get git-buildpackage working smoothly in gitlab-ci jobs

I'm testing out gitlab CI for standard Debian packages. I've noticed something odd happening, it seems that when the build runs, the git repo is in a detached state on the latest commit, and the master branch is at least one commit behind. To see this, scroll down to "git status" to see this sequence being run:

    - git status
    - git log
    - git checkout master
    - git status
    - git log

https://salsa.debian.org/eighthave/repomaker/-/jobs/66

git-buildpackage assumes that the git repo is currently on a branch, and by default that branch is master. If there is a config option to make gitlab CI make sure that master is current, that will make it easier to run git-buildpackage in CI builds.