reencrypt: how to specify old and new key-files?

Hey.

Sorry for having to ask again.

When I'm reencrypting a device in order to change the volume key and
also the keyslot (say from PBKDF2 to Argon2) wouldn't there need to be
some way to specify two different --key-file?

One for the old keyslot with the old VK, and one for the new keyslot
to be generated?

Especially if with --key-slot <old slot ID>, the old slot is
overwritten and all others removed, as explained by the manpage:
> For reencryption mode it selects specific keyslot (and passphrase)
> that can be used to unlock new volume key. If used all other keyslots
> get removed after reencryption operation is finished.

But it seems there is only the --key-file option, for which it's even
unclear to me, whether it's for the old or new keyslot/VK?


Thanks,
Philippe