adding docker-build job

docker-build/action.yaml

@@ -0,0 +1,213 @@
+name: Build Multi-Arch Image (no push)
+description: Set up a remote Docker Buildx builder over SSH and build a multi-arch image without pushing it (e.g. to validate a Dockerfile in PRs/CI).
+
+inputs:
+  ssh_key:
+    description: SSH private key for the remote Docker builder host (pass via secrets)
+    required: true
+  image:
+    description: Optional full image reference (host/path/name) without tag, used only to tag the build result
+    required: false
+    default: ""
+  image_tag:
+    description: Tag(s) to apply when `image` is set. Comma-separated for multiple tags (e.g. "latest,abc1234").
+    required: false
+    default: latest
+  registry_host:
+    description: Hostname of the container registry (only used when registry_password is set)
+    required: false
+    default: git.ivanch.me
+  registry_username:
+    description: Username for the container registry (only used when registry_password is set)
+    required: false
+    default: ivanch
+  registry_password:
+    description: Optional registry password/token. Only needed if the build pulls private base images (pass via secrets).
+    required: false
+    default: ""
+  platforms:
+    description: Comma-separated list of target platforms
+    required: false
+    default: linux/amd64,linux/arm64
+  build_context:
+    description: Docker build context path
+    required: false
+    default: .
+  build_dockerfile:
+    description: Path to the Dockerfile (relative to context)
+    required: false
+    default: Dockerfile
+  build_args:
+    description: >-
+      Optional build arguments, one per line in KEY=VALUE form. Each line is
+      appended as a `--build-arg KEY=VALUE` to the build command.
+    required: false
+    default: ""
+  docker_host:
+    description: Hostname of the remote Docker Buildx builder
+    required: false
+    default: docker-build.haven
+  docker_user:
+    description: SSH user for the remote Docker builder
+    required: false
+    default: root
+
+runs:
+  using: composite
+  steps:
+    - name: Ensure Docker CLI and Buildx are installed
+      shell: bash
+      run: |
+        if ! command -v docker >/dev/null 2>&1; then
+          echo "Docker CLI not found, attempting to install it with Buildx..."
+          if command -v apk >/dev/null 2>&1; then
+            apk add --no-cache docker-cli docker-cli-buildx
+          elif command -v apt-get >/dev/null 2>&1; then
+            export DEBIAN_FRONTEND=noninteractive
+            apt-get update -y && apt-get install -y docker.io docker-buildx
+          elif command -v dnf >/dev/null 2>&1; then
+            dnf install -y docker-cli docker-buildx
+          elif command -v yum >/dev/null 2>&1; then
+            yum install -y docker docker-buildx
+          else
+            echo "::error::Docker CLI is missing and no supported package manager (apk, apt-get, dnf, yum) was found."
+            exit 1
+          fi
+        fi
+
+        if ! docker buildx version >/dev/null 2>&1; then
+          echo "::error::Docker Buildx is required but is not installed."
+          exit 1
+        fi
+
+    - name: Log in to Container Registry (optional)
+      if: ${{ inputs.registry_password != '' }}
+      shell: bash
+      env:
+        REGISTRY_HOST: ${{ inputs.registry_host }}
+        REGISTRY_USERNAME: ${{ inputs.registry_username }}
+        REGISTRY_PASSWORD: ${{ inputs.registry_password }}
+      run: |
+        echo "${REGISTRY_PASSWORD}" \
+          | docker login "${REGISTRY_HOST}" \
+              -u "${REGISTRY_USERNAME}" \
+              --password-stdin
+
+    - name: Set up SSH key for remote builder
+      shell: bash
+      env:
+        SSH_KEY: ${{ inputs.ssh_key }}
+        BUILDER_HOST: ${{ inputs.docker_host }}
+        BUILDER_USER: ${{ inputs.docker_user }}
+      run: |
+        # Defensive: strip any stray CR (CRLF checkout via core.autocrlf).
+        SSH_KEY=$(printf '%s' "${SSH_KEY}" | tr -d '\r')
+        BUILDER_HOST=$(printf '%s' "${BUILDER_HOST}" | tr -d '\r')
+        BUILDER_USER=$(printf '%s' "${BUILDER_USER}" | tr -d '\r')
+
+        mkdir -p ~/.ssh
+        echo "${SSH_KEY}" > ~/.ssh/id_ed25519
+        chmod 600 ~/.ssh/id_ed25519
+        ssh-keyscan "${BUILDER_HOST}" >> ~/.ssh/known_hosts
+
+        # Fail fast if the runner can't reach / auth to the remote daemon.
+        echo "== probing ssh://***@${BUILDER_HOST} =="
+        if timeout 25 ssh \
+             -o BatchMode=yes \
+             -o ConnectTimeout=10 \
+             -o ServerAliveInterval=5 \
+             -o ServerAliveCountMax=2 \
+             -o StrictHostKeyChecking=accept-new \
+             -i ~/.ssh/id_ed25519 \
+             "${BUILDER_USER}@${BUILDER_HOST}" \
+             'docker version --format "server={{.Server.Version}}"'; then
+          echo "SSH probe OK"
+        else
+          rc=$?
+          echo "SSH probe FAILED (exit ${rc})"
+          if [ "${rc}" = "124" ]; then
+            echo "-> timed out: TCP opens but SSH/daemon does not answer."
+            echo "-> Check: dockerd running on ${BUILDER_HOST}? firewall path? MTU?"
+          fi
+          exit "${rc}"
+        fi
+
+    - name: Set up remote Docker context and buildx
+      shell: bash
+      env:
+        BUILDER_HOST: ${{ inputs.docker_host }}
+        BUILDER_USER: ${{ inputs.docker_user }}
+        PLATFORMS: ${{ inputs.platforms }}
+      run: |
+        # Same approach as build-and-push: plain docker context over SSH driving
+        # the remote daemon's built-in buildkit. Never set DOCKER_HOST.
+        unset DOCKER_HOST || true
+        BUILDER_HOST=$(printf '%s' "${BUILDER_HOST}" | tr -d '\r')
+        BUILDER_USER=$(printf '%s' "${BUILDER_USER}" | tr -d '\r')
+
+        docker context rm -f remote-builder 2>/dev/null || true
+        docker context create remote-builder \
+          --docker "host=ssh://${BUILDER_USER}@${BUILDER_HOST}"
+
+        # Ensure qemu/binfmt is registered on the remote for cross-arch builds.
+        if echo "${PLATFORMS}" | grep -q 'arm'; then
+          echo "== ensuring qemu/binfmt on remote for cross-arch =="
+          docker --context remote-builder run --privileged --rm \
+            tonistiigi/binfmt --install all >/dev/null 2>&1 || \
+            echo "WARN: binfmt install returned non-zero (may already be present)"
+        fi
+
+        docker --context remote-builder buildx inspect >/dev/null
+
+    - name: Generate tags list
+      id: gentags
+      shell: bash
+      env:
+        IMAGE: ${{ inputs.image }}
+        IMAGE_TAGS: ${{ inputs.image_tag }}
+      run: |
+        TAGS_ARGS=""
+        if [ -n "${IMAGE}" ]; then
+          IFS=',' read -ra ADDR <<< "${IMAGE_TAGS}"
+          for tag in "${ADDR[@]}"; do
+            trimmed_tag=$(echo "${tag}" | xargs)
+            if [ -n "${trimmed_tag}" ]; then
+              TAGS_ARGS="${TAGS_ARGS} -t ${IMAGE}:${trimmed_tag}"
+            fi
+          done
+        fi
+        echo "tag_args=${TAGS_ARGS}" >> "$GITHUB_OUTPUT"
+
+    - name: Generate build args
+      id: genbuildargs
+      shell: bash
+      env:
+        BUILD_ARGS_INPUT: ${{ inputs.build_args }}
+      run: |
+        ARGS=""
+        while IFS= read -r line; do
+          trimmed=$(printf '%s' "${line}" | tr -d '\r' | xargs)
+          if [ -n "${trimmed}" ]; then
+            ARGS="${ARGS} --build-arg ${trimmed}"
+          fi
+        done <<< "${BUILD_ARGS_INPUT}"
+        echo "build_args=${ARGS}" >> "$GITHUB_OUTPUT"
+
+    - name: Build Multi-Arch Image (no push)
+      shell: bash
+      env:
+        BUILD_CONTEXT: ${{ inputs.build_context }}
+        BUILD_DOCKERFILE: ${{ inputs.build_dockerfile }}
+        PLATFORMS: ${{ inputs.platforms }}
+        TAG_ARGS: ${{ steps.gentags.outputs.tag_args }}
+        BUILD_ARGS: ${{ steps.genbuildargs.outputs.build_args }}
+      run: |
+        unset DOCKER_HOST || true
+        # Build only: no --push / --load. The result stays in the remote
+        # builder's cache, so a failing Dockerfile still fails the step.
+        docker --context remote-builder buildx build \
+          --platform "${PLATFORMS}" \
+          --file "${BUILD_CONTEXT}/${BUILD_DOCKERFILE}" \
+          ${BUILD_ARGS} \
+          ${TAG_ARGS} \
+          "${BUILD_CONTEXT}"