$ git clone -n https://github.com/xcp-ng-rpms/opam.git /var/lib/mock/v8.3-u-psafont2-9705-28420/root/chroot_tmpdir/scmroot/opam
Cloning into '/var/lib/mock/v8.3-u-psafont2-9705-28420/root/chroot_tmpdir/scmroot/opam'...
$ git fetch origin 1ce558459df56792648a3d6012b3020e4663d4bd:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/opam
 * [new ref]         1ce558459df56792648a3d6012b3020e4663d4bd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1ce5584 bump release for test build