code: func EnsureOSes(c context.Context, cfgs []*config.OS) error {
  	t := &OSesTable{}
  	if err := t.fetch(c); err != nil {
  		return errors.Annotate(err, "failed to fetch operating systems").Err()
  	}
  	t.computeChanges(c, cfgs)
  	if err := t.add(c); err != nil {
  		return errors.Annotate(err, "failed to add operating systems").Err()
  	}
  	if err := t.remove(c); err != nil {
  		return errors.Annotate(err, "failed to remove operating systems").Err()
  	}
  	if err := t.update(c); err != nil {
  		return errors.Annotate(err, "failed to update operating systems").Err()
  	}
  	return nil
  }
docs: // EnsureOSes ensures the database contains exactly the given operating systems.