Building youtube-dl from Ports causes trouble?

[Wojciech Puchar]

>
> I updated my ports this morning, built youtube-dl, and after finding

definitely not related to youtube-dl.

> some software wouldn't work, rebooted. Now X doesn't start, and when I
> tried to start emacs, it seems that libpng, required by emacs, has
> vanished.
>
> So my current theory is that I should just rebuild all my ports? I'm
> amazed that this could happen, truthfully.

unfortunately ports subsystem is far from being good.
anyway making it good dealing with today "modern" software with enormous 
amount of dependencies is just very hard.