feat(haskell): CLI rewrite

src/ContentStore.hs

@@ -40,8 +40,15 @@ serializeNameList :: [Text] -> Text
 serializeNameList = T.intercalate "," . nub . sort
 
 initContentStore :: IO Connection
-initContentStore = do
-  dbPath <- getContentStorePath
+initContentStore = initContentStoreWithPath Nothing
+
+-- | Initialise a content store with an explicit path, or fall back
+--   to the environment variable / default location.
+initContentStoreWithPath :: Maybe FilePath -> IO Connection
+initContentStoreWithPath mPath = do
+  dbPath <- case mPath of
+    Just p  -> return p
+    Nothing -> getContentStorePath
   createDirectoryIfMissing True (takeDirectory dbPath)
   conn <- open dbPath
   setupDatabase conn