Git is a version control system. The Wikimedia Foundation is going to use it and frankly, I have no clue why. What I do understand is that the waving around of hands and the exclamation of buzz words looks good. I am not aware of the existence of a cost benefit analysis, something that would make things understandable.
My impression is that because of the introduction of git, the quality of the localisations and the internationalisations of MediaWiki and its extensions will be negatively impacted.
As it is, changes committed to Subversion, the current version control system, result in new messages in translatewiki.net within a day. These new messages become available to the twn community and as a result there is a steady stream of messages that need textual improvement and/or an explanation. As development progresses, the messages improve and the localisation is under way. At the time new functionality is ready for deployment it is localised in many languages.
With Git, there is no such thing as new messages that make their way to translatewiki.net. As I understand it this will only happen when the developer is done, the software is reviewed and is moved into "production" status. This means no internationalisation review, no textual improvements, no help texts and no localisations once software goes into production.
When a translator costs one hundredth part of a developer and we support three hundred languages then reducing the cost of development is not necessarily where we make our big wins. Our language support benefits from the current model and I fail to see why we should git going.
Really, what is the global benefit from using git over Subversion ?