infra: image: build image for branches if they dont exist

.gitea/workflows/gentoo-utils.yml

@@ -14,28 +14,38 @@ jobs:
 
       - name: Check for changes before building
         id: image-changes
+        # build image only if 1. changes are detected or 2. an image for the working branch doesnt exist
         run: |
           branch_name="${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}"
-          echo "branch_name=$branch_name" >> $GITEA_OUTPUT
 
           if [[ "$branch_name" == "${{ gitea.event.repository.default_branch }}" ]]; then
-            echo "image_tag=latest" >> $GITEA_OUTPUT
+            image_tag=latest
           else
-            echo "image_tag=$branch_name" >> $GITEA_OUTPUT
+            image_tag=$branch_name
           fi
 
+          echo "branch_name=$branch_name" >> $GITEA_OUTPUT
+          # slugify
+          echo "image_tag=$(echo "$image_tag" | sed -E 's/[^a-zA-Z0-9]/-/g')" >> $GITEA_OUTPUT
+
           if ! git diff ${{ gitea.event.before }} ${{ gitea.sha }} --no-patch --exit-code .docker; then
-            echo changes_detected=true >> $GITEA_OUTPUT
+            build_image=true
           else
-            echo changes_detected=false >> $GITEA_OUTPUT
+            if ! docker manifest inspect git.epenguin.net/${{ gitea.repository }}:${image_tag} >/dev/null 2>&1; then
+              build_image=true
+            else
+              build_image=false
+            fi
           fi
+
+          echo "build_image=$build_image" >> $GITEA_OUTPUT
           cat $GITEA_OUTPUT
       - name: Set up Docker buildx
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/setup-buildx-action@v3
 
       - name: Log in to Github Container Registry
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/login-action@v3
         with:
           registry: git.epenguin.net
@@ -43,7 +53,7 @@ jobs:
           password: ${{ secrets.CI_BOT_TOKEN }}
 
       - name: Build and push
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/build-push-action@v6
         with:
           push: true