On 2021-01-10 02:14, John Rouillard wrote:
> Sorry, I am lost here. What I understand is that the input text
> is something like:
> 
>    issuexyz
> 
> the output between the a, /a tags is `[issuexyz](issuexyz)` or is
> each of [issuexyz] and (issuezyz) a separate a tag?

No, the input is:

    [issuexyz](http://bugs.example.com/issuexyz)

And the HTML output is:

    <a href="http://bugs.example.com/issuexyz">[issuexyz](issuexyz)</a>

> Your url reference looks like it is a technique to return
> multiple matches reusing subelements that have already
> been matched. E.G. when matching three digits
> for 123456 return:
> 
>    123 234 345 456
> 
> and not
> 
>    123 456
>  
> which is I don't see as applicable here.

Maybe but the problem is that the regexp used overlaps so re.sub call
for the smallest matching but indeed we need that it calls for the
longest matching substring.