Added tentacle updater.

internal/app/tentacle_install_test.go

@@ -43,7 +43,12 @@ func install_fixture(t *testing.T) (tentacle.Repository, []byte) {
 	marker := filepath.Join(t.TempDir(), "called")
 	manifest := fmt.Sprintf("format-version=1\nid='echo'\nname='Echo'\nversion='0.1'\nruntime='native'\nplatforms=['linux']\nentry-point=['bin/echo','-test.run=^TestTentacleReaderPeer$','--','reader-peer',%q]\napis=['commands']\ncapabilities=[]\n[protocol]\nmajor=1\nminor=0\n", marker)
 	var data bytes.Buffer
-	compressed := gzip.NewWriter(&data)
+	// These fixtures test package installation, not compression ratios. This
+	// also keeps repeated update fixtures cheap under the race detector.
+	compressed, err := gzip.NewWriterLevel(&data, gzip.BestSpeed)
+	if err != nil {
+		t.Fatal(err)
+	}
 	archive := tar.NewWriter(compressed)
 	for _, item := range []struct {
 		name string