feat: Add Docker workflow for building, pushing & signing images

.github/workflows/docker.yml

@@ -0,0 +1,104 @@
+name: Build & Push Docker Image
+
+on:
+  schedule:
+    - cron: '36 2 * * *'
+  push:
+    branches: [ "$default-branch", ]
+    # Publish semver tags as releases.
+    tags: [ 'v*.*.*' ]
+  pull_request:
+    branches: [ "$default-branch" ]
+
+env:
+  # Use docker.io for Docker Hub if empty
+  REGISTRY: ghcr.io
+
+  # github.repository as <account>/<repo>
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  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
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      # Install the cosign tool except on PR
+      # https://github.com/sigstore/cosign-installer
+      - name: Install cosign
+        if: github.event_name != 'pull_request'
+        uses: sigstore/cosign-installer@v3
+        with:
+          cosign-release: 'v2.2.4'
+
+      # Set up BuildKit Docker container builder to be able to build
+      # multi-platform images and export cache
+      # https://github.com/docker/setup-buildx-action
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # Login against a Docker registry except on PR
+      # https://github.com/docker/login-action
+      - name: Log into registry ${{ env.REGISTRY }}
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          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
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=semver,pattern={{raw}},value=${{ github.ref }}
+            type=sha,value=${{ github.sha }}
+          flavor: |
+            latest=${{ github.event_name != 'pull_request' }}
+          labels: |
+            org.opencontainers.image.title=${{ github.repository }}
+            org.opencontainers.image.source="https://github.com/${{ 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@v6
+        with:
+          context: .
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          platforms: linux/amd64,linux/arm64
+
+      # Sign the resulting Docker image digest except on PRs.
+      # This will only write to the public Rekor transparency log when the Docker
+      # repository is public to avoid leaking data.  If you would like to publish
+      # transparency data even for private images, pass --force to cosign below.
+      # https://github.com/sigstore/cosign
+      - name: Sign the published Docker image
+        if: ${{ github.event_name != 'pull_request' }}
+        env:
+          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
+          TAGS: ${{ steps.meta.outputs.tags }}
+          DIGEST: ${{ steps.build-and-push.outputs.digest }}
+        # This step uses the identity token to provision an ephemeral certificate
+        # against the sigstore community Fulcio instance.
+        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}

README.md

@@ -37,7 +37,7 @@ Note that IMAPdedup doesn't *need* any installation process, however, and doesn'
 
     python3 imapdedup.py ...
 
-If you might want to modify the script yourself, I recommend using [uv](https://docs.astral.sh/uv/). You can then simply get a copy of the source and use: 
+If you might want to modify the script yourself, I recommend using [uv](https://docs.astral.sh/uv/). You can then simply get a copy of the source and use:
 
     uv run imapdedup ....
 
@@ -48,11 +48,15 @@ which will create a virtualenv for you and keep it up to date as you experiment
 To run IMAPdedup in a Docker container, you can use the following commands:
 First, build the image:
 
-    docker build -t imapdedup .
+    docker build -t ghcr.io/quentinsf/imapdedup:latest .
+
+Or pull an image from the GitHub Container Registry:
+
+    docker pull ghcr.io/quentinsf/imapdedup:latest
 
 Then you can run the container with the following command:
 
-    docker run --rm -it imapdedup --help
+    docker run --rm -it ghcr.io/quentinsf/imapdedup:latest --help
 
 See _[Simple-use](#simple-use)_ for more information on how to use IMAPdedup.
 
@@ -123,7 +127,7 @@ We don't curently have a way of storing your options in a configuration file, bu
     import imapdedup
 
     options = [
-        "-s", "imap.example.com", 
+        "-s", "imap.example.com",
         "-u", "my_user_name",
         "-w", "my_password",
         "-x"