Add container image build to CI

.github/workflows/ci.yml

@@ -49,3 +49,27 @@ jobs:
 
       - name: Build
         run: nix build --print-build-logs
+
+      - name: Build and push container image
+        if: ${{ github.ref_name == 'main' || github.ref_type == 'tag' }}
+        run: |
+          set -x
+
+          # Build image via Nix and take the resulting path as the local container registry
+          local_cr="docker-archive://$(nix build .#container-image --no-link --print-out-paths)"
+
+          # The container registry to push images to (GHCR)
+          remote_cr="docker://ghcr.io/dannixon/git-collage"
+          remote_cr_creds="${{ github.repository_owner }}:${{ github.token }}"
+
+          # Push image using the Git ref name as the image tag (i.e. "main" or the tag name)
+          skopeo copy --dest-creds="$remote_cr_creds" "$local_cr" "$remote_cr:${{ github.ref_name }}"
+
+          # Push image using the Git SHA as the image tag
+          skopeo copy --dest-creds="$remote_cr_creds" "$local_cr" "$remote_cr:${{ github.sha }}"
+
+          # If the trigger was a tag (i.e. a release)
+          if [[ "${{ github.ref_type }}" == 'tag' ]]; then
+            # Push image using the "latest" tag
+            skopeo copy --dest-creds="$remote_cr_creds" "$local_cr" "$remote_cr:latest"
+          fi