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, option_log, 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 verbosity;
  58 static int allow_rerere_auto;
  59 static int abort_current_merge;
  60
  61 static struct strategy all_strategy[] = {
  62         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  63         { "octopus",    DEFAULT_OCTOPUS },
  64         { "resolve",    0 },
  65         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  66         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  67 };
  68
  69 static const char *pull_twohead, *pull_octopus;
  70
  71 static int option_parse_message(const struct option *opt,
  72                                 const char *arg, int unset)
  73 {
  74         struct strbuf *buf = opt->value;
  75
  76         if (unset)
  77                 strbuf_setlen(buf, 0);
  78         else if (arg) {
  79                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  80                 have_message = 1;
  81         } else
  82                 return error("switch `m' requires a value");
  83         return 0;
  84 }
  85
  86 static struct strategy *get_strategy(const char *name)
  87 {
  88         int i;
  89         struct strategy *ret;
  90         static struct cmdnames main_cmds, other_cmds;
  91         static int loaded;
  92
  93         if (!name)
  94                 return NULL;
  95
  96         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  97                 if (!strcmp(name, all_strategy[i].name))
  98                         return &all_strategy[i];
  99
 100         if (!loaded) {
 101                 struct cmdnames not_strategies;
 102                 loaded = 1;
 103
 104                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 105                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 106                 for (i = 0; i < main_cmds.cnt; i++) {
 107                         int j, found = 0;
 108                         struct cmdname *ent = main_cmds.names[i];
 109                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 110                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 111                                                 && !all_strategy[j].name[ent->len])
 112                                         found = 1;
 113                         if (!found)
 114                                 add_cmdname(&not_strategies, ent->name, ent->len);
 115                 }
 116                 exclude_cmds(&main_cmds, &not_strategies);
 117         }
 118         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 119                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 120                 fprintf(stderr, "Available strategies are:");
 121                 for (i = 0; i < main_cmds.cnt; i++)
 122                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 123                 fprintf(stderr, ".\n");
 124                 if (other_cmds.cnt) {
 125                         fprintf(stderr, "Available custom strategies are:");
 126                         for (i = 0; i < other_cmds.cnt; i++)
 127                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 128                         fprintf(stderr, ".\n");
 129                 }
 130                 exit(1);
 131         }
 132
 133         ret = xcalloc(1, sizeof(struct strategy));
 134         ret->name = xstrdup(name);
 135         return ret;
 136 }
 137
 138 static void append_strategy(struct strategy *s)
 139 {
 140         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 141         use_strategies[use_strategies_nr++] = s;
 142 }
 143
 144 static int option_parse_strategy(const struct option *opt,
 145                                  const char *name, int unset)
 146 {
 147         if (unset)
 148                 return 0;
 149
 150         append_strategy(get_strategy(name));
 151         return 0;
 152 }
 153
 154 static int option_parse_x(const struct option *opt,
 155                           const char *arg, int unset)
 156 {
 157         if (unset)
 158                 return 0;
 159
 160         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 161         xopts[xopts_nr++] = xstrdup(arg);
 162         return 0;
 163 }
 164
 165 static int option_parse_n(const struct option *opt,
 166                           const char *arg, int unset)
 167 {
 168         show_diffstat = unset;
 169         return 0;
 170 }
 171
 172 static struct option builtin_merge_options[] = {
 173         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 174                 "do not show a diffstat at the end of the merge",
 175                 PARSE_OPT_NOARG, option_parse_n },
 176         OPT_BOOLEAN(0, "stat", &show_diffstat,
 177                 "show a diffstat at the end of the merge"),
 178         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 179         OPT_BOOLEAN(0, "log", &option_log,
 180                 "add list of one-line log to merge commit message"),
 181         OPT_BOOLEAN(0, "squash", &squash,
 182                 "create a single commit instead of doing a merge"),
 183         OPT_BOOLEAN(0, "commit", &option_commit,
 184                 "perform a commit if the merge succeeds (default)"),
 185         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 186                 "allow fast-forward (default)"),
 187         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 188                 "abort if fast-forward is not possible"),
 189         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 190         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 191                 "merge strategy to use", option_parse_strategy),
 192         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 193                 "option for selected merge strategy", option_parse_x),
 194         OPT_CALLBACK('m', "message", &merge_msg, "message",
 195                 "message to be used for the merge commit (if any)",
 196                 option_parse_message),
 197         OPT__VERBOSITY(&verbosity),
 198         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 199                 "abort the current in-progress merge"),
 200         OPT_END()
 201 };
 202
 203 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 204 static void drop_save(void)
 205 {
 206         unlink(git_path("MERGE_HEAD"));
 207         unlink(git_path("MERGE_MSG"));
 208         unlink(git_path("MERGE_MODE"));
 209 }
 210
 211 static void save_state(void)
 212 {
 213         int len;
 214         struct child_process cp;
 215         struct strbuf buffer = STRBUF_INIT;
 216         const char *argv[] = {"stash", "create", NULL};
 217
 218         memset(&cp, 0, sizeof(cp));
 219         cp.argv = argv;
 220         cp.out = -1;
 221         cp.git_cmd = 1;
 222
 223         if (start_command(&cp))
 224                 die("could not run stash.");
 225         len = strbuf_read(&buffer, cp.out, 1024);
 226         close(cp.out);
 227
 228         if (finish_command(&cp) || len < 0)
 229                 die("stash failed");
 230         else if (!len)
 231                 return;
 232         strbuf_setlen(&buffer, buffer.len-1);
 233         if (get_sha1(buffer.buf, stash))
 234                 die("not a valid object: %s", buffer.buf);
 235 }
 236
 237 static void reset_hard(unsigned const char *sha1, int verbose)
 238 {
 239         int i = 0;
 240         const char *args[6];
 241
 242         args[i++] = "read-tree";
 243         if (verbose)
 244                 args[i++] = "-v";
 245         args[i++] = "--reset";
 246         args[i++] = "-u";
 247         args[i++] = sha1_to_hex(sha1);
 248         args[i] = NULL;
 249
 250         if (run_command_v_opt(args, RUN_GIT_CMD))
 251                 die("read-tree failed");
 252 }
 253
 254 static void restore_state(void)
 255 {
 256         struct strbuf sb = STRBUF_INIT;
 257         const char *args[] = { "stash", "apply", NULL, NULL };
 258
 259         if (is_null_sha1(stash))
 260                 return;
 261
 262         reset_hard(head, 1);
 263
 264         args[2] = sha1_to_hex(stash);
 265
 266         /*
 267          * It is OK to ignore error here, for example when there was
 268          * nothing to restore.
 269          */
 270         run_command_v_opt(args, RUN_GIT_CMD);
 271
 272         strbuf_release(&sb);
 273         refresh_cache(REFRESH_QUIET);
 274 }
 275
 276 /* This is called when no merge was necessary. */
 277 static void finish_up_to_date(const char *msg)
 278 {
 279         if (verbosity >= 0)
 280                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 281         drop_save();
 282 }
 283
 284 static void squash_message(void)
 285 {
 286         struct rev_info rev;
 287         struct commit *commit;
 288         struct strbuf out = STRBUF_INIT;
 289         struct commit_list *j;
 290         int fd;
 291         struct pretty_print_context ctx = {0};
 292
 293         printf("Squash commit -- not updating HEAD\n");
 294         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 295         if (fd < 0)
 296                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 297
 298         init_revisions(&rev, NULL);
 299         rev.ignore_merges = 1;
 300         rev.commit_format = CMIT_FMT_MEDIUM;
 301
 302         commit = lookup_commit(head);
 303         commit->object.flags |= UNINTERESTING;
 304         add_pending_object(&rev, &commit->object, NULL);
 305
 306         for (j = remoteheads; j; j = j->next)
 307                 add_pending_object(&rev, &j->item->object, NULL);
 308
 309         setup_revisions(0, NULL, &rev, NULL);
 310         if (prepare_revision_walk(&rev))
 311                 die("revision walk setup failed");
 312
 313         ctx.abbrev = rev.abbrev;
 314         ctx.date_mode = rev.date_mode;
 315
 316         strbuf_addstr(&out, "Squashed commit of the following:\n");
 317         while ((commit = get_revision(&rev)) != NULL) {
 318                 strbuf_addch(&out, '\n');
 319                 strbuf_addf(&out, "commit %s\n",
 320                         sha1_to_hex(commit->object.sha1));
 321                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 322         }
 323         if (write(fd, out.buf, out.len) < 0)
 324                 die_errno("Writing SQUASH_MSG");
 325         if (close(fd))
 326                 die_errno("Finishing SQUASH_MSG");
 327         strbuf_release(&out);
 328 }
 329
 330 static void finish(const unsigned char *new_head, const char *msg)
 331 {
 332         struct strbuf reflog_message = STRBUF_INIT;
 333
 334         if (!msg)
 335                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 336         else {
 337                 if (verbosity >= 0)
 338                         printf("%s\n", msg);
 339                 strbuf_addf(&reflog_message, "%s: %s",
 340                         getenv("GIT_REFLOG_ACTION"), msg);
 341         }
 342         if (squash) {
 343                 squash_message();
 344         } else {
 345                 if (verbosity >= 0 && !merge_msg.len)
 346                         printf("No merge message -- not updating HEAD\n");
 347                 else {
 348                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 349                         update_ref(reflog_message.buf, "HEAD",
 350                                 new_head, head, 0,
 351                                 DIE_ON_ERR);
 352                         /*
 353                          * We ignore errors in 'gc --auto', since the
 354                          * user should see them.
 355                          */
 356                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 357                 }
 358         }
 359         if (new_head && show_diffstat) {
 360                 struct diff_options opts;
 361                 diff_setup(&opts);
 362                 opts.output_format |=
 363                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 364                 opts.detect_rename = DIFF_DETECT_RENAME;
 365                 if (diff_use_color_default > 0)
 366                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 367                 if (diff_setup_done(&opts) < 0)
 368                         die("diff_setup_done failed");
 369                 diff_tree_sha1(head, new_head, "", &opts);
 370                 diffcore_std(&opts);
 371                 diff_flush(&opts);
 372         }
 373
 374         /* Run a post-merge hook */
 375         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 376
 377         strbuf_release(&reflog_message);
 378 }
 379
 380 /* Get the name for the merge commit's message. */
 381 static void merge_name(const char *remote, struct strbuf *msg)
 382 {
 383         struct object *remote_head;
 384         unsigned char branch_head[20], buf_sha[20];
 385         struct strbuf buf = STRBUF_INIT;
 386         struct strbuf bname = STRBUF_INIT;
 387         const char *ptr;
 388         char *found_ref;
 389         int len, early;
 390
 391         strbuf_branchname(&bname, remote);
 392         remote = bname.buf;
 393
 394         memset(branch_head, 0, sizeof(branch_head));
 395         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 396         if (!remote_head)
 397                 die("'%s' does not point to a commit", remote);
 398
 399         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 400                 if (!prefixcmp(found_ref, "refs/heads/")) {
 401                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 402                                     sha1_to_hex(branch_head), remote);
 403                         goto cleanup;
 404                 }
 405                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 406                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 407                                     sha1_to_hex(branch_head), remote);
 408                         goto cleanup;
 409                 }
 410         }
 411
 412         /* See if remote matches <name>^^^.. or <name>~<number> */
 413         for (len = 0, ptr = remote + strlen(remote);
 414              remote < ptr && ptr[-1] == '^';
 415              ptr--)
 416                 len++;
 417         if (len)
 418                 early = 1;
 419         else {
 420                 early = 0;
 421                 ptr = strrchr(remote, '~');
 422                 if (ptr) {
 423                         int seen_nonzero = 0;
 424
 425                         len++; /* count ~ */
 426                         while (*++ptr && isdigit(*ptr)) {
 427                                 seen_nonzero |= (*ptr != '0');
 428                                 len++;
 429                         }
 430                         if (*ptr)
 431                                 len = 0; /* not ...~<number> */
 432                         else if (seen_nonzero)
 433                                 early = 1;
 434                         else if (len == 1)
 435                                 early = 1; /* "name~" is "name~1"! */
 436                 }
 437         }
 438         if (len) {
 439                 struct strbuf truname = STRBUF_INIT;
 440                 strbuf_addstr(&truname, "refs/heads/");
 441                 strbuf_addstr(&truname, remote);
 442                 strbuf_setlen(&truname, truname.len - len);
 443                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 444                         strbuf_addf(msg,
 445                                     "%s\t\tbranch '%s'%s of .\n",
 446                                     sha1_to_hex(remote_head->sha1),
 447                                     truname.buf + 11,
 448                                     (early ? " (early part)" : ""));
 449                         strbuf_release(&truname);
 450                         goto cleanup;
 451                 }
 452         }
 453
 454         if (!strcmp(remote, "FETCH_HEAD") &&
 455                         !access(git_path("FETCH_HEAD"), R_OK)) {
 456                 FILE *fp;
 457                 struct strbuf line = STRBUF_INIT;
 458                 char *ptr;
 459
 460                 fp = fopen(git_path("FETCH_HEAD"), "r");
 461                 if (!fp)
 462                         die_errno("could not open '%s' for reading",
 463                                   git_path("FETCH_HEAD"));
 464                 strbuf_getline(&line, fp, '\n');
 465                 fclose(fp);
 466                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 467                 if (ptr)
 468                         strbuf_remove(&line, ptr-line.buf+1, 13);
 469                 strbuf_addbuf(msg, &line);
 470                 strbuf_release(&line);
 471                 goto cleanup;
 472         }
 473         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 474                 sha1_to_hex(remote_head->sha1), remote);
 475 cleanup:
 476         strbuf_release(&buf);
 477         strbuf_release(&bname);
 478 }
 479
 480 static int git_merge_config(const char *k, const char *v, void *cb)
 481 {
 482         if (branch && !prefixcmp(k, "branch.") &&
 483                 !prefixcmp(k + 7, branch) &&
 484                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 485                 const char **argv;
 486                 int argc;
 487                 char *buf;
 488
 489                 buf = xstrdup(v);
 490                 argc = split_cmdline(buf, &argv);
 491                 if (argc < 0)
 492                         die("Bad branch.%s.mergeoptions string", branch);
 493                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 494                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 495                 argc++;
 496                 parse_options(argc, argv, NULL, builtin_merge_options,
 497                               builtin_merge_usage, 0);
 498                 free(buf);
 499         }
 500
 501         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 502                 show_diffstat = git_config_bool(k, v);
 503         else if (!strcmp(k, "pull.twohead"))
 504                 return git_config_string(&pull_twohead, k, v);
 505         else if (!strcmp(k, "pull.octopus"))
 506                 return git_config_string(&pull_octopus, k, v);
 507         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 508                 option_log = git_config_bool(k, v);
 509         return git_diff_ui_config(k, v, cb);
 510 }
 511
 512 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 513                              unsigned char *one)
 514 {
 515         int i, nr_trees = 0;
 516         struct tree *trees[MAX_UNPACK_TREES];
 517         struct tree_desc t[MAX_UNPACK_TREES];
 518         struct unpack_trees_options opts;
 519
 520         memset(&opts, 0, sizeof(opts));
 521         opts.head_idx = 2;
 522         opts.src_index = &the_index;
 523         opts.dst_index = &the_index;
 524         opts.update = 1;
 525         opts.verbose_update = 1;
 526         opts.trivial_merges_only = 1;
 527         opts.merge = 1;
 528         trees[nr_trees] = parse_tree_indirect(common);
 529         if (!trees[nr_trees++])
 530                 return -1;
 531         trees[nr_trees] = parse_tree_indirect(head);
 532         if (!trees[nr_trees++])
 533                 return -1;
 534         trees[nr_trees] = parse_tree_indirect(one);
 535         if (!trees[nr_trees++])
 536                 return -1;
 537         opts.fn = threeway_merge;
 538         cache_tree_free(&active_cache_tree);
 539         for (i = 0; i < nr_trees; i++) {
 540                 parse_tree(trees[i]);
 541                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 542         }
 543         if (unpack_trees(nr_trees, t, &opts))
 544                 return -1;
 545         return 0;
 546 }
 547
 548 static void write_tree_trivial(unsigned char *sha1)
 549 {
 550         if (write_cache_as_tree(sha1, 0, NULL))
 551                 die("git write-tree failed to write a tree");
 552 }
 553
 554 int try_merge_command(const char *strategy, struct commit_list *common,
 555                       const char *head_arg, struct commit_list *remotes)
 556 {
 557         const char **args;
 558         int i = 0, x = 0, ret;
 559         struct commit_list *j;
 560         struct strbuf buf = STRBUF_INIT;
 561
 562         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 563                         commit_list_count(remotes)) * sizeof(char *));
 564         strbuf_addf(&buf, "merge-%s", strategy);
 565         args[i++] = buf.buf;
 566         for (x = 0; x < xopts_nr; x++) {
 567                 char *s = xmalloc(strlen(xopts[x])+2+1);
 568                 strcpy(s, "--");
 569                 strcpy(s+2, xopts[x]);
 570                 args[i++] = s;
 571         }
 572         for (j = common; j; j = j->next)
 573                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 574         args[i++] = "--";
 575         args[i++] = head_arg;
 576         for (j = remotes; j; j = j->next)
 577                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 578         args[i] = NULL;
 579         ret = run_command_v_opt(args, RUN_GIT_CMD);
 580         strbuf_release(&buf);
 581         i = 1;
 582         for (x = 0; x < xopts_nr; x++)
 583                 free((void *)args[i++]);
 584         for (j = common; j; j = j->next)
 585                 free((void *)args[i++]);
 586         i += 2;
 587         for (j = remotes; j; j = j->next)
 588                 free((void *)args[i++]);
 589         free(args);
 590         discard_cache();
 591         if (read_cache() < 0)
 592                 die("failed to read the cache");
 593         resolve_undo_clear();
 594
 595         return ret;
 596 }
 597
 598 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 599                               const char *head_arg)
 600 {
 601         int index_fd;
 602         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 603
 604         index_fd = hold_locked_index(lock, 1);
 605         refresh_cache(REFRESH_QUIET);
 606         if (active_cache_changed &&
 607                         (write_cache(index_fd, active_cache, active_nr) ||
 608                          commit_locked_index(lock)))
 609                 return error("Unable to write index.");
 610         rollback_lock_file(lock);
 611
 612         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 613                 int clean, x;
 614                 struct commit *result;
 615                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 616                 int index_fd;
 617                 struct commit_list *reversed = NULL;
 618                 struct merge_options o;
 619                 struct commit_list *j;
 620
 621                 if (remoteheads->next) {
 622                         error("Not handling anything other than two heads merge.");
 623                         return 2;
 624                 }
 625
 626                 init_merge_options(&o);
 627                 if (!strcmp(strategy, "subtree"))
 628                         o.subtree_shift = "";
 629
 630                 for (x = 0; x < xopts_nr; x++) {
 631                         if (!strcmp(xopts[x], "ours"))
 632                                 o.recursive_variant = MERGE_RECURSIVE_OURS;
 633                         else if (!strcmp(xopts[x], "theirs"))
 634                                 o.recursive_variant = MERGE_RECURSIVE_THEIRS;
 635                         else if (!strcmp(xopts[x], "subtree"))
 636                                 o.subtree_shift = "";
 637                         else if (!prefixcmp(xopts[x], "subtree="))
 638                                 o.subtree_shift = xopts[x]+8;
 639                         else
 640                                 die("Unknown option for merge-recursive: -X%s", xopts[x]);
 641                 }
 642
 643                 o.branch1 = head_arg;
 644                 o.branch2 = remoteheads->item->util;
 645
 646                 for (j = common; j; j = j->next)
 647                         commit_list_insert(j->item, &reversed);
 648
 649                 index_fd = hold_locked_index(lock, 1);
 650                 clean = merge_recursive(&o, lookup_commit(head),
 651                                 remoteheads->item, reversed, &result);
 652                 if (active_cache_changed &&
 653                                 (write_cache(index_fd, active_cache, active_nr) ||
 654                                  commit_locked_index(lock)))
 655                         die ("unable to write %s", get_index_file());
 656                 rollback_lock_file(lock);
 657                 return clean ? 0 : 1;
 658         } else {
 659                 return try_merge_command(strategy, common, head_arg, remoteheads);
 660         }
 661 }
 662
 663 static void count_diff_files(struct diff_queue_struct *q,
 664                              struct diff_options *opt, void *data)
 665 {
 666         int *count = data;
 667
 668         (*count) += q->nr;
 669 }
 670
 671 static int count_unmerged_entries(void)
 672 {
 673         int i, ret = 0;
 674
 675         for (i = 0; i < active_nr; i++)
 676                 if (ce_stage(active_cache[i]))
 677                         ret++;
 678
 679         return ret;
 680 }
 681
 682 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 683 {
 684         struct tree *trees[MAX_UNPACK_TREES];
 685         struct unpack_trees_options opts;
 686         struct tree_desc t[MAX_UNPACK_TREES];
 687         int i, fd, nr_trees = 0;
 688         struct dir_struct dir;
 689         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 690
 691         refresh_cache(REFRESH_QUIET);
 692
 693         fd = hold_locked_index(lock_file, 1);
 694
 695         memset(&trees, 0, sizeof(trees));
 696         memset(&opts, 0, sizeof(opts));
 697         memset(&t, 0, sizeof(t));
 698         memset(&dir, 0, sizeof(dir));
 699         dir.flags |= DIR_SHOW_IGNORED;
 700         dir.exclude_per_dir = ".gitignore";
 701         opts.dir = &dir;
 702
 703         opts.head_idx = 1;
 704         opts.src_index = &the_index;
 705         opts.dst_index = &the_index;
 706         opts.update = 1;
 707         opts.verbose_update = 1;
 708         opts.merge = 1;
 709         opts.fn = twoway_merge;
 710         opts.msgs = get_porcelain_error_msgs();
 711
 712         trees[nr_trees] = parse_tree_indirect(head);
 713         if (!trees[nr_trees++])
 714                 return -1;
 715         trees[nr_trees] = parse_tree_indirect(remote);
 716         if (!trees[nr_trees++])
 717                 return -1;
 718         for (i = 0; i < nr_trees; i++) {
 719                 parse_tree(trees[i]);
 720                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 721         }
 722         if (unpack_trees(nr_trees, t, &opts))
 723                 return -1;
 724         if (write_cache(fd, active_cache, active_nr) ||
 725                 commit_locked_index(lock_file))
 726                 die("unable to write new index file");
 727         return 0;
 728 }
 729
 730 static void split_merge_strategies(const char *string, struct strategy **list,
 731                                    int *nr, int *alloc)
 732 {
 733         char *p, *q, *buf;
 734
 735         if (!string)
 736                 return;
 737
 738         buf = xstrdup(string);
 739         q = buf;
 740         for (;;) {
 741                 p = strchr(q, ' ');
 742                 if (!p) {
 743                         ALLOC_GROW(*list, *nr + 1, *alloc);
 744                         (*list)[(*nr)++].name = xstrdup(q);
 745                         free(buf);
 746                         return;
 747                 } else {
 748                         *p = '\0';
 749                         ALLOC_GROW(*list, *nr + 1, *alloc);
 750                         (*list)[(*nr)++].name = xstrdup(q);
 751                         q = ++p;
 752                 }
 753         }
 754 }
 755
 756 static void add_strategies(const char *string, unsigned attr)
 757 {
 758         struct strategy *list = NULL;
 759         int list_alloc = 0, list_nr = 0, i;
 760
 761         memset(&list, 0, sizeof(list));
 762         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 763         if (list) {
 764                 for (i = 0; i < list_nr; i++)
 765                         append_strategy(get_strategy(list[i].name));
 766                 return;
 767         }
 768         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 769                 if (all_strategy[i].attr & attr)
 770                         append_strategy(&all_strategy[i]);
 771
 772 }
 773
 774 static int merge_trivial(void)
 775 {
 776         unsigned char result_tree[20], result_commit[20];
 777         struct commit_list *parent = xmalloc(sizeof(*parent));
 778
 779         write_tree_trivial(result_tree);
 780         printf("Wonderful.\n");
 781         parent->item = lookup_commit(head);
 782         parent->next = xmalloc(sizeof(*parent->next));
 783         parent->next->item = remoteheads->item;
 784         parent->next->next = NULL;
 785         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 786         finish(result_commit, "In-index merge");
 787         drop_save();
 788         return 0;
 789 }
 790
 791 static int finish_automerge(struct commit_list *common,
 792                             unsigned char *result_tree,
 793                             const char *wt_strategy)
 794 {
 795         struct commit_list *parents = NULL, *j;
 796         struct strbuf buf = STRBUF_INIT;
 797         unsigned char result_commit[20];
 798
 799         free_commit_list(common);
 800         if (allow_fast_forward) {
 801                 parents = remoteheads;
 802                 commit_list_insert(lookup_commit(head), &parents);
 803                 parents = reduce_heads(parents);
 804         } else {
 805                 struct commit_list **pptr = &parents;
 806
 807                 pptr = &commit_list_insert(lookup_commit(head),
 808                                 pptr)->next;
 809                 for (j = remoteheads; j; j = j->next)
 810                         pptr = &commit_list_insert(j->item, pptr)->next;
 811         }
 812         free_commit_list(remoteheads);
 813         strbuf_addch(&merge_msg, '\n');
 814         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 815         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 816         finish(result_commit, buf.buf);
 817         strbuf_release(&buf);
 818         drop_save();
 819         return 0;
 820 }
 821
 822 static int suggest_conflicts(void)
 823 {
 824         FILE *fp;
 825         int pos;
 826
 827         fp = fopen(git_path("MERGE_MSG"), "a");
 828         if (!fp)
 829                 die_errno("Could not open '%s' for writing",
 830                           git_path("MERGE_MSG"));
 831         fprintf(fp, "\nConflicts:\n");
 832         for (pos = 0; pos < active_nr; pos++) {
 833                 struct cache_entry *ce = active_cache[pos];
 834
 835                 if (ce_stage(ce)) {
 836                         fprintf(fp, "\t%s\n", ce->name);
 837                         while (pos + 1 < active_nr &&
 838                                         !strcmp(ce->name,
 839                                                 active_cache[pos + 1]->name))
 840                                 pos++;
 841                 }
 842         }
 843         fclose(fp);
 844         rerere(allow_rerere_auto);
 845         printf("Automatic merge failed; "
 846                         "fix conflicts and then commit the result.\n");
 847         return 1;
 848 }
 849
 850 static struct commit *is_old_style_invocation(int argc, const char **argv)
 851 {
 852         struct commit *second_token = NULL;
 853         if (argc > 2) {
 854                 unsigned char second_sha1[20];
 855
 856                 if (get_sha1(argv[1], second_sha1))
 857                         return NULL;
 858                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 859                 if (!second_token)
 860                         die("'%s' is not a commit", argv[1]);
 861                 if (hashcmp(second_token->object.sha1, head))
 862                         return NULL;
 863         }
 864         return second_token;
 865 }
 866
 867 static int evaluate_result(void)
 868 {
 869         int cnt = 0;
 870         struct rev_info rev;
 871
 872         /* Check how many files differ. */
 873         init_revisions(&rev, "");
 874         setup_revisions(0, NULL, &rev, NULL);
 875         rev.diffopt.output_format |=
 876                 DIFF_FORMAT_CALLBACK;
 877         rev.diffopt.format_callback = count_diff_files;
 878         rev.diffopt.format_callback_data = &cnt;
 879         run_diff_files(&rev, 0);
 880
 881         /*
 882          * Check how many unmerged entries are
 883          * there.
 884          */
 885         cnt += count_unmerged_entries();
 886
 887         return cnt;
 888 }
 889
 890 int cmd_merge(int argc, const char **argv, const char *prefix)
 891 {
 892         unsigned char result_tree[20];
 893         struct strbuf buf = STRBUF_INIT;
 894         const char *head_arg;
 895         int flag, head_invalid = 0, i;
 896         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 897         struct commit_list *common = NULL;
 898         const char *best_strategy = NULL, *wt_strategy = NULL;
 899         struct commit_list **remotes = &remoteheads;
 900
 901         /*
 902          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 903          * current branch.
 904          */
 905         branch = resolve_ref("HEAD", head, 0, &flag);
 906         if (branch && !prefixcmp(branch, "refs/heads/"))
 907                 branch += 11;
 908         if (is_null_sha1(head))
 909                 head_invalid = 1;
 910
 911         git_config(git_merge_config, NULL);
 912
 913         /* for color.ui */
 914         if (diff_use_color_default == -1)
 915                 diff_use_color_default = git_use_color_default;
 916
 917         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 918                         builtin_merge_usage, 0);
 919
 920         if (abort_current_merge) {
 921                 int nargc = 2;
 922                 const char *nargv[] = {"reset", "--merge", NULL};
 923
 924                 if (!file_exists(git_path("MERGE_HEAD")))
 925                         die("There is no merge to abort (MERGE_HEAD missing).");
 926
 927                 /* Invoke 'git reset --merge' */
 928                 return cmd_reset(nargc, nargv, prefix);
 929         }
 930
 931         if (read_cache_unmerged())
 932                 die_resolve_conflict("merge");
 933
 934         if (file_exists(git_path("MERGE_HEAD"))) {
 935                 /*
 936                  * There is no unmerged entry, don't advise 'git
 937                  * add/rm <file>', just 'git commit'.
 938                  */
 939                 if (advice_resolve_conflict)
 940                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
 941                             "Please, commit your changes before you can merge.");
 942                 else
 943                         die("You have not concluded your merge (MERGE_HEAD exists).");
 944         }
 945         resolve_undo_clear();
 946
 947         if (verbosity < 0)
 948                 show_diffstat = 0;
 949
 950         if (squash) {
 951                 if (!allow_fast_forward)
 952                         die("You cannot combine --squash with --no-ff.");
 953                 option_commit = 0;
 954         }
 955
 956         if (!allow_fast_forward && fast_forward_only)
 957                 die("You cannot combine --no-ff with --ff-only.");
 958
 959         if (!argc)
 960                 usage_with_options(builtin_merge_usage,
 961                         builtin_merge_options);
 962
 963         /*
 964          * This could be traditional "merge <msg> HEAD <commit>..."  and
 965          * the way we can tell it is to see if the second token is HEAD,
 966          * but some people might have misused the interface and used a
 967          * committish that is the same as HEAD there instead.
 968          * Traditional format never would have "-m" so it is an
 969          * additional safety measure to check for it.
 970          */
 971
 972         if (!have_message && is_old_style_invocation(argc, argv)) {
 973                 strbuf_addstr(&merge_msg, argv[0]);
 974                 head_arg = argv[1];
 975                 argv += 2;
 976                 argc -= 2;
 977         } else if (head_invalid) {
 978                 struct object *remote_head;
 979                 /*
 980                  * If the merged head is a valid one there is no reason
 981                  * to forbid "git merge" into a branch yet to be born.
 982                  * We do the same for "git pull".
 983                  */
 984                 if (argc != 1)
 985                         die("Can merge only exactly one commit into "
 986                                 "empty head");
 987                 if (squash)
 988                         die("Squash commit into empty head not supported yet");
 989                 if (!allow_fast_forward)
 990                         die("Non-fast-forward commit does not make sense into "
 991                             "an empty head");
 992                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 993                 if (!remote_head)
 994                         die("%s - not something we can merge", argv[0]);
 995                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 996                                 DIE_ON_ERR);
 997                 reset_hard(remote_head->sha1, 0);
 998                 return 0;
 999         } else {
1000                 struct strbuf merge_names = STRBUF_INIT;
1001
1002                 /* We are invoked directly as the first-class UI. */
1003                 head_arg = "HEAD";
1004
1005                 /*
1006                  * All the rest are the commits being merged;
1007                  * prepare the standard merge summary message to
1008                  * be appended to the given message.  If remote
1009                  * is invalid we will die later in the common
1010                  * codepath so we discard the error in this
1011                  * loop.
1012                  */
1013                 for (i = 0; i < argc; i++)
1014                         merge_name(argv[i], &merge_names);
1015
1016                 if (have_message && option_log)
1017                         fmt_merge_msg_shortlog(&merge_names, &merge_msg);
1018                 else if (!have_message)
1019                         fmt_merge_msg(option_log, &merge_names, &merge_msg);
1020
1021
1022                 if (!(have_message && !option_log) && merge_msg.len)
1023                         strbuf_setlen(&merge_msg, merge_msg.len-1);
1024         }
1025
1026         if (head_invalid || !argc)
1027                 usage_with_options(builtin_merge_usage,
1028                         builtin_merge_options);
1029
1030         strbuf_addstr(&buf, "merge");
1031         for (i = 0; i < argc; i++)
1032                 strbuf_addf(&buf, " %s", argv[i]);
1033         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1034         strbuf_reset(&buf);
1035
1036         for (i = 0; i < argc; i++) {
1037                 struct object *o;
1038                 struct commit *commit;
1039
1040                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1041                 if (!o)
1042                         die("%s - not something we can merge", argv[i]);
1043                 commit = lookup_commit(o->sha1);
1044                 commit->util = (void *)argv[i];
1045                 remotes = &commit_list_insert(commit, remotes)->next;
1046
1047                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1048                 setenv(buf.buf, argv[i], 1);
1049                 strbuf_reset(&buf);
1050         }
1051
1052         if (!use_strategies) {
1053                 if (!remoteheads->next)
1054                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1055                 else
1056                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1057         }
1058
1059         for (i = 0; i < use_strategies_nr; i++) {
1060                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1061                         allow_fast_forward = 0;
1062                 if (use_strategies[i]->attr & NO_TRIVIAL)
1063                         allow_trivial = 0;
1064         }
1065
1066         if (!remoteheads->next)
1067                 common = get_merge_bases(lookup_commit(head),
1068                                 remoteheads->item, 1);
1069         else {
1070                 struct commit_list *list = remoteheads;
1071                 commit_list_insert(lookup_commit(head), &list);
1072                 common = get_octopus_merge_bases(list);
1073                 free(list);
1074         }
1075
1076         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1077                 DIE_ON_ERR);
1078
1079         if (!common)
1080                 ; /* No common ancestors found. We need a real merge. */
1081         else if (!remoteheads->next && !common->next &&
1082                         common->item == remoteheads->item) {
1083                 /*
1084                  * If head can reach all the merge then we are up to date.
1085                  * but first the most common case of merging one remote.
1086                  */
1087                 finish_up_to_date("Already up-to-date.");
1088                 return 0;
1089         } else if (allow_fast_forward && !remoteheads->next &&
1090                         !common->next &&
1091                         !hashcmp(common->item->object.sha1, head)) {
1092                 /* Again the most common case of merging one remote. */
1093                 struct strbuf msg = STRBUF_INIT;
1094                 struct object *o;
1095                 char hex[41];
1096
1097                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1098
1099                 if (verbosity >= 0)
1100                         printf("Updating %s..%s\n",
1101                                 hex,
1102                                 find_unique_abbrev(remoteheads->item->object.sha1,
1103                                 DEFAULT_ABBREV));
1104                 strbuf_addstr(&msg, "Fast-forward");
1105                 if (have_message)
1106                         strbuf_addstr(&msg,
1107                                 " (no commit created; -m option ignored)");
1108                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1109                         0, NULL, OBJ_COMMIT);
1110                 if (!o)
1111                         return 1;
1112
1113                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1114                         return 1;
1115
1116                 finish(o->sha1, msg.buf);
1117                 drop_save();
1118                 return 0;
1119         } else if (!remoteheads->next && common->next)
1120                 ;
1121                 /*
1122                  * We are not doing octopus and not fast-forward.  Need
1123                  * a real merge.
1124                  */
1125         else if (!remoteheads->next && !common->next && option_commit) {
1126                 /*
1127                  * We are not doing octopus, not fast-forward, and have
1128                  * only one common.
1129                  */
1130                 refresh_cache(REFRESH_QUIET);
1131                 if (allow_trivial && !fast_forward_only) {
1132                         /* See if it is really trivial. */
1133                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1134                         printf("Trying really trivial in-index merge...\n");
1135                         if (!read_tree_trivial(common->item->object.sha1,
1136                                         head, remoteheads->item->object.sha1))
1137                                 return merge_trivial();
1138                         printf("Nope.\n");
1139                 }
1140         } else {
1141                 /*
1142                  * An octopus.  If we can reach all the remote we are up
1143                  * to date.
1144                  */
1145                 int up_to_date = 1;
1146                 struct commit_list *j;
1147
1148                 for (j = remoteheads; j; j = j->next) {
1149                         struct commit_list *common_one;
1150
1151                         /*
1152                          * Here we *have* to calculate the individual
1153                          * merge_bases again, otherwise "git merge HEAD^
1154                          * HEAD^^" would be missed.
1155                          */
1156                         common_one = get_merge_bases(lookup_commit(head),
1157                                 j->item, 1);
1158                         if (hashcmp(common_one->item->object.sha1,
1159                                 j->item->object.sha1)) {
1160                                 up_to_date = 0;
1161                                 break;
1162                         }
1163                 }
1164                 if (up_to_date) {
1165                         finish_up_to_date("Already up-to-date. Yeeah!");
1166                         return 0;
1167                 }
1168         }
1169
1170         if (fast_forward_only)
1171                 die("Not possible to fast-forward, aborting.");
1172
1173         /* We are going to make a new commit. */
1174         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1175
1176         /*
1177          * At this point, we need a real merge.  No matter what strategy
1178          * we use, it would operate on the index, possibly affecting the
1179          * working tree, and when resolved cleanly, have the desired
1180          * tree in the index -- this means that the index must be in
1181          * sync with the head commit.  The strategies are responsible
1182          * to ensure this.
1183          */
1184         if (use_strategies_nr != 1) {
1185                 /*
1186                  * Stash away the local changes so that we can try more
1187                  * than one.
1188                  */
1189                 save_state();
1190         } else {
1191                 memcpy(stash, null_sha1, 20);
1192         }
1193
1194         for (i = 0; i < use_strategies_nr; i++) {
1195                 int ret;
1196                 if (i) {
1197                         printf("Rewinding the tree to pristine...\n");
1198                         restore_state();
1199                 }
1200                 if (use_strategies_nr != 1)
1201                         printf("Trying merge strategy %s...\n",
1202                                 use_strategies[i]->name);
1203                 /*
1204                  * Remember which strategy left the state in the working
1205                  * tree.
1206                  */
1207                 wt_strategy = use_strategies[i]->name;
1208
1209                 ret = try_merge_strategy(use_strategies[i]->name,
1210                         common, head_arg);
1211                 if (!option_commit && !ret) {
1212                         merge_was_ok = 1;
1213                         /*
1214                          * This is necessary here just to avoid writing
1215                          * the tree, but later we will *not* exit with
1216                          * status code 1 because merge_was_ok is set.
1217                          */
1218                         ret = 1;
1219                 }
1220
1221                 if (ret) {
1222                         /*
1223                          * The backend exits with 1 when conflicts are
1224                          * left to be resolved, with 2 when it does not
1225                          * handle the given merge at all.
1226                          */
1227                         if (ret == 1) {
1228                                 int cnt = evaluate_result();
1229
1230                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1231                                         best_strategy = use_strategies[i]->name;
1232                                         best_cnt = cnt;
1233                                 }
1234                         }
1235                         if (merge_was_ok)
1236                                 break;
1237                         else
1238                                 continue;
1239                 }
1240
1241                 /* Automerge succeeded. */
1242                 write_tree_trivial(result_tree);
1243                 automerge_was_ok = 1;
1244                 break;
1245         }
1246
1247         /*
1248          * If we have a resulting tree, that means the strategy module
1249          * auto resolved the merge cleanly.
1250          */
1251         if (automerge_was_ok)
1252                 return finish_automerge(common, result_tree, wt_strategy);
1253
1254         /*
1255          * Pick the result from the best strategy and have the user fix
1256          * it up.
1257          */
1258         if (!best_strategy) {
1259                 restore_state();
1260                 if (use_strategies_nr > 1)
1261                         fprintf(stderr,
1262                                 "No merge strategy handled the merge.\n");
1263                 else
1264                         fprintf(stderr, "Merge with strategy %s failed.\n",
1265                                 use_strategies[0]->name);
1266                 return 2;
1267         } else if (best_strategy == wt_strategy)
1268                 ; /* We already have its result in the working tree. */
1269         else {
1270                 printf("Rewinding the tree to pristine...\n");
1271                 restore_state();
1272                 printf("Using the %s to prepare resolving by hand.\n",
1273                         best_strategy);
1274                 try_merge_strategy(best_strategy, common, head_arg);
1275         }
1276
1277         if (squash)
1278                 finish(NULL, NULL);
1279         else {
1280                 int fd;
1281                 struct commit_list *j;
1282
1283                 for (j = remoteheads; j; j = j->next)
1284                         strbuf_addf(&buf, "%s\n",
1285                                 sha1_to_hex(j->item->object.sha1));
1286                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1287                 if (fd < 0)
1288                         die_errno("Could not open '%s' for writing",
1289                                   git_path("MERGE_HEAD"));
1290                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1291                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1292                 close(fd);
1293                 strbuf_addch(&merge_msg, '\n');
1294                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1295                 if (fd < 0)
1296                         die_errno("Could not open '%s' for writing",
1297                                   git_path("MERGE_MSG"));
1298                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1299                         merge_msg.len)
1300                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1301                 close(fd);
1302                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1303                 if (fd < 0)
1304                         die_errno("Could not open '%s' for writing",
1305                                   git_path("MERGE_MODE"));
1306                 strbuf_reset(&buf);
1307                 if (!allow_fast_forward)
1308                         strbuf_addf(&buf, "no-ff");
1309                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1310                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1311                 close(fd);
1312         }
1313
1314         if (merge_was_ok) {
1315                 fprintf(stderr, "Automatic merge went well; "
1316                         "stopped before committing as requested\n");
1317                 return 0;
1318         } else
1319                 return suggest_conflicts();
1320 }