$ git clone -n https://src.fedoraproject.org/rpms/snapshot.git /var/lib/mock/f39-build-2104514-50568/root/chroot_tmpdir/scmroot/snapshot
Cloning into '/var/lib/mock/f39-build-2104514-50568/root/chroot_tmpdir/scmroot/snapshot'...
$ git fetch origin 019ab636d73b4a8765a7ff96e57ecdf76be70c42:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/snapshot
 * [new ref]         019ab636d73b4a8765a7ff96e57ecdf76be70c42 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 019ab63 Update to 45.1