[twill] Variable expansion [PATCH]

[Titus Brown]

-> Don't know if I've just reinvented the wheel, but here's a patch which
-> implements expansion of variables within command arguments. e.g.
-> 
-> setlocal hostname example.com
-> setlocal moreurl abitmoreurl
-> 
-> go http://${hostname}/someurl/${moreurl}
-> 
-> This uses the python eval method so you can also do things like ${var1 +
-> var2} to concatenate variables etc.

Hi, Jeff,

this looks fantastic!  I would like to write some tests for it before I
actually put it in, but it is certainly not reinventing the wheel.

I was thinking about trying to use Python 2.4's Template mechanism, but
I never got around to seeing if it was possible to make it compatible
with Python 2.3.  Do you have any comments on this approach?

thanks!
--titus