Rewrite docker workflow. (#994)

* Rewrite docker workflow.

* tidy

* Create 994.misc

Signed-off-by: Will Hunt <will@half-shot.uk>

---------

Signed-off-by: Will Hunt <will@half-shot.uk>

.github/workflows/docker.yml

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+# Based on https://github.com/matrix-org/dendrite/blob/master/.github/workflows/docker-hub.yml
+
+name: "Docker"
+
+on:
+  push:
+    paths-ignore:
+      - changelog.d/**'
+  pull_request:
+    branches: [ main ]
+    paths-ignore:
+      - changelog.d/**'
+  release:
+    types: [published]
+
+  merge_group:
+
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: false
+
+env:
+  DOCKER_NAMESPACE: halfshot
+  PLATFORMS: linux/amd64
+  PLATFORMS_PUSH: linux/amd64,linux/arm64
+  # Only push if this is main, otherwise we just want to build
+  BUILD_FOR_ALL_PLATFORMS: ${{ github.ref == 'refs/heads/main' }}
+
+jobs:
+  docker-latest:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+      packages: write
+      attestations: write
+      id-token: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_TOKEN }}
+      - name: Log in to the GitHub Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          tags: |
+            type=semver,pattern={{version}}
+            type=ref,event=branch
+            type=ref,event=pr
+            type=raw,value=latest,enable={{is_default_branch}}
+          images: |
+            ${{ env.DOCKER_NAMESPACE }}/matrix-hookshot
+            ghcr.io/matrix-org/matrix-hookshot
+  
+      - name: Build and push Docker images
+        id: push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          # arm64 builds OOM without the git fetch setting. c.f.
+          # https://github.com/rust-lang/cargo/issues/10583
+          build-args: |
+            CARGO_NET_GIT_FETCH_WITH_CLI=true
+          platforms: ${{ (env.BUILD_FOR_ALL_PLATFORMS == 'true' && env.PLATFORMS_PUSH) || env.PLATFORMS }}
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

changelog.d/994.misc

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+Push Docker images to ghcr.io, and and build an image on each commit.