I’ve noticed that Octopress Deploy doesn’t appear to allow deployment using Git if GPG is enabled. What I had to do to get around it is temporarily disable GPG.
git config --global commit.gpgsign false
After disabling it I can run
octopress deploy to commit my new changes to the live site. Doesn’t appear to be any issues listed for it, so if you come across this that’s what I ended up having to do to get deploy to work.