Re: grep.el regexp

[Richard M. Stallman]

    but it will recognize lines with the leading number and colon as the
    column number (look the example in etc/grep.txt).

I don't see any lines in grep.txt which start with a number and a
colon.  So I don't understand this at all.  Would you please show
those lines you mean, instead of just describing them?

      This wouldn't be
    a problem if fontification was able to skip already fontified lines,
    and not to apply the rule with column numbers when the rule that
    accepts escape sequences for column calculation was applied.

I think there is a way to do that, but I never fully understood
all the details of these specs.  Maybe someone else knows it.