Wishlist: option to leave Last-modified unset.

[mjw-pp]

If I use mod_xsendfile to set up a URL which serves different static files depending on some external condition, then the Last-modified header taken from the file mtime can be a lie. In particular, it can go backwards and cause an if-modified-since request to incorrectly report the URL as not modified.

If I know when the condition changed I can set Last-modified from the script, but that information isn't always available, so what I'd like to be able to do is omit Last-modified altogether (Etag is still useful).

It turns out 'header unset' and 'header always unset' from mod_headers don't override mod_xsendfile, so a mod_xsendfile option to control this would be helpful. Or perhaps arranging for mod_xsendfile to take effect before mod_headers would be a reasonable alternative.