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