Improves performance of glob exclusions by avoiding extra glob IO

- IO is not necessary for exclusions because they exclude file paths that have already been discovered.  Using `file.match` / `minimatch` is sufficient.
- adds optional `excludeFn` callback to `processPatterns`. If provided, it will be called instead of `fn` for exclusion patterns.

lib/grunt/file.js

@@ -38,7 +38,8 @@ file.setBase = function() {
 
 // Process specified wildcard glob patterns or filenames against a
 // callback, excluding and uniquing files in the result set.
-var processPatterns = function(patterns, fn) {
+var processPatterns = function(patterns, fn, exclusionFn) {
+ if (typeof exclusionFn === 'undefined') { exclusionFn = fn; }
  // Filepaths to return.
  var result = [];
  // Iterate over flattened patterns array.
@@ -48,7 +49,7 @@ var processPatterns = function(patterns, fn) {
  // If the pattern is an exclusion, remove the !
  if (exclusion) { pattern = pattern.slice(1); }
  // Find all matching files for this pattern.
- var matches = fn(pattern);
+ var matches = (exclusion ? exclusionFn : fn)(pattern, result);
  if (exclusion) {
  // If an exclusion, remove matching files.
  result = grunt.util._.difference(result, matches);
@@ -104,6 +105,8 @@ file.expand = function() {
  var matches = processPatterns(patterns, function(pattern) {
  // Find all matching files for this pattern.
  return file.glob.sync(pattern, globOptions);
+ }, function(pattern, resultsThusFar) {
+ return file.match(options, [pattern], resultsThusFar);
  });
  // Filter result set?
  if (options.filter) {