$ git clone -n https://github.com/xcp-ng-rpms/gnutls.git /var/lib/mock/v8.3-incoming-10148-28716/root/chroot_tmpdir/scmroot/gnutls
Cloning into '/var/lib/mock/v8.3-incoming-10148-28716/root/chroot_tmpdir/scmroot/gnutls'...
$ git fetch origin 48dd93ccc36ccc03b285397a2910d63eefd73e76:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/gnutls
 * [new ref]         48dd93ccc36ccc03b285397a2910d63eefd73e76 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 48dd93c Make cc+ optional (disabled by default)