$ git clone -n https://github.com/xcp-ng-rpms/nettle.git /var/lib/mock/v8.3-u-pcoval2-10923-29402/root/chroot_tmpdir/scmroot/nettle
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10923-29402/root/chroot_tmpdir/scmroot/nettle'...
$ git fetch origin c2912e56599dcfb7d7278649b89727e8ff5cc17f:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/nettle
 * [new ref]         c2912e56599dcfb7d7278649b89727e8ff5cc17f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c2912e5 bump release for test build