Indexing classes distributed over multiple files

Hey,

I'm trying to index an entire Xcode project. Sadly the documentation for index is missing.
In one of the issues I've found it describes I'll have to pass more arguments such as:

sourcekitten index --file $(pwd)/MathClass.swift --compilerargs -- "-sdk $(xcrun --show-sdk-path --sdk macosx) -j4 $(pwd)/MathClass.swift"

But truthfully I have a few problems understanding what exactly these arguments mean :(

Having two classes in one file, I'll get a key.receiver_usr when calling a method from another class.
Splitting them into two and indexing them separately, I don't.
I guess I have to pass the dependencies to sourcekitten... but I don't really know how.

There is probably no option yet to parse an entire Xcode project, or is there?

Help would be greatly appreciated :)

P.S. In case I figure it out I'd love to help updating the documentation.

Start with the sourcekitten index command and the compilerargs example in the issue. Document what the arguments mean, how dependencies or multiple Swift files should be supplied, and whether indexing an entire Xcode project is supported. Done means a newcomer can follow the documentation to index classes distributed across files.