Update README / add some more inputs

Author: dsotirakis

actions/push-image-digests/README.md

@@ -0,0 +1,56 @@
+# push-image-digests
+
+This is a composite GitHub Action, used to push image digests to GitHub, so then they can be picked up by the `push-to-gar-docker-multiarch` action, to create a manifest and push the actual image to GAR.
+
+This action can be used as a standalone one for fast testing, in case the developer wants to test things on their PR.
+
+```yaml
+name: CI
+on:
+  pull_request:
+
+# These permissions are needed to assume roles from Github's OIDC.
+permissions:
+  contents: read
+  id-token: write
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+
+    steps:
+      - id: checkout
+        uses: actions/checkout@v4
+
+      - id: push-to-gar
+        uses: grafana/shared-workflows/actions/push-image-digests@main
+        with:
+          registry: "<YOUR-GAR>" # e.g. us-docker.pkg.dev, optional
+          tags: |-
+            "<IMAGE_TAG>"
+            "latest"
+          context: "<YOUR_CONTEXT>" # e.g. "." - where the Dockerfile is
+          image_name: "backstage" # name of the image to be published, required
+          environment: "dev" # can be either dev/prod
+```
+
+## Inputs
+
+| Name                   | Type    | Description                                                                                                                                                                    |
+| ---------------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| `registry`             | String  | Google Artifact Registry to store docker images in.                                                                                                                            |
+| `tags`                 | List    | Tags that should be used for the image (see the [metadata-action][mda] for details)                                                                                            |
+| `context`              | List    | Path to the Docker build context.                                                                                                                                              |
+| `environment`          | Bool    | Environment for pushing artifacts (can be either dev or prod).                                                                                                                 |
+| `image_name`           | String  | Name of the image to be pushed to GAR.                                                                                                                                         |
+| `build-args`           | String  | List of arguments necessary for the Docker image to be built.                                                                                                                  |
+| `push`                 | Boolean | Whether to push the image to the registry.                                                                                                                                     |
+| `file`                 | String  | Path and filename of the dockerfile to build from. (Default: `{context}/Dockerfile`)                                                                                           |
+| `platforms`            | List    | List of platforms the image should be built for (e.g. `linux/amd64,linux/arm64`)                                                                                               |
+| `cache-from`           | String  | Where cache should be fetched from ([more about GHA and container caching](https://www.kenmuse.com/blog/implementing-docker-layer-caching-in-github-actions/))                 |
+| `cache-to`             | String  | Where cache should be stored to ([more about GHA and container caching](https://www.kenmuse.com/blog/implementing-docker-layer-caching-in-github-actions/))                    |
+| `ssh`                  | List    | List of SSH agent socket or keys to expose to the build ([more about ssh for docker/build-push-action](https://github.com/docker/build-push-action?tab=readme-ov-file#inputs)) |
+| `build-contexts`       | List    | List of additional [build contexts](https://github.com/docker/build-push-action?tab=readme-ov-file#inputs) (e.g., `name=path`)                                                 |
+| `docker-buildx-driver` | String  | The [driver](https://github.com/docker/setup-buildx-action/tree/v3/?tab=readme-ov-file#customizing) to use for Docker Buildx                                                   |
+
+[mda]: https://github.com/docker/metadata-action?tab=readme-ov-file#tags-input

actions/push-image-digests/action.yaml

@@ -47,6 +47,16 @@ inputs:
   ssh:
     description: |
       List of SSH agent socket or keys to expose to the build
+  build-contexts:
+    description: |
+      List of additional build contexts (e.g., name=path)
+    required: false
+  docker-buildx-driver:
+    description: |
+      The driver to use for Docker Buildx
+    required: false
+    default: "docker-container"
+
 
 outputs:
   full_image_name:
@@ -107,6 +117,8 @@ runs:
         images: ${FULL_IMAGE_NAME}
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@f95db51fddba0c2d1ec667646a06c2ce06100226 # v3.0.0
+      with:
+        driver: ${{ inputs.docker-buildx-driver }}
     - name: Build the container
       uses: docker/build-push-action@4a13e500e55cf31b7a5d59a38ab2040ab0f42f56 # v5.1.0
       id: build
@@ -120,6 +132,7 @@ runs:
         file: ${{ inputs.file }}
         platforms: ${{ inputs.platform }}
         ssh: ${{ inputs.ssh }}
+        build-contexts: ${{ inputs.build-contexts }}
     - name: Export digest
       shell: bash
       run: |