lib: use some memoization for branding templating

This allievates the use of `glob.sync()`.

lib/template.js

@@ -14,11 +14,12 @@ module.exports = function(base, substitutions) {
   var onlyFor = _.map(glob.sync(path.resolve(base, '*.html')),
                       function(p) { return path.relative(base, p); });
   onlyFor = onlyFor.concat(_.map(onlyFor, function(p) { return p.slice(0, p.length - 5); }));
+  var cache = {};
 
   return function(req, res, next) {
     // Handle only GET/HEAD files
     if ((req.method !== 'GET' && req.method !== 'HEAD') ||
-        (onlyFor || []).indexOf(req.path.slice(1)) === -1) {
+        req.path.slice(1) in (onlyFor || []) === -1) {
       return next();
     }
     var write = res.write;
@@ -27,6 +28,10 @@ module.exports = function(base, substitutions) {
       _.each(substitutions, function(value, key) {
         var regex = new RegExp('"([^"]*)\\.\\.' + key.toUpperCase() + '\\.\\.([^"]*)"(\\s*)', "g");
         html = html.replace(regex, function(match, p1, p2, spaces) {
+          if (match in cache) {
+            // Do some memoization because we use glob.sync
+            return cache[match];
+          }
           var file = [p1, value, p2].join('');
           /* Is that really a file? We just check if we have a '/' */
           if (file.indexOf('/') !== -1) {
@@ -38,9 +43,9 @@ module.exports = function(base, substitutions) {
               file = path.relative(base, matches[0]);
             }
           }
-          return ['"', file, '"',
-                  new Array(spaces.length - file.length +
-                            p1.length + p2.length + key.length + 4 + 1).join(' ')].join('');
+          return (cache[match] = ['"', file, '"',
+                                  new Array(spaces.length - file.length +
+                                            p1.length + p2.length + key.length + 4 + 1).join(' ')].join(''));
         });
       });
       return write.call(res, new Buffer(html, encoding), encoding);