fix: fix Show.baddiff

Given a `BadVDiff` with at least one node, `Show.baddiff` uses
`VariationTree.toVariationDiff` which previously required all created
nodes to have `DiffType.NON`. However, `Show.baddiff` supplies nodes
with `DiffType.ADD` and `DiffType.REM` which triggered an assert in
`DiffNode.addChild` during the `VariationTree.toVariationDiff`
construction process.

Author: ibbem

src/main/java/org/variantsync/diffdetective/variation/diff/DiffNode.java

@@ -741,7 +741,7 @@ public static <T extends VariationNode<T, L1>, L1 extends Label, L2 extends Labe
 
         for (var variationChildNode : variationNode.getChildren()) {
             var diffChildNode = unchanged(convert, variationChildNode);
-            Time.forAll(time -> diffNode.addChild(diffChildNode, time));
+            diffChildNode.getDiffType().forAllTimesOfExistence(time -> diffNode.addChild(diffChildNode, time));
         }
 
         return diffNode;

src/test/java/ShowTest.java

@@ -0,0 +1,25 @@
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.variantsync.diffdetective.diff.result.DiffParseException;
+import org.variantsync.diffdetective.variation.DiffLinesLabel;
+import org.variantsync.diffdetective.variation.diff.VariationDiff;
+import org.variantsync.diffdetective.variation.diff.bad.BadVDiff;
+import org.variantsync.diffdetective.variation.diff.parse.VariationDiffParseOptions;
+
+import org.variantsync.diffdetective.show.Show;
+import org.variantsync.diffdetective.show.engine.GameEngine;
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+public class ShowTest {
+    @Disabled("GUI test, needs to be run manually")
+    @Test
+    public void toGood_after_fromGood_idempotency() throws IOException, DiffParseException {
+        final Path testfile = Constants.RESOURCE_DIR.resolve("badvdiff").resolve("1.diff");
+        final VariationDiff<DiffLinesLabel> vdiff = VariationDiff.fromFile(testfile, new VariationDiffParseOptions(false, false));
+        final BadVDiff<DiffLinesLabel> badDiff = BadVDiff.fromGood(vdiff);
+
+        GameEngine.showAndAwaitAll(Show.baddiff(badDiff));
+    }
+}