Monotone is an open source software tool for distributed revision control. Monotone tracks revisions to files, groups sets of revisions into changesets, and tracks history across renames. The focus of the project is on integrity over performance. Monotone is designed for distributed operation, and makes heavy use of cryptographic primitives to track file revisions (via the SHA-1 secure hash) and to authenticate user actions (via RSA cryptographic signatures). History Milestones Monotone version 0.26 introduced major changes to the internal database structures, including a new structure known by Monotone developers as a roster. Monotone databases created with version 0.26 can not exchange revisions with older Monotone databases. Older databases must first be upgraded to the new format. The new netsync protocol is incompatible with earlier versions of Monotone. As Git inspiration In April 2005, Monotone became the subject of increased interest in the FOSS community after Linus Torvalds mentioned it as a possible replacement for BitKeeper in the Linux development process. In a post on the Linux kernel mailing list, Torvalds praised Monotone and disparaged Subversion (and by extension, all client-server version-control systems): Instead of adopting Monotone, Torvalds decided to write his own SCM system, Git. Git's design uses some ideas from Monotone, but the two projects do not share any core source code. Git has a much stronger focus on high performance, inspired by the lengthy history and demanding distributed modes of collaboration used by Torvalds and the other Linux kernel authors. Torvalds later commented on Monotone's design and performance: A key issue debated was whether the replacement of BitKeeper should support cherry picking, whereby a tree maintainer can approve a subset of patches while rejecting others on an individual basis. Torvalds argued that this approach "results in the wrong dynamics and psychology in the system" by shifting burden to the upstream maintainers rather than forcing downstream maintainers to put more effort into keeping their trees free from garbage. He further argued that Monotone is correct in its aversion to cherry-picking as a feature, but then failed to take it far enough by not making it easy enough to "throw away" unclean working trees after their purpose is served. Torvalds also noted his perception that Monotone at that time had not achieved the performance level required by a project as large as Linux kernel development. Design Like GNU arch, and unlike Subversion, Monotone takes a distributed approach to version control.