[chef] Customizing cookbooks

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I have installed a cookbook to my chef server using knife cookbook site 
install
<COOKBOOK>, and I need to make some customizations to it. I've done that and
then pushed it up to my git repo where we're storing all of our cookbooks. 

What is the appropriate way to make sure I am receiving updates from the
opscode public repo? Do I just run knife cookbook site install <COOKBOOK> 
again
and then merge the changes with my git repo? Or is there a better way to do
that?