Charles Horowitz contributed to the CMSgov/dpc-app repository by enhancing development hygiene through a targeted update to the project's .gitignore file. He configured Git to exclude all contents within the tmp/ directory except for a .keep file, ensuring that temporary files containing sensitive data would not be accidentally committed while still supporting local development workflows. This change, rooted in configuration management best practices, improved the project's security posture with minimal disruption to developers. Charles’s work focused on practical risk reduction and compliance, leveraging his skills in Git and configuration management to address a specific need without introducing unnecessary complexity or overhead.