Get git diff between the current and last commit in GitHub Actions

git-diff-gh-actions.ts

import { simpleGit } from 'simple-git';

diff(github.context.payload.after, github.context.payload.before);

async function diff(after: string, before: string) {
  const git = simpleGit();
  const diff = await git.diffSummary([after, before]);
  console.log(diff);
}