:help clear-undo を見ると， let old_undolevels = &undolevels set undolevels=-1 exe "normal a \<BS>\<Esc>" let &undolevels = old_undolevels unlet old_undolevels とすれば，undo履歴が消去できるとのこと． しかし，コマンド normal は，マッピングを展開す</esc></bs>…