project: reorganize the structure of the project.

* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.

src/ViewModels/Discard.cs

@@ -0,0 +1,78 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels
+{
+    public class DiscardModeAll { }
+    public class DiscardModeSingle { public string File { get; set; } }
+    public class DiscardModeMulti { public int Count { get; set; } }
+
+    public class Discard : Popup
+    {
+
+        public object Mode
+        {
+            get;
+            private set;
+        }
+
+        public Discard(Repository repo)
+        {
+            _repo = repo;
+
+            Mode = new DiscardModeAll();
+            View = new Views.Discard { DataContext = this };
+        }
+
+        public Discard(Repository repo, List<Models.Change> changes, bool isUnstaged)
+        {
+            _repo = repo;
+            _changes = changes;
+            _isUnstaged = isUnstaged;
+
+            if (_changes == null)
+            {
+                Mode = new DiscardModeAll();
+            }
+            else if (_changes.Count == 1)
+            {
+                Mode = new DiscardModeSingle() { File = _changes[0].Path };
+            }
+            else
+            {
+                Mode = new DiscardModeMulti() { Count = _changes.Count };
+            }
+
+            View = new Views.Discard() { DataContext = this };
+        }
+
+        public override Task<bool> Sure()
+        {
+            _repo.SetWatcherEnabled(false);
+            ProgressDescription = _changes == null ? "Discard all local changes ..." : $"Discard total {_changes.Count} changes ...";
+
+            return Task.Run(() =>
+            {
+                if (_changes == null)
+                {
+                    Commands.Discard.All(_repo.FullPath);
+                }
+                else if (_isUnstaged)
+                {
+                    Commands.Discard.ChangesInWorkTree(_repo.FullPath, _changes);
+                }
+                else
+                {
+                    Commands.Discard.ChangesInStaged(_repo.FullPath, _changes);
+                }
+
+                CallUIThread(() => _repo.SetWatcherEnabled(true));
+                return true;
+            });
+        }
+
+        private readonly Repository _repo = null;
+        private readonly List<Models.Change> _changes = null;
+        private readonly bool _isUnstaged = true;
+    }
+}