Refactor Namespace#parents method

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/namespace.rb

@@ -172,17 +172,7 @@ class Namespace < ActiveRecord::Base
   end
 
   def parents
-    @parents ||=
-      begin
-        parents = []
-
-        if parent
-          parents << parent
-          parents += parent.parents
-        end
-
-        parents
-      end
+    @parents ||= parent ? parent.parents + [parent] : []
   end
 
   private

spec/models/namespace_spec.rb

@@ -145,7 +145,13 @@ describe Namespace, models: true do
     let(:group) { create(:group) }
     let(:nested_group) { create(:group, parent: group) }
     let(:deep_nested_group) { create(:group, parent: nested_group) }
+    let(:very_deep_nested_group) { create(:group, parent: deep_nested_group) }
 
-    it { expect(deep_nested_group.parents).to eq([nested_group, group]) }
+    it 'returns the correct parents' do
+      expect(very_deep_nested_group.parents).to eq([group, nested_group, deep_nested_group])
+      expect(deep_nested_group.parents).to eq([group, nested_group])
+      expect(nested_group.parents).to eq([group])
+      expect(group.parents).to eq([])
+    end
   end
 end