update-flake-lock/README.md

# update-flake-lock

This is a GitHub Action that will update your flake.lock file whenever it is run.

> **NOTE:** As of v3, this action will no longer automatically install Nix to the action runner. You **MUST** set up a Nix with flakes support enabled prior to running this action, or your workflow will not function as expected.

## Example

An example GitHub Action workflow using this action would look like the following:

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  schedule:
    - cron: '0 0 * * 0' # runs weekly on Sunday at 00:00

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
        with:
          extra_nix_config: |
            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}            
      - name: Update flake.lock
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          pr-title: "Update flake.lock" # Title of PR to be created
          pr-labels: |                  # Labels to be set on the PR
            dependencies
            automated
```

## Example updating specific input(s)

> **NOTE**: If any inputs have a stale reference (e.g. the lockfile thinks a git input wants its "ref" to be "nixos-unstable", but the flake.nix specifies "nixos-unstable-small"), they will also be updated. At this time, there is no known workaround.

It is also possible to update specific inputs by specifying them in a space-separated list:

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  schedule:
    - cron: '0 0 * * 0' # runs weekly on Sunday at 00:00

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
        with:
          extra_nix_config: |
            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}            
      - name: Update flake.lock
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          inputs: input1 input2 input3
```

## Example that prints the number of the created PR

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  schedule:
    - cron: '0 0 * * 0' # runs weekly on Sunday at 00:00

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
        with:
          extra_nix_config: |
            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}            
      - name: Update flake.lock
        id: update
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          inputs: input1 input2 input3
      - name: Print PR number
        run: echo Pull request number is ${{ steps.update.outputs.pull-request-number }}.
```

## Example that doesn't run on PRs

If you were to run this action as a part of your CI workflow, you may want to prevent it from running against Pull Requests.

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  pull_request: # triggers on every Pull Request
  schedule:
    - cron: '0 0 * * 0' # runs weekly on Sunday at 00:00

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
        with:
          extra_nix_config: |
            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}            
      - name: Update flake.lock
        if: ${{ github.event_name != 'pull_request' }}
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          inputs: input1 input2 input3
```

## Running GitHub Actions CI

GitHub Actions will not run workflows when a branch is pushed by or a PR is opened by a GitHub Action. There are two ways to have GitHub Actions CI run on a PR submitted by this action.

### Without a Personal Authentication Token

Without using a Personal Authentication Token, you can manually run the following to kick off a CI run:

```
git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force
```

### With a Personal Authentication Token

By providing a Personal Authentication Token, the PR will be submitted in a way that bypasses this limitation (GitHub will essentially think it is the owner of the PAT submitting the PR, and not an Action).
You can create a token by visiting https://github.com/settings/tokens and select at least the `repo` scope. Then, store this token in your repository secrets (i.e. 'https://github.com/<USER>/<REPO>/settings/secrets/actions') as `GH_TOKEN_FOR_UPDATES` and set up your workflow file like the following:

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  schedule:
    - cron: '0 0 * * 1,4' # Run twice a week

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
      - name: Update flake.lock
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          token: ${{ secrets.GH_TOKEN_FOR_UPDATES }}
```

## With GPG commit signing

It's possible for the bot to produce GPG signed commits. Associating a GPG public key to a github user account is not required but it is necessary if you want the signed commits to appear as verified in Github. This can be a compliance requirement in some cases.

You can follow [Github's guide on creating and/or adding a new GPG key to an user account](https://docs.github.com/en/authentication/managing-commit-signature-verification/adding-a-new-gpg-key-to-your-github-account). Using a specific github user account for the bot can be a good security measure to dissociate this bot's actions and commits from your personal github account.

For the bot to produce signed commits, you will have to provide the GPG private keys to this action's input parameters. You can safely do that with [Github secrets as explained here](https://github.com/crazy-max/ghaction-import-gpg#prerequisites).

When using commit signing, the commit author name and email for the commits produced by this bot would correspond to the ones associated to the GPG Public Key. 

You can find an example of how to using this action with commit signing below:

```yaml
name: update-flake-lock
on:
  workflow_dispatch: # allows manual triggering
  schedule:
    - cron: '0 0 * * 1,4' # Run twice a week

jobs:
  lockfile:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repository
        uses: actions/checkout@v2
      - name: Install Nix
        uses: cachix/install-nix-action@v16
      - name: Update flake.lock
        uses: DeterminateSystems/update-flake-lock@vX
        with:
          sign-commits: true
          gpg-private-key: ${{ secrets.GPG_PRIVATE_KEY }}
          gpg-passphrase: ${{ secrets.GPG_PASSPHRASE }}
```

## Custom PR Body

By default the generated PR body is set to be the following template:

````handlebars
Automated changes by the [update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock) GitHub Action.

```
{{ env.GIT_COMMIT_MESSAGE }}
```

### Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

```sh
git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force
```
````

However you can customize it, with variable interpolation performed with [Handlebars](https://handlebarsjs.com/). This allows you to customize the template with the following variables:
- env.GIT_AUTHOR_NAME
- env.GIT_AUTHOR_EMAIL
- env.GIT_COMMITTER_NAME
- env.GIT_COMMITTER_EMAIL
- env.GIT_COMMIT_MESSAGE

## Contributing

Feel free to send a PR or open an issue if you find something functions unexpectedly! Please make sure to test your changes and update any related documentation before submitting your PR.

### How to test changes

In order to more easily test your changes to this action, we have created a template repository that should point you in the right direction: https://github.com/DeterminateSystems/update-flake-lock-test-template. Please see the README in that repository for instructions on testing your changes.