$ git clone -n https://src.fedoraproject.org/rpms/mailman3.git /var/lib/mock/f40-build-2172957-51046/root/chroot_tmpdir/scmroot/mailman3
Cloning into '/var/lib/mock/f40-build-2172957-51046/root/chroot_tmpdir/scmroot/mailman3'...
$ git fetch origin b65aded50ec4f9510bdfa788b9fcd50697dbbac3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mailman3
 * [new ref]         b65aded50ec4f9510bdfa788b9fcd50697dbbac3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b65aded Add changelog entry