$ git clone -n https://github.com/xcp-ng-rpms/tcpdump.git /var/lib/mock/v8.3-u-pcoval2-10406-28968/root/chroot_tmpdir/scmroot/tcpdump
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10406-28968/root/chroot_tmpdir/scmroot/tcpdump'...
$ git fetch origin df59b2059ee6113e86d463bb591a7193ea06a4be:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/tcpdump
 * [new ref]         df59b2059ee6113e86d463bb591a7193ea06a4be -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at df59b20 bump release for test build