cloudbuild: limit image release tags to semver only

When doing cloudbuilds for tagged releases, limit images to only a
single tag that represents the semver tag.

The registry.k8s.io tooling uses scripts to coordinate which images and
tags are promoted from staging to release. The script don't handle image
digests with multiple tags, and COSI can assume less release breakage by
not relying on more advanced handling.

When the cloudbuild script detects a release is happening, it will now
apply only the semver tag to the image.

Signed-off-by: Blaine Gardner <[email protected]>

Author: BlaineEXE

hack/cloudbuild.sh

@@ -48,32 +48,42 @@ fi
 if [[ "${PULL_BASE_REF}" == controller/* ]]; then
   echo " ! ! ! this is a tagged controller release ! ! !"
   TAG="${PULL_BASE_REF#controller/*}"
-  ADDITIONAL_CONTROLLER_TAGS+=("${CONTROLLER_IMAGE}:${TAG}")
+  # when tagging a release image, do not apply any other tags other than the release tag
+  # the registry.k8s.io scripting does not handle images with multiple tags
+  ADDITIONAL_CONTROLLER_TAGS=()
+  CONTROLLER_TAG="${CONTROLLER_IMAGE}:${TAG}"
 fi
 
 # PULL_BASE_REF is 'sidecar/TAG' for a tagged sidecar release
 if [[ "${PULL_BASE_REF}" == sidecar/* ]]; then
   echo " ! ! ! this is a tagged sidecar release ! ! !"
   TAG="${PULL_BASE_REF#sidecar/*}"
-  ADDITIONAL_SIDECAR_TAGS+=("${SIDECAR_IMAGE}:${TAG}")
+  # when tagging a release image, do not apply any other tags other than the release tag
+  # the registry.k8s.io scripting does not handle images with multiple tags
+  ADDITIONAL_SIDECAR_TAGS=()
+  SIDECAR_TAG="${SIDECAR_IMAGE}:${TAG}"
 fi
 
 # PULL_BASE_REF is 'v0.y.z*' for tagged alpha releases where controller and sidecar are released simultaneously
 # hand wave over complex matching logic by just looking for 'v0.' prefix
 if [[ "${PULL_BASE_REF}" == 'v0.'* ]]; then
   echo " ! ! ! this is a tagged controller + sidecar release ! ! !"
   TAG="${PULL_BASE_REF}"
-  ADDITIONAL_CONTROLLER_TAGS+=("${CONTROLLER_IMAGE}:${TAG}")
-  ADDITIONAL_SIDECAR_TAGS+=("${SIDECAR_IMAGE}:${TAG}")
+  # when tagging a release image, do not apply any other tags other than the release tag
+  # the registry.k8s.io scripting does not handle images with multiple tags
+  ADDITIONAL_CONTROLLER_TAGS=()
+  ADDITIONAL_SIDECAR_TAGS=()
+  CONTROLLER_TAG="${CONTROLLER_IMAGE}:${TAG}"
+  SIDECAR_TAG="${SIDECAR_IMAGE}:${TAG}"
 fi
 
 # else, PULL_BASE_REF is something that doesn't release image(s) to staging, like:
 #  - a random branch name (e.g., feature-xyz)
 #  - a version tag for a subdir with no image associated (e.g., client/v0.2.0, proto/v0.2.0)
 
-# 'gcloud container images add-tag' within the cloudbuild infrastructure doesn't preserve the date
-# of the underlying image when adding a new tag, resulting in tags dated Dec 31, 1969 (the epoch).
-# To ensure the right date on all built image tags, do the build with '--tag' args for all tags.
+# This script's tagging should be less error-prone if 'docker buildx' has all the tags that an image
+#  will be tagged with during the build process. All tags are applied at once without need to
+# maintain tooling for adding tags to manifests after build.
 
 BUILD_ARGS="${ADDITIONAL_BUILD_ARGS}"
 for tag in "${ADDITIONAL_CONTROLLER_TAGS[@]}"; do