$ git clone -n https://github.com/xcp-ng-rpms/dummypkg.git /var/lib/mock/v8.3-lab-9424-28168/root/chroot_tmpdir/scmroot/dummypkg
Cloning into '/var/lib/mock/v8.3-lab-9424-28168/root/chroot_tmpdir/scmroot/dummypkg'...
$ git fetch origin 6d43d9144d0605a6955ec0f62a3c74903f9a9bf4:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/dummypkg
 * [new ref]         6d43d9144d0605a6955ec0f62a3c74903f9a9bf4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6d43d91 bump release for test build