Upstream's git repo uses git-lfs, but LFS assets are not downloadable.
This does not work well with Salsa's git-lfs support, so we need to be
creative.

Each new upstream release is imported from its working tree in a new orphan
commit:

    git checkout --orphan=<version>
    git add *
    git rm -f .gitattributes
    git commit -m "Snapshot of upstream <version>"
    git tag upstream/<version>

The `debian/latest` branch is then rebased to the new upstream snapshot, and
packaging can continue.

Note that the initial 2.1.1 version was started from the upstream `Publication`
branch, and upstream later on tagged version 2.1.1, which in Debian becomes
`2.1.1+deb1`
