There was some real wonkiness going on here. Essentially, the
inline function was being executed with default arguments because
a function reference was passed as-is into the templater. That
seemed odd. So now we pass an explicit generator of the function
result.
Moving this code out of makeindex() makes makeindex() small enough
to reason about. This makes it easier to see weird things, like the
fact that we're calling self.refresh() twice. Why, I'm not sure.
I'm also not sure why we need to call updatereqenv() to possibly
update the SERVER_NAME, SERVER_PORT, and SCRIPT_NAME variables as
part of rendering an index. I'll dig into these things in subsequent
commits.