14b4921a91920df25b19ff420bfe2bff8c56f71e wallet: reuse change dest when recreating TX with avoidpartialspends (Matthew Zipkin)
Pull request description:
Closes https://github.com/bitcoin/bitcoin/issues/27051
When the wallet creates a transaction internally, it will also create an alternative that spends using destination groups and see if the fee difference is negligible. If it costs the user the same to send the grouped version, we send it (even if the user has `avoidpartialspends` set to `false` which is default). This patch ensures that the second transaction creation attempt re-uses the change destination selected by the first attempt. Otherwise, the first change address remains reserved, will not be used in the second attempt, and then will never be used by the wallet, leaving gaps in the BIP44 chain.
If the user had `avoidpartialspends` set to true, there is no second version of the created transaction and the change addresses are not affected.
I believe this behavior was introduced in https://github.com/bitcoin/bitcoin/pull/14582
ACKs for top commit:
achow101:
ACK 14b4921a91920df25b19ff420bfe2bff8c56f71e
Tree-SHA512: a3d56f251ff4b333fc11325f30d05513e34ab0a2eb703fadd0ad98d167ae074493df1a24068298336c6ed2da6b31aa2befa490bc790bbc260ed357c8f2397659
