$ git clone -n https://github.com/xcp-ng-rpms/samba /var/lib/mock/v8.3-incoming-8931-27879/root/chroot_tmpdir/scmroot/samba
Cloning into '/var/lib/mock/v8.3-incoming-8931-27879/root/chroot_tmpdir/scmroot/samba'...
$ git fetch origin 83b4c5ed48a6fcd759dd167addc9dddcbae7eb9e:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/samba
 * [new ref]         83b4c5ed48a6fcd759dd167addc9dddcbae7eb9e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 83b4c5e Merge updates from XS-1586