Ask HN: Looking for old HN post of GitHub project that is internal eng. handbook

A year or three ago I saw a great post here that was a link to a GitHub repo. The link had guidance for new engineers joining their company on what they should learn or know and (I think) how to go about gaining those skills.

It was like an internal handbook they opensourced.

Anyone remember this? Looking for the link. I searched all my GitHub stars and HN upvotes and no luck so far.