Is there a way to programmatically determine if a Nixpkgs branch is deprecated?

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1

Most of my flakes contain something like this:

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11";
}

Eventually, the nixos-24.11 branch will be deprecated, and I’ll want to move my flakes to the nixos-25.05 branch. Once the nixos-24.11 branch is deprecated, I want to start getting some sort of warning or error that will tell me that the branch is deprecated. I want a warning or error because I want to make sure that I don’t forget to switch branches.

Here’s what I’ve come up with so far:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11";
    nixpkgs-master.url = "github:NixOS/nixpkgs/master";
  };
  outputs =
    {
      self,
      nixpkgs,
      nixpkgs-master,
    }:
    let
      system = "x86_64-linux";
      pkgs = nixpkgs.legacyPackages."${system}";
      removePeriod = builtins.replaceStrings [ "." ] [ "" ];
    in
    {
      checks."${system}".check-nixpkgs-version = pkgs.runCommand "check-nixpkgs-version" { } ''
        ${nixpkgs.lib.strings.toShellVars {
          nixpkgsReleaseThatsBeingUsed = removePeriod nixpkgs.lib.trivial.release;
          oldestSupportedNixpkgsRelease = nixpkgs-master.lib.trivial.oldestSupportedRelease;
        }}
        if [ "$nixpkgsReleaseThatsBeingUsed" -lt "$oldestSupportedNixpkgsRelease" ]
        then
          echo You’re using an unsupported Nixpkgs release. >&2
          exit 1
        fi
        touch "$out"
      '';
    };
}

When I run nix flake check on that flake, it will fail if I’m using an unsupported Nixpkgs release. It won’t fail if I’m using a deprecated Nixpkgs release. Is there anyway to make it fail if I’m using a deprecated Nixpkgs release? In other words, is there a way to programmatically determine if a Nixpkgs branch is deprecated?

2 
''
if [ "$(date +%y.%m --date='6 months ago')" \> "${nixpkgs.lib.trivial.release}" ]
then
  echo "It's deprecated!"
fi
''
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