ci: Use SHA instead of 'latest' tag when not on main

Signed-off-by: Phoevos Kalemkeris <[email protected]>

Author: phoevos

.github/workflows/docker.yaml

@@ -71,7 +71,7 @@ jobs:
           push: true
           tags: |
             ${{ steps.meta.outputs.tags }}
-            ${{ matrix.image }}:latest
+            ${{ matrix.image }}:${{ github.ref == 'refs/heads/main' && 'latest' || github.sha }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=local,src=/tmp/.buildx-cache
           cache-to: type=local,dest=/tmp/.buildx-cache,mode=max