The PowerMatcher repo's main branch is master. All major releases are tagged in this branch. Development is done in the development branch. To do a release, the development branch is merged into master and HEAD is tagged with the new release number.
During development of the next release, there may exist any number of feature branches. These branches exist to solve some problem or develop a certain feature and will be merged with development when the fix or feature is done.
To submit code to these branches, one can create a fork of the repo and do a pull request to the development or feature branch. See Contributing to the PM Community.