Google Code, the search giant's hosting service for open source software projects, is finally getting support for a distributed version control system. Google has announced that it will be supporting Mercurial alongside its existing support for Subversion.

Distributed version control systems (DVCS) are becoming increasingly popular in the open source software community. Many large projects have already adopted a DVCS and many more are preparing to migrate. The GNOME and Perl communities have adopted Git, MySQL and Ubuntu use Bazaar, and Mozilla and Python use Mercurial.

The trend towards DVCS has compelled some of the older open source project hosting services to hop on the bandwagon in order to remain relevant. Last month, Sourceforge announced newly added support for Git, Bazaar, and Mercurial. In light of these developments, it's unsurprising that Google is updating its own code hosting service.

Google chose Mercurial after conducting extensive analysis of the differences between Mercurial and Git. Several of the factors that influenced the decision include Mercurial's superior Windows compatibility and its more gentle learning curve. One particularly interesting technical aspect of Google's Mercurial adoption is that the company will be tying the version control system into its Bigtable distributed storage system instead of using Mercurial's native storage system.

Mercurial support is being rolled out incrementally and is not yet available to all projects. Google says that the early adopters will be helping to sort out some of the bugs before the feature is made available to everyone. You can already see it in action on some projects.