nixos-version: Add --json flag and show system.configurationRevision

nixos/doc/manual/man-nixos-version.xml

@@ -20,8 +20,14 @@
    <arg>
     <option>--revision</option>
    </arg>
+
+   <arg>
+    <option>--json</option>
+   </arg>
+
   </cmdsynopsis>
  </refsynopsisdiv>
+
  <refsection>
   <title>Description</title>
   <para>
@@ -84,12 +90,16 @@
    </variablelist>
   </para>
  </refsection>
+
  <refsection>
   <title>Options</title>
+
   <para>
    This command accepts the following options:
   </para>
+
   <variablelist>
+
    <varlistentry>
     <term>
      <option>--hash</option>
@@ -107,6 +117,21 @@
      </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term>
+     <option>--json</option>
+    </term>
+    <listitem>
+     <para>
+      Print a JSON representation of the versions of NixOS and the
+      top-level configuration flake.
+     </para>
+    </listitem>
+   </varlistentry>
+
   </variablelist>
+
  </refsection>
+
 </refentry>

nixos/modules/installer/tools/nixos-version.sh

@@ -8,6 +8,11 @@ case "$1" in
   --hash|--revision)
     echo "@revision@"
     ;;
+  --json)
+    cat <<EOF
+{"nixosVersion": "@version@", "nixpkgsRevision": "@revision@", "configurationRevision": "@configurationRevision@"}
+EOF
+    ;;
   *)
     echo "@version@ (@codeName@)"
     ;;

nixos/modules/installer/tools/tools.nix

@@ -48,6 +48,7 @@ let
     name = "nixos-version";
     src = ./nixos-version.sh;
     inherit (config.system.nixos) version codeName revision;
+    inherit (config.system) configurationRevision;
   };
 
   nixos-enter = makeProg {