feature<Cleanup>: add toolbar button to run git gc and git lfs prune

src/Commands/GC.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace SourceGit.Commands {
+    /// <summary>
+    ///     GC
+    /// </summary>
+    public class GC : Command {
+        private Action<string> handler;
+
+        public GC(string repo, Action<string> onProgress) {
+            Cwd = repo;
+            Args = "gc";
+            TraitErrorAsOutput = true;
+            handler = onProgress;
+        }
+
+        public override void OnReadline(string line) {
+            handler?.Invoke(line);
+        }
+    }
+}