find: Support --print0

It would be nice if command-specific options were supported. The first
difficulty is that which command is being called is not known until after
getopt; but that could be worked around by finding the first non-dashed
parameter. Storing the settings without putting them in the annex monad is
the next difficulty; it could perhaps be handled by making the seek stage
pass applicable settings into the start stage (and from there on to perform
as needed). But that still leaves a problem, what data type to use to
represent the options between getopt and seek?

Command/Find.hs

@@ -11,6 +11,7 @@ import Common.Annex
 import Command
 import Annex.Content
 import Limit
+import qualified Annex
 
 def :: [Command]
 def = [command "find" paramPaths seek "lists available files"]
@@ -22,6 +23,9 @@ start :: FilePath -> (Key, Backend Annex) -> CommandStart
 start file (key, _) = do
 	-- only files inAnnex are shown, unless the user has requested
 	-- others via a limit
-	whenM (liftM2 (||) (inAnnex key) limited) $
-		liftIO $ putStrLn file
+	whenM (liftM2 (||) (inAnnex key) limited) $ do
+		print0 <- Annex.getState Annex.print0
+		if print0
+			then liftIO $ putStr (file ++ "\0")
+			else liftIO $ putStrLn file
 	stop