How to make git diff show the same result as github's pull request diff?

Question

After branches are merged, and github no longer show difference when i try to make a pull request, but git diff will still show differences.

For example I have branch D, created hotfix on branch H, merged H to D, then created more stuff on D. Now git hub pull reuqest from H to D shows no difference but git diff H D show differences.

What I am trying to do is to create a commandline tool to see which old branches (there can be a lot) don't have code differences to develop. right now I have to go to github, do a pull reuqest and select each branch to see if there are difference.

Thanks

Answer 1

You probably want the "triple-dot" syntax:

git diff D...H

See also What are the differences between double-dot ".." and triple-dot "..." in Git diff commit ranges?