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