Reject missing explicit configuration files

main.go

@@ -129,6 +129,8 @@ func main() {
 	fifo := flag.String("fifo", "", "path of a FIFO from which to read commands")
 	serverSet := false
 	usernameSet := false
+	configSet := false
+	certificateSet := false
 	buffers := flag.Int("buffers", 16, "number of audio buffers to use")
 	profile := flag.Bool("profile", false, "add http server to serve profiles")
 	noiseSuppressionEnabled := flag.Bool("noise-suppression", false, "enable noise suppression for microphone input")
@@ -173,19 +175,24 @@ func main() {
 		}()
 	}
 
-	userConfig := config.NewConfig(cfgfn)
-
-	certificateSet := false
 	flag.CommandLine.Visit(func(theFlag *flag.Flag) {
 		switch theFlag.Name {
 		case "server":
 			serverSet = true
 		case "username":
 			usernameSet = true
+		case "config":
+			configSet = true
 		case "certificate":
 			certificateSet = true
 		}
 	})
+	if configSet {
+		if err := config.RequireConfigFile(*cfgfn); err != nil {
+			handle_raw_error(err)
+		}
+	}
+	userConfig := config.NewConfig(cfgfn)
 
 	if !serverSet {
 		server = userConfig.GetDefaultServer()