bug#70198: M-x shell: deal with environment variables present when tab expanding

[Federico Tedin]

Dan Jacobson <jidanni@jidanni.org> writes:

> In M-x shell
> $ dat<TAB>
> expands to date.
> Alas, unlike bash readline,
> $ LC_ALL=C dat<TAB>
> doesn't yet.
>
> emacs-version "29.3"

I took a crack at fixing this, I'm attaching a patch.

It's been some time since my last contribution, but I've kept the
copyright assignment updated (should be under federicotedin@gmail.com).
There's a chance the formatting for the patch may be a bit off too but I
tried to re-read the guide at CONTRIBUTE.

I've also found something interesting with the
`shell-dynamic-complete-command' function. I do not see it being called,
referred to, or assigned to a key anywhere in the Emacs code, but the
manual mentions it as if it being were actively used:

> Some implementation details of the shell command completion may also be found
> in the lisp documentation of the @code{shell-dynamic-complete-command}
> function.

Maybe the manual is outdated?

- Fede

0001-Fix-tab-expanding-not-working-in-shell-mode-bug-7019.patch
Description: patch