vim-patch:8.1.1242: no cmdline redraw when tabpages have different 'cmdheight'

Problem:    No cmdline redraw when tabpages have different 'cmdheight'.
Solution:   redraw the command line when 'cmdheight' changes when switching
            tabpages. (closes vim/vim#4321)
0fef0aeb1c

src/nvim/testdir/test_tabpage.vim

@@ -1,5 +1,6 @@
 " Tests for tabpage
 
+" source screendump.vim
 
 function Test_tabpage()
   bw!
@@ -555,4 +556,27 @@ func Test_tabs()
   bw!
 endfunc
 
+func Test_tabpage_cmdheight()
+  if !CanRunVimInTerminal()
+    throw 'Skipped: only works with terminal'
+  endif
+  call writefile([
+        \ 'set laststatus=2',
+        \ 'set cmdheight=2',
+        \ 'tabnew',
+        \ 'set cmdheight=3',
+        \ 'tabnext',
+        \ 'redraw!',
+        \ 'echo "hello\nthere"',
+        \ 'tabnext',
+        \ 'redraw',
+	\ ], 'XTest_tabpage_cmdheight')
+  " Check that cursor line is concealed
+  let buf = RunVimInTerminal('-S XTest_tabpage_cmdheight', {'statusoff': 3})
+  call VerifyScreenDump(buf, 'Test_tabpage_cmdheight', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XTest_conceal')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/nvim/window.c

@@ -3793,6 +3793,9 @@ static void enter_tabpage(tabpage_T *tp, buf_T *old_curbuf, int trigger_enter_au
    * the frames for that.  When the Vim window was resized need to update
    * frame sizes too.  Use the stored value of p_ch, so that it can be
    * different for each tab page. */
+  if (p_ch != curtab->tp_ch_used) {
+    clear_cmdline = true;
+  }
   p_ch = curtab->tp_ch_used;
   if (curtab->tp_old_Rows != Rows || (old_off != firstwin->w_winrow
                                       ))