cgit is a web interface (cgi) for git repositories, written in C.
The folder /var/cache/cgit, must be owned by your webserver user.
A sample /etc/cgitrc (you must provide one) is in the docs folder,
and so are some example configuration files for apache and lighttpd.
luacrypto or lua-md5 are optional dependencies (for avatars support),
but first you have to build this against lua.
If you want to use the email-libravatar-korg.lua filter or the
email-gravatar-sbo.lua one, have a look also to the suggested css
additions (in the docs folder).