This is a followup to 3f8326237d.
* guix/scripts/archive.scm (export-from-store): Warn then FILES is
empty.
* guix/scripts/build.scm (guix-build): Likewise.
* guix/scripts/copy.scm (warn-if-empty): New procedure.
(send-to-remote-host, retrieve-from-remote-host): Call it.
* guix/scripts/edit.scm (guix-edit): Warn when SPECS is empty.
* guix/scripts/environment.scm (guix-environment): Warn when MANIFEST
has zero entries.
* guix/scripts/graph.scm (guix-graph): Warn then ITEMS is empty.
* guix/scripts/package.scm (process-actions): Warn when FILES and TRANS
are both empty.
* guix/scripts/edit.scm: Make nano the default editor.
Nano is sensible default, as it is installed by base system.
For development, user can set custom value for $EDITOR.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
That way 'guix edit' doesn't need to load any package module.
* gnu/packages.scm (find-package-locations, specification->location):
New procedures.
* guix/scripts/edit.scm (package->location-specification): Rename to...
(location->location-specification): ... this. Expect a location object
instead of a package.
(guix-edit): Use 'specification->location' instead of
'specification->package'.
* tests/packages.scm ("find-package-locations")
("find-package-locations with cache")
("specification->location"): New tests.
