223 lines
7.7 KiB
Markdown
223 lines
7.7 KiB
Markdown
# Create a Container Prebuilt Action
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[](https://github.com/super-linter/super-linter)
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Use this template to bootstrap the creation of a container action. :rocket:
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This template includes compilation support, tests, a validation workflow,
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publishing, and versioning guidance. The core difference between this template
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and [`actions/container-action`](https://github.com/actions/container-action) is
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that this template does not build the container image on every action run.
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Instead, the action pulls the image from
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[GitHub Container Registry (ghcr.io)](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry).
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If you would like to use the
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[GitHub Actions Toolkit](https://github.com/actions/toolkit) in your container
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action, see the
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[Container Toolkit Action](https://github.com/actions/container-toolkit-action)
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repository.
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## Create Your Own Action
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To create your own action, you can use this repository as a template! Just
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follow the below instructions:
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1. Click the **Use this template** button at the top of the repository
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1. Select **Create a new repository**
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1. Select an owner and name for your new repository
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1. Click **Create repository**
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1. Clone your new repository
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> [!IMPORTANT]
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>
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> Make sure to remove or update the [`CODEOWNERS`](./CODEOWNERS) file! For
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> details on how to use this file, see
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> [About code owners](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners).
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## Initial Setup
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After you've cloned the repository to your local machine or codespace, you'll
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need to perform some initial setup steps before you can develop your action.
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> [!NOTE]
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>
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> You'll need to have a reasonably modern version of
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> [Docker](https://www.docker.com/get-started/) handy (e.g. docker engine
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> version 20 or later).
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1. :hammer_and_wrench: Build the container
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Make sure to replace `actions/container-prebuilt-action` with an appropriate
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label for your container.
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```bash
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docker build -t actions/container-prebuilt-action .
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```
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1. :white_check_mark: Test the container
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You can pass individual environment variables using the `--env` or `-e` flag.
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```bash
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$ docker run --env INPUT_WHO_TO_GREET="Mona Lisa Octocat" actions/container-prebuilt-action
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::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
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```
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Or you can pass a file with environment variables using `--env-file`.
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```bash
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$ cat ./.env.test
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INPUT_WHO_TO_GREET="Mona Lisa Octocat"
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$ docker run --env-file ./.env.test actions/container-prebuilt-action
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::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
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```
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## Update the Action Metadata
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The [`action.yml`](action.yml) file defines metadata about your action, such as
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input(s) and output(s). For details about this file, see
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[Metadata syntax for GitHub Actions](https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions).
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When you copy this repository, update `action.yml` with the name, description,
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inputs, and outputs for your action.
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> [!IMPORTANT]
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>
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> Make sure to update the `image` property to use your repository!
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>
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> ```yaml
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> runs:
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> using: docker
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> image: docker://ghcr.io/<owner>/<repository>:<tag>
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> ```
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## Update the Action Code
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In this template, the container action runs a shell script,
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[`entrypoint.sh`](./entrypoint.sh), when the container is launched. Since you
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can choose any base Docker image and language you like, you can change this to
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suite your needs. There are a few main things to remember when writing code for
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container actions:
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- Inputs are accessed using argument identifiers or environment variables
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(depending on what you set in your `action.yml`). For example, the first input
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to this action, `who-to-greet`, can be accessed in the entrypoint script using
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the `$INPUT_WHO_TO_GREET` environment variable.
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```bash
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GREETING="Hello, $INPUT_WHO_TO_GREET!"
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```
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- GitHub Actions supports a number of different workflow commands such as
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creating outputs, setting environment variables, and more. These are
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accomplished by writing to different `GITHUB_*` environment variables. For
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more information, see
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[Workflow commands](https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions).
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| Scenario | Example |
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| --------------------- | ----------------------------------------------- |
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| Set environment vars | `echo "MY_VAR=my-value" >> "$GITHUB_ENV"` |
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| Set outputs | `echo "greeting=$GREETING" >> "$GITHUB_OUTPUT"` |
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| Prepend to `PATH` | `echo "$HOME/.local/bin" >> "$GITHUB_PATH"` |
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| Set `pre`/`post` vars | `echo "MY_VAR=my-value" >> "$GITHUB_STATE"` |
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| Set step summary | `echo "{markdown}" >> "$GITHUB_STEP_SUMMARY"` |
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You can write multiline strings using the following syntax:
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```bash
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{
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echo "JSON_RESPONSE<<EOF"
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curl https://example.com
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echo "EOF"
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} >> "$GITHUB_ENV"
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```
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- Make sure that the script being run is executable!
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```bash
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git add entrypoint.sh
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git update-index --chmod=+x entrypoint.sh
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```
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So, what are you waiting for? Go ahead and start customizing your action!
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1. Create a new branch
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```bash
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git checkout -b releases/v1
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```
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1. Replace the contents of `entrypoint.sh` with your action code
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1. Build and test the container
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```bash
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docker build -t actions/container-prebuilt-action .
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docker run actions/container-prebuilt-action "Mona Lisa Octocat"
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```
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1. Commit your changes
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```bash
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git add .
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git commit -m "My first action is ready!"
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```
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1. Push them to your repository
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```bash
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git push -u origin releases/v1
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```
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1. Create a pull request and get feedback on your action
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1. Merge the pull request into the `main` branch
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Your action is now published! :rocket:
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For information about versioning your action, see
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[Versioning](https://github.com/actions/toolkit/blob/main/docs/action-versioning.md)
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in the GitHub Actions toolkit.
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## Releasing Versions
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By default, the [`cd.yml` workflow](./.github/workflows/cd.yml) in this
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repository is configured to release a new version of the action any time a pull
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request is merged into the default branch (`main`). In order to prevent existing
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versions from being overwritten, the
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[`version-check.yml` workflow](./.github/workflows/version-check.yml) can be
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used as a
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[required status check](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-protected-branches/about-protected-branches#require-status-checks-before-merging)
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in your branch protection rules.
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As part of the pull request, make sure to update the
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[`.version` file](./.version) to a new [Semantic Version](https://semver.org/).
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## Usage
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After testing, you can create version tag(s) that developers can use to
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reference different stable versions of your action. For more information, see
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[Versioning](https://github.com/actions/toolkit/blob/main/docs/action-versioning.md)
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in the GitHub Actions toolkit.
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To include the action in a workflow in another repository, you can use the
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`uses` syntax with the `@` symbol to reference a specific branch, tag, or commit
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hash.
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```yaml
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steps:
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- name: Checkout
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id: checkout
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uses: actions/checkout@v4
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- name: Test Local Action
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id: test-action
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uses: actions/container-prebuilt-action@v1 # Commit with the `v1` tag
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with:
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who-to-greet: Mona Lisa Octocat
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- name: Print Output
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id: output
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run: echo "${{ steps.test-action.outputs.greeting }}"
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```
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