From Apache SRE:

Hello committers,

We have received quite a few reports of github mirrors gone missing. We’ve tracked this down to an errant process at Github which appears to be deleting not only ours but also other orgs’ mirrors. We contacted Github but have yet to receive a reply. Another organization also contacted github and received the following reply: "Hi there, Sorry for the trouble! We've now had a couple of reports of this problem, and we've opened an issue internally to investigate. I don't have an ETA on a fix, but we'll be in touch if we need more information from you or if we have any information to share. Regards, Laura GitHub Support” We have no further information at this time. We have been restoring the mirrors wherever possible, but until the root cause is resolved on Github’s side, we expect mirrors to continue to be erroneously removed. Access to the repos via the usual https://git-wip-us.apache.org/ channel remains functional.