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%s", buf->len ? "\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                 }
 111                 exclude_cmds(&main_cmds, &not_strategies);
 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         opts.msgs = get_porcelain_error_msgs();
 660
 661         trees[nr_trees] = parse_tree_indirect(head);
 662         if (!trees[nr_trees++])
 663                 return -1;
 664         trees[nr_trees] = parse_tree_indirect(remote);
 665         if (!trees[nr_trees++])
 666                 return -1;
 667         for (i = 0; i < nr_trees; i++) {
 668                 parse_tree(trees[i]);
 669                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 670         }
 671         if (unpack_trees(nr_trees, t, &opts))
 672                 return -1;
 673         if (write_cache(fd, active_cache, active_nr) ||
 674                 commit_locked_index(lock_file))
 675                 die("unable to write new index file");
 676         return 0;
 677 }
 678
 679 static void split_merge_strategies(const char *string, struct strategy **list,
 680                                    int *nr, int *alloc)
 681 {
 682         char *p, *q, *buf;
 683
 684         if (!string)
 685                 return;
 686
 687         buf = xstrdup(string);
 688         q = buf;
 689         for (;;) {
 690                 p = strchr(q, ' ');
 691                 if (!p) {
 692                         ALLOC_GROW(*list, *nr + 1, *alloc);
 693                         (*list)[(*nr)++].name = xstrdup(q);
 694                         free(buf);
 695                         return;
 696                 } else {
 697                         *p = '\0';
 698                         ALLOC_GROW(*list, *nr + 1, *alloc);
 699                         (*list)[(*nr)++].name = xstrdup(q);
 700                         q = ++p;
 701                 }
 702         }
 703 }
 704
 705 static void add_strategies(const char *string, unsigned attr)
 706 {
 707         struct strategy *list = NULL;
 708         int list_alloc = 0, list_nr = 0, i;
 709
 710         memset(&list, 0, sizeof(list));
 711         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 712         if (list) {
 713                 for (i = 0; i < list_nr; i++)
 714                         append_strategy(get_strategy(list[i].name));
 715                 return;
 716         }
 717         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 718                 if (all_strategy[i].attr & attr)
 719                         append_strategy(&all_strategy[i]);
 720
 721 }
 722
 723 static int merge_trivial(void)
 724 {
 725         unsigned char result_tree[20], result_commit[20];
 726         struct commit_list *parent = xmalloc(sizeof(*parent));
 727
 728         write_tree_trivial(result_tree);
 729         printf("Wonderful.\n");
 730         parent->item = lookup_commit(head);
 731         parent->next = xmalloc(sizeof(*parent->next));
 732         parent->next->item = remoteheads->item;
 733         parent->next->next = NULL;
 734         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 735         finish(result_commit, "In-index merge");
 736         drop_save();
 737         return 0;
 738 }
 739
 740 static int finish_automerge(struct commit_list *common,
 741                             unsigned char *result_tree,
 742                             const char *wt_strategy)
 743 {
 744         struct commit_list *parents = NULL, *j;
 745         struct strbuf buf = STRBUF_INIT;
 746         unsigned char result_commit[20];
 747
 748         free_commit_list(common);
 749         if (allow_fast_forward) {
 750                 parents = remoteheads;
 751                 commit_list_insert(lookup_commit(head), &parents);
 752                 parents = reduce_heads(parents);
 753         } else {
 754                 struct commit_list **pptr = &parents;
 755
 756                 pptr = &commit_list_insert(lookup_commit(head),
 757                                 pptr)->next;
 758                 for (j = remoteheads; j; j = j->next)
 759                         pptr = &commit_list_insert(j->item, pptr)->next;
 760         }
 761         free_commit_list(remoteheads);
 762         strbuf_addch(&merge_msg, '\n');
 763         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 764         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 765         finish(result_commit, buf.buf);
 766         strbuf_release(&buf);
 767         drop_save();
 768         return 0;
 769 }
 770
 771 static int suggest_conflicts(void)
 772 {
 773         FILE *fp;
 774         int pos;
 775
 776         fp = fopen(git_path("MERGE_MSG"), "a");
 777         if (!fp)
 778                 die_errno("Could not open '%s' for writing",
 779                           git_path("MERGE_MSG"));
 780         fprintf(fp, "\nConflicts:\n");
 781         for (pos = 0; pos < active_nr; pos++) {
 782                 struct cache_entry *ce = active_cache[pos];
 783
 784                 if (ce_stage(ce)) {
 785                         fprintf(fp, "\t%s\n", ce->name);
 786                         while (pos + 1 < active_nr &&
 787                                         !strcmp(ce->name,
 788                                                 active_cache[pos + 1]->name))
 789                                 pos++;
 790                 }
 791         }
 792         fclose(fp);
 793         rerere();
 794         printf("Automatic merge failed; "
 795                         "fix conflicts and then commit the result.\n");
 796         return 1;
 797 }
 798
 799 static struct commit *is_old_style_invocation(int argc, const char **argv)
 800 {
 801         struct commit *second_token = NULL;
 802         if (argc > 2) {
 803                 unsigned char second_sha1[20];
 804
 805                 if (get_sha1(argv[1], second_sha1))
 806                         return NULL;
 807                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 808                 if (!second_token)
 809                         die("'%s' is not a commit", argv[1]);
 810                 if (hashcmp(second_token->object.sha1, head))
 811                         return NULL;
 812         }
 813         return second_token;
 814 }
 815
 816 static int evaluate_result(void)
 817 {
 818         int cnt = 0;
 819         struct rev_info rev;
 820
 821         /* Check how many files differ. */
 822         init_revisions(&rev, "");
 823         setup_revisions(0, NULL, &rev, NULL);
 824         rev.diffopt.output_format |=
 825                 DIFF_FORMAT_CALLBACK;
 826         rev.diffopt.format_callback = count_diff_files;
 827         rev.diffopt.format_callback_data = &cnt;
 828         run_diff_files(&rev, 0);
 829
 830         /*
 831          * Check how many unmerged entries are
 832          * there.
 833          */
 834         cnt += count_unmerged_entries();
 835
 836         return cnt;
 837 }
 838
 839 int cmd_merge(int argc, const char **argv, const char *prefix)
 840 {
 841         unsigned char result_tree[20];
 842         struct strbuf buf = STRBUF_INIT;
 843         const char *head_arg;
 844         int flag, head_invalid = 0, i;
 845         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 846         struct commit_list *common = NULL;
 847         const char *best_strategy = NULL, *wt_strategy = NULL;
 848         struct commit_list **remotes = &remoteheads;
 849
 850         if (file_exists(git_path("MERGE_HEAD")))
 851                 die("You have not concluded your merge. (MERGE_HEAD exists)");
 852         if (read_cache_unmerged())
 853                 die("You are in the middle of a conflicted merge."
 854                                 " (index unmerged)");
 855
 856         /*
 857          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 858          * current branch.
 859          */
 860         branch = resolve_ref("HEAD", head, 0, &flag);
 861         if (branch && !prefixcmp(branch, "refs/heads/"))
 862                 branch += 11;
 863         if (is_null_sha1(head))
 864                 head_invalid = 1;
 865
 866         git_config(git_merge_config, NULL);
 867
 868         /* for color.ui */
 869         if (diff_use_color_default == -1)
 870                 diff_use_color_default = git_use_color_default;
 871
 872         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 873                         builtin_merge_usage, 0);
 874         if (verbosity < 0)
 875                 show_diffstat = 0;
 876
 877         if (squash) {
 878                 if (!allow_fast_forward)
 879                         die("You cannot combine --squash with --no-ff.");
 880                 option_commit = 0;
 881         }
 882
 883         if (!allow_fast_forward && fast_forward_only)
 884                 die("You cannot combine --no-ff with --ff-only.");
 885
 886         if (!argc)
 887                 usage_with_options(builtin_merge_usage,
 888                         builtin_merge_options);
 889
 890         /*
 891          * This could be traditional "merge <msg> HEAD <commit>..."  and
 892          * the way we can tell it is to see if the second token is HEAD,
 893          * but some people might have misused the interface and used a
 894          * committish that is the same as HEAD there instead.
 895          * Traditional format never would have "-m" so it is an
 896          * additional safety measure to check for it.
 897          */
 898
 899         if (!have_message && is_old_style_invocation(argc, argv)) {
 900                 strbuf_addstr(&merge_msg, argv[0]);
 901                 head_arg = argv[1];
 902                 argv += 2;
 903                 argc -= 2;
 904         } else if (head_invalid) {
 905                 struct object *remote_head;
 906                 /*
 907                  * If the merged head is a valid one there is no reason
 908                  * to forbid "git merge" into a branch yet to be born.
 909                  * We do the same for "git pull".
 910                  */
 911                 if (argc != 1)
 912                         die("Can merge only exactly one commit into "
 913                                 "empty head");
 914                 if (squash)
 915                         die("Squash commit into empty head not supported yet");
 916                 if (!allow_fast_forward)
 917                         die("Non-fast-forward commit does not make sense into "
 918                             "an empty head");
 919                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 920                 if (!remote_head)
 921                         die("%s - not something we can merge", argv[0]);
 922                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 923                                 DIE_ON_ERR);
 924                 reset_hard(remote_head->sha1, 0);
 925                 return 0;
 926         } else {
 927                 struct strbuf msg = STRBUF_INIT;
 928
 929                 /* We are invoked directly as the first-class UI. */
 930                 head_arg = "HEAD";
 931
 932                 /*
 933                  * All the rest are the commits being merged;
 934                  * prepare the standard merge summary message to
 935                  * be appended to the given message.  If remote
 936                  * is invalid we will die later in the common
 937                  * codepath so we discard the error in this
 938                  * loop.
 939                  */
 940                 if (!have_message) {
 941                         for (i = 0; i < argc; i++)
 942                                 merge_name(argv[i], &msg);
 943                         fmt_merge_msg(option_log, &msg, &merge_msg);
 944                         if (merge_msg.len)
 945                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
 946                 }
 947         }
 948
 949         if (head_invalid || !argc)
 950                 usage_with_options(builtin_merge_usage,
 951                         builtin_merge_options);
 952
 953         strbuf_addstr(&buf, "merge");
 954         for (i = 0; i < argc; i++)
 955                 strbuf_addf(&buf, " %s", argv[i]);
 956         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 957         strbuf_reset(&buf);
 958
 959         for (i = 0; i < argc; i++) {
 960                 struct object *o;
 961                 struct commit *commit;
 962
 963                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 964                 if (!o)
 965                         die("%s - not something we can merge", argv[i]);
 966                 commit = lookup_commit(o->sha1);
 967                 commit->util = (void *)argv[i];
 968                 remotes = &commit_list_insert(commit, remotes)->next;
 969
 970                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 971                 setenv(buf.buf, argv[i], 1);
 972                 strbuf_reset(&buf);
 973         }
 974
 975         if (!use_strategies) {
 976                 if (!remoteheads->next)
 977                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 978                 else
 979                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 980         }
 981
 982         for (i = 0; i < use_strategies_nr; i++) {
 983                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 984                         allow_fast_forward = 0;
 985                 if (use_strategies[i]->attr & NO_TRIVIAL)
 986                         allow_trivial = 0;
 987         }
 988
 989         if (!remoteheads->next)
 990                 common = get_merge_bases(lookup_commit(head),
 991                                 remoteheads->item, 1);
 992         else {
 993                 struct commit_list *list = remoteheads;
 994                 commit_list_insert(lookup_commit(head), &list);
 995                 common = get_octopus_merge_bases(list);
 996                 free(list);
 997         }
 998
 999         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1000                 DIE_ON_ERR);
1001
1002         if (!common)
1003                 ; /* No common ancestors found. We need a real merge. */
1004         else if (!remoteheads->next && !common->next &&
1005                         common->item == remoteheads->item) {
1006                 /*
1007                  * If head can reach all the merge then we are up to date.
1008                  * but first the most common case of merging one remote.
1009                  */
1010                 finish_up_to_date("Already up-to-date.");
1011                 return 0;
1012         } else if (allow_fast_forward && !remoteheads->next &&
1013                         !common->next &&
1014                         !hashcmp(common->item->object.sha1, head)) {
1015                 /* Again the most common case of merging one remote. */
1016                 struct strbuf msg = STRBUF_INIT;
1017                 struct object *o;
1018                 char hex[41];
1019
1020                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1021
1022                 if (verbosity >= 0)
1023                         printf("Updating %s..%s\n",
1024                                 hex,
1025                                 find_unique_abbrev(remoteheads->item->object.sha1,
1026                                 DEFAULT_ABBREV));
1027                 strbuf_addstr(&msg, "Fast-forward");
1028                 if (have_message)
1029                         strbuf_addstr(&msg,
1030                                 " (no commit created; -m option ignored)");
1031                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1032                         0, NULL, OBJ_COMMIT);
1033                 if (!o)
1034                         return 1;
1035
1036                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1037                         return 1;
1038
1039                 finish(o->sha1, msg.buf);
1040                 drop_save();
1041                 return 0;
1042         } else if (!remoteheads->next && common->next)
1043                 ;
1044                 /*
1045                  * We are not doing octopus and not fast-forward.  Need
1046                  * a real merge.
1047                  */
1048         else if (!remoteheads->next && !common->next && option_commit) {
1049                 /*
1050                  * We are not doing octopus, not fast-forward, and have
1051                  * only one common.
1052                  */
1053                 refresh_cache(REFRESH_QUIET);
1054                 if (allow_trivial && !fast_forward_only) {
1055                         /* See if it is really trivial. */
1056                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1057                         printf("Trying really trivial in-index merge...\n");
1058                         if (!read_tree_trivial(common->item->object.sha1,
1059                                         head, remoteheads->item->object.sha1))
1060                                 return merge_trivial();
1061                         printf("Nope.\n");
1062                 }
1063         } else {
1064                 /*
1065                  * An octopus.  If we can reach all the remote we are up
1066                  * to date.
1067                  */
1068                 int up_to_date = 1;
1069                 struct commit_list *j;
1070
1071                 for (j = remoteheads; j; j = j->next) {
1072                         struct commit_list *common_one;
1073
1074                         /*
1075                          * Here we *have* to calculate the individual
1076                          * merge_bases again, otherwise "git merge HEAD^
1077                          * HEAD^^" would be missed.
1078                          */
1079                         common_one = get_merge_bases(lookup_commit(head),
1080                                 j->item, 1);
1081                         if (hashcmp(common_one->item->object.sha1,
1082                                 j->item->object.sha1)) {
1083                                 up_to_date = 0;
1084                                 break;
1085                         }
1086                 }
1087                 if (up_to_date) {
1088                         finish_up_to_date("Already up-to-date. Yeeah!");
1089                         return 0;
1090                 }
1091         }
1092
1093         if (fast_forward_only)
1094                 die("Not possible to fast-forward, aborting.");
1095
1096         /* We are going to make a new commit. */
1097         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1098
1099         /*
1100          * At this point, we need a real merge.  No matter what strategy
1101          * we use, it would operate on the index, possibly affecting the
1102          * working tree, and when resolved cleanly, have the desired
1103          * tree in the index -- this means that the index must be in
1104          * sync with the head commit.  The strategies are responsible
1105          * to ensure this.
1106          */
1107         if (use_strategies_nr != 1) {
1108                 /*
1109                  * Stash away the local changes so that we can try more
1110                  * than one.
1111                  */
1112                 save_state();
1113         } else {
1114                 memcpy(stash, null_sha1, 20);
1115         }
1116
1117         for (i = 0; i < use_strategies_nr; i++) {
1118                 int ret;
1119                 if (i) {
1120                         printf("Rewinding the tree to pristine...\n");
1121                         restore_state();
1122                 }
1123                 if (use_strategies_nr != 1)
1124                         printf("Trying merge strategy %s...\n",
1125                                 use_strategies[i]->name);
1126                 /*
1127                  * Remember which strategy left the state in the working
1128                  * tree.
1129                  */
1130                 wt_strategy = use_strategies[i]->name;
1131
1132                 ret = try_merge_strategy(use_strategies[i]->name,
1133                         common, head_arg);
1134                 if (!option_commit && !ret) {
1135                         merge_was_ok = 1;
1136                         /*
1137                          * This is necessary here just to avoid writing
1138                          * the tree, but later we will *not* exit with
1139                          * status code 1 because merge_was_ok is set.
1140                          */
1141                         ret = 1;
1142                 }
1143
1144                 if (ret) {
1145                         /*
1146                          * The backend exits with 1 when conflicts are
1147                          * left to be resolved, with 2 when it does not
1148                          * handle the given merge at all.
1149                          */
1150                         if (ret == 1) {
1151                                 int cnt = evaluate_result();
1152
1153                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1154                                         best_strategy = use_strategies[i]->name;
1155                                         best_cnt = cnt;
1156                                 }
1157                         }
1158                         if (merge_was_ok)
1159                                 break;
1160                         else
1161                                 continue;
1162                 }
1163
1164                 /* Automerge succeeded. */
1165                 write_tree_trivial(result_tree);
1166                 automerge_was_ok = 1;
1167                 break;
1168         }
1169
1170         /*
1171          * If we have a resulting tree, that means the strategy module
1172          * auto resolved the merge cleanly.
1173          */
1174         if (automerge_was_ok)
1175                 return finish_automerge(common, result_tree, wt_strategy);
1176
1177         /*
1178          * Pick the result from the best strategy and have the user fix
1179          * it up.
1180          */
1181         if (!best_strategy) {
1182                 restore_state();
1183                 if (use_strategies_nr > 1)
1184                         fprintf(stderr,
1185                                 "No merge strategy handled the merge.\n");
1186                 else
1187                         fprintf(stderr, "Merge with strategy %s failed.\n",
1188                                 use_strategies[0]->name);
1189                 return 2;
1190         } else if (best_strategy == wt_strategy)
1191                 ; /* We already have its result in the working tree. */
1192         else {
1193                 printf("Rewinding the tree to pristine...\n");
1194                 restore_state();
1195                 printf("Using the %s to prepare resolving by hand.\n",
1196                         best_strategy);
1197                 try_merge_strategy(best_strategy, common, head_arg);
1198         }
1199
1200         if (squash)
1201                 finish(NULL, NULL);
1202         else {
1203                 int fd;
1204                 struct commit_list *j;
1205
1206                 for (j = remoteheads; j; j = j->next)
1207                         strbuf_addf(&buf, "%s\n",
1208                                 sha1_to_hex(j->item->object.sha1));
1209                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1210                 if (fd < 0)
1211                         die_errno("Could not open '%s' for writing",
1212                                   git_path("MERGE_HEAD"));
1213                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1214                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1215                 close(fd);
1216                 strbuf_addch(&merge_msg, '\n');
1217                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1218                 if (fd < 0)
1219                         die_errno("Could not open '%s' for writing",
1220                                   git_path("MERGE_MSG"));
1221                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1222                         merge_msg.len)
1223                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1224                 close(fd);
1225                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1226                 if (fd < 0)
1227                         die_errno("Could not open '%s' for writing",
1228                                   git_path("MERGE_MODE"));
1229                 strbuf_reset(&buf);
1230                 if (!allow_fast_forward)
1231                         strbuf_addf(&buf, "no-ff");
1232                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1233                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1234                 close(fd);
1235         }
1236
1237         if (merge_was_ok) {
1238                 fprintf(stderr, "Automatic merge went well; "
1239                         "stopped before committing as requested\n");
1240                 return 0;
1241         } else
1242                 return suggest_conflicts();
1243 }