Use deepen according what we have.

If we have nothing, we just want the last commit, if we have something, we want
commits between what we have and what the server has. Then, we shallow
correctly our internal store to still keep only one commit.

src/git_kv.ml

@@ -71,7 +71,15 @@ let diff store commit0 commit1 = match commit0 with
 
 let pull t =
   let open Lwt.Infix in
-  Sync.fetch ~capabilities ~ctx:t.ctx t.edn t.store ~deepen:(`Depth 1) (`Some [ t.branch, t.branch ]) >>= fun r ->
+  ( match t.head with
+  | None -> Lwt.return (`Depth 1)
+  | Some head ->
+    Store.read_exn t.store head >>= fun value ->
+    let[@warning "-8"] Git.Value.Commit commit = value in
+    (* TODO(dinosaure): we should handle correctly [tz] and re-calculate the timestamp. *)
+    let { Git.User.date= (timestamp, _tz); _ } = Store.Value.Commit.author commit in
+    Lwt.return (`Timestamp timestamp) ) >>= fun deepen ->
+  Sync.fetch ~capabilities ~ctx:t.ctx t.edn t.store ~deepen (`Some [ t.branch, t.branch ]) >>= fun r ->
   let data =
     Result.map_error
       (fun e -> `Msg (Fmt.str "error fetching: %a" Sync.pp_error e))
@@ -80,18 +88,15 @@ let pull t =
   match data with
   | Error _ as e -> Lwt.return e
   | Ok None -> Lwt.return (Ok [])
-  | Ok Some (_, _) ->
-    Store.Ref.resolve t.store t.branch >>= fun r ->
-    let head =
-      Result.map_error
-        (fun e -> `Msg (Fmt.str "error resolving branch %a: %a"
-                          Git.Reference.pp t.branch
-                          Store.pp_error e))
-        r |> to_invalid
-    in
-    diff t.store t.head head >>= fun diff ->
-    t.head <- Some head;
-    Lwt.return (Ok diff)
+  | Ok Some (_, refs) -> match List.find (fun (r, _) -> Git.Reference.equal r t.branch) refs with
+    | (_, head) ->
+      Store.shallow t.store head >>= fun () ->
+      (* XXX(dinosaure): the shallow must be done **before** the diff. Otherwise
+         we will compare [commit0] with [commit0 <- commit1]. We want to compare
+         [commit0] and [commit1] (only). *)
+      diff t.store t.head head >>= fun diff ->
+      t.head <- Some head ; Lwt.return (Ok diff)
+    | exception Not_found -> Lwt.return_error (`Msg (Fmt.str "error fetching: %a does not exist" Git.Reference.pp t.branch))
 
 let connect ctx endpoint =
   let open Lwt.Infix in