Random but y'all might enjoy. Git client in PHP, supports reading packfiles, reftables, diff via LCS. Written by hand.

https://github.com/igorwwwwwwwwwwwwwwwwwwww/gipht-horse

Nice! This repo is a huge W for PHP I'd say.

P.S. Didn't know that plain '@' can be used instead of HEAD, but I guess it makes sense since you can omit both left and right parts of the expressions separated by '@'