update git vendor to fix wrong release commit id and add migrations （#6224） (#6300)

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

@@ -0,0 +1,11 @@
+// Copyright 2019 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
+
+// LastCommitCache cache
+type LastCommitCache interface {
+	Get(repoPath, ref, entryPath string) (*Commit, error)
+	Put(repoPath, ref, entryPath string, commit *Commit) error
+}