feature gates keyless sql diff

go/cmd/dolt/commands/diff.go

@@ -354,6 +354,17 @@ func diffUserTables(ctx context.Context, fromRoot, toRoot *doltdb.RootValue, dAr
 
 	for _, td := range tableDeltas {
 
+		if dArgs.diffOutput == SQLDiffOutput {
+			ok, err := td.IsKeyless(ctx)
+			if err != nil {
+				return errhand.VerboseErrorFromError(err)
+			}
+			if ok {
+				// todo: implement keyless SQL diff
+				continue
+			}
+		}
+
 		if !dArgs.tableSet.Contains(td.FromName) && !dArgs.tableSet.Contains(td.ToName) {
 			continue
 		}