A few days ago I stubled upon: "How do I Download Github pull request as unified diff"diff?
For example the corresponding diff for commit:
https://github.com/eclipse/virgo.kernel/master/commit/9e5af5a4608b962ff1c2 ?
The answer is pretty simple and intuitive: Simply add .patch or .diff at the end of the URL:
https://github.com/devops/foo/commit/9e5af5a4608b962ff1c2.diff
Nice.