Clone git repo
Git clone https://gitgood.2020.chall.actf.co/.git/
Find the commit logs at /.git/logs/HEAD
Get the Sha-1 hash of the first log
Git checkout 6b3c94c0b90a897f246f0f32dec3f5fd3e40abb5
(Switches to that version of the repo)
Cat thisistheflag.txt
actf{b3_car3ful_wh4t_y0u_s3rve_wi7h}