Makes a tree structure for the theme file editor’s file list.

function wp_make_theme_file_tree( $allowed_files ) {
	$tree_list = array();

	foreach ( $allowed_files as $file_name => $absolute_filename ) {
		$list     = explode( '/', $file_name );
		$last_dir = &$tree_list;

		foreach ( $list as $dir ) {
			$last_dir =& $last_dir[ $dir ];
		}

		$last_dir = $file_name;
	}

	return $tree_list;
}