Added warning for -r option plus file arg

main.cpp

@@ -139,6 +139,9 @@ int main(int argc, const char * argv[]) {
             try {
                 // process file argv[i]
                 saver = sc::plugin<ScreensaverPlugin>::get(argv[i])();
+                if (random_saver) {
+                    std::cerr << "screensaver: warning: -r option overridden by file arg\n";
+                }
                 break; // only first one used
             } catch (const std::runtime_error& ex) {
                 std::cerr << "screensaver: " << ex.what() << '\n';