The scenario is the following: inside a (somewhat) trusted LAN you would like to set up git-daemon so that your coworkers can access your repositories. This solution is not appropriate in cases where you want to share with random people on the interwebs. This short description is based loosely on this blogpost and it was updated to contain more details and tested with Ubuntu 11.04.

• install the git-daemon-runit package: sudo apt-get install git-daemon-runit
• decide where you would like to keep your git repositories – it can be your home folder, if it’s not encrypted (if it’s encrypted it won’t work because it only gets decrypted once you log in, so the git repositories won’t be available unless you log in). Lets say that you’ve decided it to be /var/git. Create it:
  sudo mkdir /var/git
  sudo chown $USER /var/git
• Now edit the file /etc/sv/git-daemon/run and make it like the following (bold marks the spots which were changed):
  #!/bin/sh
  exec 2>&1
  echo 'git-daemon starting.'
  exec chpst -ugitdaemon
    "$(git --exec-path)"/git-daemon --verbose --export-all --base-path=/var/git /var/git
• Restart the service:
  sudo sv restart git-daemon
• Enable it from the firewall:
  sudo ufw allow 9418/tcp

That’s it. Now every subdirectory from /var/git which "looks like" a git repo (has a .git subdirectory) will be available over the git protocol. Alternatively, you can remove the "–export-all" option and create a "git-daemon-export-ok" file in each subdirectory you would like to export: touch /var/git/core/git-daemon-export-ok

You can symlink the directory to your home folder for your convenience:
ln -s /var/git ~/projects/git