Side-project feature request for 'hammer mirror-*' functions

[Jonas Trollvik]

> Mirror-read: Mirror from 0000000000000002 to 0000000b84395060
> Mirror-write /usr/obj/pfs/test28-usr-obj: Did not get termination sync record, or rec_size is wrong rt=2
>

Isnt this a good time to add versioning headers to the handshake so
the clients can report errors / use backwards compatible protocol
handling in the future?

Regards,
Jonas