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