steps for "Developing a new feature" unsufficient
If one follows the steps in section "Developing a new feature", after
git merge --no-ff release-6.0
there are all changes from the merge uncommitted.
git tag -a v6.0
then tags the old (not merged) version and
git push origin v6.0
pushes the old version with the new tag.
@rakovec and I solved this by ommitting "--no-ff". If this is not supposed to be the way, more instructions are neccessary.