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 "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28
  29 #define DEFAULT_TWOHEAD (1<<0)
  30 #define DEFAULT_OCTOPUS (1<<1)
  31 #define NO_FAST_FORWARD (1<<2)
  32 #define NO_TRIVIAL      (1<<3)
  33
  34 struct strategy {
  35         const char *name;
  36         unsigned attr;
  37 };
  38
  39 static const char * const builtin_merge_usage[] = {
  40         "git merge [options] <remote>...",
  41         "git merge [options] <msg> HEAD <remote>",
  42         NULL
  43 };
  44
  45 static int show_diffstat = 1, shortlog_len, squash;
  46 static int option_commit = 1, allow_fast_forward = 1;
  47 static int fast_forward_only;
  48 static int allow_trivial = 1, have_message;
  49 static struct strbuf merge_msg;
  50 static struct commit_list *remoteheads;
  51 static unsigned char head[20], stash[20];
  52 static struct strategy **use_strategies;
  53 static size_t use_strategies_nr, use_strategies_alloc;
  54 static const char **xopts;
  55 static size_t xopts_nr, xopts_alloc;
  56 static const char *branch;
  57 static int option_renormalize;
  58 static int verbosity;
  59 static int allow_rerere_auto;
  60 static int abort_current_merge;
  61
  62 static struct strategy all_strategy[] = {
  63         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  64         { "octopus",    DEFAULT_OCTOPUS },
  65         { "resolve",    0 },
  66         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  67         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  68 };
  69
  70 static const char *pull_twohead, *pull_octopus;
  71
  72 static int option_parse_message(const struct option *opt,
  73                                 const char *arg, int unset)
  74 {
  75         struct strbuf *buf = opt->value;
  76
  77         if (unset)
  78                 strbuf_setlen(buf, 0);
  79         else if (arg) {
  80                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  81                 have_message = 1;
  82         } else
  83                 return error("switch `m' requires a value");
  84         return 0;
  85 }
  86
  87 static struct strategy *get_strategy(const char *name)
  88 {
  89         int i;
  90         struct strategy *ret;
  91         static struct cmdnames main_cmds, other_cmds;
  92         static int loaded;
  93
  94         if (!name)
  95                 return NULL;
  96
  97         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  98                 if (!strcmp(name, all_strategy[i].name))
  99                         return &all_strategy[i];
 100
 101         if (!loaded) {
 102                 struct cmdnames not_strategies;
 103                 loaded = 1;
 104
 105                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 106                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 107                 for (i = 0; i < main_cmds.cnt; i++) {
 108                         int j, found = 0;
 109                         struct cmdname *ent = main_cmds.names[i];
 110                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 111                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 112                                                 && !all_strategy[j].name[ent->len])
 113                                         found = 1;
 114                         if (!found)
 115                                 add_cmdname(&not_strategies, ent->name, ent->len);
 116                 }
 117                 exclude_cmds(&main_cmds, &not_strategies);
 118         }
 119         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 120                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 121                 fprintf(stderr, "Available strategies are:");
 122                 for (i = 0; i < main_cmds.cnt; i++)
 123                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 124                 fprintf(stderr, ".\n");
 125                 if (other_cmds.cnt) {
 126                         fprintf(stderr, "Available custom strategies are:");
 127                         for (i = 0; i < other_cmds.cnt; i++)
 128                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 129                         fprintf(stderr, ".\n");
 130                 }
 131                 exit(1);
 132         }
 133
 134         ret = xcalloc(1, sizeof(struct strategy));
 135         ret->name = xstrdup(name);
 136         ret->attr = NO_TRIVIAL;
 137         return ret;
 138 }
 139
 140 static void append_strategy(struct strategy *s)
 141 {
 142         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 143         use_strategies[use_strategies_nr++] = s;
 144 }
 145
 146 static int option_parse_strategy(const struct option *opt,
 147                                  const char *name, int unset)
 148 {
 149         if (unset)
 150                 return 0;
 151
 152         append_strategy(get_strategy(name));
 153         return 0;
 154 }
 155
 156 static int option_parse_x(const struct option *opt,
 157                           const char *arg, int unset)
 158 {
 159         if (unset)
 160                 return 0;
 161
 162         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 163         xopts[xopts_nr++] = xstrdup(arg);
 164         return 0;
 165 }
 166
 167 static int option_parse_n(const struct option *opt,
 168                           const char *arg, int unset)
 169 {
 170         show_diffstat = unset;
 171         return 0;
 172 }
 173
 174 static struct option builtin_merge_options[] = {
 175         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 176                 "do not show a diffstat at the end of the merge",
 177                 PARSE_OPT_NOARG, option_parse_n },
 178         OPT_BOOLEAN(0, "stat", &show_diffstat,
 179                 "show a diffstat at the end of the merge"),
 180         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 181         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 182           "add (at most <n>) entries from shortlog to merge commit message",
 183           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 184         OPT_BOOLEAN(0, "squash", &squash,
 185                 "create a single commit instead of doing a merge"),
 186         OPT_BOOLEAN(0, "commit", &option_commit,
 187                 "perform a commit if the merge succeeds (default)"),
 188         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 189                 "allow fast-forward (default)"),
 190         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 191                 "abort if fast-forward is not possible"),
 192         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 193         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 194                 "merge strategy to use", option_parse_strategy),
 195         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 196                 "option for selected merge strategy", option_parse_x),
 197         OPT_CALLBACK('m', "message", &merge_msg, "message",
 198                 "merge commit message (for a non-fast-forward merge)",
 199                 option_parse_message),
 200         OPT__VERBOSITY(&verbosity),
 201         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 202                 "abort the current in-progress merge"),
 203         OPT_END()
 204 };
 205
 206 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 207 static void drop_save(void)
 208 {
 209         unlink(git_path("MERGE_HEAD"));
 210         unlink(git_path("MERGE_MSG"));
 211         unlink(git_path("MERGE_MODE"));
 212 }
 213
 214 static void save_state(void)
 215 {
 216         int len;
 217         struct child_process cp;
 218         struct strbuf buffer = STRBUF_INIT;
 219         const char *argv[] = {"stash", "create", NULL};
 220
 221         memset(&cp, 0, sizeof(cp));
 222         cp.argv = argv;
 223         cp.out = -1;
 224         cp.git_cmd = 1;
 225
 226         if (start_command(&cp))
 227                 die("could not run stash.");
 228         len = strbuf_read(&buffer, cp.out, 1024);
 229         close(cp.out);
 230
 231         if (finish_command(&cp) || len < 0)
 232                 die("stash failed");
 233         else if (!len)
 234                 return;
 235         strbuf_setlen(&buffer, buffer.len-1);
 236         if (get_sha1(buffer.buf, stash))
 237                 die("not a valid object: %s", buffer.buf);
 238 }
 239
 240 static void read_empty(unsigned const char *sha1, int verbose)
 241 {
 242         int i = 0;
 243         const char *args[7];
 244
 245         args[i++] = "read-tree";
 246         if (verbose)
 247                 args[i++] = "-v";
 248         args[i++] = "-m";
 249         args[i++] = "-u";
 250         args[i++] = EMPTY_TREE_SHA1_HEX;
 251         args[i++] = sha1_to_hex(sha1);
 252         args[i] = NULL;
 253
 254         if (run_command_v_opt(args, RUN_GIT_CMD))
 255                 die("read-tree failed");
 256 }
 257
 258 static void reset_hard(unsigned const char *sha1, int verbose)
 259 {
 260         int i = 0;
 261         const char *args[6];
 262
 263         args[i++] = "read-tree";
 264         if (verbose)
 265                 args[i++] = "-v";
 266         args[i++] = "--reset";
 267         args[i++] = "-u";
 268         args[i++] = sha1_to_hex(sha1);
 269         args[i] = NULL;
 270
 271         if (run_command_v_opt(args, RUN_GIT_CMD))
 272                 die("read-tree failed");
 273 }
 274
 275 static void restore_state(void)
 276 {
 277         struct strbuf sb = STRBUF_INIT;
 278         const char *args[] = { "stash", "apply", NULL, NULL };
 279
 280         if (is_null_sha1(stash))
 281                 return;
 282
 283         reset_hard(head, 1);
 284
 285         args[2] = sha1_to_hex(stash);
 286
 287         /*
 288          * It is OK to ignore error here, for example when there was
 289          * nothing to restore.
 290          */
 291         run_command_v_opt(args, RUN_GIT_CMD);
 292
 293         strbuf_release(&sb);
 294         refresh_cache(REFRESH_QUIET);
 295 }
 296
 297 /* This is called when no merge was necessary. */
 298 static void finish_up_to_date(const char *msg)
 299 {
 300         if (verbosity >= 0)
 301                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 302         drop_save();
 303 }
 304
 305 static void squash_message(void)
 306 {
 307         struct rev_info rev;
 308         struct commit *commit;
 309         struct strbuf out = STRBUF_INIT;
 310         struct commit_list *j;
 311         int fd;
 312         struct pretty_print_context ctx = {0};
 313
 314         printf("Squash commit -- not updating HEAD\n");
 315         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 316         if (fd < 0)
 317                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 318
 319         init_revisions(&rev, NULL);
 320         rev.ignore_merges = 1;
 321         rev.commit_format = CMIT_FMT_MEDIUM;
 322
 323         commit = lookup_commit(head);
 324         commit->object.flags |= UNINTERESTING;
 325         add_pending_object(&rev, &commit->object, NULL);
 326
 327         for (j = remoteheads; j; j = j->next)
 328                 add_pending_object(&rev, &j->item->object, NULL);
 329
 330         setup_revisions(0, NULL, &rev, NULL);
 331         if (prepare_revision_walk(&rev))
 332                 die("revision walk setup failed");
 333
 334         ctx.abbrev = rev.abbrev;
 335         ctx.date_mode = rev.date_mode;
 336
 337         strbuf_addstr(&out, "Squashed commit of the following:\n");
 338         while ((commit = get_revision(&rev)) != NULL) {
 339                 strbuf_addch(&out, '\n');
 340                 strbuf_addf(&out, "commit %s\n",
 341                         sha1_to_hex(commit->object.sha1));
 342                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 343         }
 344         if (write(fd, out.buf, out.len) < 0)
 345                 die_errno("Writing SQUASH_MSG");
 346         if (close(fd))
 347                 die_errno("Finishing SQUASH_MSG");
 348         strbuf_release(&out);
 349 }
 350
 351 static void finish(const unsigned char *new_head, const char *msg)
 352 {
 353         struct strbuf reflog_message = STRBUF_INIT;
 354
 355         if (!msg)
 356                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 357         else {
 358                 if (verbosity >= 0)
 359                         printf("%s\n", msg);
 360                 strbuf_addf(&reflog_message, "%s: %s",
 361                         getenv("GIT_REFLOG_ACTION"), msg);
 362         }
 363         if (squash) {
 364                 squash_message();
 365         } else {
 366                 if (verbosity >= 0 && !merge_msg.len)
 367                         printf("No merge message -- not updating HEAD\n");
 368                 else {
 369                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 370                         update_ref(reflog_message.buf, "HEAD",
 371                                 new_head, head, 0,
 372                                 DIE_ON_ERR);
 373                         /*
 374                          * We ignore errors in 'gc --auto', since the
 375                          * user should see them.
 376                          */
 377                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 378                 }
 379         }
 380         if (new_head && show_diffstat) {
 381                 struct diff_options opts;
 382                 diff_setup(&opts);
 383                 opts.output_format |=
 384                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 385                 opts.detect_rename = DIFF_DETECT_RENAME;
 386                 if (diff_use_color_default > 0)
 387                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 388                 if (diff_setup_done(&opts) < 0)
 389                         die("diff_setup_done failed");
 390                 diff_tree_sha1(head, new_head, "", &opts);
 391                 diffcore_std(&opts);
 392                 diff_flush(&opts);
 393         }
 394
 395         /* Run a post-merge hook */
 396         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 397
 398         strbuf_release(&reflog_message);
 399 }
 400
 401 /* Get the name for the merge commit's message. */
 402 static void merge_name(const char *remote, struct strbuf *msg)
 403 {
 404         struct object *remote_head;
 405         unsigned char branch_head[20], buf_sha[20];
 406         struct strbuf buf = STRBUF_INIT;
 407         struct strbuf bname = STRBUF_INIT;
 408         const char *ptr;
 409         char *found_ref;
 410         int len, early;
 411
 412         strbuf_branchname(&bname, remote);
 413         remote = bname.buf;
 414
 415         memset(branch_head, 0, sizeof(branch_head));
 416         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 417         if (!remote_head)
 418                 die("'%s' does not point to a commit", remote);
 419
 420         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 421                 if (!prefixcmp(found_ref, "refs/heads/")) {
 422                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 423                                     sha1_to_hex(branch_head), remote);
 424                         goto cleanup;
 425                 }
 426                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 427                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 428                                     sha1_to_hex(branch_head), remote);
 429                         goto cleanup;
 430                 }
 431         }
 432
 433         /* See if remote matches <name>^^^.. or <name>~<number> */
 434         for (len = 0, ptr = remote + strlen(remote);
 435              remote < ptr && ptr[-1] == '^';
 436              ptr--)
 437                 len++;
 438         if (len)
 439                 early = 1;
 440         else {
 441                 early = 0;
 442                 ptr = strrchr(remote, '~');
 443                 if (ptr) {
 444                         int seen_nonzero = 0;
 445
 446                         len++; /* count ~ */
 447                         while (*++ptr && isdigit(*ptr)) {
 448                                 seen_nonzero |= (*ptr != '0');
 449                                 len++;
 450                         }
 451                         if (*ptr)
 452                                 len = 0; /* not ...~<number> */
 453                         else if (seen_nonzero)
 454                                 early = 1;
 455                         else if (len == 1)
 456                                 early = 1; /* "name~" is "name~1"! */
 457                 }
 458         }
 459         if (len) {
 460                 struct strbuf truname = STRBUF_INIT;
 461                 strbuf_addstr(&truname, "refs/heads/");
 462                 strbuf_addstr(&truname, remote);
 463                 strbuf_setlen(&truname, truname.len - len);
 464                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 465                         strbuf_addf(msg,
 466                                     "%s\t\tbranch '%s'%s of .\n",
 467                                     sha1_to_hex(remote_head->sha1),
 468                                     truname.buf + 11,
 469                                     (early ? " (early part)" : ""));
 470                         strbuf_release(&truname);
 471                         goto cleanup;
 472                 }
 473         }
 474
 475         if (!strcmp(remote, "FETCH_HEAD") &&
 476                         !access(git_path("FETCH_HEAD"), R_OK)) {
 477                 FILE *fp;
 478                 struct strbuf line = STRBUF_INIT;
 479                 char *ptr;
 480
 481                 fp = fopen(git_path("FETCH_HEAD"), "r");
 482                 if (!fp)
 483                         die_errno("could not open '%s' for reading",
 484                                   git_path("FETCH_HEAD"));
 485                 strbuf_getline(&line, fp, '\n');
 486                 fclose(fp);
 487                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 488                 if (ptr)
 489                         strbuf_remove(&line, ptr-line.buf+1, 13);
 490                 strbuf_addbuf(msg, &line);
 491                 strbuf_release(&line);
 492                 goto cleanup;
 493         }
 494         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 495                 sha1_to_hex(remote_head->sha1), remote);
 496 cleanup:
 497         strbuf_release(&buf);
 498         strbuf_release(&bname);
 499 }
 500
 501 static int git_merge_config(const char *k, const char *v, void *cb)
 502 {
 503         if (branch && !prefixcmp(k, "branch.") &&
 504                 !prefixcmp(k + 7, branch) &&
 505                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 506                 const char **argv;
 507                 int argc;
 508                 char *buf;
 509
 510                 buf = xstrdup(v);
 511                 argc = split_cmdline(buf, &argv);
 512                 if (argc < 0)
 513                         die("Bad branch.%s.mergeoptions string: %s", branch,
 514                             split_cmdline_strerror(argc));
 515                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 516                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 517                 argc++;
 518                 parse_options(argc, argv, NULL, builtin_merge_options,
 519                               builtin_merge_usage, 0);
 520                 free(buf);
 521         }
 522
 523         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 524                 show_diffstat = git_config_bool(k, v);
 525         else if (!strcmp(k, "pull.twohead"))
 526                 return git_config_string(&pull_twohead, k, v);
 527         else if (!strcmp(k, "pull.octopus"))
 528                 return git_config_string(&pull_octopus, k, v);
 529         else if (!strcmp(k, "merge.renormalize"))
 530                 option_renormalize = git_config_bool(k, v);
 531         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 532                 int is_bool;
 533                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 534                 if (!is_bool && shortlog_len < 0)
 535                         return error("%s: negative length %s", k, v);
 536                 if (is_bool && shortlog_len)
 537                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 538                 return 0;
 539         }
 540         return git_diff_ui_config(k, v, cb);
 541 }
 542
 543 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 544                              unsigned char *one)
 545 {
 546         int i, nr_trees = 0;
 547         struct tree *trees[MAX_UNPACK_TREES];
 548         struct tree_desc t[MAX_UNPACK_TREES];
 549         struct unpack_trees_options opts;
 550
 551         memset(&opts, 0, sizeof(opts));
 552         opts.head_idx = 2;
 553         opts.src_index = &the_index;
 554         opts.dst_index = &the_index;
 555         opts.update = 1;
 556         opts.verbose_update = 1;
 557         opts.trivial_merges_only = 1;
 558         opts.merge = 1;
 559         trees[nr_trees] = parse_tree_indirect(common);
 560         if (!trees[nr_trees++])
 561                 return -1;
 562         trees[nr_trees] = parse_tree_indirect(head);
 563         if (!trees[nr_trees++])
 564                 return -1;
 565         trees[nr_trees] = parse_tree_indirect(one);
 566         if (!trees[nr_trees++])
 567                 return -1;
 568         opts.fn = threeway_merge;
 569         cache_tree_free(&active_cache_tree);
 570         for (i = 0; i < nr_trees; i++) {
 571                 parse_tree(trees[i]);
 572                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 573         }
 574         if (unpack_trees(nr_trees, t, &opts))
 575                 return -1;
 576         return 0;
 577 }
 578
 579 static void write_tree_trivial(unsigned char *sha1)
 580 {
 581         if (write_cache_as_tree(sha1, 0, NULL))
 582                 die("git write-tree failed to write a tree");
 583 }
 584
 585 int try_merge_command(const char *strategy, struct commit_list *common,
 586                       const char *head_arg, struct commit_list *remotes)
 587 {
 588         const char **args;
 589         int i = 0, x = 0, ret;
 590         struct commit_list *j;
 591         struct strbuf buf = STRBUF_INIT;
 592
 593         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 594                         commit_list_count(remotes)) * sizeof(char *));
 595         strbuf_addf(&buf, "merge-%s", strategy);
 596         args[i++] = buf.buf;
 597         for (x = 0; x < xopts_nr; x++) {
 598                 char *s = xmalloc(strlen(xopts[x])+2+1);
 599                 strcpy(s, "--");
 600                 strcpy(s+2, xopts[x]);
 601                 args[i++] = s;
 602         }
 603         for (j = common; j; j = j->next)
 604                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 605         args[i++] = "--";
 606         args[i++] = head_arg;
 607         for (j = remotes; j; j = j->next)
 608                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 609         args[i] = NULL;
 610         ret = run_command_v_opt(args, RUN_GIT_CMD);
 611         strbuf_release(&buf);
 612         i = 1;
 613         for (x = 0; x < xopts_nr; x++)
 614                 free((void *)args[i++]);
 615         for (j = common; j; j = j->next)
 616                 free((void *)args[i++]);
 617         i += 2;
 618         for (j = remotes; j; j = j->next)
 619                 free((void *)args[i++]);
 620         free(args);
 621         discard_cache();
 622         if (read_cache() < 0)
 623                 die("failed to read the cache");
 624         resolve_undo_clear();
 625
 626         return ret;
 627 }
 628
 629 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 630                               const char *head_arg)
 631 {
 632         int index_fd;
 633         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 634
 635         index_fd = hold_locked_index(lock, 1);
 636         refresh_cache(REFRESH_QUIET);
 637         if (active_cache_changed &&
 638                         (write_cache(index_fd, active_cache, active_nr) ||
 639                          commit_locked_index(lock)))
 640                 return error("Unable to write index.");
 641         rollback_lock_file(lock);
 642
 643         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 644                 int clean, x;
 645                 struct commit *result;
 646                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 647                 int index_fd;
 648                 struct commit_list *reversed = NULL;
 649                 struct merge_options o;
 650                 struct commit_list *j;
 651
 652                 if (remoteheads->next) {
 653                         error("Not handling anything other than two heads merge.");
 654                         return 2;
 655                 }
 656
 657                 init_merge_options(&o);
 658                 if (!strcmp(strategy, "subtree"))
 659                         o.subtree_shift = "";
 660
 661                 o.renormalize = option_renormalize;
 662
 663                 for (x = 0; x < xopts_nr; x++)
 664                         if (parse_merge_opt(&o, xopts[x]))
 665                                 die("Unknown option for merge-recursive: -X%s", xopts[x]);
 666
 667                 o.branch1 = head_arg;
 668                 o.branch2 = remoteheads->item->util;
 669
 670                 for (j = common; j; j = j->next)
 671                         commit_list_insert(j->item, &reversed);
 672
 673                 index_fd = hold_locked_index(lock, 1);
 674                 clean = merge_recursive(&o, lookup_commit(head),
 675                                 remoteheads->item, reversed, &result);
 676                 if (active_cache_changed &&
 677                                 (write_cache(index_fd, active_cache, active_nr) ||
 678                                  commit_locked_index(lock)))
 679                         die ("unable to write %s", get_index_file());
 680                 rollback_lock_file(lock);
 681                 return clean ? 0 : 1;
 682         } else {
 683                 return try_merge_command(strategy, common, head_arg, remoteheads);
 684         }
 685 }
 686
 687 static void count_diff_files(struct diff_queue_struct *q,
 688                              struct diff_options *opt, void *data)
 689 {
 690         int *count = data;
 691
 692         (*count) += q->nr;
 693 }
 694
 695 static int count_unmerged_entries(void)
 696 {
 697         int i, ret = 0;
 698
 699         for (i = 0; i < active_nr; i++)
 700                 if (ce_stage(active_cache[i]))
 701                         ret++;
 702
 703         return ret;
 704 }
 705
 706 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 707 {
 708         struct tree *trees[MAX_UNPACK_TREES];
 709         struct unpack_trees_options opts;
 710         struct tree_desc t[MAX_UNPACK_TREES];
 711         int i, fd, nr_trees = 0;
 712         struct dir_struct dir;
 713         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 714
 715         refresh_cache(REFRESH_QUIET);
 716
 717         fd = hold_locked_index(lock_file, 1);
 718
 719         memset(&trees, 0, sizeof(trees));
 720         memset(&opts, 0, sizeof(opts));
 721         memset(&t, 0, sizeof(t));
 722         memset(&dir, 0, sizeof(dir));
 723         dir.flags |= DIR_SHOW_IGNORED;
 724         dir.exclude_per_dir = ".gitignore";
 725         opts.dir = &dir;
 726
 727         opts.head_idx = 1;
 728         opts.src_index = &the_index;
 729         opts.dst_index = &the_index;
 730         opts.update = 1;
 731         opts.verbose_update = 1;
 732         opts.merge = 1;
 733         opts.fn = twoway_merge;
 734         setup_unpack_trees_porcelain(&opts, "merge");
 735
 736         trees[nr_trees] = parse_tree_indirect(head);
 737         if (!trees[nr_trees++])
 738                 return -1;
 739         trees[nr_trees] = parse_tree_indirect(remote);
 740         if (!trees[nr_trees++])
 741                 return -1;
 742         for (i = 0; i < nr_trees; i++) {
 743                 parse_tree(trees[i]);
 744                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 745         }
 746         if (unpack_trees(nr_trees, t, &opts))
 747                 return -1;
 748         if (write_cache(fd, active_cache, active_nr) ||
 749                 commit_locked_index(lock_file))
 750                 die("unable to write new index file");
 751         return 0;
 752 }
 753
 754 static void split_merge_strategies(const char *string, struct strategy **list,
 755                                    int *nr, int *alloc)
 756 {
 757         char *p, *q, *buf;
 758
 759         if (!string)
 760                 return;
 761
 762         buf = xstrdup(string);
 763         q = buf;
 764         for (;;) {
 765                 p = strchr(q, ' ');
 766                 if (!p) {
 767                         ALLOC_GROW(*list, *nr + 1, *alloc);
 768                         (*list)[(*nr)++].name = xstrdup(q);
 769                         free(buf);
 770                         return;
 771                 } else {
 772                         *p = '\0';
 773                         ALLOC_GROW(*list, *nr + 1, *alloc);
 774                         (*list)[(*nr)++].name = xstrdup(q);
 775                         q = ++p;
 776                 }
 777         }
 778 }
 779
 780 static void add_strategies(const char *string, unsigned attr)
 781 {
 782         struct strategy *list = NULL;
 783         int list_alloc = 0, list_nr = 0, i;
 784
 785         memset(&list, 0, sizeof(list));
 786         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 787         if (list) {
 788                 for (i = 0; i < list_nr; i++)
 789                         append_strategy(get_strategy(list[i].name));
 790                 return;
 791         }
 792         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 793                 if (all_strategy[i].attr & attr)
 794                         append_strategy(&all_strategy[i]);
 795
 796 }
 797
 798 static void write_merge_msg(void)
 799 {
 800         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 801         if (fd < 0)
 802                 die_errno("Could not open '%s' for writing",
 803                           git_path("MERGE_MSG"));
 804         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 805                 die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
 806         close(fd);
 807 }
 808
 809 static void read_merge_msg(void)
 810 {
 811         strbuf_reset(&merge_msg);
 812         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 813                 die_errno("Could not read from '%s'", git_path("MERGE_MSG"));
 814 }
 815
 816 static void run_prepare_commit_msg(void)
 817 {
 818         write_merge_msg();
 819         run_hook(get_index_file(), "prepare-commit-msg",
 820                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 821         read_merge_msg();
 822 }
 823
 824 static int merge_trivial(void)
 825 {
 826         unsigned char result_tree[20], result_commit[20];
 827         struct commit_list *parent = xmalloc(sizeof(*parent));
 828
 829         write_tree_trivial(result_tree);
 830         printf("Wonderful.\n");
 831         parent->item = lookup_commit(head);
 832         parent->next = xmalloc(sizeof(*parent->next));
 833         parent->next->item = remoteheads->item;
 834         parent->next->next = NULL;
 835         run_prepare_commit_msg();
 836         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 837         finish(result_commit, "In-index merge");
 838         drop_save();
 839         return 0;
 840 }
 841
 842 static int finish_automerge(struct commit_list *common,
 843                             unsigned char *result_tree,
 844                             const char *wt_strategy)
 845 {
 846         struct commit_list *parents = NULL, *j;
 847         struct strbuf buf = STRBUF_INIT;
 848         unsigned char result_commit[20];
 849
 850         free_commit_list(common);
 851         if (allow_fast_forward) {
 852                 parents = remoteheads;
 853                 commit_list_insert(lookup_commit(head), &parents);
 854                 parents = reduce_heads(parents);
 855         } else {
 856                 struct commit_list **pptr = &parents;
 857
 858                 pptr = &commit_list_insert(lookup_commit(head),
 859                                 pptr)->next;
 860                 for (j = remoteheads; j; j = j->next)
 861                         pptr = &commit_list_insert(j->item, pptr)->next;
 862         }
 863         free_commit_list(remoteheads);
 864         strbuf_addch(&merge_msg, '\n');
 865         run_prepare_commit_msg();
 866         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 867         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 868         finish(result_commit, buf.buf);
 869         strbuf_release(&buf);
 870         drop_save();
 871         return 0;
 872 }
 873
 874 static int suggest_conflicts(int renormalizing)
 875 {
 876         FILE *fp;
 877         int pos;
 878
 879         fp = fopen(git_path("MERGE_MSG"), "a");
 880         if (!fp)
 881                 die_errno("Could not open '%s' for writing",
 882                           git_path("MERGE_MSG"));
 883         fprintf(fp, "\nConflicts:\n");
 884         for (pos = 0; pos < active_nr; pos++) {
 885                 struct cache_entry *ce = active_cache[pos];
 886
 887                 if (ce_stage(ce)) {
 888                         fprintf(fp, "\t%s\n", ce->name);
 889                         while (pos + 1 < active_nr &&
 890                                         !strcmp(ce->name,
 891                                                 active_cache[pos + 1]->name))
 892                                 pos++;
 893                 }
 894         }
 895         fclose(fp);
 896         rerere(allow_rerere_auto);
 897         printf("Automatic merge failed; "
 898                         "fix conflicts and then commit the result.\n");
 899         return 1;
 900 }
 901
 902 static struct commit *is_old_style_invocation(int argc, const char **argv)
 903 {
 904         struct commit *second_token = NULL;
 905         if (argc > 2) {
 906                 unsigned char second_sha1[20];
 907
 908                 if (get_sha1(argv[1], second_sha1))
 909                         return NULL;
 910                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 911                 if (!second_token)
 912                         die("'%s' is not a commit", argv[1]);
 913                 if (hashcmp(second_token->object.sha1, head))
 914                         return NULL;
 915         }
 916         return second_token;
 917 }
 918
 919 static int evaluate_result(void)
 920 {
 921         int cnt = 0;
 922         struct rev_info rev;
 923
 924         /* Check how many files differ. */
 925         init_revisions(&rev, "");
 926         setup_revisions(0, NULL, &rev, NULL);
 927         rev.diffopt.output_format |=
 928                 DIFF_FORMAT_CALLBACK;
 929         rev.diffopt.format_callback = count_diff_files;
 930         rev.diffopt.format_callback_data = &cnt;
 931         run_diff_files(&rev, 0);
 932
 933         /*
 934          * Check how many unmerged entries are
 935          * there.
 936          */
 937         cnt += count_unmerged_entries();
 938
 939         return cnt;
 940 }
 941
 942 int cmd_merge(int argc, const char **argv, const char *prefix)
 943 {
 944         unsigned char result_tree[20];
 945         struct strbuf buf = STRBUF_INIT;
 946         const char *head_arg;
 947         int flag, head_invalid = 0, i;
 948         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 949         struct commit_list *common = NULL;
 950         const char *best_strategy = NULL, *wt_strategy = NULL;
 951         struct commit_list **remotes = &remoteheads;
 952
 953         if (argc == 2 && !strcmp(argv[1], "-h"))
 954                 usage_with_options(builtin_merge_usage, builtin_merge_options);
 955
 956         /*
 957          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 958          * current branch.
 959          */
 960         branch = resolve_ref("HEAD", head, 0, &flag);
 961         if (branch && !prefixcmp(branch, "refs/heads/"))
 962                 branch += 11;
 963         if (is_null_sha1(head))
 964                 head_invalid = 1;
 965
 966         git_config(git_merge_config, NULL);
 967
 968         /* for color.ui */
 969         if (diff_use_color_default == -1)
 970                 diff_use_color_default = git_use_color_default;
 971
 972         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 973                         builtin_merge_usage, 0);
 974
 975         if (abort_current_merge) {
 976                 int nargc = 2;
 977                 const char *nargv[] = {"reset", "--merge", NULL};
 978
 979                 if (!file_exists(git_path("MERGE_HEAD")))
 980                         die("There is no merge to abort (MERGE_HEAD missing).");
 981
 982                 /* Invoke 'git reset --merge' */
 983                 return cmd_reset(nargc, nargv, prefix);
 984         }
 985
 986         if (read_cache_unmerged())
 987                 die_resolve_conflict("merge");
 988
 989         if (file_exists(git_path("MERGE_HEAD"))) {
 990                 /*
 991                  * There is no unmerged entry, don't advise 'git
 992                  * add/rm <file>', just 'git commit'.
 993                  */
 994                 if (advice_resolve_conflict)
 995                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
 996                             "Please, commit your changes before you can merge.");
 997                 else
 998                         die("You have not concluded your merge (MERGE_HEAD exists).");
 999         }
1000         resolve_undo_clear();
1001
1002         if (verbosity < 0)
1003                 show_diffstat = 0;
1004
1005         if (squash) {
1006                 if (!allow_fast_forward)
1007                         die("You cannot combine --squash with --no-ff.");
1008                 option_commit = 0;
1009         }
1010
1011         if (!allow_fast_forward && fast_forward_only)
1012                 die("You cannot combine --no-ff with --ff-only.");
1013
1014         if (!argc)
1015                 usage_with_options(builtin_merge_usage,
1016                         builtin_merge_options);
1017
1018         /*
1019          * This could be traditional "merge <msg> HEAD <commit>..."  and
1020          * the way we can tell it is to see if the second token is HEAD,
1021          * but some people might have misused the interface and used a
1022          * committish that is the same as HEAD there instead.
1023          * Traditional format never would have "-m" so it is an
1024          * additional safety measure to check for it.
1025          */
1026
1027         if (!have_message && is_old_style_invocation(argc, argv)) {
1028                 strbuf_addstr(&merge_msg, argv[0]);
1029                 head_arg = argv[1];
1030                 argv += 2;
1031                 argc -= 2;
1032         } else if (head_invalid) {
1033                 struct object *remote_head;
1034                 /*
1035                  * If the merged head is a valid one there is no reason
1036                  * to forbid "git merge" into a branch yet to be born.
1037                  * We do the same for "git pull".
1038                  */
1039                 if (argc != 1)
1040                         die("Can merge only exactly one commit into "
1041                                 "empty head");
1042                 if (squash)
1043                         die("Squash commit into empty head not supported yet");
1044                 if (!allow_fast_forward)
1045                         die("Non-fast-forward commit does not make sense into "
1046                             "an empty head");
1047                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1048                 if (!remote_head)
1049                         die("%s - not something we can merge", argv[0]);
1050                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1051                                 DIE_ON_ERR);
1052                 read_empty(remote_head->sha1, 0);
1053                 return 0;
1054         } else {
1055                 struct strbuf merge_names = STRBUF_INIT;
1056
1057                 /* We are invoked directly as the first-class UI. */
1058                 head_arg = "HEAD";
1059
1060                 /*
1061                  * All the rest are the commits being merged;
1062                  * prepare the standard merge summary message to
1063                  * be appended to the given message.  If remote
1064                  * is invalid we will die later in the common
1065                  * codepath so we discard the error in this
1066                  * loop.
1067                  */
1068                 for (i = 0; i < argc; i++)
1069                         merge_name(argv[i], &merge_names);
1070
1071                 if (!have_message || shortlog_len) {
1072                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1073                                       shortlog_len);
1074                         if (merge_msg.len)
1075                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1076                 }
1077         }
1078
1079         if (head_invalid || !argc)
1080                 usage_with_options(builtin_merge_usage,
1081                         builtin_merge_options);
1082
1083         strbuf_addstr(&buf, "merge");
1084         for (i = 0; i < argc; i++)
1085                 strbuf_addf(&buf, " %s", argv[i]);
1086         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1087         strbuf_reset(&buf);
1088
1089         for (i = 0; i < argc; i++) {
1090                 struct object *o;
1091                 struct commit *commit;
1092
1093                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1094                 if (!o)
1095                         die("%s - not something we can merge", argv[i]);
1096                 commit = lookup_commit(o->sha1);
1097                 commit->util = (void *)argv[i];
1098                 remotes = &commit_list_insert(commit, remotes)->next;
1099
1100                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1101                 setenv(buf.buf, argv[i], 1);
1102                 strbuf_reset(&buf);
1103         }
1104
1105         if (!use_strategies) {
1106                 if (!remoteheads->next)
1107                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1108                 else
1109                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1110         }
1111
1112         for (i = 0; i < use_strategies_nr; i++) {
1113                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1114                         allow_fast_forward = 0;
1115                 if (use_strategies[i]->attr & NO_TRIVIAL)
1116                         allow_trivial = 0;
1117         }
1118
1119         if (!remoteheads->next)
1120                 common = get_merge_bases(lookup_commit(head),
1121                                 remoteheads->item, 1);
1122         else {
1123                 struct commit_list *list = remoteheads;
1124                 commit_list_insert(lookup_commit(head), &list);
1125                 common = get_octopus_merge_bases(list);
1126                 free(list);
1127         }
1128
1129         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1130                 DIE_ON_ERR);
1131
1132         if (!common)
1133                 ; /* No common ancestors found. We need a real merge. */
1134         else if (!remoteheads->next && !common->next &&
1135                         common->item == remoteheads->item) {
1136                 /*
1137                  * If head can reach all the merge then we are up to date.
1138                  * but first the most common case of merging one remote.
1139                  */
1140                 finish_up_to_date("Already up-to-date.");
1141                 return 0;
1142         } else if (allow_fast_forward && !remoteheads->next &&
1143                         !common->next &&
1144                         !hashcmp(common->item->object.sha1, head)) {
1145                 /* Again the most common case of merging one remote. */
1146                 struct strbuf msg = STRBUF_INIT;
1147                 struct object *o;
1148                 char hex[41];
1149
1150                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1151
1152                 if (verbosity >= 0)
1153                         printf("Updating %s..%s\n",
1154                                 hex,
1155                                 find_unique_abbrev(remoteheads->item->object.sha1,
1156                                 DEFAULT_ABBREV));
1157                 strbuf_addstr(&msg, "Fast-forward");
1158                 if (have_message)
1159                         strbuf_addstr(&msg,
1160                                 " (no commit created; -m option ignored)");
1161                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1162                         0, NULL, OBJ_COMMIT);
1163                 if (!o)
1164                         return 1;
1165
1166                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1167                         return 1;
1168
1169                 finish(o->sha1, msg.buf);
1170                 drop_save();
1171                 return 0;
1172         } else if (!remoteheads->next && common->next)
1173                 ;
1174                 /*
1175                  * We are not doing octopus and not fast-forward.  Need
1176                  * a real merge.
1177                  */
1178         else if (!remoteheads->next && !common->next && option_commit) {
1179                 /*
1180                  * We are not doing octopus, not fast-forward, and have
1181                  * only one common.
1182                  */
1183                 refresh_cache(REFRESH_QUIET);
1184                 if (allow_trivial && !fast_forward_only) {
1185                         /* See if it is really trivial. */
1186                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1187                         printf("Trying really trivial in-index merge...\n");
1188                         if (!read_tree_trivial(common->item->object.sha1,
1189                                         head, remoteheads->item->object.sha1))
1190                                 return merge_trivial();
1191                         printf("Nope.\n");
1192                 }
1193         } else {
1194                 /*
1195                  * An octopus.  If we can reach all the remote we are up
1196                  * to date.
1197                  */
1198                 int up_to_date = 1;
1199                 struct commit_list *j;
1200
1201                 for (j = remoteheads; j; j = j->next) {
1202                         struct commit_list *common_one;
1203
1204                         /*
1205                          * Here we *have* to calculate the individual
1206                          * merge_bases again, otherwise "git merge HEAD^
1207                          * HEAD^^" would be missed.
1208                          */
1209                         common_one = get_merge_bases(lookup_commit(head),
1210                                 j->item, 1);
1211                         if (hashcmp(common_one->item->object.sha1,
1212                                 j->item->object.sha1)) {
1213                                 up_to_date = 0;
1214                                 break;
1215                         }
1216                 }
1217                 if (up_to_date) {
1218                         finish_up_to_date("Already up-to-date. Yeeah!");
1219                         return 0;
1220                 }
1221         }
1222
1223         if (fast_forward_only)
1224                 die("Not possible to fast-forward, aborting.");
1225
1226         /* We are going to make a new commit. */
1227         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1228
1229         /*
1230          * At this point, we need a real merge.  No matter what strategy
1231          * we use, it would operate on the index, possibly affecting the
1232          * working tree, and when resolved cleanly, have the desired
1233          * tree in the index -- this means that the index must be in
1234          * sync with the head commit.  The strategies are responsible
1235          * to ensure this.
1236          */
1237         if (use_strategies_nr != 1) {
1238                 /*
1239                  * Stash away the local changes so that we can try more
1240                  * than one.
1241                  */
1242                 save_state();
1243         } else {
1244                 memcpy(stash, null_sha1, 20);
1245         }
1246
1247         for (i = 0; i < use_strategies_nr; i++) {
1248                 int ret;
1249                 if (i) {
1250                         printf("Rewinding the tree to pristine...\n");
1251                         restore_state();
1252                 }
1253                 if (use_strategies_nr != 1)
1254                         printf("Trying merge strategy %s...\n",
1255                                 use_strategies[i]->name);
1256                 /*
1257                  * Remember which strategy left the state in the working
1258                  * tree.
1259                  */
1260                 wt_strategy = use_strategies[i]->name;
1261
1262                 ret = try_merge_strategy(use_strategies[i]->name,
1263                         common, head_arg);
1264                 if (!option_commit && !ret) {
1265                         merge_was_ok = 1;
1266                         /*
1267                          * This is necessary here just to avoid writing
1268                          * the tree, but later we will *not* exit with
1269                          * status code 1 because merge_was_ok is set.
1270                          */
1271                         ret = 1;
1272                 }
1273
1274                 if (ret) {
1275                         /*
1276                          * The backend exits with 1 when conflicts are
1277                          * left to be resolved, with 2 when it does not
1278                          * handle the given merge at all.
1279                          */
1280                         if (ret == 1) {
1281                                 int cnt = evaluate_result();
1282
1283                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1284                                         best_strategy = use_strategies[i]->name;
1285                                         best_cnt = cnt;
1286                                 }
1287                         }
1288                         if (merge_was_ok)
1289                                 break;
1290                         else
1291                                 continue;
1292                 }
1293
1294                 /* Automerge succeeded. */
1295                 write_tree_trivial(result_tree);
1296                 automerge_was_ok = 1;
1297                 break;
1298         }
1299
1300         /*
1301          * If we have a resulting tree, that means the strategy module
1302          * auto resolved the merge cleanly.
1303          */
1304         if (automerge_was_ok)
1305                 return finish_automerge(common, result_tree, wt_strategy);
1306
1307         /*
1308          * Pick the result from the best strategy and have the user fix
1309          * it up.
1310          */
1311         if (!best_strategy) {
1312                 restore_state();
1313                 if (use_strategies_nr > 1)
1314                         fprintf(stderr,
1315                                 "No merge strategy handled the merge.\n");
1316                 else
1317                         fprintf(stderr, "Merge with strategy %s failed.\n",
1318                                 use_strategies[0]->name);
1319                 return 2;
1320         } else if (best_strategy == wt_strategy)
1321                 ; /* We already have its result in the working tree. */
1322         else {
1323                 printf("Rewinding the tree to pristine...\n");
1324                 restore_state();
1325                 printf("Using the %s to prepare resolving by hand.\n",
1326                         best_strategy);
1327                 try_merge_strategy(best_strategy, common, head_arg);
1328         }
1329
1330         if (squash)
1331                 finish(NULL, NULL);
1332         else {
1333                 int fd;
1334                 struct commit_list *j;
1335
1336                 for (j = remoteheads; j; j = j->next)
1337                         strbuf_addf(&buf, "%s\n",
1338                                 sha1_to_hex(j->item->object.sha1));
1339                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1340                 if (fd < 0)
1341                         die_errno("Could not open '%s' for writing",
1342                                   git_path("MERGE_HEAD"));
1343                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1344                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1345                 close(fd);
1346                 strbuf_addch(&merge_msg, '\n');
1347                 write_merge_msg();
1348                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1349                 if (fd < 0)
1350                         die_errno("Could not open '%s' for writing",
1351                                   git_path("MERGE_MODE"));
1352                 strbuf_reset(&buf);
1353                 if (!allow_fast_forward)
1354                         strbuf_addf(&buf, "no-ff");
1355                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1356                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1357                 close(fd);
1358         }
1359
1360         if (merge_was_ok) {
1361                 fprintf(stderr, "Automatic merge went well; "
1362                         "stopped before committing as requested\n");
1363                 return 0;
1364         } else
1365                 return suggest_conflicts(option_renormalize);
1366 }