Pileus Git - ~andy/git/blob - 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 #include "argv-array.h"
  23
  24 static const char * const checkout_usage[] = {
  25         N_("git checkout [options] <branch>"),
  26         N_("git checkout [options] [<branch>] -- <file>..."),
  27         NULL,
  28 };
  29
  30 struct checkout_opts {
  31         int patch_mode;
  32         int quiet;
  33         int merge;
  34         int force;
  35         int force_detach;
  36         int writeout_stage;
  37         int overwrite_ignore;
  38         int ignore_skipworktree;
  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         int branch_exists;
  48         const char *prefix;
  49         struct pathspec pathspec;
  50         struct tree *source_tree;
  51 };
  52
  53 static int post_checkout_hook(struct commit *old, struct commit *new,
  54                               int changed)
  55 {
  56         return run_hook(NULL, "post-checkout",
  57                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
  58                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
  59                         changed ? "1" : "0", NULL);
  60         /* "new" can be NULL when checking out from the index before
  61            a commit exists. */
  62
  63 }
  64
  65 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  66                 const char *pathname, unsigned mode, int stage, void *context)
  67 {
  68         int len;
  69         struct cache_entry *ce;
  70
  71         if (S_ISDIR(mode))
  72                 return READ_TREE_RECURSIVE;
  73
  74         len = baselen + strlen(pathname);
  75         ce = xcalloc(1, cache_entry_size(len));
  76         hashcpy(ce->sha1, sha1);
  77         memcpy(ce->name, base, baselen);
  78         memcpy(ce->name + baselen, pathname, len - baselen);
  79         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  80         ce->ce_namelen = len;
  81         ce->ce_mode = create_ce_mode(mode);
  82         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  83         return 0;
  84 }
  85
  86 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
  87 {
  88         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
  89
  90         /* update the index with the given tree's info
  91          * for all args, expanding wildcards, and exit
  92          * with any non-zero return code.
  93          */
  94         return 0;
  95 }
  96
  97 static int skip_same_name(struct cache_entry *ce, int pos)
  98 {
  99         while (++pos < active_nr &&
 100                !strcmp(active_cache[pos]->name, ce->name))
 101                 ; /* skip */
 102         return pos;
 103 }
 104
 105 static int check_stage(int stage, struct cache_entry *ce, int pos)
 106 {
 107         while (pos < active_nr &&
 108                !strcmp(active_cache[pos]->name, ce->name)) {
 109                 if (ce_stage(active_cache[pos]) == stage)
 110                         return 0;
 111                 pos++;
 112         }
 113         if (stage == 2)
 114                 return error(_("path '%s' does not have our version"), ce->name);
 115         else
 116                 return error(_("path '%s' does not have their version"), ce->name);
 117 }
 118
 119 static int check_stages(unsigned stages, struct cache_entry *ce, int pos)
 120 {
 121         unsigned seen = 0;
 122         const char *name = ce->name;
 123
 124         while (pos < active_nr) {
 125                 ce = active_cache[pos];
 126                 if (strcmp(name, ce->name))
 127                         break;
 128                 seen |= (1 << ce_stage(ce));
 129                 pos++;
 130         }
 131         if ((stages & seen) != stages)
 132                 return error(_("path '%s' does not have all necessary versions"),
 133                              name);
 134         return 0;
 135 }
 136
 137 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 138                           struct checkout *state)
 139 {
 140         while (pos < active_nr &&
 141                !strcmp(active_cache[pos]->name, ce->name)) {
 142                 if (ce_stage(active_cache[pos]) == stage)
 143                         return checkout_entry(active_cache[pos], state, NULL);
 144                 pos++;
 145         }
 146         if (stage == 2)
 147                 return error(_("path '%s' does not have our version"), ce->name);
 148         else
 149                 return error(_("path '%s' does not have their version"), ce->name);
 150 }
 151
 152 static int checkout_merged(int pos, struct checkout *state)
 153 {
 154         struct cache_entry *ce = active_cache[pos];
 155         const char *path = ce->name;
 156         mmfile_t ancestor, ours, theirs;
 157         int status;
 158         unsigned char sha1[20];
 159         mmbuffer_t result_buf;
 160         unsigned char threeway[3][20];
 161         unsigned mode = 0;
 162
 163         memset(threeway, 0, sizeof(threeway));
 164         while (pos < active_nr) {
 165                 int stage;
 166                 stage = ce_stage(ce);
 167                 if (!stage || strcmp(path, ce->name))
 168                         break;
 169                 hashcpy(threeway[stage - 1], ce->sha1);
 170                 if (stage == 2)
 171                         mode = create_ce_mode(ce->ce_mode);
 172                 pos++;
 173                 ce = active_cache[pos];
 174         }
 175         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
 176                 return error(_("path '%s' does not have necessary versions"), path);
 177
 178         read_mmblob(&ancestor, threeway[0]);
 179         read_mmblob(&ours, threeway[1]);
 180         read_mmblob(&theirs, threeway[2]);
 181
 182         /*
 183          * NEEDSWORK: re-create conflicts from merges with
 184          * merge.renormalize set, too
 185          */
 186         status = ll_merge(&result_buf, path, &ancestor, "base",
 187                           &ours, "ours", &theirs, "theirs", NULL);
 188         free(ancestor.ptr);
 189         free(ours.ptr);
 190         free(theirs.ptr);
 191         if (status < 0 || !result_buf.ptr) {
 192                 free(result_buf.ptr);
 193                 return error(_("path '%s': cannot merge"), path);
 194         }
 195
 196         /*
 197          * NEEDSWORK:
 198          * There is absolutely no reason to write this as a blob object
 199          * and create a phony cache entry just to leak.  This hack is
 200          * primarily to get to the write_entry() machinery that massages
 201          * the contents to work-tree format and writes out which only
 202          * allows it for a cache entry.  The code in write_entry() needs
 203          * to be refactored to allow us to feed a <buffer, size, mode>
 204          * instead of a cache entry.  Such a refactoring would help
 205          * merge_recursive as well (it also writes the merge result to the
 206          * object database even when it may contain conflicts).
 207          */
 208         if (write_sha1_file(result_buf.ptr, result_buf.size,
 209                             blob_type, sha1))
 210                 die(_("Unable to add merge result for '%s'"), path);
 211         ce = make_cache_entry(mode, sha1, path, 2, 0);
 212         if (!ce)
 213                 die(_("make_cache_entry failed for path '%s'"), path);
 214         status = checkout_entry(ce, state, NULL);
 215         return status;
 216 }
 217
 218 static int checkout_paths(const struct checkout_opts *opts,
 219                           const char *revision)
 220 {
 221         int pos;
 222         struct checkout state;
 223         static char *ps_matched;
 224         unsigned char rev[20];
 225         int flag;
 226         struct commit *head;
 227         int errs = 0;
 228         int stage = opts->writeout_stage;
 229         int merge = opts->merge;
 230         int newfd;
 231         struct lock_file *lock_file;
 232
 233         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
 234                 die(_("'%s' cannot be used with updating paths"), "--track");
 235
 236         if (opts->new_branch_log)
 237                 die(_("'%s' cannot be used with updating paths"), "-l");
 238
 239         if (opts->force && opts->patch_mode)
 240                 die(_("'%s' cannot be used with updating paths"), "-f");
 241
 242         if (opts->force_detach)
 243                 die(_("'%s' cannot be used with updating paths"), "--detach");
 244
 245         if (opts->merge && opts->patch_mode)
 246                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
 247
 248         if (opts->force && opts->merge)
 249                 die(_("'%s' cannot be used with %s"), "-f", "-m");
 250
 251         if (opts->new_branch)
 252                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
 253                     opts->new_branch);
 254
 255         if (opts->patch_mode)
 256                 return run_add_interactive(revision, "--patch=checkout",
 257                                            &opts->pathspec);
 258
 259         lock_file = xcalloc(1, sizeof(struct lock_file));
 260
 261         newfd = hold_locked_index(lock_file, 1);
 262         if (read_cache_preload(&opts->pathspec) < 0)
 263                 return error(_("corrupt index file"));
 264
 265         if (opts->source_tree)
 266                 read_tree_some(opts->source_tree, &opts->pathspec);
 267
 268         ps_matched = xcalloc(1, opts->pathspec.nr);
 269
 270         /*
 271          * Make sure all pathspecs participated in locating the paths
 272          * to be checked out.
 273          */
 274         for (pos = 0; pos < active_nr; pos++) {
 275                 struct cache_entry *ce = active_cache[pos];
 276                 ce->ce_flags &= ~CE_MATCHED;
 277                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
 278                         continue;
 279                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 280                         /*
 281                          * "git checkout tree-ish -- path", but this entry
 282                          * is in the original index; it will not be checked
 283                          * out to the working tree and it does not matter
 284                          * if pathspec matched this entry.  We will not do
 285                          * anything to this entry at all.
 286                          */
 287                         continue;
 288                 /*
 289                  * Either this entry came from the tree-ish we are
 290                  * checking the paths out of, or we are checking out
 291                  * of the index.
 292                  *
 293                  * If it comes from the tree-ish, we already know it
 294                  * matches the pathspec and could just stamp
 295                  * CE_MATCHED to it from update_some(). But we still
 296                  * need ps_matched and read_tree_recursive (and
 297                  * eventually tree_entry_interesting) cannot fill
 298                  * ps_matched yet. Once it can, we can avoid calling
 299                  * match_pathspec() for _all_ entries when
 300                  * opts->source_tree != NULL.
 301                  */
 302                 if (match_pathspec_depth(&opts->pathspec, ce->name, ce_namelen(ce),
 303                                    0, ps_matched))
 304                         ce->ce_flags |= CE_MATCHED;
 305         }
 306
 307         if (report_path_error(ps_matched, opts->pathspec.raw, opts->prefix)) {
 308                 free(ps_matched);
 309                 return 1;
 310         }
 311         free(ps_matched);
 312
 313         /* "checkout -m path" to recreate conflicted state */
 314         if (opts->merge)
 315                 unmerge_marked_index(&the_index);
 316
 317         /* Any unmerged paths? */
 318         for (pos = 0; pos < active_nr; pos++) {
 319                 struct cache_entry *ce = active_cache[pos];
 320                 if (ce->ce_flags & CE_MATCHED) {
 321                         if (!ce_stage(ce))
 322                                 continue;
 323                         if (opts->force) {
 324                                 warning(_("path '%s' is unmerged"), ce->name);
 325                         } else if (stage) {
 326                                 errs |= check_stage(stage, ce, pos);
 327                         } else if (opts->merge) {
 328                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 329                         } else {
 330                                 errs = 1;
 331                                 error(_("path '%s' is unmerged"), ce->name);
 332                         }
 333                         pos = skip_same_name(ce, pos) - 1;
 334                 }
 335         }
 336         if (errs)
 337                 return 1;
 338
 339         /* Now we are committed to check them out */
 340         memset(&state, 0, sizeof(state));
 341         state.force = 1;
 342         state.refresh_cache = 1;
 343         for (pos = 0; pos < active_nr; pos++) {
 344                 struct cache_entry *ce = active_cache[pos];
 345                 if (ce->ce_flags & CE_MATCHED) {
 346                         if (!ce_stage(ce)) {
 347                                 errs |= checkout_entry(ce, &state, NULL);
 348                                 continue;
 349                         }
 350                         if (stage)
 351                                 errs |= checkout_stage(stage, ce, pos, &state);
 352                         else if (merge)
 353                                 errs |= checkout_merged(pos, &state);
 354                         pos = skip_same_name(ce, pos) - 1;
 355                 }
 356         }
 357
 358         if (write_cache(newfd, active_cache, active_nr) ||
 359             commit_locked_index(lock_file))
 360                 die(_("unable to write new index file"));
 361
 362         read_ref_full("HEAD", rev, 0, &flag);
 363         head = lookup_commit_reference_gently(rev, 1);
 364
 365         errs |= post_checkout_hook(head, head, 0);
 366         return errs;
 367 }
 368
 369 static void show_local_changes(struct object *head,
 370                                const struct diff_options *opts)
 371 {
 372         struct rev_info rev;
 373         /* I think we want full paths, even if we're in a subdirectory. */
 374         init_revisions(&rev, NULL);
 375         rev.diffopt.flags = opts->flags;
 376         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 377         diff_setup_done(&rev.diffopt);
 378         add_pending_object(&rev, head, NULL);
 379         run_diff_index(&rev, 0);
 380 }
 381
 382 static void describe_detached_head(const char *msg, struct commit *commit)
 383 {
 384         struct strbuf sb = STRBUF_INIT;
 385         parse_commit(commit);
 386         pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 387         fprintf(stderr, "%s %s... %s\n", msg,
 388                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 389         strbuf_release(&sb);
 390 }
 391
 392 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 393                       int worktree, int *writeout_error)
 394 {
 395         struct unpack_trees_options opts;
 396         struct tree_desc tree_desc;
 397
 398         memset(&opts, 0, sizeof(opts));
 399         opts.head_idx = -1;
 400         opts.update = worktree;
 401         opts.skip_unmerged = !worktree;
 402         opts.reset = 1;
 403         opts.merge = 1;
 404         opts.fn = oneway_merge;
 405         opts.verbose_update = !o->quiet && isatty(2);
 406         opts.src_index = &the_index;
 407         opts.dst_index = &the_index;
 408         parse_tree(tree);
 409         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 410         switch (unpack_trees(1, &tree_desc, &opts)) {
 411         case -2:
 412                 *writeout_error = 1;
 413                 /*
 414                  * We return 0 nevertheless, as the index is all right
 415                  * and more importantly we have made best efforts to
 416                  * update paths in the work tree, and we cannot revert
 417                  * them.
 418                  */
 419         case 0:
 420                 return 0;
 421         default:
 422                 return 128;
 423         }
 424 }
 425
 426 struct branch_info {
 427         const char *name; /* The short name used */
 428         const char *path; /* The full name of a real branch */
 429         struct commit *commit; /* The named commit */
 430 };
 431
 432 static void setup_branch_path(struct branch_info *branch)
 433 {
 434         struct strbuf buf = STRBUF_INIT;
 435
 436         strbuf_branchname(&buf, branch->name);
 437         if (strcmp(buf.buf, branch->name))
 438                 branch->name = xstrdup(buf.buf);
 439         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 440         branch->path = strbuf_detach(&buf, NULL);
 441 }
 442
 443 static int merge_working_tree(const struct checkout_opts *opts,
 444                               struct branch_info *old,
 445                               struct branch_info *new,
 446                               int *writeout_error)
 447 {
 448         int ret;
 449         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 450         int newfd = hold_locked_index(lock_file, 1);
 451
 452         if (read_cache_preload(NULL) < 0)
 453                 return error(_("corrupt index file"));
 454
 455         resolve_undo_clear();
 456         if (opts->force) {
 457                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
 458                 if (ret)
 459                         return ret;
 460         } else {
 461                 struct tree_desc trees[2];
 462                 struct tree *tree;
 463                 struct unpack_trees_options topts;
 464
 465                 memset(&topts, 0, sizeof(topts));
 466                 topts.head_idx = -1;
 467                 topts.src_index = &the_index;
 468                 topts.dst_index = &the_index;
 469
 470                 setup_unpack_trees_porcelain(&topts, "checkout");
 471
 472                 refresh_cache(REFRESH_QUIET);
 473
 474                 if (unmerged_cache()) {
 475                         error(_("you need to resolve your current index first"));
 476                         return 1;
 477                 }
 478
 479                 /* 2-way merge to the new branch */
 480                 topts.initial_checkout = is_cache_unborn();
 481                 topts.update = 1;
 482                 topts.merge = 1;
 483                 topts.gently = opts->merge && old->commit;
 484                 topts.verbose_update = !opts->quiet && isatty(2);
 485                 topts.fn = twoway_merge;
 486                 if (opts->overwrite_ignore) {
 487                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 488                         topts.dir->flags |= DIR_SHOW_IGNORED;
 489                         setup_standard_excludes(topts.dir);
 490                 }
 491                 tree = parse_tree_indirect(old->commit ?
 492                                            old->commit->object.sha1 :
 493                                            EMPTY_TREE_SHA1_BIN);
 494                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 495                 tree = parse_tree_indirect(new->commit->object.sha1);
 496                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 497
 498                 ret = unpack_trees(2, trees, &topts);
 499                 if (ret == -1) {
 500                         /*
 501                          * Unpack couldn't do a trivial merge; either
 502                          * give up or do a real merge, depending on
 503                          * whether the merge flag was used.
 504                          */
 505                         struct tree *result;
 506                         struct tree *work;
 507                         struct merge_options o;
 508                         if (!opts->merge)
 509                                 return 1;
 510
 511                         /*
 512                          * Without old->commit, the below is the same as
 513                          * the two-tree unpack we already tried and failed.
 514                          */
 515                         if (!old->commit)
 516                                 return 1;
 517
 518                         /* Do more real merge */
 519
 520                         /*
 521                          * We update the index fully, then write the
 522                          * tree from the index, then merge the new
 523                          * branch with the current tree, with the old
 524                          * branch as the base. Then we reset the index
 525                          * (but not the working tree) to the new
 526                          * branch, leaving the working tree as the
 527                          * merged version, but skipping unmerged
 528                          * entries in the index.
 529                          */
 530
 531                         add_files_to_cache(NULL, NULL, 0);
 532                         /*
 533                          * NEEDSWORK: carrying over local changes
 534                          * when branches have different end-of-line
 535                          * normalization (or clean+smudge rules) is
 536                          * a pain; plumb in an option to set
 537                          * o.renormalize?
 538                          */
 539                         init_merge_options(&o);
 540                         o.verbosity = 0;
 541                         work = write_tree_from_memory(&o);
 542
 543                         ret = reset_tree(new->commit->tree, opts, 1,
 544                                          writeout_error);
 545                         if (ret)
 546                                 return ret;
 547                         o.ancestor = old->name;
 548                         o.branch1 = new->name;
 549                         o.branch2 = "local";
 550                         merge_trees(&o, new->commit->tree, work,
 551                                 old->commit->tree, &result);
 552                         ret = reset_tree(new->commit->tree, opts, 0,
 553                                          writeout_error);
 554                         if (ret)
 555                                 return ret;
 556                 }
 557         }
 558
 559         if (write_cache(newfd, active_cache, active_nr) ||
 560             commit_locked_index(lock_file))
 561                 die(_("unable to write new index file"));
 562
 563         if (!opts->force && !opts->quiet)
 564                 show_local_changes(&new->commit->object, &opts->diff_options);
 565
 566         return 0;
 567 }
 568
 569 static void report_tracking(struct branch_info *new)
 570 {
 571         struct strbuf sb = STRBUF_INIT;
 572         struct branch *branch = branch_get(new->name);
 573
 574         if (!format_tracking_info(branch, &sb))
 575                 return;
 576         fputs(sb.buf, stdout);
 577         strbuf_release(&sb);
 578 }
 579
 580 static void update_refs_for_switch(const struct checkout_opts *opts,
 581                                    struct branch_info *old,
 582                                    struct branch_info *new)
 583 {
 584         struct strbuf msg = STRBUF_INIT;
 585         const char *old_desc, *reflog_msg;
 586         if (opts->new_branch) {
 587                 if (opts->new_orphan_branch) {
 588                         if (opts->new_branch_log && !log_all_ref_updates) {
 589                                 int temp;
 590                                 char log_file[PATH_MAX];
 591                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 592
 593                                 temp = log_all_ref_updates;
 594                                 log_all_ref_updates = 1;
 595                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
 596                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 597                                             opts->new_orphan_branch);
 598                                         log_all_ref_updates = temp;
 599                                         return;
 600                                 }
 601                                 log_all_ref_updates = temp;
 602                         }
 603                 }
 604                 else
 605                         create_branch(old->name, opts->new_branch, new->name,
 606                                       opts->new_branch_force ? 1 : 0,
 607                                       opts->new_branch_log,
 608                                       opts->new_branch_force ? 1 : 0,
 609                                       opts->quiet,
 610                                       opts->track);
 611                 new->name = opts->new_branch;
 612                 setup_branch_path(new);
 613         }
 614
 615         old_desc = old->name;
 616         if (!old_desc && old->commit)
 617                 old_desc = sha1_to_hex(old->commit->object.sha1);
 618
 619         reflog_msg = getenv("GIT_REFLOG_ACTION");
 620         if (!reflog_msg)
 621                 strbuf_addf(&msg, "checkout: moving from %s to %s",
 622                         old_desc ? old_desc : "(invalid)", new->name);
 623         else
 624                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
 625
 626         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 627                 /* Nothing to do. */
 628         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 629                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 630                            REF_NODEREF, DIE_ON_ERR);
 631                 if (!opts->quiet) {
 632                         if (old->path && advice_detached_head)
 633                                 detach_advice(new->name);
 634                         describe_detached_head(_("HEAD is now at"), new->commit);
 635                 }
 636         } else if (new->path) { /* Switch branches. */
 637                 create_symref("HEAD", new->path, msg.buf);
 638                 if (!opts->quiet) {
 639                         if (old->path && !strcmp(new->path, old->path)) {
 640                                 if (opts->new_branch_force)
 641                                         fprintf(stderr, _("Reset branch '%s'\n"),
 642                                                 new->name);
 643                                 else
 644                                         fprintf(stderr, _("Already on '%s'\n"),
 645                                                 new->name);
 646                         } else if (opts->new_branch) {
 647                                 if (opts->branch_exists)
 648                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 649                                 else
 650                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 651                         } else {
 652                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 653                                         new->name);
 654                         }
 655                 }
 656                 if (old->path && old->name) {
 657                         char log_file[PATH_MAX], ref_file[PATH_MAX];
 658
 659                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
 660                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
 661                         if (!file_exists(ref_file) && file_exists(log_file))
 662                                 remove_path(log_file);
 663                 }
 664         }
 665         remove_branch_state();
 666         strbuf_release(&msg);
 667         if (!opts->quiet &&
 668             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 669                 report_tracking(new);
 670 }
 671
 672 static int add_pending_uninteresting_ref(const char *refname,
 673                                          const unsigned char *sha1,
 674                                          int flags, void *cb_data)
 675 {
 676         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
 677         return 0;
 678 }
 679
 680 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 681 {
 682         parse_commit(commit);
 683         strbuf_addstr(sb, "  ");
 684         strbuf_addstr(sb,
 685                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 686         strbuf_addch(sb, ' ');
 687         pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 688         strbuf_addch(sb, '\n');
 689 }
 690
 691 #define ORPHAN_CUTOFF 4
 692 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 693 {
 694         struct commit *c, *last = NULL;
 695         struct strbuf sb = STRBUF_INIT;
 696         int lost = 0;
 697         while ((c = get_revision(revs)) != NULL) {
 698                 if (lost < ORPHAN_CUTOFF)
 699                         describe_one_orphan(&sb, c);
 700                 last = c;
 701                 lost++;
 702         }
 703         if (ORPHAN_CUTOFF < lost) {
 704                 int more = lost - ORPHAN_CUTOFF;
 705                 if (more == 1)
 706                         describe_one_orphan(&sb, last);
 707                 else
 708                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 709         }
 710
 711         fprintf(stderr,
 712                 Q_(
 713                 /* The singular version */
 714                 "Warning: you are leaving %d commit behind, "
 715                 "not connected to\n"
 716                 "any of your branches:\n\n"
 717                 "%s\n",
 718                 /* The plural version */
 719                 "Warning: you are leaving %d commits behind, "
 720                 "not connected to\n"
 721                 "any of your branches:\n\n"
 722                 "%s\n",
 723                 /* Give ngettext() the count */
 724                 lost),
 725                 lost,
 726                 sb.buf);
 727         strbuf_release(&sb);
 728
 729         if (advice_detached_head)
 730                 fprintf(stderr,
 731                         _(
 732                         "If you want to keep them by creating a new branch, "
 733                         "this may be a good time\nto do so with:\n\n"
 734                         " git branch new_branch_name %s\n\n"),
 735                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 736 }
 737
 738 /*
 739  * We are about to leave commit that was at the tip of a detached
 740  * HEAD.  If it is not reachable from any ref, this is the last chance
 741  * for the user to do so without resorting to reflog.
 742  */
 743 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 744 {
 745         struct rev_info revs;
 746         struct object *object = &old->object;
 747         struct object_array refs;
 748
 749         init_revisions(&revs, NULL);
 750         setup_revisions(0, NULL, &revs, NULL);
 751
 752         object->flags &= ~UNINTERESTING;
 753         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
 754
 755         for_each_ref(add_pending_uninteresting_ref, &revs);
 756         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
 757
 758         refs = revs.pending;
 759         revs.leak_pending = 1;
 760
 761         if (prepare_revision_walk(&revs))
 762                 die(_("internal error in revision walk"));
 763         if (!(old->object.flags & UNINTERESTING))
 764                 suggest_reattach(old, &revs);
 765         else
 766                 describe_detached_head(_("Previous HEAD position was"), old);
 767
 768         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 769         free(refs.objects);
 770 }
 771
 772 static int switch_branches(const struct checkout_opts *opts,
 773                            struct branch_info *new)
 774 {
 775         int ret = 0;
 776         struct branch_info old;
 777         void *path_to_free;
 778         unsigned char rev[20];
 779         int flag, writeout_error = 0;
 780         memset(&old, 0, sizeof(old));
 781         old.path = path_to_free = resolve_refdup("HEAD", rev, 0, &flag);
 782         old.commit = lookup_commit_reference_gently(rev, 1);
 783         if (!(flag & REF_ISSYMREF))
 784                 old.path = NULL;
 785
 786         if (old.path && !prefixcmp(old.path, "refs/heads/"))
 787                 old.name = old.path + strlen("refs/heads/");
 788
 789         if (!new->name) {
 790                 new->name = "HEAD";
 791                 new->commit = old.commit;
 792                 if (!new->commit)
 793                         die(_("You are on a branch yet to be born"));
 794                 parse_commit(new->commit);
 795         }
 796
 797         ret = merge_working_tree(opts, &old, new, &writeout_error);
 798         if (ret) {
 799                 free(path_to_free);
 800                 return ret;
 801         }
 802
 803         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 804                 orphaned_commit_warning(old.commit, new->commit);
 805
 806         update_refs_for_switch(opts, &old, new);
 807
 808         ret = post_checkout_hook(old.commit, new->commit, 1);
 809         free(path_to_free);
 810         return ret || writeout_error;
 811 }
 812
 813 static int git_checkout_config(const char *var, const char *value, void *cb)
 814 {
 815         if (!strcmp(var, "diff.ignoresubmodules")) {
 816                 struct checkout_opts *opts = cb;
 817                 handle_ignore_submodules_arg(&opts->diff_options, value);
 818                 return 0;
 819         }
 820
 821         if (!prefixcmp(var, "submodule."))
 822                 return parse_submodule_config_option(var, value);
 823
 824         return git_xmerge_config(var, value, NULL);
 825 }
 826
 827 struct tracking_name_data {
 828         /* const */ char *src_ref;
 829         char *dst_ref;
 830         unsigned char *dst_sha1;
 831         int unique;
 832 };
 833
 834 static int check_tracking_name(struct remote *remote, void *cb_data)
 835 {
 836         struct tracking_name_data *cb = cb_data;
 837         struct refspec query;
 838         memset(&query, 0, sizeof(struct refspec));
 839         query.src = cb->src_ref;
 840         if (remote_find_tracking(remote, &query) ||
 841             get_sha1(query.dst, cb->dst_sha1)) {
 842                 free(query.dst);
 843                 return 0;
 844         }
 845         if (cb->dst_ref) {
 846                 free(query.dst);
 847                 cb->unique = 0;
 848                 return 0;
 849         }
 850         cb->dst_ref = query.dst;
 851         return 0;
 852 }
 853
 854 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 855 {
 856         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
 857         char src_ref[PATH_MAX];
 858         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
 859         cb_data.src_ref = src_ref;
 860         cb_data.dst_sha1 = sha1;
 861         for_each_remote(check_tracking_name, &cb_data);
 862         if (cb_data.unique)
 863                 return cb_data.dst_ref;
 864         free(cb_data.dst_ref);
 865         return NULL;
 866 }
 867
 868 static int parse_branchname_arg(int argc, const char **argv,
 869                                 int dwim_new_local_branch_ok,
 870                                 struct branch_info *new,
 871                                 struct tree **source_tree,
 872                                 unsigned char rev[20],
 873                                 const char **new_branch)
 874 {
 875         int argcount = 0;
 876         unsigned char branch_rev[20];
 877         const char *arg;
 878         int has_dash_dash;
 879
 880         /*
 881          * case 1: git checkout <ref> -- [<paths>]
 882          *
 883          *   <ref> must be a valid tree, everything after the '--' must be
 884          *   a path.
 885          *
 886          * case 2: git checkout -- [<paths>]
 887          *
 888          *   everything after the '--' must be paths.
 889          *
 890          * case 3: git checkout <something> [<paths>]
 891          *
 892          *   With no paths, if <something> is a commit, that is to
 893          *   switch to the branch or detach HEAD at it.  As a special case,
 894          *   if <something> is A...B (missing A or B means HEAD but you can
 895          *   omit at most one side), and if there is a unique merge base
 896          *   between A and B, A...B names that merge base.
 897          *
 898          *   With no paths, if <something> is _not_ a commit, no -t nor -b
 899          *   was given, and there is a tracking branch whose name is
 900          *   <something> in one and only one remote, then this is a short-hand
 901          *   to fork local <something> from that remote-tracking branch.
 902          *
 903          *   Otherwise <something> shall not be ambiguous.
 904          *   - If it's *only* a reference, treat it like case (1).
 905          *   - If it's only a path, treat it like case (2).
 906          *   - else: fail.
 907          *
 908          */
 909         if (!argc)
 910                 return 0;
 911
 912         if (!strcmp(argv[0], "--"))     /* case (2) */
 913                 return 1;
 914
 915         arg = argv[0];
 916         has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
 917
 918         if (!strcmp(arg, "-"))
 919                 arg = "@{-1}";
 920
 921         if (get_sha1_mb(arg, rev)) {
 922                 if (has_dash_dash)          /* case (1) */
 923                         die(_("invalid reference: %s"), arg);
 924                 if (dwim_new_local_branch_ok &&
 925                     !check_filename(NULL, arg) &&
 926                     argc == 1) {
 927                         const char *remote = unique_tracking_name(arg, rev);
 928                         if (!remote)
 929                                 return argcount;
 930                         *new_branch = arg;
 931                         arg = remote;
 932                         /* DWIMmed to create local branch */
 933                 } else {
 934                         return argcount;
 935                 }
 936         }
 937
 938         /* we can't end up being in (2) anymore, eat the argument */
 939         argcount++;
 940         argv++;
 941         argc--;
 942
 943         new->name = arg;
 944         setup_branch_path(new);
 945
 946         if (!check_refname_format(new->path, 0) &&
 947             !read_ref(new->path, branch_rev))
 948                 hashcpy(rev, branch_rev);
 949         else
 950                 new->path = NULL; /* not an existing branch */
 951
 952         new->commit = lookup_commit_reference_gently(rev, 1);
 953         if (!new->commit) {
 954                 /* not a commit */
 955                 *source_tree = parse_tree_indirect(rev);
 956         } else {
 957                 parse_commit(new->commit);
 958                 *source_tree = new->commit->tree;
 959         }
 960
 961         if (!*source_tree)                   /* case (1): want a tree */
 962                 die(_("reference is not a tree: %s"), arg);
 963         if (!has_dash_dash) {/* case (3 -> 1) */
 964                 /*
 965                  * Do not complain the most common case
 966                  *      git checkout branch
 967                  * even if there happen to be a file called 'branch';
 968                  * it would be extremely annoying.
 969                  */
 970                 if (argc)
 971                         verify_non_filename(NULL, arg);
 972         } else {
 973                 argcount++;
 974                 argv++;
 975                 argc--;
 976         }
 977
 978         return argcount;
 979 }
 980
 981 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
 982 {
 983         int status;
 984         struct strbuf branch_ref = STRBUF_INIT;
 985
 986         if (!opts->new_branch)
 987                 die(_("You are on a branch yet to be born"));
 988         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
 989         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
 990         strbuf_release(&branch_ref);
 991         if (!opts->quiet)
 992                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
 993                         opts->new_branch);
 994         return status;
 995 }
 996
 997 static int checkout_branch(struct checkout_opts *opts,
 998                            struct branch_info *new)
 999 {
1000         if (opts->pathspec.nr)
1001                 die(_("paths cannot be used with switching branches"));
1002
1003         if (opts->patch_mode)
1004                 die(_("'%s' cannot be used with switching branches"),
1005                     "--patch");
1006
1007         if (opts->writeout_stage)
1008                 die(_("'%s' cannot be used with switching branches"),
1009                     "--ours/--theirs");
1010
1011         if (opts->force && opts->merge)
1012                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1013
1014         if (opts->force_detach && opts->new_branch)
1015                 die(_("'%s' cannot be used with '%s'"),
1016                     "--detach", "-b/-B/--orphan");
1017
1018         if (opts->new_orphan_branch) {
1019                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1020                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1021         } else if (opts->force_detach) {
1022                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1023                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1024         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1025                 opts->track = git_branch_track;
1026
1027         if (new->name && !new->commit)
1028                 die(_("Cannot switch branch to a non-commit '%s'"),
1029                     new->name);
1030
1031         if (!new->commit && opts->new_branch) {
1032                 unsigned char rev[20];
1033                 int flag;
1034
1035                 if (!read_ref_full("HEAD", rev, 0, &flag) &&
1036                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1037                         return switch_unborn_to_new_branch(opts);
1038         }
1039         return switch_branches(opts, new);
1040 }
1041
1042 int cmd_checkout(int argc, const char **argv, const char *prefix)
1043 {
1044         struct checkout_opts opts;
1045         struct branch_info new;
1046         char *conflict_style = NULL;
1047         int dwim_new_local_branch = 1;
1048         struct option options[] = {
1049                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1050                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1051                            N_("create and checkout a new branch")),
1052                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1053                            N_("create/reset and checkout a branch")),
1054                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1055                 OPT_BOOLEAN(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1056                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1057                         BRANCH_TRACK_EXPLICIT),
1058                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new branch"), N_("new unparented branch")),
1059                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1060                             2),
1061                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1062                             3),
1063                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1064                 OPT_BOOLEAN('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1065                 OPT_BOOLEAN(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1066                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1067                            N_("conflict style (merge or diff3)")),
1068                 OPT_BOOLEAN('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1069                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1070                          N_("do not limit pathspecs to sparse entries only")),
1071                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
1072                   N_("second guess 'git checkout no-such-branch'"),
1073                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
1074                 OPT_END(),
1075         };
1076
1077         memset(&opts, 0, sizeof(opts));
1078         memset(&new, 0, sizeof(new));
1079         opts.overwrite_ignore = 1;
1080         opts.prefix = prefix;
1081
1082         gitmodules_config();
1083         git_config(git_checkout_config, &opts);
1084
1085         opts.track = BRANCH_TRACK_UNSPECIFIED;
1086
1087         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1088                              PARSE_OPT_KEEP_DASHDASH);
1089
1090         if (conflict_style) {
1091                 opts.merge = 1; /* implied */
1092                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1093         }
1094
1095         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1096                 die(_("-b, -B and --orphan are mutually exclusive"));
1097
1098         /*
1099          * From here on, new_branch will contain the branch to be checked out,
1100          * and new_branch_force and new_orphan_branch will tell us which one of
1101          * -b/-B/--orphan is being used.
1102          */
1103         if (opts.new_branch_force)
1104                 opts.new_branch = opts.new_branch_force;
1105
1106         if (opts.new_orphan_branch)
1107                 opts.new_branch = opts.new_orphan_branch;
1108
1109         /* --track without -b/-B/--orphan should DWIM */
1110         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1111                 const char *argv0 = argv[0];
1112                 if (!argc || !strcmp(argv0, "--"))
1113                         die (_("--track needs a branch name"));
1114                 if (!prefixcmp(argv0, "refs/"))
1115                         argv0 += 5;
1116                 if (!prefixcmp(argv0, "remotes/"))
1117                         argv0 += 8;
1118                 argv0 = strchr(argv0, '/');
1119                 if (!argv0 || !argv0[1])
1120                         die (_("Missing branch name; try -b"));
1121                 opts.new_branch = argv0 + 1;
1122         }
1123
1124         /*
1125          * Extract branch name from command line arguments, so
1126          * all that is left is pathspecs.
1127          *
1128          * Handle
1129          *
1130          *  1) git checkout <tree> -- [<paths>]
1131          *  2) git checkout -- [<paths>]
1132          *  3) git checkout <something> [<paths>]
1133          *
1134          * including "last branch" syntax and DWIM-ery for names of
1135          * remote branches, erroring out for invalid or ambiguous cases.
1136          */
1137         if (argc) {
1138                 unsigned char rev[20];
1139                 int dwim_ok =
1140                         !opts.patch_mode &&
1141                         dwim_new_local_branch &&
1142                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1143                         !opts.new_branch;
1144                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1145                                              &new, &opts.source_tree,
1146                                              rev, &opts.new_branch);
1147                 argv += n;
1148                 argc -= n;
1149         }
1150
1151         if (argc) {
1152                 /*
1153                  * In patch mode (opts.patch_mode != 0), we pass the
1154                  * pathspec to an external program, git-add--interactive.
1155                  * Do not accept any kind of magic that that program
1156                  * cannot handle. Magic mask is pretty safe to be
1157                  * lifted for new magic when opts.patch_mode == 0.
1158                  */
1159                 parse_pathspec(&opts.pathspec, 0,
1160                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1161                                prefix, argv);
1162
1163                 if (!opts.pathspec.nr)
1164                         die(_("invalid path specification"));
1165
1166                 /*
1167                  * Try to give more helpful suggestion.
1168                  * new_branch && argc > 1 will be caught later.
1169                  */
1170                 if (opts.new_branch && argc == 1)
1171                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1172                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1173                             opts.new_branch, argv[0]);
1174
1175                 if (opts.force_detach)
1176                         die(_("git checkout: --detach does not take a path argument '%s'"),
1177                             argv[0]);
1178
1179                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1180                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1181                               "checking out of the index."));
1182         }
1183
1184         if (opts.new_branch) {
1185                 struct strbuf buf = STRBUF_INIT;
1186
1187                 opts.branch_exists =
1188                         validate_new_branchname(opts.new_branch, &buf,
1189                                                 !!opts.new_branch_force,
1190                                                 !!opts.new_branch_force);
1191
1192                 strbuf_release(&buf);
1193         }
1194
1195         if (opts.patch_mode || opts.pathspec.nr)
1196                 return checkout_paths(&opts, new.name);
1197         else
1198                 return checkout_branch(&opts, &new);
1199 }