nix: add check to assert that *-prev versions actually differ

Avoids accidentally setting the current and previous version to the same
version.

On-behalf-of: SAP julian.schindel@sap.com
Signed-off-by: Julian Schindel <julian.schindel@cyberus-technology.de>

Author: arctic-alpaca

flake.nix

@@ -71,6 +71,14 @@
         exportOutputs
         ;
     in
+    assert (
+      inputs.cloud-hypervisor.rev != inputs.cloud-hypervisor-prev.rev
+      || throw "cloud-hypervisor and cloud-hypervisor-prev must differ (both are ${toString inputs.cloud-hypervisor.rev})"
+    );
+    assert (
+      inputs.libvirt.rev != inputs.libvirt-prev.rev
+      || throw "libvirt and libvirt-prev must differ (both are ${toString inputs.libvirt.rev})"
+    );
     exportOutputs (
       {
         self,