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