blind enabling gcrypt repos on rsync.net

This pulls off quite a nice trick: When given a path on rsync.net, it
determines if it is an encrypted git repository that the user has
the key to decrypt, and merges with it. This is works even when
the local repository had no idea that the gcrypt remote exists!

(As previously done with local drives.)

This commit sponsored by Pedro Côrte-Real

Assistant/WebApp/Gpg.hs

@@ -14,8 +14,10 @@ import Assistant.Gpg
 import Utility.Gpg
 import qualified Git.Command
 import qualified Git.Remote
+import qualified Git.Construct
 import qualified Annex.Branch
 import qualified Git.GCrypt
+import qualified Remote.GCrypt as GCrypt
 import Assistant.MakeRemote
 import Logs.Remote
 
@@ -34,8 +36,11 @@ gpgKeyDisplay keyid userid = [whamlet|
 genKeyModal :: Widget
 genKeyModal = $(widgetFile "configurators/genkeymodal")
 
+isGcryptInstalled :: IO Bool
+isGcryptInstalled = inPath "git-remote-gcrypt"
+
 whenGcryptInstalled :: Handler Html -> Handler Html
-whenGcryptInstalled a = ifM (liftIO $ inPath "git-remote-gcrypt")
+whenGcryptInstalled a = ifM (liftIO isGcryptInstalled)
 	( a
 	, page "Need git-remote-gcrypt" (Just Configuration) $
 		$(widgetFile "configurators/needgcrypt")
@@ -58,7 +63,7 @@ withNewSecretKey use = do
  - branch from the gcrypt remote and merges it in, and then looks up
  - the name.
  -}
-getGCryptRemoteName :: UUID -> String -> Annex (Maybe Git.Remote.RemoteName)
+getGCryptRemoteName :: UUID -> String -> Annex Git.Remote.RemoteName
 getGCryptRemoteName u repoloc = do
 	tmpremote <- uniqueRemoteName "tmpgcryptremote" 0 <$> gitRepo
 	void $ inRepo $ Git.Command.runBool
@@ -70,9 +75,11 @@ getGCryptRemoteName u repoloc = do
 		, return Nothing
 		)
 	void $ inRepo $ Git.Remote.remove tmpremote
-	return mname
+	maybe missing return mname
+  where
+	missing = error $ "Cannot find configuration for the gcrypt remote at " ++ repoloc
 
-checkGCryptRepoEncryption :: String -> Handler Html -> Handler Html -> Handler Html
+checkGCryptRepoEncryption :: (Monad m, LiftAnnex m) => String -> m a -> m a -> m a
 checkGCryptRepoEncryption location notencrypted encrypted = 
 	dispatch =<< liftAnnex (inRepo $ Git.GCrypt.probeRepo location)
   where
@@ -80,3 +87,10 @@ checkGCryptRepoEncryption location notencrypted encrypted =
 	dispatch Git.GCrypt.NotEncrypted = notencrypted
 	dispatch Git.GCrypt.NotDecryptable =
 		error "This git repository is encrypted with a GnuPG key that you do not have."
+
+{- Gets the UUID of the gcrypt repo at a location, which may not exist.
+ - Only works if the gcrypt repo was created as a git-annex remote. -}
+probeGCryptRemoteUUID :: String -> Annex (Maybe UUID)
+probeGCryptRemoteUUID repolocation = do
+	r <- inRepo $ Git.Construct.fromRemoteLocation repolocation
+	GCrypt.getGCryptUUID False r