fetching a generated patch from github

[René J.V. Bertin]

Is there a way to get a patchfile from github other than in a pre-patch or post-fetch step with a statement like

wget "https://github.com/user/repo/compare/hashA...hashB.patch"

that gets a full patch without redistributing even a single diff of code?

I've seen examples in the guide how to fetch multiple files, but have never gotten my mind around them sufficiently to get that to work.

R.