refactor<*>: rewrite all codes...

src/Commands/QueryFileContent.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+
+namespace SourceGit.Commands {
+    /// <summary>
+    ///     取得指定提交下的某文件内容
+    /// </summary>
+    public class QueryFileContent : Command {
+        private List<Models.TextLine> lines = new List<Models.TextLine>();
+        private int added = 0;
+
+        public QueryFileContent(string repo, string commit, string path) {
+            Cwd = repo;
+            Args = $"show {commit}:\"{path}\"";
+        }
+
+        public List<Models.TextLine> Result() {
+            Exec();
+            return lines;
+        }
+
+        public override void OnReadline(string line) {
+            added++;
+            lines.Add(new Models.TextLine() { Number = added, Data = line });
+        }
+    }
+}