Update to go-git v5.1.0 (#11936)

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

vendor/github.com/imdario/mergo/doc.go

@@ -0,0 +1,44 @@
+// Copyright 2013 Dario Castañé. All rights reserved.
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package mergo merges same-type structs and maps by setting default values in zero-value fields.
+
+Mergo won't merge unexported (private) fields but will do recursively any exported one. It also won't merge structs inside maps (because they are not addressable using Go reflection).
+
+Usage
+
+From my own work-in-progress project:
+
+	type networkConfig struct {
+		Protocol string
+		Address string
+		ServerType string `json: "server_type"`
+		Port uint16
+	}
+
+	type FssnConfig struct {
+		Network networkConfig
+	}
+
+	var fssnDefault = FssnConfig {
+		networkConfig {
+			"tcp",
+			"127.0.0.1",
+			"http",
+			31560,
+		},
+	}
+
+	// Inside a function [...]
+
+	if err := mergo.Merge(&config, fssnDefault); err != nil {
+		log.Fatal(err)
+	}
+
+	// More code [...]
+
+*/
+package mergo