Copyright for igraph source package in Bionic

Format: http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: igraph
Source: https://github.com/igraph/igraph/releases

Files: *
Copyright:
 Copyright © 2005-2008 Gabor Csardi, Tamas Nepusz
License: GPL-2+
 The Debian packaging is licensed under the GPL-2 or any later version,
 see `/usr/share/common-licenses/GPL-2'

Files: debian/*
Copyright:
 Copyright 2009-2012, Mathieu Malaterre 
License: GPL-2+
 The Debian packaging is licensed under the GPL-2 or any later version,
 see `/usr/share/common-licenses/GPL-2'