FEATURE: Add request membership button for allowed groups.

app/assets/javascripts/admin/controllers/admin-group.js.es6

@@ -1,5 +1,6 @@
 import { popupAjaxError } from 'discourse/lib/ajax-error';
 import { propertyEqual } from 'discourse/lib/computed';
+import computed from 'ember-addons/ember-computed-decorators';
 
 export default Ember.Controller.extend({
   adminGroupsType: Ember.inject.controller(),
@@ -35,6 +36,16 @@ export default Ember.Controller.extend({
     ];
   }.property(),
 
+  @computed('model.visible', 'model.public', 'model.alias_level')
+  disableMembershipRequestSetting(visible, publicGroup) {
+    return !visible || publicGroup || !this.get('model.canEveryoneMention');
+  },
+
+  @computed('model.visible', 'model.allow_membership_requests')
+  disablePublicSetting(visible, allowMembershipRequests) {
+    return !visible || allowMembershipRequests;
+  },
+
   actions: {
     next() {
       if (this.get("showingLast")) { return; }

app/assets/javascripts/admin/templates/group.hbs

@@ -64,16 +64,29 @@
 
   {{#unless model.automatic}}
     <div>
-      <label for="primary_group">
-        {{input type="checkbox" checked=model.primary_group}}
-        {{i18n 'admin.groups.primary_group'}}
+      <label>
+        {{input type="checkbox"
+            checked=model.public
+            disabled=disablePublicSetting}}
+
+        {{i18n 'groups.public'}}
       </label>
     </div>
 
     <div>
       <label>
-        {{input type="checkbox" checked=model.public}}
-        {{i18n 'groups.public'}}
+        {{input type="checkbox"
+            checked=model.allow_membership_requests
+            disabled=disableMembershipRequestSetting}}
+
+        {{i18n 'groups.allow_membership_requests'}}
+      </label>
+    </div>
+
+    <div>
+      <label for="primary_group">
+        {{input type="checkbox" checked=model.primary_group}}
+        {{i18n 'admin.groups.primary_group'}}
       </label>
     </div>
   {{/unless}}