Bug#909319: Show unnecessary overrides

[Josh Triplett <josh@joshtriplett.org>]

Control: retitle -1 Doesn't show unused override

On Fri, Sep 21, 2018 at 06:41:14PM +0200, Mattia Rizzolo wrote:
> On Fri, Sep 21, 2018 at 09:12:40AM -0700, Josh Triplett wrote:
> > Sometimes an override becomes unnecessary, either because the package
> > changed to not need it or lintian changed to become more discerning and
> > no longer flags the package. Either way, at that point the override
> > becomes unnecessary. Lintian should show the unnecessary override to
> > call attention to it, so that the maintainer can remove it.
> 
> It already does it?
> 
> Check out https://lintian.debian.org/tags/unused-override.html

Interesting. I filed this because I observed lintian not raising this
when I expected it to.

For a test case, git clone https://joshtriplett.org/git/josh-meta and
run ./build in that directory. Note that the josh-dev package has a
now-unnecessary lintian override, which should trigger unused-override.