Ensembl has Migrated to Git

gitandensembl_smallToday I am happy to announce Ensembl’s migration away from CVS as our primary version control system (VCS) to Git. This migration sees the end of nearly a year’s worth of work to ensure that our Git repositories provide the same historical record as CVS.

To summarise the changes:

  • Ensembl’s code is now provided from our GitHub organisation at http://github.com/Ensembl
  • We have migrated Ensembl’s versioning back to 1999
  • We will continue to back-port changes to CVS for the next 3 releases (support ending with release 77)
  • You can still download our API release tarballs from our FTP site

CVS (Concurrent Version System) was first released in 1990 and was based on an earlier system called RCS (released in 1982). It relies on a centralised single server to hold all previous revisions with none of this information held on the client. CVS also assumes that commits to files within the same project are independent of each other. When the Ensembl project started in 1999, we chose CVS as it was one of the best available VCS in the open source community.

Since that choice, a new breed of VCS has appeared: decentralised/distributed version control systems (DVCS). These systems favour local copies of the repositories, removing the need to communicate with a centralised server, except when sending or receiving new commits, and work with sets of file changes as a single atomic block of work. According to Black Duck’s comparison of repositories, Git is the dominant DVCS in open source projects. We have decided to use the code hosting company GitHub as the location of our repositories. GitHub has been a major contributor behind the success of Git by providing an infrastructure that promotes social coding between developers.

Whilst CVS has been a very good servant to Ensembl, the time has come to move on to better tools. We have seen other projects within EMBL-EBI and the Wellcome Trust Sanger Institute make a similar transition to Git. None of them have looked back, citing better tooling, a larger support base and an ability to support both long-term and short-term development branches. We agree and cannot wait to start using this exciting technology.