Created a gentoo overlay. Right now it only has ebuilds for gitphp. You can set it up by doing something like:

git clone http://www.xiphux.com/git/gentoo.git /usr/local/portage/xiphux

And adding to your make.conf:
PORTDIR_OVERLAY="/usr/local/portage/xiphux"

The ebuild will handle changing the permissions of templates_c and will copy gitphp.conf.php.example to gitphp.conf.php, and will allow you to merge changes to gitphp.conf.php using etc-update when you upgrade.

Unfortunately, I don’t know of a good way to make webapp-config handle the templates_c directory, so when you unmerge the package you have to get rid of the templates_c directory manually (since by then the webserver has generated the compiled files in there, so webapp-config won’t remove it since it’s not empty).