Allow users to delete accidental double-spent transactions #1898

At the moment, if one accidentally performs a double-spent (or has a double-spent performed against them), the transaction is forever stored in the wallet.dat file and appears as a 0-confirmation transaction on top of the transaction history in BitcoinQT. There is no way to get rid of that transaction without purging the wallet through various workarounds through external software.

I propose adding some option of deleting double-spent transactions once their paired transactions are buried deep in the blockchain (say, 120 confirmations). This would allow the users to clean their wallets from accidental double-spend transaction without enabling one an easier way to perform double-spent attacks by deleting an unconfirmed but a valid transaction.

Well, I have this issue, and it would be great to have some option for removing the doublespent transactions.

I guess this feature might be either less or more desirable in the light of malleable transactions. More desirable since it would clear the transaction history from duplicate transactions created by changing the transactions by a third part, and less desirable since it would remove some evidence of the malicious activity.

We shouldn't delete— some kind of 'hide' would probably be fine.

Setting this to milestone 0.9.0, this suddenly became more urgent due to the malleability abuse.

This is possible now using -zapwallettx, closing.