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