Re: feature request: ability to use occur within *Occur* buffer

[Richard Stallman]

    I think that I've previously used M-x keep-lines (and also M-x
    flush-lines) in an *Occur* buffer and had it do the right thing.
    Would it work to just have M-x occur call keep-lines when the buffer
    it's used on is already an output buffer from an earlier M-x occur?

It would "work", but I think it is better to do something a little
more sophisticated which would be "just right".  For instance, it
should not depend on where point is in the *Occur* buffer and it
should not be confused by matches against the line number part.