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