$ git clone -n https://src.fedoraproject.org/rpms/opam.git /var/lib/mock/f42-build-3360688-45036/root/chroot_tmpdir/scmroot/opam
Cloning into '/var/lib/mock/f42-build-3360688-45036/root/chroot_tmpdir/scmroot/opam'...
$ git fetch origin 331d13f0f5d739f453ed621aa55e5686d8f1c8b5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/opam
 * [new ref]         331d13f0f5d739f453ed621aa55e5686d8f1c8b5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 331d13f Rebuild for z3 4.14.0