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
  22 static const char * const checkout_usage[] = {
  23         "git checkout [options] <branch>",
  24         "git checkout [options] [<branch>] -- <file>...",
  25         NULL,
  26 };
  27
  28 struct checkout_opts {
  29         int quiet;
  30         int merge;
  31         int force;
  32         int writeout_stage;
  33         int writeout_error;
  34
  35         const char *new_branch;
  36         int new_branch_log;
  37         enum branch_track track;
  38 };
  39
  40 static int post_checkout_hook(struct commit *old, struct commit *new,
  41                               int changed)
  42 {
  43         return run_hook(NULL, "post-checkout",
  44                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
  45                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
  46                         changed ? "1" : "0", NULL);
  47         /* "new" can be NULL when checking out from the index before
  48            a commit exists. */
  49
  50 }
  51
  52 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  53                 const char *pathname, unsigned mode, int stage, void *context)
  54 {
  55         int len;
  56         struct cache_entry *ce;
  57
  58         if (S_ISDIR(mode))
  59                 return READ_TREE_RECURSIVE;
  60
  61         len = baselen + strlen(pathname);
  62         ce = xcalloc(1, cache_entry_size(len));
  63         hashcpy(ce->sha1, sha1);
  64         memcpy(ce->name, base, baselen);
  65         memcpy(ce->name + baselen, pathname, len - baselen);
  66         ce->ce_flags = create_ce_flags(len, 0);
  67         ce->ce_mode = create_ce_mode(mode);
  68         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  69         return 0;
  70 }
  71
  72 static int read_tree_some(struct tree *tree, const char **pathspec)
  73 {
  74         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
  75
  76         /* update the index with the given tree's info
  77          * for all args, expanding wildcards, and exit
  78          * with any non-zero return code.
  79          */
  80         return 0;
  81 }
  82
  83 static int skip_same_name(struct cache_entry *ce, int pos)
  84 {
  85         while (++pos < active_nr &&
  86                !strcmp(active_cache[pos]->name, ce->name))
  87                 ; /* skip */
  88         return pos;
  89 }
  90
  91 static int check_stage(int stage, struct cache_entry *ce, int pos)
  92 {
  93         while (pos < active_nr &&
  94                !strcmp(active_cache[pos]->name, ce->name)) {
  95                 if (ce_stage(active_cache[pos]) == stage)
  96                         return 0;
  97                 pos++;
  98         }
  99         return error("path '%s' does not have %s version",
 100                      ce->name,
 101                      (stage == 2) ? "our" : "their");
 102 }
 103
 104 static int check_all_stages(struct cache_entry *ce, int pos)
 105 {
 106         if (ce_stage(ce) != 1 ||
 107             active_nr <= pos + 2 ||
 108             strcmp(active_cache[pos+1]->name, ce->name) ||
 109             ce_stage(active_cache[pos+1]) != 2 ||
 110             strcmp(active_cache[pos+2]->name, ce->name) ||
 111             ce_stage(active_cache[pos+2]) != 3)
 112                 return error("path '%s' does not have all three versions",
 113                              ce->name);
 114         return 0;
 115 }
 116
 117 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 118                           struct checkout *state)
 119 {
 120         while (pos < active_nr &&
 121                !strcmp(active_cache[pos]->name, ce->name)) {
 122                 if (ce_stage(active_cache[pos]) == stage)
 123                         return checkout_entry(active_cache[pos], state, NULL);
 124                 pos++;
 125         }
 126         return error("path '%s' does not have %s version",
 127                      ce->name,
 128                      (stage == 2) ? "our" : "their");
 129 }
 130
 131 /* NEEDSWORK: share with merge-recursive */
 132 static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
 133 {
 134         unsigned long size;
 135         enum object_type type;
 136
 137         if (!hashcmp(sha1, null_sha1)) {
 138                 mm->ptr = xstrdup("");
 139                 mm->size = 0;
 140                 return;
 141         }
 142
 143         mm->ptr = read_sha1_file(sha1, &type, &size);
 144         if (!mm->ptr || type != OBJ_BLOB)
 145                 die("unable to read blob object %s", sha1_to_hex(sha1));
 146         mm->size = size;
 147 }
 148
 149 static int checkout_merged(int pos, struct checkout *state)
 150 {
 151         struct cache_entry *ce = active_cache[pos];
 152         const char *path = ce->name;
 153         mmfile_t ancestor, ours, theirs;
 154         int status;
 155         unsigned char sha1[20];
 156         mmbuffer_t result_buf;
 157
 158         if (ce_stage(ce) != 1 ||
 159             active_nr <= pos + 2 ||
 160             strcmp(active_cache[pos+1]->name, path) ||
 161             ce_stage(active_cache[pos+1]) != 2 ||
 162             strcmp(active_cache[pos+2]->name, path) ||
 163             ce_stage(active_cache[pos+2]) != 3)
 164                 return error("path '%s' does not have all 3 versions", path);
 165
 166         fill_mm(active_cache[pos]->sha1, &ancestor);
 167         fill_mm(active_cache[pos+1]->sha1, &ours);
 168         fill_mm(active_cache[pos+2]->sha1, &theirs);
 169
 170         status = ll_merge(&result_buf, path, &ancestor,
 171                           &ours, "ours", &theirs, "theirs", 0);
 172         free(ancestor.ptr);
 173         free(ours.ptr);
 174         free(theirs.ptr);
 175         if (status < 0 || !result_buf.ptr) {
 176                 free(result_buf.ptr);
 177                 return error("path '%s': cannot merge", path);
 178         }
 179
 180         /*
 181          * NEEDSWORK:
 182          * There is absolutely no reason to write this as a blob object
 183          * and create a phony cache entry just to leak.  This hack is
 184          * primarily to get to the write_entry() machinery that massages
 185          * the contents to work-tree format and writes out which only
 186          * allows it for a cache entry.  The code in write_entry() needs
 187          * to be refactored to allow us to feed a <buffer, size, mode>
 188          * instead of a cache entry.  Such a refactoring would help
 189          * merge_recursive as well (it also writes the merge result to the
 190          * object database even when it may contain conflicts).
 191          */
 192         if (write_sha1_file(result_buf.ptr, result_buf.size,
 193                             blob_type, sha1))
 194                 die("Unable to add merge result for '%s'", path);
 195         ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
 196                               sha1,
 197                               path, 2, 0);
 198         if (!ce)
 199                 die("make_cache_entry failed for path '%s'", path);
 200         status = checkout_entry(ce, state, NULL);
 201         return status;
 202 }
 203
 204 static int checkout_paths(struct tree *source_tree, const char **pathspec,
 205                           struct checkout_opts *opts)
 206 {
 207         int pos;
 208         struct checkout state;
 209         static char *ps_matched;
 210         unsigned char rev[20];
 211         int flag;
 212         struct commit *head;
 213         int errs = 0;
 214         int stage = opts->writeout_stage;
 215         int merge = opts->merge;
 216         int newfd;
 217         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 218
 219         newfd = hold_locked_index(lock_file, 1);
 220         if (read_cache_preload(pathspec) < 0)
 221                 return error("corrupt index file");
 222
 223         if (source_tree)
 224                 read_tree_some(source_tree, pathspec);
 225
 226         for (pos = 0; pathspec[pos]; pos++)
 227                 ;
 228         ps_matched = xcalloc(1, pos);
 229
 230         for (pos = 0; pos < active_nr; pos++) {
 231                 struct cache_entry *ce = active_cache[pos];
 232                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 233         }
 234
 235         if (report_path_error(ps_matched, pathspec, 0))
 236                 return 1;
 237
 238         /* "checkout -m path" to recreate conflicted state */
 239         if (opts->merge)
 240                 unmerge_cache(pathspec);
 241
 242         /* Any unmerged paths? */
 243         for (pos = 0; pos < active_nr; pos++) {
 244                 struct cache_entry *ce = active_cache[pos];
 245                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 246                         if (!ce_stage(ce))
 247                                 continue;
 248                         if (opts->force) {
 249                                 warning("path '%s' is unmerged", ce->name);
 250                         } else if (stage) {
 251                                 errs |= check_stage(stage, ce, pos);
 252                         } else if (opts->merge) {
 253                                 errs |= check_all_stages(ce, pos);
 254                         } else {
 255                                 errs = 1;
 256                                 error("path '%s' is unmerged", ce->name);
 257                         }
 258                         pos = skip_same_name(ce, pos) - 1;
 259                 }
 260         }
 261         if (errs)
 262                 return 1;
 263
 264         /* Now we are committed to check them out */
 265         memset(&state, 0, sizeof(state));
 266         state.force = 1;
 267         state.refresh_cache = 1;
 268         for (pos = 0; pos < active_nr; pos++) {
 269                 struct cache_entry *ce = active_cache[pos];
 270                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 271                         if (!ce_stage(ce)) {
 272                                 errs |= checkout_entry(ce, &state, NULL);
 273                                 continue;
 274                         }
 275                         if (stage)
 276                                 errs |= checkout_stage(stage, ce, pos, &state);
 277                         else if (merge)
 278                                 errs |= checkout_merged(pos, &state);
 279                         pos = skip_same_name(ce, pos) - 1;
 280                 }
 281         }
 282
 283         if (write_cache(newfd, active_cache, active_nr) ||
 284             commit_locked_index(lock_file))
 285                 die("unable to write new index file");
 286
 287         resolve_ref("HEAD", rev, 0, &flag);
 288         head = lookup_commit_reference_gently(rev, 1);
 289
 290         errs |= post_checkout_hook(head, head, 0);
 291         return errs;
 292 }
 293
 294 static void show_local_changes(struct object *head)
 295 {
 296         struct rev_info rev;
 297         /* I think we want full paths, even if we're in a subdirectory. */
 298         init_revisions(&rev, NULL);
 299         rev.abbrev = 0;
 300         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 301         if (diff_setup_done(&rev.diffopt) < 0)
 302                 die("diff_setup_done failed");
 303         add_pending_object(&rev, head, NULL);
 304         run_diff_index(&rev, 0);
 305 }
 306
 307 static void describe_detached_head(char *msg, struct commit *commit)
 308 {
 309         struct strbuf sb = STRBUF_INIT;
 310         struct pretty_print_context ctx = {0};
 311         parse_commit(commit);
 312         pretty_print_commit(CMIT_FMT_ONELINE, commit, &sb, &ctx);
 313         fprintf(stderr, "%s %s... %s\n", msg,
 314                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 315         strbuf_release(&sb);
 316 }
 317
 318 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 319 {
 320         struct unpack_trees_options opts;
 321         struct tree_desc tree_desc;
 322
 323         memset(&opts, 0, sizeof(opts));
 324         opts.head_idx = -1;
 325         opts.update = worktree;
 326         opts.skip_unmerged = !worktree;
 327         opts.reset = 1;
 328         opts.merge = 1;
 329         opts.fn = oneway_merge;
 330         opts.verbose_update = !o->quiet;
 331         opts.src_index = &the_index;
 332         opts.dst_index = &the_index;
 333         parse_tree(tree);
 334         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 335         switch (unpack_trees(1, &tree_desc, &opts)) {
 336         case -2:
 337                 o->writeout_error = 1;
 338                 /*
 339                  * We return 0 nevertheless, as the index is all right
 340                  * and more importantly we have made best efforts to
 341                  * update paths in the work tree, and we cannot revert
 342                  * them.
 343                  */
 344         case 0:
 345                 return 0;
 346         default:
 347                 return 128;
 348         }
 349 }
 350
 351 struct branch_info {
 352         const char *name; /* The short name used */
 353         const char *path; /* The full name of a real branch */
 354         struct commit *commit; /* The named commit */
 355 };
 356
 357 static void setup_branch_path(struct branch_info *branch)
 358 {
 359         struct strbuf buf = STRBUF_INIT;
 360
 361         strbuf_branchname(&buf, branch->name);
 362         if (strcmp(buf.buf, branch->name))
 363                 branch->name = xstrdup(buf.buf);
 364         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 365         branch->path = strbuf_detach(&buf, NULL);
 366 }
 367
 368 static int merge_working_tree(struct checkout_opts *opts,
 369                               struct branch_info *old, struct branch_info *new)
 370 {
 371         int ret;
 372         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 373         int newfd = hold_locked_index(lock_file, 1);
 374
 375         if (read_cache_preload(NULL) < 0)
 376                 return error("corrupt index file");
 377
 378         resolve_undo_clear();
 379         if (opts->force) {
 380                 ret = reset_tree(new->commit->tree, opts, 1);
 381                 if (ret)
 382                         return ret;
 383         } else {
 384                 struct tree_desc trees[2];
 385                 struct tree *tree;
 386                 struct unpack_trees_options topts;
 387
 388                 memset(&topts, 0, sizeof(topts));
 389                 topts.head_idx = -1;
 390                 topts.src_index = &the_index;
 391                 topts.dst_index = &the_index;
 392
 393                 topts.msgs.not_uptodate_file = "You have local changes to '%s'; cannot switch branches.";
 394
 395                 refresh_cache(REFRESH_QUIET);
 396
 397                 if (unmerged_cache()) {
 398                         error("you need to resolve your current index first");
 399                         return 1;
 400                 }
 401
 402                 /* 2-way merge to the new branch */
 403                 topts.initial_checkout = is_cache_unborn();
 404                 topts.update = 1;
 405                 topts.merge = 1;
 406                 topts.gently = opts->merge && old->commit;
 407                 topts.verbose_update = !opts->quiet;
 408                 topts.fn = twoway_merge;
 409                 topts.dir = xcalloc(1, sizeof(*topts.dir));
 410                 topts.dir->flags |= DIR_SHOW_IGNORED;
 411                 topts.dir->exclude_per_dir = ".gitignore";
 412                 tree = parse_tree_indirect(old->commit ?
 413                                            old->commit->object.sha1 :
 414                                            (unsigned char *)EMPTY_TREE_SHA1_BIN);
 415                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 416                 tree = parse_tree_indirect(new->commit->object.sha1);
 417                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 418
 419                 ret = unpack_trees(2, trees, &topts);
 420                 if (ret == -1) {
 421                         /*
 422                          * Unpack couldn't do a trivial merge; either
 423                          * give up or do a real merge, depending on
 424                          * whether the merge flag was used.
 425                          */
 426                         struct tree *result;
 427                         struct tree *work;
 428                         struct merge_options o;
 429                         if (!opts->merge)
 430                                 return 1;
 431
 432                         /*
 433                          * Without old->commit, the below is the same as
 434                          * the two-tree unpack we already tried and failed.
 435                          */
 436                         if (!old->commit)
 437                                 return 1;
 438
 439                         /* Do more real merge */
 440
 441                         /*
 442                          * We update the index fully, then write the
 443                          * tree from the index, then merge the new
 444                          * branch with the current tree, with the old
 445                          * branch as the base. Then we reset the index
 446                          * (but not the working tree) to the new
 447                          * branch, leaving the working tree as the
 448                          * merged version, but skipping unmerged
 449                          * entries in the index.
 450                          */
 451
 452                         add_files_to_cache(NULL, NULL, 0);
 453                         init_merge_options(&o);
 454                         o.verbosity = 0;
 455                         work = write_tree_from_memory(&o);
 456
 457                         ret = reset_tree(new->commit->tree, opts, 1);
 458                         if (ret)
 459                                 return ret;
 460                         o.branch1 = new->name;
 461                         o.branch2 = "local";
 462                         merge_trees(&o, new->commit->tree, work,
 463                                 old->commit->tree, &result);
 464                         ret = reset_tree(new->commit->tree, opts, 0);
 465                         if (ret)
 466                                 return ret;
 467                 }
 468         }
 469
 470         if (write_cache(newfd, active_cache, active_nr) ||
 471             commit_locked_index(lock_file))
 472                 die("unable to write new index file");
 473
 474         if (!opts->force && !opts->quiet)
 475                 show_local_changes(&new->commit->object);
 476
 477         return 0;
 478 }
 479
 480 static void report_tracking(struct branch_info *new)
 481 {
 482         struct strbuf sb = STRBUF_INIT;
 483         struct branch *branch = branch_get(new->name);
 484
 485         if (!format_tracking_info(branch, &sb))
 486                 return;
 487         fputs(sb.buf, stdout);
 488         strbuf_release(&sb);
 489 }
 490
 491 static void update_refs_for_switch(struct checkout_opts *opts,
 492                                    struct branch_info *old,
 493                                    struct branch_info *new)
 494 {
 495         struct strbuf msg = STRBUF_INIT;
 496         const char *old_desc;
 497         if (opts->new_branch) {
 498                 create_branch(old->name, opts->new_branch, new->name, 0,
 499                               opts->new_branch_log, opts->track);
 500                 new->name = opts->new_branch;
 501                 setup_branch_path(new);
 502         }
 503
 504         old_desc = old->name;
 505         if (!old_desc && old->commit)
 506                 old_desc = sha1_to_hex(old->commit->object.sha1);
 507         strbuf_addf(&msg, "checkout: moving from %s to %s",
 508                     old_desc ? old_desc : "(invalid)", new->name);
 509
 510         if (new->path) {
 511                 create_symref("HEAD", new->path, msg.buf);
 512                 if (!opts->quiet) {
 513                         if (old->path && !strcmp(new->path, old->path))
 514                                 fprintf(stderr, "Already on '%s'\n",
 515                                         new->name);
 516                         else
 517                                 fprintf(stderr, "Switched to%s branch '%s'\n",
 518                                         opts->new_branch ? " a new" : "",
 519                                         new->name);
 520                 }
 521         } else if (strcmp(new->name, "HEAD")) {
 522                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 523                            REF_NODEREF, DIE_ON_ERR);
 524                 if (!opts->quiet) {
 525                         if (old->path)
 526                                 fprintf(stderr, "Note: moving to '%s' which isn't a local branch\nIf you want to create a new branch from this checkout, you may do so\n(now or later) by using -b with the checkout command again. Example:\n  git checkout -b <new_branch_name>\n", new->name);
 527                         describe_detached_head("HEAD is now at", new->commit);
 528                 }
 529         }
 530         remove_branch_state();
 531         strbuf_release(&msg);
 532         if (!opts->quiet && (new->path || !strcmp(new->name, "HEAD")))
 533                 report_tracking(new);
 534 }
 535
 536 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 537 {
 538         int ret = 0;
 539         struct branch_info old;
 540         unsigned char rev[20];
 541         int flag;
 542         memset(&old, 0, sizeof(old));
 543         old.path = resolve_ref("HEAD", rev, 0, &flag);
 544         old.commit = lookup_commit_reference_gently(rev, 1);
 545         if (!(flag & REF_ISSYMREF))
 546                 old.path = NULL;
 547
 548         if (old.path && !prefixcmp(old.path, "refs/heads/"))
 549                 old.name = old.path + strlen("refs/heads/");
 550
 551         if (!new->name) {
 552                 new->name = "HEAD";
 553                 new->commit = old.commit;
 554                 if (!new->commit)
 555                         die("You are on a branch yet to be born");
 556                 parse_commit(new->commit);
 557         }
 558
 559         ret = merge_working_tree(opts, &old, new);
 560         if (ret)
 561                 return ret;
 562
 563         /*
 564          * If we were on a detached HEAD, but have now moved to
 565          * a new commit, we want to mention the old commit once more
 566          * to remind the user that it might be lost.
 567          */
 568         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 569                 describe_detached_head("Previous HEAD position was", old.commit);
 570
 571         update_refs_for_switch(opts, &old, new);
 572
 573         ret = post_checkout_hook(old.commit, new->commit, 1);
 574         return ret || opts->writeout_error;
 575 }
 576
 577 static int git_checkout_config(const char *var, const char *value, void *cb)
 578 {
 579         return git_xmerge_config(var, value, cb);
 580 }
 581
 582 static int interactive_checkout(const char *revision, const char **pathspec,
 583                                 struct checkout_opts *opts)
 584 {
 585         return run_add_interactive(revision, "--patch=checkout", pathspec);
 586 }
 587
 588 struct tracking_name_data {
 589         const char *name;
 590         char *remote;
 591         int unique;
 592 };
 593
 594 static int check_tracking_name(const char *refname, const unsigned char *sha1,
 595                                int flags, void *cb_data)
 596 {
 597         struct tracking_name_data *cb = cb_data;
 598         const char *slash;
 599
 600         if (prefixcmp(refname, "refs/remotes/"))
 601                 return 0;
 602         slash = strchr(refname + 13, '/');
 603         if (!slash || strcmp(slash + 1, cb->name))
 604                 return 0;
 605         if (cb->remote) {
 606                 cb->unique = 0;
 607                 return 0;
 608         }
 609         cb->remote = xstrdup(refname);
 610         return 0;
 611 }
 612
 613 static const char *unique_tracking_name(const char *name)
 614 {
 615         struct tracking_name_data cb_data = { name, NULL, 1 };
 616         for_each_ref(check_tracking_name, &cb_data);
 617         if (cb_data.unique)
 618                 return cb_data.remote;
 619         free(cb_data.remote);
 620         return NULL;
 621 }
 622
 623 int cmd_checkout(int argc, const char **argv, const char *prefix)
 624 {
 625         struct checkout_opts opts;
 626         unsigned char rev[20];
 627         const char *arg;
 628         struct branch_info new;
 629         struct tree *source_tree = NULL;
 630         char *conflict_style = NULL;
 631         int patch_mode = 0;
 632         int dwim_new_local_branch = 1;
 633         struct option options[] = {
 634                 OPT__QUIET(&opts.quiet),
 635                 OPT_STRING('b', NULL, &opts.new_branch, "new branch", "branch"),
 636                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "log for new branch"),
 637                 OPT_SET_INT('t', "track",  &opts.track, "track",
 638                         BRANCH_TRACK_EXPLICIT),
 639                 OPT_SET_INT('2', "ours", &opts.writeout_stage, "stage",
 640                             2),
 641                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, "stage",
 642                             3),
 643                 OPT_BOOLEAN('f', "force", &opts.force, "force"),
 644                 OPT_BOOLEAN('m', "merge", &opts.merge, "merge"),
 645                 OPT_STRING(0, "conflict", &conflict_style, "style",
 646                            "conflict style (merge or diff3)"),
 647                 OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
 648                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
 649                   "second guess 'git checkout no-such-branch'",
 650                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
 651                 OPT_END(),
 652         };
 653         int has_dash_dash;
 654
 655         memset(&opts, 0, sizeof(opts));
 656         memset(&new, 0, sizeof(new));
 657
 658         git_config(git_checkout_config, NULL);
 659
 660         opts.track = BRANCH_TRACK_UNSPECIFIED;
 661
 662         argc = parse_options(argc, argv, prefix, options, checkout_usage,
 663                              PARSE_OPT_KEEP_DASHDASH);
 664
 665         if (patch_mode && (opts.track > 0 || opts.new_branch
 666                            || opts.new_branch_log || opts.merge || opts.force))
 667                 die ("--patch is incompatible with all other options");
 668
 669         /* --track without -b should DWIM */
 670         if (0 < opts.track && !opts.new_branch) {
 671                 const char *argv0 = argv[0];
 672                 if (!argc || !strcmp(argv0, "--"))
 673                         die ("--track needs a branch name");
 674                 if (!prefixcmp(argv0, "refs/"))
 675                         argv0 += 5;
 676                 if (!prefixcmp(argv0, "remotes/"))
 677                         argv0 += 8;
 678                 argv0 = strchr(argv0, '/');
 679                 if (!argv0 || !argv0[1])
 680                         die ("Missing branch name; try -b");
 681                 opts.new_branch = argv0 + 1;
 682         }
 683
 684         if (conflict_style) {
 685                 opts.merge = 1; /* implied */
 686                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
 687         }
 688
 689         if (opts.force && opts.merge)
 690                 die("git checkout: -f and -m are incompatible");
 691
 692         /*
 693          * case 1: git checkout <ref> -- [<paths>]
 694          *
 695          *   <ref> must be a valid tree, everything after the '--' must be
 696          *   a path.
 697          *
 698          * case 2: git checkout -- [<paths>]
 699          *
 700          *   everything after the '--' must be paths.
 701          *
 702          * case 3: git checkout <something> [<paths>]
 703          *
 704          *   With no paths, if <something> is a commit, that is to
 705          *   switch to the branch or detach HEAD at it.  As a special case,
 706          *   if <something> is A...B (missing A or B means HEAD but you can
 707          *   omit at most one side), and if there is a unique merge base
 708          *   between A and B, A...B names that merge base.
 709          *
 710          *   With no paths, if <something> is _not_ a commit, no -t nor -b
 711          *   was given, and there is a tracking branch whose name is
 712          *   <something> in one and only one remote, then this is a short-hand
 713          *   to fork local <something> from that remote tracking branch.
 714          *
 715          *   Otherwise <something> shall not be ambiguous.
 716          *   - If it's *only* a reference, treat it like case (1).
 717          *   - If it's only a path, treat it like case (2).
 718          *   - else: fail.
 719          *
 720          */
 721         if (argc) {
 722                 if (!strcmp(argv[0], "--")) {       /* case (2) */
 723                         argv++;
 724                         argc--;
 725                         goto no_reference;
 726                 }
 727
 728                 arg = argv[0];
 729                 has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
 730
 731                 if (!strcmp(arg, "-"))
 732                         arg = "@{-1}";
 733
 734                 if (get_sha1_mb(arg, rev)) {
 735                         if (has_dash_dash)          /* case (1) */
 736                                 die("invalid reference: %s", arg);
 737                         if (!patch_mode &&
 738                             dwim_new_local_branch &&
 739                             opts.track == BRANCH_TRACK_UNSPECIFIED &&
 740                             !opts.new_branch &&
 741                             !check_filename(NULL, arg) &&
 742                             argc == 1) {
 743                                 const char *remote = unique_tracking_name(arg);
 744                                 if (!remote || get_sha1(remote, rev))
 745                                         goto no_reference;
 746                                 opts.new_branch = arg;
 747                                 arg = remote;
 748                                 /* DWIMmed to create local branch */
 749                         }
 750                         else
 751                                 goto no_reference;
 752                 }
 753
 754                 /* we can't end up being in (2) anymore, eat the argument */
 755                 argv++;
 756                 argc--;
 757
 758                 new.name = arg;
 759                 if ((new.commit = lookup_commit_reference_gently(rev, 1))) {
 760                         setup_branch_path(&new);
 761
 762                         if ((check_ref_format(new.path) == CHECK_REF_FORMAT_OK) &&
 763                             resolve_ref(new.path, rev, 1, NULL))
 764                                 ;
 765                         else
 766                                 new.path = NULL;
 767                         parse_commit(new.commit);
 768                         source_tree = new.commit->tree;
 769                 } else
 770                         source_tree = parse_tree_indirect(rev);
 771
 772                 if (!source_tree)                   /* case (1): want a tree */
 773                         die("reference is not a tree: %s", arg);
 774                 if (!has_dash_dash) {/* case (3 -> 1) */
 775                         /*
 776                          * Do not complain the most common case
 777                          *      git checkout branch
 778                          * even if there happen to be a file called 'branch';
 779                          * it would be extremely annoying.
 780                          */
 781                         if (argc)
 782                                 verify_non_filename(NULL, arg);
 783                 }
 784                 else {
 785                         argv++;
 786                         argc--;
 787                 }
 788         }
 789
 790 no_reference:
 791
 792         if (opts.track == BRANCH_TRACK_UNSPECIFIED)
 793                 opts.track = git_branch_track;
 794
 795         if (argc) {
 796                 const char **pathspec = get_pathspec(prefix, argv);
 797
 798                 if (!pathspec)
 799                         die("invalid path specification");
 800
 801                 if (patch_mode)
 802                         return interactive_checkout(new.name, pathspec, &opts);
 803
 804                 /* Checkout paths */
 805                 if (opts.new_branch) {
 806                         if (argc == 1) {
 807                                 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]);
 808                         } else {
 809                                 die("git checkout: updating paths is incompatible with switching branches.");
 810                         }
 811                 }
 812
 813                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
 814                         die("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index.");
 815
 816                 return checkout_paths(source_tree, pathspec, &opts);
 817         }
 818
 819         if (patch_mode)
 820                 return interactive_checkout(new.name, NULL, &opts);
 821
 822         if (opts.new_branch) {
 823                 struct strbuf buf = STRBUF_INIT;
 824                 if (strbuf_check_branch_ref(&buf, opts.new_branch))
 825                         die("git checkout: we do not like '%s' as a branch name.",
 826                             opts.new_branch);
 827                 if (!get_sha1(buf.buf, rev))
 828                         die("git checkout: branch %s already exists", opts.new_branch);
 829                 strbuf_release(&buf);
 830         }
 831
 832         if (new.name && !new.commit) {
 833                 die("Cannot switch branch to a non-commit.");
 834         }
 835         if (opts.writeout_stage)
 836                 die("--ours/--theirs is incompatible with switching branches.");
 837
 838         return switch_branches(&opts, &new);
 839 }