fix up commands that are trouble on bare repos

Most will just abort. init does a basic init and gives a command to
run elsewhere to finish it.

Command/Unused.hs

@@ -32,7 +32,7 @@ seek = [withNothing start]
 
 {- Finds unused content in the annex. -} 
 start :: CommandStartNothing
-start = do
+start = notBareRepo $ do
 	showStart "unused" ""
 	return $ Just perform