$ git clone -n https://src.fedoraproject.org/rpms/opam.git /var/lib/mock/f38-build-722122-98721/root/chroot_tmpdir/scmroot/opam
Cloning into '/var/lib/mock/f38-build-722122-98721/root/chroot_tmpdir/scmroot/opam'...
$ git fetch origin 0ff9e3bc776353009f3c4dcf57d34ba9a48e2720:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/opam
 * [new ref]         0ff9e3bc776353009f3c4dcf57d34ba9a48e2720 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0ff9e3b Rebuild OCaml packages for F38