List implementation PRs for BIP-0157 #1011

Almost all BIPs that have an implementation in Bitcoin Core, also have a link to their implementation. BIP-0157 was merged into Core, but its implementation is not linked from the BIP, yet. I submit this PR to add these links to the BIP document.

This table was stolen and adapted from https://github.com/bitcoin/bitcoin/pull/18876 .

It was authored by John Newbery (@jnewbery). I would appreciate if John would tell me if it is OK that I stole it.

This BIP was authored by Laolu (@roasbeef). Laolu, you have to ack this for it to get merged. I would appreciate it.

Also pinging @aakselrod and @jimpo , they are also listed as authors.

Not sure whether it makes sense to require each BIP to include a link to the implementation in Bitcoin Core and at the same time not include implementations in other software projects. Curating a list would be a never-ending maintenance task. Including only one would imply that this is the only one and only correct one. Generally, BIPs regarding the network layer give some amount of freedom for local optimizations, as well as options when it comes to the exact network behaviour. Also, implementations (at least Bitcoin Core) often change the details of how a BIP is implemented. So if a future release of Bitcoin Core changed the internals or network behaviour slightly, would the change needed to be added to the list here as well?

If the goal here is to give an example implementation, I think it is better achieved by the already existing doc/bips.md in the Bitcoin Core source tree.

It was authored by John Newbery (@jnewbery). I would appreciate if John would tell me if it is OK that I stole it.

Obviously fine be me to include the table if other people think it's useful, although I agree with marco that it doesn't really make sense to require BIPs to link to the Bitcoin Core implementation (especially here, where there is already a link to a reference implementation).

Is a link more useful if it is consensus code? So for e.g. BIP-0141, it makes sense, but for this one, it doesn't? I think it would be best to have a consistent policy, at least.

Personally, I always liked skimming the implementation. I think it is obvious that an implementation may have changed, I don't understand how it can be a disadvantage to link the PR, since I don't think it happened very often that the initial Core PR was totally broken.

Also, it can serve to clarify any eventual ambiguities in BIPs, of which there have been many, especially in Lightning.

Many BIP readers will be more familiar with the Core codebase than the btcd codebase. It doesn't really matter which one is the "reference", it matters which one can aid understanding the BIP for the reader.

So if a future release of Bitcoin Core changed the internals or network behaviour slightly, would the change needed to be added to the list here as well?

It would be nice, but I don't think it is necessary. The initial implementation will already help a lot with understanding. In the recent years Bitcoin PRs have been reviewed thoroughly.

@ysangkok I think using https://github.com/bitcoin/bitcoin/tree/master/doc/bips.md is a better place to look for BIP implemented in Bitcoin Core.