html_context is always overriden
in the the docs - http://sphinx.pocoo.org/templating.html?highlight=html_context - it is implied that one can set a variable called `html_context` so as to provide context variables to your templates. However, AFAICT, one cannot. One may only provide template context through command line switches, since in cmdline.py, html_context is always set to be an empty dictionary and passed in as an override.
Is this an error in documentation, or in code? I can try to provide a patch for either when I have a moment spare. FWIW, I'd prefer to pass in options to the html_context in conf.py as well as as a command line switch, as storing command-line options in a Makefile instead of conf.py feels wrong.