Combine ccpkgs and nixpkgs versions together in suffix

Want a unique name for the output product of each combination for
the channel-update code.

release.nix

@@ -1,10 +1,10 @@
-{ nixpkgs                      # Checked out nixpkgs git repe
-    ? { outPath = ./upstream;
-        revCount = 56789;
-        shortRev = "gfedcba";
-      }
-, ccpkgs                       # Checked out ccpkgs git repo
+{ ccpkgs                       # Checked out ccpkgs git repo
     ? { outPath = ./.;
+        revCount = 1234;
+        shortRev = "gabcdef";
+      }
+, nixpkgs                      # Checked out nixpkgs git repe
+    ? { outPath = ./upstream;
         revCount = 56789;
         shortRev = "gfedcba";
       }
@@ -15,11 +15,10 @@
 # Free up the nixpkgs and ccpkgs name for binding to final product.
 #
 let
-  # nixpkgsGit - git checkout of nixpkgs
-  # ccpkgsGit  - git checkout of ccpkgs
+  # *Git - git checkout
   #
   nixpkgsGit = nixpkgs;
-  ccpkgsGit  = ccpkgs;
+  ccpkgsGit = ccpkgs;
 
 # Tarball hydra release product for the ccpkgs channel.
 #
@@ -34,14 +33,30 @@ in let
   #
   pkgs = import ccpkgsGit { upstream = nixpkgsGit; };
 
-  # version       - Version number of nixpkgs (and hence ccpkgs too)
-  # versionSuffix - Version suffix based on git commnit
+  # version        - Version number (e.g., "17.09")
+  # version*Suffix - Version suffix (e.g., "5678.gfedcba")
   #
   # Code lifted from nixos/release.nix.
   #
-  version = pkgs.lib.fileContents ./.version;
-  versionSuffix =
-    (if stableBranch then "." else "beta") + "${toString (nixpkgsGit.revCount - 114283)}.${nixpkgsGit.shortRev}";
+  version =
+    let
+      versionNixpkgs = pkgs.lib.fileContents (nixpkgsGit + /.version);
+      versionCcpkgs  = pkgs.lib.fileContents ./.version;
+    in
+      assert (versionNixpkgs == versionCcpkgs); versionCcpkgs;
+
+  versionSeparator = if stableBranch then "." else "beta";
+
+  mkVersion = base: git: rec {
+    count = toString (git.revCount - base);
+    commit = git.shortRev;
+    suffix = "${versionSeparator}${count}.${commit}";
+  };
+
+  nixpkgsVersion = mkVersion 114283 nixpkgsGit;
+  ccpkgsVersion  = mkVersion      0 ccpkgsGit;
+
+  versionSuffix = "${versionSeparator}${ccpkgsVersion.count}.${nixpkgsVersion.count}.${ccpkgsVersion.commit}.${nixpkgsVersion.commit}";
 
   # nixpkgs - The store path containing the unpacked nixpkgs channel.
   #
@@ -50,18 +65,14 @@ in let
   #
   nixpkgs =
     let
-      # version - Version of checked out nixpkgs
-      #
-      version = pkgs.lib.fileContents (nixpkgsGit + /.version);
-
       # channel - Store path containing the channel release tarballs.
       #
       # The nixos.channel attribute from nixos/release.nix builds the nixpkgs channel tarballs.
       #
       channel =
         ( import (nixpkgsGit + /nixos/release.nix) {
-            nixpkgs = nixpkgsGit;
             inherit stableBranch supportedSystems;
+            nixpkgs = nixpkgsGit;
           } ).channel;
 
       # nixpkgs - The store path containing the unpacked nixpkgs channel.
@@ -72,7 +83,7 @@ in let
         ( import <nix/unpack-channel.nix> rec {
            name = "nixos";
            channelName = "${name}-${version}";
-           src = channel + /tarballs + "/${name}-${version}${versionSuffix}.tar.xz";
+           src = channel + /tarballs + "/${name}-${version}${nixpkgsVersion.suffix}.tar.xz";
            binaryCacheURL = https://cache.nixos.org;
           } );
     in