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