Vimscript to Read/Write Keybase's Saltpack encrypted files

saltpack.vim

" Keybase - saltpack
augroup SALTPACK
  au!
  " Make sure nothing is written to ~/.viminfo
  au BufReadPre,FileReadPre *.saltpack set viminfo=
  " No other files with unencrypted info
  au BufReadPre,FileReadPre *.saltpack set noswapfile noundofile nobackup

  " Reading Files, assumes you can decrypt
  au BufReadPost,FileReadPost *.saltpack :%!keybase decrypt

  " Writing requires users
  au BufWritePre,FileReadPre *.saltpack let usernames = input('Users: ')
  au BufWritePre,FileReadPre *.saltpack :exec "%!keybase encrypt " . usernames
  au BufWritePost,FileReadPost *.saltpack u
augroup END