Retrieve the latest kindest/node image for tests

After talking with Release team of K8s they told me that they do not
always create images for every version of k8s. In this PR we are
changing our logic to retrieve the latest publish image of kindest/node
from docker hub itself.

As part of the change we are also adding a warning, because now these 2
versions are decoupled, whenever a new minor of k8s is released and they
do not publish a new kindest/node image, we write a warning in the
output.

Signed-off-by: Joao Pereira <joaopapereira@gmail.com>

Author: joaopapereira

.github/workflows/test-gh.yml

@@ -25,21 +25,28 @@ jobs:
       run: |
         k8s_version=${{ matrix.k8s-version }}
         if [ "${k8s_version}" = "latest" ]; then
-          k8s_version=$(curl -Ls -o /dev/null -w %{url_effective} https://github.com/kubernetes/kubernetes/releases/latest | grep -oE 'tag/v[0-9]+\.[0-9]+\.[0-9]+' | cut -d'/' -f2)
-          echo "Resolved latest k8s version to: $k8s_version"
+          # Resolve to the latest kindest/node tag available on Docker Hub (not kubernetes/kubernetes releases,
+          # which may lag behind kind image availability)
+          k8s_version=$(curl -s "https://hub.docker.com/v2/repositories/kindest/node/tags?page_size=100&ordering=last_updated" \
+            | grep -oE '"name":"v[0-9]+\.[0-9]+\.[0-9]+"' \
+            | grep -oE 'v[0-9]+\.[0-9]+\.[0-9]+' \
+            | sort -V | tail -1)
+          echo "Resolved latest kindest/node version to: $k8s_version"
+
+          # Warn if kind's latest minor version lags behind the latest upstream Kubernetes minor version
+          k8s_latest=$(curl -Ls -o /dev/null -w %{url_effective} https://github.com/kubernetes/kubernetes/releases/latest \
+            | grep -oE 'v[0-9]+\.[0-9]+\.[0-9]+')
+          kind_minor=$(echo "$k8s_version" | cut -d'.' -f2)
+          k8s_minor=$(echo "$k8s_latest" | cut -d'.' -f2)
+          if [ "$kind_minor" -lt "$k8s_minor" ]; then
+            echo "::warning::kindest/node latest is $k8s_version (minor=$kind_minor) but upstream Kubernetes latest is $k8s_latest (minor=$k8s_minor). kind has not yet published an image for the newest minor version."
+          fi
         fi
-        echo "k8s_version=$k8s_version" >> $GITHUB_ENV
-    - name: Create Kind Cluster(k8s version ${{ env.k8s_version }})
+        echo "k8s_version=${k8s_version}" >> $GITHUB_ENV
+    - name: Create Kind Cluster (k8s version ${{ env.k8s_version }})
       run: |
-        k8s_version=${{ env.k8s_version }}
-        echo "Checking if kindest/node:${k8s_version} exists..."
-        if docker pull kindest/node:${k8s_version}; then
-          echo "Using kindest/node:${k8s_version}"
-          kind create cluster --image kindest/node:${k8s_version}
-        else
-          echo "kindest/node:${k8s_version} not found. Using fallback image ghcr.io/carvel-dev/kindest/node:${k8s_version}"
-          kind create cluster --image ghcr.io/carvel-dev/kindest/node:${k8s_version}
-        fi
+        echo "Creating kind cluster with kindest/node:${{ env.k8s_version }}"
+        kind create cluster --image kindest/node:${{ env.k8s_version }}
     - name: Verify kind and k8s version
       run: |
         kind version