ci: Enable apt caching for container builds

The Dockerfile is already prepared and works locally. Now also make use
of that on github. We cache per matrix job to avoid mutual overwriting.

Signed-off-by: Jan Kiszka <[email protected]>

.github/actions/docker-init/action.yml

@@ -5,6 +5,8 @@ inputs:
     required: true
   deploy-token:
     required: true
+  cache-key:
+    required: true
 
 runs:
   using: composite
@@ -35,3 +37,27 @@ runs:
       run: |
         git clone . /home/runner/kas-clone
       shell: bash
+    - name: Cache var-cache-apt
+      id: cache-var-cache-apt
+      uses: actions/cache@v4
+      with:
+        path: var-cache-apt
+        key: var-cache-apt-${{ env.DEBIAN_TAG }}-${{ inputs.cache-key }}
+    - name: Cache var-lib-apt
+      id: cache-var-lib-apt
+      uses: actions/cache@v4
+      with:
+        path: var-lib-apt
+        key: var-lib-apt-${{ env.DEBIAN_TAG }}-${{ inputs.cache-key }}
+    - name: Inject var-cache-apt into docker
+      uses: reproducible-containers/[email protected]
+      with:
+        cache-source: var-cache-apt
+        cache-target: /var/cache/apt
+        skip-extraction: ${{ steps.cache-var-cache-apt.outputs.cache-hit }}
+    - name: Inject var-lib-apt into docker
+      uses: reproducible-containers/[email protected]
+      with:
+        cache-source: var-lib-apt
+        cache-target: /var/lib/apt
+        skip-extraction: ${{ steps.cache-var-lib-apt.outputs.cache-hit }}

.github/workflows/master.yml

@@ -30,6 +30,7 @@ jobs:
         with:
           deploy-user: ${{ github.actor }}
           deploy-token: ${{ secrets.GITHUB_TOKEN }}
+          cache-key: ${{ matrix.image-name }}
       - name: Build ${{ matrix.image-name }} image
         uses: docker/build-push-action@v5
         if: ${{ env.PUSH_MASTER }}

.github/workflows/next.yml

@@ -76,6 +76,7 @@ jobs:
         with:
           deploy-user: ${{ github.actor }}
           deploy-token: ${{ secrets.GITHUB_TOKEN }}
+          cache-key: ${{ matrix.image-name }}
 
       - name: Build ${{ matrix.image-name }} image
         uses: docker/build-push-action@v5

.github/workflows/release.yml

@@ -22,6 +22,7 @@ jobs:
         with:
           deploy-user: ${{ github.actor }}
           deploy-token: ${{ secrets.GITHUB_TOKEN }}
+          cache-key: ${{ matrix.image-name }}
       - name: Build ${{ matrix.image-name }} image
         uses: docker/build-push-action@v5
         with: