title: undo "git filter-branch ... -- --all"? in one command?
body: <p>I started messing around with <code>git filter-branch</code>.  The --all option rewrites all branches and tags.  Cool.  <code>git filter-branch</code> creates a backup of all refs it overwrites in refs/original.  Very Cool.  Now I'd like to blow all my experimenting with <code>filter-branch</code> away.</p>
  
  <p><strong>Is there an easy way to completely undo the effects of <code>git filter-branch &lt;whatever filter&gt; -- --all</code>?  I.e. to restore all of the rewritten branches to their original state all at once?</strong></p>
  
  <p>If there isn't a preexisting way, there should be.  If there isn't a preexisting way, does anybody have a short script that will do it?  </p>
  
  <p>Obviously there's workarounds.  I could restore it manually, a branch at a time, as in <a href="https://stackoverflow.com/questions/14542326/undo-git-filter-branch">this question</a>.  Or I could just nuke and re-clone.  Either would get tedious quickly in a repo with many branches/tags that is (say) being split up into smaller repos.</p>