What version control systems does Launchpad support?

Launchpad's native version control system is Bazaar, which is also known as bzr; read about it at http://bazaar-vcs.org/.

We think that Bazaar is the best choice among distributed version control systems, both in technical design and in user experience - that's why when we needed to pick one first-class version control system for Launchpad's native format, we chose Bazaar.

Launchpad supports other version control systems by doing continuous imports from them into Launchpad's code-hosting system (https://code.launchpad.net/), and making the data available as Bazaar branches. There is currently continuous import support for CVS and Subversion, and we intend to add support for more (e.g., GIT and Mercurial) in the future. Bazaar's data model is flexible enough to represent all these different kinds of versioned data accurately. Note also that other formats can inter-operate smoothly with Bazaar using plug-ins; see http://bazaar-vcs.org/BzrPlugins#interop.

See also https://bugs.edge.launchpad.net/launchpad/+bug/292557, which contains more discussion about the choice of Bazaar for Launchpad.