[Q] figuring out a system / source file

[73budden .]

I defined variables which show current component and current system.
They can be used by IDEs to navigate to sources, or by your code to do
what you need.

I suggested this as a modification of asdf, but asdf maintainers said
that special variables are dangerous. Maybe.

My code is here:
https://bitbucket.org/budden/budden-tools/src/default/asdf-3.1.4-tools.lisp?at=default&fileviewer=file-view-default