I'm looking to work with the GitHub API, but I'm having trouble finding what I need in the documentation.
There's two things I can't find.
changes
in each file. You cannot get diff for each commits in one go with the API.
You can get a global diff between arbitrary commits with an URL, or, through the API, comparing two commits, which returns a diff URL. But that won't track each intermediate commit diff.
Regarding webhook, the event you want is the push event: it will be triggered by any new commit pushed to your repository.