From 67084d2292d93f582370503df74c68c0e95bd209 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-short-revision): New function...

* lisp/vc/vc-annotate.el (vc-annotate): ... call it.

* lisp/vc/vc-git.el (vc-git-use-short-revisions): New option.
(vc-git-short-revision): New function.
(vc-git--rev-parse): Add SHORT argument.

* etc/NEWS: Announce this change (bug#67062).
---
 etc/NEWS               |  6 ++++++
 lisp/vc/vc-annotate.el |  2 +-
 lisp/vc/vc-git.el      | 20 +++++++++++++++++---
 lisp/vc/vc-hooks.el    |  8 ++++++++
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 1ff2f8a149f..a2dcdfc901a 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -457,6 +457,12 @@ 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, the Git backend supports this.
+
 ** Diff mode
 
 +++
diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index de6c3adbbdb..a63b8fe3ec2 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -397,7 +397,7 @@ vc-annotate
    (save-current-buffer
      (vc-ensure-vc-buffer)
      (list buffer-file-name
-	   (let ((def (vc-working-revision buffer-file-name)))
+	   (let ((def (vc-short-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..f8675620568 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -111,6 +111,12 @@ vc-git
   :version "24.1"
   :group 'vc)
 
+(defcustom vc-git-use-short-revisions t
+  "If non-nil, use short Git revisions when requested.
+If nil, always use full Git revisions."
+  :type 'boolean
+  :version "30.1")
+
 (defcustom vc-git-diff-switches t
   "String or list of strings specifying switches for Git diff under VC.
 If nil, use the value of `vc-diff-switches'.  If t, use no switches."
@@ -403,6 +409,11 @@ vc-git-working-revision
   (let (process-file-side-effects)
     (vc-git--rev-parse "HEAD")))
 
+(defun vc-git-short-revision (_file)
+  "Return the working revision in abbreviated form."
+  (let (process-file-side-effects)
+    (vc-git--rev-parse "HEAD" 'short)))
+
 (defun vc-git--symbolic-ref (file)
   (or
    (vc-file-getprop file 'vc-git-symbolic-ref)
@@ -1832,11 +1843,14 @@ vc-git-previous-revision
     ;; does not (and cannot) quote.
     (vc-git--rev-parse (concat rev "~1"))))
 
-(defun vc-git--rev-parse (rev)
+(defun vc-git--rev-parse (rev &optional short)
   (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 short '("--short")) ;; FIXME
+                    (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..0f36e2bc7ae 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -506,6 +506,14 @@ vc-working-revision
                            (vc-call-backend
                             backend 'working-revision file))))))
 
+(defun vc-short-revision (file &optional backend)
+  "Return the repository version for FILE in human-readable form.
+If FILE is not registered, this function always returns nil."
+  (setq backend (or backend (vc-backend file)))
+  (if (vc-find-backend-function backend 'short-revision)
+      (vc-call-backend backend 'short-revision file)
+    (vc-working-revision file backend)))
+
 (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