$ git clone -n https://src.fedoraproject.org/rpms/tcpdump.git /var/lib/mock/f40-build-798882-142038/root/chroot_tmpdir/scmroot/tcpdump
Cloning into '/var/lib/mock/f40-build-798882-142038/root/chroot_tmpdir/scmroot/tcpdump'...
$ git fetch origin 8ffc029f71586d6489b7a6a6af5e085961430210:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/tcpdump
 * [new ref]         8ffc029f71586d6489b7a6a6af5e085961430210 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8ffc029 New version of tcpslice, 1.7 (rhbz #2263644)