foo.el

  (defun magit-log-trace-definition-hacks (orig-func &rest args)
    (if (called-interactively-p 'any)
        (let ((file (or (magit-file-relative-name) (user-error "Buffer isn't visiting a file")))
              (fn (replace-regexp-in-string "^.*[#.:]+" "" (which-function)))
              (ref (or magit-buffer-refname (magit-get-current-branch) "HEAD")))
          (message "%s" fn)
          (apply orig-func (list file fn ref)))
      (apply orig-func args)
    ))
  (advice-add 'magit-log-trace-definition :around #'magit-log-trace-definition-hacks)