Composite actions for GitHub Actions

Useful actions that can be used to reduce code duplication in GitHub Actions configuration.

What is a composite action?

A composite action is a series of steps that can be used as a step itself in another workflow. This blog post has a nice example of what one looks like.

Using the actions

The actions can be used as individual steps inside jobs, e.g.:

jobs:
  python-linting:
    name: Run linting
    runs-on: ubuntu-latest
    steps:
      - uses: ucl/composite-actions/python/tox@v1
        with:
          python-version: '3.10'

Any inputs are specified using with under uses. Each action is documented in README files in their respective folders in this repository.

Versioning

Within a major version (e.g. v1, v2) all actions will be backwards compatible. New actions or bugfixes to existing actions will be released under a new minor version (e.g. v1.1).

Development

Adding new actions

To add a new action please open a pull request. The action itself should live under <language>/<description>/action.yml, e.g. python/tox-tests/action.yml. Alongside the action file should be a README that documents what the action does and any inputs/outputs. Please also add a test in .github/workflows/test-<language>-<description>.yml to check that the action works as intended.

Releasing a new version

1. Create a new release through the GitHub releases UI. Make sure you add the appropriate tag to the release.
2. If incrementing a minor version (ie. going from 2.1 > 2.2), move the major tag (e.g. =v2) to the most recent tag:

git push origin :refs/tags/<tagname>
git tag -fa <tagname>
git push upstream main --tags

This means any actions specifying (e.g.) v2 will automatically use the new minor version of the actions.