* guix/scripts/package.scm (search-path-environment-variables): Add #:kind
parameter. Pass it to 'environment-variable-definition'.
(display-search-paths): Add #:kind parameter and pass it to
'search-path-environment-variables'.
(%options): Add an optional parameter for "--search-paths".
(guix-package)[process-query]: Handle it.
* tests/guix-package-net.sh: Adjust existing test.
* tests/guix-package.sh: Adjust existing tests and add new test.
* doc/guix.texi (Invoking guix package): Document it.