fast github pr diffs with deep history without full cloning or iterative enrichment

job_def.yaml

name: SOMETHING

on:
  pull_request:
    types:
      - opened
    branches:
      - main

jobs:
  check-something:
    runs-on: ubuntu-latest
    name: Print Diff Paths
    timeout-minutes: 60
    steps:
      - uses: actions/setup-node@v3
        with:
          node-version: 18

      - name: Clone & checkout git repo
        uses: actions/checkout@v3
        with:
          fetch-depth: 1

      - name: Print Diff Paths
        uses: actions/github-script@v6
        with:
          script: |
            const script = require('./.github/workflows/script.js');
            await script({ github, context, core });

script.js

// @ts-check
const fsp = require("node:fs/promises");

// The params are ones provided by https://github.com/actions/github-script runtime.
module.exports = async ({ github, context, core }) => {
  const prMetadata = {
    owner: "YOUR_OWNER",
    repo: "YOUR_REPO",
    pull_number: context.payload.pull_request.number,
  };

  const diffPaths = await getDiffPaths({ github, prMetadata });
}

async function getDiffPaths({ github, prMetadata }) {
  /**
   * `data` is an array of items that look like this:
   * {
   *   filename: 'some/special/path/foo.ini',
   *   status: 'modified',
   *   additions: 14,
   *   deletions: 14,
   *   patch: '@@ -1,2 +1,2 @@\n' +
   *    ' [my_section]\n' +
   *    '-baz = 12345\n' +
   *    '+baz = 56789\n'
   * }
   */
  const { data } = await github.rest.pulls.listFiles(prMetadata);

  /** @type string[] */
  const diffPaths = data.map((item) => item.filename);
  console.log("(Debug) Diff paths: " + diffPaths.join(", "));

  return diffPaths;
}