look up --to and --from remote names only once

This will speed up commands like move and drop.

Seek.hs

@@ -91,9 +91,9 @@ withKeys a params = return $ map (a . parse) params
  - a conversion function, and then is passed into the seek action.
  - This ensures that the conversion function only runs once.
  -}
-withField :: String -> (Maybe String -> a) -> (a -> CommandSeek) -> CommandSeek
+withField :: String -> (Maybe String -> Annex a) -> (a -> CommandSeek) -> CommandSeek
 withField field converter a ps = do
-        f <- converter <$> Annex.getField field
+        f <- converter =<< Annex.getField field
         a f ps
 
 withNothing :: CommandStart -> CommandSeek