$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-src /var/lib/mock/v9.0-incoming-11333-29650/root/chroot_tmpdir/scmroot/xs-opam-src
Cloning into '/var/lib/mock/v9.0-incoming-11333-29650/root/chroot_tmpdir/scmroot/xs-opam-src'...
$ git fetch origin bc9a5c76b9dc08f35995aad55d8c235463a0cb3e:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-src
 * [new ref]         bc9a5c76b9dc08f35995aad55d8c235463a0cb3e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bc9a5c7 Merge pull request #1 from xcp-ng-rpms/ydi/9