New get-kube.sh option: KUBERNETES_SKIP_RELEASE_VALIDATION

cluster/get-kube.sh

@@ -56,6 +56,9 @@
 #  Set KUBERNETES_SKIP_DOWNLOAD to skip downloading a release.
 #  Set KUBERNETES_SKIP_CONFIRM to skip the installation confirmation prompt.
 #  Set KUBERNETES_SKIP_CREATE_CLUSTER to skip starting a cluster.
+#  Set KUBERNETES_SKIP_RELEASE_VALIDATION to skip trying to validate the
+#      Kubernetes release string. This implies that you know what you're doing
+#      and have set KUBERNETES_RELEASE and KUBERNETES_RELEASE_URL properly.
 
 set -o errexit
 set -o nounset
@@ -179,13 +182,15 @@ release=${KUBERNETES_RELEASE:-"release/stable"}
 # Validate Kubernetes release version.
 # Translate a published version <bucket>/<version> (e.g. "release/stable") to version number.
 set_binary_version "${release}"
-if [[ ${KUBE_VERSION} =~ ${KUBE_CI_VERSION_REGEX} ]]; then
+if [[ -z "${KUBERNETES_SKIP_RELEASE_VALIDATION-}" ]]; then
+  if [[ ${KUBE_VERSION} =~ ${KUBE_CI_VERSION_REGEX} ]]; then
     # Override KUBERNETES_RELEASE_URL to point to the CI bucket;
     # this will be used by get-kube-binaries.sh.
     KUBERNETES_RELEASE_URL="${KUBERNETES_CI_RELEASE_URL}"
-elif ! [[ ${KUBE_VERSION} =~ ${KUBE_RELEASE_VERSION_REGEX} ]]; then
+  elif ! [[ ${KUBE_VERSION} =~ ${KUBE_RELEASE_VERSION_REGEX} ]]; then
     echo "Version doesn't match regexp" >&2
     exit 1
+  fi
 fi
 kubernetes_tar_url="${KUBERNETES_RELEASE_URL}/${KUBE_VERSION}/${file}"