[bitcoin-dev] Amend the BIP 123 process to include buried deployments

[Marco Falke <falke.marco@gmail.com>]

I define a buried deployment as a consensus rule change that affects
validity of blocks that are buried by a sufficiently large number of
blocks in the current valid most-work chain, but the current block
(and all its parents) remain valid.

BIP 123 suggests that BIPs in the consensus layer should be assigned a
label "soft fork" or "hard fork". However, I think the differentiation
into soft fork or hard fork should not be made for BIPs that document
buried deployments. In contrast to soft forks and hard forks, buried
deployments do not require community and miner coordination for a safe
deployment.

For a chain fork to happen due to a buried deployment, a massive chain
reorganization must be produced off of a block in the very past. In
the extremely unlikely event of such a large chain reorganization,
Bitcoin's general security assumptions would be violated regardless of
the presence of a buried deployment.