well the top-level git data structure is pretty close to eg, Scala's Vector, which is an immutable container implemented as a tree with a high branching factor

well the top-level git data structure is pretty close to eg, Scala's Vector, which is an immutable container implemented as a tree with a high branching factor of 32. Modification to such a vector, rebound to a new variable, relies on structural sharing of the original (http://www.codecommit.com/blog/scala/implementing-persistent-vectors-in-scala http://www.codecommit.com/blog/scala/implementing-persistent...)