Re: grep.el regexp

[Richard Stallman]

    I guess the original regexp was created to match different grep output
    formats.  From this regexp I can deduce such formats that use space or
    tab as a separator between file name, line number and source line.

    I can't tell is it right to drop support for those formats.

I think that if we wrote a separate regexp for each kind of grep, all
together they would match a lot fewer different strings than the
current regexp does, and they would be much easier to understand.