Add FileSystemEntity.identical, to test if two file system objects are the same.

sdk/lib/io/file_system_entity.dart

Index: sdk/lib/io/file_system_entity.dart
diff --git a/sdk/lib/io/file_system_entity.dart b/sdk/lib/io/file_system_entity.dart
index e13477b1c41e5b6c11e732e01977ccaa47d985b9..8bbba182abc70e3dd1356bdaa294e3eeb9a60a00 100644
--- a/sdk/lib/io/file_system_entity.dart
+++ b/sdk/lib/io/file_system_entity.dart
@@ -35,6 +35,7 @@ abstract class FileSystemEntity {
   String get path;
 
   external static int _getType(String path, bool followLinks);
+  external static bool _identical(String file1, String file2);
 
   static int _getTypeSync(String path, bool followLinks) {
     var result = _getType(path, followLinks);
@@ -42,6 +43,12 @@ abstract class FileSystemEntity {
     return result;
   }
 

[Søren Gjesse, 2013/03/20 07:49:45]

I think we need a doc comment here explaining exactly what identical means. How
it deals with links and that it works for both files and directories. Should
there be a followLink optional argument here as well?

+  static bool identicalSync(String file1, String file2) {

[Søren Gjesse, 2013/03/20 07:49:45]

path1 and path2?

+    var result = _identical(file1, file2);
+    _throwIfError(result, 'Error in FileSystemEntity.identical');
+    return result;
+  }
+
   static FileSystemEntityType typeSync(String path, {bool followLinks: true})
       => FileSystemEntityType._lookup(_getTypeSync(path, followLinks));
 
@@ -57,6 +64,8 @@ abstract class FileSystemEntity {
   static _throwIfError(Object result, String msg) {
     if (result is OSError) {
       throw new FileIOException(msg, result);
+    } else if (result is ArgumentError) {
+      throw result;
     }
   }
 }