I have bundled up the suggested answer in a Git repository if anybody is interested: https://github.com/selkhateeb/hardlink
Once installed, create a hard link with:
hln source destination
I also noticed that unlink command does not work on Mac OS X v10.6 (Snow Leopard), so I added an option to unlink:
hln -u destination
To install Hardlink, use Homebrew and run:
brew install hardlink-osx