anchor.diff:            (fetchurl {
               url = "mirror://ubuntu/dists/bionic/universe/binary-amd64/Packages.xz";
               sha256 = "1832nqpn4ap95b3sj870xqayrza9in4kih9jkmjax27pq6x15v1r";
  +          })
  +        ];
  +      urlPrefix = "mirror://ubuntu";
  +      packages = commonDebPackages ++ [ "diffutils" "libc-bin" ];
  +    };
  +
  +    ubuntu2004i386 = {
  +      name = "ubuntu-20.04-focal-i386";
  +      fullName = "Ubuntu 20.04 Focal (i386)";
  +      packagesLists =
  +        [ (fetchurl {
  +            url = "mirror://ubuntu/dists/focal/main/binary-i386/Packages.xz";
  +            sha256 = "sha256-7RAYURoN3RKYQAHpwBS9TIV6vCmpURpphyMJQmV4wLc=";
  +          })
  +          (fetchurl {
  +            url = "mirror://ubuntu/dists/focal/universe/binary-i386/Packages.xz";
  +            sha256 = "sha256-oA551xVE80volUPgkMyvzpQ1d+GhuZd4DAe7dXZnULM=";
  +          })
  +        ];
  +      urlPrefix = "mirror://ubuntu";
  +      packages = commonDebPackages ++ [ "diffutils" "libc-bin" ];
  +    };
  +
  +    ubuntu2004x86_64 = {
  +      name = "ubuntu-20.04-focal-amd64";
  +      fullName = "Ubuntu 20.04 Focal (amd64)";
  +      packagesLists =
  +        [ (fetchurl {
  +            url = "mirror://ubuntu/dists/focal/main/binary-amd64/Packages.xz";
  +            sha256 = "sha256-d1eSH/j+7Zw5NKDJk21EG6SiOL7j6myMHfXLzUP8mGE=";
  +          })
  +          (fetchurl {
  +            url = "mirror://ubuntu/dists/focal/universe/binary-amd64/Packages.xz";
  +            sha256 = "sha256-RqdG2seJvZU3rKVNsWgLnf9RwkgVMRE1A4IZnX2WudE=";
             })
           ];
         urlPrefix = "mirror://ubuntu";
  
positive.code:   /* The set of supported Dpkg-based distributions. */
  
    debDistros = {
  
      # Interestingly, the SHA-256 hashes provided by Ubuntu in
      # http://nl.archive.ubuntu.com/ubuntu/dists/{gutsy,hardy}/Release are
      # wrong, but the SHA-1 and MD5 hashes are correct.  Intrepid is fine.
  
      ubuntu1204i386 = {
        name = "ubuntu-12.04-precise-i386";
        fullName = "Ubuntu 12.04 Precise (i386)";
        packagesLists =
          [ (fetchurl {
              url = "mirror://ubuntu/dists/precise/main/binary-i386/Packages.bz2";
              sha256 = "18ns9h4qhvjfcip9z55grzi371racxavgqkp6b5kfkdq2wwwax2d";
            })
            (fetchurl {
              url = "mirror://ubuntu/dists/precise/universe/binary-i386/Packages.bz2";
              sha256 = "085lkzbnzkc74kfdmwdc32sfqyfz8dr0rbiifk8kx9jih3xjw2jk";
            })
          ];
        urlPrefix = "mirror://ubuntu";
        packages = commonDebPackages ++ [ "diffutils" ];
      };
  
      ubuntu1204x86_64 = {
        name = "ubuntu-12.04-precise-amd64";
        fullName = "Ubuntu 12.04 Precise (amd64)";
        packagesLists =
          [ (fetchurl {
              url = "mirror://ubuntu/dists/precise/main/binary-amd64/Packages.bz2";
              sha256 = "1aabpn0hdih6cbabyn87yvhccqj44q9k03mqmjsb920iqlckl3fc";
            })
            (fetchurl {
              url = "mirror://ubuntu/dists/precise/universe/binary-amd64/Packages.bz2";
              sha256 = "0x4hz5aplximgb7gnpvrhkw8m7a40s80rkm5b8hil0afblwlg4vr";
            })
          ];
        urlPrefix = "mirror://ubuntu";
        packages = commonDebPackages ++ [ "diffutils" ];
      };
  
      ubuntu1404i386 = {
        name = "ubuntu-14.04-trusty-i386";
        fullName = "Ubuntu 14.04 Trusty (i386)";
  
negative.code:       packages = commonDebPackages ++ [ "diffutils" "libc-bin" ];
      };
  
      ubuntu1804i386 = {
        name = "ubuntu-18.04-bionic-i386";
        fullName = "Ubuntu 18.04 Bionic (i386)";
  