support TAP 13 for /usr/bin/prove's benefit

13 doesn't support test trees so we gotta flatten it >:(

tests/Tests.idr

@@ -1,11 +1,18 @@
 module Tests
 
-import Tests.Equal
-
+import Options
 import TAP
-
+import Tests.Lexer
+import Tests.Equal
 import System
 
-export main : IO Int
-main = exitWith =<< run
-  [Equal.tests]
+
+allTests = [Equal.tests]
+
+main = do
+  opts <- getTestOpts
+  go <- case opts.tapVersion of
+    "13" => pure TAP.mainFlat
+    "14" => pure TAP.main
+    _    => die "unrecognised TAP version; use 13 or 14"
+  go allTests