Right, all you need is a hashed object that includes the hash of the previous version. Git / most DVCSes are built on this but even they are more complicated th

Right, all you need is a hashed object that includes the hash of the previous version. Git / most DVCSes are built on this but even they are more complicated than what you need. What you actually want, I think, is a legal document that says "The parties hereby amend the contract previously agreed to on mm/dd/yy as follows: after paragraph 5, add .... For reference, a full copy of the amended contract is included. In the case of discrepancies, this description of changes, and not the following copy, is authoritative."