verify-file-sizes.sh: ensure that no large binary files get added

We recently had an accident were a 64MB executable got included in a PR and
wasn't caught during the manual review. This new verify script would have
caught that file.

The maximum file size is 10MB. This is intentionally low. If some legitimate
file needs to be added that is larger, then an entry in a .ignorefilesize file
in the directory of the large file can exclude that file from the check.

hack/verify-file-sizes.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# Copyright 2023 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.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
+source "${KUBE_ROOT}/hack/lib/init.sh"
+cd "${KUBE_ROOT}"
+
+# Files larger than 1MB need to be allowed explicitly.
+maxsize=$((1 * 1024 * 1024))
+
+# Sorted list of those exceptions.
+allowlist=(
+    staging/src/k8s.io/kubectl/images/kubectl-logo-full.png
+)
+
+
+# Files larger than 1MB get reported and verification fails, unless the file is
+# allowed to be larger. Any output or a non-zero exit status indicate a
+# failure.
+largefiles () {
+    # --eol adds information that allows detecting binary files:
+    #    i/-text w/-text attr/text=auto eol=lf 	test/images/sample-device-plugin/sampledeviceplugin
+    #
+    # shellcheck disable=SC2034 # Some variables unused and only present to capture the output field.
+    git ls-files -cm --exclude-standard ':!:vendor/*' --eol | while read -r index tree attr eol file; do
+        case "$tree" in
+            w/-text)
+                # Only binary files have a size limit.
+                size="$(stat --printf=%s "$file")"
+                if [ "${size}" -gt "$maxsize" ] &&
+                       ! kube::util::array_contains "$file" "${allowlist[@]}"; then
+                    echo    "$file is too large ($size bytes)"
+                fi
+                ;;
+            w/|w/lf|w/crlf|w/mixed|w/none)
+                # Other files are okay.
+                ;;
+            *)
+                echo "unexpected 'git ls-files --eol' output for $file: $tree"
+                ;;
+        esac
+    done
+}
+
+if ! result="$(largefiles 2>&1)" || [ "${result}" != "" ]; then
+    # Help "make verify" and Prow identify the failure message through the "ERROR" prefix.
+    sed -e 's/^/ERROR: /' <<EOF
+$result
+
+Large binary files should not be committed to git. Exceptions need to be listed in
+${BASH_SOURCE[0]}.
+EOF
+    exit 1
+fi