builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29
  30 #define DEFAULT_TWOHEAD (1<<0)
  31 #define DEFAULT_OCTOPUS (1<<1)
  32 #define NO_FAST_FORWARD (1<<2)
  33 #define NO_TRIVIAL      (1<<3)
  34
  35 struct strategy {
  36         const char *name;
  37         unsigned attr;
  38 };
  39
  40 static const char * const builtin_merge_usage[] = {
  41         "git merge [options] [<commit>...]",
  42         "git merge [options] <msg> HEAD <commit>",
  43         "git merge --abort",
  44         NULL
  45 };
  46
  47 static int show_diffstat = 1, shortlog_len, squash;
  48 static int option_commit = 1, allow_fast_forward = 1;
  49 static int fast_forward_only;
  50 static int allow_trivial = 1, have_message;
  51 static struct strbuf merge_msg;
  52 static struct commit_list *remoteheads;
  53 static unsigned char head[20], stash[20];
  54 static struct strategy **use_strategies;
  55 static size_t use_strategies_nr, use_strategies_alloc;
  56 static const char **xopts;
  57 static size_t xopts_nr, xopts_alloc;
  58 static const char *branch;
  59 static char *branch_mergeoptions;
  60 static int option_renormalize;
  61 static int verbosity;
  62 static int allow_rerere_auto;
  63 static int abort_current_merge;
  64 static int show_progress = -1;
  65 static int default_to_upstream;
  66
  67 static struct strategy all_strategy[] = {
  68         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  69         { "octopus",    DEFAULT_OCTOPUS },
  70         { "resolve",    0 },
  71         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  72         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  73 };
  74
  75 static const char *pull_twohead, *pull_octopus;
  76
  77 static int option_parse_message(const struct option *opt,
  78                                 const char *arg, int unset)
  79 {
  80         struct strbuf *buf = opt->value;
  81
  82         if (unset)
  83                 strbuf_setlen(buf, 0);
  84         else if (arg) {
  85                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  86                 have_message = 1;
  87         } else
  88                 return error(_("switch `m' requires a value"));
  89         return 0;
  90 }
  91
  92 static struct strategy *get_strategy(const char *name)
  93 {
  94         int i;
  95         struct strategy *ret;
  96         static struct cmdnames main_cmds, other_cmds;
  97         static int loaded;
  98
  99         if (!name)
 100                 return NULL;
 101
 102         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 103                 if (!strcmp(name, all_strategy[i].name))
 104                         return &all_strategy[i];
 105
 106         if (!loaded) {
 107                 struct cmdnames not_strategies;
 108                 loaded = 1;
 109
 110                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 111                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 112                 for (i = 0; i < main_cmds.cnt; i++) {
 113                         int j, found = 0;
 114                         struct cmdname *ent = main_cmds.names[i];
 115                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 116                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 117                                                 && !all_strategy[j].name[ent->len])
 118                                         found = 1;
 119                         if (!found)
 120                                 add_cmdname(&not_strategies, ent->name, ent->len);
 121                 }
 122                 exclude_cmds(&main_cmds, &not_strategies);
 123         }
 124         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 125                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 126                 fprintf(stderr, _("Available strategies are:"));
 127                 for (i = 0; i < main_cmds.cnt; i++)
 128                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 129                 fprintf(stderr, ".\n");
 130                 if (other_cmds.cnt) {
 131                         fprintf(stderr, _("Available custom strategies are:"));
 132                         for (i = 0; i < other_cmds.cnt; i++)
 133                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 134                         fprintf(stderr, ".\n");
 135                 }
 136                 exit(1);
 137         }
 138
 139         ret = xcalloc(1, sizeof(struct strategy));
 140         ret->name = xstrdup(name);
 141         ret->attr = NO_TRIVIAL;
 142         return ret;
 143 }
 144
 145 static void append_strategy(struct strategy *s)
 146 {
 147         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 148         use_strategies[use_strategies_nr++] = s;
 149 }
 150
 151 static int option_parse_strategy(const struct option *opt,
 152                                  const char *name, int unset)
 153 {
 154         if (unset)
 155                 return 0;
 156
 157         append_strategy(get_strategy(name));
 158         return 0;
 159 }
 160
 161 static int option_parse_x(const struct option *opt,
 162                           const char *arg, int unset)
 163 {
 164         if (unset)
 165                 return 0;
 166
 167         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 168         xopts[xopts_nr++] = xstrdup(arg);
 169         return 0;
 170 }
 171
 172 static int option_parse_n(const struct option *opt,
 173                           const char *arg, int unset)
 174 {
 175         show_diffstat = unset;
 176         return 0;
 177 }
 178
 179 static struct option builtin_merge_options[] = {
 180         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 181                 "do not show a diffstat at the end of the merge",
 182                 PARSE_OPT_NOARG, option_parse_n },
 183         OPT_BOOLEAN(0, "stat", &show_diffstat,
 184                 "show a diffstat at the end of the merge"),
 185         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 186         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 187           "add (at most <n>) entries from shortlog to merge commit message",
 188           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 189         OPT_BOOLEAN(0, "squash", &squash,
 190                 "create a single commit instead of doing a merge"),
 191         OPT_BOOLEAN(0, "commit", &option_commit,
 192                 "perform a commit if the merge succeeds (default)"),
 193         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 194                 "allow fast-forward (default)"),
 195         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 196                 "abort if fast-forward is not possible"),
 197         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 198         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 199                 "merge strategy to use", option_parse_strategy),
 200         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 201                 "option for selected merge strategy", option_parse_x),
 202         OPT_CALLBACK('m', "message", &merge_msg, "message",
 203                 "merge commit message (for a non-fast-forward merge)",
 204                 option_parse_message),
 205         OPT__VERBOSITY(&verbosity),
 206         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 207                 "abort the current in-progress merge"),
 208         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 209         OPT_END()
 210 };
 211
 212 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 213 static void drop_save(void)
 214 {
 215         unlink(git_path("MERGE_HEAD"));
 216         unlink(git_path("MERGE_MSG"));
 217         unlink(git_path("MERGE_MODE"));
 218 }
 219
 220 static void save_state(void)
 221 {
 222         int len;
 223         struct child_process cp;
 224         struct strbuf buffer = STRBUF_INIT;
 225         const char *argv[] = {"stash", "create", NULL};
 226
 227         memset(&cp, 0, sizeof(cp));
 228         cp.argv = argv;
 229         cp.out = -1;
 230         cp.git_cmd = 1;
 231
 232         if (start_command(&cp))
 233                 die(_("could not run stash."));
 234         len = strbuf_read(&buffer, cp.out, 1024);
 235         close(cp.out);
 236
 237         if (finish_command(&cp) || len < 0)
 238                 die(_("stash failed"));
 239         else if (!len)
 240                 return;
 241         strbuf_setlen(&buffer, buffer.len-1);
 242         if (get_sha1(buffer.buf, stash))
 243                 die(_("not a valid object: %s"), buffer.buf);
 244 }
 245
 246 static void read_empty(unsigned const char *sha1, int verbose)
 247 {
 248         int i = 0;
 249         const char *args[7];
 250
 251         args[i++] = "read-tree";
 252         if (verbose)
 253                 args[i++] = "-v";
 254         args[i++] = "-m";
 255         args[i++] = "-u";
 256         args[i++] = EMPTY_TREE_SHA1_HEX;
 257         args[i++] = sha1_to_hex(sha1);
 258         args[i] = NULL;
 259
 260         if (run_command_v_opt(args, RUN_GIT_CMD))
 261                 die(_("read-tree failed"));
 262 }
 263
 264 static void reset_hard(unsigned const char *sha1, int verbose)
 265 {
 266         int i = 0;
 267         const char *args[6];
 268
 269         args[i++] = "read-tree";
 270         if (verbose)
 271                 args[i++] = "-v";
 272         args[i++] = "--reset";
 273         args[i++] = "-u";
 274         args[i++] = sha1_to_hex(sha1);
 275         args[i] = NULL;
 276
 277         if (run_command_v_opt(args, RUN_GIT_CMD))
 278                 die(_("read-tree failed"));
 279 }
 280
 281 static void restore_state(void)
 282 {
 283         struct strbuf sb = STRBUF_INIT;
 284         const char *args[] = { "stash", "apply", NULL, NULL };
 285
 286         if (is_null_sha1(stash))
 287                 return;
 288
 289         reset_hard(head, 1);
 290
 291         args[2] = sha1_to_hex(stash);
 292
 293         /*
 294          * It is OK to ignore error here, for example when there was
 295          * nothing to restore.
 296          */
 297         run_command_v_opt(args, RUN_GIT_CMD);
 298
 299         strbuf_release(&sb);
 300         refresh_cache(REFRESH_QUIET);
 301 }
 302
 303 /* This is called when no merge was necessary. */
 304 static void finish_up_to_date(const char *msg)
 305 {
 306         if (verbosity >= 0)
 307                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 308         drop_save();
 309 }
 310
 311 static void squash_message(void)
 312 {
 313         struct rev_info rev;
 314         struct commit *commit;
 315         struct strbuf out = STRBUF_INIT;
 316         struct commit_list *j;
 317         int fd;
 318         struct pretty_print_context ctx = {0};
 319
 320         printf(_("Squash commit -- not updating HEAD\n"));
 321         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 322         if (fd < 0)
 323                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 324
 325         init_revisions(&rev, NULL);
 326         rev.ignore_merges = 1;
 327         rev.commit_format = CMIT_FMT_MEDIUM;
 328
 329         commit = lookup_commit(head);
 330         commit->object.flags |= UNINTERESTING;
 331         add_pending_object(&rev, &commit->object, NULL);
 332
 333         for (j = remoteheads; j; j = j->next)
 334                 add_pending_object(&rev, &j->item->object, NULL);
 335
 336         setup_revisions(0, NULL, &rev, NULL);
 337         if (prepare_revision_walk(&rev))
 338                 die(_("revision walk setup failed"));
 339
 340         ctx.abbrev = rev.abbrev;
 341         ctx.date_mode = rev.date_mode;
 342         ctx.fmt = rev.commit_format;
 343
 344         strbuf_addstr(&out, "Squashed commit of the following:\n");
 345         while ((commit = get_revision(&rev)) != NULL) {
 346                 strbuf_addch(&out, '\n');
 347                 strbuf_addf(&out, "commit %s\n",
 348                         sha1_to_hex(commit->object.sha1));
 349                 pretty_print_commit(&ctx, commit, &out);
 350         }
 351         if (write(fd, out.buf, out.len) < 0)
 352                 die_errno(_("Writing SQUASH_MSG"));
 353         if (close(fd))
 354                 die_errno(_("Finishing SQUASH_MSG"));
 355         strbuf_release(&out);
 356 }
 357
 358 static void finish(const unsigned char *new_head, const char *msg)
 359 {
 360         struct strbuf reflog_message = STRBUF_INIT;
 361
 362         if (!msg)
 363                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 364         else {
 365                 if (verbosity >= 0)
 366                         printf("%s\n", msg);
 367                 strbuf_addf(&reflog_message, "%s: %s",
 368                         getenv("GIT_REFLOG_ACTION"), msg);
 369         }
 370         if (squash) {
 371                 squash_message();
 372         } else {
 373                 if (verbosity >= 0 && !merge_msg.len)
 374                         printf(_("No merge message -- not updating HEAD\n"));
 375                 else {
 376                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 377                         update_ref(reflog_message.buf, "HEAD",
 378                                 new_head, head, 0,
 379                                 DIE_ON_ERR);
 380                         /*
 381                          * We ignore errors in 'gc --auto', since the
 382                          * user should see them.
 383                          */
 384                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 385                 }
 386         }
 387         if (new_head && show_diffstat) {
 388                 struct diff_options opts;
 389                 diff_setup(&opts);
 390                 opts.output_format |=
 391                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 392                 opts.detect_rename = DIFF_DETECT_RENAME;
 393                 if (diff_setup_done(&opts) < 0)
 394                         die(_("diff_setup_done failed"));
 395                 diff_tree_sha1(head, new_head, "", &opts);
 396                 diffcore_std(&opts);
 397                 diff_flush(&opts);
 398         }
 399
 400         /* Run a post-merge hook */
 401         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 402
 403         strbuf_release(&reflog_message);
 404 }
 405
 406 static struct object *want_commit(const char *name)
 407 {
 408         struct object *obj;
 409         unsigned char sha1[20];
 410         if (get_sha1(name, sha1))
 411                 return NULL;
 412         obj = parse_object(sha1);
 413         return peel_to_type(name, 0, obj, OBJ_COMMIT);
 414 }
 415
 416 /* Get the name for the merge commit's message. */
 417 static void merge_name(const char *remote, struct strbuf *msg)
 418 {
 419         struct object *remote_head;
 420         unsigned char branch_head[20], buf_sha[20];
 421         struct strbuf buf = STRBUF_INIT;
 422         struct strbuf bname = STRBUF_INIT;
 423         const char *ptr;
 424         char *found_ref;
 425         int len, early;
 426
 427         strbuf_branchname(&bname, remote);
 428         remote = bname.buf;
 429
 430         memset(branch_head, 0, sizeof(branch_head));
 431         remote_head = want_commit(remote);
 432         if (!remote_head)
 433                 die(_("'%s' does not point to a commit"), remote);
 434
 435         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 436                 if (!prefixcmp(found_ref, "refs/heads/")) {
 437                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 438                                     sha1_to_hex(branch_head), remote);
 439                         goto cleanup;
 440                 }
 441                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 442                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 443                                     sha1_to_hex(branch_head), remote);
 444                         goto cleanup;
 445                 }
 446         }
 447
 448         /* See if remote matches <name>^^^.. or <name>~<number> */
 449         for (len = 0, ptr = remote + strlen(remote);
 450              remote < ptr && ptr[-1] == '^';
 451              ptr--)
 452                 len++;
 453         if (len)
 454                 early = 1;
 455         else {
 456                 early = 0;
 457                 ptr = strrchr(remote, '~');
 458                 if (ptr) {
 459                         int seen_nonzero = 0;
 460
 461                         len++; /* count ~ */
 462                         while (*++ptr && isdigit(*ptr)) {
 463                                 seen_nonzero |= (*ptr != '0');
 464                                 len++;
 465                         }
 466                         if (*ptr)
 467                                 len = 0; /* not ...~<number> */
 468                         else if (seen_nonzero)
 469                                 early = 1;
 470                         else if (len == 1)
 471                                 early = 1; /* "name~" is "name~1"! */
 472                 }
 473         }
 474         if (len) {
 475                 struct strbuf truname = STRBUF_INIT;
 476                 strbuf_addstr(&truname, "refs/heads/");
 477                 strbuf_addstr(&truname, remote);
 478                 strbuf_setlen(&truname, truname.len - len);
 479                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 480                         strbuf_addf(msg,
 481                                     "%s\t\tbranch '%s'%s of .\n",
 482                                     sha1_to_hex(remote_head->sha1),
 483                                     truname.buf + 11,
 484                                     (early ? " (early part)" : ""));
 485                         strbuf_release(&truname);
 486                         goto cleanup;
 487                 }
 488         }
 489
 490         if (!strcmp(remote, "FETCH_HEAD") &&
 491                         !access(git_path("FETCH_HEAD"), R_OK)) {
 492                 FILE *fp;
 493                 struct strbuf line = STRBUF_INIT;
 494                 char *ptr;
 495
 496                 fp = fopen(git_path("FETCH_HEAD"), "r");
 497                 if (!fp)
 498                         die_errno(_("could not open '%s' for reading"),
 499                                   git_path("FETCH_HEAD"));
 500                 strbuf_getline(&line, fp, '\n');
 501                 fclose(fp);
 502                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 503                 if (ptr)
 504                         strbuf_remove(&line, ptr-line.buf+1, 13);
 505                 strbuf_addbuf(msg, &line);
 506                 strbuf_release(&line);
 507                 goto cleanup;
 508         }
 509         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 510                 sha1_to_hex(remote_head->sha1), remote);
 511 cleanup:
 512         strbuf_release(&buf);
 513         strbuf_release(&bname);
 514 }
 515
 516 static void parse_branch_merge_options(char *bmo)
 517 {
 518         const char **argv;
 519         int argc;
 520
 521         if (!bmo)
 522                 return;
 523         argc = split_cmdline(bmo, &argv);
 524         if (argc < 0)
 525                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 526                     split_cmdline_strerror(argc));
 527         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 528         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 529         argc++;
 530         argv[0] = "branch.*.mergeoptions";
 531         parse_options(argc, argv, NULL, builtin_merge_options,
 532                       builtin_merge_usage, 0);
 533         free(argv);
 534 }
 535
 536 static int git_merge_config(const char *k, const char *v, void *cb)
 537 {
 538         if (branch && !prefixcmp(k, "branch.") &&
 539                 !prefixcmp(k + 7, branch) &&
 540                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 541                 free(branch_mergeoptions);
 542                 branch_mergeoptions = xstrdup(v);
 543                 return 0;
 544         }
 545
 546         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 547                 show_diffstat = git_config_bool(k, v);
 548         else if (!strcmp(k, "pull.twohead"))
 549                 return git_config_string(&pull_twohead, k, v);
 550         else if (!strcmp(k, "pull.octopus"))
 551                 return git_config_string(&pull_octopus, k, v);
 552         else if (!strcmp(k, "merge.renormalize"))
 553                 option_renormalize = git_config_bool(k, v);
 554         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 555                 int is_bool;
 556                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 557                 if (!is_bool && shortlog_len < 0)
 558                         return error(_("%s: negative length %s"), k, v);
 559                 if (is_bool && shortlog_len)
 560                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 561                 return 0;
 562         } else if (!strcmp(k, "merge.ff")) {
 563                 int boolval = git_config_maybe_bool(k, v);
 564                 if (0 <= boolval) {
 565                         allow_fast_forward = boolval;
 566                 } else if (v && !strcmp(v, "only")) {
 567                         allow_fast_forward = 1;
 568                         fast_forward_only = 1;
 569                 } /* do not barf on values from future versions of git */
 570                 return 0;
 571         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 572                 default_to_upstream = git_config_bool(k, v);
 573                 return 0;
 574         }
 575         return git_diff_ui_config(k, v, cb);
 576 }
 577
 578 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 579                              unsigned char *one)
 580 {
 581         int i, nr_trees = 0;
 582         struct tree *trees[MAX_UNPACK_TREES];
 583         struct tree_desc t[MAX_UNPACK_TREES];
 584         struct unpack_trees_options opts;
 585
 586         memset(&opts, 0, sizeof(opts));
 587         opts.head_idx = 2;
 588         opts.src_index = &the_index;
 589         opts.dst_index = &the_index;
 590         opts.update = 1;
 591         opts.verbose_update = 1;
 592         opts.trivial_merges_only = 1;
 593         opts.merge = 1;
 594         trees[nr_trees] = parse_tree_indirect(common);
 595         if (!trees[nr_trees++])
 596                 return -1;
 597         trees[nr_trees] = parse_tree_indirect(head);
 598         if (!trees[nr_trees++])
 599                 return -1;
 600         trees[nr_trees] = parse_tree_indirect(one);
 601         if (!trees[nr_trees++])
 602                 return -1;
 603         opts.fn = threeway_merge;
 604         cache_tree_free(&active_cache_tree);
 605         for (i = 0; i < nr_trees; i++) {
 606                 parse_tree(trees[i]);
 607                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 608         }
 609         if (unpack_trees(nr_trees, t, &opts))
 610                 return -1;
 611         return 0;
 612 }
 613
 614 static void write_tree_trivial(unsigned char *sha1)
 615 {
 616         if (write_cache_as_tree(sha1, 0, NULL))
 617                 die(_("git write-tree failed to write a tree"));
 618 }
 619
 620 static const char *merge_argument(struct commit *commit)
 621 {
 622         if (commit)
 623                 return sha1_to_hex(commit->object.sha1);
 624         else
 625                 return EMPTY_TREE_SHA1_HEX;
 626 }
 627
 628 int try_merge_command(const char *strategy, size_t xopts_nr,
 629                       const char **xopts, struct commit_list *common,
 630                       const char *head_arg, struct commit_list *remotes)
 631 {
 632         const char **args;
 633         int i = 0, x = 0, ret;
 634         struct commit_list *j;
 635         struct strbuf buf = STRBUF_INIT;
 636
 637         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 638                         commit_list_count(remotes)) * sizeof(char *));
 639         strbuf_addf(&buf, "merge-%s", strategy);
 640         args[i++] = buf.buf;
 641         for (x = 0; x < xopts_nr; x++) {
 642                 char *s = xmalloc(strlen(xopts[x])+2+1);
 643                 strcpy(s, "--");
 644                 strcpy(s+2, xopts[x]);
 645                 args[i++] = s;
 646         }
 647         for (j = common; j; j = j->next)
 648                 args[i++] = xstrdup(merge_argument(j->item));
 649         args[i++] = "--";
 650         args[i++] = head_arg;
 651         for (j = remotes; j; j = j->next)
 652                 args[i++] = xstrdup(merge_argument(j->item));
 653         args[i] = NULL;
 654         ret = run_command_v_opt(args, RUN_GIT_CMD);
 655         strbuf_release(&buf);
 656         i = 1;
 657         for (x = 0; x < xopts_nr; x++)
 658                 free((void *)args[i++]);
 659         for (j = common; j; j = j->next)
 660                 free((void *)args[i++]);
 661         i += 2;
 662         for (j = remotes; j; j = j->next)
 663                 free((void *)args[i++]);
 664         free(args);
 665         discard_cache();
 666         if (read_cache() < 0)
 667                 die(_("failed to read the cache"));
 668         resolve_undo_clear();
 669
 670         return ret;
 671 }
 672
 673 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 674                               const char *head_arg)
 675 {
 676         int index_fd;
 677         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 678
 679         index_fd = hold_locked_index(lock, 1);
 680         refresh_cache(REFRESH_QUIET);
 681         if (active_cache_changed &&
 682                         (write_cache(index_fd, active_cache, active_nr) ||
 683                          commit_locked_index(lock)))
 684                 return error(_("Unable to write index."));
 685         rollback_lock_file(lock);
 686
 687         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 688                 int clean, x;
 689                 struct commit *result;
 690                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 691                 int index_fd;
 692                 struct commit_list *reversed = NULL;
 693                 struct merge_options o;
 694                 struct commit_list *j;
 695
 696                 if (remoteheads->next) {
 697                         error(_("Not handling anything other than two heads merge."));
 698                         return 2;
 699                 }
 700
 701                 init_merge_options(&o);
 702                 if (!strcmp(strategy, "subtree"))
 703                         o.subtree_shift = "";
 704
 705                 o.renormalize = option_renormalize;
 706                 o.show_rename_progress =
 707                         show_progress == -1 ? isatty(2) : show_progress;
 708
 709                 for (x = 0; x < xopts_nr; x++)
 710                         if (parse_merge_opt(&o, xopts[x]))
 711                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 712
 713                 o.branch1 = head_arg;
 714                 o.branch2 = remoteheads->item->util;
 715
 716                 for (j = common; j; j = j->next)
 717                         commit_list_insert(j->item, &reversed);
 718
 719                 index_fd = hold_locked_index(lock, 1);
 720                 clean = merge_recursive(&o, lookup_commit(head),
 721                                 remoteheads->item, reversed, &result);
 722                 if (active_cache_changed &&
 723                                 (write_cache(index_fd, active_cache, active_nr) ||
 724                                  commit_locked_index(lock)))
 725                         die (_("unable to write %s"), get_index_file());
 726                 rollback_lock_file(lock);
 727                 return clean ? 0 : 1;
 728         } else {
 729                 return try_merge_command(strategy, xopts_nr, xopts,
 730                                                 common, head_arg, remoteheads);
 731         }
 732 }
 733
 734 static void count_diff_files(struct diff_queue_struct *q,
 735                              struct diff_options *opt, void *data)
 736 {
 737         int *count = data;
 738
 739         (*count) += q->nr;
 740 }
 741
 742 static int count_unmerged_entries(void)
 743 {
 744         int i, ret = 0;
 745
 746         for (i = 0; i < active_nr; i++)
 747                 if (ce_stage(active_cache[i]))
 748                         ret++;
 749
 750         return ret;
 751 }
 752
 753 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 754 {
 755         struct tree *trees[MAX_UNPACK_TREES];
 756         struct unpack_trees_options opts;
 757         struct tree_desc t[MAX_UNPACK_TREES];
 758         int i, fd, nr_trees = 0;
 759         struct dir_struct dir;
 760         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 761
 762         refresh_cache(REFRESH_QUIET);
 763
 764         fd = hold_locked_index(lock_file, 1);
 765
 766         memset(&trees, 0, sizeof(trees));
 767         memset(&opts, 0, sizeof(opts));
 768         memset(&t, 0, sizeof(t));
 769         memset(&dir, 0, sizeof(dir));
 770         dir.flags |= DIR_SHOW_IGNORED;
 771         dir.exclude_per_dir = ".gitignore";
 772         opts.dir = &dir;
 773
 774         opts.head_idx = 1;
 775         opts.src_index = &the_index;
 776         opts.dst_index = &the_index;
 777         opts.update = 1;
 778         opts.verbose_update = 1;
 779         opts.merge = 1;
 780         opts.fn = twoway_merge;
 781         setup_unpack_trees_porcelain(&opts, "merge");
 782
 783         trees[nr_trees] = parse_tree_indirect(head);
 784         if (!trees[nr_trees++])
 785                 return -1;
 786         trees[nr_trees] = parse_tree_indirect(remote);
 787         if (!trees[nr_trees++])
 788                 return -1;
 789         for (i = 0; i < nr_trees; i++) {
 790                 parse_tree(trees[i]);
 791                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 792         }
 793         if (unpack_trees(nr_trees, t, &opts))
 794                 return -1;
 795         if (write_cache(fd, active_cache, active_nr) ||
 796                 commit_locked_index(lock_file))
 797                 die(_("unable to write new index file"));
 798         return 0;
 799 }
 800
 801 static void split_merge_strategies(const char *string, struct strategy **list,
 802                                    int *nr, int *alloc)
 803 {
 804         char *p, *q, *buf;
 805
 806         if (!string)
 807                 return;
 808
 809         buf = xstrdup(string);
 810         q = buf;
 811         for (;;) {
 812                 p = strchr(q, ' ');
 813                 if (!p) {
 814                         ALLOC_GROW(*list, *nr + 1, *alloc);
 815                         (*list)[(*nr)++].name = xstrdup(q);
 816                         free(buf);
 817                         return;
 818                 } else {
 819                         *p = '\0';
 820                         ALLOC_GROW(*list, *nr + 1, *alloc);
 821                         (*list)[(*nr)++].name = xstrdup(q);
 822                         q = ++p;
 823                 }
 824         }
 825 }
 826
 827 static void add_strategies(const char *string, unsigned attr)
 828 {
 829         struct strategy *list = NULL;
 830         int list_alloc = 0, list_nr = 0, i;
 831
 832         memset(&list, 0, sizeof(list));
 833         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 834         if (list) {
 835                 for (i = 0; i < list_nr; i++)
 836                         append_strategy(get_strategy(list[i].name));
 837                 return;
 838         }
 839         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 840                 if (all_strategy[i].attr & attr)
 841                         append_strategy(&all_strategy[i]);
 842
 843 }
 844
 845 static void write_merge_msg(void)
 846 {
 847         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 848         if (fd < 0)
 849                 die_errno(_("Could not open '%s' for writing"),
 850                           git_path("MERGE_MSG"));
 851         if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 852                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 853         close(fd);
 854 }
 855
 856 static void read_merge_msg(void)
 857 {
 858         strbuf_reset(&merge_msg);
 859         if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 860                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 861 }
 862
 863 static void run_prepare_commit_msg(void)
 864 {
 865         write_merge_msg();
 866         run_hook(get_index_file(), "prepare-commit-msg",
 867                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 868         read_merge_msg();
 869 }
 870
 871 static int merge_trivial(void)
 872 {
 873         unsigned char result_tree[20], result_commit[20];
 874         struct commit_list *parent = xmalloc(sizeof(*parent));
 875
 876         write_tree_trivial(result_tree);
 877         printf(_("Wonderful.\n"));
 878         parent->item = lookup_commit(head);
 879         parent->next = xmalloc(sizeof(*parent->next));
 880         parent->next->item = remoteheads->item;
 881         parent->next->next = NULL;
 882         run_prepare_commit_msg();
 883         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 884         finish(result_commit, "In-index merge");
 885         drop_save();
 886         return 0;
 887 }
 888
 889 static int finish_automerge(struct commit_list *common,
 890                             unsigned char *result_tree,
 891                             const char *wt_strategy)
 892 {
 893         struct commit_list *parents = NULL, *j;
 894         struct strbuf buf = STRBUF_INIT;
 895         unsigned char result_commit[20];
 896
 897         free_commit_list(common);
 898         if (allow_fast_forward) {
 899                 parents = remoteheads;
 900                 commit_list_insert(lookup_commit(head), &parents);
 901                 parents = reduce_heads(parents);
 902         } else {
 903                 struct commit_list **pptr = &parents;
 904
 905                 pptr = &commit_list_insert(lookup_commit(head),
 906                                 pptr)->next;
 907                 for (j = remoteheads; j; j = j->next)
 908                         pptr = &commit_list_insert(j->item, pptr)->next;
 909         }
 910         free_commit_list(remoteheads);
 911         strbuf_addch(&merge_msg, '\n');
 912         run_prepare_commit_msg();
 913         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 914         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 915         finish(result_commit, buf.buf);
 916         strbuf_release(&buf);
 917         drop_save();
 918         return 0;
 919 }
 920
 921 static int suggest_conflicts(int renormalizing)
 922 {
 923         FILE *fp;
 924         int pos;
 925
 926         fp = fopen(git_path("MERGE_MSG"), "a");
 927         if (!fp)
 928                 die_errno(_("Could not open '%s' for writing"),
 929                           git_path("MERGE_MSG"));
 930         fprintf(fp, "\nConflicts:\n");
 931         for (pos = 0; pos < active_nr; pos++) {
 932                 struct cache_entry *ce = active_cache[pos];
 933
 934                 if (ce_stage(ce)) {
 935                         fprintf(fp, "\t%s\n", ce->name);
 936                         while (pos + 1 < active_nr &&
 937                                         !strcmp(ce->name,
 938                                                 active_cache[pos + 1]->name))
 939                                 pos++;
 940                 }
 941         }
 942         fclose(fp);
 943         rerere(allow_rerere_auto);
 944         printf(_("Automatic merge failed; "
 945                         "fix conflicts and then commit the result.\n"));
 946         return 1;
 947 }
 948
 949 static struct commit *is_old_style_invocation(int argc, const char **argv)
 950 {
 951         struct commit *second_token = NULL;
 952         if (argc > 2) {
 953                 unsigned char second_sha1[20];
 954
 955                 if (get_sha1(argv[1], second_sha1))
 956                         return NULL;
 957                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 958                 if (!second_token)
 959                         die(_("'%s' is not a commit"), argv[1]);
 960                 if (hashcmp(second_token->object.sha1, head))
 961                         return NULL;
 962         }
 963         return second_token;
 964 }
 965
 966 static int evaluate_result(void)
 967 {
 968         int cnt = 0;
 969         struct rev_info rev;
 970
 971         /* Check how many files differ. */
 972         init_revisions(&rev, "");
 973         setup_revisions(0, NULL, &rev, NULL);
 974         rev.diffopt.output_format |=
 975                 DIFF_FORMAT_CALLBACK;
 976         rev.diffopt.format_callback = count_diff_files;
 977         rev.diffopt.format_callback_data = &cnt;
 978         run_diff_files(&rev, 0);
 979
 980         /*
 981          * Check how many unmerged entries are
 982          * there.
 983          */
 984         cnt += count_unmerged_entries();
 985
 986         return cnt;
 987 }
 988
 989 /*
 990  * Pretend as if the user told us to merge with the tracking
 991  * branch we have for the upstream of the current branch
 992  */
 993 static int setup_with_upstream(const char ***argv)
 994 {
 995         struct branch *branch = branch_get(NULL);
 996         int i;
 997         const char **args;
 998
 999         if (!branch)
1000                 die(_("No current branch."));
1001         if (!branch->remote)
1002                 die(_("No remote for the current branch."));
1003         if (!branch->merge_nr)
1004                 die(_("No default upstream defined for the current branch."));
1005
1006         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1007         for (i = 0; i < branch->merge_nr; i++) {
1008                 if (!branch->merge[i]->dst)
1009                         die(_("No remote tracking branch for %s from %s"),
1010                             branch->merge[i]->src, branch->remote_name);
1011                 args[i] = branch->merge[i]->dst;
1012         }
1013         args[i] = NULL;
1014         *argv = args;
1015         return i;
1016 }
1017
1018 int cmd_merge(int argc, const char **argv, const char *prefix)
1019 {
1020         unsigned char result_tree[20];
1021         struct strbuf buf = STRBUF_INIT;
1022         const char *head_arg;
1023         int flag, head_invalid = 0, i;
1024         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1025         struct commit_list *common = NULL;
1026         const char *best_strategy = NULL, *wt_strategy = NULL;
1027         struct commit_list **remotes = &remoteheads;
1028
1029         if (argc == 2 && !strcmp(argv[1], "-h"))
1030                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1031
1032         /*
1033          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1034          * current branch.
1035          */
1036         branch = resolve_ref("HEAD", head, 0, &flag);
1037         if (branch && !prefixcmp(branch, "refs/heads/"))
1038                 branch += 11;
1039         if (is_null_sha1(head))
1040                 head_invalid = 1;
1041
1042         git_config(git_merge_config, NULL);
1043
1044         if (branch_mergeoptions)
1045                 parse_branch_merge_options(branch_mergeoptions);
1046         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1047                         builtin_merge_usage, 0);
1048
1049         if (verbosity < 0 && show_progress == -1)
1050                 show_progress = 0;
1051
1052         if (abort_current_merge) {
1053                 int nargc = 2;
1054                 const char *nargv[] = {"reset", "--merge", NULL};
1055
1056                 if (!file_exists(git_path("MERGE_HEAD")))
1057                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1058
1059                 /* Invoke 'git reset --merge' */
1060                 return cmd_reset(nargc, nargv, prefix);
1061         }
1062
1063         if (read_cache_unmerged())
1064                 die_resolve_conflict("merge");
1065
1066         if (file_exists(git_path("MERGE_HEAD"))) {
1067                 /*
1068                  * There is no unmerged entry, don't advise 'git
1069                  * add/rm <file>', just 'git commit'.
1070                  */
1071                 if (advice_resolve_conflict)
1072                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1073                                   "Please, commit your changes before you can merge."));
1074                 else
1075                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1076         }
1077         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1078                 if (advice_resolve_conflict)
1079                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1080                             "Please, commit your changes before you can merge."));
1081                 else
1082                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1083         }
1084         resolve_undo_clear();
1085
1086         if (verbosity < 0)
1087                 show_diffstat = 0;
1088
1089         if (squash) {
1090                 if (!allow_fast_forward)
1091                         die(_("You cannot combine --squash with --no-ff."));
1092                 option_commit = 0;
1093         }
1094
1095         if (!allow_fast_forward && fast_forward_only)
1096                 die(_("You cannot combine --no-ff with --ff-only."));
1097
1098         if (!abort_current_merge) {
1099                 if (!argc && default_to_upstream)
1100                         argc = setup_with_upstream(&argv);
1101                 else if (argc == 1 && !strcmp(argv[0], "-"))
1102                         argv[0] = "@{-1}";
1103         }
1104         if (!argc)
1105                 usage_with_options(builtin_merge_usage,
1106                         builtin_merge_options);
1107
1108         /*
1109          * This could be traditional "merge <msg> HEAD <commit>..."  and
1110          * the way we can tell it is to see if the second token is HEAD,
1111          * but some people might have misused the interface and used a
1112          * committish that is the same as HEAD there instead.
1113          * Traditional format never would have "-m" so it is an
1114          * additional safety measure to check for it.
1115          */
1116
1117         if (!have_message && is_old_style_invocation(argc, argv)) {
1118                 strbuf_addstr(&merge_msg, argv[0]);
1119                 head_arg = argv[1];
1120                 argv += 2;
1121                 argc -= 2;
1122         } else if (head_invalid) {
1123                 struct object *remote_head;
1124                 /*
1125                  * If the merged head is a valid one there is no reason
1126                  * to forbid "git merge" into a branch yet to be born.
1127                  * We do the same for "git pull".
1128                  */
1129                 if (argc != 1)
1130                         die(_("Can merge only exactly one commit into "
1131                                 "empty head"));
1132                 if (squash)
1133                         die(_("Squash commit into empty head not supported yet"));
1134                 if (!allow_fast_forward)
1135                         die(_("Non-fast-forward commit does not make sense into "
1136                             "an empty head"));
1137                 remote_head = want_commit(argv[0]);
1138                 if (!remote_head)
1139                         die(_("%s - not something we can merge"), argv[0]);
1140                 read_empty(remote_head->sha1, 0);
1141                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1142                                 DIE_ON_ERR);
1143                 return 0;
1144         } else {
1145                 struct strbuf merge_names = STRBUF_INIT;
1146
1147                 /* We are invoked directly as the first-class UI. */
1148                 head_arg = "HEAD";
1149
1150                 /*
1151                  * All the rest are the commits being merged;
1152                  * prepare the standard merge summary message to
1153                  * be appended to the given message.  If remote
1154                  * is invalid we will die later in the common
1155                  * codepath so we discard the error in this
1156                  * loop.
1157                  */
1158                 for (i = 0; i < argc; i++)
1159                         merge_name(argv[i], &merge_names);
1160
1161                 if (!have_message || shortlog_len) {
1162                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1163                                       shortlog_len);
1164                         if (merge_msg.len)
1165                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1166                 }
1167         }
1168
1169         if (head_invalid || !argc)
1170                 usage_with_options(builtin_merge_usage,
1171                         builtin_merge_options);
1172
1173         strbuf_addstr(&buf, "merge");
1174         for (i = 0; i < argc; i++)
1175                 strbuf_addf(&buf, " %s", argv[i]);
1176         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1177         strbuf_reset(&buf);
1178
1179         for (i = 0; i < argc; i++) {
1180                 struct object *o;
1181                 struct commit *commit;
1182
1183                 o = want_commit(argv[i]);
1184                 if (!o)
1185                         die(_("%s - not something we can merge"), argv[i]);
1186                 commit = lookup_commit(o->sha1);
1187                 commit->util = (void *)argv[i];
1188                 remotes = &commit_list_insert(commit, remotes)->next;
1189
1190                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1191                 setenv(buf.buf, argv[i], 1);
1192                 strbuf_reset(&buf);
1193         }
1194
1195         if (!use_strategies) {
1196                 if (!remoteheads->next)
1197                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1198                 else
1199                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1200         }
1201
1202         for (i = 0; i < use_strategies_nr; i++) {
1203                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1204                         allow_fast_forward = 0;
1205                 if (use_strategies[i]->attr & NO_TRIVIAL)
1206                         allow_trivial = 0;
1207         }
1208
1209         if (!remoteheads->next)
1210                 common = get_merge_bases(lookup_commit(head),
1211                                 remoteheads->item, 1);
1212         else {
1213                 struct commit_list *list = remoteheads;
1214                 commit_list_insert(lookup_commit(head), &list);
1215                 common = get_octopus_merge_bases(list);
1216                 free(list);
1217         }
1218
1219         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
1220                 DIE_ON_ERR);
1221
1222         if (!common)
1223                 ; /* No common ancestors found. We need a real merge. */
1224         else if (!remoteheads->next && !common->next &&
1225                         common->item == remoteheads->item) {
1226                 /*
1227                  * If head can reach all the merge then we are up to date.
1228                  * but first the most common case of merging one remote.
1229                  */
1230                 finish_up_to_date("Already up-to-date.");
1231                 return 0;
1232         } else if (allow_fast_forward && !remoteheads->next &&
1233                         !common->next &&
1234                         !hashcmp(common->item->object.sha1, head)) {
1235                 /* Again the most common case of merging one remote. */
1236                 struct strbuf msg = STRBUF_INIT;
1237                 struct object *o;
1238                 char hex[41];
1239
1240                 strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
1241
1242                 if (verbosity >= 0)
1243                         printf(_("Updating %s..%s\n"),
1244                                 hex,
1245                                 find_unique_abbrev(remoteheads->item->object.sha1,
1246                                 DEFAULT_ABBREV));
1247                 strbuf_addstr(&msg, "Fast-forward");
1248                 if (have_message)
1249                         strbuf_addstr(&msg,
1250                                 " (no commit created; -m option ignored)");
1251                 o = want_commit(sha1_to_hex(remoteheads->item->object.sha1));
1252                 if (!o)
1253                         return 1;
1254
1255                 if (checkout_fast_forward(head, remoteheads->item->object.sha1))
1256                         return 1;
1257
1258                 finish(o->sha1, msg.buf);
1259                 drop_save();
1260                 return 0;
1261         } else if (!remoteheads->next && common->next)
1262                 ;
1263                 /*
1264                  * We are not doing octopus and not fast-forward.  Need
1265                  * a real merge.
1266                  */
1267         else if (!remoteheads->next && !common->next && option_commit) {
1268                 /*
1269                  * We are not doing octopus, not fast-forward, and have
1270                  * only one common.
1271                  */
1272                 refresh_cache(REFRESH_QUIET);
1273                 if (allow_trivial && !fast_forward_only) {
1274                         /* See if it is really trivial. */
1275                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1276                         printf(_("Trying really trivial in-index merge...\n"));
1277                         if (!read_tree_trivial(common->item->object.sha1,
1278                                         head, remoteheads->item->object.sha1))
1279                                 return merge_trivial();
1280                         printf(_("Nope.\n"));
1281                 }
1282         } else {
1283                 /*
1284                  * An octopus.  If we can reach all the remote we are up
1285                  * to date.
1286                  */
1287                 int up_to_date = 1;
1288                 struct commit_list *j;
1289
1290                 for (j = remoteheads; j; j = j->next) {
1291                         struct commit_list *common_one;
1292
1293                         /*
1294                          * Here we *have* to calculate the individual
1295                          * merge_bases again, otherwise "git merge HEAD^
1296                          * HEAD^^" would be missed.
1297                          */
1298                         common_one = get_merge_bases(lookup_commit(head),
1299                                 j->item, 1);
1300                         if (hashcmp(common_one->item->object.sha1,
1301                                 j->item->object.sha1)) {
1302                                 up_to_date = 0;
1303                                 break;
1304                         }
1305                 }
1306                 if (up_to_date) {
1307                         finish_up_to_date("Already up-to-date. Yeeah!");
1308                         return 0;
1309                 }
1310         }
1311
1312         if (fast_forward_only)
1313                 die(_("Not possible to fast-forward, aborting."));
1314
1315         /* We are going to make a new commit. */
1316         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1317
1318         /*
1319          * At this point, we need a real merge.  No matter what strategy
1320          * we use, it would operate on the index, possibly affecting the
1321          * working tree, and when resolved cleanly, have the desired
1322          * tree in the index -- this means that the index must be in
1323          * sync with the head commit.  The strategies are responsible
1324          * to ensure this.
1325          */
1326         if (use_strategies_nr != 1) {
1327                 /*
1328                  * Stash away the local changes so that we can try more
1329                  * than one.
1330                  */
1331                 save_state();
1332         } else {
1333                 memcpy(stash, null_sha1, 20);
1334         }
1335
1336         for (i = 0; i < use_strategies_nr; i++) {
1337                 int ret;
1338                 if (i) {
1339                         printf(_("Rewinding the tree to pristine...\n"));
1340                         restore_state();
1341                 }
1342                 if (use_strategies_nr != 1)
1343                         printf(_("Trying merge strategy %s...\n"),
1344                                 use_strategies[i]->name);
1345                 /*
1346                  * Remember which strategy left the state in the working
1347                  * tree.
1348                  */
1349                 wt_strategy = use_strategies[i]->name;
1350
1351                 ret = try_merge_strategy(use_strategies[i]->name,
1352                         common, head_arg);
1353                 if (!option_commit && !ret) {
1354                         merge_was_ok = 1;
1355                         /*
1356                          * This is necessary here just to avoid writing
1357                          * the tree, but later we will *not* exit with
1358                          * status code 1 because merge_was_ok is set.
1359                          */
1360                         ret = 1;
1361                 }
1362
1363                 if (ret) {
1364                         /*
1365                          * The backend exits with 1 when conflicts are
1366                          * left to be resolved, with 2 when it does not
1367                          * handle the given merge at all.
1368                          */
1369                         if (ret == 1) {
1370                                 int cnt = evaluate_result();
1371
1372                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1373                                         best_strategy = use_strategies[i]->name;
1374                                         best_cnt = cnt;
1375                                 }
1376                         }
1377                         if (merge_was_ok)
1378                                 break;
1379                         else
1380                                 continue;
1381                 }
1382
1383                 /* Automerge succeeded. */
1384                 write_tree_trivial(result_tree);
1385                 automerge_was_ok = 1;
1386                 break;
1387         }
1388
1389         /*
1390          * If we have a resulting tree, that means the strategy module
1391          * auto resolved the merge cleanly.
1392          */
1393         if (automerge_was_ok)
1394                 return finish_automerge(common, result_tree, wt_strategy);
1395
1396         /*
1397          * Pick the result from the best strategy and have the user fix
1398          * it up.
1399          */
1400         if (!best_strategy) {
1401                 restore_state();
1402                 if (use_strategies_nr > 1)
1403                         fprintf(stderr,
1404                                 _("No merge strategy handled the merge.\n"));
1405                 else
1406                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1407                                 use_strategies[0]->name);
1408                 return 2;
1409         } else if (best_strategy == wt_strategy)
1410                 ; /* We already have its result in the working tree. */
1411         else {
1412                 printf(_("Rewinding the tree to pristine...\n"));
1413                 restore_state();
1414                 printf(_("Using the %s to prepare resolving by hand.\n"),
1415                         best_strategy);
1416                 try_merge_strategy(best_strategy, common, head_arg);
1417         }
1418
1419         if (squash)
1420                 finish(NULL, NULL);
1421         else {
1422                 int fd;
1423                 struct commit_list *j;
1424
1425                 for (j = remoteheads; j; j = j->next)
1426                         strbuf_addf(&buf, "%s\n",
1427                                 sha1_to_hex(j->item->object.sha1));
1428                 fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1429                 if (fd < 0)
1430                         die_errno(_("Could not open '%s' for writing"),
1431                                   git_path("MERGE_HEAD"));
1432                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1433                         die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1434                 close(fd);
1435                 strbuf_addch(&merge_msg, '\n');
1436                 write_merge_msg();
1437                 fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1438                 if (fd < 0)
1439                         die_errno(_("Could not open '%s' for writing"),
1440                                   git_path("MERGE_MODE"));
1441                 strbuf_reset(&buf);
1442                 if (!allow_fast_forward)
1443                         strbuf_addf(&buf, "no-ff");
1444                 if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1445                         die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1446                 close(fd);
1447         }
1448
1449         if (merge_was_ok) {
1450                 fprintf(stderr, _("Automatic merge went well; "
1451                         "stopped before committing as requested\n"));
1452                 return 0;
1453         } else
1454                 return suggest_conflicts(option_renormalize);
1455 }