Respect git's ignore rules pervasively in pub.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index 0ec5e46286bcedbe52368558ac49653d55e56519..b96afdf0d8ce54bf523a1c69d5b824000dfeef89 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -329,6 +329,34 @@ Future<Map> mapMapAsync(Map map, {key(key, value), value(key, value)}) {
       value: (mapKey) => value(mapKey, map[mapKey]));
 }
 
+/// Given a list of filenames, returns a set of patterns that can be used to
+/// filter for those filenames.
+///
+/// For a given path, that path ends with some string in the returned set if
+/// and only if that path's basename is in [files].
+Set<String> createFileFilter(Iterable<String> files) {
+  return files.expand((file) {
+    var result = ["/$file"];
+    if (Platform.operatingSystem == 'windows') result.add("\\$file");
+    return result;
+  }).toSet();
+}
+
+/// Given a blacklist of directory names, returns a set of patterns that can
+/// be used to filter for those directory names.
+///
+/// For a given path, that path contains some string in the returned set if
+/// and only if one of that path's components is in [dirs].
+Set<String> createDirectoryFilter(Iterable<String> dirs) {
+  return dirs.expand((dir) {
+    var result = ["/$dir/"];
+    if (Platform.operatingSystem == 'windows') {
+      result..add("/$dir\\")..add("\\$dir/")..add("\\$dir\\");
+    }
+    return result;
+  }).toSet();
+}
+
 /// Returns the shortest path from [start] to [end] in [graph].
 ///
 /// The graph is represented by a map where each key is a vertex and the value