extra-source job; native package with non-native version

Hi. I'm generally a happy user of the salsa CI pipeline. Thanks for making it so flexible. I have a feature request.

The extract-source job can't cope with a native package with a non-native version. This arrangement is disliked by some people, but I find that it can be convenient for smallish packages, especially when working entirely from git. The Technical Committee have said that it's fine.

Here's an example of it failing: https://salsa.debian.org/debian/xtruss/-/jobs/6566845. (NB this package is new and has not yet been uploaded.)

Ideally, we would detect this situation by seeing 3.0 (native) in d/s/format. However, dpkg-source hates this (the dpkg maintainer having disregarded the TC decision), so it is necessary to use 1.0, which doesn't provide an in-tree way to specify 1.0-just-a-tarball vs 1.0-with-diff. This configuration is a minority interest, so I think it would be fine to ask people in my position to set a variable.

I think the behaviour of the new flag ought to be "please just use the git tree as provided by gitlab CI as if it were the unpacked source package". I think this would be useful for others too, since I suspect there are other possible patches-applied git-based workflows where gbp's assumptions are violated and it struggles to make a source package.

I didn't see a good way to override this job. And I'm not entirely sure what the resulting artifacts are supposed to be. The "gitarchive" branch of the big if isn't suitable because I don't want to change d/s/format.

So I'm asking for your help. Thanks in advance.