github: Partition tests by their root

magefile.go

@@ -194,6 +194,13 @@ func TestRace() error {
 			return err
 		}
 		for _, pkg := range pkgs {
+			slashCount := strings.Count(pkg, "/")
+			if slashCount > 1 {
+				continue
+			}
+			if pkg != "." {
+				pkg += "/..."
+			}
 			if err := cmp.Or(CleanTest(), UninstallAll()); err != nil {
 				return err
 			}