fuzz tester: avoid deleting entire repository (had to happen eventually, right?)

Command/FuzzTest.hs

@@ -211,9 +211,8 @@ genFuzzAction = do
 
 existingFile :: Int -> FilePath -> IO (Maybe FuzzFile)
 existingFile 0 _ = return Nothing
-existingFile n top = maybe (return Nothing) (go . toFilePath) =<< existingDir
+existingFile n top = do
-  where
+	dir <- existingDirIncludingTop
-  	go dir = do
 	contents <- catchDefaultIO [] (getDirectoryContents dir)
 	let files = filter isFuzzFile contents
 	if null files
@@ -228,14 +227,21 @@ existingFile n top = maybe (return Nothing) (go . toFilePath) =<< existingDir
 			i <- getStdRandom $ randomR (0, length files - 1)
 			return $ Just $ FuzzFile $ top </> dir </> files !! i
 
-existingDir :: IO (Maybe FuzzDir)
+existingDirIncludingTop :: IO FilePath
-existingDir = do
+existingDirIncludingTop = do
 	dirs <- filter isFuzzDir <$> getDirectoryContents "."
 	if null dirs
-		then return Nothing
+		then return "."
 		else do
 			n <- getStdRandom $ randomR (0, length dirs)
-			return $ Just $ FuzzDir $ ("." : dirs) !! n
+			return $ ("." : dirs) !! n
+
+existingDir :: IO (Maybe FuzzDir)
+existingDir = do
+	d <- existingDirIncludingTop
+	return $ if isFuzzDir d
+		then Just $ FuzzDir d
+		else Nothing
 
 newFile :: IO (Maybe FuzzFile)
 newFile = go (100 :: Int)