nixosTest: Make system.nixos.revision constant

Make the revision metadata constant, in order to avoid needless retesting.

The human version (e.g. 21.05-pre) is left as is, because it is useful
for external modules that test with e.g. nixosTest and rely on that
version number.

Changed files
+7
nixos
+7
nixos/lib/build-vms.nix
···
[ ../modules/virtualisation/qemu-vm.nix
../modules/testing/test-instrumentation.nix # !!! should only get added for automated test runs
{ key = "no-manual"; documentation.nixos.enable = false; }
+
{ key = "no-revision";
+
# Make the revision metadata constant, in order to avoid needless retesting.
+
# The human version (e.g. 21.05-pre) is left as is, because it is useful
+
# for external modules that test with e.g. nixosTest and rely on that
+
# version number.
+
config.system.nixos.revision = "constant-nixos-revision";
+
}
{ key = "nodes"; _module.args.nodes = nodes; }
] ++ optional minimal ../modules/testing/minimal-kernel.nix;
};