Feature request: Cross-database query

It's very common for a project to have many dependencies. Sometimes just analyzing application A will call a method in dependency B, and when you look at them as isolated pieces of software, codeQL might not find any problems. However, if you manually build a database containing both codebases and let codeQL analyze the whole chain, a new result is found.

My proposal is for codeQL to allow a user to have many active databases when running a query and for it to cross-reference every method, data type, class, etc., when running its queries. Another viable yet less preferable option would be to be able to merge databases.