using gitconfig to get shell access

Hello all,

If I have a bare repo that is accessed only remotely, but I
allow arbitrary 'git config' keys to be set on it by the
remote user (somehow), can any of them be used to make git
run arbitrary commands on the server?

For example, 'hooks.showrev', is a "shell command used to
format each revision in the email".

Of course that's only in contrib, but are there any like
that in the main git config settings?  I took a look through
man git-config and offhand I couldn't find any, but if
someone knows more definitively I'd appreciate hearing about
it.

Thanks,

Sitaram