bug#27659: 26.0.50; Add string-matched-text: string-match + match-string

[Stefan Monnier]

> Pushed as ad4eff3b905dbc32e2d38bfec1e4f93eceec288d.  I've renamed
> backref-var to backref as you suggested, but left `let' because I think
> that feature is important enough to deserve a short, common name.

Thanks.

> Sure! I'd suggest to change the syntax to be compatible with other
> languages:
>
> \(?<abc>[0-9]+\) or \(?'abc'[0-9+\) (Perl and .NET)
> \(?P<abc>[0-9]+\) (Python)

Fine by me.  I'm surprised they didn't use the (?<var>:...) syntax,
since it seemed such an obvious choice, but maybe they wanted to allow :
in <var>.

Feel free to adapt my patch for that.  BTW, the main reason why I didn't
push my patch originally is because of its inability to extract the
match-beginning/end of the named subgroup: it felt like
a serious shortcoming.


        Stefan