fix: make compatibility versions test use dynamic n-1 branch for test…

… (from hardcoded release-1.31)

config/jobs/kubernetes/sig-testing/compatibility-versions-e2e.yaml

@@ -35,8 +35,6 @@ periodics:
       - -c
       - curl -sSL https://kind.sigs.k8s.io/dl/latest/linux-amd64.tgz | tar xvfz - -C "${PATH%%:*}/" && ./../test-infra/experiment/compatibility-versions/e2e-k8s-compatibility-versions.sh
       env:
-      - name: EMULATED_VERSION
-        value: "1.31"  # TODO(aaron-prindle) FIXME - hardcoded for now
       - name: SKIP
         value: Alpha|Disruptive|Slow|Flaky|IPv6|LoadBalancer|PodSecurityPolicy|nfs
       - name: PARALLEL

experiment/compatibility-versions/e2e-k8s-compatibility-versions.sh

@@ -223,9 +223,6 @@ EOF
 
 # run e2es with ginkgo-e2e.sh
 run_tests() {
-  # Change to the cloned Kubernetes repository
-  pushd ../kubernetes
-
   # IPv6 clusters need some CoreDNS changes in order to work in k8s CI:
   # 1. k8s CI doesn´t offer IPv6 connectivity, so CoreDNS should be configured
   # to work in an offline environment:
@@ -286,17 +283,19 @@ run_tests() {
     "--report-dir=${ARTIFACTS}" '--disable-log-dump=true' &
   GINKGO_PID=$!
   wait "$GINKGO_PID"
-
-  # Return to the original directory
-  popd
 }
 
-# clone kubernetes repo for specific release branch
-clone_kubernetes_release() {
-  # Clone the specific Kubernetes release branch
-  # Replace "release-1.31" with the desired branch
-  KUBE_RELEASE_BRANCH=${KUBE_RELEASE_BRANCH:-release-1.31}
-  git clone --single-branch --branch "${KUBE_RELEASE_BRANCH}" https://github.com/kubernetes/kubernetes.git
+get_latest_release_version() {
+    # Fetch all branch names
+    git ls-remote --heads https://github.com/kubernetes/kubernetes.git | \
+    # Extract branch names that match release-X.Y pattern
+    grep -o 'refs/heads/release-[0-9]\+\.[0-9]\+$' | \
+    # Extract version numbers
+    sed 's/refs\/heads\/release-//' | \
+    # Sort versions by number
+    sort -t. -k1,1n -k2,2n | \
+    # Get the latest version
+    tail -n1
 }
 
 main() {
@@ -307,6 +306,8 @@ main() {
   export ARTIFACTS="${ARTIFACTS:-${PWD}/_artifacts}"
   mkdir -p "${ARTIFACTS}"
 
+  export EMULATED_VERSION=$(get_latest_release_version)
+
   # export the KUBECONFIG to a unique path for testing
   KUBECONFIG="${HOME}/.kube/kind-test-config"
   export KUBECONFIG
@@ -327,10 +328,16 @@ main() {
   res=0
   create_cluster || res=$?
 
-  # Clone the specific Kubernetes release branch
-  clone_kubernetes_release
+  # Clone the previous versions Kubernetes release branch
+  # TODO(aaron-prindle) extend the branches to test from n-1 -> n-1..3 as more k8s releases are done that support compatibility versions
+  export PREV_RELEASE_BRANCH="release-${EMULATED_VERSION}"
+  git clone --single-branch --branch "${PREV_RELEASE_BRANCH}" https://github.com/kubernetes/kubernetes.git "${PREV_RELEASE_BRANCH}"
 
+  # enter the release branch and run tests
+  pushd "${PREV_RELEASE_BRANCH}"
   run_tests || res=$?
+  popd
+
   cleanup || res=$?
   exit $res
 }