$ git clone -n https://github.com/xcp-ng-rpms/xen /var/lib/mock/v8.3-incoming-9991-28649/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-incoming-9991-28649/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 1461afbf82807183bb578184730c54f176c874b3:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         1461afbf82807183bb578184730c54f176c874b3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1461afb Add support for Intel CPU sensors (through xenpm)