diff --git a/packages/opam-core.2.1.0~rc2/opam b/packages/opam-core.2.1.0~rc2/opam
new file mode 100644
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+opam-version: "2.0"
+synopsis: "Core library for opam 2.1"
+description:
+  "Small standard library extensions, and generic system interaction modules used by opam."
+maintainer: "opam-devel@lists.ocaml.org"
+authors: [
+  "Vincent Bernardoff <vb@luminar.eu.org>"
+  "Raja Boujbel <raja.boujbel@ocamlpro.com>"
+  "Roberto Di Cosmo <roberto@dicosmo.org>"
+  "Thomas Gazagnaire <thomas@gazagnaire.org>"
+  "Louis Gesbert <louis.gesbert@ocamlpro.com>"
+  "Fabrice Le Fessant <Fabrice.Le_fessant@inria.fr>"
+  "Anil Madhavapeddy <anil@recoil.org>"
+  "Guillem Rieu <guillem.rieu@ocamlpro.com>"
+  "Ralf Treinen <ralf.treinen@pps.jussieu.fr>"
+  "Frederic Tuong <tuong@users.gforge.inria.fr>"
+]
+license: "LGPL-2.1-only WITH OCaml-LGPL-linking-exception"
+homepage: "https://opam.ocaml.org"
+bug-reports: "https://github.com/ocaml/opam/issues"
+depends: [
+  "ocaml" {>= "4.02.3"}
+  "base-unix"
+  "base-bigarray"
+  "ocamlgraph"
+  "re" {>= "1.9.0"}
+  "dune" {>= "1.11.0"}
+  "cppo" {build & >= "1.1.0"}
+]
+conflicts: ["extlib-compat"]
+build: [
+  ["./configure" "--disable-checks" "--prefix" prefix]
+  ["dune" "build" "-p" name "-j" jobs]
+]
+dev-repo: "git+https://github.com/ocaml/opam.git"
+url {
+  src: "git+https://github.com/roburio/opam.git#no-unix-environment-at-top-level"
+}