gawd: A Differencing Tool for GitHub Actions Workflows

The GitHub social coding platform introduced GitHub Actions as a way to automate different aspects of collaborative software development through the use of workflow files. It is the most popular CI/CD and workflow automation tool for GitHub. To maintain workflow code over time, it is useful to rely on differencing tools to identify the changes made during successive commits. Unfortunately, existing code differencing tools are not able to correctly identify changes made to workflow files. We therefore implemented gawd, a syntactic differencing tool for GitHub Actions workflows. The tool is capable of reporting the addition, deletion, modification and move of syntactic components in workflow files, taking into account the specific syntax of workflows. gawd has been evaluated on manually classified sets of workflow changes taken from existing commits in 40 different GitHub repositories, and was able to successfully identify these changes. gawd is publicly released as an open source Python tool distributed on PyPI.