Implement git refs API for listing references (branches, tags and other) (#5354)

* Inital routes to git refs api

* Git refs API implementation

* Update swagger

* Fix copyright

* Make swagger happy add basic test

* Fix test

* Fix test again :)

vendor/code.gitea.io/git/ref.go

@@ -0,0 +1,18 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+// Reference represents a Git ref.
+type Reference struct {
+	Name   string
+	repo   *Repository
+	Object SHA1 // The id of this commit object
+	Type   string
+}
+
+// Commit return the commit of the reference
+func (ref *Reference) Commit() (*Commit, error) {
+	return ref.repo.getCommit(ref.Object)
+}