anchor.diff:  { lib
   , buildGoModule
   , fetchFromGitHub
  -, git
   , testers
   , zlint
   }:
  
positive.code:     owner = "zmap";
      repo = "zlint";
      rev = "v${version}";
      leaveDotGit = true;
      hash = "sha256-1T8WAWsivSEB2xVEM+GpWJuD3DGXPa9uNpuN6/ABsns=";
    };
  
    modRoot = "v3";
  
negative.code:     "-X main.version=${version}"
    ];
  
    # Checks rely on .git directory, leaveDotGit makes the source derivation flaky.
    doCheck = false;
  
    passthru.tests.version = testers.testVersion {
      package = zlint;
  