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 #include "remote.h"
  29
  30 #define DEFAULT_TWOHEAD (1<<0)
  31 #define DEFAULT_OCTOPUS (1<<1)
  32 #define NO_FAST_FORWARD (1<<2)
  33 #define NO_TRIVIAL      (1<<3)
  34
  35 struct strategy {
  36         const char *name;
  37         unsigned attr;
  38 };
  39
  40 static const char * const builtin_merge_usage[] = {
  41         "git merge [options] [<commit>...]",
  42         "git merge [options] <msg> HEAD <commit>",
  43         "git merge --abort",
  44         NULL
  45 };
  46
  47 static int show_diffstat = 1, shortlog_len, squash;
  48 static int option_commit = 1, allow_fast_forward = 1;
  49 static int fast_forward_only;
  50 static int allow_trivial = 1, have_message;
  51 static struct strbuf merge_msg;
  52 static struct commit_list *remoteheads;
  53 static unsigned char head[20], stash[20];
  54 static struct strategy **use_strategies;
  55 static size_t use_strategies_nr, use_strategies_alloc;
  56 static const char **xopts;
  57 static size_t xopts_nr, xopts_alloc;
  58 static const char *branch;
  59 static int option_renormalize;
  60 static int verbosity;
  61 static int allow_rerere_auto;
  62 static int abort_current_merge;
  63 static int show_progress = -1;
  64 static int default_to_upstream;
  65
  66 static struct strategy all_strategy[] = {
  67         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  68         { "octopus",    DEFAULT_OCTOPUS },
  69         { "resolve",    0 },
  70         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  71         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  72 };
  73
  74 static const char *pull_twohead, *pull_octopus;
  75
  76 static int option_parse_message(const struct option *opt,
  77                                 const char *arg, int unset)
  78 {
  79         struct strbuf *buf = opt->value;
  80
  81         if (unset)
  82                 strbuf_setlen(buf, 0);
  83         else if (arg) {
  84                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  85                 have_message = 1;
  86         } else
  87                 return error(_("switch `m' requires a value"));
  88         return 0;
  89 }
  90
  91 static struct strategy *get_strategy(const char *name)
  92 {
  93         int i;
  94         struct strategy *ret;
  95         static struct cmdnames main_cmds, other_cmds;
  96         static int loaded;
  97
  98         if (!name)
  99                 return NULL;
 100
 101         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 102                 if (!strcmp(name, all_strategy[i].name))
 103                         return &all_strategy[i];
 104
 105         if (!loaded) {
 106                 struct cmdnames not_strategies;
 107                 loaded = 1;
 108
 109                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 110                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 111                 for (i = 0; i < main_cmds.cnt; i++) {
 112                         int j, found = 0;
 113                         struct cmdname *ent = main_cmds.names[i];
 114                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 115                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 116                                                 && !all_strategy[j].name[ent->len])
 117                                         found = 1;
 118                         if (!found)
 119                                 add_cmdname(&not_strategies, ent->name, ent->len);
 120                 }
 121                 exclude_cmds(&main_cmds, &not_strategies);
 122         }
 123         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 124                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 125                 fprintf(stderr, _("Available strategies are:"));
 126                 for (i = 0; i < main_cmds.cnt; i++)
 127                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 128                 fprintf(stderr, ".\n");
 129                 if (other_cmds.cnt) {
 130                         fprintf(stderr, _("Available custom strategies are:"));
 131                         for (i = 0; i < other_cmds.cnt; i++)
 132                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 133                         fprintf(stderr, ".\n");
 134                 }
 135                 exit(1);
 136         }
 137
 138         ret = xcalloc(1, sizeof(struct strategy));
 139         ret->name = xstrdup(name);
 140         ret->attr = NO_TRIVIAL;
 141         return ret;
 142 }
 143
 144 static void append_strategy(struct strategy *s)
 145 {
 146         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 147         use_strategies[use_strategies_nr++] = s;
 148 }
 149
 150 static int option_parse_strategy(const struct option *opt,
 151                                  const char *name, int unset)
 152 {
 153         if (unset)
 154                 return 0;
 155
 156         append_strategy(get_strategy(name));
 157         return 0;
 158 }
 159
 160 static int option_parse_x(const struct option *opt,
 161                           const char *arg, int unset)
 162 {
 163         if (unset)
 164                 return 0;
 165
 166         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 167         xopts[xopts_nr++] = xstrdup(arg);
 168         return 0;
 169 }
 170
 171 static int option_parse_n(const struct option *opt,
 172                           const char *arg, int unset)
 173 {
 174         show_diffstat = unset;
 175         return 0;
 176 }
 177
 178 static struct option builtin_merge_options[] = {
 179         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 180                 "do not show a diffstat at the end of the merge",
 181                 PARSE_OPT_NOARG, option_parse_n },
 182         OPT_BOOLEAN(0, "stat", &show_diffstat,
 183                 "show a diffstat at the end of the merge"),
 184         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 185         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 186           "add (at most <n>) entries from shortlog to merge commit message",
 187           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 188         OPT_BOOLEAN(0, "squash", &squash,
 189                 "create a single commit instead of doing a merge"),
 190         OPT_BOOLEAN(0, "commit", &option_commit,
 191                 "perform a commit if the merge succeeds (default)"),
 192         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 193                 "allow fast-forward (default)"),
 194         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 195                 "abort if fast-forward is not possible"),
 196         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 197         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 198                 "merge strategy to use", option_parse_strategy),
 199         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 200                 "option for selected merge strategy", option_parse_x),
 201         OPT_CALLBACK('m', "message", &merge_msg, "message",
 202                 "merge commit message (for a non-fast-forward merge)",
 203                 option_parse_message),
 204         OPT__VERBOSITY(&verbosity),
 205         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 206                 "abort the current in-progress merge"),
 207         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 208         OPT_END()
 209 };
 210
 211 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 212 static void drop_save(void)
 213 {
 214         unlink(git_path("MERGE_HEAD"));
 215         unlink(git_path("MERGE_MSG"));
 216         unlink(git_path("MERGE_MODE"));
 217 }
 218
 219 static void save_state(void)
 220 {
 221         int len;
 222         struct child_process cp;
 223         struct strbuf buffer = STRBUF_INIT;
 224         const char *argv[] = {"stash", "create", NULL};
 225
 226         memset(&cp, 0, sizeof(cp));
 227         cp.argv = argv;
 228         cp.out = -1;
 229         cp.git_cmd = 1;
 230
 231         if (start_command(&cp))
 232                 die(_("could not run stash."));
 233         len = strbuf_read(&buffer, cp.out, 1024);
 234         close(cp.out);
 235
 236         if (finish_command(&cp) || len < 0)
 237                 die(_("stash failed"));
 238         else if (!len)
 239                 return;
 240         strbuf_setlen(&buffer, buffer.len-1);
 241         if (get_sha1(buffer.buf, stash))
 242                 die(_("not a valid object: %s"), buffer.buf);
 243 }
 244
 245 static void read_empty(unsigned const char *sha1, int verbose)
 246 {
 247         int i = 0;
 248         const char *args[7];
 249
 250         args[i++] = "read-tree";
 251         if (verbose)
 252                 args[i++] = "-v";
 253         args[i++] = "-m";
 254         args[i++] = "-u";
 255         args[i++] = EMPTY_TREE_SHA1_HEX;
 256         args[i++] = sha1_to_hex(sha1);
 257         args[i] = NULL;
 258
 259         if (run_command_v_opt(args, RUN_GIT_CMD))
 260                 die(_("read-tree failed"));
 261 }
 262
 263 static void reset_hard(unsigned const char *sha1, int verbose)
 264 {
 265         int i = 0;
 266         const char *args[6];
 267
 268         args[i++] = "read-tree";
 269         if (verbose)
 270                 args[i++] = "-v";
 271         args[i++] = "--reset";
 272         args[i++] = "-u";
 273         args[i++] = sha1_to_hex(sha1);
 274         args[i] = NULL;
 275
 276         if (run_command_v_opt(args, RUN_GIT_CMD))
 277                 die(_("read-tree failed"));
 278 }
 279
 280 static void restore_state(void)
 281 {
 282         struct strbuf sb = STRBUF_INIT;
 283         const char *args[] = { "stash", "apply", NULL, NULL };
 284
 285         if (is_null_sha1(stash))
 286                 return;
 287
 288         reset_hard(head, 1);
 289
 290         args[2] = sha1_to_hex(stash);
 291
 292         /*
 293          * It is OK to ignore error here, for example when there was
 294          * nothing to restore.
 295          */
 296         run_command_v_opt(args, RUN_GIT_CMD);
 297
 298         strbuf_release(&sb);
 299         refresh_cache(REFRESH_QUIET);
 300 }
 301
 302 /* This is called when no merge was necessary. */
 303 static void finish_up_to_date(const char *msg)
 304 {
 305         if (verbosity >= 0)
 306                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 307         drop_save();
 308 }
 309
 310 static void squash_message(void)
 311 {
 312         struct rev_info rev;
 313         struct commit *commit;
 314         struct strbuf out = STRBUF_INIT;
 315         struct commit_list *j;
 316         int fd;
 317         struct pretty_print_context ctx = {0};
 318
 319         printf(_("Squash commit -- not updating HEAD\n"));
 320         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 321         if (fd < 0)
 322                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 323
 324         init_revisions(&rev, NULL);
 325         rev.ignore_merges = 1;
 326         rev.commit_format = CMIT_FMT_MEDIUM;
 327
 328         commit = lookup_commit(head);
 329         commit->object.flags |= UNINTERESTING;
 330         add_pending_object(&rev, &commit->object, NULL);
 331
 332         for (j = remoteheads; j; j = j->next)
 333                 add_pending_object(&rev, &j->item->object, NULL);
 334
 335         setup_revisions(0, NULL, &rev, NULL);
 336         if (prepare_revision_walk(&rev))
 337                 die(_("revision walk setup failed"));
 338
 339         ctx.abbrev = rev.abbrev;
 340         ctx.date_mode = rev.date_mode;
 341
 342         strbuf_addstr(&out, "Squashed commit of the following:\n");
 343         while ((commit = get_revision(&rev)) != NULL) {
 344                 strbuf_addch(&out, '\n');
 345                 strbuf_addf(&out, "commit %s\n",
 346                         sha1_to_hex(commit->object.sha1));
 347                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 348         }
 349         if (write(fd, out.buf, out.len) < 0)
 350                 die_errno(_("Writing SQUASH_MSG"));
 351         if (close(fd))
 352                 die_errno(_("Finishing SQUASH_MSG"));
 353         strbuf_release(&out);
 354 }
 355
 356 static void finish(const unsigned char *new_head, const char *msg)
 357 {
 358         struct strbuf reflog_message = STRBUF_INIT;
 359
 360         if (!msg)
 361                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 362         else {
 363                 if (verbosity >= 0)
 364                         printf("%s\n", msg);
 365                 strbuf_addf(&reflog_message, "%s: %s",
 366                         getenv("GIT_REFLOG_ACTION"), msg);
 367         }
 368         if (squash) {
 369                 squash_message();
 370         } else {
 371                 if (verbosity >= 0 && !merge_msg.len)
 372                         printf(_("No merge message -- not updating HEAD\n"));
 373                 else {
 374                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 375                         update_ref(reflog_message.buf, "HEAD",
 376                                 new_head, head, 0,
 377                                 DIE_ON_ERR);
 378                         /*
 379                          * We ignore errors in 'gc --auto', since the
 380                          * user should see them.
 381                          */
 382                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 383                 }
 384         }
 385         if (new_head && show_diffstat) {
 386                 struct diff_options opts;
 387                 diff_setup(&opts);
 388                 opts.output_format |=
 389                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 390                 opts.detect_rename = DIFF_DETECT_RENAME;
 391                 if (diff_use_color_default > 0)
 392                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 393                 if (diff_setup_done(&opts) < 0)
 394                         die(_("diff_setup_done failed"));
 395                 diff_tree_sha1(head, new_head, "", &opts);
 396                 diffcore_std(&opts);
 397                 diff_flush(&opts);
 398         }
 399
 400         /* Run a post-merge hook */
 401         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 402
 403         strbuf_release(&reflog_message);
 404 }
 405
 406 /* Get the name for the merge commit's message. */
 407 static void merge_name(const char *remote, struct strbuf *msg)
 408 {
 409         struct object *remote_head;
 410         unsigned char branch_head[20], buf_sha[20];
 411         struct strbuf buf = STRBUF_INIT;
 412         struct strbuf bname = STRBUF_INIT;
 413         const char *ptr;
 414         char *found_ref;
 415         int len, early;
 416
 417         strbuf_branchname(&bname, remote);
 418         remote = bname.buf;
 419
 420         memset(branch_head, 0, sizeof(branch_head));
 421         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 422         if (!remote_head)
 423                 die(_("'%s' does not point to a commit"), remote);
 424
 425         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 426                 if (!prefixcmp(found_ref, "refs/heads/")) {
 427                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 428                                     sha1_to_hex(branch_head), remote);
 429                         goto cleanup;
 430                 }
 431                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 432                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 433                                     sha1_to_hex(branch_head), remote);
 434                         goto cleanup;
 435                 }
 436         }
 437
 438         /* See if remote matches <name>^^^.. or <name>~<number> */
 439         for (len = 0, ptr = remote + strlen(remote);
 440              remote < ptr && ptr[-1] == '^';
 441              ptr--)
 442                 len++;
 443         if (len)
 444                 early = 1;
 445         else {
 446                 early = 0;
 447                 ptr = strrchr(remote, '~');
 448                 if (ptr) {
 449                         int seen_nonzero = 0;
 450
 451                         len++; /* count ~ */
 452                         while (*++ptr && isdigit(*ptr)) {
 453                                 seen_nonzero |= (*ptr != '0');
 454                                 len++;
 455                         }
 456                         if (*ptr)
 457                                 len = 0; /* not ...~<number> */
 458                         else if (seen_nonzero)
 459                                 early = 1;
 460                         else if (len == 1)
 461                                 early = 1; /* "name~" is "name~1"! */
 462                 }
 463         }
 464         if (len) {
 465                 struct strbuf truname = STRBUF_INIT;
 466                 strbuf_addstr(&truname, "refs/heads/");
 467                 strbuf_addstr(&truname, remote);
 468                 strbuf_setlen(&truname, truname.len - len);
 469                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 470                         strbuf_addf(msg,
 471                                     "%s\t\tbranch '%s'%s of .\n",
 472                                     sha1_to_hex(remote_head->sha1),
 473                                     truname.buf + 11,
 474                                     (early ? " (early part)" : ""));
 475                         strbuf_release(&truname);
 476                         goto cleanup;
 477                 }
 478         }
 479
 480         if (!strcmp(remote, "FETCH_HEAD") &&
 481                         !access(git_path("FETCH_HEAD"), R_OK)) {
 482                 FILE *fp;
 483                 struct strbuf line = STRBUF_INIT;
 484                 char *ptr;
 485
 486                 fp = fopen(git_path("FETCH_HEAD"), "r");
 487                 if (!fp)
 488                         die_errno(_("could not open '%s' for reading"),
 489                                   git_path("FETCH_HEAD"));
 490                 strbuf_getline(&line, fp, '\n');
 491                 fclose(fp);
 492                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 493                 if (ptr)
 494                         strbuf_remove(&line, ptr-line.buf+1, 13);
 495                 strbuf_addbuf(msg, &line);
 496                 strbuf_release(&line);
 497                 goto cleanup;
 498         }
 499         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 500                 sha1_to_hex(remote_head->sha1), remote);
 501 cleanup:
 502         strbuf_release(&buf);
 503         strbuf_release(&bname);
 504 }
 505
 506 static int git_merge_config(const char *k, const char *v, void *cb)
 507 {
 508         if (branch && !prefixcmp(k, "branch.") &&
 509                 !prefixcmp(k + 7, branch) &&
 510                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 511                 const char **argv;
 512                 int argc;
 513                 char *buf;
 514
 515                 buf = xstrdup(v);
 516                 argc = split_cmdline(buf, &argv);
 517                 if (argc < 0)
 518                         die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 519                             split_cmdline_strerror(argc));
 520                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 521                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 522                 argc++;
 523                 parse_options(argc, argv, NULL, builtin_merge_options,
 524                               builtin_merge_usage, 0);
 525                 free(buf);
 526         }
 527
 528         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 529                 show_diffstat = git_config_bool(k, v);
 530         else if (!strcmp(k, "pull.twohead"))
 531                 return git_config_string(&pull_twohead, k, v);
 532         else if (!strcmp(k, "pull.octopus"))
 533                 return git_config_string(&pull_octopus, k, v);
 534         else if (!strcmp(k, "merge.renormalize"))
 535                 option_renormalize = git_config_bool(k, v);
 536         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 537                 int is_bool;
 538                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 539                 if (!is_bool && shortlog_len < 0)
 540                         return error(_("%s: negative length %s"), k, v);
 541                 if (is_bool && shortlog_len)
 542                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 543                 return 0;
 544         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 545                 default_to_upstream = git_config_bool(k, v);
 546                 return 0;
 547         }
 548         return git_diff_ui_config(k, v, cb);
 549 }
 550
 551 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 552                              unsigned char *one)
 553 {
 554         int i, nr_trees = 0;
 555         struct tree *trees[MAX_UNPACK_TREES];
 556         struct tree_desc t[MAX_UNPACK_TREES];
 557         struct unpack_trees_options opts;
 558
 559         memset(&opts, 0, sizeof(opts));
 560         opts.head_idx = 2;
 561         opts.src_index = &the_index;
 562         opts.dst_index = &the_index;
 563         opts.update = 1;
 564         opts.verbose_update = 1;
 565         opts.trivial_merges_only = 1;
 566         opts.merge = 1;
 567         trees[nr_trees] = parse_tree_indirect(common);
 568         if (!trees[nr_trees++])
 569                 return -1;
 570         trees[nr_trees] = parse_tree_indirect(head);
 571         if (!trees[nr_trees++])
 572                 return -1;
 573         trees[nr_trees] = parse_tree_indirect(one);
 574         if (!trees[nr_trees++])
 575                 return -1;
 576         opts.fn = threeway_merge;
 577         cache_tree_free(&active_cache_tree);
 578         for (i = 0; i < nr_trees; i++) {
 579                 parse_tree(trees[i]);
 580                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 581         }
 582         if (unpack_trees(nr_trees, t, &opts))
 583                 return -1;
 584         return 0;
 585 }
 586
 587 static void write_tree_trivial(unsigned char *sha1)
 588 {
 589         if (write_cache_as_tree(sha1, 0, NULL))
 590                 die(_("git write-tree failed to write a tree"));
 591 }
 592
 593 int try_merge_command(const char *strategy, size_t xopts_nr,
 594                       const char **xopts, struct commit_list *common,
 595                       const char *head_arg, struct commit_list *remotes)
 596 {
 597         const char **args;
 598         int i = 0, x = 0, ret;
 599         struct commit_list *j;
 600         struct strbuf buf = STRBUF_INIT;
 601
 602         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 603                         commit_list_count(remotes)) * sizeof(char *));
 604         strbuf_addf(&buf, "merge-%s", strategy);
 605         args[i++] = buf.buf;
 606         for (x = 0; x < xopts_nr; x++) {
 607                 char *s = xmalloc(strlen(xopts[x])+2+1);
 608                 strcpy(s, "--");
 609                 strcpy(s+2, xopts[x]);
 610                 args[i++] = s;
 611         }
 612         for (j = common; j; j = j->next)
 613                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 614         args[i++] = "--";
 615         args[i++] = head_arg;
 616         for (j = remotes; j; j = j->next)
 617                 args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 618         args[i] = NULL;
 619         ret = run_command_v_opt(args, RUN_GIT_CMD);
 620         strbuf_release(&buf);
 621         i = 1;
 622         for (x = 0; x < xopts_nr; x++)
 623                 free((void *)args[i++]);
 624         for (j = common; j; j = j->next)
 625                 free((void *)args[i++]);
 626         i += 2;
 627         for (j = remotes; j; j = j->next)
 628                 free((void *)args[i++]);
 629         free(args);
 630         discard_cache();
 631         if (read_cache() < 0)
 632                 die(_("failed to read the cache"));
 633         resolve_undo_clear();
 634
 635         return ret;
 636 }
 637
 638 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 639                               const char *head_arg)
 640 {
 641         int index_fd;
 642         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 643
 644         index_fd = hold_locked_index(lock, 1);
 645         refresh_cache(REFRESH_QUIET);
 646         if (active_cache_changed &&
 647                         (write_cache(index_fd, active_cache, active_nr) ||
 648                          commit_locked_index(lock)))
 649                 return error(_("Unable to write index."));
 650         rollback_lock_file(lock);
 651
 652         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 653                 int clean, x;
 654                 struct commit *result;
 655                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 656                 int index_fd;
 657                 struct commit_list *reversed = NULL;
 658                 struct merge_options o;
 659                 struct commit_list *j;
 660
 661                 if (remoteheads->next) {
 662                         error(_("Not handling anything other than two heads merge."));
 663                         return 2;
 664                 }
 665
 666                 init_merge_options(&o);
 667                 if (!strcmp(strategy, "subtree"))
 668                         o.subtree_shift = "";
 669
 670                 o.renormalize = option_renormalize;
 671                 o.show_rename_progress =
 672                         show_progress == -1 ? isatty(2) : show_progress;
 673
 674                 for (x = 0; x < xopts_nr; x++)
 675                         if (parse_merge_opt(&o, xopts[x]))
 676                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 677
 678                 o.branch1 = head_arg;
 679                 o.branch2 = remoteheads->item->util;
 680
 681                 for (j = common; j; j = j->next)
 682                         commit_list_insert(j->item, &reversed);
 683
 684                 index_fd = hold_locked_index(lock, 1);
 685                 clean = merge_recursive(&o, lookup_commit(head),
 686                                 remoteheads->item, reversed, &result);
 687                 if (active_cache_changed &&
 688                                 (write_cache(index_fd, active_cache, active_nr) ||
 689                                  commit_locked_index(lock)))
 690                         die (_("unable to write %s"), get_index_file());
 691                 rollback_lock_file(lock);
 692                 return clean ? 0 : 1;
 693         } else {
 694                 return try_merge_command(strategy, xopts_nr, xopts,
 695                                                 common, head_arg, remoteheads);
 696         }
 697 }
 698
 699 static void count_diff_files(struct diff_queue_struct *q,
 700                              struct diff_options *opt, void *data)
 701 {
 702         int *count = data;
 703
 704         (*count) += q->nr;
 705 }
 706
 707 static int count_unmerged_entries(void)
 708 {
 709         int i, ret = 0;
 710
 711         for (i = 0; i < active_nr; i++)
 712                 if (ce_stage(active_cache[i]))
 713                         ret++;
 714
 715         return ret;
 716 }
 717
 718 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 719 {
 720         struct tree *trees[MAX_UNPACK_TREES];
 721         struct unpack_trees_options opts;
 722         struct tree_desc t[MAX_UNPACK_TREES];
 723         int i, fd, nr_trees = 0;
 724         struct dir_struct dir;
 725         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 726
 727         refresh_cache(REFRESH_QUIET);
 728
 729         fd = hold_locked_index(lock_file, 1);
 730
 731         memset(&trees, 0, sizeof(trees));
 732         memset(&opts, 0, sizeof(opts));
 733         memset(&t, 0, sizeof(t));
 734         memset(&dir, 0, sizeof(dir));
 735         dir.flags |= DIR_SHOW_IGNORED;
 736         dir.exclude_per_dir = ".gitignore";
 737         opts.dir = &dir;
 738
 739         opts.head_idx = 1;
 740         opts.src_index = &the_index;
 741         opts.dst_index = &the_index;
 742         opts.update = 1;
 743         opts.verbose_update = 1;
 744         opts.merge = 1;
 745         opts.fn = twoway_merge;
 746         setup_unpack_trees_porcelain(&opts, "merge");
 747
 748         trees[nr_trees] = parse_tree_indirect(head);
 749         if (!trees[nr_trees++])
 750                 return -1;
 751         trees[nr_trees] = parse_tree_indirect(remote);
 752         if (!trees[nr_trees++])
 753                 return -1;
 754         for (i = 0; i < nr_trees; i++) {
 755                 parse_tree(trees[i]);
 756                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 757         }
 758         if (unpack_trees(nr_trees, t, &opts))
 759                 return -1;
 760         if (write_cache(fd, active_cache, active_nr) ||
 761                 commit_locked_index(lock_file))
 762                 die(_("unable to write new index file"));
 763         return 0;
 764 }
 765
 766 static void split_merge_strategies(const char *string, struct strategy **list,
 767                                    int *nr, int *alloc)
 768 {
 769         char *p, *q, *buf;
 770
 771         if (!string)
 772                 return;
 773
 774         buf = xstrdup(string);
 775         q = buf;
 776         for (;;) {
 777                 p = strchr(q, ' ');
 778                 if (!p) {
 779                         ALLOC_GROW(*list, *nr + 1, *alloc);
 780                         (*list)[(*nr)++].name = xstrdup(q);
 781                         free(buf);
 782                         return;
 783                 } else {
 784                         *p = '\0';
 785                         ALLOC_GROW(*list, *nr + 1, *alloc);
 786                         (*list)[(*nr)++].name = xstrdup(q);
 787                         q = ++p;
 788                 }
 789         }
 790 }
 791
 792 static void add_strategies(const char *string, unsigned attr)
 793 {
 794         struct strategy *list = NULL;
 795         int list_alloc = 0, list_nr = 0, i;
 796
 797         memset(&list, 0, sizeof(list));
 798         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 799         if (list) {
 800                 for (i = 0; i < list_nr; i++)
 801                         append_strategy(get_strategy(list[i].name));
 802                 return;
 803         }
 804         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 805                 if (all_strategy[i].attr & attr)
 806                         append_strategy(&all_strategy[i]);
 807
 808 }
 809
 810 static void write_merge_msg(void)
 811 {
 812         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 813         if (fd < 0)
 814                 die_errno(_("Could not open '%s' for writing"),
 815                           git_path("MERGE_MSG"));
 816         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 817                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 818         close(fd);
 819 }
 820
 821 static void read_merge_msg(void)
 822 {
 823         strbuf_reset(&merge_msg);
 824         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 825                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 826 }
 827
 828 static void run_prepare_commit_msg(void)
 829 {
 830         write_merge_msg();
 831         run_hook(get_index_file(), "prepare-commit-msg",
 832                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 833         read_merge_msg();
 834 }
 835
 836 static int merge_trivial(void)
 837 {
 838         unsigned char result_tree[20], result_commit[20];
 839         struct commit_list *parent = xmalloc(sizeof(*parent));
 840
 841         write_tree_trivial(result_tree);
 842         printf(_("Wonderful.\n"));
 843         parent->item = lookup_commit(head);
 844         parent->next = xmalloc(sizeof(*parent->next));
 845         parent->next->item = remoteheads->item;
 846         parent->next->next = NULL;
 847         run_prepare_commit_msg();
 848         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 849         finish(result_commit, "In-index merge");
 850         drop_save();
 851         return 0;
 852 }
 853
 854 static int finish_automerge(struct commit_list *common,
 855                             unsigned char *result_tree,
 856                             const char *wt_strategy)
 857 {
 858         struct commit_list *parents = NULL, *j;
 859         struct strbuf buf = STRBUF_INIT;
 860         unsigned char result_commit[20];
 861
 862         free_commit_list(common);
 863         if (allow_fast_forward) {
 864                 parents = remoteheads;
 865                 commit_list_insert(lookup_commit(head), &parents);
 866                 parents = reduce_heads(parents);
 867         } else {
 868                 struct commit_list **pptr = &parents;
 869
 870                 pptr = &commit_list_insert(lookup_commit(head),
 871                                 pptr)->next;
 872                 for (j = remoteheads; j; j = j->next)
 873                         pptr = &commit_list_insert(j->item, pptr)->next;
 874         }
 875         free_commit_list(remoteheads);
 876         strbuf_addch(&merge_msg, '\n');
 877         run_prepare_commit_msg();
 878         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 879         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 880         finish(result_commit, buf.buf);
 881         strbuf_release(&buf);
 882         drop_save();
 883         return 0;
 884 }
 885
 886 static int suggest_conflicts(int renormalizing)
 887 {
 888         FILE *fp;
 889         int pos;
 890
 891         fp = fopen(git_path("MERGE_MSG"), "a");
 892         if (!fp)
 893                 die_errno(_("Could not open '%s' for writing"),
 894                           git_path("MERGE_MSG"));
 895         fprintf(fp, "\nConflicts:\n");
 896         for (pos = 0; pos < active_nr; pos++) {
 897                 struct cache_entry *ce = active_cache[pos];
 898
 899                 if (ce_stage(ce)) {
 900                         fprintf(fp, "\t%s\n", ce->name);
 901                         while (pos + 1 < active_nr &&
 902                                         !strcmp(ce->name,
 903                                                 active_cache[pos + 1]->name))
 904                                 pos++;
 905                 }
 906         }
 907         fclose(fp);
 908         rerere(allow_rerere_auto);
 909         printf(_("Automatic merge failed; "
 910                         "fix conflicts and then commit the result.\n"));
 911         return 1;
 912 }
 913
 914 static struct commit *is_old_style_invocation(int argc, const char **argv)
 915 {
 916         struct commit *second_token = NULL;
 917         if (argc > 2) {
 918                 unsigned char second_sha1[20];
 919
 920                 if (get_sha1(argv[1], second_sha1))
 921                         return NULL;
 922                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 923                 if (!second_token)
 924                         die(_("'%s' is not a commit"), argv[1]);
 925                 if (hashcmp(second_token->object.sha1, head))
 926                         return NULL;
 927         }
 928         return second_token;
 929 }
 930
 931 static int evaluate_result(void)
 932 {
 933         int cnt = 0;
 934         struct rev_info rev;
 935
 936         /* Check how many files differ. */
 937         init_revisions(&rev, "");
 938         setup_revisions(0, NULL, &rev, NULL);
 939         rev.diffopt.output_format |=
 940                 DIFF_FORMAT_CALLBACK;
 941         rev.diffopt.format_callback = count_diff_files;
 942         rev.diffopt.format_callback_data = &cnt;
 943         run_diff_files(&rev, 0);
 944
 945         /*
 946          * Check how many unmerged entries are
 947          * there.
 948          */
 949         cnt += count_unmerged_entries();
 950
 951         return cnt;
 952 }
 953
 954 /*
 955  * Pretend as if the user told us to merge with the tracking
 956  * branch we have for the upstream of the current branch
 957  */
 958 static int setup_with_upstream(const char ***argv)
 959 {
 960         struct branch *branch = branch_get(NULL);
 961         int i;
 962         const char **args;
 963
 964         if (!branch)
 965                 die(_("No current branch."));
 966         if (!branch->remote)
 967                 die(_("No remote for the current branch."));
 968         if (!branch->merge_nr)
 969                 die(_("No default upstream defined for the current branch."));
 970
 971         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 972         for (i = 0; i < branch->merge_nr; i++) {
 973                 if (!branch->merge[i]->dst)
 974                         die(_("No remote tracking branch for %s from %s"),
 975                             branch->merge[i]->src, branch->remote_name);
 976                 args[i] = branch->merge[i]->dst;
 977         }
 978         args[i] = NULL;
 979         *argv = args;
 980         return i;
 981 }
 982
 983 int cmd_merge(int argc, const char **argv, const char *prefix)
 984 {
 985         unsigned char result_tree[20];
 986         struct strbuf buf = STRBUF_INIT;
 987         const char *head_arg;
 988         int flag, head_invalid = 0, i;
 989         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 990         struct commit_list *common = NULL;
 991         const char *best_strategy = NULL, *wt_strategy = NULL;
 992         struct commit_list **remotes = &remoteheads;
 993
 994         if (argc == 2 && !strcmp(argv[1], "-h"))
 995                 usage_with_options(builtin_merge_usage, builtin_merge_options);
 996
 997         /*
 998          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 999          * current branch.
1000          */
1001         branch = resolve_ref("HEAD", head, 0, &flag);
1002         if (branch && !prefixcmp(branch, "refs/heads/"))
1003                 branch += 11;
1004         if (is_null_sha1(head))
1005                 head_invalid = 1;
1006
1007         git_config(git_merge_config, NULL);
1008
1009         /* for color.ui */
1010         if (diff_use_color_default == -1)
1011                 diff_use_color_default = git_use_color_default;
1012
1013         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1014                         builtin_merge_usage, 0);
1015
1016         if (verbosity < 0 && show_progress == -1)
1017                 show_progress = 0;
1018
1019         if (abort_current_merge) {
1020                 int nargc = 2;
1021                 const char *nargv[] = {"reset", "--merge", NULL};
1022
1023                 if (!file_exists(git_path("MERGE_HEAD")))
1024                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1025
1026                 /* Invoke 'git reset --merge' */
1027                 return cmd_reset(nargc, nargv, prefix);
1028         }
1029
1030         if (read_cache_unmerged())
1031                 die_resolve_conflict("merge");
1032
1033         if (file_exists(git_path("MERGE_HEAD"))) {
1034                 /*
1035                  * There is no unmerged entry, don't advise 'git
1036                  * add/rm <file>', just 'git commit'.
1037                  */
1038                 if (advice_resolve_conflict)
1039                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1040                                   "Please, commit your changes before you can merge."));
1041                 else
1042                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1043         }
1044         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1045                 if (advice_resolve_conflict)
1046                         die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1047                             "Please, commit your changes before you can merge.");
1048                 else
1049                         die("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).");
1050         }
1051         resolve_undo_clear();
1052
1053         if (verbosity < 0)
1054                 show_diffstat = 0;
1055
1056         if (squash) {
1057                 if (!allow_fast_forward)
1058                         die(_("You cannot combine --squash with --no-ff."));
1059                 option_commit = 0;
1060         }
1061
1062         if (!allow_fast_forward && fast_forward_only)
1063                 die(_("You cannot combine --no-ff with --ff-only."));
1064
1065         if (!argc && !abort_current_merge && default_to_upstream)
1066                 argc = setup_with_upstream(&argv);
1067
1068         if (!argc)
1069                 usage_with_options(builtin_merge_usage,
1070                         builtin_merge_options);
1071
1072         /*
1073          * This could be traditional "merge <msg> HEAD <commit>..."  and
1074          * the way we can tell it is to see if the second token is HEAD,
1075          * but some people might have misused the interface and used a
1076          * committish that is the same as HEAD there instead.
1077          * Traditional format never would have "-m" so it is an
1078          * additional safety measure to check for it.
1079          */
1080
1081         if (!have_message && is_old_style_invocation(argc, argv)) {
1082                 strbuf_addstr(&merge_msg, argv[0]);
1083                 head_arg = argv[1];
1084                 argv += 2;
1085                 argc -= 2;
1086         } else if (head_invalid) {
1087                 struct object *remote_head;
1088                 /*
1089                  * If the merged head is a valid one there is no reason
1090                  * to forbid "git merge" into a branch yet to be born.
1091                  * We do the same for "git pull".
1092                  */
1093                 if (argc != 1)
1094                         die(_("Can merge only exactly one commit into "
1095                                 "empty head"));
1096                 if (squash)
1097                         die(_("Squash commit into empty head not supported yet"));
1098                 if (!allow_fast_forward)
1099                         die(_("Non-fast-forward commit does not make sense into "
1100                             "an empty head"));
1101                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1102                 if (!remote_head)
1103                         die(_("%s - not something we can merge"), argv[0]);
1104                 read_empty(remote_head->sha1, 0);
1105                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1106                                 DIE_ON_ERR);
1107                 return 0;
1108         } else {
1109                 struct strbuf merge_names = STRBUF_INIT;
1110
1111                 /* We are invoked directly as the first-class UI. */
1112                 head_arg = "HEAD";
1113
1114                 /*
1115                  * All the rest are the commits being merged;
1116                  * prepare the standard merge summary message to
1117                  * be appended to the given message.  If remote
1118                  * is invalid we will die later in the common
1119                  * codepath so we discard the error in this
1120                  * loop.
1121                  */
1122                 for (i = 0; i < argc; i++)
1123                         merge_name(argv[i], &merge_names);
1124
1125                 if (!have_message || shortlog_len) {
1126                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1127                                       shortlog_len);
1128                         if (merge_msg.len)
1129                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1130                 }
1131         }
1132
1133         if (head_invalid || !argc)
1134                 usage_with_options(builtin_merge_usage,
1135                         builtin_merge_options);
1136
1137         strbuf_addstr(&buf, "merge");
1138         for (i = 0; i < argc; i++)
1139                 strbuf_addf(&buf, " %s", argv[i]);
1140         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1141         strbuf_reset(&buf);
1142
1143         for (i = 0; i < argc; i++) {
1144                 struct object *o;
1145                 struct commit *commit;
1146
1147                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1148                 if (!o)
1149                         die(_("%s - not something we can merge"), argv[i]);
1150                 commit = lookup_commit(o->sha1);
1151                 commit->util = (void *)argv[i];
1152                 remotes = &commit_list_insert(commit, remotes)->next;
1153
1154                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1155                 setenv(buf.buf, argv[i], 1);
1156                 strbuf_reset(&buf);
1157         }
1158
1159         if (!use_strategies) {
1160                 if (!remoteheads->next)
1161                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1162                 else
1163                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1164         }
1165
1166         for (i = 0; i < use_strategies_nr; i++) {
1167                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1168                         allow_fast_forward = 0;
1169                 if (use_strategies[i]->attr & NO_TRIVIAL)
1170                         allow_trivial = 0;
1171         }
1172
1173         if (!remoteheads->next)
1174                 common = get_merge_bases(lookup_commit(head),
1175                                 remoteheads->item, 1);
1176         else {
1177                 struct commit_list *list = remoteheads;
1178                 commit_list_insert(lookup_commit(head), &list);
1179                 common = get_octopus_merge_bases(list);
1180                 free(list);
1181         }
1182
1183         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1184                 DIE_ON_ERR);
1185
1186         if (!common)
1187                 ; /* No common ancestors found. We need a real merge. */
1188         else if (!remoteheads->next && !common->next &&
1189                         common->item == remoteheads->item) {
1190                 /*
1191                  * If head can reach all the merge then we are up to date.
1192                  * but first the most common case of merging one remote.
1193                  */
1194                 finish_up_to_date("Already up-to-date.");
1195                 return 0;
1196         } else if (allow_fast_forward && !remoteheads->next &&
1197                         !common->next &&
1198                         !hashcmp(common->item->object.sha1, head)) {
1199                 /* Again the most common case of merging one remote. */
1200                 struct strbuf msg = STRBUF_INIT;
1201                 struct object *o;
1202                 char hex[41];
1203
1204                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1205
1206                 if (verbosity >= 0)
1207                         printf(_("Updating %s..%s\n"),
1208                                 hex,
1209                                 find_unique_abbrev(remoteheads->item->object.sha1,
1210                                 DEFAULT_ABBREV));
1211                 strbuf_addstr(&msg, "Fast-forward");
1212                 if (have_message)
1213                         strbuf_addstr(&msg,
1214                                 " (no commit created; -m option ignored)");
1215                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1216                         0, NULL, OBJ_COMMIT);
1217                 if (!o)
1218                         return 1;
1219
1220                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1221                         return 1;
1222
1223                 finish(o->sha1, msg.buf);
1224                 drop_save();
1225                 return 0;
1226         } else if (!remoteheads->next && common->next)
1227                 ;
1228                 /*
1229                  * We are not doing octopus and not fast-forward.  Need
1230                  * a real merge.
1231                  */
1232         else if (!remoteheads->next && !common->next && option_commit) {
1233                 /*
1234                  * We are not doing octopus, not fast-forward, and have
1235                  * only one common.
1236                  */
1237                 refresh_cache(REFRESH_QUIET);
1238                 if (allow_trivial && !fast_forward_only) {
1239                         /* See if it is really trivial. */
1240                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1241                         printf(_("Trying really trivial in-index merge...\n"));
1242                         if (!read_tree_trivial(common->item->object.sha1,
1243                                         head, remoteheads->item->object.sha1))
1244                                 return merge_trivial();
1245                         printf(_("Nope.\n"));
1246                 }
1247         } else {
1248                 /*
1249                  * An octopus.  If we can reach all the remote we are up
1250                  * to date.
1251                  */
1252                 int up_to_date = 1;
1253                 struct commit_list *j;
1254
1255                 for (j = remoteheads; j; j = j->next) {
1256                         struct commit_list *common_one;
1257
1258                         /*
1259                          * Here we *have* to calculate the individual
1260                          * merge_bases again, otherwise "git merge HEAD^
1261                          * HEAD^^" would be missed.
1262                          */
1263                         common_one = get_merge_bases(lookup_commit(head),
1264                                 j->item, 1);
1265                         if (hashcmp(common_one->item->object.sha1,
1266                                 j->item->object.sha1)) {
1267                                 up_to_date = 0;
1268                                 break;
1269                         }
1270                 }
1271                 if (up_to_date) {
1272                         finish_up_to_date("Already up-to-date. Yeeah!");
1273                         return 0;
1274                 }
1275         }
1276
1277         if (fast_forward_only)
1278                 die(_("Not possible to fast-forward, aborting."));
1279
1280         /* We are going to make a new commit. */
1281         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1282
1283         /*
1284          * At this point, we need a real merge.  No matter what strategy
1285          * we use, it would operate on the index, possibly affecting the
1286          * working tree, and when resolved cleanly, have the desired
1287          * tree in the index -- this means that the index must be in
1288          * sync with the head commit.  The strategies are responsible
1289          * to ensure this.
1290          */
1291         if (use_strategies_nr != 1) {
1292                 /*
1293                  * Stash away the local changes so that we can try more
1294                  * than one.
1295                  */
1296                 save_state();
1297         } else {
1298                 memcpy(stash, null_sha1, 20);
1299         }
1300
1301         for (i = 0; i < use_strategies_nr; i++) {
1302                 int ret;
1303                 if (i) {
1304                         printf(_("Rewinding the tree to pristine...\n"));
1305                         restore_state();
1306                 }
1307                 if (use_strategies_nr != 1)
1308                         printf(_("Trying merge strategy %s...\n"),
1309                                 use_strategies[i]->name);
1310                 /*
1311                  * Remember which strategy left the state in the working
1312                  * tree.
1313                  */
1314                 wt_strategy = use_strategies[i]->name;
1315
1316                 ret = try_merge_strategy(use_strategies[i]->name,
1317                         common, head_arg);
1318                 if (!option_commit && !ret) {
1319                         merge_was_ok = 1;
1320                         /*
1321                          * This is necessary here just to avoid writing
1322                          * the tree, but later we will *not* exit with
1323                          * status code 1 because merge_was_ok is set.
1324                          */
1325                         ret = 1;
1326                 }
1327
1328                 if (ret) {
1329                         /*
1330                          * The backend exits with 1 when conflicts are
1331                          * left to be resolved, with 2 when it does not
1332                          * handle the given merge at all.
1333                          */
1334                         if (ret == 1) {
1335                                 int cnt = evaluate_result();
1336
1337                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1338                                         best_strategy = use_strategies[i]->name;
1339                                         best_cnt = cnt;
1340                                 }
1341                         }
1342                         if (merge_was_ok)
1343                                 break;
1344                         else
1345                                 continue;
1346                 }
1347
1348                 /* Automerge succeeded. */
1349                 write_tree_trivial(result_tree);
1350                 automerge_was_ok = 1;
1351                 break;
1352         }
1353
1354         /*
1355          * If we have a resulting tree, that means the strategy module
1356          * auto resolved the merge cleanly.
1357          */
1358         if (automerge_was_ok)
1359                 return finish_automerge(common, result_tree, wt_strategy);
1360
1361         /*
1362          * Pick the result from the best strategy and have the user fix
1363          * it up.
1364          */
1365         if (!best_strategy) {
1366                 restore_state();
1367                 if (use_strategies_nr > 1)
1368                         fprintf(stderr,
1369                                 _("No merge strategy handled the merge.\n"));
1370                 else
1371                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1372                                 use_strategies[0]->name);
1373                 return 2;
1374         } else if (best_strategy == wt_strategy)
1375                 ; /* We already have its result in the working tree. */
1376         else {
1377                 printf(_("Rewinding the tree to pristine...\n"));
1378                 restore_state();
1379                 printf(_("Using the %s to prepare resolving by hand.\n"),
1380                         best_strategy);
1381                 try_merge_strategy(best_strategy, common, head_arg);
1382         }
1383
1384         if (squash)
1385                 finish(NULL, NULL);
1386         else {
1387                 int fd;
1388                 struct commit_list *j;
1389
1390                 for (j = remoteheads; j; j = j->next)
1391                         strbuf_addf(&buf, "%s\n",
1392                                 sha1_to_hex(j->item->object.sha1));
1393                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1394                 if (fd < 0)
1395                         die_errno(_("Could not open '%s' for writing"),
1396                                   git_path("MERGE_HEAD"));
1397                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1398                         die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1399                 close(fd);
1400                 strbuf_addch(&merge_msg, '\n');
1401                 write_merge_msg();
1402                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1403                 if (fd < 0)
1404                         die_errno(_("Could not open '%s' for writing"),
1405                                   git_path("MERGE_MODE"));
1406                 strbuf_reset(&buf);
1407                 if (!allow_fast_forward)
1408                         strbuf_addf(&buf, "no-ff");
1409                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1410                         die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1411                 close(fd);
1412         }
1413
1414         if (merge_was_ok) {
1415                 fprintf(stderr, _("Automatic merge went well; "
1416                         "stopped before committing as requested\n"));
1417                 return 0;
1418         } else
1419                 return suggest_conflicts(option_renormalize);
1420 }