Make sure all ancestors are loaded when searching groups

app/controllers/concerns/group_tree.rb

@@ -2,7 +2,7 @@ module GroupTree
   def render_group_tree(groups)
     if params[:filter].present?
       @groups = Gitlab::GroupHierarchy.new(groups).all_groups
-      @groups = @groups.search(params[:filter])
+      @groups = Gitlab::GroupHierarchy.new(@groups.search(params[:filter])).base_and_ancestors
     else
       # Only show root groups if no parent-id is given
       @groups = groups.where(parent_id: params[:parent_id])

spec/controllers/concerns/group_tree_spec.rb

@@ -45,12 +45,12 @@ describe GroupTree do
         expect(assigns(:groups)).to contain_exactly(subgroup)
       end
 
-      it 'allows filtering for subgroups' do
+      it 'allows filtering for subgroups and includes the parents for rendering' do
         subgroup = create(:group, :public, parent: group, name: 'filter')
 
         get :index, filter: 'filt', format: :json
 
-        expect(assigns(:groups)).to contain_exactly(subgroup)
+        expect(assigns(:groups)).to contain_exactly(group, subgroup)
       end
     end