fix<Discard>: fix discard with files not only dropped changes selected but also others

src/Commands/Clean.cs

@@ -1,3 +1,6 @@
+using System.Collections.Generic;
+using System.Text;
+
 namespace SourceGit.Commands {
     /// <summary>
     ///     清理指令
@@ -8,5 +11,18 @@ namespace SourceGit.Commands {
             Cwd = repo;
             Args = "clean -qfd";
         }
+
+        public Clean(string repo, List<string> files) {
+            StringBuilder builder = new StringBuilder();
+            builder.Append("clean -qfd --");
+            foreach (var f in files) {
+                builder.Append(" \"");
+                builder.Append(f);
+                builder.Append("\"");
+            }
+
+            Cwd = repo;
+            Args = builder.ToString();
+        }
     }
 }