anchor.diff:  
     serf = buildFromGitHub {
       version = 3;
  -    rev = "91fd53b1d3e624389ed9a295a3fa380e5c7b9dfc";
  +    rev = "121978f00e9c0d81cd2f28b2e628d72b66196de8";
       owner  = "hashicorp";
       repo   = "serf";
  -    sha256 = "16ii1jkcphiihi1wwb9x62f56q9y9gwx3smpzrycx79ixsjl4xqf";
  +    sha256 = "1shav3mw8j974xhyg0hfib612h77wbl5grd7syv32kaz7na4h0rd";
   
       buildInputs = [
         armon_go-metrics
  
positive.code: 
    net = buildFromGitHub {
      version = 3;
      rev = "570fa1c91359c1869590e9cedf3b53162a51a167";
      date = "2017-07-04";
      owner  = "golang";
      repo   = "net";
      sha256 = "0xs42d3c591bhhskxji64hqmn4hx66fgirl4j2lhh0gjgxvimbd8";
      goPackagePath = "golang.org/x/net";
      goPackageAliases = [
        "github.com/hashicorp/go.net"
  
negative.code: 
    prometheus_common = buildFromGitHub {
      version = 3;
      date = "2017-07-06";
      rev = "fb369f752a7f8b880c4a5199af7bfcb8aaaabaa4";
      owner = "prometheus";
      repo = "common";
      sha256 = "1j8g90pp74b9hj1sdayri8pa7p4k6652l050ph6fi95bhmfxyz00";
      buildInputs = [
        net
        prometheus_client_model
  