builtin/checkout.c

   1 #define USE_THE_INDEX_COMPATIBILITY_MACROS
   2 #include "builtin.h"
   3 #include "config.h"
   4 #include "checkout.h"
   5 #include "lockfile.h"
   6 #include "parse-options.h"
   7 #include "refs.h"
   8 #include "object-store.h"
   9 #include "commit.h"
  10 #include "tree.h"
  11 #include "tree-walk.h"
  12 #include "cache-tree.h"
  13 #include "unpack-trees.h"
  14 #include "dir.h"
  15 #include "run-command.h"
  16 #include "merge-recursive.h"
  17 #include "branch.h"
  18 #include "diff.h"
  19 #include "revision.h"
  20 #include "remote.h"
  21 #include "blob.h"
  22 #include "xdiff-interface.h"
  23 #include "ll-merge.h"
  24 #include "resolve-undo.h"
  25 #include "submodule-config.h"
  26 #include "submodule.h"
  27 #include "advice.h"
  28
  29 static int checkout_optimize_new_branch;
  30
  31 static const char * const checkout_usage[] = {
  32         N_("git checkout [<options>] <branch>"),
  33         N_("git checkout [<options>] [<branch>] -- <file>..."),
  34         NULL,
  35 };
  36
  37 struct checkout_opts {
  38         int patch_mode;
  39         int quiet;
  40         int merge;
  41         int force;
  42         int force_detach;
  43         int writeout_stage;
  44         int overwrite_ignore;
  45         int ignore_skipworktree;
  46         int ignore_other_worktrees;
  47         int show_progress;
  48         int count_checkout_paths;
  49         /*
  50          * If new checkout options are added, skip_merge_working_tree
  51          * should be updated accordingly.
  52          */
  53
  54         const char *new_branch;
  55         const char *new_branch_force;
  56         const char *new_orphan_branch;
  57         int new_branch_log;
  58         enum branch_track track;
  59         struct diff_options diff_options;
  60
  61         int branch_exists;
  62         const char *prefix;
  63         struct pathspec pathspec;
  64         struct tree *source_tree;
  65 };
  66
  67 static int post_checkout_hook(struct commit *old_commit, struct commit *new_commit,
  68                               int changed)
  69 {
  70         return run_hook_le(NULL, "post-checkout",
  71                            oid_to_hex(old_commit ? &old_commit->object.oid : &null_oid),
  72                            oid_to_hex(new_commit ? &new_commit->object.oid : &null_oid),
  73                            changed ? "1" : "0", NULL);
  74         /* "new_commit" can be NULL when checking out from the index before
  75            a commit exists. */
  76
  77 }
  78
  79 static int update_some(const struct object_id *oid, struct strbuf *base,
  80                 const char *pathname, unsigned mode, int stage, void *context)
  81 {
  82         int len;
  83         struct cache_entry *ce;
  84         int pos;
  85
  86         if (S_ISDIR(mode))
  87                 return READ_TREE_RECURSIVE;
  88
  89         len = base->len + strlen(pathname);
  90         ce = make_empty_cache_entry(&the_index, len);
  91         oidcpy(&ce->oid, oid);
  92         memcpy(ce->name, base->buf, base->len);
  93         memcpy(ce->name + base->len, pathname, len - base->len);
  94         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  95         ce->ce_namelen = len;
  96         ce->ce_mode = create_ce_mode(mode);
  97
  98         /*
  99          * If the entry is the same as the current index, we can leave the old
 100          * entry in place. Whether it is UPTODATE or not, checkout_entry will
 101          * do the right thing.
 102          */
 103         pos = cache_name_pos(ce->name, ce->ce_namelen);
 104         if (pos >= 0) {
 105                 struct cache_entry *old = active_cache[pos];
 106                 if (ce->ce_mode == old->ce_mode &&
 107                     oideq(&ce->oid, &old->oid)) {
 108                         old->ce_flags |= CE_UPDATE;
 109                         discard_cache_entry(ce);
 110                         return 0;
 111                 }
 112         }
 113
 114         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 115         return 0;
 116 }
 117
 118 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
 119 {
 120         read_tree_recursive(the_repository, tree, "", 0, 0,
 121                             pathspec, update_some, NULL);
 122
 123         /* update the index with the given tree's info
 124          * for all args, expanding wildcards, and exit
 125          * with any non-zero return code.
 126          */
 127         return 0;
 128 }
 129
 130 static int skip_same_name(const struct cache_entry *ce, int pos)
 131 {
 132         while (++pos < active_nr &&
 133                !strcmp(active_cache[pos]->name, ce->name))
 134                 ; /* skip */
 135         return pos;
 136 }
 137
 138 static int check_stage(int stage, const struct cache_entry *ce, int pos)
 139 {
 140         while (pos < active_nr &&
 141                !strcmp(active_cache[pos]->name, ce->name)) {
 142                 if (ce_stage(active_cache[pos]) == stage)
 143                         return 0;
 144                 pos++;
 145         }
 146         if (stage == 2)
 147                 return error(_("path '%s' does not have our version"), ce->name);
 148         else
 149                 return error(_("path '%s' does not have their version"), ce->name);
 150 }
 151
 152 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
 153 {
 154         unsigned seen = 0;
 155         const char *name = ce->name;
 156
 157         while (pos < active_nr) {
 158                 ce = active_cache[pos];
 159                 if (strcmp(name, ce->name))
 160                         break;
 161                 seen |= (1 << ce_stage(ce));
 162                 pos++;
 163         }
 164         if ((stages & seen) != stages)
 165                 return error(_("path '%s' does not have all necessary versions"),
 166                              name);
 167         return 0;
 168 }
 169
 170 static int checkout_stage(int stage, const struct cache_entry *ce, int pos,
 171                           const struct checkout *state, int *nr_checkouts)
 172 {
 173         while (pos < active_nr &&
 174                !strcmp(active_cache[pos]->name, ce->name)) {
 175                 if (ce_stage(active_cache[pos]) == stage)
 176                         return checkout_entry(active_cache[pos], state,
 177                                               NULL, nr_checkouts);
 178                 pos++;
 179         }
 180         if (stage == 2)
 181                 return error(_("path '%s' does not have our version"), ce->name);
 182         else
 183                 return error(_("path '%s' does not have their version"), ce->name);
 184 }
 185
 186 static int checkout_merged(int pos, const struct checkout *state, int *nr_checkouts)
 187 {
 188         struct cache_entry *ce = active_cache[pos];
 189         const char *path = ce->name;
 190         mmfile_t ancestor, ours, theirs;
 191         int status;
 192         struct object_id oid;
 193         mmbuffer_t result_buf;
 194         struct object_id threeway[3];
 195         unsigned mode = 0;
 196
 197         memset(threeway, 0, sizeof(threeway));
 198         while (pos < active_nr) {
 199                 int stage;
 200                 stage = ce_stage(ce);
 201                 if (!stage || strcmp(path, ce->name))
 202                         break;
 203                 oidcpy(&threeway[stage - 1], &ce->oid);
 204                 if (stage == 2)
 205                         mode = create_ce_mode(ce->ce_mode);
 206                 pos++;
 207                 ce = active_cache[pos];
 208         }
 209         if (is_null_oid(&threeway[1]) || is_null_oid(&threeway[2]))
 210                 return error(_("path '%s' does not have necessary versions"), path);
 211
 212         read_mmblob(&ancestor, &threeway[0]);
 213         read_mmblob(&ours, &threeway[1]);
 214         read_mmblob(&theirs, &threeway[2]);
 215
 216         /*
 217          * NEEDSWORK: re-create conflicts from merges with
 218          * merge.renormalize set, too
 219          */
 220         status = ll_merge(&result_buf, path, &ancestor, "base",
 221                           &ours, "ours", &theirs, "theirs",
 222                           state->istate, NULL);
 223         free(ancestor.ptr);
 224         free(ours.ptr);
 225         free(theirs.ptr);
 226         if (status < 0 || !result_buf.ptr) {
 227                 free(result_buf.ptr);
 228                 return error(_("path '%s': cannot merge"), path);
 229         }
 230
 231         /*
 232          * NEEDSWORK:
 233          * There is absolutely no reason to write this as a blob object
 234          * and create a phony cache entry.  This hack is primarily to get
 235          * to the write_entry() machinery that massages the contents to
 236          * work-tree format and writes out which only allows it for a
 237          * cache entry.  The code in write_entry() needs to be refactored
 238          * to allow us to feed a <buffer, size, mode> instead of a cache
 239          * entry.  Such a refactoring would help merge_recursive as well
 240          * (it also writes the merge result to the object database even
 241          * when it may contain conflicts).
 242          */
 243         if (write_object_file(result_buf.ptr, result_buf.size, blob_type, &oid))
 244                 die(_("Unable to add merge result for '%s'"), path);
 245         free(result_buf.ptr);
 246         ce = make_transient_cache_entry(mode, &oid, path, 2);
 247         if (!ce)
 248                 die(_("make_cache_entry failed for path '%s'"), path);
 249         status = checkout_entry(ce, state, NULL, nr_checkouts);
 250         discard_cache_entry(ce);
 251         return status;
 252 }
 253
 254 static int checkout_paths(const struct checkout_opts *opts,
 255                           const char *revision)
 256 {
 257         int pos;
 258         struct checkout state = CHECKOUT_INIT;
 259         static char *ps_matched;
 260         struct object_id rev;
 261         struct commit *head;
 262         int errs = 0;
 263         struct lock_file lock_file = LOCK_INIT;
 264         int nr_checkouts = 0, nr_unmerged = 0;
 265
 266         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 267                 die(_("'%s' cannot be used with updating paths"), "--track");
 268
 269         if (opts->new_branch_log)
 270                 die(_("'%s' cannot be used with updating paths"), "-l");
 271
 272         if (opts->force && opts->patch_mode)
 273                 die(_("'%s' cannot be used with updating paths"), "-f");
 274
 275         if (opts->force_detach)
 276                 die(_("'%s' cannot be used with updating paths"), "--detach");
 277
 278         if (opts->merge && opts->patch_mode)
 279                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 280
 281         if (opts->force && opts->merge)
 282                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 283
 284         if (opts->new_branch)
 285                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 286                     opts->new_branch);
 287
 288         if (opts->patch_mode)
 289                 return run_add_interactive(revision, "--patch=checkout",
 290                                            &opts->pathspec);
 291
 292         repo_hold_locked_index(the_repository, &lock_file, LOCK_DIE_ON_ERROR);
 293         if (read_cache_preload(&opts->pathspec) < 0)
 294                 return error(_("index file corrupt"));
 295
 296         if (opts->source_tree)
 297                 read_tree_some(opts->source_tree, &opts->pathspec);
 298
 299         ps_matched = xcalloc(opts->pathspec.nr, 1);
 300
 301         /*
 302          * Make sure all pathspecs participated in locating the paths
 303          * to be checked out.
 304          */
 305         for (pos = 0; pos < active_nr; pos++) {
 306                 struct cache_entry *ce = active_cache[pos];
 307                 ce->ce_flags &= ~CE_MATCHED;
 308                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 309                         continue;
 310                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 311                         /*
 312                          * "git checkout tree-ish -- path", but this entry
 313                          * is in the original index; it will not be checked
 314                          * out to the working tree and it does not matter
 315                          * if pathspec matched this entry.  We will not do
 316                          * anything to this entry at all.
 317                          */
 318                         continue;
 319                 /*
 320                  * Either this entry came from the tree-ish we are
 321                  * checking the paths out of, or we are checking out
 322                  * of the index.
 323                  *
 324                  * If it comes from the tree-ish, we already know it
 325                  * matches the pathspec and could just stamp
 326                  * CE_MATCHED to it from update_some(). But we still
 327                  * need ps_matched and read_tree_recursive (and
 328                  * eventually tree_entry_interesting) cannot fill
 329                  * ps_matched yet. Once it can, we can avoid calling
 330                  * match_pathspec() for _all_ entries when
 331                  * opts->source_tree != NULL.
 332                  */
 333                 if (ce_path_match(&the_index, ce, &opts->pathspec, ps_matched))
 334                         ce->ce_flags |= CE_MATCHED;
 335         }
 336
 337         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
 338                 free(ps_matched);
 339                 return 1;
 340         }
 341         free(ps_matched);
 342
 343         /* "checkout -m path" to recreate conflicted state */
 344         if (opts->merge)
 345                 unmerge_marked_index(&the_index);
 346
 347         /* Any unmerged paths? */
 348         for (pos = 0; pos < active_nr; pos++) {
 349                 const struct cache_entry *ce = active_cache[pos];
 350                 if (ce->ce_flags & CE_MATCHED) {
 351                         if (!ce_stage(ce))
 352                                 continue;
 353                         if (opts->force) {
 354                                 warning(_("path '%s' is unmerged"), ce->name);
 355                         } else if (opts->writeout_stage) {
 356                                 errs |= check_stage(opts->writeout_stage, ce, pos);
 357                         } else if (opts->merge) {
 358                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 359                         } else {
 360                                 errs = 1;
 361                                 error(_("path '%s' is unmerged"), ce->name);
 362                         }
 363                         pos = skip_same_name(ce, pos) - 1;
 364                 }
 365         }
 366         if (errs)
 367                 return 1;
 368
 369         /* Now we are committed to check them out */
 370         state.force = 1;
 371         state.refresh_cache = 1;
 372         state.istate = &the_index;
 373
 374         enable_delayed_checkout(&state);
 375         for (pos = 0; pos < active_nr; pos++) {
 376                 struct cache_entry *ce = active_cache[pos];
 377                 if (ce->ce_flags & CE_MATCHED) {
 378                         if (!ce_stage(ce)) {
 379                                 errs |= checkout_entry(ce, &state,
 380                                                        NULL, &nr_checkouts);
 381                                 continue;
 382                         }
 383                         if (opts->writeout_stage)
 384                                 errs |= checkout_stage(opts->writeout_stage,
 385                                                        ce, pos,
 386                                                        &state, &nr_checkouts);
 387                         else if (opts->merge)
 388                                 errs |= checkout_merged(pos, &state,
 389                                                         &nr_unmerged);
 390                         pos = skip_same_name(ce, pos) - 1;
 391                 }
 392         }
 393         errs |= finish_delayed_checkout(&state, &nr_checkouts);
 394
 395         if (opts->count_checkout_paths) {
 396                 if (nr_unmerged)
 397                         fprintf_ln(stderr, Q_("Recreated %d merge conflict",
 398                                               "Recreated %d merge conflicts",
 399                                               nr_unmerged),
 400                                    nr_unmerged);
 401                 if (opts->source_tree)
 402                         fprintf_ln(stderr, Q_("Updated %d path from %s",
 403                                               "Updated %d paths from %s",
 404                                               nr_checkouts),
 405                                    nr_checkouts,
 406                                    find_unique_abbrev(&opts->source_tree->object.oid,
 407                                                       DEFAULT_ABBREV));
 408                 else if (!nr_unmerged || nr_checkouts)
 409                         fprintf_ln(stderr, Q_("Updated %d path from the index",
 410                                               "Updated %d paths from the index",
 411                                               nr_checkouts),
 412                                    nr_checkouts);
 413         }
 414
 415         if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 416                 die(_("unable to write new index file"));
 417
 418         read_ref_full("HEAD", 0, &rev, NULL);
 419         head = lookup_commit_reference_gently(the_repository, &rev, 1);
 420
 421         errs |= post_checkout_hook(head, head, 0);
 422         return errs;
 423 }
 424
 425 static void show_local_changes(struct object *head,
 426                                const struct diff_options *opts)
 427 {
 428         struct rev_info rev;
 429         /* I think we want full paths, even if we're in a subdirectory. */
 430         repo_init_revisions(the_repository, &rev, NULL);
 431         rev.diffopt.flags = opts->flags;
 432         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 433         diff_setup_done(&rev.diffopt);
 434         add_pending_object(&rev, head, NULL);
 435         run_diff_index(&rev, 0);
 436 }
 437
 438 static void describe_detached_head(const char *msg, struct commit *commit)
 439 {
 440         struct strbuf sb = STRBUF_INIT;
 441
 442         if (!parse_commit(commit))
 443                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 444         if (print_sha1_ellipsis()) {
 445                 fprintf(stderr, "%s %s... %s\n", msg,
 446                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
 447         } else {
 448                 fprintf(stderr, "%s %s %s\n", msg,
 449                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV), sb.buf);
 450         }
 451         strbuf_release(&sb);
 452 }
 453
 454 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 455                       int worktree, int *writeout_error)
 456 {
 457         struct unpack_trees_options opts;
 458         struct tree_desc tree_desc;
 459
 460         memset(&opts, 0, sizeof(opts));
 461         opts.head_idx = -1;
 462         opts.update = worktree;
 463         opts.skip_unmerged = !worktree;
 464         opts.reset = 1;
 465         opts.merge = 1;
 466         opts.fn = oneway_merge;
 467         opts.verbose_update = o->show_progress;
 468         opts.src_index = &the_index;
 469         opts.dst_index = &the_index;
 470         parse_tree(tree);
 471         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 472         switch (unpack_trees(1, &tree_desc, &opts)) {
 473         case -2:
 474                 *writeout_error = 1;
 475                 /*
 476                  * We return 0 nevertheless, as the index is all right
 477                  * and more importantly we have made best efforts to
 478                  * update paths in the work tree, and we cannot revert
 479                  * them.
 480                  */
 481                 /* fallthrough */
 482         case 0:
 483                 return 0;
 484         default:
 485                 return 128;
 486         }
 487 }
 488
 489 struct branch_info {
 490         const char *name; /* The short name used */
 491         const char *path; /* The full name of a real branch */
 492         struct commit *commit; /* The named commit */
 493         /*
 494          * if not null the branch is detached because it's already
 495          * checked out in this checkout
 496          */
 497         char *checkout;
 498 };
 499
 500 static void setup_branch_path(struct branch_info *branch)
 501 {
 502         struct strbuf buf = STRBUF_INIT;
 503
 504         strbuf_branchname(&buf, branch->name, INTERPRET_BRANCH_LOCAL);
 505         if (strcmp(buf.buf, branch->name))
 506                 branch->name = xstrdup(buf.buf);
 507         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 508         branch->path = strbuf_detach(&buf, NULL);
 509 }
 510
 511 /*
 512  * Skip merging the trees, updating the index and working directory if and
 513  * only if we are creating a new branch via "git checkout -b <new_branch>."
 514  */
 515 static int skip_merge_working_tree(const struct checkout_opts *opts,
 516         const struct branch_info *old_branch_info,
 517         const struct branch_info *new_branch_info)
 518 {
 519         /*
 520          * Do the merge if sparse checkout is on and the user has not opted in
 521          * to the optimized behavior
 522          */
 523         if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
 524                 return 0;
 525
 526         /*
 527          * We must do the merge if we are actually moving to a new commit.
 528          */
 529         if (!old_branch_info->commit || !new_branch_info->commit ||
 530                 !oideq(&old_branch_info->commit->object.oid,
 531                        &new_branch_info->commit->object.oid))
 532                 return 0;
 533
 534         /*
 535          * opts->patch_mode cannot be used with switching branches so is
 536          * not tested here
 537          */
 538
 539         /*
 540          * opts->quiet only impacts output so doesn't require a merge
 541          */
 542
 543         /*
 544          * Honor the explicit request for a three-way merge or to throw away
 545          * local changes
 546          */
 547         if (opts->merge || opts->force)
 548                 return 0;
 549
 550         /*
 551          * --detach is documented as "updating the index and the files in the
 552          * working tree" but this optimization skips those steps so fall through
 553          * to the regular code path.
 554          */
 555         if (opts->force_detach)
 556                 return 0;
 557
 558         /*
 559          * opts->writeout_stage cannot be used with switching branches so is
 560          * not tested here
 561          */
 562
 563         /*
 564          * Honor the explicit ignore requests
 565          */
 566         if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
 567                 opts->ignore_other_worktrees)
 568                 return 0;
 569
 570         /*
 571          * opts->show_progress only impacts output so doesn't require a merge
 572          */
 573
 574         /*
 575          * If we aren't creating a new branch any changes or updates will
 576          * happen in the existing branch.  Since that could only be updating
 577          * the index and working directory, we don't want to skip those steps
 578          * or we've defeated any purpose in running the command.
 579          */
 580         if (!opts->new_branch)
 581                 return 0;
 582
 583         /*
 584          * new_branch_force is defined to "create/reset and checkout a branch"
 585          * so needs to go through the merge to do the reset
 586          */
 587         if (opts->new_branch_force)
 588                 return 0;
 589
 590         /*
 591          * A new orphaned branch requrires the index and the working tree to be
 592          * adjusted to <start_point>
 593          */
 594         if (opts->new_orphan_branch)
 595                 return 0;
 596
 597         /*
 598          * Remaining variables are not checkout options but used to track state
 599          */
 600
 601          /*
 602           * Do the merge if this is the initial checkout. We cannot use
 603           * is_cache_unborn() here because the index hasn't been loaded yet
 604           * so cache_nr and timestamp.sec are always zero.
 605           */
 606         if (!file_exists(get_index_file()))
 607                 return 0;
 608
 609         return 1;
 610 }
 611
 612 static int merge_working_tree(const struct checkout_opts *opts,
 613                               struct branch_info *old_branch_info,
 614                               struct branch_info *new_branch_info,
 615                               int *writeout_error)
 616 {
 617         int ret;
 618         struct lock_file lock_file = LOCK_INIT;
 619
 620         hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 621         if (read_cache_preload(NULL) < 0)
 622                 return error(_("index file corrupt"));
 623
 624         resolve_undo_clear();
 625         if (opts->force) {
 626                 ret = reset_tree(get_commit_tree(new_branch_info->commit),
 627                                  opts, 1, writeout_error);
 628                 if (ret)
 629                         return ret;
 630         } else {
 631                 struct tree_desc trees[2];
 632                 struct tree *tree;
 633                 struct unpack_trees_options topts;
 634
 635                 memset(&topts, 0, sizeof(topts));
 636                 topts.head_idx = -1;
 637                 topts.src_index = &the_index;
 638                 topts.dst_index = &the_index;
 639
 640                 setup_unpack_trees_porcelain(&topts, "checkout");
 641
 642                 refresh_cache(REFRESH_QUIET);
 643
 644                 if (unmerged_cache()) {
 645                         error(_("you need to resolve your current index first"));
 646                         return 1;
 647                 }
 648
 649                 /* 2-way merge to the new branch */
 650                 topts.initial_checkout = is_cache_unborn();
 651                 topts.update = 1;
 652                 topts.merge = 1;
 653                 topts.gently = opts->merge && old_branch_info->commit;
 654                 topts.verbose_update = opts->show_progress;
 655                 topts.fn = twoway_merge;
 656                 if (opts->overwrite_ignore) {
 657                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 658                         topts.dir->flags |= DIR_SHOW_IGNORED;
 659                         setup_standard_excludes(topts.dir);
 660                 }
 661                 tree = parse_tree_indirect(old_branch_info->commit ?
 662                                            &old_branch_info->commit->object.oid :
 663                                            the_hash_algo->empty_tree);
 664                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 665                 tree = parse_tree_indirect(&new_branch_info->commit->object.oid);
 666                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 667
 668                 ret = unpack_trees(2, trees, &topts);
 669                 clear_unpack_trees_porcelain(&topts);
 670                 if (ret == -1) {
 671                         /*
 672                          * Unpack couldn't do a trivial merge; either
 673                          * give up or do a real merge, depending on
 674                          * whether the merge flag was used.
 675                          */
 676                         struct tree *result;
 677                         struct tree *work;
 678                         struct merge_options o;
 679                         if (!opts->merge)
 680                                 return 1;
 681
 682                         /*
 683                          * Without old_branch_info->commit, the below is the same as
 684                          * the two-tree unpack we already tried and failed.
 685                          */
 686                         if (!old_branch_info->commit)
 687                                 return 1;
 688
 689                         /* Do more real merge */
 690
 691                         /*
 692                          * We update the index fully, then write the
 693                          * tree from the index, then merge the new
 694                          * branch with the current tree, with the old
 695                          * branch as the base. Then we reset the index
 696                          * (but not the working tree) to the new
 697                          * branch, leaving the working tree as the
 698                          * merged version, but skipping unmerged
 699                          * entries in the index.
 700                          */
 701
 702                         add_files_to_cache(NULL, NULL, 0);
 703                         /*
 704                          * NEEDSWORK: carrying over local changes
 705                          * when branches have different end-of-line
 706                          * normalization (or clean+smudge rules) is
 707                          * a pain; plumb in an option to set
 708                          * o.renormalize?
 709                          */
 710                         init_merge_options(&o, the_repository);
 711                         o.verbosity = 0;
 712                         work = write_tree_from_memory(&o);
 713
 714                         ret = reset_tree(get_commit_tree(new_branch_info->commit),
 715                                          opts, 1,
 716                                          writeout_error);
 717                         if (ret)
 718                                 return ret;
 719                         o.ancestor = old_branch_info->name;
 720                         o.branch1 = new_branch_info->name;
 721                         o.branch2 = "local";
 722                         ret = merge_trees(&o,
 723                                           get_commit_tree(new_branch_info->commit),
 724                                           work,
 725                                           get_commit_tree(old_branch_info->commit),
 726                                           &result);
 727                         if (ret < 0)
 728                                 exit(128);
 729                         ret = reset_tree(get_commit_tree(new_branch_info->commit),
 730                                          opts, 0,
 731                                          writeout_error);
 732                         strbuf_release(&o.obuf);
 733                         if (ret)
 734                                 return ret;
 735                 }
 736         }
 737
 738         if (!active_cache_tree)
 739                 active_cache_tree = cache_tree();
 740
 741         if (!cache_tree_fully_valid(active_cache_tree))
 742                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
 743
 744         if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 745                 die(_("unable to write new index file"));
 746
 747         if (!opts->force && !opts->quiet)
 748                 show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
 749
 750         return 0;
 751 }
 752
 753 static void report_tracking(struct branch_info *new_branch_info)
 754 {
 755         struct strbuf sb = STRBUF_INIT;
 756         struct branch *branch = branch_get(new_branch_info->name);
 757
 758         if (!format_tracking_info(branch, &sb, AHEAD_BEHIND_FULL))
 759                 return;
 760         fputs(sb.buf, stdout);
 761         strbuf_release(&sb);
 762 }
 763
 764 static void update_refs_for_switch(const struct checkout_opts *opts,
 765                                    struct branch_info *old_branch_info,
 766                                    struct branch_info *new_branch_info)
 767 {
 768         struct strbuf msg = STRBUF_INIT;
 769         const char *old_desc, *reflog_msg;
 770         if (opts->new_branch) {
 771                 if (opts->new_orphan_branch) {
 772                         char *refname;
 773
 774                         refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
 775                         if (opts->new_branch_log &&
 776                             !should_autocreate_reflog(refname)) {
 777                                 int ret;
 778                                 struct strbuf err = STRBUF_INIT;
 779
 780                                 ret = safe_create_reflog(refname, 1, &err);
 781                                 if (ret) {
 782                                         fprintf(stderr, _("Can not do reflog for '%s': %s\n"),
 783                                                 opts->new_orphan_branch, err.buf);
 784                                         strbuf_release(&err);
 785                                         free(refname);
 786                                         return;
 787                                 }
 788                                 strbuf_release(&err);
 789                         }
 790                         free(refname);
 791                 }
 792                 else
 793                         create_branch(the_repository,
 794                                       opts->new_branch, new_branch_info->name,
 795                                       opts->new_branch_force ? 1 : 0,
 796                                       opts->new_branch_force ? 1 : 0,
 797                                       opts->new_branch_log,
 798                                       opts->quiet,
 799                                       opts->track);
 800                 new_branch_info->name = opts->new_branch;
 801                 setup_branch_path(new_branch_info);
 802         }
 803
 804         old_desc = old_branch_info->name;
 805         if (!old_desc && old_branch_info->commit)
 806                 old_desc = oid_to_hex(&old_branch_info->commit->object.oid);
 807
 808         reflog_msg = getenv("GIT_REFLOG_ACTION");
 809         if (!reflog_msg)
 810                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 811                         old_desc ? old_desc : "(invalid)", new_branch_info->name);
 812         else
 813                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 814
 815         if (!strcmp(new_branch_info->name, "HEAD") && !new_branch_info->path && !opts->force_detach) {
 816                 /* Nothing to do. */
 817         } else if (opts->force_detach || !new_branch_info->path) {      /* No longer on any branch. */
 818                 update_ref(msg.buf, "HEAD", &new_branch_info->commit->object.oid, NULL,
 819                            REF_NO_DEREF, UPDATE_REFS_DIE_ON_ERR);
 820                 if (!opts->quiet) {
 821                         if (old_branch_info->path &&
 822                             advice_detached_head && !opts->force_detach)
 823                                 detach_advice(new_branch_info->name);
 824                         describe_detached_head(_("HEAD is now at"), new_branch_info->commit);
 825                 }
 826         } else if (new_branch_info->path) {     /* Switch branches. */
 827                 if (create_symref("HEAD", new_branch_info->path, msg.buf) < 0)
 828                         die(_("unable to update HEAD"));
 829                 if (!opts->quiet) {
 830                         if (old_branch_info->path && !strcmp(new_branch_info->path, old_branch_info->path)) {
 831                                 if (opts->new_branch_force)
 832                                         fprintf(stderr, _("Reset branch '%s'\n"),
 833                                                 new_branch_info->name);
 834                                 else
 835                                         fprintf(stderr, _("Already on '%s'\n"),
 836                                                 new_branch_info->name);
 837                         } else if (opts->new_branch) {
 838                                 if (opts->branch_exists)
 839                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new_branch_info->name);
 840                                 else
 841                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new_branch_info->name);
 842                         } else {
 843                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 844                                         new_branch_info->name);
 845                         }
 846                 }
 847                 if (old_branch_info->path && old_branch_info->name) {
 848                         if (!ref_exists(old_branch_info->path) && reflog_exists(old_branch_info->path))
 849                                 delete_reflog(old_branch_info->path);
 850                 }
 851         }
 852         remove_branch_state(the_repository);
 853         strbuf_release(&msg);
 854         if (!opts->quiet &&
 855             (new_branch_info->path || (!opts->force_detach && !strcmp(new_branch_info->name, "HEAD"))))
 856                 report_tracking(new_branch_info);
 857 }
 858
 859 static int add_pending_uninteresting_ref(const char *refname,
 860                                          const struct object_id *oid,
 861                                          int flags, void *cb_data)
 862 {
 863         add_pending_oid(cb_data, refname, oid, UNINTERESTING);
 864         return 0;
 865 }
 866
 867 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 868 {
 869         strbuf_addstr(sb, "  ");
 870         strbuf_add_unique_abbrev(sb, &commit->object.oid, DEFAULT_ABBREV);
 871         strbuf_addch(sb, ' ');
 872         if (!parse_commit(commit))
 873                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 874         strbuf_addch(sb, '\n');
 875 }
 876
 877 #define ORPHAN_CUTOFF 4
 878 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 879 {
 880         struct commit *c, *last = NULL;
 881         struct strbuf sb = STRBUF_INIT;
 882         int lost = 0;
 883         while ((c = get_revision(revs)) != NULL) {
 884                 if (lost < ORPHAN_CUTOFF)
 885                         describe_one_orphan(&sb, c);
 886                 last = c;
 887                 lost++;
 888         }
 889         if (ORPHAN_CUTOFF < lost) {
 890                 int more = lost - ORPHAN_CUTOFF;
 891                 if (more == 1)
 892                         describe_one_orphan(&sb, last);
 893                 else
 894                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 895         }
 896
 897         fprintf(stderr,
 898                 Q_(
 899                 /* The singular version */
 900                 "Warning: you are leaving %d commit behind, "
 901                 "not connected to\n"
 902                 "any of your branches:\n\n"
 903                 "%s\n",
 904                 /* The plural version */
 905                 "Warning: you are leaving %d commits behind, "
 906                 "not connected to\n"
 907                 "any of your branches:\n\n"
 908                 "%s\n",
 909                 /* Give ngettext() the count */
 910                 lost),
 911                 lost,
 912                 sb.buf);
 913         strbuf_release(&sb);
 914
 915         if (advice_detached_head)
 916                 fprintf(stderr,
 917                         Q_(
 918                         /* The singular version */
 919                         "If you want to keep it by creating a new branch, "
 920                         "this may be a good time\nto do so with:\n\n"
 921                         " git branch <new-branch-name> %s\n\n",
 922                         /* The plural version */
 923                         "If you want to keep them by creating a new branch, "
 924                         "this may be a good time\nto do so with:\n\n"
 925                         " git branch <new-branch-name> %s\n\n",
 926                         /* Give ngettext() the count */
 927                         lost),
 928                         find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV));
 929 }
 930
 931 /*
 932  * We are about to leave commit that was at the tip of a detached
 933  * HEAD.  If it is not reachable from any ref, this is the last chance
 934  * for the user to do so without resorting to reflog.
 935  */
 936 static void orphaned_commit_warning(struct commit *old_commit, struct commit *new_commit)
 937 {
 938         struct rev_info revs;
 939         struct object *object = &old_commit->object;
 940
 941         repo_init_revisions(the_repository, &revs, NULL);
 942         setup_revisions(0, NULL, &revs, NULL);
 943
 944         object->flags &= ~UNINTERESTING;
 945         add_pending_object(&revs, object, oid_to_hex(&object->oid));
 946
 947         for_each_ref(add_pending_uninteresting_ref, &revs);
 948         add_pending_oid(&revs, "HEAD", &new_commit->object.oid, UNINTERESTING);
 949
 950         if (prepare_revision_walk(&revs))
 951                 die(_("internal error in revision walk"));
 952         if (!(old_commit->object.flags & UNINTERESTING))
 953                 suggest_reattach(old_commit, &revs);
 954         else
 955                 describe_detached_head(_("Previous HEAD position was"), old_commit);
 956
 957         /* Clean up objects used, as they will be reused. */
 958         clear_commit_marks_all(ALL_REV_FLAGS);
 959 }
 960
 961 static int switch_branches(const struct checkout_opts *opts,
 962                            struct branch_info *new_branch_info)
 963 {
 964         int ret = 0;
 965         struct branch_info old_branch_info;
 966         void *path_to_free;
 967         struct object_id rev;
 968         int flag, writeout_error = 0;
 969         memset(&old_branch_info, 0, sizeof(old_branch_info));
 970         old_branch_info.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
 971         if (old_branch_info.path)
 972                 old_branch_info.commit = lookup_commit_reference_gently(the_repository, &rev, 1);
 973         if (!(flag & REF_ISSYMREF))
 974                 old_branch_info.path = NULL;
 975
 976         if (old_branch_info.path)
 977                 skip_prefix(old_branch_info.path, "refs/heads/", &old_branch_info.name);
 978
 979         if (!new_branch_info->name) {
 980                 new_branch_info->name = "HEAD";
 981                 new_branch_info->commit = old_branch_info.commit;
 982                 if (!new_branch_info->commit)
 983                         die(_("You are on a branch yet to be born"));
 984                 parse_commit_or_die(new_branch_info->commit);
 985         }
 986
 987         /* optimize the "checkout -b <new_branch> path */
 988         if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
 989                 if (!checkout_optimize_new_branch && !opts->quiet) {
 990                         if (read_cache_preload(NULL) < 0)
 991                                 return error(_("index file corrupt"));
 992                         show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
 993                 }
 994         } else {
 995                 ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
 996                 if (ret) {
 997                         free(path_to_free);
 998                         return ret;
 999                 }
1000         }
1001
1002         if (!opts->quiet && !old_branch_info.path && old_branch_info.commit && new_branch_info->commit != old_branch_info.commit)
1003                 orphaned_commit_warning(old_branch_info.commit, new_branch_info->commit);
1004
1005         update_refs_for_switch(opts, &old_branch_info, new_branch_info);
1006
1007         ret = post_checkout_hook(old_branch_info.commit, new_branch_info->commit, 1);
1008         free(path_to_free);
1009         return ret || writeout_error;
1010 }
1011
1012 static int git_checkout_config(const char *var, const char *value, void *cb)
1013 {
1014         if (!strcmp(var, "checkout.optimizenewbranch")) {
1015                 checkout_optimize_new_branch = git_config_bool(var, value);
1016                 return 0;
1017         }
1018
1019         if (!strcmp(var, "diff.ignoresubmodules")) {
1020                 struct checkout_opts *opts = cb;
1021                 handle_ignore_submodules_arg(&opts->diff_options, value);
1022                 return 0;
1023         }
1024
1025         if (starts_with(var, "submodule."))
1026                 return git_default_submodule_config(var, value, NULL);
1027
1028         return git_xmerge_config(var, value, NULL);
1029 }
1030
1031 static int parse_branchname_arg(int argc, const char **argv,
1032                                 int dwim_new_local_branch_ok,
1033                                 struct branch_info *new_branch_info,
1034                                 struct checkout_opts *opts,
1035                                 struct object_id *rev,
1036                                 int *dwim_remotes_matched)
1037 {
1038         struct tree **source_tree = &opts->source_tree;
1039         const char **new_branch = &opts->new_branch;
1040         int argcount = 0;
1041         struct object_id branch_rev;
1042         const char *arg;
1043         int dash_dash_pos;
1044         int has_dash_dash = 0;
1045         int i;
1046
1047         /*
1048          * case 1: git checkout <ref> -- [<paths>]
1049          *
1050          *   <ref> must be a valid tree, everything after the '--' must be
1051          *   a path.
1052          *
1053          * case 2: git checkout -- [<paths>]
1054          *
1055          *   everything after the '--' must be paths.
1056          *
1057          * case 3: git checkout <something> [--]
1058          *
1059          *   (a) If <something> is a commit, that is to
1060          *       switch to the branch or detach HEAD at it.  As a special case,
1061          *       if <something> is A...B (missing A or B means HEAD but you can
1062          *       omit at most one side), and if there is a unique merge base
1063          *       between A and B, A...B names that merge base.
1064          *
1065          *   (b) If <something> is _not_ a commit, either "--" is present
1066          *       or <something> is not a path, no -t or -b was given, and
1067          *       and there is a tracking branch whose name is <something>
1068          *       in one and only one remote (or if the branch exists on the
1069          *       remote named in checkout.defaultRemote), then this is a
1070          *       short-hand to fork local <something> from that
1071          *       remote-tracking branch.
1072          *
1073          *   (c) Otherwise, if "--" is present, treat it like case (1).
1074          *
1075          *   (d) Otherwise :
1076          *       - if it's a reference, treat it like case (1)
1077          *       - else if it's a path, treat it like case (2)
1078          *       - else: fail.
1079          *
1080          * case 4: git checkout <something> <paths>
1081          *
1082          *   The first argument must not be ambiguous.
1083          *   - If it's *only* a reference, treat it like case (1).
1084          *   - If it's only a path, treat it like case (2).
1085          *   - else: fail.
1086          *
1087          */
1088         if (!argc)
1089                 return 0;
1090
1091         arg = argv[0];
1092         dash_dash_pos = -1;
1093         for (i = 0; i < argc; i++) {
1094                 if (!strcmp(argv[i], "--")) {
1095                         dash_dash_pos = i;
1096                         break;
1097                 }
1098         }
1099         if (dash_dash_pos == 0)
1100                 return 1; /* case (2) */
1101         else if (dash_dash_pos == 1)
1102                 has_dash_dash = 1; /* case (3) or (1) */
1103         else if (dash_dash_pos >= 2)
1104                 die(_("only one reference expected, %d given."), dash_dash_pos);
1105         opts->count_checkout_paths = !opts->quiet && !has_dash_dash;
1106
1107         if (!strcmp(arg, "-"))
1108                 arg = "@{-1}";
1109
1110         if (get_oid_mb(arg, rev)) {
1111                 /*
1112                  * Either case (3) or (4), with <something> not being
1113                  * a commit, or an attempt to use case (1) with an
1114                  * invalid ref.
1115                  *
1116                  * It's likely an error, but we need to find out if
1117                  * we should auto-create the branch, case (3).(b).
1118                  */
1119                 int recover_with_dwim = dwim_new_local_branch_ok;
1120
1121                 int could_be_checkout_paths = !has_dash_dash &&
1122                         check_filename(opts->prefix, arg);
1123
1124                 if (!has_dash_dash && !no_wildcard(arg))
1125                         recover_with_dwim = 0;
1126
1127                 /*
1128                  * Accept "git checkout foo" and "git checkout foo --"
1129                  * as candidates for dwim.
1130                  */
1131                 if (!(argc == 1 && !has_dash_dash) &&
1132                     !(argc == 2 && has_dash_dash))
1133                         recover_with_dwim = 0;
1134
1135                 if (recover_with_dwim) {
1136                         const char *remote = unique_tracking_name(arg, rev,
1137                                                                   dwim_remotes_matched);
1138                         if (remote) {
1139                                 if (could_be_checkout_paths)
1140                                         die(_("'%s' could be both a local file and a tracking branch.\n"
1141                                               "Please use -- (and optionally --no-guess) to disambiguate"),
1142                                             arg);
1143                                 *new_branch = arg;
1144                                 arg = remote;
1145                                 /* DWIMmed to create local branch, case (3).(b) */
1146                         } else {
1147                                 recover_with_dwim = 0;
1148                         }
1149                 }
1150
1151                 if (!recover_with_dwim) {
1152                         if (has_dash_dash)
1153                                 die(_("invalid reference: %s"), arg);
1154                         return argcount;
1155                 }
1156         }
1157
1158         /* we can't end up being in (2) anymore, eat the argument */
1159         argcount++;
1160         argv++;
1161         argc--;
1162
1163         new_branch_info->name = arg;
1164         setup_branch_path(new_branch_info);
1165
1166         if (!check_refname_format(new_branch_info->path, 0) &&
1167             !read_ref(new_branch_info->path, &branch_rev))
1168                 oidcpy(rev, &branch_rev);
1169         else
1170                 new_branch_info->path = NULL; /* not an existing branch */
1171
1172         new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
1173         if (!new_branch_info->commit) {
1174                 /* not a commit */
1175                 *source_tree = parse_tree_indirect(rev);
1176         } else {
1177                 parse_commit_or_die(new_branch_info->commit);
1178                 *source_tree = get_commit_tree(new_branch_info->commit);
1179         }
1180
1181         if (!*source_tree)                   /* case (1): want a tree */
1182                 die(_("reference is not a tree: %s"), arg);
1183         if (!has_dash_dash) {   /* case (3).(d) -> (1) */
1184                 /*
1185                  * Do not complain the most common case
1186                  *      git checkout branch
1187                  * even if there happen to be a file called 'branch';
1188                  * it would be extremely annoying.
1189                  */
1190                 if (argc)
1191                         verify_non_filename(opts->prefix, arg);
1192         } else {
1193                 argcount++;
1194                 argv++;
1195                 argc--;
1196         }
1197
1198         return argcount;
1199 }
1200
1201 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1202 {
1203         int status;
1204         struct strbuf branch_ref = STRBUF_INIT;
1205
1206         if (!opts->new_branch)
1207                 die(_("You are on a branch yet to be born"));
1208         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1209         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1210         strbuf_release(&branch_ref);
1211         if (!opts->quiet)
1212                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1213                         opts->new_branch);
1214         return status;
1215 }
1216
1217 static int checkout_branch(struct checkout_opts *opts,
1218                            struct branch_info *new_branch_info)
1219 {
1220         if (opts->pathspec.nr)
1221                 die(_("paths cannot be used with switching branches"));
1222
1223         if (opts->patch_mode)
1224                 die(_("'%s' cannot be used with switching branches"),
1225                     "--patch");
1226
1227         if (opts->writeout_stage)
1228                 die(_("'%s' cannot be used with switching branches"),
1229                     "--ours/--theirs");
1230
1231         if (opts->force && opts->merge)
1232                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1233
1234         if (opts->force_detach && opts->new_branch)
1235                 die(_("'%s' cannot be used with '%s'"),
1236                     "--detach", "-b/-B/--orphan");
1237
1238         if (opts->new_orphan_branch) {
1239                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1240                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1241         } else if (opts->force_detach) {
1242                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1243                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1244         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1245                 opts->track = git_branch_track;
1246
1247         if (new_branch_info->name && !new_branch_info->commit)
1248                 die(_("Cannot switch branch to a non-commit '%s'"),
1249                     new_branch_info->name);
1250
1251         if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
1252             !opts->ignore_other_worktrees) {
1253                 int flag;
1254                 char *head_ref = resolve_refdup("HEAD", 0, NULL, &flag);
1255                 if (head_ref &&
1256                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new_branch_info->path)))
1257                         die_if_checked_out(new_branch_info->path, 1);
1258                 free(head_ref);
1259         }
1260
1261         if (!new_branch_info->commit && opts->new_branch) {
1262                 struct object_id rev;
1263                 int flag;
1264
1265                 if (!read_ref_full("HEAD", 0, &rev, &flag) &&
1266                     (flag & REF_ISSYMREF) && is_null_oid(&rev))
1267                         return switch_unborn_to_new_branch(opts);
1268         }
1269         return switch_branches(opts, new_branch_info);
1270 }
1271
1272 int cmd_checkout(int argc, const char **argv, const char *prefix)
1273 {
1274         struct checkout_opts opts;
1275         struct branch_info new_branch_info;
1276         char *conflict_style = NULL;
1277         int dwim_new_local_branch, no_dwim_new_local_branch = 0;
1278         int dwim_remotes_matched = 0;
1279         struct option options[] = {
1280                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1281                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1282                            N_("create and checkout a new branch")),
1283                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1284                            N_("create/reset and checkout a branch")),
1285                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1286                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
1287                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1288                         BRANCH_TRACK_EXPLICIT),
1289                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1290                 OPT_SET_INT_F('2', "ours", &opts.writeout_stage,
1291                               N_("checkout our version for unmerged files"),
1292                               2, PARSE_OPT_NONEG),
1293                 OPT_SET_INT_F('3', "theirs", &opts.writeout_stage,
1294                               N_("checkout their version for unmerged files"),
1295                               3, PARSE_OPT_NONEG),
1296                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)"),
1297                            PARSE_OPT_NOCOMPLETE),
1298                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1299                 OPT_BOOL_F(0, "overwrite-ignore", &opts.overwrite_ignore,
1300                            N_("update ignored files (default)"),
1301                            PARSE_OPT_NOCOMPLETE),
1302                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1303                            N_("conflict style (merge or diff3)")),
1304                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1305                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1306                          N_("do not limit pathspecs to sparse entries only")),
1307                 OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
1308                          N_("do not second guess 'git checkout <no-such-branch>'")),
1309                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1310                          N_("do not check if another worktree is holding the given ref")),
1311                 { OPTION_CALLBACK, 0, "recurse-submodules", NULL,
1312                             "checkout", "control recursive updating of submodules",
1313                             PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
1314                 OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
1315                 OPT_END(),
1316         };
1317
1318         memset(&opts, 0, sizeof(opts));
1319         memset(&new_branch_info, 0, sizeof(new_branch_info));
1320         opts.overwrite_ignore = 1;
1321         opts.prefix = prefix;
1322         opts.show_progress = -1;
1323
1324         git_config(git_checkout_config, &opts);
1325
1326         opts.track = BRANCH_TRACK_UNSPECIFIED;
1327
1328         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1329                              PARSE_OPT_KEEP_DASHDASH);
1330
1331         dwim_new_local_branch = !no_dwim_new_local_branch;
1332         if (opts.show_progress < 0) {
1333                 if (opts.quiet)
1334                         opts.show_progress = 0;
1335                 else
1336                         opts.show_progress = isatty(2);
1337         }
1338
1339         if (conflict_style) {
1340                 opts.merge = 1; /* implied */
1341                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1342         }
1343
1344         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1345                 die(_("-b, -B and --orphan are mutually exclusive"));
1346
1347         /*
1348          * From here on, new_branch will contain the branch to be checked out,
1349          * and new_branch_force and new_orphan_branch will tell us which one of
1350          * -b/-B/--orphan is being used.
1351          */
1352         if (opts.new_branch_force)
1353                 opts.new_branch = opts.new_branch_force;
1354
1355         if (opts.new_orphan_branch)
1356                 opts.new_branch = opts.new_orphan_branch;
1357
1358         /* --track without -b/-B/--orphan should DWIM */
1359         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1360                 const char *argv0 = argv[0];
1361                 if (!argc || !strcmp(argv0, "--"))
1362                         die(_("--track needs a branch name"));
1363                 skip_prefix(argv0, "refs/", &argv0);
1364                 skip_prefix(argv0, "remotes/", &argv0);
1365                 argv0 = strchr(argv0, '/');
1366                 if (!argv0 || !argv0[1])
1367                         die(_("missing branch name; try -b"));
1368                 opts.new_branch = argv0 + 1;
1369         }
1370
1371         /*
1372          * Extract branch name from command line arguments, so
1373          * all that is left is pathspecs.
1374          *
1375          * Handle
1376          *
1377          *  1) git checkout <tree> -- [<paths>]
1378          *  2) git checkout -- [<paths>]
1379          *  3) git checkout <something> [<paths>]
1380          *
1381          * including "last branch" syntax and DWIM-ery for names of
1382          * remote branches, erroring out for invalid or ambiguous cases.
1383          */
1384         if (argc) {
1385                 struct object_id rev;
1386                 int dwim_ok =
1387                         !opts.patch_mode &&
1388                         dwim_new_local_branch &&
1389                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1390                         !opts.new_branch;
1391                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1392                                              &new_branch_info, &opts, &rev,
1393                                              &dwim_remotes_matched);
1394                 argv += n;
1395                 argc -= n;
1396         }
1397
1398         if (argc) {
1399                 parse_pathspec(&opts.pathspec, 0,
1400                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1401                                prefix, argv);
1402
1403                 if (!opts.pathspec.nr)
1404                         die(_("invalid path specification"));
1405
1406                 /*
1407                  * Try to give more helpful suggestion.
1408                  * new_branch && argc > 1 will be caught later.
1409                  */
1410                 if (opts.new_branch && argc == 1)
1411                         die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
1412                                 argv[0], opts.new_branch);
1413
1414                 if (opts.force_detach)
1415                         die(_("git checkout: --detach does not take a path argument '%s'"),
1416                             argv[0]);
1417
1418                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1419                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1420                               "checking out of the index."));
1421         }
1422
1423         if (opts.new_branch) {
1424                 struct strbuf buf = STRBUF_INIT;
1425
1426                 if (opts.new_branch_force)
1427                         opts.branch_exists = validate_branchname(opts.new_branch, &buf);
1428                 else
1429                         opts.branch_exists =
1430                                 validate_new_branchname(opts.new_branch, &buf, 0);
1431                 strbuf_release(&buf);
1432         }
1433
1434         UNLEAK(opts);
1435         if (opts.patch_mode || opts.pathspec.nr) {
1436                 int ret = checkout_paths(&opts, new_branch_info.name);
1437                 if (ret && dwim_remotes_matched > 1 &&
1438                     advice_checkout_ambiguous_remote_branch_name)
1439                         advise(_("'%s' matched more than one remote tracking branch.\n"
1440                                  "We found %d remotes with a reference that matched. So we fell back\n"
1441                                  "on trying to resolve the argument as a path, but failed there too!\n"
1442                                  "\n"
1443                                  "If you meant to check out a remote tracking branch on, e.g. 'origin',\n"
1444                                  "you can do so by fully qualifying the name with the --track option:\n"
1445                                  "\n"
1446                                  "    git checkout --track origin/<name>\n"
1447                                  "\n"
1448                                  "If you'd like to always have checkouts of an ambiguous <name> prefer\n"
1449                                  "one remote, e.g. the 'origin' remote, consider setting\n"
1450                                  "checkout.defaultRemote=origin in your config."),
1451                                argv[0],
1452                                dwim_remotes_matched);
1453                 return ret;
1454         } else {
1455                 return checkout_branch(&opts, &new_branch_info);
1456         }
1457 }