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