Add InternalStyle:rootLength to implement isAbsolute and rootPrefix.

pkg/path/lib/src/style/posix.dart

Index: pkg/path/lib/src/style/posix.dart
diff --git a/pkg/path/lib/src/style/posix.dart b/pkg/path/lib/src/style/posix.dart
index b8b82b406d33f31a08d5c4a05c67b86dbdbc4b2f..30278245400909ce685b18e2ccc60c16b3fa3c76 100644
--- a/pkg/path/lib/src/style/posix.dart
+++ b/pkg/path/lib/src/style/posix.dart
@@ -30,8 +30,14 @@ class PosixStyle extends InternalStyle {
   bool needsSeparator(String path) =>
       path.isNotEmpty && !isSeparator(path.codeUnitAt(path.length - 1));
 
+  int rootLength(String path) {
+    if (path.isNotEmpty && isSeparator(path.codeUnitAt(0))) return 1;
+    return 0;
+  }
+
   String getRoot(String path) {
-    if (path.isNotEmpty && isSeparator(path.codeUnitAt(0))) return '/';
+    int length = rootLength(path);

[Bob Nystrom, 2014/08/04 17:17:32]

int -> var, here and elsewhere. We don't type annotate locals in path (and in
most other packages for that matter).

[Anders Johnsen, 2014/08/05 08:57:13]

Done.

+    if (length > 0) return path.substring(0, length);
     return null;
   }