Author of the post here. We're actively working on this at Sourcegraph. Up until recently, we've focused on working well on large private codebases, but looking forward, we have two big efforts that will make this a reality on sourcegraph.com:

1. Vastly expanding the size of our global search index to cover every public repository on github.com, gitlab.com, and bitbucket.org. 2. Enabling LSIF indexing (https://lsif.dev) in every major language for compiler-accurate code navigation (go-to-def, find-refs) across repository/dependency boundaries.

The latter is already working on a subset of languages for private Sourcegraph instances, and we want to scale it to the entire open-source world. We think a single search box that covers all the visible code in the world and allows you to seamlessly walk the reference graph is super super powerful and someday will be a thing that most developers use every day.