wip separate RemoteConfig parsing

Remote now contains a ParsedRemoteConfig. The parsing happens when the
Remote is constructed, rather than when individual configs are used.

This is more efficient, and it lets initremote/enableremote
reject configs that have unknown fields or unparsable values.

It also allows for improved type safety, as shown in
Remote.Helper.Encryptable where things that used to match on string
configs now match on data types.

This is a work in progress, it does not build yet.

The main risk in this conversion is forgetting to add a field to
RemoteConfigParser. That will prevent using that field with
initremote/enableremote, and will prevent remotes that already are set
up from seeing that configuration. So will need to check carefully that
every field that getRemoteConfigValue is called on has been added to
RemoteConfigParser.

(One such case I need to remember is that credPairRemoteField needs to be
included in the RemoteConfigParser.)

Crypto.hs

@@ -3,7 +3,7 @@
  - Currently using gpg; could later be modified to support different
  - crypto backends if neccessary.
  -
- - Copyright 2011-2016 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -13,6 +13,7 @@
 {-# LANGUAGE Rank2Types #-}
 
 module Crypto (
+	EncryptionMethod(..),
 	Cipher,
 	KeyIds(..),
 	EncKey,
@@ -37,17 +38,24 @@ module Crypto (
 import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
 import Data.ByteString.UTF8 (fromString)
-import qualified Data.Map as M
 import Control.Monad.IO.Class
+import Data.Typeable
 
 import Annex.Common
 import qualified Utility.Gpg as Gpg
 import Types.Crypto
 import Types.Remote
 import Types.Key
-import Types.ProposedAccepted
 import Annex.SpecialRemote.Config
 
+data EncryptionMethod
+	= NoneEncryption
+	| SharedEncryption
+	| PubKeyEncryption
+	| SharedPubKeyEncryption
+	| HybridEncryption
+	deriving (Typeable, Eq)
+
 {- The beginning of a Cipher is used for MAC'ing; the remainder is used
  - as the GPG symmetric encryption passphrase when using the hybrid
  - scheme. Note that the cipher itself is base-64 encoded, hence the
@@ -233,14 +241,18 @@ class LensGpgEncParams a where
 
 {- Extract the GnuPG options from a pair of a Remote Config and a Remote
  - Git Config. -}
-instance LensGpgEncParams (RemoteConfig, RemoteGitConfig) where
+instance LensGpgEncParams (ParsedRemoteConfig, RemoteGitConfig) where
 	getGpgEncParamsBase (_c,gc) = map Param (remoteAnnexGnupgOptions gc)
 	getGpgEncParams (c,gc) = getGpgEncParamsBase (c,gc) ++
  		{- When the remote is configured to use public-key encryption,
 		 - look up the recipient keys and add them to the option list. -}
-		case fromProposedAccepted <$> M.lookup encryptionField c of
-			Just "pubkey" -> Gpg.pkEncTo $ maybe [] (splitc ',' . fromProposedAccepted) $ M.lookup cipherkeysField c
-			Just "sharedpubkey" -> Gpg.pkEncTo $ maybe [] (splitc ',' . fromProposedAccepted) $ M.lookup pubkeysField c
+		case getRemoteConfigValue encryptionField c of
+			Just PubKeyEncryption -> 
+				Gpg.pkEncTo $ maybe [] (splitc ',') $
+					getRemoteConfigValue cipherkeysField c
+			Just SharedPubKeyEncryption ->
+				Gpg.pkEncTo $ maybe [] (splitc ',') $
+					getRemoteConfigValue pubkeysField c
 			_ -> []
 	getGpgDecParams (_c,gc) = map Param (remoteAnnexGnupgDecryptOptions gc)