Properly manage swap files in vim

swap_manage.vim

augroup SwapfileManagement " From a tpope snippet.
    autocmd!
    " The trick is that resetting 'swapfile' deletes the swapfile.
    " The if is most likely for the cases when dir is nuked while editing
    autocmd CursorHold,BufWritePost,BufReadPost,BufLeave *
                \ if isdirectory(expand("<amatch>:h")) |
                \ let &swapfile = &modified | endif
augroup END