RE: Customize buttons that change user'scustomfileshouldaskforconfirmation

[Drew Adams]

                >     If it implies reading from the file, this could
                >     be used to load values from a diffent custom-file
                >     (to see what they are) before actually using them.
                >
                > No way to do that has yet been proposed. S=>F means
                > to get the values from the  custom-set* in the user's
                > .emacs (custom file). There is currently no way to
                > designate a different library to use as the source of
                > `saved' settings.
        
               M-: (setq custom-file "X")
               M-x customize
               do some editing
               save (into X)
               M-: (setq custom-file "Y")
               get (from ?)
        
               Question is "from X" or "from Y"?
        
           Good point. I would think it should be Y.
        
        Absolutely not. `(setq custom-file "Y")' means that you 
        want Custom to
        _write_ to Y.  If you want Y to be read you have to load Y...
        If you want Y to be your Custom file, write: (setq custom-file "Y")
        (load custom-file) in your .emacs, as the docstring of 
        `custom-file' recommends.
    
    The question was about "getting" values from a custom file 
    without loading that file. You are confirming, I guess, that 
    there is no way to change custom-file for purposes of 
    get-but-do-not-load.  

  If instead of `M-: (setq custom-file "Y")' we set custom-file through
  Custom, then the up to date Custom Info is _immediately_ in Y, without
  having to save any further option.  (Because saving `custom-file'
  itself took care of things.)
  So if somebody _really_ wants to change Custom file during an emacs
  session (instead of from .emacs) the way to do it is through Custom.

Got it.