GitHub Code Search has too many quirks compared to the zoekt powered alternatives (cs.android.com, cs.bazel.build) which feel far more intuitive.
I wish Microsoft would invest more in improving it - especially since Sourcegraph can't search private repositories, leaving GitHub's tool as the only real option for many codebases.
more background: https://sourcegraph.com/blog/zoekt-creating-internal-tools-a...
There's also https://github.com/google/codesearch for local only search
Excellent tool for larger codebases!
Keep in mind Source graph has done an open-source bait-and-switch before:
https://news.ycombinator.com/item?id=36584656