* Add a type to handle environment variables with the usual string

separator ":".

svn path=/nixpkgs/trunk/; revision=18239

pkgs/lib/types.nix

@@ -40,7 +40,7 @@ rec {
     };
 
     
-  types = {
+  types = rec {
 
     inferred = mkOptionType {
       name = "inferred type";
@@ -63,6 +63,12 @@ rec {
       merge = lib.concatStrings;
     };
 
+    envVar = mkOptionType {
+      name = "environment variable";
+      inherit (string) check;
+      merge = lib.concatStringsSep ":";
+    };
+
     attrs = mkOptionType {
       name = "attribute set";
       check = lib.traceValIfNot builtins.isAttrs;