Print `--help` output to stdout.

CHANGELOG.md

@@ -4,6 +4,9 @@
 ### Added
 - Add support for sending Out of Band Data (OOB).
 
+### Changed
+- Print `--help` output to stdout instead of stderr.
+
 ## [v0.5.6] 2022-11-11
 ### Added
 - Add short option `-h` for http-upload.

main.go

@@ -128,7 +128,7 @@ func main() {
 	switch {
 	case *flagHelp:
 		// If requested, show help and quit.
-		getopt.Usage()
+		getopt.PrintUsage(os.Stdout)
 		os.Exit(0)
 	case *flagVersion:
 		// If requested, show version and quit.