To support multiple gpg keys added with --add-key, propellor should * When it encrypts the privdata after a change, encrypt it to all keys listed in `privdata/keyring.gpg`. See [this post](http://laurent.bachelier.name/2013/03/gpg-encryption-to-multiple-recipients/) explaining why and how encryption with multiple recipients work. * When --add-key adds a new key, it should re-encrypt the privdata, so that this new key can access it. * When --add-key on behalf of another user, do not modify the signing key for local git. This entails either splitting this command in two, `--add-key` and `--set-signing-key`, or adding another command `--add-foreign-key`, or perhaps determining if the key being added has a known secret key. [[done]]