Pass absolute path to git (redux).

utils/pub/io.dart

Index: utils/pub/io.dart
diff --git a/utils/pub/io.dart b/utils/pub/io.dart
index cccedfc17b93098bafde5f6847aaa8d9023ba6a5..212a30e85f2fa5e85667f88fbc0ee708f25a49a5 100644
--- a/utils/pub/io.dart
+++ b/utils/pub/io.dart
@@ -373,12 +373,18 @@ Future<File> createPackageSymlink(String name, from, to,
   });
 }
 
-/**
- * Given [entry] which may be a [String], [File], or [Directory] relative to
- * the current working directory, returns its full canonicalized path.
- */
-// TODO(rnystrom): Should this be async?
-String getFullPath(entry) => new File(_getPath(entry)).fullPathSync();
+/// Given [entry] which may be a [String], [File], or [Directory] relative to
+/// the current working directory, returns its full canonicalized path.
+String getFullPath(entry) {
+  var path = new Path(_getPath(entry));
+
+  // Don't do anything if it's already absolute.
+  if (path.isAbsolute) return path.toNativePath();
+
+  // Using Path.join here instead of File().fullPathSync() because the former
+  // does not require an actual file to exist at that path.
+  return new Path.fromNative(workingDir).join(path).toNativePath();
+}
 
 // TODO(nweiz): make this configurable
 /**