Add GitHub Actions workflow for publishing images

Author: pi3-code

.github/workflows/publish-images.yml

@@ -0,0 +1,65 @@
+name: Publish Challenge Images                                                                                                      
+                                                                                                                                      
+  on:                                                                                                                                 
+    push:                                                                                                                             
+      branches: [main]                                                                                                                
+      paths:
+        - "*/Dockerfile"                                                                                                              
+        - "*/requirements.txt"
+        - "*/app/**"
+        - ".github/workflows/publish-images.yml"
+    workflow_dispatch:
+
+  env:
+    REGISTRY: ghcr.io
+
+  jobs:
+    detect-challenges:
+      runs-on: ubuntu-latest
+      outputs:
+        challenges: ${{ steps.find.outputs.challenges }}
+      steps:
+        - uses: actions/checkout@v4
+        - id: find
+          run: |
+            challenges=$(ls -d */ | grep -v '_template\|\.github' | sed 's/\///' | jq -R -s -c 'split("\n") | map(select(length >
+  0))')
+            echo "challenges=$challenges" >> "$GITHUB_OUTPUT"
+
+    build-and-push:
+      needs: detect-challenges
+      runs-on: ubuntu-latest
+      permissions:
+        contents: read
+        packages: write
+      strategy:
+        matrix:
+          challenge: ${{ fromJson(needs.detect-challenges.outputs.challenges) }}
+      steps:
+        - uses: actions/checkout@v4
+
+        - uses: docker/setup-buildx-action@v3
+
+        - uses: docker/login-action@v3
+          with:
+            registry: ${{ env.REGISTRY }}
+            username: ${{ github.actor }}
+            password: ${{ secrets.GITHUB_TOKEN }}
+
+        - id: meta
+          uses: docker/metadata-action@v5
+          with:
+            images: ${{ env.REGISTRY }}/kryptsec/oasis-challenges/${{ matrix.challenge }}
+            tags: |
+              type=raw,value=latest,enable={{is_default_branch}}
+              type=sha,prefix=
+
+        - uses: docker/build-push-action@v6
+          with:
+            context: ./${{ matrix.challenge }}
+            push: true
+            platforms: linux/amd64
+            tags: ${{ steps.meta.outputs.tags }}
+            labels: ${{ steps.meta.outputs.labels }}
+            cache-from: type=gha
+            cache-to: type=gha,mode=max