The first part of the article talks about how to use git notes and has an example commit, followed by adding the note, and then viewing the note. This is all native git.
The “problem” is that we have centralized discussions in github/gitlab comments and if we want to retain that data then we need to convert the comments into gitnotes. The CLI part is that specific discussion on how Symfony uses git notes to store github comments. It references an internal CLI but then goes through an example of how to use github api to fetch the comments, create git notes, then push those git notes to github. So while the symfony CLI is internal, it looks like we’re given an example of how to do this for github.