# File lib/nanoc/base/core_ext/pathname.rb, line 11
  def checksum
    digest = Digest::SHA1.new
    File.open(self.to_s, 'r') do |io|
      until io.eof
        data = io.read(2**10)
        digest.update(data)
      end
    end
    digest.hexdigest
  end