vimrc: add AppendModeline func

.vim/vimrc

@@ -1243,6 +1243,18 @@ set exrc
 set secure
 
 
+" Append modeline before first line in buffer.
+" Use substitute() instead of printf() to handle '%%s' modeline in LaTeX
+" files.
+function! AppendModeline()
+  let l:modeline = printf(' vim: set ts=%d ft=%s fenc=%s ff=%s :',
+        \ &tabstop, &filetype, &fileencoding, &fileformat)
+  let l:modeline = substitute(&commentstring, '%s', l:modeline, '')
+  call append (line('^'), l:modeline)
+endfunction
+nnoremap <silent> <Leader>ml :call AppendModeline()<CR>
+
+
 function! AskQuit (msg, proposed_action)
     if confirm(a:msg, "&Quit?\n" . a:proposed_action) == 1
         exit