$ git clone -n https://src.fedoraproject.org/rpms/R-snow.git /var/lib/mock/f45-build-6432-348/root/chroot_tmpdir/scmroot/R-snow
Cloning into '/var/lib/mock/f45-build-6432-348/root/chroot_tmpdir/scmroot/R-snow'...
$ git fetch origin b27debfd534ec066ccc6c6296d56d28eceb8d721:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-snow
 * [new ref]         b27debfd534ec066ccc6c6296d56d28eceb8d721 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b27debf Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild