Make rpmkeys --list show Key fingerprint and sub key IDs

[ffesti]

Currently rpmkeys --list only give the version, release and summary of the gpg-pubkey packages aka short key ID, creation time and issuer. There is now way to get the fingerprint or even long key ID from RPM for the installed GPG keys.

Make the current format more useful and also offer a long format giving the full information that's available.

Currently --list uses gpg-pubkey packages to obtain this information. This is problematic as the meta data is just copied at creation time of the pseudo package and does not directly come from the key itself. In light of #3313 this functionality should be based on the keyring so it is independent of the gpg-pubkey packages and also has access to the full keys with all their detail.

AC:

• rpmkeys --list shows Key fingerprint, issuer and creation time
• rpmkeys --list uses the keyring iterator for accessing keys, rather than gpg-pubkey pseudo-packages
• rpmkeys --list -v gives Key IDs for subkeys and all other availablke information about the key

[pmatilai]

I'd make the second point into "rpmkeys --list uses the keyring API for iterating the keys" - we don't want to replace gpg-pubkey db iteration with, say, manual fs walk to do the same, this should be in the keyring, but otherwise looks fine. Of course there's the catch that the keyring lacks any means to access the keys, so we'll need to address that first, but it's about time anyhow.

[pmatilai]

#3337 is a pre-requisite for this, AC acked.