ci: adding linter and builder github action

Fixes #869

Using popular Hadolint linter for dockers.
Using standard GitHub action for building.

Build will also publish to GHCR after PR is merged, not before.

Signed-off-by: Boris Glimcher <Boris.Glimcher@emc.com>

.github/workflows/docker.yaml

@@ -0,0 +1,75 @@
+name: Docker
+
+on:
+  workflow_dispatch:
+  workflow_call:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: hadolint/hadolint-action@v3.1.0
+        with:
+          recursive: true
+          ignore: DL3018
+
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      # This is used to complete the identity challenge
+      # with sigstore/fulcio when running outside of PRs.
+      id-token: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # Workaround: https://github.com/docker/build-push-action/issues/461
+      - name: Setup Docker buildx
+        uses: docker/setup-buildx-action@v3.0.0
+
+    #   - name: Log in to Docker Hub
+    #     if: github.event_name != 'pull_request'
+    #     uses: docker/login-action@v3.0.0
+    #     with:
+    #       username: ${{ secrets.DOCKERHUB_USERNAME }}
+    #       password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Log in to the Container registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3.0.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Extract metadata (tags, labels) for Docker
+      # https://github.com/docker/metadata-action
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5.5.0
+        with:
+          images: |
+            ghcr.io/${{ github.repository }}
+
+      # Build and push Docker image with Buildx (don't push on PR)
+      # https://github.com/docker/build-push-action
+      - name: Build and push Docker image
+        id: build-and-push
+        uses: docker/build-push-action@v5.1.0
+        with:
+          context: .
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          platforms: linux/amd64,linux/arm/v7,linux/arm/v6
+          cache-from: type=gha
+          cache-to: type=gha,mode=max