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