My first submission on Hacker News was the link below, 2 years ago. It didn't receive any upvote.
Click and see, it's fascinating.
* GitHub commit search: “remove private key”
https://news.ycombinator.com/item?id=14262124
Although most keys removed are just useless automatically generated test keys, but genuine keys do exist. Someone should write a crawler to monitor these commits, creates digital signatures from private keys to prove the leak, and notify the CA issuer to revoke them automatically.