git.oblomov.eu Git - git/blob - builtin-merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28
  29 #define DEFAULT_TWOHEAD (1<<0)
  30 #define DEFAULT_OCTOPUS (1<<1)
  31 #define NO_FAST_FORWARD (1<<2)
  32 #define NO_TRIVIAL      (1<<3)
  33
  34 struct strategy {
  35         const char *name;
  36         unsigned attr;
  37 };
  38
  39 static const char * const builtin_merge_usage[] = {
  40         "git merge [options] <remote>...",
  41         "git merge [options] <msg> HEAD <remote>",
  42         NULL
  43 };
  44
  45 static int show_diffstat = 1, option_log, squash;
  46 static int option_commit = 1, allow_fast_forward = 1;
  47 static int fast_forward_only;
  48 static int allow_trivial = 1, have_message;
  49 static struct strbuf merge_msg;
  50 static struct commit_list *remoteheads;
  51 static unsigned char head[20], stash[20];
  52 static struct strategy **use_strategies;
  53 static size_t use_strategies_nr, use_strategies_alloc;
  54 static const char *branch;
  55 static int verbosity;
  56
  57 static struct strategy all_strategy[] = {
  58         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  59         { "octopus",    DEFAULT_OCTOPUS },
  60         { "resolve",    0 },
  61         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  62         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  63 };
  64
  65 static const char *pull_twohead, *pull_octopus;
  66
  67 static int option_parse_message(const struct option *opt,
  68                                 const char *arg, int unset)
  69 {
  70         struct strbuf *buf = opt->value;
  71
  72         if (unset)
  73                 strbuf_setlen(buf, 0);
  74         else if (arg) {
  75                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  76                 have_message = 1;
  77         } else
  78                 return error("switch `m' requires a value");
  79         return 0;
  80 }
  81
  82 static struct strategy *get_strategy(const char *name)
  83 {
  84         int i;
  85         struct strategy *ret;
  86         static struct cmdnames main_cmds, other_cmds;
  87         static int loaded;
  88
  89         if (!name)
  90                 return NULL;
  91
  92         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
  93                 if (!strcmp(name, all_strategy[i].name))
  94                         return &all_strategy[i];
  95
  96         if (!loaded) {
  97                 struct cmdnames not_strategies;
  98                 loaded = 1;
  99
 100                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 101                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 102                 for (i = 0; i < main_cmds.cnt; i++) {
 103                         int j, found = 0;
 104                         struct cmdname *ent = main_cmds.names[i];
 105                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 106                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 107                                                 && !all_strategy[j].name[ent->len])
 108                                         found = 1;
 109                         if (!found)
 110                                 add_cmdname(&not_strategies, ent->name, ent->len);
 111                 }
 112                 exclude_cmds(&main_cmds, &not_strategies);
 113         }
 114         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 115                 fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
 116                 fprintf(stderr, "Available strategies are:");
 117                 for (i = 0; i < main_cmds.cnt; i++)
 118                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 119                 fprintf(stderr, ".\n");
 120                 if (other_cmds.cnt) {
 121                         fprintf(stderr, "Available custom strategies are:");
 122                         for (i = 0; i < other_cmds.cnt; i++)
 123                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 124                         fprintf(stderr, ".\n");
 125                 }
 126                 exit(1);
 127         }
 128
 129         ret = xcalloc(1, sizeof(struct strategy));
 130         ret->name = xstrdup(name);
 131         return ret;
 132 }
 133
 134 static void append_strategy(struct strategy *s)
 135 {
 136         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 137         use_strategies[use_strategies_nr++] = s;
 138 }
 139
 140 static int option_parse_strategy(const struct option *opt,
 141                                  const char *name, int unset)
 142 {
 143         if (unset)
 144                 return 0;
 145
 146         append_strategy(get_strategy(name));
 147         return 0;
 148 }
 149
 150 static int option_parse_n(const struct option *opt,
 151                           const char *arg, int unset)
 152 {
 153         show_diffstat = unset;
 154         return 0;
 155 }
 156
 157 static struct option builtin_merge_options[] = {
 158         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 159                 "do not show a diffstat at the end of the merge",
 160                 PARSE_OPT_NOARG, option_parse_n },
 161         OPT_BOOLEAN(0, "stat", &show_diffstat,
 162                 "show a diffstat at the end of the merge"),
 163         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 164         OPT_BOOLEAN(0, "log", &option_log,
 165                 "add list of one-line log to merge commit message"),
 166         OPT_BOOLEAN(0, "squash", &squash,
 167                 "create a single commit instead of doing a merge"),
 168         OPT_BOOLEAN(0, "commit", &option_commit,
 169                 "perform a commit if the merge succeeds (default)"),
 170         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 171                 "allow fast-forward (default)"),
 172         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 173                 "abort if fast-forward is not possible"),
 174         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 175                 "merge strategy to use", option_parse_strategy),
 176         OPT_CALLBACK('m', "message", &merge_msg, "message",
 177                 "message to be used for the merge commit (if any)",
 178                 option_parse_message),
 179         OPT__VERBOSITY(&verbosity),
 180         OPT_END()
 181 };
 182
 183 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 184 static void drop_save(void)
 185 {
 186         unlink(git_path("MERGE_HEAD"));
 187         unlink(git_path("MERGE_MSG"));
 188         unlink(git_path("MERGE_MODE"));
 189 }
 190
 191 static void save_state(void)
 192 {
 193         int len;
 194         struct child_process cp;
 195         struct strbuf buffer = STRBUF_INIT;
 196         const char *argv[] = {"stash", "create", NULL};
 197
 198         memset(&cp, 0, sizeof(cp));
 199         cp.argv = argv;
 200         cp.out = -1;
 201         cp.git_cmd = 1;
 202
 203         if (start_command(&cp))
 204                 die("could not run stash.");
 205         len = strbuf_read(&buffer, cp.out, 1024);
 206         close(cp.out);
 207
 208         if (finish_command(&cp) || len < 0)
 209                 die("stash failed");
 210         else if (!len)
 211                 return;
 212         strbuf_setlen(&buffer, buffer.len-1);
 213         if (get_sha1(buffer.buf, stash))
 214                 die("not a valid object: %s", buffer.buf);
 215 }
 216
 217 static void reset_hard(unsigned const char *sha1, int verbose)
 218 {
 219         int i = 0;
 220         const char *args[6];
 221
 222         args[i++] = "read-tree";
 223         if (verbose)
 224                 args[i++] = "-v";
 225         args[i++] = "--reset";
 226         args[i++] = "-u";
 227         args[i++] = sha1_to_hex(sha1);
 228         args[i] = NULL;
 229
 230         if (run_command_v_opt(args, RUN_GIT_CMD))
 231                 die("read-tree failed");
 232 }
 233
 234 static void restore_state(void)
 235 {
 236         struct strbuf sb = STRBUF_INIT;
 237         const char *args[] = { "stash", "apply", NULL, NULL };
 238
 239         if (is_null_sha1(stash))
 240                 return;
 241
 242         reset_hard(head, 1);
 243
 244         args[2] = sha1_to_hex(stash);
 245
 246         /*
 247          * It is OK to ignore error here, for example when there was
 248          * nothing to restore.
 249          */
 250         run_command_v_opt(args, RUN_GIT_CMD);
 251
 252         strbuf_release(&sb);
 253         refresh_cache(REFRESH_QUIET);
 254 }
 255
 256 /* This is called when no merge was necessary. */
 257 static void finish_up_to_date(const char *msg)
 258 {
 259         if (verbosity >= 0)
 260                 printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
 261         drop_save();
 262 }
 263
 264 static void squash_message(void)
 265 {
 266         struct rev_info rev;
 267         struct commit *commit;
 268         struct strbuf out = STRBUF_INIT;
 269         struct commit_list *j;
 270         int fd;
 271         struct pretty_print_context ctx = {0};
 272
 273         printf("Squash commit -- not updating HEAD\n");
 274         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 275         if (fd < 0)
 276                 die_errno("Could not write to '%s'", git_path("SQUASH_MSG"));
 277
 278         init_revisions(&rev, NULL);
 279         rev.ignore_merges = 1;
 280         rev.commit_format = CMIT_FMT_MEDIUM;
 281
 282         commit = lookup_commit(head);
 283         commit->object.flags |= UNINTERESTING;
 284         add_pending_object(&rev, &commit->object, NULL);
 285
 286         for (j = remoteheads; j; j = j->next)
 287                 add_pending_object(&rev, &j->item->object, NULL);
 288
 289         setup_revisions(0, NULL, &rev, NULL);
 290         if (prepare_revision_walk(&rev))
 291                 die("revision walk setup failed");
 292
 293         ctx.abbrev = rev.abbrev;
 294         ctx.date_mode = rev.date_mode;
 295
 296         strbuf_addstr(&out, "Squashed commit of the following:\n");
 297         while ((commit = get_revision(&rev)) != NULL) {
 298                 strbuf_addch(&out, '\n');
 299                 strbuf_addf(&out, "commit %s\n",
 300                         sha1_to_hex(commit->object.sha1));
 301                 pretty_print_commit(rev.commit_format, commit, &out, &ctx);
 302         }
 303         if (write(fd, out.buf, out.len) < 0)
 304                 die_errno("Writing SQUASH_MSG");
 305         if (close(fd))
 306                 die_errno("Finishing SQUASH_MSG");
 307         strbuf_release(&out);
 308 }
 309
 310 static void finish(const unsigned char *new_head, const char *msg)
 311 {
 312         struct strbuf reflog_message = STRBUF_INIT;
 313
 314         if (!msg)
 315                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 316         else {
 317                 if (verbosity >= 0)
 318                         printf("%s\n", msg);
 319                 strbuf_addf(&reflog_message, "%s: %s",
 320                         getenv("GIT_REFLOG_ACTION"), msg);
 321         }
 322         if (squash) {
 323                 squash_message();
 324         } else {
 325                 if (verbosity >= 0 && !merge_msg.len)
 326                         printf("No merge message -- not updating HEAD\n");
 327                 else {
 328                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 329                         update_ref(reflog_message.buf, "HEAD",
 330                                 new_head, head, 0,
 331                                 DIE_ON_ERR);
 332                         /*
 333                          * We ignore errors in 'gc --auto', since the
 334                          * user should see them.
 335                          */
 336                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 337                 }
 338         }
 339         if (new_head && show_diffstat) {
 340                 struct diff_options opts;
 341                 diff_setup(&opts);
 342                 opts.output_format |=
 343                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 344                 opts.detect_rename = DIFF_DETECT_RENAME;
 345                 if (diff_use_color_default > 0)
 346                         DIFF_OPT_SET(&opts, COLOR_DIFF);
 347                 if (diff_setup_done(&opts) < 0)
 348                         die("diff_setup_done failed");
 349                 diff_tree_sha1(head, new_head, "", &opts);
 350                 diffcore_std(&opts);
 351                 diff_flush(&opts);
 352         }
 353
 354         /* Run a post-merge hook */
 355         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 356
 357         strbuf_release(&reflog_message);
 358 }
 359
 360 /* Get the name for the merge commit's message. */
 361 static void merge_name(const char *remote, struct strbuf *msg)
 362 {
 363         struct object *remote_head;
 364         unsigned char branch_head[20], buf_sha[20];
 365         struct strbuf buf = STRBUF_INIT;
 366         struct strbuf bname = STRBUF_INIT;
 367         const char *ptr;
 368         char *found_ref;
 369         int len, early;
 370
 371         strbuf_branchname(&bname, remote);
 372         remote = bname.buf;
 373
 374         memset(branch_head, 0, sizeof(branch_head));
 375         remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 376         if (!remote_head)
 377                 die("'%s' does not point to a commit", remote);
 378
 379         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 380                 if (!prefixcmp(found_ref, "refs/heads/")) {
 381                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 382                                     sha1_to_hex(branch_head), remote);
 383                         goto cleanup;
 384                 }
 385                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 386                         strbuf_addf(msg, "%s\t\tremote branch '%s' of .\n",
 387                                     sha1_to_hex(branch_head), remote);
 388                         goto cleanup;
 389                 }
 390         }
 391
 392         /* See if remote matches <name>^^^.. or <name>~<number> */
 393         for (len = 0, ptr = remote + strlen(remote);
 394              remote < ptr && ptr[-1] == '^';
 395              ptr--)
 396                 len++;
 397         if (len)
 398                 early = 1;
 399         else {
 400                 early = 0;
 401                 ptr = strrchr(remote, '~');
 402                 if (ptr) {
 403                         int seen_nonzero = 0;
 404
 405                         len++; /* count ~ */
 406                         while (*++ptr && isdigit(*ptr)) {
 407                                 seen_nonzero |= (*ptr != '0');
 408                                 len++;
 409                         }
 410                         if (*ptr)
 411                                 len = 0; /* not ...~<number> */
 412                         else if (seen_nonzero)
 413                                 early = 1;
 414                         else if (len == 1)
 415                                 early = 1; /* "name~" is "name~1"! */
 416                 }
 417         }
 418         if (len) {
 419                 struct strbuf truname = STRBUF_INIT;
 420                 strbuf_addstr(&truname, "refs/heads/");
 421                 strbuf_addstr(&truname, remote);
 422                 strbuf_setlen(&truname, truname.len - len);
 423                 if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
 424                         strbuf_addf(msg,
 425                                     "%s\t\tbranch '%s'%s of .\n",
 426                                     sha1_to_hex(remote_head->sha1),
 427                                     truname.buf + 11,
 428                                     (early ? " (early part)" : ""));
 429                         strbuf_release(&truname);
 430                         goto cleanup;
 431                 }
 432         }
 433
 434         if (!strcmp(remote, "FETCH_HEAD") &&
 435                         !access(git_path("FETCH_HEAD"), R_OK)) {
 436                 FILE *fp;
 437                 struct strbuf line = STRBUF_INIT;
 438                 char *ptr;
 439
 440                 fp = fopen(git_path("FETCH_HEAD"), "r");
 441                 if (!fp)
 442                         die_errno("could not open '%s' for reading",
 443                                   git_path("FETCH_HEAD"));
 444                 strbuf_getline(&line, fp, '\n');
 445                 fclose(fp);
 446                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 447                 if (ptr)
 448                         strbuf_remove(&line, ptr-line.buf+1, 13);
 449                 strbuf_addbuf(msg, &line);
 450                 strbuf_release(&line);
 451                 goto cleanup;
 452         }
 453         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 454                 sha1_to_hex(remote_head->sha1), remote);
 455 cleanup:
 456         strbuf_release(&buf);
 457         strbuf_release(&bname);
 458 }
 459
 460 static int git_merge_config(const char *k, const char *v, void *cb)
 461 {
 462         if (branch && !prefixcmp(k, "branch.") &&
 463                 !prefixcmp(k + 7, branch) &&
 464                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 465                 const char **argv;
 466                 int argc;
 467                 char *buf;
 468
 469                 buf = xstrdup(v);
 470                 argc = split_cmdline(buf, &argv);
 471                 if (argc < 0)
 472                         die("Bad branch.%s.mergeoptions string", branch);
 473                 argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 474                 memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 475                 argc++;
 476                 parse_options(argc, argv, NULL, builtin_merge_options,
 477                               builtin_merge_usage, 0);
 478                 free(buf);
 479         }
 480
 481         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 482                 show_diffstat = git_config_bool(k, v);
 483         else if (!strcmp(k, "pull.twohead"))
 484                 return git_config_string(&pull_twohead, k, v);
 485         else if (!strcmp(k, "pull.octopus"))
 486                 return git_config_string(&pull_octopus, k, v);
 487         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
 488                 option_log = git_config_bool(k, v);
 489         return git_diff_ui_config(k, v, cb);
 490 }
 491
 492 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 493                              unsigned char *one)
 494 {
 495         int i, nr_trees = 0;
 496         struct tree *trees[MAX_UNPACK_TREES];
 497         struct tree_desc t[MAX_UNPACK_TREES];
 498         struct unpack_trees_options opts;
 499
 500         memset(&opts, 0, sizeof(opts));
 501         opts.head_idx = 2;
 502         opts.src_index = &the_index;
 503         opts.dst_index = &the_index;
 504         opts.update = 1;
 505         opts.verbose_update = 1;
 506         opts.trivial_merges_only = 1;
 507         opts.merge = 1;
 508         trees[nr_trees] = parse_tree_indirect(common);
 509         if (!trees[nr_trees++])
 510                 return -1;
 511         trees[nr_trees] = parse_tree_indirect(head);
 512         if (!trees[nr_trees++])
 513                 return -1;
 514         trees[nr_trees] = parse_tree_indirect(one);
 515         if (!trees[nr_trees++])
 516                 return -1;
 517         opts.fn = threeway_merge;
 518         cache_tree_free(&active_cache_tree);
 519         for (i = 0; i < nr_trees; i++) {
 520                 parse_tree(trees[i]);
 521                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 522         }
 523         if (unpack_trees(nr_trees, t, &opts))
 524                 return -1;
 525         return 0;
 526 }
 527
 528 static void write_tree_trivial(unsigned char *sha1)
 529 {
 530         if (write_cache_as_tree(sha1, 0, NULL))
 531                 die("git write-tree failed to write a tree");
 532 }
 533
 534 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 535                               const char *head_arg)
 536 {
 537         const char **args;
 538         int i = 0, ret;
 539         struct commit_list *j;
 540         struct strbuf buf = STRBUF_INIT;
 541         int index_fd;
 542         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 543
 544         index_fd = hold_locked_index(lock, 1);
 545         refresh_cache(REFRESH_QUIET);
 546         if (active_cache_changed &&
 547                         (write_cache(index_fd, active_cache, active_nr) ||
 548                          commit_locked_index(lock)))
 549                 return error("Unable to write index.");
 550         rollback_lock_file(lock);
 551
 552         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 553                 int clean;
 554                 struct commit *result;
 555                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 556                 int index_fd;
 557                 struct commit_list *reversed = NULL;
 558                 struct merge_options o;
 559
 560                 if (remoteheads->next) {
 561                         error("Not handling anything other than two heads merge.");
 562                         return 2;
 563                 }
 564
 565                 init_merge_options(&o);
 566                 if (!strcmp(strategy, "subtree"))
 567                         o.subtree_merge = 1;
 568
 569                 o.branch1 = head_arg;
 570                 o.branch2 = remoteheads->item->util;
 571
 572                 for (j = common; j; j = j->next)
 573                         commit_list_insert(j->item, &reversed);
 574
 575                 index_fd = hold_locked_index(lock, 1);
 576                 clean = merge_recursive(&o, lookup_commit(head),
 577                                 remoteheads->item, reversed, &result);
 578                 if (active_cache_changed &&
 579                                 (write_cache(index_fd, active_cache, active_nr) ||
 580                                  commit_locked_index(lock)))
 581                         die ("unable to write %s", get_index_file());
 582                 rollback_lock_file(lock);
 583                 return clean ? 0 : 1;
 584         } else {
 585                 args = xmalloc((4 + commit_list_count(common) +
 586                                         commit_list_count(remoteheads)) * sizeof(char *));
 587                 strbuf_addf(&buf, "merge-%s", strategy);
 588                 args[i++] = buf.buf;
 589                 for (j = common; j; j = j->next)
 590                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 591                 args[i++] = "--";
 592                 args[i++] = head_arg;
 593                 for (j = remoteheads; j; j = j->next)
 594                         args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
 595                 args[i] = NULL;
 596                 ret = run_command_v_opt(args, RUN_GIT_CMD);
 597                 strbuf_release(&buf);
 598                 i = 1;
 599                 for (j = common; j; j = j->next)
 600                         free((void *)args[i++]);
 601                 i += 2;
 602                 for (j = remoteheads; j; j = j->next)
 603                         free((void *)args[i++]);
 604                 free(args);
 605                 discard_cache();
 606                 if (read_cache() < 0)
 607                         die("failed to read the cache");
 608                 resolve_undo_clear();
 609                 return ret;
 610         }
 611 }
 612
 613 static void count_diff_files(struct diff_queue_struct *q,
 614                              struct diff_options *opt, void *data)
 615 {
 616         int *count = data;
 617
 618         (*count) += q->nr;
 619 }
 620
 621 static int count_unmerged_entries(void)
 622 {
 623         int i, ret = 0;
 624
 625         for (i = 0; i < active_nr; i++)
 626                 if (ce_stage(active_cache[i]))
 627                         ret++;
 628
 629         return ret;
 630 }
 631
 632 static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
 633 {
 634         struct tree *trees[MAX_UNPACK_TREES];
 635         struct unpack_trees_options opts;
 636         struct tree_desc t[MAX_UNPACK_TREES];
 637         int i, fd, nr_trees = 0;
 638         struct dir_struct dir;
 639         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 640
 641         refresh_cache(REFRESH_QUIET);
 642
 643         fd = hold_locked_index(lock_file, 1);
 644
 645         memset(&trees, 0, sizeof(trees));
 646         memset(&opts, 0, sizeof(opts));
 647         memset(&t, 0, sizeof(t));
 648         memset(&dir, 0, sizeof(dir));
 649         dir.flags |= DIR_SHOW_IGNORED;
 650         dir.exclude_per_dir = ".gitignore";
 651         opts.dir = &dir;
 652
 653         opts.head_idx = 1;
 654         opts.src_index = &the_index;
 655         opts.dst_index = &the_index;
 656         opts.update = 1;
 657         opts.verbose_update = 1;
 658         opts.merge = 1;
 659         opts.fn = twoway_merge;
 660         opts.msgs = get_porcelain_error_msgs();
 661
 662         trees[nr_trees] = parse_tree_indirect(head);
 663         if (!trees[nr_trees++])
 664                 return -1;
 665         trees[nr_trees] = parse_tree_indirect(remote);
 666         if (!trees[nr_trees++])
 667                 return -1;
 668         for (i = 0; i < nr_trees; i++) {
 669                 parse_tree(trees[i]);
 670                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 671         }
 672         if (unpack_trees(nr_trees, t, &opts))
 673                 return -1;
 674         if (write_cache(fd, active_cache, active_nr) ||
 675                 commit_locked_index(lock_file))
 676                 die("unable to write new index file");
 677         return 0;
 678 }
 679
 680 static void split_merge_strategies(const char *string, struct strategy **list,
 681                                    int *nr, int *alloc)
 682 {
 683         char *p, *q, *buf;
 684
 685         if (!string)
 686                 return;
 687
 688         buf = xstrdup(string);
 689         q = buf;
 690         for (;;) {
 691                 p = strchr(q, ' ');
 692                 if (!p) {
 693                         ALLOC_GROW(*list, *nr + 1, *alloc);
 694                         (*list)[(*nr)++].name = xstrdup(q);
 695                         free(buf);
 696                         return;
 697                 } else {
 698                         *p = '\0';
 699                         ALLOC_GROW(*list, *nr + 1, *alloc);
 700                         (*list)[(*nr)++].name = xstrdup(q);
 701                         q = ++p;
 702                 }
 703         }
 704 }
 705
 706 static void add_strategies(const char *string, unsigned attr)
 707 {
 708         struct strategy *list = NULL;
 709         int list_alloc = 0, list_nr = 0, i;
 710
 711         memset(&list, 0, sizeof(list));
 712         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 713         if (list) {
 714                 for (i = 0; i < list_nr; i++)
 715                         append_strategy(get_strategy(list[i].name));
 716                 return;
 717         }
 718         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 719                 if (all_strategy[i].attr & attr)
 720                         append_strategy(&all_strategy[i]);
 721
 722 }
 723
 724 static int merge_trivial(void)
 725 {
 726         unsigned char result_tree[20], result_commit[20];
 727         struct commit_list *parent = xmalloc(sizeof(*parent));
 728
 729         write_tree_trivial(result_tree);
 730         printf("Wonderful.\n");
 731         parent->item = lookup_commit(head);
 732         parent->next = xmalloc(sizeof(*parent->next));
 733         parent->next->item = remoteheads->item;
 734         parent->next->next = NULL;
 735         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 736         finish(result_commit, "In-index merge");
 737         drop_save();
 738         return 0;
 739 }
 740
 741 static int finish_automerge(struct commit_list *common,
 742                             unsigned char *result_tree,
 743                             const char *wt_strategy)
 744 {
 745         struct commit_list *parents = NULL, *j;
 746         struct strbuf buf = STRBUF_INIT;
 747         unsigned char result_commit[20];
 748
 749         free_commit_list(common);
 750         if (allow_fast_forward) {
 751                 parents = remoteheads;
 752                 commit_list_insert(lookup_commit(head), &parents);
 753                 parents = reduce_heads(parents);
 754         } else {
 755                 struct commit_list **pptr = &parents;
 756
 757                 pptr = &commit_list_insert(lookup_commit(head),
 758                                 pptr)->next;
 759                 for (j = remoteheads; j; j = j->next)
 760                         pptr = &commit_list_insert(j->item, pptr)->next;
 761         }
 762         free_commit_list(remoteheads);
 763         strbuf_addch(&merge_msg, '\n');
 764         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 765         strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 766         finish(result_commit, buf.buf);
 767         strbuf_release(&buf);
 768         drop_save();
 769         return 0;
 770 }
 771
 772 static int suggest_conflicts(void)
 773 {
 774         FILE *fp;
 775         int pos;
 776
 777         fp = fopen(git_path("MERGE_MSG"), "a");
 778         if (!fp)
 779                 die_errno("Could not open '%s' for writing",
 780                           git_path("MERGE_MSG"));
 781         fprintf(fp, "\nConflicts:\n");
 782         for (pos = 0; pos < active_nr; pos++) {
 783                 struct cache_entry *ce = active_cache[pos];
 784
 785                 if (ce_stage(ce)) {
 786                         fprintf(fp, "\t%s\n", ce->name);
 787                         while (pos + 1 < active_nr &&
 788                                         !strcmp(ce->name,
 789                                                 active_cache[pos + 1]->name))
 790                                 pos++;
 791                 }
 792         }
 793         fclose(fp);
 794         rerere();
 795         printf("Automatic merge failed; "
 796                         "fix conflicts and then commit the result.\n");
 797         return 1;
 798 }
 799
 800 static struct commit *is_old_style_invocation(int argc, const char **argv)
 801 {
 802         struct commit *second_token = NULL;
 803         if (argc > 2) {
 804                 unsigned char second_sha1[20];
 805
 806                 if (get_sha1(argv[1], second_sha1))
 807                         return NULL;
 808                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 809                 if (!second_token)
 810                         die("'%s' is not a commit", argv[1]);
 811                 if (hashcmp(second_token->object.sha1, head))
 812                         return NULL;
 813         }
 814         return second_token;
 815 }
 816
 817 static int evaluate_result(void)
 818 {
 819         int cnt = 0;
 820         struct rev_info rev;
 821
 822         /* Check how many files differ. */
 823         init_revisions(&rev, "");
 824         setup_revisions(0, NULL, &rev, NULL);
 825         rev.diffopt.output_format |=
 826                 DIFF_FORMAT_CALLBACK;
 827         rev.diffopt.format_callback = count_diff_files;
 828         rev.diffopt.format_callback_data = &cnt;
 829         run_diff_files(&rev, 0);
 830
 831         /*
 832          * Check how many unmerged entries are
 833          * there.
 834          */
 835         cnt += count_unmerged_entries();
 836
 837         return cnt;
 838 }
 839
 840 int cmd_merge(int argc, const char **argv, const char *prefix)
 841 {
 842         unsigned char result_tree[20];
 843         struct strbuf buf = STRBUF_INIT;
 844         const char *head_arg;
 845         int flag, head_invalid = 0, i;
 846         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 847         struct commit_list *common = NULL;
 848         const char *best_strategy = NULL, *wt_strategy = NULL;
 849         struct commit_list **remotes = &remoteheads;
 850
 851         if (file_exists(git_path("MERGE_HEAD")))
 852                 die("You have not concluded your merge. (MERGE_HEAD exists)");
 853         if (read_cache_unmerged())
 854                 die("You are in the middle of a conflicted merge."
 855                                 " (index unmerged)");
 856         resolve_undo_clear();
 857         /*
 858          * Check if we are _not_ on a detached HEAD, i.e. if there is a
 859          * current branch.
 860          */
 861         branch = resolve_ref("HEAD", head, 0, &flag);
 862         if (branch && !prefixcmp(branch, "refs/heads/"))
 863                 branch += 11;
 864         if (is_null_sha1(head))
 865                 head_invalid = 1;
 866
 867         git_config(git_merge_config, NULL);
 868
 869         /* for color.ui */
 870         if (diff_use_color_default == -1)
 871                 diff_use_color_default = git_use_color_default;
 872
 873         argc = parse_options(argc, argv, prefix, builtin_merge_options,
 874                         builtin_merge_usage, 0);
 875         if (verbosity < 0)
 876                 show_diffstat = 0;
 877
 878         if (squash) {
 879                 if (!allow_fast_forward)
 880                         die("You cannot combine --squash with --no-ff.");
 881                 option_commit = 0;
 882         }
 883
 884         if (!allow_fast_forward && fast_forward_only)
 885                 die("You cannot combine --no-ff with --ff-only.");
 886
 887         if (!argc)
 888                 usage_with_options(builtin_merge_usage,
 889                         builtin_merge_options);
 890
 891         /*
 892          * This could be traditional "merge <msg> HEAD <commit>..."  and
 893          * the way we can tell it is to see if the second token is HEAD,
 894          * but some people might have misused the interface and used a
 895          * committish that is the same as HEAD there instead.
 896          * Traditional format never would have "-m" so it is an
 897          * additional safety measure to check for it.
 898          */
 899
 900         if (!have_message && is_old_style_invocation(argc, argv)) {
 901                 strbuf_addstr(&merge_msg, argv[0]);
 902                 head_arg = argv[1];
 903                 argv += 2;
 904                 argc -= 2;
 905         } else if (head_invalid) {
 906                 struct object *remote_head;
 907                 /*
 908                  * If the merged head is a valid one there is no reason
 909                  * to forbid "git merge" into a branch yet to be born.
 910                  * We do the same for "git pull".
 911                  */
 912                 if (argc != 1)
 913                         die("Can merge only exactly one commit into "
 914                                 "empty head");
 915                 if (squash)
 916                         die("Squash commit into empty head not supported yet");
 917                 if (!allow_fast_forward)
 918                         die("Non-fast-forward commit does not make sense into "
 919                             "an empty head");
 920                 remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
 921                 if (!remote_head)
 922                         die("%s - not something we can merge", argv[0]);
 923                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
 924                                 DIE_ON_ERR);
 925                 reset_hard(remote_head->sha1, 0);
 926                 return 0;
 927         } else {
 928                 struct strbuf msg = STRBUF_INIT;
 929
 930                 /* We are invoked directly as the first-class UI. */
 931                 head_arg = "HEAD";
 932
 933                 /*
 934                  * All the rest are the commits being merged;
 935                  * prepare the standard merge summary message to
 936                  * be appended to the given message.  If remote
 937                  * is invalid we will die later in the common
 938                  * codepath so we discard the error in this
 939                  * loop.
 940                  */
 941                 if (!have_message) {
 942                         for (i = 0; i < argc; i++)
 943                                 merge_name(argv[i], &msg);
 944                         fmt_merge_msg(option_log, &msg, &merge_msg);
 945                         if (merge_msg.len)
 946                                 strbuf_setlen(&merge_msg, merge_msg.len-1);
 947                 }
 948         }
 949
 950         if (head_invalid || !argc)
 951                 usage_with_options(builtin_merge_usage,
 952                         builtin_merge_options);
 953
 954         strbuf_addstr(&buf, "merge");
 955         for (i = 0; i < argc; i++)
 956                 strbuf_addf(&buf, " %s", argv[i]);
 957         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 958         strbuf_reset(&buf);
 959
 960         for (i = 0; i < argc; i++) {
 961                 struct object *o;
 962                 struct commit *commit;
 963
 964                 o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
 965                 if (!o)
 966                         die("%s - not something we can merge", argv[i]);
 967                 commit = lookup_commit(o->sha1);
 968                 commit->util = (void *)argv[i];
 969                 remotes = &commit_list_insert(commit, remotes)->next;
 970
 971                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
 972                 setenv(buf.buf, argv[i], 1);
 973                 strbuf_reset(&buf);
 974         }
 975
 976         if (!use_strategies) {
 977                 if (!remoteheads->next)
 978                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 979                 else
 980                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
 981         }
 982
 983         for (i = 0; i < use_strategies_nr; i++) {
 984                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
 985                         allow_fast_forward = 0;
 986                 if (use_strategies[i]->attr & NO_TRIVIAL)
 987                         allow_trivial = 0;
 988         }
 989
 990         if (!remoteheads->next)
 991                 common = get_merge_bases(lookup_commit(head),
 992                                 remoteheads->item, 1);
 993         else {
 994                 struct commit_list *list = remoteheads;
 995                 commit_list_insert(lookup_commit(head), &list);
 996                 common = get_octopus_merge_bases(list);
 997                 free(list);
 998         }
 999
1000         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1001                 DIE_ON_ERR);
1002
1003         if (!common)
1004                 ; /* No common ancestors found. We need a real merge. */
1005         else if (!remoteheads->next && !common->next &&
1006                         common->item == remoteheads->item) {
1007                 /*
1008                  * If head can reach all the merge then we are up to date.
1009                  * but first the most common case of merging one remote.
1010                  */
1011                 finish_up_to_date("Already up-to-date.");
1012                 return 0;
1013         } else if (allow_fast_forward && !remoteheads->next &&
1014                         !common->next &&
1015                         !hashcmp(common->item->object.sha1, head)) {
1016                 /* Again the most common case of merging one remote. */
1017                 struct strbuf msg = STRBUF_INIT;
1018                 struct object *o;
1019                 char hex[41];
1020
1021                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1022
1023                 if (verbosity >= 0)
1024                         printf("Updating %s..%s\n",
1025                                 hex,
1026                                 find_unique_abbrev(remoteheads->item->object.sha1,
1027                                 DEFAULT_ABBREV));
1028                 strbuf_addstr(&msg, "Fast-forward");
1029                 if (have_message)
1030                         strbuf_addstr(&msg,
1031                                 " (no commit created; -m option ignored)");
1032                 o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1033                         0, NULL, OBJ_COMMIT);
1034                 if (!o)
1035                         return 1;
1036
1037                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1038                         return 1;
1039
1040                 finish(o->sha1, msg.buf);
1041                 drop_save();
1042                 return 0;
1043         } else if (!remoteheads->next && common->next)
1044                 ;
1045                 /*
1046                  * We are not doing octopus and not fast-forward.  Need
1047                  * a real merge.
1048                  */
1049         else if (!remoteheads->next && !common->next && option_commit) {
1050                 /*
1051                  * We are not doing octopus, not fast-forward, and have
1052                  * only one common.
1053                  */
1054                 refresh_cache(REFRESH_QUIET);
1055                 if (allow_trivial && !fast_forward_only) {
1056                         /* See if it is really trivial. */
1057                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1058                         printf("Trying really trivial in-index merge...\n");
1059                         if (!read_tree_trivial(common->item->object.sha1,
1060                                         head, remoteheads->item->object.sha1))
1061                                 return merge_trivial();
1062                         printf("Nope.\n");
1063                 }
1064         } else {
1065                 /*
1066                  * An octopus.  If we can reach all the remote we are up
1067                  * to date.
1068                  */
1069                 int up_to_date = 1;
1070                 struct commit_list *j;
1071
1072                 for (j = remoteheads; j; j = j->next) {
1073                         struct commit_list *common_one;
1074
1075                         /*
1076                          * Here we *have* to calculate the individual
1077                          * merge_bases again, otherwise "git merge HEAD^
1078                          * HEAD^^" would be missed.
1079                          */
1080                         common_one = get_merge_bases(lookup_commit(head),
1081                                 j->item, 1);
1082                         if (hashcmp(common_one->item->object.sha1,
1083                                 j->item->object.sha1)) {
1084                                 up_to_date = 0;
1085                                 break;
1086                         }
1087                 }
1088                 if (up_to_date) {
1089                         finish_up_to_date("Already up-to-date. Yeeah!");
1090                         return 0;
1091                 }
1092         }
1093
1094         if (fast_forward_only)
1095                 die("Not possible to fast-forward, aborting.");
1096
1097         /* We are going to make a new commit. */
1098         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1099
1100         /*
1101          * At this point, we need a real merge.  No matter what strategy
1102          * we use, it would operate on the index, possibly affecting the
1103          * working tree, and when resolved cleanly, have the desired
1104          * tree in the index -- this means that the index must be in
1105          * sync with the head commit.  The strategies are responsible
1106          * to ensure this.
1107          */
1108         if (use_strategies_nr != 1) {
1109                 /*
1110                  * Stash away the local changes so that we can try more
1111                  * than one.
1112                  */
1113                 save_state();
1114         } else {
1115                 memcpy(stash, null_sha1, 20);
1116         }
1117
1118         for (i = 0; i < use_strategies_nr; i++) {
1119                 int ret;
1120                 if (i) {
1121                         printf("Rewinding the tree to pristine...\n");
1122                         restore_state();
1123                 }
1124                 if (use_strategies_nr != 1)
1125                         printf("Trying merge strategy %s...\n",
1126                                 use_strategies[i]->name);
1127                 /*
1128                  * Remember which strategy left the state in the working
1129                  * tree.
1130                  */
1131                 wt_strategy = use_strategies[i]->name;
1132
1133                 ret = try_merge_strategy(use_strategies[i]->name,
1134                         common, head_arg);
1135                 if (!option_commit && !ret) {
1136                         merge_was_ok = 1;
1137                         /*
1138                          * This is necessary here just to avoid writing
1139                          * the tree, but later we will *not* exit with
1140                          * status code 1 because merge_was_ok is set.
1141                          */
1142                         ret = 1;
1143                 }
1144
1145                 if (ret) {
1146                         /*
1147                          * The backend exits with 1 when conflicts are
1148                          * left to be resolved, with 2 when it does not
1149                          * handle the given merge at all.
1150                          */
1151                         if (ret == 1) {
1152                                 int cnt = evaluate_result();
1153
1154                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1155                                         best_strategy = use_strategies[i]->name;
1156                                         best_cnt = cnt;
1157                                 }
1158                         }
1159                         if (merge_was_ok)
1160                                 break;
1161                         else
1162                                 continue;
1163                 }
1164
1165                 /* Automerge succeeded. */
1166                 write_tree_trivial(result_tree);
1167                 automerge_was_ok = 1;
1168                 break;
1169         }
1170
1171         /*
1172          * If we have a resulting tree, that means the strategy module
1173          * auto resolved the merge cleanly.
1174          */
1175         if (automerge_was_ok)
1176                 return finish_automerge(common, result_tree, wt_strategy);
1177
1178         /*
1179          * Pick the result from the best strategy and have the user fix
1180          * it up.
1181          */
1182         if (!best_strategy) {
1183                 restore_state();
1184                 if (use_strategies_nr > 1)
1185                         fprintf(stderr,
1186                                 "No merge strategy handled the merge.\n");
1187                 else
1188                         fprintf(stderr, "Merge with strategy %s failed.\n",
1189                                 use_strategies[0]->name);
1190                 return 2;
1191         } else if (best_strategy == wt_strategy)
1192                 ; /* We already have its result in the working tree. */
1193         else {
1194                 printf("Rewinding the tree to pristine...\n");
1195                 restore_state();
1196                 printf("Using the %s to prepare resolving by hand.\n",
1197                         best_strategy);
1198                 try_merge_strategy(best_strategy, common, head_arg);
1199         }
1200
1201         if (squash)
1202                 finish(NULL, NULL);
1203         else {
1204                 int fd;
1205                 struct commit_list *j;
1206
1207                 for (j = remoteheads; j; j = j->next)
1208                         strbuf_addf(&buf, "%s\n",
1209                                 sha1_to_hex(j->item->object.sha1));
1210                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1211                 if (fd < 0)
1212                         die_errno("Could not open '%s' for writing",
1213                                   git_path("MERGE_HEAD"));
1214                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1215                         die_errno("Could not write to '%s'", git_path("MERGE_HEAD"));
1216                 close(fd);
1217                 strbuf_addch(&merge_msg, '\n');
1218                 fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
1219                 if (fd < 0)
1220                         die_errno("Could not open '%s' for writing",
1221                                   git_path("MERGE_MSG"));
1222                 if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
1223                         merge_msg.len)
1224                         die_errno("Could not write to '%s'", git_path("MERGE_MSG"));
1225                 close(fd);
1226                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1227                 if (fd < 0)
1228                         die_errno("Could not open '%s' for writing",
1229                                   git_path("MERGE_MODE"));
1230                 strbuf_reset(&buf);
1231                 if (!allow_fast_forward)
1232                         strbuf_addf(&buf, "no-ff");
1233                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1234                         die_errno("Could not write to '%s'", git_path("MERGE_MODE"));
1235                 close(fd);
1236         }
1237
1238         if (merge_was_ok) {
1239                 fprintf(stderr, "Automatic merge went well; "
1240                         "stopped before committing as requested\n");
1241                 return 0;
1242         } else
1243                 return suggest_conflicts();
1244 }