how to configure the global .hgrc file from the commandline

[Uwe Brauer]

Hi 

That may sound bizarre. But lately I collaborate with colleagues, who
don't have much interest in OS details, and use different OS. So it is
sometimes not clear to me, especially for Windows users, where the
corresponding global .hgrc is located.

That's why I would like to know how one could configure the global .hgrc
file from the command-line, especially adding extensions.

I googled but could not find anything
Thanks

Uwe Brauer