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

   1 #include "builtin.h"
   2 #include "lockfile.h"
   3 #include "parse-options.h"
   4 #include "refs.h"
   5 #include "commit.h"
   6 #include "tree.h"
   7 #include "tree-walk.h"
   8 #include "cache-tree.h"
   9 #include "unpack-trees.h"
  10 #include "dir.h"
  11 #include "run-command.h"
  12 #include "merge-recursive.h"
  13 #include "branch.h"
  14 #include "diff.h"
  15 #include "revision.h"
  16 #include "remote.h"
  17 #include "blob.h"
  18 #include "xdiff-interface.h"
  19 #include "ll-merge.h"
  20 #include "resolve-undo.h"
  21 #include "submodule-config.h"
  22 #include "submodule.h"
  23
  24 static const char * const checkout_usage[] = {
  25         N_("git checkout [<options>] <branch>"),
  26         N_("git checkout [<options>] [<branch>] -- <file>..."),
  27         NULL,
  28 };
  29
  30 struct checkout_opts {
  31         int patch_mode;
  32         int quiet;
  33         int merge;
  34         int force;
  35         int force_detach;
  36         int writeout_stage;
  37         int overwrite_ignore;
  38         int ignore_skipworktree;
  39         int ignore_other_worktrees;
  40
  41         const char *new_branch;
  42         const char *new_branch_force;
  43         const char *new_orphan_branch;
  44         int new_branch_log;
  45         enum branch_track track;
  46         struct diff_options diff_options;
  47
  48         int branch_exists;
  49         const char *prefix;
  50         struct pathspec pathspec;
  51         struct tree *source_tree;
  52
  53         int new_worktree_mode;
  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                            sha1_to_hex(old ? old->object.sha1 : null_sha1),
  61                            sha1_to_hex(new ? new->object.sha1 : null_sha1),
  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->sha1, 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                     !hashcmp(ce->sha1, old->sha1)) {
  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, struct cache_entry *ce, int pos,
 159                           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, 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         unsigned char sha1[20];
 180         mmbuffer_t result_buf;
 181         unsigned char threeway[3][20];
 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                 hashcpy(threeway[stage - 1], ce->sha1);
 191                 if (stage == 2)
 192                         mode = create_ce_mode(ce->ce_mode);
 193                 pos++;
 194                 ce = active_cache[pos];
 195         }
 196         if (is_null_sha1(threeway[1]) || is_null_sha1(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 just to leak.  This hack is
 221          * primarily to get to the write_entry() machinery that massages
 222          * the contents to work-tree format and writes out which only
 223          * allows it for a cache entry.  The code in write_entry() needs
 224          * to be refactored to allow us to feed a <buffer, size, mode>
 225          * instead of a cache entry.  Such a refactoring would help
 226          * merge_recursive as well (it also writes the merge result to the
 227          * object database even when it may contain conflicts).
 228          */
 229         if (write_sha1_file(result_buf.ptr, result_buf.size,
 230                             blob_type, sha1))
 231                 die(_("Unable to add merge result for '%s'"), path);
 232         ce = make_cache_entry(mode, sha1, path, 2, 0);
 233         if (!ce)
 234                 die(_("make_cache_entry failed for path '%s'"), path);
 235         status = checkout_entry(ce, state, NULL);
 236         return status;
 237 }
 238
 239 static int checkout_paths(const struct checkout_opts *opts,
 240                           const char *revision)
 241 {
 242         int pos;
 243         struct checkout state;
 244         static char *ps_matched;
 245         unsigned char rev[20];
 246         int flag;
 247         struct commit *head;
 248         int errs = 0;
 249         struct lock_file *lock_file;
 250
 251         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 252                 die(_("'%s' cannot be used with updating paths"), "--track");
 253
 254         if (opts->new_branch_log)
 255                 die(_("'%s' cannot be used with updating paths"), "-l");
 256
 257         if (opts->force && opts->patch_mode)
 258                 die(_("'%s' cannot be used with updating paths"), "-f");
 259
 260         if (opts->force_detach)
 261                 die(_("'%s' cannot be used with updating paths"), "--detach");
 262
 263         if (opts->merge && opts->patch_mode)
 264                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 265
 266         if (opts->force && opts->merge)
 267                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 268
 269         if (opts->new_branch)
 270                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 271                     opts->new_branch);
 272
 273         if (opts->patch_mode)
 274                 return run_add_interactive(revision, "--patch=checkout",
 275                                            &opts->pathspec);
 276
 277         lock_file = xcalloc(1, sizeof(struct lock_file));
 278
 279         hold_locked_index(lock_file, 1);
 280         if (read_cache_preload(&opts->pathspec) < 0)
 281                 return error(_("corrupt index file"));
 282
 283         if (opts->source_tree)
 284                 read_tree_some(opts->source_tree, &opts->pathspec);
 285
 286         ps_matched = xcalloc(1, opts->pathspec.nr);
 287
 288         /*
 289          * Make sure all pathspecs participated in locating the paths
 290          * to be checked out.
 291          */
 292         for (pos = 0; pos < active_nr; pos++) {
 293                 struct cache_entry *ce = active_cache[pos];
 294                 ce->ce_flags &= ~CE_MATCHED;
 295                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 296                         continue;
 297                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 298                         /*
 299                          * "git checkout tree-ish -- path", but this entry
 300                          * is in the original index; it will not be checked
 301                          * out to the working tree and it does not matter
 302                          * if pathspec matched this entry.  We will not do
 303                          * anything to this entry at all.
 304                          */
 305                         continue;
 306                 /*
 307                  * Either this entry came from the tree-ish we are
 308                  * checking the paths out of, or we are checking out
 309                  * of the index.
 310                  *
 311                  * If it comes from the tree-ish, we already know it
 312                  * matches the pathspec and could just stamp
 313                  * CE_MATCHED to it from update_some(). But we still
 314                  * need ps_matched and read_tree_recursive (and
 315                  * eventually tree_entry_interesting) cannot fill
 316                  * ps_matched yet. Once it can, we can avoid calling
 317                  * match_pathspec() for _all_ entries when
 318                  * opts->source_tree != NULL.
 319                  */
 320                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
 321                         ce->ce_flags |= CE_MATCHED;
 322         }
 323
 324         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 325                 free(ps_matched);
 326                 return 1;
 327         }
 328         free(ps_matched);
 329
 330         /* "checkout -m path" to recreate conflicted state */
 331         if (opts->merge)
 332                 unmerge_marked_index(&the_index);
 333
 334         /* Any unmerged paths? */
 335         for (pos = 0; pos < active_nr; pos++) {
 336                 const struct cache_entry *ce = active_cache[pos];
 337                 if (ce->ce_flags & CE_MATCHED) {
 338                         if (!ce_stage(ce))
 339                                 continue;
 340                         if (opts->force) {
 341                                 warning(_("path '%s' is unmerged"), ce->name);
 342                         } else if (opts->writeout_stage) {
 343                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 344                         } else if (opts->merge) {
 345                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 346                         } else {
 347                                 errs = 1;
 348                                 error(_("path '%s' is unmerged"), ce->name);
 349                         }
 350                         pos = skip_same_name(ce, pos) - 1;
 351                 }
 352         }
 353         if (errs)
 354                 return 1;
 355
 356         /* Now we are committed to check them out */
 357         memset(&state, 0, sizeof(state));
 358         state.force = 1;
 359         state.refresh_cache = 1;
 360         state.istate = &the_index;
 361         for (pos = 0; pos < active_nr; pos++) {
 362                 struct cache_entry *ce = active_cache[pos];
 363                 if (ce->ce_flags & CE_MATCHED) {
 364                         if (!ce_stage(ce)) {
 365                                 errs |= checkout_entry(ce, &state, NULL);
 366                                 continue;
 367                         }
 368                         if (opts->writeout_stage)
 369                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
 370                         else if (opts->merge)
 371                                 errs |= checkout_merged(pos, &state);
 372                         pos = skip_same_name(ce, pos) - 1;
 373                 }
 374         }
 375
 376         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 377                 die(_("unable to write new index file"));
 378
 379         read_ref_full("HEAD", 0, rev, &flag);
 380         head = lookup_commit_reference_gently(rev, 1);
 381
 382         errs |= post_checkout_hook(head, head, 0);
 383         return errs;
 384 }
 385
 386 static void show_local_changes(struct object *head,
 387                                const struct diff_options *opts)
 388 {
 389         struct rev_info rev;
 390         /* I think we want full paths, even if we're in a subdirectory. */
 391         init_revisions(&rev, NULL);
 392         rev.diffopt.flags = opts->flags;
 393         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 394         diff_setup_done(&rev.diffopt);
 395         add_pending_object(&rev, head, NULL);
 396         run_diff_index(&rev, 0);
 397 }
 398
 399 static void describe_detached_head(const char *msg, struct commit *commit)
 400 {
 401         struct strbuf sb = STRBUF_INIT;
 402         if (!parse_commit(commit))
 403                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 404         fprintf(stderr, "%s %s... %s\n", msg,
 405                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 406         strbuf_release(&sb);
 407 }
 408
 409 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 410                       int worktree, int *writeout_error)
 411 {
 412         struct unpack_trees_options opts;
 413         struct tree_desc tree_desc;
 414
 415         memset(&opts, 0, sizeof(opts));
 416         opts.head_idx = -1;
 417         opts.update = worktree;
 418         opts.skip_unmerged = !worktree;
 419         opts.reset = 1;
 420         opts.merge = 1;
 421         opts.fn = oneway_merge;
 422         opts.verbose_update = !o->quiet && isatty(2);
 423         opts.src_index = &the_index;
 424         opts.dst_index = &the_index;
 425         parse_tree(tree);
 426         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 427         switch (unpack_trees(1, &tree_desc, &opts)) {
 428         case -2:
 429                 *writeout_error = 1;
 430                 /*
 431                  * We return 0 nevertheless, as the index is all right
 432                  * and more importantly we have made best efforts to
 433                  * update paths in the work tree, and we cannot revert
 434                  * them.
 435                  */
 436         case 0:
 437                 return 0;
 438         default:
 439                 return 128;
 440         }
 441 }
 442
 443 struct branch_info {
 444         const char *name; /* The short name used */
 445         const char *path; /* The full name of a real branch */
 446         struct commit *commit; /* The named commit */
 447         /*
 448          * if not null the branch is detached because it's already
 449          * checked out in this checkout
 450          */
 451         char *checkout;
 452 };
 453
 454 static void setup_branch_path(struct branch_info *branch)
 455 {
 456         struct strbuf buf = STRBUF_INIT;
 457
 458         strbuf_branchname(&buf, branch->name);
 459         if (strcmp(buf.buf, branch->name))
 460                 branch->name = xstrdup(buf.buf);
 461         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 462         branch->path = strbuf_detach(&buf, NULL);
 463 }
 464
 465 static int merge_working_tree(const struct checkout_opts *opts,
 466                               struct branch_info *old,
 467                               struct branch_info *new,
 468                               int *writeout_error)
 469 {
 470         int ret;
 471         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 472
 473         hold_locked_index(lock_file, 1);
 474         if (read_cache_preload(NULL) < 0)
 475                 return error(_("corrupt index file"));
 476
 477         resolve_undo_clear();
 478         if (opts->force) {
 479                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
 480                 if (ret)
 481                         return ret;
 482         } else {
 483                 struct tree_desc trees[2];
 484                 struct tree *tree;
 485                 struct unpack_trees_options topts;
 486
 487                 memset(&topts, 0, sizeof(topts));
 488                 topts.head_idx = -1;
 489                 topts.src_index = &the_index;
 490                 topts.dst_index = &the_index;
 491
 492                 setup_unpack_trees_porcelain(&topts, "checkout");
 493
 494                 refresh_cache(REFRESH_QUIET);
 495
 496                 if (unmerged_cache()) {
 497                         error(_("you need to resolve your current index first"));
 498                         return 1;
 499                 }
 500
 501                 /* 2-way merge to the new branch */
 502                 topts.initial_checkout = is_cache_unborn();
 503                 topts.update = 1;
 504                 topts.merge = 1;
 505                 topts.gently = opts->merge && old->commit;
 506                 topts.verbose_update = !opts->quiet && isatty(2);
 507                 topts.fn = twoway_merge;
 508                 if (opts->overwrite_ignore) {
 509                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 510                         topts.dir->flags |= DIR_SHOW_IGNORED;
 511                         setup_standard_excludes(topts.dir);
 512                 }
 513                 tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
 514                                            old->commit->object.sha1 :
 515                                            EMPTY_TREE_SHA1_BIN);
 516                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 517                 tree = parse_tree_indirect(new->commit->object.sha1);
 518                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 519
 520                 ret = unpack_trees(2, trees, &topts);
 521                 if (ret == -1) {
 522                         /*
 523                          * Unpack couldn't do a trivial merge; either
 524                          * give up or do a real merge, depending on
 525                          * whether the merge flag was used.
 526                          */
 527                         struct tree *result;
 528                         struct tree *work;
 529                         struct merge_options o;
 530                         if (!opts->merge)
 531                                 return 1;
 532
 533                         /*
 534                          * Without old->commit, the below is the same as
 535                          * the two-tree unpack we already tried and failed.
 536                          */
 537                         if (!old->commit)
 538                                 return 1;
 539
 540                         /* Do more real merge */
 541
 542                         /*
 543                          * We update the index fully, then write the
 544                          * tree from the index, then merge the new
 545                          * branch with the current tree, with the old
 546                          * branch as the base. Then we reset the index
 547                          * (but not the working tree) to the new
 548                          * branch, leaving the working tree as the
 549                          * merged version, but skipping unmerged
 550                          * entries in the index.
 551                          */
 552
 553                         add_files_to_cache(NULL, NULL, 0);
 554                         /*
 555                          * NEEDSWORK: carrying over local changes
 556                          * when branches have different end-of-line
 557                          * normalization (or clean+smudge rules) is
 558                          * a pain; plumb in an option to set
 559                          * o.renormalize?
 560                          */
 561                         init_merge_options(&o);
 562                         o.verbosity = 0;
 563                         work = write_tree_from_memory(&o);
 564
 565                         ret = reset_tree(new->commit->tree, opts, 1,
 566                                          writeout_error);
 567                         if (ret)
 568                                 return ret;
 569                         o.ancestor = old->name;
 570                         o.branch1 = new->name;
 571                         o.branch2 = "local";
 572                         merge_trees(&o, new->commit->tree, work,
 573                                 old->commit->tree, &result);
 574                         ret = reset_tree(new->commit->tree, opts, 0,
 575                                          writeout_error);
 576                         if (ret)
 577                                 return ret;
 578                 }
 579         }
 580
 581         if (!active_cache_tree)
 582                 active_cache_tree = cache_tree();
 583
 584         if (!cache_tree_fully_valid(active_cache_tree))
 585                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 586
 587         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 588                 die(_("unable to write new index file"));
 589
 590         if (!opts->force && !opts->quiet)
 591                 show_local_changes(&new->commit->object, &opts->diff_options);
 592
 593         return 0;
 594 }
 595
 596 static void report_tracking(struct branch_info *new)
 597 {
 598         struct strbuf sb = STRBUF_INIT;
 599         struct branch *branch = branch_get(new->name);
 600
 601         if (!format_tracking_info(branch, &sb))
 602                 return;
 603         fputs(sb.buf, stdout);
 604         strbuf_release(&sb);
 605 }
 606
 607 static void update_refs_for_switch(const struct checkout_opts *opts,
 608                                    struct branch_info *old,
 609                                    struct branch_info *new)
 610 {
 611         struct strbuf msg = STRBUF_INIT;
 612         const char *old_desc, *reflog_msg;
 613         if (opts->new_branch) {
 614                 if (opts->new_orphan_branch) {
 615                         if (opts->new_branch_log && !log_all_ref_updates) {
 616                                 int ret;
 617                                 char *refname;
 618                                 struct strbuf err = STRBUF_INIT;
 619
 620                                 refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
 621                                 ret = safe_create_reflog(refname, 1, &err);
 622                                 free(refname);
 623                                 if (ret) {
 624                                         fprintf(stderr, _("Can not do reflog for '%s': %s\n"),
 625                                                 opts->new_orphan_branch, err.buf);
 626                                         strbuf_release(&err);
 627                                         return;
 628                                 }
 629                                 strbuf_release(&err);
 630                         }
 631                 }
 632                 else
 633                         create_branch(old->name, opts->new_branch, new->name,
 634                                       opts->new_branch_force ? 1 : 0,
 635                                       opts->new_branch_log,
 636                                       opts->new_branch_force ? 1 : 0,
 637                                       opts->quiet,
 638                                       opts->track);
 639                 new->name = opts->new_branch;
 640                 setup_branch_path(new);
 641         }
 642
 643         old_desc = old->name;
 644         if (!old_desc && old->commit)
 645                 old_desc = sha1_to_hex(old->commit->object.sha1);
 646
 647         reflog_msg = getenv("GIT_REFLOG_ACTION");
 648         if (!reflog_msg)
 649                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 650                         old_desc ? old_desc : "(invalid)", new->name);
 651         else
 652                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 653
 654         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 655                 /* Nothing to do. */
 656         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 657                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 658                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 659                 if (!opts->quiet) {
 660                         if (old->path && advice_detached_head)
 661                                 detach_advice(new->name);
 662                         describe_detached_head(_("HEAD is now at"), new->commit);
 663                 }
 664         } else if (new->path) { /* Switch branches. */
 665                 create_symref("HEAD", new->path, msg.buf);
 666                 if (!opts->quiet) {
 667                         if (old->path && !strcmp(new->path, old->path)) {
 668                                 if (opts->new_branch_force)
 669                                         fprintf(stderr, _("Reset branch '%s'\n"),
 670                                                 new->name);
 671                                 else
 672                                         fprintf(stderr, _("Already on '%s'\n"),
 673                                                 new->name);
 674                         } else if (opts->new_branch) {
 675                                 if (opts->branch_exists)
 676                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 677                                 else
 678                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 679                         } else {
 680                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 681                                         new->name);
 682                         }
 683                 }
 684                 if (old->path && old->name) {
 685                         if (!ref_exists(old->path) && reflog_exists(old->path))
 686                                 delete_reflog(old->path);
 687                 }
 688         }
 689         remove_branch_state();
 690         strbuf_release(&msg);
 691         if (!opts->quiet &&
 692             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 693                 report_tracking(new);
 694 }
 695
 696 static int add_pending_uninteresting_ref(const char *refname,
 697                                          const struct object_id *oid,
 698                                          int flags, void *cb_data)
 699 {
 700         add_pending_sha1(cb_data, refname, oid->hash, UNINTERESTING);
 701         return 0;
 702 }
 703
 704 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 705 {
 706         strbuf_addstr(sb, "  ");
 707         strbuf_addstr(sb,
 708                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 709         strbuf_addch(sb, ' ');
 710         if (!parse_commit(commit))
 711                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 712         strbuf_addch(sb, '\n');
 713 }
 714
 715 #define ORPHAN_CUTOFF 4
 716 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 717 {
 718         struct commit *c, *last = NULL;
 719         struct strbuf sb = STRBUF_INIT;
 720         int lost = 0;
 721         while ((c = get_revision(revs)) != NULL) {
 722                 if (lost < ORPHAN_CUTOFF)
 723                         describe_one_orphan(&sb, c);
 724                 last = c;
 725                 lost++;
 726         }
 727         if (ORPHAN_CUTOFF < lost) {
 728                 int more = lost - ORPHAN_CUTOFF;
 729                 if (more == 1)
 730                         describe_one_orphan(&sb, last);
 731                 else
 732                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 733         }
 734
 735         fprintf(stderr,
 736                 Q_(
 737                 /* The singular version */
 738                 "Warning: you are leaving %d commit behind, "
 739                 "not connected to\n"
 740                 "any of your branches:\n\n"
 741                 "%s\n",
 742                 /* The plural version */
 743                 "Warning: you are leaving %d commits behind, "
 744                 "not connected to\n"
 745                 "any of your branches:\n\n"
 746                 "%s\n",
 747                 /* Give ngettext() the count */
 748                 lost),
 749                 lost,
 750                 sb.buf);
 751         strbuf_release(&sb);
 752
 753         if (advice_detached_head)
 754                 fprintf(stderr,
 755                         Q_(
 756                         /* The singular version */
 757                         "If you want to keep it by creating a new branch, "
 758                         "this may be a good time\nto do so with:\n\n"
 759                         " git branch <new-branch-name> %s\n\n",
 760                         /* The plural version */
 761                         "If you want to keep them by creating a new branch, "
 762                         "this may be a good time\nto do so with:\n\n"
 763                         " git branch <new-branch-name> %s\n\n",
 764                         /* Give ngettext() the count */
 765                         lost),
 766                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 767 }
 768
 769 /*
 770  * We are about to leave commit that was at the tip of a detached
 771  * HEAD.  If it is not reachable from any ref, this is the last chance
 772  * for the user to do so without resorting to reflog.
 773  */
 774 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 775 {
 776         struct rev_info revs;
 777         struct object *object = &old->object;
 778         struct object_array refs;
 779
 780         init_revisions(&revs, NULL);
 781         setup_revisions(0, NULL, &revs, NULL);
 782
 783         object->flags &= ~UNINTERESTING;
 784         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
 785
 786         for_each_ref(add_pending_uninteresting_ref, &revs);
 787         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
 788
 789         refs = revs.pending;
 790         revs.leak_pending = 1;
 791
 792         if (prepare_revision_walk(&revs))
 793                 die(_("internal error in revision walk"));
 794         if (!(old->object.flags & UNINTERESTING))
 795                 suggest_reattach(old, &revs);
 796         else
 797                 describe_detached_head(_("Previous HEAD position was"), old);
 798
 799         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 800         free(refs.objects);
 801 }
 802
 803 static int switch_branches(const struct checkout_opts *opts,
 804                            struct branch_info *new)
 805 {
 806         int ret = 0;
 807         struct branch_info old;
 808         void *path_to_free;
 809         unsigned char rev[20];
 810         int flag, writeout_error = 0;
 811         memset(&old, 0, sizeof(old));
 812         old.path = path_to_free = resolve_refdup("HEAD", 0, rev, &flag);
 813         old.commit = lookup_commit_reference_gently(rev, 1);
 814         if (!(flag & REF_ISSYMREF))
 815                 old.path = NULL;
 816
 817         if (old.path)
 818                 skip_prefix(old.path, "refs/heads/", &old.name);
 819
 820         if (!new->name) {
 821                 new->name = "HEAD";
 822                 new->commit = old.commit;
 823                 if (!new->commit)
 824                         die(_("You are on a branch yet to be born"));
 825                 parse_commit_or_die(new->commit);
 826         }
 827
 828         ret = merge_working_tree(opts, &old, new, &writeout_error);
 829         if (ret) {
 830                 free(path_to_free);
 831                 return ret;
 832         }
 833
 834         if (!opts->quiet && !old.path && old.commit &&
 835             new->commit != old.commit && !opts->new_worktree_mode)
 836                 orphaned_commit_warning(old.commit, new->commit);
 837
 838         update_refs_for_switch(opts, &old, new);
 839
 840         ret = post_checkout_hook(old.commit, new->commit, 1);
 841         free(path_to_free);
 842         return ret || writeout_error;
 843 }
 844
 845 static int git_checkout_config(const char *var, const char *value, void *cb)
 846 {
 847         if (!strcmp(var, "diff.ignoresubmodules")) {
 848                 struct checkout_opts *opts = cb;
 849                 handle_ignore_submodules_arg(&opts->diff_options, value);
 850                 return 0;
 851         }
 852
 853         if (starts_with(var, "submodule."))
 854                 return parse_submodule_config_option(var, value);
 855
 856         return git_xmerge_config(var, value, NULL);
 857 }
 858
 859 struct tracking_name_data {
 860         /* const */ char *src_ref;
 861         char *dst_ref;
 862         unsigned char *dst_sha1;
 863         int unique;
 864 };
 865
 866 static int check_tracking_name(struct remote *remote, void *cb_data)
 867 {
 868         struct tracking_name_data *cb = cb_data;
 869         struct refspec query;
 870         memset(&query, 0, sizeof(struct refspec));
 871         query.src = cb->src_ref;
 872         if (remote_find_tracking(remote, &query) ||
 873             get_sha1(query.dst, cb->dst_sha1)) {
 874                 free(query.dst);
 875                 return 0;
 876         }
 877         if (cb->dst_ref) {
 878                 free(query.dst);
 879                 cb->unique = 0;
 880                 return 0;
 881         }
 882         cb->dst_ref = query.dst;
 883         return 0;
 884 }
 885
 886 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 887 {
 888         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
 889         char src_ref[PATH_MAX];
 890         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
 891         cb_data.src_ref = src_ref;
 892         cb_data.dst_sha1 = sha1;
 893         for_each_remote(check_tracking_name, &cb_data);
 894         if (cb_data.unique)
 895                 return cb_data.dst_ref;
 896         free(cb_data.dst_ref);
 897         return NULL;
 898 }
 899
 900 static void check_linked_checkout(struct branch_info *new, const char *id)
 901 {
 902         struct strbuf sb = STRBUF_INIT;
 903         struct strbuf path = STRBUF_INIT;
 904         struct strbuf gitdir = STRBUF_INIT;
 905         const char *start, *end;
 906
 907         if (id)
 908                 strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);
 909         else
 910                 strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
 911
 912         if (strbuf_read_file(&sb, path.buf, 0) < 0 ||
 913             !skip_prefix(sb.buf, "ref:", &start))
 914                 goto done;
 915         while (isspace(*start))
 916                 start++;
 917         end = start;
 918         while (*end && !isspace(*end))
 919                 end++;
 920         if (strncmp(start, new->path, end - start) || new->path[end - start] != '\0')
 921                 goto done;
 922         if (id) {
 923                 strbuf_reset(&path);
 924                 strbuf_addf(&path, "%s/worktrees/%s/gitdir", get_git_common_dir(), id);
 925                 if (strbuf_read_file(&gitdir, path.buf, 0) <= 0)
 926                         goto done;
 927                 strbuf_rtrim(&gitdir);
 928         } else
 929                 strbuf_addstr(&gitdir, get_git_common_dir());
 930         die(_("'%s' is already checked out at '%s'"), new->name, gitdir.buf);
 931 done:
 932         strbuf_release(&path);
 933         strbuf_release(&sb);
 934         strbuf_release(&gitdir);
 935 }
 936
 937 static void check_linked_checkouts(struct branch_info *new)
 938 {
 939         struct strbuf path = STRBUF_INIT;
 940         DIR *dir;
 941         struct dirent *d;
 942
 943         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 944         if ((dir = opendir(path.buf)) == NULL) {
 945                 strbuf_release(&path);
 946                 return;
 947         }
 948
 949         /*
 950          * $GIT_COMMON_DIR/HEAD is practically outside
 951          * $GIT_DIR so resolve_ref_unsafe() won't work (it
 952          * uses git_path). Parse the ref ourselves.
 953          */
 954         check_linked_checkout(new, NULL);
 955
 956         while ((d = readdir(dir)) != NULL) {
 957                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
 958                         continue;
 959                 check_linked_checkout(new, d->d_name);
 960         }
 961         strbuf_release(&path);
 962         closedir(dir);
 963 }
 964
 965 static int parse_branchname_arg(int argc, const char **argv,
 966                                 int dwim_new_local_branch_ok,
 967                                 struct branch_info *new,
 968                                 struct checkout_opts *opts,
 969                                 unsigned char rev[20])
 970 {
 971         struct tree **source_tree = &opts->source_tree;
 972         const char **new_branch = &opts->new_branch;
 973         int argcount = 0;
 974         unsigned char branch_rev[20];
 975         const char *arg;
 976         int dash_dash_pos;
 977         int has_dash_dash = 0;
 978         int i;
 979
 980         /*
 981          * case 1: git checkout <ref> -- [<paths>]
 982          *
 983          *   <ref> must be a valid tree, everything after the '--' must be
 984          *   a path.
 985          *
 986          * case 2: git checkout -- [<paths>]
 987          *
 988          *   everything after the '--' must be paths.
 989          *
 990          * case 3: git checkout <something> [--]
 991          *
 992          *   (a) If <something> is a commit, that is to
 993          *       switch to the branch or detach HEAD at it.  As a special case,
 994          *       if <something> is A...B (missing A or B means HEAD but you can
 995          *       omit at most one side), and if there is a unique merge base
 996          *       between A and B, A...B names that merge base.
 997          *
 998          *   (b) If <something> is _not_ a commit, either "--" is present
 999          *       or <something> is not a path, no -t or -b was given, and
1000          *       and there is a tracking branch whose name is <something>
1001          *       in one and only one remote, then this is a short-hand to
1002          *       fork local <something> from that remote-tracking branch.
1003          *
1004          *   (c) Otherwise, if "--" is present, treat it like case (1).
1005          *
1006          *   (d) Otherwise :
1007          *       - if it's a reference, treat it like case (1)
1008          *       - else if it's a path, treat it like case (2)
1009          *       - else: fail.
1010          *
1011          * case 4: git checkout <something> <paths>
1012          *
1013          *   The first argument must not be ambiguous.
1014          *   - If it's *only* a reference, treat it like case (1).
1015          *   - If it's only a path, treat it like case (2).
1016          *   - else: fail.
1017          *
1018          */
1019         if (!argc)
1020                 return 0;
1021
1022         arg = argv[0];
1023         dash_dash_pos = -1;
1024         for (i = 0; i < argc; i++) {
1025                 if (!strcmp(argv[i], "--")) {
1026                         dash_dash_pos = i;
1027                         break;
1028                 }
1029         }
1030         if (dash_dash_pos == 0)
1031                 return 1; /* case (2) */
1032         else if (dash_dash_pos == 1)
1033                 has_dash_dash = 1; /* case (3) or (1) */
1034         else if (dash_dash_pos >= 2)
1035                 die(_("only one reference expected, %d given."), dash_dash_pos);
1036
1037         if (!strcmp(arg, "-"))
1038                 arg = "@{-1}";
1039
1040         if (get_sha1_mb(arg, rev)) {
1041                 /*
1042                  * Either case (3) or (4), with <something> not being
1043                  * a commit, or an attempt to use case (1) with an
1044                  * invalid ref.
1045                  *
1046                  * It's likely an error, but we need to find out if
1047                  * we should auto-create the branch, case (3).(b).
1048                  */
1049                 int recover_with_dwim = dwim_new_local_branch_ok;
1050
1051                 if (check_filename(NULL, arg) && !has_dash_dash)
1052                         recover_with_dwim = 0;
1053                 /*
1054                  * Accept "git checkout foo" and "git checkout foo --"
1055                  * as candidates for dwim.
1056                  */
1057                 if (!(argc == 1 && !has_dash_dash) &&
1058                     !(argc == 2 && has_dash_dash))
1059                         recover_with_dwim = 0;
1060
1061                 if (recover_with_dwim) {
1062                         const char *remote = unique_tracking_name(arg, rev);
1063                         if (remote) {
1064                                 *new_branch = arg;
1065                                 arg = remote;
1066                                 /* DWIMmed to create local branch, case (3).(b) */
1067                         } else {
1068                                 recover_with_dwim = 0;
1069                         }
1070                 }
1071
1072                 if (!recover_with_dwim) {
1073                         if (has_dash_dash)
1074                                 die(_("invalid reference: %s"), arg);
1075                         return argcount;
1076                 }
1077         }
1078
1079         /* we can't end up being in (2) anymore, eat the argument */
1080         argcount++;
1081         argv++;
1082         argc--;
1083
1084         new->name = arg;
1085         setup_branch_path(new);
1086
1087         if (!check_refname_format(new->path, 0) &&
1088             !read_ref(new->path, branch_rev))
1089                 hashcpy(rev, branch_rev);
1090         else
1091                 new->path = NULL; /* not an existing branch */
1092
1093         new->commit = lookup_commit_reference_gently(rev, 1);
1094         if (!new->commit) {
1095                 /* not a commit */
1096                 *source_tree = parse_tree_indirect(rev);
1097         } else {
1098                 parse_commit_or_die(new->commit);
1099                 *source_tree = new->commit->tree;
1100         }
1101
1102         if (!*source_tree)                   /* case (1): want a tree */
1103                 die(_("reference is not a tree: %s"), arg);
1104         if (!has_dash_dash) {/* case (3).(d) -> (1) */
1105                 /*
1106                  * Do not complain the most common case
1107                  *      git checkout branch
1108                  * even if there happen to be a file called 'branch';
1109                  * it would be extremely annoying.
1110                  */
1111                 if (argc)
1112                         verify_non_filename(NULL, arg);
1113         } else {
1114                 argcount++;
1115                 argv++;
1116                 argc--;
1117         }
1118
1119         return argcount;
1120 }
1121
1122 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1123 {
1124         int status;
1125         struct strbuf branch_ref = STRBUF_INIT;
1126
1127         if (!opts->new_branch)
1128                 die(_("You are on a branch yet to be born"));
1129         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1130         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1131         strbuf_release(&branch_ref);
1132         if (!opts->quiet)
1133                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1134                         opts->new_branch);
1135         return status;
1136 }
1137
1138 static int checkout_branch(struct checkout_opts *opts,
1139                            struct branch_info *new)
1140 {
1141         if (opts->pathspec.nr)
1142                 die(_("paths cannot be used with switching branches"));
1143
1144         if (opts->patch_mode)
1145                 die(_("'%s' cannot be used with switching branches"),
1146                     "--patch");
1147
1148         if (opts->writeout_stage)
1149                 die(_("'%s' cannot be used with switching branches"),
1150                     "--ours/--theirs");
1151
1152         if (opts->force && opts->merge)
1153                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1154
1155         if (opts->force_detach && opts->new_branch)
1156                 die(_("'%s' cannot be used with '%s'"),
1157                     "--detach", "-b/-B/--orphan");
1158
1159         if (opts->new_orphan_branch) {
1160                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1161                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1162         } else if (opts->force_detach) {
1163                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1164                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1165         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1166                 opts->track = git_branch_track;
1167
1168         if (new->name && !new->commit)
1169                 die(_("Cannot switch branch to a non-commit '%s'"),
1170                     new->name);
1171
1172         if (new->path && !opts->force_detach && !opts->new_branch) {
1173                 unsigned char sha1[20];
1174                 int flag;
1175                 char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
1176                 if (head_ref &&
1177                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
1178                     !opts->ignore_other_worktrees)
1179                         check_linked_checkouts(new);
1180                 free(head_ref);
1181         }
1182
1183         if (!new->commit && opts->new_branch) {
1184                 unsigned char rev[20];
1185                 int flag;
1186
1187                 if (!read_ref_full("HEAD", 0, rev, &flag) &&
1188                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1189                         return switch_unborn_to_new_branch(opts);
1190         }
1191         return switch_branches(opts, new);
1192 }
1193
1194 int cmd_checkout(int argc, const char **argv, const char *prefix)
1195 {
1196         struct checkout_opts opts;
1197         struct branch_info new;
1198         char *conflict_style = NULL;
1199         int dwim_new_local_branch = 1;
1200         struct option options[] = {
1201                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1202                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1203                            N_("create and checkout a new branch")),
1204                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1205                            N_("create/reset and checkout a branch")),
1206                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1207                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1208                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1209                         BRANCH_TRACK_EXPLICIT),
1210                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1211                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1212                             2),
1213                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1214                             3),
1215                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1216                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1217                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1218                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1219                            N_("conflict style (merge or diff3)")),
1220                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1221                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1222                          N_("do not limit pathspecs to sparse entries only")),
1223                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1224                                 N_("second guess 'git checkout <no-such-branch>'")),
1225                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1226                          N_("do not check if another worktree is holding the given ref")),
1227                 OPT_END(),
1228         };
1229
1230         memset(&opts, 0, sizeof(opts));
1231         memset(&new, 0, sizeof(new));
1232         opts.overwrite_ignore = 1;
1233         opts.prefix = prefix;
1234
1235         gitmodules_config();
1236         git_config(git_checkout_config, &opts);
1237
1238         opts.track = BRANCH_TRACK_UNSPECIFIED;
1239
1240         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1241                              PARSE_OPT_KEEP_DASHDASH);
1242
1243         opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
1244
1245         if (conflict_style) {
1246                 opts.merge = 1; /* implied */
1247                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1248         }
1249
1250         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1251                 die(_("-b, -B and --orphan are mutually exclusive"));
1252
1253         /*
1254          * From here on, new_branch will contain the branch to be checked out,
1255          * and new_branch_force and new_orphan_branch will tell us which one of
1256          * -b/-B/--orphan is being used.
1257          */
1258         if (opts.new_branch_force)
1259                 opts.new_branch = opts.new_branch_force;
1260
1261         if (opts.new_orphan_branch)
1262                 opts.new_branch = opts.new_orphan_branch;
1263
1264         /* --track without -b/-B/--orphan should DWIM */
1265         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1266                 const char *argv0 = argv[0];
1267                 if (!argc || !strcmp(argv0, "--"))
1268                         die (_("--track needs a branch name"));
1269                 skip_prefix(argv0, "refs/", &argv0);
1270                 skip_prefix(argv0, "remotes/", &argv0);
1271                 argv0 = strchr(argv0, '/');
1272                 if (!argv0 || !argv0[1])
1273                         die (_("Missing branch name; try -b"));
1274                 opts.new_branch = argv0 + 1;
1275         }
1276
1277         /*
1278          * Extract branch name from command line arguments, so
1279          * all that is left is pathspecs.
1280          *
1281          * Handle
1282          *
1283          *  1) git checkout <tree> -- [<paths>]
1284          *  2) git checkout -- [<paths>]
1285          *  3) git checkout <something> [<paths>]
1286          *
1287          * including "last branch" syntax and DWIM-ery for names of
1288          * remote branches, erroring out for invalid or ambiguous cases.
1289          */
1290         if (argc) {
1291                 unsigned char rev[20];
1292                 int dwim_ok =
1293                         !opts.patch_mode &&
1294                         dwim_new_local_branch &&
1295                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1296                         !opts.new_branch;
1297                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1298                                              &new, &opts, rev);
1299                 argv += n;
1300                 argc -= n;
1301         }
1302
1303         if (argc) {
1304                 parse_pathspec(&opts.pathspec, 0,
1305                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1306                                prefix, argv);
1307
1308                 if (!opts.pathspec.nr)
1309                         die(_("invalid path specification"));
1310
1311                 /*
1312                  * Try to give more helpful suggestion.
1313                  * new_branch && argc > 1 will be caught later.
1314                  */
1315                 if (opts.new_branch && argc == 1)
1316                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1317                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1318                             opts.new_branch, argv[0]);
1319
1320                 if (opts.force_detach)
1321                         die(_("git checkout: --detach does not take a path argument '%s'"),
1322                             argv[0]);
1323
1324                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1325                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1326                               "checking out of the index."));
1327         }
1328
1329         if (opts.new_branch) {
1330                 struct strbuf buf = STRBUF_INIT;
1331
1332                 opts.branch_exists =
1333                         validate_new_branchname(opts.new_branch, &buf,
1334                                                 !!opts.new_branch_force,
1335                                                 !!opts.new_branch_force);
1336
1337                 strbuf_release(&buf);
1338         }
1339
1340         if (opts.patch_mode || opts.pathspec.nr)
1341                 return checkout_paths(&opts, new.name);
1342         else
1343                 return checkout_branch(&opts, &new);
1344 }