Add temporary show=libs inspection view

Lets you browse exactly the packages that the libs section blacklist
would remove on the next import, to review them visually before
running it.

app/controllers/packages_controller.rb

@@ -381,6 +381,10 @@ class PackagesController < ApplicationController
     when 'without'
       packages = packages.without_screenshots
       logger.debug 'Limiting packages to those without screenshots'
+    when 'libs'
+      # Temporary inspection view: exactly the packages that the libs
+      # section blacklist would remove on the next import
+      packages = packages.where("section ~* '/?(old)?libs$'")
     end
 
     packages

test/controllers/packages_controller_test.rb

@@ -134,6 +134,16 @@ class PackagesControllerTest < ActionController::TestCase
     end
   end
 
+  test 'show=libs lists exactly the section-blacklist candidates' do
+    packages(:firefox).update_column(:section, 'libs')
+    packages(:vim).update_column(:section, 'editors')
+
+    get :grid, params: { show: 'libs' }
+    assert_response :success
+    assert_select 'div', text: 'firefox', count: 1
+    assert_select 'div', text: 'vim', count: 0
+  end
+
   # test 'should get thumbnail for a package and a desired version' do
   #   # get '/thumbnail-with-version/package-5/0.1'
   #   get thumbnail_with_version_url('package-5', '0.1')