From the announcement Git 1.7.10 (April 2012):
--single-branchoption to limit cloning to a single branch (surprise!); tags that do not point into the history of the branch are not fetched.
Git actually allows you to clone only one branch, for example:
git clone -b mybranch --single-branch git://sub.domain.com/repo.git
Note: Also you can add another single branch or "undo" this action.