fd leak when reading files from a checkout

[emillon]

Hi,

I'm calling the following function in a loop I'm calling this function in a loop (it's loading a bunch of opam files from a checkout of opam-repository).

    let read_opam root pkg =
      let open Lwt_result.Syntax in
      let* store = Git_unix.Store.v root in
      let* commit_id = Git_unix.Store.Ref.resolve store Git.Reference.master in
      let open Lwt.Syntax in
      let name = OpamPackage.name pkg in
      let path =
        [
          "packages";
          Format.asprintf "%a" pp_name name;
          Format.asprintf "%a" pp_package pkg;
          "opam";
        ]
      in
      let* blob_opt = Search.find store commit_id (`Commit (`Path path)) in
      match blob_opt with
      | None -> assert false
      | Some blob -> (
          let* r = Git_unix.Store.read store blob in
          match r with
          | Ok (Blob b) ->
              let s = Git.Blob.to_string b in
              let opam = OpamFile.OPAM.read_from_string s in
              Lwt.return (Ok opam)
          | _ -> assert false)

It runs out of fds. According to valgrind --tool=none --track-fds=yes, the files that are not closed are pack files (such as .git/objects/pack/pack-d73621315d08cdcf1ec645c3145974593a0aa945.pack).

I would like these fds to be closed once the data is returned, or as an alternative I think that a "fd pool" approach is possible, so that ocaml-git does not open more than N fds at a time, and closes them all at the end of the pool's lifetime.

Thanks!