It looks git-dpm will only create the upstream tag with "git-dpm tag" and
this operation can only be called when you want to tag a released package.

However when I work on a new upstream release, it might take some time
until the new release is ready for release and it would be nice if I
the upstream/<version> tag was already available for use in various
git commands (even though I can also use the tip of the corresponding
upstream branch).

Furthermore since git-dpm offers no command to build & tag the package
it looks like that I will keep using "gbp buildpackage" to build my
package from a clean state and its --git-tag option will only create the
tag for the package release, not for the upstream release. The net result
is that I will likely forget to run "git-dpm tag" and I will miss the
upstream tags.

So it would be nice if the upstream tags could be created sooner
as part of "git-dpm import-new-upstream".