bug#23779: 25.0.95; consing "SHELLVAR" onto process-environment doesn't remove it from subprocess env

[Eli Zaretskii]

> Cc: eggert@cs.ucla.edu, schwab@linux-m68k.org,
>  npostavs@users.sourceforge.net, 23779@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Fri, 17 Jun 2016 22:01:19 +0300
> 
> On 06/17/2016 08:06 PM, Eli Zaretskii wrote:
> 
> > Now that 'push' works, why do we need setenv for that?
> 
> So that the user doesn't have to (push "VAR=value"), or (push "VAR="), 
> or know the difference between the latter and (push "VAR").
> 
> setenv is a better abstraction. In fact, if you use it, you don't even 
> have to know the format of process-environment.

We will have to agree to disagree on this one.

> >> So, what are the downsides?
> >
> > That there's no way of changing the environment permanently?
> 
> The environment is changes as a result. It just doesn't modify the 
> original list, and, as such, contains duplicate values for the changed 
> variables.

What do I do if I do want to change the original one?

> > I'm not sure I see why that is nicer.
> 
> Do you know what value "PAGER=" assigns to the variable PAGER?

Not sure what that means, or why do you ask that.