prune: add --keep to not touch the working copy In order to more closely emulate strip, lets add --keep to leave the working copy untouched when we do our prune.

strip: add the option for wrapping the strip command Adds an experimental option for wrapping the existing strip command and replacing its functionality with prune. It currently doesn't handle the --keep case, but an upcoming patch will address that.

wrapcommand: fix wrapping extensions that aren't enabled The extension command wrapping would previously fail if the extension wasn't enabled. Let's just eat that silently.