Any updates on this PR?

Not yet.

I'm put off using diff2html since hogan.js is so outdated.

Not sure I understand what is the problem. hogan.js is very stable and no bugs or problems were found.
We don't have any special lock on it, we are using mustache and hogan is just the best way I found at the time to render it.

Happy to contribute if that would be helpful!

wontache was pretty early at the time I started this. With the new changes it would require some bigger rewrite and I did not have time. If you want to contribute the migration go ahead and feel free to send a PR.

But TBH wontache has no releases since last October and has no version 1.x. I am ok in releasing some parallel versions but since it is not even stable and has no active development I do not feel comfortable in putting it in master.