feature<Merge>: show progress for merge

src/Commands/Merge.cs

@@ -1,12 +1,21 @@
+using System;
+
 namespace SourceGit.Commands {
     /// <summary>
     ///     合并分支
     /// </summary>
     public class Merge : Command {
+        private Action<string> handler = null;
 
-        public Merge(string repo, string source, string mode) {
+        public Merge(string repo, string source, string mode, Action<string> onProgress) {
             Cwd = repo;
-            Args = $"merge {source} {mode}";
+            Args = $"merge --progress {source} {mode}";
+            TraitErrorAsOutput = true;
+            handler = onProgress;
+        }
+
+        public override void OnReadline(string line) {
+            handler?.Invoke(line);
         }
     }
 }

src/Views/Popups/Merge.xaml.cs

@@ -26,7 +26,7 @@ namespace SourceGit.Views.Popups {
             var mode = (cmbMode.SelectedItem as Models.MergeOption).Arg;
             return Task.Run(() => {
                 Models.Watcher.SetEnabled(repo, false);
-                new Commands.Merge(repo, source, mode).Exec();
+                new Commands.Merge(repo, source, mode, UpdateProgress).Exec();
                 Models.Watcher.SetEnabled(repo, true);
                 return true;
             });