Confused about "ident" filter

Hi!

While convincing my employer to convert to Git, I've ran into the old RCS keyword expansion problem again. They have files that they need to export to a customer, without revision history, but they need to embed an identifier that can tell them which version of the file it was.

So, I tried setting up a .gitattributes file:

   * ident

and a simple test perl script that would show me the ident:

   #!/usr/bin/perl
   print 'I am $Id$', "\n";

but I cannot figure out how to get it to actually expand the $Id$. I tried doing "git checkout test.perl", I tried "git clone" to get a new copy of the repository, but still it showed only "$Id$".

I found that "git archive" *does* work.