lift types from IO to Annex

Some remotes like External need to run store and retrieve actions in Annex,
not IO. In order to do that lift, I had to dive pretty deep into the
utilities, making Utility.Gpg and Utility.Tmp be partly converted to using
MonadIO, and Control.Monad.Catch for exception handling.

There should be no behavior changes in this commit.

This commit was sponsored by Michael Barabanov.

Crypto.hs

@@ -3,12 +3,13 @@
  - Currently using gpg; could later be modified to support different
  - crypto backends if neccessary.
  -
- - Copyright 2011-2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE Rank2Types #-}
 
 module Crypto (
 	Cipher,
@@ -35,6 +36,8 @@ import qualified Data.ByteString.Lazy as L
 import Data.ByteString.Lazy.UTF8 (fromString)
 import Control.Applicative
 import qualified Data.Map as M
+import Control.Monad.IO.Class
+import Control.Monad.Catch (MonadMask)
 
 import Common.Annex
 import qualified Utility.Gpg as Gpg
@@ -151,7 +154,7 @@ encryptKey mac c k = stubKey
 	}
 
 type Feeder = Handle -> IO ()
-type Reader a = Handle -> IO a
+type Reader m a = Handle -> m a
 
 feedFile :: FilePath -> Feeder
 feedFile f h = L.hPut h =<< L.readFile f
@@ -159,8 +162,8 @@ feedFile f h = L.hPut h =<< L.readFile f
 feedBytes :: L.ByteString -> Feeder
 feedBytes = flip L.hPut
 
-readBytes :: (L.ByteString -> IO a) -> Reader a
-readBytes a h = L.hGetContents h >>= a
+readBytes :: (MonadIO m) => (L.ByteString -> m a) -> Reader m a
+readBytes a h = liftIO (L.hGetContents h) >>= a
 
 {- Runs a Feeder action, that generates content that is symmetrically
  - encrypted with the Cipher (unless it is empty, in which case
@@ -168,7 +171,7 @@ readBytes a h = L.hGetContents h >>= a
  - read by the Reader action.  Note: For public-key encryption,
  - recipients MUST be included in 'params' (for instance using
  - 'getGpgEncParams'). -}
-encrypt :: [CommandParam] -> Cipher -> Feeder -> Reader a -> IO a
+encrypt :: (MonadIO m, MonadMask m) => [CommandParam] -> Cipher -> Feeder -> Reader m a -> m a
 encrypt params cipher = case cipher of
 	Cipher{} -> Gpg.feedRead (params ++ Gpg.stdEncryptionParams True) $
 			cipherPassphrase cipher
@@ -177,7 +180,7 @@ encrypt params cipher = case cipher of
 {- Runs a Feeder action, that generates content that is decrypted with the
  - Cipher (or using a private key if the Cipher is empty), and read by the
  - Reader action. -}
-decrypt :: Cipher -> Feeder -> Reader a -> IO a
+decrypt :: (MonadIO m, MonadMask m) => Cipher -> Feeder -> Reader m a -> m a
 decrypt cipher = case cipher of
 	Cipher{} -> Gpg.feedRead [Param "--decrypt"] $ cipherPassphrase cipher
 	MacOnlyCipher{} -> Gpg.pipeLazy [Param "--decrypt"]