Buffalo() the buffer follower

" Automatically open buffer when shortest partial tab expands to unique name
" Barry Arthur, Mar 10 2012

function! Buffalo()
  call g:bl.update()
  let cmdline = getcmdline()
  let cmd = substitute(cmdline, '^\(\w\+\s\+\).*', '\1', '')
  let partial = substitute(cmdline, '^'.cmd, '', '')
  let bl = g:bl.filter('v:val["name"] =~ "' . partial . '"')
  if len(bl.buffers) == 1
    return substitute(bl.to_s('%n'), "^".partial, '', '') . "\<CR>"
  else
    return "\<c-d>"
  endif
endfunction

cnoremap <expr> <tab> Buffalo()