Browse to the appropriate commit, e.g.
https://github.com/github/gitignore/commit/e9552d855c356b062ed82b83fcaacd230821a6eb
Edit the URL in your address bar and add
.diff
to the end, e.g.https://github.com/github/gitignore/commit/e9552d855c356b062ed82b83fcaacd230821a6eb.diff
Copy and paste (or File > Save) the unified diff
You can also use .patch
instead of .diff
, which seems to generate input suitable for application with git am
.