As for her romantically inclined co-worker -- I don't see how his behavior qualifies as sexist or hostile. Merely a bit clueless, but isn't it to be expected that employees of a tech company will be somewhat socially awkward?
EDIT: As multiple commenters have noted, ripping out someone's code commits because they rejected your romantic advances is unacceptable and unprofessional. The ripper-outer should be roasted by the project manager if there's no technical justification. Since the two employees no longer get along, one or both should be re-assigned to different projects if possible. And the offender should be disciplined (up to and including dismissal from the company) if he makes life difficult for her in the future. But his actions reflect on him, not Github as a whole. The article includes no information about whether any of his actions were reported to his supervisor or anyone else, and no information about Github's response to the incident. Without those crucial details, I think it's premature to point a finger at Github.
As for the hula hoop incident -- if the girls doing the hooping and the guys doing the watching were okay with it, and everybody kept their clothes on, that seems pretty innocent to me.