A.4. monotone

"monotone is a free distributed version control system. it provides a simple, single-file transactional version store, with fully disconnected operation and an efficient peer-to-peer synchronization protocol. it understands history-sensitive merging, lightweight branches, integrated code review and 3rd party testing. it uses cryptographic version naming and client-side RSA certificates. it has good internationalization support, has no external dependencies, runs on linux, solaris, OSX, and windows, and is licensed under the GNU GPL."

http://www.venge.net/monotone/