class Tilt::BaseMapping

def split(file)
  pattern = file.to_s.downcase
  full_pattern = pattern.dup
  until registered?(pattern)
    return if pattern.empty?
    pattern = File.basename(pattern)
    pattern.sub!(/\A[^.]*\.?/, '')
  end
  prefix_size = full_pattern.size - pattern.size
  [full_pattern[0,prefix_size-1], pattern]
end