Advise magit-git-push to ask for user confirmation

magit-push-advise.el

;; This demonstrates how to advise[1] magit functions that perform
;; potentially destructive operations (for example `magit-git-push')
;; with a confirmation prompt.
;;
;; The TL;DR of advising is that a function is "wrapped" around the
;; function to be advised, with various different behaviours that can
;; be used (e.g. only conditionally executing the original function).
;;
;; [1]: https://www.gnu.org/software/emacs/manual/html_node/elisp/Advising-Functions.html#Advising-Functions
;;

;; This defines a function that prompts a user for confirmation before
;; pushing a branch.
;;
;; #'yes-or-no-p is a built-in function in emacs that takes a prompt
;; string and shows it to the user, returning `t' (Lisp's `true'
;; value) or `nil' (Lisp's "falsy" value) depending on the user's
;; choice.
;;
;; The arguments to this function are identical to the ones received
;; by `magit-git-push' (the function to be advised itself).
(defun magit-confirm-push (branch target args)
  ;; Construct a prompt string from the supplied arguments ...
  (let ((prompt (format "Do you want to push branch '%s' to '%s'?" branch target)))
    ;; ... and prompt the user with it!
    (yes-or-no-p prompt)))


;; This call advises the function `magit-git-push' to execute the
;; prompt function defined above when it is called.
;;
;; The `:before-while' advice "place" defines that the original
;; function should only be called if the advising function returns
;; `t'.
(advice-add 'magit-git-push :before-while #'magit-confirm-push)

;; That's it, pushing in magit will now ask for confirmation!