setup-private-repo is a GitHub action that Clones a private GitHub repository using an SSH key or personal access token, and configures Git to use that local copy instead.

This action is most useful for building Go applications relying on private dependencies, as it will enable Go to find the required tag or commit from the cloned repo without requiring any ad-hoc hacks to go.mod or git configuration files. However, it is possible that it may also be useful when building code in other languages whose tooling relies on Git repo for downloading dependencies.

Four steps are run:

1. Sets ups a dedicated folder so that multiple private repos can be setup simultaneously if needed ($GITHUB_WORKSPACE/.private-repos).
2. Clones private repositories fully (history of all branches and tags) to the $GITHUB_WORKSPACE/.private-repos folder using actions/checkout.
3. Creates the local tag setup-private-repo pointing to the checked out ref. This is needed because the Go tooling only look at main branches and tags. If a PR ref is being checked out and Go imports modules referencing commit IDs that only exist in that same PR ref, those commits would not be found. See: golang/go#27043
4. Configures Git with a insteadOf directive to use the local clone whenever the HTTPS URL of the private repo is referenced.

• repository (required): the full name of the GitHub repository (e.g., alnvdl-work/setup-private-repo).
• ssh-key (recommended): a private SSH key to use for cloning. See SSH key setup.
• token: a personal access token to use for cloning. See Personal access token setup.

None.

name: Build with a dependency on a private repo

on: [push]

jobs:
  verify:
    runs-on: ubuntu-latest
    steps:
      - name: load-private-repo
        uses: alnvdl-work/setup-private-repo@v1
        with:
          repository: alnvdl-work/my-private-dep
          ssh-key: ${{ secrets.MY_PRIVATE_DEP_SSH_KEY }}
      - name: verify-that-it-worked
        run: |
          cat ~/.gitconfig
          cat $GITHUB_WORKSPACE/.private-repos/alnvdl-work/my-private-dep/LICENSE
        shell: bash

Consider the following two repos:

• my-private-dep: the private repo you are trying to clone for a build.
• my-build-repo: the repo you are building using a GitHub Actions workflow.

1. Generate a key pair without a passphrase:

   ssh-keygen -N "" -C "my-private-dep" -f ~/.ssh/my-private-dep-key

2. Obtain the public key:

   cat ~/.ssh/my-private-dep-key.pub

   Then set it up as a read-only deploy key in my-private-dep. You can do that in the GitHub settings for my-private-dep. See: https://docs.github.com/en/authentication/connecting-to-github-with-ssh/managing-deploy-keys#deploy-keys

3. Obtain the private key:

   cat ~/.ssh/my-private-dep-key

   Then set it up as a GitHub Actions secret in my-build-repo. You can do that in the GitHub settings for my-build-repo. Make sure to use an unambigous name, like MY_PRIVATE_DEP_SSH_KEY. See: https://docs.github.com/en/actions/security-guides/using-secrets-in-github-actions

4. Remove the public and private keys from your machine:

   rm -rf ~/.ssh/my-private-dep-key
   rm -rf ~/.ssh/my-private-dep-key.pub

5. In your GitHub Actions workflow in my-build-repo, make sure to set the ssh-key input for alnvdl-work/setup-private-repo@v1 with the name of the secret you configured in step 4.

If an SSH read-only deploy key cannot be used, a fine-grained personal access token can be used instead.

See: https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#fine-grained-personal-access-tokens

Make sure to only grant the minimal access possible (read-only for content and metadata, and only in the repos needed).