# File lib/merb-slices/module_mixin.rb, line 468
      def mirror_file(source, dest, copied = [], duplicated = [], postfix = '_override')
        base, rest = split_name(source)
        dst_dir = File.dirname(dest)
        dup_path = dst_dir / "#{base}#{postfix}.#{rest}"           
        if File.file?(source)
          FileUtils.mkdir_p(dst_dir) unless File.directory?(dst_dir)
          if File.exists?(dest) && !File.exists?(dup_path) && !FileUtils.identical?(source, dest)
            # copy app-level override to *_override.ext
            FileUtils.copy_entry(dest, dup_path, false, false, true)
            duplicated << dup_path.relative_path_from(Merb.root)
          end
          # copy gem-level original to location
          if !File.exists?(dest) || (File.exists?(dest) && !FileUtils.identical?(source, dest))
            FileUtils.copy_entry(source, dest, false, false, true) 
            copied << dest.relative_path_from(Merb.root)
          end
        end
      end