Disallow pushing of new trailing whitespace

[Jan Stolarek]

> The problem with this approach is that if a file already contains
> trailing whitespace, you'll introduce spurious changes in your commit.
I wouldn't call it a problem, but a feature - provided that you put whitespace changes in a separate commit. In this way we would gradually get rid of all trailing whitespaces and live happily ever after. Right now I'm facing a dilemma whether I should use mentioned emacs setting or not. If I do use it, I end up removing lots of whitespaces simply when I edit files (and I'm fine with that), but I don't know if there's any point in doing this if they keep reappearing. I can then disable this setting, but I know I'll end up adding even more whitespaces to the source code and I don't think that's a good thing to do.

Janek