ci: automatically build GCP CCM container

Signed-off-by: Paul Meyer <49727155+katexochen@users.noreply.github.com>

.github/actions/gcpccm_vers_to_build/action.yml

@@ -0,0 +1,24 @@
+name: Find GCP CCM versions that need to be build
+description: Find GCP CCM versions that need to be build
+
+inputs:
+  path:
+    description: "Path to the GCP CCM repository"
+    required: true
+
+outputs:
+  versions:
+    description: "Versions that need to be build"
+    value: ${{ steps.find-versions.outputs.versions }}
+
+runs:
+  using: "composite"
+  steps:
+    - name: Find versions that need to be build
+      id: find-versions
+      shell: bash
+      run: |
+        script=$(realpath .github/actions/gcpccm_vers_to_build/findvers.sh)
+        pushd "${{ inputs.path }}"
+        versions=$(${script})
+        echo "versions=${versions}" | tee -a "$GITHUB_OUTPUT"

.github/actions/gcpccm_vers_to_build/findvers.sh

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+function info() {
+  echo "$@" 1>&2
+}
+
+function error() {
+  echo "::err::$*"
+  exit 1
+}
+
+allCCMVersions=$(git tag | grep ccm || test $? = 1)
+if [[ -z ${allCCMVersions} ]]; then
+  error "No CCM tags found in git"
+fi
+
+allMajorVersions=()
+
+for ver in ${allCCMVersions}; do
+  major=${ver#ccm/v} # remove "ccm/v" prefix
+  major=${major%%.*} # remove everything after the first dot
+
+  if [[ ${major} -eq 0 ]]; then
+    continue # skip major version 0
+  fi
+
+  # Check if this major version is already in the list.
+  for existingMajor in "${allMajorVersions[@]}"; do
+    if [[ ${existingMajor} -eq ${major} ]]; then
+      continue 2
+    fi
+  done
+
+  info "Found major version ${major}"
+  allMajorVersions+=("${major}")
+done
+
+if [[ ${#allMajorVersions[@]} -eq 0 ]]; then
+  error "No major versions found in CCM tags"
+fi
+
+existingContainerVersions=$(crane ls "ghcr.io/edgelesssys/cloud-provider-gcp")
+if [[ -z ${existingContainerVersions} ]]; then
+  info "No existing container versions found"
+fi
+
+versionsToBuild=()
+
+for major in "${allMajorVersions[@]}"; do
+  # Get the latest released version with this major version.
+  latest=$(echo "${allCCMVersions[@]}" | grep "${major}" | sort -V | tail -n 1)
+  latest=${latest#ccm/} # remove "ccm/" prefix, keep v
+  if [[ -z ${latest} ]]; then
+    error "Could not determine latest version with major ${major}"
+  fi
+  info "Latest ${major} version is ${latest}"
+
+  # Find the latest version with this major version.
+  majorVerRegexp="v${major}.[0-9]+.[0-9]+"
+  allExistingWithMajor=$(grep -E "${majorVerRegexp}" <<< "${existingContainerVersions}" || test $? = 1)
+  latestExistingWithMinor=$(echo "${allExistingWithMajor}" | sort -V | tail -n 1)
+
+  # If there is no existing version with this major version, build the latest released version.
+  if [[ -z ${latestExistingWithMinor} ]]; then
+    info "No existing version with major ${major}, adding ${latest} to versionsToBuild"
+    versionsToBuild+=("${latest}")
+    continue
+  fi
+  info "Latest existing version with major ${major} is ${latestExistingWithMinor}"
+
+  newerVer=$(echo -e "${latest}\n${latestExistingWithMinor}" | sort -V | tail -n 1)
+  if [[ ${newerVer} == "${latestExistingWithMinor}" ]]; then
+    info "Existing version ${latestExistingWithMinor} is up to date, skipping"
+    continue
+  fi
+
+  info "Newer version ${latest} is available, existing version is ${latestExistingWithMinor}."
+  info "Adding ${latest} to versionsToBuild"
+  versionsToBuild+=("${latest}")
+done
+
+printf '%s\n' "${versionsToBuild[@]}" | jq -R | jq -sc