feat: add new tool

tools/doc-diff/src/io.ts

@@ -0,0 +1,19 @@
+import { readFileSync } from 'node:fs';
+import path from 'node:path';
+
+import { applyUpdate, Doc } from 'yjs';
+
+export function getDisplayLabel(inputPath: string) {
+  const resolved = path.resolve(process.cwd(), inputPath);
+  if (resolved === inputPath) {
+    return inputPath;
+  }
+  return `${inputPath} (${resolved})`;
+}
+
+export function readYjsDocFromFile(filePath: string): Doc {
+  const bin = readFileSync(filePath);
+  const doc = new Doc();
+  applyUpdate(doc, new Uint8Array(bin));
+  return doc;
+}