code: function env(envName, configSetters) {
    assertConfigSetters(configSetters)
  
    const currentEnv = process.env.NODE_ENV || 'development'
  
    if (currentEnv !== envName) {
      return () => config => config
    } else {
      return group(configSetters)
    }
  }
docs: Applies an array of webpack blocks only if `process.env.NODE_ENV` matches the
  given `envName`. If no `NODE_ENV` is set, it will be treated as 'development'.
  
  @param {string} envName            Environment name like 'development', 'production' or 'testing'.
  @param {Function[]} configSetters  Array of functions as returned by webpack blocks.
  @return {Function}