Act vs Meld

act is an open-source command-line tool that runs GitHub Actions workflows locally using Docker containers. It reads workflow files from .github/workflows/ and executes them with environment variables and filesystem configurations matching GitHub's hosted runners. The tool enables fast local feedback on workflow changes without requiring commits and pushes to a remote repository.

Meld is visual diff and merge tool for files, directories, and version-controlled projects. It provides comprehensive features for development workflows. The tool is actively maintained with regular updates and strong community/vendor support.