$ git clone -n https://src.fedoraproject.org/rpms/rubygem-actionpack.git /var/lib/mock/f39-build-1701103-41201/root/chroot_tmpdir/scmroot/rubygem-actionpack
Cloning into '/var/lib/mock/f39-build-1701103-41201/root/chroot_tmpdir/scmroot/rubygem-actionpack'...
$ git fetch origin 03d224b0baef3ce1c8ae984781cfb7437da5bc6a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-actionpack
 * [new ref]         03d224b0baef3ce1c8ae984781cfb7437da5bc6a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 03d224b Enable tests.