• Code to be committed must compile.
  Please make a SVN-Update of complete MATSim before committing your own code to make sure your code compiles together with the code currently in the repository. It is important that your code is written in UTF8, otherwise it may not compile on all machines.
• By default, only commit to your personal playground. Do not commit to org.matsim.* unless you are the maintainer of a package/module in org.matsim.*, then you can also commit to this package. Only a small group of persons has the right to commit code to org.matsim.core.*, if you're not one of them, do not commit code in there. Talk to one of the core committers if you need changes or want to contribute code into the core.
• If you commit code to org.matsim.*, run first the test cases before committing and make sure there are no test failures.
• Write useful commit messages.
  If you only commit to your personal playground, a commit message is optional. In all other cases, a commit message is required.
• Write your commit messages in English.
• Do not commit personal data (=non-code) files to the repository.
  Exception is data for test cases, which must be committed to test/input/*. See the detailed discussion of this topic.

KDE has a nice list of additional recommendations for committing code to a repository. The list seems mostly reasonable also for our project, but we don't want to regulate too much, but hope for people's sanity when committing code.