phase1: manually fetch remote Git refs

phase1: manually fetch remote Git refs

Buildbot never updates the remote branch reference on incremental updates,
causing scripts/getver.sh to assume a dirty tree with unpublished local
commits.

Add a manual command step to update the remote branch ref in order to bring
the remote tracking branch history in sync with the local branch.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>