This process is new and we have little experience - we expect it will evolve over time, so please send any suggestions for improving the process.

Currently the idea is:

• ​Check out the game from SVN.
• Make some changes.
• Make sure you've updated to the latest version of the code (and merged in your own changes).
• Create a patch, with svn diff (or the equivalent "create patch" feature in TortoiseSVN).
• Attach it to a Trac ticket (an existing ticket if there's a relevant one, else a new one), prefix the ticket Summary with "[PATCH]", set the ticket Milestone to the current release, and add "review" to the Keywords list. (The keyword makes it show up on this query.)
• One of the core developers should then review it and maybe suggest some changes.
• When it's considered okay, they should commit it to SVN.
• If you don't hear anything within a reasonable time period (maybe a week or two), feel free to post a reminder on the forum.

You must agree that it is your own work (or else make it clear where it came from) and agree to licensing the work as ​GPL 2+ (or in some cases ​MIT, especially for code in lib/ - check the existing copyright headers on the source files you edit).