Customization variables for HTML filenames like NODE_FILES

[Gavin Smith]

I was looking at HTML.pm to check that the rules were what I thought they 
were for the names of output files for split HTML output.  I find there 
are quite a lot of customization variables that affect this, including:

NODE_FILENAMES
NODE_FILE_EXTENSION
TOP_NODE_FILE
TOP_NODE_FILE_TARGET
USE_SETFILENAME_EXTENSION

I wonder if some or all of these can be removed in order to make the 
code simpler and clearer.

NODE_FILENAMES (and the --node-filenames option) seems to be a holdover 
from texi2html, before node filenames were named in a predictable way.

The only use I can think of for NODE_FILE_EXTENSION is to use ".htm" 
instead of ".html" on MS-DOS - not worth worrying about.

TOP_NODE_FILE and TOP_NODE_FILE_TARGET should always be "index" 
(basename of file containing "Top" node).

It is not useful to set USE_SETFILENAME_EXTENSION explicitly (the extension 
to the argument to @setfilename, usually .info, is only used for Info 
output).

I tried looking through mailing list archives to see if there was any 
discussion on the need for any of these, but didn't see anything.

In general, removing useless customization variables is a good thing, as
it makes the code clearer, and makes useful customization variables 
easier to notice in the manual.  I am not in a rush to remove as many 
customization variables as possible, but removing a few at a time seems 
like a good idea.  It would help to hold down the complexity of the 
Texinfo project, and improve its long-term maintainability, even as it
possibily gets more complex in other areas.