# File lib/librarian/cli.rb, line 76
    def config(key = nil, value = nil)
      if key
        raise Error, "cannot set both value and delete" if value && options["delete"]
        if options["delete"]
          scope = config_scope(true)
          environment.config_db[key, scope] = nil
        elsif value
          scope = config_scope(true)
          environment.config_db[key, scope] = value
        else
          scope = config_scope(false)
          if value = environment.config_db[key, scope]
            prefix = scope ? "#{key} (#{scope})" : key
            say "#{prefix}: #{value}"
          end
        end
      else
        environment.config_db.keys.each do |key|
          say "#{key}: #{environment.config_db[key]}"
        end
      end
    end