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/Fetch.cs

@@ -0,0 +1,67 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels
+{
+    public class Fetch : Popup
+    {
+        public List<Models.Remote> Remotes
+        {
+            get => _repo.Remotes;
+        }
+
+        public bool FetchAllRemotes
+        {
+            get => _fetchAllRemotes;
+            set => SetProperty(ref _fetchAllRemotes, value);
+        }
+
+        public Models.Remote SelectedRemote
+        {
+            get;
+            set;
+        }
+
+        public bool Prune
+        {
+            get;
+            set;
+        }
+
+        public Fetch(Repository repo, Models.Remote preferedRemote = null)
+        {
+            _repo = repo;
+            _fetchAllRemotes = preferedRemote == null;
+            SelectedRemote = preferedRemote != null ? preferedRemote : _repo.Remotes[0];
+            Prune = true;
+            View = new Views.Fetch() { DataContext = this };
+        }
+
+        public override Task<bool> Sure()
+        {
+            _repo.SetWatcherEnabled(false);
+            return Task.Run(() =>
+            {
+                if (FetchAllRemotes)
+                {
+                    foreach (var remote in _repo.Remotes)
+                    {
+                        SetProgressDescription($"Fetching remote: {remote.Name}");
+                        new Commands.Fetch(_repo.FullPath, remote.Name, Prune, SetProgressDescription).Exec();
+                    }
+                }
+                else
+                {
+                    SetProgressDescription($"Fetching remote: {SelectedRemote.Name}");
+                    new Commands.Fetch(_repo.FullPath, SelectedRemote.Name, Prune, SetProgressDescription).Exec();
+                }
+
+                CallUIThread(() => _repo.SetWatcherEnabled(true));
+                return true;
+            });
+        }
+
+        private readonly Repository _repo = null;
+        private bool _fetchAllRemotes = true;
+    }
+}