For repercussions, there are both official and unofficial consequences, and both of those depend on just how much of a "smoking gun" can be found.

Right now there is a DDoS attack with some strong but unspecific evidence it originated somewhere vaguely within the Chinese government. That is not much to go on, and the repercussions are likely minimal. Some "don't do that" statements by some key players, maybe some diplomats work some diplomatic channels, that's about it.

If, however, it can be tracked back to a specific people, a specific attack by a specific part of the government, then some mostly diplomatic responses from various groups are possible. In the diplomatic circles there may be some snubbing, some contracts lost or cancelled, and so on. If enough specific individuals and specific agencies can be uncovered with specific details about what they did then certain lawsuits may follow, or government orders to limit trade for a few months may follow, but those are less likely.

In the technical circles there may be some blacklists that block the DDoS that stay in place too long, effectively denying service to those whose browsers triggered the DDoS attack. Those are different repercussions than the official ones, and those rules may stay in place in various servers for quite some time.

A good compromise that would make all parties happy would be cutting the cables that connect China to the rest of the world.

It would give the Chinese government what they want (no more imperialist poisoning their people, you dirty capitalist pigs), and it would immediately stop the DDoS and a large number of other annoying hacker attacks.

(Of course it would also mean that companies like e.g. Blizzard can no longer sell their online services to Chinese customers for 1/10 of the revenue they get everywhere else, so that isn't going to happen.)

This is actually quite specific: http://insight-labs.org/?p=1682

Though there is something I don't get: As frob pointed out, one result of this is usually that the offending ip ranges are blocked and remain blocked for some time. Which, presumably, is exactly what they want: No access to those two git-hub projects from within china. But if that was their goal, why would they design the attack in a way that all the requests originate from outside of china?