$ git clone -n https://src.fedoraproject.org/rpms/subnetcalc.git /var/lib/mock/f45-build-36554-706/root/chroot_tmpdir/scmroot/subnetcalc
Cloning into '/var/lib/mock/f45-build-36554-706/root/chroot_tmpdir/scmroot/subnetcalc'...
$ git fetch origin b87f94359bc64203711c16f3d326be4b9dd983b1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/subnetcalc
 * [new ref]         b87f94359bc64203711c16f3d326be4b9dd983b1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b87f943 Update to 2.7.5