Support root-relative paths on Windows.

pkg/path/lib/path.dart

Index: pkg/path/lib/path.dart
diff --git a/pkg/path/lib/path.dart b/pkg/path/lib/path.dart
index 3c5f51eb3ea967285dfa8aee4586088c21e8a588..07bded709d6a36558fc8e7595ae34f7013c89b54 100644
--- a/pkg/path/lib/path.dart
+++ b/pkg/path/lib/path.dart
@@ -560,10 +560,13 @@ class Builder {
       if (this.isRootRelative(part) && isAbsoluteAndNotRootRelative) {
         // If the new part is root-relative, it preserves the previous root but
         // replaces the path after it.
-        var oldRoot = this.rootPrefix(buffer.toString());
+        var parsed = _parse(part);
+        parsed.root = this.rootPrefix(buffer.toString());
+        if (parsed.root.contains(style.needsSeparatorPattern)) {
+          parsed.separators[0] = style.separator;
+        }
         buffer.clear();
-        buffer.write(oldRoot);
-        buffer.write(part);
+        buffer.write(parsed.toString());

[Bob Nystrom, 2013/11/14 17:05:08]

The toString() isn't needed here.

[nweiz, 2013/11/14 21:10:17]

Done.

       } else if (this.isAbsolute(part)) {
         isAbsoluteAndNotRootRelative = !this.isRootRelative(part);
         // An absolute path discards everything before it.
@@ -982,6 +985,7 @@ class _WindowsStyle extends Style {
   final separatorPattern = new RegExp(r'[/\\]');
   final needsSeparatorPattern = new RegExp(r'[^/\\]$');
   final rootPattern = new RegExp(r'^(\\\\[^\\]+\\[^\\/]+|[a-zA-Z]:[/\\])');
+  final relativeRootPattern = new RegExp(r"^[/\\](?![/\\])");

[Bob Nystrom, 2013/11/14 17:05:08]

Doc comment for this please. Regexen are opaque.

[nweiz, 2013/11/14 21:10:17]

Done.

 
   String pathFromUri(Uri uri) {
     if (uri.scheme != '' && uri.scheme != 'file') {