Warns about Git staged binary files

git-staged-warn-binaries.sh

#!/usr/bin/env sh

# Warns about Git staged binary files
# https://gist.github.com/tkrotoff/dc49a8e501b6fdea5a4b66301f7682fc

# Capture the output of "git diff" in a temporary file
tmpfile=$(mktemp)

# https://stackoverflow.com/q/28109520
git diff -z --staged --name-only --diff-filter=ACMR > "$tmpfile"

binaries=()

while IFS= read -r -d '' filename; do
  # Examples:
  #
  # $ file --brief --mime README.md
  # text/plain; charset=utf-8
  #
  # $ file --brief --mime typescript.ts
  # text/plain; charset=us-ascii
  #
  # $ file --brief --mime package.json
  # application/json; charset=us-ascii
  #
  # $ file --brief --mime logo.png
  # image/png; charset=binary
  #
  # $ file --brief --mime doc.pdf
  # application/pdf; charset=binary
  #
  mime=$(file --brief --mime "$filename")

  if [[ $mime == *"charset=binary" ]]; then
    binaries+=("$filename")
  fi
done < "$tmpfile"

# Remove the temporary file
rm -f "$tmpfile"

if [[ ${#binaries[@]} -gt 0 ]]; then
  for filename in "${binaries[@]}"; do
    echo "$filename"
  done

  echo
  echo "Do not clutter Git with large binary files: it cannot be undone"
  echo
  echo "- Is the file really necessary?"
  echo "  - Can it be replaced by a link?"
  echo "  - Will it still be relevant in 3 years?"
  echo "- Use the appropriate format (PNG vs JPEG vs SVG)"
  echo "- Use appropriate image width × height (are you sure about that 4K image?)"
  echo "- Use lossless compression thx to ImageOptim (https://imageoptim.com/mac) or Trimage (https://trimage.org/)"
  echo "  - Do recompress several times (it might further improve the lossless compression)"
  echo
  echo "More infos: https://robinwinslow.uk/dont-ever-commit-binary-files-to-git"
  echo
  echo "Do you want to commit these binaries to the repository? (yes/no)"

  # Allows us to read user input below, assigns stdin to keyboard
  # https://stackoverflow.com/a/10015707
  exec < /dev/tty

  read answer
  if [[ "$answer" != "${answer#yes}" ]]; then
    # Success: Git commit process goes on
    exit 0
  else
    # Failure: Git commit process is aborted
    exit 1
  fi
else
  echo "Good: no staged binary file found"
fi