Use cursing to expected types when loading config.json.

      json.each_pair do |key, value|

        if key == "--"

          # filenames

          config += value.is_a?(Array) ? value : [value]

          config += Array(value).map(&:to_s)

        elsif value == true

          # simple switch

          config += [key]

        elsif value.is_a?(String)

          # option with parameter

          config += [key, value]

        elsif value.is_a?(Array)

          # one option multiple times

          value.each do |v|

            config += [key, v]

          end

          config += [key.to_s]

        else

          # ignore anything else

          # An option with value or with multiple values.

          # In the latter case, add the option multiple times.

          Array(value).each do |v|

            config += [key.to_s, v.to_s]

          end

        end

      end

      config