git.oblomov.eu Git - git/blob - builtin-merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27
  28 #define DEFAULT_TWOHEAD (1<<0)
  29 #define DEFAULT_OCTOPUS (1<<1)
  30 #define NO_FAST_FORWARD (1<<2)
  31 #define NO_TRIVIAL      (1<<3)
  32
  33 struct strategy {
  34         const char *name;
  35         unsigned attr;
  36 };
  37
  38 static const char * const builtin_merge_usage[] = {
  39         "git-merge [options] <remote>...",
  40         "git-merge [options] <msg> HEAD <remote>",
  41         NULL
  42 };
  43
  44 static int show_diffstat = 1, option_log, squash;
  45 static int option_commit = 1, allow_fast_forward = 1;
  46 static int allow_trivial = 1, have_message;
  47 static struct strbuf merge_msg;
  48 static struct commit_list *remoteheads;
  49 static unsigned char head[20], stash[20];
  50 static struct strategy **use_strategies;
  51 static size_t use_strategies_nr, use_strategies_alloc;
  52 static const char *branch;
  53 static int verbosity;
  54
  55 static struct strategy all_strategy[] = {
  56         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  57         { "octopus",    DEFAULT_OCTOPUS },
  58         { "resolve",    0 },
  59         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  60         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  61 };
  62
  63 static const char *pull_twohead, *pull_octopus;
  64
  65 static int option_parse_message(const struct option *opt,
  66                                 const char *arg, int unset)
  67 {
  68         struct strbuf *buf = opt->value;
  69
  70         if (unset)
  71                 strbuf_setlen(buf, 0);
  72         else if (arg) {
  73                 strbuf_addf(buf, "%s\n\n", arg);
  74                 have_message = 1;
  75         } else
  76                 return error("switch `m' requires a value");
  77         return 0;
  78 }
  79
  80 static struct strategy *get_strategy(const char *name)
  81 {
  82         int i;
  83         struct strategy *ret;
  84         static struct cmdnames main_cmds, other_cmds;
  85         static int loaded;
  86
  87         if (!name)
  88                 return NULL;
  89
  90         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  91                 if (!strcmp(name, all_strategy[i].name))
  92                         return &all_strategy[i];
  93
  94         if (!loaded) {
  95                 struct cmdnames not_strategies;
  96                 loaded = 1;
  97
  98                 memset(&not_strategies, 0, sizeof(struct cmdnames));
  99                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 100                 for (i = 0; i < main_cmds.cnt; i++) {
 101                         int j, found = 0;
 102                         struct cmdname *ent = main_cmds.names[i];
 103                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 104                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 105                                                 && !all_strategy[j].name[ent->len])
 106                                         found = 1;
 107                         if (!found)
 108                                 add_cmdname(&not_strategies, ent->name, ent->len);
 109                         exclude_cmds(&main_cmds, &not_strategies);
 110                 }
 111         }
 112         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 113                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 114                 fprintf(stderr, "Available strategies are:");
 115                 for (i = 0; i < main_cmds.cnt; i++)
 116                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 117                 fprintf(stderr, ".\n");
 118                 if (other_cmds.cnt) {
 119                         fprintf(stderr, "Available custom strategies are:");
 120                         for (i = 0; i < other_cmds.cnt; i++)
 121                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 122                         fprintf(stderr, ".\n");
 123                 }
 124                 exit(1);
 125         }
 126
 127         ret = xcalloc(1, sizeof(struct strategy));
 128         ret->name = xstrdup(name);
 129         return ret;
 130 }
 131
 132 static void append_strategy(struct strategy *s)
 133 {
 134         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 135         use_strategies[use_strategies_nr++] = s;
 136 }
 137
 138 static int option_parse_strategy(const struct option *opt,
 139                                  const char *name, int unset)
 140 {
 141         if (unset)
 142                 return 0;
 143
 144         append_strategy(get_strategy(name));
 145         return 0;
 146 }
 147
 148 static int option_parse_n(const struct option *opt,
 149                           const char *arg, int unset)
 150 {
 151         show_diffstat = unset;
 152         return 0;
 153 }
 154
 155 static struct option builtin_merge_options[] = {
 156         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 157                 "do not show a diffstat at the end of the merge",
 158                 PARSE_OPT_NOARG, option_parse_n },
 159         OPT_BOOLEAN(0, "stat", &show_diffstat,
 160                 "show a diffstat at the end of the merge"),
 161         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 162         OPT_BOOLEAN(0, "log", &option_log,
 163                 "add list of one-line log to merge commit message"),
 164         OPT_BOOLEAN(0, "squash", &squash,
 165                 "create a single commit instead of doing a merge"),
 166         OPT_BOOLEAN(0, "commit", &option_commit,
 167                 "perform a commit if the merge succeeds (default)"),
 168         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 169                 "allow fast forward (default)"),
 170         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 171                 "merge strategy to use", option_parse_strategy),
 172         OPT_CALLBACK('m', "message", &merge_msg, "message",
 173                 "message to be used for the merge commit (if any)",
 174                 option_parse_message),
 175         OPT__VERBOSITY(&verbosity),
 176         OPT_END()
 177 };
 178
 179 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 180 static void drop_save(void)
 181 {
 182         unlink(git_path("MERGE_HEAD"));
 183         unlink(git_path("MERGE_MSG"));
 184         unlink(git_path("MERGE_MODE"));
 185 }
 186
 187 static void save_state(void)
 188 {
 189         int len;
 190         struct child_process cp;
 191         struct strbuf buffer = STRBUF_INIT;
 192         const char *argv[] = {"stash", "create", NULL};
 193
 194         memset(&cp, 0, sizeof(cp));
 195         cp.argv = argv;
 196         cp.out = -1;
 197         cp.git_cmd = 1;
 198
 199         if (start_command(&cp))
 200                 die("could not run stash.");
 201         len = strbuf_read(&buffer, cp.out, 1024);
 202         close(cp.out);
 203
 204         if (finish_command(&cp) || len < 0)
 205                 die("stash failed");
 206         else if (!len)
 207                 return;
 208         strbuf_setlen(&buffer, buffer.len-1);
 209         if (get_sha1(buffer.buf, stash))
 210                 die("not a valid object: %s", buffer.buf);
 211 }
 212
 213 static void reset_hard(unsigned const char *sha1, int verbose)
 214 {
 215         int i = 0;
 216         const char *args[6];
 217
 218         args[i++] = "read-tree";
 219         if (verbose)
 220                 args[i++] = "-v";
 221         args[i++] = "--reset";
 222         args[i++] = "-u";
 223         args[i++] = sha1_to_hex(sha1);
 224         args[i] = NULL;
 225
 226         if (run_command_v_opt(args, RUN_GIT_CMD))
 227                 die("read-tree failed");
 228 }
 229
 230 static void restore_state(void)
 231 {
 232         struct strbuf sb = STRBUF_INIT;
 233         const char *args[] = { "stash", "apply", NULL, NULL };
 234
 235         if (is_null_sha1(stash))
 236                 return;
 237
 238         reset_hard(head, 1);
 239
 240         args[2] = sha1_to_hex(stash);
 241
 242         /*
 243          * It is OK to ignore error here, for example when there was
 244          * nothing to restore.
 245          */
 246         run_command_v_opt(args, RUN_GIT_CMD);
 247
 248         strbuf_release(&sb);
 249         refresh_cache(REFRESH_QUIET);
 250 }
 251
 252 /* This is called when no merge was necessary. */
 253 static void finish_up_to_date(const char *msg)
 254 {
 255         if (verbosity >= 0)
 256                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 257         drop_save();
 258 }
 259
 260 static void squash_message(void)
 261 {
 262         struct rev_info rev;
 263         struct commit *commit;
 264         struct strbuf out = STRBUF_INIT;
 265         struct commit_list *j;
 266         int fd;
 267
 268         printf("Squash commit -- not updating HEAD\n");
 269         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 270         if (fd < 0)
 271                 die("Could not write to %s", git_path("SQUASH_MSG"));
 272
 273         init_revisions(&rev, NULL);
 274         rev.ignore_merges = 1;
 275         rev.commit_format = CMIT_FMT_MEDIUM;
 276
 277         commit = lookup_commit(head);
 278         commit->object.flags |= UNINTERESTING;
 279         add_pending_object(&rev, &commit->object, NULL);
 280
 281         for (j = remoteheads; j; j = j->next)
 282                 add_pending_object(&rev, &j->item->object, NULL);
 283
 284         setup_revisions(0, NULL, &rev, NULL);
 285         if (prepare_revision_walk(&rev))
 286                 die("revision walk setup failed");
 287
 288         strbuf_addstr(&out, "Squashed commit of the following:\n");
 289         while ((commit = get_revision(&rev)) != NULL) {
 290                 strbuf_addch(&out, '\n');
 291                 strbuf_addf(&out, "commit %s\n",
 292                         sha1_to_hex(commit->object.sha1));
 293                 pretty_print_commit(rev.commit_format, commit, &out, rev.abbrev,
 294                         NULL, NULL, rev.date_mode, 0);
 295         }
 296         write(fd, out.buf, out.len);
 297         close(fd);
 298         strbuf_release(&out);
 299 }
 300
 301 static int run_hook(const char *name)
 302 {
 303         struct child_process hook;
 304         const char *argv[3], *env[2];
 305         char index[PATH_MAX];
 306
 307         argv[0] = git_path("hooks/%s", name);
 308         if (access(argv[0], X_OK) < 0)
 309                 return 0;
 310
 311         snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", get_index_file());
 312         env[0] = index;
 313         env[1] = NULL;
 314
 315         if (squash)
 316                 argv[1] = "1";
 317         else
 318                 argv[1] = "0";
 319         argv[2] = NULL;
 320
 321         memset(&hook, 0, sizeof(hook));
 322         hook.argv = argv;
 323         hook.no_stdin = 1;
 324         hook.stdout_to_stderr = 1;
 325         hook.env = env;
 326
 327         return run_command(&hook);
 328 }
 329
 330 static void finish(const unsigned char *new_head, const char *msg)
 331 {
 332         struct strbuf reflog_message = STRBUF_INIT;
 333
 334         if (!msg)
 335                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 336         else {
 337                 if (verbosity >= 0)
 338                         printf("%s\n", msg);
 339                 strbuf_addf(&reflog_message, "%s: %s",
 340                         getenv("GIT_REFLOG_ACTION"), msg);
 341         }
 342         if (squash) {
 343                 squash_message();
 344         } else {
 345                 if (verbosity >= 0 && !merge_msg.len)
 346                         printf("No merge message -- not updating HEAD\n");
 347                 else {
 348                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 349                         update_ref(reflog_message.buf, "HEAD",
 350                                 new_head, head, 0,
 351                                 DIE_ON_ERR);
 352                         /*
 353                          * We ignore errors in 'gc --auto', since the
 354                          * user should see them.
 355                          */
 356                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 357                 }
 358         }
 359         if (new_head && show_diffstat) {
 360                 struct diff_options opts;
 361                 diff_setup(&opts);
 362                 opts.output_format |=
 363                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 364                 opts.detect_rename = DIFF_DETECT_RENAME;
 365                 if (diff_use_color_default > 0)
 366                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 367                 if (diff_setup_done(&opts) < 0)
 368                         die("diff_setup_done failed");
 369                 diff_tree_sha1(head, new_head, "", &opts);
 370                 diffcore_std(&opts);
 371                 diff_flush(&opts);
 372         }
 373
 374         /* Run a post-merge hook */
 375         run_hook("post-merge");
 376
 377         strbuf_release(&reflog_message);
 378 }
 379
 380 /* Get the name for the merge commit's message. */
 381 static void merge_name(const char *remote, struct strbuf *msg)
 382 {
 383         struct object *remote_head;
 384         unsigned char branch_head[20], buf_sha[20];
 385         struct strbuf buf = STRBUF_INIT;
 386         const char *ptr;
 387         int len, early;
 388
 389         memset(branch_head, 0, sizeof(branch_head));
 390         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 391         if (!remote_head)
 392                 die("'%s' does not point to a commit", remote);
 393
 394         strbuf_addstr(&buf, "refs/heads/");
 395         strbuf_addstr(&buf, remote);
 396         resolve_ref(buf.buf, branch_head, 0, 0);
 397
 398         if (!hashcmp(remote_head->sha1, branch_head)) {
 399                 strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 400                         sha1_to_hex(branch_head), remote);
 401                 return;
 402         }
 403
 404         /* See if remote matches <name>^^^.. or <name>~<number> */
 405         for (len = 0, ptr = remote + strlen(remote);
 406              remote < ptr && ptr[-1] == '^';
 407              ptr--)
 408                 len++;
 409         if (len)
 410                 early = 1;
 411         else {
 412                 early = 0;
 413                 ptr = strrchr(remote, '~');
 414                 if (ptr) {
 415                         int seen_nonzero = 0;
 416
 417                         len++; /* count ~ */
 418                         while (*++ptr && isdigit(*ptr)) {
 419                                 seen_nonzero |= (*ptr != '0');
 420                                 len++;
 421                         }
 422                         if (*ptr)
 423                                 len = 0; /* not ...~<number> */
 424                         else if (seen_nonzero)
 425                                 early = 1;
 426                         else if (len == 1)
 427                                 early = 1; /* "name~" is "name~1"! */
 428                 }
 429         }
 430         if (len) {
 431                 struct strbuf truname = STRBUF_INIT;
 432                 strbuf_addstr(&truname, "refs/heads/");
 433                 strbuf_addstr(&truname, remote);
 434                 strbuf_setlen(&truname, truname.len - len);
 435                 if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
 436                         strbuf_addf(msg,
 437                                     "%s\t\tbranch '%s'%s of .\n",
 438                                     sha1_to_hex(remote_head->sha1),
 439                                     truname.buf + 11,
 440                                     (early ? " (early part)" : ""));
 441                         return;
 442                 }
 443         }
 444
 445         if (!strcmp(remote, "FETCH_HEAD") &&
 446                         !access(git_path("FETCH_HEAD"), R_OK)) {
 447                 FILE *fp;
 448                 struct strbuf line = STRBUF_INIT;
 449                 char *ptr;
 450
 451                 fp = fopen(git_path("FETCH_HEAD"), "r");
 452                 if (!fp)
 453                         die("could not open %s for reading: %s",
 454                                 git_path("FETCH_HEAD"), strerror(errno));
 455                 strbuf_getline(&line, fp, '\n');
 456                 fclose(fp);
 457                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 458                 if (ptr)
 459                         strbuf_remove(&line, ptr-line.buf+1, 13);
 460                 strbuf_addbuf(msg, &line);
 461                 strbuf_release(&line);
 462                 return;
 463         }
 464         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 465                 sha1_to_hex(remote_head->sha1), remote);
 466 }
 467
 468 static int git_merge_config(const char *k, const char *v, void *cb)
 469 {
 470         if (branch && !prefixcmp(k, "branch.") &&
 471                 !prefixcmp(k + 7, branch) &&
 472                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 473                 const char **argv;
 474                 int argc;
 475                 char *buf;
 476
 477                 buf = xstrdup(v);
 478                 argc = split_cmdline(buf, &argv);
 479                 if (argc < 0)
 480                         die("Bad branch.%s.mergeoptions string", branch);
 481                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 482                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 483                 argc++;
 484                 parse_options(argc, argv, builtin_merge_options,
 485                               builtin_merge_usage, 0);
 486                 free(buf);
 487         }
 488
 489         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 490                 show_diffstat = git_config_bool(k, v);
 491         else if (!strcmp(k, "pull.twohead"))
 492                 return git_config_string(&pull_twohead, k, v);
 493         else if (!strcmp(k, "pull.octopus"))
 494                 return git_config_string(&pull_octopus, k, v);
 495         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 496                 option_log = git_config_bool(k, v);
 497         return git_diff_ui_config(k, v, cb);
 498 }
 499
 500 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 501                              unsigned char *one)
 502 {
 503         int i, nr_trees = 0;
 504         struct tree *trees[MAX_UNPACK_TREES];
 505         struct tree_desc t[MAX_UNPACK_TREES];
 506         struct unpack_trees_options opts;
 507
 508         memset(&opts, 0, sizeof(opts));
 509         opts.head_idx = 2;
 510         opts.src_index = &the_index;
 511         opts.dst_index = &the_index;
 512         opts.update = 1;
 513         opts.verbose_update = 1;
 514         opts.trivial_merges_only = 1;
 515         opts.merge = 1;
 516         trees[nr_trees] = parse_tree_indirect(common);
 517         if (!trees[nr_trees++])
 518                 return -1;
 519         trees[nr_trees] = parse_tree_indirect(head);
 520         if (!trees[nr_trees++])
 521                 return -1;
 522         trees[nr_trees] = parse_tree_indirect(one);
 523         if (!trees[nr_trees++])
 524                 return -1;
 525         opts.fn = threeway_merge;
 526         cache_tree_free(&active_cache_tree);
 527         for (i = 0; i < nr_trees; i++) {
 528                 parse_tree(trees[i]);
 529                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 530         }
 531         if (unpack_trees(nr_trees, t, &opts))
 532                 return -1;
 533         return 0;
 534 }
 535
 536 static void write_tree_trivial(unsigned char *sha1)
 537 {
 538         if (write_cache_as_tree(sha1, 0, NULL))
 539                 die("git write-tree failed to write a tree");
 540 }
 541
 542 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 543                               const char *head_arg)
 544 {
 545         const char **args;
 546         int i = 0, ret;
 547         struct commit_list *j;
 548         struct strbuf buf = STRBUF_INIT;
 549         int index_fd;
 550         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 551
 552         index_fd = hold_locked_index(lock, 1);
 553         refresh_cache(REFRESH_QUIET);
 554         if (active_cache_changed &&
 555                         (write_cache(index_fd, active_cache, active_nr) ||
 556                          commit_locked_index(lock)))
 557                 return error("Unable to write index.");
 558         rollback_lock_file(lock);
 559
 560         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 561                 int clean;
 562                 struct commit *result;
 563                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 564                 int index_fd;
 565                 struct commit_list *reversed = NULL;
 566                 struct merge_options o;
 567
 568                 if (remoteheads->next) {
 569                         error("Not handling anything other than two heads merge.");
 570                         return 2;
 571                 }
 572
 573                 init_merge_options(&o);
 574                 if (!strcmp(strategy, "subtree"))
 575                         o.subtree_merge = 1;
 576
 577                 o.branch1 = head_arg;
 578                 o.branch2 = remoteheads->item->util;
 579
 580                 for (j = common; j; j = j->next)
 581                         commit_list_insert(j->item, &reversed);
 582
 583                 index_fd = hold_locked_index(lock, 1);
 584                 clean = merge_recursive(&o, lookup_commit(head),
 585                                 remoteheads->item, reversed, &result);
 586                 if (active_cache_changed &&
 587                                 (write_cache(index_fd, active_cache, active_nr) ||
 588                                  commit_locked_index(lock)))
 589                         die ("unable to write %s", get_index_file());
 590                 rollback_lock_file(lock);
 591                 return clean ? 0 : 1;
 592         } else {
 593                 args = xmalloc((4 + commit_list_count(common) +
 594                                         commit_list_count(remoteheads)) * sizeof(char *));
 595                 strbuf_addf(&buf, "merge-%s", strategy);
 596                 args[i++] = buf.buf;
 597                 for (j = common; j; j = j->next)
 598                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 599                 args[i++] = "--";
 600                 args[i++] = head_arg;
 601                 for (j = remoteheads; j; j = j->next)
 602                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 603                 args[i] = NULL;
 604                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 605                 strbuf_release(&buf);
 606                 i = 1;
 607                 for (j = common; j; j = j->next)
 608                         free((void *)args[i++]);
 609                 i += 2;
 610                 for (j = remoteheads; j; j = j->next)
 611                         free((void *)args[i++]);
 612                 free(args);
 613                 discard_cache();
 614                 if (read_cache() < 0)
 615                         die("failed to read the cache");
 616                 return -ret;
 617         }
 618 }
 619
 620 static void count_diff_files(struct diff_queue_struct *q,
 621                              struct diff_options *opt, void *data)
 622 {
 623         int *count = data;
 624
 625         (*count) += q->nr;
 626 }
 627
 628 static int count_unmerged_entries(void)
 629 {
 630         const struct index_state *state = &the_index;
 631         int i, ret = 0;
 632
 633         for (i = 0; i < state->cache_nr; i++)
 634                 if (ce_stage(state->cache[i]))
 635                         ret++;
 636
 637         return ret;
 638 }
 639
 640 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 641 {
 642         struct tree *trees[MAX_UNPACK_TREES];
 643         struct unpack_trees_options opts;
 644         struct tree_desc t[MAX_UNPACK_TREES];
 645         int i, fd, nr_trees = 0;
 646         struct dir_struct dir;
 647         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 648
 649         refresh_cache(REFRESH_QUIET);
 650
 651         fd = hold_locked_index(lock_file, 1);
 652
 653         memset(&trees, 0, sizeof(trees));
 654         memset(&opts, 0, sizeof(opts));
 655         memset(&t, 0, sizeof(t));
 656         memset(&dir, 0, sizeof(dir));
 657         dir.show_ignored = 1;
 658         dir.exclude_per_dir = ".gitignore";
 659         opts.dir = &dir;
 660
 661         opts.head_idx = 1;
 662         opts.src_index = &the_index;
 663         opts.dst_index = &the_index;
 664         opts.update = 1;
 665         opts.verbose_update = 1;
 666         opts.merge = 1;
 667         opts.fn = twoway_merge;
 668
 669         trees[nr_trees] = parse_tree_indirect(head);
 670         if (!trees[nr_trees++])
 671                 return -1;
 672         trees[nr_trees] = parse_tree_indirect(remote);
 673         if (!trees[nr_trees++])
 674                 return -1;
 675         for (i = 0; i < nr_trees; i++) {
 676                 parse_tree(trees[i]);
 677                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 678         }
 679         if (unpack_trees(nr_trees, t, &opts))
 680                 return -1;
 681         if (write_cache(fd, active_cache, active_nr) ||
 682                 commit_locked_index(lock_file))
 683                 die("unable to write new index file");
 684         return 0;
 685 }
 686
 687 static void split_merge_strategies(const char *string, struct strategy **list,
 688                                    int *nr, int *alloc)
 689 {
 690         char *p, *q, *buf;
 691
 692         if (!string)
 693                 return;
 694
 695         buf = xstrdup(string);
 696         q = buf;
 697         for (;;) {
 698                 p = strchr(q, ' ');
 699                 if (!p) {
 700                         ALLOC_GROW(*list, *nr + 1, *alloc);
 701                         (*list)[(*nr)++].name = xstrdup(q);
 702                         free(buf);
 703                         return;
 704                 } else {
 705                         *p = '\0';
 706                         ALLOC_GROW(*list, *nr + 1, *alloc);
 707                         (*list)[(*nr)++].name = xstrdup(q);
 708                         q = ++p;
 709                 }
 710         }
 711 }
 712
 713 static void add_strategies(const char *string, unsigned attr)
 714 {
 715         struct strategy *list = NULL;
 716         int list_alloc = 0, list_nr = 0, i;
 717
 718         memset(&list, 0, sizeof(list));
 719         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 720         if (list) {
 721                 for (i = 0; i < list_nr; i++)
 722                         append_strategy(get_strategy(list[i].name));
 723                 return;
 724         }
 725         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 726                 if (all_strategy[i].attr & attr)
 727                         append_strategy(&all_strategy[i]);
 728
 729 }
 730
 731 static int merge_trivial(void)
 732 {
 733         unsigned char result_tree[20], result_commit[20];
 734         struct commit_list *parent = xmalloc(sizeof(*parent));
 735
 736         write_tree_trivial(result_tree);
 737         printf("Wonderful.\n");
 738         parent->item = lookup_commit(head);
 739         parent->next = xmalloc(sizeof(*parent->next));
 740         parent->next->item = remoteheads->item;
 741         parent->next->next = NULL;
 742         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 743         finish(result_commit, "In-index merge");
 744         drop_save();
 745         return 0;
 746 }
 747
 748 static int finish_automerge(struct commit_list *common,
 749                             unsigned char *result_tree,
 750                             const char *wt_strategy)
 751 {
 752         struct commit_list *parents = NULL, *j;
 753         struct strbuf buf = STRBUF_INIT;
 754         unsigned char result_commit[20];
 755
 756         free_commit_list(common);
 757         if (allow_fast_forward) {
 758                 parents = remoteheads;
 759                 commit_list_insert(lookup_commit(head), &parents);
 760                 parents = reduce_heads(parents);
 761         } else {
 762                 struct commit_list **pptr = &parents;
 763
 764                 pptr = &commit_list_insert(lookup_commit(head),
 765                                 pptr)->next;
 766                 for (j = remoteheads; j; j = j->next)
 767                         pptr = &commit_list_insert(j->item, pptr)->next;
 768         }
 769         free_commit_list(remoteheads);
 770         strbuf_addch(&merge_msg, '\n');
 771         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 772         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 773         finish(result_commit, buf.buf);
 774         strbuf_release(&buf);
 775         drop_save();
 776         return 0;
 777 }
 778
 779 static int suggest_conflicts(void)
 780 {
 781         FILE *fp;
 782         int pos;
 783
 784         fp = fopen(git_path("MERGE_MSG"), "a");
 785         if (!fp)
 786                 die("Could open %s for writing", git_path("MERGE_MSG"));
 787         fprintf(fp, "\nConflicts:\n");
 788         for (pos = 0; pos < active_nr; pos++) {
 789                 struct cache_entry *ce = active_cache[pos];
 790
 791                 if (ce_stage(ce)) {
 792                         fprintf(fp, "\t%s\n", ce->name);
 793                         while (pos + 1 < active_nr &&
 794                                         !strcmp(ce->name,
 795                                                 active_cache[pos + 1]->name))
 796                                 pos++;
 797                 }
 798         }
 799         fclose(fp);
 800         rerere();
 801         printf("Automatic merge failed; "
 802                         "fix conflicts and then commit the result.\n");
 803         return 1;
 804 }
 805
 806 static struct commit *is_old_style_invocation(int argc, const char **argv)
 807 {
 808         struct commit *second_token = NULL;
 809         if (argc > 1) {
 810                 unsigned char second_sha1[20];
 811
 812                 if (get_sha1(argv[1], second_sha1))
 813                         return NULL;
 814                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 815                 if (!second_token)
 816                         die("'%s' is not a commit", argv[1]);
 817                 if (hashcmp(second_token->object.sha1, head))
 818                         return NULL;
 819         }
 820         return second_token;
 821 }
 822
 823 static int evaluate_result(void)
 824 {
 825         int cnt = 0;
 826         struct rev_info rev;
 827
 828         /* Check how many files differ. */
 829         init_revisions(&rev, "");
 830         setup_revisions(0, NULL, &rev, NULL);
 831         rev.diffopt.output_format |=
 832                 DIFF_FORMAT_CALLBACK;
 833         rev.diffopt.format_callback = count_diff_files;
 834         rev.diffopt.format_callback_data = &cnt;
 835         run_diff_files(&rev, 0);
 836
 837         /*
 838          * Check how many unmerged entries are
 839          * there.
 840          */
 841         cnt += count_unmerged_entries();
 842
 843         return cnt;
 844 }
 845
 846 int cmd_merge(int argc, const char **argv, const char *prefix)
 847 {
 848         unsigned char result_tree[20];
 849         struct strbuf buf = STRBUF_INIT;
 850         const char *head_arg;
 851         int flag, head_invalid = 0, i;
 852         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 853         struct commit_list *common = NULL;
 854         const char *best_strategy = NULL, *wt_strategy = NULL;
 855         struct commit_list **remotes = &remoteheads;
 856
 857         setup_work_tree();
 858         if (read_cache_unmerged())
 859                 die("You are in the middle of a conflicted merge.");
 860
 861         /*
 862          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 863          * current branch.
 864          */
 865         branch = resolve_ref("HEAD", head, 0, &flag);
 866         if (branch && !prefixcmp(branch, "refs/heads/"))
 867                 branch += 11;
 868         if (is_null_sha1(head))
 869                 head_invalid = 1;
 870
 871         git_config(git_merge_config, NULL);
 872
 873         /* for color.ui */
 874         if (diff_use_color_default == -1)
 875                 diff_use_color_default = git_use_color_default;
 876
 877         argc = parse_options(argc, argv, builtin_merge_options,
 878                         builtin_merge_usage, 0);
 879         if (verbosity < 0)
 880                 show_diffstat = 0;
 881
 882         if (squash) {
 883                 if (!allow_fast_forward)
 884                         die("You cannot combine --squash with --no-ff.");
 885                 option_commit = 0;
 886         }
 887
 888         if (!argc)
 889                 usage_with_options(builtin_merge_usage,
 890                         builtin_merge_options);
 891
 892         /*
 893          * This could be traditional "merge <msg> HEAD <commit>..."  and
 894          * the way we can tell it is to see if the second token is HEAD,
 895          * but some people might have misused the interface and used a
 896          * committish that is the same as HEAD there instead.
 897          * Traditional format never would have "-m" so it is an
 898          * additional safety measure to check for it.
 899          */
 900
 901         if (!have_message && is_old_style_invocation(argc, argv)) {
 902                 strbuf_addstr(&merge_msg, argv[0]);
 903                 head_arg = argv[1];
 904                 argv += 2;
 905                 argc -= 2;
 906         } else if (head_invalid) {
 907                 struct object *remote_head;
 908                 /*
 909                  * If the merged head is a valid one there is no reason
 910                  * to forbid "git merge" into a branch yet to be born.
 911                  * We do the same for "git pull".
 912                  */
 913                 if (argc != 1)
 914                         die("Can merge only exactly one commit into "
 915                                 "empty head");
 916                 if (squash)
 917                         die("Squash commit into empty head not supported yet");
 918                 if (!allow_fast_forward)
 919                         die("Non-fast-forward commit does not make sense into "
 920                             "an empty head");
 921                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 922                 if (!remote_head)
 923                         die("%s - not something we can merge", argv[0]);
 924                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 925                                 DIE_ON_ERR);
 926                 reset_hard(remote_head->sha1, 0);
 927                 return 0;
 928         } else {
 929                 struct strbuf msg = STRBUF_INIT;
 930
 931                 /* We are invoked directly as the first-class UI. */
 932                 head_arg = "HEAD";
 933
 934                 /*
 935                  * All the rest are the commits being merged;
 936                  * prepare the standard merge summary message to
 937                  * be appended to the given message.  If remote
 938                  * is invalid we will die later in the common
 939                  * codepath so we discard the error in this
 940                  * loop.
 941                  */
 942                 for (i = 0; i < argc; i++)
 943                         merge_name(argv[i], &msg);
 944                 fmt_merge_msg(option_log, &msg, &merge_msg);
 945                 if (merge_msg.len)
 946                         strbuf_setlen(&merge_msg, merge_msg.len-1);
 947         }
 948
 949         if (head_invalid || !argc)
 950                 usage_with_options(builtin_merge_usage,
 951                         builtin_merge_options);
 952
 953         strbuf_addstr(&buf, "merge");
 954         for (i = 0; i < argc; i++)
 955                 strbuf_addf(&buf, " %s", argv[i]);
 956         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 957         strbuf_reset(&buf);
 958
 959         for (i = 0; i < argc; i++) {
 960                 struct object *o;
 961                 struct commit *commit;
 962
 963                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 964                 if (!o)
 965                         die("%s - not something we can merge", argv[i]);
 966                 commit = lookup_commit(o->sha1);
 967                 commit->util = (void *)argv[i];
 968                 remotes = &commit_list_insert(commit, remotes)->next;
 969
 970                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 971                 setenv(buf.buf, argv[i], 1);
 972                 strbuf_reset(&buf);
 973         }
 974
 975         if (!use_strategies) {
 976                 if (!remoteheads->next)
 977                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 978                 else
 979                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 980         }
 981
 982         for (i = 0; i < use_strategies_nr; i++) {
 983                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 984                         allow_fast_forward = 0;
 985                 if (use_strategies[i]->attr & NO_TRIVIAL)
 986                         allow_trivial = 0;
 987         }
 988
 989         if (!remoteheads->next)
 990                 common = get_merge_bases(lookup_commit(head),
 991                                 remoteheads->item, 1);
 992         else {
 993                 struct commit_list *list = remoteheads;
 994                 commit_list_insert(lookup_commit(head), &list);
 995                 common = get_octopus_merge_bases(list);
 996                 free(list);
 997         }
 998
 999         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1000                 DIE_ON_ERR);
1001
1002         if (!common)
1003                 ; /* No common ancestors found. We need a real merge. */
1004         else if (!remoteheads->next && !common->next &&
1005                         common->item == remoteheads->item) {
1006                 /*
1007                  * If head can reach all the merge then we are up to date.
1008                  * but first the most common case of merging one remote.
1009                  */
1010                 finish_up_to_date("Already up-to-date.");
1011                 return 0;
1012         } else if (allow_fast_forward && !remoteheads->next &&
1013                         !common->next &&
1014                         !hashcmp(common->item->object.sha1, head)) {
1015                 /* Again the most common case of merging one remote. */
1016                 struct strbuf msg = STRBUF_INIT;
1017                 struct object *o;
1018                 char hex[41];
1019
1020                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1021
1022                 if (verbosity >= 0)
1023                         printf("Updating %s..%s\n",
1024                                 hex,
1025                                 find_unique_abbrev(remoteheads->item->object.sha1,
1026                                 DEFAULT_ABBREV));
1027                 strbuf_addstr(&msg, "Fast forward");
1028                 if (have_message)
1029                         strbuf_addstr(&msg,
1030                                 " (no commit created; -m option ignored)");
1031                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1032                         0, NULL, OBJ_COMMIT);
1033                 if (!o)
1034                         return 1;
1035
1036                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1037                         return 1;
1038
1039                 finish(o->sha1, msg.buf);
1040                 drop_save();
1041                 return 0;
1042         } else if (!remoteheads->next && common->next)
1043                 ;
1044                 /*
1045                  * We are not doing octopus and not fast forward.  Need
1046                  * a real merge.
1047                  */
1048         else if (!remoteheads->next && !common->next && option_commit) {
1049                 /*
1050                  * We are not doing octopus, not fast forward, and have
1051                  * only one common.
1052                  */
1053                 refresh_cache(REFRESH_QUIET);
1054                 if (allow_trivial) {
1055                         /* See if it is really trivial. */
1056                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1057                         printf("Trying really trivial in-index merge...\n");
1058                         if (!read_tree_trivial(common->item->object.sha1,
1059                                         head, remoteheads->item->object.sha1))
1060                                 return merge_trivial();
1061                         printf("Nope.\n");
1062                 }
1063         } else {
1064                 /*
1065                  * An octopus.  If we can reach all the remote we are up
1066                  * to date.
1067                  */
1068                 int up_to_date = 1;
1069                 struct commit_list *j;
1070
1071                 for (j = remoteheads; j; j = j->next) {
1072                         struct commit_list *common_one;
1073
1074                         /*
1075                          * Here we *have* to calculate the individual
1076                          * merge_bases again, otherwise "git merge HEAD^
1077                          * HEAD^^" would be missed.
1078                          */
1079                         common_one = get_merge_bases(lookup_commit(head),
1080                                 j->item, 1);
1081                         if (hashcmp(common_one->item->object.sha1,
1082                                 j->item->object.sha1)) {
1083                                 up_to_date = 0;
1084                                 break;
1085                         }
1086                 }
1087                 if (up_to_date) {
1088                         finish_up_to_date("Already up-to-date. Yeeah!");
1089                         return 0;
1090                 }
1091         }
1092
1093         /* We are going to make a new commit. */
1094         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1095
1096         /*
1097          * At this point, we need a real merge.  No matter what strategy
1098          * we use, it would operate on the index, possibly affecting the
1099          * working tree, and when resolved cleanly, have the desired
1100          * tree in the index -- this means that the index must be in
1101          * sync with the head commit.  The strategies are responsible
1102          * to ensure this.
1103          */
1104         if (use_strategies_nr != 1) {
1105                 /*
1106                  * Stash away the local changes so that we can try more
1107                  * than one.
1108                  */
1109                 save_state();
1110         } else {
1111                 memcpy(stash, null_sha1, 20);
1112         }
1113
1114         for (i = 0; i < use_strategies_nr; i++) {
1115                 int ret;
1116                 if (i) {
1117                         printf("Rewinding the tree to pristine...\n");
1118                         restore_state();
1119                 }
1120                 if (use_strategies_nr != 1)
1121                         printf("Trying merge strategy %s...\n",
1122                                 use_strategies[i]->name);
1123                 /*
1124                  * Remember which strategy left the state in the working
1125                  * tree.
1126                  */
1127                 wt_strategy = use_strategies[i]->name;
1128
1129                 ret = try_merge_strategy(use_strategies[i]->name,
1130                         common, head_arg);
1131                 if (!option_commit && !ret) {
1132                         merge_was_ok = 1;
1133                         /*
1134                          * This is necessary here just to avoid writing
1135                          * the tree, but later we will *not* exit with
1136                          * status code 1 because merge_was_ok is set.
1137                          */
1138                         ret = 1;
1139                 }
1140
1141                 if (ret) {
1142                         /*
1143                          * The backend exits with 1 when conflicts are
1144                          * left to be resolved, with 2 when it does not
1145                          * handle the given merge at all.
1146                          */
1147                         if (ret == 1) {
1148                                 int cnt = evaluate_result();
1149
1150                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1151                                         best_strategy = use_strategies[i]->name;
1152                                         best_cnt = cnt;
1153                                 }
1154                         }
1155                         if (merge_was_ok)
1156                                 break;
1157                         else
1158                                 continue;
1159                 }
1160
1161                 /* Automerge succeeded. */
1162                 write_tree_trivial(result_tree);
1163                 automerge_was_ok = 1;
1164                 break;
1165         }
1166
1167         /*
1168          * If we have a resulting tree, that means the strategy module
1169          * auto resolved the merge cleanly.
1170          */
1171         if (automerge_was_ok)
1172                 return finish_automerge(common, result_tree, wt_strategy);
1173
1174         /*
1175          * Pick the result from the best strategy and have the user fix
1176          * it up.
1177          */
1178         if (!best_strategy) {
1179                 restore_state();
1180                 if (use_strategies_nr > 1)
1181                         fprintf(stderr,
1182                                 "No merge strategy handled the merge.\n");
1183                 else
1184                         fprintf(stderr, "Merge with strategy %s failed.\n",
1185                                 use_strategies[0]->name);
1186                 return 2;
1187         } else if (best_strategy == wt_strategy)
1188                 ; /* We already have its result in the working tree. */
1189         else {
1190                 printf("Rewinding the tree to pristine...\n");
1191                 restore_state();
1192                 printf("Using the %s to prepare resolving by hand.\n",
1193                         best_strategy);
1194                 try_merge_strategy(best_strategy, common, head_arg);
1195         }
1196
1197         if (squash)
1198                 finish(NULL, NULL);
1199         else {
1200                 int fd;
1201                 struct commit_list *j;
1202
1203                 for (j = remoteheads; j; j = j->next)
1204                         strbuf_addf(&buf, "%s\n",
1205                                 sha1_to_hex(j->item->object.sha1));
1206                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1207                 if (fd < 0)
1208                         die("Could open %s for writing",
1209                                 git_path("MERGE_HEAD"));
1210                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1211                         die("Could not write to %s", git_path("MERGE_HEAD"));
1212                 close(fd);
1213                 strbuf_addch(&merge_msg, '\n');
1214                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1215                 if (fd < 0)
1216                         die("Could open %s for writing", git_path("MERGE_MSG"));
1217                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1218                         merge_msg.len)
1219                         die("Could not write to %s", git_path("MERGE_MSG"));
1220                 close(fd);
1221                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1222                 if (fd < 0)
1223                         die("Could open %s for writing", git_path("MERGE_MODE"));
1224                 strbuf_reset(&buf);
1225                 if (!allow_fast_forward)
1226                         strbuf_addf(&buf, "no-ff");
1227                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1228                         die("Could not write to %s", git_path("MERGE_MODE"));
1229                 close(fd);
1230         }
1231
1232         if (merge_was_ok) {
1233                 fprintf(stderr, "Automatic merge went well; "
1234                         "stopped before committing as requested\n");
1235                 return 0;
1236         } else
1237                 return suggest_conflicts();
1238 }