For arch.

> sudo su # keep it simple
> pacman -S git
> cd <git-home-dir>
> usermod -d `pwd` git
> usermod -s /usr/bin/git-shell # Disallow shell access.
> mkdir .ssh
> touch .ssh/authorized_keys # public keys go in here
> git init --bare <repo-name> # by convention, bare repos (like for servers, no working directory) end in .git
> chown -R git:git .

Now on a dev machine:
> git add remote <name> git@<host>:<repo-name>
or
> git clone git@<host>:<repo-name>

For example:
<git-home-dir>: /mnt/data/git-home
<repo-name>: foo.git
<name>: origin

FWIW, the git-remote string is <git-user>@<host>:<repo-path>.