A simple hack to make git notes a little bit more porcelain.
The idea is that you have only a single global note in the repository. In other words you don't need to specify (as with git-notes) a commit the note is attached to.
git note will edit (or create if not present) the note.
git note /path/to/repo if you want to edit the note in a repo located elsewhere.
Instead of using HEAD the first time the note is created, create an empty orphan commit and use that.