Use a consistent build id between bazel/kubeadm pull jobs.

Since the kubeadm e2e job uses the CI artifacts pushed by the bazel job,
make sure we use a consistent id for their storage (the Kubernetes
version isn't stable for pull jobs since each job pulls and applies the
PR at different times, resulting in different commit SHAs).

jobs/pull-kubernetes-bazel.sh

@@ -34,11 +34,11 @@ if [[ "${rc}" == 0 ]]; then
 fi
 
 if [[ "${rc}" == 0 ]]; then
-  version=$(cat bazel-genfiles/version || true)
-  if [[ -z "${version}" ]]; then
-    echo "Kubernetes version missing; not uploading ci artifacts."
+  if [[ -z "${PULL_NUMBER:-}" || -z "${PULL_REFS:-}" ]]; then
+    echo "\$PULL_NUMBER or \$PULL_REFS is empty; not uploading ci artifacts."
     rc=1
   else
+    version=${PULL_NUMBER:-}/${PULL_REFS:-}
     bazel run //:ci-artifacts -- "gs://kubernetes-release-dev/bazel/${version}" && rc=$? || rc=$?
   fi
 fi

jobs/pull-kubernetes-e2e-kubeadm-gce.sh

@@ -26,18 +26,17 @@ readonly testinfra="$(dirname "${0}")/.."
 
 export PROJECT="k8s-jkns-pr-kubeadm"
 export KUBERNETES_PROVIDER=kubernetes-anywhere
-
-# This job only runs against the kubernetes repo, and bootstrap.py leaves the
-# current working directory at the repository root. Grab the SCM_REVISION so we
-# can use the .debs built during the bazel-build job that should have already
-# succeeded.
-export SCM_VERSION=$(./hack/print-workspace-status.sh | grep ^STABLE_BUILD_SCM_REVISION | cut -d' ' -f2)
+# These deliberately do not use the :- syntax so that the nounset flag produces
+# succinct errors if either is unset. This job depends on the artifacts created
+# during pull-kubernetes-bazel, so these env vars must be set correctly to find
+# this pull's build artifacts.
+export VERSION=${PULL_NUMBER}/${PULL_REFS}
 
 export E2E_NAME="e2e-kubeadm-${BUILD_NUMBER:-0}"
 export E2E_OPT="--deployment kubernetes-anywhere --kubernetes-anywhere-path /workspace/kubernetes-anywhere"
 export E2E_OPT+=" --kubernetes-anywhere-phase2-provider kubeadm --kubernetes-anywhere-cluster ${E2E_NAME}"
 # The gs:// path given here should match jobs/pull-kubernetes-bazel.sh
-export E2E_OPT+=" --kubernetes-anywhere-kubeadm-version gs://kubernetes-release-dev/bazel/${SCM_VERSION}/build/debs/"
+export E2E_OPT+=" --kubernetes-anywhere-kubeadm-version gs://kubernetes-release-dev/bazel/${VERSION}/build/debs/"
 export GINKGO_TEST_ARGS="--ginkgo.focus=\[Conformance\]"
 
 # Resource leak detection is disabled because prow runs multiple instances of