README: document using a different Git author / committer

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 16 to 17.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v16...v17)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/ci.yml

@@ -12,6 +12,6 @@ jobs:
         with:
           fetch-depth: 0
       - name: Install Nix
-        uses: cachix/install-nix-action@v16
+        uses: cachix/install-nix-action@v17
       - name: Shellcheck
         run: nix-shell --run 'shellcheck $(find . -type f -name "*.sh" -executable)'

.github/workflows/update.yml

@@ -11,7 +11,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v16
+        uses: cachix/install-nix-action@v17
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}

README.md

@@ -122,6 +122,38 @@ jobs:
         uses: DeterminateSystems/update-flake-lock@vX
         with:
           inputs: input1 input2 input3
+          path-to-flake-dir: 'nix/' # in this example our flake doesn't sit at the root of the repository, it sits under 'nix/flake.nix'
+```
+
+## Example using a different Git user
+
+If you want to change the author and / or committer of the flake.lock update commit, you can tweak the `git-{author,committer}-{name,email}` options:
+
+```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:
+          git-author-name: 'Jane Author'
+          git-author-email: 'github-actions[bot]@users.noreply.github.com'
+          git-committer-name: 'John Committer'
+          git-committer-email: 'github-actions[bot]@users.noreply.github.com'
 ```
 
 ## Running GitHub Actions CI
@@ -143,7 +175,7 @@ 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:
+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
@@ -166,6 +198,77 @@ jobs:
           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. 
+
+If you want to sign using a subkey, you must specify the subkey fingerprint using the `gpg-fingerprint` input parameter.
+
+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-fingerprint: ${{ secrets.GPG_FINGERPRINT }} # specify subkey fingerprint (optional)
+          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.

action.yml

@@ -17,14 +17,73 @@ inputs:
     description: 'The branch of the PR to be created'
     required: false
     default: "update_flake_lock_action"
+  path-to-flake-dir:
+    description: 'The path of the directory containing `flake.nix` file within your repository. Useful when `flake.nix` cannot reside at the root of your repository.'
+    required: false
+    default: ''
   pr-title:
     description: 'The title of the PR to be created'
     required: false
     default: "flake.lock: Update"
+  pr-body:
+    description: 'The body of the PR to be created'
+    required: false
+    default: |
+      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
+      ```
+
   pr-labels:
     description: 'A comma or newline separated list of labels to set on the Pull Request to be created'
     required: false
     default: ''
+  git-author-name:
+    description: 'Author name used for commit. Only used if sign-commits is false.'
+    required: false
+    default: 'github-actions[bot]'
+  git-author-email:
+    description: 'Author email used for commit. Only used if sign-commits is false.'
+    required: false
+    default: 'github-actions[bot]@users.noreply.github.com'
+  git-committer-name:
+    description: 'Committer name used for commit. Only used if sign-commits is false.'
+    required: false
+    default: 'github-actions[bot]'
+  git-committer-email:
+    description: 'Committer email used for commit. Only used if sign-commits is false.'
+    required: false
+    default: 'github-actions[bot]@users.noreply.github.com'
+  sign-commits:
+    description: 'Set to true if the action should sign the commit with GPG'
+    required: false
+    default: 'false'
+  gpg-private-key:
+    description: 'GPG Private Key with which to sign the commits in the PR to be created'
+    required: false
+    default: ''
+  gpg-fingerprint:
+    description: 'Fingerprint of specific GPG subkey to use'
+    required: false
+  gpg-passphrase:
+    description: 'GPG Private Key Passphrase for the GPG Private Key with which to sign the commits in the PR to be created'
+    required: false
+    default: ''
 outputs:
   pull-request-number:
     description: 'The number of the opened pull request'
@@ -32,49 +91,90 @@ outputs:
 runs:
   using: "composite"
   steps:
-    - run: $GITHUB_ACTION_PATH/update-flake-lock.sh
+    - name: Import bot's GPG key for signing commits
+      if: ${{ inputs.sign-commits == 'true' }}
+      id: import-gpg
+      uses: crazy-max/ghaction-import-gpg@v5
+      with:
+        gpg_private_key: ${{ inputs.gpg-private-key }}
+        fingerprint: ${{ inputs.gpg-fingerprint }}
+        passphrase: ${{ inputs.gpg-passphrase }}
+        git_config_global: true
+        git_user_signingkey: true
+        git_commit_gpgsign: true
+    - name: Set environment variables (signed commits)
+      if: ${{ inputs.sign-commits == 'true' }}
       shell: bash
       env:
-        GIT_AUTHOR_NAME: github-actions[bot]
+        GIT_AUTHOR_NAME: ${{ steps.import-gpg.outputs.name }}
-        GIT_AUTHOR_EMAIL: <github-actions[bot]@users.noreply.github.com>
+        GIT_AUTHOR_EMAIL: ${{ steps.import-gpg.outputs.email }}
-        GIT_COMMITTER_NAME: github-actions[bot]
+        GIT_COMMITTER_NAME: ${{ steps.import-gpg.outputs.name }}
-        GIT_COMMITTER_EMAIL: <github-actions[bot]@users.noreply.github.com>
+        GIT_COMMITTER_EMAIL: ${{ steps.import-gpg.outputs.email }}
+        TARGETS: ${{ inputs.inputs }}
+      run: |
+        echo "GIT_AUTHOR_NAME=$GIT_AUTHOR_NAME" >> $GITHUB_ENV
+        echo "GIT_AUTHOR_EMAIL=<$GIT_AUTHOR_EMAIL>" >> $GITHUB_ENV
+        echo "GIT_COMMITTER_NAME=$GIT_COMMITTER_NAME" >> $GITHUB_ENV
+        echo "GIT_COMMITTER_EMAIL=<$GIT_COMMITTER_EMAIL>" >> $GITHUB_ENV
+    - name: Set environment variables (unsigned commits)
+      if: ${{ inputs.sign-commits != 'true' }}
+      shell: bash
+      run: |
+        echo "GIT_AUTHOR_NAME=${{ inputs.git-author-name }}" >> $GITHUB_ENV
+        echo "GIT_AUTHOR_EMAIL=<${{ inputs.git-author-email }}>" >> $GITHUB_ENV
+        echo "GIT_COMMITTER_NAME=${{ inputs.git-committer-name }}" >> $GITHUB_ENV
+        echo "GIT_COMMITTER_EMAIL=<${{ inputs.git-committer-email }}>" >> $GITHUB_ENV
+    - name: Run update-flake-lock.sh
+      run: $GITHUB_ACTION_PATH/update-flake-lock.sh
+      shell: bash
+      env:
+        GIT_AUTHOR_NAME: ${{ env.GIT_AUTHOR_NAME }}
+        GIT_AUTHOR_EMAIL: ${{ env.GIT_AUTHOR_EMAIL }}
+        GIT_COMMITTER_NAME: ${{ env.GIT_COMMITTER_NAME }}
+        GIT_COMMITTER_EMAIL: ${{ env.GIT_COMMITTER_EMAIL }}
         TARGETS: ${{ inputs.inputs }}
         COMMIT_MSG: ${{ inputs.commit-msg }}
-    - run: |
+        PATH_TO_FLAKE_DIR: ${{ inputs.path-to-flake-dir }}
-        content="$(git log --format=%b -n 1)"
+    - name: Save PR Body as file
-        content="${content//'%'/'%25'}"
+      uses: DamianReeves/write-file-action@v1.1
-        content="${content//$'\n'/'%0A'}"
+      with:
-        content="${content//$'\r'/'%0D'}"
+        path: pr_body.template
-        echo "::set-output name=msg::$content"
+        contents: ${{ inputs.pr-body }}
+      env: {}
+    - name: Set additional env variables (GIT_COMMIT_MESSAGE)
       shell: bash
-      id: commit_message
+      run: |
+        GIT_COMMIT_MESSAGE="$(git log --format=%b -n 1)"
+        GIT_COMMIT_MESSAGE="${GIT_COMMIT_MESSAGE//'%'/'%25'}"
+        GIT_COMMIT_MESSAGE="${GIT_COMMIT_MESSAGE//$'\n'/'%0A'}"
+        GIT_COMMIT_MESSAGE="${GIT_COMMIT_MESSAGE//$'\r'/'%0D'}"
+        echo "GIT_COMMIT_MESSAGE=$GIT_COMMIT_MESSAGE" >> $GITHUB_ENV
+        echo "GIT_COMMIT_MESSAGE is: ${GIT_COMMIT_MESSAGE}"
+    - name: Interpolate PR Body
+      uses: pedrolamas/handlebars-action@v2.0.0
+      with:
+        files: 'pr_body.template'
+        output-filename: 'pr_body.txt'
+    - name: Read pr_body.txt
+      id: pr_body
+      uses: andstor/file-reader-action@v1
+      with:
+        path: "pr_body.txt"
+    # We need to remove the pr_body files so that the
+    # peter-evans/create-pull-request action does not commit it (the
+    # action commits all new and modified files).
+    - name: Remove PR body template files
+      shell: bash
+      run: rm -f pr_body.txt pr_body.template
     - name: Create PR
       id: create-pr
       uses: peter-evans/create-pull-request@v3
       with:
         branch: ${{ inputs.branch }}
         delete-branch: true
+        committer: ${{ env.GIT_COMMITTER_NAME }} ${{ env.GIT_COMMITTER_EMAIL }}
+        author: ${{ env.GIT_AUTHOR_NAME }} ${{ env.GIT_AUTHOR_EMAIL }}
         title: ${{ inputs.pr-title }}
         token: ${{ inputs.token }}
         labels: ${{ inputs.pr-labels }}
-        body: |
+        body: ${{ steps.pr_body.outputs.contents }}
-          Automated changes by the [update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock) GitHub Action.
-
-          ```
-          ${{ steps.commit_message.outputs.msg }}
-          ```
-
-          ### 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
-          ```

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1654682581,
+        "lastModified": 1659131907,
-        "narHash": "sha256-Jb1PQCwKgwdNAp907eR5zPzuxV+kRroA3UIxUxCMJ9s=",
+        "narHash": "sha256-8bz4k18M/FuVC+EVcI4aREN2PsEKT7LGmU2orfjnpCg=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "e0169d7a9d324afebf5679551407756c77af8930",
+        "rev": "8d435fca5c561da8168abb30270788d2da2a7951",
         "type": "github"
       },
       "original": {

update-flake-lock.sh

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+if [[ -n "$PATH_TO_FLAKE_DIR" ]]; then
+  cd "$PATH_TO_FLAKE_DIR"
+fi
+
 if [[ -n "$TARGETS" ]]; then
     inputs=()
     for input in $TARGETS; do