Add note about hiding a command from completion

bash_completions.md

@@ -144,6 +144,17 @@ and you'll get something like
 -c            --container=  -p            --pod=  
 ```
 
+## Hide commands from completion
+
+If you don't want a command to show up in completion you can mark it as `Hidden`.
+
+```go
+cmd := &cobra.Command{
+    ...
+	Hidden: true,
+}
+```
+
 # Specify valid filename extensions for flags that take a filename
 
 In this example we use --filename= and expect to get a json or yaml file as the argument. To make this easier we annotate the --filename flag with valid filename extensions.