Where is the documentation for lit located?

Hello,

I was trying to expand the tests for some new features I introduced
into libclang. I had a hard time finding the documentation on the
substitution patterns for lit. The only current documentation(?) is in
the python sources.

I'd like to add them to the documentation that gets generated(?) to
http://llvm.org/docs/CommandGuide/lit.html

Where can i find it? Is it accessible via the regulare git repo?

Thank you.

Re-add cfe-dev