Push singularity .sif files to ghcr.io with tags

Fixes #12

.github/workflows/docker_build_push.yml

@@ -4,18 +4,33 @@ on:
   push:
     branches:
       - 'main'
+    tags:
+      - "v*.*.*"
 
 jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
+      - 
+        name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ghcr.io/${{ github.repository_owner }}/ldpred2        
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=sha     
       -
         name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
-      - name: Login to GitHub Container Registry
+      - 
+        name: Login to GitHub Container Registry
+        if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
         with:
           registry: ghcr.io
@@ -26,8 +41,59 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           context: "{{defaultContext}}:docker"
-          push: true
-          tags: |
-            ghcr.io/${{ github.repository_owner }}/ldpred2:latest
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
           file:
             ./dockerfiles/ldpred2/Dockerfile
+          platforms: linux/amd64
+
+  build-push-singularity-container:
+    needs: docker
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    container:
+        image: quay.io/singularity/singularity:v4.1.0
+        options: --privileged
+    name: Pull-push Singularity Container
+    steps:
+      - name: Check out code for the container builds
+        uses: actions/checkout@v4
+      - name: Install dependencies
+        run: |
+          apk add --no-cache curl
+          VERSION="1.1.0"
+          curl -LO "https://github.com/oras-project/oras/releases/download/v${VERSION}/oras_${VERSION}_linux_amd64.tar.gz"
+          mkdir -p oras-install/
+          tar -zxf oras_${VERSION}_*.tar.gz -C oras-install/
+          sudo mv oras-install/oras /usr/local/bin/
+          rm -rf oras_${VERSION}_*.tar.gz oras-install/
+      - name: Docker meta 
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ghcr.io/${{ github.repository_owner }}/ldpred2            
+          tags: |
+            type=semver,pattern={{version}}
+            type=ref,event=branch
+            type=sha   
+      - name: Pull and push Singularity container
+        run: |
+          tags="${{ steps.meta.outputs.tags }}"
+          tags_array=
+          old_ifs="$IFS"
+          IFS=$'\n'
+          for tag in $tags; do
+              tags_array="$tags_array $tag"
+          done
+          IFS="$old_ifs"
+          echo ${{ secrets.GITHUB_TOKEN }} | oras login --username ${{ github.repository_owner }} --password-stdin ghcr.io
+          for tag in $tags_array; do
+            echo "processing tag: $tag"
+            singularity pull ldpred2.sif docker://"$tag"
+            oras push "$tag" --artifact-type application/vnd.acme.rocket.config ldpred2.sif
+            rm ldpred2.sif
+          done
+        shell: sh