Bug#867325: import-dsc: do not create a debian/1.2.3-1 tag for UNRELEASED

[Johannes Schauer]

Package: git-buildpackage
Version: 0.8.12.2
Severity: wishlist

Currently, when using "gbp import-dsc" a debian/1.2.3-1 tag will be
created and for the top commit on the master branch. But this doesn't
make sense if the most recent changelog entry is marked as UNRELEASED.
In that case, no such tag should be created. Otherwise it is easy to
miss that this tag was created and to accidentally push that tag to a
remote.