Move each overlay into its own file

nix/nebula.nix

@@ -0,0 +1,25 @@
+{
+
+  buildGoModule,
+  fetchFromGitHub,
+
+}: buildGoModule rec {
+
+  pname = "nebula";
+
+  # If this changes, remember to change:
+  # - the AppDir/etc/daemon.yml vpn.firewall docs
+  # - the version imported in go-workspace
+  version = "1.4.0";
+
+  src = fetchFromGitHub {
+    owner = "slackhq";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "lu2/rSB9cFD7VUiK+niuqCX9CI2x+k4Pi+U5yksETSU=";
+  };
+
+  vendorSha256 = "p1inJ9+NAb2d81cn+y+ofhxFz9ObUiLgj+9cACa6Jqg=";
+
+  subPackages = [ "cmd/nebula" "cmd/nebula-cert" ];
+}

nix/pkgs.nix

@@ -4,19 +4,6 @@ rec {
 
     (final: prev: {
 
-      # rebase is a helper which takes all files/dirs under oldroot, and
-      # creates a new derivation with those files/dirs copied under newroot
-      # (where newroot is a relative path to the root of the derivation).
-      rebase = name: oldroot: newroot: prev.stdenv.mkDerivation {
-        name = name;
-        inherit oldroot newroot;
-        builder = builtins.toFile "builder.sh" ''
-          source $stdenv/setup
-          mkdir -p "$out"/"$newroot"
-          cp -rL "$oldroot"/* "$out"/"$newroot"
-        '';
-      };
-
       # make buildGoModule default to static compilation
       buildGoModule = args: prev.buildGoModule ({
         doCheck = false;
@@ -27,45 +14,9 @@ rec {
 
     })
 
-    (final: prev: {
-
-      yq-go = prev.buildGoModule rec {
-
-        pname = "yq-go";
-        version = "4.21.1";
-
-        src = prev.fetchFromGitHub {
-          owner = "mikefarah";
-          repo = "yq";
-          rev = "v${version}";
-          sha256 = "sha256-283xe7FVHYSsRl4cZD7WDzIW1gqNAFsNrWYJkthZheU=";
-        };
-
-        vendorSha256 = "sha256-F11FnDYJ59aKrdRXDPpKlhX52yQXdaN1sblSkVI2j9w=";
-      };
-
-      nebula = prev.buildGoModule rec {
-        pname = "nebula";
-
-        # If this changes, remember to change:
-        # - the AppDir/etc/daemon.yml vpn.firewall docs
-        # - the version imported in go-workspace
-        version = "1.4.0";
-
-        src = prev.fetchFromGitHub {
-          owner = "slackhq";
-          repo = pname;
-          rev = "v${version}";
-          sha256 = "lu2/rSB9cFD7VUiK+niuqCX9CI2x+k4Pi+U5yksETSU=";
-        };
-
-        vendorSha256 = "p1inJ9+NAb2d81cn+y+ofhxFz9ObUiLgj+9cACa6Jqg=";
-
-        subPackages = [ "cmd/nebula" "cmd/nebula-cert" ];
-      };
-
-    })
-
+    (final: prev: { rebase = prev.callPackage ./rebase.nix {}; })
+    (final: prev: { yq-go = prev.callPackage ./yq-go.nix {}; })
+    (final: prev: { nebula = prev.callPackage ./nebula.nix {}; })
   ];
 
   stableSrc = fetchTarball {

nix/rebase.nix

@@ -0,0 +1,18 @@
+# rebase is a helper which takes all files/dirs under oldroot, and
+# creates a new derivation with those files/dirs copied under newroot
+# (where newroot is a relative path to the root of the derivation).
+
+{
+
+  stdenv,
+
+}: name: oldroot: newroot: stdenv.mkDerivation {
+
+  inherit name oldroot newroot;
+
+  builder = builtins.toFile "builder.sh" ''
+    source $stdenv/setup
+    mkdir -p "$out"/"$newroot"
+    cp -rL "$oldroot"/* "$out"/"$newroot"
+  '';
+}

nix/yq-go.nix

@@ -0,0 +1,19 @@
+{
+
+  buildGoModule,
+  fetchFromGitHub,
+
+}: buildGoModule rec {
+
+  pname = "yq-go";
+  version = "4.21.1";
+
+  src = fetchFromGitHub {
+    owner = "mikefarah";
+    repo = "yq";
+    rev = "v${version}";
+    sha256 = "sha256-283xe7FVHYSsRl4cZD7WDzIW1gqNAFsNrWYJkthZheU=";
+  };
+
+  vendorSha256 = "sha256-F11FnDYJ59aKrdRXDPpKlhX52yQXdaN1sblSkVI2j9w=";
+}