Re: SCCS version control cannot cope when latest delta is of type 'removed'

[Kevin Rodgers <ihs_4664@yahoo.com>]

Chet Wood wrote:
 > In the shell using regular sccs commands, or in emacs using C-x C-q,
 > check out an sccs-versioned file that has had its latest delta
 > removed. Then, in another emacs session, VC commands, such as
 > vc-directory or vc-next-action, fail.
 >
 > When vc-sccs-workfile-version(file) searches for the latest version
 > number in the sccs file, it searches for "^Ad D". However, there can
 > be another type of delta, namely "^Ad R". In this case, the delta does
 > not really exist-- it was removed, leaving this delta entry as a
 > "bread crumb" in the sccs file. The search is limited to the first
 > delta entry, so it fails and the function returns nil, and as a
 > result, a blank version number is passed to vcdiff and it fails.
 >
 > I tried changing the search to accept [D|R] but it then returns the
 > removed delta number, which does not really exist, and other errors
 > ensue.
 >
 > (This scenario happens sometimes when the Sun CodeManager configuration
 > management tool is used. It apparently inserts its own bookkeeping
 > comments by adding and removing a delta. It seems to happen when a new
 > file is added to the workspace, then the workspace is putback to
 > another workspace.)
 >
 > Suggested Fix:
 > The search should skip the top delta in the sccs file if it is of type
 > "removed", and return the version number of the next delta.
 > But IMHO it would be more robust to run the command "sccs
 > prt filename" to obtain the version, rather than relying on the
 > internal file format, assuming this works on all platforms.

Your second suggestion may be more robust, but since vc-parse-buffer
returns a useful value to vc-sccs-workfile-version, I think we can take
advantage of that to implement a simple fix:

2006-10-27  Kevin Rodgers  <ihs_4664@yahoo.com>

	* vc-sccs.el (vc-sccs-workfile-version): If the top delta entry
           was removed, return the next entry.


*** vc-sccs.el~	2006-04-22 06:42:26.750000000 -0600
--- vc-sccs.el	2006-10-27 15:53:08.760978700 -0600
***************
*** 144,150 ****
       ;; rather than just the first entry, because the
       ;; first entry might be a deleted ("R") version.
       (vc-insert-file (vc-name file) "^\001e\n\001[^s]")
!     (vc-parse-buffer "^\001d D \\([^ ]+\\)" 1)))

   (defun vc-sccs-checkout-model (file)
     "SCCS-specific version of `vc-checkout-model'."
--- 144,155 ----
       ;; rather than just the first entry, because the
       ;; first entry might be a deleted ("R") version.
       (vc-insert-file (vc-name file) "^\001e\n\001[^s]")
!     (let ((top-delta (save-excursion	; vc-parse-buffer changes point
! 		       (vc-parse-buffer "^\001d \\([DR]\\) \\([^ ]+\\)" 2))))
!       (if (and top-delta
! 	       (equal (match-string 1) "R")) ; the delta entry was Removed
! 	  (vc-parse-buffer "^\001d D \\([^ ]+\\)" 1)
! 	top-delta))))

   (defun vc-sccs-checkout-model (file)
     "SCCS-specific version of `vc-checkout-model'."

 > A workaround is to make a change to the checked-out file (like adding
 > a blank line to the end or any other change) and check it back
 > in outside of emacs, creating a real latest delta. Then it can be
 > checked out again, and should work fine.

-- 
Kevin