From 0a48d2973363361211c2e91c4f6c7bb75f16a853 Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@janestreet.com>
Date: Fri, 13 Sep 2024 16:35:19 -0400
Subject: [PATCH] Add a "last pushed revision" default in the vc-diff prompt

C-u M-x vc-root-diff will prompt for the old revision to use for the
diff.  It includes the current working revision as a default.

Now it also includes the last pushed revision as a default, through a
new pushed-revision vc backend function.

* lisp/vc/vc-git.el (vc-git-pushed-revision): Add.
(vc-git-log-outgoing): Use vc-git-pushed-revision.
* lisp/vc/vc-hg.el (vc-hg-pushed-revision): Add.
* lisp/vc/vc.el (vc-default-pushed-revision): Add new backend function
with default implementation returning nil.
(vc-diff-build-argument-list-internal): Add the last pushed revision
as a default. (bug#62940)
---
 lisp/vc/vc-git.el | 10 +++++++---
 lisp/vc/vc-hg.el  |  6 ++++++
 lisp/vc/vc.el     |  7 +++++++
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 2a7c8ae5fc4..4afbb978a3f 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1512,6 +1512,12 @@ vc-git-print-log
                   (list "-p"))
 		'("--")))))))
 
+(defun vc-git-pushed-revision (_file &optional remote-location)
+  "Return the ref for REMOTE-LOCATION."
+  (if (and remote-location (not (string-empty-p remote-location)))
+      remote-location
+    "@{upstream}"))
+
 (defun vc-git-log-outgoing (buffer remote-location)
   (vc-setup-buffer buffer)
   (apply #'vc-git-command buffer 'async nil
@@ -1520,9 +1526,7 @@ vc-git-log-outgoing
            ,(format "--pretty=tformat:%s" (car vc-git-root-log-format))
            "--abbrev-commit"
            ,@(ensure-list vc-git-shortlog-switches)
-           ,(concat (if (string= remote-location "")
-	                "@{upstream}"
-	              remote-location)
+           ,(concat (vc-git-pushed-revision nil remote-location)
 	            "..HEAD"))))
 
 (defun vc-git-log-incoming (buffer remote-location)
diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
index 876d86dc24f..c0afb225871 100644
--- a/lisp/vc/vc-hg.el
+++ b/lisp/vc/vc-hg.el
@@ -1422,6 +1422,12 @@ vc-hg-log-incoming
   (vc-hg-command buffer 1 nil "incoming" "-n" (unless (string= remote-location "")
 						remote-location)))
 
+(defun vc-hg-pushed-revision (_file &optional remote-location)
+  "Return a revspec for the last commit not outgoing to REMOTE-LOCATION."
+  (unless remote-location
+    (setq remote-location ""))
+  (format "last(. and not outgoing(%s))" remote-location))
+
 (defun vc-hg-log-outgoing (buffer remote-location)
   (vc-setup-buffer buffer)
   (vc-hg-command buffer 1 nil "outgoing" "-n" (unless (string= remote-location "")
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 597a1622f5a..0125924cc51 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -2061,6 +2061,11 @@ vc-read-multiple-revisions
 INITIAL-INPUT are passed on to `vc-read-revision' directly."
   (vc-read-revision prompt files backend default initial-input t))
 
+(defun vc-default-pushed-revision (_file &optional _remote-location)
+  "Return the last pushed revision of FILE.
+The default is to return nil always."
+  nil)
+
 (defun vc-diff-build-argument-list-internal (&optional fileset)
   "Build argument list for calling internal diff functions."
   (let* ((vc-fileset (or fileset (vc-deduce-fileset t))) ;FIXME: why t?  --Stef
@@ -2069,6 +2074,8 @@ vc-diff-build-argument-list-internal
          (first (car files))
          (rev1-default nil)
          ) ;; (rev2-default nil)
+    (when-let ((pushed-revision (vc-call-backend backend 'pushed-revision first)))
+      (push pushed-revision rev1-default))
     (cond
      ;; someday we may be able to do revision completion on non-singleton
      ;; filesets, but not yet.
-- 
2.39.3