Git unable to create file permission denied

I believe if you run

 sudo chown -R git:git /srv/git/ 

this is coming from How to fix permission denied for .git/ directory when performing git push?

You probably didn't do this part of the tutorial:

First, the work tree (/var/www/www.example.org above) must be writable by the user who runs the hook (or the user needs sudo access to run git checkout -f, or something similar).