Restruct the browserlist:update to the latest dist tag on trunk

Gruntfile.js

@@ -3,6 +3,7 @@
 /* globals Set */
 var webpackConfig = require( './webpack.config' );
 var installChanged = require( 'install-changed' );
+const { spawnSync: spawn } = require( "child_process" );
 
 module.exports = function(grunt) {
 	var path = require('path'),
@@ -1219,22 +1220,24 @@ module.exports = function(grunt) {
 	] );
 
 	grunt.registerTask( 'sync-gutenberg-packages', function() {
-		if ( grunt.option( 'update-browserlist' ) ) {
-			/*
-			 * Updating the browserlist database is opt-in and up to the release lead.
-			 *
-			 * Browserlist database should be updated:
-			 * - In each release cycle up until RC1
-			 * - If Webpack throws a warning about an outdated database
-			 *
-			 * It should not be updated:
-			 * - After the RC1
-			 * - When backporting fixes to older WordPress releases.
-			 *
-			 * For more context, see:
-			 * https://github.com/WordPress/wordpress-develop/pull/2621#discussion_r859840515
-			 * https://core.trac.wordpress.org/ticket/55559
-			 */
+		/*
+		 * Browserlist database should be updated when the packages are
+		 * being updated to their latest version in the trunk branch.
+		 *
+		 * It should not happen during the patch releases. Otherwise,
+		 * we'd be changing the supported browsers of a WP release on patch release.
+		 *
+		 * For more context, see:
+		 *
+		 * https://github.com/WordPress/gutenberg/issues/33344
+		 * https://core.trac.wordpress.org/ticket/55559
+		 */
+		const distTag = grunt.option('dist-tag') || 'latest';
+		const currentBranch = spawn( 'git', [ 'branch', '--show-current' ], {
+			cwd: __dirname,
+		} ).stdout.toString().trim();
+
+		if ( distTag === 'latest' && currentBranch === 'trunk' ) {
 			grunt.task.run( 'browserslist:update' );
 		}