vc.el and diff-switches containing "-r"

vc.el and diff-switches containing "-r"

[Michael Ernst]

vc.el unconditionally uses `diff-switches' (though it also concatenates
`vc-diff-switches').  However, some switches that are sensible in
`diff-switches' are not sensible as arguments to (say) "cvs diff".  This
patch corrects the problem.  (Another solution would be for
`vc-diff-switches' to override `diff-switches', if set, rather than for
both to be used.)

2002-03-25  Michael Ernst  <mernst@alum.mit.edu>

	* vc.el (vc-diff-internal, vc-diff-switches-list): Remove "-r"
	from `diff-switches'.

*** /usr/local/share/emacs/21.2/lisp/vc.el	Wed Mar 13 14:51:46 2002
--- -	Mon Mar 25 16:06:25 2002
***************
*** 1815,1821 ****
      (if (and file-rel1 file-rel2)
          (apply 'vc-do-command "*vc-diff*" 1 "diff" nil
!                (append (if (listp diff-switches)
!                            diff-switches
!                          (list diff-switches))
                         (if (listp vc-diff-switches)
                             vc-diff-switches
--- 1815,1822 ----
      (if (and file-rel1 file-rel2)
          (apply 'vc-do-command "*vc-diff*" 1 "diff" nil
!                (append (remove "-r"
! 			       (if (listp diff-switches)
! 				   diff-switches
! 				 (list diff-switches)))
                         (if (listp vc-diff-switches)
                             vc-diff-switches
***************
*** 1828,1832 ****
    "Return the list of switches to use for executing diff under BACKEND."
    `(append 
!     (if (listp diff-switches) diff-switches (list diff-switches))
      (if (listp vc-diff-switches) vc-diff-switches (list vc-diff-switches))
      (let ((backend-switches 
--- 1829,1834 ----
    "Return the list of switches to use for executing diff under BACKEND."
    `(append 
!     (remove "-r"
!             (if (listp diff-switches) diff-switches (list diff-switches)))
      (if (listp vc-diff-switches) vc-diff-switches (list vc-diff-switches))
      (let ((backend-switches 

Re: vc.el and diff-switches containing "-r"

[Andre Spiegel]

Michael Ernst <mernst@alum.mit.edu> writes:

> vc.el unconditionally uses `diff-switches' (though it also concatenates
> `vc-diff-switches').  However, some switches that are sensible in
> `diff-switches' are not sensible as arguments to (say) "cvs diff".  This
> patch corrects the problem.  (Another solution would be for
> `vc-diff-switches' to override `diff-switches', if set, rather than for
> both to be used.)

Thanks for the report.  I do favour the latter approach, where
vc-diff-switches overrides diff-switches if set.  Likewise, I think
vc-cvs-diff-switches should override the other two if set, rather
than be concatenated.

I don't like the idea of treating "-r" specially as in your patch --
the same problem would be bound to come up with other options and
other backends as well.

I will change the behaviour as outlined above as soon as I find time
to rework the backend-specific variable handling, as I am planning
anyway.  It will be before the next Emacs release.  Until then, I hope
you can do with your local modification.