Once you’ve edited the file and tested it, you need to create the patch so other people can test it as well. You can create a patch a number of ways.
If you are on Windows, consider using Tortoise SVN. You can read our tutorial on creating a patch with Tortoise SVN..
Mac/Linux Command Line Mac/Linux Command Line
Make a patch, for filename.php:
$ svn diff filename.php > filename.diff
Make a patch for all files modified in the checkout:
$ svn diff > big_patch.diff
Apply a patch from someone else:
$ patch -p0 < patch.diff
There are some GUI options for the Mac, as well — you just need it to create patch files (Versions cannot, for example).
Also: creating SVN patches using Git, from Cristi Burca.