def gemset_use(gemset, options = {})
      replace_env = options.delete(:replace_env)
      result = rvm(:gemset, :use, gemset, options)
      if result.successful?
        gemset_name = self.class.identifier_to_gemset_name(result[:GEM_HOME] || result[:rvm_env_string])
        @environment_name = self.class.environment_with_gemset(@environment_name, gemset_name)
        @expanded_name    = nil
        self.class.reset_current!
        use_env_from_result! result if replace_env
        true
      end
    end
def gemset_use(gemset, options = {})
      replace_env = options.delete(:replace_env)
      result = rvm(:gemset, :use, gemset, options)
      if result.successful?
        gemset_name = self.class.identifier_to_gemset_name(result[:GEM_HOME] || result[:rvm_env_string])
        @environment_name = self.class.environment_with_gemset(@environment_name, gemset_name)
        @expanded_name    = nil
        self.class.reset_current!
        use_env_from_result! result if replace_env
        true
      end
    end
Changes the current environments gemset. If :replace_env is passed
 and the ruby is compatible, it will attempt to replace the current
 processes gem home and path with the one requested.