$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-psafont2-9633-28361/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-psafont2-9633-28361/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin fe0ce8e66161ad8a36c61916472d20b590f4f95d:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         fe0ce8e66161ad8a36c61916472d20b590f4f95d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fe0ce8e bump release for test build