fix handling of removal of keys that are not present

Remote/Directory.hs

@@ -160,9 +160,15 @@ remove d k = liftIO $ do
 	 - before it can delete them. -}
 	void $ tryIO $ mapM_ allowWrite =<< dirContents dir
 #endif
-	catchBoolIO $ do
+	ok <- catchBoolIO $ do
 		removeDirectoryRecursive dir
 		return True
+	{- Removing the subdirectory will fail if it doesn't exist.
+	 - But, we want to succeed in that case, as long as the directory
+	 - remote's top-level directory does exist. -}
+	if ok
+		then return ok
+		else doesDirectoryExist d <&&> (not <$> doesDirectoryExist dir)
   where
 	dir = storeDir d k
 

Types/Remote.hs

@@ -64,7 +64,7 @@ data RemoteA a = Remote {
 	retrieveKeyFile :: Key -> AssociatedFile -> FilePath -> MeterUpdate -> a Bool,
 	-- retrieves a key's contents to a tmp file, if it can be done cheaply
 	retrieveKeyFileCheap :: Key -> FilePath -> a Bool,
-	-- removes a key's contents
+	-- removes a key's contents (succeeds if the contents are not present)
 	removeKey :: Key -> a Bool,
 	-- Checks if a key is present in the remote; if the remote
 	-- cannot be accessed returns a Left error message.