BitKeeper is the original distributed source management system. Now available as Open Source under the Apache 2.0 License.
BitKeeper is a fast, enterprise-ready, distributed SCM that scales up to very large projects and down to tiny ones.
diff3.
$ bk clone bk://bkbits.net/bkdemo/bk_demo
$ cd bkdemo
# edit files using your favorite editor
$ bk -Ux new
$ bk commit -y"Comments"
$ bk push
$ bk init new_project
$ cd new_project
# edit files using your favorite editor
$ bk -Ux new
$ bk commit -y"Initial commit"