git.oblomov.eu Git - git/blob - builtin/checkout.c

   1 #include "builtin.h"
   2 #include "config.h"
   3 #include "lockfile.h"
   4 #include "parse-options.h"
   5 #include "refs.h"
   6 #include "commit.h"
   7 #include "tree.h"
   8 #include "tree-walk.h"
   9 #include "cache-tree.h"
  10 #include "unpack-trees.h"
  11 #include "dir.h"
  12 #include "run-command.h"
  13 #include "merge-recursive.h"
  14 #include "branch.h"
  15 #include "diff.h"
  16 #include "revision.h"
  17 #include "remote.h"
  18 #include "blob.h"
  19 #include "xdiff-interface.h"
  20 #include "ll-merge.h"
  21 #include "resolve-undo.h"
  22 #include "submodule-config.h"
  23 #include "submodule.h"
  24
  25 static const char * const checkout_usage[] = {
  26         N_("git checkout [<options>] <branch>"),
  27         N_("git checkout [<options>] [<branch>] -- <file>..."),
  28         NULL,
  29 };
  30
  31 struct checkout_opts {
  32         int patch_mode;
  33         int quiet;
  34         int merge;
  35         int force;
  36         int force_detach;
  37         int writeout_stage;
  38         int overwrite_ignore;
  39         int ignore_skipworktree;
  40         int ignore_other_worktrees;
  41         int show_progress;
  42
  43         const char *new_branch;
  44         const char *new_branch_force;
  45         const char *new_orphan_branch;
  46         int new_branch_log;
  47         enum branch_track track;
  48         struct diff_options diff_options;
  49
  50         int branch_exists;
  51         const char *prefix;
  52         struct pathspec pathspec;
  53         struct tree *source_tree;
  54 };
  55
  56 static int post_checkout_hook(struct commit *old, struct commit *new,
  57                               int changed)
  58 {
  59         return run_hook_le(NULL, "post-checkout",
  60                            oid_to_hex(old ? &old->object.oid : &null_oid),
  61                            oid_to_hex(new ? &new->object.oid : &null_oid),
  62                            changed ? "1" : "0", NULL);
  63         /* "new" can be NULL when checking out from the index before
  64            a commit exists. */
  65
  66 }
  67
  68 static int update_some(const unsigned char *sha1, struct strbuf *base,
  69                 const char *pathname, unsigned mode, int stage, void *context)
  70 {
  71         int len;
  72         struct cache_entry *ce;
  73         int pos;
  74
  75         if (S_ISDIR(mode))
  76                 return READ_TREE_RECURSIVE;
  77
  78         len = base->len + strlen(pathname);
  79         ce = xcalloc(1, cache_entry_size(len));
  80         hashcpy(ce->oid.hash, sha1);
  81         memcpy(ce->name, base->buf, base->len);
  82         memcpy(ce->name + base->len, pathname, len - base->len);
  83         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  84         ce->ce_namelen = len;
  85         ce->ce_mode = create_ce_mode(mode);
  86
  87         /*
  88          * If the entry is the same as the current index, we can leave the old
  89          * entry in place. Whether it is UPTODATE or not, checkout_entry will
  90          * do the right thing.
  91          */
  92         pos = cache_name_pos(ce->name, ce->ce_namelen);
  93         if (pos >= 0) {
  94                 struct cache_entry *old = active_cache[pos];
  95                 if (ce->ce_mode == old->ce_mode &&
  96                     !oidcmp(&ce->oid, &old->oid)) {
  97                         old->ce_flags |= CE_UPDATE;
  98                         free(ce);
  99                         return 0;
 100                 }
 101         }
 102
 103         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 104         return 0;
 105 }
 106
 107 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
 108 {
 109         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
 110
 111         /* update the index with the given tree's info
 112          * for all args, expanding wildcards, and exit
 113          * with any non-zero return code.
 114          */
 115         return 0;
 116 }
 117
 118 static int skip_same_name(const struct cache_entry *ce, int pos)
 119 {
 120         while (++pos < active_nr &&
 121                !strcmp(active_cache[pos]->name, ce->name))
 122                 ; /* skip */
 123         return pos;
 124 }
 125
 126 static int check_stage(int stage, const struct cache_entry *ce, int pos)
 127 {
 128         while (pos < active_nr &&
 129                !strcmp(active_cache[pos]->name, ce->name)) {
 130                 if (ce_stage(active_cache[pos]) == stage)
 131                         return 0;
 132                 pos++;
 133         }
 134         if (stage == 2)
 135                 return error(_("path '%s' does not have our version"), ce->name);
 136         else
 137                 return error(_("path '%s' does not have their version"), ce->name);
 138 }
 139
 140 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 141 {
 142         unsigned seen = 0;
 143         const char *name = ce->name;
 144
 145         while (pos < active_nr) {
 146                 ce = active_cache[pos];
 147                 if (strcmp(name, ce->name))
 148                         break;
 149                 seen |= (1 << ce_stage(ce));
 150                 pos++;
 151         }
 152         if ((stages & seen) != stages)
 153                 return error(_("path '%s' does not have all necessary versions"),
 154                              name);
 155         return 0;
 156 }
 157
 158 static int checkout_stage(int stage, const struct cache_entry *ce, int pos,
 159                           const struct checkout *state)
 160 {
 161         while (pos < active_nr &&
 162                !strcmp(active_cache[pos]->name, ce->name)) {
 163                 if (ce_stage(active_cache[pos]) == stage)
 164                         return checkout_entry(active_cache[pos], state, NULL);
 165                 pos++;
 166         }
 167         if (stage == 2)
 168                 return error(_("path '%s' does not have our version"), ce->name);
 169         else
 170                 return error(_("path '%s' does not have their version"), ce->name);
 171 }
 172
 173 static int checkout_merged(int pos, const struct checkout *state)
 174 {
 175         struct cache_entry *ce = active_cache[pos];
 176         const char *path = ce->name;
 177         mmfile_t ancestor, ours, theirs;
 178         int status;
 179         struct object_id oid;
 180         mmbuffer_t result_buf;
 181         struct object_id threeway[3];
 182         unsigned mode = 0;
 183
 184         memset(threeway, 0, sizeof(threeway));
 185         while (pos < active_nr) {
 186                 int stage;
 187                 stage = ce_stage(ce);
 188                 if (!stage || strcmp(path, ce->name))
 189                         break;
 190                 oidcpy(&threeway[stage - 1], &ce->oid);
 191                 if (stage == 2)
 192                         mode = create_ce_mode(ce->ce_mode);
 193                 pos++;
 194                 ce = active_cache[pos];
 195         }
 196         if (is_null_oid(&threeway[1]) || is_null_oid(&threeway[2]))
 197                 return error(_("path '%s' does not have necessary versions"), path);
 198
 199         read_mmblob(&ancestor, &threeway[0]);
 200         read_mmblob(&ours, &threeway[1]);
 201         read_mmblob(&theirs, &threeway[2]);
 202
 203         /*
 204          * NEEDSWORK: re-create conflicts from merges with
 205          * merge.renormalize set, too
 206          */
 207         status = ll_merge(&result_buf, path, &ancestor, "base",
 208                           &ours, "ours", &theirs, "theirs", NULL);
 209         free(ancestor.ptr);
 210         free(ours.ptr);
 211         free(theirs.ptr);
 212         if (status < 0 || !result_buf.ptr) {
 213                 free(result_buf.ptr);
 214                 return error(_("path '%s': cannot merge"), path);
 215         }
 216
 217         /*
 218          * NEEDSWORK:
 219          * There is absolutely no reason to write this as a blob object
 220          * and create a phony cache entry.  This hack is primarily to get
 221          * to the write_entry() machinery that massages the contents to
 222          * work-tree format and writes out which only allows it for a
 223          * cache entry.  The code in write_entry() needs to be refactored
 224          * to allow us to feed a <buffer, size, mode> instead of a cache
 225          * entry.  Such a refactoring would help merge_recursive as well
 226          * (it also writes the merge result to the object database even
 227          * when it may contain conflicts).
 228          */
 229         if (write_sha1_file(result_buf.ptr, result_buf.size,
 230                             blob_type, oid.hash))
 231                 die(_("Unable to add merge result for '%s'"), path);
 232         free(result_buf.ptr);
 233         ce = make_cache_entry(mode, oid.hash, path, 2, 0);
 234         if (!ce)
 235                 die(_("make_cache_entry failed for path '%s'"), path);
 236         status = checkout_entry(ce, state, NULL);
 237         free(ce);
 238         return status;
 239 }
 240
 241 static int checkout_paths(const struct checkout_opts *opts,
 242                           const char *revision)
 243 {
 244         int pos;
 245         struct checkout state = CHECKOUT_INIT;
 246         static char *ps_matched;
 247         struct object_id rev;
 248         struct commit *head;
 249         int errs = 0;
 250         struct lock_file *lock_file;
 251
 252         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 253                 die(_("'%s' cannot be used with updating paths"), "--track");
 254
 255         if (opts->new_branch_log)
 256                 die(_("'%s' cannot be used with updating paths"), "-l");
 257
 258         if (opts->force && opts->patch_mode)
 259                 die(_("'%s' cannot be used with updating paths"), "-f");
 260
 261         if (opts->force_detach)
 262                 die(_("'%s' cannot be used with updating paths"), "--detach");
 263
 264         if (opts->merge && opts->patch_mode)
 265                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 266
 267         if (opts->force && opts->merge)
 268                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 269
 270         if (opts->new_branch)
 271                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 272                     opts->new_branch);
 273
 274         if (opts->patch_mode)
 275                 return run_add_interactive(revision, "--patch=checkout",
 276                                            &opts->pathspec);
 277
 278         lock_file = xcalloc(1, sizeof(struct lock_file));
 279
 280         hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 281         if (read_cache_preload(&opts->pathspec) < 0)
 282                 return error(_("index file corrupt"));
 283
 284         if (opts->source_tree)
 285                 read_tree_some(opts->source_tree, &opts->pathspec);
 286
 287         ps_matched = xcalloc(opts->pathspec.nr, 1);
 288
 289         /*
 290          * Make sure all pathspecs participated in locating the paths
 291          * to be checked out.
 292          */
 293         for (pos = 0; pos < active_nr; pos++) {
 294                 struct cache_entry *ce = active_cache[pos];
 295                 ce->ce_flags &= ~CE_MATCHED;
 296                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 297                         continue;
 298                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 299                         /*
 300                          * "git checkout tree-ish -- path", but this entry
 301                          * is in the original index; it will not be checked
 302                          * out to the working tree and it does not matter
 303                          * if pathspec matched this entry.  We will not do
 304                          * anything to this entry at all.
 305                          */
 306                         continue;
 307                 /*
 308                  * Either this entry came from the tree-ish we are
 309                  * checking the paths out of, or we are checking out
 310                  * of the index.
 311                  *
 312                  * If it comes from the tree-ish, we already know it
 313                  * matches the pathspec and could just stamp
 314                  * CE_MATCHED to it from update_some(). But we still
 315                  * need ps_matched and read_tree_recursive (and
 316                  * eventually tree_entry_interesting) cannot fill
 317                  * ps_matched yet. Once it can, we can avoid calling
 318                  * match_pathspec() for _all_ entries when
 319                  * opts->source_tree != NULL.
 320                  */
 321                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
 322                         ce->ce_flags |= CE_MATCHED;
 323         }
 324
 325         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 326                 free(ps_matched);
 327                 return 1;
 328         }
 329         free(ps_matched);
 330
 331         /* "checkout -m path" to recreate conflicted state */
 332         if (opts->merge)
 333                 unmerge_marked_index(&the_index);
 334
 335         /* Any unmerged paths? */
 336         for (pos = 0; pos < active_nr; pos++) {
 337                 const struct cache_entry *ce = active_cache[pos];
 338                 if (ce->ce_flags & CE_MATCHED) {
 339                         if (!ce_stage(ce))
 340                                 continue;
 341                         if (opts->force) {
 342                                 warning(_("path '%s' is unmerged"), ce->name);
 343                         } else if (opts->writeout_stage) {
 344                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 345                         } else if (opts->merge) {
 346                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 347                         } else {
 348                                 errs = 1;
 349                                 error(_("path '%s' is unmerged"), ce->name);
 350                         }
 351                         pos = skip_same_name(ce, pos) - 1;
 352                 }
 353         }
 354         if (errs)
 355                 return 1;
 356
 357         /* Now we are committed to check them out */
 358         state.force = 1;
 359         state.refresh_cache = 1;
 360         state.istate = &the_index;
 361
 362         enable_delayed_checkout(&state);
 363         for (pos = 0; pos < active_nr; pos++) {
 364                 struct cache_entry *ce = active_cache[pos];
 365                 if (ce->ce_flags & CE_MATCHED) {
 366                         if (!ce_stage(ce)) {
 367                                 errs |= checkout_entry(ce, &state, NULL);
 368                                 continue;
 369                         }
 370                         if (opts->writeout_stage)
 371                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
 372                         else if (opts->merge)
 373                                 errs |= checkout_merged(pos, &state);
 374                         pos = skip_same_name(ce, pos) - 1;
 375                 }
 376         }
 377         errs |= finish_delayed_checkout(&state);
 378
 379         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 380                 die(_("unable to write new index file"));
 381
 382         read_ref_full("HEAD", 0, rev.hash, NULL);
 383         head = lookup_commit_reference_gently(&rev, 1);
 384
 385         errs |= post_checkout_hook(head, head, 0);
 386         return errs;
 387 }
 388
 389 static void show_local_changes(struct object *head,
 390                                const struct diff_options *opts)
 391 {
 392         struct rev_info rev;
 393         /* I think we want full paths, even if we're in a subdirectory. */
 394         init_revisions(&rev, NULL);
 395         rev.diffopt.flags = opts->flags;
 396         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 397         diff_setup_done(&rev.diffopt);
 398         add_pending_object(&rev, head, NULL);
 399         run_diff_index(&rev, 0);
 400 }
 401
 402 static void describe_detached_head(const char *msg, struct commit *commit)
 403 {
 404         struct strbuf sb = STRBUF_INIT;
 405         if (!parse_commit(commit))
 406                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 407         fprintf(stderr, "%s %s... %s\n", msg,
 408                 find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV), sb.buf);
 409         strbuf_release(&sb);
 410 }
 411
 412 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 413                       int worktree, int *writeout_error)
 414 {
 415         struct unpack_trees_options opts;
 416         struct tree_desc tree_desc;
 417
 418         memset(&opts, 0, sizeof(opts));
 419         opts.head_idx = -1;
 420         opts.update = worktree;
 421         opts.skip_unmerged = !worktree;
 422         opts.reset = 1;
 423         opts.merge = 1;
 424         opts.fn = oneway_merge;
 425         opts.verbose_update = o->show_progress;
 426         opts.src_index = &the_index;
 427         opts.dst_index = &the_index;
 428         parse_tree(tree);
 429         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 430         switch (unpack_trees(1, &tree_desc, &opts)) {
 431         case -2:
 432                 *writeout_error = 1;
 433                 /*
 434                  * We return 0 nevertheless, as the index is all right
 435                  * and more importantly we have made best efforts to
 436                  * update paths in the work tree, and we cannot revert
 437                  * them.
 438                  */
 439                 /* fallthrough */
 440         case 0:
 441                 return 0;
 442         default:
 443                 return 128;
 444         }
 445 }
 446
 447 struct branch_info {
 448         const char *name; /* The short name used */
 449         const char *path; /* The full name of a real branch */
 450         struct commit *commit; /* The named commit */
 451         /*
 452          * if not null the branch is detached because it's already
 453          * checked out in this checkout
 454          */
 455         char *checkout;
 456 };
 457
 458 static void setup_branch_path(struct branch_info *branch)
 459 {
 460         struct strbuf buf = STRBUF_INIT;
 461
 462         strbuf_branchname(&buf, branch->name, INTERPRET_BRANCH_LOCAL);
 463         if (strcmp(buf.buf, branch->name))
 464                 branch->name = xstrdup(buf.buf);
 465         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 466         branch->path = strbuf_detach(&buf, NULL);
 467 }
 468
 469 static int merge_working_tree(const struct checkout_opts *opts,
 470                               struct branch_info *old,
 471                               struct branch_info *new,
 472                               int *writeout_error)
 473 {
 474         int ret;
 475         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 476
 477         hold_locked_index(lock_file, LOCK_DIE_ON_ERROR);
 478         if (read_cache_preload(NULL) < 0)
 479                 return error(_("index file corrupt"));
 480
 481         resolve_undo_clear();
 482         if (opts->force) {
 483                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
 484                 if (ret)
 485                         return ret;
 486         } else {
 487                 struct tree_desc trees[2];
 488                 struct tree *tree;
 489                 struct unpack_trees_options topts;
 490
 491                 memset(&topts, 0, sizeof(topts));
 492                 topts.head_idx = -1;
 493                 topts.src_index = &the_index;
 494                 topts.dst_index = &the_index;
 495
 496                 setup_unpack_trees_porcelain(&topts, "checkout");
 497
 498                 refresh_cache(REFRESH_QUIET);
 499
 500                 if (unmerged_cache()) {
 501                         error(_("you need to resolve your current index first"));
 502                         return 1;
 503                 }
 504
 505                 /* 2-way merge to the new branch */
 506                 topts.initial_checkout = is_cache_unborn();
 507                 topts.update = 1;
 508                 topts.merge = 1;
 509                 topts.gently = opts->merge && old->commit;
 510                 topts.verbose_update = opts->show_progress;
 511                 topts.fn = twoway_merge;
 512                 if (opts->overwrite_ignore) {
 513                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 514                         topts.dir->flags |= DIR_SHOW_IGNORED;
 515                         setup_standard_excludes(topts.dir);
 516                 }
 517                 tree = parse_tree_indirect(old->commit ?
 518                                            &old->commit->object.oid :
 519                                            &empty_tree_oid);
 520                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 521                 tree = parse_tree_indirect(&new->commit->object.oid);
 522                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 523
 524                 ret = unpack_trees(2, trees, &topts);
 525                 if (ret == -1) {
 526                         /*
 527                          * Unpack couldn't do a trivial merge; either
 528                          * give up or do a real merge, depending on
 529                          * whether the merge flag was used.
 530                          */
 531                         struct tree *result;
 532                         struct tree *work;
 533                         struct merge_options o;
 534                         if (!opts->merge)
 535                                 return 1;
 536
 537                         /*
 538                          * Without old->commit, the below is the same as
 539                          * the two-tree unpack we already tried and failed.
 540                          */
 541                         if (!old->commit)
 542                                 return 1;
 543
 544                         /* Do more real merge */
 545
 546                         /*
 547                          * We update the index fully, then write the
 548                          * tree from the index, then merge the new
 549                          * branch with the current tree, with the old
 550                          * branch as the base. Then we reset the index
 551                          * (but not the working tree) to the new
 552                          * branch, leaving the working tree as the
 553                          * merged version, but skipping unmerged
 554                          * entries in the index.
 555                          */
 556
 557                         add_files_to_cache(NULL, NULL, 0);
 558                         /*
 559                          * NEEDSWORK: carrying over local changes
 560                          * when branches have different end-of-line
 561                          * normalization (or clean+smudge rules) is
 562                          * a pain; plumb in an option to set
 563                          * o.renormalize?
 564                          */
 565                         init_merge_options(&o);
 566                         o.verbosity = 0;
 567                         work = write_tree_from_memory(&o);
 568
 569                         ret = reset_tree(new->commit->tree, opts, 1,
 570                                          writeout_error);
 571                         if (ret)
 572                                 return ret;
 573                         o.ancestor = old->name;
 574                         o.branch1 = new->name;
 575                         o.branch2 = "local";
 576                         ret = merge_trees(&o, new->commit->tree, work,
 577                                 old->commit->tree, &result);
 578                         if (ret < 0)
 579                                 exit(128);
 580                         ret = reset_tree(new->commit->tree, opts, 0,
 581                                          writeout_error);
 582                         strbuf_release(&o.obuf);
 583                         if (ret)
 584                                 return ret;
 585                 }
 586         }
 587
 588         if (!active_cache_tree)
 589                 active_cache_tree = cache_tree();
 590
 591         if (!cache_tree_fully_valid(active_cache_tree))
 592                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 593
 594         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 595                 die(_("unable to write new index file"));
 596
 597         if (!opts->force && !opts->quiet)
 598                 show_local_changes(&new->commit->object, &opts->diff_options);
 599
 600         return 0;
 601 }
 602
 603 static void report_tracking(struct branch_info *new)
 604 {
 605         struct strbuf sb = STRBUF_INIT;
 606         struct branch *branch = branch_get(new->name);
 607
 608         if (!format_tracking_info(branch, &sb))
 609                 return;
 610         fputs(sb.buf, stdout);
 611         strbuf_release(&sb);
 612 }
 613
 614 static void update_refs_for_switch(const struct checkout_opts *opts,
 615                                    struct branch_info *old,
 616                                    struct branch_info *new)
 617 {
 618         struct strbuf msg = STRBUF_INIT;
 619         const char *old_desc, *reflog_msg;
 620         if (opts->new_branch) {
 621                 if (opts->new_orphan_branch) {
 622                         char *refname;
 623
 624                         refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
 625                         if (opts->new_branch_log &&
 626                             !should_autocreate_reflog(refname)) {
 627                                 int ret;
 628                                 struct strbuf err = STRBUF_INIT;
 629
 630                                 ret = safe_create_reflog(refname, 1, &err);
 631                                 if (ret) {
 632                                         fprintf(stderr, _("Can not do reflog for '%s': %s\n"),
 633                                                 opts->new_orphan_branch, err.buf);
 634                                         strbuf_release(&err);
 635                                         free(refname);
 636                                         return;
 637                                 }
 638                                 strbuf_release(&err);
 639                         }
 640                         free(refname);
 641                 }
 642                 else
 643                         create_branch(opts->new_branch, new->name,
 644                                       opts->new_branch_force ? 1 : 0,
 645                                       opts->new_branch_log,
 646                                       opts->new_branch_force ? 1 : 0,
 647                                       opts->quiet,
 648                                       opts->track);
 649                 new->name = opts->new_branch;
 650                 setup_branch_path(new);
 651         }
 652
 653         old_desc = old->name;
 654         if (!old_desc && old->commit)
 655                 old_desc = oid_to_hex(&old->commit->object.oid);
 656
 657         reflog_msg = getenv("GIT_REFLOG_ACTION");
 658         if (!reflog_msg)
 659                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 660                         old_desc ? old_desc : "(invalid)", new->name);
 661         else
 662                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 663
 664         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 665                 /* Nothing to do. */
 666         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 667                 update_ref(msg.buf, "HEAD", new->commit->object.oid.hash, NULL,
 668                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 669                 if (!opts->quiet) {
 670                         if (old->path &&
 671                             advice_detached_head && !opts->force_detach)
 672                                 detach_advice(new->name);
 673                         describe_detached_head(_("HEAD is now at"), new->commit);
 674                 }
 675         } else if (new->path) { /* Switch branches. */
 676                 if (create_symref("HEAD", new->path, msg.buf) < 0)
 677                         die(_("unable to update HEAD"));
 678                 if (!opts->quiet) {
 679                         if (old->path && !strcmp(new->path, old->path)) {
 680                                 if (opts->new_branch_force)
 681                                         fprintf(stderr, _("Reset branch '%s'\n"),
 682                                                 new->name);
 683                                 else
 684                                         fprintf(stderr, _("Already on '%s'\n"),
 685                                                 new->name);
 686                         } else if (opts->new_branch) {
 687                                 if (opts->branch_exists)
 688                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 689                                 else
 690                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 691                         } else {
 692                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 693                                         new->name);
 694                         }
 695                 }
 696                 if (old->path && old->name) {
 697                         if (!ref_exists(old->path) && reflog_exists(old->path))
 698                                 delete_reflog(old->path);
 699                 }
 700         }
 701         remove_branch_state();
 702         strbuf_release(&msg);
 703         if (!opts->quiet &&
 704             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 705                 report_tracking(new);
 706 }
 707
 708 static int add_pending_uninteresting_ref(const char *refname,
 709                                          const struct object_id *oid,
 710                                          int flags, void *cb_data)
 711 {
 712         add_pending_oid(cb_data, refname, oid, UNINTERESTING);
 713         return 0;
 714 }
 715
 716 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 717 {
 718         strbuf_addstr(sb, "  ");
 719         strbuf_add_unique_abbrev(sb, commit->object.oid.hash, DEFAULT_ABBREV);
 720         strbuf_addch(sb, ' ');
 721         if (!parse_commit(commit))
 722                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 723         strbuf_addch(sb, '\n');
 724 }
 725
 726 #define ORPHAN_CUTOFF 4
 727 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 728 {
 729         struct commit *c, *last = NULL;
 730         struct strbuf sb = STRBUF_INIT;
 731         int lost = 0;
 732         while ((c = get_revision(revs)) != NULL) {
 733                 if (lost < ORPHAN_CUTOFF)
 734                         describe_one_orphan(&sb, c);
 735                 last = c;
 736                 lost++;
 737         }
 738         if (ORPHAN_CUTOFF < lost) {
 739                 int more = lost - ORPHAN_CUTOFF;
 740                 if (more == 1)
 741                         describe_one_orphan(&sb, last);
 742                 else
 743                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 744         }
 745
 746         fprintf(stderr,
 747                 Q_(
 748                 /* The singular version */
 749                 "Warning: you are leaving %d commit behind, "
 750                 "not connected to\n"
 751                 "any of your branches:\n\n"
 752                 "%s\n",
 753                 /* The plural version */
 754                 "Warning: you are leaving %d commits behind, "
 755                 "not connected to\n"
 756                 "any of your branches:\n\n"
 757                 "%s\n",
 758                 /* Give ngettext() the count */
 759                 lost),
 760                 lost,
 761                 sb.buf);
 762         strbuf_release(&sb);
 763
 764         if (advice_detached_head)
 765                 fprintf(stderr,
 766                         Q_(
 767                         /* The singular version */
 768                         "If you want to keep it by creating a new branch, "
 769                         "this may be a good time\nto do so with:\n\n"
 770                         " git branch <new-branch-name> %s\n\n",
 771                         /* The plural version */
 772                         "If you want to keep them by creating a new branch, "
 773                         "this may be a good time\nto do so with:\n\n"
 774                         " git branch <new-branch-name> %s\n\n",
 775                         /* Give ngettext() the count */
 776                         lost),
 777                         find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV));
 778 }
 779
 780 /*
 781  * We are about to leave commit that was at the tip of a detached
 782  * HEAD.  If it is not reachable from any ref, this is the last chance
 783  * for the user to do so without resorting to reflog.
 784  */
 785 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 786 {
 787         struct rev_info revs;
 788         struct object *object = &old->object;
 789         struct object_array refs;
 790
 791         init_revisions(&revs, NULL);
 792         setup_revisions(0, NULL, &revs, NULL);
 793
 794         object->flags &= ~UNINTERESTING;
 795         add_pending_object(&revs, object, oid_to_hex(&object->oid));
 796
 797         for_each_ref(add_pending_uninteresting_ref, &revs);
 798         add_pending_oid(&revs, "HEAD", &new->object.oid, UNINTERESTING);
 799
 800         /* Save pending objects, so they can be cleaned up later. */
 801         refs = revs.pending;
 802         revs.leak_pending = 1;
 803
 804         /*
 805          * prepare_revision_walk (together with .leak_pending = 1) makes us
 806          * the sole owner of the list of pending objects.
 807          */
 808         if (prepare_revision_walk(&revs))
 809                 die(_("internal error in revision walk"));
 810         if (!(old->object.flags & UNINTERESTING))
 811                 suggest_reattach(old, &revs);
 812         else
 813                 describe_detached_head(_("Previous HEAD position was"), old);
 814
 815         /* Clean up objects used, as they will be reused. */
 816         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 817
 818         object_array_clear(&refs);
 819 }
 820
 821 static int switch_branches(const struct checkout_opts *opts,
 822                            struct branch_info *new)
 823 {
 824         int ret = 0;
 825         struct branch_info old;
 826         void *path_to_free;
 827         struct object_id rev;
 828         int flag, writeout_error = 0;
 829         memset(&old, 0, sizeof(old));
 830         old.path = path_to_free = resolve_refdup("HEAD", 0, rev.hash, &flag);
 831         if (old.path)
 832                 old.commit = lookup_commit_reference_gently(&rev, 1);
 833         if (!(flag & REF_ISSYMREF))
 834                 old.path = NULL;
 835
 836         if (old.path)
 837                 skip_prefix(old.path, "refs/heads/", &old.name);
 838
 839         if (!new->name) {
 840                 new->name = "HEAD";
 841                 new->commit = old.commit;
 842                 if (!new->commit)
 843                         die(_("You are on a branch yet to be born"));
 844                 parse_commit_or_die(new->commit);
 845         }
 846
 847         ret = merge_working_tree(opts, &old, new, &writeout_error);
 848         if (ret) {
 849                 free(path_to_free);
 850                 return ret;
 851         }
 852
 853         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 854                 orphaned_commit_warning(old.commit, new->commit);
 855
 856         update_refs_for_switch(opts, &old, new);
 857
 858         ret = post_checkout_hook(old.commit, new->commit, 1);
 859         free(path_to_free);
 860         return ret || writeout_error;
 861 }
 862
 863 static int git_checkout_config(const char *var, const char *value, void *cb)
 864 {
 865         if (!strcmp(var, "diff.ignoresubmodules")) {
 866                 struct checkout_opts *opts = cb;
 867                 handle_ignore_submodules_arg(&opts->diff_options, value);
 868                 return 0;
 869         }
 870
 871         if (starts_with(var, "submodule."))
 872                 return git_default_submodule_config(var, value, NULL);
 873
 874         return git_xmerge_config(var, value, NULL);
 875 }
 876
 877 struct tracking_name_data {
 878         /* const */ char *src_ref;
 879         char *dst_ref;
 880         struct object_id *dst_oid;
 881         int unique;
 882 };
 883
 884 static int check_tracking_name(struct remote *remote, void *cb_data)
 885 {
 886         struct tracking_name_data *cb = cb_data;
 887         struct refspec query;
 888         memset(&query, 0, sizeof(struct refspec));
 889         query.src = cb->src_ref;
 890         if (remote_find_tracking(remote, &query) ||
 891             get_oid(query.dst, cb->dst_oid)) {
 892                 free(query.dst);
 893                 return 0;
 894         }
 895         if (cb->dst_ref) {
 896                 free(query.dst);
 897                 cb->unique = 0;
 898                 return 0;
 899         }
 900         cb->dst_ref = query.dst;
 901         return 0;
 902 }
 903
 904 static const char *unique_tracking_name(const char *name, struct object_id *oid)
 905 {
 906         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
 907         cb_data.src_ref = xstrfmt("refs/heads/%s", name);
 908         cb_data.dst_oid = oid;
 909         for_each_remote(check_tracking_name, &cb_data);
 910         free(cb_data.src_ref);
 911         if (cb_data.unique)
 912                 return cb_data.dst_ref;
 913         free(cb_data.dst_ref);
 914         return NULL;
 915 }
 916
 917 static int parse_branchname_arg(int argc, const char **argv,
 918                                 int dwim_new_local_branch_ok,
 919                                 struct branch_info *new,
 920                                 struct checkout_opts *opts,
 921                                 struct object_id *rev)
 922 {
 923         struct tree **source_tree = &opts->source_tree;
 924         const char **new_branch = &opts->new_branch;
 925         int argcount = 0;
 926         struct object_id branch_rev;
 927         const char *arg;
 928         int dash_dash_pos;
 929         int has_dash_dash = 0;
 930         int i;
 931
 932         /*
 933          * case 1: git checkout <ref> -- [<paths>]
 934          *
 935          *   <ref> must be a valid tree, everything after the '--' must be
 936          *   a path.
 937          *
 938          * case 2: git checkout -- [<paths>]
 939          *
 940          *   everything after the '--' must be paths.
 941          *
 942          * case 3: git checkout <something> [--]
 943          *
 944          *   (a) If <something> is a commit, that is to
 945          *       switch to the branch or detach HEAD at it.  As a special case,
 946          *       if <something> is A...B (missing A or B means HEAD but you can
 947          *       omit at most one side), and if there is a unique merge base
 948          *       between A and B, A...B names that merge base.
 949          *
 950          *   (b) If <something> is _not_ a commit, either "--" is present
 951          *       or <something> is not a path, no -t or -b was given, and
 952          *       and there is a tracking branch whose name is <something>
 953          *       in one and only one remote, then this is a short-hand to
 954          *       fork local <something> from that remote-tracking branch.
 955          *
 956          *   (c) Otherwise, if "--" is present, treat it like case (1).
 957          *
 958          *   (d) Otherwise :
 959          *       - if it's a reference, treat it like case (1)
 960          *       - else if it's a path, treat it like case (2)
 961          *       - else: fail.
 962          *
 963          * case 4: git checkout <something> <paths>
 964          *
 965          *   The first argument must not be ambiguous.
 966          *   - If it's *only* a reference, treat it like case (1).
 967          *   - If it's only a path, treat it like case (2).
 968          *   - else: fail.
 969          *
 970          */
 971         if (!argc)
 972                 return 0;
 973
 974         arg = argv[0];
 975         dash_dash_pos = -1;
 976         for (i = 0; i < argc; i++) {
 977                 if (!strcmp(argv[i], "--")) {
 978                         dash_dash_pos = i;
 979                         break;
 980                 }
 981         }
 982         if (dash_dash_pos == 0)
 983                 return 1; /* case (2) */
 984         else if (dash_dash_pos == 1)
 985                 has_dash_dash = 1; /* case (3) or (1) */
 986         else if (dash_dash_pos >= 2)
 987                 die(_("only one reference expected, %d given."), dash_dash_pos);
 988
 989         if (!strcmp(arg, "-"))
 990                 arg = "@{-1}";
 991
 992         if (get_oid_mb(arg, rev)) {
 993                 /*
 994                  * Either case (3) or (4), with <something> not being
 995                  * a commit, or an attempt to use case (1) with an
 996                  * invalid ref.
 997                  *
 998                  * It's likely an error, but we need to find out if
 999                  * we should auto-create the branch, case (3).(b).
1000                  */
1001                 int recover_with_dwim = dwim_new_local_branch_ok;
1002
1003                 if (!has_dash_dash &&
1004                     (check_filename(opts->prefix, arg) || !no_wildcard(arg)))
1005                         recover_with_dwim = 0;
1006                 /*
1007                  * Accept "git checkout foo" and "git checkout foo --"
1008                  * as candidates for dwim.
1009                  */
1010                 if (!(argc == 1 && !has_dash_dash) &&
1011                     !(argc == 2 && has_dash_dash))
1012                         recover_with_dwim = 0;
1013
1014                 if (recover_with_dwim) {
1015                         const char *remote = unique_tracking_name(arg, rev);
1016                         if (remote) {
1017                                 *new_branch = arg;
1018                                 arg = remote;
1019                                 /* DWIMmed to create local branch, case (3).(b) */
1020                         } else {
1021                                 recover_with_dwim = 0;
1022                         }
1023                 }
1024
1025                 if (!recover_with_dwim) {
1026                         if (has_dash_dash)
1027                                 die(_("invalid reference: %s"), arg);
1028                         return argcount;
1029                 }
1030         }
1031
1032         /* we can't end up being in (2) anymore, eat the argument */
1033         argcount++;
1034         argv++;
1035         argc--;
1036
1037         new->name = arg;
1038         setup_branch_path(new);
1039
1040         if (!check_refname_format(new->path, 0) &&
1041             !read_ref(new->path, branch_rev.hash))
1042                 oidcpy(rev, &branch_rev);
1043         else
1044                 new->path = NULL; /* not an existing branch */
1045
1046         new->commit = lookup_commit_reference_gently(rev, 1);
1047         if (!new->commit) {
1048                 /* not a commit */
1049                 *source_tree = parse_tree_indirect(rev);
1050         } else {
1051                 parse_commit_or_die(new->commit);
1052                 *source_tree = new->commit->tree;
1053         }
1054
1055         if (!*source_tree)                   /* case (1): want a tree */
1056                 die(_("reference is not a tree: %s"), arg);
1057         if (!has_dash_dash) {   /* case (3).(d) -> (1) */
1058                 /*
1059                  * Do not complain the most common case
1060                  *      git checkout branch
1061                  * even if there happen to be a file called 'branch';
1062                  * it would be extremely annoying.
1063                  */
1064                 if (argc)
1065                         verify_non_filename(opts->prefix, arg);
1066         } else {
1067                 argcount++;
1068                 argv++;
1069                 argc--;
1070         }
1071
1072         return argcount;
1073 }
1074
1075 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1076 {
1077         int status;
1078         struct strbuf branch_ref = STRBUF_INIT;
1079
1080         if (!opts->new_branch)
1081                 die(_("You are on a branch yet to be born"));
1082         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1083         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1084         strbuf_release(&branch_ref);
1085         if (!opts->quiet)
1086                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1087                         opts->new_branch);
1088         return status;
1089 }
1090
1091 static int checkout_branch(struct checkout_opts *opts,
1092                            struct branch_info *new)
1093 {
1094         if (opts->pathspec.nr)
1095                 die(_("paths cannot be used with switching branches"));
1096
1097         if (opts->patch_mode)
1098                 die(_("'%s' cannot be used with switching branches"),
1099                     "--patch");
1100
1101         if (opts->writeout_stage)
1102                 die(_("'%s' cannot be used with switching branches"),
1103                     "--ours/--theirs");
1104
1105         if (opts->force && opts->merge)
1106                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1107
1108         if (opts->force_detach && opts->new_branch)
1109                 die(_("'%s' cannot be used with '%s'"),
1110                     "--detach", "-b/-B/--orphan");
1111
1112         if (opts->new_orphan_branch) {
1113                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1114                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1115         } else if (opts->force_detach) {
1116                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1117                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1118         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1119                 opts->track = git_branch_track;
1120
1121         if (new->name && !new->commit)
1122                 die(_("Cannot switch branch to a non-commit '%s'"),
1123                     new->name);
1124
1125         if (new->path && !opts->force_detach && !opts->new_branch &&
1126             !opts->ignore_other_worktrees) {
1127                 int flag;
1128                 char *head_ref = resolve_refdup("HEAD", 0, NULL, &flag);
1129                 if (head_ref &&
1130                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)))
1131                         die_if_checked_out(new->path, 1);
1132                 free(head_ref);
1133         }
1134
1135         if (!new->commit && opts->new_branch) {
1136                 struct object_id rev;
1137                 int flag;
1138
1139                 if (!read_ref_full("HEAD", 0, rev.hash, &flag) &&
1140                     (flag & REF_ISSYMREF) && is_null_oid(&rev))
1141                         return switch_unborn_to_new_branch(opts);
1142         }
1143         return switch_branches(opts, new);
1144 }
1145
1146 int cmd_checkout(int argc, const char **argv, const char *prefix)
1147 {
1148         struct checkout_opts opts;
1149         struct branch_info new;
1150         char *conflict_style = NULL;
1151         int dwim_new_local_branch = 1;
1152         struct option options[] = {
1153                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1154                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1155                            N_("create and checkout a new branch")),
1156                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1157                            N_("create/reset and checkout a branch")),
1158                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1159                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
1160                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1161                         BRANCH_TRACK_EXPLICIT),
1162                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1163                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1164                             2),
1165                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1166                             3),
1167                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1168                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1169                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1170                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1171                            N_("conflict style (merge or diff3)")),
1172                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1173                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1174                          N_("do not limit pathspecs to sparse entries only")),
1175                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1176                                 N_("second guess 'git checkout <no-such-branch>'")),
1177                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1178                          N_("do not check if another worktree is holding the given ref")),
1179                 { OPTION_CALLBACK, 0, "recurse-submodules", NULL,
1180                             "checkout", "control recursive updating of submodules",
1181                             PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
1182                 OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
1183                 OPT_END(),
1184         };
1185
1186         memset(&opts, 0, sizeof(opts));
1187         memset(&new, 0, sizeof(new));
1188         opts.overwrite_ignore = 1;
1189         opts.prefix = prefix;
1190         opts.show_progress = -1;
1191
1192         git_config(git_checkout_config, &opts);
1193
1194         opts.track = BRANCH_TRACK_UNSPECIFIED;
1195
1196         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1197                              PARSE_OPT_KEEP_DASHDASH);
1198
1199         if (opts.show_progress < 0) {
1200                 if (opts.quiet)
1201                         opts.show_progress = 0;
1202                 else
1203                         opts.show_progress = isatty(2);
1204         }
1205
1206         if (conflict_style) {
1207                 opts.merge = 1; /* implied */
1208                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1209         }
1210
1211         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1212                 die(_("-b, -B and --orphan are mutually exclusive"));
1213
1214         /*
1215          * From here on, new_branch will contain the branch to be checked out,
1216          * and new_branch_force and new_orphan_branch will tell us which one of
1217          * -b/-B/--orphan is being used.
1218          */
1219         if (opts.new_branch_force)
1220                 opts.new_branch = opts.new_branch_force;
1221
1222         if (opts.new_orphan_branch)
1223                 opts.new_branch = opts.new_orphan_branch;
1224
1225         /* --track without -b/-B/--orphan should DWIM */
1226         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1227                 const char *argv0 = argv[0];
1228                 if (!argc || !strcmp(argv0, "--"))
1229                         die (_("--track needs a branch name"));
1230                 skip_prefix(argv0, "refs/", &argv0);
1231                 skip_prefix(argv0, "remotes/", &argv0);
1232                 argv0 = strchr(argv0, '/');
1233                 if (!argv0 || !argv0[1])
1234                         die (_("Missing branch name; try -b"));
1235                 opts.new_branch = argv0 + 1;
1236         }
1237
1238         /*
1239          * Extract branch name from command line arguments, so
1240          * all that is left is pathspecs.
1241          *
1242          * Handle
1243          *
1244          *  1) git checkout <tree> -- [<paths>]
1245          *  2) git checkout -- [<paths>]
1246          *  3) git checkout <something> [<paths>]
1247          *
1248          * including "last branch" syntax and DWIM-ery for names of
1249          * remote branches, erroring out for invalid or ambiguous cases.
1250          */
1251         if (argc) {
1252                 struct object_id rev;
1253                 int dwim_ok =
1254                         !opts.patch_mode &&
1255                         dwim_new_local_branch &&
1256                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1257                         !opts.new_branch;
1258                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1259                                              &new, &opts, &rev);
1260                 argv += n;
1261                 argc -= n;
1262         }
1263
1264         if (argc) {
1265                 parse_pathspec(&opts.pathspec, 0,
1266                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1267                                prefix, argv);
1268
1269                 if (!opts.pathspec.nr)
1270                         die(_("invalid path specification"));
1271
1272                 /*
1273                  * Try to give more helpful suggestion.
1274                  * new_branch && argc > 1 will be caught later.
1275                  */
1276                 if (opts.new_branch && argc == 1)
1277                         die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
1278                                 argv[0], opts.new_branch);
1279
1280                 if (opts.force_detach)
1281                         die(_("git checkout: --detach does not take a path argument '%s'"),
1282                             argv[0]);
1283
1284                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1285                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1286                               "checking out of the index."));
1287         }
1288
1289         if (opts.new_branch) {
1290                 struct strbuf buf = STRBUF_INIT;
1291
1292                 opts.branch_exists =
1293                         validate_new_branchname(opts.new_branch, &buf,
1294                                                 !!opts.new_branch_force,
1295                                                 !!opts.new_branch_force);
1296
1297                 strbuf_release(&buf);
1298         }
1299
1300         UNLEAK(opts);
1301         if (opts.patch_mode || opts.pathspec.nr)
1302                 return checkout_paths(&opts, new.name);
1303         else
1304                 return checkout_branch(&opts, &new);
1305 }