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         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
  83
  84         /* update the index with the given tree's info
  85          * for all args, expanding wildcards, and exit
  86          * with any non-zero return code.
  87          */
  88         return 0;
  89 }
  90
  91 static int skip_same_name(struct cache_entry *ce, int pos)
  92 {
  93         while (++pos < active_nr &&
  94                !strcmp(active_cache[pos]->name, ce->name))
  95                 ; /* skip */
  96         return pos;
  97 }
  98
  99 static int check_stage(int stage, struct cache_entry *ce, int pos)
 100 {
 101         while (pos < active_nr &&
 102                !strcmp(active_cache[pos]->name, ce->name)) {
 103                 if (ce_stage(active_cache[pos]) == stage)
 104                         return 0;
 105                 pos++;
 106         }
 107         if (stage == 2)
 108                 return error(_("path '%s' does not have our version"), ce->name);
 109         else
 110                 return error(_("path '%s' does not have their version"), ce->name);
 111 }
 112
 113 static int check_all_stages(struct cache_entry *ce, int pos)
 114 {
 115         if (ce_stage(ce) != 1 ||
 116             active_nr <= pos + 2 ||
 117             strcmp(active_cache[pos+1]->name, ce->name) ||
 118             ce_stage(active_cache[pos+1]) != 2 ||
 119             strcmp(active_cache[pos+2]->name, ce->name) ||
 120             ce_stage(active_cache[pos+2]) != 3)
 121                 return error(_("path '%s' does not have all three versions"),
 122                              ce->name);
 123         return 0;
 124 }
 125
 126 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 127                           struct checkout *state)
 128 {
 129         while (pos < active_nr &&
 130                !strcmp(active_cache[pos]->name, ce->name)) {
 131                 if (ce_stage(active_cache[pos]) == stage)
 132                         return checkout_entry(active_cache[pos], state, NULL);
 133                 pos++;
 134         }
 135         if (stage == 2)
 136                 return error(_("path '%s' does not have our version"), ce->name);
 137         else
 138                 return error(_("path '%s' does not have their version"), ce->name);
 139 }
 140
 141 static int checkout_merged(int pos, struct checkout *state)
 142 {
 143         struct cache_entry *ce = active_cache[pos];
 144         const char *path = ce->name;
 145         mmfile_t ancestor, ours, theirs;
 146         int status;
 147         unsigned char sha1[20];
 148         mmbuffer_t result_buf;
 149
 150         if (ce_stage(ce) != 1 ||
 151             active_nr <= pos + 2 ||
 152             strcmp(active_cache[pos+1]->name, path) ||
 153             ce_stage(active_cache[pos+1]) != 2 ||
 154             strcmp(active_cache[pos+2]->name, path) ||
 155             ce_stage(active_cache[pos+2]) != 3)
 156                 return error(_("path '%s' does not have all 3 versions"), path);
 157
 158         read_mmblob(&ancestor, active_cache[pos]->sha1);
 159         read_mmblob(&ours, active_cache[pos+1]->sha1);
 160         read_mmblob(&theirs, active_cache[pos+2]->sha1);
 161
 162         /*
 163          * NEEDSWORK: re-create conflicts from merges with
 164          * merge.renormalize set, too
 165          */
 166         status = ll_merge(&result_buf, path, &ancestor, "base",
 167                           &ours, "ours", &theirs, "theirs", NULL);
 168         free(ancestor.ptr);
 169         free(ours.ptr);
 170         free(theirs.ptr);
 171         if (status < 0 || !result_buf.ptr) {
 172                 free(result_buf.ptr);
 173                 return error(_("path '%s': cannot merge"), path);
 174         }
 175
 176         /*
 177          * NEEDSWORK:
 178          * There is absolutely no reason to write this as a blob object
 179          * and create a phony cache entry just to leak.  This hack is
 180          * primarily to get to the write_entry() machinery that massages
 181          * the contents to work-tree format and writes out which only
 182          * allows it for a cache entry.  The code in write_entry() needs
 183          * to be refactored to allow us to feed a <buffer, size, mode>
 184          * instead of a cache entry.  Such a refactoring would help
 185          * merge_recursive as well (it also writes the merge result to the
 186          * object database even when it may contain conflicts).
 187          */
 188         if (write_sha1_file(result_buf.ptr, result_buf.size,
 189                             blob_type, sha1))
 190                 die(_("Unable to add merge result for '%s'"), path);
 191         ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
 192                               sha1,
 193                               path, 2, 0);
 194         if (!ce)
 195                 die(_("make_cache_entry failed for path '%s'"), path);
 196         status = checkout_entry(ce, state, NULL);
 197         return status;
 198 }
 199
 200 static int checkout_paths(struct tree *source_tree, const char **pathspec,
 201                           struct checkout_opts *opts)
 202 {
 203         int pos;
 204         struct checkout state;
 205         static char *ps_matched;
 206         unsigned char rev[20];
 207         int flag;
 208         struct commit *head;
 209         int errs = 0;
 210         int stage = opts->writeout_stage;
 211         int merge = opts->merge;
 212         int newfd;
 213         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 214
 215         newfd = hold_locked_index(lock_file, 1);
 216         if (read_cache_preload(pathspec) < 0)
 217                 return error(_("corrupt index file"));
 218
 219         if (source_tree)
 220                 read_tree_some(source_tree, pathspec);
 221
 222         for (pos = 0; pathspec[pos]; pos++)
 223                 ;
 224         ps_matched = xcalloc(1, pos);
 225
 226         for (pos = 0; pos < active_nr; pos++) {
 227                 struct cache_entry *ce = active_cache[pos];
 228                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 229         }
 230
 231         if (report_path_error(ps_matched, pathspec, 0))
 232                 return 1;
 233
 234         /* "checkout -m path" to recreate conflicted state */
 235         if (opts->merge)
 236                 unmerge_cache(pathspec);
 237
 238         /* Any unmerged paths? */
 239         for (pos = 0; pos < active_nr; pos++) {
 240                 struct cache_entry *ce = active_cache[pos];
 241                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 242                         if (!ce_stage(ce))
 243                                 continue;
 244                         if (opts->force) {
 245                                 warning(_("path '%s' is unmerged"), ce->name);
 246                         } else if (stage) {
 247                                 errs |= check_stage(stage, ce, pos);
 248                         } else if (opts->merge) {
 249                                 errs |= check_all_stages(ce, pos);
 250                         } else {
 251                                 errs = 1;
 252                                 error(_("path '%s' is unmerged"), ce->name);
 253                         }
 254                         pos = skip_same_name(ce, pos) - 1;
 255                 }
 256         }
 257         if (errs)
 258                 return 1;
 259
 260         /* Now we are committed to check them out */
 261         memset(&state, 0, sizeof(state));
 262         state.force = 1;
 263         state.refresh_cache = 1;
 264         for (pos = 0; pos < active_nr; pos++) {
 265                 struct cache_entry *ce = active_cache[pos];
 266                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 267                         if (!ce_stage(ce)) {
 268                                 errs |= checkout_entry(ce, &state, NULL);
 269                                 continue;
 270                         }
 271                         if (stage)
 272                                 errs |= checkout_stage(stage, ce, pos, &state);
 273                         else if (merge)
 274                                 errs |= checkout_merged(pos, &state);
 275                         pos = skip_same_name(ce, pos) - 1;
 276                 }
 277         }
 278
 279         if (write_cache(newfd, active_cache, active_nr) ||
 280             commit_locked_index(lock_file))
 281                 die(_("unable to write new index file"));
 282
 283         resolve_ref("HEAD", rev, 0, &flag);
 284         head = lookup_commit_reference_gently(rev, 1);
 285
 286         errs |= post_checkout_hook(head, head, 0);
 287         return errs;
 288 }
 289
 290 static void show_local_changes(struct object *head, struct diff_options *opts)
 291 {
 292         struct rev_info rev;
 293         /* I think we want full paths, even if we're in a subdirectory. */
 294         init_revisions(&rev, NULL);
 295         rev.diffopt.flags = opts->flags;
 296         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 297         if (diff_setup_done(&rev.diffopt) < 0)
 298                 die(_("diff_setup_done failed"));
 299         add_pending_object(&rev, head, NULL);
 300         run_diff_index(&rev, 0);
 301 }
 302
 303 static void describe_detached_head(const char *msg, struct commit *commit)
 304 {
 305         struct strbuf sb = STRBUF_INIT;
 306         struct pretty_print_context ctx = {0};
 307         parse_commit(commit);
 308         pretty_print_commit(CMIT_FMT_ONELINE, commit, &sb, &ctx);
 309         fprintf(stderr, "%s %s... %s\n", msg,
 310                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 311         strbuf_release(&sb);
 312 }
 313
 314 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 315 {
 316         struct unpack_trees_options opts;
 317         struct tree_desc tree_desc;
 318
 319         memset(&opts, 0, sizeof(opts));
 320         opts.head_idx = -1;
 321         opts.update = worktree;
 322         opts.skip_unmerged = !worktree;
 323         opts.reset = 1;
 324         opts.merge = 1;
 325         opts.fn = oneway_merge;
 326         opts.verbose_update = !o->quiet;
 327         opts.src_index = &the_index;
 328         opts.dst_index = &the_index;
 329         parse_tree(tree);
 330         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 331         switch (unpack_trees(1, &tree_desc, &opts)) {
 332         case -2:
 333                 o->writeout_error = 1;
 334                 /*
 335                  * We return 0 nevertheless, as the index is all right
 336                  * and more importantly we have made best efforts to
 337                  * update paths in the work tree, and we cannot revert
 338                  * them.
 339                  */
 340         case 0:
 341                 return 0;
 342         default:
 343                 return 128;
 344         }
 345 }
 346
 347 struct branch_info {
 348         const char *name; /* The short name used */
 349         const char *path; /* The full name of a real branch */
 350         struct commit *commit; /* The named commit */
 351 };
 352
 353 static void setup_branch_path(struct branch_info *branch)
 354 {
 355         struct strbuf buf = STRBUF_INIT;
 356
 357         strbuf_branchname(&buf, branch->name);
 358         if (strcmp(buf.buf, branch->name))
 359                 branch->name = xstrdup(buf.buf);
 360         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 361         branch->path = strbuf_detach(&buf, NULL);
 362 }
 363
 364 static int merge_working_tree(struct checkout_opts *opts,
 365                               struct branch_info *old, struct branch_info *new)
 366 {
 367         int ret;
 368         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 369         int newfd = hold_locked_index(lock_file, 1);
 370
 371         if (read_cache_preload(NULL) < 0)
 372                 return error(_("corrupt index file"));
 373
 374         resolve_undo_clear();
 375         if (opts->force) {
 376                 ret = reset_tree(new->commit->tree, opts, 1);
 377                 if (ret)
 378                         return ret;
 379         } else {
 380                 struct tree_desc trees[2];
 381                 struct tree *tree;
 382                 struct unpack_trees_options topts;
 383
 384                 memset(&topts, 0, sizeof(topts));
 385                 topts.head_idx = -1;
 386                 topts.src_index = &the_index;
 387                 topts.dst_index = &the_index;
 388
 389                 setup_unpack_trees_porcelain(&topts, "checkout");
 390
 391                 refresh_cache(REFRESH_QUIET);
 392
 393                 if (unmerged_cache()) {
 394                         error(_("you need to resolve your current index first"));
 395                         return 1;
 396                 }
 397
 398                 /* 2-way merge to the new branch */
 399                 topts.initial_checkout = is_cache_unborn();
 400                 topts.update = 1;
 401                 topts.merge = 1;
 402                 topts.gently = opts->merge && old->commit;
 403                 topts.verbose_update = !opts->quiet;
 404                 topts.fn = twoway_merge;
 405                 topts.dir = xcalloc(1, sizeof(*topts.dir));
 406                 topts.dir->flags |= DIR_SHOW_IGNORED;
 407                 topts.dir->exclude_per_dir = ".gitignore";
 408                 tree = parse_tree_indirect(old->commit ?
 409                                            old->commit->object.sha1 :
 410                                            EMPTY_TREE_SHA1_BIN);
 411                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 412                 tree = parse_tree_indirect(new->commit->object.sha1);
 413                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 414
 415                 ret = unpack_trees(2, trees, &topts);
 416                 if (ret == -1) {
 417                         /*
 418                          * Unpack couldn't do a trivial merge; either
 419                          * give up or do a real merge, depending on
 420                          * whether the merge flag was used.
 421                          */
 422                         struct tree *result;
 423                         struct tree *work;
 424                         struct merge_options o;
 425                         if (!opts->merge)
 426                                 return 1;
 427
 428                         /*
 429                          * Without old->commit, the below is the same as
 430                          * the two-tree unpack we already tried and failed.
 431                          */
 432                         if (!old->commit)
 433                                 return 1;
 434
 435                         /* Do more real merge */
 436
 437                         /*
 438                          * We update the index fully, then write the
 439                          * tree from the index, then merge the new
 440                          * branch with the current tree, with the old
 441                          * branch as the base. Then we reset the index
 442                          * (but not the working tree) to the new
 443                          * branch, leaving the working tree as the
 444                          * merged version, but skipping unmerged
 445                          * entries in the index.
 446                          */
 447
 448                         add_files_to_cache(NULL, NULL, 0);
 449                         /*
 450                          * NEEDSWORK: carrying over local changes
 451                          * when branches have different end-of-line
 452                          * normalization (or clean+smudge rules) is
 453                          * a pain; plumb in an option to set
 454                          * o.renormalize?
 455                          */
 456                         init_merge_options(&o);
 457                         o.verbosity = 0;
 458                         work = write_tree_from_memory(&o);
 459
 460                         ret = reset_tree(new->commit->tree, opts, 1);
 461                         if (ret)
 462                                 return ret;
 463                         o.ancestor = old->name;
 464                         o.branch1 = new->name;
 465                         o.branch2 = "local";
 466                         merge_trees(&o, new->commit->tree, work,
 467                                 old->commit->tree, &result);
 468                         ret = reset_tree(new->commit->tree, opts, 0);
 469                         if (ret)
 470                                 return ret;
 471                 }
 472         }
 473
 474         if (write_cache(newfd, active_cache, active_nr) ||
 475             commit_locked_index(lock_file))
 476                 die(_("unable to write new index file"));
 477
 478         if (!opts->force && !opts->quiet)
 479                 show_local_changes(&new->commit->object, &opts->diff_options);
 480
 481         return 0;
 482 }
 483
 484 static void report_tracking(struct branch_info *new)
 485 {
 486         struct strbuf sb = STRBUF_INIT;
 487         struct branch *branch = branch_get(new->name);
 488
 489         if (!format_tracking_info(branch, &sb))
 490                 return;
 491         fputs(sb.buf, stdout);
 492         strbuf_release(&sb);
 493 }
 494
 495 static void detach_advice(const char *old_path, const char *new_name)
 496 {
 497         const char fmt[] =
 498         "Note: checking out '%s'.\n\n"
 499         "You are in 'detached HEAD' state. You can look around, make experimental\n"
 500         "changes and commit them, and you can discard any commits you make in this\n"
 501         "state without impacting any branches by performing another checkout.\n\n"
 502         "If you want to create a new branch to retain commits you create, you may\n"
 503         "do so (now or later) by using -b with the checkout command again. Example:\n\n"
 504         "  git checkout -b new_branch_name\n\n";
 505
 506         fprintf(stderr, fmt, new_name);
 507 }
 508
 509 static void update_refs_for_switch(struct checkout_opts *opts,
 510                                    struct branch_info *old,
 511                                    struct branch_info *new)
 512 {
 513         struct strbuf msg = STRBUF_INIT;
 514         const char *old_desc;
 515         if (opts->new_branch) {
 516                 if (opts->new_orphan_branch) {
 517                         if (opts->new_branch_log && !log_all_ref_updates) {
 518                                 int temp;
 519                                 char log_file[PATH_MAX];
 520                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 521
 522                                 temp = log_all_ref_updates;
 523                                 log_all_ref_updates = 1;
 524                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
 525                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 526                                             opts->new_orphan_branch);
 527                                         log_all_ref_updates = temp;
 528                                         return;
 529                                 }
 530                                 log_all_ref_updates = temp;
 531                         }
 532                 }
 533                 else
 534                         create_branch(old->name, opts->new_branch, new->name,
 535                                       opts->new_branch_force ? 1 : 0,
 536                                       opts->new_branch_log, opts->track);
 537                 new->name = opts->new_branch;
 538                 setup_branch_path(new);
 539         }
 540
 541         old_desc = old->name;
 542         if (!old_desc && old->commit)
 543                 old_desc = sha1_to_hex(old->commit->object.sha1);
 544         strbuf_addf(&msg, "checkout: moving from %s to %s",
 545                     old_desc ? old_desc : "(invalid)", new->name);
 546
 547         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 548                 /* Nothing to do. */
 549         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 550                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 551                            REF_NODEREF, DIE_ON_ERR);
 552                 if (!opts->quiet) {
 553                         if (old->path && advice_detached_head)
 554                                 detach_advice(old->path, new->name);
 555                         describe_detached_head(_("HEAD is now at"), new->commit);
 556                 }
 557         } else if (new->path) { /* Switch branches. */
 558                 create_symref("HEAD", new->path, msg.buf);
 559                 if (!opts->quiet) {
 560                         if (old->path && !strcmp(new->path, old->path)) {
 561                                 fprintf(stderr, _("Already on '%s'\n"),
 562                                         new->name);
 563                         } else if (opts->new_branch) {
 564                                 if (opts->branch_exists)
 565                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 566                                 else
 567                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 568                         } else {
 569                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 570                                         new->name);
 571                         }
 572                 }
 573                 if (old->path && old->name) {
 574                         char log_file[PATH_MAX], ref_file[PATH_MAX];
 575
 576                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
 577                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
 578                         if (!file_exists(ref_file) && file_exists(log_file))
 579                                 remove_path(log_file);
 580                 }
 581         }
 582         remove_branch_state();
 583         strbuf_release(&msg);
 584         if (!opts->quiet &&
 585             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 586                 report_tracking(new);
 587 }
 588
 589 struct rev_list_args {
 590         int argc;
 591         int alloc;
 592         const char **argv;
 593 };
 594
 595 static void add_one_rev_list_arg(struct rev_list_args *args, const char *s)
 596 {
 597         ALLOC_GROW(args->argv, args->argc + 1, args->alloc);
 598         args->argv[args->argc++] = s;
 599 }
 600
 601 static int add_one_ref_to_rev_list_arg(const char *refname,
 602                                        const unsigned char *sha1,
 603                                        int flags,
 604                                        void *cb_data)
 605 {
 606         add_one_rev_list_arg(cb_data, refname);
 607         return 0;
 608 }
 609
 610 static int clear_commit_marks_from_one_ref(const char *refname,
 611                                       const unsigned char *sha1,
 612                                       int flags,
 613                                       void *cb_data)
 614 {
 615         struct commit *commit = lookup_commit_reference_gently(sha1, 1);
 616         if (commit)
 617                 clear_commit_marks(commit, -1);
 618         return 0;
 619 }
 620
 621 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 622 {
 623         struct pretty_print_context ctx = { 0 };
 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         pretty_print_commit(CMIT_FMT_ONELINE, commit, sb, &ctx);
 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 (!get_sha1(buf.buf, rev)) {
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 }