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