bug#81559: 31.0.91; speedbar does not follow Dired and shell-dirtrack-mode

> From: Daniel Mendler <[email protected]>
> Cc: [email protected]
> Date: Sun, 09 Aug 2026 18:10:03 +0200
> 
> Eli Zaretskii <[email protected]> writes:
> 
> >> From: Daniel Mendler <[email protected]>
> >> Cc: [email protected]
> >> Date: Wed, 05 Aug 2026 19:26:41 +0200
> >> 
> >> Eli Zaretskii <[email protected]> writes:
> >> 
> >> >> Date: Wed, 05 Aug 2026 17:40:01 +0200
> >> >> From: Daniel Mendler via "Bug reports for GNU Emacs,
> >> >>  the Swiss army knife of text editors" <[email protected]>
> >> >> 
> >> >> The speedbar does not follow the current shell directory, nor does it
> >> >> follow the current directory in Dired. In order to test:
> >> >> 
> >> >> 1. emacs -Q
> >> >> 2. M-x speedbar
> >> >> 3. M-x shell and then cd to change directories => speedbar does not follow
> >> >> 4. M-x dired, chose various directories => speedbar does not follow
> >> >
> >> > Did Speedbar ever react to Dired and shell directory changes?  If yes,
> >> > in which version of Emacs?  If it never did, this is a request for an
> >> > enhancement, right?  And I think the way to add such an enhancement is
> >> > described the node "Extending" of the Speedbar manual.
> >> 
> >> Yes, as far as I can tell, this has never worked. It is a feature
> >> request.
> >
> > Thanks, marked it as such.  Patches welcome.
> 
> The following simple patch ensures that Speedbar reacts also on buffers
> which are not backed by files (e.g. Shell with dirtrack mode or Dired).
> This should go to the master branch and we might want to guard it behind
> an option (e.g., speedbar-update-file-buffer). Eli, what do you think?

Is this useful?  I'd think we could do something more sophisticated.
E.g., just showing the files in a directory already displayed in Dired
doesn't seem to add any information, does it?