[bug#54375] Mutable guix shell environments

[Charles]

> What if instead of just "a package" I wanted to add or remove a package that 
> defines a search path

As with ~/.guix-profile, you will have to . "$GUIX_PROFILE/etc/profile" just 
like the hint says. For removing, they linger, that is exactly what the default 
profile does too.

This comes down to us disagreeing which is more important & useful: guix shell 
semantics vs profile semantics. guix shell --profile could go either way.

Another way to look at it is that I this sequence of 3 commands very useful (so 
might others). They clearly have something to do with guix profiles, and they 
spawn a new shell. Thus I thought guix shell --profile was the perfect place 
for them. You claim they do not belong there. Is there a better place you would 
suggest?