Generating AI Descriptions of Automated Pull Requests

The slack-ruby-client library, an open source Ruby gem I maintain, runs a scheduled GitHub Actions workflow that regenerates code from Slack’s API definitions and opens a pull request with the diff. The commit message and CHANGELOG entry used to be a generic “Update API (2026-08-11)”, which told a reviewer nothing about what actually changed. Here’s how we taught the workflow to describe its own diffs, using GitHub Copilot CLI, which open source maintainers can get for free. The Idea The workflow already computes a diff before opening the pull request. Instead of a boilerplate commit message, we pipe that diff through an LLM and ask it to summarize what changed, then use the response as the commit message and PR body. - name: Check for changes id: changes run: | if git diff --quiet; then echo "changed=false" >> "$GITHUB_OUTPUT" else echo "changed=true" >> "$GITHUB_OUTPUT" fi - name: Prepare diff for AI summary if: steps.changes.outputs.changed == 'true' run: | git diff --stat | sed…