webapp: Support storing encrypted git repositories on rsync.net.

Does not yet support re-enabling such a repository though.

This commit was sponsored by Jan Pieper.

Assistant/Gpg.hs

@@ -0,0 +1,36 @@
+{- git-annex assistant gpg stuff
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+{-# LANGUAGE QuasiQuotes, TemplateHaskell, OverloadedStrings #-}
+
+module Assistant.Gpg where
+
+import Utility.Gpg
+import Utility.UserInfo
+import Types.Remote (RemoteConfigKey)
+
+import qualified Data.Map as M
+
+{- Generates a gpg user id that is not used by any existing secret key -}
+newUserId :: IO UserId
+newUserId = do
+	oldkeys <- secretKeys
+	username <- myUserName
+  	let basekeyname = username ++ "'s git-annex encryption key"
+	return $ Prelude.head $ filter (\n -> M.null $ M.filter (== n) oldkeys)
+		( basekeyname
+		: map (\n -> basekeyname ++ show n) ([2..] :: [Int])
+		)
+
+data EnableEncryption = HybridEncryption | SharedEncryption | NoEncryption
+	deriving (Eq)
+
+{- Generates Remote configuration for encryption. -}
+configureEncryption :: EnableEncryption -> (RemoteConfigKey, String)
+configureEncryption SharedEncryption = ("encryption", "shared")
+configureEncryption NoEncryption = ("encryption", "none")
+configureEncryption HybridEncryption = ("encryption", "hybrid")