$ git clone -n https://github.com/xcp-ng-rpms/xen /var/lib/mock/v8.3-u-tae2-9175-27989/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-tae2-9175-27989/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 7efcf003074f46d71b960645774ee67843f33cc7:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         7efcf003074f46d71b960645774ee67843f33cc7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7efcf00 bump release for test build