feat: set up docker buildx builder

.github/workflows/pr-checks.yaml

@@ -43,4 +43,9 @@ jobs:
         role: ${{ steps.baseproject.outputs.gha_vault_role }}
         secrets: |
           zon/v1/github-actions-baseproject-tests/example foo | EXAMPLE_VAULT_VALUE ;
-
+
+    - name: '[TEST] Run docker build'
+      run: |
+        docker buildx build --output type=docker \
+          --cache-from type=gha --cache-to type=gha,mode=max \
+          --tag test ./test

README.md

@@ -67,6 +67,17 @@ jobs:
 ```
 
 
+### Set up docker buildx
+
+For both convenience and consistency this action can also set up a `docker buildx` builder.
+
+This behaviour is controlled by the `setup_buildx` input, which defaults to "do nothing";
+set it to "true" to enable.
+Setting `gar_docker_auth` also enables this implicitly
+(with the assumption, if you want to push a docker image, you probably want to build one first),
+if this is not desired, set `setup_buildx` to "false" explicitly.
+
+
 ## Reference
 
 Here are all the inputs available through `with`:
@@ -82,6 +93,7 @@ Here are all the inputs available through `with`:
 | `gar_docker_auth`    | Authenticate to GAR (Google Artifact Registry) for Docker                         | `false` |          |
 | `python_registry`    | Setup dependencies for Python Registry (Google Artifact Registry)                 | `false` |          |
 | `vault_export_token` | Get a Vault Token and export it as VAULT_TOKEN                                    | `false` |          |
+| `setup_buildx`       | Set up docker buildx                                                              | `unset` |          |
 
 
 ## Releases

action.yml

@@ -43,6 +43,12 @@ inputs:
     required: false
     default: 'false'
 
+  # docker setup, both for convenience and centralization
+  setup_buildx:
+    description: 'Setup docker buildx. Enabling gar_docker_auth implies this; set explicitly to "false" to disable'
+    required: false
+    default: 'unset'
+
 outputs:
   project_name:
     value: ${{ steps.baseproject-config.outputs.project_name }}
@@ -209,3 +215,20 @@ runs:
       shell: bash
       run: |
         python -m pip install --upgrade --upgrade-strategy eager setuptools twine keyrings.google-artifactregistry-auth
+
+    - name: Parse setup docker buildx input
+      shell: bash
+      run: |
+        setup_buildx="${{ inputs.setup_buildx }}"
+        if [[ "$setup_buildx" != "false" && "${{ inputs.gar_docker_auth }}" = "true" ]]; then
+            setup_build="true"
+        fi
+        echo "setup_buildx=$setup_buildx" >> $GITHUB_ENV
+    - name: Setup docker buildx container
+      if: env.setup_buildx == 'true'
+      uses: docker/[email protected]
+    # Support `docker buildx build --cache-[from}to] type=gha` directly,
+    # and not just via docker/build-push-action.
+    - name: Setup docker buildx environment
+      if: env.setup_buildx == 'true'
+      uses: crazy-max/[email protected]

test/Dockerfile

@@ -0,0 +1 @@
+FROM nginx:latest