code: func (pa *preparedApp) relAppPaths(paths []string) []string {
  	out := make([]string, 0, len(paths))
  	for _, p := range paths {
  		out = append(out, filepath.Join(common.RelAppRootfsPath(pa.app.Name), p))
  	}
  	return out
  }
docs: // relAppPaths prepends the relative app path (/opt/stage1/rootfs/) to a list
  // of paths. Useful for systemd unit directives.