$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-src /var/lib/mock/v9.0-u-ydi1-11211-29593/root/chroot_tmpdir/scmroot/xs-opam-src
Cloning into '/var/lib/mock/v9.0-u-ydi1-11211-29593/root/chroot_tmpdir/scmroot/xs-opam-src'...
$ git fetch origin 12daf717995a7577775ff5300295c155dab05d17:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-src
 * [new ref]         12daf717995a7577775ff5300295c155dab05d17 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 12daf71 bump release for test build