> If the peer's revocation basepoint is unknown (e.g. `open_channel2`),
> a temporary `channel_id` should be found by using a zeroed out basepoint
> for the unknown peer.
We consolidate to the latest/singular RFC patch for dual-funding, so
there's just a single patchfile for the change. Plus we move back to the
opener setting the desired feerate, the accepter merely declines to
participate if they disagree with the set rate.
v2 of channel open uses the channel revocation basepoints to calculate
the channel_id, instead of the funding_txid + outnum
Moving away from the funding_txid opens the way for splicing + rbf
