$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.2-incoming-8895-27849/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.2-incoming-8895-27849/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 218a728eeda3ced428b2d1b473d9e76437d1dcf4:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         218a728eeda3ced428b2d1b473d9e76437d1dcf4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 218a728 Merge pull request #66 from xcp-ng-rpms/8.2-xsa471