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

   1 #include "builtin.h"
   2 #include "config.h"
   3 #include "checkout.h"
   4 #include "lockfile.h"
   5 #include "parse-options.h"
   6 #include "refs.h"
   7 #include "object-store.h"
   8 #include "commit.h"
   9 #include "tree.h"
  10 #include "tree-walk.h"
  11 #include "cache-tree.h"
  12 #include "unpack-trees.h"
  13 #include "dir.h"
  14 #include "run-command.h"
  15 #include "merge-recursive.h"
  16 #include "branch.h"
  17 #include "diff.h"
  18 #include "revision.h"
  19 #include "remote.h"
  20 #include "blob.h"
  21 #include "xdiff-interface.h"
  22 #include "ll-merge.h"
  23 #include "resolve-undo.h"
  24 #include "submodule-config.h"
  25 #include "submodule.h"
  26 #include "advice.h"
  27
  28 static int checkout_optimize_new_branch;
  29
  30 static const char * const checkout_usage[] = {
  31         N_("git checkout [<options>] <branch>"),
  32         N_("git checkout [<options>] [<branch>] -- <file>..."),
  33         NULL,
  34 };
  35
  36 struct checkout_opts {
  37         int patch_mode;
  38         int quiet;
  39         int merge;
  40         int force;
  41         int force_detach;
  42         int writeout_stage;
  43         int overwrite_ignore;
  44         int ignore_skipworktree;
  45         int ignore_other_worktrees;
  46         int show_progress;
  47         int count_checkout_paths;
  48         /*
  49          * If new checkout options are added, skip_merge_working_tree
  50          * should be updated accordingly.
  51          */
  52
  53         const char *new_branch;
  54         const char *new_branch_force;
  55         const char *new_orphan_branch;
  56         int new_branch_log;
  57         enum branch_track track;
  58         struct diff_options diff_options;
  59
  60         int branch_exists;
  61         const char *prefix;
  62         struct pathspec pathspec;
  63         struct tree *source_tree;
  64 };
  65
  66 static int post_checkout_hook(struct commit *old_commit, struct commit *new_commit,
  67                               int changed)
  68 {
  69         return run_hook_le(NULL, "post-checkout",
  70                            oid_to_hex(old_commit ? &old_commit->object.oid : &null_oid),
  71                            oid_to_hex(new_commit ? &new_commit->object.oid : &null_oid),
  72                            changed ? "1" : "0", NULL);
  73         /* "new_commit" can be NULL when checking out from the index before
  74            a commit exists. */
  75
  76 }
  77
  78 static int update_some(const struct object_id *oid, struct strbuf *base,
  79                 const char *pathname, unsigned mode, int stage, void *context)
  80 {
  81         int len;
  82         struct cache_entry *ce;
  83         int pos;
  84
  85         if (S_ISDIR(mode))
  86                 return READ_TREE_RECURSIVE;
  87
  88         len = base->len + strlen(pathname);
  89         ce = make_empty_cache_entry(&the_index, len);
  90         oidcpy(&ce->oid, oid);
  91         memcpy(ce->name, base->buf, base->len);
  92         memcpy(ce->name + base->len, pathname, len - base->len);
  93         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  94         ce->ce_namelen = len;
  95         ce->ce_mode = create_ce_mode(mode);
  96
  97         /*
  98          * If the entry is the same as the current index, we can leave the old
  99          * entry in place. Whether it is UPTODATE or not, checkout_entry will
 100          * do the right thing.
 101          */
 102         pos = cache_name_pos(ce->name, ce->ce_namelen);
 103         if (pos >= 0) {
 104                 struct cache_entry *old = active_cache[pos];
 105                 if (ce->ce_mode == old->ce_mode &&
 106                     oideq(&ce->oid, &old->oid)) {
 107                         old->ce_flags |= CE_UPDATE;
 108                         discard_cache_entry(ce);
 109                         return 0;
 110                 }
 111         }
 112
 113         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 114         return 0;
 115 }
 116
 117 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
 118 {
 119         read_tree_recursive(the_repository, tree, "", 0, 0,
 120                             pathspec, update_some, NULL);
 121
 122         /* update the index with the given tree's info
 123          * for all args, expanding wildcards, and exit
 124          * with any non-zero return code.
 125          */
 126         return 0;
 127 }
 128
 129 static int skip_same_name(const struct cache_entry *ce, int pos)
 130 {
 131         while (++pos < active_nr &&
 132                !strcmp(active_cache[pos]->name, ce->name))
 133                 ; /* skip */
 134         return pos;
 135 }
 136
 137 static int check_stage(int stage, const struct cache_entry *ce, int pos)
 138 {
 139         while (pos < active_nr &&
 140                !strcmp(active_cache[pos]->name, ce->name)) {
 141                 if (ce_stage(active_cache[pos]) == stage)
 142                         return 0;
 143                 pos++;
 144         }
 145         if (stage == 2)
 146                 return error(_("path '%s' does not have our version"), ce->name);
 147         else
 148                 return error(_("path '%s' does not have their version"), ce->name);
 149 }
 150
 151 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 152 {
 153         unsigned seen = 0;
 154         const char *name = ce->name;
 155
 156         while (pos < active_nr) {
 157                 ce = active_cache[pos];
 158                 if (strcmp(name, ce->name))
 159                         break;
 160                 seen |= (1 << ce_stage(ce));
 161                 pos++;
 162         }
 163         if ((stages & seen) != stages)
 164                 return error(_("path '%s' does not have all necessary versions"),
 165                              name);
 166         return 0;
 167 }
 168
 169 static int checkout_stage(int stage, const struct cache_entry *ce, int pos,
 170                           const struct checkout *state, int *nr_checkouts)
 171 {
 172         while (pos < active_nr &&
 173                !strcmp(active_cache[pos]->name, ce->name)) {
 174                 if (ce_stage(active_cache[pos]) == stage)
 175                         return checkout_entry(active_cache[pos], state,
 176                                               NULL, nr_checkouts);
 177                 pos++;
 178         }
 179         if (stage == 2)
 180                 return error(_("path '%s' does not have our version"), ce->name);
 181         else
 182                 return error(_("path '%s' does not have their version"), ce->name);
 183 }
 184
 185 static int checkout_merged(int pos, const struct checkout *state, int *nr_checkouts)
 186 {
 187         struct cache_entry *ce = active_cache[pos];
 188         const char *path = ce->name;
 189         mmfile_t ancestor, ours, theirs;
 190         int status;
 191         struct object_id oid;
 192         mmbuffer_t result_buf;
 193         struct object_id threeway[3];
 194         unsigned mode = 0;
 195
 196         memset(threeway, 0, sizeof(threeway));
 197         while (pos < active_nr) {
 198                 int stage;
 199                 stage = ce_stage(ce);
 200                 if (!stage || strcmp(path, ce->name))
 201                         break;
 202                 oidcpy(&threeway[stage - 1], &ce->oid);
 203                 if (stage == 2)
 204                         mode = create_ce_mode(ce->ce_mode);
 205                 pos++;
 206                 ce = active_cache[pos];
 207         }
 208         if (is_null_oid(&threeway[1]) || is_null_oid(&threeway[2]))
 209                 return error(_("path '%s' does not have necessary versions"), path);
 210
 211         read_mmblob(&ancestor, &threeway[0]);
 212         read_mmblob(&ours, &threeway[1]);
 213         read_mmblob(&theirs, &threeway[2]);
 214
 215         /*
 216          * NEEDSWORK: re-create conflicts from merges with
 217          * merge.renormalize set, too
 218          */
 219         status = ll_merge(&result_buf, path, &ancestor, "base",
 220                           &ours, "ours", &theirs, "theirs",
 221                           state->istate, NULL);
 222         free(ancestor.ptr);
 223         free(ours.ptr);
 224         free(theirs.ptr);
 225         if (status < 0 || !result_buf.ptr) {
 226                 free(result_buf.ptr);
 227                 return error(_("path '%s': cannot merge"), path);
 228         }
 229
 230         /*
 231          * NEEDSWORK:
 232          * There is absolutely no reason to write this as a blob object
 233          * and create a phony cache entry.  This hack is primarily to get
 234          * to the write_entry() machinery that massages the contents to
 235          * work-tree format and writes out which only allows it for a
 236          * cache entry.  The code in write_entry() needs to be refactored
 237          * to allow us to feed a <buffer, size, mode> instead of a cache
 238          * entry.  Such a refactoring would help merge_recursive as well
 239          * (it also writes the merge result to the object database even
 240          * when it may contain conflicts).
 241          */
 242         if (write_object_file(result_buf.ptr, result_buf.size, blob_type, &oid))
 243                 die(_("Unable to add merge result for '%s'"), path);
 244         free(result_buf.ptr);
 245         ce = make_transient_cache_entry(mode, &oid, path, 2);
 246         if (!ce)
 247                 die(_("make_cache_entry failed for path '%s'"), path);
 248         status = checkout_entry(ce, state, NULL, nr_checkouts);
 249         discard_cache_entry(ce);
 250         return status;
 251 }
 252
 253 static int checkout_paths(const struct checkout_opts *opts,
 254                           const char *revision)
 255 {
 256         int pos;
 257         struct checkout state = CHECKOUT_INIT;
 258         static char *ps_matched;
 259         struct object_id rev;
 260         struct commit *head;
 261         int errs = 0;
 262         struct lock_file lock_file = LOCK_INIT;
 263         int nr_checkouts = 0;
 264
 265         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 266                 die(_("'%s' cannot be used with updating paths"), "--track");
 267
 268         if (opts->new_branch_log)
 269                 die(_("'%s' cannot be used with updating paths"), "-l");
 270
 271         if (opts->force && opts->patch_mode)
 272                 die(_("'%s' cannot be used with updating paths"), "-f");
 273
 274         if (opts->force_detach)
 275                 die(_("'%s' cannot be used with updating paths"), "--detach");
 276
 277         if (opts->merge && opts->patch_mode)
 278                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 279
 280         if (opts->force && opts->merge)
 281                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 282
 283         if (opts->new_branch)
 284                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 285                     opts->new_branch);
 286
 287         if (opts->patch_mode)
 288                 return run_add_interactive(revision, "--patch=checkout",
 289                                            &opts->pathspec);
 290
 291         hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 292         if (read_cache_preload(&opts->pathspec) < 0)
 293                 return error(_("index file corrupt"));
 294
 295         if (opts->source_tree)
 296                 read_tree_some(opts->source_tree, &opts->pathspec);
 297
 298         ps_matched = xcalloc(opts->pathspec.nr, 1);
 299
 300         /*
 301          * Make sure all pathspecs participated in locating the paths
 302          * to be checked out.
 303          */
 304         for (pos = 0; pos < active_nr; pos++) {
 305                 struct cache_entry *ce = active_cache[pos];
 306                 ce->ce_flags &= ~CE_MATCHED;
 307                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 308                         continue;
 309                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 310                         /*
 311                          * "git checkout tree-ish -- path", but this entry
 312                          * is in the original index; it will not be checked
 313                          * out to the working tree and it does not matter
 314                          * if pathspec matched this entry.  We will not do
 315                          * anything to this entry at all.
 316                          */
 317                         continue;
 318                 /*
 319                  * Either this entry came from the tree-ish we are
 320                  * checking the paths out of, or we are checking out
 321                  * of the index.
 322                  *
 323                  * If it comes from the tree-ish, we already know it
 324                  * matches the pathspec and could just stamp
 325                  * CE_MATCHED to it from update_some(). But we still
 326                  * need ps_matched and read_tree_recursive (and
 327                  * eventually tree_entry_interesting) cannot fill
 328                  * ps_matched yet. Once it can, we can avoid calling
 329                  * match_pathspec() for _all_ entries when
 330                  * opts->source_tree != NULL.
 331                  */
 332                 if (ce_path_match(&the_index, ce, &opts->pathspec, ps_matched))
 333                         ce->ce_flags |= CE_MATCHED;
 334         }
 335
 336         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 337                 free(ps_matched);
 338                 return 1;
 339         }
 340         free(ps_matched);
 341
 342         /* "checkout -m path" to recreate conflicted state */
 343         if (opts->merge)
 344                 unmerge_marked_index(&the_index);
 345
 346         /* Any unmerged paths? */
 347         for (pos = 0; pos < active_nr; pos++) {
 348                 const struct cache_entry *ce = active_cache[pos];
 349                 if (ce->ce_flags & CE_MATCHED) {
 350                         if (!ce_stage(ce))
 351                                 continue;
 352                         if (opts->force) {
 353                                 warning(_("path '%s' is unmerged"), ce->name);
 354                         } else if (opts->writeout_stage) {
 355                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 356                         } else if (opts->merge) {
 357                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 358                         } else {
 359                                 errs = 1;
 360                                 error(_("path '%s' is unmerged"), ce->name);
 361                         }
 362                         pos = skip_same_name(ce, pos) - 1;
 363                 }
 364         }
 365         if (errs)
 366                 return 1;
 367
 368         /* Now we are committed to check them out */
 369         state.force = 1;
 370         state.refresh_cache = 1;
 371         state.istate = &the_index;
 372
 373         enable_delayed_checkout(&state);
 374         for (pos = 0; pos < active_nr; pos++) {
 375                 struct cache_entry *ce = active_cache[pos];
 376                 if (ce->ce_flags & CE_MATCHED) {
 377                         if (!ce_stage(ce)) {
 378                                 errs |= checkout_entry(ce, &state,
 379                                                        NULL, &nr_checkouts);
 380                                 continue;
 381                         }
 382                         if (opts->writeout_stage)
 383                                 errs |= checkout_stage(opts->writeout_stage,
 384                                                        ce, pos,
 385                                                        &state, &nr_checkouts);
 386                         else if (opts->merge)
 387                                 errs |= checkout_merged(pos, &state,
 388                                                         &nr_checkouts);
 389                         pos = skip_same_name(ce, pos) - 1;
 390                 }
 391         }
 392         errs |= finish_delayed_checkout(&state, &nr_checkouts);
 393
 394         if (opts->count_checkout_paths) {
 395                 if (opts->source_tree)
 396                         fprintf_ln(stderr, Q_("Checked out %d path out of %s",
 397                                               "Checked out %d paths out of %s",
 398                                               nr_checkouts),
 399                                    nr_checkouts,
 400                                    find_unique_abbrev(&opts->source_tree->object.oid,
 401                                                       DEFAULT_ABBREV));
 402                 else
 403                         fprintf_ln(stderr, Q_("Checked out %d path out of the index",
 404                                               "Checked out %d paths out of the index",
 405                                               nr_checkouts),
 406                                    nr_checkouts);
 407         }
 408
 409         if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 410                 die(_("unable to write new index file"));
 411
 412         read_ref_full("HEAD", 0, &rev, NULL);
 413         head = lookup_commit_reference_gently(the_repository, &rev, 1);
 414
 415         errs |= post_checkout_hook(head, head, 0);
 416         return errs;
 417 }
 418
 419 static void show_local_changes(struct object *head,
 420                                const struct diff_options *opts)
 421 {
 422         struct rev_info rev;
 423         /* I think we want full paths, even if we're in a subdirectory. */
 424         repo_init_revisions(the_repository, &rev, NULL);
 425         rev.diffopt.flags = opts->flags;
 426         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 427         diff_setup_done(&rev.diffopt);
 428         add_pending_object(&rev, head, NULL);
 429         run_diff_index(&rev, 0);
 430 }
 431
 432 static void describe_detached_head(const char *msg, struct commit *commit)
 433 {
 434         struct strbuf sb = STRBUF_INIT;
 435
 436         if (!parse_commit(commit))
 437                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 438         if (print_sha1_ellipsis()) {
 439                 fprintf(stderr, "%s %s... %s\n", msg,
 440                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
 441         } else {
 442                 fprintf(stderr, "%s %s %s\n", msg,
 443                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
 444         }
 445         strbuf_release(&sb);
 446 }
 447
 448 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 449                       int worktree, int *writeout_error)
 450 {
 451         struct unpack_trees_options opts;
 452         struct tree_desc tree_desc;
 453
 454         memset(&opts, 0, sizeof(opts));
 455         opts.head_idx = -1;
 456         opts.update = worktree;
 457         opts.skip_unmerged = !worktree;
 458         opts.reset = 1;
 459         opts.merge = 1;
 460         opts.fn = oneway_merge;
 461         opts.verbose_update = o->show_progress;
 462         opts.src_index = &the_index;
 463         opts.dst_index = &the_index;
 464         parse_tree(tree);
 465         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 466         switch (unpack_trees(1, &tree_desc, &opts)) {
 467         case -2:
 468                 *writeout_error = 1;
 469                 /*
 470                  * We return 0 nevertheless, as the index is all right
 471                  * and more importantly we have made best efforts to
 472                  * update paths in the work tree, and we cannot revert
 473                  * them.
 474                  */
 475                 /* fallthrough */
 476         case 0:
 477                 return 0;
 478         default:
 479                 return 128;
 480         }
 481 }
 482
 483 struct branch_info {
 484         const char *name; /* The short name used */
 485         const char *path; /* The full name of a real branch */
 486         struct commit *commit; /* The named commit */
 487         /*
 488          * if not null the branch is detached because it's already
 489          * checked out in this checkout
 490          */
 491         char *checkout;
 492 };
 493
 494 static void setup_branch_path(struct branch_info *branch)
 495 {
 496         struct strbuf buf = STRBUF_INIT;
 497
 498         strbuf_branchname(&buf, branch->name, INTERPRET_BRANCH_LOCAL);
 499         if (strcmp(buf.buf, branch->name))
 500                 branch->name = xstrdup(buf.buf);
 501         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 502         branch->path = strbuf_detach(&buf, NULL);
 503 }
 504
 505 /*
 506  * Skip merging the trees, updating the index and working directory if and
 507  * only if we are creating a new branch via "git checkout -b <new_branch>."
 508  */
 509 static int skip_merge_working_tree(const struct checkout_opts *opts,
 510         const struct branch_info *old_branch_info,
 511         const struct branch_info *new_branch_info)
 512 {
 513         /*
 514          * Do the merge if sparse checkout is on and the user has not opted in
 515          * to the optimized behavior
 516          */
 517         if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
 518                 return 0;
 519
 520         /*
 521          * We must do the merge if we are actually moving to a new commit.
 522          */
 523         if (!old_branch_info->commit || !new_branch_info->commit ||
 524                 !oideq(&old_branch_info->commit->object.oid,
 525                        &new_branch_info->commit->object.oid))
 526                 return 0;
 527
 528         /*
 529          * opts->patch_mode cannot be used with switching branches so is
 530          * not tested here
 531          */
 532
 533         /*
 534          * opts->quiet only impacts output so doesn't require a merge
 535          */
 536
 537         /*
 538          * Honor the explicit request for a three-way merge or to throw away
 539          * local changes
 540          */
 541         if (opts->merge || opts->force)
 542                 return 0;
 543
 544         /*
 545          * --detach is documented as "updating the index and the files in the
 546          * working tree" but this optimization skips those steps so fall through
 547          * to the regular code path.
 548          */
 549         if (opts->force_detach)
 550                 return 0;
 551
 552         /*
 553          * opts->writeout_stage cannot be used with switching branches so is
 554          * not tested here
 555          */
 556
 557         /*
 558          * Honor the explicit ignore requests
 559          */
 560         if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
 561                 opts->ignore_other_worktrees)
 562                 return 0;
 563
 564         /*
 565          * opts->show_progress only impacts output so doesn't require a merge
 566          */
 567
 568         /*
 569          * If we aren't creating a new branch any changes or updates will
 570          * happen in the existing branch.  Since that could only be updating
 571          * the index and working directory, we don't want to skip those steps
 572          * or we've defeated any purpose in running the command.
 573          */
 574         if (!opts->new_branch)
 575                 return 0;
 576
 577         /*
 578          * new_branch_force is defined to "create/reset and checkout a branch"
 579          * so needs to go through the merge to do the reset
 580          */
 581         if (opts->new_branch_force)
 582                 return 0;
 583
 584         /*
 585          * A new orphaned branch requrires the index and the working tree to be
 586          * adjusted to <start_point>
 587          */
 588         if (opts->new_orphan_branch)
 589                 return 0;
 590
 591         /*
 592          * Remaining variables are not checkout options but used to track state
 593          */
 594
 595         return 1;
 596 }
 597
 598 static int merge_working_tree(const struct checkout_opts *opts,
 599                               struct branch_info *old_branch_info,
 600                               struct branch_info *new_branch_info,
 601                               int *writeout_error)
 602 {
 603         int ret;
 604         struct lock_file lock_file = LOCK_INIT;
 605
 606         hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 607         if (read_cache_preload(NULL) < 0)
 608                 return error(_("index file corrupt"));
 609
 610         resolve_undo_clear();
 611         if (opts->force) {
 612                 ret = reset_tree(get_commit_tree(new_branch_info->commit),
 613                                  opts, 1, writeout_error);
 614                 if (ret)
 615                         return ret;
 616         } else {
 617                 struct tree_desc trees[2];
 618                 struct tree *tree;
 619                 struct unpack_trees_options topts;
 620
 621                 memset(&topts, 0, sizeof(topts));
 622                 topts.head_idx = -1;
 623                 topts.src_index = &the_index;
 624                 topts.dst_index = &the_index;
 625
 626                 setup_unpack_trees_porcelain(&topts, "checkout");
 627
 628                 refresh_cache(REFRESH_QUIET);
 629
 630                 if (unmerged_cache()) {
 631                         error(_("you need to resolve your current index first"));
 632                         return 1;
 633                 }
 634
 635                 /* 2-way merge to the new branch */
 636                 topts.initial_checkout = is_cache_unborn();
 637                 topts.update = 1;
 638                 topts.merge = 1;
 639                 topts.gently = opts->merge && old_branch_info->commit;
 640                 topts.verbose_update = opts->show_progress;
 641                 topts.fn = twoway_merge;
 642                 if (opts->overwrite_ignore) {
 643                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 644                         topts.dir->flags |= DIR_SHOW_IGNORED;
 645                         setup_standard_excludes(topts.dir);
 646                 }
 647                 tree = parse_tree_indirect(old_branch_info->commit ?
 648                                            &old_branch_info->commit->object.oid :
 649                                            the_hash_algo->empty_tree);
 650                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 651                 tree = parse_tree_indirect(&new_branch_info->commit->object.oid);
 652                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 653
 654                 ret = unpack_trees(2, trees, &topts);
 655                 clear_unpack_trees_porcelain(&topts);
 656                 if (ret == -1) {
 657                         /*
 658                          * Unpack couldn't do a trivial merge; either
 659                          * give up or do a real merge, depending on
 660                          * whether the merge flag was used.
 661                          */
 662                         struct tree *result;
 663                         struct tree *work;
 664                         struct merge_options o;
 665                         if (!opts->merge)
 666                                 return 1;
 667
 668                         /*
 669                          * Without old_branch_info->commit, the below is the same as
 670                          * the two-tree unpack we already tried and failed.
 671                          */
 672                         if (!old_branch_info->commit)
 673                                 return 1;
 674
 675                         /* Do more real merge */
 676
 677                         /*
 678                          * We update the index fully, then write the
 679                          * tree from the index, then merge the new
 680                          * branch with the current tree, with the old
 681                          * branch as the base. Then we reset the index
 682                          * (but not the working tree) to the new
 683                          * branch, leaving the working tree as the
 684                          * merged version, but skipping unmerged
 685                          * entries in the index.
 686                          */
 687
 688                         add_files_to_cache(NULL, NULL, 0);
 689                         /*
 690                          * NEEDSWORK: carrying over local changes
 691                          * when branches have different end-of-line
 692                          * normalization (or clean+smudge rules) is
 693                          * a pain; plumb in an option to set
 694                          * o.renormalize?
 695                          */
 696                         init_merge_options(&o);
 697                         o.verbosity = 0;
 698                         work = write_tree_from_memory(&o);
 699
 700                         ret = reset_tree(get_commit_tree(new_branch_info->commit),
 701                                          opts, 1,
 702                                          writeout_error);
 703                         if (ret)
 704                                 return ret;
 705                         o.ancestor = old_branch_info->name;
 706                         o.branch1 = new_branch_info->name;
 707                         o.branch2 = "local";
 708                         ret = merge_trees(&o,
 709                                           get_commit_tree(new_branch_info->commit),
 710                                           work,
 711                                           get_commit_tree(old_branch_info->commit),
 712                                           &result);
 713                         if (ret < 0)
 714                                 exit(128);
 715                         ret = reset_tree(get_commit_tree(new_branch_info->commit),
 716                                          opts, 0,
 717                                          writeout_error);
 718                         strbuf_release(&o.obuf);
 719                         if (ret)
 720                                 return ret;
 721                 }
 722         }
 723
 724         if (!active_cache_tree)
 725                 active_cache_tree = cache_tree();
 726
 727         if (!cache_tree_fully_valid(active_cache_tree))
 728                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 729
 730         if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 731                 die(_("unable to write new index file"));
 732
 733         if (!opts->force && !opts->quiet)
 734                 show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
 735
 736         return 0;
 737 }
 738
 739 static void report_tracking(struct branch_info *new_branch_info)
 740 {
 741         struct strbuf sb = STRBUF_INIT;
 742         struct branch *branch = branch_get(new_branch_info->name);
 743
 744         if (!format_tracking_info(branch, &sb, AHEAD_BEHIND_FULL))
 745                 return;
 746         fputs(sb.buf, stdout);
 747         strbuf_release(&sb);
 748 }
 749
 750 static void update_refs_for_switch(const struct checkout_opts *opts,
 751                                    struct branch_info *old_branch_info,
 752                                    struct branch_info *new_branch_info)
 753 {
 754         struct strbuf msg = STRBUF_INIT;
 755         const char *old_desc, *reflog_msg;
 756         if (opts->new_branch) {
 757                 if (opts->new_orphan_branch) {
 758                         char *refname;
 759
 760                         refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
 761                         if (opts->new_branch_log &&
 762                             !should_autocreate_reflog(refname)) {
 763                                 int ret;
 764                                 struct strbuf err = STRBUF_INIT;
 765
 766                                 ret = safe_create_reflog(refname, 1, &err);
 767                                 if (ret) {
 768                                         fprintf(stderr, _("Can not do reflog for '%s': %s\n"),
 769                                                 opts->new_orphan_branch, err.buf);
 770                                         strbuf_release(&err);
 771                                         free(refname);
 772                                         return;
 773                                 }
 774                                 strbuf_release(&err);
 775                         }
 776                         free(refname);
 777                 }
 778                 else
 779                         create_branch(the_repository,
 780                                       opts->new_branch, new_branch_info->name,
 781                                       opts->new_branch_force ? 1 : 0,
 782                                       opts->new_branch_force ? 1 : 0,
 783                                       opts->new_branch_log,
 784                                       opts->quiet,
 785                                       opts->track);
 786                 new_branch_info->name = opts->new_branch;
 787                 setup_branch_path(new_branch_info);
 788         }
 789
 790         old_desc = old_branch_info->name;
 791         if (!old_desc && old_branch_info->commit)
 792                 old_desc = oid_to_hex(&old_branch_info->commit->object.oid);
 793
 794         reflog_msg = getenv("GIT_REFLOG_ACTION");
 795         if (!reflog_msg)
 796                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 797                         old_desc ? old_desc : "(invalid)", new_branch_info->name);
 798         else
 799                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 800
 801         if (!strcmp(new_branch_info->name, "HEAD") && !new_branch_info->path && !opts->force_detach) {
 802                 /* Nothing to do. */
 803         } else if (opts->force_detach || !new_branch_info->path) {      /* No longer on any branch. */
 804                 update_ref(msg.buf, "HEAD", &new_branch_info->commit->object.oid, NULL,
 805                            REF_NO_DEREF, UPDATE_REFS_DIE_ON_ERR);
 806                 if (!opts->quiet) {
 807                         if (old_branch_info->path &&
 808                             advice_detached_head && !opts->force_detach)
 809                                 detach_advice(new_branch_info->name);
 810                         describe_detached_head(_("HEAD is now at"), new_branch_info->commit);
 811                 }
 812         } else if (new_branch_info->path) {     /* Switch branches. */
 813                 if (create_symref("HEAD", new_branch_info->path, msg.buf) < 0)
 814                         die(_("unable to update HEAD"));
 815                 if (!opts->quiet) {
 816                         if (old_branch_info->path && !strcmp(new_branch_info->path, old_branch_info->path)) {
 817                                 if (opts->new_branch_force)
 818                                         fprintf(stderr, _("Reset branch '%s'\n"),
 819                                                 new_branch_info->name);
 820                                 else
 821                                         fprintf(stderr, _("Already on '%s'\n"),
 822                                                 new_branch_info->name);
 823                         } else if (opts->new_branch) {
 824                                 if (opts->branch_exists)
 825                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new_branch_info->name);
 826                                 else
 827                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new_branch_info->name);
 828                         } else {
 829                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 830                                         new_branch_info->name);
 831                         }
 832                 }
 833                 if (old_branch_info->path && old_branch_info->name) {
 834                         if (!ref_exists(old_branch_info->path) && reflog_exists(old_branch_info->path))
 835                                 delete_reflog(old_branch_info->path);
 836                 }
 837         }
 838         remove_branch_state(the_repository);
 839         strbuf_release(&msg);
 840         if (!opts->quiet &&
 841             (new_branch_info->path || (!opts->force_detach && !strcmp(new_branch_info->name, "HEAD"))))
 842                 report_tracking(new_branch_info);
 843 }
 844
 845 static int add_pending_uninteresting_ref(const char *refname,
 846                                          const struct object_id *oid,
 847                                          int flags, void *cb_data)
 848 {
 849         add_pending_oid(cb_data, refname, oid, UNINTERESTING);
 850         return 0;
 851 }
 852
 853 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 854 {
 855         strbuf_addstr(sb, "  ");
 856         strbuf_add_unique_abbrev(sb, &commit->object.oid, DEFAULT_ABBREV);
 857         strbuf_addch(sb, ' ');
 858         if (!parse_commit(commit))
 859                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 860         strbuf_addch(sb, '\n');
 861 }
 862
 863 #define ORPHAN_CUTOFF 4
 864 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 865 {
 866         struct commit *c, *last = NULL;
 867         struct strbuf sb = STRBUF_INIT;
 868         int lost = 0;
 869         while ((c = get_revision(revs)) != NULL) {
 870                 if (lost < ORPHAN_CUTOFF)
 871                         describe_one_orphan(&sb, c);
 872                 last = c;
 873                 lost++;
 874         }
 875         if (ORPHAN_CUTOFF < lost) {
 876                 int more = lost - ORPHAN_CUTOFF;
 877                 if (more == 1)
 878                         describe_one_orphan(&sb, last);
 879                 else
 880                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 881         }
 882
 883         fprintf(stderr,
 884                 Q_(
 885                 /* The singular version */
 886                 "Warning: you are leaving %d commit behind, "
 887                 "not connected to\n"
 888                 "any of your branches:\n\n"
 889                 "%s\n",
 890                 /* The plural version */
 891                 "Warning: you are leaving %d commits behind, "
 892                 "not connected to\n"
 893                 "any of your branches:\n\n"
 894                 "%s\n",
 895                 /* Give ngettext() the count */
 896                 lost),
 897                 lost,
 898                 sb.buf);
 899         strbuf_release(&sb);
 900
 901         if (advice_detached_head)
 902                 fprintf(stderr,
 903                         Q_(
 904                         /* The singular version */
 905                         "If you want to keep it by creating a new branch, "
 906                         "this may be a good time\nto do so with:\n\n"
 907                         " git branch <new-branch-name> %s\n\n",
 908                         /* The plural version */
 909                         "If you want to keep them by creating a new branch, "
 910                         "this may be a good time\nto do so with:\n\n"
 911                         " git branch <new-branch-name> %s\n\n",
 912                         /* Give ngettext() the count */
 913                         lost),
 914                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV));
 915 }
 916
 917 /*
 918  * We are about to leave commit that was at the tip of a detached
 919  * HEAD.  If it is not reachable from any ref, this is the last chance
 920  * for the user to do so without resorting to reflog.
 921  */
 922 static void orphaned_commit_warning(struct commit *old_commit, struct commit *new_commit)
 923 {
 924         struct rev_info revs;
 925         struct object *object = &old_commit->object;
 926
 927         repo_init_revisions(the_repository, &revs, NULL);
 928         setup_revisions(0, NULL, &revs, NULL);
 929
 930         object->flags &= ~UNINTERESTING;
 931         add_pending_object(&revs, object, oid_to_hex(&object->oid));
 932
 933         for_each_ref(add_pending_uninteresting_ref, &revs);
 934         add_pending_oid(&revs, "HEAD", &new_commit->object.oid, UNINTERESTING);
 935
 936         if (prepare_revision_walk(&revs))
 937                 die(_("internal error in revision walk"));
 938         if (!(old_commit->object.flags & UNINTERESTING))
 939                 suggest_reattach(old_commit, &revs);
 940         else
 941                 describe_detached_head(_("Previous HEAD position was"), old_commit);
 942
 943         /* Clean up objects used, as they will be reused. */
 944         clear_commit_marks_all(ALL_REV_FLAGS);
 945 }
 946
 947 static int switch_branches(const struct checkout_opts *opts,
 948                            struct branch_info *new_branch_info)
 949 {
 950         int ret = 0;
 951         struct branch_info old_branch_info;
 952         void *path_to_free;
 953         struct object_id rev;
 954         int flag, writeout_error = 0;
 955         memset(&old_branch_info, 0, sizeof(old_branch_info));
 956         old_branch_info.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
 957         if (old_branch_info.path)
 958                 old_branch_info.commit = lookup_commit_reference_gently(the_repository, &rev, 1);
 959         if (!(flag & REF_ISSYMREF))
 960                 old_branch_info.path = NULL;
 961
 962         if (old_branch_info.path)
 963                 skip_prefix(old_branch_info.path, "refs/heads/", &old_branch_info.name);
 964
 965         if (!new_branch_info->name) {
 966                 new_branch_info->name = "HEAD";
 967                 new_branch_info->commit = old_branch_info.commit;
 968                 if (!new_branch_info->commit)
 969                         die(_("You are on a branch yet to be born"));
 970                 parse_commit_or_die(new_branch_info->commit);
 971         }
 972
 973         /* optimize the "checkout -b <new_branch> path */
 974         if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
 975                 if (!checkout_optimize_new_branch && !opts->quiet) {
 976                         if (read_cache_preload(NULL) < 0)
 977                                 return error(_("index file corrupt"));
 978                         show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
 979                 }
 980         } else {
 981                 ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
 982                 if (ret) {
 983                         free(path_to_free);
 984                         return ret;
 985                 }
 986         }
 987
 988         if (!opts->quiet && !old_branch_info.path && old_branch_info.commit && new_branch_info->commit != old_branch_info.commit)
 989                 orphaned_commit_warning(old_branch_info.commit, new_branch_info->commit);
 990
 991         update_refs_for_switch(opts, &old_branch_info, new_branch_info);
 992
 993         ret = post_checkout_hook(old_branch_info.commit, new_branch_info->commit, 1);
 994         free(path_to_free);
 995         return ret || writeout_error;
 996 }
 997
 998 static int git_checkout_config(const char *var, const char *value, void *cb)
 999 {
1000         if (!strcmp(var, "checkout.optimizenewbranch")) {
1001                 checkout_optimize_new_branch = git_config_bool(var, value);
1002                 return 0;
1003         }
1004
1005         if (!strcmp(var, "diff.ignoresubmodules")) {
1006                 struct checkout_opts *opts = cb;
1007                 handle_ignore_submodules_arg(&opts->diff_options, value);
1008                 return 0;
1009         }
1010
1011         if (starts_with(var, "submodule."))
1012                 return git_default_submodule_config(var, value, NULL);
1013
1014         return git_xmerge_config(var, value, NULL);
1015 }
1016
1017 static int parse_branchname_arg(int argc, const char **argv,
1018                                 int dwim_new_local_branch_ok,
1019                                 struct branch_info *new_branch_info,
1020                                 struct checkout_opts *opts,
1021                                 struct object_id *rev,
1022                                 int *dwim_remotes_matched)
1023 {
1024         struct tree **source_tree = &opts->source_tree;
1025         const char **new_branch = &opts->new_branch;
1026         int argcount = 0;
1027         struct object_id branch_rev;
1028         const char *arg;
1029         int dash_dash_pos;
1030         int has_dash_dash = 0;
1031         int i;
1032
1033         /*
1034          * case 1: git checkout <ref> -- [<paths>]
1035          *
1036          *   <ref> must be a valid tree, everything after the '--' must be
1037          *   a path.
1038          *
1039          * case 2: git checkout -- [<paths>]
1040          *
1041          *   everything after the '--' must be paths.
1042          *
1043          * case 3: git checkout <something> [--]
1044          *
1045          *   (a) If <something> is a commit, that is to
1046          *       switch to the branch or detach HEAD at it.  As a special case,
1047          *       if <something> is A...B (missing A or B means HEAD but you can
1048          *       omit at most one side), and if there is a unique merge base
1049          *       between A and B, A...B names that merge base.
1050          *
1051          *   (b) If <something> is _not_ a commit, either "--" is present
1052          *       or <something> is not a path, no -t or -b was given, and
1053          *       and there is a tracking branch whose name is <something>
1054          *       in one and only one remote (or if the branch exists on the
1055          *       remote named in checkout.defaultRemote), then this is a
1056          *       short-hand to fork local <something> from that
1057          *       remote-tracking branch.
1058          *
1059          *   (c) Otherwise, if "--" is present, treat it like case (1).
1060          *
1061          *   (d) Otherwise :
1062          *       - if it's a reference, treat it like case (1)
1063          *       - else if it's a path, treat it like case (2)
1064          *       - else: fail.
1065          *
1066          * case 4: git checkout <something> <paths>
1067          *
1068          *   The first argument must not be ambiguous.
1069          *   - If it's *only* a reference, treat it like case (1).
1070          *   - If it's only a path, treat it like case (2).
1071          *   - else: fail.
1072          *
1073          */
1074         if (!argc)
1075                 return 0;
1076
1077         arg = argv[0];
1078         dash_dash_pos = -1;
1079         for (i = 0; i < argc; i++) {
1080                 if (!strcmp(argv[i], "--")) {
1081                         dash_dash_pos = i;
1082                         break;
1083                 }
1084         }
1085         if (dash_dash_pos == 0)
1086                 return 1; /* case (2) */
1087         else if (dash_dash_pos == 1)
1088                 has_dash_dash = 1; /* case (3) or (1) */
1089         else if (dash_dash_pos >= 2)
1090                 die(_("only one reference expected, %d given."), dash_dash_pos);
1091         opts->count_checkout_paths = !opts->quiet && !has_dash_dash;
1092
1093         if (!strcmp(arg, "-"))
1094                 arg = "@{-1}";
1095
1096         if (get_oid_mb(arg, rev)) {
1097                 /*
1098                  * Either case (3) or (4), with <something> not being
1099                  * a commit, or an attempt to use case (1) with an
1100                  * invalid ref.
1101                  *
1102                  * It's likely an error, but we need to find out if
1103                  * we should auto-create the branch, case (3).(b).
1104                  */
1105                 int recover_with_dwim = dwim_new_local_branch_ok;
1106
1107                 int could_be_checkout_paths = !has_dash_dash &&
1108                         check_filename(opts->prefix, arg);
1109
1110                 if (!has_dash_dash && !no_wildcard(arg))
1111                         recover_with_dwim = 0;
1112
1113                 /*
1114                  * Accept "git checkout foo" and "git checkout foo --"
1115                  * as candidates for dwim.
1116                  */
1117                 if (!(argc == 1 && !has_dash_dash) &&
1118                     !(argc == 2 && has_dash_dash))
1119                         recover_with_dwim = 0;
1120
1121                 if (recover_with_dwim) {
1122                         const char *remote = unique_tracking_name(arg, rev,
1123                                                                   dwim_remotes_matched);
1124                         if (remote) {
1125                                 if (could_be_checkout_paths)
1126                                         die(_("'%s' could be both a local file and a tracking branch.\n"
1127                                               "Please use -- (and optionally --no-guess) to disambiguate"),
1128                                             arg);
1129                                 *new_branch = arg;
1130                                 arg = remote;
1131                                 /* DWIMmed to create local branch, case (3).(b) */
1132                         } else {
1133                                 recover_with_dwim = 0;
1134                         }
1135                 }
1136
1137                 if (!recover_with_dwim) {
1138                         if (has_dash_dash)
1139                                 die(_("invalid reference: %s"), arg);
1140                         return argcount;
1141                 }
1142         }
1143
1144         /* we can't end up being in (2) anymore, eat the argument */
1145         argcount++;
1146         argv++;
1147         argc--;
1148
1149         new_branch_info->name = arg;
1150         setup_branch_path(new_branch_info);
1151
1152         if (!check_refname_format(new_branch_info->path, 0) &&
1153             !read_ref(new_branch_info->path, &branch_rev))
1154                 oidcpy(rev, &branch_rev);
1155         else
1156                 new_branch_info->path = NULL; /* not an existing branch */
1157
1158         new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
1159         if (!new_branch_info->commit) {
1160                 /* not a commit */
1161                 *source_tree = parse_tree_indirect(rev);
1162         } else {
1163                 parse_commit_or_die(new_branch_info->commit);
1164                 *source_tree = get_commit_tree(new_branch_info->commit);
1165         }
1166
1167         if (!*source_tree)                   /* case (1): want a tree */
1168                 die(_("reference is not a tree: %s"), arg);
1169         if (!has_dash_dash) {   /* case (3).(d) -> (1) */
1170                 /*
1171                  * Do not complain the most common case
1172                  *      git checkout branch
1173                  * even if there happen to be a file called 'branch';
1174                  * it would be extremely annoying.
1175                  */
1176                 if (argc)
1177                         verify_non_filename(opts->prefix, arg);
1178         } else {
1179                 argcount++;
1180                 argv++;
1181                 argc--;
1182         }
1183
1184         return argcount;
1185 }
1186
1187 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1188 {
1189         int status;
1190         struct strbuf branch_ref = STRBUF_INIT;
1191
1192         if (!opts->new_branch)
1193                 die(_("You are on a branch yet to be born"));
1194         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1195         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1196         strbuf_release(&branch_ref);
1197         if (!opts->quiet)
1198                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1199                         opts->new_branch);
1200         return status;
1201 }
1202
1203 static int checkout_branch(struct checkout_opts *opts,
1204                            struct branch_info *new_branch_info)
1205 {
1206         if (opts->pathspec.nr)
1207                 die(_("paths cannot be used with switching branches"));
1208
1209         if (opts->patch_mode)
1210                 die(_("'%s' cannot be used with switching branches"),
1211                     "--patch");
1212
1213         if (opts->writeout_stage)
1214                 die(_("'%s' cannot be used with switching branches"),
1215                     "--ours/--theirs");
1216
1217         if (opts->force && opts->merge)
1218                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1219
1220         if (opts->force_detach && opts->new_branch)
1221                 die(_("'%s' cannot be used with '%s'"),
1222                     "--detach", "-b/-B/--orphan");
1223
1224         if (opts->new_orphan_branch) {
1225                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1226                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1227         } else if (opts->force_detach) {
1228                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1229                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1230         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1231                 opts->track = git_branch_track;
1232
1233         if (new_branch_info->name && !new_branch_info->commit)
1234                 die(_("Cannot switch branch to a non-commit '%s'"),
1235                     new_branch_info->name);
1236
1237         if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
1238             !opts->ignore_other_worktrees) {
1239                 int flag;
1240                 char *head_ref = resolve_refdup("HEAD", 0, NULL, &flag);
1241                 if (head_ref &&
1242                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new_branch_info->path)))
1243                         die_if_checked_out(new_branch_info->path, 1);
1244                 free(head_ref);
1245         }
1246
1247         if (!new_branch_info->commit && opts->new_branch) {
1248                 struct object_id rev;
1249                 int flag;
1250
1251                 if (!read_ref_full("HEAD", 0, &rev, &flag) &&
1252                     (flag & REF_ISSYMREF) && is_null_oid(&rev))
1253                         return switch_unborn_to_new_branch(opts);
1254         }
1255         return switch_branches(opts, new_branch_info);
1256 }
1257
1258 int cmd_checkout(int argc, const char **argv, const char *prefix)
1259 {
1260         struct checkout_opts opts;
1261         struct branch_info new_branch_info;
1262         char *conflict_style = NULL;
1263         int dwim_new_local_branch, no_dwim_new_local_branch = 0;
1264         int dwim_remotes_matched = 0;
1265         struct option options[] = {
1266                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1267                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1268                            N_("create and checkout a new branch")),
1269                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1270                            N_("create/reset and checkout a branch")),
1271                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1272                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
1273                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1274                         BRANCH_TRACK_EXPLICIT),
1275                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1276                 OPT_SET_INT_F('2', "ours", &opts.writeout_stage,
1277                               N_("checkout our version for unmerged files"),
1278                               2, PARSE_OPT_NONEG),
1279                 OPT_SET_INT_F('3', "theirs", &opts.writeout_stage,
1280                               N_("checkout their version for unmerged files"),
1281                               3, PARSE_OPT_NONEG),
1282                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)"),
1283                            PARSE_OPT_NOCOMPLETE),
1284                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1285                 OPT_BOOL_F(0, "overwrite-ignore", &opts.overwrite_ignore,
1286                            N_("update ignored files (default)"),
1287                            PARSE_OPT_NOCOMPLETE),
1288                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1289                            N_("conflict style (merge or diff3)")),
1290                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1291                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1292                          N_("do not limit pathspecs to sparse entries only")),
1293                 OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
1294                          N_("do not second guess 'git checkout <no-such-branch>'")),
1295                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1296                          N_("do not check if another worktree is holding the given ref")),
1297                 { OPTION_CALLBACK, 0, "recurse-submodules", NULL,
1298                             "checkout", "control recursive updating of submodules",
1299                             PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
1300                 OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
1301                 OPT_END(),
1302         };
1303
1304         memset(&opts, 0, sizeof(opts));
1305         memset(&new_branch_info, 0, sizeof(new_branch_info));
1306         opts.overwrite_ignore = 1;
1307         opts.prefix = prefix;
1308         opts.show_progress = -1;
1309
1310         git_config(git_checkout_config, &opts);
1311
1312         opts.track = BRANCH_TRACK_UNSPECIFIED;
1313
1314         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1315                              PARSE_OPT_KEEP_DASHDASH);
1316
1317         dwim_new_local_branch = !no_dwim_new_local_branch;
1318         if (opts.show_progress < 0) {
1319                 if (opts.quiet)
1320                         opts.show_progress = 0;
1321                 else
1322                         opts.show_progress = isatty(2);
1323         }
1324
1325         if (conflict_style) {
1326                 opts.merge = 1; /* implied */
1327                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1328         }
1329
1330         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1331                 die(_("-b, -B and --orphan are mutually exclusive"));
1332
1333         /*
1334          * From here on, new_branch will contain the branch to be checked out,
1335          * and new_branch_force and new_orphan_branch will tell us which one of
1336          * -b/-B/--orphan is being used.
1337          */
1338         if (opts.new_branch_force)
1339                 opts.new_branch = opts.new_branch_force;
1340
1341         if (opts.new_orphan_branch)
1342                 opts.new_branch = opts.new_orphan_branch;
1343
1344         /* --track without -b/-B/--orphan should DWIM */
1345         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1346                 const char *argv0 = argv[0];
1347                 if (!argc || !strcmp(argv0, "--"))
1348                         die(_("--track needs a branch name"));
1349                 skip_prefix(argv0, "refs/", &argv0);
1350                 skip_prefix(argv0, "remotes/", &argv0);
1351                 argv0 = strchr(argv0, '/');
1352                 if (!argv0 || !argv0[1])
1353                         die(_("missing branch name; try -b"));
1354                 opts.new_branch = argv0 + 1;
1355         }
1356
1357         /*
1358          * Extract branch name from command line arguments, so
1359          * all that is left is pathspecs.
1360          *
1361          * Handle
1362          *
1363          *  1) git checkout <tree> -- [<paths>]
1364          *  2) git checkout -- [<paths>]
1365          *  3) git checkout <something> [<paths>]
1366          *
1367          * including "last branch" syntax and DWIM-ery for names of
1368          * remote branches, erroring out for invalid or ambiguous cases.
1369          */
1370         if (argc) {
1371                 struct object_id rev;
1372                 int dwim_ok =
1373                         !opts.patch_mode &&
1374                         dwim_new_local_branch &&
1375                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1376                         !opts.new_branch;
1377                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1378                                              &new_branch_info, &opts, &rev,
1379                                              &dwim_remotes_matched);
1380                 argv += n;
1381                 argc -= n;
1382         }
1383
1384         if (argc) {
1385                 parse_pathspec(&opts.pathspec, 0,
1386                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1387                                prefix, argv);
1388
1389                 if (!opts.pathspec.nr)
1390                         die(_("invalid path specification"));
1391
1392                 /*
1393                  * Try to give more helpful suggestion.
1394                  * new_branch && argc > 1 will be caught later.
1395                  */
1396                 if (opts.new_branch && argc == 1)
1397                         die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
1398                                 argv[0], opts.new_branch);
1399
1400                 if (opts.force_detach)
1401                         die(_("git checkout: --detach does not take a path argument '%s'"),
1402                             argv[0]);
1403
1404                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1405                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1406                               "checking out of the index."));
1407         }
1408
1409         if (opts.new_branch) {
1410                 struct strbuf buf = STRBUF_INIT;
1411
1412                 if (opts.new_branch_force)
1413                         opts.branch_exists = validate_branchname(opts.new_branch, &buf);
1414                 else
1415                         opts.branch_exists =
1416                                 validate_new_branchname(opts.new_branch, &buf, 0);
1417                 strbuf_release(&buf);
1418         }
1419
1420         UNLEAK(opts);
1421         if (opts.patch_mode || opts.pathspec.nr) {
1422                 int ret = checkout_paths(&opts, new_branch_info.name);
1423                 if (ret && dwim_remotes_matched > 1 &&
1424                     advice_checkout_ambiguous_remote_branch_name)
1425                         advise(_("'%s' matched more than one remote tracking branch.\n"
1426                                  "We found %d remotes with a reference that matched. So we fell back\n"
1427                                  "on trying to resolve the argument as a path, but failed there too!\n"
1428                                  "\n"
1429                                  "If you meant to check out a remote tracking branch on, e.g. 'origin',\n"
1430                                  "you can do so by fully qualifying the name with the --track option:\n"
1431                                  "\n"
1432                                  "    git checkout --track origin/<name>\n"
1433                                  "\n"
1434                                  "If you'd like to always have checkouts of an ambiguous <name> prefer\n"
1435                                  "one remote, e.g. the 'origin' remote, consider setting\n"
1436                                  "checkout.defaultRemote=origin in your config."),
1437                                argv[0],
1438                                dwim_remotes_matched);
1439                 return ret;
1440         } else {
1441                 return checkout_branch(&opts, &new_branch_info);
1442         }
1443 }