List available backups for restore

lib/backup/manager.rb

@@ -108,7 +108,12 @@ module Backup
           $progress.puts "Please make sure that file name ends with #{FILE_NAME_SUFFIX}"
           exit 1
         elsif backup_file_list.many? && ENV["BACKUP"].nil?
-          $progress.puts 'Found more than one backup, please specify which one you want to restore:'
+          $progress.puts 'Found more than one backup:'
+          # print list of available backups
+          backup_file_list.each do |item|
+            $progress.puts " " + item.gsub("#{FILE_NAME_SUFFIX}", "")
+          end
+          $progress.puts 'Please specify which one you want to restore:'
           $progress.puts 'rake gitlab:backup:restore BACKUP=timestamp_of_backup'
           exit 1
         end

spec/lib/backup/manager_spec.rb

@@ -194,6 +194,13 @@ describe Backup::Manager do
         )
       end
 
+      it 'prints the list of available backups' do
+        expect(progress).to have_received(:puts)
+          .with(a_string_matching('1451606400_2016_01_01_1.2.3'))
+        expect(progress).to have_received(:puts)
+          .with(a_string_matching('1451520000_2015_12_31'))
+      end
+
       it 'fails the operation and prints an error' do
         expect { subject.unpack }.to raise_error SystemExit
         expect(progress).to have_received(:puts)