svn co https://core.svn.wordpress.org/trunk/ your-dir-here
Edit some files, then create a patch
svn diff > my-patch-name.patch
Review your patch
$ git clone git://develop.git.wordpress.org/ your-dir
$ npm install
$ grunt
Install WordPress
Edit some files in the /src/ dir, run grunt then git diff
After installing you get:
http://local.wordpress-trunk.dev
Edit some files in the /src/ dir, run grunt then svn diff