title: Git smudge filter
body: <p>I am trying to setup a filter so that on checkout it will inject some git related information to my file and on commit it will remove this information. I have verified that when I commit the file it is properly cleaned. Also if I delete the file and then do a checkout the file is properly smudged.</p>
  
  <p>My problem is the following. <strong>If I make a change to the file and I commit the change, the smudge filter does not run.</strong> Is this the expected behavior? Is there a way to have the smudge filter run on commit? (perhaps by having a commit followed immediately by a checkout?)</p>