Revert the disputed VC change and update the tests

* lisp/vc/vc-hooks.el (vc-working-revision):
Remove the previous change.
(vc-state): Same.  And update the old, incorrect comment about
unregistered files
(http://lists.gnu.org/archive/html/emacs-devel/2016-04/msg00526.html).

* test/lisp/vc/vc-tests.el (vc-test--state): Remove the check
calling `vc-state' on default-directory (VC state is undefined
for directories).  Check that `vc-state' returns nil where it
returned `unregistered' before.  Remove all checks comparing
invocations with the backend passed in explictly and without.
(vc-test--working-revision): Remove all checks comparing
invocations with the backend passed in explictly and without.
Update comments, and add a new one.

1 files changed, 16 insertions, 14 deletions

diff --git a/lisp/vc/vc-hooks.el b/lisp/vc/vc-hooks.el
index 4047bca046a..6b4cd6acd03 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -468,18 +468,21 @@ status of this file.  Otherwise, the value returned is one of:
 
   `unregistered'     The file is not under version control."
 
-  ;; Note: in Emacs 22 and older, return of nil meant the file was
-  ;; unregistered.  This is potentially a source of
-  ;; backward-compatibility bugs.
+  ;; Note: we usually return nil here for unregistered files anyway
+  ;; when called with only one argument.  This doesn't seem to cause
+  ;; any problems.  But if we wanted to change that, we should
+  ;; probably opt for redefining the `registered' command to return
+  ;; non-nil even for unregistered files (maybe also rename it), and
+  ;; then make sure that all `state' implementations handle
+  ;; unregistered file appropriately.
 
   ;; FIXME: New (sub)states needed (?):
   ;; - `copied' and `moved' (might be handled by `removed' and `added')
   (or (vc-file-getprop file 'vc-state)
-      (and (not (vc-registered file)) 'unregistered)
       (when (> (length file) 0)         ;Why??  --Stef
-        (setq backend (or backend (vc-responsible-backend file)))
-        (when backend
-          (vc-state-refresh file backend)))))
+        (setq backend (or backend (vc-backend file)))
+        (when backend
+          (vc-state-refresh file backend)))))
 
 (defun vc-state-refresh (file backend)
   "Quickly recompute the `state' of FILE."
@@ -495,13 +498,12 @@ status of this file.  Otherwise, the value returned is one of:
   "Return the repository version from which FILE was checked out.
 If FILE is not registered, this function always returns nil."
   (or (vc-file-getprop file 'vc-working-revision)
-      (and (vc-registered file)
-           (progn
-             (setq backend (or backend (vc-responsible-backend file)))
-             (when backend
-               (vc-file-setprop file 'vc-working-revision
-                                (vc-call-backend
-                                 backend 'working-revision file)))))))
+      (progn
+        (setq backend (or backend (vc-backend file)))
+        (when backend
+          (vc-file-setprop file 'vc-working-revision
+                           (vc-call-backend
+                            backend 'working-revision file))))))
 
 ;; Backward compatibility.
 (define-obsolete-function-alias