$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v9.0-u-ydi1-11363-29668/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v9.0-u-ydi1-11363-29668/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin b73c45bb885be1f221ff9f0bfe7456469ec25c38:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         b73c45bb885be1f221ff9f0bfe7456469ec25c38 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b73c45b bump release for test build