chanbackup: add SCB support for new anchor commitments

chanbackup/single_test.go

@@ -229,12 +229,20 @@ func TestSinglePackUnpack(t *testing.T) {
 			valid:   true,
 		},
 
-		// The new tweakless version, should pack/unpack with no problem.
+		// The new tweakless version, should pack/unpack with no
+		// problem.
 		{
 			version: TweaklessCommitVersion,
 			valid:   true,
 		},
 
+		// The new anchor version, should pack/unpack with no
+		// problem.
+		{
+			version: AnchorsCommitVersion,
+			valid:   true,
+		},
+
 		// A non-default version, atm this should result in a failure.
 		{
 			version: 99,