bug#39722: Support for bookmark.el in VC directory buffers

[Matthias Meulien]

> (...) Thanks, this is a useful addition. Please push it after 
> fixing minor details: 

Thanks Juri for your remark. I updated the patch. Unfortunately I 
am not authorized to push.

> According to the documentation standard described in (info 
> "(elisp) Documentation Tips") the first line of the docstring 
> should consist of a complete sentence.

I'll keep this in mind.

>From 4d4d3e819dc849268e7b3a15ea0d2390c337c23c Mon Sep 17 00:00:00 2001
From: Matthias Meulien <orontee@gmail.com>
Date: Fri, 21 Feb 2020 22:13:48 +0100
Subject: [PATCH] Bookmark locations can refer to VC directory buffers

* etc/NEWS: Document feature
* lisp/vc/vc-dir.el (vc-dir-mode): Set local bookmark-make-record-function
(bookmark-make-record-default)
(bookmark-prop-get)
(bookmark-default-handler)
(bookmark-get-bookmark-record): Declarations
(vc-dir-bookmark-make-record): Make record used to bookmark a `vc-dir' buffer.
(vc-dir-bookmark-jump): Provides the bookmark-jump behavior for a `vc-dir' 
buffer.
---
 etc/NEWS          |  4 ++++
 lisp/vc/vc-dir.el | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index ae676a9bf8..01c584833b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -348,6 +348,10 @@ symbol property to the browsing functions.  With a new 
command
 'browse-url-with-browser-kind', an URL can explicitly be browsed with
 either an internal or external browser.
 
+** vc-dir.el
+
+*** Support for bookmark.el.
+Bookmark locations can refer to VC directory buffers.
 
 * New Modes and Packages in Emacs 28.1
 
diff --git a/lisp/vc/vc-dir.el b/lisp/vc/vc-dir.el
index 0c9e656add..a86c37c24a 100644
--- a/lisp/vc/vc-dir.el
+++ b/lisp/vc/vc-dir.el
@@ -1106,6 +1106,7 @@ vc-dir-mode
   (set (make-local-variable 'vc-dir-backend) use-vc-backend)
   (set (make-local-variable 'desktop-save-buffer)
        'vc-dir-desktop-buffer-misc-data)
+  (setq-local bookmark-make-record-function #'vc-dir-bookmark-make-record)
   (setq buffer-read-only t)
   (when (boundp 'tool-bar-map)
     (set (make-local-variable 'tool-bar-map) vc-dir-tool-bar-map))
@@ -1466,6 +1467,41 @@ vc-dir-restore-desktop-buffer
             '(vc-dir-mode . vc-dir-restore-desktop-buffer))
 
 
+;;; Support for bookmark.el (adapted from what info.el does).
+
+(declare-function bookmark-make-record-default
+                  "bookmark" (&optional no-file no-context posn))
+(declare-function bookmark-prop-get "bookmark" (bookmark prop))
+(declare-function bookmark-default-handler "bookmark" (bmk))
+(declare-function bookmark-get-bookmark-record "bookmark" (bmk))
+
+(defun vc-dir-bookmark-make-record ()
+  "Make record used to bookmark a `vc-dir' buffer.
+This implements the `bookmark-make-record-function' type for
+`vc-dir' buffers."
+  (let* ((bookmark-name
+          (concat "(" (symbol-name vc-dir-backend) ") "
+                  (file-name-nondirectory
+                   (directory-file-name default-directory))))
+         (defaults (list bookmark-name default-directory)))
+    `(,bookmark-name
+      ,@(bookmark-make-record-default 'no-file)
+      (filename . ,default-directory)
+      (handler . vc-dir-bookmark-jump)
+      (defaults . ,defaults))))
+
+;;;###autoload
+(defun vc-dir-bookmark-jump (bmk)
+  "Provides the bookmark-jump behavior for a `vc-dir' buffer.
+This implements the `handler' function interface for the record
+type returned by `vc-dir-bookmark-make-record'."
+  (let* ((file (bookmark-prop-get bmk 'filename))
+         (buf (save-window-excursion
+                 (vc-dir file) (current-buffer))))
+    (bookmark-default-handler
+     `("" (buffer . ,buf) . ,(bookmark-get-bookmark-record bmk)))))
+
+
 (provide 'vc-dir)
 
 ;;; vc-dir.el ends here
-- 
2.20.1


--
Matthias Meulien