The procedure to update to a new upstream release goes usually like
this:

# git checkout upstream
# git reset --hard <new upstream tag>
# git checkout -b master-new
# git merge -s ours <previous upstream tag on master>
# git merge master
# git branch -M master
# dch -v <new version>; git commit -a -m "version bump"
# fakeroot debian/rules vendor-tarball
