return 2 on commandline argument errors like wesnoth

src/server/server.cpp

@@ -2387,7 +2387,7 @@ int main(int argc, char** argv) {
 			size_t p = val.find('=');
 			if (p == std::string::npos) {
 				std::cerr << "unknown option: " << val << '\n';
-				return 0;
+				return 2;
 			}
 			std::string s = val.substr(6, p - 6);
 			int severity;
@@ -2397,14 +2397,14 @@ int main(int argc, char** argv) {
 			else if (s == "debug") severity = 3;
 			else {
 				std::cerr << "unknown debug level: " << s << '\n';
-				return 0;
+				return 2;
 			}
 			while (p != std::string::npos) {
 				size_t q = val.find(',', p + 1);
 				s = val.substr(p + 1, q == std::string::npos ? q : q - (p + 1));
 				if (!lg::set_log_domain_severity(s, severity)) {
 					std::cerr << "unknown debug domain: " << s << '\n';
-					return 0;
+					return 2;
 				}
 				p = q;
 			}
@@ -2457,7 +2457,7 @@ int main(int argc, char** argv) {
 			request_sample_frequency = atoi(argv[++arg]);
 		} else {
 			ERR_SERVER << "unknown option: " << val << "\n";
-			//return 0;
+			return 2;
 		}
 	}