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