code: func (m *Meta) PlanFile(path string) (*planfile.Reader, error) {
  	fi, err := os.Stat(path)
  	if err != nil {
  		return nil, err
  	}
  
  	if fi.IsDir() {
  		// Looks like a configuration directory.
  		return nil, nil
  	}
  
  	return planfile.Open(path)
  }
docs: // PlanFile returns a reader for the plan file at the given path.
  //
  // If the return value and error are both nil, the given path exists but seems
  // to be a configuration directory instead.
  //
  // Error will be non-nil if path refers to something which looks like a plan
  // file and loading the file fails.