An Action which runs a command and fails if it changes anything.

It's ideal for catching situations where tools like Dependabot might not bump other dependencies, like with tools like Appraisal's gemfiles or native iOS dependencies (ios/Podfile.lock) when updating npm dependencies on React Native.

The results are reported with a failed action run, and presented in the job summary.

.github/workflows/diff-check.yml:

---
name: diff-check
on: [push]

jobs:
  demo:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: nickcharlton/diff-check@main
        with:
          command: echo "hello world" >> README.md