Rename -rescan because it confuses people #1912

It's now almost a daily event that I see people on IRC saying they used -rescan or telling people to use rescan when it makes no sense and should have no effect at all. Because it takes a little while some things that just take time to resolve (e.g. confirmation count going up on transactions) is very aggressively believed to be the magical cure all.

Either that or there are a whole litany of nasty bugs all over the client, some totally unrelated to the wallet, which are cured by rescan which aren't being reported because people have a workaround.

Instead perhaps we should rename rescan to -frobnicate-wallet-transaction-index.

People also regularly confuse options that affect the wallet with those that affect block chain indexing. Which is not strange; -rescan and -reindex both sound the same, from the name you wouldn't guess they do entirely different things. 'namespacing' the options by what they affect would have been a good idea. Then again, at least that problem will go away when the wallet is separate.

If we believe that a rescan should never be needed, and I think we do— then perhaps we should rename and hide the option. Since rescanning will not be available for a pruned node doing this will help prepare the software (and the users) for a future time when being able to willy-nilly rescan when its not needed is no longer a cheap option.

OTOH Even SPV wallets commonly expose a re-scan option in case the wallet gets the transactions wrong. It needs to re-fetch all the filtered blocks starting from the birthdate of the wallet, so it's not cheap. In Android Wallet it is called 'Reset blockchain'. Well, thinking about it, it's more like a -zapwallettx than a -rescan.

Why not prepend the scope of the commands. E.g. -wallet-rescan or -blockdb-reindex?

I agree with the sentiment, but deliberately renaming an option to prevent it from being overused (and break backwards compatibility) seems a step too far for me. In practice I can only see this generate complaints, especially as we don't fail on unknown options (#1044), so I'm going to close this.

Why not prepend the scope of the commands. E.g. -wallet-rescan or -blockdb-reindex?

...deliberately renaming an option to prevent it from being overused (and break backwards compatibility) seems a step too far for me.

Given the new info changes, I guess no one cares about that idea anymore.