builtin-merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27
  28 #define DEFAULT_TWOHEAD (1<<0)
  29 #define DEFAULT_OCTOPUS (1<<1)
  30 #define NO_FAST_FORWARD (1<<2)
  31 #define NO_TRIVIAL      (1<<3)
  32
  33 struct strategy {
  34         const char *name;
  35         unsigned attr;
  36 };
  37
  38 static const char * const builtin_merge_usage[] = {
  39         "git-merge [options] <remote>...",
  40         "git-merge [options] <msg> HEAD <remote>",
  41         NULL
  42 };
  43
  44 static int show_diffstat = 1, option_log, squash;
  45 static int option_commit = 1, allow_fast_forward = 1;
  46 static int allow_trivial = 1, have_message;
  47 static struct strbuf merge_msg;
  48 static struct commit_list *remoteheads;
  49 static unsigned char head[20], stash[20];
  50 static struct strategy **use_strategies;
  51 static size_t use_strategies_nr, use_strategies_alloc;
  52 static const char *branch;
  53
  54 static struct strategy all_strategy[] = {
  55         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  56         { "octopus",    DEFAULT_OCTOPUS },
  57         { "resolve",    0 },
  58         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  59         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  60 };
  61
  62 static const char *pull_twohead, *pull_octopus;
  63
  64 static int option_parse_message(const struct option *opt,
  65                                 const char *arg, int unset)
  66 {
  67         struct strbuf *buf = opt->value;
  68
  69         if (unset)
  70                 strbuf_setlen(buf, 0);
  71         else if (arg) {
  72                 strbuf_addf(buf, "%s\n\n", arg);
  73                 have_message = 1;
  74         } else
  75                 return error("switch `m' requires a value");
  76         return 0;
  77 }
  78
  79 static struct strategy *get_strategy(const char *name)
  80 {
  81         int i;
  82         struct strategy *ret;
  83         static struct cmdnames main_cmds, other_cmds;
  84         static int loaded;
  85
  86         if (!name)
  87                 return NULL;
  88
  89         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  90                 if (!strcmp(name, all_strategy[i].name))
  91                         return &all_strategy[i];
  92
  93         if (!loaded) {
  94                 struct cmdnames not_strategies;
  95                 loaded = 1;
  96
  97                 memset(&not_strategies, 0, sizeof(struct cmdnames));
  98                 load_command_list("git-merge-", &main_cmds, &other_cmds);
  99                 for (i = 0; i < main_cmds.cnt; i++) {
 100                         int j, found = 0;
 101                         struct cmdname *ent = main_cmds.names[i];
 102                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 103                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 104                                                 && !all_strategy[j].name[ent->len])
 105                                         found = 1;
 106                         if (!found)
 107                                 add_cmdname(&not_strategies, ent->name, ent->len);
 108                         exclude_cmds(&main_cmds, &not_strategies);
 109                 }
 110         }
 111         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 112                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 113                 fprintf(stderr, "Available strategies are:");
 114                 for (i = 0; i < main_cmds.cnt; i++)
 115                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 116                 fprintf(stderr, ".\n");
 117                 if (other_cmds.cnt) {
 118                         fprintf(stderr, "Available custom strategies are:");
 119                         for (i = 0; i < other_cmds.cnt; i++)
 120                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 121                         fprintf(stderr, ".\n");
 122                 }
 123                 exit(1);
 124         }
 125
 126         ret = xcalloc(1, sizeof(struct strategy));
 127         ret->name = xstrdup(name);
 128         return ret;
 129 }
 130
 131 static void append_strategy(struct strategy *s)
 132 {
 133         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 134         use_strategies[use_strategies_nr++] = s;
 135 }
 136
 137 static int option_parse_strategy(const struct option *opt,
 138                                  const char *name, int unset)
 139 {
 140         if (unset)
 141                 return 0;
 142
 143         append_strategy(get_strategy(name));
 144         return 0;
 145 }
 146
 147 static int option_parse_n(const struct option *opt,
 148                           const char *arg, int unset)
 149 {
 150         show_diffstat = unset;
 151         return 0;
 152 }
 153
 154 static struct option builtin_merge_options[] = {
 155         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 156                 "do not show a diffstat at the end of the merge",
 157                 PARSE_OPT_NOARG, option_parse_n },
 158         OPT_BOOLEAN(0, "stat", &show_diffstat,
 159                 "show a diffstat at the end of the merge"),
 160         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 161         OPT_BOOLEAN(0, "log", &option_log,
 162                 "add list of one-line log to merge commit message"),
 163         OPT_BOOLEAN(0, "squash", &squash,
 164                 "create a single commit instead of doing a merge"),
 165         OPT_BOOLEAN(0, "commit", &option_commit,
 166                 "perform a commit if the merge succeeds (default)"),
 167         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 168                 "allow fast forward (default)"),
 169         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 170                 "merge strategy to use", option_parse_strategy),
 171         OPT_CALLBACK('m', "message", &merge_msg, "message",
 172                 "message to be used for the merge commit (if any)",
 173                 option_parse_message),
 174         OPT_END()
 175 };
 176
 177 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 178 static void drop_save(void)
 179 {
 180         unlink(git_path("MERGE_HEAD"));
 181         unlink(git_path("MERGE_MSG"));
 182         unlink(git_path("MERGE_MODE"));
 183 }
 184
 185 static void save_state(void)
 186 {
 187         int len;
 188         struct child_process cp;
 189         struct strbuf buffer = STRBUF_INIT;
 190         const char *argv[] = {"stash", "create", NULL};
 191
 192         memset(&cp, 0, sizeof(cp));
 193         cp.argv = argv;
 194         cp.out = -1;
 195         cp.git_cmd = 1;
 196
 197         if (start_command(&cp))
 198                 die("could not run stash.");
 199         len = strbuf_read(&buffer, cp.out, 1024);
 200         close(cp.out);
 201
 202         if (finish_command(&cp) || len < 0)
 203                 die("stash failed");
 204         else if (!len)
 205                 return;
 206         strbuf_setlen(&buffer, buffer.len-1);
 207         if (get_sha1(buffer.buf, stash))
 208                 die("not a valid object: %s", buffer.buf);
 209 }
 210
 211 static void reset_hard(unsigned const char *sha1, int verbose)
 212 {
 213         int i = 0;
 214         const char *args[6];
 215
 216         args[i++] = "read-tree";
 217         if (verbose)
 218                 args[i++] = "-v";
 219         args[i++] = "--reset";
 220         args[i++] = "-u";
 221         args[i++] = sha1_to_hex(sha1);
 222         args[i] = NULL;
 223
 224         if (run_command_v_opt(args, RUN_GIT_CMD))
 225                 die("read-tree failed");
 226 }
 227
 228 static void restore_state(void)
 229 {
 230         struct strbuf sb = STRBUF_INIT;
 231         const char *args[] = { "stash", "apply", NULL, NULL };
 232
 233         if (is_null_sha1(stash))
 234                 return;
 235
 236         reset_hard(head, 1);
 237
 238         args[2] = sha1_to_hex(stash);
 239
 240         /*
 241          * It is OK to ignore error here, for example when there was
 242          * nothing to restore.
 243          */
 244         run_command_v_opt(args, RUN_GIT_CMD);
 245
 246         strbuf_release(&sb);
 247         refresh_cache(REFRESH_QUIET);
 248 }
 249
 250 /* This is called when no merge was necessary. */
 251 static void finish_up_to_date(const char *msg)
 252 {
 253         printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 254         drop_save();
 255 }
 256
 257 static void squash_message(void)
 258 {
 259         struct rev_info rev;
 260         struct commit *commit;
 261         struct strbuf out = STRBUF_INIT;
 262         struct commit_list *j;
 263         int fd;
 264
 265         printf("Squash commit -- not updating HEAD\n");
 266         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 267         if (fd < 0)
 268                 die("Could not write to %s", git_path("SQUASH_MSG"));
 269
 270         init_revisions(&rev, NULL);
 271         rev.ignore_merges = 1;
 272         rev.commit_format = CMIT_FMT_MEDIUM;
 273
 274         commit = lookup_commit(head);
 275         commit->object.flags |= UNINTERESTING;
 276         add_pending_object(&rev, &commit->object, NULL);
 277
 278         for (j = remoteheads; j; j = j->next)
 279                 add_pending_object(&rev, &j->item->object, NULL);
 280
 281         setup_revisions(0, NULL, &rev, NULL);
 282         if (prepare_revision_walk(&rev))
 283                 die("revision walk setup failed");
 284
 285         strbuf_addstr(&out, "Squashed commit of the following:\n");
 286         while ((commit = get_revision(&rev)) != NULL) {
 287                 strbuf_addch(&out, '\n');
 288                 strbuf_addf(&out, "commit %s\n",
 289                         sha1_to_hex(commit->object.sha1));
 290                 pretty_print_commit(rev.commit_format, commit, &out, rev.abbrev,
 291                         NULL, NULL, rev.date_mode, 0);
 292         }
 293         write(fd, out.buf, out.len);
 294         close(fd);
 295         strbuf_release(&out);
 296 }
 297
 298 static int run_hook(const char *name)
 299 {
 300         struct child_process hook;
 301         const char *argv[3], *env[2];
 302         char index[PATH_MAX];
 303
 304         argv[0] = git_path("hooks/%s", name);
 305         if (access(argv[0], X_OK) < 0)
 306                 return 0;
 307
 308         snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", get_index_file());
 309         env[0] = index;
 310         env[1] = NULL;
 311
 312         if (squash)
 313                 argv[1] = "1";
 314         else
 315                 argv[1] = "0";
 316         argv[2] = NULL;
 317
 318         memset(&hook, 0, sizeof(hook));
 319         hook.argv = argv;
 320         hook.no_stdin = 1;
 321         hook.stdout_to_stderr = 1;
 322         hook.env = env;
 323
 324         return run_command(&hook);
 325 }
 326
 327 static void finish(const unsigned char *new_head, const char *msg)
 328 {
 329         struct strbuf reflog_message = STRBUF_INIT;
 330
 331         if (!msg)
 332                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 333         else {
 334                 printf("%s\n", msg);
 335                 strbuf_addf(&reflog_message, "%s: %s",
 336                         getenv("GIT_REFLOG_ACTION"), msg);
 337         }
 338         if (squash) {
 339                 squash_message();
 340         } else {
 341                 if (!merge_msg.len)
 342                         printf("No merge message -- not updating HEAD\n");
 343                 else {
 344                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 345                         update_ref(reflog_message.buf, "HEAD",
 346                                 new_head, head, 0,
 347                                 DIE_ON_ERR);
 348                         /*
 349                          * We ignore errors in 'gc --auto', since the
 350                          * user should see them.
 351                          */
 352                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 353                 }
 354         }
 355         if (new_head && show_diffstat) {
 356                 struct diff_options opts;
 357                 diff_setup(&opts);
 358                 opts.output_format |=
 359                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 360                 opts.detect_rename = DIFF_DETECT_RENAME;
 361                 if (diff_use_color_default > 0)
 362                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 363                 if (diff_setup_done(&opts) < 0)
 364                         die("diff_setup_done failed");
 365                 diff_tree_sha1(head, new_head, "", &opts);
 366                 diffcore_std(&opts);
 367                 diff_flush(&opts);
 368         }
 369
 370         /* Run a post-merge hook */
 371         run_hook("post-merge");
 372
 373         strbuf_release(&reflog_message);
 374 }
 375
 376 /* Get the name for the merge commit's message. */
 377 static void merge_name(const char *remote, struct strbuf *msg)
 378 {
 379         struct object *remote_head;
 380         unsigned char branch_head[20], buf_sha[20];
 381         struct strbuf buf = STRBUF_INIT;
 382         const char *ptr;
 383         int len, early;
 384
 385         memset(branch_head, 0, sizeof(branch_head));
 386         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 387         if (!remote_head)
 388                 die("'%s' does not point to a commit", remote);
 389
 390         strbuf_addstr(&buf, "refs/heads/");
 391         strbuf_addstr(&buf, remote);
 392         resolve_ref(buf.buf, branch_head, 0, 0);
 393
 394         if (!hashcmp(remote_head->sha1, branch_head)) {
 395                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 396                         sha1_to_hex(branch_head), remote);
 397                 return;
 398         }
 399
 400         /* See if remote matches <name>^^^.. or <name>~<number> */
 401         for (len = 0, ptr = remote + strlen(remote);
 402              remote < ptr && ptr[-1] == '^';
 403              ptr--)
 404                 len++;
 405         if (len)
 406                 early = 1;
 407         else {
 408                 early = 0;
 409                 ptr = strrchr(remote, '~');
 410                 if (ptr) {
 411                         int seen_nonzero = 0;
 412
 413                         len++; /* count ~ */
 414                         while (*++ptr && isdigit(*ptr)) {
 415                                 seen_nonzero |= (*ptr != '0');
 416                                 len++;
 417                         }
 418                         if (*ptr)
 419                                 len = 0; /* not ...~<number> */
 420                         else if (seen_nonzero)
 421                                 early = 1;
 422                         else if (len == 1)
 423                                 early = 1; /* "name~" is "name~1"! */
 424                 }
 425         }
 426         if (len) {
 427                 struct strbuf truname = STRBUF_INIT;
 428                 strbuf_addstr(&truname, "refs/heads/");
 429                 strbuf_addstr(&truname, remote);
 430                 strbuf_setlen(&truname, truname.len - len);
 431                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
 432                         strbuf_addf(msg,
 433                                     "%s\t\tbranch '%s'%s of .\n",
 434                                     sha1_to_hex(remote_head->sha1),
 435                                     truname.buf + 11,
 436                                     (early ? " (early part)" : ""));
 437                         return;
 438                 }
 439         }
 440
 441         if (!strcmp(remote, "FETCH_HEAD") &&
 442                         !access(git_path("FETCH_HEAD"), R_OK)) {
 443                 FILE *fp;
 444                 struct strbuf line = STRBUF_INIT;
 445                 char *ptr;
 446
 447                 fp = fopen(git_path("FETCH_HEAD"), "r");
 448                 if (!fp)
 449                         die("could not open %s for reading: %s",
 450                                 git_path("FETCH_HEAD"), strerror(errno));
 451                 strbuf_getline(&line, fp, '\n');
 452                 fclose(fp);
 453                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 454                 if (ptr)
 455                         strbuf_remove(&line, ptr-line.buf+1, 13);
 456                 strbuf_addbuf(msg, &line);
 457                 strbuf_release(&line);
 458                 return;
 459         }
 460         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 461                 sha1_to_hex(remote_head->sha1), remote);
 462 }
 463
 464 static int git_merge_config(const char *k, const char *v, void *cb)
 465 {
 466         if (branch && !prefixcmp(k, "branch.") &&
 467                 !prefixcmp(k + 7, branch) &&
 468                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 469                 const char **argv;
 470                 int argc;
 471                 char *buf;
 472
 473                 buf = xstrdup(v);
 474                 argc = split_cmdline(buf, &argv);
 475                 if (argc < 0)
 476                         die("Bad branch.%s.mergeoptions string", branch);
 477                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 478                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 479                 argc++;
 480                 parse_options(argc, argv, builtin_merge_options,
 481                               builtin_merge_usage, 0);
 482                 free(buf);
 483         }
 484
 485         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 486                 show_diffstat = git_config_bool(k, v);
 487         else if (!strcmp(k, "pull.twohead"))
 488                 return git_config_string(&pull_twohead, k, v);
 489         else if (!strcmp(k, "pull.octopus"))
 490                 return git_config_string(&pull_octopus, k, v);
 491         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 492                 option_log = git_config_bool(k, v);
 493         return git_diff_ui_config(k, v, cb);
 494 }
 495
 496 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 497                              unsigned char *one)
 498 {
 499         int i, nr_trees = 0;
 500         struct tree *trees[MAX_UNPACK_TREES];
 501         struct tree_desc t[MAX_UNPACK_TREES];
 502         struct unpack_trees_options opts;
 503
 504         memset(&opts, 0, sizeof(opts));
 505         opts.head_idx = 2;
 506         opts.src_index = &the_index;
 507         opts.dst_index = &the_index;
 508         opts.update = 1;
 509         opts.verbose_update = 1;
 510         opts.trivial_merges_only = 1;
 511         opts.merge = 1;
 512         trees[nr_trees] = parse_tree_indirect(common);
 513         if (!trees[nr_trees++])
 514                 return -1;
 515         trees[nr_trees] = parse_tree_indirect(head);
 516         if (!trees[nr_trees++])
 517                 return -1;
 518         trees[nr_trees] = parse_tree_indirect(one);
 519         if (!trees[nr_trees++])
 520                 return -1;
 521         opts.fn = threeway_merge;
 522         cache_tree_free(&active_cache_tree);
 523         for (i = 0; i < nr_trees; i++) {
 524                 parse_tree(trees[i]);
 525                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 526         }
 527         if (unpack_trees(nr_trees, t, &opts))
 528                 return -1;
 529         return 0;
 530 }
 531
 532 static void write_tree_trivial(unsigned char *sha1)
 533 {
 534         if (write_cache_as_tree(sha1, 0, NULL))
 535                 die("git write-tree failed to write a tree");
 536 }
 537
 538 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 539                               const char *head_arg)
 540 {
 541         const char **args;
 542         int i = 0, ret;
 543         struct commit_list *j;
 544         struct strbuf buf = STRBUF_INIT;
 545         int index_fd;
 546         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 547
 548         index_fd = hold_locked_index(lock, 1);
 549         refresh_cache(REFRESH_QUIET);
 550         if (active_cache_changed &&
 551                         (write_cache(index_fd, active_cache, active_nr) ||
 552                          commit_locked_index(lock)))
 553                 return error("Unable to write index.");
 554         rollback_lock_file(lock);
 555
 556         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 557                 int clean;
 558                 struct commit *result;
 559                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 560                 int index_fd;
 561                 struct commit_list *reversed = NULL;
 562                 struct merge_options o;
 563
 564                 if (remoteheads->next) {
 565                         error("Not handling anything other than two heads merge.");
 566                         return 2;
 567                 }
 568
 569                 init_merge_options(&o);
 570                 if (!strcmp(strategy, "subtree"))
 571                         o.subtree_merge = 1;
 572
 573                 o.branch1 = head_arg;
 574                 o.branch2 = remoteheads->item->util;
 575
 576                 for (j = common; j; j = j->next)
 577                         commit_list_insert(j->item, &reversed);
 578
 579                 index_fd = hold_locked_index(lock, 1);
 580                 clean = merge_recursive(&o, lookup_commit(head),
 581                                 remoteheads->item, reversed, &result);
 582                 if (active_cache_changed &&
 583                                 (write_cache(index_fd, active_cache, active_nr) ||
 584                                  commit_locked_index(lock)))
 585                         die ("unable to write %s", get_index_file());
 586                 rollback_lock_file(lock);
 587                 return clean ? 0 : 1;
 588         } else {
 589                 args = xmalloc((4 + commit_list_count(common) +
 590                                         commit_list_count(remoteheads)) * sizeof(char *));
 591                 strbuf_addf(&buf, "merge-%s", strategy);
 592                 args[i++] = buf.buf;
 593                 for (j = common; j; j = j->next)
 594                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 595                 args[i++] = "--";
 596                 args[i++] = head_arg;
 597                 for (j = remoteheads; j; j = j->next)
 598                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 599                 args[i] = NULL;
 600                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 601                 strbuf_release(&buf);
 602                 i = 1;
 603                 for (j = common; j; j = j->next)
 604                         free((void *)args[i++]);
 605                 i += 2;
 606                 for (j = remoteheads; j; j = j->next)
 607                         free((void *)args[i++]);
 608                 free(args);
 609                 discard_cache();
 610                 if (read_cache() < 0)
 611                         die("failed to read the cache");
 612                 return -ret;
 613         }
 614 }
 615
 616 static void count_diff_files(struct diff_queue_struct *q,
 617                              struct diff_options *opt, void *data)
 618 {
 619         int *count = data;
 620
 621         (*count) += q->nr;
 622 }
 623
 624 static int count_unmerged_entries(void)
 625 {
 626         const struct index_state *state = &the_index;
 627         int i, ret = 0;
 628
 629         for (i = 0; i < state->cache_nr; i++)
 630                 if (ce_stage(state->cache[i]))
 631                         ret++;
 632
 633         return ret;
 634 }
 635
 636 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 637 {
 638         struct tree *trees[MAX_UNPACK_TREES];
 639         struct unpack_trees_options opts;
 640         struct tree_desc t[MAX_UNPACK_TREES];
 641         int i, fd, nr_trees = 0;
 642         struct dir_struct dir;
 643         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 644
 645         refresh_cache(REFRESH_QUIET);
 646
 647         fd = hold_locked_index(lock_file, 1);
 648
 649         memset(&trees, 0, sizeof(trees));
 650         memset(&opts, 0, sizeof(opts));
 651         memset(&t, 0, sizeof(t));
 652         memset(&dir, 0, sizeof(dir));
 653         dir.show_ignored = 1;
 654         dir.exclude_per_dir = ".gitignore";
 655         opts.dir = &dir;
 656
 657         opts.head_idx = 1;
 658         opts.src_index = &the_index;
 659         opts.dst_index = &the_index;
 660         opts.update = 1;
 661         opts.verbose_update = 1;
 662         opts.merge = 1;
 663         opts.fn = twoway_merge;
 664
 665         trees[nr_trees] = parse_tree_indirect(head);
 666         if (!trees[nr_trees++])
 667                 return -1;
 668         trees[nr_trees] = parse_tree_indirect(remote);
 669         if (!trees[nr_trees++])
 670                 return -1;
 671         for (i = 0; i < nr_trees; i++) {
 672                 parse_tree(trees[i]);
 673                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 674         }
 675         if (unpack_trees(nr_trees, t, &opts))
 676                 return -1;
 677         if (write_cache(fd, active_cache, active_nr) ||
 678                 commit_locked_index(lock_file))
 679                 die("unable to write new index file");
 680         return 0;
 681 }
 682
 683 static void split_merge_strategies(const char *string, struct strategy **list,
 684                                    int *nr, int *alloc)
 685 {
 686         char *p, *q, *buf;
 687
 688         if (!string)
 689                 return;
 690
 691         buf = xstrdup(string);
 692         q = buf;
 693         for (;;) {
 694                 p = strchr(q, ' ');
 695                 if (!p) {
 696                         ALLOC_GROW(*list, *nr + 1, *alloc);
 697                         (*list)[(*nr)++].name = xstrdup(q);
 698                         free(buf);
 699                         return;
 700                 } else {
 701                         *p = '\0';
 702                         ALLOC_GROW(*list, *nr + 1, *alloc);
 703                         (*list)[(*nr)++].name = xstrdup(q);
 704                         q = ++p;
 705                 }
 706         }
 707 }
 708
 709 static void add_strategies(const char *string, unsigned attr)
 710 {
 711         struct strategy *list = NULL;
 712         int list_alloc = 0, list_nr = 0, i;
 713
 714         memset(&list, 0, sizeof(list));
 715         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 716         if (list) {
 717                 for (i = 0; i < list_nr; i++)
 718                         append_strategy(get_strategy(list[i].name));
 719                 return;
 720         }
 721         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 722                 if (all_strategy[i].attr & attr)
 723                         append_strategy(&all_strategy[i]);
 724
 725 }
 726
 727 static int merge_trivial(void)
 728 {
 729         unsigned char result_tree[20], result_commit[20];
 730         struct commit_list *parent = xmalloc(sizeof(*parent));
 731
 732         write_tree_trivial(result_tree);
 733         printf("Wonderful.\n");
 734         parent->item = lookup_commit(head);
 735         parent->next = xmalloc(sizeof(*parent->next));
 736         parent->next->item = remoteheads->item;
 737         parent->next->next = NULL;
 738         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 739         finish(result_commit, "In-index merge");
 740         drop_save();
 741         return 0;
 742 }
 743
 744 static int finish_automerge(struct commit_list *common,
 745                             unsigned char *result_tree,
 746                             const char *wt_strategy)
 747 {
 748         struct commit_list *parents = NULL, *j;
 749         struct strbuf buf = STRBUF_INIT;
 750         unsigned char result_commit[20];
 751
 752         free_commit_list(common);
 753         if (allow_fast_forward) {
 754                 parents = remoteheads;
 755                 commit_list_insert(lookup_commit(head), &parents);
 756                 parents = reduce_heads(parents);
 757         } else {
 758                 struct commit_list **pptr = &parents;
 759
 760                 pptr = &commit_list_insert(lookup_commit(head),
 761                                 pptr)->next;
 762                 for (j = remoteheads; j; j = j->next)
 763                         pptr = &commit_list_insert(j->item, pptr)->next;
 764         }
 765         free_commit_list(remoteheads);
 766         strbuf_addch(&merge_msg, '\n');
 767         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 768         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 769         finish(result_commit, buf.buf);
 770         strbuf_release(&buf);
 771         drop_save();
 772         return 0;
 773 }
 774
 775 static int suggest_conflicts(void)
 776 {
 777         FILE *fp;
 778         int pos;
 779
 780         fp = fopen(git_path("MERGE_MSG"), "a");
 781         if (!fp)
 782                 die("Could open %s for writing", git_path("MERGE_MSG"));
 783         fprintf(fp, "\nConflicts:\n");
 784         for (pos = 0; pos < active_nr; pos++) {
 785                 struct cache_entry *ce = active_cache[pos];
 786
 787                 if (ce_stage(ce)) {
 788                         fprintf(fp, "\t%s\n", ce->name);
 789                         while (pos + 1 < active_nr &&
 790                                         !strcmp(ce->name,
 791                                                 active_cache[pos + 1]->name))
 792                                 pos++;
 793                 }
 794         }
 795         fclose(fp);
 796         rerere();
 797         printf("Automatic merge failed; "
 798                         "fix conflicts and then commit the result.\n");
 799         return 1;
 800 }
 801
 802 static struct commit *is_old_style_invocation(int argc, const char **argv)
 803 {
 804         struct commit *second_token = NULL;
 805         if (argc > 1) {
 806                 unsigned char second_sha1[20];
 807
 808                 if (get_sha1(argv[1], second_sha1))
 809                         return NULL;
 810                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 811                 if (!second_token)
 812                         die("'%s' is not a commit", argv[1]);
 813                 if (hashcmp(second_token->object.sha1, head))
 814                         return NULL;
 815         }
 816         return second_token;
 817 }
 818
 819 static int evaluate_result(void)
 820 {
 821         int cnt = 0;
 822         struct rev_info rev;
 823
 824         /* Check how many files differ. */
 825         init_revisions(&rev, "");
 826         setup_revisions(0, NULL, &rev, NULL);
 827         rev.diffopt.output_format |=
 828                 DIFF_FORMAT_CALLBACK;
 829         rev.diffopt.format_callback = count_diff_files;
 830         rev.diffopt.format_callback_data = &cnt;
 831         run_diff_files(&rev, 0);
 832
 833         /*
 834          * Check how many unmerged entries are
 835          * there.
 836          */
 837         cnt += count_unmerged_entries();
 838
 839         return cnt;
 840 }
 841
 842 int cmd_merge(int argc, const char **argv, const char *prefix)
 843 {
 844         unsigned char result_tree[20];
 845         struct strbuf buf = STRBUF_INIT;
 846         const char *head_arg;
 847         int flag, head_invalid = 0, i;
 848         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 849         struct commit_list *common = NULL;
 850         const char *best_strategy = NULL, *wt_strategy = NULL;
 851         struct commit_list **remotes = &remoteheads;
 852
 853         setup_work_tree();
 854         if (read_cache_unmerged())
 855                 die("You are in the middle of a conflicted merge.");
 856
 857         /*
 858          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 859          * current branch.
 860          */
 861         branch = resolve_ref("HEAD", head, 0, &flag);
 862         if (branch && !prefixcmp(branch, "refs/heads/"))
 863                 branch += 11;
 864         if (is_null_sha1(head))
 865                 head_invalid = 1;
 866
 867         git_config(git_merge_config, NULL);
 868
 869         /* for color.ui */
 870         if (diff_use_color_default == -1)
 871                 diff_use_color_default = git_use_color_default;
 872
 873         argc = parse_options(argc, argv, builtin_merge_options,
 874                         builtin_merge_usage, 0);
 875
 876         if (squash) {
 877                 if (!allow_fast_forward)
 878                         die("You cannot combine --squash with --no-ff.");
 879                 option_commit = 0;
 880         }
 881
 882         if (!argc)
 883                 usage_with_options(builtin_merge_usage,
 884                         builtin_merge_options);
 885
 886         /*
 887          * This could be traditional "merge <msg> HEAD <commit>..."  and
 888          * the way we can tell it is to see if the second token is HEAD,
 889          * but some people might have misused the interface and used a
 890          * committish that is the same as HEAD there instead.
 891          * Traditional format never would have "-m" so it is an
 892          * additional safety measure to check for it.
 893          */
 894
 895         if (!have_message && is_old_style_invocation(argc, argv)) {
 896                 strbuf_addstr(&merge_msg, argv[0]);
 897                 head_arg = argv[1];
 898                 argv += 2;
 899                 argc -= 2;
 900         } else if (head_invalid) {
 901                 struct object *remote_head;
 902                 /*
 903                  * If the merged head is a valid one there is no reason
 904                  * to forbid "git merge" into a branch yet to be born.
 905                  * We do the same for "git pull".
 906                  */
 907                 if (argc != 1)
 908                         die("Can merge only exactly one commit into "
 909                                 "empty head");
 910                 if (squash)
 911                         die("Squash commit into empty head not supported yet");
 912                 if (!allow_fast_forward)
 913                         die("Non-fast-forward commit does not make sense into "
 914                             "an empty head");
 915                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 916                 if (!remote_head)
 917                         die("%s - not something we can merge", argv[0]);
 918                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 919                                 DIE_ON_ERR);
 920                 reset_hard(remote_head->sha1, 0);
 921                 return 0;
 922         } else {
 923                 struct strbuf msg = STRBUF_INIT;
 924
 925                 /* We are invoked directly as the first-class UI. */
 926                 head_arg = "HEAD";
 927
 928                 /*
 929                  * All the rest are the commits being merged;
 930                  * prepare the standard merge summary message to
 931                  * be appended to the given message.  If remote
 932                  * is invalid we will die later in the common
 933                  * codepath so we discard the error in this
 934                  * loop.
 935                  */
 936                 for (i = 0; i < argc; i++)
 937                         merge_name(argv[i], &msg);
 938                 fmt_merge_msg(option_log, &msg, &merge_msg);
 939                 if (merge_msg.len)
 940                         strbuf_setlen(&merge_msg, merge_msg.len-1);
 941         }
 942
 943         if (head_invalid || !argc)
 944                 usage_with_options(builtin_merge_usage,
 945                         builtin_merge_options);
 946
 947         strbuf_addstr(&buf, "merge");
 948         for (i = 0; i < argc; i++)
 949                 strbuf_addf(&buf, " %s", argv[i]);
 950         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 951         strbuf_reset(&buf);
 952
 953         for (i = 0; i < argc; i++) {
 954                 struct object *o;
 955                 struct commit *commit;
 956
 957                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 958                 if (!o)
 959                         die("%s - not something we can merge", argv[i]);
 960                 commit = lookup_commit(o->sha1);
 961                 commit->util = (void *)argv[i];
 962                 remotes = &commit_list_insert(commit, remotes)->next;
 963
 964                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 965                 setenv(buf.buf, argv[i], 1);
 966                 strbuf_reset(&buf);
 967         }
 968
 969         if (!use_strategies) {
 970                 if (!remoteheads->next)
 971                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 972                 else
 973                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 974         }
 975
 976         for (i = 0; i < use_strategies_nr; i++) {
 977                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 978                         allow_fast_forward = 0;
 979                 if (use_strategies[i]->attr & NO_TRIVIAL)
 980                         allow_trivial = 0;
 981         }
 982
 983         if (!remoteheads->next)
 984                 common = get_merge_bases(lookup_commit(head),
 985                                 remoteheads->item, 1);
 986         else {
 987                 struct commit_list *list = remoteheads;
 988                 commit_list_insert(lookup_commit(head), &list);
 989                 common = get_octopus_merge_bases(list);
 990                 free(list);
 991         }
 992
 993         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
 994                 DIE_ON_ERR);
 995
 996         if (!common)
 997                 ; /* No common ancestors found. We need a real merge. */
 998         else if (!remoteheads->next && !common->next &&
 999                         common->item == remoteheads->item) {
1000                 /*
1001                  * If head can reach all the merge then we are up to date.
1002                  * but first the most common case of merging one remote.
1003                  */
1004                 finish_up_to_date("Already up-to-date.");
1005                 return 0;
1006         } else if (allow_fast_forward && !remoteheads->next &&
1007                         !common->next &&
1008                         !hashcmp(common->item->object.sha1, head)) {
1009                 /* Again the most common case of merging one remote. */
1010                 struct strbuf msg = STRBUF_INIT;
1011                 struct object *o;
1012                 char hex[41];
1013
1014                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1015
1016                 printf("Updating %s..%s\n",
1017                         hex,
1018                         find_unique_abbrev(remoteheads->item->object.sha1,
1019                         DEFAULT_ABBREV));
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 }