheads->next) {
 656                         error(_("Not handling anything other than two heads merge."));
 657                         return 2;
 658                 }
 659
 660                 init_merge_options(&o);
 661                 if (!strcmp(strategy, "subtree"))
 662                         o.subtree_shift = "";
 663
 664                 o.renormalize = option_renormalize;
 665                 o.show_rename_progress =
 666                         show_progress == -1 ? isatty(2) : show_progress;
 667
 668                 for (x = 0; x < xopts_nr; x++)
 669                         if (parse_merge_opt(&o, xopts[x]))
 670                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 671
 672                 o.branch1 = head_arg;
 673                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 674
 675                 for (j = common; j; j = j->next)
 676                         commit_list_insert(j->item, &reversed);
 677
 678                 hold_locked_index(&lock, 1);
 679                 clean = merge_recursive(&o, head,
 680                                 remoteheads->item, reversed, &result);
 681                 if (active_cache_changed &&
 682                     write_locked_index(&the_index, &lock, COMMIT_LOCK))
 683                         die (_("unable to write %s"), get_index_file());
 684                 rollback_lock_file(&lock);
 685                 return clean ? 0 : 1;
 686         } else {
 687                 return try_merge_command(strategy, xopts_nr, xopts,
 688                                                 common, head_arg, remoteheads);
 689         }
 690 }
 691
 692 static void count_diff_files(struct diff_queue_struct *q,
 693                              struct diff_options *opt, void *data)
 694 {
 695         int *count = data;
 696
 697         (*count) += q->nr;
 698 }
 699
 700 static int count_unmerged_entries(void)
 701 {
 702         int i, ret = 0;
 703
 704         for (i = 0; i < active_nr; i++)
 705                 if (ce_stage(active_cache[i]))
 706                         ret++;
 707
 708         return ret;
 709 }
 710
 711 static void split_merge_strategies(const char *string, struct strategy **list,
 712                                    int *nr, int *alloc)
 713 {
 714         char *p, *q, *buf;
 715
 716         if (!string)
 717                 return;
 718
 719         buf = xstrdup(string);
 720         q = buf;
 721         for (;;) {
 722                 p = strchr(q, ' ');
 723                 if (!p) {
 724                         ALLOC_GROW(*list, *nr + 1, *alloc);
 725                         (*list)[(*nr)++].name = xstrdup(q);
 726                         free(buf);
 727                         return;
 728                 } else {
 729                         *p = '\0';
 730                         ALLOC_GROW(*list, *nr + 1, *alloc);
 731                         (*list)[(*nr)++].name = xstrdup(q);
 732                         q = ++p;
 733                 }
 734         }
 735 }
 736
 737 static void add_strategies(const char *string, unsigned attr)
 738 {
 739         struct strategy *list = NULL;
 740         int list_alloc = 0, list_nr = 0, i;
 741
 742         memset(&list, 0, sizeof(list));
 743         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 744         if (list) {
 745                 for (i = 0; i < list_nr; i++)
 746                         append_strategy(get_strategy(list[i].name));
 747                 return;
 748         }
 749         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 750                 if (all_strategy[i].attr & attr)
 751                         append_strategy(&all_strategy[i]);
 752
 753 }
 754
 755 static void write_merge_msg(struct strbuf *msg)
 756 {
 757         const char *filename = git_path("MERGE_MSG");
 758         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 759         if (fd < 0)
 760                 die_errno(_("Could not open '%s' for writing"),
 761                           filename);
 762         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 763                 die_errno(_("Could not write to '%s'"), filename);
 764         close(fd);
 765 }
 766
 767 static void read_merge_msg(struct strbuf *msg)
 768 {
 769         const char *filename = git_path("MERGE_MSG");
 770         strbuf_reset(msg);
 771         if (strbuf_read_file(msg, filename, 0) < 0)
 772                 die_errno(_("Could not read from '%s'"), filename);
 773 }
 774
 775 static void write_merge_state(struct commit_list *);
 776 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 777 {
 778         if (err_msg)
 779                 error("%s", err_msg);
 780         fprintf(stderr,
 781                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 782         write_merge_state(remoteheads);
 783         exit(1);
 784 }
 785
 786 static const char merge_editor_comment[] =
 787 N_("Please enter a commit message to explain why this merge is necessary,\n"
 788    "especially if it merges an updated upstream into a topic branch.\n"
 789    "\n"
 790    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 791    "the commit.\n");
 792
 793 static void prepare_to_commit(struct commit_list *remoteheads)
 794 {
 795         struct strbuf msg = STRBUF_INIT;
 796         strbuf_addbuf(&msg, &merge_msg);
 797         strbuf_addch(&msg, '\n');
 798         if (0 < option_edit)
 799                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 800         write_merge_msg(&msg);
 801         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 802                             git_path("MERGE_MSG"), "merge", NULL))
 803                 abort_commit(remoteheads, NULL);
 804         if (0 < option_edit) {
 805                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 806                         abort_commit(remoteheads, NULL);
 807         }
 808         read_merge_msg(&msg);
 809         stripspace(&msg, 0 < option_edit);
 810         if (!msg.len)
 811                 abort_commit(remoteheads, _("Empty commit message."));
 812         strbuf_release(&merge_msg);
 813         strbuf_addbuf(&merge_msg, &msg);
 814         strbuf_release(&msg);
 815 }
 816
 817 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 818 {
 819         unsigned char result_tree[20], result_commit[20];
 820         struct commit_list *parents, **pptr = &parents;
 821
 822         write_tree_trivial(result_tree);
 823         printf(_("Wonderful.\n"));
 824         pptr = commit_list_append(head, pptr);
 825         pptr = commit_list_append(remoteheads->item, pptr);
 826         prepare_to_commit(remoteheads);
 827         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 828                         result_commit, NULL, sign_commit))
 829                 die(_("failed to write commit object"));
 830         finish(head, remoteheads, result_commit, "In-index merge");
 831         drop_save();
 832         return 0;
 833 }
 834
 835 static int finish_automerge(struct commit *head,
 836                             int head_subsumed,
 837                             struct commit_list *common,
 838                             struct commit_list *remoteheads,
 839                             unsigned char *result_tree,
 840                             const char *wt_strategy)
 841 {
 842         struct commit_list *parents = NULL;
 843         struct strbuf buf = STRBUF_INIT;
 844         unsigned char result_commit[20];
 845
 846         free_commit_list(common);
 847         parents = remoteheads;
 848         if (!head_subsumed || fast_forward == FF_NO)
 849                 commit_list_insert(head, &parents);
 850         strbuf_addch(&merge_msg, '\n');
 851         prepare_to_commit(remoteheads);
 852         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 853                         result_commit, NULL, sign_commit))
 854                 die(_("failed to write commit object"));
 855         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 856         finish(head, remoteheads, result_commit, buf.buf);
 857         strbuf_release(&buf);
 858         drop_save();
 859         return 0;
 860 }
 861
 862 static int suggest_conflicts(void)
 863 {
 864         const char *filename;
 865         FILE *fp;
 866         struct strbuf msgbuf = STRBUF_INIT;
 867
 868         filename = git_path("MERGE_MSG");
 869         fp = fopen(filename, "a");
 870         if (!fp)
 871                 die_errno(_("Could not open '%s' for writing"), filename);
 872
 873         append_conflicts_hint(&msgbuf);
 874         fputs(msgbuf.buf, fp);
 875         strbuf_release(&msgbuf);
 876         fclose(fp);
 877         rerere(allow_rerere_auto);
 878         printf(_("Automatic merge failed; "
 879                         "fix conflicts and then commit the result.\n"));
 880         return 1;
 881 }
 882
 883 static struct commit *is_old_style_invocation(int argc, const char **argv,
 884                                               const unsigned char *head)
 885 {
 886         struct commit *second_token = NULL;
 887         if (argc > 2) {
 888                 unsigned char second_sha1[20];
 889
 890                 if (get_sha1(argv[1], second_sha1))
 891                         return NULL;
 892                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 893                 if (!second_token)
 894                         die(_("'%s' is not a commit"), argv[1]);
 895                 if (hashcmp(second_token->object.sha1, head))
 896                         return NULL;
 897         }
 898         return second_token;
 899 }
 900
 901 static int evaluate_result(void)
 902 {
 903         int cnt = 0;
 904         struct rev_info rev;
 905
 906         /* Check how many files differ. */
 907         init_revisions(&rev, "");
 908         setup_revisions(0, NULL, &rev, NULL);
 909         rev.diffopt.output_format |=
 910                 DIFF_FORMAT_CALLBACK;
 911         rev.diffopt.format_callback = count_diff_files;
 912         rev.diffopt.format_callback_data = &cnt;
 913         run_diff_files(&rev, 0);
 914
 915         /*
 916          * Check how many unmerged entries are
 917          * there.
 918          */
 919         cnt += count_unmerged_entries();
 920
 921         return cnt;
 922 }
 923
 924 /*
 925  * Pretend as if the user told us to merge with the remote-tracking
 926  * branch we have for the upstream of the current branch
 927  */
 928 static int setup_with_upstream(const char ***argv)
 929 {
 930         struct branch *branch = branch_get(NULL);
 931         int i;
 932         const char **args;
 933
 934         if (!branch)
 935                 die(_("No current branch."));
 936         if (!branch->remote_name)
 937                 die(_("No remote for the current branch."));
 938         if (!branch->merge_nr)
 939                 die(_("No default upstream defined for the current branch."));
 940
 941         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 942         for (i = 0; i < branch->merge_nr; i++) {
 943                 if (!branch->merge[i]->dst)
 944                         die(_("No remote-tracking branch for %s from %s"),
 945                             branch->merge[i]->src, branch->remote_name);
 946                 args[i] = branch->merge[i]->dst;
 947         }
 948         args[i] = NULL;
 949         *argv = args;
 950         return i;
 951 }
 952
 953 static void write_merge_state(struct commit_list *remoteheads)
 954 {
 955         const char *filename;
 956         int fd;
 957         struct commit_list *j;
 958         struct strbuf buf = STRBUF_INIT;
 959
 960         for (j = remoteheads; j; j = j->next) {
 961                 unsigned const char *sha1;
 962                 struct commit *c = j->item;
 963                 if (c->util && merge_remote_util(c)->obj) {
 964                         sha1 = merge_remote_util(c)->obj->sha1;
 965                 } else {
 966                         sha1 = c->object.sha1;
 967                 }
 968                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
 969         }
 970         filename = git_path("MERGE_HEAD");
 971         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 972         if (fd < 0)
 973                 die_errno(_("Could not open '%s' for writing"), filename);
 974         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 975                 die_errno(_("Could not write to '%s'"), filename);
 976         close(fd);
 977         strbuf_addch(&merge_msg, '\n');
 978         write_merge_msg(&merge_msg);
 979
 980         filename = git_path("MERGE_MODE");
 981         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
 982         if (fd < 0)
 983                 die_errno(_("Could not open '%s' for writing"), filename);
 984         strbuf_reset(&buf);
 985         if (fast_forward == FF_NO)
 986                 strbuf_addf(&buf, "no-ff");
 987         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
 988                 die_errno(_("Could not write to '%s'"), filename);
 989         close(fd);
 990 }
 991
 992 static int default_edit_option(void)
 993 {
 994         static const char name[] = "GIT_MERGE_AUTOEDIT";
 995         const char *e = getenv(name);
 996         struct stat st_stdin, st_stdout;
 997
 998         if (have_message)
 999                 /* an explicit -m msg without --[no-]edit */
1000                 return 0;
1001
1002         if (e) {
1003                 int v = git_config_maybe_bool(name, e);
1004                 if (v < 0)
1005                         die("Bad value '%s' in environment '%s'", e, name);
1006                 return v;
1007         }
1008
1009         /* Use editor if stdin and stdout are the same and is a tty */
1010         return (!fstat(0, &st_stdin) &&
1011                 !fstat(1, &st_stdout) &&
1012                 isatty(0) && isatty(1) &&
1013                 st_stdin.st_dev == st_stdout.st_dev &&
1014                 st_stdin.st_ino == st_stdout.st_ino &&
1015                 st_stdin.st_mode == st_stdout.st_mode);
1016 }
1017
1018 static struct commit_list *reduce_parents(struct commit *head_commit,
1019                                           int *head_subsumed,
1020                                           struct commit_list *remoteheads)
1021 {
1022         struct commit_list *parents, *next, **remotes = &remoteheads;
1023
1024         /*
1025          * Is the current HEAD reachable from another commit being
1026          * merged?  If so we do not want to record it as a parent of
1027          * the resulting merge, unless --no-ff is given.  We will flip
1028          * this variable to 0 when we find HEAD among the independent
1029          * tips being merged.
1030          */
1031         *head_subsumed = 1;
1032
1033         /* Find what parents to record by checking independent ones. */
1034         parents = reduce_heads(remoteheads);
1035
1036         for (remoteheads = NULL, remotes = &remoteheads;
1037              parents;
1038              parents = next) {
1039                 struct commit *commit = parents->item;
1040                 next = parents->next;
1041                 if (commit == head_commit)
1042                         *head_subsumed = 0;
1043                 else
1044                         remotes = &commit_list_insert(commit, remotes)->next;
1045                 free(parents);
1046         }
1047         return remoteheads;
1048 }
1049
1050 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1051 {
1052         struct fmt_merge_msg_opts opts;
1053
1054         memset(&opts, 0, sizeof(opts));
1055         opts.add_title = !have_message;
1056         opts.shortlog_len = shortlog_len;
1057         opts.credit_people = (0 < option_edit);
1058
1059         fmt_merge_msg(merge_names, merge_msg, &opts);
1060         if (merge_msg->len)
1061                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1062 }
1063
1064 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1065 {
1066         const char *filename;
1067         int fd, pos, npos;
1068         struct strbuf fetch_head_file = STRBUF_INIT;
1069
1070         if (!merge_names)
1071                 merge_names = &fetch_head_file;
1072
1073         filename = git_path("FETCH_HEAD");
1074         fd = open(filename, O_RDONLY);
1075         if (fd < 0)
1076                 die_errno(_("could not open '%s' for reading"), filename);
1077
1078         if (strbuf_read(merge_names, fd, 0) < 0)
1079                 die_errno(_("could not read '%s'"), filename);
1080         if (close(fd) < 0)
1081                 die_errno(_("could not close '%s'"), filename);
1082
1083         for (pos = 0; pos < merge_names->len; pos = npos) {
1084                 unsigned char sha1[20];
1085                 char *ptr;
1086                 struct commit *commit;
1087
1088                 ptr = strchr(merge_names->buf + pos, '\n');
1089                 if (ptr)
1090                         npos = ptr - merge_names->buf + 1;
1091                 else
1092                         npos = merge_names->len;
1093
1094                 if (npos - pos < 40 + 2 ||
1095                     get_sha1_hex(merge_names->buf + pos, sha1))
1096                         commit = NULL; /* bad */
1097                 else if (memcmp(merge_names->buf + pos + 40, "\t\t", 2))
1098                         continue; /* not-for-merge */
1099                 else {
1100                         char saved = merge_names->buf[pos + 40];
1101                         merge_names->buf[pos + 40] = '\0';
1102                         commit = get_merge_parent(merge_names->buf + pos);
1103                         merge_names->buf[pos + 40] = saved;
1104                 }
1105                 if (!commit) {
1106                         if (ptr)
1107                                 *ptr = '\0';
1108                         die("not something we can merge in %s: %s",
1109                             filename, merge_names->buf + pos);
1110                 }
1111                 remotes = &commit_list_insert(commit, remotes)->next;
1112         }
1113
1114         if (merge_names == &fetch_head_file)
1115                 strbuf_release(&fetch_head_file);
1116 }
1117
1118 static struct commit_list *collect_parents(struct commit *head_commit,
1119                                            int *head_subsumed,
1120                                            int argc, const char **argv,
1121                                            struct strbuf *merge_msg)
1122 {
1123         int i;
1124         struct commit_list *remoteheads = NULL;
1125         struct commit_list **remotes = &remoteheads;
1126         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1127
1128         if (merge_msg && (!have_message || shortlog_len))
1129                 autogen = &merge_names;
1130
1131         if (head_commit)
1132                 remotes = &commit_list_insert(head_commit, remotes)->next;
1133
1134         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1135                 handle_fetch_head(remotes, autogen);
1136                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1137         } else {
1138                 for (i = 0; i < argc; i++) {
1139                         struct commit *commit = get_merge_parent(argv[i]);
1140                         if (!commit)
1141                                 help_unknown_ref(argv[i], "merge",
1142                                                  "not something we can merge");
1143                         remotes = &commit_list_insert(commit, remotes)->next;
1144                 }
1145                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1146                 if (autogen) {
1147                         struct commit_list *p;
1148                         for (p = remoteheads; p; p = p->next)
1149                                 merge_name(merge_remote_util(p->item)->name, autogen);
1150                 }
1151         }
1152
1153         if (autogen) {
1154                 prepare_merge_message(autogen, merge_msg);
1155                 strbuf_release(autogen);
1156         }
1157
1158         return remoteheads;
1159 }
1160
1161 int cmd_merge(int argc, const char **argv, const char *prefix)
1162 {
1163         unsigned char result_tree[20];
1164         unsigned char stash[20];
1165         unsigned char head_sha1[20];
1166         struct commit *head_commit;
1167         struct strbuf buf = STRBUF_INIT;
1168         const char *head_arg;
1169         int flag, i, ret = 0, head_subsumed;
1170         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1171         struct commit_list *common = NULL;
1172         const char *best_strategy = NULL, *wt_strategy = NULL;
1173         struct commit_list *remoteheads, *p;
1174         void *branch_to_free;
1175
1176         if (argc == 2 && !strcmp(argv[1], "-h"))
1177                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1178
1179         /*
1180          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1181          * current branch.
1182          */
1183         branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1184         if (branch && starts_with(branch, "refs/heads/"))
1185                 branch += 11;
1186         if (!branch || is_null_sha1(head_sha1))
1187                 head_commit = NULL;
1188         else
1189                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1190
1191         git_config(git_merge_config, NULL);
1192
1193         if (branch_mergeoptions)
1194                 parse_branch_merge_options(branch_mergeoptions);
1195         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1196                         builtin_merge_usage, 0);
1197         if (shortlog_len < 0)
1198                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1199
1200         if (verbosity < 0 && show_progress == -1)
1201                 show_progress = 0;
1202
1203         if (abort_current_merge) {
1204                 int nargc = 2;
1205                 const char *nargv[] = {"reset", "--merge", NULL};
1206
1207                 if (!file_exists(git_path("MERGE_HEAD")))
1208                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1209
1210                 /* Invoke 'git reset --merge' */
1211                 ret = cmd_reset(nargc, nargv, prefix);
1212                 goto done;
1213         }
1214
1215         if (read_cache_unmerged())
1216                 die_resolve_conflict("merge");
1217
1218         if (file_exists(git_path("MERGE_HEAD"))) {
1219                 /*
1220                  * There is no unmerged entry, don't advise 'git
1221                  * add/rm <file>', just 'git commit'.
1222                  */
1223                 if (advice_resolve_conflict)
1224                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1225                                   "Please, commit your changes before you merge."));
1226                 else
1227                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1228         }
1229         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1230                 if (advice_resolve_conflict)
1231                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1232                             "Please, commit your changes before you merge."));
1233                 else
1234                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1235         }
1236         resolve_undo_clear();
1237
1238         if (verbosity < 0)
1239                 show_diffstat = 0;
1240
1241         if (squash) {
1242                 if (fast_forward == FF_NO)
1243                         die(_("You cannot combine --squash with --no-ff."));
1244                 option_commit = 0;
1245         }
1246
1247         if (!argc) {
1248                 if (default_to_upstream)
1249                         argc = setup_with_upstream(&argv);
1250                 else
1251                         die(_("No commit specified and merge.defaultToUpstream not set."));
1252         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1253                 argv[0] = "@{-1}";
1254         }
1255
1256         if (!argc)
1257                 usage_with_options(builtin_merge_usage,
1258                         builtin_merge_options);
1259
1260         if (!head_commit) {
1261                 struct commit *remote_head;
1262                 /*
1263                  * If the merged head is a valid one there is no reason
1264                  * to forbid "git merge" into a branch yet to be born.
1265                  * We do the same for "git pull".
1266                  */
1267                 if (squash)
1268                         die(_("Squash commit into empty head not supported yet"));
1269                 if (fast_forward == FF_NO)
1270                         die(_("Non-fast-forward commit does not make sense into "
1271                             "an empty head"));
1272                 remoteheads = collect_parents(head_commit, &head_subsumed,
1273                                               argc, argv, NULL);
1274                 remote_head = remoteheads->item;
1275                 if (!remote_head)
1276                         die(_("%s - not something we can merge"), argv[0]);
1277                 if (remoteheads->next)
1278                         die(_("Can merge only exactly one commit into empty head"));
1279                 read_empty(remote_head->object.sha1, 0);
1280                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1281                            NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1282                 goto done;
1283         }
1284
1285         /*
1286          * This could be traditional "merge <msg> HEAD <commit>..."  and
1287          * the way we can tell it is to see if the second token is HEAD,
1288          * but some people might have misused the interface and used a
1289          * commit-ish that is the same as HEAD there instead.
1290          * Traditional format never would have "-m" so it is an
1291          * additional safety measure to check for it.
1292          */
1293         if (!have_message &&
1294             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1295                 warning("old-style 'git merge <msg> HEAD <commit>' is deprecated.");
1296                 strbuf_addstr(&merge_msg, argv[0]);
1297                 head_arg = argv[1];
1298                 argv += 2;
1299                 argc -= 2;
1300                 remoteheads = collect_parents(head_commit, &head_subsumed,
1301                                               argc, argv, NULL);
1302         } else {
1303                 /* We are invoked directly as the first-class UI. */
1304                 head_arg = "HEAD";
1305
1306                 /*
1307                  * All the rest are the commits being merged; prepare
1308                  * the standard merge summary message to be appended
1309                  * to the given message.
1310                  */
1311                 remoteheads = collect_parents(head_commit, &head_subsumed,
1312                                               argc, argv, &merge_msg);
1313         }
1314
1315         if (!head_commit || !argc)
1316                 usage_with_options(builtin_merge_usage,
1317                         builtin_merge_options);
1318
1319         if (verify_signatures) {
1320                 for (p = remoteheads; p; p = p->next) {
1321                         struct commit *commit = p->item;
1322                         char hex[41];
1323                         struct signature_check signature_check;
1324                         memset(&signature_check, 0, sizeof(signature_check));
1325
1326                         check_commit_signature(commit, &signature_check);
1327
1328                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1329                         switch (signature_check.result) {
1330                         case 'G':
1331                                 break;
1332                         case 'U':
1333                                 die(_("Commit %s has an untrusted GPG signature, "
1334                                       "allegedly by %s."), hex, signature_check.signer);
1335                         case 'B':
1336                                 die(_("Commit %s has a bad GPG signature "
1337                                       "allegedly by %s."), hex, signature_check.signer);
1338                         default: /* 'N' */
1339                                 die(_("Commit %s does not have a GPG signature."), hex);
1340                         }
1341                         if (verbosity >= 0 && signature_check.result == 'G')
1342                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1343                                        hex, signature_check.signer);
1344
1345                         signature_check_clear(&signature_check);
1346                 }
1347         }
1348
1349         strbuf_addstr(&buf, "merge");
1350         for (p = remoteheads; p; p = p->next)
1351                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1352         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1353         strbuf_reset(&buf);
1354
1355         for (p = remoteheads; p; p = p->next) {
1356                 struct commit *commit = p->item;
1357                 strbuf_addf(&buf, "GITHEAD_%s",
1358                             sha1_to_hex(commit->object.sha1));
1359                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1360                 strbuf_reset(&buf);
1361                 if (fast_forward != FF_ONLY &&
1362                     merge_remote_util(commit) &&
1363                     merge_remote_util(commit)->obj &&
1364                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1365                         fast_forward = FF_NO;
1366         }
1367
1368         if (option_edit < 0)
1369                 option_edit = default_edit_option();
1370
1371         if (!use_strategies) {
1372                 if (!remoteheads)
1373                         ; /* already up-to-date */
1374                 else if (!remoteheads->next)
1375                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1376                 else
1377                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1378         }
1379
1380         for (i = 0; i < use_strategies_nr; i++) {
1381                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1382                         fast_forward = FF_NO;
1383                 if (use_strategies[i]->attr & NO_TRIVIAL)
1384                         allow_trivial = 0;
1385         }
1386
1387         if (!remoteheads)
1388                 ; /* already up-to-date */
1389         else if (!remoteheads->next)
1390                 common = get_merge_bases(head_commit, remoteheads->item);
1391         else {
1392                 struct commit_list *list = remoteheads;
1393                 commit_list_insert(head_commit, &list);
1394                 common = get_octopus_merge_bases(list);
1395                 free(list);
1396         }
1397
1398         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1399                    NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1400
1401         if (remoteheads && !common)
1402                 ; /* No common ancestors found. We need a real merge. */
1403         else if (!remoteheads ||
1404                  (!remoteheads->next && !common->next &&
1405                   common->item == remoteheads->item)) {
1406                 /*
1407                  * If head can reach all the merge then we are up to date.
1408                  * but first the most common case of merging one remote.
1409                  */
1410                 finish_up_to_date("Already up-to-date.");
1411                 goto done;
1412         } else if (fast_forward != FF_NO && !remoteheads->next &&
1413                         !common->next &&
1414                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1415                 /* Again the most common case of merging one remote. */
1416                 struct strbuf msg = STRBUF_INIT;
1417                 struct commit *commit;
1418                 char hex[41];
1419
1420                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1421
1422                 if (verbosity >= 0)
1423                         printf(_("Updating %s..%s\n"),
1424                                 hex,
1425                                 find_unique_abbrev(remoteheads->item->object.sha1,
1426                                 DEFAULT_ABBREV));
1427                 strbuf_addstr(&msg, "Fast-forward");
1428                 if (have_message)
1429                         strbuf_addstr(&msg,
1430                                 " (no commit created; -m option ignored)");
1431                 commit = remoteheads->item;
1432                 if (!commit) {
1433                         ret = 1;
1434                         goto done;
1435                 }
1436
1437                 if (checkout_fast_forward(head_commit->object.sha1,
1438                                           commit->object.sha1,
1439                                           overwrite_ignore)) {
1440                         ret = 1;
1441                         goto done;
1442                 }
1443
1444                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1445                 drop_save();
1446                 goto done;
1447         } else if (!remoteheads->next && common->next)
1448                 ;
1449                 /*
1450                  * We are not doing octopus and not fast-forward.  Need
1451                  * a real merge.
1452                  */
1453         else if (!remoteheads->next && !common->next && option_commit) {
1454                 /*
1455                  * We are not doing octopus, not fast-forward, and have
1456                  * only one common.
1457                  */
1458                 refresh_cache(REFRESH_QUIET);
1459                 if (allow_trivial && fast_forward != FF_ONLY) {
1460                         /* See if it is really trivial. */
1461                         git_committer_info(IDENT_STRICT);
1462                         printf(_("Trying really trivial in-index merge...\n"));
1463                         if (!read_tree_trivial(common->item->object.sha1,
1464                                                head_commit->object.sha1,
1465                                                remoteheads->item->object.sha1)) {
1466                                 ret = merge_trivial(head_commit, remoteheads);
1467                                 goto done;
1468                         }
1469                         printf(_("Nope.\n"));
1470                 }
1471         } else {
1472                 /*
1473                  * An octopus.  If we can reach all the remote we are up
1474                  * to date.
1475                  */
1476                 int up_to_date = 1;
1477                 struct commit_list *j;
1478
1479                 for (j = remoteheads; j; j = j->next) {
1480                         struct commit_list *common_one;
1481
1482                         /*
1483                          * Here we *have* to calculate the individual
1484                          * merge_bases again, otherwise "git merge HEAD^
1485                          * HEAD^^" would be missed.
1486                          */
1487                         common_one = get_merge_bases(head_commit, j->item);
1488                         if (hashcmp(common_one->item->object.sha1,
1489                                 j->item->object.sha1)) {
1490                                 up_to_date = 0;
1491                                 break;
1492                         }
1493                 }
1494                 if (up_to_date) {
1495                         finish_up_to_date("Already up-to-date. Yeeah!");
1496                         goto done;
1497                 }
1498         }
1499
1500         if (fast_forward == FF_ONLY)
1501                 die(_("Not possible to fast-forward, aborting."));
1502
1503         /* We are going to make a new commit. */
1504         git_committer_info(IDENT_STRICT);
1505
1506         /*
1507          * At this point, we need a real merge.  No matter what strategy
1508          * we use, it would operate on the index, possibly affecting the
1509          * working tree, and when resolved cleanly, have the desired
1510          * tree in the index -- this means that the index must be in
1511          * sync with the head commit.  The strategies are responsible
1512          * to ensure this.
1513          */
1514         if (use_strategies_nr == 1 ||
1515             /*
1516              * Stash away the local changes so that we can try more than one.
1517              */
1518             save_state(stash))
1519                 hashcpy(stash, null_sha1);
1520
1521         for (i = 0; i < use_strategies_nr; i++) {
1522                 int ret;
1523                 if (i) {
1524                         printf(_("Rewinding the tree to pristine...\n"));
1525                         restore_state(head_commit->object.sha1, stash);
1526                 }
1527                 if (use_strategies_nr != 1)
1528                         printf(_("Trying merge strategy %s...\n"),
1529                                 use_strategies[i]->name);
1530                 /*
1531                  * Remember which strategy left the state in the working
1532                  * tree.
1533                  */
1534                 wt_strategy = use_strategies[i]->name;
1535
1536                 ret = try_merge_strategy(use_strategies[i]->name,
1537                                          common, remoteheads,
1538                                          head_commit, head_arg);
1539                 if (!option_commit && !ret) {
1540                         merge_was_ok = 1;
1541                         /*
1542                          * This is necessary here just to avoid writing
1543                          * the tree, but later we will *not* exit with
1544                          * status code 1 because merge_was_ok is set.
1545                          */
1546                         ret = 1;
1547                 }
1548
1549                 if (ret) {
1550                         /*
1551                          * The backend exits with 1 when conflicts are
1552                          * left to be resolved, with 2 when it does not
1553                          * handle the given merge at all.
1554                          */
1555                         if (ret == 1) {
1556                                 int cnt = evaluate_result();
1557
1558                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1559                                         best_strategy = use_strategies[i]->name;
1560                                         best_cnt = cnt;
1561                                 }
1562                         }
1563                         if (merge_was_ok)
1564                                 break;
1565                         else
1566                                 continue;
1567                 }
1568
1569                 /* Automerge succeeded. */
1570                 write_tree_trivial(result_tree);
1571                 automerge_was_ok = 1;
1572                 break;
1573         }
1574
1575         /*
1576          * If we have a resulting tree, that means the strategy module
1577          * auto resolved the merge cleanly.
1578          */
1579         if (automerge_was_ok) {
1580                 ret = finish_automerge(head_commit, head_subsumed,
1581                                        common, remoteheads,
1582                                        result_tree, wt_strategy);
1583                 goto done;
1584         }
1585
1586         /*
1587          * Pick the result from the best strategy and have the user fix
1588          * it up.
1589          */
1590         if (!best_strategy) {
1591                 restore_state(head_commit->object.sha1, stash);
1592                 if (use_strategies_nr > 1)
1593                         fprintf(stderr,
1594                                 _("No merge strategy handled the merge.\n"));
1595                 else
1596                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1597                                 use_strategies[0]->name);
1598                 ret = 2;
1599                 goto done;
1600         } else if (best_strategy == wt_strategy)
1601                 ; /* We already have its result in the working tree. */
1602         else {
1603                 printf(_("Rewinding the tree to pristine...\n"));
1604                 restore_state(head_commit->object.sha1, stash);
1605                 printf(_("Using the %s to prepare resolving by hand.\n"),
1606                         best_strategy);
1607                 try_merge_strategy(best_strategy, common, remoteheads,
1608                                    head_commit, head_arg);
1609         }
1610
1611         if (squash)
1612                 finish(head_commit, remoteheads, NULL, NULL);
1613         else
1614                 write_merge_state(remoteheads);
1615
1616         if (merge_was_ok)
1617                 fprintf(stderr, _("Automatic merge went well; "
1618                         "stopped before committing as requested\n"));
1619         else
1620                 ret = suggest_conflicts();
1621
1622 done:
1623         free(branch_to_free);
1624         return ret;
1625 }