-;; vc-cvs-checkin used to take a 'rev' second argument that allowed
-;; checking in onto a specified branch tip rather than the current
-;; default branch, but nothing in the entire rest of VC exercised
-;; this code. Removing it simplifies the backend interface for all
-;; modes.
-;;
-;; Here's the setup code preserved in amber, in case the logic needs
-;; to be broken out into a method someday; (if rev (concat "-r" rev))
-;; used to be part of the switches passed to vc-cvs-command.
-;;
-;; (unless (or (not rev) (vc-cvs-valid-revision-number-p rev))
-;; (if (not (vc-cvs-valid-symbolic-tag-name-p rev))
-;; (error "%s is not a valid symbolic tag name" rev)
-;; ;; If the input revision is a valid symbolic tag name, we create it
-;; ;; as a branch, commit and switch to it.
-;; (apply 'vc-cvs-command nil 0 files "tag" "-b" (list rev))
-;; (apply 'vc-cvs-command nil 0 files "update" "-r" (list rev))
-;; (mapc (lambda (file) (vc-file-setprop file 'vc-cvs-sticky-tag rev))
-;; files)))
-;;
-;; The following postamble cleaned up after the branch change:
-;;
-;; ;; if this was an explicit check-in (does not include creation of
-;; ;; a branch), remove the sticky tag.
-;; (if (and rev (not (vc-cvs-valid-symbolic-tag-name-p rev)))
-;; (vc-cvs-command nil 0 files "update" "-A"))))
-;; files)))
-;;
-(defun vc-cvs-checkin (files comment)