feat(tiller): re-use values during upgrade

When `helm install -f foo.yaml bar` is called, and then the release is
upgraded with `helm upgrade happy-panda bar`, this will now re-use the
values that were submitted with `-f foo.yaml`. The same is true for
values specified with `--set`.

Closes #1227

cmd/tiller/release_server.go

@@ -341,6 +341,12 @@ func (s *releaseServer) prepareUpdate(req *services.UpdateReleaseRequest) (*rele
 		return nil, nil, err
 	}
 
+	// If new values were not supplied in the upgrade, re-use the existing values.
+	if (req.Values == nil || req.Values.Raw == "") && currentRelease.Config != nil && currentRelease.Config.Raw != "" {
+		log.Printf("Copying values from %s (v%d) to new release.", currentRelease.Name, currentRelease.Version)
+		req.Values = currentRelease.Config
+	}
+
 	ts := timeconv.Now()
 	options := chartutil.ReleaseOptions{
 		Name:      req.Name,

cmd/tiller/release_server_test.go

@@ -110,7 +110,7 @@ func namedReleaseStub(name string, status release.Status_Code) *release.Release
 			Status:        &release.Status{Code: status},
 		},
 		Chart:   chartStub(),
-		Config:  &chart.Config{Raw: `name = "value"`},
+		Config:  &chart.Config{Raw: `name: value`},
 		Version: 1,
 		Hooks: []*release.Hook{
 			{
@@ -568,6 +568,12 @@ func TestUpdateRelease(t *testing.T) {
 		t.Errorf("No manifest returned: %v", res.Release)
 	}
 
+	if res.Release.Config == nil {
+		t.Errorf("Got release without config: %#v", res.Release)
+	} else if res.Release.Config.Raw != rel.Config.Raw {
+		t.Errorf("Expected release values %q, got %q", rel.Config.Raw, res.Release.Config.Raw)
+	}
+
 	if len(updated.Manifest) == 0 {
 		t.Errorf("Expected manifest in %v", res)
 	}