How to migrate a grunt project into ember-cli project

I have a js project using ember.js, which is managed by grunt. But when ember-cli is trend of ember.js management tool, I want to migrate the existing grunt project into ember-cli project.

According to the ember-cli manual, I tried the Ember CLI migrator, but it require the existing project is a git version-controlled project, otherwise it cannot migrate. Is there a good way to migrate the existing project without git repo?