git.oblomov.eu Git - git/blob - 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 #include "resolve-undo.h"
  28
  29 #define DEFAULT_TWOHEAD (1<<0)
  30 #define DEFAULT_OCTOPUS (1<<1)
  31 #define NO_FAST_FORWARD (1<<2)
  32 #define NO_TRIVIAL      (1<<3)
  33
  34 struct strategy {
  35         const char *name;
  36         unsigned attr;
  37 };
  38
  39 static const char * const builtin_merge_usage[] = {
  40         "git merge [options] <remote>...",
  41         "git merge [options] <msg> HEAD <remote>",
  42         NULL
  43 };
  44
  45 static int show_diffstat = 1, option_log, squash;
  46 static int option_commit = 1, allow_fast_forward = 1;
  47 static int fast_forward_only;
  48 static int allow_trivial = 1, have_message;
  49 static struct strbuf merge_msg;
  50 static struct commit_list *remoteheads;
  51 static unsigned char head[20], stash[20];
  52 static struct strategy **use_strategies;
  53 static size_t use_strategies_nr, use_strategies_alloc;
  54 static const char *branch;
  55 static int verbosity;
  56 static int allow_rerere_auto;
  57
  58 static struct strategy all_strategy[] = {
  59         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  60         { "octopus",    DEFAULT_OCTOPUS },
  61         { "resolve",    0 },
  62         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  63         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  64 };
  65
  66 static const char *pull_twohead, *pull_octopus;
  67
  68 static int option_parse_message(const struct option *opt,
  69                                 const char *arg, int unset)
  70 {
  71         struct strbuf *buf = opt->value;
  72
  73         if (unset)
  74                 strbuf_setlen(buf, 0);
  75         else if (arg) {
  76                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  77                 have_message = 1;
  78         } else
  79                 return error("switch `m' requires a value");
  80         return 0;
  81 }
  82
  83 static struct strategy *get_strategy(const char *name)
  84 {
  85         int i;
  86         struct strategy *ret;
  87         static struct cmdnames main_cmds, other_cmds;
  88         static int loaded;
  89
  90         if (!name)
  91                 return NULL;
  92
  93         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  94                 if (!strcmp(name, all_strategy[i].name))
  95                         return &all_strategy[i];
  96
  97         if (!loaded) {
  98                 struct cmdnames not_strategies;
  99                 loaded = 1;
 100
 101                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 102                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 103                 for (i = 0; i < main_cmds.cnt; i++) {
 104                         int j, found = 0;
 105                         struct cmdname *ent = main_cmds.names[i];
 106                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 107                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 108                                                 && !all_strategy[j].name[ent->len])
 109                                         found = 1;
 110                         if (!found)
 111                                 add_cmdname(&not_strategies, ent->name, ent->len);
 112                 }
 113                 exclude_cmds(&main_cmds, &not_strategies);
 114         }
 115         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 116                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 117                 fprintf(stderr, "Available strategies are:");
 118                 for (i = 0; i < main_cmds.cnt; i++)
 119                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 120                 fprintf(stderr, ".\n");
 121                 if (other_cmds.cnt) {
 122                         fprintf(stderr, "Available custom strategies are:");
 123                         for (i = 0; i < other_cmds.cnt; i++)
 124                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 125                         fprintf(stderr, ".\n");
 126                 }
 127                 exit(1);
 128         }
 129
 130         ret = xcalloc(1, sizeof(struct strategy));
 131         ret->name = xstrdup(name);
 132         return ret;
 133 }
 134
 135 static void append_strategy(struct strategy *s)
 136 {
 137         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 138         use_strategies[use_strategies_nr++] = s;
 139 }
 140
 141 static int option_parse_strategy(const struct option *opt,
 142                                  const char *name, int unset)
 143 {
 144         if (unset)
 145                 return 0;
 146
 147         append_strategy(get_strategy(name));
 148         return 0;
 149 }
 150
 151 static int option_parse_n(const struct option *opt,
 152                           const char *arg, int unset)
 153 {
 154         show_diffstat = unset;
 155         return 0;
 156 }
 157
 158 static struct option builtin_merge_options[] = {
 159         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 160                 "do not show a diffstat at the end of the merge",
 161                 PARSE_OPT_NOARG, option_parse_n },
 162         OPT_BOOLEAN(0, "stat", &show_diffstat,
 163                 "show a diffstat at the end of the merge"),
 164         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 165         OPT_BOOLEAN(0, "log", &option_log,
 166                 "add list of one-line log to merge commit message"),
 167         OPT_BOOLEAN(0, "squash", &squash,
 168                 "create a single commit instead of doing a merge"),
 169         OPT_BOOLEAN(0, "commit", &option_commit,
 170                 "perform a commit if the merge succeeds (default)"),
 171         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 172                 "allow fast-forward (default)"),
 173         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 174                 "abort if fast-forward is not possible"),
 175         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 176         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 177                 "merge strategy to use", option_parse_strategy),
 178         OPT_CALLBACK('m', "message", &merge_msg, "message",
 179                 "message to be used for the merge commit (if any)",
 180                 option_parse_message),
 181         OPT__VERBOSITY(&verbosity),
 182         OPT_END()
 183 };
 184
 185 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 186 static void drop_save(void)
 187 {
 188         unlink(git_path("MERGE_HEAD"));
 189         unlink(git_path("MERGE_MSG"));
 190         unlink(git_path("MERGE_MODE"));
 191 }
 192
 193 static void save_state(void)
 194 {
 195         int len;
 196         struct child_process cp;
 197         struct strbuf buffer = STRBUF_INIT;
 198         const char *argv[] = {"stash", "create", NULL};
 199
 200         memset(&cp, 0, sizeof(cp));
 201         cp.argv = argv;
 202         cp.out = -1;
 203         cp.git_cmd = 1;
 204
 205         if (start_command(&cp))
 206                 die("could not run stash.");
 207         len = strbuf_read(&buffer, cp.out, 1024);
 208         close(cp.out);
 209
 210         if (finish_command(&cp) || len < 0)
 211                 die("stash failed");
 212         else if (!len)
 213                 return;
 214         strbuf_setlen(&buffer, buffer.len-1);
 215         if (get_sha1(buffer.buf, stash))
 216                 die("not a valid object: %s", buffer.buf);
 217 }
 218
 219 static void reset_hard(unsigned const char *sha1, int verbose)
 220 {
 221         int i = 0;
 222         const char *args[6];
 223
 224         args[i++] = "read-tree";
 225         if (verbose)
 226                 args[i++] = "-v";
 227         args[i++] = "--reset";
 228         args[i++] = "-u";
 229         args[i++] = sha1_to_hex(sha1);
 230         args[i] = NULL;
 231
 232         if (run_command_v_opt(args, RUN_GIT_CMD))
 233                 die("read-tree failed");
 234 }
 235
 236 static void restore_state(void)
 237 {
 238         struct strbuf sb = STRBUF_INIT;
 239         const char *args[] = { "stash", "apply", NULL, NULL };
 240
 241         if (is_null_sha1(stash))
 242                 return;
 243
 244         reset_hard(head, 1);
 245
 246         args[2] = sha1_to_hex(stash);
 247
 248         /*
 249          * It is OK to ignore error here, for example when there was
 250          * nothing to restore.
 251          */
 252         run_command_v_opt(args, RUN_GIT_CMD);
 253
 254         strbuf_release(&sb);
 255         refresh_cache(REFRESH_QUIET);
 256 }
 257
 258 /* This is called when no merge was necessary. */
 259 static void finish_up_to_date(const char *msg)
 260 {
 261         if (verbosity >= 0)
 262                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 263         drop_save();
 264 }
 265
 266 static void squash_message(void)
 267 {
 268         struct rev_info rev;
 269         struct commit *commit;
 270         struct strbuf out = STRBUF_INIT;
 271         struct commit_list *j;
 272         int fd;
 273         struct pretty_print_context ctx = {0};
 274
 275         printf("Squash commit -- not updating HEAD\n");
 276         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 277         if (fd < 0)
 278                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 279
 280         init_revisions(&rev, NULL);
 281         rev.ignore_merges = 1;
 282         rev.commit_format = CMIT_FMT_MEDIUM;
 283
 284         commit = lookup_commit(head);
 285         commit->object.flags |= UNINTERESTING;
 286         add_pending_object(&rev, &commit->object, NULL);
 287
 288         for (j = remoteheads; j; j = j->next)
 289                 add_pending_object(&rev, &j->item->object, NULL);
 290
 291         setup_revisions(0, NULL, &rev, NULL);
 292         if (prepare_revision_walk(&rev))
 293                 die("revision walk setup failed");
 294
 295         ctx.abbrev = rev.abbrev;
 296         ctx.date_mode = rev.date_mode;
 297
 298         strbuf_addstr(&out, "Squashed commit of the following:\n");
 299         while ((commit = get_revision(&rev)) != NULL) {
 300                 strbuf_addch(&out, '\n');
 301                 strbuf_addf(&out, "commit %s\n",
 302                         sha1_to_hex(commit->object.sha1));
 303                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 304         }
 305         if (write(fd, out.buf, out.len) < 0)
 306                 die_errno("Writing SQUASH_MSG");
 307         if (close(fd))
 308                 die_errno("Finishing SQUASH_MSG");
 309         strbuf_release(&out);
 310 }
 311
 312 static void finish(const unsigned char *new_head, const char *msg)
 313 {
 314         struct strbuf reflog_message = STRBUF_INIT;
 315
 316         if (!msg)
 317                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 318         else {
 319                 if (verbosity >= 0)
 320                         printf("%s\n", msg);
 321                 strbuf_addf(&reflog_message, "%s: %s",
 322                         getenv("GIT_REFLOG_ACTION"), msg);
 323         }
 324         if (squash) {
 325                 squash_message();
 326         } else {
 327                 if (verbosity >= 0 && !merge_msg.len)
 328                         printf("No merge message -- not updating HEAD\n");
 329                 else {
 330                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 331                         update_ref(reflog_message.buf, "HEAD",
 332                                 new_head, head, 0,
 333                                 DIE_ON_ERR);
 334                         /*
 335                          * We ignore errors in 'gc --auto', since the
 336                          * user should see them.
 337                          */
 338                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 339                 }
 340         }
 341         if (new_head && show_diffstat) {
 342                 struct diff_options opts;
 343                 diff_setup(&opts);
 344                 opts.output_format |=
 345                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 346                 opts.detect_rename = DIFF_DETECT_RENAME;
 347                 if (diff_use_color_default > 0)
 348                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 349                 if (diff_setup_done(&opts) < 0)
 350                         die("diff_setup_done failed");
 351                 diff_tree_sha1(head, new_head, "", &opts);
 352                 diffcore_std(&opts);
 353                 diff_flush(&opts);
 354         }
 355
 356         /* Run a post-merge hook */
 357         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 358
 359         strbuf_release(&reflog_message);
 360 }
 361
 362 /* Get the name for the merge commit's message. */
 363 static void merge_name(const char *remote, struct strbuf *msg)
 364 {
 365         struct object *remote_head;
 366         unsigned char branch_head[20], buf_sha[20];
 367         struct strbuf buf = STRBUF_INIT;
 368         struct strbuf bname = STRBUF_INIT;
 369         const char *ptr;
 370         char *found_ref;
 371         int len, early;
 372
 373         strbuf_branchname(&bname, remote);
 374         remote = bname.buf;
 375
 376         memset(branch_head, 0, sizeof(branch_head));
 377         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 378         if (!remote_head)
 379                 die("'%s' does not point to a commit", remote);
 380
 381         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 382                 if (!prefixcmp(found_ref, "refs/heads/")) {
 383                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 384                                     sha1_to_hex(branch_head), remote);
 385                         goto cleanup;
 386                 }
 387                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 388                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 389                                     sha1_to_hex(branch_head), remote);
 390                         goto cleanup;
 391                 }
 392         }
 393
 394         /* See if remote matches <name>^^^.. or <name>~<number> */
 395         for (len = 0, ptr = remote + strlen(remote);
 396              remote < ptr && ptr[-1] == '^';
 397              ptr--)
 398                 len++;
 399         if (len)
 400                 early = 1;
 401         else {
 402                 early = 0;
 403                 ptr = strrchr(remote, '~');
 404                 if (ptr) {
 405                         int seen_nonzero = 0;
 406
 407                         len++; /* count ~ */
 408                         while (*++ptr && isdigit(*ptr)) {
 409                                 seen_nonzero |= (*ptr != '0');
 410                                 len++;
 411                         }
 412                         if (*ptr)
 413                                 len = 0; /* not ...~<number> */
 414                         else if (seen_nonzero)
 415                                 early = 1;
 416                         else if (len == 1)
 417                                 early = 1; /* "name~" is "name~1"! */
 418                 }
 419         }
 420         if (len) {
 421                 struct strbuf truname = STRBUF_INIT;
 422                 strbuf_addstr(&truname, "refs/heads/");
 423                 strbuf_addstr(&truname, remote);
 424                 strbuf_setlen(&truname, truname.len - len);
 425                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 426                         strbuf_addf(msg,
 427                                     "%s\t\tbranch '%s'%s of .\n",
 428                                     sha1_to_hex(remote_head->sha1),
 429                                     truname.buf + 11,
 430                                     (early ? " (early part)" : ""));
 431                         strbuf_release(&truname);
 432                         goto cleanup;
 433                 }
 434         }
 435
 436         if (!strcmp(remote, "FETCH_HEAD") &&
 437                         !access(git_path("FETCH_HEAD"), R_OK)) {
 438                 FILE *fp;
 439                 struct strbuf line = STRBUF_INIT;
 440                 char *ptr;
 441
 442                 fp = fopen(git_path("FETCH_HEAD"), "r");
 443                 if (!fp)
 444                         die_errno("could not open '%s' for reading",
 445                                   git_path("FETCH_HEAD"));
 446                 strbuf_getline(&line, fp, '\n');
 447                 fclose(fp);
 448                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 449                 if (ptr)
 450                         strbuf_remove(&line, ptr-line.buf+1, 13);
 451                 strbuf_addbuf(msg, &line);
 452                 strbuf_release(&line);
 453                 goto cleanup;
 454         }
 455         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 456                 sha1_to_hex(remote_head->sha1), remote);
 457 cleanup:
 458         strbuf_release(&buf);
 459         strbuf_release(&bname);
 460 }
 461
 462 static int git_merge_config(const char *k, const char *v, void *cb)
 463 {
 464         if (branch && !prefixcmp(k, "branch.") &&
 465                 !prefixcmp(k + 7, branch) &&
 466                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 467                 const char **argv;
 468                 int argc;
 469                 char *buf;
 470
 471                 buf = xstrdup(v);
 472                 argc = split_cmdline(buf, &argv);
 473                 if (argc < 0)
 474                         die("Bad branch.%s.mergeoptions string", branch);
 475                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 476                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 477                 argc++;
 478                 parse_options(argc, argv, NULL, builtin_merge_options,
 479                               builtin_merge_usage, 0);
 480                 free(buf);
 481         }
 482
 483         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 484                 show_diffstat = git_config_bool(k, v);
 485         else if (!strcmp(k, "pull.twohead"))
 486                 return git_config_string(&pull_twohead, k, v);
 487         else if (!strcmp(k, "pull.octopus"))
 488                 return git_config_string(&pull_octopus, k, v);
 489         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 490                 option_log = git_config_bool(k, v);
 491         return git_diff_ui_config(k, v, cb);
 492 }
 493
 494 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 495                              unsigned char *one)
 496 {
 497         int i, nr_trees = 0;
 498         struct tree *trees[MAX_UNPACK_TREES];
 499         struct tree_desc t[MAX_UNPACK_TREES];
 500         struct unpack_trees_options opts;
 501
 502         memset(&opts, 0, sizeof(opts));
 503         opts.head_idx = 2;
 504         opts.src_index = &the_index;
 505         opts.dst_index = &the_index;
 506         opts.update = 1;
 507         opts.verbose_update = 1;
 508         opts.trivial_merges_only = 1;
 509         opts.merge = 1;
 510         trees[nr_trees] = parse_tree_indirect(common);
 511         if (!trees[nr_trees++])
 512                 return -1;
 513         trees[nr_trees] = parse_tree_indirect(head);
 514         if (!trees[nr_trees++])
 515                 return -1;
 516         trees[nr_trees] = parse_tree_indirect(one);
 517         if (!trees[nr_trees++])
 518                 return -1;
 519         opts.fn = threeway_merge;
 520         cache_tree_free(&active_cache_tree);
 521         for (i = 0; i < nr_trees; i++) {
 522                 parse_tree(trees[i]);
 523                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 524         }
 525         if (unpack_trees(nr_trees, t, &opts))
 526                 return -1;
 527         return 0;
 528 }
 529
 530 static void write_tree_trivial(unsigned char *sha1)
 531 {
 532         if (write_cache_as_tree(sha1, 0, NULL))
 533                 die("git write-tree failed to write a tree");
 534 }
 535
 536 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 537                               const char *head_arg)
 538 {
 539         const char **args;
 540         int i = 0, ret;
 541         struct commit_list *j;
 542         struct strbuf buf = STRBUF_INIT;
 543         int index_fd;
 544         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 545
 546         index_fd = hold_locked_index(lock, 1);
 547         refresh_cache(REFRESH_QUIET);
 548         if (active_cache_changed &&
 549                         (write_cache(index_fd, active_cache, active_nr) ||
 550                          commit_locked_index(lock)))
 551                 return error("Unable to write index.");
 552         rollback_lock_file(lock);
 553
 554         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 555                 int clean;
 556                 struct commit *result;
 557                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 558                 int index_fd;
 559                 struct commit_list *reversed = NULL;
 560                 struct merge_options o;
 561
 562                 if (remoteheads->next) {
 563                         error("Not handling anything other than two heads merge.");
 564                         return 2;
 565                 }
 566
 567                 init_merge_options(&o);
 568                 if (!strcmp(strategy, "subtree"))
 569                         o.subtree_merge = 1;
 570
 571                 o.branch1 = head_arg;
 572                 o.branch2 = remoteheads->item->util;
 573
 574                 for (j = common; j; j = j->next)
 575                         commit_list_insert(j->item, &reversed);
 576
 577                 index_fd = hold_locked_index(lock, 1);
 578                 clean = merge_recursive(&o, lookup_commit(head),
 579                                 remoteheads->item, reversed, &result);
 580                 if (active_cache_changed &&
 581                                 (write_cache(index_fd, active_cache, active_nr) ||
 582                                  commit_locked_index(lock)))
 583                         die ("unable to write %s", get_index_file());
 584                 rollback_lock_file(lock);
 585                 return clean ? 0 : 1;
 586         } else {
 587                 args = xmalloc((4 + commit_list_count(common) +
 588                                         commit_list_count(remoteheads)) * sizeof(char *));
 589                 strbuf_addf(&buf, "merge-%s", strategy);
 590                 args[i++] = buf.buf;
 591                 for (j = common; j; j = j->next)
 592                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 593                 args[i++] = "--";
 594                 args[i++] = head_arg;
 595                 for (j = remoteheads; j; j = j->next)
 596                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 597                 args[i] = NULL;
 598                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 599                 strbuf_release(&buf);
 600                 i = 1;
 601                 for (j = common; j; j = j->next)
 602                         free((void *)args[i++]);
 603                 i += 2;
 604                 for (j = remoteheads; j; j = j->next)
 605                         free((void *)args[i++]);
 606                 free(args);
 607                 discard_cache();
 608                 if (read_cache() < 0)
 609                         die("failed to read the cache");
 610                 resolve_undo_clear();
 611                 return ret;
 612         }
 613 }
 614
 615 static void count_diff_files(struct diff_queue_struct *q,
 616                              struct diff_options *opt, void *data)
 617 {
 618         int *count = data;
 619
 620         (*count) += q->nr;
 621 }
 622
 623 static int count_unmerged_entries(void)
 624 {
 625         int i, ret = 0;
 626
 627         for (i = 0; i < active_nr; i++)
 628                 if (ce_stage(active_cache[i]))
 629                         ret++;
 630
 631         return ret;
 632 }
 633
 634 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 635 {
 636         struct tree *trees[MAX_UNPACK_TREES];
 637         struct unpack_trees_options opts;
 638         struct tree_desc t[MAX_UNPACK_TREES];
 639         int i, fd, nr_trees = 0;
 640         struct dir_struct dir;
 641         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 642
 643         refresh_cache(REFRESH_QUIET);
 644
 645         fd = hold_locked_index(lock_file, 1);
 646
 647         memset(&trees, 0, sizeof(trees));
 648         memset(&opts, 0, sizeof(opts));
 649         memset(&t, 0, sizeof(t));
 650         memset(&dir, 0, sizeof(dir));
 651         dir.flags |= DIR_SHOW_IGNORED;
 652         dir.exclude_per_dir = ".gitignore";
 653         opts.dir = &dir;
 654
 655         opts.head_idx = 1;
 656         opts.src_index = &the_index;
 657         opts.dst_index = &the_index;
 658         opts.update = 1;
 659         opts.verbose_update = 1;
 660         opts.merge = 1;
 661         opts.fn = twoway_merge;
 662         opts.msgs = get_porcelain_error_msgs();
 663
 664         trees[nr_trees] = parse_tree_indirect(head);
 665         if (!trees[nr_trees++])
 666                 return -1;
 667         trees[nr_trees] = parse_tree_indirect(remote);
 668         if (!trees[nr_trees++])
 669                 return -1;
 670         for (i = 0; i < nr_trees; i++) {
 671                 parse_tree(trees[i]);
 672                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 673         }
 674         if (unpack_trees(nr_trees, t, &opts))
 675                 return -1;
 676         if (write_cache(fd, active_cache, active_nr) ||
 677                 commit_locked_index(lock_file))
 678                 die("unable to write new index file");
 679         return 0;
 680 }
 681
 682 static void split_merge_strategies(const char *string, struct strategy **list,
 683                                    int *nr, int *alloc)
 684 {
 685         char *p, *q, *buf;
 686
 687         if (!string)
 688                 return;
 689
 690         buf = xstrdup(string);
 691         q = buf;
 692         for (;;) {
 693                 p = strchr(q, ' ');
 694                 if (!p) {
 695                         ALLOC_GROW(*list, *nr + 1, *alloc);
 696                         (*list)[(*nr)++].name = xstrdup(q);
 697                         free(buf);
 698                         return;
 699                 } else {
 700                         *p = '\0';
 701                         ALLOC_GROW(*list, *nr + 1, *alloc);
 702                         (*list)[(*nr)++].name = xstrdup(q);
 703                         q = ++p;
 704                 }
 705         }
 706 }
 707
 708 static void add_strategies(const char *string, unsigned attr)
 709 {
 710         struct strategy *list = NULL;
 711         int list_alloc = 0, list_nr = 0, i;
 712
 713         memset(&list, 0, sizeof(list));
 714         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 715         if (list) {
 716                 for (i = 0; i < list_nr; i++)
 717                         append_strategy(get_strategy(list[i].name));
 718                 return;
 719         }
 720         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 721                 if (all_strategy[i].attr & attr)
 722                         append_strategy(&all_strategy[i]);
 723
 724 }
 725
 726 static int merge_trivial(void)
 727 {
 728         unsigned char result_tree[20], result_commit[20];
 729         struct commit_list *parent = xmalloc(sizeof(*parent));
 730
 731         write_tree_trivial(result_tree);
 732         printf("Wonderful.\n");
 733         parent->item = lookup_commit(head);
 734         parent->next = xmalloc(sizeof(*parent->next));
 735         parent->next->item = remoteheads->item;
 736         parent->next->next = NULL;
 737         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 738         finish(result_commit, "In-index merge");
 739         drop_save();
 740         return 0;
 741 }
 742
 743 static int finish_automerge(struct commit_list *common,
 744                             unsigned char *result_tree,
 745                             const char *wt_strategy)
 746 {
 747         struct commit_list *parents = NULL, *j;
 748         struct strbuf buf = STRBUF_INIT;
 749         unsigned char result_commit[20];
 750
 751         free_commit_list(common);
 752         if (allow_fast_forward) {
 753                 parents = remoteheads;
 754                 commit_list_insert(lookup_commit(head), &parents);
 755                 parents = reduce_heads(parents);
 756         } else {
 757                 struct commit_list **pptr = &parents;
 758
 759                 pptr = &commit_list_insert(lookup_commit(head),
 760                                 pptr)->next;
 761                 for (j = remoteheads; j; j = j->next)
 762                         pptr = &commit_list_insert(j->item, pptr)->next;
 763         }
 764         free_commit_list(remoteheads);
 765         strbuf_addch(&merge_msg, '\n');
 766         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 767         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 768         finish(result_commit, buf.buf);
 769         strbuf_release(&buf);
 770         drop_save();
 771         return 0;
 772 }
 773
 774 static int suggest_conflicts(void)
 775 {
 776         FILE *fp;
 777         int pos;
 778
 779         fp = fopen(git_path("MERGE_MSG"), "a");
 780         if (!fp)
 781                 die_errno("Could not open '%s' for writing",
 782                           git_path("MERGE_MSG"));
 783         fprintf(fp, "\nConflicts:\n");
 784         for (pos = 0; pos < active_nr; pos++) {
 785                 struct cache_entry *ce = active_cache[pos];
 786
 787                 if (ce_stage(ce)) {
 788                         fprintf(fp, "\t%s\n", ce->name);
 789                         while (pos + 1 < active_nr &&
 790                                         !strcmp(ce->name,
 791                                                 active_cache[pos + 1]->name))
 792                                 pos++;
 793                 }
 794         }
 795         fclose(fp);
 796         rerere(allow_rerere_auto);
 797         printf("Automatic merge failed; "
 798                         "fix conflicts and then commit the result.\n");
 799         return 1;
 800 }
 801
 802 static struct commit *is_old_style_invocation(int argc, const char **argv)
 803 {
 804         struct commit *second_token = NULL;
 805         if (argc > 2) {
 806                 unsigned char second_sha1[20];
 807
 808                 if (get_sha1(argv[1], second_sha1))
 809                         return NULL;
 810                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 811                 if (!second_token)
 812                         die("'%s' is not a commit", argv[1]);
 813                 if (hashcmp(second_token->object.sha1, head))
 814                         return NULL;
 815         }
 816         return second_token;
 817 }
 818
 819 static int evaluate_result(void)
 820 {
 821         int cnt = 0;
 822         struct rev_info rev;
 823
 824         /* Check how many files differ. */
 825         init_revisions(&rev, "");
 826         setup_revisions(0, NULL, &rev, NULL);
 827         rev.diffopt.output_format |=
 828                 DIFF_FORMAT_CALLBACK;
 829         rev.diffopt.format_callback = count_diff_files;
 830         rev.diffopt.format_callback_data = &cnt;
 831         run_diff_files(&rev, 0);
 832
 833         /*
 834          * Check how many unmerged entries are
 835          * there.
 836          */
 837         cnt += count_unmerged_entries();
 838
 839         return cnt;
 840 }
 841
 842 int cmd_merge(int argc, const char **argv, const char *prefix)
 843 {
 844         unsigned char result_tree[20];
 845         struct strbuf buf = STRBUF_INIT;
 846         const char *head_arg;
 847         int flag, head_invalid = 0, i;
 848         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 849         struct commit_list *common = NULL;
 850         const char *best_strategy = NULL, *wt_strategy = NULL;
 851         struct commit_list **remotes = &remoteheads;
 852
 853         if (read_cache_unmerged()) {
 854                 die_resolve_conflict("merge");
 855         }
 856         if (file_exists(git_path("MERGE_HEAD"))) {
 857                 /*
 858                  * There is no unmerged entry, don't advise 'git
 859                  * add/rm <file>', just 'git commit'.
 860                  */
 861                 if (advice_resolve_conflict)
 862                         die("You have not concluded your merge (MERGE_HEAD exists).\n"
 863                             "Please, commit your changes before you can merge.");
 864                 else
 865                         die("You have not concluded your merge (MERGE_HEAD exists).");
 866         }
 867
 868         resolve_undo_clear();
 869         /*
 870          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 871          * current branch.
 872          */
 873         branch = resolve_ref("HEAD", head, 0, &flag);
 874         if (branch && !prefixcmp(branch, "refs/heads/"))
 875                 branch += 11;
 876         if (is_null_sha1(head))
 877                 head_invalid = 1;
 878
 879         git_config(git_merge_config, NULL);
 880
 881         /* for color.ui */
 882         if (diff_use_color_default == -1)
 883                 diff_use_color_default = git_use_color_default;
 884
 885         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 886                         builtin_merge_usage, 0);
 887         if (verbosity < 0)
 888                 show_diffstat = 0;
 889
 890         if (squash) {
 891                 if (!allow_fast_forward)
 892                         die("You cannot combine --squash with --no-ff.");
 893                 option_commit = 0;
 894         }
 895
 896         if (!allow_fast_forward && fast_forward_only)
 897                 die("You cannot combine --no-ff with --ff-only.");
 898
 899         if (!argc)
 900                 usage_with_options(builtin_merge_usage,
 901                         builtin_merge_options);
 902
 903         /*
 904          * This could be traditional "merge <msg> HEAD <commit>..."  and
 905          * the way we can tell it is to see if the second token is HEAD,
 906          * but some people might have misused the interface and used a
 907          * committish that is the same as HEAD there instead.
 908          * Traditional format never would have "-m" so it is an
 909          * additional safety measure to check for it.
 910          */
 911
 912         if (!have_message && is_old_style_invocation(argc, argv)) {
 913                 strbuf_addstr(&merge_msg, argv[0]);
 914                 head_arg = argv[1];
 915                 argv += 2;
 916                 argc -= 2;
 917         } else if (head_invalid) {
 918                 struct object *remote_head;
 919                 /*
 920                  * If the merged head is a valid one there is no reason
 921                  * to forbid "git merge" into a branch yet to be born.
 922                  * We do the same for "git pull".
 923                  */
 924                 if (argc != 1)
 925                         die("Can merge only exactly one commit into "
 926                                 "empty head");
 927                 if (squash)
 928                         die("Squash commit into empty head not supported yet");
 929                 if (!allow_fast_forward)
 930                         die("Non-fast-forward commit does not make sense into "
 931                             "an empty head");
 932                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 933                 if (!remote_head)
 934                         die("%s - not something we can merge", argv[0]);
 935                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 936                                 DIE_ON_ERR);
 937                 reset_hard(remote_head->sha1, 0);
 938                 return 0;
 939         } else {
 940                 struct strbuf msg = STRBUF_INIT;
 941
 942                 /* We are invoked directly as the first-class UI. */
 943                 head_arg = "HEAD";
 944
 945                 /*
 946                  * All the rest are the commits being merged;
 947                  * prepare the standard merge summary message to
 948                  * be appended to the given message.  If remote
 949                  * is invalid we will die later in the common
 950                  * codepath so we discard the error in this
 951                  * loop.
 952                  */
 953                 if (!have_message) {
 954                         for (i = 0; i < argc; i++)
 955                                 merge_name(argv[i], &msg);
 956                         fmt_merge_msg(option_log, &msg, &merge_msg);
 957                         if (merge_msg.len)
 958                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
 959                 }
 960         }
 961
 962         if (head_invalid || !argc)
 963                 usage_with_options(builtin_merge_usage,
 964                         builtin_merge_options);
 965
 966         strbuf_addstr(&buf, "merge");
 967         for (i = 0; i < argc; i++)
 968                 strbuf_addf(&buf, " %s", argv[i]);
 969         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 970         strbuf_reset(&buf);
 971
 972         for (i = 0; i < argc; i++) {
 973                 struct object *o;
 974                 struct commit *commit;
 975
 976                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 977                 if (!o)
 978                         die("%s - not something we can merge", argv[i]);
 979                 commit = lookup_commit(o->sha1);
 980                 commit->util = (void *)argv[i];
 981                 remotes = &commit_list_insert(commit, remotes)->next;
 982
 983                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 984                 setenv(buf.buf, argv[i], 1);
 985                 strbuf_reset(&buf);
 986         }
 987
 988         if (!use_strategies) {
 989                 if (!remoteheads->next)
 990                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 991                 else
 992                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 993         }
 994
 995         for (i = 0; i < use_strategies_nr; i++) {
 996                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 997                         allow_fast_forward = 0;
 998                 if (use_strategies[i]->attr & NO_TRIVIAL)
 999                         allow_trivial = 0;
1000         }
1001
1002         if (!remoteheads->next)
1003                 common = get_merge_bases(lookup_commit(head),
1004                                 remoteheads->item, 1);
1005         else {
1006                 struct commit_list *list = remoteheads;
1007                 commit_list_insert(lookup_commit(head), &list);
1008                 common = get_octopus_merge_bases(list);
1009                 free(list);
1010         }
1011
1012         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1013                 DIE_ON_ERR);
1014
1015         if (!common)
1016                 ; /* No common ancestors found. We need a real merge. */
1017         else if (!remoteheads->next && !common->next &&
1018                         common->item == remoteheads->item) {
1019                 /*
1020                  * If head can reach all the merge then we are up to date.
1021                  * but first the most common case of merging one remote.
1022                  */
1023                 finish_up_to_date("Already up-to-date.");
1024                 return 0;
1025         } else if (allow_fast_forward && !remoteheads->next &&
1026                         !common->next &&
1027                         !hashcmp(common->item->object.sha1, head)) {
1028                 /* Again the most common case of merging one remote. */
1029                 struct strbuf msg = STRBUF_INIT;
1030                 struct object *o;
1031                 char hex[41];
1032
1033                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1034
1035                 if (verbosity >= 0)
1036                         printf("Updating %s..%s\n",
1037                                 hex,
1038                                 find_unique_abbrev(remoteheads->item->object.sha1,
1039                                 DEFAULT_ABBREV));
1040                 strbuf_addstr(&msg, "Fast-forward");
1041                 if (have_message)
1042                         strbuf_addstr(&msg,
1043                                 " (no commit created; -m option ignored)");
1044                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1045                         0, NULL, OBJ_COMMIT);
1046                 if (!o)
1047                         return 1;
1048
1049                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1050                         return 1;
1051
1052                 finish(o->sha1, msg.buf);
1053                 drop_save();
1054                 return 0;
1055         } else if (!remoteheads->next && common->next)
1056                 ;
1057                 /*
1058                  * We are not doing octopus and not fast-forward.  Need
1059                  * a real merge.
1060                  */
1061         else if (!remoteheads->next && !common->next && option_commit) {
1062                 /*
1063                  * We are not doing octopus, not fast-forward, and have
1064                  * only one common.
1065                  */
1066                 refresh_cache(REFRESH_QUIET);
1067                 if (allow_trivial && !fast_forward_only) {
1068                         /* See if it is really trivial. */
1069                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1070                         printf("Trying really trivial in-index merge...\n");
1071                         if (!read_tree_trivial(common->item->object.sha1,
1072                                         head, remoteheads->item->object.sha1))
1073                                 return merge_trivial();
1074                         printf("Nope.\n");
1075                 }
1076         } else {
1077                 /*
1078                  * An octopus.  If we can reach all the remote we are up
1079                  * to date.
1080                  */
1081                 int up_to_date = 1;
1082                 struct commit_list *j;
1083
1084                 for (j = remoteheads; j; j = j->next) {
1085                         struct commit_list *common_one;
1086
1087                         /*
1088                          * Here we *have* to calculate the individual
1089                          * merge_bases again, otherwise "git merge HEAD^
1090                          * HEAD^^" would be missed.
1091                          */
1092                         common_one = get_merge_bases(lookup_commit(head),
1093                                 j->item, 1);
1094                         if (hashcmp(common_one->item->object.sha1,
1095                                 j->item->object.sha1)) {
1096                                 up_to_date = 0;
1097                                 break;
1098                         }
1099                 }
1100                 if (up_to_date) {
1101                         finish_up_to_date("Already up-to-date. Yeeah!");
1102                         return 0;
1103                 }
1104         }
1105
1106         if (fast_forward_only)
1107                 die("Not possible to fast-forward, aborting.");
1108
1109         /* We are going to make a new commit. */
1110         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1111
1112         /*
1113          * At this point, we need a real merge.  No matter what strategy
1114          * we use, it would operate on the index, possibly affecting the
1115          * working tree, and when resolved cleanly, have the desired
1116          * tree in the index -- this means that the index must be in
1117          * sync with the head commit.  The strategies are responsible
1118          * to ensure this.
1119          */
1120         if (use_strategies_nr != 1) {
1121                 /*
1122                  * Stash away the local changes so that we can try more
1123                  * than one.
1124                  */
1125                 save_state();
1126         } else {
1127                 memcpy(stash, null_sha1, 20);
1128         }
1129
1130         for (i = 0; i < use_strategies_nr; i++) {
1131                 int ret;
1132                 if (i) {
1133                         printf("Rewinding the tree to pristine...\n");
1134                         restore_state();
1135                 }
1136                 if (use_strategies_nr != 1)
1137                         printf("Trying merge strategy %s...\n",
1138                                 use_strategies[i]->name);
1139                 /*
1140                  * Remember which strategy left the state in the working
1141                  * tree.
1142                  */
1143                 wt_strategy = use_strategies[i]->name;
1144
1145                 ret = try_merge_strategy(use_strategies[i]->name,
1146                         common, head_arg);
1147                 if (!option_commit && !ret) {
1148                         merge_was_ok = 1;
1149                         /*
1150                          * This is necessary here just to avoid writing
1151                          * the tree, but later we will *not* exit with
1152                          * status code 1 because merge_was_ok is set.
1153                          */
1154                         ret = 1;
1155                 }
1156
1157                 if (ret) {
1158                         /*
1159                          * The backend exits with 1 when conflicts are
1160                          * left to be resolved, with 2 when it does not
1161                          * handle the given merge at all.
1162                          */
1163                         if (ret == 1) {
1164                                 int cnt = evaluate_result();
1165
1166                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1167                                         best_strategy = use_strategies[i]->name;
1168                                         best_cnt = cnt;
1169                                 }
1170                         }
1171                         if (merge_was_ok)
1172                                 break;
1173                         else
1174                                 continue;
1175                 }
1176
1177                 /* Automerge succeeded. */
1178                 write_tree_trivial(result_tree);
1179                 automerge_was_ok = 1;
1180                 break;
1181         }
1182
1183         /*
1184          * If we have a resulting tree, that means the strategy module
1185          * auto resolved the merge cleanly.
1186          */
1187         if (automerge_was_ok)
1188                 return finish_automerge(common, result_tree, wt_strategy);
1189
1190         /*
1191          * Pick the result from the best strategy and have the user fix
1192          * it up.
1193          */
1194         if (!best_strategy) {
1195                 restore_state();
1196                 if (use_strategies_nr > 1)
1197                         fprintf(stderr,
1198                                 "No merge strategy handled the merge.\n");
1199                 else
1200                         fprintf(stderr, "Merge with strategy %s failed.\n",
1201                                 use_strategies[0]->name);
1202                 return 2;
1203         } else if (best_strategy == wt_strategy)
1204                 ; /* We already have its result in the working tree. */
1205         else {
1206                 printf("Rewinding the tree to pristine...\n");
1207                 restore_state();
1208                 printf("Using the %s to prepare resolving by hand.\n",
1209                         best_strategy);
1210                 try_merge_strategy(best_strategy, common, head_arg);
1211         }
1212
1213         if (squash)
1214                 finish(NULL, NULL);
1215         else {
1216                 int fd;
1217                 struct commit_list *j;
1218
1219                 for (j = remoteheads; j; j = j->next)
1220                         strbuf_addf(&buf, "%s\n",
1221                                 sha1_to_hex(j->item->object.sha1));
1222                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1223                 if (fd < 0)
1224                         die_errno("Could not open '%s' for writing",
1225                                   git_path("MERGE_HEAD"));
1226                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1227                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1228                 close(fd);
1229                 strbuf_addch(&merge_msg, '\n');
1230                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1231                 if (fd < 0)
1232                         die_errno("Could not open '%s' for writing",
1233                                   git_path("MERGE_MSG"));
1234                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1235                         merge_msg.len)
1236                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1237                 close(fd);
1238                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1239                 if (fd < 0)
1240                         die_errno("Could not open '%s' for writing",
1241                                   git_path("MERGE_MODE"));
1242                 strbuf_reset(&buf);
1243                 if (!allow_fast_forward)
1244                         strbuf_addf(&buf, "no-ff");
1245                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1246                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1247                 close(fd);
1248         }
1249
1250         if (merge_was_ok) {
1251                 fprintf(stderr, "Automatic merge went well; "
1252                         "stopped before committing as requested\n");
1253                 return 0;
1254         } else
1255                 return suggest_conflicts();
1256 }