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/Commands/LFS.cs

@@ -0,0 +1,49 @@
+using System;
+using System.IO;
+
+namespace SourceGit.Commands
+{
+    public class LFS
+    {
+        class PruneCmd : Command
+        {
+            public PruneCmd(string repo, Action<string> onProgress)
+            {
+                WorkingDirectory = repo;
+                Context = repo;
+                Args = "lfs prune";
+                TraitErrorAsOutput = true;
+                _outputHandler = onProgress;
+            }
+
+            protected override void OnReadline(string line)
+            {
+                _outputHandler?.Invoke(line);
+            }
+
+            private readonly Action<string> _outputHandler;
+        }
+
+        public LFS(string repo)
+        {
+            _repo = repo;
+        }
+
+        public bool IsEnabled()
+        {
+            var path = Path.Combine(_repo, ".git", "hooks", "pre-push");
+            if (!File.Exists(path))
+                return false;
+
+            var content = File.ReadAllText(path);
+            return content.Contains("git lfs pre-push");
+        }
+
+        public void Prune(Action<string> outputHandler)
+        {
+            new PruneCmd(_repo, outputHandler).Exec();
+        }
+
+        private readonly string _repo;
+    }
+}