Added Rake task to remove duplicate screenshots

lib/tasks/remove_image_duplicates.rake

@@ -0,0 +1,31 @@
+namespace :debshots do
+  desc "Remove duplicate images"
+
+  task :remove_duplicate_images => :environment do
+    Rails.logger = Logger.new(STDOUT)
+    Rails.logger.level = Logger::INFO
+    #Rails.logger.level = Logger::DEBUG
+
+    Rails.logger.info "Removing packages with 'nil' screenshots"
+
+    Screenshot.where(image_fingerprint: nil).each do |ss|
+      Rails.logger.info "Destroying screenshots #{ss.id} of package #{ss.package.name} that has nil data"
+      ss.destroy
+    end
+
+    Rails.logger.info "Removing packages with duplicate screenshot checksums"
+
+    loop do
+      destroyed = 0
+      Screenshot.select(:package_id, :image_fingerprint).group(:package_id, :image_fingerprint).having("count(*) > 1").each do |ss|
+        # Look again for screenshots of this fingerprint.
+        # This extra step may seem stupid but the above query lead to package_id=NULL results sometimes.
+        del = Screenshot.find_by(image_fingerprint: ss.image_fingerprint)
+        Rails.logger.info "Destroying duplicate screenshots #{del.id} of package #{del.package.name}"
+        del.destroy
+        destroyed += 1
+      end
+      break if destroyed == 0
+    end
+  end
+end