Switching github users when using magit

switch-github-user.el

;; make sure we always use the correct user for git when using magit, and save it off for later as well
;; in the local user property for the repo
(require 'subr-x)

(defun yammer-git-repo-p ()
  (string-match "int.yammer.com" (shell-command-to-string "git config --get remote.origin.url")))

(defun yammer-git-property (prop)
  (string-trim (shell-command-to-string (format "git config --get %s" prop))))

(defcustom yammer-git-user-key
  "user.yam-name"
  "key for the global git property which holds the internal github user, default: user.yam-name")
(defcustom yammer-git-email-key
  "user.yam-email"
  "key for the global git property which holds the internal github email, default: user.yam-email")

(defun local-user-overwrite-set-p ()
  (not (string-empty-p (shell-command-to-string "git config --local --get user.name"))))

(defun set-yammer-user-for-git ()
  (interactive)
  (if (yammer-git-repo-p)
      (if (not (local-user-overwrite-set-p))
          (let ((name (yammer-git-property yammer-git-user-key))
                (email (yammer-git-property yammer-git-email-key)))
            (message (format "Setting user.name %s and user.email %s" name email))
            (shell-command (format "git config --local --add user.name %s" name))
            (shell-command (format "git config --local --add user.email %s" email)))
        (message "local user overwrite already set"))
    (message "Not a yammer git repository")))

(add-hook 'magit-mode-hook #'set-yammer-user-for-git)