code: function ensure (env, options, names) {
    for (let k of Object.keys(names)) {
      let v = names[k]
  
      if (options[v]) {
        env[k] = options[v]
        env[k + 'Cwd'] = true
      }
    }
  }
docs: Ensure that CLI options take precedence over configuration values.
  
  For each name/option tuple, if the option is set, override configuration
  value.