src/Pure/General/file.scala

   def is_executable(path: Path): Boolean = {
     if (Platform.is_windows) Isabelle_System.bash("test -x " + bash_path(path)).check.ok
     else path.file.canExecute
   }
 
-  def set_executable(path: Path, flag: Boolean = false): Unit = {
-    if (Platform.is_windows && flag) Isabelle_System.chmod("a+x", path)
-    else if (Platform.is_windows) Isabelle_System.chmod("a-x", path)
-    else path.file.setExecutable(flag, false)
+  def set_executable(path: Path, reset: Boolean = false): Unit = {
+    if (Platform.is_windows) Isabelle_System.chmod(if (reset) "a-x" else "a+x", path)
+    else path.file.setExecutable(!reset, false)
   }
 
 
   /* content */