better streaming while encrypting/decrypting

Both the directory and webdav special remotes used to have to buffer
the whole file contents before it could be decrypted, as they read
from chunks. Now the chunks are streamed through gpg with no buffering.

Utility/Gpg.hs

@@ -7,7 +7,6 @@
 
 module Utility.Gpg where
 
-import qualified Data.ByteString.Lazy as L
 import System.Posix.Types
 import Control.Applicative
 import Control.Concurrent
@@ -54,14 +53,15 @@ pipeStrict params input = do
 		hClose to
 		hGetContentsStrict from
 
-{- Runs gpg with some parameters, first feeding it a passphrase via
- - --passphrase-fd, then feeding it an input, and passing a handle
- - to its output to an action.
+{- Runs gpg with some parameters. First sends it a passphrase via
+ - --passphrase-fd. Then runs a feeder action that is passed a handle and
+ - should write to it all the data to input to gpg. Finally, runs
+ - a reader action that is passed a handle to gpg's output. 
  -
  - Note that to avoid deadlock with the cleanup stage,
- - the action must fully consume gpg's input before returning. -}
-passphraseHandle :: [CommandParam] -> String -> IO L.ByteString -> (Handle -> IO a) -> IO a
-passphraseHandle params passphrase a b = do
+ - the reader must fully consume gpg's input before returning. -}
+feedRead :: [CommandParam] -> String -> (Handle -> IO ()) -> (Handle -> IO a) -> IO a
+feedRead params passphrase feeder reader = do
 	-- pipe the passphrase into gpg on a fd
 	(frompipe, topipe) <- createPipe
 	void $ forkIO $ do
@@ -77,9 +77,9 @@ passphraseHandle params passphrase a b = do
 	where
 		go (to, from) = do
 			void $ forkIO $ do
-				L.hPut to =<< a
+				feeder to
 				hClose to
-			b from
+			reader from
 
 {- Finds gpg public keys matching some string. (Could be an email address,
  - a key id, or a name. -}