pre-commit

#!/bin/sh

STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACM | grep -iE '\.(cpp|h|c|hpp)$')

if [ -z "$STAGED_FILES" ]; then
  exit 0
fi

NEEDS_FORMATTING=0

# Run clang-format on the changed lines of each staged file
for FILE in $STAGED_FILES; do
  echo Formatting "$FILE" ...
  # Format the originally staged changed lines
  CHANGED_LINES=$(git diff --cached -U0 -- "$FILE" | grep -E '^@@' | awk '{print $3}' | cut -d',' -f1)

  for LINE in $CHANGED_LINES; do
    LINE_START=$(echo "$LINE" | cut -d'+' -f2)
    [ -z "$LINE_START" ] && continue
    clang-format -i --lines="$LINE_START:$LINE_START" "$FILE"
  done

  # clang-format can cascade into adjacent lines; loop until the file stabilises
  MAX_ITER=5
  ITER=0
  while [ $ITER -lt $MAX_ITER ]; do
    PREV=$(cksum "$FILE")
    NEW_LINES=$(git diff -U0 -- "$FILE" | grep -E '^@@' | awk '{print $3}' | cut -d',' -f1)
    for LINE in $NEW_LINES; do
      LINE_START=$(echo "$LINE" | cut -d'+' -f2)
      [ -z "$LINE_START" ] && continue
      clang-format -i --lines="$LINE_START:$LINE_START" "$FILE"
    done
    [ "$(cksum "$FILE")" = "$PREV" ] && break
    ITER=$((ITER + 1))
  done

  if ! git diff --quiet "$FILE"; then
    NEEDS_FORMATTING=1
    echo "$FILE"
  fi
done

if [ $NEEDS_FORMATTING -eq 1 ]; then
  echo "The above files were auto-formatted. Please review and commit again."
  exit 1
fi

exit 0