I do this mistake too often...

gistfile1.sh

#!/bin/sh
if git rev-parse --verify HEAD >/dev/null 2>&1
then
  against=HEAD
else
	# Initial commit: diff against an empty tree object
	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

VAR=$(git grep --cached debugger)

# Check if contains 'debugger'
if [ ! -z "$VAR" ]
then
  echo 'DUMB! You are about to commit line with debugger statement!'
  exit 1
fi
exit