post-checkout

#!/bin/sh

# Put this in your .git/hooks/post-checkout and smoke it.

function current_branch_name {
  git symbolic-ref HEAD | cut -d '/' -f 3
}

if [ $(current_branch_name) == 'master' ]; then
    lines[0]="Master, Master, where's the dreams that I've been after?"
    lines[1]="Master, Master, you promised only lies"
    lines[2]="Laughter, laughter, all I hear or see is laughter"
    lines[3]="Laughter, laughter, laughing at my cries"
    echo "  ${lines[$((RANDOM%${#lines[*]}))]}";
fi

answer is here.

also, git name-rev --name-only HEAD is more succint but does not work in all cases

i'm so good at finding answers on SO ;)