Git post-receive hook to update a local clone owned by a different user

Question

I'm trying to set up a git post-receive hook such that when a commit is received, another clone of the repository on the machine gets updated (i.e. does a git pull origin master). I'm using gitosis to serve the repository and as such I believe a post-receive hook will be run as the gitosis user, whereas the repository I want to update on a receive is owned by www-data. How should I go about doing this?

I've heard about setuid scripts but I'm not sure whether this might be a security risk? And if it's not a security risk, how would I go about doing this? I'm guessing I would do something like make the script owned by www-data and make it world-executable and enable the setuid bit? I guess this script would be pretty much harmless since all it does is update the repository, but I want to be sure. Thanks!

Edit: Is there any way to do this using sudo? Would that be more secure than setuid? I mean, I don't think there's much issue with setuid if the user isn't root, but all the same it seems like I'd have to jump through a few hoops to get a setuid script to run.

Second edit: It seems like I might be able to do this with some /etc/sudoers magic and sudo -u. Perhaps I should have posted this on ServerFault instead, but at least I've learned a bit from this endeavor.

Answer 1

IMHO This should be on serverfault, but here's the answer nevertheless;

Add:

gitosis ALL=(www-data) NOPASSWD: /path/to/git

to /etc/sudoers

and run the command as sudo -u www-data <whatever the command is>