anchor.diff:  }
   
   Future _doDocsPopulate(TaskContext ctx, TempDir dir, Collection<String> libs,
  -                       String packageDir, List<String> excludeList, bool linkApi) {
  +                       String packageDir, List<String> excludeList,
  +                       bool linkApi, Func2<TaskContext, String, Future> postBuild) {
     final args = ['--pkg', packageDir, '--omit-generation-time', '--out', dir.path, '--verbose'];
   
     if(linkApi) {
  
positive.code:     targetBranch = ctx.arguments[_targetBranchArg];
  
      return _compileDocs(ctx, targetBranch, delayedLibraryList, packageDir,
          excludeLibs, linkApi);
    },
    description: 'Generate documentation for the provided libraries.',
    config: (parser) => _dartDocParserConfig(parser, targetBranch));
  
negative.code: 
          // yeah, silly. ctx.fail should blow up. Should not get heer
          assert(dartDocSuccess);
  
          if(postBuild != null) {
            // TODO: this should be platfrom specific...pathos?
            return postBuild(ctx.getSubLogger('post-build'), dir.path);
          }
        });
  }
  