release_process: insufficient git fetch?

Spotted during the 3.12 release process, in the Prepare upgrade-description files section: we have two such constructs (non-final vs. final) →

cd ${MASTER_CHECKOUT:?} && \
git fetch && \
[…]
git push origin master:master

The git fetch doesn’t help much, as any remote changes aren’t taken into account. We should probably add git rebase origin/master?

(I had spotted it during previous releases, but that wasn’t a practical issue; with the delays during 3.12, that became an issue.)

Original created by @CyrilBrulebois on 16401 (Redmine)