title: Change branching point in git
body: <p>We have two branches Branch1 and Branch2 which differs each other by 100 commits. I had created a new branch BranchA from Branch1. No commits have been made on BranchA.</p>
  
  <p>Is there a way to change BranchA to appear it was branched from Branch2, so that I can make a commit and raise a pull request against Branch2 - but it won't carry any commits from Branch1?</p>