bug#67062: 30.0.50; [PATCH] Abbreviate the revision in 'vc-annotate' (for Git)

[Jim Porter <jporterbugs@gmail.com>]

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On 12/14/2023 4:06 PM, Jim Porter wrote:
> While this patch does add a new backend action, it's purely optional and 
> no other backend needs to be aware of it at all. I suppose I could 
> hardcode the Git behavior in 'vc-short-revision', but that didn't seem 
> to me to have any benefits over this version.

Actually, now that I think about it, I could add the 'vc-short-revision' 
function and then use *that* to set a special variable, like so (see 
attached). I'm not sure how much I like this, but it does completely 
avoid adding any new backend functions (not even optional ones).

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From a5a564a90166933a1664e49243a31aa7b5996edf Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Thu, 14 Dec 2023 11:31:27 -0800
Subject: [PATCH] Abbreviate the VC revision in vc-annotate's buffer name

* lisp/vc/vc-hooks.el (vc-use-short-revision): New variable.
(vc-short-revision): New function.

* lisp/vc/vc-annotate.el (vc-annotate-use-short-revision): New
option...
(vc-annotate): ... use it.

* lisp/vc/vc-git.el (vc-git--rev-parse): Consult
'vc-use-short-revision'.

* etc/NEWS: Announce this change (bug#67062).
---
 etc/NEWS               |  8 ++++++++
 lisp/vc/vc-annotate.el | 10 +++++++++-
 lisp/vc/vc-git.el      |  7 +++++--
 lisp/vc/vc-hooks.el    |  9 +++++++++
 4 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 1ff2f8a149f..d8e7fd1d67f 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -457,6 +457,14 @@ With this value only the revision number is displayed on the mode-line.
 *** Obsolete command 'vc-switch-backend' re-added as 'vc-change-backend'.
 The command was previously obsoleted and unbound in Emacs 28.
 
+---
+*** 'vc-annotate' can now abbreviate the revision in the buffer name.
+VC backends with a 'vc-BACKEND-short-revision' function can show the
+revision in a shorter form, and 'vc-annotate' will use this form in
+its buffer name.  Currently, this only applies to the Git backend.  To
+restore the previous behavior, set 'vc-annotate-use-short-revision' to
+nil.
+
 ** Diff mode
 
 +++
diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index de6c3adbbdb..cfca7cbfac0 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -162,6 +162,11 @@ vc-annotate-menu-elements
   :type '(repeat number)
   :group 'vc)
 
+(defcustom vc-annotate-use-short-revision t
+  "If non-nil, \\[vc-annotate] will use short revisions in its buffer name."
+  :type 'boolean
+  :group 'vc)
+
 (defvar-keymap vc-annotate-mode-map
   :doc "Local keymap used for VC-Annotate mode."
   "a"   #'vc-annotate-revision-previous-to-line
@@ -397,7 +402,10 @@ vc-annotate
    (save-current-buffer
      (vc-ensure-vc-buffer)
      (list buffer-file-name
-	   (let ((def (vc-working-revision buffer-file-name)))
+	   (let ((def (funcall (if vc-annotate-use-short-revision
+                                   #'vc-short-revision
+                                 #'vc-working-revision)
+                               buffer-file-name)))
 	     (if (null current-prefix-arg) def
 	       (vc-read-revision
 		(format-prompt "Annotate from revision" def)
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 2e057ecfaa7..cc96ae8510a 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1835,8 +1835,11 @@ vc-git-previous-revision
 (defun vc-git--rev-parse (rev)
   (with-temp-buffer
     (and
-     (vc-git--out-ok "rev-parse" rev)
-     (buffer-substring-no-properties (point-min) (+ (point-min) 40)))))
+     (apply #'vc-git--out-ok "rev-parse"
+            (append (when vc-use-short-revision '("--short"))
+                    (list rev)))
+     (goto-char (point-min))
+     (buffer-substring-no-properties (point) (pos-eol)))))
 
 (defun vc-git-next-revision (file rev)
   "Git-specific version of `vc-next-revision'."
diff --git a/lisp/vc/vc-hooks.el b/lisp/vc/vc-hooks.el
index 8451128286b..a2d3a2616f6 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -506,6 +506,15 @@ vc-working-revision
                            (vc-call-backend
                             backend 'working-revision file))))))
 
+(defvar vc-use-short-revision nil)
+
+(defun vc-short-revision (file &optional backend)
+  "Return the repository version for FILE in a shortened form.
+If FILE is not registered, this function always returns nil."
+  (let ((vc-use-short-revision t))
+    (vc-call-backend (or backend (vc-backend file))
+                     'working-revision file)))
+
 (defun vc-default-registered (backend file)
   "Check if FILE is registered in BACKEND using vc-BACKEND-master-templates."
   (let ((sym (vc-make-backend-sym backend 'master-templates)))
-- 
2.25.1