Build: Fix copying top-level demos files

* Build: Remove dead code, make the `external` variable local

1. Remove the `externalDir` variable that was computed but not used.
2. Remove the local unused `globalize` variable.
3. Declare the local `external` variable - previously, build code was
   overwriting the `external` global.

* Build: Fix copying top-level demos files

The logic to copy files from demos was faulty for top-level files - it was
copying them to the `undefined` subdirectory. This is now fixed.

Also, dot-files are no longer copied; we don't need the ESLint config copied,
for example.

Closes gh-216
Ref jquery/jquery-ui#2274

Gruntfile.js

@@ -105,7 +105,7 @@ grunt.registerTask( "build-demos", function() {
  return a.title.toLowerCase() > b.title.toLowerCase() ? 1 : -1;
  }
 
- var demosDir, externalDir, jqueryCore, repoDir, pkg, subdir,
+ var demosDir, jqueryCore, repoDir, pkg, subdir,
  path = require( "path" ),
  cheerio = require( "cheerio" ),
  targetDir = grunt.config( "wordpress.dir" ) + "/resources/demos",
@@ -123,21 +123,24 @@ grunt.registerTask( "build-demos", function() {
  repoDir = path.resolve( repoDir );
 
  demosDir = path.join( repoDir, "demos" );
- externalDir = path.join( repoDir, "external" ).replace( process.cwd() + "/", "" );
  pkg = require( path.join( repoDir, "package" ) );
  jqueryCore = fs.readFileSync( path.join( repoDir, "external/jquery/jquery.js" ) )
  .toString().match( /jQuery JavaScript Library v([0-9.]*)/ )[ 1 ];
 
  // Copy all demos files to /resources/demos
  grunt.file.recurse( demosDir, function( abspath, rootdir, subdir, filename ) {
+ if ( filename.startsWith( "." ) ) {
+ return;
+ }
+
  if ( filename === "index.html" ) {
  return;
  }
 
  var content, $,
- destDir = targetDir + "/" + subdir + "/",
+ destDir = `${ targetDir }${ subdir ? `/${ subdir }` : "" }/`,
  dest = destDir + filename,
- highlightDest = highlightDir + "/" + subdir + "/" + filename;
+ highlightDest = `${ highlightDir }${ subdir ? `/${ subdir }` : "" }/${ filename }`;
 
  if ( /html$/.test( filename ) ) {
  content = replaceResources( grunt.file.read( abspath ) );
@@ -180,7 +183,7 @@ grunt.registerTask( "build-demos", function() {
  grunt.file.write( targetDir + "/demo-list.json", JSON.stringify( demoList, null, "\t" ) );
 
  function deAmd( $, destDir ) {
- var i18n, globalize,
+ var i18n, external,
  bootstrap = $( "script[src='../bootstrap.js']" ),
  require = $( "script[src='../../external/requirejs/require.js']" ),
  extra = bootstrap.attr( "data-modules" );