bug#62528: 28.2; Emacsclient doesn't use COLORTERM

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Vojtěch Balák <vojtech@balak.me>,
>   62528@debbugs.gnu.org
> Date: Thu, 30 Mar 2023 10:59:32 +0200
> 
> >>>>> On Thu, 30 Mar 2023 09:49:56 +0200, Vojtěch Balák <vojtech@balak.me> 
> >>>>> said:
> 
>     >> COLORTERM should be in the environment of emacs when it starts, not in
>     >> the environment of emacsclient.
> 
> Thatʼs because we look it up using `getenv' in init_tty. If we used
> `egetenv' instead, then we could honour the value of "COLORTERM" sent
> by emacsclient.

But egetenv would be wrong here, because it looks in
process-environment.

This is _exactly_ the issue here: emacsclient puts the environment of
the parent shell into process-environment, so that it could be
inherited by sub-processes, but Emacs itself should _not_ be sensitive
to the environment it prepares for sub-processes.