Split installing a package locally from symlinking to it.

sdk/lib/_internal/pub/lib/src/source/path.dart

Index: sdk/lib/_internal/pub/lib/src/source/path.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source/path.dart b/sdk/lib/_internal/pub/lib/src/source/path.dart
index 4a92d770b7485159d8a00b082a32ba8089dcee37..808742ba5e558df836ebe4987e65d628d0d1c909 100644
--- a/sdk/lib/_internal/pub/lib/src/source/path.dart
+++ b/sdk/lib/_internal/pub/lib/src/source/path.dart
@@ -33,12 +33,13 @@ class PathSource extends Source {
     return path1 == path2;
   }
 
-  /// Create a symlink from the source path directly to the destination
-  /// directory.
-  Future get(PackageId id, String destination) {
+  /// Path dependencies are already local.
+  Future ensureLocal(PackageId id) => new Future.value();
+
+  Future get(PackageId id, String symlink) {
     return syncFuture(() {
       var dir = _validatePath(id.name, id.description);
-      createPackageSymlink(id.name, dir, destination,
+      createPackageSymlink(id.name, dir, symlink,
           relative: id.description["relative"]);
     });
   }