These are the Hakyll sources for my blog.
I use site deploy to rsync the output files into the main repo.
If clean would not just wipe the _site folder, but ignore some configurable
subfolders, then it would be easy to keep the sources in the main repo.
You would just set destinationDirectory to .. and add a _config.yml
with an ignore: src inside so Github's Jakyll would skip the sources when rendering.
I tried it, it works, except for the clean/rebuild thing.