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/gopkg.in/src-d/go-git.v4/storage/filesystem/deltaobject.go

@@ -0,0 +1,37 @@
+package filesystem
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+type deltaObject struct {
+	plumbing.EncodedObject
+	base plumbing.Hash
+	hash plumbing.Hash
+	size int64
+}
+
+func newDeltaObject(
+	obj plumbing.EncodedObject,
+	hash plumbing.Hash,
+	base plumbing.Hash,
+	size int64) plumbing.DeltaObject {
+	return &deltaObject{
+		EncodedObject: obj,
+		hash:          hash,
+		base:          base,
+		size:          size,
+	}
+}
+
+func (o *deltaObject) BaseHash() plumbing.Hash {
+	return o.base
+}
+
+func (o *deltaObject) ActualSize() int64 {
+	return o.size
+}
+
+func (o *deltaObject) ActualHash() plumbing.Hash {
+	return o.hash
+}