Before GA and, in order to not have master code in stable repos  by accident we can disable fallback_to_master in the dlrn instance. This means we should set souce-branch for all projects which does not have stable/<release> branch to a tag, hash or branch explicitely. We can find what packages are falling back to master in DLRN run logs.

To find out the projects that fall back to default branch (i.e master):

grep -e "Falling back" dlrn-logs/<latest_run>.log