title: Git revert in master reverting commits when merged into feature branch
body: <p>I have been developing a major, long-term feature on a separate branch, <code>big-feature</code>. During its development, I have also been making smaller unrelated updates on <code>master</code> (well, technically I have been making the smaller updates on their own branches from <code>master</code> and then merging them into <code>master</code>.)</p>
  <p>Each time I complete some changes to <code>master</code>, I have been in the habit of also merging <code>master</code> into <code>big-feature</code> so that the feature branch doesn't stray too far from <code>master</code> and the merge will be hopefully easier when the big feature is complete.</p>
  <p>However, after some recent work, I accidentally merged <code>big-feature</code> into <code>master</code>. I attempted to rectify this with <code>revert</code>, and indeed the previous code state seems to have been restored. However, I still see the full history of commits from <code>big-feature</code> listed in the commit history of <code>master</code>, plus a <code>merge</code> and <code>revert</code> at the top.</p>
  <p>The problem is, when I now make a small change on <code>master</code> and attempt to merge <code>master</code> into <code>big-feature</code>, all of <code>big-feature</code>'s code reverts to that of <code>master</code>. I can only guess that the <code>revert</code> from <code>master</code> is being merged into <code>big-feature</code> and removing all the commits in <code>big-feature</code>.</p>
  <p>Hopefully this is semi-coherent.</p>
  <p>Questions:</p>
  <ol>
  <li>Is my diagnosis correct?</li>
  <li>Is my strategy of periodically merging <code>master</code> into <code>big-feature</code> a bad idea?</li>
  <li>The main question: how do I fix this?</li>
  </ol>
  <p>P.S. I also tried a <code>hard reset</code> of <code>master</code> to the commit before the erroneous merge, but this didn't remove all of the commits from <code>big-feature</code>, which surprised me?</p>