How can I download the changes contained in a Github pull request as a unified diff?

To view a commit as a diff/patch file, just add .diff or .patch to the end of the URL, for example:

• https://github.com/weppos/whois/pull/90
• https://github.com/weppos/whois/pull/90.diff
• https://github.com/weppos/whois/pull/90.patch