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 int run_hook(const char *name)
 304 {
 305         struct child_process hook;
 306         const char *argv[3], *env[2];
 307         char index[PATH_MAX];
 308
 309         argv[0] = git_path("hooks/%s", name);
 310         if (access(argv[0], X_OK) < 0)
 311                 return 0;
 312
 313         snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", get_index_file());
 314         env[0] = index;
 315         env[1] = NULL;
 316
 317         if (squash)
 318                 argv[1] = "1";
 319         else
 320                 argv[1] = "0";
 321         argv[2] = NULL;
 322
 323         memset(&hook, 0, sizeof(hook));
 324         hook.argv = argv;
 325         hook.no_stdin = 1;
 326         hook.stdout_to_stderr = 1;
 327         hook.env = env;
 328
 329         return run_command(&hook);
 330 }
 331
 332 static void finish(const unsigned char *new_head, const char *msg)
 333 {
 334         struct strbuf reflog_message = STRBUF_INIT;
 335
 336         if (!msg)
 337                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 338         else {
 339                 if (verbosity >= 0)
 340                         printf("%s\n", msg);
 341                 strbuf_addf(&reflog_message, "%s: %s",
 342                         getenv("GIT_REFLOG_ACTION"), msg);
 343         }
 344         if (squash) {
 345                 squash_message();
 346         } else {
 347                 if (verbosity >= 0 && !merge_msg.len)
 348                         printf("No merge message -- not updating HEAD\n");
 349                 else {
 350                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 351                         update_ref(reflog_message.buf, "HEAD",
 352                                 new_head, head, 0,
 353                                 DIE_ON_ERR);
 354                         /*
 355                          * We ignore errors in 'gc --auto', since the
 356                          * user should see them.
 357                          */
 358                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 359                 }
 360         }
 361         if (new_head && show_diffstat) {
 362                 struct diff_options opts;
 363                 diff_setup(&opts);
 364                 opts.output_format |=
 365                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 366                 opts.detect_rename = DIFF_DETECT_RENAME;
 367                 if (diff_use_color_default > 0)
 368                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 369                 if (diff_setup_done(&opts) < 0)
 370                         die("diff_setup_done failed");
 371                 diff_tree_sha1(head, new_head, "", &opts);
 372                 diffcore_std(&opts);
 373                 diff_flush(&opts);
 374         }
 375
 376         /* Run a post-merge hook */
 377         run_hook("post-merge");
 378
 379         strbuf_release(&reflog_message);
 380 }
 381
 382 /* Get the name for the merge commit's message. */
 383 static void merge_name(const char *remote, struct strbuf *msg)
 384 {
 385         struct object *remote_head;
 386         unsigned char branch_head[20], buf_sha[20];
 387         struct strbuf buf = STRBUF_INIT;
 388         const char *ptr;
 389         int len, early;
 390
 391         memset(branch_head, 0, sizeof(branch_head));
 392         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 393         if (!remote_head)
 394                 die("'%s' does not point to a commit", remote);
 395
 396         strbuf_addstr(&buf, "refs/heads/");
 397         strbuf_addstr(&buf, remote);
 398         resolve_ref(buf.buf, branch_head, 0, 0);
 399
 400         if (!hashcmp(remote_head->sha1, branch_head)) {
 401                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 402                         sha1_to_hex(branch_head), remote);
 403                 return;
 404         }
 405
 406         /* See if remote matches <name>^^^.. or <name>~<number> */
 407         for (len = 0, ptr = remote + strlen(remote);
 408              remote < ptr && ptr[-1] == '^';
 409              ptr--)
 410                 len++;
 411         if (len)
 412                 early = 1;
 413         else {
 414                 early = 0;
 415                 ptr = strrchr(remote, '~');
 416                 if (ptr) {
 417                         int seen_nonzero = 0;
 418
 419                         len++; /* count ~ */
 420                         while (*++ptr && isdigit(*ptr)) {
 421                                 seen_nonzero |= (*ptr != '0');
 422                                 len++;
 423                         }
 424                         if (*ptr)
 425                                 len = 0; /* not ...~<number> */
 426                         else if (seen_nonzero)
 427                                 early = 1;
 428                         else if (len == 1)
 429                                 early = 1; /* "name~" is "name~1"! */
 430                 }
 431         }
 432         if (len) {
 433                 struct strbuf truname = STRBUF_INIT;
 434                 strbuf_addstr(&truname, "refs/heads/");
 435                 strbuf_addstr(&truname, remote);
 436                 strbuf_setlen(&truname, truname.len - len);
 437                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
 438                         strbuf_addf(msg,
 439                                     "%s\t\tbranch '%s'%s of .\n",
 440                                     sha1_to_hex(remote_head->sha1),
 441                                     truname.buf + 11,
 442                                     (early ? " (early part)" : ""));
 443                         return;
 444                 }
 445         }
 446
 447         if (!strcmp(remote, "FETCH_HEAD") &&
 448                         !access(git_path("FETCH_HEAD"), R_OK)) {
 449                 FILE *fp;
 450                 struct strbuf line = STRBUF_INIT;
 451                 char *ptr;
 452
 453                 fp = fopen(git_path("FETCH_HEAD"), "r");
 454                 if (!fp)
 455                         die("could not open %s for reading: %s",
 456                                 git_path("FETCH_HEAD"), strerror(errno));
 457                 strbuf_getline(&line, fp, '\n');
 458                 fclose(fp);
 459                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 460                 if (ptr)
 461                         strbuf_remove(&line, ptr-line.buf+1, 13);
 462                 strbuf_addbuf(msg, &line);
 463                 strbuf_release(&line);
 464                 return;
 465         }
 466         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 467                 sha1_to_hex(remote_head->sha1), remote);
 468 }
 469
 470 static int git_merge_config(const char *k, const char *v, void *cb)
 471 {
 472         if (branch && !prefixcmp(k, "branch.") &&
 473                 !prefixcmp(k + 7, branch) &&
 474                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 475                 const char **argv;
 476                 int argc;
 477                 char *buf;
 478
 479                 buf = xstrdup(v);
 480                 argc = split_cmdline(buf, &argv);
 481                 if (argc < 0)
 482                         die("Bad branch.%s.mergeoptions string", branch);
 483                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 484                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 485                 argc++;
 486                 parse_options(argc, argv, builtin_merge_options,
 487                               builtin_merge_usage, 0);
 488                 free(buf);
 489         }
 490
 491         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 492                 show_diffstat = git_config_bool(k, v);
 493         else if (!strcmp(k, "pull.twohead"))
 494                 return git_config_string(&pull_twohead, k, v);
 495         else if (!strcmp(k, "pull.octopus"))
 496                 return git_config_string(&pull_octopus, k, v);
 497         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 498                 option_log = git_config_bool(k, v);
 499         return git_diff_ui_config(k, v, cb);
 500 }
 501
 502 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 503                              unsigned char *one)
 504 {
 505         int i, nr_trees = 0;
 506         struct tree *trees[MAX_UNPACK_TREES];
 507         struct tree_desc t[MAX_UNPACK_TREES];
 508         struct unpack_trees_options opts;
 509
 510         memset(&opts, 0, sizeof(opts));
 511         opts.head_idx = 2;
 512         opts.src_index = &the_index;
 513         opts.dst_index = &the_index;
 514         opts.update = 1;
 515         opts.verbose_update = 1;
 516         opts.trivial_merges_only = 1;
 517         opts.merge = 1;
 518         trees[nr_trees] = parse_tree_indirect(common);
 519         if (!trees[nr_trees++])
 520                 return -1;
 521         trees[nr_trees] = parse_tree_indirect(head);
 522         if (!trees[nr_trees++])
 523                 return -1;
 524         trees[nr_trees] = parse_tree_indirect(one);
 525         if (!trees[nr_trees++])
 526                 return -1;
 527         opts.fn = threeway_merge;
 528         cache_tree_free(&active_cache_tree);
 529         for (i = 0; i < nr_trees; i++) {
 530                 parse_tree(trees[i]);
 531                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 532         }
 533         if (unpack_trees(nr_trees, t, &opts))
 534                 return -1;
 535         return 0;
 536 }
 537
 538 static void write_tree_trivial(unsigned char *sha1)
 539 {
 540         if (write_cache_as_tree(sha1, 0, NULL))
 541                 die("git write-tree failed to write a tree");
 542 }
 543
 544 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 545                               const char *head_arg)
 546 {
 547         const char **args;
 548         int i = 0, ret;
 549         struct commit_list *j;
 550         struct strbuf buf = STRBUF_INIT;
 551         int index_fd;
 552         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 553
 554         index_fd = hold_locked_index(lock, 1);
 555         refresh_cache(REFRESH_QUIET);
 556         if (active_cache_changed &&
 557                         (write_cache(index_fd, active_cache, active_nr) ||
 558                          commit_locked_index(lock)))
 559                 return error("Unable to write index.");
 560         rollback_lock_file(lock);
 561
 562         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 563                 int clean;
 564                 struct commit *result;
 565                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 566                 int index_fd;
 567                 struct commit_list *reversed = NULL;
 568                 struct merge_options o;
 569
 570                 if (remoteheads->next) {
 571                         error("Not handling anything other than two heads merge.");
 572                         return 2;
 573                 }
 574
 575                 init_merge_options(&o);
 576                 if (!strcmp(strategy, "subtree"))
 577                         o.subtree_merge = 1;
 578
 579                 o.branch1 = head_arg;
 580                 o.branch2 = remoteheads->item->util;
 581
 582                 for (j = common; j; j = j->next)
 583                         commit_list_insert(j->item, &reversed);
 584
 585                 index_fd = hold_locked_index(lock, 1);
 586                 clean = merge_recursive(&o, lookup_commit(head),
 587                                 remoteheads->item, reversed, &result);
 588                 if (active_cache_changed &&
 589                                 (write_cache(index_fd, active_cache, active_nr) ||
 590                                  commit_locked_index(lock)))
 591                         die ("unable to write %s", get_index_file());
 592                 rollback_lock_file(lock);
 593                 return clean ? 0 : 1;
 594         } else {
 595                 args = xmalloc((4 + commit_list_count(common) +
 596                                         commit_list_count(remoteheads)) * sizeof(char *));
 597                 strbuf_addf(&buf, "merge-%s", strategy);
 598                 args[i++] = buf.buf;
 599                 for (j = common; j; j = j->next)
 600                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 601                 args[i++] = "--";
 602                 args[i++] = head_arg;
 603                 for (j = remoteheads; j; j = j->next)
 604                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 605                 args[i] = NULL;
 606                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 607                 strbuf_release(&buf);
 608                 i = 1;
 609                 for (j = common; j; j = j->next)
 610                         free((void *)args[i++]);
 611                 i += 2;
 612                 for (j = remoteheads; j; j = j->next)
 613                         free((void *)args[i++]);
 614                 free(args);
 615                 discard_cache();
 616                 if (read_cache() < 0)
 617                         die("failed to read the cache");
 618                 return -ret;
 619         }
 620 }
 621
 622 static void count_diff_files(struct diff_queue_struct *q,
 623                              struct diff_options *opt, void *data)
 624 {
 625         int *count = data;
 626
 627         (*count) += q->nr;
 628 }
 629
 630 static int count_unmerged_entries(void)
 631 {
 632         const struct index_state *state = &the_index;
 633         int i, ret = 0;
 634
 635         for (i = 0; i < state->cache_nr; i++)
 636                 if (ce_stage(state->cache[i]))
 637                         ret++;
 638
 639         return ret;
 640 }
 641
 642 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 643 {
 644         struct tree *trees[MAX_UNPACK_TREES];
 645         struct unpack_trees_options opts;
 646         struct tree_desc t[MAX_UNPACK_TREES];
 647         int i, fd, nr_trees = 0;
 648         struct dir_struct dir;
 649         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 650
 651         refresh_cache(REFRESH_QUIET);
 652
 653         fd = hold_locked_index(lock_file, 1);
 654
 655         memset(&trees, 0, sizeof(trees));
 656         memset(&opts, 0, sizeof(opts));
 657         memset(&t, 0, sizeof(t));
 658         memset(&dir, 0, sizeof(dir));
 659         dir.show_ignored = 1;
 660         dir.exclude_per_dir = ".gitignore";
 661         opts.dir = &dir;
 662
 663         opts.head_idx = 1;
 664         opts.src_index = &the_index;
 665         opts.dst_index = &the_index;
 666         opts.update = 1;
 667         opts.verbose_update = 1;
 668         opts.merge = 1;
 669         opts.fn = twoway_merge;
 670
 671         trees[nr_trees] = parse_tree_indirect(head);
 672         if (!trees[nr_trees++])
 673                 return -1;
 674         trees[nr_trees] = parse_tree_indirect(remote);
 675         if (!trees[nr_trees++])
 676                 return -1;
 677         for (i = 0; i < nr_trees; i++) {
 678                 parse_tree(trees[i]);
 679                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 680         }
 681         if (unpack_trees(nr_trees, t, &opts))
 682                 return -1;
 683         if (write_cache(fd, active_cache, active_nr) ||
 684                 commit_locked_index(lock_file))
 685                 die("unable to write new index file");
 686         return 0;
 687 }
 688
 689 static void split_merge_strategies(const char *string, struct strategy **list,
 690                                    int *nr, int *alloc)
 691 {
 692         char *p, *q, *buf;
 693
 694         if (!string)
 695                 return;
 696
 697         buf = xstrdup(string);
 698         q = buf;
 699         for (;;) {
 700                 p = strchr(q, ' ');
 701                 if (!p) {
 702                         ALLOC_GROW(*list, *nr + 1, *alloc);
 703                         (*list)[(*nr)++].name = xstrdup(q);
 704                         free(buf);
 705                         return;
 706                 } else {
 707                         *p = '\0';
 708                         ALLOC_GROW(*list, *nr + 1, *alloc);
 709                         (*list)[(*nr)++].name = xstrdup(q);
 710                         q = ++p;
 711                 }
 712         }
 713 }
 714
 715 static void add_strategies(const char *string, unsigned attr)
 716 {
 717         struct strategy *list = NULL;
 718         int list_alloc = 0, list_nr = 0, i;
 719
 720         memset(&list, 0, sizeof(list));
 721         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 722         if (list) {
 723                 for (i = 0; i < list_nr; i++)
 724                         append_strategy(get_strategy(list[i].name));
 725                 return;
 726         }
 727         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 728                 if (all_strategy[i].attr & attr)
 729                         append_strategy(&all_strategy[i]);
 730
 731 }
 732
 733 static int merge_trivial(void)
 734 {
 735         unsigned char result_tree[20], result_commit[20];
 736         struct commit_list *parent = xmalloc(sizeof(*parent));
 737
 738         write_tree_trivial(result_tree);
 739         printf("Wonderful.\n");
 740         parent->item = lookup_commit(head);
 741         parent->next = xmalloc(sizeof(*parent->next));
 742         parent->next->item = remoteheads->item;
 743         parent->next->next = NULL;
 744         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 745         finish(result_commit, "In-index merge");
 746         drop_save();
 747         return 0;
 748 }
 749
 750 static int finish_automerge(struct commit_list *common,
 751                             unsigned char *result_tree,
 752                             const char *wt_strategy)
 753 {
 754         struct commit_list *parents = NULL, *j;
 755         struct strbuf buf = STRBUF_INIT;
 756         unsigned char result_commit[20];
 757
 758         free_commit_list(common);
 759         if (allow_fast_forward) {
 760                 parents = remoteheads;
 761                 commit_list_insert(lookup_commit(head), &parents);
 762                 parents = reduce_heads(parents);
 763         } else {
 764                 struct commit_list **pptr = &parents;
 765
 766                 pptr = &commit_list_insert(lookup_commit(head),
 767                                 pptr)->next;
 768                 for (j = remoteheads; j; j = j->next)
 769                         pptr = &commit_list_insert(j->item, pptr)->next;
 770         }
 771         free_commit_list(remoteheads);
 772         strbuf_addch(&merge_msg, '\n');
 773         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 774         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 775         finish(result_commit, buf.buf);
 776         strbuf_release(&buf);
 777         drop_save();
 778         return 0;
 779 }
 780
 781 static int suggest_conflicts(void)
 782 {
 783         FILE *fp;
 784         int pos;
 785
 786         fp = fopen(git_path("MERGE_MSG"), "a");
 787         if (!fp)
 788                 die("Could not open %s for writing", git_path("MERGE_MSG"));
 789         fprintf(fp, "\nConflicts:\n");
 790         for (pos = 0; pos < active_nr; pos++) {
 791                 struct cache_entry *ce = active_cache[pos];
 792
 793                 if (ce_stage(ce)) {
 794                         fprintf(fp, "\t%s\n", ce->name);
 795                         while (pos + 1 < active_nr &&
 796                                         !strcmp(ce->name,
 797                                                 active_cache[pos + 1]->name))
 798                                 pos++;
 799                 }
 800         }
 801         fclose(fp);
 802         rerere();
 803         printf("Automatic merge failed; "
 804                         "fix conflicts and then commit the result.\n");
 805         return 1;
 806 }
 807
 808 static struct commit *is_old_style_invocation(int argc, const char **argv)
 809 {
 810         struct commit *second_token = NULL;
 811         if (argc > 1) {
 812                 unsigned char second_sha1[20];
 813
 814                 if (get_sha1(argv[1], second_sha1))
 815                         return NULL;
 816                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 817                 if (!second_token)
 818                         die("'%s' is not a commit", argv[1]);
 819                 if (hashcmp(second_token->object.sha1, head))
 820                         return NULL;
 821         }
 822         return second_token;
 823 }
 824
 825 static int evaluate_result(void)
 826 {
 827         int cnt = 0;
 828         struct rev_info rev;
 829
 830         /* Check how many files differ. */
 831         init_revisions(&rev, "");
 832         setup_revisions(0, NULL, &rev, NULL);
 833         rev.diffopt.output_format |=
 834                 DIFF_FORMAT_CALLBACK;
 835         rev.diffopt.format_callback = count_diff_files;
 836         rev.diffopt.format_callback_data = &cnt;
 837         run_diff_files(&rev, 0);
 838
 839         /*
 840          * Check how many unmerged entries are
 841          * there.
 842          */
 843         cnt += count_unmerged_entries();
 844
 845         return cnt;
 846 }
 847
 848 int cmd_merge(int argc, const char **argv, const char *prefix)
 849 {
 850         unsigned char result_tree[20];
 851         struct strbuf buf = STRBUF_INIT;
 852         const char *head_arg;
 853         int flag, head_invalid = 0, i;
 854         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 855         struct commit_list *common = NULL;
 856         const char *best_strategy = NULL, *wt_strategy = NULL;
 857         struct commit_list **remotes = &remoteheads;
 858
 859         setup_work_tree();
 860         if (read_cache_unmerged())
 861                 die("You are in the middle of a conflicted merge.");
 862
 863         /*
 864          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 865          * current branch.
 866          */
 867         branch = resolve_ref("HEAD", head, 0, &flag);
 868         if (branch && !prefixcmp(branch, "refs/heads/"))
 869                 branch += 11;
 870         if (is_null_sha1(head))
 871                 head_invalid = 1;
 872
 873         git_config(git_merge_config, NULL);
 874
 875         /* for color.ui */
 876         if (diff_use_color_default == -1)
 877                 diff_use_color_default = git_use_color_default;
 878
 879         argc = parse_options(argc, argv, builtin_merge_options,
 880                         builtin_merge_usage, 0);
 881         if (verbosity < 0)
 882                 show_diffstat = 0;
 883
 884         if (squash) {
 885                 if (!allow_fast_forward)
 886                         die("You cannot combine --squash with --no-ff.");
 887                 option_commit = 0;
 888         }
 889
 890         if (!argc)
 891                 usage_with_options(builtin_merge_usage,
 892                         builtin_merge_options);
 893
 894         /*
 895          * This could be traditional "merge <msg> HEAD <commit>..."  and
 896          * the way we can tell it is to see if the second token is HEAD,
 897          * but some people might have misused the interface and used a
 898          * committish that is the same as HEAD there instead.
 899          * Traditional format never would have "-m" so it is an
 900          * additional safety measure to check for it.
 901          */
 902
 903         if (!have_message && is_old_style_invocation(argc, argv)) {
 904                 strbuf_addstr(&merge_msg, argv[0]);
 905                 head_arg = argv[1];
 906                 argv += 2;
 907                 argc -= 2;
 908         } else if (head_invalid) {
 909                 struct object *remote_head;
 910                 /*
 911                  * If the merged head is a valid one there is no reason
 912                  * to forbid "git merge" into a branch yet to be born.
 913                  * We do the same for "git pull".
 914                  */
 915                 if (argc != 1)
 916                         die("Can merge only exactly one commit into "
 917                                 "empty head");
 918                 if (squash)
 919                         die("Squash commit into empty head not supported yet");
 920                 if (!allow_fast_forward)
 921                         die("Non-fast-forward commit does not make sense into "
 922                             "an empty head");
 923                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 924                 if (!remote_head)
 925                         die("%s - not something we can merge", argv[0]);
 926                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 927                                 DIE_ON_ERR);
 928                 reset_hard(remote_head->sha1, 0);
 929                 return 0;
 930         } else {
 931                 struct strbuf msg = STRBUF_INIT;
 932
 933                 /* We are invoked directly as the first-class UI. */
 934                 head_arg = "HEAD";
 935
 936                 /*
 937                  * All the rest are the commits being merged;
 938                  * prepare the standard merge summary message to
 939                  * be appended to the given message.  If remote
 940                  * is invalid we will die later in the common
 941                  * codepath so we discard the error in this
 942                  * loop.
 943                  */
 944                 for (i = 0; i < argc; i++)
 945                         merge_name(argv[i], &msg);
 946                 fmt_merge_msg(option_log, &msg, &merge_msg);
 947                 if (merge_msg.len)
 948                         strbuf_setlen(&merge_msg, merge_msg.len-1);
 949         }
 950
 951         if (head_invalid || !argc)
 952                 usage_with_options(builtin_merge_usage,
 953                         builtin_merge_options);
 954
 955         strbuf_addstr(&buf, "merge");
 956         for (i = 0; i < argc; i++)
 957                 strbuf_addf(&buf, " %s", argv[i]);
 958         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 959         strbuf_reset(&buf);
 960
 961         for (i = 0; i < argc; i++) {
 962                 struct object *o;
 963                 struct commit *commit;
 964
 965                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 966                 if (!o)
 967                         die("%s - not something we can merge", argv[i]);
 968                 commit = lookup_commit(o->sha1);
 969                 commit->util = (void *)argv[i];
 970                 remotes = &commit_list_insert(commit, remotes)->next;
 971
 972                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 973                 setenv(buf.buf, argv[i], 1);
 974                 strbuf_reset(&buf);
 975         }
 976
 977         if (!use_strategies) {
 978                 if (!remoteheads->next)
 979                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 980                 else
 981                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 982         }
 983
 984         for (i = 0; i < use_strategies_nr; i++) {
 985                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 986                         allow_fast_forward = 0;
 987                 if (use_strategies[i]->attr & NO_TRIVIAL)
 988                         allow_trivial = 0;
 989         }
 990
 991         if (!remoteheads->next)
 992                 common = get_merge_bases(lookup_commit(head),
 993                                 remoteheads->item, 1);
 994         else {
 995                 struct commit_list *list = remoteheads;
 996                 commit_list_insert(lookup_commit(head), &list);
 997                 common = get_octopus_merge_bases(list);
 998                 free(list);
 999         }
1000
1001         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1002                 DIE_ON_ERR);
1003
1004         if (!common)
1005                 ; /* No common ancestors found. We need a real merge. */
1006         else if (!remoteheads->next && !common->next &&
1007                         common->item == remoteheads->item) {
1008                 /*
1009                  * If head can reach all the merge then we are up to date.
1010                  * but first the most common case of merging one remote.
1011                  */
1012                 finish_up_to_date("Already up-to-date.");
1013                 return 0;
1014         } else if (allow_fast_forward && !remoteheads->next &&
1015                         !common->next &&
1016                         !hashcmp(common->item->object.sha1, head)) {
1017                 /* Again the most common case of merging one remote. */
1018                 struct strbuf msg = STRBUF_INIT;
1019                 struct object *o;
1020                 char hex[41];
1021
1022                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1023
1024                 if (verbosity >= 0)
1025                         printf("Updating %s..%s\n",
1026                                 hex,
1027                                 find_unique_abbrev(remoteheads->item->object.sha1,
1028                                 DEFAULT_ABBREV));
1029                 strbuf_addstr(&msg, "Fast forward");
1030                 if (have_message)
1031                         strbuf_addstr(&msg,
1032                                 " (no commit created; -m option ignored)");
1033                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1034                         0, NULL, OBJ_COMMIT);
1035                 if (!o)
1036                         return 1;
1037
1038                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1039                         return 1;
1040
1041                 finish(o->sha1, msg.buf);
1042                 drop_save();
1043                 return 0;
1044         } else if (!remoteheads->next && common->next)
1045                 ;
1046                 /*
1047                  * We are not doing octopus and not fast forward.  Need
1048                  * a real merge.
1049                  */
1050         else if (!remoteheads->next && !common->next && option_commit) {
1051                 /*
1052                  * We are not doing octopus, not fast forward, and have
1053                  * only one common.
1054                  */
1055                 refresh_cache(REFRESH_QUIET);
1056                 if (allow_trivial) {
1057                         /* See if it is really trivial. */
1058                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1059                         printf("Trying really trivial in-index merge...\n");
1060                         if (!read_tree_trivial(common->item->object.sha1,
1061                                         head, remoteheads->item->object.sha1))
1062                                 return merge_trivial();
1063                         printf("Nope.\n");
1064                 }
1065         } else {
1066                 /*
1067                  * An octopus.  If we can reach all the remote we are up
1068                  * to date.
1069                  */
1070                 int up_to_date = 1;
1071                 struct commit_list *j;
1072
1073                 for (j = remoteheads; j; j = j->next) {
1074                         struct commit_list *common_one;
1075
1076                         /*
1077                          * Here we *have* to calculate the individual
1078                          * merge_bases again, otherwise "git merge HEAD^
1079                          * HEAD^^" would be missed.
1080                          */
1081                         common_one = get_merge_bases(lookup_commit(head),
1082                                 j->item, 1);
1083                         if (hashcmp(common_one->item->object.sha1,
1084                                 j->item->object.sha1)) {
1085                                 up_to_date = 0;
1086                                 break;
1087                         }
1088                 }
1089                 if (up_to_date) {
1090                         finish_up_to_date("Already up-to-date. Yeeah!");
1091                         return 0;
1092                 }
1093         }
1094
1095         /* We are going to make a new commit. */
1096         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1097
1098         /*
1099          * At this point, we need a real merge.  No matter what strategy
1100          * we use, it would operate on the index, possibly affecting the
1101          * working tree, and when resolved cleanly, have the desired
1102          * tree in the index -- this means that the index must be in
1103          * sync with the head commit.  The strategies are responsible
1104          * to ensure this.
1105          */
1106         if (use_strategies_nr != 1) {
1107                 /*
1108                  * Stash away the local changes so that we can try more
1109                  * than one.
1110                  */
1111                 save_state();
1112         } else {
1113                 memcpy(stash, null_sha1, 20);
1114         }
1115
1116         for (i = 0; i < use_strategies_nr; i++) {
1117                 int ret;
1118                 if (i) {
1119                         printf("Rewinding the tree to pristine...\n");
1120                         restore_state();
1121                 }
1122                 if (use_strategies_nr != 1)
1123                         printf("Trying merge strategy %s...\n",
1124                                 use_strategies[i]->name);
1125                 /*
1126                  * Remember which strategy left the state in the working
1127                  * tree.
1128                  */
1129                 wt_strategy = use_strategies[i]->name;
1130
1131                 ret = try_merge_strategy(use_strategies[i]->name,
1132                         common, head_arg);
1133                 if (!option_commit && !ret) {
1134                         merge_was_ok = 1;
1135                         /*
1136                          * This is necessary here just to avoid writing
1137                          * the tree, but later we will *not* exit with
1138                          * status code 1 because merge_was_ok is set.
1139                          */
1140                         ret = 1;
1141                 }
1142
1143                 if (ret) {
1144                         /*
1145                          * The backend exits with 1 when conflicts are
1146                          * left to be resolved, with 2 when it does not
1147                          * handle the given merge at all.
1148                          */
1149                         if (ret == 1) {
1150                                 int cnt = evaluate_result();
1151
1152                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1153                                         best_strategy = use_strategies[i]->name;
1154                                         best_cnt = cnt;
1155                                 }
1156                         }
1157                         if (merge_was_ok)
1158                                 break;
1159                         else
1160                                 continue;
1161                 }
1162
1163                 /* Automerge succeeded. */
1164                 write_tree_trivial(result_tree);
1165                 automerge_was_ok = 1;
1166                 break;
1167         }
1168
1169         /*
1170          * If we have a resulting tree, that means the strategy module
1171          * auto resolved the merge cleanly.
1172          */
1173         if (automerge_was_ok)
1174                 return finish_automerge(common, result_tree, wt_strategy);
1175
1176         /*
1177          * Pick the result from the best strategy and have the user fix
1178          * it up.
1179          */
1180         if (!best_strategy) {
1181                 restore_state();
1182                 if (use_strategies_nr > 1)
1183                         fprintf(stderr,
1184                                 "No merge strategy handled the merge.\n");
1185                 else
1186                         fprintf(stderr, "Merge with strategy %s failed.\n",
1187                                 use_strategies[0]->name);
1188                 return 2;
1189         } else if (best_strategy == wt_strategy)
1190                 ; /* We already have its result in the working tree. */
1191         else {
1192                 printf("Rewinding the tree to pristine...\n");
1193                 restore_state();
1194                 printf("Using the %s to prepare resolving by hand.\n",
1195                         best_strategy);
1196                 try_merge_strategy(best_strategy, common, head_arg);
1197         }
1198
1199         if (squash)
1200                 finish(NULL, NULL);
1201         else {
1202                 int fd;
1203                 struct commit_list *j;
1204
1205                 for (j = remoteheads; j; j = j->next)
1206                         strbuf_addf(&buf, "%s\n",
1207                                 sha1_to_hex(j->item->object.sha1));
1208                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1209                 if (fd < 0)
1210                         die("Could open %s for writing",
1211                                 git_path("MERGE_HEAD"));
1212                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1213                         die("Could not write to %s", git_path("MERGE_HEAD"));
1214                 close(fd);
1215                 strbuf_addch(&merge_msg, '\n');
1216                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1217                 if (fd < 0)
1218                         die("Could open %s for writing", git_path("MERGE_MSG"));
1219                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1220                         merge_msg.len)
1221                         die("Could not write to %s", git_path("MERGE_MSG"));
1222                 close(fd);
1223                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1224                 if (fd < 0)
1225                         die("Could open %s for writing", git_path("MERGE_MODE"));
1226                 strbuf_reset(&buf);
1227                 if (!allow_fast_forward)
1228                         strbuf_addf(&buf, "no-ff");
1229                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1230                         die("Could not write to %s", git_path("MERGE_MODE"));
1231                 close(fd);
1232         }
1233
1234         if (merge_was_ok) {
1235                 fprintf(stderr, "Automatic merge went well; "
1236                         "stopped before committing as requested\n");
1237                 return 0;
1238         } else
1239                 return suggest_conflicts();
1240 }