Add the branch accessor

src/git_kv.ml

@@ -107,6 +107,8 @@ let connect ctx endpoint =
   let _r = to_invalid r in
   Lwt.return t
 
+let branch t = t.branch
+
 type key = Mirage_kv.Key.t
 
 type change = [

src/git_kv.mli

@@ -40,6 +40,8 @@ val connect : Mimic.ctx -> string -> t Lwt.t
     @raise [Invalid_argument _] if we can not initialize the store, or if
     we can not fetch the given [remote]. *)
 
+val branch : t -> Git.Reference.t
+
 val to_octets : t -> string Lwt.t
 (** [to_octets store] returns a serialized version of the given [store]. *)