anchor.diff:    src = fetchFromGitHub {
       owner = "Ardour";
       repo = "ardour";
  -    rev = "b00d75adf63db155ef2873bd9d259dc8ca256be6";
  -    sha256 = "1gnrcnq2ksnh7fsa301v1c4p5dqrbqpjylf02rg3za3ab58wxi7l";
  +    rev = "d84a8222f2b6dab5028b2586f798535a8766670e";
  +    sha256 = "149gswphz77m3pkzsn2nqbm6yvcfa3fva560bcvjzlgb73f64q5l";
     };
   
     buildInputs =
  
positive.code:     ];
  
    # ardour's wscript has a "tarball" target but that required the git revision
    # be available. Since this is an unzipped tarball fetched from github we 
    # have to do that ourself.
    patchPhase = ''
      printf '#include "libs/ardour/ardour/revision.h"\nnamespace ARDOUR { const char* revision = \"${tag}-${builtins.substring 0 8 src.rev}\"; }\n' > libs/ardour/revision.cc
  
negative.code:   # "git describe" when _not_ on an annotated tag(!): MAJOR.MINOR-REV-HASH.
  
    # Version to build.
    tag = "4.7";
  
  in
  
  