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/Remote.cs

@@ -0,0 +1,41 @@
+namespace SourceGit.Commands
+{
+    public class Remote : Command
+    {
+        public Remote(string repo)
+        {
+            WorkingDirectory = repo;
+            Context = repo;
+        }
+
+        public bool Add(string name, string url)
+        {
+            Args = $"remote add {name} {url}";
+            return Exec();
+        }
+
+        public bool Delete(string name)
+        {
+            Args = $"remote remove {name}";
+            return Exec();
+        }
+
+        public bool Rename(string name, string to)
+        {
+            Args = $"remote rename {name} {to}";
+            return Exec();
+        }
+
+        public bool Prune(string name)
+        {
+            Args = $"remote prune {name}";
+            return Exec();
+        }
+
+        public bool SetURL(string name, string url)
+        {
+            Args = $"remote set-url {name} {url}";
+            return Exec();
+        }
+    }
+}