bug#61637: 30.0.50; Fix Eglot tests that need HOME=~USER

[Eli Zaretskii <eliz@gnu.org>]

> From: João Távora <joaotavora@gmail.com>
> Cc: contovob@tcd.ie,  61637@debbugs.gnu.org
> Date: Sat, 04 Mar 2023 13:23:32 +0000
> 
> > You disregarded the second part of my reasoning, which has to do with
> > the test results being non-deterministic once the user's real home
> > directory is accessible to Emacs.  How do we overcome that?
> 
> Sorry I didn't mean to disregard, I just missed it.  Well, it's not
> accessible to Emacs, only to LSP servers.  Eglot's tests are fairly are
> deterministic, all other things like LSP server versions being equal.
> 
> I'd say Eglot's tests are even robust to any changes in LSP server's
> user init files.  See how XDG_CONFIG_HOME is spooffed in eglot-tests.el
> to this effect.  It has been effective AFAICT for some time.  And that's
> only for those few servers that do offer these mechanisms: most of them
> rely on project-local configurations which is fine because Eglot creates
> a temporary project for each test.
> 
> All in all, I think the problem of user file clobbering and determinism
> are exaggerated -- in this specific case of course.  They are secondary
> to the fact that it's tricky, noisy, or even impossible to run Eglot
> tests ever since Eglot moved to Emacs core.  
> 
> I propose we install my patch and then perfect the solution.  Again,
> we're only affecting those devs who _do_ have these local installations,
> and that affection is much, much more likely to be beneficial than
> harmful.

OK, please go ahead, and thanks.