code: func (b *Builder) Config() *docker.Config {
  	config := b.RunConfig
  	if config.OnBuild == nil {
  		config.OnBuild = []string{}
  	}
  	if config.Entrypoint == nil {
  		config.Entrypoint = []string{}
  	}
  	config.Image = ""
  	return &config
  }
docs: // Config returns a snapshot of the current RunConfig intended for
  // use with a container commit.