$ git clone -n https://src.fedoraproject.org/rpms/slick-greeter.git /var/lib/mock/f45-build-46381-834/root/chroot_tmpdir/scmroot/slick-greeter
Cloning into '/var/lib/mock/f45-build-46381-834/root/chroot_tmpdir/scmroot/slick-greeter'...
$ git fetch origin b9f38a9957b827924c204bcffcd0a850c4323f26:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/slick-greeter
 * [new ref]         b9f38a9957b827924c204bcffcd0a850c4323f26 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b9f38a9 fix