bug#24194: GUIX gc - add warning

[Leo Famulari]

On Tue, Aug 09, 2016 at 07:59:28PM -0400, J. Eppler wrote:
> Hello,
>  
> I used GUIX for the first time and invoked: guix gc. The command deleted
> all my bootstrap files (gcc, binutils, findutils etc.). There should be
> a warning added to the manual page:
> 
> https://www.gnu.org/software/guix/manual/html_node/Invoking-guix-gc.html

I think the concept of garbage collector roots should be clarified in
the manual somehow and linked to from 'Invoking guix gc'. Or it could
even go in that section.

I was surprised to find that the string 'gcroots' does not appear in the
manual.

> I was actually assuming that guix gc removes orphan packages,
> build-caches, temporary files etc., but it does not seem to only do that.

In your case, things that are not garbage collector roots (that is, not
reachable from /var/guix/gcroots) could be considered orphans or
temporary. I agree the documentation should be improved.