add support of dune

README.md

@@ -9,6 +9,7 @@ code formatters.
 `merge-fmt` currently only knows about the following formatters:
 - [ocamlformat](https://github.com/ocaml-ppx/ocamlformat) for OCaml.
 - [refmt](https://github.com/facebook/reason) for reason.
+- [dune](https://github.com/ocaml/dune) for dune.
 
 Note that supporting new code formatters is trivial.
 
@@ -47,4 +48,4 @@ Install
 -------
 ```sh
 $ opam pin add merge-fmt git@github.com:hhugo/merge-fmt.git
-```
+```

merge-fmt-help.txt

@@ -17,6 +17,9 @@ COMMANDS
            Register the [merge-fmt] mergetool in git
 
 OPTIONS
+       --dune=VAL
+           dune path
+
        --echo
            Echo all commands.
 

merge-fmt-mergetool-help.txt

@@ -9,6 +9,9 @@ OPTIONS
 
        --current=<current-file>
 
+       --dune=VAL
+           dune path
+
        --echo
            Echo all commands.
 

src/fmters.ml

@@ -4,6 +4,7 @@ open Common
 type config =
   { ocamlformat_path : string option
   ; refmt_path : string option
+  ; dune_path : string option
   }
 
 type t = string
@@ -15,12 +16,19 @@ let ocamlformat ~bin ~name =
 
 let refmt ~bin = sprintf "%s --inplace" (Option.value ~default:"refmt" bin)
 
+let dune ~bin ~filename =
+  sprintf "%s format-dune-file %s > %s"
+    (Option.value ~default:"dune" bin)
+    filename filename
+
 let find ~config ~filename ~name =
   let filename = Option.value ~default:filename name in
-  match (Caml.Filename.extension filename, config) with
-  | (".ml" | ".mli"), { ocamlformat_path; _ } ->
+  match (filename, Caml.Filename.extension filename, config) with
+  | _, (".ml" | ".mli"), { ocamlformat_path; _ } ->
       Some (ocamlformat ~bin:ocamlformat_path ~name)
-  | (".re" | ".rei"), { refmt_path; _ } -> Some (refmt ~bin:refmt_path)
+  | _, (".re" | ".rei"), { refmt_path; _ } -> Some (refmt ~bin:refmt_path)
+  | ("dune" | "dune-project" | "dune-workspace"), "", { dune_path; _ } ->
+      Some (dune ~bin:dune_path ~filename)
   | _ -> None
 
 let run t ~echo ~filename = system ~echo "%s %s" t filename
@@ -36,9 +44,13 @@ module Flags = struct
     let doc = "refmt path" in
     Arg.(value & opt (some string) None & info [ "refmt" ] ~doc)
 
+  let dune_path =
+    let doc = "dune path" in
+    Arg.(value & opt (some string) None & info [ "dune" ] ~doc)
+
   let t =
     Term.(
-      const (fun ocamlformat_path refmt_path ->
-          { ocamlformat_path; refmt_path })
-      $ ocamlformat_path $ refmt_path)
+      const (fun ocamlformat_path refmt_path dune_path ->
+          { ocamlformat_path; refmt_path; dune_path })
+      $ ocamlformat_path $ refmt_path $ dune_path)
 end