nixpkgs/pkgs/build-support/src-only/default.nix

{ stdenv }@orig:
# srcOnly is a utility builder that only fetches and unpacks the given `src`,
# maybe pathings it in the process with the optional `patches` and
# `buildInputs` attributes.
#
# It can be invoked directly, or be used to wrap an existing derivation. Eg:
#
# > srcOnly pkgs.hello
#
{ name
, src
, stdenv ? orig.stdenv
, patches ? []
, buildInputs ? []
, ... # needed when passing an existing derivation
}:
stdenv.mkDerivation {
  inherit src buildInputs patches name;
  installPhase = "cp -r . $out";
  phases = ["unpackPhase" "patchPhase" "installPhase"];
}