I see, thanks!
The sink option can be really useful for you to find how two things supposedly related to each other. For example: mix xref graph --sink lib/ecto/query.ex in Ecto will show all the paths that reach lib/ecto/query.ex. Some of those are quite long but it does provide the relationship information.
We could also add functionality to provide all paths between two places in particular. Right now it is not possible to filter with a source and sink at the same time.
