bug#29659: 25.2; better rmail-summary-by-topic

[Francesco Potortì]

>
>> Date: Mon, 11 Dec 2017 16:50:14 +0100
>> From: Francesco Potortì <pot@gnu.org>
>> Cc: 29659@debbugs.gnu.org
>> 
>> >> Maybe this can be simply incorporated into rmail-simplified-subject: it
>> >> is able to remove prefixes like
>> >> 
>> >> Re: [Topic] Fwd: Re: Fwd:
>> >> 
>> >> and in practice I find it very useful
>> 
>> >Indeed, and so I wonder why did you need the advice?  Which prefixes
>> >does rmail-simplified-subject not handle correctly?
>> 
>> It is much more primitive, it only removes a single Re: prefix.
>
>So you are saying that we need to convert an 'if' to a 'while', and
>then Bob'll be our uncle?

It's simpler than that: just use the RE that I used in my advice rather
than the 'if' series that's in rmail-simplified-subject.

I can test and provide a patch, if someone is interested in installing it.