builtin/checkout.c

   1 #include "cache.h"
   2 #include "builtin.h"
   3 #include "parse-options.h"
   4 #include "refs.h"
   5 #include "commit.h"
   6 #include "tree.h"
   7 #include "tree-walk.h"
   8 #include "cache-tree.h"
   9 #include "unpack-trees.h"
  10 #include "dir.h"
  11 #include "run-command.h"
  12 #include "merge-recursive.h"
  13 #include "branch.h"
  14 #include "diff.h"
  15 #include "revision.h"
  16 #include "remote.h"
  17 #include "blob.h"
  18 #include "xdiff-interface.h"
  19 #include "ll-merge.h"
  20 #include "resolve-undo.h"
  21 #include "submodule.h"
  22
  23 static const char * const checkout_usage[] = {
  24         "git checkout [options] <branch>",
  25         "git checkout [options] [<branch>] -- <file>...",
  26         NULL,
  27 };
  28
  29 struct checkout_opts {
  30         int quiet;
  31         int merge;
  32         int force;
  33         int force_detach;
  34         int writeout_stage;
  35         int writeout_error;
  36
  37         /* not set by parse_options */
  38         int branch_exists;
  39
  40         const char *new_branch;
  41         const char *new_branch_force;
  42         const char *new_orphan_branch;
  43         int new_branch_log;
  44         enum branch_track track;
  45         struct diff_options diff_options;
  46 };
  47
  48 static int post_checkout_hook(struct commit *old, struct commit *new,
  49                               int changed)
  50 {
  51         return run_hook(NULL, "post-checkout",
  52                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
  53                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
  54                         changed ? "1" : "0", NULL);
  55         /* "new" can be NULL when checking out from the index before
  56            a commit exists. */
  57
  58 }
  59
  60 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  61                 const char *pathname, unsigned mode, int stage, void *context)
  62 {
  63         int len;
  64         struct cache_entry *ce;
  65
  66         if (S_ISDIR(mode))
  67                 return READ_TREE_RECURSIVE;
  68
  69         len = baselen + strlen(pathname);
  70         ce = xcalloc(1, cache_entry_size(len));
  71         hashcpy(ce->sha1, sha1);
  72         memcpy(ce->name, base, baselen);
  73         memcpy(ce->name + baselen, pathname, len - baselen);
  74         ce->ce_flags = create_ce_flags(len, 0);
  75         ce->ce_mode = create_ce_mode(mode);
  76         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  77         return 0;
  78 }
  79
  80 static int read_tree_some(struct tree *tree, const char **pathspec)
  81 {
  82         struct pathspec ps;
  83         init_pathspec(&ps, pathspec);
  84         read_tree_recursive(tree, "", 0, 0, &ps, update_some, NULL);
  85         free_pathspec(&ps);
  86
  87         /* update the index with the given tree's info
  88          * for all args, expanding wildcards, and exit
  89          * with any non-zero return code.
  90          */
  91         return 0;
  92 }
  93
  94 static int skip_same_name(struct cache_entry *ce, int pos)
  95 {
  96         while (++pos < active_nr &&
  97                !strcmp(active_cache[pos]->name, ce->name))
  98                 ; /* skip */
  99         return pos;
 100 }
 101
 102 static int check_stage(int stage, struct cache_entry *ce, int pos)
 103 {
 104         while (pos < active_nr &&
 105                !strcmp(active_cache[pos]->name, ce->name)) {
 106                 if (ce_stage(active_cache[pos]) == stage)
 107                         return 0;
 108                 pos++;
 109         }
 110         if (stage == 2)
 111                 return error(_("path '%s' does not have our version"), ce->name);
 112         else
 113                 return error(_("path '%s' does not have their version"), ce->name);
 114 }
 115
 116 static int check_all_stages(struct cache_entry *ce, int pos)
 117 {
 118         if (ce_stage(ce) != 1 ||
 119             active_nr <= pos + 2 ||
 120             strcmp(active_cache[pos+1]->name, ce->name) ||
 121             ce_stage(active_cache[pos+1]) != 2 ||
 122             strcmp(active_cache[pos+2]->name, ce->name) ||
 123             ce_stage(active_cache[pos+2]) != 3)
 124                 return error(_("path '%s' does not have all three versions"),
 125                              ce->name);
 126         return 0;
 127 }
 128
 129 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 130                           struct checkout *state)
 131 {
 132         while (pos < active_nr &&
 133                !strcmp(active_cache[pos]->name, ce->name)) {
 134                 if (ce_stage(active_cache[pos]) == stage)
 135                         return checkout_entry(active_cache[pos], state, NULL);
 136                 pos++;
 137         }
 138         if (stage == 2)
 139                 return error(_("path '%s' does not have our version"), ce->name);
 140         else
 141                 return error(_("path '%s' does not have their version"), ce->name);
 142 }
 143
 144 static int checkout_merged(int pos, struct checkout *state)
 145 {
 146         struct cache_entry *ce = active_cache[pos];
 147         const char *path = ce->name;
 148         mmfile_t ancestor, ours, theirs;
 149         int status;
 150         unsigned char sha1[20];
 151         mmbuffer_t result_buf;
 152
 153         if (ce_stage(ce) != 1 ||
 154             active_nr <= pos + 2 ||
 155             strcmp(active_cache[pos+1]->name, path) ||
 156             ce_stage(active_cache[pos+1]) != 2 ||
 157             strcmp(active_cache[pos+2]->name, path) ||
 158             ce_stage(active_cache[pos+2]) != 3)
 159                 return error(_("path '%s' does not have all 3 versions"), path);
 160
 161         read_mmblob(&ancestor, active_cache[pos]->sha1);
 162         read_mmblob(&ours, active_cache[pos+1]->sha1);
 163         read_mmblob(&theirs, active_cache[pos+2]->sha1);
 164
 165         /*
 166          * NEEDSWORK: re-create conflicts from merges with
 167          * merge.renormalize set, too
 168          */
 169         status = ll_merge(&result_buf, path, &ancestor, "base",
 170                           &ours, "ours", &theirs, "theirs", NULL);
 171         free(ancestor.ptr);
 172         free(ours.ptr);
 173         free(theirs.ptr);
 174         if (status < 0 || !result_buf.ptr) {
 175                 free(result_buf.ptr);
 176                 return error(_("path '%s': cannot merge"), path);
 177         }
 178
 179         /*
 180          * NEEDSWORK:
 181          * There is absolutely no reason to write this as a blob object
 182          * and create a phony cache entry just to leak.  This hack is
 183          * primarily to get to the write_entry() machinery that massages
 184          * the contents to work-tree format and writes out which only
 185          * allows it for a cache entry.  The code in write_entry() needs
 186          * to be refactored to allow us to feed a <buffer, size, mode>
 187          * instead of a cache entry.  Such a refactoring would help
 188          * merge_recursive as well (it also writes the merge result to the
 189          * object database even when it may contain conflicts).
 190          */
 191         if (write_sha1_file(result_buf.ptr, result_buf.size,
 192                             blob_type, sha1))
 193                 die(_("Unable to add merge result for '%s'"), path);
 194         ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
 195                               sha1,
 196                               path, 2, 0);
 197         if (!ce)
 198                 die(_("make_cache_entry failed for path '%s'"), path);
 199         status = checkout_entry(ce, state, NULL);
 200         return status;
 201 }
 202
 203 static int checkout_paths(struct tree *source_tree, const char **pathspec,
 204                           struct checkout_opts *opts)
 205 {
 206         int pos;
 207         struct checkout state;
 208         static char *ps_matched;
 209         unsigned char rev[20];
 210         int flag;
 211         struct commit *head;
 212         int errs = 0;
 213         int stage = opts->writeout_stage;
 214         int merge = opts->merge;
 215         int newfd;
 216         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 217
 218         newfd = hold_locked_index(lock_file, 1);
 219         if (read_cache_preload(pathspec) < 0)
 220                 return error(_("corrupt index file"));
 221
 222         if (source_tree)
 223                 read_tree_some(source_tree, pathspec);
 224
 225         for (pos = 0; pathspec[pos]; pos++)
 226                 ;
 227         ps_matched = xcalloc(1, pos);
 228
 229         for (pos = 0; pos < active_nr; pos++) {
 230                 struct cache_entry *ce = active_cache[pos];
 231                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 232         }
 233
 234         if (report_path_error(ps_matched, pathspec, 0))
 235                 return 1;
 236
 237         /* "checkout -m path" to recreate conflicted state */
 238         if (opts->merge)
 239                 unmerge_cache(pathspec);
 240
 241         /* Any unmerged paths? */
 242         for (pos = 0; pos < active_nr; pos++) {
 243                 struct cache_entry *ce = active_cache[pos];
 244                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 245                         if (!ce_stage(ce))
 246                                 continue;
 247                         if (opts->force) {
 248                                 warning(_("path '%s' is unmerged"), ce->name);
 249                         } else if (stage) {
 250                                 errs |= check_stage(stage, ce, pos);
 251                         } else if (opts->merge) {
 252                                 errs |= check_all_stages(ce, pos);
 253                         } else {
 254                                 errs = 1;
 255                                 error(_("path '%s' is unmerged"), ce->name);
 256                         }
 257                         pos = skip_same_name(ce, pos) - 1;
 258                 }
 259         }
 260         if (errs)
 261                 return 1;
 262
 263         /* Now we are committed to check them out */
 264         memset(&state, 0, sizeof(state));
 265         state.force = 1;
 266         state.refresh_cache = 1;
 267         for (pos = 0; pos < active_nr; pos++) {
 268                 struct cache_entry *ce = active_cache[pos];
 269                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 270                         if (!ce_stage(ce)) {
 271                                 errs |= checkout_entry(ce, &state, NULL);
 272                                 continue;
 273                         }
 274                         if (stage)
 275                                 errs |= checkout_stage(stage, ce, pos, &state);
 276                         else if (merge)
 277                                 errs |= checkout_merged(pos, &state);
 278                         pos = skip_same_name(ce, pos) - 1;
 279                 }
 280         }
 281
 282         if (write_cache(newfd, active_cache, active_nr) ||
 283             commit_locked_index(lock_file))
 284                 die(_("unable to write new index file"));
 285
 286         resolve_ref("HEAD", rev, 0, &flag);
 287         head = lookup_commit_reference_gently(rev, 1);
 288
 289         errs |= post_checkout_hook(head, head, 0);
 290         return errs;
 291 }
 292
 293 static void show_local_changes(struct object *head, struct diff_options *opts)
 294 {
 295         struct rev_info rev;
 296         /* I think we want full paths, even if we're in a subdirectory. */
 297         init_revisions(&rev, NULL);
 298         rev.diffopt.flags = opts->flags;
 299         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 300         if (diff_setup_done(&rev.diffopt) < 0)
 301                 die(_("diff_setup_done failed"));
 302         add_pending_object(&rev, head, NULL);
 303         run_diff_index(&rev, 0);
 304 }
 305
 306 static void describe_detached_head(const char *msg, struct commit *commit)
 307 {
 308         struct strbuf sb = STRBUF_INIT;
 309         parse_commit(commit);
 310         pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 311         fprintf(stderr, "%s %s... %s\n", msg,
 312                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 313         strbuf_release(&sb);
 314 }
 315
 316 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 317 {
 318         struct unpack_trees_options opts;
 319         struct tree_desc tree_desc;
 320
 321         memset(&opts, 0, sizeof(opts));
 322         opts.head_idx = -1;
 323         opts.update = worktree;
 324         opts.skip_unmerged = !worktree;
 325         opts.reset = 1;
 326         opts.merge = 1;
 327         opts.fn = oneway_merge;
 328         opts.verbose_update = !o->quiet;
 329         opts.src_index = &the_index;
 330         opts.dst_index = &the_index;
 331         parse_tree(tree);
 332         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 333         switch (unpack_trees(1, &tree_desc, &opts)) {
 334         case -2:
 335                 o->writeout_error = 1;
 336                 /*
 337                  * We return 0 nevertheless, as the index is all right
 338                  * and more importantly we have made best efforts to
 339                  * update paths in the work tree, and we cannot revert
 340                  * them.
 341                  */
 342         case 0:
 343                 return 0;
 344         default:
 345                 return 128;
 346         }
 347 }
 348
 349 struct branch_info {
 350         const char *name; /* The short name used */
 351         const char *path; /* The full name of a real branch */
 352         struct commit *commit; /* The named commit */
 353 };
 354
 355 static void setup_branch_path(struct branch_info *branch)
 356 {
 357         struct strbuf buf = STRBUF_INIT;
 358
 359         strbuf_branchname(&buf, branch->name);
 360         if (strcmp(buf.buf, branch->name))
 361                 branch->name = xstrdup(buf.buf);
 362         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 363         branch->path = strbuf_detach(&buf, NULL);
 364 }
 365
 366 static int merge_working_tree(struct checkout_opts *opts,
 367                               struct branch_info *old, struct branch_info *new)
 368 {
 369         int ret;
 370         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 371         int newfd = hold_locked_index(lock_file, 1);
 372
 373         if (read_cache_preload(NULL) < 0)
 374                 return error(_("corrupt index file"));
 375
 376         resolve_undo_clear();
 377         if (opts->force) {
 378                 ret = reset_tree(new->commit->tree, opts, 1);
 379                 if (ret)
 380                         return ret;
 381         } else {
 382                 struct tree_desc trees[2];
 383                 struct tree *tree;
 384                 struct unpack_trees_options topts;
 385
 386                 memset(&topts, 0, sizeof(topts));
 387                 topts.head_idx = -1;
 388                 topts.src_index = &the_index;
 389                 topts.dst_index = &the_index;
 390
 391                 setup_unpack_trees_porcelain(&topts, "checkout");
 392
 393                 refresh_cache(REFRESH_QUIET);
 394
 395                 if (unmerged_cache()) {
 396                         error(_("you need to resolve your current index first"));
 397                         return 1;
 398                 }
 399
 400                 /* 2-way merge to the new branch */
 401                 topts.initial_checkout = is_cache_unborn();
 402                 topts.update = 1;
 403                 topts.merge = 1;
 404                 topts.gently = opts->merge && old->commit;
 405                 topts.verbose_update = !opts->quiet;
 406                 topts.fn = twoway_merge;
 407                 topts.dir = xcalloc(1, sizeof(*topts.dir));
 408                 topts.dir->flags |= DIR_SHOW_IGNORED;
 409                 topts.dir->exclude_per_dir = ".gitignore";
 410                 tree = parse_tree_indirect(old->commit ?
 411                                            old->commit->object.sha1 :
 412                                            EMPTY_TREE_SHA1_BIN);
 413                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 414                 tree = parse_tree_indirect(new->commit->object.sha1);
 415                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 416
 417                 ret = unpack_trees(2, trees, &topts);
 418                 if (ret == -1) {
 419                         /*
 420                          * Unpack couldn't do a trivial merge; either
 421                          * give up or do a real merge, depending on
 422                          * whether the merge flag was used.
 423                          */
 424                         struct tree *result;
 425                         struct tree *work;
 426                         struct merge_options o;
 427                         if (!opts->merge)
 428                                 return 1;
 429
 430                         /*
 431                          * Without old->commit, the below is the same as
 432                          * the two-tree unpack we already tried and failed.
 433                          */
 434                         if (!old->commit)
 435                                 return 1;
 436
 437                         /* Do more real merge */
 438
 439                         /*
 440                          * We update the index fully, then write the
 441                          * tree from the index, then merge the new
 442                          * branch with the current tree, with the old
 443                          * branch as the base. Then we reset the index
 444                          * (but not the working tree) to the new
 445                          * branch, leaving the working tree as the
 446                          * merged version, but skipping unmerged
 447                          * entries in the index.
 448                          */
 449
 450                         add_files_to_cache(NULL, NULL, 0);
 451                         /*
 452                          * NEEDSWORK: carrying over local changes
 453                          * when branches have different end-of-line
 454                          * normalization (or clean+smudge rules) is
 455                          * a pain; plumb in an option to set
 456                          * o.renormalize?
 457                          */
 458                         init_merge_options(&o);
 459                         o.verbosity = 0;
 460                         work = write_tree_from_memory(&o);
 461
 462                         ret = reset_tree(new->commit->tree, opts, 1);
 463                         if (ret)
 464                                 return ret;
 465                         o.ancestor = old->name;
 466                         o.branch1 = new->name;
 467                         o.branch2 = "local";
 468                         merge_trees(&o, new->commit->tree, work,
 469                                 old->commit->tree, &result);
 470                         ret = reset_tree(new->commit->tree, opts, 0);
 471                         if (ret)
 472                                 return ret;
 473                 }
 474         }
 475
 476         if (write_cache(newfd, active_cache, active_nr) ||
 477             commit_locked_index(lock_file))
 478                 die(_("unable to write new index file"));
 479
 480         if (!opts->force && !opts->quiet)
 481                 show_local_changes(&new->commit->object, &opts->diff_options);
 482
 483         return 0;
 484 }
 485
 486 static void report_tracking(struct branch_info *new)
 487 {
 488         struct strbuf sb = STRBUF_INIT;
 489         struct branch *branch = branch_get(new->name);
 490
 491         if (!format_tracking_info(branch, &sb))
 492                 return;
 493         fputs(sb.buf, stdout);
 494         strbuf_release(&sb);
 495 }
 496
 497 static void detach_advice(const char *old_path, const char *new_name)
 498 {
 499         const char fmt[] =
 500         "Note: checking out '%s'.\n\n"
 501         "You are in 'detached HEAD' state. You can look around, make experimental\n"
 502         "changes and commit them, and you can discard any commits you make in this\n"
 503         "state without impacting any branches by performing another checkout.\n\n"
 504         "If you want to create a new branch to retain commits you create, you may\n"
 505         "do so (now or later) by using -b with the checkout command again. Example:\n\n"
 506         "  git checkout -b new_branch_name\n\n";
 507
 508         fprintf(stderr, fmt, new_name);
 509 }
 510
 511 static void update_refs_for_switch(struct checkout_opts *opts,
 512                                    struct branch_info *old,
 513                                    struct branch_info *new)
 514 {
 515         struct strbuf msg = STRBUF_INIT;
 516         const char *old_desc;
 517         if (opts->new_branch) {
 518                 if (opts->new_orphan_branch) {
 519                         if (opts->new_branch_log && !log_all_ref_updates) {
 520                                 int temp;
 521                                 char log_file[PATH_MAX];
 522                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 523
 524                                 temp = log_all_ref_updates;
 525                                 log_all_ref_updates = 1;
 526                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
 527                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 528                                             opts->new_orphan_branch);
 529                                         log_all_ref_updates = temp;
 530                                         return;
 531                                 }
 532                                 log_all_ref_updates = temp;
 533                         }
 534                 }
 535                 else
 536                         create_branch(old->name, opts->new_branch, new->name,
 537                                       opts->new_branch_force ? 1 : 0,
 538                                       opts->new_branch_log, opts->track);
 539                 new->name = opts->new_branch;
 540                 setup_branch_path(new);
 541         }
 542
 543         old_desc = old->name;
 544         if (!old_desc && old->commit)
 545                 old_desc = sha1_to_hex(old->commit->object.sha1);
 546         strbuf_addf(&msg, "checkout: moving from %s to %s",
 547                     old_desc ? old_desc : "(invalid)", new->name);
 548
 549         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 550                 /* Nothing to do. */
 551         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 552                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 553                            REF_NODEREF, DIE_ON_ERR);
 554                 if (!opts->quiet) {
 555                         if (old->path && advice_detached_head)
 556                                 detach_advice(old->path, new->name);
 557                         describe_detached_head(_("HEAD is now at"), new->commit);
 558                 }
 559         } else if (new->path) { /* Switch branches. */
 560                 create_symref("HEAD", new->path, msg.buf);
 561                 if (!opts->quiet) {
 562                         if (old->path && !strcmp(new->path, old->path)) {
 563                                 fprintf(stderr, _("Already on '%s'\n"),
 564                                         new->name);
 565                         } else if (opts->new_branch) {
 566                                 if (opts->branch_exists)
 567                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 568                                 else
 569                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 570                         } else {
 571                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 572                                         new->name);
 573                         }
 574                 }
 575                 if (old->path && old->name) {
 576                         char log_file[PATH_MAX], ref_file[PATH_MAX];
 577
 578                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
 579                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
 580                         if (!file_exists(ref_file) && file_exists(log_file))
 581                                 remove_path(log_file);
 582                 }
 583         }
 584         remove_branch_state();
 585         strbuf_release(&msg);
 586         if (!opts->quiet &&
 587             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 588                 report_tracking(new);
 589 }
 590
 591 struct rev_list_args {
 592         int argc;
 593         int alloc;
 594         const char **argv;
 595 };
 596
 597 static void add_one_rev_list_arg(struct rev_list_args *args, const char *s)
 598 {
 599         ALLOC_GROW(args->argv, args->argc + 1, args->alloc);
 600         args->argv[args->argc++] = s;
 601 }
 602
 603 static int add_one_ref_to_rev_list_arg(const char *refname,
 604                                        const unsigned char *sha1,
 605                                        int flags,
 606                                        void *cb_data)
 607 {
 608         add_one_rev_list_arg(cb_data, refname);
 609         return 0;
 610 }
 611
 612 static int clear_commit_marks_from_one_ref(const char *refname,
 613                                       const unsigned char *sha1,
 614                                       int flags,
 615                                       void *cb_data)
 616 {
 617         struct commit *commit = lookup_commit_reference_gently(sha1, 1);
 618         if (commit)
 619                 clear_commit_marks(commit, -1);
 620         return 0;
 621 }
 622
 623 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 624 {
 625         parse_commit(commit);
 626         strbuf_addstr(sb, "  ");
 627         strbuf_addstr(sb,
 628                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 629         strbuf_addch(sb, ' ');
 630         pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 631         strbuf_addch(sb, '\n');
 632 }
 633
 634 #define ORPHAN_CUTOFF 4
 635 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 636 {
 637         struct commit *c, *last = NULL;
 638         struct strbuf sb = STRBUF_INIT;
 639         int lost = 0;
 640         while ((c = get_revision(revs)) != NULL) {
 641                 if (lost < ORPHAN_CUTOFF)
 642                         describe_one_orphan(&sb, c);
 643                 last = c;
 644                 lost++;
 645         }
 646         if (ORPHAN_CUTOFF < lost) {
 647                 int more = lost - ORPHAN_CUTOFF;
 648                 if (more == 1)
 649                         describe_one_orphan(&sb, last);
 650                 else
 651                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 652         }
 653
 654         fprintf(stderr,
 655                 Q_(
 656                 /* The singular version */
 657                 "Warning: you are leaving %d commit behind, "
 658                 "not connected to\n"
 659                 "any of your branches:\n\n"
 660                 "%s\n"
 661                 "If you want to keep it by creating a new branch, "
 662                 "this may be a good time\nto do so with:\n\n"
 663                 " git branch new_branch_name %s\n\n",
 664                 /* The plural version */
 665                 "Warning: you are leaving %d commits behind, "
 666                 "not connected to\n"
 667                 "any of your branches:\n\n"
 668                 "%s\n"
 669                 "If you want to keep them by creating a new branch, "
 670                 "this may be a good time\nto do so with:\n\n"
 671                 " git branch new_branch_name %s\n\n",
 672                 /* Give ngettext() the count */
 673                 lost),
 674                 lost,
 675                 sb.buf,
 676                 sha1_to_hex(commit->object.sha1));
 677         strbuf_release(&sb);
 678 }
 679
 680 /*
 681  * We are about to leave commit that was at the tip of a detached
 682  * HEAD.  If it is not reachable from any ref, this is the last chance
 683  * for the user to do so without resorting to reflog.
 684  */
 685 static void orphaned_commit_warning(struct commit *commit)
 686 {
 687         struct rev_list_args args = { 0, 0, NULL };
 688         struct rev_info revs;
 689
 690         add_one_rev_list_arg(&args, "(internal)");
 691         add_one_rev_list_arg(&args, sha1_to_hex(commit->object.sha1));
 692         add_one_rev_list_arg(&args, "--not");
 693         for_each_ref(add_one_ref_to_rev_list_arg, &args);
 694         add_one_rev_list_arg(&args, "--");
 695         add_one_rev_list_arg(&args, NULL);
 696
 697         init_revisions(&revs, NULL);
 698         if (setup_revisions(args.argc - 1, args.argv, &revs, NULL) != 1)
 699                 die(_("internal error: only -- alone should have been left"));
 700         if (prepare_revision_walk(&revs))
 701                 die(_("internal error in revision walk"));
 702         if (!(commit->object.flags & UNINTERESTING))
 703                 suggest_reattach(commit, &revs);
 704         else
 705                 describe_detached_head(_("Previous HEAD position was"), commit);
 706
 707         clear_commit_marks(commit, -1);
 708         for_each_ref(clear_commit_marks_from_one_ref, NULL);
 709 }
 710
 711 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 712 {
 713         int ret = 0;
 714         struct branch_info old;
 715         unsigned char rev[20];
 716         int flag;
 717         memset(&old, 0, sizeof(old));
 718         old.path = resolve_ref("HEAD", rev, 0, &flag);
 719         old.commit = lookup_commit_reference_gently(rev, 1);
 720         if (!(flag & REF_ISSYMREF))
 721                 old.path = NULL;
 722
 723         if (old.path && !prefixcmp(old.path, "refs/heads/"))
 724                 old.name = old.path + strlen("refs/heads/");
 725
 726         if (!new->name) {
 727                 new->name = "HEAD";
 728                 new->commit = old.commit;
 729                 if (!new->commit)
 730                         die(_("You are on a branch yet to be born"));
 731                 parse_commit(new->commit);
 732         }
 733
 734         ret = merge_working_tree(opts, &old, new);
 735         if (ret)
 736                 return ret;
 737
 738         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 739                 orphaned_commit_warning(old.commit);
 740
 741         update_refs_for_switch(opts, &old, new);
 742
 743         ret = post_checkout_hook(old.commit, new->commit, 1);
 744         return ret || opts->writeout_error;
 745 }
 746
 747 static int git_checkout_config(const char *var, const char *value, void *cb)
 748 {
 749         if (!strcmp(var, "diff.ignoresubmodules")) {
 750                 struct checkout_opts *opts = cb;
 751                 handle_ignore_submodules_arg(&opts->diff_options, value);
 752                 return 0;
 753         }
 754
 755         if (!prefixcmp(var, "submodule."))
 756                 return parse_submodule_config_option(var, value);
 757
 758         return git_xmerge_config(var, value, NULL);
 759 }
 760
 761 static int interactive_checkout(const char *revision, const char **pathspec,
 762                                 struct checkout_opts *opts)
 763 {
 764         return run_add_interactive(revision, "--patch=checkout", pathspec);
 765 }
 766
 767 struct tracking_name_data {
 768         const char *name;
 769         char *remote;
 770         int unique;
 771 };
 772
 773 static int check_tracking_name(const char *refname, const unsigned char *sha1,
 774                                int flags, void *cb_data)
 775 {
 776         struct tracking_name_data *cb = cb_data;
 777         const char *slash;
 778
 779         if (prefixcmp(refname, "refs/remotes/"))
 780                 return 0;
 781         slash = strchr(refname + 13, '/');
 782         if (!slash || strcmp(slash + 1, cb->name))
 783                 return 0;
 784         if (cb->remote) {
 785                 cb->unique = 0;
 786                 return 0;
 787         }
 788         cb->remote = xstrdup(refname);
 789         return 0;
 790 }
 791
 792 static const char *unique_tracking_name(const char *name)
 793 {
 794         struct tracking_name_data cb_data = { NULL, NULL, 1 };
 795         cb_data.name = name;
 796         for_each_ref(check_tracking_name, &cb_data);
 797         if (cb_data.unique)
 798                 return cb_data.remote;
 799         free(cb_data.remote);
 800         return NULL;
 801 }
 802
 803 static int parse_branchname_arg(int argc, const char **argv,
 804                                 int dwim_new_local_branch_ok,
 805                                 struct branch_info *new,
 806                                 struct tree **source_tree,
 807                                 unsigned char rev[20],
 808                                 const char **new_branch)
 809 {
 810         int argcount = 0;
 811         unsigned char branch_rev[20];
 812         const char *arg;
 813         int has_dash_dash;
 814
 815         /*
 816          * case 1: git checkout <ref> -- [<paths>]
 817          *
 818          *   <ref> must be a valid tree, everything after the '--' must be
 819          *   a path.
 820          *
 821          * case 2: git checkout -- [<paths>]
 822          *
 823          *   everything after the '--' must be paths.
 824          *
 825          * case 3: git checkout <something> [<paths>]
 826          *
 827          *   With no paths, if <something> is a commit, that is to
 828          *   switch to the branch or detach HEAD at it.  As a special case,
 829          *   if <something> is A...B (missing A or B means HEAD but you can
 830          *   omit at most one side), and if there is a unique merge base
 831          *   between A and B, A...B names that merge base.
 832          *
 833          *   With no paths, if <something> is _not_ a commit, no -t nor -b
 834          *   was given, and there is a tracking branch whose name is
 835          *   <something> in one and only one remote, then this is a short-hand
 836          *   to fork local <something> from that remote-tracking branch.
 837          *
 838          *   Otherwise <something> shall not be ambiguous.
 839          *   - If it's *only* a reference, treat it like case (1).
 840          *   - If it's only a path, treat it like case (2).
 841          *   - else: fail.
 842          *
 843          */
 844         if (!argc)
 845                 return 0;
 846
 847         if (!strcmp(argv[0], "--"))     /* case (2) */
 848                 return 1;
 849
 850         arg = argv[0];
 851         has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
 852
 853         if (!strcmp(arg, "-"))
 854                 arg = "@{-1}";
 855
 856         if (get_sha1_mb(arg, rev)) {
 857                 if (has_dash_dash)          /* case (1) */
 858                         die(_("invalid reference: %s"), arg);
 859                 if (dwim_new_local_branch_ok &&
 860                     !check_filename(NULL, arg) &&
 861                     argc == 1) {
 862                         const char *remote = unique_tracking_name(arg);
 863                         if (!remote || get_sha1(remote, rev))
 864                                 return argcount;
 865                         *new_branch = arg;
 866                         arg = remote;
 867                         /* DWIMmed to create local branch */
 868                 } else {
 869                         return argcount;
 870                 }
 871         }
 872
 873         /* we can't end up being in (2) anymore, eat the argument */
 874         argcount++;
 875         argv++;
 876         argc--;
 877
 878         new->name = arg;
 879         setup_branch_path(new);
 880
 881         if (check_ref_format(new->path) == CHECK_REF_FORMAT_OK &&
 882             resolve_ref(new->path, branch_rev, 1, NULL))
 883                 hashcpy(rev, branch_rev);
 884         else
 885                 new->path = NULL; /* not an existing branch */
 886
 887         new->commit = lookup_commit_reference_gently(rev, 1);
 888         if (!new->commit) {
 889                 /* not a commit */
 890                 *source_tree = parse_tree_indirect(rev);
 891         } else {
 892                 parse_commit(new->commit);
 893                 *source_tree = new->commit->tree;
 894         }
 895
 896         if (!*source_tree)                   /* case (1): want a tree */
 897                 die(_("reference is not a tree: %s"), arg);
 898         if (!has_dash_dash) {/* case (3 -> 1) */
 899                 /*
 900                  * Do not complain the most common case
 901                  *      git checkout branch
 902                  * even if there happen to be a file called 'branch';
 903                  * it would be extremely annoying.
 904                  */
 905                 if (argc)
 906                         verify_non_filename(NULL, arg);
 907         } else {
 908                 argcount++;
 909                 argv++;
 910                 argc--;
 911         }
 912
 913         return argcount;
 914 }
 915
 916 int cmd_checkout(int argc, const char **argv, const char *prefix)
 917 {
 918         struct checkout_opts opts;
 919         unsigned char rev[20];
 920         struct branch_info new;
 921         struct tree *source_tree = NULL;
 922         char *conflict_style = NULL;
 923         int patch_mode = 0;
 924         int dwim_new_local_branch = 1;
 925         struct option options[] = {
 926                 OPT__QUIET(&opts.quiet, "suppress progress reporting"),
 927                 OPT_STRING('b', NULL, &opts.new_branch, "branch",
 928                            "create and checkout a new branch"),
 929                 OPT_STRING('B', NULL, &opts.new_branch_force, "branch",
 930                            "create/reset and checkout a branch"),
 931                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "create reflog for new branch"),
 932                 OPT_BOOLEAN(0, "detach", &opts.force_detach, "detach the HEAD at named commit"),
 933                 OPT_SET_INT('t', "track",  &opts.track, "set upstream info for new branch",
 934                         BRANCH_TRACK_EXPLICIT),
 935                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, "new branch", "new unparented branch"),
 936                 OPT_SET_INT('2', "ours", &opts.writeout_stage, "checkout our version for unmerged files",
 937                             2),
 938                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, "checkout their version for unmerged files",
 939                             3),
 940                 OPT__FORCE(&opts.force, "force checkout (throw away local modifications)"),
 941                 OPT_BOOLEAN('m', "merge", &opts.merge, "perform a 3-way merge with the new branch"),
 942                 OPT_STRING(0, "conflict", &conflict_style, "style",
 943                            "conflict style (merge or diff3)"),
 944                 OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
 945                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
 946                   "second guess 'git checkout no-such-branch'",
 947                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
 948                 OPT_END(),
 949         };
 950
 951         memset(&opts, 0, sizeof(opts));
 952         memset(&new, 0, sizeof(new));
 953
 954         gitmodules_config();
 955         git_config(git_checkout_config, &opts);
 956
 957         opts.track = BRANCH_TRACK_UNSPECIFIED;
 958
 959         argc = parse_options(argc, argv, prefix, options, checkout_usage,
 960                              PARSE_OPT_KEEP_DASHDASH);
 961
 962         /* we can assume from now on new_branch = !new_branch_force */
 963         if (opts.new_branch && opts.new_branch_force)
 964                 die(_("-B cannot be used with -b"));
 965
 966         /* copy -B over to -b, so that we can just check the latter */
 967         if (opts.new_branch_force)
 968                 opts.new_branch = opts.new_branch_force;
 969
 970         if (patch_mode && (opts.track > 0 || opts.new_branch
 971                            || opts.new_branch_log || opts.merge || opts.force
 972                            || opts.force_detach))
 973                 die (_("--patch is incompatible with all other options"));
 974
 975         if (opts.force_detach && (opts.new_branch || opts.new_orphan_branch))
 976                 die(_("--detach cannot be used with -b/-B/--orphan"));
 977         if (opts.force_detach && 0 < opts.track)
 978                 die(_("--detach cannot be used with -t"));
 979
 980         /* --track without -b should DWIM */
 981         if (0 < opts.track && !opts.new_branch) {
 982                 const char *argv0 = argv[0];
 983                 if (!argc || !strcmp(argv0, "--"))
 984                         die (_("--track needs a branch name"));
 985                 if (!prefixcmp(argv0, "refs/"))
 986                         argv0 += 5;
 987                 if (!prefixcmp(argv0, "remotes/"))
 988                         argv0 += 8;
 989                 argv0 = strchr(argv0, '/');
 990                 if (!argv0 || !argv0[1])
 991                         die (_("Missing branch name; try -b"));
 992                 opts.new_branch = argv0 + 1;
 993         }
 994
 995         if (opts.new_orphan_branch) {
 996                 if (opts.new_branch)
 997                         die(_("--orphan and -b|-B are mutually exclusive"));
 998                 if (opts.track > 0)
 999                         die(_("--orphan cannot be used with -t"));
1000                 opts.new_branch = opts.new_orphan_branch;
1001         }
1002
1003         if (conflict_style) {
1004                 opts.merge = 1; /* implied */
1005                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1006         }
1007
1008         if (opts.force && opts.merge)
1009                 die(_("git checkout: -f and -m are incompatible"));
1010
1011         /*
1012          * Extract branch name from command line arguments, so
1013          * all that is left is pathspecs.
1014          *
1015          * Handle
1016          *
1017          *  1) git checkout <tree> -- [<paths>]
1018          *  2) git checkout -- [<paths>]
1019          *  3) git checkout <something> [<paths>]
1020          *
1021          * including "last branch" syntax and DWIM-ery for names of
1022          * remote branches, erroring out for invalid or ambiguous cases.
1023          */
1024         if (argc) {
1025                 int dwim_ok =
1026                         !patch_mode &&
1027                         dwim_new_local_branch &&
1028                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1029                         !opts.new_branch;
1030                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1031                                 &new, &source_tree, rev, &opts.new_branch);
1032                 argv += n;
1033                 argc -= n;
1034         }
1035
1036         if (opts.track == BRANCH_TRACK_UNSPECIFIED)
1037                 opts.track = git_branch_track;
1038
1039         if (argc) {
1040                 const char **pathspec = get_pathspec(prefix, argv);
1041
1042                 if (!pathspec)
1043                         die(_("invalid path specification"));
1044
1045                 if (patch_mode)
1046                         return interactive_checkout(new.name, pathspec, &opts);
1047
1048                 /* Checkout paths */
1049                 if (opts.new_branch) {
1050                         if (argc == 1) {
1051                                 die(_("git checkout: updating paths is incompatible with switching branches.\nDid you intend to checkout '%s' which can not be resolved as commit?"), argv[0]);
1052                         } else {
1053                                 die(_("git checkout: updating paths is incompatible with switching branches."));
1054                         }
1055                 }
1056
1057                 if (opts.force_detach)
1058                         die(_("git checkout: --detach does not take a path argument"));
1059
1060                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1061                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index."));
1062
1063                 return checkout_paths(source_tree, pathspec, &opts);
1064         }
1065
1066         if (patch_mode)
1067                 return interactive_checkout(new.name, NULL, &opts);
1068
1069         if (opts.new_branch) {
1070                 struct strbuf buf = STRBUF_INIT;
1071                 if (strbuf_check_branch_ref(&buf, opts.new_branch))
1072                         die(_("git checkout: we do not like '%s' as a branch name."),
1073                             opts.new_branch);
1074                 if (ref_exists(buf.buf)) {
1075                         opts.branch_exists = 1;
1076                         if (!opts.new_branch_force)
1077                                 die(_("git checkout: branch %s already exists"),
1078                                     opts.new_branch);
1079                 }
1080                 strbuf_release(&buf);
1081         }
1082
1083         if (new.name && !new.commit) {
1084                 die(_("Cannot switch branch to a non-commit."));
1085         }
1086         if (opts.writeout_stage)
1087                 die(_("--ours/--theirs is incompatible with switching branches."));
1088
1089         return switch_branches(&opts, &new);
1090 }