post-update hook

I have a set up where I have a local git repo (local1) that I make
changes to and two public repos (remote1, remote2) that hold the
current state of the repo for other applications to access.  So my
plan is to make the change is local1, then
git commit
git push remote1 master
git push remote2 master

However, the remotes currently have master checked out so though the
repo gets updated the working directory does not.  I tried editting
the post-update hook as follows

#!/bin/sh
echo Update changes...
git checkout master .

but it does not seem to make any difference.  Am I missing something
in the way post-update works?  It would be really nice to get this
working so I don't have to log into each remote and do a pull.  local1
is running git version 1.6.0.2. remotes are running git version 1.5.6.

Thanks!
Jeremy