Improve nested path detection across app

ts/util/isPathInside.ts

@@ -0,0 +1,16 @@
+// This is inspired by the `is-path-inside` module on npm.
+import * as path from 'path';
+
+export function isPathInside(childPath: string, parentPath: string): boolean {
+  const childPathResolved = path.resolve(childPath);
+
+  let parentPathResolved = path.resolve(parentPath);
+  if (!parentPathResolved.endsWith(path.sep)) {
+    parentPathResolved += path.sep;
+  }
+
+  return (
+    childPathResolved !== parentPathResolved &&
+    childPathResolved.startsWith(parentPathResolved)
+  );
+}