"
" undoskip.vim: Don't save undo history for temporary or secure files.
"
" Author: Tom Ryder <tom@sanctum.geek.nz>
" License: Same as Vim itself
"
if exists('loaded_undoskip') || &compatible
  finish
endif
if !has('persistent_undo') || !exists('*glob2regpat')
  finish
endif
let loaded_undoskip = 1

" Set default list of patterns to exclude; mirror documented 'backupskip'
" behavior
if !exists('g:undoskip')
  let g:undoskip = []
  if has('mac')
    call add(g:undoskip, '/private/tmp/*')
  elseif has('unix')
    call add(g:undoskip, '/tmp/*')
  endif
  call extend(g:undoskip, map(
        \ filter([$TMPDIR, $TMP, $TEMP], 'v:val !=# '''''),
        \ 'v:val.''/*'''
        \))
endif

" Internal function returns a local value for 'undofile'
function s:CheckUndoSkip() abort

  " If this isn't a normal buffer, don't save undo data
  if &buftype !=# ''
    return 0
  endif

  " Get the path from the buffer name; if that path matches any of the
  " patterns, don't save undo data
  let path = bufname('%')
  for glob in g:undoskip
    if path =~# glob2regpat(glob)
      return 0
    endif
  endfor

  " Otherwise, we'll use whatever the global setting is
  return &g:undofile

endfunction

" Command interface into the private function's value, does the actual set
command -nargs=0 CheckUndoSkip
      \ let &l:undofile = s:CheckUndoSkip()

" Check the path on every buffer rename, create, or read
augroup undoskip
  autocmd!
  autocmd BufAdd,BufNewFile,BufRead *
        \ CheckUndoSkip
augroup END