[Bitcoin-development] Re-enabling simple tx replacement

[Ross Nicoll <jrn@jrn.me.uk>]

Dear all,

I've been looking at atomic cross-chain trading (
https://en.bitcoin.it/wiki/Atomic_cross-chain_trading ) between the
Bitcoin and Dogecoin blockchains, and have a mostly functional
prototype. However as it stands if the refund transaction is relayed
before the actual spend transaction, it "blocks" the legitimate spend
transaction from being accepted into the memory pool.

I'd like to enable TX replacement in the case where all conflicting
transactions are not final, and the replacement is final. While yes,
this still leaves scope for "unpaid for" bandwidth, hopefully being able
to do a single replacement isn't a major issue.

For those wanting background on this,
https://github.com/bitcoin/bitcoin/pull/2516 may be useful reading.

I've drafted a patch for this
https://github.com/rnicoll/bitcoin/commit/e668d36607f008990ccaac7275e463a6efdd9b5a
but have not yet raised a PR, as historically this has lead to a lot of
discussion in Github which is better suited to this mailing list.

I'm therefore looking for feedback while I continue testing that patch,
and any comments would be welcomed.

Ross