dgit needs to manipulate source packages, including temporary packages
it has just generated, which, naturally, are unsigned.

This causes messages like this:

  dpkg-source: warning: extracting unsigned source package (/home/ian/.../work/../bpd/example_1.0-1.dsc)

I looked in the manual and found `--no-check` but that says it doesn't
check checksums either, which is not what's wanted here.  There's also
-q but that seems excessive.

TBH I don't think I agree with this warning in general, so I would be
quite happy to see it deleted entirely.  I think almost everyone who
works with source packages will have become inured to this warning,
since they will see it so often in such variety of situations.

I guess you won't agree though.  In any case, I think manipulating
locally generated, unsigned, source packages is normal, and there
should be a way to do it that doesn't produce warnings, and that
doesn't involve a big hammer like -q.

As an addiitonal complication, I would ideally like an option which
would be accepted by old versions of dpkg-source.  (This situation is
similar to an analogous one in gcc, where we eventually persuaded gcc
upstream that -Wno-some-warning-that-this-gcc-does-not-understand
ought to be a silent no-op, and not generate any warnings unless there
are other warnings being generated already.)  An environment variable
would be one way of achieving this.

In #1131881 you suggested filtering the stderr of dpkg-genchanges.
dgit could of course take a similar approach with dpkg-source.
But that wouldn't solve the problem for other people and other tools.

Thanks,
Ian.