Use new semantics of is_bare/inside_git_dir/inside_work_tree

Up to now to check for a working tree this was used:
	!is_bare && !inside_git_dir
(the check for bare is redundant because is_inside_git_dir
returned already 1 for bare repositories).
Now the check is:
	inside_work_tree && !inside_git_dir

Signed-off-by: Matthias Lederhofer <matled@gmx.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

setup.c

@@ -95,7 +95,7 @@ void verify_non_filename(const char *prefix, const char *arg)
 	const char *name;
 	struct stat st;
 
-	if (is_inside_git_dir())
+	if (!is_inside_work_tree() || is_inside_git_dir())
 		return;
 	if (*arg == '-')
 		return; /* flag */