# File lib/buildr/java/packaging.rb, line 75
          def update_manifest(file)
            manifest = from_zip(file)
            result = yield manifest
            Zip::ZipFile.open(file.to_s) do |zip|
              zip.get_output_stream('META-INF/MANIFEST.MF') do |out|
                out.write manifest.to_s
                out.write "\n"
              end
            end
            result
          end