While having rules affecting several branches makes the yaml file
smaller, it is way easier to maintain if each branch has their own set
of rules. It's easier to remove old branches, and to avoid issues when
branching out new releases.
Actions don't run in a shell, so in order to expand the environment
variable it is necessary to wrap the command in a shell invocation.
Signed-off-by: Nikola Forró <nforro@redhat.com>