vim-patch:8.0.1705: when making a vertical split the mode message isn't updated

Problem:    When making a vertical split the mode message isn't always
            updated, "VISUAL" remains. (Alexei Averchenko)
Solution:   Only reset clear_cmdline when filling all columns of the last
            screen line. (Tom M. closes vim/vim#2611)
5bab555c2f

src/nvim/screen.c

@@ -5816,7 +5816,8 @@ void screen_fill(int start_row, int end_row, int start_col, int end_col, int c1,
     // TODO(bfredl): The relevant caller should do this
     if (row == Rows - 1) {  // overwritten the command line
       redraw_cmdline = true;
-      if (c1 == ' ' && c2 == ' ') {
+      if (start_col == 0 && end_col == Columns
+          && c1 == ' ' && c2 == ' ' && attr == 0) {
         clear_cmdline = false;  // command line has been cleared
       }
       if (start_col == 0) {

src/nvim/testdir/test_window_cmd.vim

@@ -466,4 +466,28 @@ func Test_access_freed_mem()
   bwipe xxx
 endfunc
 
+func Test_visual_cleared_after_window_split()
+  new | only!
+  let smd_save = &showmode
+  set showmode
+  let ls_save = &laststatus
+  set laststatus=1
+  call setline(1, ['a', 'b', 'c', 'd', ''])
+  norm! G
+  exe "norm! kkvk"
+  redraw
+  exe "norm! \<C-W>v"
+  redraw
+  " check if '-- VISUAL --' disappeared from command line
+  let columns = range(1, &columns)
+  let cmdlinechars = map(columns, 'nr2char(screenchar(&lines, v:val))')
+  let cmdline = join(cmdlinechars, '')
+  let cmdline_ltrim = substitute(cmdline, '^\s*', "", "")
+  let mode_shown = substitute(cmdline_ltrim, '\s*$', "", "")
+  call assert_equal('', mode_shown)
+  let &showmode = smd_save
+  let &laststatus = ls_save
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab