def update_with_file_contents(digest, filename)
      File.open(filename) do |io|
        while (chunk = io.read(1024 * 8))
          digest.update(chunk)
        end
      end
    end
def update_with_file_contents(digest, filename)
      File.open(filename) do |io|
        while (chunk = io.read(1024 * 8))
          digest.update(chunk)
        end
      end
    end
Update the digest with the given contents of the file, reading in small
 chunks to reduce memory. This method will update the given +digest+
 parameter, but returns nothing.

 @param [Digest] digest
   the digest to update
 @param [String] filename
   the path to the file on disk to read

 @return [void]