code: public void setOptB(Ref newBranch) {
      CheckUtilities.validateArgumentRefType(newBranch, RefType.BRANCH, "New Branch Name");
      optB = newBranch;
    }
docs: Sets the name of the new branch that need to be created from the base branch.
  
  @param newBranch
  New branch of type <code>Ref</code> that will be created by &lt;git-checkout&gt;.