anchor.diff:  ::
   :: %~1 - the directory's path
   :: %~2 - /P to force prepending to %PATH%, or empty
  +
   :shellenv.select.path
   
   :: Only one of these paths will be appended to %PATH%
  
positive.code: :: the specified path, otherwise 0.
  ::
  :: %~1 - the directory's path
  :shellenv.check.path
  :: Skip if the path is specified in %PATH%
  for %%p in ( "%PATH:;=" "%" ) do if /i "%~1" == "%%~p" exit /b 1
  
  
negative.code: ::
  :: %~1 - the directory's path
  :: %~2 - /P to force prepending to %PATH%, or empty
  
  :shellenv.set.path
  
  :: Check if the path is not specified in %PATH% and contains executables
  call :shellenv.check.path "%~1" || goto :EOF
  
  