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 #include "fmt-merge-msg.h"
  30 #include "gpg-interface.h"
  31
  32 #define DEFAULT_TWOHEAD (1<<0)
  33 #define DEFAULT_OCTOPUS (1<<1)
  34 #define NO_FAST_FORWARD (1<<2)
  35 #define NO_TRIVIAL      (1<<3)
  36
  37 struct strategy {
  38         const char *name;
  39         unsigned attr;
  40 };
  41
  42 static const char * const builtin_merge_usage[] = {
  43         "git merge [options] [<commit>...]",
  44         "git merge [options] <msg> HEAD <commit>",
  45         "git merge --abort",
  46         NULL
  47 };
  48
  49 static int show_diffstat = 1, shortlog_len = -1, squash;
  50 static int option_commit = 1, allow_fast_forward = 1;
  51 static int fast_forward_only, option_edit = -1;
  52 static int allow_trivial = 1, have_message;
  53 static int overwrite_ignore = 1;
  54 static struct strbuf merge_msg = STRBUF_INIT;
  55 static struct commit_list *remoteheads;
  56 static struct strategy **use_strategies;
  57 static size_t use_strategies_nr, use_strategies_alloc;
  58 static const char **xopts;
  59 static size_t xopts_nr, xopts_alloc;
  60 static const char *branch;
  61 static char *branch_mergeoptions;
  62 static int option_renormalize;
  63 static int verbosity;
  64 static int allow_rerere_auto;
  65 static int abort_current_merge;
  66 static int show_progress = -1;
  67 static int default_to_upstream;
  68 static const char *sign_commit;
  69
  70 static struct strategy all_strategy[] = {
  71         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  72         { "octopus",    DEFAULT_OCTOPUS },
  73         { "resolve",    0 },
  74         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  75         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  76 };
  77
  78 static const char *pull_twohead, *pull_octopus;
  79
  80 static int option_parse_message(const struct option *opt,
  81                                 const char *arg, int unset)
  82 {
  83         struct strbuf *buf = opt->value;
  84
  85         if (unset)
  86                 strbuf_setlen(buf, 0);
  87         else if (arg) {
  88                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  89                 have_message = 1;
  90         } else
  91                 return error(_("switch `m' requires a value"));
  92         return 0;
  93 }
  94
  95 static struct strategy *get_strategy(const char *name)
  96 {
  97         int i;
  98         struct strategy *ret;
  99         static struct cmdnames main_cmds, other_cmds;
 100         static int loaded;
 101
 102         if (!name)
 103                 return NULL;
 104
 105         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 106                 if (!strcmp(name, all_strategy[i].name))
 107                         return &all_strategy[i];
 108
 109         if (!loaded) {
 110                 struct cmdnames not_strategies;
 111                 loaded = 1;
 112
 113                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 114                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 115                 for (i = 0; i < main_cmds.cnt; i++) {
 116                         int j, found = 0;
 117                         struct cmdname *ent = main_cmds.names[i];
 118                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 119                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 120                                                 && !all_strategy[j].name[ent->len])
 121                                         found = 1;
 122                         if (!found)
 123                                 add_cmdname(&not_strategies, ent->name, ent->len);
 124                 }
 125                 exclude_cmds(&main_cmds, &not_strategies);
 126         }
 127         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 128                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 129                 fprintf(stderr, _("Available strategies are:"));
 130                 for (i = 0; i < main_cmds.cnt; i++)
 131                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 132                 fprintf(stderr, ".\n");
 133                 if (other_cmds.cnt) {
 134                         fprintf(stderr, _("Available custom strategies are:"));
 135                         for (i = 0; i < other_cmds.cnt; i++)
 136                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 137                         fprintf(stderr, ".\n");
 138                 }
 139                 exit(1);
 140         }
 141
 142         ret = xcalloc(1, sizeof(struct strategy));
 143         ret->name = xstrdup(name);
 144         ret->attr = NO_TRIVIAL;
 145         return ret;
 146 }
 147
 148 static void append_strategy(struct strategy *s)
 149 {
 150         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 151         use_strategies[use_strategies_nr++] = s;
 152 }
 153
 154 static int option_parse_strategy(const struct option *opt,
 155                                  const char *name, int unset)
 156 {
 157         if (unset)
 158                 return 0;
 159
 160         append_strategy(get_strategy(name));
 161         return 0;
 162 }
 163
 164 static int option_parse_x(const struct option *opt,
 165                           const char *arg, int unset)
 166 {
 167         if (unset)
 168                 return 0;
 169
 170         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 171         xopts[xopts_nr++] = xstrdup(arg);
 172         return 0;
 173 }
 174
 175 static int option_parse_n(const struct option *opt,
 176                           const char *arg, int unset)
 177 {
 178         show_diffstat = unset;
 179         return 0;
 180 }
 181
 182 static struct option builtin_merge_options[] = {
 183         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 184                 "do not show a diffstat at the end of the merge",
 185                 PARSE_OPT_NOARG, option_parse_n },
 186         OPT_BOOLEAN(0, "stat", &show_diffstat,
 187                 "show a diffstat at the end of the merge"),
 188         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 189         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 190           "add (at most <n>) entries from shortlog to merge commit message",
 191           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 192         OPT_BOOLEAN(0, "squash", &squash,
 193                 "create a single commit instead of doing a merge"),
 194         OPT_BOOLEAN(0, "commit", &option_commit,
 195                 "perform a commit if the merge succeeds (default)"),
 196         OPT_BOOL('e', "edit", &option_edit,
 197                 "edit message before committing"),
 198         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 199                 "allow fast-forward (default)"),
 200         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 201                 "abort if fast-forward is not possible"),
 202         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 203         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 204                 "merge strategy to use", option_parse_strategy),
 205         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 206                 "option for selected merge strategy", option_parse_x),
 207         OPT_CALLBACK('m', "message", &merge_msg, "message",
 208                 "merge commit message (for a non-fast-forward merge)",
 209                 option_parse_message),
 210         OPT__VERBOSITY(&verbosity),
 211         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 212                 "abort the current in-progress merge"),
 213         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 214         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, "key id",
 215           "GPG sign commit", PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 216         OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
 217         OPT_END()
 218 };
 219
 220 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 221 static void drop_save(void)
 222 {
 223         unlink(git_path("MERGE_HEAD"));
 224         unlink(git_path("MERGE_MSG"));
 225         unlink(git_path("MERGE_MODE"));
 226 }
 227
 228 static int save_state(unsigned char *stash)
 229 {
 230         int len;
 231         struct child_process cp;
 232         struct strbuf buffer = STRBUF_INIT;
 233         const char *argv[] = {"stash", "create", NULL};
 234
 235         memset(&cp, 0, sizeof(cp));
 236         cp.argv = argv;
 237         cp.out = -1;
 238         cp.git_cmd = 1;
 239
 240         if (start_command(&cp))
 241                 die(_("could not run stash."));
 242         len = strbuf_read(&buffer, cp.out, 1024);
 243         close(cp.out);
 244
 245         if (finish_command(&cp) || len < 0)
 246                 die(_("stash failed"));
 247         else if (!len)          /* no changes */
 248                 return -1;
 249         strbuf_setlen(&buffer, buffer.len-1);
 250         if (get_sha1(buffer.buf, stash))
 251                 die(_("not a valid object: %s"), buffer.buf);
 252         return 0;
 253 }
 254
 255 static void read_empty(unsigned const char *sha1, int verbose)
 256 {
 257         int i = 0;
 258         const char *args[7];
 259
 260         args[i++] = "read-tree";
 261         if (verbose)
 262                 args[i++] = "-v";
 263         args[i++] = "-m";
 264         args[i++] = "-u";
 265         args[i++] = EMPTY_TREE_SHA1_HEX;
 266         args[i++] = sha1_to_hex(sha1);
 267         args[i] = NULL;
 268
 269         if (run_command_v_opt(args, RUN_GIT_CMD))
 270                 die(_("read-tree failed"));
 271 }
 272
 273 static void reset_hard(unsigned const char *sha1, int verbose)
 274 {
 275         int i = 0;
 276         const char *args[6];
 277
 278         args[i++] = "read-tree";
 279         if (verbose)
 280                 args[i++] = "-v";
 281         args[i++] = "--reset";
 282         args[i++] = "-u";
 283         args[i++] = sha1_to_hex(sha1);
 284         args[i] = NULL;
 285
 286         if (run_command_v_opt(args, RUN_GIT_CMD))
 287                 die(_("read-tree failed"));
 288 }
 289
 290 static void restore_state(const unsigned char *head,
 291                           const unsigned char *stash)
 292 {
 293         struct strbuf sb = STRBUF_INIT;
 294         const char *args[] = { "stash", "apply", NULL, NULL };
 295
 296         if (is_null_sha1(stash))
 297                 return;
 298
 299         reset_hard(head, 1);
 300
 301         args[2] = sha1_to_hex(stash);
 302
 303         /*
 304          * It is OK to ignore error here, for example when there was
 305          * nothing to restore.
 306          */
 307         run_command_v_opt(args, RUN_GIT_CMD);
 308
 309         strbuf_release(&sb);
 310         refresh_cache(REFRESH_QUIET);
 311 }
 312
 313 /* This is called when no merge was necessary. */
 314 static void finish_up_to_date(const char *msg)
 315 {
 316         if (verbosity >= 0)
 317                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 318         drop_save();
 319 }
 320
 321 static void squash_message(struct commit *commit)
 322 {
 323         struct rev_info rev;
 324         struct strbuf out = STRBUF_INIT;
 325         struct commit_list *j;
 326         const char *filename;
 327         int fd;
 328         struct pretty_print_context ctx = {0};
 329
 330         printf(_("Squash commit -- not updating HEAD\n"));
 331         filename = git_path("SQUASH_MSG");
 332         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 333         if (fd < 0)
 334                 die_errno(_("Could not write to '%s'"), filename);
 335
 336         init_revisions(&rev, NULL);
 337         rev.ignore_merges = 1;
 338         rev.commit_format = CMIT_FMT_MEDIUM;
 339
 340         commit->object.flags |= UNINTERESTING;
 341         add_pending_object(&rev, &commit->object, NULL);
 342
 343         for (j = remoteheads; j; j = j->next)
 344                 add_pending_object(&rev, &j->item->object, NULL);
 345
 346         setup_revisions(0, NULL, &rev, NULL);
 347         if (prepare_revision_walk(&rev))
 348                 die(_("revision walk setup failed"));
 349
 350         ctx.abbrev = rev.abbrev;
 351         ctx.date_mode = rev.date_mode;
 352         ctx.fmt = rev.commit_format;
 353
 354         strbuf_addstr(&out, "Squashed commit of the following:\n");
 355         while ((commit = get_revision(&rev)) != NULL) {
 356                 strbuf_addch(&out, '\n');
 357                 strbuf_addf(&out, "commit %s\n",
 358                         sha1_to_hex(commit->object.sha1));
 359                 pretty_print_commit(&ctx, commit, &out);
 360         }
 361         if (write(fd, out.buf, out.len) < 0)
 362                 die_errno(_("Writing SQUASH_MSG"));
 363         if (close(fd))
 364                 die_errno(_("Finishing SQUASH_MSG"));
 365         strbuf_release(&out);
 366 }
 367
 368 static void finish(struct commit *head_commit,
 369                    const unsigned char *new_head, const char *msg)
 370 {
 371         struct strbuf reflog_message = STRBUF_INIT;
 372         const unsigned char *head = head_commit->object.sha1;
 373
 374         if (!msg)
 375                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 376         else {
 377                 if (verbosity >= 0)
 378                         printf("%s\n", msg);
 379                 strbuf_addf(&reflog_message, "%s: %s",
 380                         getenv("GIT_REFLOG_ACTION"), msg);
 381         }
 382         if (squash) {
 383                 squash_message(head_commit);
 384         } else {
 385                 if (verbosity >= 0 && !merge_msg.len)
 386                         printf(_("No merge message -- not updating HEAD\n"));
 387                 else {
 388                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 389                         update_ref(reflog_message.buf, "HEAD",
 390                                 new_head, head, 0,
 391                                 DIE_ON_ERR);
 392                         /*
 393                          * We ignore errors in 'gc --auto', since the
 394                          * user should see them.
 395                          */
 396                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 397                 }
 398         }
 399         if (new_head && show_diffstat) {
 400                 struct diff_options opts;
 401                 diff_setup(&opts);
 402                 opts.output_format |=
 403                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 404                 opts.detect_rename = DIFF_DETECT_RENAME;
 405                 if (diff_setup_done(&opts) < 0)
 406                         die(_("diff_setup_done failed"));
 407                 diff_tree_sha1(head, new_head, "", &opts);
 408                 diffcore_std(&opts);
 409                 diff_flush(&opts);
 410         }
 411
 412         /* Run a post-merge hook */
 413         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 414
 415         strbuf_release(&reflog_message);
 416 }
 417
 418 /* Get the name for the merge commit's message. */
 419 static void merge_name(const char *remote, struct strbuf *msg)
 420 {
 421         struct commit *remote_head;
 422         unsigned char branch_head[20];
 423         struct strbuf buf = STRBUF_INIT;
 424         struct strbuf bname = STRBUF_INIT;
 425         const char *ptr;
 426         char *found_ref;
 427         int len, early;
 428
 429         strbuf_branchname(&bname, remote);
 430         remote = bname.buf;
 431
 432         memset(branch_head, 0, sizeof(branch_head));
 433         remote_head = get_merge_parent(remote);
 434         if (!remote_head)
 435                 die(_("'%s' does not point to a commit"), remote);
 436
 437         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 438                 if (!prefixcmp(found_ref, "refs/heads/")) {
 439                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 440                                     sha1_to_hex(branch_head), remote);
 441                         goto cleanup;
 442                 }
 443                 if (!prefixcmp(found_ref, "refs/tags/")) {
 444                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 445                                     sha1_to_hex(branch_head), remote);
 446                         goto cleanup;
 447                 }
 448                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 449                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 450                                     sha1_to_hex(branch_head), remote);
 451                         goto cleanup;
 452                 }
 453         }
 454
 455         /* See if remote matches <name>^^^.. or <name>~<number> */
 456         for (len = 0, ptr = remote + strlen(remote);
 457              remote < ptr && ptr[-1] == '^';
 458              ptr--)
 459                 len++;
 460         if (len)
 461                 early = 1;
 462         else {
 463                 early = 0;
 464                 ptr = strrchr(remote, '~');
 465                 if (ptr) {
 466                         int seen_nonzero = 0;
 467
 468                         len++; /* count ~ */
 469                         while (*++ptr && isdigit(*ptr)) {
 470                                 seen_nonzero |= (*ptr != '0');
 471                                 len++;
 472                         }
 473                         if (*ptr)
 474                                 len = 0; /* not ...~<number> */
 475                         else if (seen_nonzero)
 476                                 early = 1;
 477                         else if (len == 1)
 478                                 early = 1; /* "name~" is "name~1"! */
 479                 }
 480         }
 481         if (len) {
 482                 struct strbuf truname = STRBUF_INIT;
 483                 strbuf_addstr(&truname, "refs/heads/");
 484                 strbuf_addstr(&truname, remote);
 485                 strbuf_setlen(&truname, truname.len - len);
 486                 if (ref_exists(truname.buf)) {
 487                         strbuf_addf(msg,
 488                                     "%s\t\tbranch '%s'%s of .\n",
 489                                     sha1_to_hex(remote_head->object.sha1),
 490                                     truname.buf + 11,
 491                                     (early ? " (early part)" : ""));
 492                         strbuf_release(&truname);
 493                         goto cleanup;
 494                 }
 495         }
 496
 497         if (!strcmp(remote, "FETCH_HEAD") &&
 498                         !access(git_path("FETCH_HEAD"), R_OK)) {
 499                 const char *filename;
 500                 FILE *fp;
 501                 struct strbuf line = STRBUF_INIT;
 502                 char *ptr;
 503
 504                 filename = git_path("FETCH_HEAD");
 505                 fp = fopen(filename, "r");
 506                 if (!fp)
 507                         die_errno(_("could not open '%s' for reading"),
 508                                   filename);
 509                 strbuf_getline(&line, fp, '\n');
 510                 fclose(fp);
 511                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 512                 if (ptr)
 513                         strbuf_remove(&line, ptr-line.buf+1, 13);
 514                 strbuf_addbuf(msg, &line);
 515                 strbuf_release(&line);
 516                 goto cleanup;
 517         }
 518         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 519                 sha1_to_hex(remote_head->object.sha1), remote);
 520 cleanup:
 521         strbuf_release(&buf);
 522         strbuf_release(&bname);
 523 }
 524
 525 static void parse_branch_merge_options(char *bmo)
 526 {
 527         const char **argv;
 528         int argc;
 529
 530         if (!bmo)
 531                 return;
 532         argc = split_cmdline(bmo, &argv);
 533         if (argc < 0)
 534                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 535                     split_cmdline_strerror(argc));
 536         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 537         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 538         argc++;
 539         argv[0] = "branch.*.mergeoptions";
 540         parse_options(argc, argv, NULL, builtin_merge_options,
 541                       builtin_merge_usage, 0);
 542         free(argv);
 543 }
 544
 545 static int git_merge_config(const char *k, const char *v, void *cb)
 546 {
 547         int status;
 548
 549         if (branch && !prefixcmp(k, "branch.") &&
 550                 !prefixcmp(k + 7, branch) &&
 551                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 552                 free(branch_mergeoptions);
 553                 branch_mergeoptions = xstrdup(v);
 554                 return 0;
 555         }
 556
 557         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 558                 show_diffstat = git_config_bool(k, v);
 559         else if (!strcmp(k, "pull.twohead"))
 560                 return git_config_string(&pull_twohead, k, v);
 561         else if (!strcmp(k, "pull.octopus"))
 562                 return git_config_string(&pull_octopus, k, v);
 563         else if (!strcmp(k, "merge.renormalize"))
 564                 option_renormalize = git_config_bool(k, v);
 565         else if (!strcmp(k, "merge.ff")) {
 566                 int boolval = git_config_maybe_bool(k, v);
 567                 if (0 <= boolval) {
 568                         allow_fast_forward = boolval;
 569                 } else if (v && !strcmp(v, "only")) {
 570                         allow_fast_forward = 1;
 571                         fast_forward_only = 1;
 572                 } /* do not barf on values from future versions of git */
 573                 return 0;
 574         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 575                 default_to_upstream = git_config_bool(k, v);
 576                 return 0;
 577         }
 578
 579         status = fmt_merge_msg_config(k, v, cb);
 580         if (status)
 581                 return status;
 582         status = git_gpg_config(k, v, NULL);
 583         if (status)
 584                 return status;
 585         return git_diff_ui_config(k, v, cb);
 586 }
 587
 588 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 589                              unsigned char *one)
 590 {
 591         int i, nr_trees = 0;
 592         struct tree *trees[MAX_UNPACK_TREES];
 593         struct tree_desc t[MAX_UNPACK_TREES];
 594         struct unpack_trees_options opts;
 595
 596         memset(&opts, 0, sizeof(opts));
 597         opts.head_idx = 2;
 598         opts.src_index = &the_index;
 599         opts.dst_index = &the_index;
 600         opts.update = 1;
 601         opts.verbose_update = 1;
 602         opts.trivial_merges_only = 1;
 603         opts.merge = 1;
 604         trees[nr_trees] = parse_tree_indirect(common);
 605         if (!trees[nr_trees++])
 606                 return -1;
 607         trees[nr_trees] = parse_tree_indirect(head);
 608         if (!trees[nr_trees++])
 609                 return -1;
 610         trees[nr_trees] = parse_tree_indirect(one);
 611         if (!trees[nr_trees++])
 612                 return -1;
 613         opts.fn = threeway_merge;
 614         cache_tree_free(&active_cache_tree);
 615         for (i = 0; i < nr_trees; i++) {
 616                 parse_tree(trees[i]);
 617                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 618         }
 619         if (unpack_trees(nr_trees, t, &opts))
 620                 return -1;
 621         return 0;
 622 }
 623
 624 static void write_tree_trivial(unsigned char *sha1)
 625 {
 626         if (write_cache_as_tree(sha1, 0, NULL))
 627                 die(_("git write-tree failed to write a tree"));
 628 }
 629
 630 static const char *merge_argument(struct commit *commit)
 631 {
 632         if (commit)
 633                 return sha1_to_hex(commit->object.sha1);
 634         else
 635                 return EMPTY_TREE_SHA1_HEX;
 636 }
 637
 638 int try_merge_command(const char *strategy, size_t xopts_nr,
 639                       const char **xopts, struct commit_list *common,
 640                       const char *head_arg, struct commit_list *remotes)
 641 {
 642         const char **args;
 643         int i = 0, x = 0, ret;
 644         struct commit_list *j;
 645         struct strbuf buf = STRBUF_INIT;
 646
 647         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 648                         commit_list_count(remotes)) * sizeof(char *));
 649         strbuf_addf(&buf, "merge-%s", strategy);
 650         args[i++] = buf.buf;
 651         for (x = 0; x < xopts_nr; x++) {
 652                 char *s = xmalloc(strlen(xopts[x])+2+1);
 653                 strcpy(s, "--");
 654                 strcpy(s+2, xopts[x]);
 655                 args[i++] = s;
 656         }
 657         for (j = common; j; j = j->next)
 658                 args[i++] = xstrdup(merge_argument(j->item));
 659         args[i++] = "--";
 660         args[i++] = head_arg;
 661         for (j = remotes; j; j = j->next)
 662                 args[i++] = xstrdup(merge_argument(j->item));
 663         args[i] = NULL;
 664         ret = run_command_v_opt(args, RUN_GIT_CMD);
 665         strbuf_release(&buf);
 666         i = 1;
 667         for (x = 0; x < xopts_nr; x++)
 668                 free((void *)args[i++]);
 669         for (j = common; j; j = j->next)
 670                 free((void *)args[i++]);
 671         i += 2;
 672         for (j = remotes; j; j = j->next)
 673                 free((void *)args[i++]);
 674         free(args);
 675         discard_cache();
 676         if (read_cache() < 0)
 677                 die(_("failed to read the cache"));
 678         resolve_undo_clear();
 679
 680         return ret;
 681 }
 682
 683 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 684                               struct commit *head, const char *head_arg)
 685 {
 686         int index_fd;
 687         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 688
 689         index_fd = hold_locked_index(lock, 1);
 690         refresh_cache(REFRESH_QUIET);
 691         if (active_cache_changed &&
 692                         (write_cache(index_fd, active_cache, active_nr) ||
 693                          commit_locked_index(lock)))
 694                 return error(_("Unable to write index."));
 695         rollback_lock_file(lock);
 696
 697         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 698                 int clean, x;
 699                 struct commit *result;
 700                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 701                 int index_fd;
 702                 struct commit_list *reversed = NULL;
 703                 struct merge_options o;
 704                 struct commit_list *j;
 705
 706                 if (remoteheads->next) {
 707                         error(_("Not handling anything other than two heads merge."));
 708                         return 2;
 709                 }
 710
 711                 init_merge_options(&o);
 712                 if (!strcmp(strategy, "subtree"))
 713                         o.subtree_shift = "";
 714
 715                 o.renormalize = option_renormalize;
 716                 o.show_rename_progress =
 717                         show_progress == -1 ? isatty(2) : show_progress;
 718
 719                 for (x = 0; x < xopts_nr; x++)
 720                         if (parse_merge_opt(&o, xopts[x]))
 721                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 722
 723                 o.branch1 = head_arg;
 724                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 725
 726                 for (j = common; j; j = j->next)
 727                         commit_list_insert(j->item, &reversed);
 728
 729                 index_fd = hold_locked_index(lock, 1);
 730                 clean = merge_recursive(&o, head,
 731                                 remoteheads->item, reversed, &result);
 732                 if (active_cache_changed &&
 733                                 (write_cache(index_fd, active_cache, active_nr) ||
 734                                  commit_locked_index(lock)))
 735                         die (_("unable to write %s"), get_index_file());
 736                 rollback_lock_file(lock);
 737                 return clean ? 0 : 1;
 738         } else {
 739                 return try_merge_command(strategy, xopts_nr, xopts,
 740                                                 common, head_arg, remoteheads);
 741         }
 742 }
 743
 744 static void count_diff_files(struct diff_queue_struct *q,
 745                              struct diff_options *opt, void *data)
 746 {
 747         int *count = data;
 748
 749         (*count) += q->nr;
 750 }
 751
 752 static int count_unmerged_entries(void)
 753 {
 754         int i, ret = 0;
 755
 756         for (i = 0; i < active_nr; i++)
 757                 if (ce_stage(active_cache[i]))
 758                         ret++;
 759
 760         return ret;
 761 }
 762
 763 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 764 {
 765         struct tree *trees[MAX_UNPACK_TREES];
 766         struct unpack_trees_options opts;
 767         struct tree_desc t[MAX_UNPACK_TREES];
 768         int i, fd, nr_trees = 0;
 769         struct dir_struct dir;
 770         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 771
 772         refresh_cache(REFRESH_QUIET);
 773
 774         fd = hold_locked_index(lock_file, 1);
 775
 776         memset(&trees, 0, sizeof(trees));
 777         memset(&opts, 0, sizeof(opts));
 778         memset(&t, 0, sizeof(t));
 779         if (overwrite_ignore) {
 780                 memset(&dir, 0, sizeof(dir));
 781                 dir.flags |= DIR_SHOW_IGNORED;
 782                 setup_standard_excludes(&dir);
 783                 opts.dir = &dir;
 784         }
 785
 786         opts.head_idx = 1;
 787         opts.src_index = &the_index;
 788         opts.dst_index = &the_index;
 789         opts.update = 1;
 790         opts.verbose_update = 1;
 791         opts.merge = 1;
 792         opts.fn = twoway_merge;
 793         setup_unpack_trees_porcelain(&opts, "merge");
 794
 795         trees[nr_trees] = parse_tree_indirect(head);
 796         if (!trees[nr_trees++])
 797                 return -1;
 798         trees[nr_trees] = parse_tree_indirect(remote);
 799         if (!trees[nr_trees++])
 800                 return -1;
 801         for (i = 0; i < nr_trees; i++) {
 802                 parse_tree(trees[i]);
 803                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 804         }
 805         if (unpack_trees(nr_trees, t, &opts))
 806                 return -1;
 807         if (write_cache(fd, active_cache, active_nr) ||
 808                 commit_locked_index(lock_file))
 809                 die(_("unable to write new index file"));
 810         return 0;
 811 }
 812
 813 static void split_merge_strategies(const char *string, struct strategy **list,
 814                                    int *nr, int *alloc)
 815 {
 816         char *p, *q, *buf;
 817
 818         if (!string)
 819                 return;
 820
 821         buf = xstrdup(string);
 822         q = buf;
 823         for (;;) {
 824                 p = strchr(q, ' ');
 825                 if (!p) {
 826                         ALLOC_GROW(*list, *nr + 1, *alloc);
 827                         (*list)[(*nr)++].name = xstrdup(q);
 828                         free(buf);
 829                         return;
 830                 } else {
 831                         *p = '\0';
 832                         ALLOC_GROW(*list, *nr + 1, *alloc);
 833                         (*list)[(*nr)++].name = xstrdup(q);
 834                         q = ++p;
 835                 }
 836         }
 837 }
 838
 839 static void add_strategies(const char *string, unsigned attr)
 840 {
 841         struct strategy *list = NULL;
 842         int list_alloc = 0, list_nr = 0, i;
 843
 844         memset(&list, 0, sizeof(list));
 845         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 846         if (list) {
 847                 for (i = 0; i < list_nr; i++)
 848                         append_strategy(get_strategy(list[i].name));
 849                 return;
 850         }
 851         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 852                 if (all_strategy[i].attr & attr)
 853                         append_strategy(&all_strategy[i]);
 854
 855 }
 856
 857 static void write_merge_msg(struct strbuf *msg)
 858 {
 859         const char *filename = git_path("MERGE_MSG");
 860         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 861         if (fd < 0)
 862                 die_errno(_("Could not open '%s' for writing"),
 863                           filename);
 864         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 865                 die_errno(_("Could not write to '%s'"), filename);
 866         close(fd);
 867 }
 868
 869 static void read_merge_msg(struct strbuf *msg)
 870 {
 871         const char *filename = git_path("MERGE_MSG");
 872         strbuf_reset(msg);
 873         if (strbuf_read_file(msg, filename, 0) < 0)
 874                 die_errno(_("Could not read from '%s'"), filename);
 875 }
 876
 877 static void write_merge_state(void);
 878 static void abort_commit(const char *err_msg)
 879 {
 880         if (err_msg)
 881                 error("%s", err_msg);
 882         fprintf(stderr,
 883                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 884         write_merge_state();
 885         exit(1);
 886 }
 887
 888 static const char merge_editor_comment[] =
 889 N_("Please enter a commit message to explain why this merge is necessary,\n"
 890    "especially if it merges an updated upstream into a topic branch.\n"
 891    "\n"
 892    "Lines starting with '#' will be ignored, and an empty message aborts\n"
 893    "the commit.\n");
 894
 895 static void prepare_to_commit(void)
 896 {
 897         struct strbuf msg = STRBUF_INIT;
 898         const char *comment = _(merge_editor_comment);
 899         strbuf_addbuf(&msg, &merge_msg);
 900         strbuf_addch(&msg, '\n');
 901         if (0 < option_edit)
 902                 strbuf_add_lines(&msg, "# ", comment, strlen(comment));
 903         write_merge_msg(&msg);
 904         run_hook(get_index_file(), "prepare-commit-msg",
 905                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 906         if (option_edit) {
 907                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 908                         abort_commit(NULL);
 909         }
 910         read_merge_msg(&msg);
 911         stripspace(&msg, option_edit);
 912         if (!msg.len)
 913                 abort_commit(_("Empty commit message."));
 914         strbuf_release(&merge_msg);
 915         strbuf_addbuf(&merge_msg, &msg);
 916         strbuf_release(&msg);
 917 }
 918
 919 static int merge_trivial(struct commit *head)
 920 {
 921         unsigned char result_tree[20], result_commit[20];
 922         struct commit_list *parent = xmalloc(sizeof(*parent));
 923
 924         write_tree_trivial(result_tree);
 925         printf(_("Wonderful.\n"));
 926         parent->item = head;
 927         parent->next = xmalloc(sizeof(*parent->next));
 928         parent->next->item = remoteheads->item;
 929         parent->next->next = NULL;
 930         prepare_to_commit();
 931         if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
 932                         sign_commit))
 933                 die(_("failed to write commit object"));
 934         finish(head, result_commit, "In-index merge");
 935         drop_save();
 936         return 0;
 937 }
 938
 939 static int finish_automerge(struct commit *head,
 940                             struct commit_list *common,
 941                             unsigned char *result_tree,
 942                             const char *wt_strategy)
 943 {
 944         struct commit_list *parents = NULL, *j;
 945         struct strbuf buf = STRBUF_INIT;
 946         unsigned char result_commit[20];
 947
 948         free_commit_list(common);
 949         if (allow_fast_forward) {
 950                 parents = remoteheads;
 951                 commit_list_insert(head, &parents);
 952                 parents = reduce_heads(parents);
 953         } else {
 954                 struct commit_list **pptr = &parents;
 955
 956                 pptr = &commit_list_insert(head,
 957                                 pptr)->next;
 958                 for (j = remoteheads; j; j = j->next)
 959                         pptr = &commit_list_insert(j->item, pptr)->next;
 960         }
 961         strbuf_addch(&merge_msg, '\n');
 962         prepare_to_commit();
 963         free_commit_list(remoteheads);
 964         if (commit_tree(&merge_msg, result_tree, parents, result_commit,
 965                         NULL, sign_commit))
 966                 die(_("failed to write commit object"));
 967         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 968         finish(head, result_commit, buf.buf);
 969         strbuf_release(&buf);
 970         drop_save();
 971         return 0;
 972 }
 973
 974 static int suggest_conflicts(int renormalizing)
 975 {
 976         const char *filename;
 977         FILE *fp;
 978         int pos;
 979
 980         filename = git_path("MERGE_MSG");
 981         fp = fopen(filename, "a");
 982         if (!fp)
 983                 die_errno(_("Could not open '%s' for writing"), filename);
 984         fprintf(fp, "\nConflicts:\n");
 985         for (pos = 0; pos < active_nr; pos++) {
 986                 struct cache_entry *ce = active_cache[pos];
 987
 988                 if (ce_stage(ce)) {
 989                         fprintf(fp, "\t%s\n", ce->name);
 990                         while (pos + 1 < active_nr &&
 991                                         !strcmp(ce->name,
 992                                                 active_cache[pos + 1]->name))
 993                                 pos++;
 994                 }
 995         }
 996         fclose(fp);
 997         rerere(allow_rerere_auto);
 998         printf(_("Automatic merge failed; "
 999                         "fix conflicts and then commit the result.\n"));
1000         return 1;
1001 }
1002
1003 static struct commit *is_old_style_invocation(int argc, const char **argv,
1004                                               const unsigned char *head)
1005 {
1006         struct commit *second_token = NULL;
1007         if (argc > 2) {
1008                 unsigned char second_sha1[20];
1009
1010                 if (get_sha1(argv[1], second_sha1))
1011                         return NULL;
1012                 second_token = lookup_commit_reference_gently(second_sha1, 0);
1013                 if (!second_token)
1014                         die(_("'%s' is not a commit"), argv[1]);
1015                 if (hashcmp(second_token->object.sha1, head))
1016                         return NULL;
1017         }
1018         return second_token;
1019 }
1020
1021 static int evaluate_result(void)
1022 {
1023         int cnt = 0;
1024         struct rev_info rev;
1025
1026         /* Check how many files differ. */
1027         init_revisions(&rev, "");
1028         setup_revisions(0, NULL, &rev, NULL);
1029         rev.diffopt.output_format |=
1030                 DIFF_FORMAT_CALLBACK;
1031         rev.diffopt.format_callback = count_diff_files;
1032         rev.diffopt.format_callback_data = &cnt;
1033         run_diff_files(&rev, 0);
1034
1035         /*
1036          * Check how many unmerged entries are
1037          * there.
1038          */
1039         cnt += count_unmerged_entries();
1040
1041         return cnt;
1042 }
1043
1044 /*
1045  * Pretend as if the user told us to merge with the tracking
1046  * branch we have for the upstream of the current branch
1047  */
1048 static int setup_with_upstream(const char ***argv)
1049 {
1050         struct branch *branch = branch_get(NULL);
1051         int i;
1052         const char **args;
1053
1054         if (!branch)
1055                 die(_("No current branch."));
1056         if (!branch->remote)
1057                 die(_("No remote for the current branch."));
1058         if (!branch->merge_nr)
1059                 die(_("No default upstream defined for the current branch."));
1060
1061         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1062         for (i = 0; i < branch->merge_nr; i++) {
1063                 if (!branch->merge[i]->dst)
1064                         die(_("No remote tracking branch for %s from %s"),
1065                             branch->merge[i]->src, branch->remote_name);
1066                 args[i] = branch->merge[i]->dst;
1067         }
1068         args[i] = NULL;
1069         *argv = args;
1070         return i;
1071 }
1072
1073 static void write_merge_state(void)
1074 {
1075         const char *filename;
1076         int fd;
1077         struct commit_list *j;
1078         struct strbuf buf = STRBUF_INIT;
1079
1080         for (j = remoteheads; j; j = j->next) {
1081                 unsigned const char *sha1;
1082                 struct commit *c = j->item;
1083                 if (c->util && merge_remote_util(c)->obj) {
1084                         sha1 = merge_remote_util(c)->obj->sha1;
1085                 } else {
1086                         sha1 = c->object.sha1;
1087                 }
1088                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1089         }
1090         filename = git_path("MERGE_HEAD");
1091         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1092         if (fd < 0)
1093                 die_errno(_("Could not open '%s' for writing"), filename);
1094         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1095                 die_errno(_("Could not write to '%s'"), filename);
1096         close(fd);
1097         strbuf_addch(&merge_msg, '\n');
1098         write_merge_msg(&merge_msg);
1099
1100         filename = git_path("MERGE_MODE");
1101         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1102         if (fd < 0)
1103                 die_errno(_("Could not open '%s' for writing"), filename);
1104         strbuf_reset(&buf);
1105         if (!allow_fast_forward)
1106                 strbuf_addf(&buf, "no-ff");
1107         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1108                 die_errno(_("Could not write to '%s'"), filename);
1109         close(fd);
1110 }
1111
1112 static int default_edit_option(void)
1113 {
1114         static const char name[] = "GIT_MERGE_AUTOEDIT";
1115         const char *e = getenv(name);
1116         struct stat st_stdin, st_stdout;
1117
1118         if (have_message)
1119                 /* an explicit -m msg without --[no-]edit */
1120                 return 0;
1121
1122         if (e) {
1123                 int v = git_config_maybe_bool(name, e);
1124                 if (v < 0)
1125                         die("Bad value '%s' in environment '%s'", e, name);
1126                 return v;
1127         }
1128
1129         /* Use editor if stdin and stdout are the same and is a tty */
1130         return (!fstat(0, &st_stdin) &&
1131                 !fstat(1, &st_stdout) &&
1132                 isatty(0) && isatty(1) &&
1133                 st_stdin.st_dev == st_stdout.st_dev &&
1134                 st_stdin.st_ino == st_stdout.st_ino &&
1135                 st_stdin.st_mode == st_stdout.st_mode);
1136 }
1137
1138
1139 int cmd_merge(int argc, const char **argv, const char *prefix)
1140 {
1141         unsigned char result_tree[20];
1142         unsigned char stash[20];
1143         unsigned char head_sha1[20];
1144         struct commit *head_commit;
1145         struct strbuf buf = STRBUF_INIT;
1146         const char *head_arg;
1147         int flag, i, ret = 0;
1148         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1149         struct commit_list *common = NULL;
1150         const char *best_strategy = NULL, *wt_strategy = NULL;
1151         struct commit_list **remotes = &remoteheads;
1152         void *branch_to_free;
1153
1154         if (argc == 2 && !strcmp(argv[1], "-h"))
1155                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1156
1157         /*
1158          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1159          * current branch.
1160          */
1161         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1162         if (branch && !prefixcmp(branch, "refs/heads/"))
1163                 branch += 11;
1164         if (!branch || is_null_sha1(head_sha1))
1165                 head_commit = NULL;
1166         else
1167                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1168
1169         git_config(git_merge_config, NULL);
1170
1171         if (branch_mergeoptions)
1172                 parse_branch_merge_options(branch_mergeoptions);
1173         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1174                         builtin_merge_usage, 0);
1175         if (shortlog_len < 0)
1176                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1177
1178         if (verbosity < 0 && show_progress == -1)
1179                 show_progress = 0;
1180
1181         if (abort_current_merge) {
1182                 int nargc = 2;
1183                 const char *nargv[] = {"reset", "--merge", NULL};
1184
1185                 if (!file_exists(git_path("MERGE_HEAD")))
1186                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1187
1188                 /* Invoke 'git reset --merge' */
1189                 ret = cmd_reset(nargc, nargv, prefix);
1190                 goto done;
1191         }
1192
1193         if (read_cache_unmerged())
1194                 die_resolve_conflict("merge");
1195
1196         if (file_exists(git_path("MERGE_HEAD"))) {
1197                 /*
1198                  * There is no unmerged entry, don't advise 'git
1199                  * add/rm <file>', just 'git commit'.
1200                  */
1201                 if (advice_resolve_conflict)
1202                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1203                                   "Please, commit your changes before you can merge."));
1204                 else
1205                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1206         }
1207         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1208                 if (advice_resolve_conflict)
1209                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1210                             "Please, commit your changes before you can merge."));
1211                 else
1212                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1213         }
1214         resolve_undo_clear();
1215
1216         if (verbosity < 0)
1217                 show_diffstat = 0;
1218
1219         if (squash) {
1220                 if (!allow_fast_forward)
1221                         die(_("You cannot combine --squash with --no-ff."));
1222                 option_commit = 0;
1223         }
1224
1225         if (!allow_fast_forward && fast_forward_only)
1226                 die(_("You cannot combine --no-ff with --ff-only."));
1227
1228         if (!abort_current_merge) {
1229                 if (!argc) {
1230                         if (default_to_upstream)
1231                                 argc = setup_with_upstream(&argv);
1232                         else
1233                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1234                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1235                         argv[0] = "@{-1}";
1236         }
1237         if (!argc)
1238                 usage_with_options(builtin_merge_usage,
1239                         builtin_merge_options);
1240
1241         /*
1242          * This could be traditional "merge <msg> HEAD <commit>..."  and
1243          * the way we can tell it is to see if the second token is HEAD,
1244          * but some people might have misused the interface and used a
1245          * committish that is the same as HEAD there instead.
1246          * Traditional format never would have "-m" so it is an
1247          * additional safety measure to check for it.
1248          */
1249
1250         if (!have_message && head_commit &&
1251             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1252                 strbuf_addstr(&merge_msg, argv[0]);
1253                 head_arg = argv[1];
1254                 argv += 2;
1255                 argc -= 2;
1256         } else if (!head_commit) {
1257                 struct commit *remote_head;
1258                 /*
1259                  * If the merged head is a valid one there is no reason
1260                  * to forbid "git merge" into a branch yet to be born.
1261                  * We do the same for "git pull".
1262                  */
1263                 if (argc != 1)
1264                         die(_("Can merge only exactly one commit into "
1265                                 "empty head"));
1266                 if (squash)
1267                         die(_("Squash commit into empty head not supported yet"));
1268                 if (!allow_fast_forward)
1269                         die(_("Non-fast-forward commit does not make sense into "
1270                             "an empty head"));
1271                 remote_head = get_merge_parent(argv[0]);
1272                 if (!remote_head)
1273                         die(_("%s - not something we can merge"), argv[0]);
1274                 read_empty(remote_head->object.sha1, 0);
1275                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1276                            NULL, 0, DIE_ON_ERR);
1277                 goto done;
1278         } else {
1279                 struct strbuf merge_names = STRBUF_INIT;
1280
1281                 /* We are invoked directly as the first-class UI. */
1282                 head_arg = "HEAD";
1283
1284                 /*
1285                  * All the rest are the commits being merged; prepare
1286                  * the standard merge summary message to be appended
1287                  * to the given message.
1288                  */
1289                 for (i = 0; i < argc; i++)
1290                         merge_name(argv[i], &merge_names);
1291
1292                 if (!have_message || shortlog_len) {
1293                         struct fmt_merge_msg_opts opts;
1294                         memset(&opts, 0, sizeof(opts));
1295                         opts.add_title = !have_message;
1296                         opts.shortlog_len = shortlog_len;
1297
1298                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1299                         if (merge_msg.len)
1300                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1301                 }
1302         }
1303
1304         if (!head_commit || !argc)
1305                 usage_with_options(builtin_merge_usage,
1306                         builtin_merge_options);
1307
1308         strbuf_addstr(&buf, "merge");
1309         for (i = 0; i < argc; i++)
1310                 strbuf_addf(&buf, " %s", argv[i]);
1311         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1312         strbuf_reset(&buf);
1313
1314         for (i = 0; i < argc; i++) {
1315                 struct commit *commit = get_merge_parent(argv[i]);
1316                 if (!commit)
1317                         die(_("%s - not something we can merge"), argv[i]);
1318                 remotes = &commit_list_insert(commit, remotes)->next;
1319                 strbuf_addf(&buf, "GITHEAD_%s",
1320                             sha1_to_hex(commit->object.sha1));
1321                 setenv(buf.buf, argv[i], 1);
1322                 strbuf_reset(&buf);
1323                 if (!fast_forward_only &&
1324                     merge_remote_util(commit) &&
1325                     merge_remote_util(commit)->obj &&
1326                     merge_remote_util(commit)->obj->type == OBJ_TAG) {
1327                         if (option_edit < 0)
1328                                 option_edit = default_edit_option();
1329                         allow_fast_forward = 0;
1330                 }
1331         }
1332
1333         if (option_edit < 0)
1334                 option_edit = 0;
1335
1336         if (!use_strategies) {
1337                 if (!remoteheads->next)
1338                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1339                 else
1340                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1341         }
1342
1343         for (i = 0; i < use_strategies_nr; i++) {
1344                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1345                         allow_fast_forward = 0;
1346                 if (use_strategies[i]->attr & NO_TRIVIAL)
1347                         allow_trivial = 0;
1348         }
1349
1350         if (!remoteheads->next)
1351                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1352         else {
1353                 struct commit_list *list = remoteheads;
1354                 commit_list_insert(head_commit, &list);
1355                 common = get_octopus_merge_bases(list);
1356                 free(list);
1357         }
1358
1359         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1360                    NULL, 0, DIE_ON_ERR);
1361
1362         if (!common)
1363                 ; /* No common ancestors found. We need a real merge. */
1364         else if (!remoteheads->next && !common->next &&
1365                         common->item == remoteheads->item) {
1366                 /*
1367                  * If head can reach all the merge then we are up to date.
1368                  * but first the most common case of merging one remote.
1369                  */
1370                 finish_up_to_date("Already up-to-date.");
1371                 goto done;
1372         } else if (allow_fast_forward && !remoteheads->next &&
1373                         !common->next &&
1374                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1375                 /* Again the most common case of merging one remote. */
1376                 struct strbuf msg = STRBUF_INIT;
1377                 struct commit *commit;
1378                 char hex[41];
1379
1380                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1381
1382                 if (verbosity >= 0)
1383                         printf(_("Updating %s..%s\n"),
1384                                 hex,
1385                                 find_unique_abbrev(remoteheads->item->object.sha1,
1386                                 DEFAULT_ABBREV));
1387                 strbuf_addstr(&msg, "Fast-forward");
1388                 if (have_message)
1389                         strbuf_addstr(&msg,
1390                                 " (no commit created; -m option ignored)");
1391                 commit = remoteheads->item;
1392                 if (!commit) {
1393                         ret = 1;
1394                         goto done;
1395                 }
1396
1397                 if (checkout_fast_forward(head_commit->object.sha1,
1398                                           commit->object.sha1)) {
1399                         ret = 1;
1400                         goto done;
1401                 }
1402
1403                 finish(head_commit, commit->object.sha1, msg.buf);
1404                 drop_save();
1405                 goto done;
1406         } else if (!remoteheads->next && common->next)
1407                 ;
1408                 /*
1409                  * We are not doing octopus and not fast-forward.  Need
1410                  * a real merge.
1411                  */
1412         else if (!remoteheads->next && !common->next && option_commit) {
1413                 /*
1414                  * We are not doing octopus, not fast-forward, and have
1415                  * only one common.
1416                  */
1417                 refresh_cache(REFRESH_QUIET);
1418                 if (allow_trivial && !fast_forward_only) {
1419                         /* See if it is really trivial. */
1420                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1421                         printf(_("Trying really trivial in-index merge...\n"));
1422                         if (!read_tree_trivial(common->item->object.sha1,
1423                                                head_commit->object.sha1,
1424                                                remoteheads->item->object.sha1)) {
1425                                 ret = merge_trivial(head_commit);
1426                                 goto done;
1427                         }
1428                         printf(_("Nope.\n"));
1429                 }
1430         } else {
1431                 /*
1432                  * An octopus.  If we can reach all the remote we are up
1433                  * to date.
1434                  */
1435                 int up_to_date = 1;
1436                 struct commit_list *j;
1437
1438                 for (j = remoteheads; j; j = j->next) {
1439                         struct commit_list *common_one;
1440
1441                         /*
1442                          * Here we *have* to calculate the individual
1443                          * merge_bases again, otherwise "git merge HEAD^
1444                          * HEAD^^" would be missed.
1445                          */
1446                         common_one = get_merge_bases(head_commit, j->item, 1);
1447                         if (hashcmp(common_one->item->object.sha1,
1448                                 j->item->object.sha1)) {
1449                                 up_to_date = 0;
1450                                 break;
1451                         }
1452                 }
1453                 if (up_to_date) {
1454                         finish_up_to_date("Already up-to-date. Yeeah!");
1455                         goto done;
1456                 }
1457         }
1458
1459         if (fast_forward_only)
1460                 die(_("Not possible to fast-forward, aborting."));
1461
1462         /* We are going to make a new commit. */
1463         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1464
1465         /*
1466          * At this point, we need a real merge.  No matter what strategy
1467          * we use, it would operate on the index, possibly affecting the
1468          * working tree, and when resolved cleanly, have the desired
1469          * tree in the index -- this means that the index must be in
1470          * sync with the head commit.  The strategies are responsible
1471          * to ensure this.
1472          */
1473         if (use_strategies_nr == 1 ||
1474             /*
1475              * Stash away the local changes so that we can try more than one.
1476              */
1477             save_state(stash))
1478                 hashcpy(stash, null_sha1);
1479
1480         for (i = 0; i < use_strategies_nr; i++) {
1481                 int ret;
1482                 if (i) {
1483                         printf(_("Rewinding the tree to pristine...\n"));
1484                         restore_state(head_commit->object.sha1, stash);
1485                 }
1486                 if (use_strategies_nr != 1)
1487                         printf(_("Trying merge strategy %s...\n"),
1488                                 use_strategies[i]->name);
1489                 /*
1490                  * Remember which strategy left the state in the working
1491                  * tree.
1492                  */
1493                 wt_strategy = use_strategies[i]->name;
1494
1495                 ret = try_merge_strategy(use_strategies[i]->name,
1496                                          common, head_commit, head_arg);
1497                 if (!option_commit && !ret) {
1498                         merge_was_ok = 1;
1499                         /*
1500                          * This is necessary here just to avoid writing
1501                          * the tree, but later we will *not* exit with
1502                          * status code 1 because merge_was_ok is set.
1503                          */
1504                         ret = 1;
1505                 }
1506
1507                 if (ret) {
1508                         /*
1509                          * The backend exits with 1 when conflicts are
1510                          * left to be resolved, with 2 when it does not
1511                          * handle the given merge at all.
1512                          */
1513                         if (ret == 1) {
1514                                 int cnt = evaluate_result();
1515
1516                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1517                                         best_strategy = use_strategies[i]->name;
1518                                         best_cnt = cnt;
1519                                 }
1520                         }
1521                         if (merge_was_ok)
1522                                 break;
1523                         else
1524                                 continue;
1525                 }
1526
1527                 /* Automerge succeeded. */
1528                 write_tree_trivial(result_tree);
1529                 automerge_was_ok = 1;
1530                 break;
1531         }
1532
1533         /*
1534          * If we have a resulting tree, that means the strategy module
1535          * auto resolved the merge cleanly.
1536          */
1537         if (automerge_was_ok) {
1538                 ret = finish_automerge(head_commit, common, result_tree,
1539                                        wt_strategy);
1540                 goto done;
1541         }
1542
1543         /*
1544          * Pick the result from the best strategy and have the user fix
1545          * it up.
1546          */
1547         if (!best_strategy) {
1548                 restore_state(head_commit->object.sha1, stash);
1549                 if (use_strategies_nr > 1)
1550                         fprintf(stderr,
1551                                 _("No merge strategy handled the merge.\n"));
1552                 else
1553                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1554                                 use_strategies[0]->name);
1555                 ret = 2;
1556                 goto done;
1557         } else if (best_strategy == wt_strategy)
1558                 ; /* We already have its result in the working tree. */
1559         else {
1560                 printf(_("Rewinding the tree to pristine...\n"));
1561                 restore_state(head_commit->object.sha1, stash);
1562                 printf(_("Using the %s to prepare resolving by hand.\n"),
1563                         best_strategy);
1564                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1565         }
1566
1567         if (squash)
1568                 finish(head_commit, NULL, NULL);
1569         else
1570                 write_merge_state();
1571
1572         if (merge_was_ok)
1573                 fprintf(stderr, _("Automatic merge went well; "
1574                         "stopped before committing as requested\n"));
1575         else
1576                 ret = suggest_conflicts(option_renormalize);
1577
1578 done:
1579         free(branch_to_free);
1580         return ret;
1581 }