git checkout [-q] [-f] [-m] --orphan []
Create a new orphan branch, named <new_branch>, started from <start_point> and switch to it. The first commit made on this new branch will have no parents and it will be the root of a new history totally disconnected from all the other branches and commits.
[…]
This can be useful when you want to publish the tree from a commit without exposing its full history. […]
If you want to start a disconnected history that records a set of paths that is totally different from the one of <start_point>, then you should clear the index and the working tree right after creating the orphan branch by running git rm -rf . from the top level of the working tree. […]
Source: http://git-scm.com/docs/git-checkout/
git checkout --orphan newbranch
git rm -rf .
[...]
git add files
git commit -m 'Initial commit'