$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-pcoval2-10170-28759/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10170-28759/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 1da149481c2fc6afb9618c926dee20dc922a47c0:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         1da149481c2fc6afb9618c926dee20dc922a47c0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1da1494 bump release for test build