Prev/next will (re-)scroll to first/last change-block in edge-cases

I.e when unset or already at first/last change-block (or the only one).

Author: goran-w

src/ViewModels/DiffContext.cs

@@ -78,9 +78,15 @@ public void PrevChange()
             if (_content is Models.TextDiff textDiff)
             {
                 if (textDiff.CurrentChangeBlockIdx > 0)
+                {
                     textDiff.CurrentChangeBlockIdx--;
-                else if (textDiff.CurrentChangeBlockIdx == -1 && textDiff.ChangeBlocks.Count > 0)
-                    textDiff.CurrentChangeBlockIdx = 0; // Jump to first change block
+                }
+                else if (textDiff.ChangeBlocks.Count > 0)
+                {
+                    // Force property value change and (re-)jump to first change block
+                    textDiff.CurrentChangeBlockIdx = -1;
+                    textDiff.CurrentChangeBlockIdx = 0;
+                }
             }
         }
 
@@ -89,7 +95,15 @@ public void NextChange()
             if (_content is Models.TextDiff textDiff)
             {
                 if (textDiff.CurrentChangeBlockIdx < textDiff.ChangeBlocks.Count - 1)
+                {
                     textDiff.CurrentChangeBlockIdx++;
+                }
+                else if (textDiff.ChangeBlocks.Count > 0)
+                {
+                    // Force property value change and (re-)jump to last change block
+                    textDiff.CurrentChangeBlockIdx = -1;
+                    textDiff.CurrentChangeBlockIdx = textDiff.ChangeBlocks.Count - 1;
+                }
             }
         }