title: How do you mirror a specific branch to a branch in another repository?
body: <p>I want to mirror only the master branch in "old repository" to a branch "X" in the 
  "new repository". How do i do this? [To be clear I do not want to mirror the whole repo or the other branches]</p>
  
  <p>Once i mirror this, at some point I will want to take "X" and merge all the new changes into the "master" of the "new repository". I know i can do a pull request but how would i do this through the terminal?</p>
  
  <p>Thanks for all the help. </p>