$ git clone -n https://github.com/xcp-ng-rpms/nettle.git /var/lib/mock/v8.3-u-pcoval1-11012-29446/root/chroot_tmpdir/scmroot/nettle
Cloning into '/var/lib/mock/v8.3-u-pcoval1-11012-29446/root/chroot_tmpdir/scmroot/nettle'...
$ git fetch origin 6185670dea1265fede09ca2835ba1e2c62bd8617:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/nettle
 * [new ref]         6185670dea1265fede09ca2835ba1e2c62bd8617 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6185670 bump release for test build