Add "check for updates" button to "about" page

src/mibew/configs/routing.yml

@@ -759,6 +759,13 @@ update_run:
         _access_check: Mibew\AccessControl\Check\PermissionsCheck
         _access_permissions: [CAN_ADMINISTRATE]
 
+update_check:
+    path: /update/check
+    defaults:
+        _controller: Mibew\Controller\UpdateController::checkUpdatesAction
+        _access_check: Mibew\AccessControl\Check\PermissionsCheck
+        _access_permissions: [CAN_ADMINISTRATE]
+
 ## Users (visitors avaiting page)
 users:
     path: /operator/users

src/mibew/libs/classes/Mibew/Controller/UpdateController.php

@@ -19,6 +19,7 @@
 
 namespace Mibew\Controller;
 
+use Mibew\Maintenance\UpdateChecker;
 use Mibew\Maintenance\Updater;
 use Mibew\Style\PageStyle;
 use Symfony\Component\HttpFoundation\Request;
@@ -33,6 +34,11 @@ class UpdateController extends AbstractController
      */
     protected $updater = null;
 
+    /**
+     * @var UpdateChecker|null
+     */
+    protected $updateChecker = null;
+
     /**
      * Renders update intro page.
      *
@@ -74,6 +80,26 @@ class UpdateController extends AbstractController
         return $this->render('update_progress', $parameters);
     }
 
+    /**
+     * Runs the Update checker.
+     *
+     * @param Request $request Incoming request.
+     * @return Response|string Rendered page contents or Symfony's response
+     *   object.
+     */
+    public function checkUpdatesAction(Request $request)
+    {
+        $checker = $this->getUpdateChecker();
+        $success = $checker->run();
+        if (!$success) {
+            foreach ($checker->getErrors() as $error) {
+                trigger_error('Update checking failed: ' . $error, E_USER_WARNING);
+            }
+        }
+
+        return $this->redirect($this->generateUrl('about'));
+    }
+
     /**
      * {@inheritdoc}
      */
@@ -99,4 +125,18 @@ class UpdateController extends AbstractController
 
         return $this->updater;
     }
+
+    /**
+     * Returns an instance of Update Checker.
+     *
+     * @return UpdateChecker
+     */
+    protected function getUpdateChecker()
+    {
+        if (is_null($this->updateChecker)) {
+            $this->updateChecker = new UpdateChecker();
+        }
+
+        return $this->updateChecker;
+    }
 }

src/mibew/styles/pages/default/templates_src/server_side/about.handlebars

@@ -34,8 +34,8 @@
 
                     <br/><br/>
 
-                    {{#if availableUpdates}}
                     <h2>{{l10n "Available updates"}}</h2>
+                    {{#if availableUpdates}}
                         {{#each availableUpdates}}
                             <h3>{{title}} ({{version}})</h3>
                             {{#if description}}
@@ -47,7 +47,10 @@
 
                             <br/>
                         {{/each}}
+                    {{else}}
+                        There is no available updates.<br/><br/>
                     {{/if}}
+                    <a href="{{route "update_check"}}">{{l10n "Check for available updates"}}</a>
                 </div>
 
                 <div class="form-footer">