Based on your use of "campaign" (the older name for Batch Changes), it sounds like you were looking into Sourcegraph about 2.5 years ago or before that. Lots has changed since then.

We recently released a new indexer scip-clang (https://about.sourcegraph.com/blog/announcing-scip-clang), which we've used to successfully index large codebases like Chromium. The indexer relies on a JSON compilation database (same as our older indexer lsif-clang) which is easy to produce from CMake, Bazel, Meson, Make etc.

We've also added support for cross-repo code navigation for C++ recently. (https://about.sourcegraph.com/blog/c-cpp-cross-repo)