* lisp/vc/vc-bzr.el (vc-bzr--pushpull): Return buffer's process.

* lisp/vc/vc-git.el (vc-git--pushpull): Add comment.

* lisp/vc/vc.el (vc-pull-and-push): Expand docstring about
prerequisites for backend to support this command (bug#60569).

etc/NEWS

@@ -2080,7 +2080,7 @@ This is in addition to the old keybindings 'C-c C-n' and 'C-c C-p'.
 ---
 *** New command 'vc-pull-and-push'.
 This commands first does a "pull" command, and if that is successful,
-does a "push" command afterwards.
+does a "push" command afterwards.  Currently supported in Git and Bzr.
 
 +++
 *** 'C-x v b' prefix key is used now for branch commands.

lisp/vc/vc-bzr.el

@@ -381,7 +381,9 @@ If PROMPT is non-nil, prompt for the Bzr command to run."
           (setq-local compile-command
                       (concat vc-bzr-program " " command " "
                               (if args (mapconcat #'identity args " ") "")))))
-      (vc-set-async-update buf))))
+      (vc-set-async-update buf)
+      ;; Return the process for `vc-pull-and-push'
+      (get-buffer-process buf))))
 
 (defun vc-bzr-pull (prompt)
   "Pull changes into the current Bzr branch.

lisp/vc/vc-git.el

@@ -1168,6 +1168,7 @@ If PROMPT is non-nil, prompt for the Git command to run."
                           (lambda (_name-of-mode) buffer)
                           nil))))
     (vc-set-async-update buffer)
+    ;; Return the process for `vc-pull-and-push'
     proc))
 
 (defun vc-git-pull (prompt)

lisp/vc/vc.el

@@ -3064,7 +3064,8 @@ On a distributed version control system, this runs a \"pull\"
 operation on the current branch, prompting for the precise
 command if required.  Optional prefix ARG non-nil forces a prompt
 for the VCS command to run.  If this is successful, a \"push\"
-operation will then be done.
+operation will then be done.  This is supported only in backends
+where the pull operation returns a process.
 
 On a non-distributed version control system, this signals an error.
 It also signals an error in a Bazaar bound branch."