vim-patch:8.2.2595: setting 'winminheight' may cause 'lines' to change

Problem:    Setting 'winminheight' may cause 'lines' to change.
Solution:   Also take minimal height of other tabpages into account. (vim/vim#7899)
9e813b3dea

src/nvim/testdir/test_options.vim

@@ -634,6 +634,28 @@ func Test_opt_winminheight_term()
   call delete('Xwinminheight')
 endfunc
 
+func Test_opt_winminheight_term_tabs()
+  " See test/functional/legacy/options_spec.lua
+  CheckRunVimInTerminal
+
+  " The tabline should be taken into account.
+  let lines =<< trim END
+    set wmh=0 stal=2
+    split
+    split
+    split
+    split
+    tabnew
+  END
+  call writefile(lines, 'Xwinminheight')
+  let buf = RunVimInTerminal('-S Xwinminheight', #{rows: 11})
+  call term_sendkeys(buf, ":set wmh=1\n")
+  call WaitForAssert({-> assert_match('E36: Not enough room', term_getline(buf, 11))})
+
+  call StopVimInTerminal(buf)
+  call delete('Xwinminheight')
+endfunc
+
 " Test for setting option value containing spaces with isfname+=32
 func Test_isfname_with_options()
   set isfname+=32

src/nvim/window.c

@@ -5501,8 +5501,8 @@ void win_setminheight(void)
 
   // loop until there is a 'winminheight' that is possible
   while (p_wmh > 0) {
-    const int room = Rows - p_ch - tabline_height();
+    const int room = Rows - p_ch;
-    const int needed = frame_minheight(topframe, NULL);
+    const int needed = min_rows() - 1;  // 1 was added for the cmdline
     if (room >= needed) {
       break;
     }

test/functional/legacy/options_spec.lua

@@ -42,6 +42,20 @@ describe('set', function()
     matches('E36: Not enough room', exc_exec('set wmh=1'))
   end)
 
+  it('winminheight works with tabline', function()
+    local screen = Screen.new(20, 11)
+    screen:attach()
+    source([[
+      set wmh=0 stal=2
+      split
+      split
+      split
+      split
+      tabnew
+    ]])
+    matches('E36: Not enough room', exc_exec('set wmh=1'))
+  end)
+
   it('scroll works', function()
     local screen = Screen.new(42, 16)
     screen:attach()