Merge branch 'jk/fail-show-toplevel-outside-working-tree'

"git rev-parse --show-toplevel" run outside of any working tree did
not error out, which has been corrected.

* jk/fail-show-toplevel-outside-working-tree:
  rev-parse: make --show-toplevel without a worktree an error

Documentation/git-rev-parse.txt

@@ -262,7 +262,8 @@ print a message to stderr and exit with nonzero status.
 	directory.
 
 --show-toplevel::
-	Show the absolute path of the top-level directory.
+	Show the absolute path of the top-level directory of the working
+	tree. If there is no working tree, report an error.
 
 --show-superproject-working-tree::
 	Show the absolute path of the root of the superproject's

builtin/rev-parse.c

@@ -803,6 +803,8 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				const char *work_tree = get_git_work_tree();
 				if (work_tree)
 					puts(work_tree);
+				else
+					die("this operation must be run in a work tree");
 				continue;
 			}
 			if (!strcmp(arg, "--show-superproject-working-tree")) {

t/t1500-rev-parse.sh

@@ -146,6 +146,16 @@ test_expect_success 'rev-parse --show-object-format in repo' '
 	grep "unknown mode for --show-object-format: squeamish-ossifrage" err
 '
 
+test_expect_success '--show-toplevel from subdir of working tree' '
+	pwd >expect &&
+	git -C sub/dir rev-parse --show-toplevel >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--show-toplevel from inside .git' '
+	test_must_fail git -C .git rev-parse --show-toplevel
+'
+
 test_expect_success 'showing the superproject correctly' '
 	git rev-parse --show-superproject-working-tree >out &&
 	test_must_be_empty out &&