def set_cvs_service(username = nil, password = nil)
      self.user_name = username
      self.password  = password
      self.service   = Credential::Service::CVS
    end
def set_cvs_service(username = nil, password = nil)
      self.user_name = username
      self.password  = password
      self.service   = Credential::Service::CVS
    end
sets the Concurrent Versioning System (CVS) service