title: Merging branch and sub-branch back to master
body: <p>I have limited knowledge of git.</p>
  
  <p>I have created a branch B1 from master, made some edits and committed to this branch.</p>
  
  <p>I want to create another branch B2 from B1, I make some edits in B2</p>
  
  <p>And I also want to commit and push B2 (with edits from B2 and B1) back to master</p>
  
  <p>How do I do this, the documentation assumes you are always creating a branch from master , not another branch. I apologise for my git stupidity.</p>