rsync special remote: Include annex-rsync-options when running rsync to test a key's presence.

Also, use the new withQuietOutput function to avoid running the shell to
/dev/null stderr in two other places.

Utility/Process.hs

@@ -23,6 +23,7 @@ module Utility.Process (
 	createBackgroundProcess,
 	withHandle,
 	withBothHandles,
+	withQuietOutput,
 	createProcess,
 	runInteractiveProcess,
 	stdinHandle,
@@ -185,6 +186,19 @@ withBothHandles creator p a = creator p' $ a . bothHandles
 			, std_err = Inherit
 			}
 
+{- Forces the CreateProcessRunner to run quietly;
+ - both stdout and stderr are discarded. -}
+withQuietOutput
+	:: CreateProcessRunner
+	-> CreateProcess
+	-> IO ()
+withQuietOutput creator p = withFile "/dev/null" WriteMode $ \devnull -> do
+	let p' = p
+		{ std_out = UseHandle devnull
+		, std_err = UseHandle devnull
+		}
+	creator p' $ const $ return ()
+
 {- Extract a desired handle from createProcess's tuple.
  - These partial functions are safe as long as createProcess is run
  - with appropriate parameters to set up the desired handle.