master b49da1b7e0e: vc-git, vc-hg log outgoing: Avoid unnecessary mergebase calls

branch: master
commit b49da1b7e0e639092edff2959720b4df4b86fcc2
Author: Sean Whitton <[email protected]>
Commit: Sean Whitton <[email protected]>

    vc-git, vc-hg log outgoing: Avoid unnecessary mergebase calls
    
    * lisp/vc/vc.el (vc-standard-log-outgoing): New function.
    (vc-default-log-outgoing):
    * lisp/vc/vc-git.el (vc-git-log-outgoing):
    * lisp/vc/vc-hg.el (vc-hg-log-outgoing): Use it.
---
 lisp/vc/vc-git.el |  5 +++++
 lisp/vc/vc-hg.el  |  5 +++++
 lisp/vc/vc.el     | 28 +++++++++++++++++++++++-----
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index e68945cda8d..312abcbb975 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -909,6 +909,11 @@ them one-by-one, accepting the first that has an upstream.)"
               (when-let* ((upstream (branch-upstream target)))
                 (throw 'ret upstream))))))))))
 
+(declare-function vc-standard-log-outgoing "vc")
+
+(defun vc-git-log-outgoing (buffer upstream-location)
+  (vc-standard-log-outgoing 'Git buffer upstream-location 'skip-mergebase))
+
 (defun vc-git-dir--branch-headers ()
   "Return headers for branch-related information."
   (let ((branch (vc-git-working-branch))
diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
index 0fa22d97fad..c00723af102 100644
--- a/lisp/vc/vc-hg.el
+++ b/lisp/vc/vc-hg.el
@@ -2015,6 +2015,11 @@ This is based on the following assumptions:
 (ii) there is only one remote head for the current branch."
   (cdr (assq 'branch (vc-hg--working-branch))))
 
+(declare-function vc-standard-log-outgoing "vc")
+
+(defun vc-hg-log-outgoing (buffer upstream-location)
+  (vc-standard-log-outgoing 'Hg buffer upstream-location 'skip-mergebase))
+
 (provide 'vc-hg)
 
 ;;; vc-hg.el ends here
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index ddac5724f63..46715d01693 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -460,17 +460,21 @@
 ;;   revision shown, rather than the working revision, which is normally
 ;;   the case).  Not all backends support this.
 ;;
-;; - log-outgoing (buffer upstream-location) (DEPRECATED)
+;; - log-outgoing (buffer upstream-location) (SOFT DEPRECATED)
 ;;
 ;;   Insert in BUFFER the revision log for the changes that will be
 ;;   sent when performing a push operation to UPSTREAM-LOCATION.
-;;   Deprecated: implement incoming-revision and mergebase instead.
+;;   Deprecated: implement incoming-revision and mergebase instead,
+;;   unless what `vc-default-log-outgoing' does with those is too slow
+;;   for this backend.
 ;;
-;; - log-incoming (buffer upstream-location) (DEPRECATED)
+;; - log-incoming (buffer upstream-location) (SOFT DEPRECATED)
 ;;
 ;;   Insert in BUFFER the revision log for the changes that will be
 ;;   received when performing a pull operation from UPSTREAM-LOCATION.
-;;   Deprecated: implement incoming-revision and mergebase instead.
+;;   Deprecated: implement incoming-revision and mergebase instead,
+;;   unless what `vc-default-log-incoming' does with those is too slow
+;;   for this backend.
 ;;
 ;; * incoming-revision (&optional upstream-location refresh)
 ;;
@@ -4710,11 +4714,25 @@ can be a remote branch name."
   "31.1")
 
 (defun vc-default-log-outgoing (backend buffer upstream-location)
+  (vc-standard-log-outgoing backend buffer upstream-location nil))
+
+(defun vc-standard-log-outgoing
+    (backend buffer upstream-location &optional skip-mergebase)
+  "VC `log-outgoing' in terms of `incoming-revision' and `mergebase'.
+BACKEND is the VC backend, BUFFER is the buffer to log to,
+UPSTREAM-LOCATION is the place to which the changes are outgoing.
+Optional argument SKIP-MERGEBASE, if non-nil, skips calling `mergebase'
+and instead passes `incoming-revision' directly as the log limit.
+For some backends this is equivalent, and saves running one external
+command.  Whether this equivalence holds depends on the details of the
+`print-log' implementation for BACKEND when `vc-log-view-types' contains
+`log-outgoing'."
   (let ((incoming (vc--incoming-revision backend upstream-location))
         (default-directory (vc-root-dir backend)))
     (vc-call-backend backend 'print-log (list default-directory)
                      buffer t ""
-                     (vc-call-backend backend 'mergebase incoming))))
+                     (if skip-mergebase incoming
+                       (vc-call-backend backend 'mergebase incoming)))))
 
 ;;;###autoload
 (defun vc-log-search (pattern)