vim-patch:8.2.1401: cannot jump to the last used tabpage

Problem:    Cannot jump to the last used tabpage.
Solution:   Add g<Tab> and tabpagnr('#'). (Yegappan Lakshmanan, closes vim/vim#6661,
            neovim #11626)
https://github.com/vim/vim/commit/62a232506d06f6d1b3b7271801c907d6294dfe84

Nvim implemented this feature before Vim, but Vim made some useful changes (e.g:
beeping on failure). Port the changes to closer match Vim (also makes porting
future patches easier).

Also note that because CHECK_CMDWIN was added to goto_tabpage_tp, there is no
need to do the extra work with tabpage_index and goto_tabpage inside
goto_tabpage_lastused to fix cmdwin issues any more (#11692).
Note that while goto_tabpage_tp doesn't check for textlock like goto_tabpage
does, it shouldn't matter as it is already checked for earlier.

Add tags for <C-Tab> to tabpage.txt, and refer to <C-Tab> over CTRL-Tab to be
consistent with other docs like the patch.
Remove mention of "previous tabpage" (it can be confused with the tabpage to the
left, e.g: `:tabprevious`).
Similarly, don't rename old_curtab to last_tab in enter_tabpage (it might be
confused with the right-most tabpage, e.g: `:tablast`).

Cherry-pick Test_tabpage change from v8.2.0634.
https://github.com/vim/vim/commit/92b83ccfda7a1d654ccaaf161a9c8a8e01fbcf76

1 files changed, 14 insertions, 10 deletions

diff --git a/src/nvim/window.c b/src/nvim/window.c
index f2b84a4124..a235b07b47 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -530,10 +530,6 @@ wingotofile:
       do_nv_ident('g', xchar);
       break;
 
-    case TAB:
-      goto_tabpage_lastused();
-      break;
-
     case 'f':                       // CTRL-W gf: "gf" in a new tab page
     case 'F':                       // CTRL-W gF: "gF" in a new tab page
       cmdmod.tab = tabpage_index(curtab) + 1;
@@ -547,6 +543,12 @@ wingotofile:
       goto_tabpage(-(int)Prenum1);
       break;
 
+    case TAB:                       // CTRL-W g<Tab>: go to last used tab page
+      if (!goto_tabpage_lastused()) {
+        beep_flush();
+      }
+      break;
+
     case 'e':
       if (curwin->w_floating || !ui_has(kUIMultigrid)) {
         beep_flush();
@@ -4119,8 +4121,8 @@ static void enter_tabpage(tabpage_T *tp, buf_T *old_curbuf, bool trigger_enter_a
 {
   int old_off = tp->tp_firstwin->w_winrow;
   win_T *next_prevwin = tp->tp_prevwin;
-
   tabpage_T *old_curtab = curtab;
+
   curtab = tp;
   firstwin = tp->tp_firstwin;
   lastwin = tp->tp_lastwin;
@@ -4291,13 +4293,15 @@ void goto_tabpage_tp(tabpage_T *tp, bool trigger_enter_autocmds, bool trigger_le
   }
 }
 
-// Go to the last accessed tab page, if there is one.
-void goto_tabpage_lastused(void)
+/// Go to the last accessed tab page, if there is one.
+/// @return true if the tab page is valid, false otherwise.
+bool goto_tabpage_lastused(void)
 {
-  int index = tabpage_index(lastused_tabpage);
-  if (index < tabpage_index(NULL)) {
-    goto_tabpage(index);
+  if (valid_tabpage(lastused_tabpage)) {
+    goto_tabpage_tp(lastused_tabpage, true, true);
+    return true;
   }
+  return false;
 }
 
 /*