def applied_patches_inverse
      result = {}
      applied_patches.each do |name, sig|
        raise DuplicateError, [result[sig], name] if result.key?(sig)
        result[sig] = name
      end
      result
    end
def applied_patches_inverse
      result = {}
      applied_patches.each do |name, sig|
        raise DuplicateError, [result[sig], name] if result.key?(sig)
        result[sig] = name
      end
      result
    end
Fetches the information about applied patches and
 returns it as { signature => name } hash.