Better re-exports (and improved docs).

src/Database/Esqueleto.hs

@@ -1,5 +1,19 @@
 {-# LANGUAGE FlexibleContexts, FlexibleInstances, GADTs #-}
-
+-- | Main module of Esqueleto.  This module replaces
+-- @Database.Persist@, so instead of importing that module you
+-- should just import this one:
+--
+-- @
+-- import Database.Esqueleto
+-- @
+--
+-- If you still have legacy code using @Database.Persist.Query@
+-- (which is exported by @Database.Persist@), you may import it
+-- qualified:
+--
+-- @
+-- import qualified Database.Persist.Query as OldQuery
+-- @
 module Database.Esqueleto
   ( -- * Esqueleto's Language
     Esqueleto(..)
@@ -12,11 +26,18 @@ module Database.Esqueleto
   , selectSource
 
     -- * Re-exports
+    -- $reexports
+  , Single(..)
   , module Database.Persist.Store
-  , module Database.Persist.GenericSql
   ) where
 
 import Database.Esqueleto.Internal.Language
 import Database.Esqueleto.Internal.Sql
 import Database.Persist.Store
-import Database.Persist.GenericSql
+import Database.Persist.GenericSql (Single(..))
+
+-- $reexports
+--
+-- We re-export @Database.Persist.Store@ for convenience, since
+-- Esqueleto currently does not provide a way of doing @insert@s
+-- or @update@s.