How does Mercurial store its data?
The fundamental storage type in Mercurial is a revlog. A revlog is the set of all revisions of a named object. Each revision is either stored compressed in its entirety or as a compressed binary delta against the previous version. The decision of when to store a full version is made based on how much data would be needed to reconstruct the file. This lets us ensure that we never need to read huge amounts of data to reconstruct a object, regardless of how many revisions of it we store.
