Make pubspec.lock keep relative path if it is originally specified as relative in pubspec.yaml (iss…

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 9af0fd11e2320dd384e522050023134efde49613..2dfe1520c6b0ae9164ee035a3877175c1eca1338 100644
--- a/sdk/lib/_internal/pub/lib/src/source/path.dart
+++ b/sdk/lib/_internal/pub/lib/src/source/path.dart
@@ -90,7 +90,8 @@ class PathSource extends Source {
       // local file system.
       assert(containingPath != null);
 
-      description = path.join(path.dirname(containingPath), description);
+      description = path.normalize(
+          path.join(path.dirname(containingPath), description));
     }
 
     return {
@@ -99,6 +100,19 @@ class PathSource extends Source {
     };
   }
 
+  /// Serializes path dependency's [description]. For the descriptions where
+  /// `relative` attribute is `true`, tries to make `path` relative to the
+  /// specified [containingPath].
+  dynamic serializeDescription(String containingPath, description) {
+    if (description["relative"]) {
+      return {
+        "path": path.relative(description['path'], from: containingPath), 
+        "relative": true
+      };
+    }
+    return description;
+  }
+
   /// Ensures that [description] is a valid path description and returns a
   /// normalized path to the package.
   ///
@@ -106,7 +120,7 @@ class PathSource extends Source {
   /// existing directory. Throws an [ApplicationException] if the path is
   /// invalid.
   String _validatePath(String name, description) {
-    var dir = path.normalize(description["path"]);
+    var dir = description["path"];
 
     if (dirExists(dir)) return dir;