src/Pure/General/file.scala

     if (path.is_file) move(path, path.backup2)
     write(path, text)
   }
 
 
+  /* change */
+
+  def change(file: JFile, f: String => String): Unit = write(file, f(read(file)))
+  def change(path: Path, f: String => String): Unit = write(path, f(read(path)))
+
+
   /* append */
 
   def append(file: JFile, text: CharSequence): Unit =
     Files.write(file.toPath, UTF8.bytes(text.toString),
       StandardOpenOption.APPEND, StandardOpenOption.CREATE)