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