I just came back from Paternity leave in the Eclipse SDK milestone (M3) week. The leave was great. Coming back was, as always, exciting. A slightly misconfigured tool had removed branches and tags (and an aggressive prune/gc had removed commits) during a push to our eclipse.platform.ui repo, leading to Bug 361707 - I have broken the platform-ui git repository. Because tags and commits were gone, we also broke all of the warmup I builds for our M3 week. My apologies to all that suffered.
These are all done by legitimate actions supported by git ... it just turns out that if you have a process backed by a central canonical repository, you really don't want your source disappearing out from under you. "I might have pushed back most of our repo" is not an acceptable level of support :-)
We were able to find a mostly complete repo, disable the Eclipse Foundation commit hook and push back the repo. We are discussing ways to limit this kind of damage in the future. See