Re: 23.0.50; vc-diff needs CVS repository now

[Dan Nicolaescu]

"Eric S. Raymond" <address@hidden> writes:

  > Glenn Morris <address@hidden>:
  > > Any comment on this? The part of vc-diff-internal that does a local
  > > diff where possible seems to have disappeared in the 2007-10-10 change
  > > "rewrite for filesets".
  > 
  > That's right, because the front end was the wrong place to do it.  
  > Modern VCS diff tools automatically stay local when they can.
  > Subversion diff does the right thing, and it's not even an issue
  > in the 3G systems (they keep local repositories).  It's the
  > kind of variation that should be handled in the VCS-specific back ends.
  > 
  > Actually CVS is the only awkward case.  So what ought to happen is
  > for something like the old stay-local logic to be implemented in the CVS 
  > back end.
  > 
  > This is one of my two remaining to-do items for the mode.  But someone
  > who is more of a CVS expert than I might get it done faster.

I adapted the old vc-diff-internal logic to vc-cvs-diff. After the
patch below the CVS repository is not needed if backup files are
present.

Not sure what is the "correct" return value for vc-cvs-diff in the
case when the CVS repository is not accessed (i.e. when using plain
"diff" instead of "cvs diff").

*** vc-cvs.el.~1.93.~   Fri Nov  9 22:02:03 2007
--- vc-cvs.el   Sun Nov 11 12:38:37 2007
***************
*** 515,526 ****
    "Get a difference report using CVS between two revisions of FILE."
      (let* ((async (and (not vc-disable-async-diff) 
                       (vc-stay-local-p files)))
!          (status (apply 'vc-cvs-command (or buffer "*vc-diff*")
!                         (if async 'async 1)
!                         files "diff"
!                         (and oldvers (concat "-r" oldvers))
!                         (and newvers (concat "-r" newvers))
!                         (vc-switches 'CVS 'diff))))
        (if async 1 status)))           ; async diff, pessimistic assumption
  
  (defun vc-cvs-diff-tree (dir &optional rev1 rev2)
--- 515,554 ----
    "Get a difference report using CVS between two revisions of FILE."
      (let* ((async (and (not vc-disable-async-diff) 
                       (vc-stay-local-p files)))
!          (invoke-cvs-diff-list nil)
!          status)
!       ;; Look through the file list and see if any files have backups
!       ;; that can be used to do a plain "diff" instead of "cvs diff".
!       (dolist (file files)
!       (let ((ov oldvers)
!             (nv newvers))
!         (when (or (not ov) (string-equal ov ""))
!           (setq ov (vc-workfile-version file)))
!         (when (string-equal nv "")
!           (setq nv nil))
!         (let ((file-oldvers (vc-version-backup-file file ov))
!               (file-newvers (if (not nv)
!                                 file
!                               (vc-version-backup-file file nv)))
!               (coding-system-for-read (vc-coding-system-for-diff file)))
!           (if (and file-oldvers file-newvers)
!               (apply 'vc-do-command (or buffer "*vc-diff*") 1 "diff" nil
!                      (append (if (listp diff-switches)
!                                  diff-switches
!                                (list diff-switches))
!                              (if (listp vc-diff-switches)
!                                  vc-diff-switches
!                                (list vc-diff-switches))
!                              (list (file-relative-name file-oldvers)
!                                    (file-relative-name file-newvers))))
!             (push file invoke-cvs-diff-list)))))
!       (when invoke-cvs-diff-list
!       (setq status (apply 'vc-cvs-command (or buffer "*vc-diff*")
!                           (if async 'async 1)
!                           invoke-cvs-diff-list "diff"
!                           (and oldvers (concat "-r" oldvers))
!                           (and newvers (concat "-r" newvers))
!                           (vc-switches 'CVS 'diff))))
        (if async 1 status)))           ; async diff, pessimistic assumption
  
  (defun vc-cvs-diff-tree (dir &optional rev1 rev2)