def check_identifier
      return true unless Gitnesse::Config.instance.annotate_results
      identifier = Gitnesse::Config.instance.identifier
      if identifier.nil? || identifier.empty?
        add_error "You must specify identifier to use the annotate_results option"
      else
        true
      end
    end
def check_identifier
      return true unless Gitnesse::Config.instance.annotate_results
      identifier = Gitnesse::Config.instance.identifier
      if identifier.nil? || identifier.empty?
        add_error "You must specify identifier to use the annotate_results option"
      else
        true
      end
    end
Checks that identifier is set in Gitnesse::Config, if annotate_results is
 set.

 Returns true or raises DependencyNotMetError if identifier isn't set