Owncloud

Install:

git clone https://github.com/owncloud/core.git owncloud
cd owncloud
git submodule init  # 3rdparty directory
git submodule update

There's a command-line tool for administering it:

sudo -u www-data php occ

Use this for upgrading point releases, adding and managing users, enabling and disabling apps, etc.

Upgrading from before version 6.x

After version 6 the calendar and contacts apps were moved from core to the third party repository. You may need to disable them before upgrading from 6 to newer 8.x versions, and sort them out afterwards.