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