hack: add default-branches-report.sh

outputs a github-flavored markdown checklist of repos per org, with
checkboxes checked if their default branch is named something other than
'master'

run with no args to target the orgs managed by the kubernetes
github-management subproject

hack/default-branches-report.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+
+# Copyright 2021 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.
+
+readonly kubernetes_orgs=(
+    kubernetes
+    kubernetes-sigs
+    kubernetes-client
+    kubernetes-csi
+)
+
+readonly gh_api_cmd=(
+    gh api
+    --field=per_page=100
+    --paginate
+    --method=GET
+)
+
+function ensure_dependencies() {
+  if ! command -f gh >/dev/null; then
+      >&2 echo "gh not found. Please install: https://cli.github.com/manual/installation"
+      exit 1
+  fi
+}
+
+function main() {
+  local orgs=("$@")
+  ensure_dependencies
+  for org in "${orgs[@]}"; do
+      echo "* ${org}"
+      "${gh_api_cmd[@]}" "/orgs/${org}/repos" \
+          --field=sort=full_name \
+          --template \
+          '{{range .}}  * [{{if eq .default_branch "master"}} {{else}}X{{end}}] [{{.full_name}}]({{.html_url}}) {{"\n"}}{{end}}'
+  done
+  echo
+  echo "Manual inspection required if you want to link issues that tracked default branch name migration"
+}
+
+args=("${@:1}")
+if [ ${#args[@]} -eq 0 ]; then 
+  args=("${kubernetes_orgs[@]}")
+fi
+
+main "${args[@]}"