Wrap git's shell script to add bashrc or equivalent start-up commands

My server has a git user that handles all git access. You can't log in with it. It's only for git access. That works because GIT comes with a handly shell /usr/bin/git-shell.

Login feedback:

fatal: What do you think I am? A shell?
Coection to example.com closed.

That works beautifully. But the shell doesn't have a .bashrc or .profile etc. I want to add

export LD_LIBRARY_PATH=/lib64

so my git stops complaining about some custom build stuff. (Everything works, but it keeps waing about a missing version.)

I've added that to /etc/bashrc, so all 'normal' users don't have it, but git is special. Is there a way to add that export to my git shell? Can I wrap it or something? (I've no idea how passwd works.)