neovim clipboard provider for tmux and OSC 52

.vimrc

function! ClipboardCopy(lines, regtype)
  let sum = TryClipboardCmd('md5sum', a:lines)
  call writefile(sum, s:regtype_sum, 'S')
  call writefile([a:regtype], s:regtype_txt, 'S')
  return TryClipboardCmd('clipboard-provider copy', a:lines)
endfunction

function! ClipboardPaste()
  let lines = TryClipboardCmd('clipboard-provider paste')
  let regtype = 'V'
  if filereadable(s:regtype_sum) && filereadable(s:regtype_txt)
    let actual = TryClipboardCmd('md5sum', lines)
    let expected = readfile(s:regtype_sum)
    if actual == expected
      let regtype = readfile(s:regtype_txt)[0]
    endif
  endif
  return [lines, regtype]
endfunction

let g:clipboard = {
      \ 'copy': {
      \     '+': function('ClipboardCopy'),
      \     '*': WithEnv({'COPY_PROVIDERS': 'tmux'}, function('ClipboardCopy')),
      \ },
      \ 'paste': {
      \     '+': function('ClipboardPaste'),
      \     '*': WithEnv({'PASTE_PROVIDERS': 'tmux'}, function('ClipboardPaste')),
      \ }}

clipboard-provider

#!/bin/bash
#
# clipboard provider for neovim
#
# :help provider-clipboard

#exec 2>> ~/clipboard-provider.out
#set -x

: ${COPY_PROVIDERS:=tmux osc52}
: ${PASTE_PROVIDERS:=tmux}
: ${TTY:=`(tty || tty </proc/$PPID/fd/0) 2>/dev/null | grep /dev/`}

main() {
    declare p status=99

    case $1 in
        copy)
            slurp
            for p in $COPY_PROVIDERS; do
                $p-provider copy && status=0
            done ;;

        paste)
            for p in $PASTE_PROVIDERS; do
                $p-provider paste && status=0 && break
            done ;;
    esac

    exit $status
}

# N.B. buffer is global for simplicity
slurp() { buffer=$(base64); }
spit() { base64 --decode <<<"$buffer"; }

tmux-provider() {
    [[ -n $TMUX ]] || return
    case $1 in
        copy) spit | tmux load-buffer - ;;
        paste) tmux save-buffer - ;;
    esac
}

osc52-provider() {
    case $1 in
        copy) [[ -n "$TTY" ]] && printf $'\e]52;c;%s\a' "$buffer" > "$TTY" ;;
        paste) return 1 ;;
    esac
}

main "$@"