Add Stanza.file_kind

Signed-off-by: Jeremie Dimino <jeremie@dimino.org>

src/action.ml

@@ -89,14 +89,22 @@ struct
         ; "diff",
           (path >>= fun file1 ->
            path >>= fun file2 ->
-           Syntax.get_exn Stanza.syntax >>| fun ver ->
-           let mode = if ver < (1, 0) then Diff_mode.Text_jbuild else Text in
+           Stanza.file_kind () >>| fun kind ->
+           let mode =
+             match kind with
+             | Jbuild -> Diff_mode.Text_jbuild
+             | Dune   -> Text
+           in
            Diff { optional = false; file1; file2; mode })
         ; "diff?",
           (path >>= fun file1 ->
            path >>= fun file2 ->
-           Syntax.get_exn Stanza.syntax >>| fun ver ->
-           let mode = if ver < (1, 0) then Diff_mode.Text_jbuild else Text in
+           Stanza.file_kind () >>| fun kind ->
+           let mode =
+             match kind with
+             | Jbuild -> Diff_mode.Text_jbuild
+             | Dune   -> Text
+           in
            Diff { optional = true; file1; file2; mode })
         ; "cmp",
           (Syntax.since Stanza.syntax (1, 0) >>= fun () ->

src/stanza.ml

@@ -11,3 +11,12 @@ let syntax =
     [ (0, 0) (* Jbuild syntax *)
     ; (1, 0)
     ]
+
+module File_kind = struct
+  type t = Jbuild | Dune
+end
+
+let file_kind () =
+  let open Sexp.Of_sexp in
+  Syntax.get_exn syntax >>| fun ver ->
+  if ver < (1, 0) then File_kind.Jbuild else Dune

src/stanza.mli

@@ -16,3 +16,10 @@ end
     the Jbuild language while versions from [(1, 0)] correspond to the
     Dune one. *)
 val syntax : Syntax.t
+
+module File_kind : sig
+  type t = Jbuild | Dune
+end
+
+(** Whether we are parsing a [jbuild] or [dune] file. *)
+val file_kind : unit -> (File_kind.t, _) Sexp.Of_sexp.parser