ci: add workflow for creating snapshot container images

Signed-off-by: László Várady <laszlo.varady@anno.io>

.github/workflows/axosyslog-docker.yml

@@ -6,6 +6,10 @@ on:
       type:
         required: true
         type: string  # stable / snapshot
+      platforms:
+        required: false
+        type: string
+        default: linux/amd64,linux/arm64,linux/arm/v7
       snapshot-tarball-artifact:
         required: false
         type: string
@@ -21,17 +25,27 @@ env:
   DEBUG_PLATFORM: linux/amd64
 
 jobs:
+  prepare:
+    runs-on: ubuntu-latest
+    outputs:
+      platform-matrix: ${{ steps.platforms.outputs.platform-matrix }}
+    steps:
+      - id: platforms
+        env:
+          PLATFORMS: ${{ inputs.platforms }}
+        run: |
+          PLATFORM_MATRIX="$(echo "$PLATFORMS" | jq 'split(",")' -Rc)"
+          echo "platform-matrix=$PLATFORM_MATRIX" >> $GITHUB_OUTPUT
+
   image-build:
     if: github.repository_owner == 'axoflow'
     runs-on: ubuntu-latest
+    needs: prepare
 
     strategy:
       fail-fast: false
       matrix:
-        platform:
-          - linux/amd64
-          - linux/arm64
-          - linux/arm/v7
+        platform: ${{ fromJSON(needs.prepare.outputs.platform-matrix) }}
 
     steps:
       - name: Prepare

.github/workflows/axosyslog-image-snapshot.yml

@@ -0,0 +1,52 @@
+name: AxoSyslog Docker snapshot image
+
+on:
+  workflow_dispatch:
+    inputs:
+      platforms:
+        default: "linux/amd64,linux/arm64,linux/arm/v7"
+  push:
+    branches:
+      - main
+
+jobs:
+  tarball:
+    runs-on: ubuntu-latest
+    outputs:
+      snapshot-version: ${{ steps.snapshot-version.outputs.SNAPSHOT_VERSION }}
+    steps:
+      - name: Checkout AxoSyslog source
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Prepare docker image
+        run: ./dbld/rules cache-image-tarball
+
+      - name: Create source tarball
+        run: ./dbld/rules pkg-tarball
+
+      - name: Determine snapshot version
+        id: snapshot-version
+        run: |
+          tarball_filename="$(find dbld/build -name '*.tar.*' -printf '%f\n')"
+          tarball_name="${tarball_filename/\.tar.*}"
+          tarball_version="${tarball_name/axosyslog-}"
+          pkg_version="$(echo $tarball_version | sed -E 's|(([0-9]+\.){2}[0-9]+).*|\1|')_git$(date +%Y%m%d)"
+          echo "SNAPSHOT_VERSION=${pkg_version}" >> $GITHUB_OUTPUT
+
+      - name: Store source tarball as artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: source-tarball
+          path: dbld/build/*.tar.*
+
+  publish-image:
+    uses: ./.github/workflows/axosyslog-docker.yml
+    needs: tarball
+    with:
+      type: snapshot
+      platforms: ${{ inputs.platforms || 'linux/amd64' }}
+      snapshot-tarball-artifact: source-tarball
+      snapshot-version: ${{ needs.tarball.outputs.snapshot-version }}
+      snapshot-tags: dev-${{ github.ref_name }}