feat: add new ElectronSquirrelPreventDowngrades flag (#38625)

* sketch

* feat: add new ElectronSquirrelPreventDowngrades flag

* test: remove only

* chore: fix lint

spec/fixtures/auto-update/update-stack/index.js

@@ -0,0 +1,57 @@
+const fs = require('node:fs');
+const path = require('node:path');
+
+process.on('uncaughtException', (err) => {
+  console.error(err);
+  process.exit(1);
+});
+
+const { app, autoUpdater } = require('electron');
+
+autoUpdater.on('error', (err) => {
+  console.error(err);
+  process.exit(1);
+});
+
+const urlPath = path.resolve(__dirname, '../../../../url.txt');
+let feedUrl = process.argv[1];
+
+if (feedUrl === 'remain-open') {
+  // Hold the event loop
+  setInterval(() => {});
+} else {
+  if (!feedUrl || !feedUrl.startsWith('http')) {
+    feedUrl = `${fs.readFileSync(urlPath, 'utf8')}/${app.getVersion()}`;
+  } else {
+    fs.writeFileSync(urlPath, `${feedUrl}/updated`);
+  }
+
+  autoUpdater.setFeedURL({
+    url: feedUrl
+  });
+
+  autoUpdater.checkForUpdates();
+
+  autoUpdater.on('update-available', () => {
+    console.log('Update Available');
+  });
+
+  let updateStackCount = 0;
+
+  autoUpdater.on('update-downloaded', () => {
+    updateStackCount++;
+    console.log('Update Downloaded');
+    if (updateStackCount > 1) {
+      autoUpdater.quitAndInstall();
+    } else {
+      setTimeout(() => {
+        autoUpdater.checkForUpdates();
+      }, 1000);
+    }
+  });
+
+  autoUpdater.on('update-not-available', () => {
+    console.error('No update available');
+    process.exit(1);
+  });
+}

spec/fixtures/auto-update/update-stack/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "electron-test-update-stack",
+  "version": "1.0.0",
+  "main": "./index.js"
+}