No way for a page to know the source_suffix of it's source

[ericholscher]

We want to be able to link to the GitHub repo for a specific page when we build it. With the availability of multiple source_suffix's, we need to know what the actual suffix was for the specific file we're rendering is.

It feels like it should be included in the get_doc_context function: https://github.com/sphinx-doc/sphinx/blob/master/sphinx/builders/html.py#L360-L428 -- but I don't know the best way to pull it off. I could call doc2path, but if a specific docname has multiple extensions (eg. foo.rst and foo.md) in a directory, then I think that will result in a bug. It seems we should be passing the extension in, as we render the specific file.

I'll look into it a bit more and hopefully have a patch for this soon.

[ericholscher]

Upon further thought, we can only output one page per docname, so using doc2path on the env is the proper solution.