commit https://github.com/vim/vim/commit/7069bf18e1b1b7bc7640335e07d1022b5acc9048 Author: Bram Moolenaar <Bram@vim.org> Date: Sat Jan 7 20:39:53 2017 +0100 patch 8.0.0150: completion for :filter does not skip the pattern Problem: When the pattern of :filter does not have a separator then completion of the command fails. Solution: Skip over the pattern. (Ozaki Kiichi, clodes #1299)

" Test for joining lines.

func Test_join_with_count()
  new
  call setline(1, ['one', 'two', 'three', 'four'])
  normal J
  call assert_equal('one two', getline(1))
  %del
  call setline(1, ['one', 'two', 'three', 'four'])
  normal 10J
  call assert_equal('one two three four', getline(1))
  quit!
endfunc