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.

wrapcommand: allow adding additional arguments to commands This allows eh.wrapcommand to specify additional parameters to be added to the commands being wrapped. This will be useful when wrapping strip in the future.