Update MenuFlags to work as expected

* 'popParent' has been removed
* 'noHistory' now works as expected
* Mods that explicitly want noHistory can state such in their constructor()

core/menu_module.js

@@ -20,6 +20,23 @@ const assert = require('assert');
 const _ = require('lodash');
 const iconvDecode = require('iconv-lite').decode;
 
+const MenuFlags = {
+    // When leaving this menu to load/chain to another, remove this
+    // menu from history. In other words, the fallback from
+    // the next menu would *not* be this one, but the previous.
+    NoHistory: 'noHistory',
+
+    // Generally used in code only: Request that any flags from menu.hjson
+    // are merged in to the total set of flags vs overriding the default.
+    MergeFlags: 'mergeFlags',
+
+    //  Forward this menu's 'extraArgs' to the next.
+    ForwardArgs: 'forwardArgs',
+};
+
+exports.MenuFlags = MenuFlags;
+
+
 exports.MenuModule = class MenuModule extends PluginModule {
     constructor(options) {
         super(options);
@@ -48,6 +65,11 @@ exports.MenuModule = class MenuModule extends PluginModule {
         });
     }
 
+    setMergedFlag(flag) {
+        this.menuConfig.config.menuFlags.push(flag);
+        this.menuConfig.config.menuFlags = [...new Set([...this.menuConfig.config.menuFlags, MenuFlags.MergeFlags])];
+    }
+
     static get InterruptTypes() {
         return {
             Never: 'never',