How do I create a new GitHub repo from a branch in an existing repo?

I started with @user292677's idea, and refined it to solve my problem:

1. Create the new-repo in github.
2. cd to your local copy of the old repo you want to extract from, which is set up to track the new-project branch that will become the new-repo's master.
3. $ git push https://github.com/accountname/new-repo.git +new-project:master

The new Github repo is finished. The result is;

• a new Github repository named new-repo,
• whose master corresponds to the old repo's new-project, with
• all history preserved.

In fact, I found that by using this method, I could create the new repo with a hand-picked selection of branches, renamed as I wanted:

$ git push [email protected]:accountname/new_repo +new-project:master +site3a:rails3

The result is that the pre-existing site3a branch is now also moved to the new repo and will appear as rails3. This works really well: the network diagram shows the new master and rails3 with full history and in their correct relationship to each other.

Update 2013-12-07: Used this with another project, and verified that this recipe still works.

Update 2018-01-11: Updated step 3. to use GitHub recommendation for https protocol. Recipe still works.

Update:

cd to local repo containing old_branch and:

$ git push https://github.com/accountname/new_repo.git +old_branch:master