CSH Constitution
The master branch's HEAD is the current legal constitution of CSH.
Modifying the Constitution
Do not make changes to master without their passing the proper house voting procedures. (At the very least, not text changes, anyways)
You can demo changes etc on forks or branches though. In fact, the diff of this branch/fork and the head of constitution/master would make it extremely easy to illustrate the changes you've made relative to the current constitution, or for people to annotate your changes with comments, etc.