optimize<CommitGraph>: remove unused code

src/Helpers/CommitGraph.cs

@@ -140,11 +140,6 @@ namespace SourceGit.Helpers {
         /// </summary>
         public List<Dot> Dots { get; set; } = new List<Dot>();
 
-        /// <summary>
-        ///     Highlight commit id.
-        /// </summary>
-        public string Highlight { get; set; }
-
         /// <summary>
         ///     Parse commits.
         /// </summary>
@@ -168,11 +163,6 @@ namespace SourceGit.Helpers {
                 // 更新Y坐标
                 offsetY += UNIT_HEIGHT;
 
-                // 找到当前的分支的HEAD，用于默认选中
-                if (maker.Highlight == null && commit.IsHEAD) {
-                    maker.Highlight = commit.SHA;
-                }
-
                 // 找到第一个依赖于本提交的树，将其他依赖于本提交的树标记为终止，并对已存在的线路调整（防止线重合）
                 double offsetX = -HALF_WIDTH;
                 foreach (var l in unsolved) {
@@ -268,11 +258,6 @@ namespace SourceGit.Helpers {
             }
             unsolved.Clear();
 
-            // 处理默认选中异常
-            if (maker.Highlight == null && commits.Count > 0) {
-                maker.Highlight = commits[0].SHA;
-            }
-
             return maker;
         }
     }

src/UI/Histories.xaml.cs

@@ -169,7 +169,6 @@ namespace SourceGit.UI {
                 maker.Dots.Clear();
 
                 commitList.ItemsSource = new List<Git.Commit>(cachedCommits);
-                // Navigate(maker.Highlight);
                 SetLoadingEnabled(false);
             });
         }