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