Simple git pre-commit hook that checks IPython/Jupyter notebooks for output

pre-commit

#!/bin/sh

# Check for .ipynb files with output cells;
# ask the user if they really want to commit them
ipynb_files=`git diff --staged --name-only | awk "/.ipynb/"`
have_output=""

if [ -n "$ipynb_files" ]; then
  while read filename; do
    if [ $(git show :$filename | grep -cm1 "\"output_type\":") -ge 1 ]; then
      have_output="${have_output}"$'\n'"$filename"
    fi
  done <<< $ipynb_files
  # use here string to run in main shell: https://stackoverflow.com/a/16854326
fi

if [ -n "$have_output" ]; then
  # https://stackoverflow.com/a/10015707
  exec < /dev/tty # allows us to grab user input

  echo "You appear to be committing Jupyter notebooks"
  echo "that contain output:"
  echo "$have_output"$'\n'
  while true; do
    read -p "Proceed with commit (y/n)?: " resp
    case $resp in
      [Yy]* ) exit_status=0; break;;
      [Nn]* ) exit_status=1; break;;
          * ) echo "Please answer y or n";;
    esac
  done

  exit $exit_status
fi

I've already made a couple updates to this thing, so I decided to make it a gist. See here for a description of the use case and those updates.