;;; -*- Mode:LISP; Base:10; Readtable:CL -*-

;;;
;;; PROPOSED MODIFICATION TO THE META-X BUFFER EDIT COMMAND
;;;

;;;
;;; The current implementation of Meta-X Buffer Edit (same as Meta-X Edit Buffers)
;;; uses the command COM-EDIT-BUFFERS-REVERT and marks a buffer line with an `R'
;;; when the user indicates that a revert is desired:

	    R    * BARNEY.LISP#> L.ZWEI; DJ:

;;; [Other line property indicators in a Buffer Edit session are:
;;; 	    S    Save current buffer into associated pathname
;;; 	    W    Write buffe into a file associated with a pathname specified by the user
;;; 	    ~    Set this buffer's Modified bit to nil (i.e., Set Not Modified)
;;;         P    Attempt to print buffer
;;;         .    Select this buffer upon exiting Buffer Edit Mode
;;;         K    Kill this buffer]
;;;
;;; The following is the implementation of COM-EDIT-BUFFERS-REVERT; it immediately
;;; suggests the template for more useful Buffer Edit startup functions.
;;;
;(DEFCOM COM-EDIT-BUFFERS-REVERT "Mark buffer(s) to be reverted." ()
;  (EDIT-BUFFERS-MAP-OVER-LINES *NUMERIC-ARG* 
;			       (LAMBDA (LINE)
;				 ;; Only buffers with files can be reverted.
;				 (IF (BUFFER-PATHNAME (EDIT-BUFFERS-LINE-BUFFER LINE))
;				     (CLEAR-LINE-PATHNAME LINE #/R)))))


;;;
;;; I propose that upon initial invocation, Meta-X Buffer Edit poll all
;;; buffers associated with files which were not read in with specific
;;; version numbers.  If a later version is found for such a buffer's
;;; associated file, then that line is marked with the symbol ">>", to
;;; be placed between the `.' ("select me as current buffer upon quit")
;;; and the `*' ("I have been modified") column.
;;;
;;; There are then four cases:
;;; 
;;; 	I.   Buffer not modified, no more recent file version extant
;;; 	II.  Buffer not modified, more recent file extant
;;; 	III. Buffer modified, no more recent file version extant
;;; 	IV.  Buffer modified, more recent file extant
;;;
;;; I propose that, upon invocation, all lines be marked as follows:

(I)	      .    FLINTSTONES.SPECIFICATION#> SAZ; DJ:
(II)	    R  >>  WILMA.LISP#> L.ZWEI; DJ:
(III)	    S    * FRED.LISP#> L.ZWEI; DJ:
(IV)	       >>* BARNEY.LISP#> L.ZWEI; DJ:

;;; The last case (type IV.) is clearly the most difficult one to
;;; establish defaults for: in this case, two users have "forked", and
;;; it is not clear who has the "right of way" for saving.  Therefore I
;;; propose that any files which have ">>*" (type IV.) line properties
;;; should choose neither `R' nor `S' properties upon invocation.
;;; However, upon exit of Buffer Edit, the user should be queried to
;;; choose one of the following five options:

;;; 	1. Save the modified buffer into the current filename, as the most recent version
;;;     2. Save the modified buffer into a new filename, to be read in from the keyboard.
;;; 	3. Revert buffer to the most recent version available, flushing current modifications
;;; 	4. Revert buffer to the version of the file originally read in, flushing current modifications
;;; 	5. Run a Source Compare comparing:
;;; 		i.   The original version of the file read in and the current buffer
;;; 		ii.  The most current version of the file written and the current buffer
;;; 		iii. The original version of the file and the most current version.
;;; 	6. Do nothing -- simply return to editing the modified buffer (this is the default).
;;; 		
;;; Clearly, two users who continue to choose option 1 will get into deep trouble after a while;
;;; their concepts of the file in question will be utterly different, and later reconciliation
;;; (possibly extremely time-consuming) will be required.  Clearly, Option 1 cannot be the default,
;;; and, arguably, should be deleted from the query.
;;;

;;;
;;; PROPOSED NEW ZMACS COMMAND -- META-X MAYBE REVERT BUFFER
;;;

;;; I propose that the function invoked by this extended command perform a two-step operation:
;;;
;;; 	I.   Determine if the current buffer is believed by the running ZMACS environment
;;; 	     to be the most recent (">") version
;;;
;;;	IIa.  If so, determine whether or not this belief is accurate; i.e., poll 
;;;    	      the file server for a more recent version than the actual version 
;;;           originally read in.
;;;
;;;	[IIb. If not, do nothing (i.e., determine that the user wanted to see a
;;;           particular file version, not the latest file)]
;;;		 
;;; 	III. If such a more recent version exists, query the user for confirmation, printing
;;; 	     out both the (numeric) file version read in and the highest (numeric) file version
;;; 	     currently in existence during the query.
;;;
;;; 	IV.  Upon confirmation, a Meta-X Revert Buffer should be performed.  
;;;
;;;

;;;
;;; PROPOSED EXTENSION -- META-X MAYBE REVERT ALL BUFFERS
;;;

;;;
;;; I propose the following extension to the above command (it may be implemented either
;;; as a separate extended command, or as a numeric argument hook to the original):
;;; 
;;;     I. For each existing buffer (that is associated with a file), perform the function
;;;        on the buffer that would be performed had the user selected that buffer and
;;;        typed Meta-X Maybe Revert Buffer.
;;;