Move BlogFilter_GridField to its own class

.upgrade.yml

@@ -4,7 +4,7 @@ mappings:
   GridFieldMergeAction: SilverStripe\Blog\Admin\GridFieldMergeAction
   BlogCommentExtension: SilverStripe\Blog\Model\BlogCommentExtension
   BlogFilter: SilverStripe\Blog\Model\BlogFilter
-  BlogFilter_GridField: SilverStripe\Blog\Model\BlogFilter_GridField
+  BlogFilter_GridField: SilverStripe\Blog\Model\BlogFilter\BlogFilterGridField
   BlogMemberExtension: SilverStripe\Blog\Model\BlogMemberExtension
   BlogPostFilter: SilverStripe\Blog\Model\BlogPostFilter
   BlogPostNotifications: SilverStripe\Blog\Model\BlogPostNotifications

src/Model/BlogFilter.php

@@ -3,11 +3,11 @@
 namespace SilverStripe\Blog\Model;
 
 use SilverStripe\Blog\Model\Blog;
+use SilverStripe\Blog\Model\BlogFilter\BlogFilterGridField;
 use SilverStripe\Blog\Model\BlogPost;
 use SilverStripe\Core\ClassInfo;
 use SilverStripe\Core\Convert;
 use SilverStripe\Forms\FieldList;
-use SilverStripe\Forms\FormTransformation;
 use SilverStripe\Forms\GridField\GridField;
 use SilverStripe\Forms\Tab;
 use SilverStripe\Lumberjack\Model\Lumberjack;
@@ -59,7 +59,7 @@ class BlogFilter extends Lumberjack
      */
     protected function subclassForBlog()
     {
-        return in_array(get_class($this->owner), ClassInfo::subclassesFor('SilverStripe\\Blog\\Model\\Blog'));
+        return in_array(get_class($this->owner), ClassInfo::subclassesFor(Blog::class));
     }
 
     /**
@@ -104,7 +104,7 @@ class BlogFilter extends Lumberjack
                 'ClassName' => $excluded
             ));
 
-            $gridField = BlogFilter_GridField::create(
+            $gridField = BlogFilterGridField::create(
                 'ChildPages',
                 $this->getLumberjackTitle(),
                 $pages,
@@ -117,20 +117,3 @@ class BlogFilter extends Lumberjack
         }
     }
 }
-
-
-/**
- * Enables children of non-editable pages to be edited.
- */
-class BlogFilter_GridField extends GridField
-{
-    /**
-     * @param FormTransformation $transformation
-     *
-     * @return $this
-     */
-    public function transform(FormTransformation $transformation)
-    {
-        return $this;
-    }
-}

src/Model/BlogFilter/BlogFilterGridField.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace SilverStripe\Blog\Model\BlogFilter;
+
+use SilverStripe\Forms\FormTransformation;
+
+/**
+ * Enables children of non-editable pages to be edited.
+ */
+class BlogFilterGridField extends GridField
+{
+    /**
+     * @param FormTransformation $transformation
+     *
+     * @return $this
+     */
+    public function transform(FormTransformation $transformation)
+    {
+        return $this;
+    }
+}