This is the packaging source for glusterfs that is used to build the community Debian & Ubuntu packages of glusterfs, glusterd2, glusterfs-core-utils, storhaug, etc., on download.gluster.org and in the Community GlusterFS Launchpad PPAs, respectively.
Instructions for adding the PPA are on the Launchpad PPAs web page.
The interesting stuff is in branches dedicated to glusterfs & distro releases.
Attention: If you're trying to install GlusterFS on, e.g. Bionic, and you're getting GlusterFS-3.13, this is an indication that you haven't added/installed the PPA and are getting the packages from the Ubuntu base repository. If that's really what you want, contact Canonical for support.