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