Say you want to identify which changes you made to a configuration file in /etc on a Debian system. If you have set up a tol like etckeeper you can just use it, but what if you haven't? A simple idea is to just diff your file against the original configuration file that shipped with the corresponding Debian package.

I was surprised that there was no automatic tool to identify the right Debian package with apt-file, retrieve it with apt-get download, and perform the diff, so I wrote it: debdiffconf.