CLI: resolve parent/subcommand option collisions (#18725)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: b7e51cf90950cdd3049ac3c7a3a949717b8ba261
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/cli/command-options.ts

@@ -6,3 +6,39 @@ export function hasExplicitOptions(command: Command, names: readonly string[]):
   }
   return names.some((name) => command.getOptionValueSource(name) === "cli");
 }
+
+function getOptionSource(command: Command, name: string): string | undefined {
+  if (typeof command.getOptionValueSource !== "function") {
+    return undefined;
+  }
+  return command.getOptionValueSource(name);
+}
+
+// Defensive guardrail: allow expected parent/grandparent inheritance without unbounded deep traversal.
+const MAX_INHERIT_DEPTH = 2;
+
+export function inheritOptionFromParent<T = unknown>(
+  command: Command | undefined,
+  name: string,
+): T | undefined {
+  if (!command) {
+    return undefined;
+  }
+
+  const childSource = getOptionSource(command, name);
+  if (childSource && childSource !== "default") {
+    return undefined;
+  }
+
+  let depth = 0;
+  let ancestor = command.parent;
+  while (ancestor && depth < MAX_INHERIT_DEPTH) {
+    const source = getOptionSource(ancestor, name);
+    if (source && source !== "default") {
+      return ancestor.opts<Record<string, unknown>>()[name] as T | undefined;
+    }
+    depth += 1;
+    ancestor = ancestor.parent;
+  }
+  return undefined;
+}