Show (up to a max of) 5 most recently checked out branches in Git

gistfile1.sh

git reflog \
  | awk '{ print $3, $NF }' \
  | grep "^checkout:" \
  | awk '{ print $2 }' \
  | egrep -v '^([0-9a-f]{40}|[0-9a-f]{7}$)' \
  | perl -ne 'print unless $a{$_}++' \
  | head -5