Files changed on GitHub differs from the result of git diff master

What is going on here?

GitHub pull requests use git diff master... , which compares the tip of current with its branch point from master.

That is not the same as git diff master , which compares the tip of current with the tip of master.

The official docs have a precise summary of the comparison types.

So, run git diff master... locally to see the same output that GitHub shows in its pull requests.