bug#33618: 27.0.50; ada-mode breaks M-x grep

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Date: Tue, 04 Dec 2018 19:02:35 -0500
> Cc: Stephen Leake <stephen_leake@member.fsf.org>
> 
> > Opening a file in ada-mode using the new ada-mode from GNU ELPA globally
> > sets compilation-search-path (for me, it got set to `("~/tmp")`
> > probably because the Ada file was in ~/tmp), which in
> > turn breaks M-x grep in the sense that clicking on a match doesn't jump
> > to the file but prompts you to find the file (unless you happened to
> > grep from one of the directories mentioned in the
> > compilation-search-path, of course).
> 
> I use the patch below currently to work around this problem.
> Should I install it into `master` (with a few more comments and
> probably etc/NEWS or even manual updates)?

If the problem is in ada-mode in ELPA, it should be fixed there, IMO.
Why do we need to change our code to cater to problems in packages,
even if those packages are on ELPA?  It sounds wrong to me, FWIW.