option('notify',
  type: 'feature',
  value: 'disabled',
  description: 'notifications using libnotify'
)
option('json',
  type: 'feature',
  value: 'auto',
  description: 'dump configuration using JSON'
)
option('docs',
  type: 'feature',
  value: 'auto',
  description: 'doxygen API documentation'
)
option('tests',
  type: 'feature',
  value: 'auto',
  description: 'run tests'
)