bug#54001: 29.0.50; abbreviate-file-name has side-effects

[Stefan Monnier]

>> I suggest we take a step back and think of how to get that feature
>> without having to contact any remote host during `abbreviate-file-name`.
>> Maybe we can do that by making Tramp opportunistically add entries to
>> `directory-abbrev-alist` when it performs expansion?
>
> I think Michael Albinus suggested doing that in the original bug, although
> I was concerned about modifying defcustoms invisibly like that. Is that ok
> to do?

No it's not, but we can add a non-defcustom'd variable holding
additional entries to circumvent this problem.

> Another option might be to store the abbreviations for a given
> file-name-handler somewhere internally and consult that when calling that
> file-name-handler's implementation of `abbreviate-file-name'.

That would work as well.


        Stefan