I'm in the same position trying to build Neovim, but I have all the sources downloaded already since libmpack always times out. Maybe someone browsing this thread who can't work right now can help: does anyone know how to force/suggest to Cmake that the dependencies it needs are already downloaded and in some src directory?

Even worse if libraries / packages are only hosted on Github. Then the main ecosystem of a language dependent on those packages can grind to a full stop from there.

I'm looking at all of you CocoaPods, SwiftPM, npm, Cargo, vgo.

Insanity. Having an emergency mirror on standby is not hard when it's critical infrastructure. Surely npm/Cargo/etc.. could do this.

I think I'll set this up now https://github.com/local-npm/local-npm

The npm registry itself does not depend on GitHub.

It's true that most developers rely on GitHub for pushing to the registry, but there are a handful that use GitLab or self host that would be totally unaffected.

AdoptOpenJDK builds are hosted there too; found out about the outage trying to download one.

I heard that maven is also considering to move it's central repo to github.com.