[wp-hackers] Disabling automatic plugin upgrade for specific plugin?

[Ozh]

you can just change the plugin folder, plugin filename and plugin name 
within the plugin header (the "/* Plugin Name") stuff so that it won't be 
recognised as a plugin hosted on wp.org

----- Original Message -----
From: "Glenn Ansley" <glenn at glennansley.com>

Hi,
If I've made substantial edits to a plugin for a single client's
specific use and I don't want them to ever automatically upgrade it in
the future (or me either for that matter), is that as simple as
changing the plugin's name or are there SVN hooks/externals or
something else that I need to disable?