fix: honor klog -stderrthreshold when -logtostderr is enabled

klog v2 defaults -logtostderr to true. When this flag is active, the
-stderrthreshold flag is silently ignored — all log messages are
unconditionally written to stderr regardless of severity.

Opt into the fixed behavior introduced in klog v2.140.0 by setting
legacy_stderr_threshold_behavior=false. The default stderrthreshold
remains INFO so the observable behavior is unchanged — users who want
filtering can now pass -stderrthreshold=WARNING and it will take effect.

Ref: kubernetes/klog#212, kubernetes/klog#432
Signed-off-by: Pierluigi Lenoci <pierluigilenoci@gmail.com>

Author: pierluigilenoci

cmd/root.go

@@ -117,6 +117,11 @@ func init() {
 	rootCmd.AddCommand(detectCmd)
 
 	klog.InitFlags(nil)
+	// Opt into the new klog behavior so that -stderrthreshold is honored even
+	// when -logtostderr=true (the default).
+	// Ref: kubernetes/klog#212, kubernetes/klog#432
+	_ = flag.Set("legacy_stderr_threshold_behavior", "false") //nolint:errcheck
+	_ = flag.Set("stderrthreshold", "INFO")                   //nolint:errcheck
 	pflag.CommandLine.AddGoFlag(flag.CommandLine.Lookup("v"))
 }