bootstrap/specs/mix/template/.githooks/pre-commit

#!/usr/bin/env bash
set -e

STAGED=$(
  git --no-pager diff --name-only --no-color --cached --diff-filter=d |
    # Remove quotations used to surrounding filenames with special characters.
    sed -e "s/^\"//" -e "s/\"$//g"
)

TARGETS=()
while IFS= read -r FILENAME
do
  if [[ "$FILENAME" =~ .*\.exs? ]]; then
    TARGETS+=("${FILENAME}")
  fi
done <<< "$STAGED"

if (( ${#TARGETS[@]} )); then
  mix format "${TARGETS[@]}"
  git add "${TARGETS[@]}"
fi