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