ocaml-ng.ocamlPackages_4_07.seq: dummy package with just a META file

Imitate opam which installs the real seq package only for OCaml < 4.07 and only a META file for OCaml >= 4.07.

pkgs/development/ocaml-modules/seq/default.nix

···
 { stdenv, fetchFromGitHub, ocaml, findlib, ocamlbuild }:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation ({
   version = "0.1";
-  name = "ocaml${ocaml.version}-seq-${version}";
+  name = "ocaml${ocaml.version}-seq-0.1";
+
+  meta = {
+    license = stdenv.lib.licenses.lgpl21;
+    maintainers = [ stdenv.lib.maintainers.vbgl ];
+    homepage = "https://github.com/c-cube/seq";
+    inherit (ocaml.meta) platforms;
+  };
+
+} // (if stdenv.lib.versionOlder ocaml.version "4.07" then {
 
   src = fetchFromGitHub {
     owner = "c-cube";
     repo = "seq";
-    rev = version;
+    rev = "0.1";
     sha256 = "1cjpsc7q76yfgq9iyvswxgic4kfq2vcqdlmxjdjgd4lx87zvcwrv";
   };
 
···
 
   createFindlibDestdir = true;
 
-  meta = {
-    description = "Compatibility package for OCaml’s standard iterator type starting from 4.07";
-    license = stdenv.lib.licenses.lgpl21;
-    maintainers = [ stdenv.lib.maintainers.vbgl ];
-    inherit (src.meta) homepage;
-    inherit (ocaml.meta) platforms;
-  };
-}
+  meta.description = "Compatibility package for OCaml’s standard iterator type starting from 4.07";
+
+} else {
+
+  src = ./src-base;
+
+  dontBuild = true;
+
+  installPhase = ''
+    mkdir -p $out/lib/ocaml/${ocaml.version}/site-lib/seq
+    cp META $out/lib/ocaml/${ocaml.version}/site-lib/seq
+  '';
+
+  meta.description = "dummy backward-compatibility package for iterators";
+
+}))

pkgs/development/ocaml-modules/seq/src-base/META

···
+name="seq"
+version="[distributed with OCaml 4.07 or above]"
+description="dummy backward-compatibility package for iterators"
+requires=""