The correct way to provide a patch is to use git format-patch to provide a clean patch against the git master branch of the Xfce repositories. To do so, you should develop your changes in a separate branch, commit your changes with a meaningful commit message then use git format-patch to produce a .patch file.

Once you have your patch ready you can attach it to a bugzilla report. Don't hesitate to get in touch with the developers on the development mailing list or on IRC if you need help.

Thanks