$ git clone -n https://src.fedoraproject.org/rpms/vsftpd.git /var/lib/mock/f42-build-3285373-41413/root/chroot_tmpdir/scmroot/vsftpd
Cloning into '/var/lib/mock/f42-build-3285373-41413/root/chroot_tmpdir/scmroot/vsftpd'...
$ git fetch origin c31087744900967ff4d572706a296bf6c8c4a68e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/vsftpd
 * [new ref]         c31087744900967ff4d572706a296bf6c8c4a68e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c310877 Correct the definition of setup_bio_callbacks() in ssl.c.