enhance: keep navigation state after switch view mode in text diff view (#1952)

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/ViewModels/DiffContext.cs

@@ -273,9 +273,9 @@ private void LoadContent()
                         IsTextDiff = true;
 
                         if (Preferences.Instance.UseSideBySideDiff)
-                            Content = new TwoSideTextDiff(_option, cur, _content as TwoSideTextDiff);
+                            Content = new TwoSideTextDiff(_option, cur, _content as TextDiffContext);
                         else
-                            Content = new CombinedTextDiff(_option, cur, _content as CombinedTextDiff);
+                            Content = new CombinedTextDiff(_option, cur, _content as TextDiffContext);
                     }
                     else
                     {

src/ViewModels/TextDiffContext.cs

@@ -167,7 +167,7 @@ protected void TryKeepPrevState(TextDiffContext prev, List<Models.TextDiffLine>
 
     public class CombinedTextDiff : TextDiffContext
     {
-        public CombinedTextDiff(Models.DiffOption option, Models.TextDiff diff, CombinedTextDiff previous = null)
+        public CombinedTextDiff(Models.DiffOption option, Models.TextDiff diff, TextDiffContext previous = null)
         {
             _option = option;
             _data = diff;
@@ -177,7 +177,7 @@ public CombinedTextDiff(Models.DiffOption option, Models.TextDiff diff, Combined
 
         public override TextDiffContext SwitchMode()
         {
-            return new TwoSideTextDiff(_option, _data);
+            return new TwoSideTextDiff(_option, _data, this);
         }
     }
 
@@ -186,7 +186,7 @@ public class TwoSideTextDiff : TextDiffContext
         public List<Models.TextDiffLine> Old { get; } = [];
         public List<Models.TextDiffLine> New { get; } = [];
 
-        public TwoSideTextDiff(Models.DiffOption option, Models.TextDiff diff, TwoSideTextDiff previous = null)
+        public TwoSideTextDiff(Models.DiffOption option, Models.TextDiff diff, TextDiffContext previous = null)
         {
             _option = option;
             _data = diff;
@@ -220,7 +220,7 @@ public override bool IsSideBySide()
 
         public override TextDiffContext SwitchMode()
         {
-            return new CombinedTextDiff(_option, _data);
+            return new CombinedTextDiff(_option, _data, this);
         }
 
         public void ConvertsToCombinedRange(ref int startLine, ref int endLine, bool isOldSide)