code: func AddTargetToAllSignableRoles(repo client.Repository, target *client.Target) error {
  	signableRoles, err := trust.GetSignableRoles(repo, target)
  	if err != nil {
  		return err
  	}
  
  	return repo.AddTarget(target, signableRoles...)
  }
docs: // AddTargetToAllSignableRoles attempts to add the image target to all the top level delegation roles we can
  // (based on whether we have the signing key and whether the role's path allows
  // us to).
  // If there are no delegation roles, we add to the targets role.