Use hash of directory to disambiguate libraries instead of random ID

This has the advantage that the rewriting step is reproducible.

lib/dune_file.ml

@@ -72,16 +72,10 @@ module Packages = struct
   module Set = Set.Make (String)
   module Map = Map.Make (String)
 
-  type t = Random.State.t
+  type t = Digest.t
 
-  let init = Random.State.make_self_init
-
-  let random_valid_identifier t =
-    let int_range ~start ~end_ = Random.State.int t (end_ - start) + start in
-    let lower_case_letter_range () = int_range ~start:97 ~end_:122 in
-    (* Seq.init exists only in 4.14+ *)
-    List.init ~len:8 ~f:(fun _ -> Char.chr (lower_case_letter_range ()))
-    |> List.to_seq |> String.of_seq
+  let init disambiguation = Digest.string disambiguation
+  let random_valid_identifier t = Digest.to_hex t
 
   let random_public_name v original =
     let suffix = random_valid_identifier v in

lib/dune_file.mli

@@ -34,7 +34,7 @@ module Packages : sig
 
   type t
 
-  val init : unit -> t
+  val init : string -> t
 
   type 'a rename_result = {
     changed : bool;

lib/pull.ml

@@ -51,14 +51,14 @@ let rec pp_sexp ppf = function
           let s = String.escaped s in
           Fmt.pf ppf {|"%s"|} s)
 
-let postprocess_project ~keep directory =
+let postprocess_project ~keep ~disambiguation directory =
   let open Result.O in
   let is_dune_file path =
     let filename = Fpath.filename path in
     Ok (String.equal filename "dune")
   in
   let elements = `Sat is_dune_file in
-  let dfp = Dune_file.Packages.init () in
+  let dfp = Dune_file.Packages.init disambiguation in
   let renames = Dune_file.Packages.Map.empty in
   (* determine files and their mappings first *)
   let* files, renames =
@@ -99,7 +99,9 @@ let pull ?(trim_clone = false) ~global_state ~duniverse_dir src_dep =
     Opam.pull_tree ~url ~hashes ~dir:output_dir global_state @@| fun result ->
     let* () = result in
     let* () = if trim_clone then do_trim_clone output_dir else Ok () in
-    let* () = postprocess_project ~keep:dune_packages output_dir in
+    let* () =
+      postprocess_project ~keep:dune_packages ~disambiguation:dir output_dir
+    in
     Ok ()
   else
     let error =