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

[Stefan Monnier]

Package: Emacs
Version: 29.0.50


Since:

    commit bf505a63f98ed61934a8fb81ec65c96859606b6e
    Author: Jim Porter <jporterbugs@gmail.com>
    Date:   Mon Nov 15 13:33:07 2021 +0100

    Support abbreviating home directory of Tramp filenames

`abbreviate-file-name` has significantly changed in its behavior:
- it's slower (because it goes through file-name-handlers)
- it can have very visible side effects like prompting the user for a password.

I haven't measured the slowdown, so I'll assume it's acceptable, but
asking for a password (or contacting a remote host) is not.

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?


        Stefan