Source file `diff.ml`

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(*****************************************************************************)
(* Open Source License                                                       *)
(* Copyright (c) 2021 Valentin Chaboche                                      *)
(* Copyright (c) 2021 Nomadic Labs, <contact@nomadic-labs.com>               *)
(*                                                                           *)
(* Permission is hereby granted, free of charge, to any person obtaining a   *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
(* and/or sell copies of the Software, and to permit persons to whom the     *)
(* Software is furnished to do so, subject to the following conditions:      *)
(*                                                                           *)
(* The above copyright notice and this permission notice shall be included   *)
(* in all copies or substantial portions of the Software.                    *)
(*                                                                           *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
(*****************************************************************************)

type t =
  | Same  (** old and new version are equals *)
  | Diff of string  (** difference between old and new *)
  | New of string  (** only new version *)

let pp fmt = function
  | Same -> Format.pp_print_string fmt "Same"
  | Diff s -> Format.pp_print_string fmt @@ "Diff " ^ s
  | New s -> Format.pp_print_string fmt @@ "New " ^ s

let diff ~path ~prev ~next =
  match prev with
  | None -> New next
  | Some prev -> (
      let cmd =
        Printf.sprintf
          "git diff --exit-code --no-index %s %s --output=%s"
          prev
          next
          path
      in
      match Unix.system cmd with
      | WEXITED 0 -> Same
      | WEXITED _ ->
          let diff = Common.read_file path in
          Diff diff
      | WSIGNALED _ | WSTOPPED _ -> failwith (cmd ^ " was killed or stopped"))