bug#63689: 29.0.91; vc-annotate-mode-menu: Cannot open file vc-nil

[Juri Linkov]

0. emacs-29 -Q
1. Eval:

   (context-menu-mode)
   (setq debug-on-error t)
   (require 'vc-annotate)

2. Open any vc-controlled file and type 'C-x v g' (vc-annotate)

3. Click the right mouse button for Context menu with "VC-Annotate" submenu

  Debugger entered--Lisp error: (file-missing "Cannot open load file" "No such 
file or directory" "vc-nil")
    vc-find-backend-function(nil revision-granularity)
    vc-call-backend(nil revision-granularity)
    (eq 'repository (vc-call-backend nil 'revision-granularity))

The error is caused by 'vc-annotate-mode-menu' that contains:

  (keymap "VC-Annotate" ...
    (Show\ changeset\ diff\ of\ revision\ at\ line
     menu-item
     "Show changeset diff of revision at line"
     vc-annotate-show-changeset-diff-revision-at-line
     :enable (eq 'repository (vc-call-backend nil 'revision-granularity))

Note how it tries to use the backend 'nil'.

This is because 'vc-annotate-backend' is evaluated when calling
(require 'vc-annotate) in the *scratch* buffer where it's nil.

Here is the fix for emacs-29:

diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index 70057a6aac7..d83660f9d79 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -330,7 +330,7 @@ vc-annotate-mode-menu
     ["Show changeset diff of revision at line"
      vc-annotate-show-changeset-diff-revision-at-line
      :enable
-     (eq 'repository (vc-call-backend ,vc-annotate-backend 
'revision-granularity))
+     (eq 'repository (vc-call-backend vc-annotate-backend 
'revision-granularity))
      :help "Visit the diff of the revision at line from its previous revision"]
     ["Visit revision at line" vc-annotate-find-revision-at-line
      :help "Visit the revision identified in the current line"]))