task :rcov_overlay do
        path = ENV["FILE"]
        rcov, eol = Marshal.load(File.read("coverage.info")).last[path], 1
        puts rcov[:lines].zip(rcov[:coverage]).map { |line, coverage|
          bol, eol = eol, eol + line.length
          [bol, eol, "#ffcccc"] unless coverage
        }.compact.inspect
      end