bug#51622: 29.0.50; [PATCH] Abbreviate remote home directories in `abbreviate-file-name'

[Eli Zaretskii]

> From: Jim Porter <jporterbugs@gmail.com>
> Date: Fri, 5 Nov 2021 20:44:44 -0700
> 
> Second, I removed the caching of the abbreviated home dir. Since adding 
> TRAMP support means there are multiple home dirs (one per host), keeping 
> the caching would have been fairly complex, and it's already the source 
> of potential bugs (e.g. when temporarily setting HOME to something 
> else). I did some benchmarking on this (see attached), and while it is 
> indeed slower without the caching, I don't think it's worth keeping the 
> caching around.

If some user never uses Tramp, this removal will be a net loss for
that user.  So I think we should have this customizable.  Or maybe
even better: as long as Tramp is not used, keep the cache, and only
stop updating it when Tramp is being used.