Repo on https://github.com/NetBSD/src vastly diverged on commits

[Henryk Paluch <hpaluch%seznam.cz@localhost>]

Hello!

For some time I'm tracking NetBSD sources changes on 
https://github.com/NetBSD/src.git, but today I got for the first time:

$ git pull

Your branch and 'origin/trunk' have diverged,
and have 313571 and 313656 different commits each, respectively.
  (use "git pull" if you want to integrate the remote branch with yours)


Also when I look on Activity: https://github.com/NetBSD/src/activity 
there is a lot of commits with "Force push" tag.

Does anybody know what happened? Is that GitHub repo safe to use?

Best regards
  --Henryk Paluch