Git pre-commit hook to reject RSpec files with 'focus: true' in them

pre-commit

#!/bin/sh

function check_diffs () {
  FOLDER_PATTERN="$1"
  FILES_PATTERN="$2"
  FORBIDDEN="$3"
  FORBIDDEN_PRINTABLE="${4:-$3}"
  CHANGED_FILES=$(git diff --cached --name-only | egrep $FOLDER_PATTERN | egrep $FILES_PATTERN)
  OK=1
  for FILE in $CHANGED_FILES ; do
    git diff --cached --no-color -U0 $FILE | egrep '^\+[^\+]' | egrep -q "$FORBIDDEN"
    if [[ "$?" -eq 0 ]]; then
      OK=0
      echo "$FILE"
    fi
  done
  if [[ "$OK" -eq 0 ]]; then
    echo "COMMIT REJECTED: found '$FORBIDDEN_PRINTABLE' references. Please remove them before committing."
    exit 1
  fi
}

check_diffs '^spec/' '\.rb(\..+)?$' 'focus:\s*true' 'focus: true'
check_diffs '^(app|spec)/' '\.e?rb(\..+)?$' 'byebug'

exit 0

Can it be somehow hooked to https://github.com/pre-commit/pre-commit-hooks?