revert: revert changes to read diff lines

`StringReader.ReadLine()` will trim the ending `\r` if the line-ending of this file is `\r\n`. We need to restore the line-endings in `TextDiffView` by append a single '\n'

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

Author: love-linger

src/Commands/Diff.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
@@ -40,10 +39,20 @@ public Diff(string repo, Models.DiffOption opt, int unified, bool ignoreWhitespa
         public async Task<Models.DiffResult> ReadAsync()
         {
             var rs = await ReadToEndAsync().ConfigureAwait(false);
-            var sr = new StringReader(rs.StdOut);
-            while (sr.ReadLine() is { } line)
+            var start = 0;
+            var end = rs.StdOut.IndexOf('\n', start);
+            while (end > 0)
+            {
+                var line = rs.StdOut.Substring(start, end - start);
                 ParseLine(line);
 
+                start = end + 1;
+                end = rs.StdOut.IndexOf('\n', start);
+            }
+
+            if (start < rs.StdOut.Length)
+                ParseLine(rs.StdOut.Substring(start));
+
             if (_result.IsBinary || _result.IsLFS || _result.TextDiff.Lines.Count == 0)
             {
                 _result.TextDiff = null;