vim-bracketed-paste/plugin/bracketed-paste.vim

" Code from:
" http://stackoverflow.com/questions/5585129/pasting-code-into-terminal-window-into-vim-on-mac-os-x
" then https://coderwall.com/p/if9mda
" Docs on bracketed paste mode:
" http://www.xfree86.org/current/ctlseqs.html
if &term =~ "xterm.*" || &term =~ "screen*"
  function! WrapForTmux(s)
    if !exists('$TMUX')
      return a:s
    endif

    let tmux_start = "\<Esc>Ptmux;"
    let tmux_end = "\<Esc>\\"

    return tmux_start . substitute(a:s, "\<Esc>", "\<Esc>\<Esc>", 'g') . tmux_end
  endfunction

  let &t_SI .= WrapForTmux("\<Esc>[?2004h")
  let &t_EI .= WrapForTmux("\<Esc>[?2004l")

  function! XTermPasteBegin()
    set pastetoggle=<Esc>[201~
    set paste
    return ""
  endfunction
  inoremap <special> <expr> <Esc>[200~ XTermPasteBegin()
endif