Git alias to checkout someone elses PR

gitpr.zsh

gitpr() {
  GIT=`which -p git`
  if [ "$1" ]; then
    if [ "$2" ]; then
    command $GIT fetch upstream pull/$1/head:$2
    command $GIT checkout $2
    else 
      echo "You need to specify two parameters, gitpr <PR #> <BRANCHNAME>"
    fi
  else
      echo "You need to specify two parameters, gitpr <PR #> <BRANCHNAME>"
  fi
}