Upstream packaging has switched to mesonpy as the build backend. mesonpy
makes use of .gitattributes to configure `git archive` as the way to
control what files are in the Python sdist; unfortunately, that means there
can be no distinction between the tarball of the project that the Debian
packaging would like to contain (with additional files like documentation,
test data etc), and the Python sdist.

Packaging must therefore be done by directly consuming the upstream git.

The workflow for this is...

Set up:

$ gbp clone https://salsa.debian.org/python-team/packages/refnx.git
$ cd refnx
$ git remote add upstreamvcs https://github.com/refnx/refnx.git
$ git fetch upstreamvcs

And to import a new upstream release $VERSION:

$ git fetch upstreamvcs
$ git checkout upstream/latest
$ git merge v$VERSION
$ git tag upstream/$VERSION
$ git checkout debian/master
$ gbp import-ref -u $VERSION

Note: presumably there is a way to get `gbp import-ref` to do the right
thing here without quite so many manual steps.
