$ git clone -n https://github.com/xcp-ng-rpms/nettle.git /var/lib/mock/v8.3-incoming-10907-29394/root/chroot_tmpdir/scmroot/nettle
Cloning into '/var/lib/mock/v8.3-incoming-10907-29394/root/chroot_tmpdir/scmroot/nettle'...
$ git fetch origin 8bfdba492cad17f4ec776d713ed88176a6df49d3:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/nettle
 * [new ref]         8bfdba492cad17f4ec776d713ed88176a6df49d3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8bfdba4 Import nettle-3.10-2.xs8.src.rpm