refactor<*>: rewrite all codes...

src/Commands/Branch.cs

@@ -0,0 +1,33 @@
+namespace SourceGit.Commands {
+    /// <summary>
+    ///     分支相关操作
+    /// </summary>
+    class Branch : Command {
+        private string target = null;
+
+        public Branch(string repo, string branch) {
+            Cwd = repo;
+            target = branch;
+        }
+
+        public void Create(string basedOn) {
+            Args = $"branch {target} {basedOn}";
+            Exec();
+        }
+
+        public void Rename(string to) {
+            Args = $"branch -M {target} {to}";
+            Exec();
+        }
+
+        public void SetUpstream(string upstream) {
+            Args = $"branch {target} -u {upstream}";
+            Exec();
+        }
+
+        public void Delete() {
+            Args = $"branch -D {target}";
+            Exec();
+        }
+    }
+}