bug#42045: 27.0.91; display-format-alist for X11 does not recognize DISPLAY with IPv6 literal

[Robert Pluim]

>>>>> On Thu, 25 Jun 2020 22:20:05 +0300, Valtteri Vuorikoski 
>>>>> <vuori@notcom.org> said:

    Valtteri> If the DISPLAY environment variable is to an IPv6 literal such as
    Valtteri> [::1]:1, the regexp that x-win.el adds to the 
display-format-alist to
    Valtteri> recognize X11 does not match, which results in breakage.

    Valtteri> x-win.el should probably add a second regexp to the alist, such 
as:
    Valtteri> (add-to-list 'display-format-alist 
'("\\`\\[[^]]*\\]:[0-9]+\\(\\.[0-9]+\\)?\\'" . x))

That regexp won't work, since now youʼre requiring the '[' and ']' to
be present.

"\\`\\[?[^]]*\\]?:[0-9]+\\(\\.[0-9]+\\)?\\'" would fix that, but since
we donʼt really care what comes before the ':', so would

"\\`.*:[0-9]+\\(\\.[0-9]+\\)?\\'"

Robert