Git has a built-in persistent store for objects based on Merkle trees. It is tailored to store files and directories, but these are just specializations of trees of blobs. There is no reason it couldn't be used to store Lisp objects. Githack is a Lisp object store that uses Git as its backend. It is a simple library that provides persistent objects for Lisp and a transactional interface for manipulating them. Simple atomic objects are stored as blobs and composite objects are stored as trees. Standard composite Lisp objects, such as lists, vectors, and hash tables, are supported. Custom composite...