How to fork my own repo into a new project?
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I was developing an HTML5 game engine, called Irenic. I used Git as the SVC, and GitHub to actually host the project.

I've made some substantial changes in the design (mainly switching to the Entity System paradigm), and I think it's time for a new engine.

I would like to base it off the old engine, as there is a lot of code that I can use.

What would be the standard way of doing this? The new engine will have a new name, and the old one will be considered "finished".