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.h"
  22
  23 static const char * const checkout_usage[] = {
  24         N_("git checkout [<options>] <branch>"),
  25         N_("git checkout [<options>] [<branch>] -- <file>..."),
  26         NULL,
  27 };
  28
  29 struct checkout_opts {
  30         int patch_mode;
  31         int quiet;
  32         int merge;
  33         int force;
  34         int force_detach;
  35         int writeout_stage;
  36         int overwrite_ignore;
  37         int ignore_skipworktree;
  38         int ignore_other_worktrees;
  39
  40         const char *new_branch;
  41         const char *new_branch_force;
  42         const char *new_orphan_branch;
  43         int new_branch_log;
  44         enum branch_track track;
  45         struct diff_options diff_options;
  46
  47         int branch_exists;
  48         const char *prefix;
  49         struct pathspec pathspec;
  50         struct tree *source_tree;
  51
  52         int new_worktree_mode;
  53 };
  54
  55 static int post_checkout_hook(struct commit *old, struct commit *new,
  56                               int changed)
  57 {
  58         return run_hook_le(NULL, "post-checkout",
  59                            sha1_to_hex(old ? old->object.sha1 : null_sha1),
  60                            sha1_to_hex(new ? new->object.sha1 : null_sha1),
  61                            changed ? "1" : "0", NULL);
  62         /* "new" can be NULL when checking out from the index before
  63            a commit exists. */
  64
  65 }
  66
  67 static int update_some(const unsigned char *sha1, struct strbuf *base,
  68                 const char *pathname, unsigned mode, int stage, void *context)
  69 {
  70         int len;
  71         struct cache_entry *ce;
  72         int pos;
  73
  74         if (S_ISDIR(mode))
  75                 return READ_TREE_RECURSIVE;
  76
  77         len = base->len + strlen(pathname);
  78         ce = xcalloc(1, cache_entry_size(len));
  79         hashcpy(ce->sha1, sha1);
  80         memcpy(ce->name, base->buf, base->len);
  81         memcpy(ce->name + base->len, pathname, len - base->len);
  82         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  83         ce->ce_namelen = len;
  84         ce->ce_mode = create_ce_mode(mode);
  85
  86         /*
  87          * If the entry is the same as the current index, we can leave the old
  88          * entry in place. Whether it is UPTODATE or not, checkout_entry will
  89          * do the right thing.
  90          */
  91         pos = cache_name_pos(ce->name, ce->ce_namelen);
  92         if (pos >= 0) {
  93                 struct cache_entry *old = active_cache[pos];
  94                 if (ce->ce_mode == old->ce_mode &&
  95                     !hashcmp(ce->sha1, old->sha1)) {
  96                         old->ce_flags |= CE_UPDATE;
  97                         free(ce);
  98                         return 0;
  99                 }
 100         }
 101
 102         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 103         return 0;
 104 }
 105
 106 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
 107 {
 108         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
 109
 110         /* update the index with the given tree's info
 111          * for all args, expanding wildcards, and exit
 112          * with any non-zero return code.
 113          */
 114         return 0;
 115 }
 116
 117 static int skip_same_name(const struct cache_entry *ce, int pos)
 118 {
 119         while (++pos < active_nr &&
 120                !strcmp(active_cache[pos]->name, ce->name))
 121                 ; /* skip */
 122         return pos;
 123 }
 124
 125 static int check_stage(int stage, const struct cache_entry *ce, int pos)
 126 {
 127         while (pos < active_nr &&
 128                !strcmp(active_cache[pos]->name, ce->name)) {
 129                 if (ce_stage(active_cache[pos]) == stage)
 130                         return 0;
 131                 pos++;
 132         }
 133         if (stage == 2)
 134                 return error(_("path '%s' does not have our version"), ce->name);
 135         else
 136                 return error(_("path '%s' does not have their version"), ce->name);
 137 }
 138
 139 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 140 {
 141         unsigned seen = 0;
 142         const char *name = ce->name;
 143
 144         while (pos < active_nr) {
 145                 ce = active_cache[pos];
 146                 if (strcmp(name, ce->name))
 147                         break;
 148                 seen |= (1 << ce_stage(ce));
 149                 pos++;
 150         }
 151         if ((stages & seen) != stages)
 152                 return error(_("path '%s' does not have all necessary versions"),
 153                              name);
 154         return 0;
 155 }
 156
 157 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 158                           struct checkout *state)
 159 {
 160         while (pos < active_nr &&
 161                !strcmp(active_cache[pos]->name, ce->name)) {
 162                 if (ce_stage(active_cache[pos]) == stage)
 163                         return checkout_entry(active_cache[pos], state, NULL);
 164                 pos++;
 165         }
 166         if (stage == 2)
 167                 return error(_("path '%s' does not have our version"), ce->name);
 168         else
 169                 return error(_("path '%s' does not have their version"), ce->name);
 170 }
 171
 172 static int checkout_merged(int pos, struct checkout *state)
 173 {
 174         struct cache_entry *ce = active_cache[pos];
 175         const char *path = ce->name;
 176         mmfile_t ancestor, ours, theirs;
 177         int status;
 178         unsigned char sha1[20];
 179         mmbuffer_t result_buf;
 180         unsigned char threeway[3][20];
 181         unsigned mode = 0;
 182
 183         memset(threeway, 0, sizeof(threeway));
 184         while (pos < active_nr) {
 185                 int stage;
 186                 stage = ce_stage(ce);
 187                 if (!stage || strcmp(path, ce->name))
 188                         break;
 189                 hashcpy(threeway[stage - 1], ce->sha1);
 190                 if (stage == 2)
 191                         mode = create_ce_mode(ce->ce_mode);
 192                 pos++;
 193                 ce = active_cache[pos];
 194         }
 195         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
 196                 return error(_("path '%s' does not have necessary versions"), path);
 197
 198         read_mmblob(&ancestor, threeway[0]);
 199         read_mmblob(&ours, threeway[1]);
 200         read_mmblob(&theirs, threeway[2]);
 201
 202         /*
 203          * NEEDSWORK: re-create conflicts from merges with
 204          * merge.renormalize set, too
 205          */
 206         status = ll_merge(&result_buf, path, &ancestor, "base",
 207                           &ours, "ours", &theirs, "theirs", NULL);
 208         free(ancestor.ptr);
 209         free(ours.ptr);
 210         free(theirs.ptr);
 211         if (status < 0 || !result_buf.ptr) {
 212                 free(result_buf.ptr);
 213                 return error(_("path '%s': cannot merge"), path);
 214         }
 215
 216         /*
 217          * NEEDSWORK:
 218          * There is absolutely no reason to write this as a blob object
 219          * and create a phony cache entry just to leak.  This hack is
 220          * primarily to get to the write_entry() machinery that massages
 221          * the contents to work-tree format and writes out which only
 222          * allows it for a cache entry.  The code in write_entry() needs
 223          * to be refactored to allow us to feed a <buffer, size, mode>
 224          * instead of a cache entry.  Such a refactoring would help
 225          * merge_recursive as well (it also writes the merge result to the
 226          * object database even when it may contain conflicts).
 227          */
 228         if (write_sha1_file(result_buf.ptr, result_buf.size,
 229                             blob_type, sha1))
 230                 die(_("Unable to add merge result for '%s'"), path);
 231         ce = make_cache_entry(mode, sha1, path, 2, 0);
 232         if (!ce)
 233                 die(_("make_cache_entry failed for path '%s'"), path);
 234         status = checkout_entry(ce, state, NULL);
 235         return status;
 236 }
 237
 238 static int checkout_paths(const struct checkout_opts *opts,
 239                           const char *revision)
 240 {
 241         int pos;
 242         struct checkout state;
 243         static char *ps_matched;
 244         unsigned char rev[20];
 245         int flag;
 246         struct commit *head;
 247         int errs = 0;
 248         struct lock_file *lock_file;
 249
 250         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 251                 die(_("'%s' cannot be used with updating paths"), "--track");
 252
 253         if (opts->new_branch_log)
 254                 die(_("'%s' cannot be used with updating paths"), "-l");
 255
 256         if (opts->force && opts->patch_mode)
 257                 die(_("'%s' cannot be used with updating paths"), "-f");
 258
 259         if (opts->force_detach)
 260                 die(_("'%s' cannot be used with updating paths"), "--detach");
 261
 262         if (opts->merge && opts->patch_mode)
 263                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 264
 265         if (opts->force && opts->merge)
 266                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 267
 268         if (opts->new_branch)
 269                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 270                     opts->new_branch);
 271
 272         if (opts->patch_mode)
 273                 return run_add_interactive(revision, "--patch=checkout",
 274                                            &opts->pathspec);
 275
 276         lock_file = xcalloc(1, sizeof(struct lock_file));
 277
 278         hold_locked_index(lock_file, 1);
 279         if (read_cache_preload(&opts->pathspec) < 0)
 280                 return error(_("corrupt index file"));
 281
 282         if (opts->source_tree)
 283                 read_tree_some(opts->source_tree, &opts->pathspec);
 284
 285         ps_matched = xcalloc(1, opts->pathspec.nr);
 286
 287         /*
 288          * Make sure all pathspecs participated in locating the paths
 289          * to be checked out.
 290          */
 291         for (pos = 0; pos < active_nr; pos++) {
 292                 struct cache_entry *ce = active_cache[pos];
 293                 ce->ce_flags &= ~CE_MATCHED;
 294                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 295                         continue;
 296                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 297                         /*
 298                          * "git checkout tree-ish -- path", but this entry
 299                          * is in the original index; it will not be checked
 300                          * out to the working tree and it does not matter
 301                          * if pathspec matched this entry.  We will not do
 302                          * anything to this entry at all.
 303                          */
 304                         continue;
 305                 /*
 306                  * Either this entry came from the tree-ish we are
 307                  * checking the paths out of, or we are checking out
 308                  * of the index.
 309                  *
 310                  * If it comes from the tree-ish, we already know it
 311                  * matches the pathspec and could just stamp
 312                  * CE_MATCHED to it from update_some(). But we still
 313                  * need ps_matched and read_tree_recursive (and
 314                  * eventually tree_entry_interesting) cannot fill
 315                  * ps_matched yet. Once it can, we can avoid calling
 316                  * match_pathspec() for _all_ entries when
 317                  * opts->source_tree != NULL.
 318                  */
 319                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
 320                         ce->ce_flags |= CE_MATCHED;
 321         }
 322
 323         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 324                 free(ps_matched);
 325                 return 1;
 326         }
 327         free(ps_matched);
 328
 329         /* "checkout -m path" to recreate conflicted state */
 330         if (opts->merge)
 331                 unmerge_marked_index(&the_index);
 332
 333         /* Any unmerged paths? */
 334         for (pos = 0; pos < active_nr; pos++) {
 335                 const struct cache_entry *ce = active_cache[pos];
 336                 if (ce->ce_flags & CE_MATCHED) {
 337                         if (!ce_stage(ce))
 338                                 continue;
 339                         if (opts->force) {
 340                                 warning(_("path '%s' is unmerged"), ce->name);
 341                         } else if (opts->writeout_stage) {
 342                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 343                         } else if (opts->merge) {
 344                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 345                         } else {
 346                                 errs = 1;
 347                                 error(_("path '%s' is unmerged"), ce->name);
 348                         }
 349                         pos = skip_same_name(ce, pos) - 1;
 350                 }
 351         }
 352         if (errs)
 353                 return 1;
 354
 355         /* Now we are committed to check them out */
 356         memset(&state, 0, sizeof(state));
 357         state.force = 1;
 358         state.refresh_cache = 1;
 359         state.istate = &the_index;
 360         for (pos = 0; pos < active_nr; pos++) {
 361                 struct cache_entry *ce = active_cache[pos];
 362                 if (ce->ce_flags & CE_MATCHED) {
 363                         if (!ce_stage(ce)) {
 364                                 errs |= checkout_entry(ce, &state, NULL);
 365                                 continue;
 366                         }
 367                         if (opts->writeout_stage)
 368                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
 369                         else if (opts->merge)
 370                                 errs |= checkout_merged(pos, &state);
 371                         pos = skip_same_name(ce, pos) - 1;
 372                 }
 373         }
 374
 375         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 376                 die(_("unable to write new index file"));
 377
 378         read_ref_full("HEAD", 0, rev, &flag);
 379         head = lookup_commit_reference_gently(rev, 1);
 380
 381         errs |= post_checkout_hook(head, head, 0);
 382         return errs;
 383 }
 384
 385 static void show_local_changes(struct object *head,
 386                                const struct diff_options *opts)
 387 {
 388         struct rev_info rev;
 389         /* I think we want full paths, even if we're in a subdirectory. */
 390         init_revisions(&rev, NULL);
 391         rev.diffopt.flags = opts->flags;
 392         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 393         diff_setup_done(&rev.diffopt);
 394         add_pending_object(&rev, head, NULL);
 395         run_diff_index(&rev, 0);
 396 }
 397
 398 static void describe_detached_head(const char *msg, struct commit *commit)
 399 {
 400         struct strbuf sb = STRBUF_INIT;
 401         if (!parse_commit(commit))
 402                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 403         fprintf(stderr, "%s %s... %s\n", msg,
 404                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 405         strbuf_release(&sb);
 406 }
 407
 408 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 409                       int worktree, int *writeout_error)
 410 {
 411         struct unpack_trees_options opts;
 412         struct tree_desc tree_desc;
 413
 414         memset(&opts, 0, sizeof(opts));
 415         opts.head_idx = -1;
 416         opts.update = worktree;
 417         opts.skip_unmerged = !worktree;
 418         opts.reset = 1;
 419         opts.merge = 1;
 420         opts.fn = oneway_merge;
 421         opts.verbose_update = !o->quiet && isatty(2);
 422         opts.src_index = &the_index;
 423         opts.dst_index = &the_index;
 424         parse_tree(tree);
 425         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 426         switch (unpack_trees(1, &tree_desc, &opts)) {
 427         case -2:
 428                 *writeout_error = 1;
 429                 /*
 430                  * We return 0 nevertheless, as the index is all right
 431                  * and more importantly we have made best efforts to
 432                  * update paths in the work tree, and we cannot revert
 433                  * them.
 434                  */
 435         case 0:
 436                 return 0;
 437         default:
 438                 return 128;
 439         }
 440 }
 441
 442 struct branch_info {
 443         const char *name; /* The short name used */
 444         const char *path; /* The full name of a real branch */
 445         struct commit *commit; /* The named commit */
 446         /*
 447          * if not null the branch is detached because it's already
 448          * checked out in this checkout
 449          */
 450         char *checkout;
 451 };
 452
 453 static void setup_branch_path(struct branch_info *branch)
 454 {
 455         struct strbuf buf = STRBUF_INIT;
 456
 457         strbuf_branchname(&buf, branch->name);
 458         if (strcmp(buf.buf, branch->name))
 459                 branch->name = xstrdup(buf.buf);
 460         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 461         branch->path = strbuf_detach(&buf, NULL);
 462 }
 463
 464 static int merge_working_tree(const struct checkout_opts *opts,
 465                               struct branch_info *old,
 466                               struct branch_info *new,
 467                               int *writeout_error)
 468 {
 469         int ret;
 470         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 471
 472         hold_locked_index(lock_file, 1);
 473         if (read_cache_preload(NULL) < 0)
 474                 return error(_("corrupt index file"));
 475
 476         resolve_undo_clear();
 477         if (opts->force) {
 478                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
 479                 if (ret)
 480                         return ret;
 481         } else {
 482                 struct tree_desc trees[2];
 483                 struct tree *tree;
 484                 struct unpack_trees_options topts;
 485
 486                 memset(&topts, 0, sizeof(topts));
 487                 topts.head_idx = -1;
 488                 topts.src_index = &the_index;
 489                 topts.dst_index = &the_index;
 490
 491                 setup_unpack_trees_porcelain(&topts, "checkout");
 492
 493                 refresh_cache(REFRESH_QUIET);
 494
 495                 if (unmerged_cache()) {
 496                         error(_("you need to resolve your current index first"));
 497                         return 1;
 498                 }
 499
 500                 /* 2-way merge to the new branch */
 501                 topts.initial_checkout = is_cache_unborn();
 502                 topts.update = 1;
 503                 topts.merge = 1;
 504                 topts.gently = opts->merge && old->commit;
 505                 topts.verbose_update = !opts->quiet && isatty(2);
 506                 topts.fn = twoway_merge;
 507                 if (opts->overwrite_ignore) {
 508                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 509                         topts.dir->flags |= DIR_SHOW_IGNORED;
 510                         setup_standard_excludes(topts.dir);
 511                 }
 512                 tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
 513                                            old->commit->object.sha1 :
 514                                            EMPTY_TREE_SHA1_BIN);
 515                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 516                 tree = parse_tree_indirect(new->commit->object.sha1);
 517                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 518
 519                 ret = unpack_trees(2, trees, &topts);
 520                 if (ret == -1) {
 521                         /*
 522                          * Unpack couldn't do a trivial merge; either
 523                          * give up or do a real merge, depending on
 524                          * whether the merge flag was used.
 525                          */
 526                         struct tree *result;
 527                         struct tree *work;
 528                         struct merge_options o;
 529                         if (!opts->merge)
 530                                 return 1;
 531
 532                         /*
 533                          * Without old->commit, the below is the same as
 534                          * the two-tree unpack we already tried and failed.
 535                          */
 536                         if (!old->commit)
 537                                 return 1;
 538
 539                         /* Do more real merge */
 540
 541                         /*
 542                          * We update the index fully, then write the
 543                          * tree from the index, then merge the new
 544                          * branch with the current tree, with the old
 545                          * branch as the base. Then we reset the index
 546                          * (but not the working tree) to the new
 547                          * branch, leaving the working tree as the
 548                          * merged version, but skipping unmerged
 549                          * entries in the index.
 550                          */
 551
 552                         add_files_to_cache(NULL, NULL, 0);
 553                         /*
 554                          * NEEDSWORK: carrying over local changes
 555                          * when branches have different end-of-line
 556                          * normalization (or clean+smudge rules) is
 557                          * a pain; plumb in an option to set
 558                          * o.renormalize?
 559                          */
 560                         init_merge_options(&o);
 561                         o.verbosity = 0;
 562                         work = write_tree_from_memory(&o);
 563
 564                         ret = reset_tree(new->commit->tree, opts, 1,
 565                                          writeout_error);
 566                         if (ret)
 567                                 return ret;
 568                         o.ancestor = old->name;
 569                         o.branch1 = new->name;
 570                         o.branch2 = "local";
 571                         merge_trees(&o, new->commit->tree, work,
 572                                 old->commit->tree, &result);
 573                         ret = reset_tree(new->commit->tree, opts, 0,
 574                                          writeout_error);
 575                         if (ret)
 576                                 return ret;
 577                 }
 578         }
 579
 580         if (!active_cache_tree)
 581                 active_cache_tree = cache_tree();
 582
 583         if (!cache_tree_fully_valid(active_cache_tree))
 584                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 585
 586         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 587                 die(_("unable to write new index file"));
 588
 589         if (!opts->force && !opts->quiet)
 590                 show_local_changes(&new->commit->object, &opts->diff_options);
 591
 592         return 0;
 593 }
 594
 595 static void report_tracking(struct branch_info *new)
 596 {
 597         struct strbuf sb = STRBUF_INIT;
 598         struct branch *branch = branch_get(new->name);
 599
 600         if (!format_tracking_info(branch, &sb))
 601                 return;
 602         fputs(sb.buf, stdout);
 603         strbuf_release(&sb);
 604 }
 605
 606 static void update_refs_for_switch(const struct checkout_opts *opts,
 607                                    struct branch_info *old,
 608                                    struct branch_info *new)
 609 {
 610         struct strbuf msg = STRBUF_INIT;
 611         const char *old_desc, *reflog_msg;
 612         if (opts->new_branch) {
 613                 if (opts->new_orphan_branch) {
 614                         if (opts->new_branch_log && !log_all_ref_updates) {
 615                                 int ret;
 616                                 char *refname;
 617                                 struct strbuf err = STRBUF_INIT;
 618
 619                                 refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
 620                                 ret = safe_create_reflog(refname, 1, &err);
 621                                 free(refname);
 622                                 if (ret) {
 623                                         fprintf(stderr, _("Can not do reflog for '%s': %s\n"),
 624                                                 opts->new_orphan_branch, err.buf);
 625                                         strbuf_release(&err);
 626                                         return;
 627                                 }
 628                                 strbuf_release(&err);
 629                         }
 630                 }
 631                 else
 632                         create_branch(old->name, opts->new_branch, new->name,
 633                                       opts->new_branch_force ? 1 : 0,
 634                                       opts->new_branch_log,
 635                                       opts->new_branch_force ? 1 : 0,
 636                                       opts->quiet,
 637                                       opts->track);
 638                 new->name = opts->new_branch;
 639                 setup_branch_path(new);
 640         }
 641
 642         old_desc = old->name;
 643         if (!old_desc && old->commit)
 644                 old_desc = sha1_to_hex(old->commit->object.sha1);
 645
 646         reflog_msg = getenv("GIT_REFLOG_ACTION");
 647         if (!reflog_msg)
 648                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 649                         old_desc ? old_desc : "(invalid)", new->name);
 650         else
 651                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 652
 653         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 654                 /* Nothing to do. */
 655         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 656                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 657                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 658                 if (!opts->quiet) {
 659                         if (old->path && advice_detached_head)
 660                                 detach_advice(new->name);
 661                         describe_detached_head(_("HEAD is now at"), new->commit);
 662                 }
 663         } else if (new->path) { /* Switch branches. */
 664                 create_symref("HEAD", new->path, msg.buf);
 665                 if (!opts->quiet) {
 666                         if (old->path && !strcmp(new->path, old->path)) {
 667                                 if (opts->new_branch_force)
 668                                         fprintf(stderr, _("Reset branch '%s'\n"),
 669                                                 new->name);
 670                                 else
 671                                         fprintf(stderr, _("Already on '%s'\n"),
 672                                                 new->name);
 673                         } else if (opts->new_branch) {
 674                                 if (opts->branch_exists)
 675                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 676                                 else
 677                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 678                         } else {
 679                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 680                                         new->name);
 681                         }
 682                 }
 683                 if (old->path && old->name) {
 684                         if (!ref_exists(old->path) && reflog_exists(old->path))
 685                                 delete_reflog(old->path);
 686                 }
 687         }
 688         remove_branch_state();
 689         strbuf_release(&msg);
 690         if (!opts->quiet &&
 691             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 692                 report_tracking(new);
 693 }
 694
 695 static int add_pending_uninteresting_ref(const char *refname,
 696                                          const struct object_id *oid,
 697                                          int flags, void *cb_data)
 698 {
 699         add_pending_sha1(cb_data, refname, oid->hash, UNINTERESTING);
 700         return 0;
 701 }
 702
 703 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 704 {
 705         strbuf_addstr(sb, "  ");
 706         strbuf_addstr(sb,
 707                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 708         strbuf_addch(sb, ' ');
 709         if (!parse_commit(commit))
 710                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 711         strbuf_addch(sb, '\n');
 712 }
 713
 714 #define ORPHAN_CUTOFF 4
 715 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 716 {
 717         struct commit *c, *last = NULL;
 718         struct strbuf sb = STRBUF_INIT;
 719         int lost = 0;
 720         while ((c = get_revision(revs)) != NULL) {
 721                 if (lost < ORPHAN_CUTOFF)
 722                         describe_one_orphan(&sb, c);
 723                 last = c;
 724                 lost++;
 725         }
 726         if (ORPHAN_CUTOFF < lost) {
 727                 int more = lost - ORPHAN_CUTOFF;
 728                 if (more == 1)
 729                         describe_one_orphan(&sb, last);
 730                 else
 731                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 732         }
 733
 734         fprintf(stderr,
 735                 Q_(
 736                 /* The singular version */
 737                 "Warning: you are leaving %d commit behind, "
 738                 "not connected to\n"
 739                 "any of your branches:\n\n"
 740                 "%s\n",
 741                 /* The plural version */
 742                 "Warning: you are leaving %d commits behind, "
 743                 "not connected to\n"
 744                 "any of your branches:\n\n"
 745                 "%s\n",
 746                 /* Give ngettext() the count */
 747                 lost),
 748                 lost,
 749                 sb.buf);
 750         strbuf_release(&sb);
 751
 752         if (advice_detached_head)
 753                 fprintf(stderr,
 754                         Q_(
 755                         /* The singular version */
 756                         "If you want to keep it by creating a new branch, "
 757                         "this may be a good time\nto do so with:\n\n"
 758                         " git branch <new-branch-name> %s\n\n",
 759                         /* The plural version */
 760                         "If you want to keep them by creating a new branch, "
 761                         "this may be a good time\nto do so with:\n\n"
 762                         " git branch <new-branch-name> %s\n\n",
 763                         /* Give ngettext() the count */
 764                         lost),
 765                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 766 }
 767
 768 /*
 769  * We are about to leave commit that was at the tip of a detached
 770  * HEAD.  If it is not reachable from any ref, this is the last chance
 771  * for the user to do so without resorting to reflog.
 772  */
 773 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 774 {
 775         struct rev_info revs;
 776         struct object *object = &old->object;
 777         struct object_array refs;
 778
 779         init_revisions(&revs, NULL);
 780         setup_revisions(0, NULL, &revs, NULL);
 781
 782         object->flags &= ~UNINTERESTING;
 783         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
 784
 785         for_each_ref(add_pending_uninteresting_ref, &revs);
 786         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
 787
 788         refs = revs.pending;
 789         revs.leak_pending = 1;
 790
 791         if (prepare_revision_walk(&revs))
 792                 die(_("internal error in revision walk"));
 793         if (!(old->object.flags & UNINTERESTING))
 794                 suggest_reattach(old, &revs);
 795         else
 796                 describe_detached_head(_("Previous HEAD position was"), old);
 797
 798         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 799         free(refs.objects);
 800 }
 801
 802 static int switch_branches(const struct checkout_opts *opts,
 803                            struct branch_info *new)
 804 {
 805         int ret = 0;
 806         struct branch_info old;
 807         void *path_to_free;
 808         unsigned char rev[20];
 809         int flag, writeout_error = 0;
 810         memset(&old, 0, sizeof(old));
 811         old.path = path_to_free = resolve_refdup("HEAD", 0, rev, &flag);
 812         old.commit = lookup_commit_reference_gently(rev, 1);
 813         if (!(flag & REF_ISSYMREF))
 814                 old.path = NULL;
 815
 816         if (old.path)
 817                 skip_prefix(old.path, "refs/heads/", &old.name);
 818
 819         if (!new->name) {
 820                 new->name = "HEAD";
 821                 new->commit = old.commit;
 822                 if (!new->commit)
 823                         die(_("You are on a branch yet to be born"));
 824                 parse_commit_or_die(new->commit);
 825         }
 826
 827         ret = merge_working_tree(opts, &old, new, &writeout_error);
 828         if (ret) {
 829                 free(path_to_free);
 830                 return ret;
 831         }
 832
 833         if (!opts->quiet && !old.path && old.commit &&
 834             new->commit != old.commit && !opts->new_worktree_mode)
 835                 orphaned_commit_warning(old.commit, new->commit);
 836
 837         update_refs_for_switch(opts, &old, new);
 838
 839         ret = post_checkout_hook(old.commit, new->commit, 1);
 840         free(path_to_free);
 841         return ret || writeout_error;
 842 }
 843
 844 static int git_checkout_config(const char *var, const char *value, void *cb)
 845 {
 846         if (!strcmp(var, "diff.ignoresubmodules")) {
 847                 struct checkout_opts *opts = cb;
 848                 handle_ignore_submodules_arg(&opts->diff_options, value);
 849                 return 0;
 850         }
 851
 852         if (starts_with(var, "submodule."))
 853                 return parse_submodule_config_option(var, value);
 854
 855         return git_xmerge_config(var, value, NULL);
 856 }
 857
 858 struct tracking_name_data {
 859         /* const */ char *src_ref;
 860         char *dst_ref;
 861         unsigned char *dst_sha1;
 862         int unique;
 863 };
 864
 865 static int check_tracking_name(struct remote *remote, void *cb_data)
 866 {
 867         struct tracking_name_data *cb = cb_data;
 868         struct refspec query;
 869         memset(&query, 0, sizeof(struct refspec));
 870         query.src = cb->src_ref;
 871         if (remote_find_tracking(remote, &query) ||
 872             get_sha1(query.dst, cb->dst_sha1)) {
 873                 free(query.dst);
 874                 return 0;
 875         }
 876         if (cb->dst_ref) {
 877                 free(query.dst);
 878                 cb->unique = 0;
 879                 return 0;
 880         }
 881         cb->dst_ref = query.dst;
 882         return 0;
 883 }
 884
 885 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 886 {
 887         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
 888         char src_ref[PATH_MAX];
 889         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
 890         cb_data.src_ref = src_ref;
 891         cb_data.dst_sha1 = sha1;
 892         for_each_remote(check_tracking_name, &cb_data);
 893         if (cb_data.unique)
 894                 return cb_data.dst_ref;
 895         free(cb_data.dst_ref);
 896         return NULL;
 897 }
 898
 899 static void check_linked_checkout(struct branch_info *new, const char *id)
 900 {
 901         struct strbuf sb = STRBUF_INIT;
 902         struct strbuf path = STRBUF_INIT;
 903         struct strbuf gitdir = STRBUF_INIT;
 904         const char *start, *end;
 905
 906         if (id)
 907                 strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);
 908         else
 909                 strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
 910
 911         if (strbuf_read_file(&sb, path.buf, 0) < 0 ||
 912             !skip_prefix(sb.buf, "ref:", &start))
 913                 goto done;
 914         while (isspace(*start))
 915                 start++;
 916         end = start;
 917         while (*end && !isspace(*end))
 918                 end++;
 919         if (strncmp(start, new->path, end - start) || new->path[end - start] != '\0')
 920                 goto done;
 921         if (id) {
 922                 strbuf_reset(&path);
 923                 strbuf_addf(&path, "%s/worktrees/%s/gitdir", get_git_common_dir(), id);
 924                 if (strbuf_read_file(&gitdir, path.buf, 0) <= 0)
 925                         goto done;
 926                 strbuf_rtrim(&gitdir);
 927         } else
 928                 strbuf_addstr(&gitdir, get_git_common_dir());
 929         die(_("'%s' is already checked out at '%s'"), new->name, gitdir.buf);
 930 done:
 931         strbuf_release(&path);
 932         strbuf_release(&sb);
 933         strbuf_release(&gitdir);
 934 }
 935
 936 static void check_linked_checkouts(struct branch_info *new)
 937 {
 938         struct strbuf path = STRBUF_INIT;
 939         DIR *dir;
 940         struct dirent *d;
 941
 942         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 943         if ((dir = opendir(path.buf)) == NULL) {
 944                 strbuf_release(&path);
 945                 return;
 946         }
 947
 948         /*
 949          * $GIT_COMMON_DIR/HEAD is practically outside
 950          * $GIT_DIR so resolve_ref_unsafe() won't work (it
 951          * uses git_path). Parse the ref ourselves.
 952          */
 953         check_linked_checkout(new, NULL);
 954
 955         while ((d = readdir(dir)) != NULL) {
 956                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
 957                         continue;
 958                 check_linked_checkout(new, d->d_name);
 959         }
 960         strbuf_release(&path);
 961         closedir(dir);
 962 }
 963
 964 static int parse_branchname_arg(int argc, const char **argv,
 965                                 int dwim_new_local_branch_ok,
 966                                 struct branch_info *new,
 967                                 struct checkout_opts *opts,
 968                                 unsigned char rev[20])
 969 {
 970         struct tree **source_tree = &opts->source_tree;
 971         const char **new_branch = &opts->new_branch;
 972         int argcount = 0;
 973         unsigned char branch_rev[20];
 974         const char *arg;
 975         int dash_dash_pos;
 976         int has_dash_dash = 0;
 977         int i;
 978
 979         /*
 980          * case 1: git checkout <ref> -- [<paths>]
 981          *
 982          *   <ref> must be a valid tree, everything after the '--' must be
 983          *   a path.
 984          *
 985          * case 2: git checkout -- [<paths>]
 986          *
 987          *   everything after the '--' must be paths.
 988          *
 989          * case 3: git checkout <something> [--]
 990          *
 991          *   (a) If <something> is a commit, that is to
 992          *       switch to the branch or detach HEAD at it.  As a special case,
 993          *       if <something> is A...B (missing A or B means HEAD but you can
 994          *       omit at most one side), and if there is a unique merge base
 995          *       between A and B, A...B names that merge base.
 996          *
 997          *   (b) If <something> is _not_ a commit, either "--" is present
 998          *       or <something> is not a path, no -t or -b was given, and
 999          *       and there is a tracking branch whose name is <something>
1000          *       in one and only one remote, then this is a short-hand to
1001          *       fork local <something> from that remote-tracking branch.
1002          *
1003          *   (c) Otherwise, if "--" is present, treat it like case (1).
1004          *
1005          *   (d) Otherwise :
1006          *       - if it's a reference, treat it like case (1)
1007          *       - else if it's a path, treat it like case (2)
1008          *       - else: fail.
1009          *
1010          * case 4: git checkout <something> <paths>
1011          *
1012          *   The first argument must not be ambiguous.
1013          *   - If it's *only* a reference, treat it like case (1).
1014          *   - If it's only a path, treat it like case (2).
1015          *   - else: fail.
1016          *
1017          */
1018         if (!argc)
1019                 return 0;
1020
1021         arg = argv[0];
1022         dash_dash_pos = -1;
1023         for (i = 0; i < argc; i++) {
1024                 if (!strcmp(argv[i], "--")) {
1025                         dash_dash_pos = i;
1026                         break;
1027                 }
1028         }
1029         if (dash_dash_pos == 0)
1030                 return 1; /* case (2) */
1031         else if (dash_dash_pos == 1)
1032                 has_dash_dash = 1; /* case (3) or (1) */
1033         else if (dash_dash_pos >= 2)
1034                 die(_("only one reference expected, %d given."), dash_dash_pos);
1035
1036         if (!strcmp(arg, "-"))
1037                 arg = "@{-1}";
1038
1039         if (get_sha1_mb(arg, rev)) {
1040                 /*
1041                  * Either case (3) or (4), with <something> not being
1042                  * a commit, or an attempt to use case (1) with an
1043                  * invalid ref.
1044                  *
1045                  * It's likely an error, but we need to find out if
1046                  * we should auto-create the branch, case (3).(b).
1047                  */
1048                 int recover_with_dwim = dwim_new_local_branch_ok;
1049
1050                 if (check_filename(NULL, arg) && !has_dash_dash)
1051                         recover_with_dwim = 0;
1052                 /*
1053                  * Accept "git checkout foo" and "git checkout foo --"
1054                  * as candidates for dwim.
1055                  */
1056                 if (!(argc == 1 && !has_dash_dash) &&
1057                     !(argc == 2 && has_dash_dash))
1058                         recover_with_dwim = 0;
1059
1060                 if (recover_with_dwim) {
1061                         const char *remote = unique_tracking_name(arg, rev);
1062                         if (remote) {
1063                                 *new_branch = arg;
1064                                 arg = remote;
1065                                 /* DWIMmed to create local branch, case (3).(b) */
1066                         } else {
1067                                 recover_with_dwim = 0;
1068                         }
1069                 }
1070
1071                 if (!recover_with_dwim) {
1072                         if (has_dash_dash)
1073                                 die(_("invalid reference: %s"), arg);
1074                         return argcount;
1075                 }
1076         }
1077
1078         /* we can't end up being in (2) anymore, eat the argument */
1079         argcount++;
1080         argv++;
1081         argc--;
1082
1083         new->name = arg;
1084         setup_branch_path(new);
1085
1086         if (!check_refname_format(new->path, 0) &&
1087             !read_ref(new->path, branch_rev))
1088                 hashcpy(rev, branch_rev);
1089         else
1090                 new->path = NULL; /* not an existing branch */
1091
1092         new->commit = lookup_commit_reference_gently(rev, 1);
1093         if (!new->commit) {
1094                 /* not a commit */
1095                 *source_tree = parse_tree_indirect(rev);
1096         } else {
1097                 parse_commit_or_die(new->commit);
1098                 *source_tree = new->commit->tree;
1099         }
1100
1101         if (!*source_tree)                   /* case (1): want a tree */
1102                 die(_("reference is not a tree: %s"), arg);
1103         if (!has_dash_dash) {/* case (3).(d) -> (1) */
1104                 /*
1105                  * Do not complain the most common case
1106                  *      git checkout branch
1107                  * even if there happen to be a file called 'branch';
1108                  * it would be extremely annoying.
1109                  */
1110                 if (argc)
1111                         verify_non_filename(NULL, arg);
1112         } else {
1113                 argcount++;
1114                 argv++;
1115                 argc--;
1116         }
1117
1118         return argcount;
1119 }
1120
1121 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1122 {
1123         int status;
1124         struct strbuf branch_ref = STRBUF_INIT;
1125
1126         if (!opts->new_branch)
1127                 die(_("You are on a branch yet to be born"));
1128         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1129         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1130         strbuf_release(&branch_ref);
1131         if (!opts->quiet)
1132                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1133                         opts->new_branch);
1134         return status;
1135 }
1136
1137 static int checkout_branch(struct checkout_opts *opts,
1138                            struct branch_info *new)
1139 {
1140         if (opts->pathspec.nr)
1141                 die(_("paths cannot be used with switching branches"));
1142
1143         if (opts->patch_mode)
1144                 die(_("'%s' cannot be used with switching branches"),
1145                     "--patch");
1146
1147         if (opts->writeout_stage)
1148                 die(_("'%s' cannot be used with switching branches"),
1149                     "--ours/--theirs");
1150
1151         if (opts->force && opts->merge)
1152                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1153
1154         if (opts->force_detach && opts->new_branch)
1155                 die(_("'%s' cannot be used with '%s'"),
1156                     "--detach", "-b/-B/--orphan");
1157
1158         if (opts->new_orphan_branch) {
1159                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1160                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1161         } else if (opts->force_detach) {
1162                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1163                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1164         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1165                 opts->track = git_branch_track;
1166
1167         if (new->name && !new->commit)
1168                 die(_("Cannot switch branch to a non-commit '%s'"),
1169                     new->name);
1170
1171         if (new->path && !opts->force_detach && !opts->new_branch) {
1172                 unsigned char sha1[20];
1173                 int flag;
1174                 char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
1175                 if (head_ref &&
1176                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
1177                     !opts->ignore_other_worktrees)
1178                         check_linked_checkouts(new);
1179                 free(head_ref);
1180         }
1181
1182         if (!new->commit && opts->new_branch) {
1183                 unsigned char rev[20];
1184                 int flag;
1185
1186                 if (!read_ref_full("HEAD", 0, rev, &flag) &&
1187                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1188                         return switch_unborn_to_new_branch(opts);
1189         }
1190         return switch_branches(opts, new);
1191 }
1192
1193 int cmd_checkout(int argc, const char **argv, const char *prefix)
1194 {
1195         struct checkout_opts opts;
1196         struct branch_info new;
1197         char *conflict_style = NULL;
1198         int dwim_new_local_branch = 1;
1199         struct option options[] = {
1200                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1201                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1202                            N_("create and checkout a new branch")),
1203                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1204                            N_("create/reset and checkout a branch")),
1205                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1206                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1207                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1208                         BRANCH_TRACK_EXPLICIT),
1209                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1210                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1211                             2),
1212                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1213                             3),
1214                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1215                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1216                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1217                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1218                            N_("conflict style (merge or diff3)")),
1219                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1220                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1221                          N_("do not limit pathspecs to sparse entries only")),
1222                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1223                                 N_("second guess 'git checkout <no-such-branch>'")),
1224                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1225                          N_("do not check if another worktree is holding the given ref")),
1226                 OPT_END(),
1227         };
1228
1229         memset(&opts, 0, sizeof(opts));
1230         memset(&new, 0, sizeof(new));
1231         opts.overwrite_ignore = 1;
1232         opts.prefix = prefix;
1233
1234         gitmodules_config();
1235         git_config(git_checkout_config, &opts);
1236
1237         opts.track = BRANCH_TRACK_UNSPECIFIED;
1238
1239         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1240                              PARSE_OPT_KEEP_DASHDASH);
1241
1242         opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
1243
1244         if (conflict_style) {
1245                 opts.merge = 1; /* implied */
1246                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1247         }
1248
1249         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1250                 die(_("-b, -B and --orphan are mutually exclusive"));
1251
1252         /*
1253          * From here on, new_branch will contain the branch to be checked out,
1254          * and new_branch_force and new_orphan_branch will tell us which one of
1255          * -b/-B/--orphan is being used.
1256          */
1257         if (opts.new_branch_force)
1258                 opts.new_branch = opts.new_branch_force;
1259
1260         if (opts.new_orphan_branch)
1261                 opts.new_branch = opts.new_orphan_branch;
1262
1263         /* --track without -b/-B/--orphan should DWIM */
1264         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1265                 const char *argv0 = argv[0];
1266                 if (!argc || !strcmp(argv0, "--"))
1267                         die (_("--track needs a branch name"));
1268                 skip_prefix(argv0, "refs/", &argv0);
1269                 skip_prefix(argv0, "remotes/", &argv0);
1270                 argv0 = strchr(argv0, '/');
1271                 if (!argv0 || !argv0[1])
1272                         die (_("Missing branch name; try -b"));
1273                 opts.new_branch = argv0 + 1;
1274         }
1275
1276         /*
1277          * Extract branch name from command line arguments, so
1278          * all that is left is pathspecs.
1279          *
1280          * Handle
1281          *
1282          *  1) git checkout <tree> -- [<paths>]
1283          *  2) git checkout -- [<paths>]
1284          *  3) git checkout <something> [<paths>]
1285          *
1286          * including "last branch" syntax and DWIM-ery for names of
1287          * remote branches, erroring out for invalid or ambiguous cases.
1288          */
1289         if (argc) {
1290                 unsigned char rev[20];
1291                 int dwim_ok =
1292                         !opts.patch_mode &&
1293                         dwim_new_local_branch &&
1294                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1295                         !opts.new_branch;
1296                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1297                                              &new, &opts, rev);
1298                 argv += n;
1299                 argc -= n;
1300         }
1301
1302         if (argc) {
1303                 parse_pathspec(&opts.pathspec, 0,
1304                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1305                                prefix, argv);
1306
1307                 if (!opts.pathspec.nr)
1308                         die(_("invalid path specification"));
1309
1310                 /*
1311                  * Try to give more helpful suggestion.
1312                  * new_branch && argc > 1 will be caught later.
1313                  */
1314                 if (opts.new_branch && argc == 1)
1315                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1316                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1317                             opts.new_branch, argv[0]);
1318
1319                 if (opts.force_detach)
1320                         die(_("git checkout: --detach does not take a path argument '%s'"),
1321                             argv[0]);
1322
1323                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1324                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1325                               "checking out of the index."));
1326         }
1327
1328         if (opts.new_branch) {
1329                 struct strbuf buf = STRBUF_INIT;
1330
1331                 opts.branch_exists =
1332                         validate_new_branchname(opts.new_branch, &buf,
1333                                                 !!opts.new_branch_force,
1334                                                 !!opts.new_branch_force);
1335
1336                 strbuf_release(&buf);
1337         }
1338
1339         if (opts.patch_mode || opts.pathspec.nr)
1340                 return checkout_paths(&opts, new.name);
1341         else
1342                 return checkout_branch(&opts, &new);
1343 }