I don't know about Canada but, the US has a form of this ala amendments. Its not as easy as pushing changes in github, but it shouldn't be. Jefferson envisioned a revolution every 20 years, he was soundly rebuffed for this notion by other founding fathers. The constitution is more like the  freedoms than regular laws. it sets up the basic structure that says "here are the unbendable rules, everything else must be conforming to the notions placed here" Having a just straight fluid rulebook from top to bottom is bad. what happens when the people submitting changes and the people approving them conspire to oppress some other group?