I had the same question, but then I realized where this tip is useful: for open-source projects where the PR came from someone else's fork. With this tip, you don't have to add the forked remote in order to pull it.
Re:Checkout github pull requests locally
by kyleslattery on Monday March 25, 2013 @11:50AM
(#5437641)
Also, if you delete the original branch that the PR refers to, the PR branch still has all of the commits.
Re:Checkout github pull requests locally
by propelledjeans on Monday March 25, 2013 @11:12AM
(#5437380)
'doh! Thanks!
e.g. I push feature/foo to origin and open a pull request base develop. Why would one not just pull down feature/foo?