nix: Pass the backwards compatible fetchgit to python and node packages.

default.nix

@@ -4,14 +4,55 b''
 # derivation. For advanced tweaks to pimp up the development environment we use
 # "shell.nix" so that it does not have to clutter this file.
 
-{ pkgs ? (import <nixpkgs> {})
-, pythonPackages ? "python27Packages"
+args@
+{ pythonPackages ? "python27Packages"
 , pythonExternalOverrides ? self: super: {}
 , doCheck ? true
+, ...
 }:
 
 let
-  inherit (pkgs.lib) fix extends;
+
+  # Use nixpkgs from args or import them. We use this indirect approach
+  # through args to be able to use the name `pkgs` for our customized packages.
+  # Otherwise we will end up with an infinite recursion.
+  nixpkgs = args.pkgs or (import <nixpkgs> { });
+
+  # johbo: Interim bridge which allows us to build with the upcoming
+  # nixos.16.09 branch (unstable at the moment of writing this note) and the
+  # current stable nixos-16.03.
+  backwardsCompatibleFetchgit = { ... }@args:
+    let
+      origSources = nixpkgs.fetchgit args;
+    in
+    nixpkgs.lib.overrideDerivation origSources (oldAttrs: {
+      NIX_PREFETCH_GIT_CHECKOUT_HOOK = ''
+        find $out -name '.git*' -print0 | xargs -0 rm -rf
+      '';
+    });
+
+  # Create a customized version of nixpkgs which should be used throughout the
+  # rest of this file.
+  pkgs = nixpkgs.overridePackages (self: super: {
+    fetchgit = backwardsCompatibleFetchgit;
+  });
+
+  # Evaluates to the last segment of a file system path.
+  basename = path: with pkgs.lib; last (splitString "/" path);
+
+  # source code filter used as arugment to builtins.filterSource.
+  src-filter = path: type: with pkgs.lib;
+    let
+      ext = last (splitString "." path);
+    in
+      !builtins.elem (basename path) [
+        ".git" ".hg" "__pycache__" ".eggs"
+        "bower_components" "node_modules"
+        "build" "data" "result" "tmp"] &&
+      !builtins.elem ext ["egg-info" "pyc"] &&
+      # TODO: johbo: This check is wrong, since "path" contains an absolute path,
+      # it would still be good to restore it since we want to ignore "result-*".
+      !hasPrefix "result" path;
 
   basePythonPackages = with builtins; if isAttrs pythonPackages
     then pythonPackages
@@ -21,25 +62,6 b' let'
     pkgs.buildBowerComponents or
     (import ./pkgs/backport-16.03-build-bower-components.nix { inherit pkgs; });
 
-  elem = builtins.elem;
-  basename = path: with pkgs.lib; last (splitString "/" path);
-  startsWith = prefix: full: let
-    actualPrefix = builtins.substring 0 (builtins.stringLength prefix) full;
-  in actualPrefix == prefix;
-
-  src-filter = path: type: with pkgs.lib;
-    let
-      ext = last (splitString "." path);
-    in
-      !elem (basename path) [
-        ".git" ".hg" "__pycache__" ".eggs"
-        "bower_components" "node_modules"
-        "build" "data" "result" "tmp"] &&
-      !elem ext ["egg-info" "pyc"] &&
-      # TODO: johbo: This check is wrong, since "path" contains an absolute path,
-      # it would still be good to restore it since we want to ignore "result-*".
-      !startsWith "result" path;
-
   sources = pkgs.config.rc.sources or {};
   version = builtins.readFile ./rhodecode/VERSION;
   rhodecode-enterprise-ce-src = builtins.filterSource src-filter ./.;
@@ -218,11 +240,11 b' let'
   });
 
   # Apply all overrides and fix the final package set
-  myPythonPackagesUnfix =
+  myPythonPackagesUnfix = with pkgs.lib;
     (extends pythonExternalOverrides
     (extends pythonLocalOverrides
     (extends pythonOverrides
              pythonGeneratedPackages)));
-  myPythonPackages = (fix myPythonPackagesUnfix);
+  myPythonPackages = (pkgs.lib.fix myPythonPackagesUnfix);
 
 in myPythonPackages.rhodecode-enterprise-ce

pkgs/python-packages-overrides.nix

@@ -15,19 +15,6 b' let'
     };
   };
 
-  # johbo: Interim bridge which allows us to build with the upcoming
-  # nixos.16.09 branch (unstable at the moment of writing this note) and the
-  # current stable nixos-16.03.
-  backwardsCompatibleFetchgit = { ... }@args:
-    let
-      origSources = pkgs.fetchgit args;
-    in
-    pkgs.lib.overrideDerivation origSources (oldAttrs: {
-      NIX_PREFETCH_GIT_CHECKOUT_HOOK = ''
-        find $out -name '.git*' -print0 | xargs -0 rm -rf
-      '';
-    });
-
 in
 
 self: super: {
@@ -110,7 +97,7 b' self: super: {'
   });
 
   py-gfm = super.py-gfm.override  {
-    src = backwardsCompatibleFetchgit {
+    src = pkgs.fetchgit {
       url = "https://code.rhodecode.com/upstream/py-gfm";
       rev = "0d66a19bc16e3d49de273c0f797d4e4781e8c0f2";
       sha256 = "0ryp74jyihd3ckszq31bml5jr3bciimhfp7va7kw6ld92930ksv3";
@@ -134,7 +121,7 b' self: super: {'
 
   Pylons = super.Pylons.override (attrs: {
     name = "Pylons-1.0.1-patch1";
-    src = backwardsCompatibleFetchgit {
+    src = pkgs.fetchgit {
       url = "https://code.rhodecode.com/upstream/pylons";
       rev = "707354ee4261b9c10450404fc9852ccea4fd667d";
       sha256 = "b2763274c2780523a335f83a1df65be22ebe4ff413a7bc9e9288d23c1f62032e";