Set the NixOS version to something useful when building from Git

modules/installer/tools/nixos-rebuild.sh

@@ -140,6 +140,16 @@ if [ -n "$buildNix" ]; then
 fi
 
 
+# Update the version suffix if we're building from Git (so that
+# nixos-version shows something useful).
+if nixos=$(nix-instantiate --find-file nixos "${extraBuildFlags[@]}"); then
+    suffix=$($SHELL $nixos/modules/installer/tools/get-version-suffix "${extraBuildFlags[@]}")
+    if [ -n "$suffix" ]; then
+        echo -n "$suffix" > "$nixos/.version-suffix"
+    fi
+fi
+
+
 # Either upgrade the configuration in the system profile (for "switch"
 # or "boot"), or just build it and create a symlink "result" in the
 # current directory (for "build" and "test").

modules/misc/version.nix

@@ -7,16 +7,23 @@ with pkgs.lib;
   options = {
 
     system.nixosVersion = mkOption {
-      default =
-        builtins.readFile ../../.version
-        + (if builtins.pathExists ../../.version-suffix then builtins.readFile ../../.version-suffix else "pre-git");
       description = "NixOS version.";
     };
 
+    system.nixosVersionSuffix = mkOption {
+      description = "NixOS version suffix.";
+    };
+
   };
 
   config = {
 
+    system.nixosVersion =
+      builtins.readFile ../../.version + config.system.nixosVersionSuffix;
+
+    system.nixosVersionSuffix =
+      if builtins.pathExists ../../.version-suffix then builtins.readFile ../../.version-suffix else "pre-git";
+
     # Generate /etc/os-release.  See
     # http://0pointer.de/public/systemd-man/os-release.html for the
     # format.

release.nix

@@ -20,7 +20,7 @@ let
     let
 
       versionModule =
-        { system.nixosVersion = version + (lib.optionalString (!officialRelease) versionSuffix);
+        { system.nixosVersionSuffix = lib.optionalString (!officialRelease) versionSuffix;
           isoImage.isoBaseName = "nixos-${type}";
         };
 
@@ -55,7 +55,7 @@ let
 
     with import <nixpkgs> {inherit system;};
     let
-      versionModule = { system.nixosVersion = version + (lib.optionalString (!officialRelease) versionSuffix); };
+      versionModule = { system.nixosVersionSuffix = lib.optionalString (!officialRelease) versionSuffix; };
 
       config = (import lib/eval-config.nix {
         inherit system;