Add a build task which bumps package.json and LKG together to a nightly

Herebyfile.mjs

@@ -6,6 +6,7 @@ import { task } from "hereby";
 import _glob from "glob";
 import util from "util";
 import chalk from "chalk";
+import fsExtra from "fs-extra";
 import { Debouncer, Deferred, exec, getDiffTool, getDirSize, memoize, needsUpdate, readJson } from "./scripts/build/utils.mjs";
 import { localBaseline, localRwcBaseline, refBaseline, refRwcBaseline, runConsoleTests } from "./scripts/build/tests.mjs";
 import { buildProject, cleanProject, watchProject } from "./scripts/build/projects.mjs";
@@ -854,3 +855,14 @@ export const help = task({
     hiddenFromTaskList: true,
     run: () => exec("hereby", ["--tasks"], { hidePrompt: true }),
 });
+
+export const bumpLkgToNightly = task({
+    name: "bump-lkg-to-nightly",
+    description: "Bumps typescript in package.json to the latest nightly and copies it to LKG.",
+    run: async () => {
+        await exec("npm", ["install", "--save-dev", "--save-exact", "typescript@next"]);
+        await fs.promises.rm("lib", { recursive: true, force: true });
+        await fsExtra.copy("node_modules/typescript/lib", "lib");
+        await fs.promises.writeFile("lib/.gitattributes", "* text eol=lf");
+    }
+});