Mercurial hook not executing properly

This should be a very simple thing to have run, but for some reason it won't work with my Mercurial repository. All I want is for the remote repo to automatically run hg update whenever someone pushes to it. So I have this in my .hg/hgrc file:

[hook]
 changegroup = hg update
 

Simple, right? But for some reason, this never executes. I also tried writing a shell script that did this. .hg/hgrc looked like this:

[hooks]
 changegroup = /home/marc/bin/hg-update
 

and hg-update looked like this:

#!/bin/sh
 hg help >> /home/marc/works.txt;
 hg update >> /home/marc/works.txt;
 exit 0;
 

But again, this doesn't update. The contents of hg help are written out to works.txt, but nothing is written out for hg update. Is there something obvious I'm missing here? This has been plaguing me for days and I just can't seem to get it to work.

Update

Okay so again, using the -v switch on the command line from my workstation pushing to the remote repo doesn't print any verbose messages even when I have those echo lines in .hg/hgrc. However, when I do a push from a clone of the repo on the same filesystem (I'm logged in via SSH), this is what I get:

 bash-3.00$ hg -v push ../test-repo/
 pushing to ../test-repo/
 searching for changes
 1 changesets found
 running hook prechangegroup: echo "Remote repo is at `hg tip -q`"
 echo "Remote repo wdir is at `hg parents -q`"
 Remote repo is at 821:1f2656753c98
 Remote repo wdir is at 821:1f2656753c98
 adding changesets
 adding manifests
 adding file changes
 added 1 changesets with 1 changes to 1 files
 running hook changegroup: echo "Updating.... `hg update -v`"
 echo "Remote repo is at `hg tip -q`"
 echo "Remote repo wdir is at `hg parents -q`"
 Updating.... resolving manifests
 getting license.txt
 1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 Remote repo is at 822:389a6c7276c6
 Remote repo wdir is at 822:389a6c7276c6
 

So it works, but again only when I push from the same filesystem. It doesn't work if I try pushing to the repo from another workstation over the network.

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