$ git clone -n https://src.fedoraproject.org/rpms/arm-trusted-firmware.git /var/lib/mock/f42-build-side-1-3586225-46914/root/chroot_tmpdir/scmroot/arm-trusted-firmware
Cloning into '/var/lib/mock/f42-build-side-1-3586225-46914/root/chroot_tmpdir/scmroot/arm-trusted-firmware'...
$ git fetch origin 85cfaf2cf8b556f7e3408723d158b8cbbacfab6c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/arm-trusted-firmware
 * [new ref]         85cfaf2cf8b556f7e3408723d158b8cbbacfab6c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 85cfaf2 2.12.4