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IDLE reading IDLESTARTUP or PYTHONSTARTUP on restart

I have a small change (shown below) to PyShell.py in idlelib that causes the subprocess interpreter to read IDLESTARTUP or PYTHONSTARTUP each time it restarts. To me this would make IDLE much more useful for myself and students I teach. It isn't quite clear what behavior to install with the enabling patch, so I would like some feedback before submitting it. The main question is:

Shouldn't IDLE always read IDLESTARTUP (if defined) or PYTHONSTARTUP (if IDLESTARTUP is not defined and PYTHONSTARTUP is) when it starts rather than that requiring a command-line switch as it does now? This is the behavior of python, and I don't see why it should be any different for IDLE. More importantly, there is no convenient way to say "and read my startup file" when double-clicking the IDLE icon. (I'm on a Mac. On Windows the -s switch could be added to an icon for IDLE, but that's still awkward.)

Secondary questions;

If IDLE is changed to read a startup file, should the -s switch be dropped altogether? If so, should a -q switch be added (as with emacs) to start without loading the startup file? I think yes to both.

When the subprocess interpreter is restarted should it look in the environment for the current values of IDLESTARTUP and PYTHONSTARTUP, or should IDLE store those values in a property of the subprocess interpreter when first started and have restart go directly to the saved path even if the value of IDLESTARTUP or PYTHONSTARTUP has changed since IDLE had been started. I think restart should go to the path as it was when IDLE was started and ignore subsequent changes. Or at least the reststart should notice the change and present a dialog asking the user to choose between the old path and the new one.

The diff modifies PyShell by copying the four lines of code that load IDLESTARTUP or PYTHONSTARTUP from where they appear in the initial startup code and adding to where the subprocess interpreter writes "RESTART" to the console.

@@ -434,6 +434,10 @@
         console.write(halfbar \+ ' RESTART ' + halfbar)
         console.text.mark\_set("restart", "end-1c")
         console.text.mark\_gravity("restart", "left")
+        filename = os.environ.get("IDLESTARTUP") or \\
+                   os.environ.get("PYTHONSTARTUP")
+        if filename and os.path.isfile(filename):
+            self.execfile(filename)
         console.showprompt()
         # restart subprocess debugger
         if debug: