🐛 Fixed browser back button behaviour after clicking "x posts" on tags screen (#1306)

closes https://github.com/TryGhost/Ghost/issues/11057

- removed static "replace" configuration of posts/pages query params
- used the router service to register a `willTransition` event handler which handles conditional replaceState transition behaviour only when filters are changed whilst already on the posts/pages route

ghost/admin/app/routes/posts.js

@@ -5,30 +5,36 @@ import {inject as service} from '@ember/service';
 
 export default AuthenticatedRoute.extend({
     infinity: service(),
+    router: service(),
 
     queryParams: {
-        type: {
-            refreshModel: true,
-            replace: true
-        },
-        author: {
-            refreshModel: true,
-            replace: true
-        },
-        tag: {
-            refreshModel: true,
-            replace: true
-        },
-        order: {
-            refreshModel: true,
-            replace: true
-        }
+        type: {refreshModel: true},
+        author: {refreshModel: true},
+        tag: {refreshModel: true},
+        order: {refreshModel: true}
     },
 
     modelName: 'post',
 
     perPage: 30,
 
+    init() {
+        this._super(...arguments);
+
+        // if we're already on this route and we're transiting _to_ this route
+        // then the filters are being changed and we shouldn't create a new
+        // browser history entry
+        // see https://github.com/TryGhost/Ghost/issues/11057
+        this.router.on('routeWillChange', (transition) => {
+            if (transition.to && (this.routeName === 'posts' || this.routeName === 'pages')) {
+                let toThisRoute = transition.to.find(route => route.name === this.routeName);
+                if (transition.from && transition.from.name === this.routeName && toThisRoute) {
+                    transition.method('replace');
+                }
+            }
+        });
+    },
+
     model(params) {
         return this.session.user.then((user) => {
             let queryParams = {};