Allow updater save a function for each download

There are source that can be downloaded as archive, for example cloning
repositories with submodules. So how source are downloaded should be
changable per download.

lib/SlackBuilder/Package.hs

@@ -17,7 +17,6 @@ import qualified Text.URI as URI
 import Crypto.Hash (Digest, MD5)
 import SlackBuilder.Trans
 import Control.Monad.Catch (MonadThrow)
-import System.Process (CmdSpec(..))
 
 -- | Contains information how a package can be updated.
 data Package = Package
@@ -25,7 +24,6 @@ data Package = Package
     , downloaders :: [Updater]
     , category :: Text
     , name :: Text
-    , reupload :: Maybe [CmdSpec]
     }
 
 -- | Download URI with the MD5 checksum of the target.
@@ -79,4 +77,7 @@ renderDownloadWithVersion (DownloadTemplate components) version =
     f VersionPlaceholder = (version <>)
 
 -- | Function used to get the latest version of a source.
-data Updater = Updater (SlackBuilderT (Maybe Text)) DownloadTemplate
+data Updater = Updater
+    { detectLatest :: SlackBuilderT (Maybe Text)
+    , getVersion :: Text -> Text -> SlackBuilderT (URI, Digest MD5)
+    }