$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.3-incoming-11392-29703/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-incoming-11392-29703/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin c541af9ff3424c91cee0684514b9b3b6568d1bc2:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         c541af9ff3424c91cee0684514b9b3b6568d1bc2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c541af9 Merge pull request #85 from xcp-ng-rpms/dnt-XCPNG-3106