$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.3-u-qcasasnovas1-11513-29825/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-qcasasnovas1-11513-29825/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin aadf3d7d44cf98d44be694ad59671a89656e9d85:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         aadf3d7d44cf98d44be694ad59671a89656e9d85 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at aadf3d7 bump release for test build