[Backport] Burndown chart for group milestone

app/helpers/gitlab_routing_helper.rb

@@ -81,6 +81,14 @@ module GitlabRoutingHelper
     end
   end
 
+  def edit_milestone_path(entity, *args)
+    if entity.parent.is_a?(Group)
+      edit_group_milestone_path(entity.parent, entity, *args)
+    else
+      edit_project_milestone_path(entity.parent, entity, *args)
+    end
+  end
+
   def toggle_subscription_path(entity, *args)
     if entity.is_a?(Issue)
       toggle_subscription_project_issue_path(entity.project, entity)

spec/helpers/gitlab_routing_helper_spec.rb

@@ -89,4 +89,19 @@ describe GitlabRoutingHelper do
       expect(preview_markdown_path(project)).to eq("/#{project.full_path}/preview_markdown")
     end
   end
+
+  describe '#edit_milestone_path' do
+    it 'returns group milestone edit path when given entity parent is a Group' do
+      group = create(:group)
+      milestone = create(:milestone, group: group)
+
+      expect(edit_milestone_path(milestone)).to eq("/groups/#{group.path}/-/milestones/#{milestone.iid}/edit")
+    end
+
+    it 'returns project milestone edit path when given entity parent is not a Group' do
+      milestone = create(:milestone, group: nil)
+
+      expect(edit_milestone_path(milestone)).to eq("/#{milestone.project.full_path}/milestones/#{milestone.iid}/edit")
+    end
+  end
 end