Checkout pull request from GitHub repo.

checkoutGitHubPR.sh

#!/bin/bash

#ex: /usr/local/bin/checkoutGitHubPR.sh 1234

REMOTE_REPO=origin     ## name of your git remote.. typically origin or upstream
MERGE_STATE=merge      ## set to "merge" to checkout PR merged against repo, or set to "head" to checkout PR unmerged 
PR=${1}                ## github pull request number

git fetch -v ${REMOTE_REPO} +refs/pull/${PR}*:refs/remotes/${REMOTE_REPO}/pull/${PR}*
git checkout -f ${REMOTE_REPO}/pull/${PR}/${MERGE_STATE}