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 read_empty(unsigned const char *sha1, int verbose)
 235 {
 236         int i = 0;
 237         const char *args[7];
 238
 239         args[i++] = "read-tree";
 240         if (verbose)
 241                 args[i++] = "-v";
 242         args[i++] = "-m";
 243         args[i++] = "-u";
 244         args[i++] = EMPTY_TREE_SHA1_HEX;
 245         args[i++] = sha1_to_hex(sha1);
 246         args[i] = NULL;
 247
 248         if (run_command_v_opt(args, RUN_GIT_CMD))
 249                 die("read-tree failed");
 250 }
 251
 252 static void reset_hard(unsigned const char *sha1, int verbose)
 253 {
 254         int i = 0;
 255         const char *args[6];
 256
 257         args[i++] = "read-tree";
 258         if (verbose)
 259                 args[i++] = "-v";
 260         args[i++] = "--reset";
 261         args[i++] = "-u";
 262         args[i++] = sha1_to_hex(sha1);
 263         args[i] = NULL;
 264
 265         if (run_command_v_opt(args, RUN_GIT_CMD))
 266                 die("read-tree failed");
 267 }
 268
 269 static void restore_state(void)
 270 {
 271         struct strbuf sb = STRBUF_INIT;
 272         const char *args[] = { "stash", "apply", NULL, NULL };
 273
 274         if (is_null_sha1(stash))
 275                 return;
 276
 277         reset_hard(head, 1);
 278
 279         args[2] = sha1_to_hex(stash);
 280
 281         /*
 282          * It is OK to ignore error here, for example when there was
 283          * nothing to restore.
 284          */
 285         run_command_v_opt(args, RUN_GIT_CMD);
 286
 287         strbuf_release(&sb);
 288         refresh_cache(REFRESH_QUIET);
 289 }
 290
 291 /* This is called when no merge was necessary. */
 292 static void finish_up_to_date(const char *msg)
 293 {
 294         if (verbosity >= 0)
 295                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 296         drop_save();
 297 }
 298
 299 static void squash_message(void)
 300 {
 301         struct rev_info rev;
 302         struct commit *commit;
 303         struct strbuf out = STRBUF_INIT;
 304         struct commit_list *j;
 305         int fd;
 306         struct pretty_print_context ctx = {0};
 307
 308         printf("Squash commit -- not updating HEAD\n");
 309         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 310         if (fd < 0)
 311                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 312
 313         init_revisions(&rev, NULL);
 314         rev.ignore_merges = 1;
 315         rev.commit_format = CMIT_FMT_MEDIUM;
 316
 317         commit = lookup_commit(head);
 318         commit->object.flags |= UNINTERESTING;
 319         add_pending_object(&rev, &commit->object, NULL);
 320
 321         for (j = remoteheads; j; j = j->next)
 322                 add_pending_object(&rev, &j->item->object, NULL);
 323
 324         setup_revisions(0, NULL, &rev, NULL);
 325         if (prepare_revision_walk(&rev))
 326                 die("revision walk setup failed");
 327
 328         ctx.abbrev = rev.abbrev;
 329         ctx.date_mode = rev.date_mode;
 330
 331         strbuf_addstr(&out, "Squashed commit of the following:\n");
 332         while ((commit = get_revision(&rev)) != NULL) {
 333                 strbuf_addch(&out, '\n');
 334                 strbuf_addf(&out, "commit %s\n",
 335                         sha1_to_hex(commit->object.sha1));
 336                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 337         }
 338         if (write(fd, out.buf, out.len) < 0)
 339                 die_errno("Writing SQUASH_MSG");
 340         if (close(fd))
 341                 die_errno("Finishing SQUASH_MSG");
 342         strbuf_release(&out);
 343 }
 344
 345 static void finish(const unsigned char *new_head, const char *msg)
 346 {
 347         struct strbuf reflog_message = STRBUF_INIT;
 348
 349         if (!msg)
 350                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 351         else {
 352                 if (verbosity >= 0)
 353                         printf("%s\n", msg);
 354                 strbuf_addf(&reflog_message, "%s: %s",
 355                         getenv("GIT_REFLOG_ACTION"), msg);
 356         }
 357         if (squash) {
 358                 squash_message();
 359         } else {
 360                 if (verbosity >= 0 && !merge_msg.len)
 361                         printf("No merge message -- not updating HEAD\n");
 362                 else {
 363                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 364                         update_ref(reflog_message.buf, "HEAD",
 365                                 new_head, head, 0,
 366                                 DIE_ON_ERR);
 367                         /*
 368                          * We ignore errors in 'gc --auto', since the
 369                          * user should see them.
 370                          */
 371                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 372                 }
 373         }
 374         if (new_head && show_diffstat) {
 375                 struct diff_options opts;
 376                 diff_setup(&opts);
 377                 opts.output_format |=
 378                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 379                 opts.detect_rename = DIFF_DETECT_RENAME;
 380                 if (diff_use_color_default > 0)
 381                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 382                 if (diff_setup_done(&opts) < 0)
 383                         die("diff_setup_done failed");
 384                 diff_tree_sha1(head, new_head, "", &opts);
 385                 diffcore_std(&opts);
 386                 diff_flush(&opts);
 387         }
 388
 389         /* Run a post-merge hook */
 390         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 391
 392         strbuf_release(&reflog_message);
 393 }
 394
 395 /* Get the name for the merge commit's message. */
 396 static void merge_name(const char *remote, struct strbuf *msg)
 397 {
 398         struct object *remote_head;
 399         unsigned char branch_head[20], buf_sha[20];
 400         struct strbuf buf = STRBUF_INIT;
 401         struct strbuf bname = STRBUF_INIT;
 402         const char *ptr;
 403         char *found_ref;
 404         int len, early;
 405
 406         strbuf_branchname(&bname, remote);
 407         remote = bname.buf;
 408
 409         memset(branch_head, 0, sizeof(branch_head));
 410         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 411         if (!remote_head)
 412                 die("'%s' does not point to a commit", remote);
 413
 414         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 415                 if (!prefixcmp(found_ref, "refs/heads/")) {
 416                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 417                                     sha1_to_hex(branch_head), remote);
 418                         goto cleanup;
 419                 }
 420                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 421                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 422                                     sha1_to_hex(branch_head), remote);
 423                         goto cleanup;
 424                 }
 425         }
 426
 427         /* See if remote matches <name>^^^.. or <name>~<number> */
 428         for (len = 0, ptr = remote + strlen(remote);
 429              remote < ptr && ptr[-1] == '^';
 430              ptr--)
 431                 len++;
 432         if (len)
 433                 early = 1;
 434         else {
 435                 early = 0;
 436                 ptr = strrchr(remote, '~');
 437                 if (ptr) {
 438                         int seen_nonzero = 0;
 439
 440                         len++; /* count ~ */
 441                         while (*++ptr && isdigit(*ptr)) {
 442                                 seen_nonzero |= (*ptr != '0');
 443                                 len++;
 444                         }
 445                         if (*ptr)
 446                                 len = 0; /* not ...~<number> */
 447                         else if (seen_nonzero)
 448                                 early = 1;
 449                         else if (len == 1)
 450                                 early = 1; /* "name~" is "name~1"! */
 451                 }
 452         }
 453         if (len) {
 454                 struct strbuf truname = STRBUF_INIT;
 455                 strbuf_addstr(&truname, "refs/heads/");
 456                 strbuf_addstr(&truname, remote);
 457                 strbuf_setlen(&truname, truname.len - len);
 458                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 459                         strbuf_addf(msg,
 460                                     "%s\t\tbranch '%s'%s of .\n",
 461                                     sha1_to_hex(remote_head->sha1),
 462                                     truname.buf + 11,
 463                                     (early ? " (early part)" : ""));
 464                         strbuf_release(&truname);
 465                         goto cleanup;
 466                 }
 467         }
 468
 469         if (!strcmp(remote, "FETCH_HEAD") &&
 470                         !access(git_path("FETCH_HEAD"), R_OK)) {
 471                 FILE *fp;
 472                 struct strbuf line = STRBUF_INIT;
 473                 char *ptr;
 474
 475                 fp = fopen(git_path("FETCH_HEAD"), "r");
 476                 if (!fp)
 477                         die_errno("could not open '%s' for reading",
 478                                   git_path("FETCH_HEAD"));
 479                 strbuf_getline(&line, fp, '\n');
 480                 fclose(fp);
 481                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 482                 if (ptr)
 483                         strbuf_remove(&line, ptr-line.buf+1, 13);
 484                 strbuf_addbuf(msg, &line);
 485                 strbuf_release(&line);
 486                 goto cleanup;
 487         }
 488         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 489                 sha1_to_hex(remote_head->sha1), remote);
 490 cleanup:
 491         strbuf_release(&buf);
 492         strbuf_release(&bname);
 493 }
 494
 495 static int git_merge_config(const char *k, const char *v, void *cb)
 496 {
 497         if (branch && !prefixcmp(k, "branch.") &&
 498                 !prefixcmp(k + 7, branch) &&
 499                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 500                 const char **argv;
 501                 int argc;
 502                 char *buf;
 503
 504                 buf = xstrdup(v);
 505                 argc = split_cmdline(buf, &argv);
 506                 if (argc < 0)
 507                         die("Bad branch.%s.mergeoptions string", branch);
 508                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 509                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 510                 argc++;
 511                 parse_options(argc, argv, NULL, builtin_merge_options,
 512                               builtin_merge_usage, 0);
 513                 free(buf);
 514         }
 515
 516         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 517                 show_diffstat = git_config_bool(k, v);
 518         else if (!strcmp(k, "pull.twohead"))
 519                 return git_config_string(&pull_twohead, k, v);
 520         else if (!strcmp(k, "pull.octopus"))
 521                 return git_config_string(&pull_octopus, k, v);
 522         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 523                 option_log = git_config_bool(k, v);
 524         return git_diff_ui_config(k, v, cb);
 525 }
 526
 527 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 528                              unsigned char *one)
 529 {
 530         int i, nr_trees = 0;
 531         struct tree *trees[MAX_UNPACK_TREES];
 532         struct tree_desc t[MAX_UNPACK_TREES];
 533         struct unpack_trees_options opts;
 534
 535         memset(&opts, 0, sizeof(opts));
 536         opts.head_idx = 2;
 537         opts.src_index = &the_index;
 538         opts.dst_index = &the_index;
 539         opts.update = 1;
 540         opts.verbose_update = 1;
 541         opts.trivial_merges_only = 1;
 542         opts.merge = 1;
 543         trees[nr_trees] = parse_tree_indirect(common);
 544         if (!trees[nr_trees++])
 545                 return -1;
 546         trees[nr_trees] = parse_tree_indirect(head);
 547         if (!trees[nr_trees++])
 548                 return -1;
 549         trees[nr_trees] = parse_tree_indirect(one);
 550         if (!trees[nr_trees++])
 551                 return -1;
 552         opts.fn = threeway_merge;
 553         cache_tree_free(&active_cache_tree);
 554         for (i = 0; i < nr_trees; i++) {
 555                 parse_tree(trees[i]);
 556                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 557         }
 558         if (unpack_trees(nr_trees, t, &opts))
 559                 return -1;
 560         return 0;
 561 }
 562
 563 static void write_tree_trivial(unsigned char *sha1)
 564 {
 565         if (write_cache_as_tree(sha1, 0, NULL))
 566                 die("git write-tree failed to write a tree");
 567 }
 568
 569 int try_merge_command(const char *strategy, struct commit_list *common,
 570                       const char *head_arg, struct commit_list *remotes)
 571 {
 572         const char **args;
 573         int i = 0, x = 0, ret;
 574         struct commit_list *j;
 575         struct strbuf buf = STRBUF_INIT;
 576
 577         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 578                         commit_list_count(remotes)) * sizeof(char *));
 579         strbuf_addf(&buf, "merge-%s", strategy);
 580         args[i++] = buf.buf;
 581         for (x = 0; x < xopts_nr; x++) {
 582                 char *s = xmalloc(strlen(xopts[x])+2+1);
 583                 strcpy(s, "--");
 584                 strcpy(s+2, xopts[x]);
 585                 args[i++] = s;
 586         }
 587         for (j = common; j; j = j->next)
 588                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 589         args[i++] = "--";
 590         args[i++] = head_arg;
 591         for (j = remotes; j; j = j->next)
 592                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 593         args[i] = NULL;
 594         ret = run_command_v_opt(args, RUN_GIT_CMD);
 595         strbuf_release(&buf);
 596         i = 1;
 597         for (x = 0; x < xopts_nr; x++)
 598                 free((void *)args[i++]);
 599         for (j = common; j; j = j->next)
 600                 free((void *)args[i++]);
 601         i += 2;
 602         for (j = remotes; j; j = j->next)
 603                 free((void *)args[i++]);
 604         free(args);
 605         discard_cache();
 606         if (read_cache() < 0)
 607                 die("failed to read the cache");
 608         resolve_undo_clear();
 609
 610         return ret;
 611 }
 612
 613 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 614                               const char *head_arg)
 615 {
 616         int index_fd;
 617         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 618
 619         index_fd = hold_locked_index(lock, 1);
 620         refresh_cache(REFRESH_QUIET);
 621         if (active_cache_changed &&
 622                         (write_cache(index_fd, active_cache, active_nr) ||
 623                          commit_locked_index(lock)))
 624                 return error("Unable to write index.");
 625         rollback_lock_file(lock);
 626
 627         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 628                 int clean, x;
 629                 struct commit *result;
 630                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 631                 int index_fd;
 632                 struct commit_list *reversed = NULL;
 633                 struct merge_options o;
 634                 struct commit_list *j;
 635
 636                 if (remoteheads->next) {
 637                         error("Not handling anything other than two heads merge.");
 638                         return 2;
 639                 }
 640
 641                 init_merge_options(&o);
 642                 if (!strcmp(strategy, "subtree"))
 643                         o.subtree_shift = "";
 644
 645                 for (x = 0; x < xopts_nr; x++) {
 646                         if (!strcmp(xopts[x], "ours"))
 647                                 o.recursive_variant = MERGE_RECURSIVE_OURS;
 648                         else if (!strcmp(xopts[x], "theirs"))
 649                                 o.recursive_variant = MERGE_RECURSIVE_THEIRS;
 650                         else if (!strcmp(xopts[x], "subtree"))
 651                                 o.subtree_shift = "";
 652                         else if (!prefixcmp(xopts[x], "subtree="))
 653                                 o.subtree_shift = xopts[x]+8;
 654                         else
 655                                 die("Unknown option for merge-recursive: -X%s", xopts[x]);
 656                 }
 657
 658                 o.branch1 = head_arg;
 659                 o.branch2 = remoteheads->item->util;
 660
 661                 for (j = common; j; j = j->next)
 662                         commit_list_insert(j->item, &reversed);
 663
 664                 index_fd = hold_locked_index(lock, 1);
 665                 clean = merge_recursive(&o, lookup_commit(head),
 666                                 remoteheads->item, reversed, &result);
 667                 if (active_cache_changed &&
 668                                 (write_cache(index_fd, active_cache, active_nr) ||
 669                                  commit_locked_index(lock)))
 670                         die ("unable to write %s", get_index_file());
 671                 rollback_lock_file(lock);
 672                 return clean ? 0 : 1;
 673         } else {
 674                 return try_merge_command(strategy, common, head_arg, remoteheads);
 675         }
 676 }
 677
 678 static void count_diff_files(struct diff_queue_struct *q,
 679                              struct diff_options *opt, void *data)
 680 {
 681         int *count = data;
 682
 683         (*count) += q->nr;
 684 }
 685
 686 static int count_unmerged_entries(void)
 687 {
 688         int i, ret = 0;
 689
 690         for (i = 0; i < active_nr; i++)
 691                 if (ce_stage(active_cache[i]))
 692                         ret++;
 693
 694         return ret;
 695 }
 696
 697 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 698 {
 699         struct tree *trees[MAX_UNPACK_TREES];
 700         struct unpack_trees_options opts;
 701         struct tree_desc t[MAX_UNPACK_TREES];
 702         int i, fd, nr_trees = 0;
 703         struct dir_struct dir;
 704         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 705
 706         refresh_cache(REFRESH_QUIET);
 707
 708         fd = hold_locked_index(lock_file, 1);
 709
 710         memset(&trees, 0, sizeof(trees));
 711         memset(&opts, 0, sizeof(opts));
 712         memset(&t, 0, sizeof(t));
 713         memset(&dir, 0, sizeof(dir));
 714         dir.flags |= DIR_SHOW_IGNORED;
 715         dir.exclude_per_dir = ".gitignore";
 716         opts.dir = &dir;
 717
 718         opts.head_idx = 1;
 719         opts.src_index = &the_index;
 720         opts.dst_index = &the_index;
 721         opts.update = 1;
 722         opts.verbose_update = 1;
 723         opts.merge = 1;
 724         opts.fn = twoway_merge;
 725         opts.msgs = get_porcelain_error_msgs();
 726
 727         trees[nr_trees] = parse_tree_indirect(head);
 728         if (!trees[nr_trees++])
 729                 return -1;
 730         trees[nr_trees] = parse_tree_indirect(remote);
 731         if (!trees[nr_trees++])
 732                 return -1;
 733         for (i = 0; i < nr_trees; i++) {
 734                 parse_tree(trees[i]);
 735                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 736         }
 737         if (unpack_trees(nr_trees, t, &opts))
 738                 return -1;
 739         if (write_cache(fd, active_cache, active_nr) ||
 740                 commit_locked_index(lock_file))
 741                 die("unable to write new index file");
 742         return 0;
 743 }
 744
 745 static void split_merge_strategies(const char *string, struct strategy **list,
 746                                    int *nr, int *alloc)
 747 {
 748         char *p, *q, *buf;
 749
 750         if (!string)
 751                 return;
 752
 753         buf = xstrdup(string);
 754         q = buf;
 755         for (;;) {
 756                 p = strchr(q, ' ');
 757                 if (!p) {
 758                         ALLOC_GROW(*list, *nr + 1, *alloc);
 759                         (*list)[(*nr)++].name = xstrdup(q);
 760                         free(buf);
 761                         return;
 762                 } else {
 763                         *p = '\0';
 764                         ALLOC_GROW(*list, *nr + 1, *alloc);
 765                         (*list)[(*nr)++].name = xstrdup(q);
 766                         q = ++p;
 767                 }
 768         }
 769 }
 770
 771 static void add_strategies(const char *string, unsigned attr)
 772 {
 773         struct strategy *list = NULL;
 774         int list_alloc = 0, list_nr = 0, i;
 775
 776         memset(&list, 0, sizeof(list));
 777         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 778         if (list) {
 779                 for (i = 0; i < list_nr; i++)
 780                         append_strategy(get_strategy(list[i].name));
 781                 return;
 782         }
 783         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 784                 if (all_strategy[i].attr & attr)
 785                         append_strategy(&all_strategy[i]);
 786
 787 }
 788
 789 static int merge_trivial(void)
 790 {
 791         unsigned char result_tree[20], result_commit[20];
 792         struct commit_list *parent = xmalloc(sizeof(*parent));
 793
 794         write_tree_trivial(result_tree);
 795         printf("Wonderful.\n");
 796         parent->item = lookup_commit(head);
 797         parent->next = xmalloc(sizeof(*parent->next));
 798         parent->next->item = remoteheads->item;
 799         parent->next->next = NULL;
 800         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 801         finish(result_commit, "In-index merge");
 802         drop_save();
 803         return 0;
 804 }
 805
 806 static int finish_automerge(struct commit_list *common,
 807                             unsigned char *result_tree,
 808                             const char *wt_strategy)
 809 {
 810         struct commit_list *parents = NULL, *j;
 811         struct strbuf buf = STRBUF_INIT;
 812         unsigned char result_commit[20];
 813
 814         free_commit_list(common);
 815         if (allow_fast_forward) {
 816                 parents = remoteheads;
 817                 commit_list_insert(lookup_commit(head), &parents);
 818                 parents = reduce_heads(parents);
 819         } else {
 820                 struct commit_list **pptr = &parents;
 821
 822                 pptr = &commit_list_insert(lookup_commit(head),
 823                                 pptr)->next;
 824                 for (j = remoteheads; j; j = j->next)
 825                         pptr = &commit_list_insert(j->item, pptr)->next;
 826         }
 827         free_commit_list(remoteheads);
 828         strbuf_addch(&merge_msg, '\n');
 829         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 830         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 831         finish(result_commit, buf.buf);
 832         strbuf_release(&buf);
 833         drop_save();
 834         return 0;
 835 }
 836
 837 static int suggest_conflicts(void)
 838 {
 839         FILE *fp;
 840         int pos;
 841
 842         fp = fopen(git_path("MERGE_MSG"), "a");
 843         if (!fp)
 844                 die_errno("Could not open '%s' for writing",
 845                           git_path("MERGE_MSG"));
 846         fprintf(fp, "\nConflicts:\n");
 847         for (pos = 0; pos < active_nr; pos++) {
 848                 struct cache_entry *ce = active_cache[pos];
 849
 850                 if (ce_stage(ce)) {
 851                         fprintf(fp, "\t%s\n", ce->name);
 852                         while (pos + 1 < active_nr &&
 853                                         !strcmp(ce->name,
 854                                                 active_cache[pos + 1]->name))
 855                                 pos++;
 856                 }
 857         }
 858         fclose(fp);
 859         rerere(allow_rerere_auto);
 860         printf("Automatic merge failed; "
 861                         "fix conflicts and then commit the result.\n");
 862         return 1;
 863 }
 864
 865 static struct commit *is_old_style_invocation(int argc, const char **argv)
 866 {
 867         struct commit *second_token = NULL;
 868         if (argc > 2) {
 869                 unsigned char second_sha1[20];
 870
 871                 if (get_sha1(argv[1], second_sha1))
 872                         return NULL;
 873                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 874                 if (!second_token)
 875                         die("'%s' is not a commit", argv[1]);
 876                 if (hashcmp(second_token->object.sha1, head))
 877                         return NULL;
 878         }
 879         return second_token;
 880 }
 881
 882 static int evaluate_result(void)
 883 {
 884         int cnt = 0;
 885         struct rev_info rev;
 886
 887         /* Check how many files differ. */
 888         init_revisions(&rev, "");
 889         setup_revisions(0, NULL, &rev, NULL);
 890         rev.diffopt.output_format |=
 891                 DIFF_FORMAT_CALLBACK;
 892         rev.diffopt.format_callback = count_diff_files;
 893         rev.diffopt.format_callback_data = &cnt;
 894         run_diff_files(&rev, 0);
 895
 896         /*
 897          * Check how many unmerged entries are
 898          * there.
 899          */
 900         cnt += count_unmerged_entries();
 901
 902         return cnt;
 903 }
 904
 905 int cmd_merge(int argc, const char **argv, const char *prefix)
 906 {
 907         unsigned char result_tree[20];
 908         struct strbuf buf = STRBUF_INIT;
 909         const char *head_arg;
 910         int flag, head_invalid = 0, i;
 911         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 912         struct commit_list *common = NULL;
 913         const char *best_strategy = NULL, *wt_strategy = NULL;
 914         struct commit_list **remotes = &remoteheads;
 915
 916         if (read_cache_unmerged()) {
 917                 die_resolve_conflict("merge");
 918         }
 919         if (file_exists(git_path("MERGE_HEAD"))) {
 920                 /*
 921                  * There is no unmerged entry, don't advise 'git
 922                  * add/rm <file>', just 'git commit'.
 923                  */
 924                 if (advice_resolve_conflict)
 925                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
 926                             "Please, commit your changes before you can merge.");
 927                 else
 928                         die("You have not concluded your merge (MERGE_HEAD exists).");
 929         }
 930
 931         resolve_undo_clear();
 932         /*
 933          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 934          * current branch.
 935          */
 936         branch = resolve_ref("HEAD", head, 0, &flag);
 937         if (branch && !prefixcmp(branch, "refs/heads/"))
 938                 branch += 11;
 939         if (is_null_sha1(head))
 940                 head_invalid = 1;
 941
 942         git_config(git_merge_config, NULL);
 943
 944         /* for color.ui */
 945         if (diff_use_color_default == -1)
 946                 diff_use_color_default = git_use_color_default;
 947
 948         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 949                         builtin_merge_usage, 0);
 950         if (verbosity < 0)
 951                 show_diffstat = 0;
 952
 953         if (squash) {
 954                 if (!allow_fast_forward)
 955                         die("You cannot combine --squash with --no-ff.");
 956                 option_commit = 0;
 957         }
 958
 959         if (!allow_fast_forward && fast_forward_only)
 960                 die("You cannot combine --no-ff with --ff-only.");
 961
 962         if (!argc)
 963                 usage_with_options(builtin_merge_usage,
 964                         builtin_merge_options);
 965
 966         /*
 967          * This could be traditional "merge <msg> HEAD <commit>..."  and
 968          * the way we can tell it is to see if the second token is HEAD,
 969          * but some people might have misused the interface and used a
 970          * committish that is the same as HEAD there instead.
 971          * Traditional format never would have "-m" so it is an
 972          * additional safety measure to check for it.
 973          */
 974
 975         if (!have_message && is_old_style_invocation(argc, argv)) {
 976                 strbuf_addstr(&merge_msg, argv[0]);
 977                 head_arg = argv[1];
 978                 argv += 2;
 979                 argc -= 2;
 980         } else if (head_invalid) {
 981                 struct object *remote_head;
 982                 /*
 983                  * If the merged head is a valid one there is no reason
 984                  * to forbid "git merge" into a branch yet to be born.
 985                  * We do the same for "git pull".
 986                  */
 987                 if (argc != 1)
 988                         die("Can merge only exactly one commit into "
 989                                 "empty head");
 990                 if (squash)
 991                         die("Squash commit into empty head not supported yet");
 992                 if (!allow_fast_forward)
 993                         die("Non-fast-forward commit does not make sense into "
 994                             "an empty head");
 995                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 996                 if (!remote_head)
 997                         die("%s - not something we can merge", argv[0]);
 998                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 999                                 DIE_ON_ERR);
1000                 read_empty(remote_head->sha1, 0);
1001                 return 0;
1002         } else {
1003                 struct strbuf merge_names = STRBUF_INIT;
1004
1005                 /* We are invoked directly as the first-class UI. */
1006                 head_arg = "HEAD";
1007
1008                 /*
1009                  * All the rest are the commits being merged;
1010                  * prepare the standard merge summary message to
1011                  * be appended to the given message.  If remote
1012                  * is invalid we will die later in the common
1013                  * codepath so we discard the error in this
1014                  * loop.
1015                  */
1016                 for (i = 0; i < argc; i++)
1017                         merge_name(argv[i], &merge_names);
1018
1019                 if (have_message && option_log)
1020                         fmt_merge_msg_shortlog(&merge_names, &merge_msg);
1021                 else if (!have_message)
1022                         fmt_merge_msg(option_log, &merge_names, &merge_msg);
1023
1024
1025                 if (!(have_message && !option_log) && merge_msg.len)
1026                         strbuf_setlen(&merge_msg, merge_msg.len-1);
1027         }
1028
1029         if (head_invalid || !argc)
1030                 usage_with_options(builtin_merge_usage,
1031                         builtin_merge_options);
1032
1033         strbuf_addstr(&buf, "merge");
1034         for (i = 0; i < argc; i++)
1035                 strbuf_addf(&buf, " %s", argv[i]);
1036         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1037         strbuf_reset(&buf);
1038
1039         for (i = 0; i < argc; i++) {
1040                 struct object *o;
1041                 struct commit *commit;
1042
1043                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1044                 if (!o)
1045                         die("%s - not something we can merge", argv[i]);
1046                 commit = lookup_commit(o->sha1);
1047                 commit->util = (void *)argv[i];
1048                 remotes = &commit_list_insert(commit, remotes)->next;
1049
1050                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1051                 setenv(buf.buf, argv[i], 1);
1052                 strbuf_reset(&buf);
1053         }
1054
1055         if (!use_strategies) {
1056                 if (!remoteheads->next)
1057                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1058                 else
1059                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1060         }
1061
1062         for (i = 0; i < use_strategies_nr; i++) {
1063                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1064                         allow_fast_forward = 0;
1065                 if (use_strategies[i]->attr & NO_TRIVIAL)
1066                         allow_trivial = 0;
1067         }
1068
1069         if (!remoteheads->next)
1070                 common = get_merge_bases(lookup_commit(head),
1071                                 remoteheads->item, 1);
1072         else {
1073                 struct commit_list *list = remoteheads;
1074                 commit_list_insert(lookup_commit(head), &list);
1075                 common = get_octopus_merge_bases(list);
1076                 free(list);
1077         }
1078
1079         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1080                 DIE_ON_ERR);
1081
1082         if (!common)
1083                 ; /* No common ancestors found. We need a real merge. */
1084         else if (!remoteheads->next && !common->next &&
1085                         common->item == remoteheads->item) {
1086                 /*
1087                  * If head can reach all the merge then we are up to date.
1088                  * but first the most common case of merging one remote.
1089                  */
1090                 finish_up_to_date("Already up-to-date.");
1091                 return 0;
1092         } else if (allow_fast_forward && !remoteheads->next &&
1093                         !common->next &&
1094                         !hashcmp(common->item->object.sha1, head)) {
1095                 /* Again the most common case of merging one remote. */
1096                 struct strbuf msg = STRBUF_INIT;
1097                 struct object *o;
1098                 char hex[41];
1099
1100                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1101
1102                 if (verbosity >= 0)
1103                         printf("Updating %s..%s\n",
1104                                 hex,
1105                                 find_unique_abbrev(remoteheads->item->object.sha1,
1106                                 DEFAULT_ABBREV));
1107                 strbuf_addstr(&msg, "Fast-forward");
1108                 if (have_message)
1109                         strbuf_addstr(&msg,
1110                                 " (no commit created; -m option ignored)");
1111                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1112                         0, NULL, OBJ_COMMIT);
1113                 if (!o)
1114                         return 1;
1115
1116                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1117                         return 1;
1118
1119                 finish(o->sha1, msg.buf);
1120                 drop_save();
1121                 return 0;
1122         } else if (!remoteheads->next && common->next)
1123                 ;
1124                 /*
1125                  * We are not doing octopus and not fast-forward.  Need
1126                  * a real merge.
1127                  */
1128         else if (!remoteheads->next && !common->next && option_commit) {
1129                 /*
1130                  * We are not doing octopus, not fast-forward, and have
1131                  * only one common.
1132                  */
1133                 refresh_cache(REFRESH_QUIET);
1134                 if (allow_trivial && !fast_forward_only) {
1135                         /* See if it is really trivial. */
1136                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1137                         printf("Trying really trivial in-index merge...\n");
1138                         if (!read_tree_trivial(common->item->object.sha1,
1139                                         head, remoteheads->item->object.sha1))
1140                                 return merge_trivial();
1141                         printf("Nope.\n");
1142                 }
1143         } else {
1144                 /*
1145                  * An octopus.  If we can reach all the remote we are up
1146                  * to date.
1147                  */
1148                 int up_to_date = 1;
1149                 struct commit_list *j;
1150
1151                 for (j = remoteheads; j; j = j->next) {
1152                         struct commit_list *common_one;
1153
1154                         /*
1155                          * Here we *have* to calculate the individual
1156                          * merge_bases again, otherwise "git merge HEAD^
1157                          * HEAD^^" would be missed.
1158                          */
1159                         common_one = get_merge_bases(lookup_commit(head),
1160                                 j->item, 1);
1161                         if (hashcmp(common_one->item->object.sha1,
1162                                 j->item->object.sha1)) {
1163                                 up_to_date = 0;
1164                                 break;
1165                         }
1166                 }
1167                 if (up_to_date) {
1168                         finish_up_to_date("Already up-to-date. Yeeah!");
1169                         return 0;
1170                 }
1171         }
1172
1173         if (fast_forward_only)
1174                 die("Not possible to fast-forward, aborting.");
1175
1176         /* We are going to make a new commit. */
1177         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1178
1179         /*
1180          * At this point, we need a real merge.  No matter what strategy
1181          * we use, it would operate on the index, possibly affecting the
1182          * working tree, and when resolved cleanly, have the desired
1183          * tree in the index -- this means that the index must be in
1184          * sync with the head commit.  The strategies are responsible
1185          * to ensure this.
1186          */
1187         if (use_strategies_nr != 1) {
1188                 /*
1189                  * Stash away the local changes so that we can try more
1190                  * than one.
1191                  */
1192                 save_state();
1193         } else {
1194                 memcpy(stash, null_sha1, 20);
1195         }
1196
1197         for (i = 0; i < use_strategies_nr; i++) {
1198                 int ret;
1199                 if (i) {
1200                         printf("Rewinding the tree to pristine...\n");
1201                         restore_state();
1202                 }
1203                 if (use_strategies_nr != 1)
1204                         printf("Trying merge strategy %s...\n",
1205                                 use_strategies[i]->name);
1206                 /*
1207                  * Remember which strategy left the state in the working
1208                  * tree.
1209                  */
1210                 wt_strategy = use_strategies[i]->name;
1211
1212                 ret = try_merge_strategy(use_strategies[i]->name,
1213                         common, head_arg);
1214                 if (!option_commit && !ret) {
1215                         merge_was_ok = 1;
1216                         /*
1217                          * This is necessary here just to avoid writing
1218                          * the tree, but later we will *not* exit with
1219                          * status code 1 because merge_was_ok is set.
1220                          */
1221                         ret = 1;
1222                 }
1223
1224                 if (ret) {
1225                         /*
1226                          * The backend exits with 1 when conflicts are
1227                          * left to be resolved, with 2 when it does not
1228                          * handle the given merge at all.
1229                          */
1230                         if (ret == 1) {
1231                                 int cnt = evaluate_result();
1232
1233                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1234                                         best_strategy = use_strategies[i]->name;
1235                                         best_cnt = cnt;
1236                                 }
1237                         }
1238                         if (merge_was_ok)
1239                                 break;
1240                         else
1241                                 continue;
1242                 }
1243
1244                 /* Automerge succeeded. */
1245                 write_tree_trivial(result_tree);
1246                 automerge_was_ok = 1;
1247                 break;
1248         }
1249
1250         /*
1251          * If we have a resulting tree, that means the strategy module
1252          * auto resolved the merge cleanly.
1253          */
1254         if (automerge_was_ok)
1255                 return finish_automerge(common, result_tree, wt_strategy);
1256
1257         /*
1258          * Pick the result from the best strategy and have the user fix
1259          * it up.
1260          */
1261         if (!best_strategy) {
1262                 restore_state();
1263                 if (use_strategies_nr > 1)
1264                         fprintf(stderr,
1265                                 "No merge strategy handled the merge.\n");
1266                 else
1267                         fprintf(stderr, "Merge with strategy %s failed.\n",
1268                                 use_strategies[0]->name);
1269                 return 2;
1270         } else if (best_strategy == wt_strategy)
1271                 ; /* We already have its result in the working tree. */
1272         else {
1273                 printf("Rewinding the tree to pristine...\n");
1274                 restore_state();
1275                 printf("Using the %s to prepare resolving by hand.\n",
1276                         best_strategy);
1277                 try_merge_strategy(best_strategy, common, head_arg);
1278         }
1279
1280         if (squash)
1281                 finish(NULL, NULL);
1282         else {
1283                 int fd;
1284                 struct commit_list *j;
1285
1286                 for (j = remoteheads; j; j = j->next)
1287                         strbuf_addf(&buf, "%s\n",
1288                                 sha1_to_hex(j->item->object.sha1));
1289                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1290                 if (fd < 0)
1291                         die_errno("Could not open '%s' for writing",
1292                                   git_path("MERGE_HEAD"));
1293                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1294                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1295                 close(fd);
1296                 strbuf_addch(&merge_msg, '\n');
1297                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1298                 if (fd < 0)
1299                         die_errno("Could not open '%s' for writing",
1300                                   git_path("MERGE_MSG"));
1301                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1302                         merge_msg.len)
1303                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1304                 close(fd);
1305                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1306                 if (fd < 0)
1307                         die_errno("Could not open '%s' for writing",
1308                                   git_path("MERGE_MODE"));
1309                 strbuf_reset(&buf);
1310                 if (!allow_fast_forward)
1311                         strbuf_addf(&buf, "no-ff");
1312                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1313                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1314                 close(fd);
1315         }
1316
1317         if (merge_was_ok) {
1318                 fprintf(stderr, "Automatic merge went well; "
1319                         "stopped before committing as requested\n");
1320                 return 0;
1321         } else
1322                 return suggest_conflicts();
1323 }