git remote -v
should give something like
origin git@github.com:<user>/<project>.git (fetch)
origin git@github.com:<user>/<project>.git (push)
git remote set-url --push origin git@github.com:<new-user>/<project>.git
git remote -v
should show something like
origin git@github.com:<user>/<project>.git (fetch)
origin git@github.com:<new-user>/<project>.git (push)
Reference: http://sleepycoders.blogspot.com.au/2012/05/different-git-push-pullfetch-urls.html