This is very cool. If you start to hit API rate limits for these services, you can try using the Sourcegraph API (email me sqs@sourcegraph.com and I can make sure your API key isn't rate-limited). Sourcegraph indexes all of these Git platforms and has a search API: https://about.sourcegraph.com/docs/features/api.
(Sourcegraph CEO here.) Yes, Sourcegraph does support this, with a caveat. You can query Sourcegraph for things like "repo:saml2" at https://sourcegraph.com/search?q=repo%3Asaml2 to find matching repositories. But currently we limit the number of matching repositories for interactive queries on Sourcegraph.com, so you need to use a sufficiently distinct query term.
This is because we built Sourcegraph for the more common code search use case: searching for text/regexp matches across all the code that matters to me (up to ~30k repositories). That's something that devs inside companies with large codebases do 5-20+ times per day.
As it turns out, searching across millions of open-source repositories is a less common use case (overall), only needed 0-3 times per week on average. We want to support this use case better, too, but it's not our priority based on what we've learned from devs.
Interestingly, some people look at Sourcegraph and say "I don't think code search is very useful" because they are thinking of the open-source code search use case. Anyone who's worked at Google/Facebook or a company that has Sourcegraph/OpenGrok/Hound/etc. understands that code search is super valuable. It is amazing to be able to search across all the code that matters to you in 1.5 seconds with a single hotkey (for me, it's alt-tab to Chrome, ctrl+L, src<TAB>, because I'm using our browser extension: https://about.sourcegraph.com/docs/features/browser-extensio...).
