When the owner/defender of a Linux system refuses to pay anything (only beer-free software) and demands every undocumented hardware supported by windows to be supported by Linux for free;
and when the attacker is paid $250K a shot ( http://www.schneier.com/blog/archives/2012/06/the_vulnera... )
I am not sure it can "absolutely be done" (not that Windows, Mac,... are so more protected).
I am waiting the day $250K is injected every few days into securing Linux, obviously Git comments will not be of real importance then.