Matthias suggested, it would be good to collect nixpkgs mailing list
scripts somewhere. I've put up the notmuch-am script on a repo I've
thrown up on my personal git server:
you can clone via:
git clone git://git.jb55.com/nixpkgs-ml-tools
See the HACKING file for sending patches. I figured it would be easiest
to send patches to here for now.