add git protocol v2 support via SSH on Docker image (#5520)

* add git protocol v2 support via SSH on Docker image

* remove new layer on dockerfile

docker/etc/ssh/sshd_config

@@ -29,3 +29,5 @@ AllowUsers git
 
 Banner none
 Subsystem sftp /usr/lib/ssh/sftp-server
+
+AcceptEnv GIT_PROTOCOL