title: Git rebase feature branch to another branch
body: <p>I have forked repo <code>A</code>. I have pulled it locally and checked out branch <code>b1</code>.
  I have created a new feature branch of <code>b1</code> (and not master):</p>
  
  <pre><code>git checkout -b my-feature b1
  </code></pre>
  
  <p>I have made a PR and pushed my changes to my own forked branch.</p>
  
  <p>1 month has passed, my PR isn't merged yet, now I need to do a rebase, how do I do it?</p>
  
  <p>I need to rebase to <code>b1</code> and not master.</p>
  
  <p>I have tried the following:</p>
  
  <pre><code>git fetch
  git rebase origin/b1
  </code></pre>
  
  <p>but it keeps saying</p>
  
  <pre><code>Current branch my-feature is up to date.
  </code></pre>