Forking only a specific branch from Github repository
fork, git, github
Solution
You can pull his branch into your local git repo, and then push it up to your GitHub hosted repo.
First, add a remote to this other users's GitHub page
git remote add other-user http://github.com/otheruser/repo
Then make a local checkout of that branch in your repo.
git checkout -b B4 other-user/B4
Finally, push that branch up to your repo hosted on GitHub.
git push origin B4:B4
Problem
Suppose there's an official repo maintained called `O` with branches `B1`, `B2` & `B3`. One user, who has forked it onto his Github account, made another branch for himself called `B4` and is publicly available. I've also forked the same official repo but I want to fork that user's `B4` branch also without affecting my original copy. I cannot fork the whole official repo again as I've made several custom branches for myself. So, how can I fork a particular branch onto my Github repo?