The Opscode community offers a wide variety of ready-made cookbooks for many major software packages. They're a great starting point for your own infrastructure. But, usually you need to modify these cookbooks to suit your needs. Modifying your local copy of a community cookbook leaves you in the dilemma of not being able to update to the latest version of the community cookbook without losing your local changes.
You'll need to make sure that your local Git repository is clean and does not have any uncommitted changes:
mma@laptop:~/chef-repo $ git status
# On branch master nothing to commit (working directory clean)
Carry out the following ...