title: How to merge branch of forked repo into master branch of original repo?
body: <p>There is an open source project on GitHub. Its original repo contains the most recent master branch. Now there is someone (not me) who has forked this repo, created a development branch from the master branch and added stuff to the development branch. What I would like to do now is to merge the development branch back to the master branch. Unfortunately, the master branch of the forked repo is not up-to-date. Also note that I'm not in possession of the two respective remote repos. </p>
  
  <p>At the moment, I have cloned both the original repo and the forked repo to my local machine using <code>git clone</code>. How can I merge the development branch of the forked repo into the master branch of the original repo on my local machine (i.e. not on the remote server which is not possible anyway)?</p>