code: func (u *user) Proto() (ret *git.Commit_User, err error) {
  	ret = &git.Commit_User{
  		Name:  u.Name,
  		Email: u.Email,
  	}
  	if !u.Time.IsZero() {
  		ret.Time, err = ptypes.TimestampProto(u.Time.Time)
  		err = errors.Annotate(err, "encoding time").Err()
  	}
  	return
  }
docs: // Proto converts this User to its protobuf equivalent.