always format pointer file with a trailing newline

Before the smudge filter added a trailing newline, but other things that
wrote formatPointer to a file did not.

also some new pointer staging code to use later

Command/Smudge.hs

@@ -99,4 +99,4 @@ ingest file = do
 	return k
 
 emitPointer :: Key -> IO ()
-emitPointer = putStrLn . formatPointer
+emitPointer = putStr . formatPointer