# File mk, line 495
def findsource
  tried = []
  base = (ARGV[0]||'').sub(/\.$/,'')
  dir = File.dirname(base)
  base = File.basename(base)
  base = @default if base.empty?

  ret = tryfile(dir,base,tried) and return ret
  ret = tryfile(@altdir,base,tried) and return ret
  ret = tryfile("#{@altdir}/#{base}",@default,tried) and return ret

  puts ["File not found; I tried:",tried].join("\n")

  return nil
end