Blacksmith Checkout

This is Blacksmith's fork of the actions/checkout action, built on top of our Sticky Disk primitive. The action is a drop-in replacement for actions/checkout and provides caching of git repositories to speed up large repository checkouts.

How It Works

useblacksmith/checkout uses a persistent git mirror cache to speed up subsequent repository checkouts:

1. First Run (Hydration): On the very first checkout for a repository, the action creates a full git mirror of your repo on a Sticky Disk. This initial hydration may take longer as it mirrors your entire repository, but it only happens once for each repository.

2. Incremental Updates: After the initial hydration, the git mirror is updated incrementally on each workflow run using git fetch --prune to fetch only new refs and objects. The mirror is always a complete clone, but your workspace respects the fetch-depth input — git's alternates mechanism allows the workspace to reference objects from the mirror without copying them, keeping shallow checkouts fast.

3. Concurrent Job Handling: While the first hydration is in progress, any concurrent job runs will automatically fall back to the standard actions/checkout behavior. Once the mirror is fully hydrated, all subsequent jobs will use the cached mirror.

Why Use Blacksmith Checkout?

This action is most beneficial for:

• Large repositories (multiple GBs in size) where cloning from GitHub is slow
• Deep fetch depths (fetch-depth: 0 or large values) where you need extensive commit history
• Frequent CI runs on the same repository where the mirror stays warm

For these use cases, the persistent git mirror enables incremental updates rather than full clones, significantly reducing checkout times. For smaller repositories with shallow checkouts (fetch-depth: 1), checkout times will be comparable to the standard actions/checkout.

Key benefits:

• Reduced Network Load: Minimize traffic to GitHub by fetching only new changes incrementally
• Drop-in Replacement: All actions/checkout options work exactly the same

---

Note: This is a fork of actions/checkout. All options and behaviors from the upstream action are preserved. The documentation below is from the upstream project.

---

Usage

- uses: actions/checkout@v6
  with:
    # Repository name with owner. For example, actions/checkout
    # Default: ${{ github.repository }}
    repository: ''

    # The branch, tag or SHA to checkout. When checking out the repository that
    # triggered a workflow, this defaults to the reference or SHA for that event.
    # Otherwise, uses the default branch.
    ref: ''

    # Personal access token (PAT) used to fetch the repository. The PAT is configured
    # with the local git config, which enables your scripts to run authenticated git
    # commands. The post-job step removes the PAT.
    #
    # We recommend using a service account with the least permissions necessary. Also
    # when generating a new PAT, select the least scopes necessary.
    #
    # [Learn more about creating and using encrypted secrets](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets)
    #
    # Default: ${{ github.token }}
    token: ''

    # SSH key used to fetch the repository. The SSH key is configured with the local
    # git config, which enables your scripts to run authenticated git commands. The
    # post-job step removes the SSH key.
    #
    # We recommend using a service account with the least permissions necessary.
    #
    # [Learn more about creating and using encrypted secrets](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets)
    ssh-key: ''

    # Known hosts in addition to the user and global host key database. The public SSH
    # keys for a host may be obtained using the utility `ssh-keyscan`. For example,
    # `ssh-keyscan github.com`. The public key for github.com is always implicitly
    # added.
    ssh-known-hosts: ''

    # Whether to perform strict host key checking. When true, adds the options
    # `StrictHostKeyChecking=yes` and `CheckHostIP=no` to the SSH command line. Use
    # the input `ssh-known-hosts` to configure additional hosts.
    # Default: true
    ssh-strict: ''

    # The user to use when connecting to the remote SSH host. By default 'git' is
    # used.
    # Default: git
    ssh-user: ''

    # Whether to configure the token or SSH key with the local git config
    # Default: true
    persist-credentials: ''

    # Relative path under $GITHUB_WORKSPACE to place the repository
    path: ''

    # Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching
    # Default: true
    clean: ''

    # Partially clone against a given filter. Overrides sparse-checkout if set.
    # Default: null
    filter: ''

    # Do a sparse checkout on given patterns. Each pattern should be separated with
    # new lines.
    # Default: null
    sparse-checkout: ''

    # Specifies whether to use cone-mode when doing a sparse checkout.
    # Default: true
    sparse-checkout-cone-mode: ''

    # Number of commits to fetch. 0 indicates all history for all branches and tags.
    # Default: 1
    fetch-depth: ''

    # Whether to fetch tags, even if fetch-depth > 0.
    # Default: false
    fetch-tags: ''

    # Whether to show progress status output when fetching.
    # Default: true
    show-progress: ''

    # Whether to download Git-LFS files
    # Default: false
    lfs: ''

    # Whether to checkout submodules: `true` to checkout submodules or `recursive` to
    # recursively checkout submodules.
    #
    # When the `ssh-key` input is not provided, SSH URLs beginning with
    # `git@github.com:` are converted to HTTPS.
    #
    # Default: false
    submodules: ''

    # Add repository path as safe.directory for Git global config by running `git
    # config --global --add safe.directory <path>`
    # Default: true
    set-safe-directory: ''

    # The base URL for the GitHub instance that you are trying to clone from, will use
    # environment defaults to fetch from the same instance that the workflow is
    # running from unless specified. Example URLs are https://github.com or
    # https://my-ghes-server.example.com
    github-server-url: ''

    # Copy objects from Blacksmith git mirror cache to make checkout independent. Use
    # this when running Docker-based actions that may not have access to the mirror
    # mount.
    # Default: false
    dissociate: ''

Scenarios

• Checkout V5
  • What's new
• Checkout V4
  • Note
• What's new
• Usage
• Scenarios
  • Fetch only the root files
  • Fetch only the root files and .github and src folder
  • Fetch only a single file
  • Fetch all history for all tags and branches
  • Checkout a different branch
  • Checkout HEAD^
  • Checkout multiple repos (side by side)
  • Checkout multiple repos (nested)
  • Checkout multiple repos (private)
  • Checkout pull request HEAD commit instead of merge commit
  • Checkout pull request on closed event
  • Push a commit using the built-in token
  • Push a commit to a PR using the built-in token
• Recommended permissions
• License

Fetch only the root files

- uses: actions/checkout@v6
  with:
    sparse-checkout: .

Fetch only the root files and .github and src folder

- uses: actions/checkout@v6
  with:
    sparse-checkout: |
      .github
      src

Fetch only a single file

- uses: actions/checkout@v6
  with:
    sparse-checkout: |
      README.md
    sparse-checkout-cone-mode: false

Fetch all history for all tags and branches

- uses: actions/checkout@v6
  with:
    fetch-depth: 0

Checkout a different branch

- uses: actions/checkout@v6
  with:
    ref: my-branch

Checkout HEAD^

- uses: actions/checkout@v6
  with:
    fetch-depth: 2
- run: git checkout HEAD^

Checkout multiple repos (side by side)

- name: Checkout
  uses: actions/checkout@v6
  with:
    path: main

- name: Checkout tools repo
  uses: actions/checkout@v6
  with:
    repository: my-org/my-tools
    path: my-tools

• If your secondary repository is private or internal you will need to add the option noted in Checkout multiple repos (private)

Checkout multiple repos (nested)

- name: Checkout
  uses: actions/checkout@v6

- name: Checkout tools repo
  uses: actions/checkout@v6
  with:
    repository: my-org/my-tools
    path: my-tools

• If your secondary repository is private or internal you will need to add the option noted in Checkout multiple repos (private)

Checkout multiple repos (private)

- name: Checkout
  uses: actions/checkout@v6
  with:
    path: main

- name: Checkout private tools
  uses: actions/checkout@v6
  with:
    repository: my-org/my-private-tools
    token: ${{ secrets.GH_PAT }} # `GH_PAT` is a secret that contains your PAT
    path: my-tools

• ${{ github.token }} is scoped to the current repository, so if you want to checkout a different repository that is private you will need to provide your own PAT.

Checkout pull request HEAD commit instead of merge commit

- uses: actions/checkout@v6
  with:
    ref: ${{ github.event.pull_request.head.sha }}

Checkout pull request on closed event

on:
  pull_request:
    branches: [main]
    types: [opened, synchronize, closed]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6

Push a commit using the built-in token

on: push
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - run: |
          date > generated.txt
          # Note: the following account information will not work on GHES
          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git add .
          git commit -m "generated"
          git push

NOTE: The user email is {user.id}+{user.login}@users.noreply.github.com. See users API: https://api.github.com/users/github-actions%5Bbot%5D

Push a commit to a PR using the built-in token

In a pull request trigger, ref is required as GitHub Actions checks out in detached HEAD mode, meaning it doesn’t check out your branch by default.

on: pull_request
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
        with:
          ref: ${{ github.head_ref }}
      - run: |
          date > generated.txt
          # Note: the following account information will not work on GHES
          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git add .
          git commit -m "generated"
          git push

NOTE: The user email is {user.id}+{user.login}@users.noreply.github.com. See users API: https://api.github.com/users/github-actions%5Bbot%5D

Recommended permissions

When using the checkout action in your GitHub Actions workflow, it is recommended to set the following GITHUB_TOKEN permissions to ensure proper functionality, unless alternative auth is provided via the token or ssh-key inputs:

permissions:
  contents: read

License

The scripts and documentation in this project are released under the MIT License