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

[Jim Porter <jporterbugs@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1424 bytes --]

On 11/11/2023 10:03 PM, Eli Zaretskii wrote:
>> Date: Sun, 12 Nov 2023 00:00:13 +0200
>> Cc: 67062@debbugs.gnu.org
>> From: Dmitry Gutov <dmitry@gutov.dev>
>>
>> Our general approach is to prefer global options and dynamic dispatch on
>> backends, resorting to using per-backend options when it's much easier
>> to do.
> 
> Which I think is the case here.  What other VC backend has such long
> revision strings?  I couldn't think of any.

Game of Trees[1] is one, though you could argue that that's cheating 
because it uses the Git repository format. It does have a GNU ELPA 
package though, so the author would probably want to add a 
'vc-got-short-revision' function. (Or something similar depending on 
what this patch looks like if/when it merges.) Looking at some GoT 
repositories, they *do* still use the long SHA-1 hashes for revision 
identifiers.

In fact, there are at least a couple Git-compatible VCSes now. Facebook 
wrote one called "Sapling", though I haven't used it. Based on some 
screenshots at least, it looks like Sapling also uses SHA-1 hashes for 
revision IDs.

In any case, we don't necessarily need to provide a default 
implementation for the 'short-revision' function. What about something 
like this? I'm not sure it's better, but it does let us avoid defining a 
no-op implementation for the "default backend".

[1] https://gameoftrees.org/index.html

[2] https://github.com/facebook/sapling

[-- Attachment #2: 0001-Abbreviate-the-VC-revision-in-vc-annotate-s-buffer-n.patch --]
[-- Type: text/plain, Size: 3351 bytes --]

From 0d55915e1984cb002b0f7b9a9e22d03c8b9431a7 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): Try to call 'short-revision'.

* lisp/vc/vc-git.el (vc-git-short-revision): New function.
(vc-git--rev-parse): New optional argument SHORT.

* etc/NEWS: Announce this change (bug#67062).
---
 etc/NEWS               |  6 ++++++
 lisp/vc/vc-annotate.el |  6 +++++-
 lisp/vc/vc-git.el      | 14 +++++++++++---
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 767e4c27b43..0632001648c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -396,6 +396,12 @@ switches for shortlogs, such as the one produced by 'C-x v L'.
 *** 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' functions can convert a
+revision to 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..bee8cf23872 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -409,7 +409,11 @@ 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* ((short-rev (or (ignore-errors (vc-call-backend (vc-backend file)
+                                                        'short-revision rev))
+                        rev))
+         (temp-buffer-name (format "*Annotate %s (rev %s)*" (buffer-name)
+                                   short-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'."
-- 
2.25.1