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

[Jim Porter <jporterbugs@gmail.com>]

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Currently, when running 'vc-annotate' for a Git repo, the buffer name is 
very long: it has the form "*Annotate FILE (rev REVISION)*", and for 
Git, REVISION is 40(?) characters long. Seeing the full Git SHA isn't 
(in my opinion) useful, especially not in a space-limited area like the 
mode line. At the default width of 80 columns, this pushes much of the 
mode line information off-screen.

Attached is a patch to add a 'short-revision' function for VC backends, 
and a Git implementation for it.

Does this make sense? Should there be an option to restore the previous 
behavior? (I'm not sure why anyone would *want* the old behavior, but 
I'm not opposed to adding an option.)

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From 9103aa64b64d0a79835c072086d040734ddf1c2a Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Fri, 10 Nov 2023 18:42:29 -0800
Subject: [PATCH] Abbreviate the VC revision in vc-annotate's buffer name

* lisp/vc/vc-annotate.el (vc-annotate): Call 'short-revision'

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

* lisp/vc/vc-git.el (vc-git-short-revision): New function.
(vc-git--rev-parse): New optional argument SHORT.
---
 lisp/vc/vc-annotate.el |  4 +++-
 lisp/vc/vc-git.el      | 14 +++++++++++---
 lisp/vc/vc-hooks.el    |  5 +++++
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index de6c3adbbdb..85161347cbf 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -409,7 +409,9 @@ vc-annotate
 				  nil nil "20")))))))
   (vc-ensure-vc-buffer)
   (setq vc-annotate-display-mode display-mode) ;Not sure why.  --Stef
-  (let* ((temp-buffer-name (format "*Annotate %s (rev %s)*" (buffer-name) rev))
+  (let* ((temp-buffer-name (format "*Annotate %s (rev %s)*" (buffer-name)
+                                   (vc-call-backend (vc-backend file)
+                                                    'short-revision rev)))
          (temp-buffer-show-function 'vc-annotate-display-select)
          ;; If BUF is specified, we presume the caller maintains current line,
          ;; so we don't need to do it here.  This implementation may give
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 707fc7cfc07..2ff6f5564ed 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -403,6 +403,11 @@ vc-git-working-revision
   (let (process-file-side-effects)
     (vc-git--rev-parse "HEAD")))
 
+(defun vc-git-short-revision (rev)
+  "Git-specific version of `vc-short-revision'."
+  (let (process-file-side-effects)
+    (vc-git--rev-parse rev 'short)))
+
 (defun vc-git--symbolic-ref (file)
   (or
    (vc-file-getprop file 'vc-git-symbolic-ref)
@@ -1830,11 +1835,14 @@ 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"))
+                    (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 c16fb63b2ff..38c84a0ceea 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -502,6 +502,11 @@ vc-working-revision
                            (vc-call-backend
                             backend 'working-revision file))))))
 
+(defun vc-default-short-revision (_backend rev)
+  "Return a \"shortened\" version of the revision REV.
+This default implementation simply returns REV unchanged."
+  rev)
+
 (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