Disable alpha kustomize commands by default.

- enable alpha commands with env KUSTOMIZE_SHOW_ALPHA_COMMANDS=true

kyaml/commandutil/commandutil.go

@@ -0,0 +1,14 @@
+package commandutil
+
+import (
+	"os"
+)
+
+// EnabkeAlphaCommmandsEnvName is the environment variable used to enable Alpha kustomize commands.
+//If set to "true" alpha commands will be enabled.
+const EnableAlphaCommmandsEnvName = "KUSTOMIZE_ENABLE_ALPHA_COMMANDS"
+
+// GetAlphaEnabled returns true if alpha commands should be enabled.
+func GetAlphaEnabled() bool {
+	return os.Getenv(EnableAlphaCommmandsEnvName) == "true"
+}