Re: GUIX_PACKAGE_PATH doesn't have priority over official guix packages

[Phil]

Tobias Geerinckx-Rice writes:

>  “Any packages they define will be added to the pool of available
>  packages.  Standard package specification rules apply: when 
>  given a package name without an unambiguous version number, Guix
>  will always pick the highest version of that package regardless 
>  of where it came from.”

Makes sense to me - only thing I'd add, assuming my analysis is right,
I'd highlight that when 2 packages exist with identical verison number,
and one package is specified as local (via -L or GUIX_PACKAGE_PATH),
that local version is preferred over a git-hosted channel.

This has consequences if you want to alter a package locally. Although
I'd recommend defining the package to have a different variable name and
refer to it using "-e" to make intentions explicit in any command/manifest.