" Yank  filename to to '0, with spaces quoted
" (Note: '" doesn't follow '0, so use the former so that they both get updated.)
nmap <silent> <Leader>%   :let @" = substitute(@%, ' ', '\\ ', 'g')<CR>
" Yank file name into '0
" (@" represents the unnamed register and '0)
nmap <silent> <Leader>y     :let @" = bufname()<CR>