Add script to check CAPI version alignment

This script validates that Cluster API versions are consistent across
the codebase by reading the desired version from go.mod and checking
for mismatches in Makefile, Tiltfile, and test configurations.

Documentation files (*.md) are excluded as they may contain example
output that doesn't need to be kept in sync.

Fixes #1705

Author: s04

hack/check-capi-version.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# Copyright 2025 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Bash Strict Mode: https://github.com/guettli/bash-strict-mode
+trap 'echo -e "\n🤷 🚨 🔥 Warning: A command has failed. Exiting the script. Line was ($0:$LINENO): $(sed -n "${LINENO}p" "$0" 2>/dev/null || true) 🔥 🚨 🤷 "; exit 3' ERR
+set -Eeuo pipefail
+
+# Get the directory of the script
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+cd "${REPO_ROOT}"
+
+# Extract the desired CAPI version from go.mod
+DESIRED_VERSION=$(grep -E 'sigs.k8s.io/cluster-api v' go.mod | grep -v '/test' | awk '{print $2}')
+
+if [[ -z "${DESIRED_VERSION}" ]]; then
+    echo "❌ Could not find cluster-api version in go.mod"
+    exit 1
+fi
+
+echo "✓ Desired CAPI version from go.mod: ${DESIRED_VERSION}"
+echo ""
+
+# Find all non-documentation files with cluster-api/clusterctl version mismatches
+# Docs are excluded as they can contain example output that doesn't need to be in sync
+if git ls-files | grep -v vendor | grep -v '\.md$' | xargs grep -nH -E '(cluster-api|clusterctl|capi_version)' 2>/dev/null | grep -E 'v1\.[0-9]+\.[0-9]+' | grep -v "${DESIRED_VERSION}"; then
+    echo ""
+    echo "❌ Version mismatches found! Expected: ${DESIRED_VERSION}"
+    echo "Please update the mismatched files to use the version from go.mod"
+    exit 1
+fi
+
+echo "✅ All CAPI versions are in sync with go.mod (${DESIRED_VERSION})"