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 **xopts;
  54 static size_t xopts_nr, xopts_alloc;
  55 static const char *branch;
  56 static int verbosity;
  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\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_x(const struct option *opt,
 152                           const char *arg, int unset)
 153 {
 154         if (unset)
 155                 return 0;
 156
 157         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 158         xopts[xopts_nr++] = xstrdup(arg);
 159         return 0;
 160 }
 161
 162 static int option_parse_n(const struct option *opt,
 163                           const char *arg, int unset)
 164 {
 165         show_diffstat = unset;
 166         return 0;
 167 }
 168
 169 static struct option builtin_merge_options[] = {
 170         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 171                 "do not show a diffstat at the end of the merge",
 172                 PARSE_OPT_NOARG, option_parse_n },
 173         OPT_BOOLEAN(0, "stat", &show_diffstat,
 174                 "show a diffstat at the end of the merge"),
 175         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 176         OPT_BOOLEAN(0, "log", &option_log,
 177                 "add list of one-line log to merge commit message"),
 178         OPT_BOOLEAN(0, "squash", &squash,
 179                 "create a single commit instead of doing a merge"),
 180         OPT_BOOLEAN(0, "commit", &option_commit,
 181                 "perform a commit if the merge succeeds (default)"),
 182         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 183                 "allow fast-forward (default)"),
 184         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 185                 "abort if fast-forward is not possible"),
 186         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 187                 "merge strategy to use", option_parse_strategy),
 188         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 189                 "option for selected merge strategy", option_parse_x),
 190         OPT_CALLBACK('m', "message", &merge_msg, "message",
 191                 "message to be used for the merge commit (if any)",
 192                 option_parse_message),
 193         OPT__VERBOSITY(&verbosity),
 194         OPT_END()
 195 };
 196
 197 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 198 static void drop_save(void)
 199 {
 200         unlink(git_path("MERGE_HEAD"));
 201         unlink(git_path("MERGE_MSG"));
 202         unlink(git_path("MERGE_MODE"));
 203 }
 204
 205 static void save_state(void)
 206 {
 207         int len;
 208         struct child_process cp;
 209         struct strbuf buffer = STRBUF_INIT;
 210         const char *argv[] = {"stash", "create", NULL};
 211
 212         memset(&cp, 0, sizeof(cp));
 213         cp.argv = argv;
 214         cp.out = -1;
 215         cp.git_cmd = 1;
 216
 217         if (start_command(&cp))
 218                 die("could not run stash.");
 219         len = strbuf_read(&buffer, cp.out, 1024);
 220         close(cp.out);
 221
 222         if (finish_command(&cp) || len < 0)
 223                 die("stash failed");
 224         else if (!len)
 225                 return;
 226         strbuf_setlen(&buffer, buffer.len-1);
 227         if (get_sha1(buffer.buf, stash))
 228                 die("not a valid object: %s", buffer.buf);
 229 }
 230
 231 static void reset_hard(unsigned const char *sha1, int verbose)
 232 {
 233         int i = 0;
 234         const char *args[6];
 235
 236         args[i++] = "read-tree";
 237         if (verbose)
 238                 args[i++] = "-v";
 239         args[i++] = "--reset";
 240         args[i++] = "-u";
 241         args[i++] = sha1_to_hex(sha1);
 242         args[i] = NULL;
 243
 244         if (run_command_v_opt(args, RUN_GIT_CMD))
 245                 die("read-tree failed");
 246 }
 247
 248 static void restore_state(void)
 249 {
 250         struct strbuf sb = STRBUF_INIT;
 251         const char *args[] = { "stash", "apply", NULL, NULL };
 252
 253         if (is_null_sha1(stash))
 254                 return;
 255
 256         reset_hard(head, 1);
 257
 258         args[2] = sha1_to_hex(stash);
 259
 260         /*
 261          * It is OK to ignore error here, for example when there was
 262          * nothing to restore.
 263          */
 264         run_command_v_opt(args, RUN_GIT_CMD);
 265
 266         strbuf_release(&sb);
 267         refresh_cache(REFRESH_QUIET);
 268 }
 269
 270 /* This is called when no merge was necessary. */
 271 static void finish_up_to_date(const char *msg)
 272 {
 273         if (verbosity >= 0)
 274                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 275         drop_save();
 276 }
 277
 278 static void squash_message(void)
 279 {
 280         struct rev_info rev;
 281         struct commit *commit;
 282         struct strbuf out = STRBUF_INIT;
 283         struct commit_list *j;
 284         int fd;
 285         struct pretty_print_context ctx = {0};
 286
 287         printf("Squash commit -- not updating HEAD\n");
 288         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 289         if (fd < 0)
 290                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 291
 292         init_revisions(&rev, NULL);
 293         rev.ignore_merges = 1;
 294         rev.commit_format = CMIT_FMT_MEDIUM;
 295
 296         commit = lookup_commit(head);
 297         commit->object.flags |= UNINTERESTING;
 298         add_pending_object(&rev, &commit->object, NULL);
 299
 300         for (j = remoteheads; j; j = j->next)
 301                 add_pending_object(&rev, &j->item->object, NULL);
 302
 303         setup_revisions(0, NULL, &rev, NULL);
 304         if (prepare_revision_walk(&rev))
 305                 die("revision walk setup failed");
 306
 307         ctx.abbrev = rev.abbrev;
 308         ctx.date_mode = rev.date_mode;
 309
 310         strbuf_addstr(&out, "Squashed commit of the following:\n");
 311         while ((commit = get_revision(&rev)) != NULL) {
 312                 strbuf_addch(&out, '\n');
 313                 strbuf_addf(&out, "commit %s\n",
 314                         sha1_to_hex(commit->object.sha1));
 315                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 316         }
 317         if (write(fd, out.buf, out.len) < 0)
 318                 die_errno("Writing SQUASH_MSG");
 319         if (close(fd))
 320                 die_errno("Finishing SQUASH_MSG");
 321         strbuf_release(&out);
 322 }
 323
 324 static void finish(const unsigned char *new_head, const char *msg)
 325 {
 326         struct strbuf reflog_message = STRBUF_INIT;
 327
 328         if (!msg)
 329                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 330         else {
 331                 if (verbosity >= 0)
 332                         printf("%s\n", msg);
 333                 strbuf_addf(&reflog_message, "%s: %s",
 334                         getenv("GIT_REFLOG_ACTION"), msg);
 335         }
 336         if (squash) {
 337                 squash_message();
 338         } else {
 339                 if (verbosity >= 0 && !merge_msg.len)
 340                         printf("No merge message -- not updating HEAD\n");
 341                 else {
 342                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 343                         update_ref(reflog_message.buf, "HEAD",
 344                                 new_head, head, 0,
 345                                 DIE_ON_ERR);
 346                         /*
 347                          * We ignore errors in 'gc --auto', since the
 348                          * user should see them.
 349                          */
 350                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 351                 }
 352         }
 353         if (new_head && show_diffstat) {
 354                 struct diff_options opts;
 355                 diff_setup(&opts);
 356                 opts.output_format |=
 357                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 358                 opts.detect_rename = DIFF_DETECT_RENAME;
 359                 if (diff_use_color_default > 0)
 360                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 361                 if (diff_setup_done(&opts) < 0)
 362                         die("diff_setup_done failed");
 363                 diff_tree_sha1(head, new_head, "", &opts);
 364                 diffcore_std(&opts);
 365                 diff_flush(&opts);
 366         }
 367
 368         /* Run a post-merge hook */
 369         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 370
 371         strbuf_release(&reflog_message);
 372 }
 373
 374 /* Get the name for the merge commit's message. */
 375 static void merge_name(const char *remote, struct strbuf *msg)
 376 {
 377         struct object *remote_head;
 378         unsigned char branch_head[20], buf_sha[20];
 379         struct strbuf buf = STRBUF_INIT;
 380         struct strbuf bname = STRBUF_INIT;
 381         const char *ptr;
 382         char *found_ref;
 383         int len, early;
 384
 385         strbuf_branchname(&bname, remote);
 386         remote = bname.buf;
 387
 388         memset(branch_head, 0, sizeof(branch_head));
 389         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 390         if (!remote_head)
 391                 die("'%s' does not point to a commit", remote);
 392
 393         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 394                 if (!prefixcmp(found_ref, "refs/heads/")) {
 395                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 396                                     sha1_to_hex(branch_head), remote);
 397                         goto cleanup;
 398                 }
 399                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 400                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 401                                     sha1_to_hex(branch_head), remote);
 402                         goto cleanup;
 403                 }
 404         }
 405
 406         /* See if remote matches <name>^^^.. or <name>~<number> */
 407         for (len = 0, ptr = remote + strlen(remote);
 408              remote < ptr && ptr[-1] == '^';
 409              ptr--)
 410                 len++;
 411         if (len)
 412                 early = 1;
 413         else {
 414                 early = 0;
 415                 ptr = strrchr(remote, '~');
 416                 if (ptr) {
 417                         int seen_nonzero = 0;
 418
 419                         len++; /* count ~ */
 420                         while (*++ptr && isdigit(*ptr)) {
 421                                 seen_nonzero |= (*ptr != '0');
 422                                 len++;
 423                         }
 424                         if (*ptr)
 425                                 len = 0; /* not ...~<number> */
 426                         else if (seen_nonzero)
 427                                 early = 1;
 428                         else if (len == 1)
 429                                 early = 1; /* "name~" is "name~1"! */
 430                 }
 431         }
 432         if (len) {
 433                 struct strbuf truname = STRBUF_INIT;
 434                 strbuf_addstr(&truname, "refs/heads/");
 435                 strbuf_addstr(&truname, remote);
 436                 strbuf_setlen(&truname, truname.len - len);
 437                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 438                         strbuf_addf(msg,
 439                                     "%s\t\tbranch '%s'%s of .\n",
 440                                     sha1_to_hex(remote_head->sha1),
 441                                     truname.buf + 11,
 442                                     (early ? " (early part)" : ""));
 443                         strbuf_release(&truname);
 444                         goto cleanup;
 445                 }
 446         }
 447
 448         if (!strcmp(remote, "FETCH_HEAD") &&
 449                         !access(git_path("FETCH_HEAD"), R_OK)) {
 450                 FILE *fp;
 451                 struct strbuf line = STRBUF_INIT;
 452                 char *ptr;
 453
 454                 fp = fopen(git_path("FETCH_HEAD"), "r");
 455                 if (!fp)
 456                         die_errno("could not open '%s' for reading",
 457                                   git_path("FETCH_HEAD"));
 458                 strbuf_getline(&line, fp, '\n');
 459                 fclose(fp);
 460                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 461                 if (ptr)
 462                         strbuf_remove(&line, ptr-line.buf+1, 13);
 463                 strbuf_addbuf(msg, &line);
 464                 strbuf_release(&line);
 465                 goto cleanup;
 466         }
 467         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 468                 sha1_to_hex(remote_head->sha1), remote);
 469 cleanup:
 470         strbuf_release(&buf);
 471         strbuf_release(&bname);
 472 }
 473
 474 static int git_merge_config(const char *k, const char *v, void *cb)
 475 {
 476         if (branch && !prefixcmp(k, "branch.") &&
 477                 !prefixcmp(k + 7, branch) &&
 478                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 479                 const char **argv;
 480                 int argc;
 481                 char *buf;
 482
 483                 buf = xstrdup(v);
 484                 argc = split_cmdline(buf, &argv);
 485                 if (argc < 0)
 486                         die("Bad branch.%s.mergeoptions string", branch);
 487                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 488                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 489                 argc++;
 490                 parse_options(argc, argv, NULL, builtin_merge_options,
 491                               builtin_merge_usage, 0);
 492                 free(buf);
 493         }
 494
 495         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 496                 show_diffstat = git_config_bool(k, v);
 497         else if (!strcmp(k, "pull.twohead"))
 498                 return git_config_string(&pull_twohead, k, v);
 499         else if (!strcmp(k, "pull.octopus"))
 500                 return git_config_string(&pull_octopus, k, v);
 501         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 502                 option_log = git_config_bool(k, v);
 503         return git_diff_ui_config(k, v, cb);
 504 }
 505
 506 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 507                              unsigned char *one)
 508 {
 509         int i, nr_trees = 0;
 510         struct tree *trees[MAX_UNPACK_TREES];
 511         struct tree_desc t[MAX_UNPACK_TREES];
 512         struct unpack_trees_options opts;
 513
 514         memset(&opts, 0, sizeof(opts));
 515         opts.head_idx = 2;
 516         opts.src_index = &the_index;
 517         opts.dst_index = &the_index;
 518         opts.update = 1;
 519         opts.verbose_update = 1;
 520         opts.trivial_merges_only = 1;
 521         opts.merge = 1;
 522         trees[nr_trees] = parse_tree_indirect(common);
 523         if (!trees[nr_trees++])
 524                 return -1;
 525         trees[nr_trees] = parse_tree_indirect(head);
 526         if (!trees[nr_trees++])
 527                 return -1;
 528         trees[nr_trees] = parse_tree_indirect(one);
 529         if (!trees[nr_trees++])
 530                 return -1;
 531         opts.fn = threeway_merge;
 532         cache_tree_free(&active_cache_tree);
 533         for (i = 0; i < nr_trees; i++) {
 534                 parse_tree(trees[i]);
 535                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 536         }
 537         if (unpack_trees(nr_trees, t, &opts))
 538                 return -1;
 539         return 0;
 540 }
 541
 542 static void write_tree_trivial(unsigned char *sha1)
 543 {
 544         if (write_cache_as_tree(sha1, 0, NULL))
 545                 die("git write-tree failed to write a tree");
 546 }
 547
 548 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 549                               const char *head_arg)
 550 {
 551         const char **args;
 552         int i = 0, x = 0, ret;
 553         struct commit_list *j;
 554         struct strbuf buf = STRBUF_INIT;
 555         int index_fd;
 556         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 557
 558         index_fd = hold_locked_index(lock, 1);
 559         refresh_cache(REFRESH_QUIET);
 560         if (active_cache_changed &&
 561                         (write_cache(index_fd, active_cache, active_nr) ||
 562                          commit_locked_index(lock)))
 563                 return error("Unable to write index.");
 564         rollback_lock_file(lock);
 565
 566         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 567                 int clean;
 568                 struct commit *result;
 569                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 570                 int index_fd;
 571                 struct commit_list *reversed = NULL;
 572                 struct merge_options o;
 573
 574                 if (remoteheads->next) {
 575                         error("Not handling anything other than two heads merge.");
 576                         return 2;
 577                 }
 578
 579                 init_merge_options(&o);
 580                 if (!strcmp(strategy, "subtree"))
 581                         o.recursive_variant = MERGE_RECURSIVE_SUBTREE;
 582
 583                 for (x = 0; x < xopts_nr; x++) {
 584                         if (!strcmp(xopts[x], "ours"))
 585                                 o.recursive_variant = MERGE_RECURSIVE_OURS;
 586                         else if (!strcmp(xopts[x], "theirs"))
 587                                 o.recursive_variant = MERGE_RECURSIVE_THEIRS;
 588                         else if (!strcmp(xopts[x], "subtree"))
 589                                 o.recursive_variant = MERGE_RECURSIVE_SUBTREE;
 590                         else
 591                                 die("Unknown option for merge-recursive: -X%s", xopts[x]);
 592                 }
 593
 594                 o.branch1 = head_arg;
 595                 o.branch2 = remoteheads->item->util;
 596
 597                 for (j = common; j; j = j->next)
 598                         commit_list_insert(j->item, &reversed);
 599
 600                 index_fd = hold_locked_index(lock, 1);
 601                 clean = merge_recursive(&o, lookup_commit(head),
 602                                 remoteheads->item, reversed, &result);
 603                 if (active_cache_changed &&
 604                                 (write_cache(index_fd, active_cache, active_nr) ||
 605                                  commit_locked_index(lock)))
 606                         die ("unable to write %s", get_index_file());
 607                 rollback_lock_file(lock);
 608                 return clean ? 0 : 1;
 609         } else {
 610                 args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 611                                         commit_list_count(remoteheads)) * sizeof(char *));
 612                 strbuf_addf(&buf, "merge-%s", strategy);
 613                 args[i++] = buf.buf;
 614                 for (x = 0; x < xopts_nr; x++) {
 615                         char *s = xmalloc(strlen(xopts[x])+2+1);
 616                         strcpy(s, "--");
 617                         strcpy(s+2, xopts[x]);
 618                         args[i++] = s;
 619                 }
 620                 for (j = common; j; j = j->next)
 621                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 622                 args[i++] = "--";
 623                 args[i++] = head_arg;
 624                 for (j = remoteheads; j; j = j->next)
 625                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 626                 args[i] = NULL;
 627                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 628                 strbuf_release(&buf);
 629                 i = 1;
 630                 for (x = 0; x < xopts_nr; x++)
 631                         free((void *)args[i++]);
 632                 for (j = common; j; j = j->next)
 633                         free((void *)args[i++]);
 634                 i += 2;
 635                 for (j = remoteheads; j; j = j->next)
 636                         free((void *)args[i++]);
 637                 free(args);
 638                 discard_cache();
 639                 if (read_cache() < 0)
 640                         die("failed to read the cache");
 641                 return ret;
 642         }
 643 }
 644
 645 static void count_diff_files(struct diff_queue_struct *q,
 646                              struct diff_options *opt, void *data)
 647 {
 648         int *count = data;
 649
 650         (*count) += q->nr;
 651 }
 652
 653 static int count_unmerged_entries(void)
 654 {
 655         const struct index_state *state = &the_index;
 656         int i, ret = 0;
 657
 658         for (i = 0; i < state->cache_nr; i++)
 659                 if (ce_stage(state->cache[i]))
 660                         ret++;
 661
 662         return ret;
 663 }
 664
 665 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 666 {
 667         struct tree *trees[MAX_UNPACK_TREES];
 668         struct unpack_trees_options opts;
 669         struct tree_desc t[MAX_UNPACK_TREES];
 670         int i, fd, nr_trees = 0;
 671         struct dir_struct dir;
 672         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 673
 674         refresh_cache(REFRESH_QUIET);
 675
 676         fd = hold_locked_index(lock_file, 1);
 677
 678         memset(&trees, 0, sizeof(trees));
 679         memset(&opts, 0, sizeof(opts));
 680         memset(&t, 0, sizeof(t));
 681         memset(&dir, 0, sizeof(dir));
 682         dir.flags |= DIR_SHOW_IGNORED;
 683         dir.exclude_per_dir = ".gitignore";
 684         opts.dir = &dir;
 685
 686         opts.head_idx = 1;
 687         opts.src_index = &the_index;
 688         opts.dst_index = &the_index;
 689         opts.update = 1;
 690         opts.verbose_update = 1;
 691         opts.merge = 1;
 692         opts.fn = twoway_merge;
 693
 694         trees[nr_trees] = parse_tree_indirect(head);
 695         if (!trees[nr_trees++])
 696                 return -1;
 697         trees[nr_trees] = parse_tree_indirect(remote);
 698         if (!trees[nr_trees++])
 699                 return -1;
 700         for (i = 0; i < nr_trees; i++) {
 701                 parse_tree(trees[i]);
 702                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 703         }
 704         if (unpack_trees(nr_trees, t, &opts))
 705                 return -1;
 706         if (write_cache(fd, active_cache, active_nr) ||
 707                 commit_locked_index(lock_file))
 708                 die("unable to write new index file");
 709         return 0;
 710 }
 711
 712 static void split_merge_strategies(const char *string, struct strategy **list,
 713                                    int *nr, int *alloc)
 714 {
 715         char *p, *q, *buf;
 716
 717         if (!string)
 718                 return;
 719
 720         buf = xstrdup(string);
 721         q = buf;
 722         for (;;) {
 723                 p = strchr(q, ' ');
 724                 if (!p) {
 725                         ALLOC_GROW(*list, *nr + 1, *alloc);
 726                         (*list)[(*nr)++].name = xstrdup(q);
 727                         free(buf);
 728                         return;
 729                 } else {
 730                         *p = '\0';
 731                         ALLOC_GROW(*list, *nr + 1, *alloc);
 732                         (*list)[(*nr)++].name = xstrdup(q);
 733                         q = ++p;
 734                 }
 735         }
 736 }
 737
 738 static void add_strategies(const char *string, unsigned attr)
 739 {
 740         struct strategy *list = NULL;
 741         int list_alloc = 0, list_nr = 0, i;
 742
 743         memset(&list, 0, sizeof(list));
 744         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 745         if (list) {
 746                 for (i = 0; i < list_nr; i++)
 747                         append_strategy(get_strategy(list[i].name));
 748                 return;
 749         }
 750         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 751                 if (all_strategy[i].attr & attr)
 752                         append_strategy(&all_strategy[i]);
 753
 754 }
 755
 756 static int merge_trivial(void)
 757 {
 758         unsigned char result_tree[20], result_commit[20];
 759         struct commit_list *parent = xmalloc(sizeof(*parent));
 760
 761         write_tree_trivial(result_tree);
 762         printf("Wonderful.\n");
 763         parent->item = lookup_commit(head);
 764         parent->next = xmalloc(sizeof(*parent->next));
 765         parent->next->item = remoteheads->item;
 766         parent->next->next = NULL;
 767         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 768         finish(result_commit, "In-index merge");
 769         drop_save();
 770         return 0;
 771 }
 772
 773 static int finish_automerge(struct commit_list *common,
 774                             unsigned char *result_tree,
 775                             const char *wt_strategy)
 776 {
 777         struct commit_list *parents = NULL, *j;
 778         struct strbuf buf = STRBUF_INIT;
 779         unsigned char result_commit[20];
 780
 781         free_commit_list(common);
 782         if (allow_fast_forward) {
 783                 parents = remoteheads;
 784                 commit_list_insert(lookup_commit(head), &parents);
 785                 parents = reduce_heads(parents);
 786         } else {
 787                 struct commit_list **pptr = &parents;
 788
 789                 pptr = &commit_list_insert(lookup_commit(head),
 790                                 pptr)->next;
 791                 for (j = remoteheads; j; j = j->next)
 792                         pptr = &commit_list_insert(j->item, pptr)->next;
 793         }
 794         free_commit_list(remoteheads);
 795         strbuf_addch(&merge_msg, '\n');
 796         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 797         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 798         finish(result_commit, buf.buf);
 799         strbuf_release(&buf);
 800         drop_save();
 801         return 0;
 802 }
 803
 804 static int suggest_conflicts(void)
 805 {
 806         FILE *fp;
 807         int pos;
 808
 809         fp = fopen(git_path("MERGE_MSG"), "a");
 810         if (!fp)
 811                 die_errno("Could not open '%s' for writing",
 812                           git_path("MERGE_MSG"));
 813         fprintf(fp, "\nConflicts:\n");
 814         for (pos = 0; pos < active_nr; pos++) {
 815                 struct cache_entry *ce = active_cache[pos];
 816
 817                 if (ce_stage(ce)) {
 818                         fprintf(fp, "\t%s\n", ce->name);
 819                         while (pos + 1 < active_nr &&
 820                                         !strcmp(ce->name,
 821                                                 active_cache[pos + 1]->name))
 822                                 pos++;
 823                 }
 824         }
 825         fclose(fp);
 826         rerere();
 827         printf("Automatic merge failed; "
 828                         "fix conflicts and then commit the result.\n");
 829         return 1;
 830 }
 831
 832 static struct commit *is_old_style_invocation(int argc, const char **argv)
 833 {
 834         struct commit *second_token = NULL;
 835         if (argc > 1) {
 836                 unsigned char second_sha1[20];
 837
 838                 if (get_sha1(argv[1], second_sha1))
 839                         return NULL;
 840                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 841                 if (!second_token)
 842                         die("'%s' is not a commit", argv[1]);
 843                 if (hashcmp(second_token->object.sha1, head))
 844                         return NULL;
 845         }
 846         return second_token;
 847 }
 848
 849 static int evaluate_result(void)
 850 {
 851         int cnt = 0;
 852         struct rev_info rev;
 853
 854         /* Check how many files differ. */
 855         init_revisions(&rev, "");
 856         setup_revisions(0, NULL, &rev, NULL);
 857         rev.diffopt.output_format |=
 858                 DIFF_FORMAT_CALLBACK;
 859         rev.diffopt.format_callback = count_diff_files;
 860         rev.diffopt.format_callback_data = &cnt;
 861         run_diff_files(&rev, 0);
 862
 863         /*
 864          * Check how many unmerged entries are
 865          * there.
 866          */
 867         cnt += count_unmerged_entries();
 868
 869         return cnt;
 870 }
 871
 872 int cmd_merge(int argc, const char **argv, const char *prefix)
 873 {
 874         unsigned char result_tree[20];
 875         struct strbuf buf = STRBUF_INIT;
 876         const char *head_arg;
 877         int flag, head_invalid = 0, i;
 878         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 879         struct commit_list *common = NULL;
 880         const char *best_strategy = NULL, *wt_strategy = NULL;
 881         struct commit_list **remotes = &remoteheads;
 882
 883         if (file_exists(git_path("MERGE_HEAD")))
 884                 die("You have not concluded your merge. (MERGE_HEAD exists)");
 885         if (read_cache_unmerged())
 886                 die("You are in the middle of a conflicted merge."
 887                                 " (index unmerged)");
 888
 889         /*
 890          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 891          * current branch.
 892          */
 893         branch = resolve_ref("HEAD", head, 0, &flag);
 894         if (branch && !prefixcmp(branch, "refs/heads/"))
 895                 branch += 11;
 896         if (is_null_sha1(head))
 897                 head_invalid = 1;
 898
 899         git_config(git_merge_config, NULL);
 900
 901         /* for color.ui */
 902         if (diff_use_color_default == -1)
 903                 diff_use_color_default = git_use_color_default;
 904
 905         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 906                         builtin_merge_usage, 0);
 907         if (verbosity < 0)
 908                 show_diffstat = 0;
 909
 910         if (squash) {
 911                 if (!allow_fast_forward)
 912                         die("You cannot combine --squash with --no-ff.");
 913                 option_commit = 0;
 914         }
 915
 916         if (!allow_fast_forward && fast_forward_only)
 917                 die("You cannot combine --no-ff with --ff-only.");
 918
 919         if (!argc)
 920                 usage_with_options(builtin_merge_usage,
 921                         builtin_merge_options);
 922
 923         /*
 924          * This could be traditional "merge <msg> HEAD <commit>..."  and
 925          * the way we can tell it is to see if the second token is HEAD,
 926          * but some people might have misused the interface and used a
 927          * committish that is the same as HEAD there instead.
 928          * Traditional format never would have "-m" so it is an
 929          * additional safety measure to check for it.
 930          */
 931
 932         if (!have_message && is_old_style_invocation(argc, argv)) {
 933                 strbuf_addstr(&merge_msg, argv[0]);
 934                 head_arg = argv[1];
 935                 argv += 2;
 936                 argc -= 2;
 937         } else if (head_invalid) {
 938                 struct object *remote_head;
 939                 /*
 940                  * If the merged head is a valid one there is no reason
 941                  * to forbid "git merge" into a branch yet to be born.
 942                  * We do the same for "git pull".
 943                  */
 944                 if (argc != 1)
 945                         die("Can merge only exactly one commit into "
 946                                 "empty head");
 947                 if (squash)
 948                         die("Squash commit into empty head not supported yet");
 949                 if (!allow_fast_forward)
 950                         die("Non-fast-forward commit does not make sense into "
 951                             "an empty head");
 952                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 953                 if (!remote_head)
 954                         die("%s - not something we can merge", argv[0]);
 955                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 956                                 DIE_ON_ERR);
 957                 reset_hard(remote_head->sha1, 0);
 958                 return 0;
 959         } else {
 960                 struct strbuf msg = STRBUF_INIT;
 961
 962                 /* We are invoked directly as the first-class UI. */
 963                 head_arg = "HEAD";
 964
 965                 /*
 966                  * All the rest are the commits being merged;
 967                  * prepare the standard merge summary message to
 968                  * be appended to the given message.  If remote
 969                  * is invalid we will die later in the common
 970                  * codepath so we discard the error in this
 971                  * loop.
 972                  */
 973                 for (i = 0; i < argc; i++)
 974                         merge_name(argv[i], &msg);
 975                 fmt_merge_msg(option_log, &msg, &merge_msg);
 976                 if (merge_msg.len)
 977                         strbuf_setlen(&merge_msg, merge_msg.len-1);
 978         }
 979
 980         if (head_invalid || !argc)
 981                 usage_with_options(builtin_merge_usage,
 982                         builtin_merge_options);
 983
 984         strbuf_addstr(&buf, "merge");
 985         for (i = 0; i < argc; i++)
 986                 strbuf_addf(&buf, " %s", argv[i]);
 987         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 988         strbuf_reset(&buf);
 989
 990         for (i = 0; i < argc; i++) {
 991                 struct object *o;
 992                 struct commit *commit;
 993
 994                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 995                 if (!o)
 996                         die("%s - not something we can merge", argv[i]);
 997                 commit = lookup_commit(o->sha1);
 998                 commit->util = (void *)argv[i];
 999                 remotes = &commit_list_insert(commit, remotes)->next;
1000
1001                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1002                 setenv(buf.buf, argv[i], 1);
1003                 strbuf_reset(&buf);
1004         }
1005
1006         if (!use_strategies) {
1007                 if (!remoteheads->next)
1008                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1009                 else
1010                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1011         }
1012
1013         for (i = 0; i < use_strategies_nr; i++) {
1014                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1015                         allow_fast_forward = 0;
1016                 if (use_strategies[i]->attr & NO_TRIVIAL)
1017                         allow_trivial = 0;
1018         }
1019
1020         if (!remoteheads->next)
1021                 common = get_merge_bases(lookup_commit(head),
1022                                 remoteheads->item, 1);
1023         else {
1024                 struct commit_list *list = remoteheads;
1025                 commit_list_insert(lookup_commit(head), &list);
1026                 common = get_octopus_merge_bases(list);
1027                 free(list);
1028         }
1029
1030         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1031                 DIE_ON_ERR);
1032
1033         if (!common)
1034                 ; /* No common ancestors found. We need a real merge. */
1035         else if (!remoteheads->next && !common->next &&
1036                         common->item == remoteheads->item) {
1037                 /*
1038                  * If head can reach all the merge then we are up to date.
1039                  * but first the most common case of merging one remote.
1040                  */
1041                 finish_up_to_date("Already up-to-date.");
1042                 return 0;
1043         } else if (allow_fast_forward && !remoteheads->next &&
1044                         !common->next &&
1045                         !hashcmp(common->item->object.sha1, head)) {
1046                 /* Again the most common case of merging one remote. */
1047                 struct strbuf msg = STRBUF_INIT;
1048                 struct object *o;
1049                 char hex[41];
1050
1051                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1052
1053                 if (verbosity >= 0)
1054                         printf("Updating %s..%s\n",
1055                                 hex,
1056                                 find_unique_abbrev(remoteheads->item->object.sha1,
1057                                 DEFAULT_ABBREV));
1058                 strbuf_addstr(&msg, "Fast-forward");
1059                 if (have_message)
1060                         strbuf_addstr(&msg,
1061                                 " (no commit created; -m option ignored)");
1062                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1063                         0, NULL, OBJ_COMMIT);
1064                 if (!o)
1065                         return 1;
1066
1067                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1068                         return 1;
1069
1070                 finish(o->sha1, msg.buf);
1071                 drop_save();
1072                 return 0;
1073         } else if (!remoteheads->next && common->next)
1074                 ;
1075                 /*
1076                  * We are not doing octopus and not fast-forward.  Need
1077                  * a real merge.
1078                  */
1079         else if (!remoteheads->next && !common->next && option_commit) {
1080                 /*
1081                  * We are not doing octopus, not fast-forward, and have
1082                  * only one common.
1083                  */
1084                 refresh_cache(REFRESH_QUIET);
1085                 if (allow_trivial && !fast_forward_only) {
1086                         /* See if it is really trivial. */
1087                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1088                         printf("Trying really trivial in-index merge...\n");
1089                         if (!read_tree_trivial(common->item->object.sha1,
1090                                         head, remoteheads->item->object.sha1))
1091                                 return merge_trivial();
1092                         printf("Nope.\n");
1093                 }
1094         } else {
1095                 /*
1096                  * An octopus.  If we can reach all the remote we are up
1097                  * to date.
1098                  */
1099                 int up_to_date = 1;
1100                 struct commit_list *j;
1101
1102                 for (j = remoteheads; j; j = j->next) {
1103                         struct commit_list *common_one;
1104
1105                         /*
1106                          * Here we *have* to calculate the individual
1107                          * merge_bases again, otherwise "git merge HEAD^
1108                          * HEAD^^" would be missed.
1109                          */
1110                         common_one = get_merge_bases(lookup_commit(head),
1111                                 j->item, 1);
1112                         if (hashcmp(common_one->item->object.sha1,
1113                                 j->item->object.sha1)) {
1114                                 up_to_date = 0;
1115                                 break;
1116                         }
1117                 }
1118                 if (up_to_date) {
1119                         finish_up_to_date("Already up-to-date. Yeeah!");
1120                         return 0;
1121                 }
1122         }
1123
1124         if (fast_forward_only)
1125                 die("Not possible to fast-forward, aborting.");
1126
1127         /* We are going to make a new commit. */
1128         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1129
1130         /*
1131          * At this point, we need a real merge.  No matter what strategy
1132          * we use, it would operate on the index, possibly affecting the
1133          * working tree, and when resolved cleanly, have the desired
1134          * tree in the index -- this means that the index must be in
1135          * sync with the head commit.  The strategies are responsible
1136          * to ensure this.
1137          */
1138         if (use_strategies_nr != 1) {
1139                 /*
1140                  * Stash away the local changes so that we can try more
1141                  * than one.
1142                  */
1143                 save_state();
1144         } else {
1145                 memcpy(stash, null_sha1, 20);
1146         }
1147
1148         for (i = 0; i < use_strategies_nr; i++) {
1149                 int ret;
1150                 if (i) {
1151                         printf("Rewinding the tree to pristine...\n");
1152                         restore_state();
1153                 }
1154                 if (use_strategies_nr != 1)
1155                         printf("Trying merge strategy %s...\n",
1156                                 use_strategies[i]->name);
1157                 /*
1158                  * Remember which strategy left the state in the working
1159                  * tree.
1160                  */
1161                 wt_strategy = use_strategies[i]->name;
1162
1163                 ret = try_merge_strategy(use_strategies[i]->name,
1164                         common, head_arg);
1165                 if (!option_commit && !ret) {
1166                         merge_was_ok = 1;
1167                         /*
1168                          * This is necessary here just to avoid writing
1169                          * the tree, but later we will *not* exit with
1170                          * status code 1 because merge_was_ok is set.
1171                          */
1172                         ret = 1;
1173                 }
1174
1175                 if (ret) {
1176                         /*
1177                          * The backend exits with 1 when conflicts are
1178                          * left to be resolved, with 2 when it does not
1179                          * handle the given merge at all.
1180                          */
1181                         if (ret == 1) {
1182                                 int cnt = evaluate_result();
1183
1184                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1185                                         best_strategy = use_strategies[i]->name;
1186                                         best_cnt = cnt;
1187                                 }
1188                         }
1189                         if (merge_was_ok)
1190                                 break;
1191                         else
1192                                 continue;
1193                 }
1194
1195                 /* Automerge succeeded. */
1196                 write_tree_trivial(result_tree);
1197                 automerge_was_ok = 1;
1198                 break;
1199         }
1200
1201         /*
1202          * If we have a resulting tree, that means the strategy module
1203          * auto resolved the merge cleanly.
1204          */
1205         if (automerge_was_ok)
1206                 return finish_automerge(common, result_tree, wt_strategy);
1207
1208         /*
1209          * Pick the result from the best strategy and have the user fix
1210          * it up.
1211          */
1212         if (!best_strategy) {
1213                 restore_state();
1214                 if (use_strategies_nr > 1)
1215                         fprintf(stderr,
1216                                 "No merge strategy handled the merge.\n");
1217                 else
1218                         fprintf(stderr, "Merge with strategy %s failed.\n",
1219                                 use_strategies[0]->name);
1220                 return 2;
1221         } else if (best_strategy == wt_strategy)
1222                 ; /* We already have its result in the working tree. */
1223         else {
1224                 printf("Rewinding the tree to pristine...\n");
1225                 restore_state();
1226                 printf("Using the %s to prepare resolving by hand.\n",
1227                         best_strategy);
1228                 try_merge_strategy(best_strategy, common, head_arg);
1229         }
1230
1231         if (squash)
1232                 finish(NULL, NULL);
1233         else {
1234                 int fd;
1235                 struct commit_list *j;
1236
1237                 for (j = remoteheads; j; j = j->next)
1238                         strbuf_addf(&buf, "%s\n",
1239                                 sha1_to_hex(j->item->object.sha1));
1240                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1241                 if (fd < 0)
1242                         die_errno("Could not open '%s' for writing",
1243                                   git_path("MERGE_HEAD"));
1244                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1245                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1246                 close(fd);
1247                 strbuf_addch(&merge_msg, '\n');
1248                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1249                 if (fd < 0)
1250                         die_errno("Could not open '%s' for writing",
1251                                   git_path("MERGE_MSG"));
1252                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1253                         merge_msg.len)
1254                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1255                 close(fd);
1256                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1257                 if (fd < 0)
1258                         die_errno("Could not open '%s' for writing",
1259                                   git_path("MERGE_MODE"));
1260                 strbuf_reset(&buf);
1261                 if (!allow_fast_forward)
1262                         strbuf_addf(&buf, "no-ff");
1263                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1264                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1265                 close(fd);
1266         }
1267
1268         if (merge_was_ok) {
1269                 fprintf(stderr, "Automatic merge went well; "
1270                         "stopped before committing as requested\n");
1271                 return 0;
1272         } else
1273                 return suggest_conflicts();
1274 }