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