Add path filter

pkg/analyzer/lib/source/path_filter.dart

Index: pkg/analyzer/lib/source/path_filter.dart
diff --git a/pkg/analyzer/lib/source/path_filter.dart b/pkg/analyzer/lib/source/path_filter.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9ee0070b7d8d83bf593f17552b9bc472c65c7891
--- /dev/null
+++ b/pkg/analyzer/lib/source/path_filter.dart
@@ -0,0 +1,61 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library source.path_filter;
+
+import 'package:glob/glob.dart' as glob;
+import 'package:path/path.dart' as pos;
+
+/// Filter paths against a set of [ignorePatterns] relative to a [root]
+/// directory. Paths outside of [root] are also ignored.
+class PathFilter {
+  /// Construct a new path filter rooted at [root] with [ignorePatterns].
+  PathFilter(this.root, List<String> ignorePatterns) {
+    setIgnorePatterns(ignorePatterns);
+  }
+
+  /// Set the ignore patterns.
+  void setIgnorePatterns(List<String> ignorePatterns) {
+    _ignorePatterns.clear();
+    if (ignorePatterns != null) {
+      for (var ignorePattern in ignorePatterns) {
+        _ignorePatterns.add(new glob.Glob(ignorePattern));
+      }
+    }
+  }
+
+  /// Returns true if [path] should be ignored. A path is ignored if it is not
+  /// contained in [root] or matches one of the ignore patterns.
+  /// [path] is absolute or relative to [root].
+  bool ignored(String path) {
+    path = _canonicalize(path);
+    return !_contained(path) || _match(path);
+  }
+
+  /// Returns the absolute path of [path], relative to [root].
+  String _canonicalize(String path) => pos.normalize(pos.join(root, path));
+
+  /// Returns the relative portion of [path] from [root].
+  String _relative(String path) => pos.relative(path, from:root);
+
+  /// Returns true when [path] is contained inside [root].
+  bool _contained(String path) => path.startsWith(root);
+
+  /// Returns true if [path] matches any ignore patterns.
+  bool _match(String path) {
+    path = _relative(path);
+    for (var glob in _ignorePatterns) {
+      if (glob.matches(path)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /// Path that all ignore patterns are relative to.
+  final String root;
+
+  /// List of ignore patterns that paths are tested against.
+  final List<glob.Glob> _ignorePatterns = new List<glob.Glob>();
+}