1 files changed, 17 insertions, 9 deletions
diff --git a/nixos/modules/misc/version.nix b/nixos/modules/misc/version.nix
index 0540b493003f..9557def622d8 100644
--- a/nixos/modules/misc/version.nix
+++ b/nixos/modules/misc/version.nix
@@ -4,9 +4,6 @@ with lib;
 
 let
   cfg = config.system.nixos;
-
-  gitRepo      = "${toString pkgs.path}/.git";
-  gitCommitId  = lib.substring 0 7 (commitIdFromGitRepo gitRepo);
 in
 
 {
@@ -41,8 +38,8 @@ in
 
     nixos.revision = mkOption {
       internal = true;
-      type = types.str;
-      default = trivial.revisionWithDefault "master";
+      type = types.nullOr types.str;
+      default = trivial.revisionWithDefault null;
       description = "The Git revision from which this NixOS configuration was built.";
     };
 
@@ -61,11 +58,18 @@ in
         configuration defaults in a way incompatible with stateful
         data. For instance, if the default version of PostgreSQL
         changes, the new version will probably be unable to read your
-        existing databases. To prevent such breakage, you can set the
+        existing databases. To prevent such breakage, you should set the
         value of this option to the NixOS release with which you want
-        to be compatible. The effect is that NixOS will option
+        to be compatible. The effect is that NixOS will use
         defaults corresponding to the specified release (such as using
         an older version of PostgreSQL).
+        It‘s perfectly fine and recommended to leave this value at the
+        release version of the first install of this system.
+        Changing this option will not upgrade your system. In fact it
+        is meant to stay constant exactly when you upgrade your system.
+        You should only bump this option, if you are sure that you can
+        or have migrated all state on your system which is affected
+        by this option.
       '';
     };
 
@@ -76,6 +80,12 @@ in
       description = "Default NixOS channel to which the root user is subscribed.";
     };
 
+    configurationRevision = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = "The Git revision of the top-level flake from which this configuration was built.";
+    };
+
   };
 
   config = {
@@ -84,8 +94,6 @@ in
       # These defaults are set here rather than up there so that
       # changing them would not rebuild the manual
       version = mkDefault (cfg.release + cfg.versionSuffix);
-      revision      = mkIf (pathIsDirectory gitRepo) (mkDefault            gitCommitId);
-      versionSuffix = mkIf (pathIsDirectory gitRepo) (mkDefault (".git." + gitCommitId));
     };
 
     # Generate /etc/os-release.  See