store /etc in git, mercurial, bzr or darcs

 The etckeeper program is a tool to let /etc be stored in a git, mercurial,
 bzr or darcs repository. It hooks into APT to automatically commit changes
 made to /etc during package upgrades. It tracks file metadata that version
 control systems do not normally support, but that is important for /etc, such
 as the permissions of /etc/shadow. It's quite modular and configurable, while
 also being simple to use if you understand the basics of working with version
 control.