Without the change the eval fails as:

$ nix build --no-link -f. diffoscope
error:
   … while evaluating the attribute 'drvPath'
     at lib/customisation.nix:416:7:
      415|     // {
      416|       drvPath =
         |       ^
      417|         assert condition;

   … while calling the 'derivationStrict' builtin
     at <nix/derivation-internal.nix>:34:12:
       33|
       34|   strict = derivationStrict drvAttrs;
         |            ^
       35|

   (stack trace truncated; use '--show-trace' to show the full, detailed trace)

   error: fetchFromGitHub requires one of either `rev` or `tag` to be provided (not both).

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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