guix environment --ad-hoc should work the other way round

[Hartmut Goebel <h.goebel@crazy-compilers.com>]

Hi,

being quite new to guix and playing around with `guix environment`. I
find it confusing and IMHO it is working the wrong way round:

I'd expect it to get me an environment where the specified packages are
installed. So I could easily test if a new version of a program works as
expected. Instead I get an environment where the tools for building
these packages are installed.

What I actually need to type      | What I'd expect to type
------------------------------------------------------------------
guix env --ad-hoc python-2.7      | guix env python-2.7
guix env python-2.7 --ad-hoc git  | guix env git --XXX python-2.7

(Where XXX is placeholder for something like --for-building ;-)

So basically I'd expect the meaning for the packages in front of
`--ad-hock` exchanged with those behind.

Please note that these are two different views on environments: The
currently implemented view i the one of a developer, who wants to set up
an environment for building quick. The other view is the one of a user,
who wants to test packages.

I'm in favor of changing `guix environment` to take the seconds view,
since I assume, this will be the case uses much more often. (Even given
that there ought to be no difference between developers and users, as
most users simply will not even think about something like a
build-environments.)

-- 
Regards
Hartmut Goebel

| Hartmut Goebel          | h.goebel@crazy-compilers.com               |
| www.crazy-compilers.com | compilers which you thought are impossible |