Adjust Git_kv.commit to report staging status

The implementation is a bit too naïve and will report the commit dirty
even when there are no staged changes. It only detects if we're inside a
`change_and_push`.

src/git_kv.ml

@@ -109,7 +109,13 @@ let connect ctx endpoint =
 
 let branch t = t.branch
 
-let commit t = t.head
+let commit t =
+  match t.head, t.committed with
+  | None, _ -> None
+  | Some commit, None -> Some (`Clean commit)
+  | Some commit, Some _ ->
+    (* XXX: this is not precise as we can have made zero changes *)
+    Some (`Dirty commit)
 
 type key = Mirage_kv.Key.t
 

src/git_kv.mli

@@ -43,8 +43,10 @@ val connect : Mimic.ctx -> string -> t Lwt.t
 val branch : t -> Git.Reference.t
 (** [branch t] returns the branch used by the given [t]. *)
 
-val commit : t -> Digestif.SHA1.t option
-(** [commit t] returns the commit used by the given [t]. *)
+val commit : t -> [ `Clean of Digestif.SHA1.t | `Dirty of Digestif.SHA1.t ] option
+(** [commit t] returns the commit used by the given [t]. The commit is either
+    marked [`Dirty _] if we're inside a [change_and_push] or [`Clean _]
+    otherwise. *)
 
 val to_octets : ?level:int -> t -> string Lwt_stream.t
 (** [to_octets ?level store] returns a serialized version of the given [store].