>    I've not approached them for anything like this, but I would imagine a
>    single manifest file would not work at all for all of github's
>    repositories. The largest collection we currently manage with grokmirror
>    is 5,500 repositories and though it does admirably well, it's getting to
>    the point where parsing/writing the manifest file is taking upwards of a
>    second. They could probably generate a manifest file per user, but not a
>    single manifest for all the repositories they host.

Per-user or per-organization might already just do the job. Tbh, I was even
thinking of a per-project manifest.