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 fast_forward_only;
  47 static int allow_trivial = 1, have_message;
  48 static struct strbuf merge_msg;
  49 static struct commit_list *remoteheads;
  50 static unsigned char head[20], stash[20];
  51 static struct strategy **use_strategies;
  52 static size_t use_strategies_nr, use_strategies_alloc;
  53 static const char *branch;
  54 static int verbosity;
  55 static int allow_rerere_auto;
  56
  57 static struct strategy all_strategy[] = {
  58         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  59         { "octopus",    DEFAULT_OCTOPUS },
  60         { "resolve",    0 },
  61         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  62         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  63 };
  64
  65 static const char *pull_twohead, *pull_octopus;
  66
  67 static int option_parse_message(const struct option *opt,
  68                                 const char *arg, int unset)
  69 {
  70         struct strbuf *buf = opt->value;
  71
  72         if (unset)
  73                 strbuf_setlen(buf, 0);
  74         else if (arg) {
  75                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  76                 have_message = 1;
  77         } else
  78                 return error("switch `m' requires a value");
  79         return 0;
  80 }
  81
  82 static struct strategy *get_strategy(const char *name)
  83 {
  84         int i;
  85         struct strategy *ret;
  86         static struct cmdnames main_cmds, other_cmds;
  87         static int loaded;
  88
  89         if (!name)
  90                 return NULL;
  91
  92         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  93                 if (!strcmp(name, all_strategy[i].name))
  94                         return &all_strategy[i];
  95
  96         if (!loaded) {
  97                 struct cmdnames not_strategies;
  98                 loaded = 1;
  99
 100                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 101                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 102                 for (i = 0; i < main_cmds.cnt; i++) {
 103                         int j, found = 0;
 104                         struct cmdname *ent = main_cmds.names[i];
 105                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 106                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 107                                                 && !all_strategy[j].name[ent->len])
 108                                         found = 1;
 109                         if (!found)
 110                                 add_cmdname(&not_strategies, ent->name, ent->len);
 111                 }
 112                 exclude_cmds(&main_cmds, &not_strategies);
 113         }
 114         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 115                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 116                 fprintf(stderr, "Available strategies are:");
 117                 for (i = 0; i < main_cmds.cnt; i++)
 118                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 119                 fprintf(stderr, ".\n");
 120                 if (other_cmds.cnt) {
 121                         fprintf(stderr, "Available custom strategies are:");
 122                         for (i = 0; i < other_cmds.cnt; i++)
 123                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 124                         fprintf(stderr, ".\n");
 125                 }
 126                 exit(1);
 127         }
 128
 129         ret = xcalloc(1, sizeof(struct strategy));
 130         ret->name = xstrdup(name);
 131         return ret;
 132 }
 133
 134 static void append_strategy(struct strategy *s)
 135 {
 136         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 137         use_strategies[use_strategies_nr++] = s;
 138 }
 139
 140 static int option_parse_strategy(const struct option *opt,
 141                                  const char *name, int unset)
 142 {
 143         if (unset)
 144                 return 0;
 145
 146         append_strategy(get_strategy(name));
 147         return 0;
 148 }
 149
 150 static int option_parse_n(const struct option *opt,
 151                           const char *arg, int unset)
 152 {
 153         show_diffstat = unset;
 154         return 0;
 155 }
 156
 157 static struct option builtin_merge_options[] = {
 158         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 159                 "do not show a diffstat at the end of the merge",
 160                 PARSE_OPT_NOARG, option_parse_n },
 161         OPT_BOOLEAN(0, "stat", &show_diffstat,
 162                 "show a diffstat at the end of the merge"),
 163         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 164         OPT_BOOLEAN(0, "log", &option_log,
 165                 "add list of one-line log to merge commit message"),
 166         OPT_BOOLEAN(0, "squash", &squash,
 167                 "create a single commit instead of doing a merge"),
 168         OPT_BOOLEAN(0, "commit", &option_commit,
 169                 "perform a commit if the merge succeeds (default)"),
 170         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 171                 "allow fast-forward (default)"),
 172         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 173                 "abort if fast-forward is not possible"),
 174         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 175         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 176                 "merge strategy to use", option_parse_strategy),
 177         OPT_CALLBACK('m', "message", &merge_msg, "message",
 178                 "message to be used for the merge commit (if any)",
 179                 option_parse_message),
 180         OPT__VERBOSITY(&verbosity),
 181         OPT_END()
 182 };
 183
 184 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 185 static void drop_save(void)
 186 {
 187         unlink(git_path("MERGE_HEAD"));
 188         unlink(git_path("MERGE_MSG"));
 189         unlink(git_path("MERGE_MODE"));
 190 }
 191
 192 static void save_state(void)
 193 {
 194         int len;
 195         struct child_process cp;
 196         struct strbuf buffer = STRBUF_INIT;
 197         const char *argv[] = {"stash", "create", NULL};
 198
 199         memset(&cp, 0, sizeof(cp));
 200         cp.argv = argv;
 201         cp.out = -1;
 202         cp.git_cmd = 1;
 203
 204         if (start_command(&cp))
 205                 die("could not run stash.");
 206         len = strbuf_read(&buffer, cp.out, 1024);
 207         close(cp.out);
 208
 209         if (finish_command(&cp) || len < 0)
 210                 die("stash failed");
 211         else if (!len)
 212                 return;
 213         strbuf_setlen(&buffer, buffer.len-1);
 214         if (get_sha1(buffer.buf, stash))
 215                 die("not a valid object: %s", buffer.buf);
 216 }
 217
 218 static void reset_hard(unsigned const char *sha1, int verbose)
 219 {
 220         int i = 0;
 221         const char *args[6];
 222
 223         args[i++] = "read-tree";
 224         if (verbose)
 225                 args[i++] = "-v";
 226         args[i++] = "--reset";
 227         args[i++] = "-u";
 228         args[i++] = sha1_to_hex(sha1);
 229         args[i] = NULL;
 230
 231         if (run_command_v_opt(args, RUN_GIT_CMD))
 232                 die("read-tree failed");
 233 }
 234
 235 static void restore_state(void)
 236 {
 237         struct strbuf sb = STRBUF_INIT;
 238         const char *args[] = { "stash", "apply", NULL, NULL };
 239
 240         if (is_null_sha1(stash))
 241                 return;
 242
 243         reset_hard(head, 1);
 244
 245         args[2] = sha1_to_hex(stash);
 246
 247         /*
 248          * It is OK to ignore error here, for example when there was
 249          * nothing to restore.
 250          */
 251         run_command_v_opt(args, RUN_GIT_CMD);
 252
 253         strbuf_release(&sb);
 254         refresh_cache(REFRESH_QUIET);
 255 }
 256
 257 /* This is called when no merge was necessary. */
 258 static void finish_up_to_date(const char *msg)
 259 {
 260         if (verbosity >= 0)
 261                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 262         drop_save();
 263 }
 264
 265 static void squash_message(void)
 266 {
 267         struct rev_info rev;
 268         struct commit *commit;
 269         struct strbuf out = STRBUF_INIT;
 270         struct commit_list *j;
 271         int fd;
 272         struct pretty_print_context ctx = {0};
 273
 274         printf("Squash commit -- not updating HEAD\n");
 275         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 276         if (fd < 0)
 277                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 278
 279         init_revisions(&rev, NULL);
 280         rev.ignore_merges = 1;
 281         rev.commit_format = CMIT_FMT_MEDIUM;
 282
 283         commit = lookup_commit(head);
 284         commit->object.flags |= UNINTERESTING;
 285         add_pending_object(&rev, &commit->object, NULL);
 286
 287         for (j = remoteheads; j; j = j->next)
 288                 add_pending_object(&rev, &j->item->object, NULL);
 289
 290         setup_revisions(0, NULL, &rev, NULL);
 291         if (prepare_revision_walk(&rev))
 292                 die("revision walk setup failed");
 293
 294         ctx.abbrev = rev.abbrev;
 295         ctx.date_mode = rev.date_mode;
 296
 297         strbuf_addstr(&out, "Squashed commit of the following:\n");
 298         while ((commit = get_revision(&rev)) != NULL) {
 299                 strbuf_addch(&out, '\n');
 300                 strbuf_addf(&out, "commit %s\n",
 301                         sha1_to_hex(commit->object.sha1));
 302                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 303         }
 304         if (write(fd, out.buf, out.len) < 0)
 305                 die_errno("Writing SQUASH_MSG");
 306         if (close(fd))
 307                 die_errno("Finishing SQUASH_MSG");
 308         strbuf_release(&out);
 309 }
 310
 311 static void finish(const unsigned char *new_head, const char *msg)
 312 {
 313         struct strbuf reflog_message = STRBUF_INIT;
 314
 315         if (!msg)
 316                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 317         else {
 318                 if (verbosity >= 0)
 319                         printf("%s\n", msg);
 320                 strbuf_addf(&reflog_message, "%s: %s",
 321                         getenv("GIT_REFLOG_ACTION"), msg);
 322         }
 323         if (squash) {
 324                 squash_message();
 325         } else {
 326                 if (verbosity >= 0 && !merge_msg.len)
 327                         printf("No merge message -- not updating HEAD\n");
 328                 else {
 329                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 330                         update_ref(reflog_message.buf, "HEAD",
 331                                 new_head, head, 0,
 332                                 DIE_ON_ERR);
 333                         /*
 334                          * We ignore errors in 'gc --auto', since the
 335                          * user should see them.
 336                          */
 337                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 338                 }
 339         }
 340         if (new_head && show_diffstat) {
 341                 struct diff_options opts;
 342                 diff_setup(&opts);
 343                 opts.output_format |=
 344                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 345                 opts.detect_rename = DIFF_DETECT_RENAME;
 346                 if (diff_use_color_default > 0)
 347                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 348                 if (diff_setup_done(&opts) < 0)
 349                         die("diff_setup_done failed");
 350                 diff_tree_sha1(head, new_head, "", &opts);
 351                 diffcore_std(&opts);
 352                 diff_flush(&opts);
 353         }
 354
 355         /* Run a post-merge hook */
 356         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 357
 358         strbuf_release(&reflog_message);
 359 }
 360
 361 /* Get the name for the merge commit's message. */
 362 static void merge_name(const char *remote, struct strbuf *msg)
 363 {
 364         struct object *remote_head;
 365         unsigned char branch_head[20], buf_sha[20];
 366         struct strbuf buf = STRBUF_INIT;
 367         struct strbuf bname = STRBUF_INIT;
 368         const char *ptr;
 369         char *found_ref;
 370         int len, early;
 371
 372         strbuf_branchname(&bname, remote);
 373         remote = bname.buf;
 374
 375         memset(branch_head, 0, sizeof(branch_head));
 376         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 377         if (!remote_head)
 378                 die("'%s' does not point to a commit", remote);
 379
 380         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 381                 if (!prefixcmp(found_ref, "refs/heads/")) {
 382                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 383                                     sha1_to_hex(branch_head), remote);
 384                         goto cleanup;
 385                 }
 386                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 387                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 388                                     sha1_to_hex(branch_head), remote);
 389                         goto cleanup;
 390                 }
 391         }
 392
 393         /* See if remote matches <name>^^^.. or <name>~<number> */
 394         for (len = 0, ptr = remote + strlen(remote);
 395              remote < ptr && ptr[-1] == '^';
 396              ptr--)
 397                 len++;
 398         if (len)
 399                 early = 1;
 400         else {
 401                 early = 0;
 402                 ptr = strrchr(remote, '~');
 403                 if (ptr) {
 404                         int seen_nonzero = 0;
 405
 406                         len++; /* count ~ */
 407                         while (*++ptr && isdigit(*ptr)) {
 408                                 seen_nonzero |= (*ptr != '0');
 409                                 len++;
 410                         }
 411                         if (*ptr)
 412                                 len = 0; /* not ...~<number> */
 413                         else if (seen_nonzero)
 414                                 early = 1;
 415                         else if (len == 1)
 416                                 early = 1; /* "name~" is "name~1"! */
 417                 }
 418         }
 419         if (len) {
 420                 struct strbuf truname = STRBUF_INIT;
 421                 strbuf_addstr(&truname, "refs/heads/");
 422                 strbuf_addstr(&truname, remote);
 423                 strbuf_setlen(&truname, truname.len - len);
 424                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 425                         strbuf_addf(msg,
 426                                     "%s\t\tbranch '%s'%s of .\n",
 427                                     sha1_to_hex(remote_head->sha1),
 428                                     truname.buf + 11,
 429                                     (early ? " (early part)" : ""));
 430                         strbuf_release(&truname);
 431                         goto cleanup;
 432                 }
 433         }
 434
 435         if (!strcmp(remote, "FETCH_HEAD") &&
 436                         !access(git_path("FETCH_HEAD"), R_OK)) {
 437                 FILE *fp;
 438                 struct strbuf line = STRBUF_INIT;
 439                 char *ptr;
 440
 441                 fp = fopen(git_path("FETCH_HEAD"), "r");
 442                 if (!fp)
 443                         die_errno("could not open '%s' for reading",
 444                                   git_path("FETCH_HEAD"));
 445                 strbuf_getline(&line, fp, '\n');
 446                 fclose(fp);
 447                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 448                 if (ptr)
 449                         strbuf_remove(&line, ptr-line.buf+1, 13);
 450                 strbuf_addbuf(msg, &line);
 451                 strbuf_release(&line);
 452                 goto cleanup;
 453         }
 454         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 455                 sha1_to_hex(remote_head->sha1), remote);
 456 cleanup:
 457         strbuf_release(&buf);
 458         strbuf_release(&bname);
 459 }
 460
 461 static int git_merge_config(const char *k, const char *v, void *cb)
 462 {
 463         if (branch && !prefixcmp(k, "branch.") &&
 464                 !prefixcmp(k + 7, branch) &&
 465                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 466                 const char **argv;
 467                 int argc;
 468                 char *buf;
 469
 470                 buf = xstrdup(v);
 471                 argc = split_cmdline(buf, &argv);
 472                 if (argc < 0)
 473                         die("Bad branch.%s.mergeoptions string", branch);
 474                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 475                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 476                 argc++;
 477                 parse_options(argc, argv, NULL, builtin_merge_options,
 478                               builtin_merge_usage, 0);
 479                 free(buf);
 480         }
 481
 482         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 483                 show_diffstat = git_config_bool(k, v);
 484         else if (!strcmp(k, "pull.twohead"))
 485                 return git_config_string(&pull_twohead, k, v);
 486         else if (!strcmp(k, "pull.octopus"))
 487                 return git_config_string(&pull_octopus, k, v);
 488         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 489                 option_log = git_config_bool(k, v);
 490         return git_diff_ui_config(k, v, cb);
 491 }
 492
 493 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 494                              unsigned char *one)
 495 {
 496         int i, nr_trees = 0;
 497         struct tree *trees[MAX_UNPACK_TREES];
 498         struct tree_desc t[MAX_UNPACK_TREES];
 499         struct unpack_trees_options opts;
 500
 501         memset(&opts, 0, sizeof(opts));
 502         opts.head_idx = 2;
 503         opts.src_index = &the_index;
 504         opts.dst_index = &the_index;
 505         opts.update = 1;
 506         opts.verbose_update = 1;
 507         opts.trivial_merges_only = 1;
 508         opts.merge = 1;
 509         trees[nr_trees] = parse_tree_indirect(common);
 510         if (!trees[nr_trees++])
 511                 return -1;
 512         trees[nr_trees] = parse_tree_indirect(head);
 513         if (!trees[nr_trees++])
 514                 return -1;
 515         trees[nr_trees] = parse_tree_indirect(one);
 516         if (!trees[nr_trees++])
 517                 return -1;
 518         opts.fn = threeway_merge;
 519         cache_tree_free(&active_cache_tree);
 520         for (i = 0; i < nr_trees; i++) {
 521                 parse_tree(trees[i]);
 522                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 523         }
 524         if (unpack_trees(nr_trees, t, &opts))
 525                 return -1;
 526         return 0;
 527 }
 528
 529 static void write_tree_trivial(unsigned char *sha1)
 530 {
 531         if (write_cache_as_tree(sha1, 0, NULL))
 532                 die("git write-tree failed to write a tree");
 533 }
 534
 535 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 536                               const char *head_arg)
 537 {
 538         const char **args;
 539         int i = 0, ret;
 540         struct commit_list *j;
 541         struct strbuf buf = STRBUF_INIT;
 542         int index_fd;
 543         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 544
 545         index_fd = hold_locked_index(lock, 1);
 546         refresh_cache(REFRESH_QUIET);
 547         if (active_cache_changed &&
 548                         (write_cache(index_fd, active_cache, active_nr) ||
 549                          commit_locked_index(lock)))
 550                 return error("Unable to write index.");
 551         rollback_lock_file(lock);
 552
 553         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 554                 int clean;
 555                 struct commit *result;
 556                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 557                 int index_fd;
 558                 struct commit_list *reversed = NULL;
 559                 struct merge_options o;
 560
 561                 if (remoteheads->next) {
 562                         error("Not handling anything other than two heads merge.");
 563                         return 2;
 564                 }
 565
 566                 init_merge_options(&o);
 567                 if (!strcmp(strategy, "subtree"))
 568                         o.subtree_merge = 1;
 569
 570                 o.branch1 = head_arg;
 571                 o.branch2 = remoteheads->item->util;
 572
 573                 for (j = common; j; j = j->next)
 574                         commit_list_insert(j->item, &reversed);
 575
 576                 index_fd = hold_locked_index(lock, 1);
 577                 clean = merge_recursive(&o, lookup_commit(head),
 578                                 remoteheads->item, reversed, &result);
 579                 if (active_cache_changed &&
 580                                 (write_cache(index_fd, active_cache, active_nr) ||
 581                                  commit_locked_index(lock)))
 582                         die ("unable to write %s", get_index_file());
 583                 rollback_lock_file(lock);
 584                 return clean ? 0 : 1;
 585         } else {
 586                 args = xmalloc((4 + commit_list_count(common) +
 587                                         commit_list_count(remoteheads)) * sizeof(char *));
 588                 strbuf_addf(&buf, "merge-%s", strategy);
 589                 args[i++] = buf.buf;
 590                 for (j = common; j; j = j->next)
 591                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 592                 args[i++] = "--";
 593                 args[i++] = head_arg;
 594                 for (j = remoteheads; j; j = j->next)
 595                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 596                 args[i] = NULL;
 597                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 598                 strbuf_release(&buf);
 599                 i = 1;
 600                 for (j = common; j; j = j->next)
 601                         free((void *)args[i++]);
 602                 i += 2;
 603                 for (j = remoteheads; j; j = j->next)
 604                         free((void *)args[i++]);
 605                 free(args);
 606                 discard_cache();
 607                 if (read_cache() < 0)
 608                         die("failed to read the cache");
 609                 return ret;
 610         }
 611 }
 612
 613 static void count_diff_files(struct diff_queue_struct *q,
 614                              struct diff_options *opt, void *data)
 615 {
 616         int *count = data;
 617
 618         (*count) += q->nr;
 619 }
 620
 621 static int count_unmerged_entries(void)
 622 {
 623         const struct index_state *state = &the_index;
 624         int i, ret = 0;
 625
 626         for (i = 0; i < state->cache_nr; i++)
 627                 if (ce_stage(state->cache[i]))
 628                         ret++;
 629
 630         return ret;
 631 }
 632
 633 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 634 {
 635         struct tree *trees[MAX_UNPACK_TREES];
 636         struct unpack_trees_options opts;
 637         struct tree_desc t[MAX_UNPACK_TREES];
 638         int i, fd, nr_trees = 0;
 639         struct dir_struct dir;
 640         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 641
 642         refresh_cache(REFRESH_QUIET);
 643
 644         fd = hold_locked_index(lock_file, 1);
 645
 646         memset(&trees, 0, sizeof(trees));
 647         memset(&opts, 0, sizeof(opts));
 648         memset(&t, 0, sizeof(t));
 649         memset(&dir, 0, sizeof(dir));
 650         dir.flags |= DIR_SHOW_IGNORED;
 651         dir.exclude_per_dir = ".gitignore";
 652         opts.dir = &dir;
 653
 654         opts.head_idx = 1;
 655         opts.src_index = &the_index;
 656         opts.dst_index = &the_index;
 657         opts.update = 1;
 658         opts.verbose_update = 1;
 659         opts.merge = 1;
 660         opts.fn = twoway_merge;
 661         opts.msgs = get_porcelain_error_msgs();
 662
 663         trees[nr_trees] = parse_tree_indirect(head);
 664         if (!trees[nr_trees++])
 665                 return -1;
 666         trees[nr_trees] = parse_tree_indirect(remote);
 667         if (!trees[nr_trees++])
 668                 return -1;
 669         for (i = 0; i < nr_trees; i++) {
 670                 parse_tree(trees[i]);
 671                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 672         }
 673         if (unpack_trees(nr_trees, t, &opts))
 674                 return -1;
 675         if (write_cache(fd, active_cache, active_nr) ||
 676                 commit_locked_index(lock_file))
 677                 die("unable to write new index file");
 678         return 0;
 679 }
 680
 681 static void split_merge_strategies(const char *string, struct strategy **list,
 682                                    int *nr, int *alloc)
 683 {
 684         char *p, *q, *buf;
 685
 686         if (!string)
 687                 return;
 688
 689         buf = xstrdup(string);
 690         q = buf;
 691         for (;;) {
 692                 p = strchr(q, ' ');
 693                 if (!p) {
 694                         ALLOC_GROW(*list, *nr + 1, *alloc);
 695                         (*list)[(*nr)++].name = xstrdup(q);
 696                         free(buf);
 697                         return;
 698                 } else {
 699                         *p = '\0';
 700                         ALLOC_GROW(*list, *nr + 1, *alloc);
 701                         (*list)[(*nr)++].name = xstrdup(q);
 702                         q = ++p;
 703                 }
 704         }
 705 }
 706
 707 static void add_strategies(const char *string, unsigned attr)
 708 {
 709         struct strategy *list = NULL;
 710         int list_alloc = 0, list_nr = 0, i;
 711
 712         memset(&list, 0, sizeof(list));
 713         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 714         if (list) {
 715                 for (i = 0; i < list_nr; i++)
 716                         append_strategy(get_strategy(list[i].name));
 717                 return;
 718         }
 719         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 720                 if (all_strategy[i].attr & attr)
 721                         append_strategy(&all_strategy[i]);
 722
 723 }
 724
 725 static int merge_trivial(void)
 726 {
 727         unsigned char result_tree[20], result_commit[20];
 728         struct commit_list *parent = xmalloc(sizeof(*parent));
 729
 730         write_tree_trivial(result_tree);
 731         printf("Wonderful.\n");
 732         parent->item = lookup_commit(head);
 733         parent->next = xmalloc(sizeof(*parent->next));
 734         parent->next->item = remoteheads->item;
 735         parent->next->next = NULL;
 736         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 737         finish(result_commit, "In-index merge");
 738         drop_save();
 739         return 0;
 740 }
 741
 742 static int finish_automerge(struct commit_list *common,
 743                             unsigned char *result_tree,
 744                             const char *wt_strategy)
 745 {
 746         struct commit_list *parents = NULL, *j;
 747         struct strbuf buf = STRBUF_INIT;
 748         unsigned char result_commit[20];
 749
 750         free_commit_list(common);
 751         if (allow_fast_forward) {
 752                 parents = remoteheads;
 753                 commit_list_insert(lookup_commit(head), &parents);
 754                 parents = reduce_heads(parents);
 755         } else {
 756                 struct commit_list **pptr = &parents;
 757
 758                 pptr = &commit_list_insert(lookup_commit(head),
 759                                 pptr)->next;
 760                 for (j = remoteheads; j; j = j->next)
 761                         pptr = &commit_list_insert(j->item, pptr)->next;
 762         }
 763         free_commit_list(remoteheads);
 764         strbuf_addch(&merge_msg, '\n');
 765         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 766         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 767         finish(result_commit, buf.buf);
 768         strbuf_release(&buf);
 769         drop_save();
 770         return 0;
 771 }
 772
 773 static int suggest_conflicts(void)
 774 {
 775         FILE *fp;
 776         int pos;
 777
 778         fp = fopen(git_path("MERGE_MSG"), "a");
 779         if (!fp)
 780                 die_errno("Could not open '%s' for writing",
 781                           git_path("MERGE_MSG"));
 782         fprintf(fp, "\nConflicts:\n");
 783         for (pos = 0; pos < active_nr; pos++) {
 784                 struct cache_entry *ce = active_cache[pos];
 785
 786                 if (ce_stage(ce)) {
 787                         fprintf(fp, "\t%s\n", ce->name);
 788                         while (pos + 1 < active_nr &&
 789                                         !strcmp(ce->name,
 790                                                 active_cache[pos + 1]->name))
 791                                 pos++;
 792                 }
 793         }
 794         fclose(fp);
 795         rerere(allow_rerere_auto);
 796         printf("Automatic merge failed; "
 797                         "fix conflicts and then commit the result.\n");
 798         return 1;
 799 }
 800
 801 static struct commit *is_old_style_invocation(int argc, const char **argv)
 802 {
 803         struct commit *second_token = NULL;
 804         if (argc > 2) {
 805                 unsigned char second_sha1[20];
 806
 807                 if (get_sha1(argv[1], second_sha1))
 808                         return NULL;
 809                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 810                 if (!second_token)
 811                         die("'%s' is not a commit", argv[1]);
 812                 if (hashcmp(second_token->object.sha1, head))
 813                         return NULL;
 814         }
 815         return second_token;
 816 }
 817
 818 static int evaluate_result(void)
 819 {
 820         int cnt = 0;
 821         struct rev_info rev;
 822
 823         /* Check how many files differ. */
 824         init_revisions(&rev, "");
 825         setup_revisions(0, NULL, &rev, NULL);
 826         rev.diffopt.output_format |=
 827                 DIFF_FORMAT_CALLBACK;
 828         rev.diffopt.format_callback = count_diff_files;
 829         rev.diffopt.format_callback_data = &cnt;
 830         run_diff_files(&rev, 0);
 831
 832         /*
 833          * Check how many unmerged entries are
 834          * there.
 835          */
 836         cnt += count_unmerged_entries();
 837
 838         return cnt;
 839 }
 840
 841 int cmd_merge(int argc, const char **argv, const char *prefix)
 842 {
 843         unsigned char result_tree[20];
 844         struct strbuf buf = STRBUF_INIT;
 845         const char *head_arg;
 846         int flag, head_invalid = 0, i;
 847         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 848         struct commit_list *common = NULL;
 849         const char *best_strategy = NULL, *wt_strategy = NULL;
 850         struct commit_list **remotes = &remoteheads;
 851
 852         if (read_cache_unmerged()) {
 853                 die_resolve_conflict("merge");
 854         }
 855         if (file_exists(git_path("MERGE_HEAD"))) {
 856                 /*
 857                  * There is no unmerged entry, don't advise 'git
 858                  * add/rm <file>', just 'git commit'.
 859                  */
 860                 if (advice_resolve_conflict)
 861                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
 862                             "Please, commit your changes before you can merge.");
 863                 else
 864                         die("You have not concluded your merge (MERGE_HEAD exists).");
 865         }
 866
 867         /*
 868          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 869          * current branch.
 870          */
 871         branch = resolve_ref("HEAD", head, 0, &flag);
 872         if (branch && !prefixcmp(branch, "refs/heads/"))
 873                 branch += 11;
 874         if (is_null_sha1(head))
 875                 head_invalid = 1;
 876
 877         git_config(git_merge_config, NULL);
 878
 879         /* for color.ui */
 880         if (diff_use_color_default == -1)
 881                 diff_use_color_default = git_use_color_default;
 882
 883         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 884                         builtin_merge_usage, 0);
 885         if (verbosity < 0)
 886                 show_diffstat = 0;
 887
 888         if (squash) {
 889                 if (!allow_fast_forward)
 890                         die("You cannot combine --squash with --no-ff.");
 891                 option_commit = 0;
 892         }
 893
 894         if (!allow_fast_forward && fast_forward_only)
 895                 die("You cannot combine --no-ff with --ff-only.");
 896
 897         if (!argc)
 898                 usage_with_options(builtin_merge_usage,
 899                         builtin_merge_options);
 900
 901         /*
 902          * This could be traditional "merge <msg> HEAD <commit>..."  and
 903          * the way we can tell it is to see if the second token is HEAD,
 904          * but some people might have misused the interface and used a
 905          * committish that is the same as HEAD there instead.
 906          * Traditional format never would have "-m" so it is an
 907          * additional safety measure to check for it.
 908          */
 909
 910         if (!have_message && is_old_style_invocation(argc, argv)) {
 911                 strbuf_addstr(&merge_msg, argv[0]);
 912                 head_arg = argv[1];
 913                 argv += 2;
 914                 argc -= 2;
 915         } else if (head_invalid) {
 916                 struct object *remote_head;
 917                 /*
 918                  * If the merged head is a valid one there is no reason
 919                  * to forbid "git merge" into a branch yet to be born.
 920                  * We do the same for "git pull".
 921                  */
 922                 if (argc != 1)
 923                         die("Can merge only exactly one commit into "
 924                                 "empty head");
 925                 if (squash)
 926                         die("Squash commit into empty head not supported yet");
 927                 if (!allow_fast_forward)
 928                         die("Non-fast-forward commit does not make sense into "
 929                             "an empty head");
 930                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 931                 if (!remote_head)
 932                         die("%s - not something we can merge", argv[0]);
 933                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 934                                 DIE_ON_ERR);
 935                 reset_hard(remote_head->sha1, 0);
 936                 return 0;
 937         } else {
 938                 struct strbuf msg = STRBUF_INIT;
 939
 940                 /* We are invoked directly as the first-class UI. */
 941                 head_arg = "HEAD";
 942
 943                 /*
 944                  * All the rest are the commits being merged;
 945                  * prepare the standard merge summary message to
 946                  * be appended to the given message.  If remote
 947                  * is invalid we will die later in the common
 948                  * codepath so we discard the error in this
 949                  * loop.
 950                  */
 951                 if (!have_message) {
 952                         for (i = 0; i < argc; i++)
 953                                 merge_name(argv[i], &msg);
 954                         fmt_merge_msg(option_log, &msg, &merge_msg);
 955                         if (merge_msg.len)
 956                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
 957                 }
 958         }
 959
 960         if (head_invalid || !argc)
 961                 usage_with_options(builtin_merge_usage,
 962                         builtin_merge_options);
 963
 964         strbuf_addstr(&buf, "merge");
 965         for (i = 0; i < argc; i++)
 966                 strbuf_addf(&buf, " %s", argv[i]);
 967         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 968         strbuf_reset(&buf);
 969
 970         for (i = 0; i < argc; i++) {
 971                 struct object *o;
 972                 struct commit *commit;
 973
 974                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 975                 if (!o)
 976                         die("%s - not something we can merge", argv[i]);
 977                 commit = lookup_commit(o->sha1);
 978                 commit->util = (void *)argv[i];
 979                 remotes = &commit_list_insert(commit, remotes)->next;
 980
 981                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 982                 setenv(buf.buf, argv[i], 1);
 983                 strbuf_reset(&buf);
 984         }
 985
 986         if (!use_strategies) {
 987                 if (!remoteheads->next)
 988                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 989                 else
 990                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 991         }
 992
 993         for (i = 0; i < use_strategies_nr; i++) {
 994                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 995                         allow_fast_forward = 0;
 996                 if (use_strategies[i]->attr & NO_TRIVIAL)
 997                         allow_trivial = 0;
 998         }
 999
1000         if (!remoteheads->next)
1001                 common = get_merge_bases(lookup_commit(head),
1002                                 remoteheads->item, 1);
1003         else {
1004                 struct commit_list *list = remoteheads;
1005                 commit_list_insert(lookup_commit(head), &list);
1006                 common = get_octopus_merge_bases(list);
1007                 free(list);
1008         }
1009
1010         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1011                 DIE_ON_ERR);
1012
1013         if (!common)
1014                 ; /* No common ancestors found. We need a real merge. */
1015         else if (!remoteheads->next && !common->next &&
1016                         common->item == remoteheads->item) {
1017                 /*
1018                  * If head can reach all the merge then we are up to date.
1019                  * but first the most common case of merging one remote.
1020                  */
1021                 finish_up_to_date("Already up-to-date.");
1022                 return 0;
1023         } else if (allow_fast_forward && !remoteheads->next &&
1024                         !common->next &&
1025                         !hashcmp(common->item->object.sha1, head)) {
1026                 /* Again the most common case of merging one remote. */
1027                 struct strbuf msg = STRBUF_INIT;
1028                 struct object *o;
1029                 char hex[41];
1030
1031                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1032
1033                 if (verbosity >= 0)
1034                         printf("Updating %s..%s\n",
1035                                 hex,
1036                                 find_unique_abbrev(remoteheads->item->object.sha1,
1037                                 DEFAULT_ABBREV));
1038                 strbuf_addstr(&msg, "Fast-forward");
1039                 if (have_message)
1040                         strbuf_addstr(&msg,
1041                                 " (no commit created; -m option ignored)");
1042                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1043                         0, NULL, OBJ_COMMIT);
1044                 if (!o)
1045                         return 1;
1046
1047                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1048                         return 1;
1049
1050                 finish(o->sha1, msg.buf);
1051                 drop_save();
1052                 return 0;
1053         } else if (!remoteheads->next && common->next)
1054                 ;
1055                 /*
1056                  * We are not doing octopus and not fast-forward.  Need
1057                  * a real merge.
1058                  */
1059         else if (!remoteheads->next && !common->next && option_commit) {
1060                 /*
1061                  * We are not doing octopus, not fast-forward, and have
1062                  * only one common.
1063                  */
1064                 refresh_cache(REFRESH_QUIET);
1065                 if (allow_trivial && !fast_forward_only) {
1066                         /* See if it is really trivial. */
1067                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1068                         printf("Trying really trivial in-index merge...\n");
1069                         if (!read_tree_trivial(common->item->object.sha1,
1070                                         head, remoteheads->item->object.sha1))
1071                                 return merge_trivial();
1072                         printf("Nope.\n");
1073                 }
1074         } else {
1075                 /*
1076                  * An octopus.  If we can reach all the remote we are up
1077                  * to date.
1078                  */
1079                 int up_to_date = 1;
1080                 struct commit_list *j;
1081
1082                 for (j = remoteheads; j; j = j->next) {
1083                         struct commit_list *common_one;
1084
1085                         /*
1086                          * Here we *have* to calculate the individual
1087                          * merge_bases again, otherwise "git merge HEAD^
1088                          * HEAD^^" would be missed.
1089                          */
1090                         common_one = get_merge_bases(lookup_commit(head),
1091                                 j->item, 1);
1092                         if (hashcmp(common_one->item->object.sha1,
1093                                 j->item->object.sha1)) {
1094                                 up_to_date = 0;
1095                                 break;
1096                         }
1097                 }
1098                 if (up_to_date) {
1099                         finish_up_to_date("Already up-to-date. Yeeah!");
1100                         return 0;
1101                 }
1102         }
1103
1104         if (fast_forward_only)
1105                 die("Not possible to fast-forward, aborting.");
1106
1107         /* We are going to make a new commit. */
1108         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1109
1110         /*
1111          * At this point, we need a real merge.  No matter what strategy
1112          * we use, it would operate on the index, possibly affecting the
1113          * working tree, and when resolved cleanly, have the desired
1114          * tree in the index -- this means that the index must be in
1115          * sync with the head commit.  The strategies are responsible
1116          * to ensure this.
1117          */
1118         if (use_strategies_nr != 1) {
1119                 /*
1120                  * Stash away the local changes so that we can try more
1121                  * than one.
1122                  */
1123                 save_state();
1124         } else {
1125                 memcpy(stash, null_sha1, 20);
1126         }
1127
1128         for (i = 0; i < use_strategies_nr; i++) {
1129                 int ret;
1130                 if (i) {
1131                         printf("Rewinding the tree to pristine...\n");
1132                         restore_state();
1133                 }
1134                 if (use_strategies_nr != 1)
1135                         printf("Trying merge strategy %s...\n",
1136                                 use_strategies[i]->name);
1137                 /*
1138                  * Remember which strategy left the state in the working
1139                  * tree.
1140                  */
1141                 wt_strategy = use_strategies[i]->name;
1142
1143                 ret = try_merge_strategy(use_strategies[i]->name,
1144                         common, head_arg);
1145                 if (!option_commit && !ret) {
1146                         merge_was_ok = 1;
1147                         /*
1148                          * This is necessary here just to avoid writing
1149                          * the tree, but later we will *not* exit with
1150                          * status code 1 because merge_was_ok is set.
1151                          */
1152                         ret = 1;
1153                 }
1154
1155                 if (ret) {
1156                         /*
1157                          * The backend exits with 1 when conflicts are
1158                          * left to be resolved, with 2 when it does not
1159                          * handle the given merge at all.
1160                          */
1161                         if (ret == 1) {
1162                                 int cnt = evaluate_result();
1163
1164                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1165                                         best_strategy = use_strategies[i]->name;
1166                                         best_cnt = cnt;
1167                                 }
1168                         }
1169                         if (merge_was_ok)
1170                                 break;
1171                         else
1172                                 continue;
1173                 }
1174
1175                 /* Automerge succeeded. */
1176                 write_tree_trivial(result_tree);
1177                 automerge_was_ok = 1;
1178                 break;
1179         }
1180
1181         /*
1182          * If we have a resulting tree, that means the strategy module
1183          * auto resolved the merge cleanly.
1184          */
1185         if (automerge_was_ok)
1186                 return finish_automerge(common, result_tree, wt_strategy);
1187
1188         /*
1189          * Pick the result from the best strategy and have the user fix
1190          * it up.
1191          */
1192         if (!best_strategy) {
1193                 restore_state();
1194                 if (use_strategies_nr > 1)
1195                         fprintf(stderr,
1196                                 "No merge strategy handled the merge.\n");
1197                 else
1198                         fprintf(stderr, "Merge with strategy %s failed.\n",
1199                                 use_strategies[0]->name);
1200                 return 2;
1201         } else if (best_strategy == wt_strategy)
1202                 ; /* We already have its result in the working tree. */
1203         else {
1204                 printf("Rewinding the tree to pristine...\n");
1205                 restore_state();
1206                 printf("Using the %s to prepare resolving by hand.\n",
1207                         best_strategy);
1208                 try_merge_strategy(best_strategy, common, head_arg);
1209         }
1210
1211         if (squash)
1212                 finish(NULL, NULL);
1213         else {
1214                 int fd;
1215                 struct commit_list *j;
1216
1217                 for (j = remoteheads; j; j = j->next)
1218                         strbuf_addf(&buf, "%s\n",
1219                                 sha1_to_hex(j->item->object.sha1));
1220                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1221                 if (fd < 0)
1222                         die_errno("Could not open '%s' for writing",
1223                                   git_path("MERGE_HEAD"));
1224                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1225                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1226                 close(fd);
1227                 strbuf_addch(&merge_msg, '\n');
1228                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1229                 if (fd < 0)
1230                         die_errno("Could not open '%s' for writing",
1231                                   git_path("MERGE_MSG"));
1232                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1233                         merge_msg.len)
1234                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1235                 close(fd);
1236                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1237                 if (fd < 0)
1238                         die_errno("Could not open '%s' for writing",
1239                                   git_path("MERGE_MODE"));
1240                 strbuf_reset(&buf);
1241                 if (!allow_fast_forward)
1242                         strbuf_addf(&buf, "no-ff");
1243                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1244                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1245                 close(fd);
1246         }
1247
1248         if (merge_was_ok) {
1249                 fprintf(stderr, "Automatic merge went well; "
1250                         "stopped before committing as requested\n");
1251                 return 0;
1252         } else
1253                 return suggest_conflicts();
1254 }