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 #include "argv-array.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
  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         const char *new_worktree;
  53         const char **saved_argv;
  54         int new_worktree_mode;
  55 };
  56
  57 static int post_checkout_hook(struct commit *old, struct commit *new,
  58                               int changed)
  59 {
  60         return run_hook_le(NULL, "post-checkout",
  61                            sha1_to_hex(old ? old->object.sha1 : null_sha1),
  62                            sha1_to_hex(new ? new->object.sha1 : null_sha1),
  63                            changed ? "1" : "0", NULL);
  64         /* "new" can be NULL when checking out from the index before
  65            a commit exists. */
  66
  67 }
  68
  69 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  70                 const char *pathname, unsigned mode, int stage, void *context)
  71 {
  72         int len;
  73         struct cache_entry *ce;
  74
  75         if (S_ISDIR(mode))
  76                 return READ_TREE_RECURSIVE;
  77
  78         len = baselen + strlen(pathname);
  79         ce = xcalloc(1, cache_entry_size(len));
  80         hashcpy(ce->sha1, sha1);
  81         memcpy(ce->name, base, baselen);
  82         memcpy(ce->name + baselen, pathname, len - baselen);
  83         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  84         ce->ce_namelen = len;
  85         ce->ce_mode = create_ce_mode(mode);
  86         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  87         return 0;
  88 }
  89
  90 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
  91 {
  92         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
  93
  94         /* update the index with the given tree's info
  95          * for all args, expanding wildcards, and exit
  96          * with any non-zero return code.
  97          */
  98         return 0;
  99 }
 100
 101 static int skip_same_name(const struct cache_entry *ce, int pos)
 102 {
 103         while (++pos < active_nr &&
 104                !strcmp(active_cache[pos]->name, ce->name))
 105                 ; /* skip */
 106         return pos;
 107 }
 108
 109 static int check_stage(int stage, const struct cache_entry *ce, int pos)
 110 {
 111         while (pos < active_nr &&
 112                !strcmp(active_cache[pos]->name, ce->name)) {
 113                 if (ce_stage(active_cache[pos]) == stage)
 114                         return 0;
 115                 pos++;
 116         }
 117         if (stage == 2)
 118                 return error(_("path '%s' does not have our version"), ce->name);
 119         else
 120                 return error(_("path '%s' does not have their version"), ce->name);
 121 }
 122
 123 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 124 {
 125         unsigned seen = 0;
 126         const char *name = ce->name;
 127
 128         while (pos < active_nr) {
 129                 ce = active_cache[pos];
 130                 if (strcmp(name, ce->name))
 131                         break;
 132                 seen |= (1 << ce_stage(ce));
 133                 pos++;
 134         }
 135         if ((stages & seen) != stages)
 136                 return error(_("path '%s' does not have all necessary versions"),
 137                              name);
 138         return 0;
 139 }
 140
 141 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 142                           struct checkout *state)
 143 {
 144         while (pos < active_nr &&
 145                !strcmp(active_cache[pos]->name, ce->name)) {
 146                 if (ce_stage(active_cache[pos]) == stage)
 147                         return checkout_entry(active_cache[pos], state, NULL);
 148                 pos++;
 149         }
 150         if (stage == 2)
 151                 return error(_("path '%s' does not have our version"), ce->name);
 152         else
 153                 return error(_("path '%s' does not have their version"), ce->name);
 154 }
 155
 156 static int checkout_merged(int pos, struct checkout *state)
 157 {
 158         struct cache_entry *ce = active_cache[pos];
 159         const char *path = ce->name;
 160         mmfile_t ancestor, ours, theirs;
 161         int status;
 162         unsigned char sha1[20];
 163         mmbuffer_t result_buf;
 164         unsigned char threeway[3][20];
 165         unsigned mode = 0;
 166
 167         memset(threeway, 0, sizeof(threeway));
 168         while (pos < active_nr) {
 169                 int stage;
 170                 stage = ce_stage(ce);
 171                 if (!stage || strcmp(path, ce->name))
 172                         break;
 173                 hashcpy(threeway[stage - 1], ce->sha1);
 174                 if (stage == 2)
 175                         mode = create_ce_mode(ce->ce_mode);
 176                 pos++;
 177                 ce = active_cache[pos];
 178         }
 179         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
 180                 return error(_("path '%s' does not have necessary versions"), path);
 181
 182         read_mmblob(&ancestor, threeway[0]);
 183         read_mmblob(&ours, threeway[1]);
 184         read_mmblob(&theirs, threeway[2]);
 185
 186         /*
 187          * NEEDSWORK: re-create conflicts from merges with
 188          * merge.renormalize set, too
 189          */
 190         status = ll_merge(&result_buf, path, &ancestor, "base",
 191                           &ours, "ours", &theirs, "theirs", NULL);
 192         free(ancestor.ptr);
 193         free(ours.ptr);
 194         free(theirs.ptr);
 195         if (status < 0 || !result_buf.ptr) {
 196                 free(result_buf.ptr);
 197                 return error(_("path '%s': cannot merge"), path);
 198         }
 199
 200         /*
 201          * NEEDSWORK:
 202          * There is absolutely no reason to write this as a blob object
 203          * and create a phony cache entry just to leak.  This hack is
 204          * primarily to get to the write_entry() machinery that massages
 205          * the contents to work-tree format and writes out which only
 206          * allows it for a cache entry.  The code in write_entry() needs
 207          * to be refactored to allow us to feed a <buffer, size, mode>
 208          * instead of a cache entry.  Such a refactoring would help
 209          * merge_recursive as well (it also writes the merge result to the
 210          * object database even when it may contain conflicts).
 211          */
 212         if (write_sha1_file(result_buf.ptr, result_buf.size,
 213                             blob_type, sha1))
 214                 die(_("Unable to add merge result for '%s'"), path);
 215         ce = make_cache_entry(mode, sha1, path, 2, 0);
 216         if (!ce)
 217                 die(_("make_cache_entry failed for path '%s'"), path);
 218         status = checkout_entry(ce, state, NULL);
 219         return status;
 220 }
 221
 222 static int checkout_paths(const struct checkout_opts *opts,
 223                           const char *revision)
 224 {
 225         int pos;
 226         struct checkout state;
 227         static char *ps_matched;
 228         unsigned char rev[20];
 229         int flag;
 230         struct commit *head;
 231         int errs = 0;
 232         struct lock_file *lock_file;
 233
 234         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 235                 die(_("'%s' cannot be used with updating paths"), "--track");
 236
 237         if (opts->new_branch_log)
 238                 die(_("'%s' cannot be used with updating paths"), "-l");
 239
 240         if (opts->force && opts->patch_mode)
 241                 die(_("'%s' cannot be used with updating paths"), "-f");
 242
 243         if (opts->force_detach)
 244                 die(_("'%s' cannot be used with updating paths"), "--detach");
 245
 246         if (opts->merge && opts->patch_mode)
 247                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 248
 249         if (opts->force && opts->merge)
 250                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 251
 252         if (opts->new_branch)
 253                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 254                     opts->new_branch);
 255
 256         if (opts->new_worktree)
 257                 die(_("'%s' cannot be used with updating paths"), "--to");
 258
 259         if (opts->patch_mode)
 260                 return run_add_interactive(revision, "--patch=checkout",
 261                                            &opts->pathspec);
 262
 263         lock_file = xcalloc(1, sizeof(struct lock_file));
 264
 265         hold_locked_index(lock_file, 1);
 266         if (read_cache_preload(&opts->pathspec) < 0)
 267                 return error(_("corrupt index file"));
 268
 269         if (opts->source_tree)
 270                 read_tree_some(opts->source_tree, &opts->pathspec);
 271
 272         ps_matched = xcalloc(1, opts->pathspec.nr);
 273
 274         /*
 275          * Make sure all pathspecs participated in locating the paths
 276          * to be checked out.
 277          */
 278         for (pos = 0; pos < active_nr; pos++) {
 279                 struct cache_entry *ce = active_cache[pos];
 280                 ce->ce_flags &= ~CE_MATCHED;
 281                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 282                         continue;
 283                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 284                         /*
 285                          * "git checkout tree-ish -- path", but this entry
 286                          * is in the original index; it will not be checked
 287                          * out to the working tree and it does not matter
 288                          * if pathspec matched this entry.  We will not do
 289                          * anything to this entry at all.
 290                          */
 291                         continue;
 292                 /*
 293                  * Either this entry came from the tree-ish we are
 294                  * checking the paths out of, or we are checking out
 295                  * of the index.
 296                  *
 297                  * If it comes from the tree-ish, we already know it
 298                  * matches the pathspec and could just stamp
 299                  * CE_MATCHED to it from update_some(). But we still
 300                  * need ps_matched and read_tree_recursive (and
 301                  * eventually tree_entry_interesting) cannot fill
 302                  * ps_matched yet. Once it can, we can avoid calling
 303                  * match_pathspec() for _all_ entries when
 304                  * opts->source_tree != NULL.
 305                  */
 306                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
 307                         ce->ce_flags |= CE_MATCHED;
 308         }
 309
 310         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 311                 free(ps_matched);
 312                 return 1;
 313         }
 314         free(ps_matched);
 315
 316         /* "checkout -m path" to recreate conflicted state */
 317         if (opts->merge)
 318                 unmerge_marked_index(&the_index);
 319
 320         /* Any unmerged paths? */
 321         for (pos = 0; pos < active_nr; pos++) {
 322                 const struct cache_entry *ce = active_cache[pos];
 323                 if (ce->ce_flags & CE_MATCHED) {
 324                         if (!ce_stage(ce))
 325                                 continue;
 326                         if (opts->force) {
 327                                 warning(_("path '%s' is unmerged"), ce->name);
 328                         } else if (opts->writeout_stage) {
 329                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 330                         } else if (opts->merge) {
 331                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 332                         } else {
 333                                 errs = 1;
 334                                 error(_("path '%s' is unmerged"), ce->name);
 335                         }
 336                         pos = skip_same_name(ce, pos) - 1;
 337                 }
 338         }
 339         if (errs)
 340                 return 1;
 341
 342         /* Now we are committed to check them out */
 343         memset(&state, 0, sizeof(state));
 344         state.force = 1;
 345         state.refresh_cache = 1;
 346         state.istate = &the_index;
 347         for (pos = 0; pos < active_nr; pos++) {
 348                 struct cache_entry *ce = active_cache[pos];
 349                 if (ce->ce_flags & CE_MATCHED) {
 350                         if (!ce_stage(ce)) {
 351                                 errs |= checkout_entry(ce, &state, NULL);
 352                                 continue;
 353                         }
 354                         if (opts->writeout_stage)
 355                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
 356                         else if (opts->merge)
 357                                 errs |= checkout_merged(pos, &state);
 358                         pos = skip_same_name(ce, pos) - 1;
 359                 }
 360         }
 361
 362         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 363                 die(_("unable to write new index file"));
 364
 365         read_ref_full("HEAD", 0, rev, &flag);
 366         head = lookup_commit_reference_gently(rev, 1);
 367
 368         errs |= post_checkout_hook(head, head, 0);
 369         return errs;
 370 }
 371
 372 static void show_local_changes(struct object *head,
 373                                const struct diff_options *opts)
 374 {
 375         struct rev_info rev;
 376         /* I think we want full paths, even if we're in a subdirectory. */
 377         init_revisions(&rev, NULL);
 378         rev.diffopt.flags = opts->flags;
 379         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 380         diff_setup_done(&rev.diffopt);
 381         add_pending_object(&rev, head, NULL);
 382         run_diff_index(&rev, 0);
 383 }
 384
 385 static void describe_detached_head(const char *msg, struct commit *commit)
 386 {
 387         struct strbuf sb = STRBUF_INIT;
 388         if (!parse_commit(commit))
 389                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 390         fprintf(stderr, "%s %s... %s\n", msg,
 391                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 392         strbuf_release(&sb);
 393 }
 394
 395 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 396                       int worktree, int *writeout_error)
 397 {
 398         struct unpack_trees_options opts;
 399         struct tree_desc tree_desc;
 400
 401         memset(&opts, 0, sizeof(opts));
 402         opts.head_idx = -1;
 403         opts.update = worktree;
 404         opts.skip_unmerged = !worktree;
 405         opts.reset = 1;
 406         opts.merge = 1;
 407         opts.fn = oneway_merge;
 408         opts.verbose_update = !o->quiet && isatty(2);
 409         opts.src_index = &the_index;
 410         opts.dst_index = &the_index;
 411         parse_tree(tree);
 412         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 413         switch (unpack_trees(1, &tree_desc, &opts)) {
 414         case -2:
 415                 *writeout_error = 1;
 416                 /*
 417                  * We return 0 nevertheless, as the index is all right
 418                  * and more importantly we have made best efforts to
 419                  * update paths in the work tree, and we cannot revert
 420                  * them.
 421                  */
 422         case 0:
 423                 return 0;
 424         default:
 425                 return 128;
 426         }
 427 }
 428
 429 struct branch_info {
 430         const char *name; /* The short name used */
 431         const char *path; /* The full name of a real branch */
 432         struct commit *commit; /* The named commit */
 433 };
 434
 435 static void setup_branch_path(struct branch_info *branch)
 436 {
 437         struct strbuf buf = STRBUF_INIT;
 438
 439         strbuf_branchname(&buf, branch->name);
 440         if (strcmp(buf.buf, branch->name))
 441                 branch->name = xstrdup(buf.buf);
 442         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 443         branch->path = strbuf_detach(&buf, NULL);
 444 }
 445
 446 static int merge_working_tree(const struct checkout_opts *opts,
 447                               struct branch_info *old,
 448                               struct branch_info *new,
 449                               int *writeout_error)
 450 {
 451         int ret;
 452         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 453
 454         hold_locked_index(lock_file, 1);
 455         if (read_cache_preload(NULL) < 0)
 456                 return error(_("corrupt index file"));
 457
 458         resolve_undo_clear();
 459         if (opts->force) {
 460                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
 461                 if (ret)
 462                         return ret;
 463         } else {
 464                 struct tree_desc trees[2];
 465                 struct tree *tree;
 466                 struct unpack_trees_options topts;
 467
 468                 memset(&topts, 0, sizeof(topts));
 469                 topts.head_idx = -1;
 470                 topts.src_index = &the_index;
 471                 topts.dst_index = &the_index;
 472
 473                 setup_unpack_trees_porcelain(&topts, "checkout");
 474
 475                 refresh_cache(REFRESH_QUIET);
 476
 477                 if (unmerged_cache()) {
 478                         error(_("you need to resolve your current index first"));
 479                         return 1;
 480                 }
 481
 482                 /* 2-way merge to the new branch */
 483                 topts.initial_checkout = is_cache_unborn();
 484                 topts.update = 1;
 485                 topts.merge = 1;
 486                 topts.gently = opts->merge && old->commit;
 487                 topts.verbose_update = !opts->quiet && isatty(2);
 488                 topts.fn = twoway_merge;
 489                 if (opts->overwrite_ignore) {
 490                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 491                         topts.dir->flags |= DIR_SHOW_IGNORED;
 492                         setup_standard_excludes(topts.dir);
 493                 }
 494                 tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
 495                                            old->commit->object.sha1 :
 496                                            EMPTY_TREE_SHA1_BIN);
 497                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 498                 tree = parse_tree_indirect(new->commit->object.sha1);
 499                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 500
 501                 ret = unpack_trees(2, trees, &topts);
 502                 if (ret == -1) {
 503                         /*
 504                          * Unpack couldn't do a trivial merge; either
 505                          * give up or do a real merge, depending on
 506                          * whether the merge flag was used.
 507                          */
 508                         struct tree *result;
 509                         struct tree *work;
 510                         struct merge_options o;
 511                         if (!opts->merge)
 512                                 return 1;
 513
 514                         /*
 515                          * Without old->commit, the below is the same as
 516                          * the two-tree unpack we already tried and failed.
 517                          */
 518                         if (!old->commit)
 519                                 return 1;
 520
 521                         /* Do more real merge */
 522
 523                         /*
 524                          * We update the index fully, then write the
 525                          * tree from the index, then merge the new
 526                          * branch with the current tree, with the old
 527                          * branch as the base. Then we reset the index
 528                          * (but not the working tree) to the new
 529                          * branch, leaving the working tree as the
 530                          * merged version, but skipping unmerged
 531                          * entries in the index.
 532                          */
 533
 534                         add_files_to_cache(NULL, NULL, 0);
 535                         /*
 536                          * NEEDSWORK: carrying over local changes
 537                          * when branches have different end-of-line
 538                          * normalization (or clean+smudge rules) is
 539                          * a pain; plumb in an option to set
 540                          * o.renormalize?
 541                          */
 542                         init_merge_options(&o);
 543                         o.verbosity = 0;
 544                         work = write_tree_from_memory(&o);
 545
 546                         ret = reset_tree(new->commit->tree, opts, 1,
 547                                          writeout_error);
 548                         if (ret)
 549                                 return ret;
 550                         o.ancestor = old->name;
 551                         o.branch1 = new->name;
 552                         o.branch2 = "local";
 553                         merge_trees(&o, new->commit->tree, work,
 554                                 old->commit->tree, &result);
 555                         ret = reset_tree(new->commit->tree, opts, 0,
 556                                          writeout_error);
 557                         if (ret)
 558                                 return ret;
 559                 }
 560         }
 561
 562         if (!active_cache_tree)
 563                 active_cache_tree = cache_tree();
 564
 565         if (!cache_tree_fully_valid(active_cache_tree))
 566                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 567
 568         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 569                 die(_("unable to write new index file"));
 570
 571         if (!opts->force && !opts->quiet)
 572                 show_local_changes(&new->commit->object, &opts->diff_options);
 573
 574         return 0;
 575 }
 576
 577 static void report_tracking(struct branch_info *new)
 578 {
 579         struct strbuf sb = STRBUF_INIT;
 580         struct branch *branch = branch_get(new->name);
 581
 582         if (!format_tracking_info(branch, &sb))
 583                 return;
 584         fputs(sb.buf, stdout);
 585         strbuf_release(&sb);
 586 }
 587
 588 static void update_refs_for_switch(const struct checkout_opts *opts,
 589                                    struct branch_info *old,
 590                                    struct branch_info *new)
 591 {
 592         struct strbuf msg = STRBUF_INIT;
 593         const char *old_desc, *reflog_msg;
 594         if (opts->new_branch) {
 595                 if (opts->new_orphan_branch) {
 596                         if (opts->new_branch_log && !log_all_ref_updates) {
 597                                 int temp;
 598                                 struct strbuf log_file = STRBUF_INIT;
 599                                 int ret;
 600                                 const char *ref_name;
 601
 602                                 ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 603                                 temp = log_all_ref_updates;
 604                                 log_all_ref_updates = 1;
 605                                 ret = log_ref_setup(ref_name, &log_file);
 606                                 log_all_ref_updates = temp;
 607                                 strbuf_release(&log_file);
 608                                 if (ret) {
 609                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 610                                             opts->new_orphan_branch);
 611                                         return;
 612                                 }
 613                         }
 614                 }
 615                 else
 616                         create_branch(old->name, opts->new_branch, new->name,
 617                                       opts->new_branch_force ? 1 : 0,
 618                                       opts->new_branch_log,
 619                                       opts->new_branch_force ? 1 : 0,
 620                                       opts->quiet,
 621                                       opts->track);
 622                 new->name = opts->new_branch;
 623                 setup_branch_path(new);
 624         }
 625
 626         old_desc = old->name;
 627         if (!old_desc && old->commit)
 628                 old_desc = sha1_to_hex(old->commit->object.sha1);
 629
 630         reflog_msg = getenv("GIT_REFLOG_ACTION");
 631         if (!reflog_msg)
 632                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 633                         old_desc ? old_desc : "(invalid)", new->name);
 634         else
 635                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 636
 637         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 638                 /* Nothing to do. */
 639         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 640                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 641                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 642                 if (!opts->quiet) {
 643                         if (old->path && advice_detached_head)
 644                                 detach_advice(new->name);
 645                         describe_detached_head(_("HEAD is now at"), new->commit);
 646                 }
 647         } else if (new->path) { /* Switch branches. */
 648                 create_symref("HEAD", new->path, msg.buf);
 649                 if (!opts->quiet) {
 650                         if (old->path && !strcmp(new->path, old->path)) {
 651                                 if (opts->new_branch_force)
 652                                         fprintf(stderr, _("Reset branch '%s'\n"),
 653                                                 new->name);
 654                                 else
 655                                         fprintf(stderr, _("Already on '%s'\n"),
 656                                                 new->name);
 657                         } else if (opts->new_branch) {
 658                                 if (opts->branch_exists)
 659                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 660                                 else
 661                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 662                         } else {
 663                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 664                                         new->name);
 665                         }
 666                 }
 667                 if (old->path && old->name) {
 668                         if (!ref_exists(old->path) && reflog_exists(old->path))
 669                                 delete_reflog(old->path);
 670                 }
 671         }
 672         remove_branch_state();
 673         strbuf_release(&msg);
 674         if (!opts->quiet &&
 675             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 676                 report_tracking(new);
 677 }
 678
 679 static int add_pending_uninteresting_ref(const char *refname,
 680                                          const unsigned char *sha1,
 681                                          int flags, void *cb_data)
 682 {
 683         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
 684         return 0;
 685 }
 686
 687 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 688 {
 689         strbuf_addstr(sb, "  ");
 690         strbuf_addstr(sb,
 691                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 692         strbuf_addch(sb, ' ');
 693         if (!parse_commit(commit))
 694                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 695         strbuf_addch(sb, '\n');
 696 }
 697
 698 #define ORPHAN_CUTOFF 4
 699 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 700 {
 701         struct commit *c, *last = NULL;
 702         struct strbuf sb = STRBUF_INIT;
 703         int lost = 0;
 704         while ((c = get_revision(revs)) != NULL) {
 705                 if (lost < ORPHAN_CUTOFF)
 706                         describe_one_orphan(&sb, c);
 707                 last = c;
 708                 lost++;
 709         }
 710         if (ORPHAN_CUTOFF < lost) {
 711                 int more = lost - ORPHAN_CUTOFF;
 712                 if (more == 1)
 713                         describe_one_orphan(&sb, last);
 714                 else
 715                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 716         }
 717
 718         fprintf(stderr,
 719                 Q_(
 720                 /* The singular version */
 721                 "Warning: you are leaving %d commit behind, "
 722                 "not connected to\n"
 723                 "any of your branches:\n\n"
 724                 "%s\n",
 725                 /* The plural version */
 726                 "Warning: you are leaving %d commits behind, "
 727                 "not connected to\n"
 728                 "any of your branches:\n\n"
 729                 "%s\n",
 730                 /* Give ngettext() the count */
 731                 lost),
 732                 lost,
 733                 sb.buf);
 734         strbuf_release(&sb);
 735
 736         if (advice_detached_head)
 737                 fprintf(stderr,
 738                         _(
 739                         "If you want to keep them by creating a new branch, "
 740                         "this may be a good time\nto do so with:\n\n"
 741                         " git branch new_branch_name %s\n\n"),
 742                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 743 }
 744
 745 /*
 746  * We are about to leave commit that was at the tip of a detached
 747  * HEAD.  If it is not reachable from any ref, this is the last chance
 748  * for the user to do so without resorting to reflog.
 749  */
 750 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 751 {
 752         struct rev_info revs;
 753         struct object *object = &old->object;
 754         struct object_array refs;
 755
 756         init_revisions(&revs, NULL);
 757         setup_revisions(0, NULL, &revs, NULL);
 758
 759         object->flags &= ~UNINTERESTING;
 760         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
 761
 762         for_each_ref(add_pending_uninteresting_ref, &revs);
 763         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
 764
 765         refs = revs.pending;
 766         revs.leak_pending = 1;
 767
 768         if (prepare_revision_walk(&revs))
 769                 die(_("internal error in revision walk"));
 770         if (!(old->object.flags & UNINTERESTING))
 771                 suggest_reattach(old, &revs);
 772         else
 773                 describe_detached_head(_("Previous HEAD position was"), old);
 774
 775         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 776         free(refs.objects);
 777 }
 778
 779 static int switch_branches(const struct checkout_opts *opts,
 780                            struct branch_info *new)
 781 {
 782         int ret = 0;
 783         struct branch_info old;
 784         void *path_to_free;
 785         unsigned char rev[20];
 786         int flag, writeout_error = 0;
 787         memset(&old, 0, sizeof(old));
 788         old.path = path_to_free = resolve_refdup("HEAD", 0, rev, &flag);
 789         old.commit = lookup_commit_reference_gently(rev, 1);
 790         if (!(flag & REF_ISSYMREF))
 791                 old.path = NULL;
 792
 793         if (old.path)
 794                 skip_prefix(old.path, "refs/heads/", &old.name);
 795
 796         if (!new->name) {
 797                 new->name = "HEAD";
 798                 new->commit = old.commit;
 799                 if (!new->commit)
 800                         die(_("You are on a branch yet to be born"));
 801                 parse_commit_or_die(new->commit);
 802         }
 803
 804         ret = merge_working_tree(opts, &old, new, &writeout_error);
 805         if (ret) {
 806                 free(path_to_free);
 807                 return ret;
 808         }
 809
 810         if (!opts->quiet && !old.path && old.commit &&
 811             new->commit != old.commit && !opts->new_worktree_mode)
 812                 orphaned_commit_warning(old.commit, new->commit);
 813
 814         update_refs_for_switch(opts, &old, new);
 815
 816         ret = post_checkout_hook(old.commit, new->commit, 1);
 817         free(path_to_free);
 818         return ret || writeout_error;
 819 }
 820
 821 static int prepare_linked_checkout(const struct checkout_opts *opts,
 822                                    struct branch_info *new)
 823 {
 824         struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
 825         struct strbuf sb = STRBUF_INIT;
 826         const char *path = opts->new_worktree, *name;
 827         struct stat st;
 828         struct child_process cp;
 829         int counter = 0, len, ret;
 830
 831         if (!new->commit)
 832                 die(_("no branch specified"));
 833         if (file_exists(path))
 834                 die(_("'%s' already exists"), path);
 835
 836         len = strlen(path);
 837         while (len && is_dir_sep(path[len - 1]))
 838                 len--;
 839
 840         for (name = path + len - 1; name > path; name--)
 841                 if (is_dir_sep(*name)) {
 842                         name++;
 843                         break;
 844                 }
 845         strbuf_addstr(&sb_repo,
 846                       git_path("worktrees/%.*s", (int)(path + len - name), name));
 847         len = sb_repo.len;
 848         if (safe_create_leading_directories_const(sb_repo.buf))
 849                 die_errno(_("could not create leading directories of '%s'"),
 850                           sb_repo.buf);
 851         while (!stat(sb_repo.buf, &st)) {
 852                 counter++;
 853                 strbuf_setlen(&sb_repo, len);
 854                 strbuf_addf(&sb_repo, "%d", counter);
 855         }
 856         name = strrchr(sb_repo.buf, '/') + 1;
 857         if (mkdir(sb_repo.buf, 0777))
 858                 die_errno(_("could not create directory of '%s'"), sb_repo.buf);
 859
 860         /*
 861          * lock the incomplete repo so prune won't delete it, unlock
 862          * after the preparation is over.
 863          */
 864         strbuf_addf(&sb, "%s/locked", sb_repo.buf);
 865         write_file(sb.buf, 1, "initializing\n");
 866
 867         strbuf_addf(&sb_git, "%s/.git", path);
 868         if (safe_create_leading_directories_const(sb_git.buf))
 869                 die_errno(_("could not create leading directories of '%s'"),
 870                           sb_git.buf);
 871
 872         strbuf_reset(&sb);
 873         strbuf_addf(&sb, "%s/gitdir", sb_repo.buf);
 874         write_file(sb.buf, 1, "%s\n", real_path(sb_git.buf));
 875         write_file(sb_git.buf, 1, "gitdir: %s/worktrees/%s\n",
 876                    real_path(get_git_common_dir()), name);
 877         /*
 878          * This is to keep resolve_ref() happy. We need a valid HEAD
 879          * or is_git_directory() will reject the directory. Any valid
 880          * value would do because this value will be ignored and
 881          * replaced at the next (real) checkout.
 882          */
 883         strbuf_reset(&sb);
 884         strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
 885         write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
 886         strbuf_reset(&sb);
 887         strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 888         write_file(sb.buf, 1, "../..\n");
 889
 890         if (!opts->quiet)
 891                 fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
 892
 893         setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
 894         setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);
 895         setenv(GIT_WORK_TREE_ENVIRONMENT, path, 1);
 896         memset(&cp, 0, sizeof(cp));
 897         cp.git_cmd = 1;
 898         cp.argv = opts->saved_argv;
 899         ret = run_command(&cp);
 900         strbuf_reset(&sb);
 901         strbuf_addf(&sb, "%s/locked", sb_repo.buf);
 902         unlink_or_warn(sb.buf);
 903         return ret;
 904 }
 905
 906 static int git_checkout_config(const char *var, const char *value, void *cb)
 907 {
 908         if (!strcmp(var, "diff.ignoresubmodules")) {
 909                 struct checkout_opts *opts = cb;
 910                 handle_ignore_submodules_arg(&opts->diff_options, value);
 911                 return 0;
 912         }
 913
 914         if (starts_with(var, "submodule."))
 915                 return parse_submodule_config_option(var, value);
 916
 917         return git_xmerge_config(var, value, NULL);
 918 }
 919
 920 struct tracking_name_data {
 921         /* const */ char *src_ref;
 922         char *dst_ref;
 923         unsigned char *dst_sha1;
 924         int unique;
 925 };
 926
 927 static int check_tracking_name(struct remote *remote, void *cb_data)
 928 {
 929         struct tracking_name_data *cb = cb_data;
 930         struct refspec query;
 931         memset(&query, 0, sizeof(struct refspec));
 932         query.src = cb->src_ref;
 933         if (remote_find_tracking(remote, &query) ||
 934             get_sha1(query.dst, cb->dst_sha1)) {
 935                 free(query.dst);
 936                 return 0;
 937         }
 938         if (cb->dst_ref) {
 939                 free(query.dst);
 940                 cb->unique = 0;
 941                 return 0;
 942         }
 943         cb->dst_ref = query.dst;
 944         return 0;
 945 }
 946
 947 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 948 {
 949         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
 950         char src_ref[PATH_MAX];
 951         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
 952         cb_data.src_ref = src_ref;
 953         cb_data.dst_sha1 = sha1;
 954         for_each_remote(check_tracking_name, &cb_data);
 955         if (cb_data.unique)
 956                 return cb_data.dst_ref;
 957         free(cb_data.dst_ref);
 958         return NULL;
 959 }
 960
 961 static int parse_branchname_arg(int argc, const char **argv,
 962                                 int dwim_new_local_branch_ok,
 963                                 struct branch_info *new,
 964                                 struct tree **source_tree,
 965                                 unsigned char rev[20],
 966                                 const char **new_branch)
 967 {
 968         int argcount = 0;
 969         unsigned char branch_rev[20];
 970         const char *arg;
 971         int dash_dash_pos;
 972         int has_dash_dash = 0;
 973         int i;
 974
 975         /*
 976          * case 1: git checkout <ref> -- [<paths>]
 977          *
 978          *   <ref> must be a valid tree, everything after the '--' must be
 979          *   a path.
 980          *
 981          * case 2: git checkout -- [<paths>]
 982          *
 983          *   everything after the '--' must be paths.
 984          *
 985          * case 3: git checkout <something> [--]
 986          *
 987          *   (a) If <something> is a commit, that is to
 988          *       switch to the branch or detach HEAD at it.  As a special case,
 989          *       if <something> is A...B (missing A or B means HEAD but you can
 990          *       omit at most one side), and if there is a unique merge base
 991          *       between A and B, A...B names that merge base.
 992          *
 993          *   (b) If <something> is _not_ a commit, either "--" is present
 994          *       or <something> is not a path, no -t or -b was given, and
 995          *       and there is a tracking branch whose name is <something>
 996          *       in one and only one remote, then this is a short-hand to
 997          *       fork local <something> from that remote-tracking branch.
 998          *
 999          *   (c) Otherwise, if "--" is present, treat it like case (1).
1000          *
1001          *   (d) Otherwise :
1002          *       - if it's a reference, treat it like case (1)
1003          *       - else if it's a path, treat it like case (2)
1004          *       - else: fail.
1005          *
1006          * case 4: git checkout <something> <paths>
1007          *
1008          *   The first argument must not be ambiguous.
1009          *   - If it's *only* a reference, treat it like case (1).
1010          *   - If it's only a path, treat it like case (2).
1011          *   - else: fail.
1012          *
1013          */
1014         if (!argc)
1015                 return 0;
1016
1017         arg = argv[0];
1018         dash_dash_pos = -1;
1019         for (i = 0; i < argc; i++) {
1020                 if (!strcmp(argv[i], "--")) {
1021                         dash_dash_pos = i;
1022                         break;
1023                 }
1024         }
1025         if (dash_dash_pos == 0)
1026                 return 1; /* case (2) */
1027         else if (dash_dash_pos == 1)
1028                 has_dash_dash = 1; /* case (3) or (1) */
1029         else if (dash_dash_pos >= 2)
1030                 die(_("only one reference expected, %d given."), dash_dash_pos);
1031
1032         if (!strcmp(arg, "-"))
1033                 arg = "@{-1}";
1034
1035         if (get_sha1_mb(arg, rev)) {
1036                 /*
1037                  * Either case (3) or (4), with <something> not being
1038                  * a commit, or an attempt to use case (1) with an
1039                  * invalid ref.
1040                  *
1041                  * It's likely an error, but we need to find out if
1042                  * we should auto-create the branch, case (3).(b).
1043                  */
1044                 int recover_with_dwim = dwim_new_local_branch_ok;
1045
1046                 if (check_filename(NULL, arg) && !has_dash_dash)
1047                         recover_with_dwim = 0;
1048                 /*
1049                  * Accept "git checkout foo" and "git checkout foo --"
1050                  * as candidates for dwim.
1051                  */
1052                 if (!(argc == 1 && !has_dash_dash) &&
1053                     !(argc == 2 && has_dash_dash))
1054                         recover_with_dwim = 0;
1055
1056                 if (recover_with_dwim) {
1057                         const char *remote = unique_tracking_name(arg, rev);
1058                         if (remote) {
1059                                 *new_branch = arg;
1060                                 arg = remote;
1061                                 /* DWIMmed to create local branch, case (3).(b) */
1062                         } else {
1063                                 recover_with_dwim = 0;
1064                         }
1065                 }
1066
1067                 if (!recover_with_dwim) {
1068                         if (has_dash_dash)
1069                                 die(_("invalid reference: %s"), arg);
1070                         return argcount;
1071                 }
1072         }
1073
1074         /* we can't end up being in (2) anymore, eat the argument */
1075         argcount++;
1076         argv++;
1077         argc--;
1078
1079         new->name = arg;
1080         setup_branch_path(new);
1081
1082         if (!check_refname_format(new->path, 0) &&
1083             !read_ref(new->path, branch_rev))
1084                 hashcpy(rev, branch_rev);
1085         else
1086                 new->path = NULL; /* not an existing branch */
1087
1088         new->commit = lookup_commit_reference_gently(rev, 1);
1089         if (!new->commit) {
1090                 /* not a commit */
1091                 *source_tree = parse_tree_indirect(rev);
1092         } else {
1093                 parse_commit_or_die(new->commit);
1094                 *source_tree = new->commit->tree;
1095         }
1096
1097         if (!*source_tree)                   /* case (1): want a tree */
1098                 die(_("reference is not a tree: %s"), arg);
1099         if (!has_dash_dash) {/* case (3).(d) -> (1) */
1100                 /*
1101                  * Do not complain the most common case
1102                  *      git checkout branch
1103                  * even if there happen to be a file called 'branch';
1104                  * it would be extremely annoying.
1105                  */
1106                 if (argc)
1107                         verify_non_filename(NULL, arg);
1108         } else {
1109                 argcount++;
1110                 argv++;
1111                 argc--;
1112         }
1113
1114         return argcount;
1115 }
1116
1117 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1118 {
1119         int status;
1120         struct strbuf branch_ref = STRBUF_INIT;
1121
1122         if (!opts->new_branch)
1123                 die(_("You are on a branch yet to be born"));
1124         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1125         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1126         strbuf_release(&branch_ref);
1127         if (!opts->quiet)
1128                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1129                         opts->new_branch);
1130         return status;
1131 }
1132
1133 static int checkout_branch(struct checkout_opts *opts,
1134                            struct branch_info *new)
1135 {
1136         if (opts->pathspec.nr)
1137                 die(_("paths cannot be used with switching branches"));
1138
1139         if (opts->patch_mode)
1140                 die(_("'%s' cannot be used with switching branches"),
1141                     "--patch");
1142
1143         if (opts->writeout_stage)
1144                 die(_("'%s' cannot be used with switching branches"),
1145                     "--ours/--theirs");
1146
1147         if (opts->force && opts->merge)
1148                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1149
1150         if (opts->force_detach && opts->new_branch)
1151                 die(_("'%s' cannot be used with '%s'"),
1152                     "--detach", "-b/-B/--orphan");
1153
1154         if (opts->new_orphan_branch) {
1155                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1156                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1157         } else if (opts->force_detach) {
1158                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1159                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1160         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1161                 opts->track = git_branch_track;
1162
1163         if (new->name && !new->commit)
1164                 die(_("Cannot switch branch to a non-commit '%s'"),
1165                     new->name);
1166
1167         if (opts->new_worktree)
1168                 return prepare_linked_checkout(opts, new);
1169
1170         if (!new->commit && opts->new_branch) {
1171                 unsigned char rev[20];
1172                 int flag;
1173
1174                 if (!read_ref_full("HEAD", 0, rev, &flag) &&
1175                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1176                         return switch_unborn_to_new_branch(opts);
1177         }
1178         return switch_branches(opts, new);
1179 }
1180
1181 int cmd_checkout(int argc, const char **argv, const char *prefix)
1182 {
1183         struct checkout_opts opts;
1184         struct branch_info new;
1185         char *conflict_style = NULL;
1186         int dwim_new_local_branch = 1;
1187         struct option options[] = {
1188                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1189                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1190                            N_("create and checkout a new branch")),
1191                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1192                            N_("create/reset and checkout a branch")),
1193                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1194                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1195                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1196                         BRANCH_TRACK_EXPLICIT),
1197                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1198                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1199                             2),
1200                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1201                             3),
1202                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1203                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1204                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1205                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1206                            N_("conflict style (merge or diff3)")),
1207                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1208                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1209                          N_("do not limit pathspecs to sparse entries only")),
1210                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1211                                 N_("second guess 'git checkout no-such-branch'")),
1212                 OPT_FILENAME(0, "to", &opts.new_worktree,
1213                            N_("check a branch out in a separate working directory")),
1214                 OPT_END(),
1215         };
1216
1217         memset(&opts, 0, sizeof(opts));
1218         memset(&new, 0, sizeof(new));
1219         opts.overwrite_ignore = 1;
1220         opts.prefix = prefix;
1221
1222         opts.saved_argv = xmalloc(sizeof(const char *) * (argc + 2));
1223         memcpy(opts.saved_argv, argv, sizeof(const char *) * (argc + 1));
1224
1225         gitmodules_config();
1226         git_config(git_checkout_config, &opts);
1227
1228         opts.track = BRANCH_TRACK_UNSPECIFIED;
1229
1230         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1231                              PARSE_OPT_KEEP_DASHDASH);
1232
1233         /* recursive execution from checkout_new_worktree() */
1234         opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
1235         if (opts.new_worktree_mode)
1236                 opts.new_worktree = NULL;
1237
1238         if (conflict_style) {
1239                 opts.merge = 1; /* implied */
1240                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1241         }
1242
1243         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1244                 die(_("-b, -B and --orphan are mutually exclusive"));
1245
1246         /*
1247          * From here on, new_branch will contain the branch to be checked out,
1248          * and new_branch_force and new_orphan_branch will tell us which one of
1249          * -b/-B/--orphan is being used.
1250          */
1251         if (opts.new_branch_force)
1252                 opts.new_branch = opts.new_branch_force;
1253
1254         if (opts.new_orphan_branch)
1255                 opts.new_branch = opts.new_orphan_branch;
1256
1257         /* --track without -b/-B/--orphan should DWIM */
1258         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1259                 const char *argv0 = argv[0];
1260                 if (!argc || !strcmp(argv0, "--"))
1261                         die (_("--track needs a branch name"));
1262                 skip_prefix(argv0, "refs/", &argv0);
1263                 skip_prefix(argv0, "remotes/", &argv0);
1264                 argv0 = strchr(argv0, '/');
1265                 if (!argv0 || !argv0[1])
1266                         die (_("Missing branch name; try -b"));
1267                 opts.new_branch = argv0 + 1;
1268         }
1269
1270         /*
1271          * Extract branch name from command line arguments, so
1272          * all that is left is pathspecs.
1273          *
1274          * Handle
1275          *
1276          *  1) git checkout <tree> -- [<paths>]
1277          *  2) git checkout -- [<paths>]
1278          *  3) git checkout <something> [<paths>]
1279          *
1280          * including "last branch" syntax and DWIM-ery for names of
1281          * remote branches, erroring out for invalid or ambiguous cases.
1282          */
1283         if (argc) {
1284                 unsigned char rev[20];
1285                 int dwim_ok =
1286                         !opts.patch_mode &&
1287                         dwim_new_local_branch &&
1288                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1289                         !opts.new_branch;
1290                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1291                                              &new, &opts.source_tree,
1292                                              rev, &opts.new_branch);
1293                 argv += n;
1294                 argc -= n;
1295         }
1296
1297         if (argc) {
1298                 parse_pathspec(&opts.pathspec, 0,
1299                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1300                                prefix, argv);
1301
1302                 if (!opts.pathspec.nr)
1303                         die(_("invalid path specification"));
1304
1305                 /*
1306                  * Try to give more helpful suggestion.
1307                  * new_branch && argc > 1 will be caught later.
1308                  */
1309                 if (opts.new_branch && argc == 1)
1310                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1311                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1312                             opts.new_branch, argv[0]);
1313
1314                 if (opts.force_detach)
1315                         die(_("git checkout: --detach does not take a path argument '%s'"),
1316                             argv[0]);
1317
1318                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1319                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1320                               "checking out of the index."));
1321         }
1322
1323         if (opts.new_branch) {
1324                 struct strbuf buf = STRBUF_INIT;
1325
1326                 opts.branch_exists =
1327                         validate_new_branchname(opts.new_branch, &buf,
1328                                                 !!opts.new_branch_force,
1329                                                 !!opts.new_branch_force);
1330
1331                 strbuf_release(&buf);
1332         }
1333
1334         if (opts.patch_mode || opts.pathspec.nr)
1335                 return checkout_paths(&opts, new.name);
1336         else
1337                 return checkout_branch(&opts, &new);
1338 }