builtin-merge.c

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